JP6262479B2 - Antenna drive device - Google Patents

Description

  The present invention relates to an antenna driving device.

  Conventionally, a transmission antenna (LC antenna or RLC antenna) has a resonance frequency f (= 1 / (2π√LC)) in a vehicle smart entry system, a tire pressure monitoring system, and a non-contact type automatic ticket gate system. An antenna driving device that is driven by the above is used.

  In addition, Patent Document 1 and Patent Document 2 can be cited as examples of related art related to the above.

JP 2007-216869 A JP 2011-120216 A

  By the way, in the conventional antenna driving device, generally, either one of the sine wave driving method and the rectangular wave driving method has been adopted as the antenna driving method. However, although the sine wave driving method hardly generates harmonic noise, there is a problem that power consumption and heat generation are large, and the rectangular wave driving method has a problem that harmonic noise is easily generated although power consumption and heat generation are small.

  Note that Patent Document 1 discloses an in-vehicle device remote control device that can switch between a sine wave driving method and a rectangular wave driving method depending on the use situation, but the antenna driving method switching method is a separate configuration. There was room to consider.

  In the conventional antenna driving apparatus, the radio wave transmission range is determined by the magnitude of the driving current flowing through the transmission antenna. Therefore, in order to accurately control the radio wave transmission range, a current feedback control system that controls the output voltage of the power supply circuit (supply voltage to the antenna drive circuit) so that the drive current flowing through the transmission antenna is maintained at a constant value. Becomes effective. However, since the current feedback control method requires more time to start up the power supply circuit as compared with the voltage feedback control method in which the output voltage of the power supply circuit is maintained at a constant value, the system operation may be restricted.

  In view of the above-described problems, an object of the present invention is to provide an antenna driving device capable of performing appropriate antenna driving according to the use situation.

<First invention>
Among various inventions disclosed in the present specification, an antenna driving device according to a first invention includes an antenna driving unit including a linear amplifier for driving a transmission antenna with a sine wave and a driver for driving a rectangular wave. And a logic circuit that controls the antenna driving unit so as to operate only one of the linear amplifier and the driver (first-first configuration).

  In the antenna driving apparatus having the configuration 1-1, the antenna driving unit includes an upper switch connected between the output terminal to which the transmission antenna is connected, the first voltage terminal, and the second voltage terminal. And the lower switch, wherein the linear amplifier drives the upper switch and the lower switch according to a sine wave signal, respectively, and the driver controls the upper switch and the lower switch according to a rectangular wave signal. It is good to make it the structure which drives each (1-2 structure).

  The antenna driving device having the 1-2 configuration may be configured to further include a digital / analog conversion unit that converts digital sine wave data into the analog sine wave signal (1-3 configuration). .

  In the antenna driving device having the first to third configurations, the antenna driving unit may be configured to be individually provided for a plurality of transmission antennas (first to fourth configurations).

  In the antenna driving device having the first to fourth configurations, the digital / analog converter may be configured to be provided in common for a plurality of transmission antennas (first to fifth configurations).

  In the antenna driving device having the first to fifth configurations, the logic circuit controls the antenna driving unit so as to simultaneously drive or time-division drive a plurality of transmitting antennas (first to sixth configurations). It is good to do.

  In addition, the antenna driving device having any one of the first to first to sixth configurations further includes a jamming driving unit that applies an intentional noise signal to the non-transmission transmitting antenna (first to seventh configurations). ).

  The vehicle according to the first aspect of the invention controls the antenna driving device having any one of the first to first to seventh configurations, the transmission antenna driven by the antenna driving device, and the antenna driving device. It is set as the structure (1-8 structure) which has a microcomputer and the battery which supplies electric power to the said antenna drive device.

  In the vehicle having the first to eighth configurations, the transmission antenna may be configured to be provided in a door and a cabin (first to ninth configuration) as one component of the smart entry system.

  In the vehicle having the first to eighth configurations, the transmitting antenna may be configured to be provided on a tire or a wheel (the first to tenth configurations) as one component of the tire pressure monitoring system.

<Second invention>
Of the various inventions disclosed in this specification, an antenna driving device according to a second invention includes an antenna driving circuit that generates a driving current for a transmitting antenna, and an output voltage generated from an input voltage. A power supply circuit that supplies the antenna drive circuit; and a logic circuit that controls the antenna drive circuit and the power supply circuit, wherein the power supply circuit maintains the output voltage at a constant value and the drive current. Is configured to have a function of switching the output feedback system in accordance with an instruction from the logic circuit so as to perform any one of the current feedback control for maintaining the current at a constant value (2-1 configuration). .

  In the antenna driving device having the configuration of (2-1), the power supply circuit has a difference between a lower one of a predetermined reference voltage and a soft start voltage that gently rises after startup and a feedback voltage corresponding to the output voltage. An error amplifier that generates a corresponding error signal, and an output voltage generation unit that generates the output voltage from the input voltage according to the error signal. During the current feedback control, the reference voltage and the soft start voltage And, it is preferable that either of the feedback voltages is variably controlled according to the drive current (2-2 configuration).

  In the antenna driving apparatus having the configuration 2-2, the output voltage generation unit compares the error signal and the slope signal with a slope signal generation unit that generates a slope signal, and compares the error signal with the slope signal. A configuration that includes a PWM comparator that generates a signal, a driver that generates a switch drive signal in response to the PWM signal, and a switching drive stage that is driven in response to the switch drive signal (configuration 2-3) It is good to do.

  In the antenna driving device having the configuration of 2-2 or 2-3, the power supply circuit switches the reference voltage so that the reference voltage is always higher than the soft start voltage during the current feedback control. A selector, a sample / hold unit for generating a peak signal by sampling / holding a peak value of a current feedback signal corresponding to the driving current, and a charge / discharge control signal are generated by comparing the peak signal with a predetermined threshold value And a charge / discharge control unit that generates the soft start voltage by charging / discharging a capacitor in accordance with the charge / discharge control signal.

  Further, in the antenna driving device having the second to fourth configurations, the power supply circuit further includes a first switch for conducting / cutting off between the charge / discharge control unit and the capacitor (second to fifth configurations). ).

  Further, in the antenna drive device having the second to fifth configurations, the power supply circuit further includes a second switch that conducts / cuts off between the feedback voltage application terminal and the capacitor (second to sixth configurations). ).

  Further, in the antenna driving device having any one of the second to fourth to sixth configurations, the power supply circuit selects one of the plurality of current feedback signals obtained for each of the plurality of transmission antennas and selects the sample / A configuration (second configuration 7-7) further including a multiplexer that outputs to the hold unit is preferable.

  A vehicle according to a second aspect of the present invention controls the antenna driving device having any one of the configurations of 2-1 to 2-7, a transmission antenna driven by the antenna driving device, and the antenna driving device. The configuration includes a microcomputer and a battery that supplies power to the antenna driving device (second to eighth configuration).

  In the vehicle having the second to eighth configuration, the transmission antenna may be configured to be provided in a door and a cabin (second to ninth configuration) as one component of the smart entry system.

  Further, in the vehicle having the second to eighth configuration, the transmission antenna may have a configuration (second to 10th configuration) provided in a tire or a wheel as one component of the tire pressure monitoring system.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the antenna drive device which can perform an appropriate antenna drive according to a use condition.

Block diagram showing the overall configuration of a vehicle equipped with an antenna drive device Schematic plan view showing an example of antenna installation points and radio wave coverage Circuit block diagram showing a configuration example of an antenna drive circuit Table for explaining switching function of antenna drive system Circuit block diagram showing one configuration example of switching power supply circuit Table for explaining output feedback switching function Timing chart showing an operation example of a switching power supply circuit Timing chart for explaining initial start-up function of soft start voltage

<Overall configuration>
FIG. 1 is a block diagram showing the overall configuration of a vehicle equipped with an antenna driving device. The vehicle 1 of this configuration example includes an antenna driving device 10, a transmission antenna unit 20, a microcomputer 30, and a battery 40.

  The antenna driving device 10 is a semiconductor integrated circuit device (so-called antenna driver IC) that operates by receiving an input voltage VB (for example, 12 V) from the battery 40 and drives the transmission antenna unit 20 in accordance with an instruction from the microcomputer 30. is there. The antenna driving device 10 is integrated with an antenna driving circuit 100, a switching power supply circuit 200, and a logic circuit 300 as main circuits.

  The antenna drive circuit 100 operates by receiving an output voltage VS (for example, 20 to 30 V) from the switching power supply circuit 200, and generates drive currents I1 to I6 of the transmission antenna unit 20 in response to an instruction from the logic circuit 300. . The configuration and operation of the antenna drive circuit 100 will be described in detail later.

  The switching power supply circuit 200 generates an output voltage VS from the input voltage VB and supplies it to the antenna drive circuit 100. The configuration and operation of the switching power supply circuit 200 will be described in detail later.

  The logic circuit 300 controls each of the antenna drive circuit 100 and the switching power supply circuit 200 in accordance with an instruction from the microcomputer 30. The logic circuit 300 is a serial communication bus (in this configuration example, a 4-wire SPI (serial peripheral interface) bus using a chip select signal SCSB, a clock signal SCK, an input data signal SDI, and an output data signal SDO). Via the microcomputer 30 receives instructions (including various commands). The antenna driving device 10 includes various data input terminals in addition to the serial communication interface terminal, and the logic circuit 300 transmits the transmission data signal DIN1 from the microcomputer 30 without using the serial communication bus. And DIN2.

  The transmission antenna unit 20 is a load driven by the antenna driving device 10, and includes 6-channel transmission antennas 21 to 26 (an LC antenna or an RLC antenna having a resonance frequency f in an LF [Low Frequency] band (for example, 125 kHz)). including. However, the number of channels of the transmission antenna unit 20 is not limited to the above, and the increase or decrease of the number of channels is arbitrary.

  The microcomputer 30 is a control main body of the antenna driving device 10, and for example, an ECU (electronic control unit) corresponds to this.

  The battery 40 supplies power to each part of the vehicle 1 (including the antenna driving device 10 and the microcomputer 30). In addition, as the battery 40, a lead storage battery etc. can be used suitably.

  FIG. 2 is a schematic plan view illustrating an example of an antenna installation point and a radio wave reachable range. The vehicle 1 of this configuration example is configured to lock a door lock mechanism (not shown) according to the success or failure of two-way communication with a remote control key (not shown) carried by a driver (or a passenger, the same applies hereinafter). / The smart entry system that performs unlocking, etc. is mounted, and the transmission antennas 21 to 26 are the doors (driving) of the vehicle 1 as one component of the smart entry system (means for transmitting a request signal to the remote control key). Seat door knobs, passenger door knobs, trunk door knobs) and cabins (front, rear, in the trunk).

  In addition, the vehicle 1 includes a receiving antenna that receives a response signal from a remote control key and transmits it to the microcomputer 30 as other components included in the smart entry system, and a contact that detects gripping of the doorknob and notifies the microcomputer 30 A sensor, a locking button that is pressed when locking the door lock mechanism, a start button that is pressed when starting the engine or motor, and the like (all not shown) are provided.

  For example, in the vehicle 1 in which the door lock mechanism is locked, when the grip of the door knob is detected by the contact sensor, the microcomputer 30 causes the antenna drive device 10 to transmit a request signal from the transmission antenna unit 20 to the remote control key. Control. At that time, only the transmission antenna of the door where the grip is detected may be driven, or all the transmission antennas 21 to 26 may be driven.

  At this time, if the driver carrying the remote control key is present in the vicinity of the vehicle 1 (within the radio wave reachable range of the transmitting antenna unit 20), a response signal is returned from the remote control key that has received the request signal. On the other hand, if the driver carrying the remote control key does not exist near the vehicle 1, no response signal is returned. Therefore, the microcomputer 30 unlocks the door lock mechanism when the response signal is returned within a predetermined time after transmitting the request signal, and maintains the locked state of the door lock mechanism when the response signal is not returned. .

  Two-way communication with the remote control key (confirmation of the presence or absence of the remote control key) is performed not only when the door lock mechanism is unlocked but also periodically after the door lock mechanism is unlocked, and the vehicle 1 is started. It is also performed as needed when locking the door lock mechanism. For the various operations of such a smart entry system, it is sufficient to apply a well-known technique, and therefore a detailed description thereof will be omitted.

  In addition, about the transmission antennas 21-23 provided in the door of the vehicle 1, it is desirable to expand each radio | wireless reach range a1-a3 to some extent, in order to communicate with the remote control key which exists outside a vehicle reliably. On the other hand, for the transmission antennas 24 to 26 provided in the cabin of the vehicle 1, it is desirable to limit the radio wave arrival ranges a4 to a6 within the cabin in order to prevent leakage of radio waves to the outside of the vehicle. The radio wave reach ranges a1 to a6 include, for example, appropriately selecting resistance values of resistors Ra1 to Ra6 (see FIG. 3 described later) connected in series to the transmission antennas 21 to 26 to adjust the drive currents I1 to I6. Therefore, it is possible to set arbitrarily.

<Antenna drive circuit>
FIG. 3 is a circuit block diagram illustrating a configuration example of the antenna driving circuit 100. The antenna driving circuit 100 of this configuration example includes a digital / analog conversion unit 110, antenna driving units 120-1 to 120-6, and a jamming driving unit 130.

  The digital / analog conversion unit 110 converts the digital sine wave data SD input from the logic circuit 300 into an analog sine wave signal SA and outputs the analog sine wave signal SA to the antenna driving units 120-1 to 120-6. As described above, the digital / analog conversion unit 110 is provided in common to the 6-channel antenna driving units 120-1 to 120-6 (and thus the 6-channel transmission antennas 21 to 26).

  The antenna driving units 120-1 to 120-6 are individually provided for the transmission antennas 21 to 26 connected to the antenna driving device 10, and are respectively a linear amplifier 121, gate drivers 122 and 123, and P. A channel type MOS [metal oxide semiconductor] field effect transistor 124 and an N channel type MOS field effect transistor 125 are included. In FIG. 3, only the internal configuration of the antenna drive unit 120-1 is depicted, but the internal configurations of the other antenna drive units 120-2 to 120-6 are the same. Hereinafter, for convenience of explanation, detailed description will be given focusing on the antenna driving unit 120-1.

  The linear amplifier 121 is means for driving the transmission antenna 21 in a sine wave, and a sine wave signal SA applied to the non-inverting input terminal (+) and an output signal OUT1 applied to the inverting input terminal (−). So that the gate voltages of the transistors 124 and 125 are linearly changed. More specifically, the linear amplifier 121 includes each gate of the transistors 124 and 125 so that the conductivity of the transistor 124 is increased and the conductivity of the transistor 125 is decreased as the output signal OUT1 is lower than the sine wave signal SA. Change the voltage. Conversely, the linear amplifier 121 changes the gate voltages of the transistors 124 and 125 so that the higher the output signal OUT1 is than the sine wave signal SA, the lower the conductivity of the transistor 124 and the higher the conductivity of the transistor 125. .

  Each of the gate drivers 122 and 123 is a means for driving the transmission antenna 21 to a rectangular wave. The gate drivers 122 and 123 respectively change the gate voltages of the transistors 124 and 125 according to the rectangular wave signals S1H and S1L input from the logic circuit 300, respectively. Change in pulses. More specifically, each of the gate drivers 122 and 123 reduces the gate voltages of the transistors 124 and 125 so that the transistor 124 is turned on and the transistor 125 is turned off when the output signal OUT1 is set to a high level. Level. Conversely, when the output signals OUT1 are set to the low level, the gate drivers 122 and 123 set the gate voltages of the transistors 124 and 125 to the high level so that the transistor 124 is turned off and the transistor 125 is turned on.

  The transistor 124 is an upper switch that conducts / cuts off between the application terminal of the output signal OUT1 and the application terminal (first voltage terminal) of the output voltage VS. The source of the transistor 124 is connected to the application terminal for the output voltage VS. The drain of the transistor 124 is connected to the application terminal of the output signal OUT1. The gate of the transistor 124 is connected to the first output terminal of the linear amplifier 121 and the output terminal of the gate driver 122.

  The transistor 125 is a lower switch that conducts / cuts off between the application terminal of the output signal OUT1 and the ground terminal (second voltage terminal). The source of the transistor 125 is connected to the ground terminal. The drain of the transistor 125 is connected to the application terminal of the output signal OUT1. The gate of the transistor 125 is connected to the second output terminal of the linear amplifier 121 and the output terminal of the gate driver 123.

  In addition, outside the antenna driving device 10, between the application terminals of the output signals OUT1 to OUT6 and the ground terminal, resistors Ra1 to Ra6 and transmission antennas 21 to 26 (coils L21 to L26 and capacitors C21 to C26), respectively. LC resonance circuit) is connected in series. The transmission antennas 21 to 26 are supplied with drive currents I1 to I6 that are sine wave driven or rectangular wave driven at respective resonance frequencies f (= 1 / (2π√LC)).

  The jamming driving unit 130 outputs the pseudo noise signals JO1 to JO6 input from the logic circuit 300 to the transmission antenna in the non-communication state. By providing such a jamming drive unit 130, for example, even when a radio wave circulates from a communication state transmission antenna to a non-communication state transmission antenna and an unnecessary radio wave is output from the non-communication state transmission antenna. Since an intentional noise component can be superimposed on the output radio wave, establishment of erroneous communication can be inhibited.

  Note that the jamming intensity (the magnitude of the superimposed noise component) is appropriately selected from the resistance values of the resistors Rb1 to Rb6 connected between the application ends of the pseudo noise signals JO1 to JO6 and the transmitting antennas 21 to 26. Therefore, it can be set arbitrarily.

  In the antenna driving apparatus 10 of this configuration example, it is also possible to perform a jamming operation similar to the above using the antenna driving units 120-1 to 120-6 without using the jamming driving unit 130. Note that when performing the jamming operation, which of the jamming driving unit 130 and the antenna driving units 120-1 to 120-6 is used can be arbitrarily set by inputting a command to the logic circuit 300.

  FIG. 4 is a table for explaining the switching function of the antenna driving method by the logic circuit 300. In the antenna driving device 10 of this configuration example, the logic circuit 300 causes the antenna driving unit 120 to operate only one of the linear amplifier 121 and the gate drivers 122 and 123 in accordance with the SPI command input from the microcomputer 30. A function of switching between sine wave driving or rectangular wave driving of the output signal OUT * (where * = 1, 2,..., 6 and so on) by controlling −1 to 120-6. It has.

  More specifically, when the output signal OUT * is driven in a sine wave, the linear amplifier 121 is set in an operating state (O) and the gate drivers 122 and 123 are set in a non-operating state (X). At this time, the gate drivers 122 and 123 are both in an output high impedance state and are disconnected from the gates of the transistors 124 and 125.

  On the other hand, when the output signal OUT * is driven in a rectangular wave, the gate drivers 122 and 123 are set in an operating state (◯), and the linear amplifier 121 is set in a non-operating state (×). At this time, the linear amplifier 121 is in an output high impedance state and is disconnected from the gates of the transistors 124 and 125.

  By adopting such a configuration, it is possible to perform appropriate antenna driving according to the usage status of the transmission antennas 21 to 26. For example, before unlocking the vehicle 1 (before the driver gets on board), there is little need to consider the influence of harmonic noise generated when the antenna is driven on the on-vehicle equipment. Therefore, under such usage conditions, it is possible to give priority to the reduction of power consumption and heat generation by driving the transmission antennas 21 to 26 to rectangular waves.

  On the other hand, after unlocking the vehicle 1 (after the driver has boarded), the influence of harmonic noise generated when the antenna is driven on the in-vehicle device cannot be ignored. Therefore, under such a use situation, it is possible to give priority to the reduction of harmonic noise by driving the transmission antennas 21 to 26 with a sine wave.

  The logic circuit 300 also has a function of controlling the antenna driving units 120-1 to 120-6 so that the transmission antennas 21 to 26 are simultaneously driven or time-division driven. For example, when the transmission antennas 21 to 26 are driven in a rectangular wave, the heat generated by the antenna driving can be suppressed to a small value, so that multi-channel simultaneous driving can be performed. On the other hand, when the transmitting antennas 21 to 26 are driven in a sine wave, the heat generated by the antenna driving increases, so that only one channel can be driven alone, or a plurality of channels can be driven sequentially in a time division manner. desirable.

  The logic circuit 300 outputs sine wave data SD or rectangular wave signals S * H and S * L when the transmission data signal DIN1 input from the microcomputer 30 is at a high level, and the transmission data signal DIN1 is at a low level. When, the output of the sine wave data SD and the rectangular wave signals S * H and S * L is stopped. Therefore, the output signal OUT * is sine-wave driven or rectangular-wave driven at the resonance frequency f of the transmission antennas 21 to 26 only when the transmission data signal DIN1 is at a high level.

  However, when the transmission antennas 21 to 26 are driven by the rectangular wave, the transmission data signal DIN2 that is driven by the rectangular wave at the resonance frequency f of the transmission antennas 21 to 26 is input from the microcomputer 30 to the logic circuit 300, and this is input to the rectangular wave signal S *. It is also possible to output through from the logic circuit 300 to the transmitting antennas 21 to 26 as H and S * L. Note that which of the transmission data signals DIN 1 and DIN 2 is used can be arbitrarily set by inputting a command to the logic circuit 300.

<Switching power supply circuit>
FIG. 5 is a circuit block diagram illustrating a configuration example of the switching power supply circuit 200. The switching power supply circuit 200 of this configuration example is a step-up DC / DC converter that boosts an input voltage VB to generate an output voltage VS. The antenna driving device 10 is provided with external terminals T1 to T4 and external terminals T5 (1) to (6) in order to establish an electrical connection between the switching power supply circuit 200 and the outside of the device. As a discrete element constituting the switching power supply circuit 200, a coil L1, capacitors C1 to C3, a diode D1, and resistors R1 and Rs1 to Rs6 are externally attached.

  Outside the antenna driving apparatus 10, the external terminal T1 is connected to the first end of the coil L1 and the anode of the diode D1. The second end of the coil L1 is connected to the application end of the input voltage VB. The cathode of the diode D1 is connected to the first end of the capacitor C1. The second end of the capacitor C1 is connected to the ground end. The external terminal T2 is connected to the first end (corresponding to the application end of the output voltage VS) of the capacitor C1. A phase compensation resistor R1 and a capacitor C2 are connected in series between the external terminal T3 and the ground terminal. A soft start capacitor C3 is connected between the external terminal T4 and the ground terminal. Current sensing resistors Rs1 to Rs6 that generate current feedback signals CS1 to CS6 (voltage signals) corresponding to the drive currents I1 to I6 are connected between the transmission antenna unit 20 and the ground terminal. The external terminals T5 (1) to T5 (6) are connected to the high potential ends (corresponding to the application ends of the current feedback signals CS1 to CS6) of the resistors Rs1 to Rs6, respectively.

  The switching power supply circuit 200 includes an N-channel MOS field effect transistor 201, a gate driver 202, a PWM comparator 203, and a slope signal generation unit 204 as semiconductor elements and semiconductor circuit units integrated in the antenna driving device 10. An error amplifier 205, a reference voltage generation unit 206, a digital / analog conversion unit 207, a selector 208, a multiplexer 209, a sample / hold unit 210, a comparator 211, a charge / discharge control unit 212, and an analog switch. 213 and 214, a buffer 215, resistors 216 and 217, and a P-channel MOS field effect transistor 218. It should be noted that the switching power supply circuit 200 may appropriately incorporate an abnormality protection circuit in addition to the various circuit units described above.

  The transistor 201, together with the coil L1, the diode D1, and the capacitor C1, forms a switching drive stage that is driven according to the switch drive signal Sg. The drain of the transistor 201 is connected to the external terminal T1. The source of the transistor 201 is connected to the ground terminal. The gate of the transistor 201 is connected to the output terminal of the gate driver 202.

  The gate driver 202 generates a switch drive signal Sg in which the current capability of the PWM signal Sp is increased, and outputs this to the gate of the transistor 201.

  The PWM comparator 203 compares the error signal ERR applied to the non-inverting input terminal (+) and the slope signal SLP applied to the inverting input terminal (−) to generate the PWM signal Sp. The PWM signal Sp becomes a high level when the error signal ERR is higher than the slope signal SLP, and becomes a low level when the error signal ERR is lower than the slope signal SLP.

  The slope signal generation unit 204 generates a triangular wave (or sawtooth) slope signal SLP. The slope signal generation unit 204 can arbitrarily set the oscillation frequency (switching frequency) of the slope signal SLP according to an instruction from the logic circuit 300.

  Note that each of the transistor 201, the gate driver 202, the PWM comparator 203, and the slope signal generation unit 204 described above is a configuration of the output voltage generation unit that generates the output voltage VS from the input voltage VB according to the error signal ERR. Acts as an element.

  The error amplifier 205 determines the difference between the lower one of the reference voltage REF and the soft start voltage SS applied to the two non-inverting input terminals (+) and the feedback voltage FB applied to the inverting input terminal (−). A corresponding error signal ERR is generated. A phase compensation resistor R1 and a capacitor C2 are connected to the output terminal of the error amplifier 205 via an external terminal T3.

  The reference voltage generation unit 206 generates a predetermined reference voltage REF0 (eg, 1.28V).

  The digital / analog conversion unit 207 operates in response to the supply of the reference voltage REF0, and converts the digital reference voltage data SV input from the logic circuit 300 into an analog reference voltage REF1 (for example, 40 mV to 1 V).

  The selector 208 selects one of the reference voltages REF0 and REF1 according to an instruction from the logic circuit 300, and outputs this as the reference voltage REF.

  The multiplexer 209 selects any one of the current feedback signals CS1 to CS6 obtained for each of the transmission antennas 21 to 26 in accordance with an instruction from the logic circuit 300, and uses the current feedback signal CS0 as the current feedback signal CS0. Output to.

  The sample / hold unit 210 generates a peak signal SHO by sampling / holding the peak value (maximum value) of the current feedback signal CS0 in accordance with an instruction from the logic circuit 300. Note that the hold timing of the current feedback signal CS0 may be, for example, the time when a predetermined time (for example, 2 μs) has elapsed since the zero crossing of the current feedback signal CS0.

  The comparator 211 compares the reference voltage REF1 applied to the non-inverting input terminal (+) and the peak signal SHO applied to the inverting input terminal (−) to generate the charge / discharge control signal Sc. The charge / discharge control signal Sc is at a low level when the peak signal SHO is higher than the reference voltage REF1, and is at a high level when the peak signal SHO is lower than the reference voltage REF1.

  The charge / discharge control unit 212 generates the soft start voltage SS by charging / discharging the capacitor C3 according to the charge / discharge control signal Sc. More specifically, the charge / discharge control unit 212 charges the capacitor C3 to increase the soft start voltage SS when the charge / discharge control signal Sc is at a high level, and conversely, the charge / discharge control signal Sc is low. When it is at the level, the capacitor C3 is discharged to lower the soft start voltage SS.

  The analog switch 213 functions as a first switch that conducts / cuts off between the charge / discharge control unit 212 and the capacitor C3 in accordance with an instruction from the logic circuit 300.

  The analog switch 214 functions as a second switch that conducts / cuts off between the output terminal of the buffer 215 (corresponding to the application terminal of the feedback voltage FB) and the capacitor C3 in accordance with an instruction from the logic circuit 300.

  The buffer 215 buffers the feedback voltage FB and outputs it to the subsequent stage.

  The resistors 216 and 217 are connected in series between the external terminal T2 (corresponding to the application terminal of the output voltage VS) and the ground terminal, and the output voltage VS is applied at a predetermined voltage dividing ratio α (for example, α = 1/40). The voltage is divided to generate a feedback voltage FB (for example, 225 mV to 1 V). A connection node between the resistor 216 and the resistor 217 is connected to each input terminal of the error amplifier 205 and the buffer 215 as an application terminal of the feedback voltage FB.

  The transistor 218 functions as a third switch that conducts / cuts off between the external terminal T <b> 2 and the resistor 216 in accordance with the enable signal EN of the antenna driving device 10. The transistor 218 is turned on when the enable signal EN is at a low level (logic level when the antenna driving device 10 is in an operating state), and the transistor 218 is at a high level (when the antenna driving device 10 is in an inoperative state). Off). With such a configuration, when the antenna driving apparatus 10 is not operating, the input terminal of the input voltage VB is connected to the ground terminal via the coil L1, the diode D1, the external terminal T2, the transistor 218, and the resistors 216 and 217. Therefore, the standby current of the antenna drive device 10 can be reduced.

  A basic operation (generation operation of the output voltage VS) of the switching power supply circuit 200 configured as described above will be described. When the transistor 201 is turned on, a switch current flows through the coil L1 toward the ground terminal via the transistor 201, and the electric energy is stored. At this time, since the potential of the external terminal T1 drops to almost the ground potential via the transistor 201, the diode D1 is in a reverse bias state, and no current flows from the capacitor C1 toward the transistor 201. On the other hand, when the transistor 201 is turned off, the electric energy stored therein is released by the counter electromotive voltage generated in the coil L1. At this time, since the diode D1 is in the forward bias state, the current flowing through the diode D1 charges the capacitor C1. By repeating the above operation, an output voltage VS obtained by boosting the input voltage VB is generated at the external terminal T2.

  Next, output feedback control of the switching power supply circuit 200 will be described. The switching power supply circuit 200 is instructed by the logic circuit 300 to perform either one of voltage feedback control for maintaining the output voltage VS at a constant value and current feedback control for maintaining the drive currents I1 to I6 at a constant value. It has a function to switch the output feedback system accordingly.

  When switching the output feedback system of the switching power supply circuit 200, the logic circuit 300 refers to the register value DCON set by the microcomputer 30 and controls the switching power supply circuit 200 to perform voltage feedback control when DCON = 1. When DCON = 0, the switching power supply circuit 200 is controlled to perform current feedback control.

  FIG. 6 is a table for explaining the switching function of the output feedback system, and shows the operation states of the selector 208 and the multiplexer 209 according to the register value DCON.

  At the time of voltage feedback control (DCON = 1), the multiplexer 209 is in an output high impedance state. At this time, since the peak value of the current feedback signal CS0 is not detected in the sample / hold unit 210, the peak signal SHO is always lower than the reference voltage REF1, and the charge control signal Sc is always at the high level (the logic at the time of charging). Level). Therefore, since the capacitor C3 is always maintained in a charged state regardless of fluctuations in the drive currents I1 to I6, the soft start voltage SS gradually rises after the antenna drive device 10 is activated, and finally the reference The voltage value is maintained higher than the voltage REF1.

  At the time of voltage feedback control (DCON = 1), the selector 208 is in a state of selectively outputting the reference voltage REF1. Therefore, after the antenna driving device 10 is activated, when a predetermined soft start period T1 (for example, 500 μs) elapses and the soft start voltage SS becomes higher than the reference voltage REF1, the error amplifier 205 causes the reference voltage REF1 and the feedback voltage FB. An error signal ERR corresponding to the difference between the two is generated, and the output voltage generation unit (201 to 204) in the subsequent stage performs PWM driving (duty control) of the transistor 201 according to the error signal ERR. By forming such an output feedback loop, in the switching power supply circuit 200, the output voltage VS is maintained at a constant value corresponding to the reference voltage REF1.

  On the other hand, during the current feedback control (DCON = 0), the multiplexer 209 is in a state of selectively outputting any one of the current feedback signals CS1 to CS6 as the current feedback signal CS0. At this time, the peak signal SHO generated by the sample / hold unit 210 varies in accordance with the peak value of the current feedback signal CS0 (and thus the peak value of the drive current I * that is monitored). Therefore, the logic level of the charge control signal Sc (the charge / discharge state of the capacitor C3) is switched according to whether the peak signal SHO is higher or lower than the reference voltage REF1.

  More specifically, when the monitored drive current I * is smaller than the target value and the peak signal SHO is lower than the reference voltage REF1, the charge control signal Sc is at a high level, and the capacitor C3 is in the charged state. Therefore, the soft start voltage SS is raised. Conversely, when the monitored drive current I * is larger than the target value and the peak signal SHO is higher than the reference voltage REF1, the charge control signal Sc is at a low level, and the capacitor C3 is in a discharged state. The start voltage SS is lowered.

  As described above, during the current feedback control (DCON = 0), the soft start voltage SS is variably controlled according to the monitored drive current I *.

  At the time of current feedback control (DCON = 0), the selector 208 is in a state of selectively outputting the reference voltage REF0. The reference voltage REF0 is set to a voltage value that is higher than the upper limit of variation of the soft start voltage SS. Accordingly, the error amplifier 205 always generates an error signal ERR corresponding to the difference between the soft start voltage SS and the feedback voltage FB, and the output voltage generation unit (201 to 204) in the subsequent stage generates a transistor according to the error signal ERR. 201 PWM drive (duty control) is performed. By forming such an output feedback loop, the switching power supply circuit 200 performs variable control of the output voltage VS so that the monitored drive current I * becomes a constant value according to the reference voltage REF1.

  The radio wave transmission range of the transmission antennas 21 to 26 is determined by the magnitudes of the drive currents I1 to I6. Therefore, it is possible to arbitrarily set the radio wave transmission range of the transmission antennas 21 to 26 by adjusting the reference voltage REF1 compared with the peak signal SHO.

  As described above, the switching power supply circuit 200 of the present configuration example performs either one of voltage feedback control that maintains the output voltage VS at a constant value and current feedback control that maintains the drive currents I1 to I6 at a constant value. In addition, a function of switching the output feedback system according to an instruction from the logic circuit 300 is provided. By adopting such a configuration, it becomes possible to select an appropriate output feedback method according to the usage status of the transmission antennas 21 to 26 (radio frequency transmission frequency, transmission interval, etc.) or system specifications.

  For example, when the antenna driving apparatus 10 is activated, switching the switching power supply circuit 200 to the voltage feedback control method can give priority to shortening the activation time. On the other hand, after the start of the antenna driving apparatus 10 is completed, it is possible to give priority to improving the accuracy of the radio wave transmission range by switching the switching power supply circuit 200 to the current feedback control method.

  Note that the switching power supply circuit 200 of this configuration example is configured to variably control the soft start voltage SS at the time of current feedback control (DCON = 0), but the variable control target is not limited to this, The reference voltage REF and the feedback voltage FB may be variably controlled according to the drive current I *.

  FIG. 7 is a timing chart showing an example of operation of the switching power supply circuit 200 (during current feedback control). The transmission data signal DIN1, the output voltage VS, the output signal OUT *, and the current feedback signal CS * are sequentially shown from the upper side of the drawing. And the peak signal SHO is depicted.

  As shown in this figure, during the high level period of the transmission data signal DIN1, the output signal OUT * is sinusoidally driven (or rectangular wave driven) at the resonance frequency f of the transmission antennas 21 to 26, so that radio waves are generated. Is output. On the other hand, during the low level period of the transmission data signal DIN1, the output signal OUT * is not driven and the output of radio waves is stopped. Therefore, data transmission to the remote control key can be performed by switching the high level / low level of the transmission data signal DIN1 to turn on / off the radio wave output.

  When the transmission data signal DIN1 is first raised to a high level at time t11 after the antenna driving device 10 is activated, the soft start operation of the switching power supply circuit 200 is performed, and the output voltage VS is set to the soft start period T1 ( It is started up slowly over time t11 to t13). At this time, the peak values of the output signal OUT * and the current feedback signal CS * also gradually increase with the output voltage VS. The sample / hold operation of the current feedback signal CS * is started during the soft start period T1 (time t12).

  When the transmission data signal DIN1 falls to the low level at time t14, the sine wave drive of the output signal OUT * is stopped, and the current feedback signal CS * becomes zero. Here, it is desirable that the drive stop period T2 (time t14 to t15) required until the sine wave drive of the output signal OUT * is stopped after the transmission data signal DIN1 falls to the low level is as short as possible. (For example, a maximum of 16 μs).

  During the low level period of the transmission data signal DIN1, the analog switch 213 is turned off and the charge / discharge control of the capacitor C3 by the charge / discharge control unit 212 is prohibited. By adopting such a configuration, the soft start voltage SS can be held in the state immediately before being turned off until the transmission data signal DIN1 is raised to the high level next time, so that the output voltage VS is maintained at the target value. Is possible.

  When the transmission data signal DIN rises to the high level again at time t16, the sine wave drive of the output signal OUT * is resumed and the analog switch 213 is turned on to charge / discharge the capacitor C3 by the charge / discharge control unit 212. Control (current feedback control) is resumed. Note that the peak stabilization period T3 (time t16 to t17) required until the peak value of the current feedback signal CS * is stabilized after the transmission data signal DIN1 is raised to the high level is from the previous soft start period T1. Will also be short.

  FIG. 8 is a timing chart for explaining the initial start-up function of the soft start voltage SS using the analog switch 214. The behavior of the feedback voltage FB (see the solid line) and the soft start voltage SS (see the broken line) is shown. It is shown. Note that the behavior when the initial startup function is not provided is depicted in the (a) column, and the behavior when the initial startup function is provided is depicted in the (b) column.

  The initial start-up function of the soft start voltage SS is to turn on the analog switch 214 for a short period when the antenna driving apparatus 10 is started, and to short-circuit between the application end of the soft start voltage SS and the application end of the feedback voltage FB. Thus, the soft start voltage SS is raised to the same voltage as the feedback voltage FB at once.

  In the step-up switching power supply circuit 200, the output voltage VS close to the input voltage VB is output even when the switching operation is not started, so that the feedback voltage FB (= α) input to the error amplifier 205 is output. The initial value of (VS) is not zero.

  As shown in the column (a), when the initial start-up function of the soft start voltage SS is not provided, the soft start voltage SS gradually decreases from the zero value (GND) after the antenna driving device 10 is started at time t21. Stand up to. However, until the soft start voltage SS exceeds the feedback voltage FB, the error signal ERR remains stuck at a low level, so that the switching drive of the transistor 201 is not started. Thereafter, when the soft start voltage SS exceeds the feedback voltage FB at time t22, the switching drive of the transistor 201 is finally started, and the output voltage VS (and thus the feedback voltage FB) gradually follows the soft start voltage SS. Begin to. As described above, when the function of initial startup of the soft start voltage SS is not provided, the activation of the switching power supply circuit 200 is delayed by the period Td (time t21 to t22).

  On the other hand, as shown in the column (b), when the initial start function of the soft start voltage SS is provided, the analog switch 214 is turned on for a short period when the antenna driving device 10 is started at time t21. The soft start voltage SS is pulled up to the same voltage as the feedback voltage FB. Therefore, since the output voltage VS (and thus the feedback voltage FB) starts to rise gently following the soft start voltage SS immediately after the start of the antenna drive device 10, the start delay of the switching power supply circuit 200 can be eliminated. It becomes possible.

<Other variations>
In the above embodiment, the antenna driving device used in the smart entry system of the vehicle has been described as an example. However, the scope of application of the present invention is not limited to this, and is used for other purposes. The present invention can be widely applied to antenna driving devices.

  For example, when the present invention is applied to an antenna drive device used in a tire pressure monitoring system for a vehicle, the transmission antenna described above is provided not on the door or cabin of the vehicle but on the tire or wheel.

  Various technical features disclosed in the present specification can be variously modified within the scope of the technical creation in addition to the above-described embodiment. For example, mutual replacement of a bipolar transistor and a MOS field effect transistor and logic level inversion of various signals are arbitrary. That is, the above-described embodiment is an example in all respects and should not be considered as limiting, and the technical scope of the present invention is not the description of the above-described embodiment, but the claims. It should be understood that all modifications that come within the meaning and range of equivalents of the claims are included.

  The antenna driving device according to the present invention can be used for a tire pressure monitoring system, a non-contact type automatic ticket gate system, and the like in addition to a smart entry system.

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Antenna drive device 20 Transmission antenna part 21-26 Transmission antenna 30 Microcomputer 40 Battery 100 Antenna drive circuit 110 Digital / analog conversion part 120-1-120-6 Antenna drive part 121 Linear amplifier 122, 123 Gate driver 124 P channel Type MOS field effect transistor 125 N channel type MOS field effect transistor 130 jamming driving unit 200 switching power supply circuit 201 N channel type MOS field effect transistor 202 gate driver 203 comparator 204 slope signal generation unit 205 error amplifier 206 reference voltage generation unit 207 digital / Analog conversion unit 208 Selector 209 Multiplexer 210 Sample / hold unit 211 Comparator 212 Charge / discharge control unit 13, 214 Analog switch 215 Buffer 216, 217 Resistance 218 P-channel MOS field effect transistor 300 Logic circuit a1-a6 Radio wave reach L1, L21-L26 Coils C1-C3, C21-C26 Capacitors R1, Ra1-Ra6, Rb1- Rb6, Rs1 to Rs6 Resistor D1 Diode T1 to T4, T5 (1) to (6) External terminal

Claims (12)

A plurality of antenna drive units each including a linear amplifier for driving a transmission antenna with a sine wave and a driver for driving the transmission antenna with a rectangular wave;
It includes a common output unit that outputs a common operation signal to each of the linear amplifiers and a plurality of individual output units that output individual operation signals to the respective drivers, and operates only one of the linear amplifier and the driver. A logic circuit for controlling each of the plurality of antenna driving units,
An antenna driving device comprising: The antenna driving unit further includes an upper switch and a lower switch respectively connected between an output terminal to which the transmission antenna is connected and a first voltage terminal and a second voltage terminal,
Each of the linear amplifiers drives the upper switch and the lower switch according to a common sine wave signal output from the common output unit of the logic circuit, and each of the drivers is connected to the logic circuit. The antenna driving apparatus according to claim 1, wherein the upper switch and the lower switch are each driven according to an individual rectangular wave signal output from the individual output unit.   3. The antenna driving apparatus according to claim 2, further comprising a digital / analog conversion unit that converts common digital sine wave data input from the common output unit into the analog sine wave signal.   The antenna driving apparatus according to claim 3, wherein the digital / analog conversion unit is provided in common for the plurality of transmission antennas.   The antenna driving apparatus according to claim 4, wherein the logic circuit controls the plurality of antenna driving units so that the plurality of transmission antennas are simultaneously driven or time-division driven.   6. The logic circuit according to claim 1, further comprising: a first input terminal to which a first transmission data signal is input; and a second input terminal to which a second transmission data signal is input. The antenna drive device as described in any one of Claims.   The antenna driving apparatus according to claim 6, wherein the logic circuit outputs a rectangular wave signal to the plurality of antenna driving units based on the first transmission data signal and the second transmission data signal. The logic circuit sends an intentional noise signal to a transmission antenna in a non-transmission state different from a transmission antenna in a transmission state driven by a rectangular wave based on an operation signal output from one of the individual output units. 8. The antenna driving apparatus according to claim 1, wherein the non- transmission transmitting antenna is driven by jamming by outputting from another one of the output units. The logic circuit is
The antenna driving apparatus according to any one of claims 1 to 8, wherein the individual operation signals are simultaneously output from the plurality of individual output units. The antenna driving device according to any one of claims 1 to 9,
A transmitting antenna driven by the antenna driving device;
A microcomputer for controlling the antenna driving device;
A battery for supplying power to the antenna driving device;
The vehicle characterized by having.   The vehicle according to claim 10, wherein the transmission antenna is provided in a door and a cabin as a component of a smart entry system.   The vehicle according to claim 10, wherein the transmission antenna is provided on a tire or a wheel as a component of a tire pressure monitoring system.

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