JP2013241080A - Vehicular power control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicular power control device capable of efficiently supplying stable D.C. power from a battery to a load circuit even at battery voltage drop.SOLUTION: A first diode 50 is connected to be set in a forward direction from a voltage input part M to the gate G of a P-channel FET element 10; a capacitor 60 is connected between the cathode and the gate G of the first diode 50; a switch means 20 connects the gate G to a ground GND to charge the capacitor 60 based on input of an operation signal; an impedance adjustment means 40 adjusts impedance of a path between the gate G and the ground GND connected by the switch means 20 to set the impedance in charging the capacitor 60 lower than that when the voltage V1 of a power source 200 drops by the beginning of the start of an engine 700.

Description

  The present invention supplies a DC power from a DC power source to a load circuit by turning on an FET (field effect transistor) mounted on the vehicle such as an automobile and disposed between the DC power source and the load circuit. The present invention relates to a vehicle power supply control circuit.

  A conventional vehicle power supply control circuit is disclosed, for example, in Patent Document 1, in which a P-channel FET element is inserted in series with a battery line, and a gate-source voltage is set to a predetermined gate threshold value during standby. The supply of DC power from the DC power supply to the load circuit is cut off by setting the voltage to be equal to or lower than the voltage, and during normal operation, by increasing the gate-source voltage of the P-channel FET above the gate threshold voltage, The P-channel FET is turned on, the drain-source on-resistance is lowered, and DC power is supplied from the DC power source to the load circuit with low loss.

JP 2001-341595 A

  However, due to a decrease in battery voltage when starting the vehicle engine, the gate-source voltage of the FET is lowered, the on-resistance of the FET is increased, and sufficient drain current cannot be supplied, so it is connected to the drain. This may cause a problem that the load circuit to be operated cannot be operated.

  Accordingly, the present invention has been made in light of the above-described problems, and provides a vehicle power supply control circuit that can efficiently supply stable DC power from a battery to a load circuit even when the battery voltage drops. .

Therefore, the present invention employs the following means in order to solve the above problems.
That is, the present invention includes a voltage input unit that inputs a voltage from a power source that supplies power to an engine starting unit that starts an engine of a vehicle, a voltage output unit that outputs a voltage to a load circuit of the vehicle, and the voltage input unit and the voltage A P-channel FET element connected between the output part, a signal input part for inputting a predetermined operation signal of the vehicle, and a first input connected from the voltage input part to the gate of the P-channel FET element in the forward direction. One diode, a capacitor connected between the cathode and gate of the first diode, switch means for controlling connection or disconnection between the gate and ground, and between the gate and ground connected by the switch means The impedance between the gate connected by the switch means and the ground when charging the capacitor is adjusted by the start of engine start. And an impedance adjusting means for lowering the impedance between the gate connected by the switch means and the ground when the voltage of the power supply is lowered, and being discharged from the capacitor when the power supply voltage is lowered by starting the engine after the capacitor is charged. The gist of the invention is to maintain the on state of the P-channel FET element even if the source voltage of the P-channel FET element is lowered by starting the engine by making the gate voltage lower than the ground voltage by electrons.

  In order to solve the above-described problems, the first invention is a voltage input for inputting a voltage from a power source 200 that is mounted on a vehicle having an engine 700 and supplies power to an engine starter 500 that starts the engine 700. Unit M, a voltage output unit N that outputs a voltage to the load circuit 300 of the vehicle, a P-channel FET element 10 connected between the voltage input unit M and the voltage output unit N, and a predetermined operation signal from the vehicle An operation signal input unit (12) for inputting a voltage, a first diode 50 connected in a forward direction from the voltage input unit M to the gate G of the P-channel FET element 10, and a cathode and a gate G of the first diode 50 And the switch 60 for charging the capacitor 60 by connecting the gate G and the ground GND based on the input of the operation signal. The impedance of the path between the gate G connected by the means 20 and the ground GND is adjusted, and the impedance when the capacitor 60 is charged is determined from the impedance when the voltage V1 of the power source 200 is reduced by starting the engine 700. With this configuration, the gate voltage of the P-channel FET element is maintained at a negative voltage lower than the ground voltage for a certain period of time by the electrons charged in the capacitor 60. Even if the voltage of the power supply (source voltage of the P-channel FET element) is reduced by starting, stable DC power can be efficiently supplied from the power supply to the load circuit.

  Moreover, 2nd invention is equipped with the 1st impedance circuit (41) which has a 1st impedance, and the 2nd impedance circuit (42) which has a 2nd impedance higher than a 1st impedance, the impedance adjustment means 40, The impedance is adjusted by switching the path of the gate current flowing from the gate G to the ground GND between the first impedance circuit (41) and the second impedance circuit (42).

  The third invention includes a second diode 23 connected in the reverse direction from the first impedance circuit (41) to the gate G.

  In the fourth aspect of the invention, the engine starter 500 includes the timing adjusting means 70 for delaying the timing for starting the engine 700 with respect to the timing when the operation signal is input. Since the capacitor can be charged with a high power supply voltage before dropping by starting the operation, the gate voltage of the P-channel FET element is set to a negative voltage lower than the ground voltage for a longer time after starting the engine. Can keep.

  In the fifth invention, each of the first impedance circuit and the second impedance circuit includes at least one resistor (41, 42).

  In the sixth aspect of the invention, the first impedance circuit and the second impedance circuit have a common resistor in the overlapping path, and the path through which the gate current flows is overlapped at least at one place.

  In the seventh invention, the switch means 20 is provided in each of the first impedance circuit and the second impedance circuit.

  Provided is a vehicle power supply control circuit capable of efficiently supplying stable DC power from a battery to a load circuit even when the battery voltage drops.

It is an electrical block diagram of the vehicle power supply control circuit which is embodiment of this invention. It is an electrical block diagram of the 1st modification of the vehicle power supply control circuit which is embodiment of this invention. It is an electrical block diagram of the 2nd modification of the power supply control circuit for vehicles which is embodiment of this invention. It is an operation | movement flowchart of the vehicle power supply control circuit of the said invention.

  The vehicle power supply control circuit 100 is connected between a battery (power supply) 200 mounted on the vehicle and a load circuit 300 such as an audio device or a vehicle display device mounted on the vehicle. The power supply from 200 to the load circuit 300 is on / off controlled.

  The battery 200 supplies electric power to the cell motor 600 that starts the engine 700 of the vehicle and the vehicle power supply control circuit 100 when the operator turns on an ignition switch (hereinafter, IGN switch) 400 of the vehicle. is there.

  Embodiments of a vehicle power supply control circuit 100 according to the present invention will be described below with reference to the drawings. First, FIG. 1 is an electrical configuration diagram of an embodiment of a vehicle power supply control circuit 100 of the present invention.

  The vehicle power supply control circuit 100 is connected between the battery 200 and the load circuit 300, electrically connects the source S to the voltage input unit M that inputs the first voltage V <b> 1 from the battery 200, and connects to the load circuit 300. A drain D is electrically connected to a voltage output section N that outputs the second voltage V2, and a gate G is electrically connected to a switch means 20 described later, and a gate G of the P channel FET element 10 Switch means 20 connected between the gate and GND (ground) and operating the connection between the gate G and GND, the control means 30 driven by the first voltage V1 to control the on / off of the switch means 11, and the switch An impedance adjusting means 40 for adjusting the impedance between the gate G and the GND connected by the means 20; a voltage input unit M and a P-channel FET element; A first diode 50 connected in a forward direction from the 10 sources S to the gate G of the P-channel FET element 10, and a capacitor 60 connected between the first diode 50 and the gate G of the P-channel FET element 10. , And a timing adjustment means 70 for adjusting the start timing of the start of the cell motor 600 via the engine start section 500 in response to the ON operation of the IGN switch 400, and the first voltage V 1 from the battery 200 is supplied from the voltage input section M. The second voltage V2 corresponding to the first voltage V1 is output from the voltage output unit N to the load circuit 300, and the first voltage is supplied from the voltage input unit M to the source S of the P-channel FET element 10. V1 is applied, the gate voltage Vg is applied to the gate G by the switch means 20, and the first voltage V1 applied to the source S and the gate By making the gate-source voltage Vgs, which is the difference from the gate voltage Vg applied to, larger than a predetermined threshold voltage, the P-channel FET element 10 is turned on, current flows from the source S to the drain D, and the gate -By making the source-to-source voltage Vgs smaller than a predetermined threshold voltage, the P-channel FET element 10 is turned off and the current is cut off from the source S to the drain D. The power supply from the power source 200 to the load circuit 300 is connected / disconnected by the on / off control.

  In the P-channel FET element 10, the voltage input unit M and the anode of the first diode 50 are electrically connected to the source S, the voltage output unit N is electrically connected to the drain D, and the timing adjustment unit 70 is connected to the gate G. And the switch means 20 via the impedance adjusting means 40 are electrically connected, and the gate voltage Vg applied to the gate G is lowered by a predetermined threshold voltage from the first voltage V1 applied to the source S, thereby turning on. When the P-channel FET element 10 is turned on, the second voltage V2 based on the first voltage V1 is applied to the voltage output unit N connected to the drain D. The switching means 11 is connected to the gate G via the impedance adjusting means 40. When the switching means 11 is turned on, the gate G is connected to the GND, and the voltage of the source S (the voltage of the battery 200). Based on the potential difference between the one voltage V1) and the gate voltage Vg (GND), the P-channel FET element 10 is turned on.

  The switch means 20 is connected between the gate G and GND of the P-channel FET element 10 and connects or disconnects the gate G and GND based on a signal from the control means 30 described later. The impedance between the gate G connected to the ground GND is adjusted by the impedance adjusting means 40 described later, the first transistor 21 connected in series to the first resistor 41 described later, and the second transistor described later. The second transistor 22 connected in series with the resistor 42, the second diode 23 connected in the forward direction from the first resistor 41 to the collector of the first transistor 21, and the forward from the emitter of the second transistor 22 to the collector. And a third diode 24 connected in parallel in the direction.

  When the operation of the IGN switch 400 is input, the first transistor 21 is turned on by the control means 30, connecting the gate G and GND of the P-channel FET element 10 and turning on the P-channel FET element 10. The capacitor 60 is charged. The capacitor 60 is charged by turning on the first transistor 21 and generating a potential difference due to the first voltage V1 and GND at both ends of the capacitor 60, accumulating holes on the first diode 50 side of the capacitor 60, Electrons supplied from GND are accumulated on the gate G side of the capacitor 60. Since the first transistor 21 is connected to the first resistor 41 having a low resistance value, the capacitor 60 can be charged at a high speed. The first transistor 21 is turned off by the control means 30 when the capacitor 60 is fully charged. It is desirable that the first transistor 21 is turned off immediately after the operation of the IGN switch 400 is input, and when the capacitor 60 is charged, the first transistor 21 is immediately turned off in order to reduce power consumption.

  The second transistor 22 is turned on by at least the control means 30 until a timing adjusting means 70 (to be described later) starts the engine 700 via the engine starting unit 500, and the second transistor 22 is turned on by the gate G and the GND of the P-channel FET element 10. To turn on the P-channel FET element 10. The second transistor 22 is kept on until it is instructed to shut off the power supply from the battery 200 to the load circuit 300 by turning off the IGN switch 400 after being turned on. When the timing adjusting unit 70 starts the engine 700 via the engine starting unit 500, electric power is supplied from the battery 200 to the engine starting unit 500, and the first voltage V1 that is a voltage applied from the battery 200 decreases. When the voltage applied to the capacitor 60 decreases, electrons on the gate G side of the capacitor 60 are emitted, and the gate G becomes a negative voltage lower than GND. Since the gate G becomes a negative voltage in this way, even if the first voltage V1 decreases due to the start of the engine 700, the gate-source potential necessary for turning on the P-channel FET element 10 is sufficiently high. The on-resistance between the drain and source of the P-channel FET element 10 can be kept low, and stable power can be efficiently supplied to the load circuit 300. In addition, since the second resistor 42 having a high resistance value is connected to the second transistor 22, the discharge on the gate G side of the capacitor 60 can be delayed, and the engine 700 is started after starting the engine 700. The gate voltage Vg can be maintained at a negative voltage until the start of the operation is completed, and even if the first voltage V1 is lowered, the P-channel FET element 10 is turned on, and stable power is efficiently supplied to the load circuit 300. Can continue to be supplied.

  The second diode 23 is a rectifier diode connected in series from the first resistor 41 to the first transistor 21 so as to be in the forward direction. When a negative voltage is applied to the gate G as described above, This prevents a reverse current such as a drift current from flowing through the transistor 21.

  The third diode 24 is a commutation diode connected in parallel from the collector of the second transistor 22 in the direction opposite to the emitter direction. When a negative voltage is applied to the gate G as described above, the second transistor 22 is excessively large. This prevents the reverse bias and destruction. When the resistance value of the second resistor 42 connected in series to the second transistor 22 is sufficiently large and the reverse current of the second transistor 22 is not so large, an excessive reverse bias is applied to the second transistor 22. This third diode 24 may be omitted because it is not present.

The control unit 30 includes an I / F circuit (operation signal input unit) that inputs an operation of a microcomputer or an IGN switch 400 including a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores programs executed by the CPU, and the like. ), And is driven by the first voltage V1, and can be driven even if the P-channel FET element 10 is turned on and the second voltage V2 is not generated. Based on the input and the operation of the IGN switch 400, the switch means 20 is on / off controlled. Further, it may be configured by a CAN transceiver, an A / D converter circuit, or a D / A converter circuit that inputs an operation of the IGN switch 400 without using a microcomputer or the like and outputs a signal to the switch means 20. Regarding the input of the operation information of the IGN switch 400, the operation of the IGN switch 400 may be detected by inputting an operation signal of the IGN switch 400 from an ECU (not shown) on the vehicle side, and supplied from the battery 200. The operation of the IGN switch 400 may be detected by detecting the voltage of the first voltage V1.
Further, the control means 30 not only turns on the switch means 20 based on the operation signal input from the IGN switch 400 as described above, but also, for example, an ACC on signal of an accessory switch (ACC) or a vehicle door. Various vehicle operation signals such as a door signal by opening or a door unlocking signal by keyless are inputted as operation signals using in-vehicle communication such as CAN communication, and the switch means 20 is turned on based on these operation signals. Also good.

The impedance adjusting means 40 adjusts the impedance between the gate G and GND when the switch means 20 is turned on, and includes a first resistor 41 connected in series to the first transistor 21, a second resistor A second resistor 42 connected in series to the transistor 22 and having a higher resistance value than the first resistor. With such a configuration, the control unit 30 can adjust the impedance between the gate G and GND by switching the first transistor 21 or the second transistor 22 on. For example, only the second transistor 22 is turned on. Thus, the impedance between the gate G and GND can be increased, and the impedance between the gate G and GND can be decreased by turning on only the first transistor 21, and the first transistor 21 and By turning on both of the second transistors 22, the impedance between the gate G and GND can be further reduced. In the present embodiment, the path through which the first transistor 21 is turned on and the gate current passes through the first resistor 42 is called a first impedance circuit having a high impedance, and the second transistor 22 is turned on. A path through which the gate current passes through the second resistor 42 is referred to as a second impedance circuit having a low impedance.
In addition, as shown in FIG. 1, resistors having different resistance values such as the first resistor 41 and the second resistor 42 are provided, and the impedance is not switched by switching the current flow path, as shown in FIG. 2. In addition, an impedance adjustment unit 40a may be provided in series with the switch unit 20, and the impedance may be adjusted according to an instruction from the control unit 30 (first modification).
In addition, as shown in FIG. 3, a common resistor 41b may be provided in a route where the first impedance circuit and the second impedance circuit overlap (second modification).

  The first diode 50 is a rectifier diode that is connected in the forward direction from the voltage input unit M and the source S of the P-channel FET element 10 to the gate G of the P-channel FET element 10. Even if the first voltage V1 decreases after charging, current does not flow in the direction of the voltage input M or the source S of the P-channel FET element 10, and the holes of the capacitor 60 are held for a certain period of time. The electrons of the gate G can also be held for a certain period of time, and the first diode 50 holds the electrons on the gate G side of the capacitor 60 and the electrons on the gate G side of the capacitor 60 due to the high impedance in the second impedance circuit. The discharge can be delayed, and the engine 700 is started after the engine 700 is started. In the meantime, the gate voltage Vg becomes a negative voltage even if the first voltage V1 decreases, and the source-gate voltage Vgs is sufficiently secured, so that the P-channel FET element 10 is reliably turned on, and the load It is possible to continue supplying stable power to the circuit 300 efficiently.

  The capacitor 60 is an electric double-layer capacitor or the like. When the IGN switch 400 is turned on, the first transistor 21 is turned on, so that the first resistor 41 having a low resistance value passes through the first resistor 41. When charging is completed at a high speed (via the first impedance circuit) and the charging is completed, the timing adjusting means 70 described later starts the engine 700 via the engine starting unit 500 and turns on the first transistor 21. The second transistor 22 is turned on by turning it off. By starting the engine 700, the first voltage V1 rapidly decreases and the capacitor 60 starts discharging. The first diode 60 has a rectified current and a gate through the second resistor 42 having a large resistance value. Since the capacitor 60 is slowly discharged by the current, the gate voltage Vg becomes a negative voltage lower than GND by the electrons charged in the capacitor 60, and this state is maintained for a certain period. Since the gate voltage Vg becomes a negative voltage even if the first voltage V1 decreases until the start of the engine 700 is completed, the source-gate voltage Vgs is sufficiently secured. Thus, it is possible to continuously supply stable power to the load circuit 300.

  The timing adjustment unit 70 outputs an engine start signal for starting the engine 700 to the engine start unit 500 at a timing when the charging of the capacitor 60 is completed. With such a configuration, it is possible to start the engine 700 after charging the capacitor 60 with electrons sufficient to hold the gate voltage G at a negative voltage for a certain period of time, and the voltage of the battery 200 decreases as the engine 700 starts. Even in this case, the gate voltage Vg is held at a negative voltage for a certain period of time by the electrons charged in the capacitor 60. Therefore, even if the first voltage V1 decreases due to the start of the engine 700, the P channel FET element 10 is maintained for a certain period of time. The source-gate voltage Vgs is sufficiently larger than the threshold voltage, and even if the first voltage V1 decreases from the start of the engine 700 to the completion of the start of the engine 700, the P-channel FET element 10 Can be reliably turned on, and stable power can be efficiently supplied to the load circuit 300.

  The above is the configuration of the vehicle power supply control device 100 of the present invention. The operation flow of the vehicle power supply control circuit 100 of the present invention will be described with reference to FIG. FIG. 4 is an operation flowchart in the embodiment of the vehicle power supply control circuit 100 of the present invention.

  In step H1, the control means 30 detects the on operation of the IGN switch 400, and when detecting the on operation of the IGN switch 400, in step H2, the control means 30 turns on the first transistor (first impedance circuit) 21; The gate G of the P-channel FET element 10 is connected to GND, so that the P-channel FET element 10 is turned on (Step H3a), and the capacitor 60 is charged (Step H3b), and the capacitor 60 is completely charged. Then, in step H4, the control means 30 turns on the second transistor (second impedance circuit) (step H5a), turns off the first transistor (first impedance circuit) (step H5b), In step H5c, the timing adjusting means 70 An engine start signal is output to the engine start unit 500 to start the engine, and the second transistor 21 is turned on in step H5a, so that in step H6, the P-channel FET element 10 causes the second transistor 21 in step H3a to The on state by the one transistor 21 shifts to the on state by the second transistor 22 as it is. As described above, by turning on the first transistor 21 after the operation of the IGN switch 400 is input, a gate current flows through a low impedance path, the P-channel FET 10 is turned on, and the capacitor 60 is rapidly turned on. After the capacitor 60 is charged, the second transistor 22 is turned on and the first transistor 21 is turned off, so that the gate current has a high impedance path through the second transistor 22 (second impedance circuit). ), The gate voltage Vg is maintained at a negative voltage state from GND for a predetermined time by the electrons charged in the capacitor 60, and during that time, the engine starts and the first voltage V1 applied to the source decreases. Also, the source-gate voltage Vgs of the P-channel FET element 10 is the threshold voltage. The P-channel FET element 10 is reliably turned on from the start of the engine 700 until the start is completed, and stable power is efficiently supplied to the load circuit 300. Can continue.

100 Vehicle power supply control circuit 200 Battery (power supply)
300 Load circuit 400 IGN switch 500 Cell motor (engine starter)
600 engine

DESCRIPTION OF SYMBOLS 10 P channel FET element 20 Switch means 21 1st transistor 22 2nd transistor 23 2nd diode 24 3rd diode 30 Control means 40 Impedance adjustment means 41 1st resistor (1st impedance circuit)
42 Second resistor (second impedance circuit)
50 First diode 60 Capacitor 70 Timing adjustment means

Claims (7)

Mounted in a vehicle with an engine,
A voltage input unit that inputs a voltage from a power source that supplies electric power to an engine starting unit that starts the engine;
A voltage output unit for outputting a voltage to the load circuit of the vehicle;
A P-channel FET element connected between the voltage input unit and the voltage output unit;
An operation signal input unit for inputting a predetermined operation signal from the vehicle;
A first diode connected in a forward direction from the voltage input to the gate of the P-channel FET element;
A capacitor connected between the cathode and the gate of the first diode;
Based on the input of the operation signal, switch means for connecting the gate and ground and charging the capacitor;
The impedance of the path between the gate connected by the switch means and the ground is adjusted, and the impedance when charging the capacitor is more than the impedance when the voltage of the power supply is reduced by starting the engine. A vehicle power supply control circuit, comprising: an impedance adjusting means for lowering.   The impedance adjusting means includes a first impedance circuit having a first impedance and a second impedance circuit having a second impedance higher than the first impedance, and a path of a gate current flowing from the gate to the ground is the first impedance circuit. The vehicle power supply control circuit according to claim 1, wherein the impedance is adjusted by switching between the one impedance circuit and the second impedance circuit.   The vehicle power supply control circuit according to claim 2, further comprising a second diode connected in a reverse direction from the first impedance circuit to the gate.   4. The vehicle power source according to claim 1, further comprising a timing adjusting unit that delays a timing at which the engine start unit starts the engine with respect to a timing at which the operation signal is input. Control circuit.   5. The vehicle power supply control circuit according to claim 2, wherein each of the first impedance circuit and the second impedance circuit includes at least one resistor.   6. The vehicle according to claim 5, wherein the first impedance circuit and the second impedance circuit have a path through which the gate current flows in at least one place, and a common resistor is provided in the overlapped path. Power supply control circuit. The vehicle power supply control circuit according to any one of claims 2 to 6, wherein the switch means is provided in each of the first impedance circuit and the second impedance circuit.

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