JP2003324939A - Starter circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a starter circuit which limits a drive current flowing through a coil when an output voltage abruptly rises without using an outside attaching time constant setting capacitor and which can arbitrarily set a starting speed. <P>SOLUTION: The set voltage of a variable reference voltage generating means 27 connected to a digital-analog converter 26, the stepwise rising waveform set by a pulse converter/counter 25, and the reference wave of a reference wave oscillator 14, are compared by a pulse width modulator circuit 13, the on-duty of the output pulse is gradually increased, and the output voltage of an output terminal 3 is risen so as to be raised in response to the increase in the pulse width. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a starter circuit of a constant voltage output circuit device used for mobile phones, personal digital assistants, and the like.

[0002]

2. Description of the Related Art FIG. 3 shows the configuration of a DC-DC converter (buck converter) which is an example of a conventional constant voltage circuit device. In this circuit, a P-channel MOS transistor 9 (hereinafter Pch-MOS) is connected between the coil drive terminal 8 of the LSI and the power supply terminal 1, and an N-channel MOS transistor 10 (hereinafter Nch-) is connected between the coil drive terminal 8 and the ground terminal 11. M
OS) and the Schottky diode 7, and the coil 2 is connected between the output terminal 3 and the Schottky diode 7. An output capacitance 4, a negative feedback resistance 5 and a negative feedback resistance 6 are connected between the output terminal 3 and a ground terminal 11, and the resistance division value of the output voltage by the negative feedback resistance 5 and the negative feedback resistance 6 is the error amplifier 15 to the inverting input terminal via a negative feedback connection terminal 20 is a negative feedback input, with the reference voltage 21. The error amplifier 15 forms an integrator with the capacitor 18 and the resistor 19, and the output voltage thereof is input to the inverting amplification terminal 17 of the pulse width modulation circuit 13. The inverting amplification terminal 16 of the pulse width modulation circuit 13 has a constant current source 22 composed of the power supply terminal 1 and a capacitance connection terminal 23.
Is connected to the capacitance connection terminal 23 and the time constant setting capacitance 24
Are connected. Further, the reference oscillator 14 is connected to the non-inverting amplification terminal of the pulse width modulation circuit 13, and the output voltage of the pulse width modulation circuit 13 is output to the gate terminals of the Pch-MOS and the Nch-MOS by the output MOS transistor drive circuit 12, respectively. Is entered.

Next, the operation when this circuit is started at an arbitrary time A will be described with reference to FIG. At the same time when the circuit is started up, the voltage of the capacitance connection terminal 23 first linearly rises from the voltage of the ground terminal 11 to an arbitrary set voltage by the time constant setting capacitance 24. The voltage of the capacitance connection terminal 23 is V1 = I1 × t / C (where V1 is the voltage of the capacitance connection terminal 23, I1 is the current value of the constant current circuit 22, t is an arbitrary time, and C is the capacitance connection terminal 23). Is expressed by the conductance of the time constant setting capacitance 24 connected to. Here, the time until the voltage of the capacitance connection terminal 23 reaches the minimum voltage value of the triangular wave oscillator 14 serving as a reference is set to T1. Error amplifier 1
In the output voltage of 5, the resistance division value of the negative feedback resistor 5 and the negative feedback resistor 6 of the voltage of the output terminal 3 is lower than the reference voltage 21, so from time B, the output voltage of the triangular wave oscillator 14 and the capacitance connection terminal The voltage is compared with the voltage of 23 and the pulse is output by the pulse width modulation circuit 13. The pulse width modulation circuit 13
With respect to the output pulse width of, the on-duty (pulse on-time) gradually increases depending on the rising rate of the voltage of the capacitance connection terminal 23. The generated pulse is controlled by the output MOS transistor drive circuit 12 so that it is not turned on at the same time by the P-MO.
The coil 2 is driven by controlling ON / OFF of S9 and the N-MOS 10. The coil drive terminal 8 is supplied with the voltage of the ground terminal 11 or the power supply voltage 1, but the on-duty of the output pulse of the pulse width modulation circuit 13 is gradually increased, so that the time for supplying the power supply voltage 1 is gradually increased.
The drive current of the coil 2 is I2 = (Vin−Vout) × t
On / L (where I2 is the coil drive current, Vin is the power supply voltage 1, Vout is the voltage of the output terminal 3, ton is the pulse on-duty, L is the coil inductance), and the drive current gradually increases. Therefore, the voltage of the output terminal 3 also gradually starts to rise. When the resistance division value of the voltage of the output terminal 3 by the negative feedback resistance 5 and the negative feedback resistance 6 becomes substantially equal to the reference voltage 21 (= time C), the output voltage of the error amplifier 15 starts to drop and time D ( Between the time when the output voltage of the error amplifier 15 is equal to the maximum voltage of the output voltage of the triangular wave oscillator 14) to the time E (time when the output voltage of the error amplifier 15 is less than or equal to the minimum voltage of the output voltage of the triangular wave oscillator 14) The voltage of the connection terminal 23 and the potential of the error amplifier 15 are reversed. Here, from time B (time when the voltage of the capacitor connection terminal 23 becomes equal to the minimum voltage value of the output voltage of the triangular wave oscillator 14) to time C (resistance division value of the voltage of the output terminal 3 by the negative feedback resistor 5 and the negative feedback resistor 6). T2 is the time until the voltage becomes substantially equal to the reference voltage 21. After the voltage of the capacitance connection terminal 23 and the output voltage of the error amplifier 15 are reversed, the output voltage of the error amplifier 15 and the output voltage of the triangular wave oscillator 14 are compared and the pulse width modulation circuit 13 generates a pulse.
In the steady state stable state F, the output terminal 3 is set to an arbitrary voltage set by the negative feedback resistor 5, the negative feedback resistor 6 and the reference voltage 21.
The voltage stabilizes. Here, T3 is from time C to time F.

As described above, the starter circuit gradually increases the on-duty of the pulse by the conductance of the time constant setting capacitance 24 connected to the capacitance connection terminal 23 and the time constant set by the current value of the constant current source 22. The circuit configuration is such that the output voltage suddenly rises and the drive current flowing through the coil 2 is limited.

[0005]

For mobile phones and personal digital assistants, it is indispensable to extract the cost merit by reducing the weight of the set and reducing the number of parts. In a DC-DC converter (or AC-DC converter) that converts a DC power supply (or AC power supply) to a DC voltage, integration (LS
Reduction of the number of parts and integrated circuit (LS)
I) Reduction of pins is an issue. Further, increasing the output voltage while limiting the abrupt increase in the output voltage and the drive current flowing through the coil is an essential function in terms of safety and reliability. Further, when the conventional time constant setting capacitance 24 is used, T1 time (the capacitance connecting terminal 23 is the ground terminal 1
The time from the voltage of 1 to the minimum voltage value of the output voltage of the triangular wave oscillator 14 serving as the reference) is a waste of the startup time irrelevant to the startup of the operation.

If the external time constant setting capacitance is not used, the number of integrated circuit (LSI) pins can be reduced and the number of parts can be reduced.

The present invention solves the above-mentioned conventional problems, and realizes the original function of limiting abrupt increase of output voltage and drive current flowing in a coil and without using an external time constant setting capacity. In addition, an object of the present invention is to provide a starter circuit that realizes an operation of arbitrarily setting the rising speed.

[0008]

A starter circuit according to claim 1 is a DC-DC converter (or AC-DC converter) for converting a DC power supply or an AC power supply into a DC voltage, and the output voltage rapidly rises. And a reference oscillator for limiting and suppressing the inrush current from the DC power supply or the AC power supply, and means for generating an output voltage that gradually increases,
A starter that has a pulse width modulation circuit that compares the output voltage with respect to the signal of the reference oscillator and outputs a pulse whose pulse width gradually increases, and starts a gradually increasing output voltage based on the pulse. A circuit,
The means is configured by a digital / analog converter that converts a digital signal into an analog signal and the output voltage rises stepwise, and the pulse width modulation circuit is the digital / analog converter with respect to the signal of the reference oscillator. It is characterized in that a pulse whose pulse width is increased stepwise is output by comparing the output voltages of.

According to the starter circuit of the first aspect, instead of the conventional constant current source and the linear rising voltage set by the time constant setting capacity, for example, a digital / analog converter having a pulse counter and a variable reference voltage is used. A stepwise rising voltage created by arbitrarily setting the divided value of the output voltage, the minimum voltage, the maximum voltage and the output voltage rising change time is used. By comparing the output voltage of the triangular wave oscillator and the stepwise rising voltage, the on-duty of the pulse output of the pulse width modulation circuit is increased stepwise.

As a result, a DC power supply (or AC power supply) can be used without using the externally set time constant setting capacity that has been conventionally required.
In a DC-DC converter (or an AC-DC converter) that converts a DC voltage into a DC voltage, a sudden increase in output voltage and a drive current flowing through a coil can be limited.

According to a second aspect of the present invention, there is provided a starter circuit according to the first aspect.
In the digital / analog converter, a variable reference voltage generating means for increasing its output voltage stepwise,
A pulse counter for outputting a digital signal to the digital / analog converter is provided.

According to the starter circuit of the second aspect, in addition to the same effect as the first aspect, the set voltage, the set time, and the resolution can be arbitrarily set, and the rising speed can be arbitrarily set. That is, since the digital / analog converter has a variable reference voltage, an arbitrary output voltage / resolution can be generated, and the output voltage rise time of the digital / analog converter can be arbitrarily set by the pulse counter.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION One embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a starter circuit according to an embodiment of the present invention, which raises the output voltage while limiting the driving current flowing through the coil and the sudden rise of the output voltage without using the conventionally required external time constant setting capacity. Then, FIG. 2 shows operation waveforms at the time of circuit startup in the embodiment of the present invention. L in the circuit of FIG.
A P-channel MOS transistor 9 (hereinafter Pch-MOS) is connected between the SI coil drive terminal 8 and the power supply terminal 1, and an N-channel MOS transistor 10 (hereinafter Nch-MOS) is connected between the SI terminal and the ground terminal 11. The Schottky diode 7 is connected, and the coil 2 is connected between the Schottky diode 7 and the output terminal 3. An output capacitance 4, a negative feedback resistor 5 and a negative feedback resistor 6 are connected between the output terminal 3 and a ground terminal 11, and the resistance division value of the output voltage by the negative feedback resistor 5 and the negative feedback resistor 6 is the inversion of the error amplifier 15. Negative feedback connection is made to the input terminal via the negative feedback connection terminal 20, and the voltage is compared with the reference voltage 21. The error amplifier 15 comprises an integrator with a capacitor 18 and a resistor 19,
The output voltage is the inverting amplification terminal 1 of the pulse width modulation circuit 13.
Connected to 7. At the inverting amplification terminal 16 of the pulse width modulation circuit 13, a pulse converter / counter 25 for counting the output voltage of the triangular wave oscillator 14 and a variable reference voltage generating means 27.
Is connected to the output of the digital / analog converter 26. Further, the reference oscillator 14 is connected to the non-inverting amplification terminal of the pulse width modulation circuit 13, and the output voltage of the pulse width modulation circuit 13 is P by the output MOS transistor drive circuit 12.
It is input to the gate terminals of the ch-MOS and the Nch-MOS, respectively.

Next, the operation when this circuit is started up at an arbitrary time A will be described with reference to FIG. At the same time when the circuit is started up, the output voltage of the digital / analog converter 26 is first set by the variable reference voltage generating means 27 to be equal to or lower than the minimum voltage of the output voltage of the triangular wave oscillator 14, and changed by the pulse converter / counter 25. The voltage starts to rise on the stairs depending on the time. The voltage of the digital / analog converter 26 is V2 = (Vmax−Vmin) × N / 2
ⁿ (here, V2 is the voltage of the digital / analog converter 26, Vmax is the maximum voltage of the variable reference voltage generating means 27,
Vmin is the minimum voltage of the variable reference voltage generating means 27, N is the number of pulse counts of the pulse converter / counter 25, n
Is represented by the number of bits of the digital / analog converter 26). Here, the time required for the voltage of the digital / analog converter 26 to reach the minimum voltage value of the triangular wave oscillator 14 serving as the reference is set to T1. As for the output voltage of the error amplifier 15, since the resistance division value of the negative feedback resistor 5 and the negative feedback resistor 6 of the voltage of the output terminal 3 is lower than the reference voltage 21, from the time B, the output voltage of the triangular wave oscillator 14 and the digital voltage / Analog converter 2
The pulse width modulation circuit 13 compares the voltage with the voltage of 6 and outputs a pulse. The on-duty (pulse on-time) of the output pulse width of the pulse-width output circuit 13 gradually increases depending on the rising rate of the voltage of the digital / analog converter 26. The generated pulse is controlled by the output MOS transistor drive circuit 12 so that it is not turned on at the same time by the P-MOS.
9 and N-MOS 10 are turned on / off to drive the coil 2. Although the voltage of the ground terminal 11 or the voltage of the power supply terminal 1 is applied to the coil drive terminal 8, the pulse width modulation circuit 1
As the on-duty of the output pulse of No. 3 gradually increases, the time during which the power supply voltage 1 is applied gradually increases. The drive current of the coil 2 is I2 = (Vin−Vout)
* Ton / L (where Vin is the voltage of power supply terminal 1, Vo
ut is represented by the voltage of the output terminal 3, ton is represented by the on-duty of the pulse, and L is the inductance of the coil. Since the drive current gradually increases, the voltage of the output terminal 3 also gradually increases. When the resistance division value of the voltage of the output terminal 3 by the negative feedback resistance 5 and the negative feedback resistance 6 becomes substantially equal to the reference voltage 21 (= time C), the output voltage of the error amplifier 15 starts to drop and time D ( Between the time when the output voltage of the error amplifier 15 is equal to the maximum voltage of the output voltage of the triangular wave oscillator 14) and the time E (time when the output voltage of the error amplifier 15 is less than or equal to the minimum voltage of the output voltage of the triangular wave oscillator 14) The voltage of the converter 26 and the potential of the error amplifier 15 are reversed. Here, from time B (time when the voltage of the digital / analog converter 26 becomes equal to the minimum voltage value of the output voltage of the triangular wave oscillator 14) to time C (resistance of the negative feedback resistor 5 and the negative feedback resistor 6 of the voltage of the output terminal 3). The time until the divided value becomes substantially equal to the reference voltage 21) is T2. After the voltage of the digital / analog converter 26 and the output voltage of the error amplifier 15 are reversed, the output voltage of the error amplifier 15 and the output voltage of the triangular wave oscillator 14 are compared and the pulse width modulation circuit 13 generates a pulse. In the steady state stable state F, the voltage of the output terminal 3 stabilizes at an arbitrary voltage set by the negative feedback resistor 5, the negative feedback resistor 6 and the reference voltage 21. Here, T3 is from time C to time F.

As described above, the digital / analog converter 2
The on-duty of the pulse is gradually increased by the set voltage of the variable reference voltage generating means 27 connected to the voltage of 6 and the stepwise rising waveform set by the pulse counter 25, and the output voltage is rapidly increased and the coil 2 is driven to flow. The voltage of the output terminal 3 is increased while limiting the current.

Here, the digital / analog converter 26, the pulse counter 25, and the variable reference voltage 27 are outside the integrated circuit, and the P-channel type MOS transistor 9 (which is connected between the coil drive terminal 8 and the power supply terminal 1) After that Pch-
Instead of the N-channel type MOS transistor 10 (hereinafter referred to as Nch-MOS) connected between the MOS) and the ground terminal 11, an NPN transistor / PNP transistor / P-channel type MOS transistor / N-channel type MOS transistor is arbitrarily combined. Similar effects can be obtained also in a DC-DC converter or an AC-DC converter having a circuit configuration.

[0017]

According to the starter circuit of the first aspect,
Sudden rise in output voltage in a DC-DC converter (or AC-DC converter) that converts from a DC power supply (or AC power supply) to a DC voltage without using the externally set time constant setting capacity that was conventionally required The drive current flowing in the coil can be limited.

According to the starter circuit of the second aspect, in addition to the same effect as the first aspect, the set voltage, the set time, and the resolution can be arbitrarily set, and the rising speed can be arbitrarily set.

[Brief description of drawings]

FIG. 1 is a starter circuit according to an embodiment of the present invention.

FIG. 2 is an operation waveform diagram at the time of starting the circuit in the embodiment of the present invention.

FIG. 3 is a starter circuit diagram using a conventional external time constant setting capacitance.

FIG. 4 is an operation waveform diagram at the time of starting a circuit using a conventional external capacitor.

[Explanation of symbols]

1 power supply terminal 2 coils 3 output terminals 4 output capacity 5 Output voltage negative feedback resistance 6 Output voltage negative feedback resistor 7 Schottky diode 8 coil drive terminals 9-output P-channel MOS transistor 10-output N-channel MOS transistor 11 Ground terminal 12 output MOS transistor drive circuit 13 Pulse width modulation circuit 14 Triangular wave oscillator 15 Error amplifier 16 Error amplifier inverting input terminal 17 Error amplifier inverting input terminal 18 Integral capacity 19 Integral resistance 20 Negative feedback connection terminal 21 Reference voltage 22 constant current circuit 23 Capacitance connection terminal 24 time constant setting capacity 25 pulse converter / counter 26 Digital / Analog Converter 27 Variable reference voltage generating means

Claims (2)

[Claims] 1. A DC-DC converter (or AC-DC converter) for converting a DC power supply or an AC power supply into a DC voltage.
In order to limit and suppress the sudden rise of the output voltage and the inrush current from the DC power supply or the AC power supply, a reference oscillator, a means for generating an gradually increasing output voltage, and a signal of the reference oscillator. A starter circuit that has a pulse width modulation circuit that outputs a pulse whose pulse width gradually increases by comparing the output voltages, and is a starter circuit that raises the gradually increasing output voltage based on the pulse, , A digital / analog converter that converts a digital signal into an analog signal and the output voltage rises stepwise, and the pulse width modulation circuit outputs the output voltage of the digital / analog converter with respect to the signal of the reference oscillator. A starter circuit, which outputs a pulse whose pulse width increases stepwise by comparing 2. The digital / analog converter has a variable reference voltage generating means for increasing its output voltage stepwise, and a pulse counter for outputting a digital signal to the digital / analog converter. Starter circuit.