JP2009118692A - Dc-dc converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC-DC converter inexpensively coping with changes in an output current, and having an excellent current control method. <P>SOLUTION: In the DC-DC converter of the current control method, a resistance element, as an output voltage setting means in which an output voltage is divided and fed back to an IN terminal of a control circuit IC, is externally attached to the control circuit IC to set a desired output voltage. When a voltage required by an IC as a load is changed, it is only required to replace the resistance element externally attached to the control circuit IC without redesigning, thus reducing development cost and man hours. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a DC-DC converter that converts a voltage value of a DC voltage, and more particularly, to a DC-DC converter for keeping a voltage used inside an electronic device composed of a semiconductor circuit or the like constant.

  More particularly, the present invention relates to a DC-DC converter that converts a voltage value of a DC voltage by a current control method, and more particularly to a DC-DC converter that can be inexpensively adapted to a change in output current.

  In an electronic device composed of a semiconductor circuit or the like, the battery output is made constant by a DC-DC converter (hereinafter also referred to as “DC / DC converter”) in order to keep the voltage used internally constant. Is common. For example, in the case of a battery-powered electronic device such as a notebook PC, the operation time and the output terminal voltage of the friend's battery decrease. There is.

  When the electronic device is activated, there is a possibility that inrush current or output voltage oscillation may occur in the DC / DC converter. On the other hand, by adopting a voltage control method and performing a soft start in which the reference voltage is gradually increased by a capacitor at start-up, inrush current and output voltage oscillation can be suppressed (see, for example, Patent Document 1). )

FIG. 3 shows a configuration example of a voltage control type DC / DC converter. The illustrated DC / DC converter 1 includes a control circuit 11, a choke coil L1, and a capacitor C1. One end of the choke coil L1 is connected to the LX terminal of the control circuit 11, and the other end is grounded via the capacitor C1. Voltage between the choke coil L1 and the capacitor C1 is DC / DC converter output voltage V _o. The output voltage V _o is fed back to the IN terminal of the control circuit 11.

In the control circuit 11, the comparator 21 compares the voltage obtained by dividing the output voltage V _o fed back to the IN terminal by the resistors R 1 and R 2 with the reference voltage V _REF generated by the variable reference voltage source. The comparison result, that is, the voltage V _FB obtained by amplifying the difference between the two inputs is further compared with the triangular wave V _CT supplied from the triangular wave oscillator 24 in the comparator 23 in the subsequent stage. The comparison result, that is, a voltage signal obtained by amplifying the difference between V _FB and V _CT is supplied to a PWM (Pulse Wide Modulation) control FET (Field Effect Transistor) drive circuit 25 as a control signal. The PWM control FET drive circuit 25 outputs a pulse wave having a pulse width based on this control signal. This output pulse wave is supplied to the gate of each switching FET (switch N1 and switch N2) that controls the voltage applied to the choke coil L1 and the capacitor C1. That is, the output pulse of the PWM control FET drive circuit 25, the switching operation of the switches N1 and the switch N2 is controlled, as a result, the duty value of the voltage applied to the choke coil L1 and the capacitor C1, that is, the output voltage V _o is controlled Is done.

That is, in the illustrated voltage control type DC / DC converter 1, the value of V _FB is suppressed to a low level by lowering the reference voltage V _REF at the time of startup, and the output pulse width of the PWM control FET drive circuit 25 is also narrow. Thus, the duty value of voltage application, that is, the output voltage V _o is also lowered. Therefore, the soft start is performed so that the reference voltage source gradually increases the reference voltage V _REF at the start-up, so that the output voltage V _o is also controlled to increase gradually. Oscillation can be suppressed.

  In addition, due to the improvement in operating frequency associated with the recent miniaturization of semiconductor circuit manufacturing processes, DC / DC converters are also required to have faster response characteristics. In the above-described voltage control type DC / DC converter, the frequency characteristics are narrow and it is difficult to control the phase compensation in the feedback control, so it is difficult to improve the response characteristics. Therefore, there is a method using a current control type DC / DC converter instead of the voltage control type DC / DC converter. Since the current control type DC / DC converter has a good response characteristic and a wide frequency characteristic, it is possible to realize a DC / DC converter that operates at high speed easily and inexpensively.

FIG. 4 shows a configuration example of a current control type DC / DC converter. The illustrated DC / DC converter 101 includes a control circuit 111, a choke coil L1, and a capacitor C1. One end of the choke coil L1 is connected to the LX terminal of the control circuit 111, and the other end is grounded via the capacitor C1. Voltage between the choke coil L1 and the capacitor C1 is DC / DC converter output voltage V _o. The output voltage V _o is fed back to the IN terminal of the control circuit 111.

In the control circuit 111, the comparator 121 compares the voltage obtained by dividing the output voltage V _o fed back to the IN terminal by the resistors R1 and R2 with the reference voltage V _REF generated by the variable reference voltage source. . On the other hand, the current flowing through the resistor R5 connected to the drain of the switch N1 is detected by the current detection amplifier 124, and the output current of the current detection amplifier 124 flows through the resistor R _S to generate the voltage V _RS . The comparator 123 compares this voltage V _RS with the comparison result V _FB from the previous stage comparator 121 and supplies the comparison result to the reset terminal of the RS flip-flop 127. A predetermined clock signal CLK is supplied from the clock signal generator 128 to the set terminal of the RS flip-flop 127. The RS flip-flop 127 supplies a control signal to the PWM control FET drive circuit 129 based on these signals.

That is, when the output voltage V _o decreases, the amount of current flowing through the resistor R5 decreases, the voltage V _RS decreases, and the output of the comparator 123 goes low, so the output pulse width of the PWM control FET drive circuit 129 Increases, and the duty value of voltage application to the choke coil L1 and the capacitor C1 increases (that is, the output voltage V _o increases). On the contrary, when the potential of the output voltage V _o increases, the difference from the reference voltage V _REF decreases, the value of the output V _FB of the comparator 121 decreases, and the output of the comparator 123 at the subsequent stage becomes high level. Therefore, the output pulse width of the PWM control FET drive circuit 129 is narrowed, and the duty value of voltage application to the choke coil L1 and the capacitor C1 is reduced (that is, the output voltage _o is reduced).

Here, the slope compensation circuit 125 generates a slope current I _slope for compensating the slope of the waveform of the current flowing through the resistor R5 connected to the drain of the switch N1 detected by the current detection amplifier 124. . Slope compensation circuit 125, becomes maximum immediately after startup, drops in accordance with the boosting of the reference voltage V _REF, to vary the slope current I _slope so as to minimize the time the reference voltage V _REF reaches a predetermined voltage Thus, it is possible to suppress the occurrence of an inrush current and an excessive voltage at the time of start-up, and oscillation of the output voltage (see, for example, Patent Document 2).

  The voltage used in the electronic device is not normally one type but a plurality of voltages are required, and the same number of DC / DC converters as the type of voltage required by the apparatus are prepared. In addition, the voltage of semiconductor integrated circuits is rapidly decreasing, and the voltage required for each circuit changes frequently. In such a case, there is a problem that a DC / DC converter must be newly designed.

For example, DC / DC converter or the voltage control system shown in FIG. 3, the DC / DC converter of the current control system shown in FIG. 4, on the line for feeding back the output voltage V _o to the IN terminal, the control circuit 11 ( or disposed external to become voltage conversion buffer 111), it is possible to change the output voltage V _o by returning the same voltage value as the nominal output voltage.

  5 and 6 are circuit configuration examples in which an external voltage conversion buffer is provided for the voltage control type DC / DC converter shown in FIG. 3 and the current control type DC / DC converter shown in FIG. Respectively. In each figure, the specified output voltage of the DC / DC converter is 5.0V, but when changing to 2.5V output, the output voltage is boosted by using an external buffer and a resistor, and the same voltage as the specified output voltage. The output voltage is changed by returning the value to the IN terminal. In a voltage-controlled DC / DC converter, a product that supports voltage change by an external buffer of a control circuit is already generally used.

  However, if an external voltage conversion buffer is provided in the control circuit IC, there is a problem that the cost increases.

JP 2003-224967 A JP 2007-236071 A

  An object of the present invention is to provide an excellent DC-DC converter for keeping a voltage used inside an electronic device constituted by a semiconductor circuit or the like constant.

  A further object of the present invention is to provide a DC-DC converter with an excellent current control method, which has good response characteristics and wide frequency characteristics, and can be easily and inexpensively operated at high speed. .

  A further object of the present invention is to provide an excellent DC-DC converter that can cope with a change in output current at low cost.

The present invention has been made in consideration of the above problems, and is a DC-DC converter that converts the level of a DC voltage,
A control circuit that feeds back the output voltage at the input terminal and controls the output voltage;
A coil having one end connected to the voltage output terminal of the control circuit and the other end grounded via a capacitor;
By dividing the output voltage using one or more resistance elements arranged on a feedback path that feeds back the output voltage to the input terminal of the control circuit, using the voltage between the coil and the capacitor as an output voltage. Output voltage setting means for setting the level;
It is a DC-DC converter characterized by comprising.

  In an electronic device composed of a semiconductor circuit or the like, in order to keep the voltage used internally constant, the battery output is generally made constant by a DC-DC converter. In recent years, due to the improvement in operating frequency associated with the recent miniaturization of semiconductor circuit manufacturing processes, DC-DC converters are also required to have high-speed response characteristics, and the response characteristics are good and the frequency characteristics are also wide. A current control type DC-DC conversion circuit having a feature has been proposed.

  In addition, since a plurality of voltages are used in an electronic device and a use voltage is frequently changed due to a low voltage of a semiconductor integrated circuit, the DC-DC converter needs to cope with the voltage change. In a voltage-controlled DC-DC converter or the like, there is an example in which the voltage level is changed by externally attaching a voltage conversion buffer that returns the same voltage value as the specified output voltage to the control circuit, but this increases the cost.

  In contrast, the present invention includes a control circuit for controlling an output voltage, and a coil having one end connected to the voltage output terminal of the control circuit and the other end grounded via a capacitor. This type of DC-DC converter uses the voltage between the two as an output voltage, but the voltage can be changed by providing output voltage setting means on the feedback path that feeds back the output voltage to the input terminal of the control circuit. I try to correspond. The output voltage setting means sets the level by dividing the output voltage using one or more resistance elements.

  The resistance element has less variation than a resistor mounted on an IC circuit, and the output voltage accuracy of the DC-DC converter is high by using a highly accurate resistor. In addition, when the voltage required by the load IC is changed, it is possible to respond by simply replacing the resistance element externally attached to the control circuit IC without performing a new design each time. Development costs and man-hours can be reduced.

  Here, the control circuit controls the output voltage by the current control method, so that the DC-DC converter has good response characteristics and wide frequency characteristics, so that it can operate easily and inexpensively at high speed. It becomes like this.

  Specifically, the control circuit of the current control system includes a switching unit that controls voltage application to the coil by a switching operation, a switch current detection unit that detects a first current flowing into the switching unit, and the voltage Based on the output voltage output from the output terminal and the first current detected by the switch current detecting means, the switching control means for controlling the switching operation of the switching means can be used.

  In addition, the current control type control circuit has problems such as inrush current at start-up, generation of excessive voltage, and oscillation of output voltage.

  Therefore, the control circuit further includes a current generation unit that generates a second current that compensates for a slope with respect to the waveform of the first current detected by the switch current detection unit, and the switch control unit includes: The switching operation of the switching unit may be controlled based on the output voltage output from the voltage output terminal and the first current to which the second current generated by the current generation unit is added. Good.

  In such a case, the current control means becomes the maximum immediately after startup, decreases in accordance with the increase of the reference voltage, and the current value fluctuates so as to become the minimum when the reference voltage reaches a predetermined voltage. By generating the current, it is possible to suitably suppress the occurrence of an inrush current and an excessive voltage at the start-up and oscillation of the output voltage.

  As described above, the current control type DC-DC converter has good response characteristics and wide frequency characteristics, and therefore can operate easily and inexpensively at high speed. Therefore, sufficient frequency characteristics can be ensured even if a phase compensation constant is incorporated. Therefore, there is no problem even if the control circuit inserts a buffer after the input terminal. By providing each terminal of the buffer to the pin of the control circuit IC, a function for setting the output voltage of the DC-DC converter is suitably realized by the resistance ratio of the voltage dividing resistor constituting the output voltage setting means. be able to. In general, since an external resistor is more accurate than a resistor mounted in an IC circuit, the DC-DC converter according to the present invention can obtain high output voltage accuracy.

  According to the present invention, since the response characteristics are good and the frequency characteristics are wide, it is possible to provide a DC-DC converter excellent in a current control system that can operate easily and inexpensively at high speed.

  Further, according to the present invention, it is possible to provide a direct current-direct current converter having an excellent current control method that can cope with a change in output current at low cost.

  The DC / DC converter of the current control system to which the present invention is applied can be obtained by externally attaching a resistance element as output voltage setting means for dividing the output voltage and feeding back to the IN terminal of the control circuit IC to the control circuit IC. Output voltage can be set. In general, a resistance element has less variation than a resistor mounted on an IC circuit, and the output voltage accuracy is high by using a highly accurate resistor. In addition, when the voltage required by the load IC is changed, it is possible to respond by simply replacing the resistance element externally attached to the control circuit IC without newly designing a DC / DC converter. It is possible to reduce development costs and man-hours.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a configuration of a DC / DC converter according to an embodiment of the present invention. The illustrated DC / DC converter 100 is a current control system, and includes a control circuit 111, a choke coil L1, a capacitor C1, and resistors R3 and R4 for voltage division. One end of the choke coil L1 is connected to the LX terminal of the control circuit 111, and the other end is connected to the output terminal of the DC / CD converter 100. This output terminal is grounded via a capacitor C1. An output voltage V _o from this output terminal is supplied to a load (such as an electronic device not shown). The output terminal is grounded via two resistors R 3 and R 4, and the connection point of these resistors R 3 and R 4 is connected to the buffer 130 after the IN terminal of the control circuit 111. In other words, the output voltage V _o is divided by the resistors R 3 and R 4 and then input to the buffer 130 after the IN terminal of the control circuit 111. In the present specification, the choke coil L1 has been described as using a choke coil as an example, but other types of coils may be used. Similarly, the type of capacitor used as the capacitor C1 is not limited.

  Inside the control circuit 111, a buffer 130 is inserted after the IN terminal, and the buffer output is grounded via a resistor R1 and a resistor R2 connected in series. A connection point between the resistors R1 and R2 is connected to an inverting input terminal of the comparator 121 that compares two input voltages.

The non-inverting input terminal of the comparator 121 is connected to the positive terminal of a variable reference voltage source that supplies the reference voltage V _REF . The negative terminal of the variable voltage source is grounded. The output terminal of the comparator 121 is connected to the inverting input terminal of the comparator 123 at the subsequent stage.

The non-inverting input terminal of the comparator 123 is grounded via the resistor RS and is connected to the output of the adder 126. Two inputs of the adder 126 are connected to the output terminal of the current detection amplifier 124 and the output terminal of the slope compensation circuit 125 that outputs the slope compensation current I _slope according to the value of the reference voltage V _REF . The current detection amplifier 124 detects a current flowing through the resistor RS connected to the switch N1.

The slope compensation circuit 125 is a circuit for maintaining the pulse waveform of the voltage applied to the non-inverting input terminal of the comparator 123 even when the output current of the current detection amplifier 124 is small. By generating a slope compensation current I _slope that decreases as the reference voltage increases and becomes a minimum when the reference voltage reaches a predetermined voltage, an inrush current at startup or Generation of excessive voltage and oscillation of output voltage are preferably suppressed. For the configuration of the slope compensation circuit 125 and its operating characteristics, see, for example, Japanese Patent Application Laid-Open No. 2007-236071 (paragraphs 0048 to 0070) already assigned to the present applicant.

  The output of the comparator 123 is connected to the reset terminal R of the RS flip-flop 127, and the output terminal of the clock signal generator 128 that outputs the pulse wave clock signal CLK is connected to the set terminal S. The output terminal Q of the RS flip-flop 127 is connected to the input terminal of the PWM control FET drive circuit 129 that drives the switching FET.

  The PWM control FET drive circuit 129 is a circuit that outputs drive signals for the two switches N1 and N2 made of switching FETs. That is, the output terminal of the PWM control FET drive circuit 129 is connected to the gates of the switch N1 and the switch N2, and the switching operation of the switch N1 and the switch N2 based on the pulse width of the control signal supplied from the RS flip-flop 127 ( By switching on / off, the duty value of the output pulse output from the LX terminal is controlled.

  The drain of the switch N1 is connected to the UNREG terminal of the control circuit 111 via the resistor R5, and the source is connected to the LX terminal of the control circuit 111 together with the drain of the switch N2. The source of the switch N2 is grounded via the GND terminal of the control circuit 111.

  Next, the operation of the control circuit 111 will be described.

The output voltage V _o is divided by the voltage dividing resistors R3 and R4 to R4 / (R3 + R4) and then fed back to the IN terminal. A buffer is inserted after the IN terminal, and the IC pin as the IN terminal can be kept at high impedance. The buffer output is divided by the voltage resistor R1 and the resistor R2, and then compared with the reference voltage _VREF in the comparator 121. This comparison result V _FB is further supplied to the inverting input terminal of the comparator 123 at the subsequent stage.

The current detection amplifier 124 detects and outputs the current flowing through the resistor R5, that is, the current flowing through the drain of the switch N1. The slope compensation circuit 125 outputs a slope compensation current I _slope corresponding to the reference voltage V _REF . The adder 126 adds the output current of the current detection amplifier 124 and the slope compensation current I _slope output from the slope compensation circuit 125. This added current flows through the resistor RS, and a voltage V _RS is generated. This voltage V _RS is applied to the non-inverting input terminal of the comparator 123.

For example, immediately after startup, since the current flowing through the resistor R3 is small, the output current of the current detection amplifier 124 is also small, and the voltage V _RS hardly changes depending on the output current. For this reason, the voltage applied to the non-inverting input terminal of the comparator 123 is fixed by a low bell, and an inrush current may occur in the choke coil L1. Therefore, the slope compensation circuit 125 outputs a slope compensation current I _slope based on the value of the reference voltage V _REF , and even if it is in a state immediately after startup, it appears that a current is virtually flowing through the resistor R3. The linear waveform slope is compensated for the pulse waveform of the voltage V _RS and the waveform is shaped.

Based on the value of the reference voltage V _REF , the slope compensation circuit 125 outputs a large slope compensation current I _slope so that a slope appears in the applied voltage when the output current of the current detection amplifier 124 is small immediately after startup, for example. . The slope compensation circuit 125 outputs a small slope compensation current I _slope so that the applied voltage does not exceed the dynamic range when the output current of the current detection amplifier 124 is large during normal operation or the like.

The comparator 123 compares the comparison result V _FB by the preceding comparator 121 with the voltage V _RS and supplies the comparison result, that is, the amplified difference to the reset terminal R of the RS flip-flop 127. The clock signal generator 128 supplies a predetermined clock signal CLK to the set terminal S of the RS flip-flop 127. The RS flip-flop 127 generates a control signal based on these signals, outputs it from the output terminal Q, and supplies it to the PWM control FET drive circuit 129.

The PWM control FET drive circuit 129 outputs a pulse wave based on the control signal from the RS flip-flop 127, and controls the switching operation of the switch N1 and the switch N2 according to the pulse width. That, PWM control FET drive circuit 129, the magnitude of the pulse width of the output pulse, the voltage application amount to the choke coil L1 and the capacitor C1, i.e., to adjust the duty value, controls the value of the output voltage V _o I have to.

  Since the DC / DC converter 100 shown in FIG. 1 is a current control system, it has a good response characteristic and a wide frequency characteristic, so that it can operate easily and inexpensively at high speed.

Also, even if the phase compensation constant is built in the control circuit 101, sufficient frequency characteristics can be secured, so there is no problem even if a buffer is inserted after the IN terminal. Then, by providing each terminal of the buffer to the pin of the circuit IC, as described above, the voltage V _o fed back from the output of the DC / DC converter 100 is divided by the resistors R3 and R4. To the IN terminal of the control circuit 101. Therefore, the function of setting the output voltage of the DC / DC converter 100 can be realized by the resistance ratio of the resistors R3 and R4. According to DC / DC converter 100 shown in FIG. 1, with respect to the reference voltage V _REF in the control circuit 101, changing the output voltage V _o of the following formula (1) by voltage dividing resistors R3 and R4 Can do.

  In general, since an external resistor is more accurate than a resistor mounted in an IC circuit, the DC / DC converter 100 can obtain higher output voltage accuracy.

FIG. 2 shows the configuration of a DC / DC converter according to another embodiment of the present invention. The output voltage V _o is the same as that in FIG. 1 in that it is divided by the resistors R 3 and R 4 and then input to the IN terminal of the control circuit 111. In the example shown in FIG. 1, the output terminal of the DC / DC converter 100 is grounded via two resistors R3 and R4, and the connection point of these resistors R3 and R4 is a buffer of the IN terminal of the control circuit 111. It is connected. On the other hand, in FIG. 2, the output terminal of the DC / DC converter 100-2 is connected to the non-inverting input terminal of the buffer after the IN terminal, and the output terminal of the buffer is connected via two resistors R3 and R4. The connection point of these resistors R3 and R4 is connected to the inverting input terminal of the buffer.

Thus, in the circuit configuration shown in FIG. 2, with respect to the reference voltage V _REF in the control circuit 101 can be changed to the output voltage V _o of the following formula (2) by voltage dividing resistors R3 and R4.

The circuit configuration shown in FIG. 1 can be used in applications that mainly changes increase output voltage V _o, conversely, the circuit configuration shown in FIG. 2 be used in applications that mainly changes low output voltage V _o Can do.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  The DC-DC converter according to the present invention can be applied as a power supply circuit for various electronic devices including semiconductor circuits.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1 is a diagram showing a configuration of a DC / DC converter according to an embodiment of the present invention. FIG. 2 is a diagram showing a configuration of a DC / DC converter according to another embodiment of the present invention. FIG. 3 is a diagram illustrating a configuration example of a voltage control type DC / DC converter. FIG. 4 is a diagram illustrating a configuration example of a current control type DC / DC converter. FIG. 5 is a diagram showing a configuration example in which an external buffer for changing the output voltage is provided to the control circuit of the voltage control type DC / DC converter shown in FIG. FIG. 6 is a diagram showing a configuration example in which an external buffer for changing the output voltage is provided in the control circuit of the current control type DC / DC converter shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... DC / DC converter 111 ... Control circuit 121 ... Comparator 123 ... Comparator 124 ... Current detection amplifier 125 ... Slope compensation circuit 126 ... Adder 127 ... RS flip-flop 128 ... Clock signal generator 129 ... PWM control FET circuit 130 …buffer

Claims (5)

A DC-DC converter for converting a DC voltage level,
A control circuit that feeds back the output voltage at the input terminal and controls the output voltage;
A coil having one end connected to the voltage output terminal of the control circuit and the other end grounded via a capacitor;
By dividing the output voltage using one or more resistance elements arranged on a feedback path that feeds back the output voltage to the input terminal of the control circuit, using the voltage between the coil and the capacitor as an output voltage. Output voltage setting means for setting the level;
A DC-DC converter characterized by comprising: The control circuit includes:
Switching means for controlling voltage application to the coil by a switching operation;
Switch current detection means for detecting a first current flowing into the switching means;
Switch control means for controlling the switching operation of the switching means based on the output voltage output from the voltage output terminal and the first current detected by the switch current detection means;
The DC-DC converter according to claim 1, comprising: The control circuit includes:
Switching means for controlling voltage application to the coil by a switching operation;
Switch current detection means for detecting a first current flowing into the switching means;
Current generating means for generating a second current that compensates for a slope with respect to the waveform of the first current detected by the switch current detecting means;
Switch control means for controlling the switching operation of the switching means based on the output voltage output from the voltage output terminal and the first current to which the second current generated by the current generating means is added. When,
The DC-DC converter according to claim 1, comprising: The control circuit includes a buffer after the input terminal,
The DC-DC converter according to claim 1. The current generating means has a maximum immediately after startup, decreases in accordance with the boost of the reference voltage, and the current value fluctuates so as to be minimum when the reference voltage reaches the predetermined voltage. Generate current,
The DC-DC converter according to any one of claims 2 and 3.

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