Control circuit for DC-DC converter, DC-DC converter, and method for controlling DC-DC converter

1. A DC-DC converter control circuit comprising:

a slope signal generation circuit that generates a reference voltage by superimposing a slope voltage onto a standard voltage;

a comparator that performs comparison of the reference voltage with an output voltage and generates a comparator output signal according to a result of the comparison, a not-inverting input terminal of the comparator coupled to the reference voltage and an inverting input terminal of the comparator coupled to the output voltage;

an oscillator that generates a pulse signal with a substantially constant cycle;

a control signal generation circuit that generates a control signal that controls to turns on a switch based on the comparator output signal and turns off the switch based on the pulse signal; and

a voltage correction circuit that corrects the reference voltage according to one of an input voltage and a differential voltage of the input voltage and the output voltage,

wherein the control signal generation circuit includes a RS flip-flop circuit having a set terminal coupled to an output of the comparator and a reset terminal coupled to an output of the oscillator,

wherein the RS flip-flop circuit is set by supplying the output of the comparator to the set terminal and is reset by supplying the output of the oscillator to the reset terminal,

wherein the slope signal generation circuit controls the slope amount so that a slope voltage increase rate becomes larger than an output voltage increase rate according to one of the input voltage and the differential voltage of the input voltage and the output voltage,

wherein the voltage correction circuit decreases the reference voltage when the slope voltage increase rate becomes larger than the output voltage increase rate.

2. A DC-DC converter control circuit comprising:

a control circuit that controls a switch coupled between an input end to which an input voltage is applied and an output end from which an output voltage is output, and the input end by a switching control signal according to a comparison between a reference voltage with a slope and the output voltage;

a slope signal generation circuit that controls a slope amount of the slope voltage according to any of the input voltage and a differential voltage of the input voltage and the output voltage to generate a reference voltage; and

a voltage correction circuit that corrects the reference voltage according to one or the input voltage and the differential voltage of the input voltage and the output voltage,

wherein the control signal generation circuit includes:

a comparator that performs comparison of the reference voltage with the output voltage and generates a signal according to a result of the comparison, a not-inverting input terminal of the comparator coupled to the reference voltage and an inverting input terminal of the comparator coupled to the output voltage;

an oscillator that generates a pulse signal with a substantially constant cycle; and

a RS flip-flop circuit having a set terminal coupled to an output of the comparator and a reset terminal coupled to an output of the oscillator,

wherein the RS flip-flop circuit is set by supplying the output of the comparator to the set terminal and is reset by supplying the output of the oscillator to the reset terminal,

wherein the slope signal generation circuit controls the slope amount so that a slope voltage increase rate becomes larger than an output voltage increase rate according to one of the input voltage and the differential voltage of the input voltage and the output voltage, and

wherein the voltage correction circuit decreases the reference voltage when the slope voltage increase rate becomes larger than the output voltage increase rate.

3. The DC-DC converter control circuit according to claim 2 , wherein the voltage correction circuit further corrects the reference voltage according to a duty of the switch.

4. The DC-DC converter control circuit according to claim 2 , wherein the voltage correction circuit includes: a duty conversion circuit that generates a first voltage according to an on-duty of the switch; a standard voltage generation circuit that generates a second voltage according to a standard duty of the switch; a differential circuit that shunts a current from a current source into a first route and a second route according to a potential difference of the first voltage and the second voltage; and a potential difference generation circuit that generates a potential difference between both terminals of an element according to a current that flows through the first route, wherein the voltage correction circuit corrects the reference voltage by the potential difference between the both terminals of the element.

5. The DC-DC converter control circuit according to claim 2 , wherein the slope signal generation circuit generates a second slope voltage that is proportional to the slope voltage, and the voltage correction circuit generates a first corrected voltage that is obtained by decreasing a given voltage by an integral multiple of a correction amount that corrects the reference voltage and includes a synthesis circuit that generates the reference voltage by synthesizing the second slope voltage and the first corrected voltage.

6. The DC-DC converter control circuit according to claim 2 , wherein the slope signal generation circuit includes: a capacitor; a switch that is coupled in parallel with the capacitor; and a current generation circuit that supplies a current to the capacitor, charges and discharges the capacitor by turning on and off the switch according to a switching cycle of the switch, and generates the slope voltage with an accumulated electric charge of the capacitor.

7. The control circuit of the DC-DC converter according to claim 6 , wherein the voltage correction circuit includes: an element that causes a potential difference between a first terminal and a second terminal; a current source that supplies a current so as to cause a potential difference between the first terminal and the second terminal of the element according to a potential difference between both terminals of the capacitor; and an operational amplifier that receives inputs of a voltage between the current source and the element and a given voltage, and that includes an output terminal which is coupled to the second terminal of the element.

8. The DC-DC converter control circuit according to claim 6 , wherein the voltage correction circuit includes: a second capacitor; a second switch that is coupled in parallel with the second capacitor; a current source that supplies a current so as to cause a potential difference between a first terminal and a second terminal of the second capacitor according to a potential difference of both terminals of the capacitor; a low-pass filter that is coupled between the first terminal and the second terminal of the second capacitor; and an operational amplifier that receives a voltage obtained by smoothing a voltage at the first terminal of the second capacitor by the low-pass filter and a given voltage, and that includes an output terminal which is coupled to the second terminal of the second capacitor.

9. The DC-DC converter control circuit according to claim 2 , comprising a low-pass filter that receives the output voltage, wherein the low-pass filter includes a first resistor and a capacitor that are coupled in series and a given voltage is supplied to a coupling point between the first resistor and the capacitor through a second resistor, and the slope signal generation circuit generates the reference voltage by superimposing the slope voltage onto a voltage at the coupling point.

10. A DC-DC converter comprising:

an inductor that is coupled between an input end to which an input voltage is applied and an output end to which an output voltage is applied;

a switch that is coupled between the input end and the inductor;

a control circuit that performs switching control of the switch according to a comparison of a reference voltage with a slope and the output voltage;

a slope signal generation circuit that changes a slope amount of the slope voltage according to one of the input voltage and a differential voltage of the input voltage and the output voltage to generate a reference voltage; and

a voltage correction circuit that corrects the reference voltage according to one of the input voltage and the differential voltage of the input voltage and the output voltage,

wherein the control signal generation circuit includes:

a comparator that performs comparison of the reference voltage with the output voltage and generates a signal according to a result of the comparison, a not-inverting input terminal of the comparator coupled to the reference voltage and an inverting input terminal of the comparator coupled to the output voltage;

an oscillator that generates a pulse signal with a substantially constant cycle; and

a RS flip-flop circuit having a set terminal coupled to an output of the comparator and a reset terminal coupled to an output of the oscillator,

wherein the RS flip-flop circuit is set by supplying the output of the comparator to the set terminal and is reset by supplying the output of the oscillator to the reset terminal,

wherein the slope signal generation circuit controls the slope amount so that a slope voltage increase rate becomes larger than an output voltage increase rate according to one of the input voltage and the differential voltage of the input voltage and the output voltage, and

wherein the voltage correction circuit decreases the reference voltage when the slope voltage increase rate becomes larger than the output voltage increase rate.

11. A DC-DC converter control method comprising:

generating a second voltage by superimposing a slope voltage onto one of a standard voltage and a voltage proportional to an output voltage, when a first voltage is assumed to be one of the standard voltage; generating the second voltage by superimposing the slope voltage onto the standard voltage when the first voltage is assumed to be the voltage proportional to the output voltage;

turning a switch to an on-state based on a comparison result of the first voltage and the second voltage, and turning the switch to an off-state based on a pulse signal that is output in substantially constant cycle;

correcting the reference voltage according to one of the input voltage and a differential voltage of the input voltage and the output voltage;

controlling the slope amount so that a slope voltage increase rate becomes larger than an output voltage increase rate according to one of the input voltage and a differential voltage of the input voltage and the output voltage; and

decreasing the reference voltage when the slope voltage increase rate becomes larger than the output voltage increase rate,

wherein the turning is controlled based on a control signal which is generated by a control signal generation circuit, and

wherein the control signal generation circuit includes:

a comparator that performs comparison of the second voltage with the output voltage and generates the comparison result, a not-inverting input terminal of the comparator coupled to the reference voltage and an inverting input terminal of the comparator coupled to the output voltage;

an oscillator that generates a pulse signal with a substantially constant cycle; and

a RS flip-flop circuit having a set terminal coupled to an output of the comparator and a reset terminal coupled to an output of the oscillator,

wherein the RS flip-flop circuit is set by supplying the output of the comparator to the set terminal and is reset by supplying the output of the oscillator to the reset terminal.

12. A DC-DC converter control method comprising:

comparing a voltage that is proportional to an output voltage with a reference voltage with a slope;

outputting the output voltage by switching control of a switch coupled in series with an inductor based on a result of the comparing;

changing a slope amount of the slope according to one of the input voltage and the differential voltage of the input voltage and the output voltage;

correcting the reference voltage according to one of the input voltage and a differential voltage of the input voltage and the output voltage;

controlling the slope amount so that a slope voltage increase rate becomes larger than an output voltage increase rate according to one of the input voltage and a differential voltage of the input voltage and the output voltage; and

decreasing the reference voltage when the slope voltage increase rate becomes larger than the output voltage increase rate,

wherein the switching control is controlled based on a control signal which is generated by a control signal generation circuit, and

wherein the control signal generation circuit includes:

a comparator that performs comparison of the reference voltage with the output voltage and generates the comparison result; a not-inverting input terminal of the comparator coupled to the reference voltage and an inverting input terminal of the comparator coupled to the output voltage;

an oscillator that generates a pulse signal with a substantially constant cycle; and

a RS flip-flop circuit having a set terminal coupled to an output of the comparator and a reset terminal coupled to an output of the oscillator,

wherein the RS flip-flop circuit is set by supplying the output of the comparator to the set terminal and is reset by supplying the output of the oscillator to the reset terminal.

13. The DC-DC converter control method according to claim 12 , further comprising: correcting the reference voltage according to a duty of the switch.

14. The DC-DC converter control method according to claim 12 , further comprising:

generating a second slope voltage that is proportional to the slope voltage and a first corrected voltage that is obtained by decreasing a given voltage by an integral multiple of a correction amount that corrects the reference voltage; and synthesizing the second slope voltage and the first corrected voltage to generate the reference voltage.