Power supply apparatus, control apparatus, and program therefor

1. A power supply apparatus comprising:

a DC/DC converter comprising:

an inductor to which an input voltage is applied;

a switching element that switches a current flowing to the inductor on and off so as to cause an induced voltage to be generated;

an electrolytic capacitor that smoothes a voltage responsive to the induced voltage and outputs the voltage to a load; and

a control circuit that controls the switching element,

wherein the control circuit

outputs, to the switching element, a second control signal obtained by superimposing an estimation signal on a first control signal, wherein the first control signal performs on and off control on the switching element at a switching frequency and changes a duty cycle so that an output voltage becomes a predetermined voltage, and the estimation signal has an estimation-purpose frequency lower than the switching frequency,

detects the output voltage, the output voltage being based on switching performed by the switching element, the switching being controlled by the second control signal, and

estimates capacitance of the electrolytic capacitor by using the detected output voltage, the duty cycle of the first control signal, and a frequency component of the estimation signal contained in the detected output voltage.

2. The power supply apparatus according to claim 1 ,

wherein the control circuit

estimates a load current of the DC/DC converter by using the detected output voltage and the duty cycle, and

estimates the capacitance of the electrolytic capacitor from the load current and an estimation-purpose frequency component contained in the output voltage based on a correspondence relationship between the capacitance of the electrolytic capacitor, the load current and the estimation-purpose frequency component contained in the output voltage.

3. The power supply apparatus according to claim 2 ,

wherein the control circuit

calculates an output current output to the load of the DC/DC converter by dividing a difference between a value obtained by multiplying the input voltage by the duty cycle and the output voltage, by an internal resistance value of the DC/DC converter including internal resistances of the inductor and the switching element, and

estimates, as the load current, a current obtained by extracting at least a frequency component lower than the estimation-purpose frequency component from the calculated output current.

4. The power supply apparatus according to claim 2 ,

wherein the control circuit has a table indicating the estimation-purpose frequency component of the output voltage seen when the load current and the capacitance of the electrolytic capacitor are each changed.

5. The power supply apparatus according to claim 3 ,

wherein the control circuit removes at least the frequency component not lower than the estimation-purpose frequency component from the output current, and

estimates that an average value of the output current from which the frequency component not lower than the estimation-purpose frequency component has been removed is the load current.

6. A control apparatus that controls a DC/DC converter including:

an inductor to which an input voltage is applied,

a switching element that switches a current flowing to the inductor on and off so as to cause an induced voltage to be generated, and

an electrolytic capacitor that smoothes a voltage responsive to the induced voltage and outputs the voltage to a load,

wherein the control apparatus

outputs, to the switching element, a second control signal obtained by superimposing an estimation signal on a first control signal, wherein the first control signal performs on and off control on the switching element at a switching frequency and changes a duty cycle so that an output voltage becomes a predetermined voltage, and the estimation signal has an estimation-purpose frequency lower than the switching frequency,

detects the output voltage, the output voltage being based on switching performed by the switching element, the switching being controlled by the second control signal, and

estimates capacitance of the electrolytic capacitor by using the detected output voltage, the duty cycle of the first control signal, and a frequency component of the estimation signal contained in the detected output voltage.

7. A computer-readable and non-transitory storage medium storing a program that controls a DC/DC converter including:

an inductor to which an input voltage is applied,

a switching element that switches a current flowing to the inductor on and off so as to cause an induced voltage to be generated, and

an electrolytic capacitor that smoothes a voltage responsive to the induced voltage and outputs the voltage to a load,

wherein the computer program causes a control apparatus to execute an operation, the operation comprising:

outputting, to the switching element, a second control signal obtained by superimposing an estimation signal on a first control signal, wherein the first control signal performs on and off control on the switching element at a switching frequency and changes a duty cycle so that an output voltage becomes a predetermined voltage, and the estimation signal has an estimation-purpose frequency lower than the switching frequency;

detecting the output voltage, the output voltage being based on switching performed by the switching element, the switching being controlled by the second control signal; and

estimating capacitance of the electrolytic capacitor by using the detected output voltage, the duty cycle of the first control signal, and a frequency component of the estimation signal contained in the detected output voltage.