Dc/dc converter

A DC/DC converter configured to convert a first DC voltage into a second DC voltage by turning on and off a switching element in accordance with a drive signal generated by a control circuit, wherein

• the control circuit includes:
• an oscillator configured to output pulses at a predetermined frequency;
• an error amplifier configured to amplify an error between the second DC voltage and a reference voltage and output a first amplified error signal;
• a low-pass filter circuit including an adjustment element configured to adjust a time constant, the low-pass filter circuit configured to generate a second amplified error signal based on the first amplified error signal by use of the adjustment element;
• a current detection circuit configured to detect a current flowing in the switching element and output a current signal;
• a current comparator configured to compare the second amplified error signal and the current signal and output a reset signal for turning off the switching element, the reset signal being outputted based on an output of the comparison;
• an inductor connected to the switching element and an output terminal of the second DC voltage;
• a zero crossing detection circuit configured to output a zero crossing signal when a regeneration period of the inductor is completed;
• a light load detection circuit configured to compare the second amplified error signal from the low-pass filter circuit and a threshold and output a light load signal;
• a voltage superimposition circuit connected to an input terminal of the error amplifier;
• a timer circuit configured to output an intermittent operation enabling signal after an elapse of a predetermined period of time based on the light load signal from the light load detection circuit and the zero crossing signal from the zero crossing detection circuit, and output an intermittent operation disabling signal when a period without output of the zero crossing signal continues for a predetermined period of time;
• and
• an ON-OFF control controller configured to turn off the switching element when the second amplified error signal falls below the threshold while the timer circuit is outputting the intermittent operation enabling signal, and turn on the switching element when the second amplified error signal at least reaches or exceeds the threshold while the timer circuit is outputting the intermittent operation enabling signal, and
• the voltage superimposition circuit superimposes a voltage signal onto the input terminal of the error amplifier for a predetermined period of time, when the current comparator outputs the reset signal while the timer circuit is outputting the intermittent operation enabling signal.

A DC/DC converter configured to convert a first DC voltage into a second DC voltage by turning on and off a switching element in accordance with a drive signal generated by a control circuit, wherein

• the control circuit includes:
• an oscillator configured to output pulses at a predetermined frequency;
• an error amplifier configured to amplify an error between a voltage corresponding to the second DC voltage and a reference voltage and output a first amplified error signal;
• a low-pass filter circuit including an adjustment element configured to adjust a time constant, the low-pass filter circuit configured to generate a second amplified error signal based on the first amplified error signal by use of the adjustment element;
• a current detection circuit configured to detect a current flowing in the switching element and output a current signal;
• a current comparator configured to compare the second amplified error signal and the current signal and output a reset signal for turning off the switching element, the reset signal being outputted based on an output of the comparison;
• an inductor connected to the switching element and an output terminal of the second DC voltage;
• a zero crossing detection circuit configured to output a zero crossing signal when a regeneration period of the inductor is completed;
• a light load detection circuit configured to compare the second amplified error signal from the low-pass filter circuit and a threshold and output a light load signal;
• a timer circuit configured to output an intermittent operation enabling signal after an elapse of a predetermined period of time based on the light load signal from the light load detection circuit and the zero crossing signal from the zero crossing detection circuit, and output an intermittent operation disabling signal when a period without output of the zero crossing signal continues for a predetermined period of time;
• and
• an ON-OFF control controller configured to turn off the switching element when the second amplified error signal falls below the threshold while the timer circuit is outputting the intermittent operation enabling signal, and turn on the switching element when the second amplified error signal at least reaches or exceeds the threshold while the timer circuit is outputting the intermittent operation enabling signal, and
• the reference voltage of the error amplifier is lowered for a predetermined period of time, when the current comparator outputs the reset signal while the timer circuit is outputting the intermittent operation enabling signal.