Dc/dc converter and game machine using it

A DC/DC converter comprising:

• an input line to which a DC input voltage is supplied;
• a smoothing circuit that includes an output line and at least one output capacitor connected to the output line;
• N switching circuits that each include a switching transistor and a synchronous rectifier transistor provided in series between the input line and a ground line, and each generate a switching voltage at a switching node that is a connecting node of the switching transistor and the synchronous rectifier transistor according to an input pulse signal, wherein N is an integer at least 2;
• N inductors that are each provided for a respective one of the switching circuits and are each provided between the switching node of the switching circuit that corresponds and the output line;
• a pulse modulator that generates the pulse signal whose duty ratio is so adjusted that a feedback voltage depending on an output voltage of the output line corresponds with a predetermined reference voltage;
• a phase controller that decides the number K of drive phases;
• and
• a distributor that selects K switching circuits among the N switching circuits and distributes the pulse signal to each of the selected K switching circuits with a phase difference of 360/K degrees,
• wherein
• frequency of the pulse signal for each of the numbers of drive phases is so set that a ripple of the output voltage becomes smaller compared with a case in which the frequency of the pulse signal is set constant irrespective of the number of drive phases.

A game machine comprising

• a DC/DC converter including:
• an input line to which a DC input voltage is supplied;
• a smoothing circuit that includes an output line and at least one output capacitor connected to the output line;
• N switching circuits that each include a switching transistor and a synchronous rectifier transistor provided in series between the input line and a ground line, and each generate a switching voltage at a switching node that is a connecting node of the switching transistor and the synchronous rectifier transistor according to an input pulse signal, wherein N is an integer at least 2;
• N inductors that are each provided for a respective one of the switching circuits and are each provided between the switching node of the switching circuit that corresponds and the output line;
• a phase controller that dynamically switches the number K of drive phases according to a state of the DC/DC converter at the time, wherein K is an integer up to N;
• a pulse modulator that generates the pulse signal whose duty ratio is so adjusted that a feedback voltage depending on an output voltage of the output line corresponds with a predetermined reference voltage and whose frequency changes according to the number K of drive phases;
• and
• a distributor that selects K switching circuits among the N switching circuits and distributes the pulse signal to each of the selected K switching circuits with a phase difference of 360/K degrees.