POWER SUPPLY CIRCUIT AND CONTROL METHOD THEREOF

摘要

According to one embodiment, a power supply circuit includes a switching element to which a drive signal is supplied, a control value generating circuit that compares an output voltage and a reference voltage to generate a control value, and a comparison circuit that compares a feedback current and the control value. The power supply circuit has a generating circuit that generates a clock signal having a constant period in a PWM control mode and a clock signal according to the output voltage in a PFM control mode. The control value of the control value generating circuit is changed so that averages of the feedback current before and after the control mode switching become equal.

主权项

1. A power supply circuit comprising:
a switching element of which a main current path is connected between an input end to which to apply a direct-current input voltage and an output end outputting an output voltage, the switching element being controlled to be on/off by a drive signal applied to the control electrode thereof; a control value generating circuit that compares the output voltage and a predetermined reference voltage to generate a control value based on the comparing result; a first comparison circuit that compares a feedback current corresponding to an output current and the control value to output an output signal corresponding to the comparing result; a switching signal generating circuit that generates a switching signal having a constant period in a PWM control mode and generates a switching signal at timings when the output voltage becomes less than a threshold voltage in a PFM control mode; a drive signal generating circuit that generates the drive signal in response to the switching signal from the switching signal generating circuit and the output signal of the comparison circuit; and a control circuit that, in switching a control mode between the PWM control mode and the PFM control mode, changes the control value of the control value generating circuit to a new control value so that an average of the feedback current after the control mode switching becomes equal to an average of the feedback current before the control mode switching.