Apparatus and method for controlling switching power supply

摘要

An output voltage error detection unit outputs an auxiliary winding voltage generated across an auxiliary winding having the same number of turns as a secondary winding a certain period after a secondary conduction period starts. A correction amount calculation unit calculates a secondary voltage drop caused by a secondary current flowing in the conduction period based on a primary current flowing when the conduction period starts and outputs a calculation result as a correction amount. A reference voltage generation unit generates a reference voltage by adding the correction amount to the output voltage. A control unit generates a feedback signal to minimize the error between the auxiliary winding voltage obtained after a certain delay period and the reference voltage. A PWM signal generation unit controls a PWM signal based on the feedback signal, adjusts switching of the switching element, and maintains the output voltage at a constant level.

主权项

1. An apparatus for controlling a switching power supply that causes a transformer to convert an input voltage on a primary side into a direct-current output voltage on a secondary side based on switching of a switching element and to supply the output voltage to load, the apparatus comprising:
an output voltage error detection unit configured to output an auxiliary winding voltage generated across an auxiliary winding having the same number of turns as a secondary winding of the transformer a certain period after a secondary conduction period of the transformer starts; a correction amount calculation unit configured to calculate a secondary voltage drop caused by a secondary current flowing in the secondary conduction period based on a primary current flowing through the switching element arranged on the primary side when the secondary conduction period starts and output a result of the calculation as a correction amount to be added to a target value for the output voltage; a reference voltage generation unit configured to generate a reference voltage by adding a voltage corresponding to the correction amount to a target voltage for the output voltage; a control unit configured to perform feedback control to minimize an error between the auxiliary winding voltage obtained after a certain delay period and the reference voltage and generate a feedback signal; and a pulse width modulation (PWM) generation unit configured to control a PWM signal based on the feedback signal, adjust switching of the switching element, and perform a control operation to maintain the output voltage at a constant level.