Controller for regulating output current at the primary side of a power supply

摘要

A controller controlling the output current at the primary side of a power supply is provided. A waveform detector generates a current-waveform signal. A second control circuit generates an oscillation signal for determining the switching frequency of a switching signal. An integrator generates an integrated signal by integrating an average current signal with a time signal. The average current signal is generated in response to the current-waveform signal. The time signal is generated in accordance with said oscillation signal. The time constant of the integrator is correlated with the switching period of the switching signal, therefore the integrated signal is proportional to the output current. A first control circuit generates the switching signal in correlated with the integrated signal, the oscillation signal and a reference voltage. Wherein the first control circuit controls the pulse width of the switching signal. Therefore, the output current of the power supply can be regulated.