Patent ID: 8027178

Claim:
A power conversion apparatus, comprising: a transformer, having a primary side and a secondary side, wherein a first terminal of the primary side receives an input voltage, and the secondary side supplies an output voltage to an electronic device; a power switch, having a first terminal coupled to a second terminal of the primary side and a control terminal for receiving a pulse width modulation (PWM) signal; a resistor, coupled between a second terminal of the power switch and a ground voltage; a leading edge blanking (LEB) unit, coupled to a first node between the resistor and the second terminal of the power switch, for generating a variable or fixed LEB signal according to rising and falling edges of a spike signal on the first node and the PWM signal; a PWM signal generator, coupled to the control terminal of the power switch and the LEB unit, for generating and modulating the PWM signal according to a loading status of the electronic device; and an over current protection (OCP) unit, coupled to the LEB unit and the PWM signal generator, for receiving the variable or fixed LEB signal, and for controlling the PWM signal generator to constantly generate the PWM signal during an enabling period/phase of the variable or fixed LEB signal and determining whether to activate an OCP mechanism by constantly detecting a voltage on the first node during a disabling period/phase of the variable or fixed LEB signal.