Abstract: A PWM controller compensates a maximum output power of a power converter, and includes a PWM unit and a compensation circuit. The PWM unit generates a PWM signal for controlling a power switch to switch a power transformer, which has a primary winding connected to the power switch and is supplied with an input voltage of the power converter. A pulse width of the PWM signal is correlated to an amplitude of the input voltage. The compensation circuit generates a current boost signal in response to the PWM signal by pushing up a peak value of a current-sense signal generated by a current-sense device in response to a primary-side switching current of the power transformer. A peak value of the current boost signal is adjusted by the pulse width of the PWM signal for compensating a difference of the maximum output power caused by the amplitude of the input voltage.

Abstract: The present invention provides a method and a control circuit to detect an input voltage for the control and protections of a power converter. It includes a current sense circuit for generating a current signal in response to a switching current of a transformer. A detection circuit is coupled to sense the current signal for generating a slope signal in response to a slope of the current signal. A protection circuit is further developed to control the switching signal in accordance with the slope signal. The level of the slope signal is corrected to the input voltage of the power converter.

Abstract: The present invention provides a method and circuit for detecting an input voltage of a power converter. It includes a current sense circuit for generating a current signal in response to a switching current of an inductive device. A detection circuit is coupled to sense the current signal for generating a slope signal in response to a slope of the current signal. A signal generation circuit is further developed to generate an input-voltage signal in accordance with the slope signal. The level of the input-voltage signal is corrected to the input voltage of the power converter.

Abstract: The invention presents a surge output protection for a control circuit of power converter. It comprises an input circuit for generating a threshold signal. A first comparator is coupled to receive a signal representative the current through a power switch. The first comparator further generates a control signal in response to the signal and the threshold signal. A timer circuit is utilized to generate a time-out signal in response to the control signal. The time-out signal is coupled to turn off the power switch.

Abstract: An integrated control circuit for a resonant power converter includes a minimum-frequency programming circuit connected a first resistor to program a minimum switching frequency of the power converter. A feedback circuit is coupled to a feedback terminal to receive a feedback signal for generating an adjustment signal. A maximum-frequency programming circuit connects a second resistor to determine a maximum switching frequency in response to the adjustment signal. An oscillator is coupled to the minimum-frequency programming circuit and the maximum-frequency programming circuit to generate an oscillation signal for determining the switching frequency of the power converter. A feed-forward circuit is connected to a feed-forward terminal to receive a feed-forward signal represents the input voltage of the power converter. The switching frequency is increased in response to decrease of the feedback signal, and the switching frequency is increased in response to the increase of the feed-forward signal.

Abstract: A switching power supply control-circuit according to the present invention uses bleeding resistors to charge a start-up capacitor and discharge an EMI filter. No extra discharge device is needed to accelerate the discharge of the input capacitor, since the start-up capacitor is charged up by the AC input source. A latch circuit of the power supply can be quickly reset after the AC input source is shut off. After the control-circuit begins to operate, the auxiliary winding of the transformer will power the control-circuit. To further reduce power consumption, the auxiliary winding generates a bias voltage to enable line-voltage detection. This allows the power supply to perform line-voltage detection and startup, without having to connect resistors or transistors to the input capacitor.