Abstract: A control circuit of a power supply is provided. The control circuit includes a circuit and a PWM circuit. The circuit generates a limit signal in response to an output voltage of the power supply for limiting a switching current of a transformer of the power supply. The PWM circuit generates a switching signal in response to a feedback signal and the limit signal for switching the transformer and regulating the output voltage of the power supply. A level of the feedback signal is related to a level of the output voltage of the power supply. The output voltage of the power supply is programmable.

Abstract: A power converter in a powered device (PD) of Power-over-Ethernet (PoE) system and a control method are provided. The power converter includes a transformer, a PD interface, a primary-side controller and a detecting circuit. The PD interface receives an input voltage to determine a PoE protocol type of the input voltage, so as to generate a first power type signal. The primary-side controller receives the first power type signal to adjust a primary-side control signal, wherein a primary-side switch is controlled by the primary-side control signal. The detecting circuit detects a mapping signal generated in a secondary-side winding according to the primary-side control signal to generate a second power type signal, wherein the second power type signal indicates the PoE protocol type of the input voltage.

Abstract: A method for controlling an active-clamp flyback power converter is provided. The control method comprises: generating a first switch signal according to an output voltage and a current sensing signal, and selectively generating a second switch signal in a complementary or non-complementary control mode according to the current sensing signal and the first switch signal. The first switch signal is coupled to drive a low-side power switch for switching a transformer and the output voltage regulation of the active-clamp flyback power converter. The second switch signal is coupled to drive a high-side power switch for recycling leakage energy of the transformer and achieving a soft-switching of the low-side power switch. With the control method, the high-side power switch can adaptively switch in a complementary or non-complementary control mode depending on the output load and input voltage conditions.

Abstract: A power converter and a control method therefor are provided. The power converter includes a transformer, synchronous rectifier and a control circuit. A primary side of the transformer receives an input voltage, and a secondary side of the transformer generates a sensing signal. The synchronous rectifier is coupled to the secondary side of the transformer. The control circuit receives the sensing signal and detects a changing slope of the sensing signal, and accordingly generates a control signal to control the synchronous rectifier to be turned on or turned off, so as to regulate an output voltage of the power converter.

Abstract: A protection circuit of a power converter without an input capacitor is disclosed. The protection circuit comprises a high voltage switch, a detection circuit and a control circuit. The switch senses an input voltage of the power converter via a resistor for generating a first signal. The detection circuit coupled to a transformer senses the input voltage of the power converter for generating a second signal. The control circuit controls a switching signal in response to the first signal and the second signal. The switching signal is utilized to switching the transformer for regulating the power converter; and the level of the first signal and the second signal is correlated a level of the input voltage of the power converter.

Abstract: The invention discloses a method for controlling a synchronous rectifier of a power converter and a control circuit using the same. The method includes the following steps. A control signal is generated to control a synchronous rectification transistor in response to an on-time of a switching signal, a level of a transformer voltage and an output voltage of the power converter. The switching signal is used for switching a transformer. The control signal is generated once the switching signal is turned off. A transformer signal is related to an input voltage of the power converter. The control signal is generated when the on-time of the switching signal is longer than a first time threshold.

Abstract: The present invention proposes a method for controlling an adaptive power converter. The method comprises: generating an output-sense signal by sampling a reflected voltage of a transformer; receiving a feedback signal related to an output power of the adaptive power converter; generating a clock signal in response to the feedback signal and the output-sense signal; generating a switching signal for switching the transformer and regulating an output voltage of the adaptive power converter. The reflected voltage is correlated to the output voltage of the adaptive power converter. The switching signal is generated in response to the feedback signal. The frequency of the switching signal is determined by the clock signal. The frequency of the switching signal is decreased in response to a decrement of the feedback signal.

Abstract: The present invention provides a circuit for controlling a programmable power converter. The circuit includes a micro-controller, a controller, and a timer. The controller includes a voltage error amplifier. The micro-controller has a program memory and a data memory. The controller generates switching signals in response to a voltage-feedback signal for regulating an output voltage of the programmable power converter. The voltage error amplifier generates the voltage-feedback signal according to a voltage reference signal and the output voltage of the programmable power converter. A gain of the voltage error amplifier and a value of the reference signal are programmed by the micro-controller.

Abstract: A control circuit of a power converter and a method therefore are provided. The control circuit comprises an input circuit, an amplifier, a PWM circuit, and a power management circuit. The input circuit is coupled to a transformer to generate a sensing signal related to an output voltage of the power converter. The amplifier generates a feedback signal according to the sensing signal and a reference signal. The PWM circuit generates a switching signal according to the feedback signal for switching the transformer and regulating the output voltage of the power converter. The power management circuit controls the reference signal according to the feedback signal. The power management circuit includes a timer for determining a period, and the output voltage of the power converter decreases while an output power of the power converter is lower than a light-load threshold. A method for controlling the control circuit is also disclosed.

Abstract: A discharge circuit for an electromagnetic interference (EMI) filter is provided. The discharge circuit includes a switch circuit, a control circuit, and a detection circuit. The switch circuit is coupled to an X-capacitor of the EMI filter. The control circuit is coupled to the switch circuit and configured to turn on the switch circuit in a predetermined period to provide a discharge path. The detection circuit is coupled to the discharge path. In the predetermined period, the detection circuit detects whether a cross point occurs between a discharge voltage signal on the discharge path and a reference voltage signal to generate a detection signal which is provided to the control circuit. When the detection circuit detects that the cross point does not occur, the control circuit continuously turns on the switch circuit according to the detection signal after the predetermined period has elapsed.

Abstract: An active clamp circuit for a flyback power converter is provided. The active clamp circuit includes a power transistor, a capacitor, a high-side transistor driver, a charge-pump circuit, and a controller. The power transistor is coupled in series with a capacitor to develop an active-clamper. The active-damper is coupled in parallel with a primary winding of a transformer of the flyback power converter. The high-side transistor driver is coupled to drive the power transistor. The charge-pump circuit is coupled to a voltage source and the high-side transistor driver to provide a power supply to the high-side transistor driver. The controller generates a control signal coupled to control the high-side transistor driver. The control signal is generated in response to a demagnetizing time of the transformer.

Abstract: A control circuit and a method for controlling a power converter are provided. The method for controlling the power converter includes the following steps. A detection signal is received from the secondary side of the power transformer and a first switching signal is generated in accordance with the detection signal. A second switching signal is generated in accordance with the first switching signal. A voltage signal is generated in accordance with the second switching signal. A comparison signal is generated in accordance with the first switching signal and the second switching signal. The voltage signal and the comparison signal are compared for outputting a comparison result. A gate signal is generated in accordance with the detection signal and the comparison result to control on and off states of a synchronization switch.