Abstract: A control circuit is configured to control a flyback circuit comprising a primary-side switch, a secondary-side rectifier and a transformer. The control circuit comprises a feedback control circuit configured to generate a secondary-side control signal based on a current ripple signal of the transformer, and at least one of a direct-current component of an output voltage signal and a direct-current component of an output current signal of a secondary side of the flyback circuit, wherein the secondary-side control signal is configured to control a turn-off of the secondary-side rectifier, an isolated transmission circuit coupled to the feedback control circuit and configured to generate a first primary-side control signal based on the secondary-side control signal, and a primary control circuit coupled to the isolated transmission circuit and configured to control a turn-on of the primary-side switch in response to receiving the first primary-side control signal.

Abstract: A synchronous rectifier control apparatus includes a continuous conduction mode detection circuit configured to receive a voltage across a synchronous rectifier switch and determine whether the synchronous rectifier switch operates in a continuous conduction mode based on a rising slope of the voltage across the synchronous rectifier switch, a turn-off timer control circuit configured to measure a conduction time of the synchronous rectifier switch and turn off the synchronous rectifier switch after the conduction time of the synchronous rectifier switch in a current cycle is substantially equal to the conduction time measured in an immediately previous cycle, and a drive voltage control circuit configured to reduce a gate drive voltage of the synchronous rectifier switch after the conduction time of the synchronous rectifier switch in the current cycle is substantially equal to the conduction time measured in the immediately previous cycle multiplied by a predetermined percentage.

Abstract: A synchronous rectifier control apparatus includes a continuous conduction mode detection circuit configured to receive a voltage across a synchronous rectifier switch and determine whether the synchronous rectifier switch operates in a continuous conduction mode based on a rising slope of the voltage across the synchronous rectifier switch, a turn-off timer control circuit configured to measure a conduction time of the synchronous rectifier switch and turn off the synchronous rectifier switch after the conduction time of the synchronous rectifier switch in a current cycle is substantially equal to the conduction time measured in an immediately previous cycle, and a drive voltage control circuit configured to reduce a gate drive voltage of the synchronous rectifier switch after the conduction time of the synchronous rectifier switch in the current cycle is substantially equal to the conduction time measured in the immediately previous cycle multiplied by a predetermined percentage.

Abstract: A control circuit is configured to control a flyback circuit comprising a primary-side switch, a secondary-side rectifier and a transformer. The control circuit comprises a feedback control circuit configured to generate a secondary-side control signal based on a current ripple signal of the transformer, and at least one of a direct-current component of an output voltage signal and a direct-current component of an output current signal of a secondary side of the flyback circuit, wherein the secondary-side control signal is configured to control a turn-off of the secondary-side rectifier, an isolated transmission circuit coupled to the feedback control circuit and configured to generate a first primary-side control signal based on the secondary-side control signal, and a primary control circuit coupled to the isolated transmission circuit and configured to control a turn-on of the primary-side switch in response to receiving the first primary-side control signal.

Abstract: A controller is for use in a power converter having a flyback transformer having a primary winding switched by a primary side transistor and a secondary winding switched by a secondary side transistor. The controller includes a line voltage detection circuit that activates a high line detect signal in response to detecting that an input line voltage is greater than a first threshold, a discontinuous conduction mode detection circuit activates a discontinuous conduction mode signal in response to detecting that the controller is operating in discontinuous conduction mode, and a switching controller coupled to the line voltage detection circuit and to the discontinuous conduction mode detection circuit that controls the primary side transistor and the secondary side transistor using partial zero voltage switching in response to an activation of the high line detect signal and the discontinuous conduction mode signal, and without using partial zero voltage switching otherwise.

Abstract: A controller is for use in a power converter having a flyback transformer having a primary winding switched by a primary side transistor and a secondary winding switched by a secondary side transistor. The controller includes a line voltage detection circuit that activates a high line detect signal in response to detecting that an input line voltage is greater than a first threshold, a discontinuous conduction mode detection circuit activates a discontinuous conduction mode signal in response to detecting that the controller is operating in discontinuous conduction mode, and a switching controller coupled to the line voltage detection circuit and to the discontinuous conduction mode detection circuit that controls the primary side transistor and the secondary side transistor using partial zero voltage switching in response to an activation of the high line detect signal and the discontinuous conduction mode signal, and without using partial zero voltage switching otherwise.

Abstract: A switched-mode power supply with near valley switching includes a quasi-resonant converter. The converter includes a switch element that is turned on not only at the valley, but also in a window range of ?tNVW close to the valley, where the voltage across the switch element is at its minimum. This advantageously reduces switching loss and maintains a balance between efficiency and frequency variation.

Abstract: A synchronous rectifier (SR) controller includes a controller having an input adapted to be coupled to a drain of an SR transistor, and an output for providing a drive signal in response thereto, a gate driver having an input coupled to the output of the controller, and an output adapted to be coupled to a gate of the SR transistor for providing a gate signal thereto, a first transistor having a drain coupled to the gate terminal, a gate, and a source coupled to ground, and a protection circuit having an input coupled to the drain terminal, and an output coupled to the gate of the first transistor. The protection circuit is responsive to a voltage on the drain terminal exceeding a first voltage to provide a voltage on the gate of the first transistor greater than a turn-on voltage and less than an overvoltage of the first transistor.

Abstract: A switched-mode power supply with near valley switching includes a quasi-resonant converter. The converter includes a switch element that is turned on not only at the valley, but also in a window range of ?tNVW close to the valley, where the voltage across the switch element is at its minimum. This advantageously reduces switching loss and maintains a balance between efficiency and frequency variation.

Abstract: A switched-mode power supply with near valley switching includes a quasi-resonant converter. The converter includes a switch element that is turned on not only at the valley, but also in a window range of ?tNVW close to the valley, where the voltage across the switch element is at its minimum. This advantageously reduces switching loss and maintains a balance between efficiency and frequency variation.

Abstract: A synchronous rectifier (SR) controller includes a controller having an input adapted to be coupled to a drain of an SR transistor, and an output for providing a drive signal in response thereto, a gate driver having an input coupled to the output of the controller, and an output adapted to be coupled to a gate of the SR transistor for providing a gate signal thereto, a first transistor having a drain coupled to the gate terminal, a gate, and a source coupled to ground, and a protection circuit having an input coupled to the drain terminal, and an output coupled to the gate of the first transistor. The protection circuit is responsive to a voltage on the drain terminal exceeding a first voltage to provide a voltage on the gate of the first transistor greater than a turn-on voltage and less than an overvoltage of the first transistor.

Abstract: A switched-mode power supply with near valley switching includes a quasi-resonant converter. The converter includes a switch element that is turned on not only at the valley, but also in a window range of ?tNVW close to the valley, where the voltage across the switch element is at its minimum. This advantageously reduces switching loss and maintains a balance between efficiency and frequency variation.

Abstract: A control circuit of a flyback power converter according to the present invention comprises a low-side transistor, an active-clamper, a high-side drive circuit, and a controller. The low-side transistor is coupled to switch a transformer. The active-clamper is coupled in parallel with the transformer. The high-side drive circuit is coupled to drive the active-clamper. The controller generates a switching signal and an active-clamp signal. The switching signal is coupled to drive the low-side transistor. The switching signal is generated in accordance with a feedback signal for regulating an output of the flyback power converter. The active-clamp signal is coupled to control the high-side drive circuit and the active-clamper. The active-clamp signal is generated in response to a demagnetizing time of the transformer. The pulse number of the active-clamp signal is less than the pulse number of the switching signal in a light load condition.

Abstract: A control circuit of a power converter according to the present invention comprises a switching circuit, a sample-and-hold circuit and a current source. The switching circuit generates a switching signal in response to a feedback signal. The sample-and-hold circuit samples the feedback signal. The current source is coupled to a feedback terminal for generating a programming voltage. A programmable signal is generated in accordance with the programming voltage and the feedback signal, and the programmable signal is coupled to set a parameter.

Abstract: A control circuit of a flyback power converter according to the present invention comprises a low-side transistor, an active-damper, a high-side drive circuit, and a controller. The low-side transistor is coupled to switch a transformer. The active-damper is coupled in parallel with the transformer. The high-side drive circuit is coupled to drive the active-clamper. The controller generates a switching signal and an active-clamp signal. The switching signal is coupled to drive the low-side transistor. The switching signal is generated in accordance with a feedback signal for regulating an output of the flyback power converter. The active-clamp signal is coupled to control the high-side drive circuit and the active-damper. The active-clamp signal is generated in response to a demagnetizing time of the transformer. The pulse number of the active-clamp signal is less than the pulse number of the switching signal in a light load condition.

Abstract: The present invention provides a high-side signal sensing circuit. The high-side signal sensing circuit comprises a signal-to-current converter, a second transistor and a resistor. The signal-to-current converter has a first transistor generating a mirror current in response to an input signal. The second transistor cascaded with the first transistor is coupled to receive the mirror current. The resistor generates an output signal in response to the mirror current. Wherein, the level of the output signal is corrected to the level of the input signal.

Abstract: The present invention provides a high-side signal sensing circuit. The high-side signal sensing circuit comprises a signal-to-current converter, a second transistor and a resistor. The signal-to-current converter has a first transistor generating a mirror current in response to an input signal. The second transistor cascaded with the first transistor is coupled to receive the mirror current. The resistor generates an output signal in response to the mirror current. Wherein, the level of the output signal is corrected to the level of the input signal.

Abstract: A control circuit of a power converter according to the present invention comprises a switching circuit, a sample-and-hold circuit and a current source. The switching circuit generates a switching signal in response to a feedback signal. The sample-and-hold circuit samples the feedback signal. The current source is coupled to a feedback terminal for generating a programming voltage. A programmable signal is generated in accordance with the programming voltage and the feedback signal, and the programmable signal is coupled to set a parameter.