Abstract: A ZVS (zero voltage switching) control circuit for use in a flyback power converter includes a primary side controller circuit, a secondary side controller circuit, and a pulse transformer. In one switching cycle, a synchronous rectifier transistor is turned ON twice to generate a circulation current at the primary side winding, and after the synchronous rectifier transistor is turned OFF, the power transistor is turned ON for zero voltage switching. A synchronous signal coupled between the primary side and the secondary side is employed to synchronize the power transistor and the synchronous transistor. The synchronous signal also triggers an SR-ZVS pulse to turn ON the synchronous rectifier transistor for achieving the zero voltage switching when the power transistor is turned ON.

Abstract: A ZVS (zero voltage switching) control circuit for use in a flyback power converter includes a primary side controller circuit, a secondary side controller circuit, and a pulse transformer. In one switching cycle, a synchronous rectifier transistor is turned ON twice to generate a circulation current at the primary side winding, and after the synchronous rectifier transistor is turned OFF, the power transistor is turned ON for zero voltage switching. A synchronous signal coupled between the primary side and the secondary side is employed to synchronize the power transistor and the synchronous transistor. The synchronous signal also triggers an SR-ZVS pulse to turn ON the synchronous rectifier transistor for achieving the zero voltage switching when the power transistor is turned ON.

Abstract: A flyback power converter includes a transformer, a power switch, a power switch control circuit, a synchronous rectification (SR) switch, an SR switch control circuit, and a signal coupler circuit. The signal coupler circuit includes a primary port and a secondary port, wherein the primary port is electrically connected to the power switch control circuit, and the secondary port is electrically connected to the SR switch control circuit. The primary port and the secondary port receive different signals generated by the power switch control circuit and the SR switch control circuit respectively, and the signal coupler circuit senses and converts the different signals to generate corresponding converted signals at the secondary port and the primary port respectively in different and non-overlapping time periods, without direct contact or direct connection between the primary side and the secondary side of the transformer.

Abstract: A flyback power converter includes a transformer, a power switch, a power switch control circuit, a synchronous rectification (SR) switch, an SR switch control circuit, and a signal coupler circuit. The signal coupler circuit includes a primary port and a secondary port, wherein the primary port is electrically connected to the power switch control circuit, and the secondary port is electrically connected to the SR switch control circuit. The primary port and the secondary port receive different signals generated by the power switch control circuit and the SR switch control circuit respectively, and the signal coupler circuit senses and converts the different signals to generate corresponding converted signals at the secondary port and the primary port respectively in different and non-overlapping time periods, without direct contact or direct connection between the primary side and the secondary side of the transformer.

Abstract: The present invention discloses a power converter with synchronous control function and control method thereof. The power converter includes: a transformer, a power switch, a switch control unit, a signal coupling circuit, a synchronous rectifying switch and a secondary side control circuit. The switch control unit generates an operation signal according to a feedback signal, and generates a first synchronous signal which is related to the operation signal. The signal coupling circuit couples the first synchronous signal to generate a second synchronous signal. The synchronous rectifying switch is turned ON/OFF according to a synchronous rectifying switch signal, for synchronous rectification. The secondary side control circuit generates the synchronous rectifying switch signal according to a secondary side level detection signal and the second synchronous signal, to control the synchronous rectifying switch. The ON time of the power switch and the ON time of the synchronous rectifying switch do not overlap.

Abstract: The present invention provides a flyback power converter and a control circuit thereof. The flyback power converter includes a transformer, a power switch, a driver, a synchronous rectification (SR) switch, a controller, and a signal coupler circuit. The transformer has a primary winding and a secondary winding. The power switch controls the conduction time of the primary winding; and the SR switch controls the conduction time of the secondary winding. The controller controls the SR switch and generates an ON pulse signal and an OFF pulse signal in a normal operation mode. When an output voltage reaches a lower limit voltage, the flyback power converter operates in the normal operation mode. The driver generates a switching signal according to the ON pulse signal and the OFF pulse signal in the normal operation mode, to determine a start conduction time point and an end conduction time point of the primary winding.

Abstract: The present invention provides a flyback power converter and a control circuit and a control method thereof. The flyback power converter includes: a power stage circuit, a voltage sense circuit, a current sense circuit, and a control circuit. When the flyback power converter operates in a quasi-resonant mode, the control circuit determines a time point of turning OFF a power switch in the power stage circuit according to a current sense signal, a pulse width modulation (PWM) frequency of a PWM signal, and a predetermined threshold, wherein the control circuit adaptively adjusts an ON period of the power switch, or adaptively adjusts an operation bandwidth or an amplifier gain of an error amplifier circuit in a feedback control loop according to the PWM frequency to mitigate an output voltage ripple.

Abstract: The present invention discloses a power converter with synchronous control function and control method thereof. The power converter includes: a transformer, a power switch, a switch control unit, a signal coupling circuit, a synchronous rectifying switch and a secondary side control circuit. The switch control unit generates an operation signal according to a feedback signal, and generates a first synchronous signal which is related to the operation signal. The signal coupling circuit couples the first synchronous signal to generate a second synchronous signal. The synchronous rectifying switch is turned ON/OFF according to a synchronous rectifying switch signal, for synchronous rectification. The secondary side control circuit generates the synchronous rectifying switch signal according to a secondary side level detection signal and the second synchronous signal, to control the synchronous rectifying switch. The ON time of the power switch and the ON time of the synchronous rectifying switch do not overlap.

Abstract: The present invention provides a flyback power converter and a control circuit thereof. The flyback power converter includes a transformer, a power switch, a driver, a synchronous rectification (SR) switch, a controller, and a signal coupler circuit. The transformer has a primary winding and a secondary winding. The power switch controls the conduction time of the primary winding; and the SR switch controls the conduction time of the secondary winding. The controller controls the SR switch and generates an ON pulse signal and an OFF pulse signal in a normal operation mode. When an output voltage reaches a lower limit voltage, the flyback power converter operates in the normal operation mode. The driver generates a switching signal according to the ON pulse signal and the OFF pulse signal in the normal operation mode, to determine a start conduction time point and an end conduction time point of the primary winding.

Abstract: The present invention provides a flyback power converter and a control circuit and a control method thereof. The flyback power converter includes: a power stage circuit, a voltage sense circuit, a current sense circuit, and a control circuit. When the flyback power converter operates in a quasi-resonant mode, the control circuit determines a time point of turning OFF a power switch in the power stage circuit according to a current sense signal, a pulse width modulation (PWM) frequency of a PWM signal, and a predetermined threshold, wherein the control circuit adaptively adjusts an ON period of the power switch, or adaptively adjusts an operation bandwidth or an amplifier gain of an error amplifier circuit in a feedback control loop according to the PWM frequency to mitigate an output voltage ripple.