Abstract: A flyback power converter includes a hybrid clamp circuit and a corresponding power management unit that substantially optimizes the performance of the flyback power converter in its entire line and load ranges. The clamp circuit, which is connected in parallel to a primary winding of the flyback transformer, includes a parallel combination of a capacitor and resistor that is connected in series with a parallel combination of a switch and a diode. By sensing the operating conditions, the power management circuit configures the clamp circuit either as a passive clamp or as an active clamp. In the passive-clamp configuration, the switch is kept turned off. In the active-clamp configuration, the switch operates with pulse-width modulation (PWM) which enables ZVS turn-on of the main switch.

Abstract: A flyback power converter includes a hybrid clamp circuit and a corresponding power management unit that substantially optimizes the performance of the flyback power converter in its entire line and load ranges. The clamp circuit, which is connected in parallel to a primary winding of the flyback transformer, includes a parallel combination of a capacitor and resistor that is connected in series with a parallel combination of a switch and a diode. By sensing the operating conditions, the power management circuit configures the clamp circuit either as a passive clamp or as an active clamp. In the passive-clamp configuration, the switch is kept turned off. In the active-clamp configuration, the switch operates with pulse-width modulation (PWM) which enables ZVS turn-on of the main switch.

Abstract: A time delay synchronous control scheme for a power supply, which has multiple outputs and tight output regulations, is provided. The switching mode power supply includes (1) a front-end DC/DC converter with current mode output, which can be a LLC Series Resonant converter (SRC) or a flyback converter; (2) one or several post buck converters directly cascaded from the output capacitor of the front-end DC/DC converter; (3) a new scheme of time delay synchronous control used to make the post buck synchronize and modulate from the front-end LLC-SRC or flyback converter. The proposed time delay synchronous control circuit can eliminate the conventional input filter of the post buck converters, as well as reduce the ripple current on the output capacitor of the front-end DC/DC converter, as a result of which, a high efficiency for the overall architecture can be obtained.

Abstract: A driving circuit comprises an input terminal receiving an input of a PWM signal, a first output terminal connected to a main switch for outputting a low-side driving signal, a second output terminal connected to an active switch for outputting a high-side driving signal, a first branch having a voltage level shifting capacitor and a first buffer connected in series between the input terminal and the second output terminal; and a second branch having a delay circuit and a second buffer connected in series between the input terminal and the first output terminal. When the input of the PWM signal turns from a low level to a high level, the voltage level shifting capacitor transmits the input of PWM signal to the first buffer for turning off the active switch and then triggering the second buffer to turn on the main switch with a short time delay.

Abstract: This invention provides an AC-to-DC power converter that improves the overall conversion efficiency especially that at the minimum input ac voltage for universal input operation design by adopting a new combination of control strategies and topologies for the PFC pre-regulator and DC-to-DC converter. The PFC pre-regulator was arranged to provide a regulated bus voltage of which the amplitude is varied in accordance with input ac voltage by a follower boost controller to achieve best efficiency in minimum input ac voltage operation. A synchronous rectifier dual boost PFC pre-regulator was present for further reduction of the power loss in the converter. Symmetrical half-bridge or symmetrical full bridge switch devices were arranged for the primary side of DC-to-DC converter and synchronous rectification circuit with two synchronous rectifier were arranged for the secondary side of the DC-to-DC converter as combination of the AC-to-DC converter.

Abstract: The present invention proposes an improved circuit design and configuration of a DC-DC converter with resonant reset. In this present invention, the active resonant snubber in parallel to a primary winding of a transformer of a DC-DC converter for resetting the transformer includes a resonant capacitor, an active switch connected to the resonant capacitor in series, an auxiliary diode coupled across the active switch in parallel, and an auxiliary winding coupled with the transformer. When a main switch of the DC-DC converter is turned off, the auxiliary winding turns on the active switch, and then the transformer is reset by a resonance between a magnetizing inductor of the transformer and the resonant capacitor.

Abstract: The present invention discloses a circuit that generates a variable frequency pulse width modulation (VF PWM) signal. Different from the conventional PWM controller, the frequency and duty cycle of the output PWM signal vary with the error-amplified voltage of the feedback loop simultaneously in this invention. The higher the error-amplified voltage of the feedback loop is, the lower the duty cycle with lower frequency will be. A very low duty cycle PWM signal can be generated stably while its frequency is very low.

Abstract: A power supply has a normal operation mode and a standby operation mode. The power supply includes a main circuit, a first control circuit, a second control circuit, and a switching controller. The main circuit has at least one output port for converting an input voltage into an output voltage at the output port. The first control circuit is used for controlling the main circuit under the normal operation mode. The second control circuit is used for controlling the main circuit under the standby operation mode. And, the switching controller processes a control signal to control the first control circuit and the second control circuit under either of the normal operation mode and the standby operation mode in response to a load status of the output port.