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: 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.

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: A cost effective circuit improves the cross regulation of multiple outputs converter, especially for that output chokes are coupled and a synchronous rectifier is applied to one of the outputs. A DC/DC converter includes a transformer having a primary winding and two secondary windings. The first secondary winding is coupled to a synchronous rectifier and a first output choke. The second secondary winding is coupled to a diode rectifier and a second output choke. The first output choke and the second output choke are coupled. A low power MOSFET switch is added to the diode rectifier for avoiding the diode rectifier operating in DCM when light loaded.

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 proposes a synchronous rectifier with burst mode control.

Abstract: The present invention proposes a new structure for a high input VRM. This structure is similar to a simple buck converter and can simplify the 48V input VRM design. In this present invention, the interleaved voltage regulator is provided. The interleaved voltage regulator includes an integrated magnetic device for performing both transformer and output choke filter function, a first switch, a second switch, a third switch, and a fourth switch, wherein the integrated magnetic device includes a transformer having a first primary winding, a second primary winding, a first secondary winding, and a second secondary winding, a first choke filter having one end coupled to a first terminal of the first secondary winding, and a second choke filter having one end coupled to a first terminal of the second secondary winding, and the other end of the second choke filter coupled to the other end of the first choke filter to form the output terminal of the isolated voltage regulator.

Abstract: A cost effective circuit improves the cross regulation of multiple outputs converter, especially for that output chokes are coupled and a synchronous rectifier is applied to one of the outputs. A DC/DC converter includes a transformer having a primary winding and two secondary windings. The first secondary winding is coupled to a synchronous rectifier and a first output choke. The second secondary winding is coupled to a diode rectifier and a second output choke. The first output choke and the second output choke are coupled. A low power MOSFET switch is added to the diode rectifier for avoiding the diode rectifier operating in DCM when light loaded.

Abstract: The present invention proposes a new structure for a high input VRM. This structure is similar to a simple buck converter and can simplify the 48V input VRM design. In this present invention, the interleaved voltage regulator is provided. The interleaved voltage regulator includes an integrated magnetic device for performing both transformer and output choke filter function, a first switch, a second switch, a third switch, and a fourth switch, wherein the integrated magnetic device includes a transformer having a first primary winding, a second primary winding, a first secondary winding, and a second secondary winding, a first choke filter having one end coupled to a first terminal of the first secondary winding, and a second choke filter having one end coupled to a first terminal of the second secondary winding, and the other end of the second choke filter coupled to the other end of the first choke filter to form the output terminal of the isolated voltage regulator.

Abstract: A transformer isolated gate driver for realizing the driving of a power switch (a MOSFET) includes a PWM driver, an input capacitor, a transformer, an output diode, a active switch (a small power MOSFET) having a gate and a source connected to the first and second terminals of the secondary winding of the transformer respectively, an output capacitor connected to one of the first terminal of the transformer and a drain of the active switch in series, and a series connected circuit having the first and second terminals of the transformer, the output capacitor, the output diode, and the active switch. The charges across an equivalent input capacitor of the power switch are discharged through the series connected circuit. When the PWM signal is pulled to zero from normal operation, the driving signal on the power switch is kept zero also.

Abstract: The invention relates to an active snubber for synchronous rectifier. The active snubber is coupled across a synchronous rectifier having a first synchronous MOSFET and a second synchronous MOSFET coupled to a transformer in a power converter. The active snubber includes a series-coupled active switch and first snubber capacitor which is coupled between a drain terminal and a source terminal of the first synchronous MOSFET, a gate driver operative to keep the active switch conducting a specified period of time during a non-conduction interval of the first synchronous MOSFET. The gate driver is composed of an auxiliary winding, a capacitor, and a resistor, wherein the auxiliary winding and the capacitor are connected in series and then coupled across the resistor in parallel, which is coupled between a gate and a source of the active switch.

Abstract: The present invention proposes a synchronous rectifier with burst mode control.

Abstract: A package for power converters in which all parts are electrically connected with one multi-layer circuit board. A sub-package with at least a power-dissipating chip, having a bare top up-facing heat-slug is electrically connected with the board by a plurality of symmetric leads. A heat spreader is directly attached onto the bare top heat-slug of the sub-packages, planar magnetic parts and top surfaces of other components with thermally conductive insulator. The heat dissipated by the sub-packages is transferred to the attached heat spreader by the bare top heat-slug, and further transferred to the ambient. The assembly features compact and inexpensive power converter package with improved electrical performance and enhanced thermal management.

Abstract: An active clamped-mode DC-to-DC converter with synchronous rectifiers and a combined transformer-inductor device is provided. The power converter includes a combined transformer-inductor device having a primary winding, a secondary winding, and an auxiliary winding where the primary and the secondary windings perform a transformer function and the auxiliary winding performs an output filter function, a switching circuit for periodically providing a positive voltage to the primary winding and a negative voltage to reset the primary winding, and a synchronous rectification circuit connected for enabling conduction from the secondary winding to an output port in which the auxiliary winding is coupled between the output port and the synchronous rectification circuit for providing an inductance to filter an output signal.

Abstract: A constant voltage reset circuit used in a forward converter for the holdup time requirement or the wide input voltage range is disclosed. In one embodiment, the constant voltage reset circuit comprises a reset capacitor, a parallel-coupled switch, and a diode coupled in series with the reset capacitor which is configured to cooperate therewith to reset an energy from the transformer. The forward converter employing the reset circuit or the method achieves a higher efficiency with a larger turn ratio and without the 50% limitation of maximum duty cycle.

Abstract: A package for power converters in which all parts are electrically connected with one multi-layer circuit board. A sub-package with at least a power-dissipating chip, having a bare top up-facing heat-slug is electrically connected with the board by a plurality of symmetric leads. A heat spreader is directly attached onto the bare top heat-slug of the sub-packages, planar magnetic parts and top surfaces of other components with thermally conductive insulator. The heat dissipated by the sub-packages is transferred to the attached heat spreader by the bare top heat-slug, and further transferred to the ambient. The assembly features compact and inexpensive power converter package with improved electrical performance and enhanced thermal management.

Abstract: An active clamped-mode DC-to-DC converter with synchronous rectifiers and a combined transformer-inductor device is provided. The power converter includes a combined transformer-inductor device having a primary winding, a secondary winding, and an auxiliary winding where the primary and the secondary windings perform a transformer function and the auxiliary winding performs an output filter function, a switching circuit for periodically providing a positive voltage to the primary winding and a negative voltage to reset the primary winding, and a synchronous rectification circuit connected for enabling conduction from the secondary winding to an output port in which the auxiliary winding is coupled between the output port and the synchronous rectification circuit for providing an inductance to filter an output signal.

Abstract: A constant voltage reset circuit used in a forward converter for holdup time requirement or wide input voltage range is disclosed. In one embodiment, the constant voltage reset circuit comprises (1) a reset capacitor, and (2) a parallel-coupled switch and a diode coupled in series with the reset capacitor which is configured to cooperate therewith to reset an energy from the transformer. The forward converter employing the reset circuit or the method achieves high efficiency with large turn ratio and without 50% limitation of maximum duty cycle.

Abstract: An energy storage circuit for a wide input voltage range DC-DC converter with holdup time requirement. The energy storage circuit comprises (1) an energy storage capacitor, (2) a charging path including a diode connected in series with a current limiting resistor coupled in series with the energy storage capacitor, (3) a discharging path including a parallel-coupled switch and a diode coupled in series with a filtering inductor which is coupled in series with the energy storage capacitor, and (4) a logic control unit coupled to the switch for turning the switch of the discharge path on and off.