Power-one Limited

Amrit P Patel

A multiple output voltage power supply includes a transformer having a primary winding and a plurality of secondary windings. The primary winding is adapted to have an input voltage coupled thereto. A primary side switch is coupled to the primary winding and is adapted to control power applied to the transformer in a power cycle responsive to a peak current mode control signal. A plurality of output circuits are coupled to respective ones of the plurality of secondary windings and provide respective output voltages. The plurality of output circuits each further includes a forward rectifier adapted to rectify power during a positive portion of the power cycle and a free-wheeling rectifier adapted to rectify power during a negative portion of the power cycle. One of the plurality of output circuits further includes a bypass switch adapted to interrupt operation of the respective forward rectifier. A secondary side post regulation circuit controls operation of the bypass switch. The post regulation circuit further includes a signal generator adapted to receive a synchronization signal corresponding to the power cycle. The signal generator generates a sawtooth waveform that rises during a positive portion of the synchronization signal and falls during a zero portion of the synchronization signal. A Schmidt trigger coupled to the signal generator has an enabled state when a leading edge of the sawtooth waveform reaches a threshold level and a disabled state when the synchronization signal falls to zero. A driver coupled to the Schmidt trigger generates a drive signal used to control the bypass switch in accordance with the enabled and disabled states of the Schmidt trigger.

Leading edge modulator for post regulation of multiple output voltage power supplies

A forward converter circuit has substantially reduced switching losses to provide greater efficiency than the aforementioned conventional circuit. A first switch is coupled to a primary winding of a transformer and adapted to selectively couple a bus voltage terminal to a first terminal of the primary winding. A second switch is coupled to the transformer and adapted to selectively couple a second terminal of the primary winding to ground. The first and second switches are triggered in response to a first periodic gate control signal. A diode is coupled between the bus voltage terminal and the second terminal of the primary winding of the transformer. A third switch is coupled to the transformer and adapted to selectively couple the first terminal of the primary winding of the transformer to ground. The third switch is triggered in response to a second periodic gate control signal. The second periodic gate control signal is substantially inverted with respect to the first periodic gate control signal. A capacitor is coupled in parallel with the second switch. Power from the bus voltage terminal is transferred from the primary winding to the secondary winding of the transformer during a portion of an operational cycle of the forward converter circuit with the first and second switches being in a conductive state responsive to the first periodic gate control signal.

Forward converter circuit having reduced switching losses

A power converter has a self-driven synchronous rectification circuit that can operate efficiently with a non-optimal reset secondary voltage waveform that remains at a zero voltage level during a portion of the switching cycle. The power converter circuit includes a transformer having a primary winding and a secondary winding, in which primary winding is supplied with a non-optimal reset waveform that remains at a zero voltage level for a portion of a power cycle thereof. A first synchronous rectifier is connected in series with the first end of the secondary winding and is controlled by a voltage at the second end of the secondary winding. A second synchronous rectifier is connected in series with the second end of the secondary winding, and is further connected to an output terminal of the power converter circuit through a storage choke. A saturable reactor is connected in series between the first synchronous rectifier and the first end of the secondary winding. A switching device is connected to the first end of the secondary winding and is controlled by the voltage at the second end of the secondary winding. The switching device further controls the second synchronous rectifier. A capacitor is connected to the second synchronous rectifier, and is charged by operation of the switching device to maintain the second synchronous rectifier in a conductive state during the zero voltage level portion of the non-optimal reset waveform. Upon transition to a positive voltage level portion of the waveform following the zero voltage level portion, the capacitor discharges through the switching device. The saturable reactor precludes current from flowing through the first synchronous rectifier for a period of time sufficient to allow the capacitor to discharge.

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Camarillo, CA, United States of America

Amrit P Patel