Abstract:
A rectifier circuit for use in a power supply to convert ac input power to dc output power to supply a dc load provides for reduced rectifier circuit power dissipation. The power supply includes a first ac source input line, a second ac source input line, a DC power supply line, and a DC power return line. The rectifier circuit includes a first field effect transistor (FET) having its drain coupled to the first ac source input line and its source coupled to the DC power return line, and a second FET having its drain coupled to the second ac source input line and its source coupled to the DC power return line. During an ac cycle, the first FET closes during the positive half cycle and the second FET closes during the negative half cycle.
Abstract:
A method and apparatus for converting AC power to DC power with increased efficiency. One embodiment of the method adjusts the switching frequency of the AC to DC converter base on the load. Another embodiment of the method optimizes the output boost voltage of the AC to DC converter.
Abstract:
An AC-DC power converter controls an external upstream switching device, which supplies it power to be converted. Power conversion is initiated when an external signal requests power be converted or when a program within the AC-DC power converter detects the need for power conversion. When this occurs, the AC-DC power converter signals the external switching device, which is upstream of the AC-DC power converter to turn on, thereby supplying the power to be converted to the AC-DC power converter.
Abstract:
A self-driven synchronous rectifier circuit (50) for a DC-DC power converter. The circuit comprises a primary transformer (16), a first synchronous rectifier (SQ1) coupled to the primary transformer (16), a second synchronous rectifier (SQ2) coupled to the primary transformer (16), an external drive circuit (18). The circuit (50) also comprises a plurality of switches (SQ3, SQ4) controllably coupled to second synchronous rectifier (SQ2). The external drive circuit (18) provides turn-off signaling for both synchronous rectifiers (SQ1, SQ2). Turn-on signaling provided for first synchronous rectifier (SQ1) by the primary transformer (16) turn-on signaling for second synchronous rectifier (SQ2) is provided by the external drive circuit (18).
Abstract:
The present invention provides a method for preventing a fault condition in a DC-DC converter (10, 20, 50) having a first secondary winding (Ns1) coupled to a first synchronous rectifier (SQ1) and a second secondary winding (Ns2) coupled to a second synchronous rectifier (SQ2). The first synchronous rectifier (SQ1) is turned on based on a voltage across the first secondary winding (Ns1) and is turned off based on a first driver signal. The second synchronous rectifier (SQ2) is turned on based on a voltage across the second secondary winding (Ns2) and is turned off based on a second driver signal. The present invention also provides a DC-DC converter (10, 20, 50) wherein a first control circuit is coupled to and controls the first synchronous rectifier (SQ1) pursuant to the method described above, and a second control circuit is coupled to and controls the second synchronous rectifier (SQ2) pursuant to the method described above.