A synchronous rectifier circuit employs therein a pair of synchronously-operated switches, each switch being coupled between a separate respective input terminal and an output terminal of the circuit. One of the synchronously-operated switches is gated ON when a voltage applied across the synchronous rectifier circuit input terminals is of one polarity, and is gated OFF when current therein becomes substantially zero. The second switch is gated ON when a voltage applied across the input terminals is of the opposite polarity, and is gated OFF when current therein becomes substantially zero.
For use in a power converter having a power switch and a synchronous rectifier device coupled between input and output thereof, a control circuit, method of disabling a synchronous rectifier device and power converter employing the control circuit and method. In one embodiment, the control circuit includes a synchronous rectifier controller, coupled to the output of the converter and the synchronous rectifier device, that senses time derivative of the output voltage and disables the synchronous rectifier when derivative is negative and greater than a predetermined magnitude.
A power supply Active Bleed Voltage Balancing Circuit for attachment to the outputs of a regulated power supply having at least a first output and a second output to shunt load power from an output that has become unloaded and has an output voltage that is rising past an acceptable limit. The Active Bleed Voltage Balancing Circuit has an inductor with a first terminal coupled to the first power supply output. The second output voltage exceeds the first output voltage. An oscillator driven totem-pole driver alternately drives the inductors second terminal to the power supply second output and then to ground. The duty cycle ratio is adjusted to equalize the volt-seconds applied in each position. An alternative circuit uses a multiple winding inductor with a 50/50 duty cycle and with balancing achieved by adjusting the turns ratio to equal the ratio of the output voltages.
A method and apparatus are disclosed for sustaining efficiency of switched mode power converters over wide load ranges. The method and apparatus can be used with any switched mode power converter having at least one synchronous rectifier (Q.sub.2) capable of being enabled or disabled and coupled, either by direct connection or otherwise, to an inductor (L.sub.1) and a diode rectifier (D.sub.1), to provide a current path for the inductor current when the synchronous rectifier (Q.sub.2) is disabled. The power converter is initialized by enabling the synchronous rectifier (Q.sub.2). Occasionally, the synchronous rectifier (Q.sub.2) is disabled, and the energy stored in the inductor (L.sub.1) is detected by sensing a voltage representative of the energy stored in the inductor (L.sub.1). A power level signal is then generated indicating whether the power converter is operating above a selected threshold. The power converter is configured in response to the power level signal by enabling the synchronous rectifier (Q.sub.2) if the power level is above the threshold or by disabling the synchronous rectifier (Q.sub.2) otherwise. The steps of disabling, detecting, generating, and configuring are repeated.
The present invention sets forth multiple embodiments of an electrical circuit which rectifies alternating current in a manner which results in very little electrical loss. This is in contrast to conventional rectifier circuits that use simple diode configurations which typically give rise to voltage losses from 0.4 volts to 1.0 volts.
A pulse-width modulated, bi-directional DC-to-DC voltage converter having a regulated output, and capable of converting between a high-potential direct current voltage and a low-potential direct current voltage. The converter's magnetic components, as well as several of its semiconductor rectifiers, perform dual functions (one in the step-up mode, and another in the step-down mode), which serves to minimize the total component count, and allows the converter to be both compact and lightweight.
