A drive circuit for driving a rectifier switch, a method of driving the rectifier switch and a power converter employing the drive circuit or the method. In one embodiment, the drive circuit includes (1) a blocking diode couplable to a bias energy source and configured to block reverse current flow thereto, (2) an inductor coupled to the rectifier switch, and (3) a switching circuit, coupled to the blocking diode and the inductor, configured to: (3a) resonantly transfer energy from the bias energy source to a control terminal of the rectifier switch via the inductor to turn the rectifier switch ON, and (3b) resonantly discharge the energy through the control terminal to turn the rectifier switch OFF.
A MOSFET is used as a synchronous rectifier in a fly-back DC/DC converter and connected in series with a secondary winding of a transformer. The MOSFET is repetitively turned on and off in response to the turning off and on of a primary switch connected in series with a primary winding of the transformer. Circuit elements on the secondary winding side detect voltage transients across the MOSFET caused by reverse currents when it is turned off and shorten at least a next on-period of the MOSFET in response to the detection of such transients.
A DC-DC converter having a switching element and a synchronous rectifier, the switching element undergoing a switching operation, the converter performing a voltage conversion of an input voltage to provide a converted output voltage at an output/input conversion ratio that is determined by the switching operation of said switching element, the converter delivering the converted output voltage to a load, said DC-DC converter further comprising: a reverse current detector for detecting a reverse current which flows from an output of the converter to an input of the converter, and a reverse current suppressor, the reverse current suppressor controlling the switching operation of said switching element so as to increase the output/input conversion ratio when a reverse current is detected by the reverse current detector, thereby suppressing the reverse current.
A switch mode power supply (200, FIG. 2; 600, FIG. 6) includes a transformer (208), a transistor (212) that drives the primary winding of the transformer, and a controller (210, 610). The controller senses whether or not the transformer is reset and applies a switching control signal to a control terminal (220) of the transistor, accordingly. The signal is produced at a switching frequency, and the signal has a duty cycle that is limited based on whether or not the transformer is reset.
A circuit for synchronous rectification including two power MOSFET transistor switches in which the bottom switch is a P channel MOSFET, rather than an N channel MOSFET. The circuit of the present invention uses a single channel driver, rather than a dual driver and eliminates the deadtime associated with conventional circuits, thus minimizing reverse recovery losses. In an alternative arrangement, the position of the output filter is switched so that the N channel MOSFET conducts during the freewheeling time and the P channel MOSFET (with a larger RDSON) conducts during the conductor charge cycle.
The present invention provides a self-driving circuit of a low voltage, large current, and high power density DC/DC converter. The converter comprises a transformer, power MOS transistors (S), output rectification portion (SRb 1, SR2), filter portion and demagnetizing portion. The first configuration of the self-driving circuit consists of Da, Ra, Ca, Qa for self-driving SR2; and the second configuration consists of Da, Ra, Sa, a delay driving circuit and an isolation differential circuit, for self-driving SR2. The self-driving circuit of the present invention may reduce the cross-conductive loss, and increase the converting efficiency.
