A power-factor-corrected switching power supply includes a power-factor-corrector cell followed by a current-fed dc/dc converter cell. Both cells operate in discontinuous current mode. A duty cycle modulator has its input coupled to the output of the current-fed dc/dc converter cell and its output coupled to the switch control inputs of both the PFC cell and the current-fed dc/dc converter cell so that both cells receive the same control signal.

A transformer assembly in which an isolation transformer and two additional inductor elements of a series/parallel resonant converter are physically integrated in a cost and space-efficient design. The transformer and two inductors are integrated through the simultaneous control of the leakage inductance and the magnetizing inductance of the assembly. The primary and secondary windings of the transformer are wound in a prescribed manner on a closed-path ferromagnetic core, the magnetizing inductance of the unit being determined by the desired inductance of second inductor, and the leakage inductance of the unit being determined by the inductance of the first inductor, which predominates the total series inductance of the tank circuit. The desired magnetizing inductance is achieved by controlling an air gap disposed in the magnetic flux path of the core, while the desired leakage inductance is achieved by winding a certain portion of the secondary turns on a loosely coupled leg of the core. A non-magnetic housing and spring clamp hold the assembly and maintain the air gap constant.

A series resonant circuit device and a voltage stabilizing method thereof are provided. The series resonant circuit device includes a resonant circuit having at least a resonant capacitor and a resonant inductor, an equivalent capacitor electrically coupled to the resonant circuit, a magnetizing inductor electrically connected to the equivalent capacitor in parallel, a transformer having a primary winding electrically connected to the magnetizing inductor in parallel, and a current impulse circuit electrically coupled to the resonant circuit and synchronized with an input voltage of the series resonant circuit device. The voltage stabilizing method is to provide a current impulse to the equivalent capacitor so as to decrease a current difference between the resonant inductor and the magnetizing inductor when the input voltage varies.

The present invention relates to a power converter which uses pulse width modulated (PWM) control to provide a galvanically isolated dc output. Topologically, the converter uses a full-bridge switching scheme with a boost converter, and can be referred to as an isolated boost converter. The converter includes an ancillary circuit comprised of a switch transistor and a series connected capacitor which act as an active clamp. The converter of the present invention allows for a number of significant advantages. The converter provides zero voltage transitions in all switches, thereby preventing losses due to leakage currents in the switching transistors during switching transitions. The converter further provides a path for transformer magnetizing current flow, and also clamps the leakage inductance related to voltage spikes across the switches. These advantages allow the converter to keep stress on the active components low which makes the circuit more efficient. The circuit of the present invention has a simple structure which gives it good power density and makes it inexpensive, and is also capable of high frequency operation.

In a power factor corrected AC-to-DC power supply system, a DC-to-DC power converter is coupled to the output of an AC-to-DC power converter in order to produce a regulated DC output signal from a rectified AC input signal. The AC-to-DC power converter and the DC-to-DC power converter each includes a switch for controlling the operation of their respective power converter. The AC-to-DC converter includes an inductor. The system provides power factor correction for minimizing harmonic distortion by including a controller that receives the regulated DC output voltage as a feedback signal, and in response, produces a series of drive pulses having predetermined constant duty cycle. These pulses are simultaneously fed to each switch, to operate the respective converters alternately between ON and OFF states. When the AC-to-DC converter is driven by a fixed duty cycle of the series of pulses, power factor correction is improved since the current flowing through the inductor is substantially proportional to the waveform of the rectified AC input signal. By preselecting the value of the inductor, the AC-to-DC converter is operable in a discontinuous mode when the instantaneous rectified AC input signal is low and in a continuous mode when the instantaneous rectified AC input signal is high.