Abstract: A single-stage input-current-shaping (S.sup.2 ICS) converter of the present invention integrates a voltage-doubler-rectifier front-end with a DC/DC output stage. Two families of voltage-doubler S.sup.2 ICS converters are disclosed. In one family, a 2-terminal dither source is provided between a boost inductor and a common input terminal of a storage capacitor and the DC/DC output stage. The 2-terminal dither source includes two paths connected in parallel: a first path for charging and a second path for discharging the boost inductor at a high frequency (HF). In the other family, a 3-terminal dither source includes a third terminal coupled to a pulsating node of the DC/DC output stage.

Abstract: A circuit technique substantially reduces the switching losses of a pulse-width-modulated (PWM) converter caused by the turning-on (closing) and turning-off (opening) characteristic of the switch and the reverse-recovery characteristic of the rectifier. The losses are reduced by using a new switch cell which includes a snubber inductor, a clamp diode, a clamp capacitor, a main switch, and an auxiliary switch. The reverse-recovery-related losses are reduced by the snubber inductor connected in series with the main switch and the rectifier to control the rate of change of rectifier current during its turn-off. In addition, the main switch operates with zero-current and zero-voltage switching, while the auxiliary switch operates with zero-voltage switching. A proper operation of the proposed circuit requires overlapping gate drives of the main and the auxiliary switches. The circuit technique can be applied to any member of the PWM converter family.

Abstract: A three-phase discontinuous-conduction-mode (DCM), pulse-width-modulated (PWM) boost rectifier using harmonic-injection control is provided with a feedforward path to vary the duty cycle of the PWM modulator according to the input voltage, so as to provide improved transient response. In one embodiment, the feedforward path provides to the PWM modulator a ramp voltage that has a slope proportional to the magnitude of the input line voltage. In one embodiment, the harmonic injection signal is summed with the error signal of an output feedback loop. In another embodiment, the harmonic injection signal is integrated and summed with the ramp voltage of the feedforward path. Moreover, by adding a nonlinear gain control circuit, the DC gain of the DCM boost rectifier at light load is adaptively reduced to achieve stability of the rectifier at light load.

Abstract: A boost converter includes a novel active snubber which reduces losses caused by the reverse-recovery characteristic of the boost rectifier. The active snubber includes a snubber inductor, a ground-referenced referenced auxiliary switch, and a snubber rectifier. The losses are reduced by inserting the snubber inductor in series with the boost switch and the boost rectifier, so as to control the rate of change (di/dt) of the boost rectifier current during the rectifier's turn-off. A proper operation of the proposed circuit requires overlapping gate drives of the main and the auxiliary switches. The component voltage and current stresses in the proposed circuit are similar to those in the conventional, "hard-switched" boost converter.

Abstract: A new single stage, single switch input current shaping circuit features substantially reduced turn-on switching losses of the switch in the flyback-converter. In this technique, the turn-on switching losses due to the discharge of the output capacitance of the switch are reduced by turning on the switch when its voltage is minimal or close to the minimal. To achieve the turn-on loss reduction for a wide range of line and load conditions, the flyback-converter stage is continuously operated at the boundary of the CCM and DCM by employing a variable-frequency control. In this technique the boost inductor can work either in the DCM or the CCM. The wide-bandwidth, variable-frequency control is implemented by detecting the onset of the DCM/CCM boundary and, subsequently, turning the switch on at the minimum switch voltage. The switch is turned off when the increasing primary current reaches a reference level set by the output-voltage feedback control circuit.

Abstract: A boost converter employs an isolated active snubber to reduce the losses caused by the reverse-recovery characteristic of a boost rectifier and the turn-on discharge loss of the output capacitance of the boost switch. The losses are reduced by inserting the primary winding of a coupled-inductor in the series path of the boost switch and the rectifier, to control the rate of current change (i.e., the di/dt rate) of the rectifier during its turn-off, and to create the conditions for zero-voltage turn-on for the boost switch. The energy from the inductor, after the boost-switch is turned off, is delivered to the output via the secondary winding of the coupled-inductor which is connected in series with a clamping capacitor and an auxiliary switch to form an isolated active snubber. The same technique can be extended to any member of the PWM-converter family.

Abstract: In a single-switch, three-phase DCM boost rectifier, a voltage signal proportional to the inverted ac component of the rectified, three-phase, line-to-line input voltages is injected as a modulating signal into the control circuit to vary the duty cycle of the rectifier within one line cycle. As a result of its generation method, the injected signal is naturally synchronized with the three-phase, line-to-neutral input voltage. In addition, the injection method of this invention does not affect the closed-loop feedback control of the DCM boost rectifier since the injected signal is generated in an open-loop fashion. Three alternative methods to generate the injection signal are described. One method uses three low-frequency, step down transformers in generating the injection signal. The other two methods use operational amplifiers instead of the transformers.

Abstract: A new single-stage, single-switch, input-current-shaping technique which combines the boost-like input-current shaper with a continuous-conduction-mode dc/dc output stage is described. Due to the ability to keep a relatively low voltage (<450 Vdc) on the energy-storage capacitor, this technique is suitable for the universal line-voltage applications. The voltage on the energy-storage capacitor is kept within the desirable range by the addition of two transformer windings. One winding appears in series with the boost inductor during the on time, whereas the other winding appears in series with the same inductor during the off time. By connecting the windings so that the voltages across them when they conduct the inductor current are in opposition to the input voltage, the volt-second balance of the boost-inductor core is achieved at a substantially lower voltage of the energy-storage capacitor compared to the other known approaches.

Abstract: A circuit technique that substantially reduces the boost-converter losses caused by the reverse-recovery characteristics of the rectifier is described. The losses are reduced by inserting an inductor in the series path of the boost switch and the rectifier to control the di/dt rate of the rectifier during its turn-off. The energy from the inductor after the boost switch turn-off is returned to the input or delivered to the output via an active snubber. The same technique can be extended to any member of the PWM-converter family.

Abstract: An isolated zero-voltage-switching converter in which the magnetizing inductance of the isolating transformer is a resonant element and an open circuit is provided on the secondary side of the transformer during the time interval when both primary switches are off. When the secondary of the transformer is open, the magnetizing inductance is in series with the capacitances of the primary switches, thus forming a resonant circuit.

Abstract: A half-bridge zero-voltage-switched multi-resonant converter. The converter basically comprises a device for converting an input voltage signal to a DC output signal to be imposed across a load. The device includes input terminals for receiving the input signal and output terminals for imposing the DC output signal across the load. Serially connected first and second switching assemblies are connected in parallel across the input terminals. Each of the first and second switching assemblies includes a transistor switch, a diode and a capacitor all arranged in parallel. The device further includes a transformer having a primary winding and serially connected first and second secondary windings. A first rectifier in parallel with a first resonant capacitor is used to connect the first secondary winding across the output terminals. Circuitry is provided for connecting the primary winding of the transformer to the input terminals and to the serial connection between the first and second switching assemblies.