Abstract: A high-performance contactless electrical energy transmission (CEET) technique which employs the inductive energy transmission principle is described. The proposed technique enables the implementation of high-efficiency, high-power-density, fully-regulated CEET systems suitable for applications with a wide input range and a wide load range. The CEET system in this invention consists of an input-side variable-frequency inverter and an output-side regulated rectifier. A high efficiency of the system is achieved by recovering the energy stored in the leakage inductances of the transformer by incorporating them in the operation of the circuit, and by employing high-frequency-inverter and controlled-rectifier topologies that allow a controlled bi-directional power flow through the transformer. A feed forward, variable-switching-frequency control of the inverter is used to maintain a substantially constant power transfer through the transformer when the input voltage changes.

Abstract: A constant frequency, DC/AC inverters that employs a coupled inductor to achieve ZVS in a wide range of load current and input voltage with a reduced circulating energy. In the circuits of the invention, the two windings of the coupled inductors are connected in series and their common terminal is connected to one end of the primary winding of the isolation transformer, which has the other end of the primary winding connected to ground. Each of the other two terminals of the coupled inductors is coupled to the midpoint of the corresponding bridge leg through a series connection of the resonant inductor and a resonant or blocking capacitor. For non-isolated inverter implementations, the common terminal of the coupled inductor is connected directly to the load. The output voltage regulation in the inverters is achieved by a constant-frequency phase shifted control.

Abstract: A two-switch, two-inductor boost converter achieves output-voltage regulation in a wide input-voltage and load-current range using a constant-frequency by employing an auxiliary transformer to couple current paths of the two boost inductors so that both inductors carry the same current. By forcing the current through the boost inductors to be the same, the energy in both inductors is forced to change in unison, i.e., both inductors increase the energy when both switches are turned on simultaneously and decrease (transfer) energy when either of the converter's two switches is turned off. As a result, the stored and transferred energy of both inductors can be controlled in a wide input-voltage and load range using a constant-frequency control by controlling the time duration that the two switches are simultaneously on.

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 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: This patent disclosure describes new non-linear carrier-pulse-width modulators for control of high power-factor boost rectifiers. In the new modulators, the switch duty ratio is determined by comparing a signal derived from the main switch current with a periodic, nonlinear carrier signal .nu..sub.c (t, .nu..sub.m). The shape of the carrier is selected so that the resulting input current follows the input voltage, as required for unity-power-factor rectification. A slowly-varying modulating input .nu..sub.m can be used to adjust the power level and to regulate the output dc voltage. The controller based on the new non-linear-carrier modulator has a number of advantageous properties: sensing of the input line voltage is eliminated; for current shaping, only sensing of the power switch current is needed; current shaping does not require an error amplifier with feedback loop compensation; the multiplier in the voltage feedback loop is eliminated; and the converter operates in the continuous conduction mode.

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.