Lambda Electronics, Inc.

Other

Veeco Instruments Inc.

Itzchak Cohen

An apparatus is disclosed for maintaining accurate control of the maximum duty cycle generated by pulse width modulators. The output signal of a pulse width modulation comparator is averaged and compared to a reference value. This reference value is proportional to the peak value of the comparator's output voltage. A closed loop circuit continually adjusts the duty cycle so the difference between the reference value and the average comparator output is nulled thereby providing an accurate maximum duty cycle output.

Maximum duty cycle limiting of pulse width modulators

A high frequency self-oscillating inverter including a snubber circuit for minimizing both turn-on and turn-off switching losses. The inverter converts a DC supply to an AC load current and includes a saturating transformer for alternatively driving first and second switching devices during subsequent unsaturated states. During the time the transformer is saturated, both switching devices are kept off. The snubber circuit includes a first capacitor across the first switching device, a second capacitor across the second switching device, and an inductance. During saturation the two capacitors and inductance form a resonance circuit, wherein the inductance has a resonant half sine wave current, one capacitor discharges, and the other capacitor charges. Turn off switching losses are made negligible by selecting capacitors such that the fall time of the corresponding switching device is much faster than the time to charge the capacitor to a significant voltage. Turn on switching losses are made negligible by having the capacitor across the on-going switching device discharge to approximately zero during saturation before the transformer returns to an unsaturated state to turn-on the on-going switching device.

High frequency self-oscillating inverter with negligible switching losses

Disclosed are circuits for indirectly sensing and controlling the output current of switching type DC to DC converters utilizing capacitance which follows the output voltage by being responsive to switching current during the conduction period and being controllably discharged as a function of output voltage during the non-conduction period.

Indirect current sensing of DC to DC converters

A demagnetization circuit for use with a forward converter includes a drive winding magnetically coupled to the primary winding of the forward converter, a capacitor for absorbing leakage and magnetization energies from the primary winding when the forward converter is switched off, an inductor for absorbing energy from the capacitor, and a switching circuit for selectively connecting the inductor to the input voltage source of the forward converter.

Demagnetization circuit for forward converter

A two quadrant power modulator using bi-directional and uni-directional flyback converters in which output waveshape is determined by the modulation of the pulse repetition rate and width. The output voltage is equal to the square root of the driving function. A large number of converters may be paralleled with sequential switching to raise the output power and raise the output ripple frequency, thereby simplifying filtering. Output voltage is constant with varying load condition irrespective of the reactive or non-linear nature of the load. A two quadrant power modulator using flyback converters to generate a time varying voltage. Dynamic regulation and low output impedance are achieved without use of closed loop control. Input voltage is not distorted by reactive and/or non-linear loads.

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Dix Hills, NY, United States of America

Itzchak Cohen