Abstract: A high power factor converter system comprises an input rectifier, a converter and a booster circuit. The input rectifier is configured for rectifying an input ac voltage. The converter is configured for generating an output voltage for the high power factor converter system. The converter comprises several converter switches and inverse parallel diodes. The booster circuit comprises an inductor and at least one converter switch and an inverse parallel diode of the converter. The inductor is coupled between the input rectifier and the converter. The booster circuit is configured for controlling the supply of a booster current through the inductor to be discontinuous when the instantaneous voltage level is less than a predetermined fraction of a dc voltage level across the converter and continuous when the instantaneous voltage level is greater than the predetermined fraction of the dc voltage level.

Abstract: A circuit for loading the rectified AC voltage bus in a housekeeping power supply for an electronically controlled load is provided for avoiding large increases in the rectified AC bus voltage upon disconnecting the load. The load circuit includes a current sink, a relatively small energy storage capacitance, and a negative feedback circuit. The current sink includes a resistance coupled to the rectified AC voltage bus for sinking current whenever the semiconductor switch is on. When the semiconductor switch is off, the small capacitance discharges through the resistive voltage divider. When the voltage across the small capacitance decreases to a threshold mean AC rectified voltage bus value, then the negative feedback circuit provides sufficient current to turn the semiconductor switch back on and thus provide approximately the threshold mean AC rectified voltage bus value.

Abstract: A dc-to-dc converter is provided with overvoltage protection circuitry while still providing normal output voltage. Such overvoltage protection circuitry does not require resetting. The overvoltage protection circuitry includes a first switching device connected between the input bridge and a dc output voltage bus and further includes an overvoltage current path. The overvoltage current path includes a complementary switching device in series with Zener diode circuitry having a predetermined breakdown voltage, and further has a transition current path. The first switching device is closed for nominal input voltage and is open for overvoltages. When the input voltage exceeds the Zener diode breakdown voltage, the transition current path conducts current. When the threshold voltage of the complementary switching device is exceeded, the complementary switching device turns on and conducts current through the overvoltage current path.

Abstract: A push-pull converter, coupled through an isolation transformer to a crowbar circuit for controlling an isolated output voltage across an output capacitor, has a compact circuit arrangement with a minimal number of components. The switching devices of the push-pull converter have integrated, ultra-fast anti-parallel diodes. The crowbar circuit is a voltage-controlled bi-directional switch coupled between the transformer and the output capacitor. The converter is controlled in an output-voltage-on mode by turning on and off the first switching device, and in an output-voltage-off mode by applying a gating signal to the second switching device sufficient to both activate the crowbar circuit and discharge the output capacitor for very fast isolated output voltage turn-off. In addition, a primary-side circuit comprising a switch and a resistance can be used to avoid excessive residual output voltage build-up.

Abstract: A single power supply circuit, including a push-pull input converter stage and a voltage-controlled latch circuit output stage isolated from each other by a transformer, provides both voltage gridding and biasing functions in, for example, an x-ray tube application. In the gridding mode, a first voltage level supplies the push-pull converter to provide an output voltage that is sufficiently high to trigger the voltage-controlled latch circuit and thereby provide grid control via a grid control electrode. In the biasing mode, a lower voltage level supplies the push-pull converter such that the output voltage is insufficient to trigger the voltage-controlled latch circuit. As a result, a resistive voltage divider provides a predetermined biasing voltage on a bias control electrode.

Abstract: A forward converter, having a single switching device, is coupled through an isolation transformer to a crowbar circuit and an output capacitor for controlling the isolated output voltage turn-off. The crowbar circuit, including a trigger device and a resistor, is coupled between the transformer and the output capacitor. The conduction times of the converter switching device are controlled to regulate the energy stored in the transformer and to generate a reverse voltage having a predetermined amplitude. During the output voltage-on mode, the amplitude of the reverse voltage swing is controlled to be sufficiently low such that the converter operates as a conventional forward converter. For output voltage turn-off, the conduction time of the switching device is controlled to obtain a voltage swing of sufficient magnitude to trigger the crowbar circuit, and thus rapidly discharge the output capacitor.

Abstract: A forward converter useful in a power supply utilizing an isolation transformer includes a crowbar circuit and control such that turn-off by discharging an output capacitor is made advantageously faster than conventional circuits. The forward converter has a push-pull arrangement of two switching devices. For operation in the output voltage-on mode, the forward converter transfers energy in a peak forward converter mode with the first switching device being turned on and off. For output voltage turn-off, the crowbar circuit is activated by turning on the second switching device which results in a reverse voltage at the secondary winding of the isolation transformer. The reverse voltage is superimposed on the converter output voltage, the sum of the converter output voltage and the reverse voltage being imposed across the crowbar circuit.