A circuit employing a transformer secondary winding having a fraction of its turns tapped across the base-emitter junction of a power transistor. A silicon controlled rectifier is connected from the transistor base across the entire secondary winding providing control of the power transistor conduction and reverse base drive upon power transistor turn-off. Synchronous control signals for the controlled rectifier may be developed by an additional secondary winding wrapped on the same core as the secondary winding driving the power transistor.

A switched mode regulated DC to DC converter for supplying a regulated voltage to a load includes a switching frequency generator of a switching cycle having positive and negative portions. A device, responsive to the outputs of the switching frequency generator, accumulates a voltage during the positive and negative portions of the switching cycle. The demand for voltage by a load is sensed and circuitry generates a first and second trigger otuput during the respective positive and negative portion of the switching cycle when the accumulated voltage equals the sensed load voltage demand, the time required to generate the second trigger output being equal to the time required to generate the first trigger output. A transformer apparatus, responsive to the first and second generated trigger outputs, generates currents of positive and negative polarity during the positive and negative portions of the switching cycle. A first electronic switch, responsive to the generated currents of positive polarity, connects a load voltage source to a load during the positive portion of the switching cycle. Similarly, a second electronic switch, responsive to the generated currents of positive polarity, connects the load voltage source to the load during the negative portion of the switching cycle.

An X-ray apparatus, after an AC output from an AC power source is rectified by a first rectifier circuit, supplies it to a primary winding side of a high-tension transformer through a bridge inverter. The bridge inverter includes first and second switching elements arranged at its first and second arms and operating as high-frequency choppers, a third switching element and first parallel circuit arranged at its third arm and forming a closed circuit together with the primary winding of the high-tension transformer, and a fourth switching element Q.sub.4 and second parallel circuit arranged at its fourth arm and forming a closed circuit together with the primary winding of the high-frequency transformer, the first parallel circuit being connected in series with the third switching element and comprised of a diode and resistor and the second parallel circuit being connected in series with the fourth switching element and comprised of a diode and resistor. An energy stored in the primary winding of the high-tension transformer is released through the closed circuit. A high-voltage output induced in the secondary winding of the high-tension transformer is applied to the X-ray tube through a second rectifier circuit. A voltage applied to the X-ray tube is detected at a voltage detection circuit and controlled in the feedback control circuit. Control signals are supplied to the respective arms of the bridge inverter so that the voltage to be applied to the X-ray tube becomes a predetermined value.

The bead source for the thermionic detector of a gas chromatograph is heated by the secondary winding of a transformer having a center-tapped primary and operating in the push-pull configuration. The voltage drop across the bead is compared with a preselected reference voltage and an error signal is generated. The error signal is used to control the output of a pulse width modulation control which supplies the transformer primary winding.

A primary winding of a power transformer is coupled to a source of DC voltage. First and second controllable switches are coupled to the primary winding in a push-pull arrangement. A control circuit responsive to a deflection rate input signal that is synchronized with deflection circuit scanning applies a turn-off switching signal alternately to the two controllable switches during each deflection cycle. In response to the turnoff of each one of the two controllable switches, a turn-on switching signal is applied to the other switch to develop a deflection rate alternating polarity output voltage across an output winding of the power transformer. The output voltage is rectified and applied to a deflection generator to thereby energize the generator into developing scanning current in a deflection winding.