Inverter-rectifier combinations of the type which include at least a pair of transistors for alternately applying DC current to a transformer to generate alternating voltage from a DC source, and a digital semiconductor type driving means for alternately providing voltage pulses of given duration and at a periodic repetition rate at each of two outputs for controlling such alternating operation of the transistors is improved in a combination containing a protective circuit located in between the driving circuit and the inputs to the inverter transistors. The protective circuit contains first and second inputs and corresponding first and second outputs with the inputs being connected to an associated one of the two driving means outputs, and the outputs being connected to an associated one of the two inverter transistors; cross-gating means, including linear semiconductor switch means, for producing a driving output pulse on a one of the outputs responsive to the presence of a voltage pulse at an associated one of said inputs and only during the absence of a voltage pulse at the other one of said inputs; and delay means for inhibiting the application of said driving output pulse at a one of said circuit outputs until the lapse of a predetermined interval of time subsequent to the termination of application of a driving output pulse to the other one of said circuit outputs, the predetermined time interval being at least as great as the defined charge storage time of the inverter transistors and less than half the duration preferably of the pulses supplied by the digital control circuit; whereby the inverter transistors are not driven into overlapping operation.

A voltage regulator circuit for a switching type converter operates by applying full power to the output if it falls below a reference value and zero power if the reference value is exceeded. The switching device of the voltage regulator is operated at a first high frequency and is periodically enabled to supply power to the output for discrete operative clock cycles at a second lower clock frequency in accord with the output signal level. An interval of off-time follows each operative cycle. In another embodiment operation of the switching devices is continuous, but power flow to the output is significantly reduced when the output voltage is overlimit.

An electric control circuit for the supply of ohmic-inductive loads via direct-current pulses with changeable pulse use-ration encompasses a regulator featuring a transformer (T) wherein the transformer is designed as an autotransformer with a single continuous winding with center tap and taps symmetrical to the center tap, is connected on the primary side via electronic switches (Q.sub.3, Q.sub.4) bridged by freewheeling diodes in push-pull arrangement to a direct-voltage source (B) and, on the secondary side, is connected via electronic switches (Q.sub.5, Q.sub.6) which are symmetrical to the transformer (T) and are bridged by freewheeling diodes. Between the connection point of the connections facing away from the transformer (T) of the electronic switches (Q.sub.5, Q.sub.6) on the secondary side, and the pole of the direct-voltage source (B) which pole faces away from transformer (T), there is connected at least one series circuit of two electronic switches (Q.sub.1, Q.sub.2) which are bridged by freewheeling diodes, whose freewheeling diodes lie in reverse position to the freewheeling diodes of the two electronic switches (Q.sub.5, Q.sub.6) on the secondary side, wherein the load (M) is connected in parallel to one of the electronic switches connected in series.

An alternating current power source which controls its own alternating current output through a feedback circuit which monitors the alternating current output is disclosed. The power source can be used as a backup to a primary power supply which provides power to a load. The present invention continuously monitors such primary power supply to detect power interruptions in the primary power supply. When an interruption is detected, monitoring logic circuitry of the alternating current power source disconnects the primary power supply from the load and energizes line driver circuitry of the present invention which provides the alternating current output. When the power interruption ceases, the monitoring logic circuitry reconnects the primary power supply to the load and disables the line driver circuitry so that alternating current is not provided by the present invention to the load. The alternating current power source includes an internal power supply which can be recharged through the line driver circuitry by the primary power supply when there is no power interruption in the primary power supply.

A MOSFET power switching transistor in a DC-to-DC converter of a television apparatus has a drain electrode that is coupled via a primary winding of a chopper transformer to an input supply voltage. A first signal at a given frequency causes, during normal operation, alternate conduction and nonconduction in the transistor. A second signal is generated that is proportional to the voltage developed across the internal "on" resistance of the transistor when the transistor is conductive. The second signal is clamped when the MOSFET transistor is nonconductive. The second signal is coupled via a current sensing arrangement to the transistor gate. The second signal prevents the transistor from further conducting when the amplitude of the second signal exceeds a predetermined value that corresponds with a predetermined limiting threshold level of current in the transistor.