Abstract: A driver circuit for one or more gas discharge lamps (102, 104, 106) includes: a self-oscillating, series-resonant oscillator (196, 198, 178, 180) for producing a constant-frequency, high-frequency output voltage for application to the lamps; an inductive voltage boost IC (144) for causing the oscillator to produce a temporary excessive boosted output voltage (300 V) when the voltage boost IC is initially activated and a steady-state boosted output voltage (250 V) thereafter, ensuring striking of the lamps and prolonging their life.

Abstract: A half-bridge inverter is powered from a constant DC voltage and provides an AC output voltage that is--in contrast with the usual squarewave voltage--describable as being a sinusoidal waveform with the tops clipped off at some fixed magnitude; or, described differently, a waveform composed of truncated sinusoidal waves; or, described still differently, a waveform having trapezoidally shaped half-cycles. This AC voltage is applied across the primary winding of a so-called reactance transformer, whose loosely coupled secondary winding is connected across a gas discharge lamp. The internal inductive reactance of the secondary winding constitutes a lamp ballasting means by way of limiting the magnitude of the resulting lamp current to a pre-established desired level.

Abstract: Power to a self-oscillating inverter ballast is supplied from a DC voltage source through an inductor means having two separate windings on a common magnetic core--with one winding being positioned in each leg of the power supply. The inverter is loaded by way of a parallel-tuned L-C circuit connected across the inverter's output, thereby providing a sinusoidal voltage thereat. A fluorescent lamp is connected by way of a current-limiting capacitor with the inverter's output.

Abstract: A high frequency power supply for neon and mercury luminous tubes including means for simultaneously suppressing bubbles formed in neon tubes and for minimizing migration of mercury commonly associated with the use of solid-state luminous tube power supplies.

Abstract: A low pressure discharge lamp apparatus has a low pressure discharge lamp with an arc tube. The arc tube has a first end and a second end, each with electrodes which define a discharge space therebetween. A mercury/rare gas is sealed in the arc tube. The low pressure discharge lamp apparatus further has a lighting circuit apparatus for lighting the lamp by supplying a current with a polarity reversed for each half cycle to electrodes in the first and second ends of the arc tube. The lighting circuit apparatus supplies, to the lamp, a current whose waveform has a flat peak for each half cycle and a maximum current value of the current is restricted to less than a level in which the excitation of mercury atoms is saturated.

Abstract: A half-bridge inverter is powered from a constant-magnitude DC supply voltage and provides at the inverter's output a first AC output voltage that is describable as a modified squarewave voltage. This first AC voltage is applied across a series-combination of an inductor and a capacitor, the junction between which is clamped to the DC supply voltage. As a result, a second AC voltage gets established across the capacitor; which second AC voltae is also describable as being a modified squarewave voltage. However, the phasing of the second AC voltage is delayed by approximately 90 degrees with respect to the first AC voltage; which results in the voltage across the inductor being of approximately sinuosidal waveform. A fluorescent lamp is connected in series with a ballast capacitor; and the lamp-capacitor series combination is connected across the inductor, thereby reslting in a nearly sinusoidal current being provided to the fluorescent lamp.

Abstract: A circuit arrangement suitable for operating a low pressure mercury discharge lamp by means of a high-frequency pulsatory current comprising circuitry for generating a high-frequency pulsatory current from a supply voltage with a modulator for modulating the high-frequency pulsatory current into a substantially square-wave shape voltage with a current amplitude A, with a modulation frequency f and a duty cycle DC together with circuitry for adjusting the duty cycle DC and circuitry for adjusting the amplitude A.

Abstract: To permit the more cost-effective use of low voltage lamps (especially 12 Volt Halogen lamps) in track lighting systems, the power track is supplied from the power line by way of a frequency-converting power supply providing onto the track conductors a voltage of normal power line voltage magnitude (120 Volt RMS) but of an exceptionally high frequency (30 kHz). As a result, the individual step-down voltage transformer required to provide the proper low voltage for operating each of the low voltage lamps becomes very light, small and inexpensive. Yet, in contrast with situations where the whole track may be provided with low voltage from a single step-down voltage transformer, there will be no unusual limitations in respect to track length and/or the number of low voltage lamps that can be used with a given track. Moreover, there will be no problem with using regular high voltage incandescent lamps intermixed with low voltage lamps.

Abstract: In a power-factor-corrected electronic ballast, an AC/DC converter comprises a half-bridge electronic self-oscillating inverter powered from non-filtered full-wave-rectified 120 Volt/60 HZ power line voltage, and its resulting amplitude-modulated 30 kHz output voltage is applied to a series-resonant L-C circuit. The 30 kHz voltage developing across the tank capacitor of this L-C circuit is rectified and applied as direct current to an energy-storing capacitor, from which a DC supply voltage is provided to a frequency-converting ballast which, in turn, provides a substantially non-modulated high-frequency AC output voltage used for powering a gas discharge lamp via a current-limiting inductor. Trigger pulses are provided to trigger the inverter into self-oscillation at the beginning of each pulse of DC voltage provided by the unfiltered rectified power line voltage. As soon as the magnitude of the DC voltage across the energy-storing capacitor exceeds a first level, the trigger pulses cease to be provided.

Abstract: A high-frequency electronic ballast for fluorescent lamps has a first inverter for controllably providing heating power to the lamp cathodes and a second inverter for controllably providing main lamp operating power. The two inverters are separately and independently controllable, thereby: i) to permit adjustment of lamp current so as to provide full or reduced light output in accordance with requirements, ii) to permit cathode heating power to be removed under conditions of providing full light output, thereby to maximize efficiency, and iii) to permit cathode heating power to be restored under conditions of reduced light output, thereby to prevent premature lamp failure.

Abstract: A dimmer with reduced filtering losses is connected into a conductor supplying power to a load from a mains power supply. It conventionally comprises a triac in series with a filter inductor between an input terminal and an output terminal and a circuit generating triggering signals for the triac. To reduce the losses in the inductor, which conventionally is in series with the load at all times but is active only during moments following triggering of the triac, to reduce the amplitude of the transient currents, a second triac triggered by a circuit with a time-delay greater than the time constant defined by the filter capacitor and inductor diverts the load current. An auxiliary low-value inductor attenuates transients due to triggering of the second triac.

Abstract: An apparatus for operating discharge lamp. The apparatus includes a source of electrical power, switching devices for switching the electrical power, a control circuit for controlling the switching devices, a transformer having a primary winding for receiving the electrical power switched by the switching devices and a secondary winding for supplying power to the lighting apparatus, a resonant circuit including an inductor and a capacitor for regulating the frequency of the electrical power and a circuit for powering the control circuit, the powering circuit including a secondary winding on the inductor and an additional winding on the transformer connected in a differential manner.

Abstract: For coupling one, or more, gaseous discharge lamps to a high-frequency AC power-source a ballasting (current-limiting) network employs a first capacitor, a second inductor, and a transformer having a primary winding coupled to the high-frequency AC power-source by the first capacitor and a secondary winding coupled to the gaseous discharge lamp by the second inductor.

Abstract: The present invention provides a rare gas discharge fluorescent lamp device which is long in life and high in brightness and efficiency. The lamp device basically comprises a rare gas discharge fluroescent lamp wherein rare gas is enclosed in the inside of a glass bulb which has a fluorescent layer formed on an inner face thereof and has a pair of electrodes at the opposite ends thereof. In one embodiment, it further comprises a dc power source and a resonance circuit for generating pulse-like voltage across the pair of electrodes having the time rate of energization time to a period higher than 5% but lower than 70% and the energization time within a period shorter than 150 .mu.

Abstract: High-efficiency inverter circuits, particularly half-bridge devices, are especially suitable for energizing gas discharge lamps. The inverters preferably employ a series-connected combination of an inductor and a capacitor to be energized upon periodic transistor conduction. Transistor drive current is preferably provided through the use of at least one saturable inductor to control the transistor inversion frequency to be equal to or higher than the natural resonant frequency of the inductor and capacitor combination. The inverters can develop high output voltages to supply external loads connected to the inductor-capacitor combinations.

Abstract: The discharge lamp operating circuit comprises two series circuits, each including two switching devices, connected in parallel with the power supply, a series circuit, including a choke coil, a first capacitor, and a parallel circuit with a discharge lamp and a second capacitor, and connected between the middle points of the one and the other series circuit, reverse-direction rectifiers connected in parallel with the corresponding switching devices, said discharge lamp operating circuit turning on and off said discharge lamp by turning on and off the switching devices alternately. In this discharge lamp operating circuit, the timing of switching the switching devices is set from the closed condition to the open condition at a time when the current flowing through the switching devices is almost at zero level.

Abstract: A circuit arrangement suitable for operating a low pressure mercury discharge lamp by means of a high-frequency pulsatory current comprising circuitry for generating a high-frequency pulsatory current from a supply voltage with a modulator for modulating the high-frequency pulsatory current into a substantially square-wave shaped voltage with an amplitude A, a modulation frequency f and a duty cycle DC together with circuitry for adjusting the modulation frequency f and circuitry for adjusting the duty cycle DC.

Abstract: A circuit arrangement suitable for operating a low pressure mercury discharge lamp by means of a high-frequency pulsatory current comprising circuitry for generating a high-frequency pulsatory current from a supply voltage with a modulator for modulating the high-frequency pulsatory current into a substantially square-wave shape voltage with a current amplitude A, a modulation frequency f and a duty cycle DC together with circuitry for adjusting the modulation frequency f and circuitry for adjusting the amplitude A and circuitry for adjusting the duty cycle DC.

Abstract: The actuator is connected in series between the power supply and the flashing light. It includes a switch which is connected in series between the power supply and the flashing light so that when the switch is closed the light turns on and when the switch is open the light is turned off. A comparator controls the opening and closing of the switch at a frequency determined by an RC timer. Also, the duty cycle of the flashing light is controlled by the timer. A current overload protector lowers the duty cycle of the flashing light as the magnitude of the overload is increased and, in the event of a short circuit, decreases the duty cycle to approximately zero.

Abstract: High-efficiency inverter circuits, particularly half-bridge devices, are especially suitable for energizing gas discharge lamps. The inverters preferably employ a series-connected combination of an inductor and a capacitor to be energized upon periodic transistor conduction. Transistor drive current is provided through the use of at least one saturable inductor to control the transistor inversion frequency to be equal to or higher than the natural resonant frequency of the inductor and capacitor combination. The inverters can develop high output voltages to supply external loads connected to the inductor-capacitor combination.

Abstract: A high efficiency, self-oscillating LC resonant multivibrator-inverter circuit employing a pair of switching transistor (Q1, Q2), two magnetically independent resonant inductors (L1, L2) and one common resonant capacitor (CR). Two secondary windings (NB2, NB1) of the resonant inductors provide feedback control for the switching transistors' bases, to provide intermittent feedback current to effect alternate and periodic conduction of the transistors. This results in the DC voltage rectified from the source S being converted to relatively high frequency AC voltage across output terminals (O1, O2). Such an arrangement enables construction of a cost effective, highly efficient, and highly reliable electronic ballast for fluorescent lamps.

Abstract: An improved tapped-inductor boost converter for operating a gas discharge lamp is disclosed. The converter includes a pair of input terminals connected to a power source supplying an input voltage, a pair of output terminals for providing an output voltage greater than or equal to the input voltage to the lamp, or other load, a tapped-inductor having first and second windings, an active switch for controlling current flow through the first winding for variably controlling the output voltage, a passive switch for controlling current flow through the second winding, and a first capacitor. The converter further includes an arrangement for varying the clamping voltage at the active switch in response to variations in the output voltage and also includes a clamping capacitor for transferring energy stored in the leakage inductance of the tapped-inductor to the load for improved efficiency.

Abstract: A circuit arrangement comprising a DC/AC converter for supplying power to a lamp upon receiving energy from a DC voltage source; the converter includes a branch A having at least one switching element and a control branch connected to the switching element; the control branch comprises a coil shunted by a capacitor; the circuit arrangement also includes a load branch with an inductor connected to a parallel arrangement of an inductance and capacitance.

Abstract: An apparatus for operating a discharge lamp is disclosed in which a voltage supplied from a commercial alternating current source is fed to a feedback-controlled, saturable current transformer having a primary winding, secondary windings and control winding and to a self-excited inverter circuit having a rectifier circuit. The discharge lame is lit upon receipt of an AC output obtained through reconversion by the inverter circuit. An impedance circuit varies an impedance so as to control a current in the control winding. The current in the control winding varies in accordance with a varied impedance to vary a saturation time of the variable current transformer in the inverter circuit and hence an output of the inverter circuit.

Abstract: A circuit for dimmably driving fluorescent lamps (102, 104, 106) from a DC supply voltage includes: input nodes (174, 176) having input capacitors (184, 186) connected therebetween; a half-bridge transistor inverter (178, 180) connected between the input terminals; a series-resonant LC oscillator (196, 198) coupled in series between the half-bridge transistors and the input capacitors; an output transformer (212) having a primary winding (214) connected in series with the LC inductor (196) and in parallel with the LC capacitor (198) and a secondary winding (216) for connection to the lamp load; and first and second voltage clamp diodes (215A, 215B) connected between an intermediate point on the primary winding and the input nodes respectively.

Abstract: A circuit (100) for driving fluorescent lamps (102, 104, 106) and including: a half-bridge inverter (112) receiving a unidirectional voltage and producing an alternating voltage, and having control inputs (156, 166); a series-resonant oscillator (126) coupled to the inverter output (116) for producing an alternating signal; and a non-saturating feedback transformer (146) having a primary winding (148) coupled in series between the inverter and the oscillator and secondary winding (150, 152) coupled respectively to the control inputs of the inverter. Since the feedback transformer is non-saturating it provides to the inverter control inputs a linear feedback signal from the inverter. This results in safe, stable, predictable and well-defined circuit operation, in which the possibility of the inverter transistors being destroyed by cross-conduction is substantially removed, and the amount of input voltage "ripple" present in the signal applied to the lamps is reduced.

Abstract: A circuit for starting and operating a discharge lamp, such as a compact fluorescent lamp, at high frequency from an 60 Hz AC supply. The circuit includes a power supply for generating a DC voltage coupled to a pair of AC input terminals. A DC/AC converter includes an oscillator having a pair of semiconductor switches coupled in parallel with the DC power supply. an oscillator starting circuit is coupled to one of the semiconductor switches and includes a series circuit comprising a resistor, capacitor and threshold element. The input of the oscillator starting circuit is coupled to one of the AC input terminals so as to prevent a momentary flicker in the lamp after the AC supply is removed and the lamp has extinguished. In accordance with another aspect of the invention, the oscillator includes fusible circuit elements which render the oscillator inoperable upon failure of the lamp due to depletion of emissive material on at least one of the lamp electrodes.

Abstract: The invention relates to a modular system and method for converting sinusoidal AC waves into a DC pulse train of extremely narrow pulse width which are amplified and directed to a fast switching power transistor. When the power transistor conducts, DC current flows from the module through the load for a time interval equal to the rectangular pulse width. The resting time between pulses, which is considerably greater than the pulse width, accounts for a significant saving in energy.

Abstract: A lighting device for a hot cathode fluorescent lamp used for a back light of a liquid crystal display or the like attempts to prolong the life of a lamp in a lighting device for a low consumption wattage fluorescent lamp. More specifically, the hot cathode fluorescent lamp is started while being pre-heated, and even after starting, a pre-heat current keeps flowing. The pre-heat current value after starting is set to be smaller than that at the time of starting for the purpose of optimizing the hot spot temperature. With employment of the configuration as described above, the lifetime of the hot cathode fluorescent lamp when used as a back light can extend to 10,000 hours or more.

Abstract: A direct current power supply which incorporates an alternating current circuit segment so as to enable the use of a reactive component as an impedance limiting circuit element. The alternating current is produced by pulse width modulation regulation of raw direct current and DC to AC inversion. A feedback circuit is provided to regulate the pulse width modulation in accordance with the direct current output by the power supply so as to obtain a desired output current.

Abstract: A lamp power control circuit for electric equipment which has a power supply, supplies power to incandescent lamps fitted to operating parts of electric equipment and is provided with a current-direction inverter unit. This current-direction inverter unit inverts the direction of the electric current flowing through an incandescent lamp in response to a signal generated in response to manual operation of the operating parts. Consequently the effect of electromigration on filaments of incandescent lamps is decreased and occurrence of the notching is reduced, thus extending the life of lamps.

Abstract: Miniature high pressure arc lamps containing a substantial pressure of xenon, in addition to metal halide and mercury, can provide instant light at turn-on and are suitable for automotive headlamps. The high pressure of xenon aggravates convection which causes arc bowing and overheating of the envelope above the arc. By operating the lamp at high frequency within selected bands, acoustic modes are excited in the fill which straighten the arc and make the envelope more isothermal. Frequency modulation of the input can be used to broaden the band selected for acoustic operation and relax the tolerance on arc tube and circuit parameters needed for a match. Acoustic operation may also be used to effect physical displacement of the arc for beam switching.

Abstract: An improved electronic ballast inverter for a gas discharge lamp includes an oscillator having at least two switching transistors for operating the gas discharge lamp at a high frequency during steady-state operation, a triggering circuit for initiating the operation of the oscillator, and an electrical circuit connected to the oscillator for gradually increasing the base current of at least one of the switching transistors immediately after start-up in order to delay the gas breakdown and thereby to produce preheating of the gas discharge lamp during startup.

Abstract: A charging method within a glass tube using a direct current of low voltage is provided in order to obtain a small fluorescent lamp with a light emission of high luminance. Two distinct discharges are achieved through use of one negative electrode. The filament-like negative electrode is arranged at a short spaced relation to a positive electrode at one end of the glass tube and upon application of the direct current voltage becomes the preliminary discharge. A second positive electrode is positioned at the opposite end of the glass tube and has a greater-spaced relation to the negative electrode resulting in the second discharge.

Abstract: A device for alternating the polarity of an illuminated DC fluorescent light bulb to eliminate cathodic degeneration while avoiding the visible effects of flicker to maintain a constant lighting effect.

Abstract: The present invention describes a method and apparatus for a high frequency switching gas discharge tube supply which suppresses or eliminates the "bubble effect" in gas discharge tubes containing argon-mercury gas or other gases and which eliminates the migration of mercury or other migratory gases toward one electrode over time. To prevent mercury migration to one electrode over time within an argon-mercury gas discharge tube, the DC bias is periodically reversed in direction resulting in a gas discharge tube display which is uniform in intensity of light over the length of the tube.

Abstract: The invention relates to a switching arrangement for operating a high-pressure sodium lamp which radiates white light in stable operating conditions. The switching arrangement is provided with switching means for switching current through the lamp by means of a drive signal generated in a drive circuit, which signal is based on a comparison between a reference value C and drive signal V+.beta.I, in which V is the lamp voltage, I is the lamp current, and .beta. is a constant. According to the invention, C may be adjusted in steps in dependence on the lamp voltage. Thus the duration over which the lamp radiates white light can be prolonged and brought into better accordance with the electrical lamp life.

Abstract: For coupling one, or more, gaseous discharge lamps to a high-frequency AC power-source a ballasting (current-limiting) network employs a first capacitor, a second capacitor, and a transformer having a primary winding coupled to the high-frequency AC power-source by the first capacitor and a secondary winding coupled to the gaseous discharge lamp by the second capacitor.

Abstract: A fluorescent lamp control system operable from either an AC power supply of a first frequency or a power supply of a second frequency and which operates the lamp in a dimmed condition when the power supply is that of the second frequency.

Abstract: A switchmode DC to AC converter, and particularly a master-slave half-bridge converter. The slave half-bridge power converter is controlled by a lower power self-oscillating half-bridge master converter. More particularly, the invention pertains to a high frequency ballast for gas discharge devices, especially, for high pressure sodium lamps, completed by a high voltage ignition apparatus.

Abstract: A self contained battery operated table lamp for use in restaurants, and the like. The lamp includes an electric light which is energized on an intermittent basis by a switching circuit to assure long battery life. A feed back loop is included in the switching circuit for establishing the duty cycle of the energizing power intermittingly applied to the lamp. A flicker signal generator is connected to the energizing circuit of the light to introduce a flicker into the output of the light. The flicker signal generator incorporates a plurality of independent oscillators, each operating at a slightly different frequency. The outputs of the various oscillators are summed in a summing network with each being given a slightly different weighting factor, and the resulting signal is injected into a feedback loop to modify the average voltage of the light. The lamp is caused to provide a pseudo-random candle simulating effect.

Abstract: A discharge lamp lighting device includes a pair of main switching transistors and a feedback transformer. Each of the main switching transistors has a control electrode to form a push-pull circuit and which is switched on and off responsive to a given oscillating frequency. The feedback transformer has a pair of drive windings and serves to positively feed back the output of the push-pull circuit to each of the control electrodes of the paired main switching transistors. A first control circuit is connected to each of the bases of the main switching transistors and includes a variable impedance element to control the oscillating frequency by varying the impedance of this variable impedance element. A second control circuit has a level shift circuit and serves to control the level of signal applied to the first control circuit so as to change the impedance of the variable impedance element so that the on-off operation of each of the paired main switching transistors can be controlled.

Abstract: The invention relates to a switching arrangement suitable for ignition and operation of a high-pressure discharge lamp by means of a plulsatory current of changing polarity. For this purpose, the switching arrangement is provided with a bridge network (II), which includes a switching means (21) switched alternately to the conducting and the non-conducting state. The switching means is provided with a control electrode (215) and a main electrode (211), between which a shortcircuit is maintained by means of a shortcircuit switch (27) for the time in which the switching means is in the non-conducting state. According to the invention, the shortcircuit switch is controlled by means of a controlled current source (28).

Abstract: A lighting device for an electric discharge lamp comprises an LC series resonant circuit, and control means for controlling an inverter circuit. Immediately after the occurrence of a dielectric breakdown in the electric discharge lamp. AC voltage with a relatively low frequency is applied to the lamp so as to pass a heavy current therethrough. Subsequently, the frequency is increased stepwise by a relatively small variation until a terminal voltage of the electric discharge lamp reaches a predetermined value. Thereafter, the frequency is increased stepwise by a relatiely large variation until the electric discharge lamp assumes a discharge stable state.

Abstract: The invention relates to a circuit arrangement for operating a discharge lamp, comprising a DC-AC converter provided with switching elements and a drive circuit for rendering the switching elements alternately conducting. The circuit arrangement is furthermore provided with a control circuit C for controlling the power consumed by the lamp. To this end, the control circuit is coupled to a current sensor. According to the invention, the current sensor is so positioned that the power consumed by the lamp can be controlled independently of the build-up of the drive circuit and that a simple construction of the control circuit C is possible.

Abstract: The invention relates to a circuit arrangement for operating a discharge lamp, comprising a DC-AC converter provided with a switching element for generating a current whose polarity changes with a frequency f, a current sensor (SE), a drive circuit (III) for generating a drive signal to make the switching elements alternately conducting with the frequency f, a measuring circuit (I) coupled to the current sensor and having at least one switching element for generating a control signal which is dependent on a phase difference between a voltage across the load circuit B and a current through the load circuit B and on a second signal which is a measure for a minimum required phase difference, and a control circuit (II) for effecting a change in an operating condition of the DC-AC converter, this change being dependent on the control signal.

Abstract: The invention circuit for a discharge lamp comprising a first switching circuit, a series resonant circuit, and a current transformer. The series resonant circuit energizes the discharge lamp by means of resonant output corresponding to the output from the first switching circuit. The current transformer incorporates the first, second, and the third windings. When the first winding inserted in the series resonant circuit is driven, the first winding outputs a predetermined amount of current to the second and third windings. The inverter circuit further comprises a second switching circuit, a pair of time constant circuits, and a control circuit. The second switching circuit controls ON-OFF operation of the first switching circuit in response to the output from the second winding.

Abstract: The invention provides a rare gas discharge fluorescent lamp device which is long in life and high in brightness and efficiency. The lamp device comprises a rare gas discharge fluorescent lamp including a glass bulb having xenon, argon or krypton gas enclosed therein, a fluorescent layer formed on an inner face of the bulb, and a pair of electrodes located at the opposite ends of the bulb. A pulse-like voltage wherein the ratio of an energization period with respect to one cycle is higher than 5% but lower than 70% (xenon or krypton gas) or 80% (argon gas) and the energization period is shorter than 150 .mu.sec is applied between the electrodes of the lamp. Such pulse-like voltage is produced from a circuit including a dc power source, a pulse signal source, and a switching element for controlling application of a voltage of the dc power source or such voltage boosted by a boosting transformer or a resonance circuit.

Abstract: A supply circuit is proposed for high-frequency operation of one low-pressure discharge lamp or several low-pressure discharge lamps connected in parallel. The switching unit includes--a power rectifier followed by an active harmonic oscillation filter and a filter capacitor and a single-phase high-frequency generator comprising a switching transistor, a switching inductance and an oscillating capacitor, said generator being supplied from said filter capacitor and being decoupled from the power supply by means of two diodes.

Abstract: A switched bridge circuit has semiconductor bridge elements (T1,T2) which are arranged to provide a commutated output from a d.c. source (+300V). The commutation is effected by a switching signal from a control circuit. The control circuit for switching the bridge elements is coupled with the output by a capacitor (C2) such that switching of the bridge elements is prevented while there is a flow of current through the capacitor, the current through the capacitor is indicative of a changing output voltage and a confirmation that the voltage across the bridge elements is not approximately zero or +300V.