Abstract: Disclosed is a base drive circuit that provides a base drive current particularly adapted to switch a switching power transistor ON and OFF quickly. The base drive current includes a variable AC impedance device that responds to a control pulse to form a base drive having (a) an initial forward base drive peak that drives the switching power transistor toward deep saturation momentarily, followed by (b) an intermediate drive current of lower magnitude, sufficient to keep a high-power transistor at or near saturation, and (c) a high-amplitude reverse drive current for high-speed turn-off of the transistor.

Abstract: A DC to square wave inverter (100) includes a saturable transformer (T102). The current through the saturable transformer (T102) is determined by the load current of the inverter (100). Current through the saturable transformer (T102) flows through two diodes (D100, D101) and through the base emitter junction of a power transistor (Q101). As the load current increases, the current through the diodes (D100, D101) and the power transistor (Q101) increases. This causes an increase in the voltage across the saturable transformer (T102), thus decreasing the amount of time it takes for the saturable transformer to go into saturation. A negative resistance element is coupled in series between the diodes (D100, D101) and the saturable transformer (T102). The voltage rise across the negative resistance element increases in response to increased current coming out of the saturable transformer (T102) and through the diodes (D100, D101).

Abstract: A monolithically integratable control circuit for switching inductive loads, comprising a Darlington-type final stage, is described. The base of the Darlington control transistor is coupled to the collector of a transistor for extracting charge, the transistor conducting in phase opposition to the Darlington control transistor. The emitter of the transistor for extracting charge is coupled to the negative supply terminal and to the output terminal of the final stage, via a first and a second diode respectively.

Abstract: A switching power source circuit intermittently switches a current at a primary winding of a transformer in accordance with the repeated switching of a bipolar transistor so as to rectify and smooth a voltage induced at a secondary winding of the transformer, thereby obtaining an output voltage. A capacitor is charged by a voltage induced by a feedback winding of the transformer. The base-emitter path of the bipolar transistor is reverse biased by this charge voltage so as to perform high-speed switching, so that a compact transformer and capacitor can be used and the switching power source circuit becomes low in cost.The application of the reverse bias voltage is performed by a transistor which is turned on when an emitter (grounded through a resistor) voltage of the bipolar transistor is increased to a predetermined level (threshold). A switching period of the bipolar transistor is determined by a period determining circuit consisting of a timing capacitor and a resistor.

Abstract: A switch mode converter is disclosed which has an improved base drive therefor. The switch mode converter includes a pair of primary transistor switches each of which is connected to a transformer having a feedback winding connected to the respective transistor in a proportional base drive configuration. A controller circuit controls a switch connected in series with the primary winding of each transformer to switch the current supplied to the primary winding of each transformer from first and second current supplying circuits. Each second current supplying circuit temporarily supplies current to the transformer during the time that the respective transistor is being switched off to shorten the turn-off time of the transistor. The second current supplying circuits are coupled to the output of the primary switches and each is supplied with energy only when the respective transistor is switched on, and therefore do not saturate the transformer or continuously dissipate power.

Abstract: A low current, high voltage power supply for gas discharge devices, such as neon tubes. The power supply has a free-running oscillator which generates a high frequency voltage signal which drives a light-weight, compact transformer. The oscillator has a power transistor drive, and a second transistor is used to remove the base drive of the power transistor to render it non-conductive. The second transistor also provides a path for rapid evacuation of the charge carriers stored in the base-emitter junction of the power transistor to rapidly render it non-conductive when the second transistor is energized. A safety bypass circuit is provided should a fault occur with the gas discharge device.

Abstract: A switching power supply that comprises a base drive transformer, a switch device connected to one end of the transformer's primary winding, and a transistor having its base connected to one end of the secondary winding and its emitter connected to the other end of the secondary winding, also comprises a current-dependent voltage clamp connected across one winding of the transformer. The clamp circuit prevents the voltage across the primary winding from exceeding a predetermined value so long as the magnetizing current that flows in the primary winding when the switch device is opened does not exceed a predetermined value.

Abstract: A switching control circuit has a switching control transistor between a base current path of a switching power transistor and an emitter current limiting resistor. A collector current flows through the switching control transistor in the same direction as that of an emitter current flowing through the emitter current limiting resistor when the switching power transistor is held in an ON state. The direction of a current flowing through the emitter current limiting resistor does not change even if the switching control transistor is turned on so as to turn off the switching power transistor.

Abstract: In order to provide rapid turn-off of a transistor (or thyristor) having its emitter (or cathode) at a floating potential, on drive is removed from the base of the transistor T1 and almost simultaneously a switch SW1 is closed. This causes a proportion of the current which flows through a capacitor C on turn-off of the transistor T1 to flow through a resistor R1 by way of the base of the transistor T1, thus providing a reverse base current which rapidly turns-off the transistor T1. In a practical implementation of this circuit the switching device is a transistor T.sub.off and the circuit employs a self-timing approach in which removal of an "on" control signal from the gate of a field-effect transistor T7 automatically actuates the reverse current drive.

Abstract: A circuit for controlling the base drive of switching transistor in a power supply wherein the switching transistor is coupled to the primary winding of a transformer linking the primary and secondary circuits of the power supply. Optimum operation of the switching transistor implies a desired level of saturation thereof. Base drive for the switching transistor is provided by a second conducting transistor. An excess of current flowing in the switching transistor is sensed, thereby effecting a reduction in the current flow in the second transistor. The latter condition causes a diminution in the base drive of the switching transistor and a return to its desired level of saturation.

Abstract: An electrical drive circuit arrangement to control the energization of a reactive load with a high voltage including a control stage, an electrically isolating control signal transformer and an output stage including power control semiconductor devices and having an energization input for a high voltage electrical supply and an output for the connection of a reactive load, the high voltage being prevented from reaching the control stage via the input of the output stage by the isolating transformer, the control stage including a noise-resistant guard responsive to circuit condition signals to permit or prevent generation of the control signal, the transformer restricting the signal to the output stage to a permitted control signal and the output stage generating a protection signal on a current surge in a connected reactive load, the protection signal being a potential low enough for direct application to the control stage without the need for isolating transfer to protect against the high voltage reaching th

Abstract: A DC-to-AC voltage converter for the supply of power to at least one load, comprising an input circuit and at least one output circuit galvanically separated from said input circuit, and a converter transformer. According to the invention a primary winding of the converter transformer is series-connected to a switching transistor, which series circuit arrangement is connected between a positive input terminal and a negative input terminal, with one or more resonance capacitors being connected in parallel with the collector-emitter circuit of the switching transistor and/or in parallel with said primary winding.

Abstract: The invention relates to a base control circuit for a switching transistor in which diodes are utilized to maintain the base-emitter voltage at a higher level than the collector-emitter voltage, upon the turn-on voltage being applied, to minimize switching-on losses while operating to avoid saturation.

Abstract: A circuit for preventing excessive power dissipation and for avoiding latch-up, in power switching semiconductor devices, monitors the forward conduction drop of the switching semiconductor device and removes the control electrode drive signal provided thereto, if the drive signal is insufficient for supporting the load current flowing through the driven device. The voltage across the controlled-conduction portion of the switching device is monitored and compared to a reference voltage, which may be also related to the load current, to remove switching device drive if the controlled-conduction portion voltage exceeds the reference comparison voltage.

Abstract: A switching amplifier in a bridge circuit configuration is provided with an improved base drive circuit which is highly efficient. The base drive circuit includes a base current shunting transistor across the base-to-emitter circuit of each high current transistor. The first and second high current transistors have their base-to-emitter circuits connected across the supply voltage terminals of the bridge in series with first and second inductors and in series with a first base current regulating transistor. The current in the first and second inductors increases while the first base current regulating transistor is turned on. The first and second diodes provide respective current paths for current through the first and second inductors and the base-to-emitter circuits of the first and second high current transistors when the first base current regulating transistor is turned off.

Abstract: An off-line switching regulated power supply employing a switching transistor, wherein the base drive system is improved to supply a reverse base current, remaining an interval after the termination of a forward base current, thereby the influence of the storage time of the switching transistor is removed and various drawbacks including the problem due to the incompatible characteristics of a breakdown voltage and switching speed, the problem due to delay in turning-off and the problem of overheating, are removed, resultantly enabling to provide a switching power supply which is allowed to employ a higher switching frequency.

Abstract: A drive transformer for use in a p.w.m. power supply which has alternately conducting power switching devices. The single transformer includes a primary winding, a secondary winding and a regenerative winding. When one of the devices finally becomes nonconductive the other of the devices may turnon. The regenerative winding aids the conduction of that device and also reinforces the drive signal to the device which receives from the drive circuitry of the supply a turnon drive signal.

Abstract: The high voltage field effect transistor has a drive circuit for pulse width modulation, which includes a small transformer coupled to the gate and source with a diode in series at the gate, so that a very short on-drive pulse charges the gate capacitance, and the charge is held by the diode. Another FET has its output connected between the gate and source of the high voltage FET, and its input coupled to another small transformer so that it is turned on for a short time by a very short off-drive pulse to discharge the gate capacitance and thus turn off the high voltage FET. A transformer drive circuit includes two one-shot devices connected to the pulse width modulator as leading and trailing edge detectors respectively, with their outputs connected via FET's to the on-drive and off-drive transformer primaries respectively, to provide pulses of 100-200 nanoseconds.

Abstract: A push-pull inverter circuit for an inductive load such as a fluorescent lamp. A pair of transistors alternately and repetitively apply energy to the load, and are alternately rendered conductive by stored charges produced by flyback induced voltage in the load, in cooperation with a single mutual control circuit which repetitively renders the push-pull transistors nonconductive and removes their stored charges.

Abstract: A base drive circuit for power transistors uses a base drive transformer in a dual mode, as a voltage transformer when it is driven to switch on or off, and as a circuit transformer when the transistor is conducting. Particularly a single base drive is used to drive a plurality of base drive transformer, each base drive transformer acting in the dual mode. This isolates the power transistors from each other and avoids differences in switching characteristics of the power transistors from affecting each other.

Abstract: The invention includes a first switching transistor which is actuated by a logic signal. This switching transistor is disposed in a current path from the base of the power transistor. When this switch is actuated, the invention provides a large steady state base drive current superimposed with a base current peaking pulse from a current generator. The invention also includes a second switch which applies a reverse potential to the base of the switching transistor for fast turnoff. The specific embodiments disclose circuitry for regulating forward base drive current to minimize line voltage variations and component tolerances. An improved bipolar power transistor base drive circuit for switching regulator and DC to DC converter power supplies is disclosed.

Abstract: An induction heating apparatus which includes an induction coil with an associated load and a resonant inverter circuit coupled to a DC power supply for energizing the heating coil. The inverter circuit includes a gate controlled thyristor which is cyclically gated to produce a conductive first period followed by an nonconductive second period in order to energize the heating coil. A diode of opposite polarity to the gate controlled thyristor is coupled in parallel therewith and has an impedance connected in series. The voltage across this series impedance is coupled to the gate of the gate controlled thyristor. The inverter circuit additionally includes an improper load check circuit for disabling the gating of the thyristor in the event of an improper load coupled to the heating coil, and a gate triggered timing generator for adjusting the timing of production of thyristor gate pulses to maintain substantially constant power to proper heating coil loads.

Abstract: A control circuit for a main switching transistor in a switching regulator, wherein PWM pulses are produced by varying a DC bias of triangular-wave pulses in response to a detected error signal, and which pulses are provided as a control signal for switching on and off the main switching transistor. In order to reduce power dissipation due to carrier storage at each turn-off operation of the switching transistor, a negative voltage potential is produced by a diode and a capacitor from square-wave pulses of a constant repetition frequency from which pulses the triangular-wave pulses are formed, and is applied to an emitter of an NPN transistor which operates as a variable impedance circuit for varying the DC bias of the triangular-wave pulses in response to the error signal, so that the triangular-wave pulses are biased to a negative voltage potential.

Abstract: A high voltage, pulse width regulator circuit wherein the input voltage may be up to twice the voltage rating of pass or switching transistors used in the circuit is disclosed. This is accomplished by dividing the input unregulated DC voltage or full wave rectified AC voltage in half. The divided voltage is placed on each of two input lines. The pulse width regulator utilizes two transistors or other semiconductor switches, each receiving one half the input voltage. To insure a properly regulated voltage on the output and to avoid the possibility of one of the transistors receiving more than one half the input voltage, means are provided for insuring that the voltage drop across either transistor will be limited to approximately one half the input voltage at all times. By utilizing the teachings of this invention, a pulse width regulator capable of handling an input voltage of at least twice the rating of the transistors employed in the regulator is obtained.

Abstract: A voltage regulator and switching circuit for a flash lamp control unit. A silicon transistor is used to switch on an incandescent lamp and to regulate the voltage across the lamp. A driver transistor is connected to the switch transistor in a darlington connection with the collectors connected by a diode. During initial turn on of the lamp, its filament draws a heavy current furnished by the darlington circuit. As the filament heats, its current drops to a low value. Drive current then flows through the drive transistor and a resistor to ground, reverse biasing the diode and changing the circuit to a single transistor circuit. The driver transistor is controlled by a differential amplifier having a first transistor biased by a first voltage divider network connected across the power supply and a second transistor biased by a second voltage divider network connected across the regulated voltage.

Abstract: A high-power, solid-state switching circuit includes in a preferred embodiment a first switching device susceptible to damage from excessive peak power dissipation at times of turn-on and turn-off in switching high currents from a relatively high-voltage supply, the first switching device having its main current path connected in parallel with the main current path of a second switching device that is substantially less susceptible to such damage from excessive peak power dissipation, but which has a substantially higher impedance in its main current path than the first device when turned on, the devices complementing one another via the operation of said switching circuit for turning on the second device before the first device, thereby substantially lowering the voltage across the main current path of the first device, allowing the latter to be turned on and turned off with substantially reduced peak power dissipation via the snubbing effect of the second device, and the first device relative to the second

Abstract: A dc/dc converter for controlling the current through a load which comprises a switching transistor having its emitter-collector circuit coupled between an input voltage source and the load. A control transformer having first, second and third electromagnetically coupled windings is also provided, the second winding of the transformer being electrically connected between the base and emitter of the switching transistor. A control switching logic circuit selectively generates pulses for determining the beginning and the end of the conducting period of the switching transistor, and a control circuit coupled to the logic circuit selectively short circuits the third winding thereby reducing the voltage across the second winding and driving the switching transistor into its non-conducting state.

Abstract: An improved proportional base drive circuit for rapidly and efficiently switching a high current bipolar transistor includes a transformer having first and second serially connected windings coupled in a load current path between the emitter terminal of the transistor and a load. A base terminal of the transistor is connected to a junction intermediate the two windings by a base bias circuit. The turns ratio between the two windings is selected to force a proportional base current to flow to the transistor. A third winding is provided, along with switching apparatus for exciting the third winding, whereby conduction of the load transistor can be initiated by energizing the third winding. A diverter circuit connected to the third winding allows rapid removal of current from the base of the load transistor for fast turn-off. In an alternative embodiment, a fourth winding is arranged to provide a driving current for more rapid forcing of current from the base drive circuit at turn-off.

Abstract: 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.

Abstract: A driving circuit for a power transistor switch in which a feedback transformer between the collector path of the power transistor and that of the driver transistor is used to provide a current drive to the power transistor that is proportional to the load current, and in which a reverse current drive, also proportional to the load current is applied by way of a third winding on the transformer to the emitter-base circuit of the power transistor to decrease the switching-off time of that transistor.

Abstract: A synchronized electric modulator for the control in synchronized conductance control mode of a regulation unit, thereby to assure a close control of the current peak value. A current reference is generated which varies as a function of a command signal representing the deviation of a parameter value in a system from its reference value. The current through the load is monitored and sensed to be compared to the current reference so as to produce a control signal for the regulation unit, which is dependent on the variation of the sensed current under the synchronization of external clock pulses.

Abstract: The base electrode of the switching transistor in a converter is resistively connected to the output terminal of a pulse width modulator and connected through first and second series connected diodes to a ground reference potential which is also connected to the emitter of the transistor, the junction between the diodes being electrically connected through a large capacitor to the modulator output terminal. Voltage pulses at the output terminal cause the transistor to pass collector current and the second diode to conduct for charging the capacitor. On termination of voltage pulses, the modulator connects the output terminal thereof to ground. This causes the charge voltage on the capacitor to turn the first diode on to pull the base voltage sharply negative for rapidly drawing minority carriers out of the base region.

Abstract: A base drive circuit particularly well adapted for use with bipolar power transistors in high frequency power conversion systems. When utilized in a transformer isolated inverter system, the base drive circuits present a polarity insensitive input impedance which eliminates the effects of cross-conduction between base drive circuits connected to the secondary side of the transformer.

Abstract: A base drive circuit particularly well adapted for use with bipolar transistors in high frequency power conversion schemes. The base drive circuit allows achieving desired values for both forward and reverse base drive currents simultaneously regardless of the characteristics of the bipolar transistor driven. When utilized in a transformer isolated inverter system, the base drive circuit additionally presents a polarity insensitive input impedance which eliminates the effects of cross-conduction between base drive circuits connected to the secondary side of the isolation transformer.