Abstract: The present invention provides a method for detecting the anti-island protection performance of an inverter. An RLC circuit is serially connected between the inverter and a grid connection switch, the resonant frequency of the RLC load is set as three different numerical values for enabling the same to present resistance, capacitance and inductance, and a time value from the disconnection of the grid connection switch to the operation stop of the inverter under detection is recorded after a fundamental current value of the grid connection switch is set to a different value each time; and weighted calculation is performed on the time value to obtain a test result and grade evaluation of the anti-island protection ability of the inverter.

Abstract: The present invention provides a phase control device applied to a three-phase circuit including a three-phase transformer and a three-phase breaker that turns on/off the transformer. The device suppresses an excitation rush current generated in the transformer. The device includes a controller that closes any one phase of the breaker as a closing first phase and subsequently closes the other phases, a determiner that determines the closing first phase based on residual magnetic fluxes of the respective phases in the transformer, a determiner that determines, based on a pre-arc characteristic and a closing time variation characteristic of the breaker, target closing phases and target closing times of the closing first phase and the other phases, a calculator that calculates a closing time of each phase of the breaker, and an operation time table that stores, as a median of the variation characteristic represented by a normal distribution, the calculated time.

Abstract: This invention describes a method and an electrical circuit for controlling the closing of a three-phase circuit breaker with simultaneous pole operation to mitigate the inrush current resulting from power transformer energization by taking into account the residual magnetic flux in the transformer's magnetic core. It is disclosed a method to perform controlled switching on transformer and therefore mitigate the inrush current. It is disclosed that this method can be applied to any configuration of transformers which can be, but not limited to, Y-?, Y-Y, ?-? and ?-Y with either floating or grounded neutral.

Abstract: A method is disclosed of performing point on wave switching in a multiphase electrical system having a first circuit breaker connected a first bus, the first circuit breaker being operated by a first controller, a second circuit breaker connected to a second bus, the second circuit breaker being operated by a second controller, and a subsystem transferred from the first bus to the second bus. The method can include receiving, by the second controller, system characteristics data of the subsystem, estimating, by the second controller, a time for switching based on the received system characteristics data of the subsystem and operating time of the second circuit breaker, and operating, by the second controller, the second circuit breaker at the estimated time for switching, for switching the subsystem.

Abstract: A multi-phase voltage regulator module system includes a VRM and a phase control circuit. The VRM is capable of outputting a load detecting voltage which is direct proportion to the load of the CPU. The phase control circuit outputs a first level phase switching signal to the VRM, and a core voltage outputted by the VRM to the CPU is changed from N phases to M phases when the load detecting voltage increases to a first voltage. The phase control circuit a second level phase switching signal to the VRM, and the core voltage outputted by the VRM to the CPU from M phases to N phases when the load detecting voltage decreases to a second voltage. The first voltage is higher than the second voltage. M is larger than N.

Abstract: A power distribution system (that can detect an unsafe fault condition where an individual or object has come in contact with the power conductors) regulates the transfer of energy from a source to a load. Periodically, the source controller opens an S1 disconnect switch, a and load controller opens an S2 disconnect switch. A capacitor represents the capacitance across the load terminals. If the capacitor discharges at a rate higher or lower than predetermined values after the S1 and S2 disconnect switches are opened, then a fault condition is registered, and the S1 and S2 switches will not be commanded to return to a closed position, thus isolating the fault from both the source and the load.

Abstract: An apparatus and method for protecting a power system comprising a generator providing power to an alternating current bus, a power converter for converting alternating current power on the alternating current bus to direct current power on a direct current bus, and a direct current load powered by the direct current power on the direct current bus. An undesired condition is identified at the input to the power converter from the alternating current bus. The undesired condition is caused by at least one of the power converter, the direct current bus, or the load. The power converter is disconnected from the alternating current bus in response to identifying the undesired condition for at least a time delay. The time delay is selected such that the power converter is disconnected from the alternating current bus before the alternating current bus is disconnected from the generator due to the undesired condition.

Abstract: This present inversion relates to a detection system and detection method of distributed generation islanding based on power frequency carrier. The system includes a power frequency carrier signal generating device near the terminal power distribution substation, a power frequency carrier signal detection device in distributed power grid; the power frequency carrier signal generating device is connected to the substation bus through a signal coupling transformer; the power frequency carrier signal generating device is connected with signal coupling transformer though phase A, B C live wires and the N middle wire, that results in the signal can be send by anyone signal phase, any two phases parallel way or three phases parallel way. The power frequency carrier signal detection device is connected with the low voltage power network though phase A, B and C live wires and the N middle wire.

Abstract: A system for supplying an electrical system with direct current, the system including at least two direct current power supply devices each having means of electrical connection to an alternating current power supply source and an AC/DC converter of alternating current into direct current, a module for managing the power supply of the electrical system which, after reception of an information of failure of a first active power supply device, transmits a command to start up a second inactive power supply device and a back up electrical energy storage device electrically by-pass connected between the power supply devices and the electrical system. The management module also receives the information of failure from the back up device and/or from the electrical system and transmits the command to start up the second power supply device during a discharge phase of the back up device.

Abstract: The electrical power distribution network comprises a medium-voltage feeder having an upstream end intended to be connected to a power source. The feeder includes at least first and second consecutive protection relays positioned along the feeder and defining the ends of a first element to be monitored. The first protection relay includes a search module configured to trip a breaker to interrupt the electrical power distribution: after a first time delay when the search module detects a single-phase permanent fault in a monitoring area of the first element; and after a second time delay longer than the first time delay when the search module detects a single-phase permanent fault in an additional monitoring area located downstream of the area.

Abstract: The electronic device for protecting against a polarity reversal of a DC power supply voltage comprises, produced within one and the same integrated circuit, an N-channel main transistor (TP) mounted on the line of expected positive polarity of the power supply voltage and command means (MCM) for the main transistor comprising a charging pump circuit (CP), associated with a dynamic biasing circuit (MCTRL) for the substrate regions of active components connected to the main transistor.

Abstract: Provided is a battery state monitoring circuit which detects that a voltage of a secondary battery has decreased abruptly because of an overcurrent, thereby being capable of protecting a battery device from an abrupt decrease in voltage of the secondary battery caused by the overcurrent. The battery state monitoring circuit includes a voltage comparator circuit and a power supply voltage detection circuit for detecting an abrupt decrease in power supply voltage, in which the voltage comparator circuit detects a normal overcurrent while the power supply voltage detection circuit detects the abrupt decrease in power supply voltage caused by load short-circuit.

Abstract: Methods and techniques to implement a digital signal processor for avoidance of audio feedback are disclosed, in particular, audio signal processing systems that reduce the requirement for physical segregation of sound acquisition and diffusion zones. In a more general aspect, the components and techniques described herein provide a for a sound space and sound processing equipment such that sound travelling electronically in a loop through the sound processing equipment that is output into a physical sound diffusion zone, received at the input to the sound processing equipment, and then re-amplified, etc. is attenuated over that loop by frequency modification. The frequency modification is such that, at least for some signals, on each pass through the loop, the sound processing equipment will attenuate or amplify individual sub-bands of the frequency spectrum of the audio signal that is received at the input of the sound processing equipment.

Abstract: A system comprises an AC/DC adapter having a connector. The system also comprises a portable computer that receives said connector. The portable computer comprising a delay circuit coupled to a power transistor that is coupled in parallel with a resistor. The delay circuit causes the power transistor to activate following a time delay after current from the adapter begins to flow through the resistor. As a result of a user beginning to remove the connector from the portable computer, a control transistor is activated to reset the delay circuit.

Abstract: Provided is a battery state monitoring circuit which detects that a voltage of a secondary battery has decreased abruptly because of an overcurrent, thereby being capable of protecting a battery device from an abrupt decrease in voltage of the secondary battery caused by the overcurrent. The battery state monitoring circuit includes a voltage comparator circuit and a power supply voltage detection circuit for detecting an abrupt decrease in power supply voltage, in which the voltage comparator circuit detects a normal overcurrent while the power supply voltage detection circuit detects the abrupt decrease in power supply voltage caused by load short-circuit.

Abstract: A resettable short-circuit protection circuit can terminate excessive fault currents automatically and quickly. The short-circuit protection circuit is switchable and has a low input impedance during normal operation so that there is not a significant voltage drop across the switching elements of the protection circuit. The short-circuit protection circuit allows a power source internal to a portable device to be safely connected to an external accessory where there exists the possibility that the connection could be shorted at the time power is first supplied to the external accessory or a short develops afterwards. After terminating a short-circuit condition, the protection circuit may be reset by cycling an enable signal. The fault termination and reset timing may be configured by selection of internal resistance and capacitance values.

Abstract: Method, and apparatus for operating a power feed in a computing system. One exemplary embodiment includes monitoring the power feed to ensure the power level of the entire system never remains above a first power level and only remains above a second power level for a period of time determined by a timer level.

Abstract: A method and an apparatus for monitoring a load driven by a power semiconductor switch. The method may comprise, for example: driving a control electrode of the power semiconductor switch, in such a way that a rise in the load current through the power semiconductor switch is effected after a delay time; generating a diagnostic current flowing through the load, wherein the diagnostic current brings about a voltage drop across the load before the delay time has elapsed; and evaluating the voltage drop across the load before the delay time has elapsed.

Abstract: A system and method for accomplishing power swing blocking and unstable power swing tripping schemes during disturbances of electrical networks is disclosed. The disclosed system and method eliminates the requirement of stability studies. The no-setting scheme utilizes the swing center voltage of the electrical network to carry out its functions.

Abstract: A test device is provided for testing stability of a computer when the computer is started up or shut down. The test device includes a monolithic chip and a switch module. The monolithic chip includes an input port and an output port. The input port receives a high level or a low level signal from the computer. A test control module is disposed in the monolithic chip. The switch module includes an input pin coupled to the output port of the monolithic chip and a pair of output pins corresponding to the input pin. The pair of output pins is connected to the computer, for controlling the computer to be started up or shut down. The input port of the monolithic chip is connected to the computer for detecting a state of the computer.

Abstract: A reverse current protection device includes one or more contactors in a power circuit that open to prevent current flow and close to allow current flow; an impedance buffer to invert voltage across the diode; a threshold detector to compare inverted voltage to a reference voltage to determine a good or fault diode condition; an opto-isolator actuatable by the threshold detector when at least one of a good diode condition is determined and a fault diode condition is determined; and a relay in communication with the opto-isolator to cause at least one of the one or more contantors to close in a good diode condition and open in a fault diode condition.

Abstract: The present invention relates to electrostatic discharge (ESD) protection and, more particularly, to methods and systems for improving response times of ESD triggering and clamping circuitry. An ESD protection circuit protects ESD circuitry from direct current (DC) voltage stress during normal operations by reducing terminal pad voltage level. A frequency bypass circuit implemented across an ESD protection circuit essentially acts as a short circuit during ESD events and essentially acts as an open circuit during normal operations. A frequency bypass circuit implemented in conjunction with an ESD protection circuit enables ESD triggering and clamping circuitry to react to ESD events without undue delay. Unlike an ESD protection circuit, a frequency bypass circuit does not result in substantial voltage reduction across its terminals. In an embodiment, the frequency bypass circuit includes one or more capacitors.

Abstract: The fault detection system includes at least one valid zero sequence voltage source, either from a local relay or a remote relay on a protected line. Zero sequence current is selected between total (vector sum from both ends of the protected line) measured zero sequence current or calculated zero sequence current. A zero sequence impedance-based calculation is then made and the result is compared against a threshold value to produce a trip decision. The trip decision is then applied through a normal tripping circuit or a slow tripping circuit, depending upon selected circuit conditions, involving the local and remote ends of the line.

Abstract: A connection system for communicating multiple signals between a steering wheel and a steering column of a vehicle over a single wire is provided that uses time division to multiplex multiple signals. A plurality of signals are multiplexed together ranging from two to as many signals as desired. Input switches are grouped together to form a ladder multiplexer, such as a resistive multiplexer, that includes voltage and current muxing. A plurality of ladder multiplexers are joined together in a time division multiplexing scheme that operates continuously. An analog line may be added as a single channel. A marker pulse is used to signal the start of each time window to be divided for all the channels. Time division multiplexing is provided by a number of switching means.

Abstract: A power providing device that has a battery, a protective housing a terminal cap, and a fuse on a substrate.

Abstract: A close control signal or an open control signal is outputted after a wait time of a half cycle or less upon a close command or an open command to a breaker in order to make a breaker at a predetermined interpole voltage phase or to open a main circuit current at a predetermined phase. When the close command or the open command is detected, a delay time is determined based on latest zero point time and a predicted close time or a predicted open time, and the close control signal or the open control signal is outputted after a lapse of the delay time so as to make or to open a pole at the predetermined phase of the interpole voltage or the main circuit current.

Abstract: A protection circuit for a boost power converter provides input under-voltage protection and output over-voltage and over-current protection. The protection circuit includes a control power MOSFET connected in series between the ground of the boost power converter and the ground of the load. The arrangement of the circuit makes it easy to drive the gate of an N-channel power MOSFET and is ideal for current-limiting control, which utilizes the Rds-on of the MOSFET as a current sensing element. Neither a specific gate-driver nor a current sensing resistor is required, and thus high efficiency can be achieved. Furthermore, the slow slew-rate at the gate of the MOSFET provides a soft-start to the load. The protection circuit includes a temperature compensation circuitry to offset the variation of the Rds-on. A time delay circuit prevents the switching elements and protection elements from overload damage.

Abstract: For an electronic device having at least one power switch for each of two or more power sources such that the power switches can be selectively activated or deactivated depending on a signal supplied to them, a protection circuit having a current-sense circuit coupled to measure the current from the two or more power sources, and a latch for producing a switch deactivating signal and applying it to the switches in response to an over-current signal from the current-sense circuit can protect the switches and the electronic device from soft-short circuits and absolute short circuits. Bypass resistors coupled to the switches allow the electronic device to receive a small current ("pre-charge") before any of the switches are activated so that a comparator can test for the presence of various types of short circuits. Additionally, the precharging brings the electronic device to a higher voltage (as compared to no pre-charging) when one of the switches is activated, thereby helping to reduce in-rush currents.

Abstract: The electrical power to a device, such as a pump, is monitored by multiplying a current signal with a voltage signal to provide a power signal. Typically when the power signal is outside a predetermined range, power to the device is interrupted.

Abstract: A programmable control unit for protecting an appliance connected to a household power source comprises a modular unit plugged into a household power socket. The modular unit presents a socket for plugging a household appliance therein. An internal microprocessor has program logic for analyzing the period of current flow to the household appliance and/or the power consumed thereby. Once the time period of operation and/or rate of energy consumption exceeds preselected values, the program logic of the microprocessor opens a relay so as to cease current flow to the appliance. The maximum threshold values of time and/or energy can be varied by the user according to the utilized appliance. The use of the intermediate unit enables a plurality of appliances to be safely coupled to the household power.

Abstract: The invention relates to a method for protecting an I/O electronic circuit against overvoltages. The I/O circuit of the electronic circuit is provided with a current path (1) comprising a first diode (V1N), through which current path a current (ip) flows when the mains voltage is negative, and with a second current path (2) comprising a second diode (V1P) and a thyristor (T1), the thyristor (T1) being fired by a time-delay circuit charged by a positive voltage, and that the current flowing through the current paths (1,2) is used to trigger a protection device.

Abstract: In a relay protective system a method of providing volts per Hz, loss of field, ground differential, phase distance and over voltage protective relay functions. In addition, the inventive method provides an improved method to selectively block any of the above functions in response to input contacts and selectively activate output contacts in response to operation of the above functions using programmable inputs and outputs.

Abstract: A protective circuit is used in conjunction with a switching power source for protecting the latter from overload and from short circuits. It is detected whether the current at the primary winding current of a switching power source transformer, the load current of the switching power source, or both exceed predetermined reference voltages. If so, supply of power to the switching power source is interrupted for a predetermined period of time, thereby bringing the switching power source into inoperable condition in this duration.

Abstract: An overcurrent protection circuit for a power transistor for generating a main current in response to a gate drive voltage generated by a gate circuit. The overcurrent protection circuit includes a current detection circuit for detecting the main current flowing in the power transistor to generate a detection voltage corresponding to the main current, and a level detection circuit connected to receive the detection voltage for generating a control current corresponding to a difference between the detection voltage and a prescribed value when the detection voltage exceeds the prescribed value. The overcurrent protection circuit further includes a current control circuit connected to receive the control current for limiting the main current by regulating the gate drive voltage based on the control current, and a drive instruction control circuit connected to receive the control current for making the main current zero by controlling the gate drive voltage to an OFF condition based on the control current.

Abstract: An electronic automatic energizing damping device for connection to a source of electrical energy to protect and safeguard continuously all the devices, instruments, equipment and systems, connected to the source. The device comprises a control stage and a power stage. The control stage monitors the operating conditions of both the A.C. line and the load energized by it via the power stage, in order to detect irregularities in any of the programmed parameters of the voltage or the current, and supplies control signals that regulate the power stage. The power stage supplies the energy of the network to the load, according to the commands of the control stage. The control stage features a voltage sensor circuit, a current sensing circuit, a comparison circuit to receive the output of the voltage sensor circuit and an energy relay control circuit. The power stage comprises a surge breaker and suppressor, and an optical interface circuit.

Abstract: The invention is directed to an improved method and apparatus for monitoring the status of an AC electrical transmission line connected between first and second locations. In a disclosed embodiment of the method of the invention, first signal parameter values are generated, for the first location, by time integrating between zero-crossings of an AC signal parameter measured at the first location. Second signal parameter values are generated, for the second location, by time integrating between zero-crossings of the AC signal parameter measured at the second location. The second signal parameter values are transmitted to the first location. In a form of this embodiment, the second signal parameter values transmitted for each of the three phases are transmitted only for time periods between successive zero-crossings beginning with a zero-crossing of one sense (e.g.

Abstract: An electronic fuse is intended to be triggered should the current from a load (LA) exceed a predetermined value. The load current is restricted first by a switch in series with the load, the switch being kept in a closed or open state by pulses from a pulse length modulator (PB). The pulse length of the modulator is controlled by a sensing circuit (AK) such that when the load current exceeds the predetermined value, the circuit sends a control signal varying as the load current, so that the closing time of the switch (OM) decreases with increasing load current. After a practically contant time the switch is thereafter set to a permanently open state.

Abstract: It is desirable to provide remote digital protection of distribution transformers. This specification discloses a protection system able to measure and compare increases in both negative and positive phase reference currents on a distribution cable feeding a transformer and to trigger a circuit breaker to isolate the cable only if the negative sequence current increase exceeds a predetermined proportion of any simultaneous positive sequence current increase. Consequently, engergizing with a 12.5% unbalance current has been found possible without false tripping.

Abstract: An inverter having an output connected to a load through a reactor and an output filter capacitor terminal voltage of the capacitor is monitored, and an interlock operation for interrupting the delivery of the inverter transistor drive signals is released when the terminal voltage does not exceed a predetermined level. When the interlock operation for cutting off the drive signals of the transistors has started and continued for a predetermined time, it is further continued when the terminal voltage of the output filter capacitor does not drop below a set level and is released for the first time when the output filter capacitor is sufficiently discharged to render the terminal voltage the set level or below.

Abstract: The invention concerns a system for monitoring the operating condition of a switch by utilizing one or more integrating stages to determine the switching capacity and prevent overstresses. One or more monitoring devices for current, switch action rate, arc quench chamber insulation, contact condition, mechanical condition, operating temperature, or contact voltage are provided, which report the equipment condition, particularly the switching capacity. The sensors are functionally connected with the switchgear drive via a processing stage. The current sensors, together with a counting device, can report the .intg. i.n.dt, i.e. a measure of the stressing of the switch, and in doing so can disable the drive of the equipment. The invention serves the early detection of switchgear which is no longer fully operational, so that these can be replaced before an overstress occurs.

Abstract: An induction heating apparatus includes an inverter (5) which is driven by a DC power supply (3), and the inverter (5) includes a heating coil (9) and a switching transistor (11) which is connected thereto in series. The switching transistor (11) is turned on or off by a control circuit (35) to control a current flowing through the heating coil (9). The control circuit (35) takes a collector voltage of this switching transistor (11) from the point where the heating coil (9) and the switching transistor (11) are connected in series through a terminal (39). An integrated voltage of this collector voltage is generated in the control circuit (35), and the collector voltage is compared with the integrated voltage. When the former becomes lower than the latter, after a certain delay time, a switching signal is outputted from the control circuit (35), and the switching transistor (11) is turned on. Such a delay time is preferably varied in response to the magnitude of the collector voltage.

Abstract: A supervisory control system for microprocessor based appliance controls, the supervisory control system incorporating means for detecting dynamic failure of a microprocessor incorporated in the appliance control, means for disabling the high energy circuits in the associated appliance if the microprocessor is not operating in a normal mode and switch means requiring a physical or mechanical operation to enable energization of the high energy circuits of the associated appliance whereby the high energy circuits of the associated appliance are disabled unless at least two predetermined criteria are met.

Abstract: Apparatus is provided for detecting the presence of a high impedance arcing fault on an electrical circuit, particularly a high voltage power line. Detection of a high impedance fault is realized by monitoring the high frequency components of the alternating current in the circuit, and evaluating the high frequency components of each cycle of the alternating current using a microcomputer operating in accordance with a program of instructions, to determine the occurrence of a significant increase in magnitude of the high frequency components, and then to determine whether the increase exists for a prescribed period of time and follows a prescribed pattern. The high frequency components are monitored using a current-to-voltage transducer coupled to the electrical circuit, bandpass filters coupled to the transducer, and an analog-to-digital converter providing digitized samples of the filtered transducer output voltage signal.

Abstract: In a digital protective relaying device for protecting electric power transmission line including an electric station at each end thereof, and each electric station including at least one circuit breaker to be tripped by a protective relay for protecting the own station, a digital protective relay provided with a computer is further provided at each end so as to receive electrical data in digital form from the electric stations for operating in an ordinary protective operation. As a control condition occurs in one station, the condition is sent to a digital protective relay provided at the other end of the transmission line, thereby changing the operational steps of the computer included in the protective relay.

Abstract: The energy interlock system contains a measuring device, a discriminator and a switch. The measuring device determines the level of the particle beam pulses which are emitted by the accelerator. For this purpose it contains a target which is exposed to the particle beam pulses. The discriminator determines whether the level of the particle pulses has crossed a predetermined value. The switch is operated by the discriminator. It is connected for supervision of the accelerator.

Abstract: A protective relay circuit includes a first a-c level detector or bi-polar threshold circuit to which a polarizing signal V.sub.POL is applied. An output is provided from the first a-c level detector only when the magnitude of V.sub.POL exceeds a predetermined value. Also included is a second a-c level detector or bi-polar threshold circuit to which an operating signal V.sub.OP is applied. An output is provided from the second a-c level detector only when the magnitude of V.sub.OP exceeds a predetermined value. The output of the first level detector is compared in a coincidence circuit with the output of the second level detector. The detection of coincidence for a predetermined time period, as measured by a characteristic timer, results in an output signal for use in controlling operation of a trip coil of a circuit breaker.

Abstract: An electric control system is provided for a motor vehicle which automatically disconnects electric loads from the battery of the vehicle when the vehicle is not in use, and in the event that the driver leaves the vehicle without turning off the headlights, radio, or other accessories. The control system is connected to the battery of the vehicle, as well as to the generator and to the ignition switch. The system senses excess current from the battery under conditions when the generator is not functioning and when the ignition is turned off. However, a particular current threshold is established, so the system will not respond to normal current drain, such as from electric clocks, and the like. Also, a predetermined time delay is built into the system, so that the headlights, and other accessories will not be turned off the moment the driver stops his vehicle and turns off the ignition.

Abstract: Protective relay apparatus for developing signals responsive to subsynchronous current oscillations in a three-phase electrical power system, and for analyzing the signals to determine when corrective action is necessary. The positive sequence component of a subsynchronous current oscillation is developed via a summing arrangement, which eliminates the need for sequence filters. The positive sequence component of a subsynchronous current oscillation is processed to determine if it is an electrical transient which would shock the mechanical system of a turbine generator, or machine, to be protected, into mechanical resonance. It is also processed to determine if it is due to a growing mechanical oscillation of a turbine generator, such as might be initiated by a change in a parameter related to the turbine generator.

Abstract: Transient voltage overshoot is known to occur when primary current in a multi-phase X-ray generator high voltage transformer is switched on. Transient overshoot is supressed by connecting an impedance in series with the primary current switch. A second switch short circuits the series impedance after a time delay whose length is controlled as a direct function of the primary voltage and as an inverse function of the primary current.The secondary switch and time delay circuits may comprise self-powered modules which may be added to the primary circuits of existing X-ray generators without additional sensing or power supply connections.

Abstract: The present invention provides means for sequencing various supply voltages to electronic circuits and devices to thereby protect those circuits and devices from exposure to deleterious voltages. A first transistor switch connects a first voltage source to a first output terminal. A second transistor switch is connected to the control electrode of the first transistor switch. The second transistor switch, when conducting, causes the first transistor switch to conduct. The second transistor switch is turned on by a second voltage source which is connected through a delay circuit to the control electrode of the second transistor switch. The second voltage source also is connected through a diode and capacitor circuit to a second output terminal.