Thomson-Csf

Sgs-Thomson Microelectronics S.r.l.

Sgs-Thomson Microelectronics S.a.

Klaus Rischmuller

Claudio Diazzi

Bruno Murari

Andrea Cuomo

A gate control circuit is provided for a power MOS transistor (T) having an input capacitance (C.sub.e). The transistor gate is in series with an inductance (L). The inductance is initially precharged. First switch, element (T2, T3) transfers the energy stored in the inductance towards the input capacitance during a switching on condition of the power MOS transistor. Second switch element (T1, T4) transfers back the energy stored in the input capacitance back to the inductance during a switching off condition.

Gate control circuit for MOS transistor

A series of Zener diodes (25) and an electronic power switch, such as an IGBT (18), are connected across a power supply. A circuit including a resistor (20) in series on the electronic switch, a threshold device (36, 38) connected to the resistor and a ramp generator with multiplier (40, 42, 44, 46, FIG. 2) or a thermal sensor (50, 44, 46 FIG. 3) detect the energy level dissipated in the electronic power switch when a transient occurs when the level exceeds a present value, the circuit supplies an output signal to a monostable circuit (26, 28, 48) to drive the electronic power switch with low resistance conditions for a preset time starting from the occurrence of the output signal. Another threshold device, connected to a resistor (30, 32), preferably senses the instantaneous power dissipated in the electronic switch to control the monostable circuit when the instantaneous power is higher than a preset threshold.

Device for protecting semiconductor circuits against transients on the

In a power converter circuit directly or indirectly connected to the power distribution network, the protection from voltage spikes which may occur on the power supply rail is implemented in a manner as to consent the utilization of at least a portion of the energy associated with the spike by storing portion of said energy in the reactive components of the converter circuit itself instead of dissipating completely the energy through a dissipating elements as in prior art arrangements. The novel circuit arrangement utilizes one or two spike sensors the output signal or signals of which are fed to logic gates which determine a certain configuration of the analog switches of the converter circuit. A protection voltage limiting element (zener diode, avalanche diode, voltage-dependent resistor, etc.) is functionally connected across the analog switch connected between the reactive element of the converter circuit and the power supply rail and limits to its intrinsic breakdown voltage the maximum voltage across the switch.

Protection of power converters from voltage spikes

A switching control circuit for a power transistor is provided. For applying an initial negative base current for disabling of the power transistor, a capacitor is provided which stores the energy required by charging not only when the power transistor is enabled but also when it is disabled. The capacitor discharges through a circuit for a time fixed by the time constant of a series RC network; this time is chosen of the order of time required for destoring the charges of the power transistor.

Transistor base control circuit for high frequency operation

A switch comprising two transistors connected in the form of a mixed Darlington circuit. The base of the second transistor is connected to the collector of a third transistor. The emitters of the first and third transistors are interconnected and the base of the third transistor is connected to the base of the third transistor, which is itself connected to the collector of the second transistor and to earth via a polarization resistor. An example of an integrated embodiment is disclosed.

Switch controllable off and on by pulses

A process for using a Darlington circuit comprising a main transistor and a pilot transistor wherein the collector voltage of the main transistor is compared with its base voltage. The resulting signal is transmitted to a switch feeding a control current to the base of the pilot transistor or the base of the main transistor. Thus, the circuit operates as a Darlington circuit or else the main transistor operates independently according to the level of the collector current.

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Aix en Provence, France

Klaus Rischmuller