Electrical transmission or interconnection systems – With nonswitching means responsive to external nonelectrical... – Temperature responsive
Patent
1986-08-05
1988-01-05
Zazworsky, John
Electrical transmission or interconnection systems
With nonswitching means responsive to external nonelectrical...
Temperature responsive
307647, H03K 1772
Patent
active
047178418
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a static power switch apparatus comprising controlled semiconductor components and usable as single pole or multipole static relay or contactor for alternatig currents.
In power switching it is known to use static relays having a bidirectional power switch member comprising controlled semiconductor components, this power switch member being formed by two antiparallel thyristors or by a triac whose power terminals are connectable to a source of AC electric power in series with a load.
Generally, the power required for switching on the power semiconductor components comes either from a transfer through the control circuit of the gates of the semiconductor components, or from a leak current through the load.
In the first case, the power required has little relation with the levels available at the outputs of the circuits of electronic detection, measurement or data processing equipment.
In the second case, it is necessary to use a very sensitive control state for reducing as much as possible the leak current and including the most often a sensitive thyristor able to respond to the difficult compromise between resistance to high peak voltages, resistance to high dV/dts and a low gate current.
However, in the absence of a control signal, the energy for switching on the sensitive thyristor is derived in an inhibition circuit; the presence of the control signal suppresses this inhibition.
The purpose of the present invention is in particular to avoid these drawbacks and to create a static power switch apparatus for alternating currents having a power stage comprising controlled semiconductor component and a circuit controlling this power stage, the control circuit using a positive logic switch with low control energy reducing as much as possible the leak current through the power circuit.
In the case where it is desired to control switching on of the power semiconductor component close to the voltage zero, the purpose of the invention is to add to the positive logic switch an appropriate circuit for allowing polarizable switching on by high impedance means for minimizing the leak current of the power circuit.
The invention relates to a static power switch circuit including; one controlled semiconductor component of the thyristor or triac type whose power terminals may be connected to an AC source in series with a load, first control switch whose current path is connected to the gate of the power semiconductor component through a full wave rectifier bridge, this switch being connected to a circuit able to generate control energy of the switch in response to an input signal.
According to the invention, the control switch is a field-effect transistor with isolated gate, preferably of the high voltage MOS type, whose drain-source path is connected to the DC voltage terminals of the rectifier bridge for being connected through the bridge and at least one current limiting member at the gate(s) of the semiconductor component(s) and whose gate is connected to an output of the control energy generating circuit, which circuit comprises a galvanic isolating means.
The connection of the drain-source path of the MOS is achieved in the case of two thyristors mounted in antiparallel with the gates of these two thyristors and in the case of a triac with the gate and the electrode No. 2 of the triac.
The control circuit associated with the controlled semiconductor components thus allows the control switch to be supplied with low energy of a level equivalent to that practiced in optically-coupled isolators.
It is particularly simple and inexpensive when it comprises a transformer without ferromagnetic core or a piezoelectric ceramic for transmitting to the gate of the MOS a control signal while ensuring galvanic isolation with respect to the circuit delivering the input signal.
A second control switch may advantageously be disposed in parallel with the source-gate current path of the first MOS control switch, the second switch being controlled by a signal representative of the voltage across the DC
REFERENCES:
patent: 3221183 (1965-11-01), White
patent: 3307042 (1967-02-01), Fogleman
patent: 3328606 (1967-06-01), Pinckaers
patent: 3524997 (1970-08-01), Harnden, Jr. et al.
patent: 3648075 (1972-03-01), Mankovitz
patent: 3693060 (1972-09-01), Joyce
patent: 3801832 (1974-04-01), Joyce
Dumortier Bernard
Gast Jean-Noel
Sauvel Francois
Drucker William A.
La Telemecanique Electrique
Zazworsky John
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