GB2048596A

GB2048596A - Device for switching D-C circuits

Info

Publication number: GB2048596A
Application number: GB7914715A
Authority: GB
Original assignee: CH POLT I
Current assignee: CH POLT I
Priority date: 1979-04-27
Filing date: 1979-04-27
Publication date: 1980-12-10
Also published as: GB2048596B

Abstract

The present invention relates to a device for switching d-c circuits. The switching device comprises a transistor gate (1) having power electrodes (2,3) connectable in a d-c circuit. A control electrode (8) is electrically coupled to a movable contact (9) of a switch (10) of a control unit (11). The control unit (11) includes a capacitor (12) connected between the control electrode (8) and the power electrode (3) and two d-c generators (13, 14). The d.c. generators have one pair of opposite-polarity leads, i.e. one of each generator, electrically coupled to stationary contacts (15, 16) of the switch (10) and each of the other pair of opposite-polarity leads connected to at least one of the power electrodes (2, 3) of the transistor gate (1). This switching device is primarily designed to effect contactless and continuous switching in the circuits of self-contained electrical systems on aircraft, helicopters, and motor vehicles. <IMAGE>

Description

SPECIFICATION Device for switching d-c circuits The present invention relates to a device for switching a d-c circuit.

The invention provides a device for switching d-c circuits, comprising a transistor gate having power electrodes connectable in a d-c circuit and a control electrode electrically coupled to a movable contact of a switch of a transistor gate control unit, the con trol unit including a capacitor connected between the control electrode and one of the power electrodes of the transistor gate, and two d-e generators having one pair of opposite-polarity leads, i.e. one of each generator, connected to stationary contacts of said switch and each of the other pair of opposite-polarity leads connected to at least one of the power electrodes of said transistor gate.

Provision in the switching of a capacitor between the control electrode and one of the power electrodes of the transistor gate permits continuous switching in the control electrode circuit of the trans istorgate, which enhances reliability of the device.

Provision of two d-c generators electrically coupled to the movable contact of the switch and of the aforesaid capacitor permits switching in d-c circuits in accordance with a linear or an exponential law, which in effect decreases switching variations at the bus bars of a power source.

The invention will now be more particularly described with reference to the accompanying drawings, wherein: Figure 1 is a circuit diagram of one embodiment of a device for switching d-c circuits according to the invention; and Figure 2 (a and b) illustrate signalwaveforms at the outputs of circuit elements of the device shown in Figure 1.

Referring to the drawings the device for switching d-c circuits comprises a transistor gate 1 (Figure 1) whose power electrodes 2 and 3 are placed in a d-c circuit. As shown, the d-c circuit incorporates a d-c power source 4 whose equivalent circuit includes an e.m.f. source 5 and an internal resistor 6. A powerconsuming unit 7 is connected in series with the d-c power source 4.

A control electrode 8 of the transistor gate is electrically coupled to a movable contact 9 of a switch 10 of a transistor gate control unit 11. In the preferred embodiment of the invention the transistor gate 1 employs a unipolartransistor.

The control unit 11 includes a capacitor 12 inserted between the control electrode 8 and one of the power electrodes 3 of the transistor gate 1.

The control unit 11 also incorporntes two d-c generators 13 and 14. One pair of combined opposite-polarity leads of the generators 13 and 14 is connected to the power electrode 3 of the transistor gate 1, while the other pair of opposite-polarity leads thereof is connected to stationary contacts 15 and 16 of the switch 10.

In another embodiment of the invention the opposite-polarity leads of the generators 13 and 14 are not combined, being connected to both power electrodes (2 and 3) of the transistor gate 1.

In the preferred embodiment of the invention the d-c generators 13 and 14 employ current regulators and voltage sources. The regulated current flowing through the capacitor 12 produces a linearly-varying voltage, which results in linear variation of current in the power-consuming circuit 7.

In still another embodiment of the invention the d-c generators 13 and 14 comprise d-c power sources with resistors connected thereto. In this case, the voltage across the capacitor 12 varies exponentially, which results in exponential variation of current in the power-consuming circuit 7.

The power electrodes 2 and 3 of the transistor gate 1 are connected to positive and negative supply bus bars 17 and 18 through the power-consuming circuit 7.

The timing diagrams of Figure 2 show signal waveforms at the outputs of the circuit elements to enable a better understanding of the operation of the preferred embodimentofthe invention. In Figure 2, the diagram "a" shows a current waveform at the output of the device with switching effected according to the linear law and the diagram "b" shows a voltage waveform at the supply bus bars 17 and 18.

the hereinproposed device for switching d-c circuits operates in the following manner.

In the initial ("off") position, the contact 9 (Figure 1 ) of the switch 10 is closed to the contact 16, the voltage across the capacitor 12 being negative with respect to the bus bar 18. This voltage is applied between the control electrode 8 and the power electrode 3 so that it cuts off the transistor gate 1 preventing the passage of current through the powerconsuming circuit 7.

Turning the switch 10 to the "oh" position closes the contact 9 to the contact 15 and causes the current of the generator 14 to flow through the capacitor 12.

The current 1 (Figure 2a) increases in the powerconsuming circuit 7 (Figure 1) until the transistor gate 1 is made fully conductive.

The switching variation A U1 (Figure 2b) of the voltage of the power source 4 (Figure 1), equal to the difference between the instantaneous value of voltage across the buses 17, 18 and the rated value of voltage U1 (Figure 2b) of the power source 4 (Figure 1), is determined from the formula: A Ut = Lt' (1) ti where L = inductance of the resistor6 of the power source 4; L1 = rated current of the power-consuming circuit 7; and t, = time at which the transistor gate 1 is changed over from the "off' to the "on" state.

With preset values of Land Lt, the value A U, (Figure 2b) is decreased as desired by changing the time t1. The time t1 is dependent on the capacitance of the capacitor 12 (Figure 1 ) and on the current of the generator 14.

Turning the switch 10 to the "off" position closes the contact 9 to the contact 16 and causes the charg ing current to flow from the generator 13 to the capacitor 12. As a result, the capacitor 12 will be charged and the transistor gate 1 will be turned off in accordance with the linear law. As this happens, the current 1 (Figure 2a) will also be decreased in the power-consuming circuit 7 in accordance with the linear law.

In this case, the voltage switching variation A U2 (Figure 2b) is determined from the formula: iN U2 = L l2 (2) t2 where t2 = time at which the transistor gate 1 is changed over from the "on" to the "off" state.

The switching variations depend on the time t2 which, in its turn, is dependent on the rated capacitance of the capacitor 12 (Figure 1 ) and on the current of the generator 13.

No account is taken in the formulas (1) and (2) of a voltage drop due to the active component of the internal resistor 6 of the power source 4. The existing error is, however, small since a switching drop in voltage due to the active component of the internal resistor 6 is substantially smallerthan the switching variations due to the inductive component of the resistor 6.

It is, therefore, possible to decrease as desired the voltage switching variations A U1 and A U2 by changing the switching times tl and t2. This is done by varying the currents of the generators 13 and 14 and the rated capacitor 12.

The above switching device is primarily designed to effect contactless and continuous switching in the circuits of self-contained electrical systems on aircraft, helicopters and motor vehicles.

Claims

CLAIMS 1. Adeviceforswitching d-ccircuits, comprising a transistor gate having power electrodes connected able in a d-c circuit and a control electrode electrically coupled to a movable contact of a switch of a transistor gate control unit, the control unit including a capacitor connected between the control electrode and one of the power electrodes of the transistor gate, and two d-c generators having one pair of opposite-polarity leads, i.e. one of each generator, connected to stationary contacts of said switch and each of the other pair of opposite-polarity leads connected to at least one of the power electrodes of said transistor gate.
2. A device for switching d-c circuits as hereinbefore described with reference to, and as shown in the accompanying drawings.