Electrical transmission or interconnection systems – Personnel safety or limit control features – Interlock
Patent
1983-01-27
1985-09-03
Miller, Stanley D.
Electrical transmission or interconnection systems
Personnel safety or limit control features
Interlock
307270, 307310, 307317R, H03K 326, H03K 3313
Patent
active
045394920
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a Darlington transistor circuit.
BACKGROUND
It is known to provide a Darlington transistor circuit having a power transistor and a driver transistor, the collector of which is connected to the collector of the power transistor and the emitter of which is connected to the base of the power transistor, and having an initial transistor, the collector of which is connected to the collector of the power transistor and the emitter of which is connected to the base of the driver transistor and the base of which is triggerable by means of an input signal. A Darlington transistor circuit of this general type is already known from FIG. 8 of U.S. Pat. No. 2,663,806, Darlington.
THE INVENTION
It is an object to control the temperature dependency of the switch-on voltage of a Darlington transistor circuit in accordance with a predetermined desired relationship.
Briefly, a Darlington transistor circuit which has a power transistor and a driver transistor includes a series connection of a Zener diode and a voltage divider, the base of the driver transistor being connected to the tap or junction circuit between two resistors of the voltage divider circuit. One of the resistors has its terminal remote from the junction connected to the Zener diode which, in turn, is connected for example through an inductive load to a tap point of another voltage divider; the second resistor of the first voltage divider has its terminal remote from the junction connected to the emitter of the driver transistor which, in accordance with standard Darlington circuitry, also includes a connection to the base of the output transistor.
When a predetermined voltage is placed on a cathode of the Zener diode, the driver transistor and the power transistor are both switched ON. In accordance with an advantage of the present invention, the temperature dependency of this switch-on voltage can be adjusted by adjusting the ratio of resistances between the first and second resistors forming the first voltage divider. The switch-on voltage can be transformed up as a collector-emitter limiting via the second voltage divider to the junction or tap point, of which, for example, the anode of the Zener diode is connected.
The circuit has the additional advantage that the switching time, for example to disconnect an inductive load, can be shortened and improved energy distribution can be obtained during clamped operation.
Some of the circuit elements, typically the first voltage divider resistor and the Zener diode, can be monolithically integrated with the Darlington transistor structure.
DRAWING
The single FIGURE shows the electrical circuit diagram of a Darlington transistor circuit according to the invention.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT
A first current supply line 10 is connected with the terminal B.sup.+ of a positive supply voltage. A second current supply line 11 is connected to ground. An n-p-n power transistor T.sub.3 is connected with its emitter to the second current supply line 11 and with its collector, via an inductive load ZS, to the first current supply line 10. An n-p-n driver transistor T.sub.2 is connected at the input side of the n-p-n power transistor T.sub.3. The collectors of the two transistors T.sub.2 and T.sub.3 are thereby connected, while the emitter of the driver transistor T.sub.2 is connected to the base of the power transistor T.sub.3. An n-p-n initial transistor T.sub.1 is connected at the input side of the n-p-n driver transistor T.sub.2. The collectors of the two transistors T.sub.2 and T.sub.1 are likewise connected to one another, while the emitter of the initial transistor T.sub.1 is connected to the base of the driver transistor T.sub.2. The circuit device comprising the three transistors T.sub.1, T.sub.2 and T.sub.3 is generally known as a three-stage Darlington circuit. The base of the initial transistor T.sub.1 is triggerable by means of an input signal.
Connected to the base of the driver transistor T.sub.2 is the series circuit comprising a first resistor R.sub
REFERENCES:
patent: 2663806 (1953-12-01), Darlington
patent: 3281639 (1966-10-01), Potter et al.
patent: 3390247 (1968-06-01), Webb
patent: 3454737 (1969-07-01), Pfau et al.
patent: 3465480 (1969-09-01), Hausermann
patent: 4020816 (1977-05-01), Chateau
IBM Technical Disclosure Bulletin, vol. 15, No. 4, 9-72, Self Clamping Driver, p. 1246.
Gademann Lothar
Jesse Erich
Michel Hartmut
Davis B. P.
Miller Stanley D.
Robert & Bosch GmbH
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