Switch device suitable for use in automotive vehicles

• US 5,412,255 A
• Filed: 11/04/1993
• Issued: 05/02/1995
• Est. Priority Date: 05/07/1991
• Status: Expired due to Term

• Current Assignee: VDO Adolf Schindling AG (Vodafone Group PLC)
• Original Assignee: VDO Adolf Schindling AG (Vodafone Group PLC)
• Inventors: Wallrafen, Werner
• Primary Examiner(s): Pellinen, A. D.
• Assistant Examiner(s): Fleming, Fritz M.
• Application Number:
  US08/148,033
• Time in Patent Office: 544 Days
• Field of Search: 307/9.1, 307/10.1, 307/116-118, 307/308, 307/310, 307/239, 307/240, 307/125, 307/119-124, 307/126-131, 307/139, 307/143, 307/144, 361/170, 340/438, 340/442, 340/449, 340/450, 340/450.1, 340/450.2, 340/450.3, 340/451, 340/452, 340/453, 340/455
• US Class Current: 307/116
• CPC Class Codes: H03K 17/951 Measures for supplying operating voltage to the detector circuit

Abstract

In a switch device, suitable for use as active sensor in an automotive vehicle, wherein current through a load can be switched as a function of a physical variable acting on the switch device, two terminals of the switch device can be connected together via a semiconductor switch. They also form the input of a current supply circuit. A sensor produces an electric signal which represents the physical variable and which can be fed to a threshold circuit. The semiconductor switch is controllable in pulsating manner as a function of the output signal of the threshold circuit.

Claims

1. A switch device serving to switch current through a load as a function of a physical variable acting on the switch device, the switch device comprising:

two terminals serving to connect the switch device to said load;

a semiconductor switch interconnecting the two terminals and having a control electrode;

a voltage stabilization circuit having an output terminal and being connected between the two terminals to be energizable via the two terminals;

a sensor which produces an electric signal representing a physical variable, the sensor being connected between the output terminal of the voltage stabilization circuit and one of the two terminals;

a threshold circuit coupled to an output terminal of said sensor; and

pulsating means for operating the semiconductor switch in pulsating manner as a function of an output signal of the threshold circuit;

wherein said pulsating means include a pulse generator and a logic element, said generator producing a train of output pulse signals at a predetermined frequency, output signals of the threshold circuit and of the pulse generator being applied via the logic element to the control electrode of the semiconductor switch;

in a first state of the semiconductor switch, the pulsating means places the semiconductor switch in a mainly nonconductive mode allowing for pulsations with a large pulse-duty factor including 1.0; and

in a second state of the semiconductor switch, the pulsating means places the semiconductor switch in a pulsating nonconductive mode with a small pulse-duty factor.

2. A switch device according to claim 1, wherein said voltage stabilization circuit comprises

a rectifier diode and a capacitor connected in series with said diode between said two terminals;

and

a stabilizing circuit having a first input terminal connected to a first terminal of said capacitor, and a second input terminal connected to a second terminal of said capacitor.

3. A switch device according to claim 2, wherein

the semiconductor switch is operative to be continuously non-conductive in said first switch state and is mainly conductive in said second switch state.

4. A switch device according to claim 3, wherein the pulse-duty factor in said second switch state is less than 0.10.

5. A switch device according to claim 3, wherein

said logic element is an AND circuit.

6. A switch device according to claim 3, wherein

said logic element is an exclusive-OR circuit.

7. A switch device according to claim 3, wherein

pulsating control of the semiconductor switch enables error diagnosis.

8. A switch device according to claim 1, wherein

the semiconductor switch is operative to be continuously non-conductive in said first switch state and is mainly conductive in said second switch state.

9. A switch device according to claim 8, wherein

the pulse-duty factor in said second switch state is less than 0.10.

10. A switch device according to claim 1, wherein

said logic element is an AND circuit.

11. A switch device according to claim 1, wherein

the pulse-duty factor in the first switch state is greater than 0.90 and the pulse-duty factor in the second switch state is less than 0.1.

12. A switch device according to claim 1, wherein

said logic element is an exclusive-OR circuit.

13. A switch device according to claim 1, wherein

said semiconductor switch is a field-effect transistor.

14. A switch device according to claim 1, wherein

pulsating control of the semiconductor switch enables error diagnosis.

15. A switch device serving to switch current through a load as a function of a physical variable acting on the switch device, the switch device comprising:

a first terminal and a second terminal by which the switch device is to be connected to the load and to a source of power, the source of power providing power to the load and to the switch device;

a semiconductor switch interconnecting said first terminal and said second terminal;

a diode rectifier connected to said first terminal, and a capacitor connected in series between said diode rectifier and said second terminal;

a voltage stabilization circuit connected to a junction of said diode rectifier and said capacitor, a reference voltage source connected to said second terminal, and a sensor connected between said voltage stabilization circuit and said second terminal;

a threshold circuit having a first input terminal for receiving an output signal of said sensor, and a second input terminal for receiving a reference voltage outputted by said reference-voltage source; and

pulsating means for operating the semiconductor switch in a pulsating manner as a function of an output signal of the threshold circuit to provide a pulsating current to the load, the pulsating means including a pulse generator and a logic element, said logic element receiving signals outputted by said pulse generator and said threshold circuit, said logic element outputting a pulsating signal to a control terminal of said switch wherein a pulse duty factor of the pulsating signal and of the pulsating current is varied by the sensor output.

16. A switch device according to claim 15, wherein said logic element is an AND gate or an EXCLUSIVE-OR gate, and a presence of the pulsating current is an indication of proper operation of said switch device.

17. A switch device according to claim 15, wherein

said pulse generator applies pulses to said logic element, and said threshold circuit signals said logic element via a low level signal or a high level signal as to whether the magnitude of the output signal of said sensor be below or above the magnitude of the reference voltage of said reference-voltage source;

in the presence of the low level threshold-circuit signal, said logic element is operative to place said semiconductor switch in a state of nonconduction to allow a relatively small current to flow through the switch device for powering the switch device without activating the load; and

in the presence of the high level threshold-circuit signal, said logic element operates said semiconductor switch in a pulsing mode alternating between states of conduction and nonconduction to draw pulses of a relatively large current through the load for activating the load, while allowing the powering of the switch device during intervals between the current pulses.