Monitoring apparatus for monitoring temperature in a circuit arrangement

• US 4,851,954 A
• Filed: 10/13/1988
• Issued: 07/25/1989
• Est. Priority Date: 10/15/1987
• Status: Expired due to Fees

• Current Assignee: Dragerwerkk AG Moislinger Allee
• Original Assignee: Dragerwerk AG
• Inventors: Surig, Andreas
• Primary Examiner(s): Pellinen, A. D.
• Assistant Examiner(s): WILLIAMS, HOWARD L
• Application Number:
  US07/256,994
• Time in Patent Office: 285 Days
• Field of Search: 361/100, 361/101, 361/103, 361/106, 361/18, 307/310, 323/271, 323/272, 323/907
• US Class Current: 361/103
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor
• CPC Class Codes: Y10S 323/907 Temperature compensation of semiconductor

Abstract

Apparatus for monitoring the temperature of a circuit component in a circuit arrangement wherein the circuit can be influenced via a temperature sensor when a predetermined value is exceeded for the purpose of preventing undesired high temperatures. This apparatus is improved for its use in inherently safe electronic switching circuits in that it provides the smallest possible volumetric configuration and, in addition, enables a reliable switching characteristic to be realized which is selectable within narrow temperature ranges. It is intended that the testing of its functional capability should be possible with the aid of simple means when in the built-in condition. For this purpose, a plurality of circuit components are connected in series or in parallel.

Claims

1. The combination of an apparatus for supplying load current to a load and an arrangement for monitoring a switching component which can influence the load current, the combination comprising:

at least two of said switching components connected to each other and each of which generates heat in the presence of a defect condition;

a first temperature sensor corresponding to one of said switching components for detecting the heat generated therein in the event of a defect condition;

first circuit means for operatively connecting said first temperature sensor to the other one of said switching components for actuating the latter in response to said defect condition to thereby influence said load current to prevent said one switching component from becoming heated to unwanted higher temperatures;

a second temperature sensor corresponding to the other one of said switching components for detecting the heat generated therein in the event of a defect condition; and

,

second circuit means for operatively connecting said second temperature sensor to said one switching component for actuating the latter in response to said defect condition to thereby influence said load current to prevent said other one of said switching components from becoming heated to unwanted higher temperatures.

2. The combination of claim 1, wherein said switching components are connected to each other in series and said first and second temperature sensors are respective temperature-dependent resistors.

3. The combination of claim 1, wherein said switching components are connected in parallel with each other and said first and second temperature sensors are respective temperature-dependent resistors.

4. The combination of an apparatus for supplying load current to a load and an arrangement for monitoring a switching transistor which can influence the load current, the combination comprising:

at least two of said switching transistors connected to each other and each of which generates heat in the presence of a defect condition;

a first temperature-dependent resistor having a resistance varying with temperature and corresponding to one of said switching transistors for detecting the heat generated therein in the event of a defect condition;

first circuit means for operatively connecting said first temperature-dependent resistor to the other one of said switching transistors for actuating the latter in response to said defect condition in said one switching transistor to thereby influence said load current to prevent said one switching transistor from becoming heated to unwanted higher temperatures;

said first circuit means including;

a first bridge circuit incorporating said first temperature-dependent resistor which becomes unbalanced in response to a change in the resistance of the latter to cause said first bridge circuit to deliver a first signal; and

, a first comparator interconnecting said first bridge circuit and said other one of said switching transistors for actuating the latter in response to said first signal thereby influencing said load current;

a second temperature-dependent resistor having a resistance varying with temperature and corresponding to the other one of said switching transistors for detecting the heat generated therein in the event of a defect condition;

second circuit means for operatively connecting said second temperature-dependent resistor to said one switching transistor for actuating the latter in response to said defect condition in said other one of said switching transistors to thereby influence said load current to prevent said other one of said switching transistors from becoming heated to unwanted higher temperatures; and

,

said second circuit means including;

a second bridge circuit incorporating said second temperature-dependent resistor which becomes unbalanced in response to a change in the resistance of the latter to cause said second bridge circuit to deliver a second signal; and

, a second comparator interconnecting said second bridge circuit and said one switching transistor for actuating the latter in response to said second signal thereby influencing said load current.

5. The combination of claim 4, wherein said switching transistors are connected in series with each other and with the load.

6. The combination of claim 4, wherein said switching transistors are connected in parallel and across the load.