GB2273213A - Thermal protection of electronic devices - Google Patents

Thermal protection of electronic devices Download PDF

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Publication number
GB2273213A
GB2273213A GB9225486A GB9225486A GB2273213A GB 2273213 A GB2273213 A GB 2273213A GB 9225486 A GB9225486 A GB 9225486A GB 9225486 A GB9225486 A GB 9225486A GB 2273213 A GB2273213 A GB 2273213A
Authority
GB
United Kingdom
Prior art keywords
electrical circuit
voltage
circuit according
input
control means
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9225486A
Other versions
GB2273213B (en
GB9225486D0 (en
Inventor
Kevin Trevor Talbot
Alan Rowe
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
MG Rover Group Ltd
Original Assignee
MG Rover Group Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by MG Rover Group Ltd filed Critical MG Rover Group Ltd
Priority to GB9225486A priority Critical patent/GB2273213B/en
Publication of GB9225486D0 publication Critical patent/GB9225486D0/en
Publication of GB2273213A publication Critical patent/GB2273213A/en
Application granted granted Critical
Publication of GB2273213B publication Critical patent/GB2273213B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/08—Modifications for protecting switching circuit against overcurrent or overvoltage
    • H03K17/081—Modifications for protecting switching circuit against overcurrent or overvoltage without feedback from the output circuit to the control circuit
    • H03K17/0812—Modifications for protecting switching circuit against overcurrent or overvoltage without feedback from the output circuit to the control circuit by measures taken in the control circuit
    • H03K17/08126—Modifications for protecting switching circuit against overcurrent or overvoltage without feedback from the output circuit to the control circuit by measures taken in the control circuit in bipolar transitor switches
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H5/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection
    • H02H5/04—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature
    • H02H5/044—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature using a semiconductor device to sense the temperature
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/08—Modifications for protecting switching circuit against overcurrent or overvoltage
    • H03K2017/0806—Modifications for protecting switching circuit against overcurrent or overvoltage against excessive temperature

Abstract

A control chip 10 controls an internal load 12 and an external load 14 via switch devices 16, 18 mounted on a common die. The characteristics of the switch devices are temperature dependent. The voltage Vx at the input to one of the switch devices 16 is monitored by the control chip which turns off the power to the external load on detection of a pre-determined change in this voltage. Such a change may be caused by an increase in the temperature of the switch devices due to, for example, a short in the external load. <IMAGE>

Description

THERMAL PROTECTION OF ELECTRONIC DEVICES The present invention relates to the protection from overload of an electronic circuit component such as a power device using the thermal characteristics of the component. In particular it concerns the protection of a switching component which is controlled by a control means to drive a load. The present invention is, for example, suitable for application in the electrical systems of vehicles.
It is known to protect electronic components by current sensing or voltage sensing. It is also known to use a temperature sensor, such as a temperature depenaent thyristor, to sense the temperature of a component such 5 a power switch, and to turn off the power switch if its temperature rises too much. However this type of temperature sensing is expensive.
The present invention provides an electrical circuit comprising a control means and switch means having one input connected to an output of the control means and one output for driving a load wherein said one input is connected to an input of the control means, the voltage ot said one input is dependent upon the temperature of the switch means and the control means is arranged to monitor the voltage at said one input and turn off the power to the load in response to a preaetermined change in said voltage.
Accordingly the present invention can provide a simple and cheap way of protecting a switch means which is controlled by a control means by using the control means also to monitor the temperature of the switch means.
The switch means may include a plurality of switch devices which are preferably thermally coupled to one another, for example by being mounted on the same die. The switch may include two switch devices, one having the said one input and the other driving said load.
The present invention also provides an electrical circuit comprising an electrical component controlled by a control means, the component having a voltage associated with it that is temperature dependent, and the control means being arranged to monitor said voltage and alter an input to the component in response to a pre-determined change in said voltage.
The electrical compontent may comprise a plurality of sub-components, said voltage being associated with one of said sub-components and said input being associated with another of said sub-components.
Said pre-determined change may comprise passing through a threshold voltage, to either a higher or a lower voltage, or exceeding a pre-determined rate of change.
Preferably the control means includes a memory, such as E2ROM, onto which the character of said pre-determined change can be written. This enables the temperature monitoring to be matched accurately to the switch means.
Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a circuit diagram of an embodiment of the invention; and Figure 2 is a graph of the input voltage to a switch means of the embodiment of Figure 1 as a function of temperature.
A control chip 10 forming part of a control unit 8 is arranged to control first and second loads 12, 14 via a switch means 15. The switch means 15 comprises two switch devices 16, 18, each being made up of a pair of bi-polar transistors in a Darlington configuration. Each of the switch devices 16, 18 has an input 20, 22 connected via a resistor 21, 23 to a respective output 24, 26 of the control chip 10, a collector output 28, 30 connected to a respective one of the loads 12, 14 and an emitter 32, 34 connected to earth. The switch devices 16, 18 are therefore controlled independently of each other by the control chip 10 to drive the loads 12, 14. The first load 12 is in this case a fixed load internal to the control unit 8, and the second load is an external load, in this case a relay coil.
The switching devices 16, 18 are mounted on a common die 36 close to one another. Because the die 36 on which the switching devices 16, 18 are mounted is thermally conductive the switching devices are thermally coupled to one another so that if one of them heats up for any reason, the other one heats up also.
The switching devices 16, 18 have characteristics which are thermally dependent, and therefore the voltages on their inputs and outputs vary if the devices are subjected to temperature changes. In particular the voltage Vx at the input 20 to the first switch device 16 decreases as the temperature of that device increases, as shown in Figure 2, at a rate of about 8 mV per aegree Celsius.
The input 20 to the first switch device 16 is connected to an A/D input of the control chip 10 so that the control chip 10 can monitor the voltage Vx.
Under normal use, because the second load 14 is external, it will vary slightly and so the current through the second switch device 18 will vary slightly. This will affect the temperature of the two switch devices 16, 18 and therefore the voltage Vx. Because the first load 12 is internal it is fixed and therefore has little or no effect on the temperature of the switch devices or the voltage Vx.
The control chip 10 monitors the temperature of the switch means 15 by repeatedly checking the voltage Vx against a value Vm stored in E2ROM memory in the control chip to check that Vx does not fall below Vm.
In the event of overheating of the control means 15, either because of a short on the external load 14 or because of heat reaching the switching means from some other source, the control chip detects that the voltage Vx has dropped below Vm and turns off the power to the external load 14.
It would obviously be possible in other circumstances for the control chip to turn off the power to any number of loads which it controlled depending on what was required for the greatest safety.

Claims (15)

1. An electrical circuit comprising a control means and switch means having one input connected to an output of the control means and one output for driving a load wherein said one input is connected to an input of the control means, the voltage of said one input is dependent upon the temperature of the switch means and the control means is arranged to monitor the voltage at said one input and turn off the power to the load in response to a pre-determined change in said voltage.
2. An electrical circuit according to claim 1 wherein the switch means includes a plurality of switch devices.
3. An electrical circuit according to claim 2 wherein the switch means includes two switch devices, one having said one input and the other driving said load.
4. An electrical circuit according to claim 2 or claim 3 wherein the switch devices are thermally coupled to one another.
5. An electrical circuit according to claim 4 wherein the switch devices are mounted on a common die.
6. An electrical circuit according to any foregoing claim wherein said pre-determined change comprises passing through a threshola voltage.
7. An electrical circuit according to any foregoing claim wherein said pre-determined change comprises exceeding a pre-determined rate of change.
8. An electrical circuit according to any foregoing claim wherein the control means includes a memory onto which the character of said pre-determined change can be written.
9. An electrical circuit according to Claim 8 wherein said memory comprises E2ROM.
10. An electrical circuit according to any foregoing claim wherein the switch means comprises at least one transistor.
11. An electrical circuit according to claim 10 wherein the switch means comprises at least one pair of transistors in a Darlington configuration.
12. An electrical circuit according to claim 10 or claim 11 wherein at least one of the transistors is a field effect transistor.
13. An electrical circuit comprising an electrical component controlled by a control means, the component having a voltage associated with it that is temperature dependent, and the control means being arranged to monitor said voltage and alter an input to the component in response to a pre determined change in said voltage.
14. An electrical circuit according to claim 13 wherein the electrical component comprises a plurality of sub-components, said voltage being associated with one of said sub-components and said input being an input to another of said sub-components.
15. An electrical circuit substantially as hereinbefore described with reference to the accompanying drawings.
GB9225486A 1992-12-05 1992-12-05 Thermal protection of electronic devices Expired - Fee Related GB2273213B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9225486A GB2273213B (en) 1992-12-05 1992-12-05 Thermal protection of electronic devices

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9225486A GB2273213B (en) 1992-12-05 1992-12-05 Thermal protection of electronic devices

Publications (3)

Publication Number Publication Date
GB9225486D0 GB9225486D0 (en) 1993-01-27
GB2273213A true GB2273213A (en) 1994-06-08
GB2273213B GB2273213B (en) 1996-05-01

Family

ID=10726199

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9225486A Expired - Fee Related GB2273213B (en) 1992-12-05 1992-12-05 Thermal protection of electronic devices

Country Status (1)

Country Link
GB (1) GB2273213B (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2319414A (en) * 1996-11-16 1998-05-20 Rover Group Thermal protection of electronic switches
GB2393339A (en) * 2002-08-01 2004-03-24 Sony Corp Multichip module with high temperature shutdown

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4039928A (en) * 1976-07-19 1977-08-02 Pertron Controls Corporation Electrical operating circuit having semiconductor device junction temperature monitoring
US4092693A (en) * 1976-03-12 1978-05-30 Pioneer Electronic Corporation Temperature sensing protection circuit for ic power chip having thermal hysteresis characteristic
US4669026A (en) * 1985-09-09 1987-05-26 National Semiconductor Corporation Power transistor thermal shutdown circuit
US4896245A (en) * 1989-03-13 1990-01-23 Motorola Inc. FET overtemperature protection circuit
GB2223636A (en) * 1988-09-28 1990-04-11 Borletti Climatizzazione Electric motor control and cutoff device
US4982307A (en) * 1989-12-04 1991-01-01 Ag Communication Systems Corporation Thermal protection circuit for an integrated circuit subscriber line interface
US5001593A (en) * 1989-04-20 1991-03-19 Siemens Aktiengesellschaft Circuit configuration for temperature monitoring of power switching transistors integrated in a semiconductor circuit
GB2248151A (en) * 1990-09-24 1992-03-25 Philips Electronic Associated Temperature sensing and protection circuit.

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0496267A (en) * 1990-08-03 1992-03-27 Sharp Corp Semiconductor integrated circuit

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4092693A (en) * 1976-03-12 1978-05-30 Pioneer Electronic Corporation Temperature sensing protection circuit for ic power chip having thermal hysteresis characteristic
US4039928A (en) * 1976-07-19 1977-08-02 Pertron Controls Corporation Electrical operating circuit having semiconductor device junction temperature monitoring
US4669026A (en) * 1985-09-09 1987-05-26 National Semiconductor Corporation Power transistor thermal shutdown circuit
GB2223636A (en) * 1988-09-28 1990-04-11 Borletti Climatizzazione Electric motor control and cutoff device
US4896245A (en) * 1989-03-13 1990-01-23 Motorola Inc. FET overtemperature protection circuit
US5001593A (en) * 1989-04-20 1991-03-19 Siemens Aktiengesellschaft Circuit configuration for temperature monitoring of power switching transistors integrated in a semiconductor circuit
US4982307A (en) * 1989-12-04 1991-01-01 Ag Communication Systems Corporation Thermal protection circuit for an integrated circuit subscriber line interface
GB2248151A (en) * 1990-09-24 1992-03-25 Philips Electronic Associated Temperature sensing and protection circuit.

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2319414A (en) * 1996-11-16 1998-05-20 Rover Group Thermal protection of electronic switches
GB2393339A (en) * 2002-08-01 2004-03-24 Sony Corp Multichip module with high temperature shutdown
GB2393339B (en) * 2002-08-01 2004-07-28 Sony Corp Multichip module and multichip shutdown method
US7006341B2 (en) 2002-08-01 2006-02-28 Sony Corporation Multichip module and multichip shutdown method

Also Published As

Publication number Publication date
GB2273213B (en) 1996-05-01
GB9225486D0 (en) 1993-01-27

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Legal Events

Date Code Title Description
732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
PCNP Patent ceased through non-payment of renewal fee

Effective date: 20001205