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GB2632265A - Circuit protection apparatus - Google Patents

Circuit protection apparatus Download PDF

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Publication number
GB2632265A
GB2632265A GB2311649.4A GB202311649A GB2632265A GB 2632265 A GB2632265 A GB 2632265A GB 202311649 A GB202311649 A GB 202311649A GB 2632265 A GB2632265 A GB 2632265A
Authority
GB
United Kingdom
Prior art keywords
thermostat
protection apparatus
breaker unit
terminal
circuit protection
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.)
Pending
Application number
GB2311649.4A
Other versions
GB202311649D0 (en
Inventor
Malara Carmelo
Szalai Lajos
Ciurea Alexe
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.)
Jaguar Land Rover Ltd
Original Assignee
Jaguar Land Rover 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 Jaguar Land Rover Ltd filed Critical Jaguar Land Rover Ltd
Priority to GB2311649.4A priority Critical patent/GB2632265A/en
Publication of GB202311649D0 publication Critical patent/GB202311649D0/en
Publication of GB2632265A publication Critical patent/GB2632265A/en
Pending legal-status Critical Current

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Classifications

    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L3/00—Electric devices on electrically-propelled vehicles for safety purposes; Monitoring operating variables, e.g. speed, deceleration or energy consumption
    • B60L3/04—Cutting off the power supply under fault conditions
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
    • H02H3/085—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current making use of a thermal sensor, e.g. thermistor, heated by the excess current

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Power Engineering (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Protection Of Static Devices (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

A circuit protection apparatus 50, for fitting in an electrical circuit of a motor vehicle, includes an input terminal 54, an output terminal 56, and a breaker unit 60 electrically coupled between the input terminal and output terminals. The breaker unit is operable in a closed circuit state in which current is permitted to flow between the input terminal and output terminals and in an open circuit state in which current flow is prevented. A thermostat 70 generates a thermostat output signal 73 responsive to temperature, e.g. predetermined fault temperature, and the protection apparatus is configured to trigger the breaker unit into the open circuit state in response to the thermostat output signal. A method of isolating an electrical circuit of a motor vehicle using the circuit protection device is also provided. The breaker unit may be connected to the input and output terminals by first and second busbars and the thermostat, which may be a pyrofuse, may be coupled to one of the busbars. The protection apparatus may be connected between a battery 10 and a DC-DC converter 30 of a motor vehicle powertrain and may include a plurality of thermostats (70A-C, Fig.11), each capable of triggering the breaker unit.

Description

CIRCUIT PROTECTION APPARATUS
TECHNICAL FIELD
The present disclosure relates to a circuit protection apparatus, a motor vehicle powertrain comprising the circuit protection apparatus, a motor vehicle and a method of isolating an electrical circuit.
BACKGROUND
It is known to provide some protection for an electrical circuit by fitting a fuse or breaker unit in the electrical circuit. The fuse or breaker unit typically activates in response to an excessive current flow in the electrical circuit.
It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.
SUMMARY OF THE INVENTION
Aspects and embodiments of the invention provide a circuit protection apparatus, a motor vehicle powertrain comprising the circuit protection apparatus, a motor vehicle and a method of isolating an electrical circuit as claimed in the appended claims.
According to an aspect of the present invention there is provided a circuit protection apparatus for fitting in an electrical circuit of a motor vehicle, comprising: an input terminal; an output terminal; a breaker unit electrically coupled between the input terminal and the output terminal and operable in a closed circuit state in which current is permitted to flow between the input terminal and the output terminal and in an open circuit state in which current flow is prevented between the input terminal and the output terminal; and a thermostat configured to generate a thermostat output signal responsive to temperature, wherein the circuit protection apparatus is configured to trigger the breaker unit into the open circuit state in response to the thermostat output signal.
Embodiments of the invention have an advantage that a thermal event associated with a fault may be detected by the circuit protection apparatus and activate the breaker unit. The breaker unit can safely isolate the electrical circuit. The circuit protection apparatus may be activated when a fault is not detected by one or more other protection devices or systems, such as protective devices which respond to excessive current or voltage.
The circuit protection apparatus may be activated when one or more other protection devices or systems are not operational, such as a solid state isolating switch.
Optionally, the breaker unit comprises a pyrofuse. A pyrofuse is capable of quickly isolating the electrical circuit, once activated. A pyrofuse is typically capable of being activated or triggered once. Once the pyrofuse has been activated, the pyrofuse remains open circuit and cannot be reset. This can help to prevent a re-occurrence of the same fault until a specialist has investigated the fault.
Optionally, the breaker unit comprises a first breaker unit terminal and a second breaker unit terminal, and the circuit protection apparatus comprises at least one of: a first bus bar element connected between the input terminal and the first breaker unit terminal and a second bus bar element connected between the output terminal and the second breaker unit terminal. Providing one or more busbar elements allows some flexibility in fitting the circuit protection apparatus. The busbar elements may be straight or shaped in some way, such as angled.
Optionally, the thermostat is thermally coupled to the first bus bar element or the second bus bar element. The thermostat can respond to an increase in temperature of the busbar element.
Optionally, the thermostat is mounted to the first bus bar element or the second bus bar element.
Optionally, the thermostat is configured to detect a predetermined fault temperature and generate the thermostat output signal in response to detecting the predetermined fault temperature.
Optionally, the thermostat has a first thermostat electrical terminal and a second thermostat electrical terminal; the breaker unit has a first breaker unit electrical terminal and a second breaker unit electrical terminal; wherein the first thermostat electrical terminal and the second breaker unit electrical terminal are configured to conned to an electrical supply, wherein the second thermostat electrical terminal and the first breaker unit electrical terminal are electrically connected, and wherein the thermostat is configured to close an electrical circuit between the first thermostat electrical terminal and the second thermostat electrical terminal at a predetermined fault temperature and thereby generate the thermostat output signal to trigger the breaker unit into the open circuit state.
This arrangement has an advantage that the thermostat output signal can be generated by a simple electrical circuit. This can provide a more reliable activation of the breaker unit. For example, the breaker unit may be activated without the need for a processor or other electrical circuitry.
According to another aspect of the invention, there is provided a motor vehicle powertrain comprising the circuit protection apparatus of the previous aspect.
Optionally, the motor vehicle powertrain comprises: a battery; and a DC-DC converter, wherein the circuit protection apparatus is electrically connected between the battery and the DC-DC converter and wherein the breaker unit is configured to prevent current flow between the DC-DC converter and the battery when the breaker unit is in the open circuit state.
Optionally, the battery has a first operating voltage and the DC-DC converter is configured to convert to a second operating voltage which is higher than the first operating voltage.
Optionally, the thermostat of the circuit protection apparatus is mounted on, or alongside, the DC-DC converter, or positioned within the DC-DC converter. The thermostat may be mounted close to a potential point of failure in the DC-DC converter, where heat may be generated in the event of the failure occurring. The circuit protection apparatus may be in the form of a module which includes the thermostat. The circuit protection apparatus may be positioned alongside the DC-DC converter such that the thermostat is near to, or in contact with, the DC-DC converter. Alternatively, the thermostat of the circuit protection apparatus may be separate to other parts of the circuit protection apparatus, with the thermostat electrically connected to the breaker unit.
The thermostat may be positioned within the DC-DC converter, or within (or near to) another electrical or electronic module. This can allow some flexibility to the positioning of the circuit protection apparatus, such as where there is insufficient space to mount the circuit protection apparatus next to the DC-DC converter.
Optionally, the circuit protection apparatus is mounted on, or alongside, the DC-DC converter. This allows the thermostat to be mounted close to a potential point of failure in the DC-DC converter, where heat may be generated in the event of the failure occurring.
Optionally, the circuit protection apparatus comprises a plurality of thermostats each configured to generate the thermostat output signal responsive to temperature, wherein the circuit protection apparatus is configured to trigger the breaker unit into the open circuit state in response to any of the plurality of thermostats generating the thermostat output signal.
According to another aspect of the invention, there is provided a motor vehicle comprising the circuit protection apparatus of a previous aspect or the motor vehicle powertrain of a previous aspect.
According to another aspect of the invention, there is provided a method of isolating an electrical circuit of a motor vehicle comprising: providing a circuit protection apparatus in the electrical circuit comprising an input terminal, an output terminal, a breaker unit electrically coupled between the input terminal and the output terminal, and a thermostat; generating a thermostat output signal responsive to temperature; and using the thermostat output signal to trigger the breaker unit into an open circuit state, wherein in the open circuit state current flow is prevented between the input terminal and the output terminal.
Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.
BRIEF DESCRIPTION OF THE DRAWINGS
One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows an example of a circuit protection apparatus and an electrical circuit of a vehicle; Figure 2 shows another an example of a circuit protection apparatus; Figure 3 shows another an example of a circuit protection apparatus; Figures 4A-4C show a sequence of operating states of one of the circuit protection apparatus; Figure 5 shows another an example of a circuit protection apparatus; Figure 6 shows another an example of a circuit protection apparatus; Figure 7 shows a plan view of a circuit protection apparatus and a DC-DC converter; Figure 8 shows a side view of the circuit protection apparatus and DC-DC converter of Figure 7; Figure 9 shows a circuit protection apparatus with an external thermostat; Figure 10 shows a circuit protection apparatus with a thermostat within a DC-DC converter; Figure 11 shows an example of a circuit protection apparatus with a plurality of thermostats; Figure 12 shows a vehicle incorporating a circuit protection apparatus; Figure 13 schematically shows functional units of the vehicle; Figure 14 shows a method of isolating an electrical circuit of a motor vehicle.
DETAILED DESCRIPTION
Figure 1 shows an example of an electrical circuit with a circuit protection apparatus 50. The electrical circuit comprises a first battery 10, a DC-DC converter 30 and a second battery 20. The circuit protection apparatus connects in series with an electrical circuit between a positive terminal 11 of the battery 10 and a positive terminal 31 of the DC-DC converter 30. The first battery 10 has a first operating voltage and the second battery 20 has a second operating voltage. In use, the DC-DC converter 30 converts the DC supply received from the battery 10 to a DC supply at a different DC voltage. In this example, the first battery 10 has a DC voltage of 12V, the second battery 20 has a DC voltage of 48V and the DC-DC converter 30 up-converts the 12V DC supply to a 48V DC supply. Other voltages are possible.
The second battery 20 may be used to power part of a powertrain of the vehicle. One possible use is to power a motor in a mild hybrid electric vehicle (MHEV).
The circuit protection apparatus 50 comprises an input terminal 54 and an output terminal 56. The input terminal 54 may connect to an electrical cable, such as a cable 13 which connects to the positive terminal 11 of the first battery 10. The output terminal 56 may connect to an electrical cable, such as a cable which connects to the positive terminal 31 of the DC-DC converter 30. Alternatively, the output terminal 56 may directly connect to the positive terminal (stud) 31 of the DC-DC converter 30.
The circuit protection apparatus 50 comprises a breaker unit 60. The breaker unit 60 comprises a first breaker unit terminal 63 and a second breaker unit terminal 64. The breaker unit 60 is electrically coupled between the input terminal 54 and the output terminal 56. The breaker unit 60 is operable in a closed circuit state in which current is permitted to flow between the input terminal 54 and the output terminal 56. The breaker unit 60 is also operable in an open circuit state in which current flow is prevented between the input terminal 54 and the output terminal 56. The circuit protection apparatus 50 electrically isolates the first battery 10 from the DC-DC converter 30. Once the breaker unit 60 is activated into the open circuit state, it remains in the open circuit state and cannot be reset. The electrical circuit can be restored by replacing the breaker unit 60.
An advantageous form of the breaker unit 60 is a pyrofuse. A pyrofuse comprises a conductor and an explosive device which can be triggered, or activated, to break the conductor and thereby prevent current flow along the conductor. The conductor may have a line of weakness which is designed to break when the explosive device is activated.
The circuit protection apparatus 50 may comprise one or more busbar elements 51, 52. A busbar is an electrical conductor which carries electrical current. The busbar elements 51, 52 are suitably dimensioned to carry the expected electrical current demand of the electrical circuit into which the circuit protection apparatus 50 is fitted. In this example, the circuit protection apparatus 50 comprises a first busbar element 51 and a second busbar element 52. The first busbar element 51 connects between the input terminal 54 and the first breaker unit terminal 63. The second bus bar element 52 is connected between the second breaker unit terminal 64 and the output terminal 56. The input terminal 54 is provided on the first busbar element 51. Optionally, a fixing 55 is provided to secure the first busbar element 51 to the first breaker unit terminal 63. The second busbar element 52 connects to a second end of the breaker unit 60. The output terminal 56 is provided on the second busbar element 52. Optionally, a fixing 57 is provided to secure the second busbar element 52 to the second breaker unit terminal 64. Each of the first busbar element 51 and the second busbar element 52 may be a straight element or a shaped element, such as an L-shaped element. The first busbar element 51 and/or the second busbar element 52 may be positioned at an angle to the breaker unit.
The circuit protection apparatus 50 comprises a thermostat 70 which is configured to generate a thermostat output signal responsive to temperature. In this example, the thermostat 70 is mounted to the second busbar element 52. The thermostat 70 is supported by the second busbar element 52. The thermostat 70 is thermally coupled to the second busbar element 52. The thermostat 70 can respond to a temperature of the second busbar element 52. In other examples, the thermostat 70 may be mounted to the first busbar element 51. The thermostat 70 may comprise a bimetallic strip which is responsive to temperature of the busbar element 52.
At a predetermined temperature, the bimetallic strip forms an electrical path between the thermostat terminals 71, 72. This causes the thermostat output signal to trigger the breaker unit 60 into the open circuit state.
The circuit protection apparatus 50 comprises a trigger circuit to activate the breaker unit 60. The trigger circuit is separate to the main (protected) electrical circuit between terminals 11 and 31. The trigger circuit comprises electrical connections between the battery 10, thermostat 70 and breaker unit 60. The thermostat 70 has a first thermostat electrical terminal 71 and a second thermostat electrical terminal 72. The breaker unit 60 has a first breaker unit electrical terminal 61 and a second breaker unit electrical terminal 62. The first thermostat electrical terminal 71 and the second breaker unit electrical terminal 62 are connected to the battery 10. The first thermostat electrical terminal 71 connects to the positive terminal 11 of the battery 10 and the second breaker unit electrical terminal 62 connects to the negative/ground terminal 12 of the battery 10. The second thermostat electrical terminal 72 and the first breaker unit electrical terminal 61 are electrically connected. When the thermostat reaches a threshold temperature, the thermostat electrically connects terminals 71 and 72. This completes the trigger circuit and allows a current to flow between terminals 11 and 12 of the battery 10. This generates the thermostat output signal to trigger the breaker unit 60 into the open circuit state.
The provision of the busbar elements allows some flexibility in mounting the circuit protection apparatus 50 within the confines of a vehicle.
Figures 2 and 3 show some other examples of circuit protection apparatus 150. Figures 2 and 3 each show a circuit protection apparatus 150 in which the first busbar element 51 is omitted. The input terminal 54 is provided on the first breaker unit terminal 63 of the breaker unit 60. Figure 3 shows a circuit protection apparatus 150 in which the second busbar element 51 is mounted at 90 degrees to the breaker unit 60. Fixing 57 is provided to secure the second busbar element 52 to the second breaker unit terminal 64 of the breaker unit 60.
Figures 4A-4C shows a sequence of operating states of the circuit protection apparatus 50, 150. In Figure 4A, the temperature of the busbar element is below the predetermined threshold temperature. The terminals 71 and 72 of the thermostat 70 are not electrically connected. The thermostat 70 does not output the thermostat output signal. The breaker unit 60 is in the closed circuit state. Current flows 14 between the input terminal 54 and the output terminal 56.
In Figure 4B, the temperature of the busbar element has reached the predetermined threshold temperature. There is thermal transfer 58 along the busbar between the DC-DC converter 30 (or other functional unit) and the thermostat 70. The terminals 71 and 72 of the thermostat 70 are electrically connected. The thermostat 70 outputs the thermostat output signal 73, which activates the breaker unit 60 into the open circuit state. Current does not flow between the input terminal 54 and the output terminal 56.
Figure 4C shows the circuit protection apparatus 50 at a later time. The temperature of the busbar element has dropped below the predetermined threshold temperature. The terminals 71 and 72 of the thermostat 70 are not electrically connected. The thermostat 70 does not output the thermostat output signal. The breaker unit 60 remains in the open circuit state. Current does not flow between the input terminal 54 and the output terminal 56.
An advantage of the circuit protection apparatus is that the breaker unit 60 can be activated in response to a thermal event which is not detected by one or more other protection devices or systems. such as an isolation switch within the DC-DC converter 30.
Figure 5 shows another example of a circuit protection apparatus 250 fitted to a DC-DC converter 30. This example has a shaped busbar element. The circuit protection apparatus 250 comprises an input terminal 54 and an output terminal 56. The output terminal 56 directly connects to the positive terminal (stud) of the DC-DC converter 30. The circuit protection apparatus 250 comprises a second busbar element 52. The circuit protection apparatus 250 comprises a breaker unit 60 in the form of a pyrofuse. The circuit protection apparatus 250 comprises a thermostat 70 which is mounted to the second busbar element 52. In this example, the second busbar element 52 is a shaped planar element with an "L" shape. Fixing 57 connects the second busbar element 52 to the breaker unit 60. In this example, a support bracket 53 connects to the input terminal 54 to provide support for the circuit protection apparatus 250.
Figure 6 shows another example of a circuit protection apparatus 350 with a different arrangement of shaped busbar elements. The circuit protection apparatus 350 comprises an input terminal 54 and an output terminal 56. The circuit protection apparatus 350 comprises a first busbar element 51 and a second busbar element 52. The circuit protection apparatus 350 comprises a breaker unit 60 in the form of a pyrofuse. A first end of the breaker unit 60 connects to the first busbar element 51 by fixing 55 and a second end of the breaker unit 60 connects to the second busbar element 52 by fixing 57. The input terminal 54 connects to an electrical cable 13 which connects to the positive terminal 11 of the first battery 10 (not shown). The circuit protection apparatus 350 comprises a thermostat 70 which is mounted to the second busbar element 52. The breaker unit 50 and the thermostat 70 operate in the same manner as described earlier for breaker unit 50 and thermostat 70. In this example, the second busbar element 52 has a first portion and a second portion which is perpendicular to the first portion. The first busbar element 51 is planar. Connector 18 provides electrical connections for the trigger circuit which connects to the thermostat 70 and the breaker unit 60.
Figures 7 and 8 show another example of a circuit protection apparatus 450 and a DC-DC converter 30. The circuit protection apparatus 450 comprises a bracket 80 which is configured to mount the circuit protection apparatus 450 around the DC-DC converter 30. An advantage of this arrangement is that the thermostat 70 can be mounted above a potential point of failure 32 in the DC-DC converter 30. This can allow the thermostat 70 to respond to an increase in temperature when a fault occurs. The bracket 80 supports the breaker unit 60 and the thermostat 70. The bracket 80 positions the thermostat 70 alongside the DC-DC converter 30. A first end of the breaker unit 60 has an input terminal 54 which connects to a 12V cable 13. The input terminal 54 directly connects to the first breaker unit terminal 63. A second busbar element 52 connects between the second breaker terminal 64 of the breaker unit 60 and the positive terminal (stud) of the DC-DC converter 30. The bracket 80 does not form part of the electrical circuit. It is noted there are some differences between the shape of components of the circuit protection apparatus 450 shown in Figures 7 and 8, but the main features are the same.
In the examples shown in Figures 1 to 8, the circuit protection apparatus is in the form of a module, with the thermostat 70 mounted on one of the busbars 51, 52 or on a bracket 80. Figures 9 and 10 show some examples where the thermostat 70 is not mounted in this way.
Figure 9 shows a circuit protection apparatus 550 with an external thermostat 70. The thermostat 70 is not mounted to one of the busbars 51, 52 of the circuit protection apparatus 50. The thermostat 70 is electrically connected to the breaker unit 60 of the circuit protection apparatus 550. For example, a cable 74 connects the second thermostat electrical terminal 72 to the first breaker unit electrical terminal 61.
Figure 10 shows a circuit protection apparatus 650 with a thermostat 70 mounted within a DC-DC converter 30. For example, the thermostat 70 may be mounted on a printed circuit board (PCB) of the DC-DC converter 30, such as at a position near to a potential point of failure. The thermostat 70 is electrically connected to the breaker unit 60 of the circuit protection apparatus 650.
The circuit protection apparatus shown in the above examples has a single thermostat 70. Figure 11 shows an example of a circuit protection apparatus 850 with a plurality of thermostats 70A, 70B, 70C. The plurality of thermostats 70A, 70B, 70C are connected in parallel between the battery 10 and the breaker unit 60. In use, any one of the plurality of thermostats 70A, 70B, 70C can trigger the breaker unit 60 into the open circuit state. Each of the plurality of thermostats 70A, 70B, 70C can be mounted where a thermal event may be detected. One of the thermostats may be mounted on one of the busbar elements 51, 52, similar to Figure 1. The plurality of thermostats 70A, 70B, 70C may be configured to activate at the same threshold temperature. Alternatively, at least two of the plurality of thermostats 70A, 70B, 70C may be configured to activate at different threshold temperatures.
In another example, not shown, the plurality of thermostats 70A, 70B, 70C are connected in series between the battery 10 and the breaker unit 60. In use, all of the plurality of thermostats 70A, 70B, 70C must respond to a threshold temperature to generate the thermostat output signal to the trigger the breaker unit 60 into the open circuit state.
Figures 12 and 13 show an example of a vehicle 900 in which a circuit protection apparatus 950 may be used. The circuit protection apparatus 950 may be the circuit protection apparatus 50, 150, 250, 350, 450, 650 or 750 described above. The vehicle 900 comprises a pair of front wheels 902 and a pair of rear wheels 904. The vehicle 900 is a hybrid vehicle (HEV) with a propulsion system comprising an internal combustion engine 990 and a motor 980. Torque from the propulsion system is applied to a transmission 924 and front axles 928 to drive the front wheels 902. For clarity, only the front wheels 902 are driven in this example vehicle. It will be understood that the rear wheels 904 may also be driven by the same propulsion system 980, 990, or by a separate propulsion system.
The vehicle 900 comprises a first battery 910, a second battery 920 and a DC-DC converter 930. The first battery 910, the second battery 920 and the DC-DC converter 930 correspond to similar items 10, 20, 30 shown in Figure 1. The circuit protection apparatus 950 is connected between the first battery 910 and the DC-DC converter 930. The motor 980 may be an integrated starter generator (ISG) motor which is mounted around a drive shaft of the engine 990. In use, controller 940 controls the motor 980 and the engine 990 to supply torque to meet a required torque demand. The controller 940 is configured to control the motor 980 and the engine 990 to generate torque in parallel. The controller 940 is also configured to control only the engine 990 to generate torque. In a mild hybrid system, the controller 940 can control the motor 980 and the engine 990 to generate torque in parallel, but does not control the motor 980 to generate torque by itself. In a fully hybrid system, the controller 940 can control the motor 980 to generate torque while the engine 990 is not operating. The controller 940 is configured to output a control signal 942 to control the DC-DC converter 930.
In a first operating mode, the DC-DC converter 930 is configured to convert energy from the first battery 910 to top up a charge level of the second battery 920, such as converting from 12V to 48V. Current flows from the first battery 910, via the circuit protection apparatus 950 and the DC-DC converter 930, to the second battery 920. In a second operating mode, the DC-DC converter 930 is configured to convert energy from the second battery 920 to top up a charge level of the first battery 910, such as converting from 48V to 12V.
Current flows from the second battery 920, via the DC-DC converter 930 and the circuit protection apparatus 950, to the first battery 910.
While Figure 13 shows a hybrid vehicle, the circuit protection apparatus 950 may be used in an electrical circuit of a fully electric vehicle.
The circuit protection apparatus 50 may be used in other types of electrical circuit. Some other possible applications of the circuit protection apparatus 50 are: * Off-grid unattended charging of a vehicle battery pack. In this application, the electrical circuit comprises a charger unit which converts AC to DC, a battery pack, and a circuit protection apparatus between the charger unit and the battery pack. The thermostat of the circuit protection apparatus 50 may be positioned near the battery pack. If the battery pack should undergo a catastrophic failure that leads to thermal runaway, the thermostat can detect an increase in temperature and isolate the AC supply.
* Super-capacitor systems on a vehicle. Some on-board systems, such as suspension systems (e.g. active ride-height or active air suspension) comprise an electrical circuit which connects between 48V and 12V DC supplies. These systems include solid-state isolation switches that could fail short circuit. The circuit protection apparatus 50 may be connected in series with the electrical circuit. The thermostat of the circuit protection apparatus 50 may be positioned near to a potential point of failure where heat will be generated.
* Lithium ion battery packs. These battery packs may be used as part of an electrical circuit with a solid state isolation switch instead of a mechanical relay. The circuit protection apparatus 50 may be connected in series with the electrical circuit. The thermostat of the circuit protection apparatus 50 may be positioned near to a potential point of failure where heat will be generated. In the event that the isolation switch fails, the large amount of heat produced can be sensed and used to isolate the battery pack.
Figure 14 shows a method 100 of isolating an electrical circuit of a motor vehicle. The method comprises providing 102 a circuit protection apparatus 50 in the electrical circuit. The circuit protection apparatus 50 comprises an input terminal 54, an output terminal 56, a breaker unit 60 electrically coupled between the input terminal 54 and the output terminal 56, and a thermostat 70. The method comprises generating 104 a thermostat output signal responsive to temperature. The method comprises using 106 the thermostat output signal to trigger the breaker unit 60 into an open circuit state. In the open circuit state current flow is prevented between the input terminal 54 and the output terminal 56.
A mechanical thermostat 70, such as a thermostat which uses a bimetallic strip, offers a robust and reliable detection of temperature. There is no current flow through the thermostat 70 until the point at which the thermostat reaches the predetermined activation temperature of the thermostat. This prevents current drain during standby. It also avoids the need for the supply of an operating voltage or current biasing. During a fault, the circuitry which provides the operating voltage or biasing current may not be available. In other examples, it is possible to use an electronic thermostat as the thermostat 70.
It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims (15)

  1. CLAIMS1. A circuit protection apparatus for fitting in an electrical circuit of a motor vehicle, comprising: an input terminal; an output terminal; a breaker unit electrically coupled between the input terminal and the output terminal and operable in a closed circuit state in which current is permitted to flow between the input terminal and the output terminal and in an open circuit state in which current flow is prevented between the input terminal and the output terminal; and a thermostat configured to generate a thermostat output signal responsive to temperature, wherein the circuit protection apparatus is configured to trigger the breaker unit into the open circuit state in response to the thermostat output signal.
  2. 2. The circuit protection apparatus of claim 1 wherein the breaker unit comprises a pyrofuse.
  3. 3. The circuit protection apparatus of claim 1 or claim 2 wherein the breaker unit comprises a first breaker unit terminal and a second breaker unit terminal, and the circuit protection apparatus comprises at least one of: a first bus bar element connected between the input terminal and the first breaker unit terminal and a second bus bar element connected between the output terminal and the second breaker unit terminal.
  4. 4. The circuit protection apparatus of claim 3 wherein the thermostat is thermally coupled to the first bus bar element or the second bus bar element.
  5. 5. The circuit protection apparatus of claim 4 wherein the thermostat is mounted to the first bus bar element or the second bus bar element.
  6. 6. The circuit protection apparatus of any one of the preceding claims wherein the thermostat is configured to detect a predetermined fault temperature and generate the thermostat output signal in response to detecting the predetermined fault temperature.
  7. 7. The circuit protection apparatus of any one of the preceding claims wherein: the thermostat has a first thermostat electrical terminal and a second thermostat electrical terminal; the breaker unit has a first breaker unit electrical terminal and a second breaker unit electrical terminal; wherein the first thermostat electrical terminal and the second breaker unit electrical terminal are configured to connect to an electrical supply, wherein the second thermostat electrical terminal and the first breaker unit electrical terminal are electrically connected, and wherein the thermostat is configured to close an electrical circuit between the first thermostat electrical terminal and the second thermostat electrical terminal at a predetermined fault temperature and thereby generate the thermostat output signal to trigger the breaker unit into the open circuit state.
  8. 8. A motor vehicle powertrain comprising the circuit protection apparatus of any one of the preceding claims.
  9. 9. The motor vehicle powertrain of claim 8 comprising: a battery; and a DC-DC converter, wherein the circuit protection apparatus is electrically connected between the battery and the DC-DC converter and wherein the breaker unit is configured to prevent current flow between the DC-DC converter and the battery when the breaker unit is in the open circuit state.
  10. 10. The motor vehicle powertrain of claim 9 wherein the battery has a first operating voltage and the DC-DC converter is configured to convert to a second operating voltage which is higher than the first operating voltage.
  11. 11. The motor vehicle powertrain of any one of claims 8 to 10 wherein the thermostat of the circuit protection apparatus is mounted on, or alongside, the DC-DC converter, or positioned within the DC-DC converter.
  12. 12. The motor vehicle powertrain of any one of claims 8 to 11 wherein the circuit protection apparatus is mounted on, or alongside, the DC-DC converter.
  13. 13. The motor vehicle powertrain of any one of claims 8 to 11 wherein the circuit protection apparatus comprises a plurality of thermostats each configured to generate the thermostat output signal responsive to temperature, wherein the circuit protection apparatus is configured to trigger the breaker unit into the open circuit state in response to any of the plurality of thermostats generating the thermostat output signal.
  14. 14. A motor vehicle comprising the circuit protection apparatus of any one of claims 1 to 7 or the motor vehicle powertrain of any one of claims 8 to 13. 30
  15. 15. A method of isolating an electrical circuit of a motor vehicle comprising: providing a circuit protection apparatus in the electrical circuit comprising an input terminal, an output terminal, a breaker unit electrically coupled between the input terminal and the output terminal, and a thermostat; generating a thermostat output signal responsive to temperature; and using the thermostat output signal to trigger the breaker unit into an open circuit state, wherein in the open circuit state current flow is prevented between the input terminal and the output terminal.
GB2311649.4A 2023-07-28 2023-07-28 Circuit protection apparatus Pending GB2632265A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
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Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2311649.4A GB2632265A (en) 2023-07-28 2023-07-28 Circuit protection apparatus

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GB2632265A true GB2632265A (en) 2025-02-05

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5463521A (en) * 1992-11-06 1995-10-31 Caterpillar Inc. Power supply protection circuit
US20130286526A1 (en) * 2012-04-26 2013-10-31 Calsonic Kansei Corporation Vehicle safety device
WO2017096464A1 (en) * 2015-12-11 2017-06-15 Blue Solutions Canada Inc. Battery protection device
JP2017229132A (en) * 2016-06-21 2017-12-28 パナソニックＩｐマネジメント株式会社 Power supply unit for vehicle and power supply controller

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5463521A (en) * 1992-11-06 1995-10-31 Caterpillar Inc. Power supply protection circuit
US20130286526A1 (en) * 2012-04-26 2013-10-31 Calsonic Kansei Corporation Vehicle safety device
WO2017096464A1 (en) * 2015-12-11 2017-06-15 Blue Solutions Canada Inc. Battery protection device
JP2017229132A (en) * 2016-06-21 2017-12-28 パナソニックＩｐマネジメント株式会社 Power supply unit for vehicle and power supply controller

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Publication number Publication date
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