Method and system for voltage detection

Abstract

A method and system for voltage detection. The present disclosure relates to a system for indicating a voltage level at a point of interest. The system includes a first circuit including a point of interest and a second circuit electrically isolated from the first circuit. The system also includes a transmitter electrically connected to the first circuit and a receiver electrically connected to the second circuit. The second circuit includes a comparator configured to provide an output signal indicative of a voltage level at the point of interest based on a comparison between the input received from the receiver and a reference voltage (VREF). The disclosure also relates to a method of determining a voltage level.

Description

Technical Field

[0001] The present disclosure relates to methods and systems for detecting or determining a voltage. More specifically, the present disclosure relates to methods and systems for detecting or determining a voltage level relative to a specific threshold. The present disclosure particularly relates to the detection of a voltage in a first circuit operating in a first voltage range, wherein the detection is performed in a second circuit operating in a different voltage range. The present disclosure also relates to such methods and systems for detecting a voltage in an electric or hybrid vehicle, more specifically in the high-voltage system of the vehicle (such as the junction box of such a vehicle). Background Art

[0002] The battery of an electric or hybrid vehicle can power an electric motor as an energy storage element, enabling the vehicle to move. The battery can include a number of battery cells grouped into modules, such as lithium-ion battery cells. Even though the following will refer to an electric vehicle (EV), it should be understood that the present disclosure is equally applicable to hybrid vehicles.

[0003] To drive the vehicle, the battery can be connected to one or more electric motors. The electric motor or "traction motor" can drive the axle. For example, the front axle can be driven by a front traction motor, and the rear axle can be driven by a rear traction motor. It is also possible to drive a single axle by a single traction motor.

[0004] The term "battery" in the present disclosure can be understood to refer to a battery or battery pack for propulsion. The battery can operate at a voltage level, for example, between 400 and 1000 V and forms part of the high-voltage circuit of an electric vehicle.

[0005] The electrical junction box includes a housing that houses electrical connectors. The junction box is generally used to protect these electrical connectors. The junction box in a vehicle can be provided, for example, to electrically connect the electrodes (positive and negative or "cathode" and "anode") of the battery to the inverter of the traction motor and / or other electrical components or circuits. Such a junction box typically can include a housing having a plurality of busbars to conduct current. In the junction box, other electrical components such as fuses, different types of relays, and common-mode filters can also be provided. The connectors inside the junction box can selectively distribute the power from the battery to other electrical systems, such as the aforementioned inverter.

[0006] It may be necessary to determine the voltage level in the high-voltage circuit of the vehicle, for example, at the location in the junction box. Such a determination of the voltage level can be used, for example, to detect a short circuit in the battery, an electrical contact fault, or others.

[0007] To determine the voltage level in a high-voltage circuit, it is known to provide a voltage measurement system in the high-voltage circuit. However, such a voltage measurement system typically requires a separate low-voltage power supply, which is disadvantageous as it complicates the system and increases costs. It is known in the art to use a microprocessor circuit to provide the voltage measurement system. However, it is desirable to avoid using such a microprocessor circuit to reduce costs while maintaining or improving reliability.

[0008] In an example of the present disclosure, at least some of the above needs are met. Summary of the Invention

[0009] In one aspect of the present disclosure, a system for indicating the voltage level at a point of interest is provided. The system includes: a first circuit including the point of interest, and a second circuit; and an isolation barrier that connects the first circuit to the second circuit and electrically isolates the first circuit from the second circuit. The isolation barrier further includes a transmitter electrically connected to the first circuit and a receiver electrically connected to the second circuit. The transmitter is arranged such that the current level through the transmitter indicates the voltage level at the point of interest. The second circuit includes a comparator configured to provide an output signal indicating the voltage level at the point of interest based at least on a comparison between an input received from the receiver and a reference voltage.

[0010] According to this aspect, a system is provided that is capable of indicating the voltage level in a first circuit without the need to provide a specific power supply for the measurement system in the first circuit. The voltage indication provided by the first circuit and its processing also do not rely on a microprocessor. Instead, a cost-effective and reliable hardware solution is provided.

[0011] The first circuit may be a high-voltage circuit of a vehicle, and the second circuit may be a low-voltage circuit of the vehicle. The high-voltage circuit may herein be regarded as a vehicle circuit including a battery pack, a bus, and components connected thereto (such as an inverter, a traction motor). The low-voltage circuit may herein be regarded as a secondary circuit including auxiliary components of the vehicle and their (low-voltage) power supply. For example, the voltage level may be measured at a junction box, i.e., the point of interest may be a specific point in the junction box.

[0012] The high-voltage circuit is configured to operate at a higher voltage level than the low-voltage circuit. In a non-limiting example, the high-voltage circuit may operate at a voltage of 60V or higher, specifically 100V or higher, particularly 400 to 1000V, and the low-voltage circuit may operate at a voltage level of 40V or lower, specifically 16V or lower.

[0013] In some examples, the system may include an optical coupler, and the transmitter may be the optical transmitter of the optical coupler, and wherein the receiver may be the optical receiver of the optical coupler. The isolation barrier may include the optical coupler.

[0014] The output signal of the comparator may be further processed to derive or determine the voltage level at the point of interest. In an example, the system may include a signal processing unit configured to receive the output signal of the comparator. The signal processing unit may provide a signal to an electronic control unit (ECU), or may include the ECU. In some examples, the ECU may receive the output signal of the comparator directly or indirectly (e.g., after further processing) to determine the voltage level at the point of interest. Preferably, the ECU may be configured to determine whether the voltage level at the point of interest is equal to or exceeds a predefined value or threshold. The electronic control unit may further be configured to determine the normal operation of the high voltage circuit of the vehicle and / or derive a fault based on the output of the hysteresis comparator.

[0015] In this document, determining the voltage level at the point of interest may be regarded as including not only an indication of a specific voltage level (i.e., a specific value), but also a comparison of the voltage level with a threshold (i.e., higher or lower than the threshold).

[0016] In an example, the comparator may be a hysteresis comparator to reduce or avoid hysteresis. The hysteresis comparator may be regarded herein as including a comparator with positive feedback to the comparator. The hysteresis comparator may avoid or reduce the influence of temperature changes.

[0017] In some examples, the system may further include a voltage reference module for providing a reference voltage to the comparator. Specifically, the low voltage battery powers the voltage reference module, wherein the voltage reference module is configured to provide a reference voltage whose variation is less than the voltage of the low voltage battery. The voltage reference module can be used to provide a more constant input to the hysteresis comparator. Thus, the comparison between the signal received through the optical coupler (indicating the voltage level to be determined) and the reference voltage can be more reliable and accurate.

[0018] In some examples, the first circuit may include a voltage divider, which includes a first branch that electrically connects the point of interest to the optical coupler and includes a first resistor, and a second branch that electrically connects the optical coupler to ground and includes one or more impedances. Specifically, the second branch may include one or more Zener diodes. A suitable level of the Zener level of the diode can be selected for a specific threshold expected at the point of interest. Using one or more Zener diodes can improve the accuracy of detecting a voltage level above the threshold by reducing the error range.

[0019] In another aspect of the present disclosure, a vehicle is provided that includes a system for indicating a voltage level according to any example disclosed herein. The vehicle can be an electric vehicle or a hybrid vehicle.

[0020] In another aspect of the present disclosure, a method for detecting a voltage level at a point of interest in a first circuit is provided. The method includes electrically connecting the point of interest to a transmitter such that the current received by the transmitter depends on the voltage level at the point of interest. The method further includes receiving a transmitted signal in a second circuit that is electrically isolated from the first circuit. The electrical signal in the second circuit is coupled to a first input of a comparator, and the comparator receives a reference voltage as a second input. And the method further includes the comparator providing an output signal that depends on a comparison between the first input and the second input. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Non-limiting examples of the present disclosure will be described hereinafter with reference to the drawings, in which:

[0022] Figure 1A An example of a system for determining a voltage level is schematically illustrated;

[0023] Figure 1B Schematically illustrates Figure 1A further details of an example of

[0024] Figure 1C The voltage-current characteristic of a Zener diode is schematically illustrated; and

[0025] Figure 2A and Figure 2B Schematically illustrates how the use of a Zener diode, due to its specific characteristics, can improve the accuracy of voltage measurement results at a point of interest.

[0026] The drawings relate to example implementations and are only used to assist in understanding the claimed subject matter and do not limit it in any way. DETAILED DESCRIPTION

[0027] Figure 1A An example of a system for determining or indicating a voltage level is schematically illustrated. The system can be part of an electric vehicle (EV). The system of this example includes a high voltage (HV) side and a low voltage (LV) side. The HV side of the system can include a junction box connected to a traction battery.

[0028] In one aspect of the present disclosure, a voltage detection system is provided that is configured to detect or otherwise determine the voltage level at a point of interest. In particular, in this example, the voltage detection system can be configured to measure or otherwise determine the voltage level on the first circuit or the high voltage (HV) side, e.g., at a junction box. It should be clear that in other examples, the point of interest may be elsewhere, e.g., at an on-board charger or any other electrical device.

[0029] In particular, the system can be configured to determine whether the voltage level is higher than a voltage threshold. In some examples, the voltage threshold can be 60V, but obviously, in other examples, other thresholds can be defined. In another aspect of the present disclosure, a vehicle is provided that includes a body and also includes a voltage detection system according to any example herein.

[0030] The HV side is electrically isolated from the LV side. The presence or absence of voltage at the junction box is detected at block 10. In some examples, the presence of high voltage can indicate normal operation, while the absence of high voltage can indicate a problem or fault. In the case of normal operation, certain functions (e.g., charging, starting the engine, or other functions) can be enabled, while certain functions may be disabled in case of a fault.

[0031] The output signal from the voltage measurement result can be fed to the input of a comparator 20 (specifically a hysteresis comparator) (for more details of a specific example, see Figure 1B ). The comparator 20 can compare the received input with the voltage reference provided by the voltage reference module 40. The output of the comparator can be to determine the presence or absence of a voltage level higher than the threshold. This finding will indicate the voltage level on the HV side.

[0032] The output of the comparator can be provided to the signal processing unit 30. The signal processing unit can include or be connected to the vehicle's ECU. Thus, the vehicle's ECU can determine whether a certain voltage level exists at the point of interest on the first circuit (in this example, the junction box), and specifically, it can determine whether the voltage level at the junction box is higher or lower than a predetermined threshold. The ECU can also send a control signal in response to this determination, e.g., in case of a problem, an alarm can be generated, a protection system can be activated, functions can be enabled or disabled based on this finding, or others.

[0033] Figure 1B is schematically illustrated Figure 1A for further details of the example of Figure 1B As shown, a system for indicating the voltage level at a point of interest 11 is provided. The system includes a first circuit (in this example, the HV side) that includes the point of interest 11. The system includes a second circuit (in this example, the LV side) that is electrically isolated from the first circuit.

[0034] The system includes an isolation barrier for electrically isolating the HV side from the LV side. The transmitter can be arranged on the HV side and the receiver on the LV side. The transmitter can be configured to generate a signal and transmit the signal without establishing an electrical connection with the receiver. The signal generated by the transmitter can depend in particular on the current supplied to the transmitter.

[0035] The system in this example includes an optocoupler 13, which includes an optical transmitter 51 electrically connected to a first circuit and an optical receiver 53 electrically connected to a second circuit. The optocoupler can be powered by the second circuit (i.e., the LV side). A low-voltage battery can power the optocoupler. The optical transmitter 51 can be or include an LED, in particular an LED configured to transmit infrared light.

[0036] The first circuit in this example is substantially configured as a voltage divider including a first branch and a second branch. The first branch electrically connects the point of interest 11 to one side (the optical transmitter side) of the optocoupler 13, and the second branch electrically connects the same side of the optocoupler 13 to ground (GRD).

[0037] The first branch can include one or more resistors 12. The second branch can also include one or more impedances.

[0038] In this specific example, the second branch of the first circuit includes one or more Zener diodes 14. The Zener voltage of the Zener diode can be set to an appropriate level related to the threshold determined for the point of interest 11. In a specific example, the threshold of the voltage to be detected can be 60V. In such an example, the Zener voltage of the Zener diode 14 can be set to, for example, approximately 40 volts.

[0039] A Zener diode is a diode designed to reliably allow current to flow "backward" (reverse polarity) when a certain set reverse voltage (called the Zener voltage) is reached. Figure 1C The characteristic voltage-current curve of the Zener diode is illustrated.

[0040] As Figure 1C shown, when the voltage at the point of interest is relatively low, the Zener diode 14 substantially blocks the current from flowing in one direction (region A). When the voltage at the point of interest is high (region C), the Zener diode substantially acts as a classical resistor. At a voltage level near the Zener voltage (region B), the current flowing through the diode changes significantly with a slight increase in voltage, for example, exponentially. Using one or more Zener diodes in the second branch of the voltage divider can reduce the operating range of the voltage applied to the optical transmitter of the optocoupler, as will be illustrated herein with reference to Figure 2A and Figure 2B illustrated. Due to the reduced operating range, the accuracy of voltage measurement can be improved.

[0041] The voltage level applied to the LED of the optocoupler will depend on the voltage level at the point of interest 11. The voltage applied to LED 51 will cause current to flow through the LED. The (infrared) light transmitted is received by the optical receiver 53 (specifically, an optical sensor). The optical receiver 53 can be a phototransistor in this particular example. In other examples, the sensor can be a photoresistor or, for example, a photodiode.

[0042] The current level through the optical transmitter 51 of the optocoupler indicates the voltage level at the point of interest. Thus, the amount of radiation (light) transmitted by LED 51 and received by the phototransistor 53 can directly depend on the voltage level at the point of interest 11. The output signal or output voltage of the optocoupler on the low voltage side will thus depend on the voltage detection at the point of interest 11.

[0043] The values of the resistor and the Zener voltage can be selected such that at the voltage threshold used for detection, the Zener diode operates near Figure 1C region B.

[0044] The second circuit in this example includes a comparator 20 that is configured to provide an output signal indicating the voltage level at the point of interest based on a comparison between an input 61 received from the optical receiver 53 of the optocoupler 13 and another input 63 (reference voltage V REF ).

[0045] In this example, a voltage divider is arranged between the side of the optical receiver 53 of the optocoupler 13 and one input terminal of the comparator 23. The voltage divider includes a first branch and a second branch. The first branch includes a first resistor 21, and the second branch includes a second resistor 22. The second resistor can be a thermal resistor RTH. The voltage supplied to the comparator 61 is arranged between the first branch and the second branch. Since the voltage on the side of the optical receiver 53 directly depends on the voltage level at the point of interest 11, the input 61 of the comparator also directly depends on the voltage level at the point of interest 11.

[0046] The comparator in this example also includes a hysteresis resistor 24 and is configured as a hysteresis comparator.

[0047] In this example, a voltage reference module 40 is arranged to provide a second input to the hysteresis comparator 20, that is, the reference voltage V REF . A low voltage battery can supply power to the voltage reference module. In the example, the low voltage battery can form part of the voltage reference module.

[0048] In this example, the voltage reference module 40 includes a voltage divider that includes a connection from the low voltage battery V BATA first branch to a reference and including a first resistor 41, and a second branch from the reference to ground (of the second circuit) including a second resistor 43. The voltage reference module further includes a Zener diode 44 in a third branch between the reference and ground. The voltage V at the reference point REF is provided as a second input to a comparator.

[0049] Including a third branch having one or more Zener diodes can reduce fluctuations in the reference voltage when there are voltage variations at a low-voltage battery (e.g., between 6–16 V). In this particular example, the third branch may include an additional resistor 42.

[0050] The output signal of the optocoupler is provided as an input to the comparator 23 through a resistor 21. Another input to the provided comparator is the reference voltage V provided by module 40. REF . Based on the comparison between the signal received from the optocoupler 13 and the reference voltage V REF , the output of the hysteresis comparator can indicate that the voltage level at point 11 is higher than a predetermined threshold, or alternatively can indicate that the voltage level at point 11 is lower than a predetermined threshold. In this particular example, if it is found to be higher than the threshold, the output of the comparator is the voltage level of the low-voltage battery. Alternatively, the output is 0 V.

[0051] In this particular example, the system may further include a signal processing unit 30 configured to receive the output of the hysteresis comparator. The signal processing unit may include the vehicle's ECU. In a further example, the output of the signal processing unit can be provided directly or after further processing to the ECU. Based on the received signal, the ECU can determine whether the HV side is at an appropriate level.

[0052] In a specific example, the voltage level of the low-voltage battery may change. And the output of the signal processing unit 30 can depend on the voltage of the low-voltage battery. Since the input of the signal processing unit is also related to the voltage of the low-voltage battery, the influence of the low-voltage battery voltage change can be reduced or avoided.

[0053] The signal processing unit can be configured in various ways, depending on what (additional) information needs to be extracted.

[0054] As described herein, a method for detecting the voltage level at a point of interest in a first circuit is provided. The method includes: electrically connecting the point of interest to a transmitter such that the current received by the transmitter depends on the voltage level at the point of interest. The method further includes receiving the transmitted signal in a second circuit, the second circuit being electrically isolated from the first circuit. The electrical signal in the second circuit is coupled to a first input of a comparator, and the comparator receives a reference voltage as a second input. The comparator provides an output signal that depends on the comparison between the first input and the second input.

[0055] The method may further include providing an output signal of a (hysteresis) comparator to an output circuit configured to determine a voltage level at a point of interest.

[0056] The signal received in the second circuit and the reference voltage are related to the voltage level of the low-voltage battery. In this example, the output signal of the comparator is also related to the low battery voltage.

[0057] Figure 2A and Figure 2B Schematically illustrates how a Zener diode, due to its specific characteristics, can improve the accuracy of the voltage measurement result at the point of interest.

[0058] Figure 2A With V HI Illustrates a sweep voltage signal of the voltage in the HV circuit, particularly at the point of interest. Figure 2A Illustrates the current level I on the light-emitting side of the optocoupler IN , where a classical resistor is provided in the second branch of the voltage divider instead of a Zener diode. As the voltage increases linearly, the current flowing through the LED of the optocoupler also increases linearly. The current on the light-receiving side of the optocoupler is shown as I OUT .

[0059] In Figure 2A the lower half, a comparison is made between the voltage level input to the comparator and the voltage reference provided by the voltage reference module, assuming here that the voltage reference is constant. When the voltage input is higher than the reference voltage, the output of the comparator is "1" or positive. This can cover a certain voltage range, indicated as V RANGE . It should be noted here that the voltage range shown in the figure corresponds to a sweep signal including increasing and decreasing voltages. Different values can be obtained for different voltages at the low-voltage battery and different operating temperatures, although the reference voltage is not or hardly affected by these changes.

[0060] Figure 2B For comparison with the case where the second branch of the voltage divider of the HV circuit includes a Zener diode 14. As long as the voltage across the Zener diode is lower than the Zener voltage, the Zener diode substantially completely blocks the current. When higher than the Zener voltage, the current I IN flowing through the LED of the optocoupler increases linearly. The current on the light-receiving side of the optocoupler is shown as I OUT , which shows the same pattern.

[0061] In Figure 2BThe lower part compares the voltage level input of the comparator with the voltage reference provided by the voltage reference module, assuming that the voltage reference is constant here. When the voltage input is higher than the reference voltage, the output of the comparator is "1" or positive. This can cover a certain voltage range, indicated as V RANGE . It should be noted here that the voltage range shown in the figure corresponds to the scan signal including the increasing voltage and the decreasing voltage. Since the voltage range for detection decreases after using the Zener diode, the accuracy of voltage detection can be improved in a corresponding manner.

[0062] Although only some examples are disclosed herein, other alternatives, modifications, uses, and / or equivalents are possible. In addition, all possible combinations of the described examples are also covered. Therefore, the scope of the present disclosure should not be limited by the specific examples, but should be determined only by a fair interpretation of the appended claims.

Claims

1. A system for indicating a voltage level at a point of interest, the system comprising: a first circuit including the point of interest; Second Circuit; an isolation barrier that couples the first circuit to the second circuit and electrically isolates the first circuit from the second circuit; The isolation barrier includes a transmitter electrically connected to the first circuit and a receiver electrically connected to the second circuit, and wherein a current level through the transmitter indicates a voltage level at the point of interest, and wherein, The second circuit includes a comparator configured to provide an output signal indicative of a voltage level at the point of interest based at least on a comparison between an input received from the receiver and a reference voltage.

2. The system according to claim 1, wherein: The transmitter is an optical transmitter of an optical coupler, and wherein the receiver is an optical receiver of the optical coupler.

3. The system according to claim 1 or 2, wherein: The comparator is a hysteresis comparator. 4 . The system according to claim 1 , further comprising a voltage reference module for providing the reference voltage to the comparator. 5 .

5. The system according to claim 4, wherein: A low voltage battery powers the voltage reference module, and wherein the voltage reference module is configured to provide a reference voltage that varies less than a voltage of the low voltage battery.

6. The system according to any one of claims 1 to 5, wherein: The voltage reference module comprises a voltage divider comprising a first branch from the low voltage battery to a reference and comprising a first resistor and a second branch from the reference to ground comprising a second resistor, and the voltage reference module further comprises a Zener diode in a third branch between the reference and ground, and optionally, wherein the third branch comprises an additional resistor.

7. A system according to any one of claims 1 to 6, wherein: The first circuit includes a voltage divider including a first branch electrically connecting the point of interest with the transmitter and including a first resistor, and a second branch electrically connecting the transmitter with ground and including an impedance.

8. The system according to claim 7, wherein: The impedance of the second branch includes a Zener diode. 9 . The system according to claim 1 , further comprising a signal processing unit configured to receive the output signal of the comparator.

10. The system according to any one of claims 1 to 9, wherein: The output of the comparator is provided to an electronic control unit.

11. The system according to claim 10, wherein: The electronic control unit is configured to determine whether a voltage level at the point of interest is above a voltage threshold.

12. The system according to any one of claims 1 to 11, wherein: The first circuit is a high voltage circuit, and the second circuit is a low voltage circuit.

13. The system according to any one of claims 1 to 12, wherein: The point of interest is in the vehicle's junction box.

14. A method of detecting a voltage level at a point of interest in a first circuit, the method comprising the steps of: electrically connecting the point of interest to an input side of a transmitter so that the current received by the transmitter depends on the voltage level at the point of interest; receiving a signal from the transmitter in a second circuit, the second circuit being electrically isolated from the first circuit; The voltage in the second circuit is coupled to a first input of a hysteresis comparator, and the hysteresis comparator receives a reference voltage as a second input; as well as The hysteresis comparator provides an output signal that is dependent on a comparison between the first input and the second input. 15 . The method of claim 14 , further comprising providing the output signal of the comparator to an output circuit configured to determine a voltage level at the point of interest.

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