A contactor diagnosis / total voltage acquisition circuit for a vehicle power battery

Abstract

The present invention relates to a contactor diagnosis / total voltage acquisition circuit for a vehicle power battery. The circuit includes a sampling circuit and a detection branch. The first end of the detection branch is connected to the end of the contactor currently to be detected that is away from the power battery, and the second end of the detection branch is connected to the end of the contactor not currently to be detected that is closer to the power battery. The detection branch is provided with a first switch connected to the first end, a second switch connected to the second end, a plurality of voltage-dividing resistors, and a reference voltage source for providing a forward bias for the sampling point of the sampling circuit. The first switch, the reference voltage source, the first voltage-dividing resistor, the third voltage-dividing resistor, and the second switch are sequentially connected in series. The reference voltage source and the first voltage-dividing resistor are connected in series and then in parallel with the second voltage-dividing resistor. The sampling point of the sampling circuit is connected to the series connection point of the first and third voltage-dividing resistors. This circuit not only enables contactor diagnosis but also can acquire the total voltage of the contactor, greatly reducing the difficulty of measuring the voltage at the contactor terminal.

Description

Technical Field

[0001] The invention relates to a contactor diagnosis / total voltage acquisition circuit for a vehicle power battery, belonging to the technical field of high voltage. Background Art

[0002] In high-voltage electrical system applications, in order to control the on / off of the high-voltage electrical system and ensure the safety of the high-voltage loop, it is necessary to introduce a high-voltage contactor to control the on / off of the loop. In a high-voltage embodiment, a high-voltage switch called a high-voltage contactor is set in the electrical circuit on the high-voltage bus between the battery pack and other protected devices. When the high-voltage electrical system is not in use, the battery pack is automatically disconnected from other protected devices at the back end. The high-voltage contactor uses an electromagnet to open and close the conductive mechanical contacts connected to the high-voltage bus. The closing of the mechanical contacts forms a low-resistance circuit connection; the opening of the mechanical contacts controls the load (i.e., other protected devices) to disconnect the circuit from the battery pack, thereby disconnecting the battery pack.

[0003] The high-voltage contactor is a very important electrical control device in the battery system of electric vehicles. The safety status of the high-voltage contactor determines the safety of the entire high-voltage electrical system. Therefore, when the vehicle is stationary and running, the on-off status of the high-voltage contactor needs to be diagnosed to ensure that the status of the high-voltage contactor is consistent with the actual requirements.

[0004] In the current high-voltage contactor status diagnosis method, it is necessary to use a diagnostic circuit to perform on-off diagnosis on each contactor, and the diagnostic circuit is separate and independent for the diagnosis of the positive contactor and the negative contactor. In addition, in general, the contactor diagnostic circuit is also separate from the system total voltage acquisition circuit, which increases the cost of the system circuit and makes the circuit complex. The current high-voltage contactor diagnostic circuit has its reference ground and the point to be diagnosed connected in series with a voltage divider resistor. When in the working state, high voltage will be introduced to the point to be diagnosed (i.e., the sampling point). For example: the Chinese invention patent application document with application publication number CN 106427614 A, but the problem with this document is that there are many sampling points, and the positive and negative of the positive contactor and the positive and negative of the negative contactor are not easy to detect, and are easily affected by virtual pressure. Summary of the Invention

[0005] The purpose of the present invention is to provide a contactor diagnosis / total voltage acquisition circuit for a vehicle power battery, which is used to solve the problem of difficulty and high cost in measuring the terminal voltage of the positive contactor and the negative contactor in the prior art.

[0006] To achieve the above-mentioned objectives, the present invention proposes a contactor diagnosis / total voltage acquisition circuit for a vehicle power battery, the contactor diagnosis / total voltage acquisition circuit comprising a sampling circuit and at least one detection branch, wherein the first end of the detection branch is connected to the end of the contactor currently to be detected away from the power battery, and the second end of the detection branch is connected to the end of the contactor not currently to be detected close to the power battery; the detection branch is provided with a first switch connected to the first end, a second switch connected to the second end, a plurality of voltage-dividing resistors, and a reference voltage source for providing a forward bias for a sampling point of the sampling circuit; the first switch, the reference voltage source, the first voltage-dividing resistor, the third voltage-dividing resistor, and the second switch are connected in series in sequence, and the reference voltage source and the first voltage-dividing resistor are connected in series and then connected in parallel with the second voltage-dividing resistor; the sampling point of the sampling circuit is connected to the series connection point of the first voltage-dividing resistor and the third voltage-dividing resistor.

[0007] The beneficial effects are as follows: the present invention calculates the total voltage of the contactor by collecting the voltage at the sampling point of the sampling circuit, thereby realizing the collection of the total voltage of the contactor (i.e., the terminal voltage of the contactor). The calculated total voltage of the contactor is then compared with the voltage of the power battery to obtain the state of the contactor, thereby realizing the diagnosis of the contactor. The circuit diagnoses contactor faults based on the total voltage collection, thereby improving the reliability of contactor diagnosis. Moreover, the circuit can directly collect the voltage at the sampling point to obtain the terminal voltage of the contactor, greatly reducing the difficulty of measuring the terminal voltage of the contactor and saving costs.

[0008] Furthermore, the contactor diagnosis / total voltage acquisition circuit includes a first detection branch and a second detection branch, and the first detection branch and the second detection branch share a reference voltage source, a first voltage divider resistor, a second voltage divider resistor and a third voltage divider resistor.

[0009] The beneficial effect is that the first and second detection branches are used for diagnosing the positive contactor and the negative contactor respectively, and the two detection branches share a reference voltage source, a first voltage divider resistor, a second voltage divider resistor and a third voltage divider resistor, which further simplifies the circuit and saves costs.

[0010] Furthermore, the first switch and the second switch are relay switches.

[0011] The beneficial effect is that the use of a relay switch can more reliably control the opening and closing of the switch, making the diagnosis result more accurate.

[0012] Furthermore, the resistance values ​​of the first voltage-dividing resistor and the second voltage-dividing resistor are the same.

[0013] The beneficial effect is that the first voltage-dividing resistor and the second voltage-dividing resistor have the same resistance value, which can simplify the calculation process and improve the diagnosis / total pressure collection efficiency.

[0014] Furthermore, the sampling circuit includes an ADC circuit.

[0015] The beneficial effect is that the voltage of the sampling point can be collected more accurately through the ADC circuit, so that the obtained total voltage of the contactor is more accurate, thereby making the diagnosis of the contactor more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a circuit diagram of embodiment 1 of a contactor diagnosis / total voltage acquisition circuit for a vehicle power battery according to the present invention;

[0017] Figure 2 This is a circuit diagram of embodiment 2 of the contactor diagnosis / total voltage acquisition circuit for a vehicle power battery of the present invention. DETAILED DESCRIPTION

[0018] Example 1 of contactor diagnosis / total voltage acquisition circuit for vehicle power battery:

[0019] The contactor diagnosis / total voltage acquisition circuit design concept of the vehicle power battery proposed in this embodiment is to perform contactor diagnosis based on the acquisition of the contactor total voltage. This embodiment only acquires and diagnoses the total voltage of the positive contactor Relay P. The specific circuit is as follows Figure 1 As shown, when detecting the positive contactor Relay P (i.e., the positive control contactor of the high-voltage electrical loop), the contactor diagnosis / total voltage acquisition circuit includes a sampling circuit and a detection branch. The first end of the detection branch is connected to the end of the positive contactor Relay P away from the power battery (here, the end away from the power battery is the end of the positive contactor Relay P connected to other protection devices), and the second end of the detection branch is connected to the end of the negative contactor Relay N (the negative control contactor of the high-voltage electrical loop) close to the power battery (here, the end close to the power battery is the negative output end of the power battery).

[0020] The detection branch is provided with a first switch SW3 connected to the first end and a second switch SW2 connected to the second end; a plurality of voltage dividing resistors and a sampling point V for the sampling circuit are also provided. adc Provides a forward biased reference voltage source V ref , a plurality of voltage-dividing resistors include a first voltage-dividing resistor R1, a second voltage-dividing resistor R2, and a third voltage-dividing resistor R3; a first switch SW3, a reference voltage source V ref , the first voltage dividing resistor R1, the third voltage dividing resistor R3, and the second switch SW2 are connected in series in sequence, and the reference voltage source V ref The sampling point V of the sampling circuit is connected in series with the first voltage dividing resistor R1 and then in parallel with the second voltage dividing resistor R2. adc A series connection point is connected between the first voltage-dividing resistor R1 and the third voltage-dividing resistor R3.

[0021] The principle of this circuit is that by closing the first switch SW3 and the second switch SW2, the voltage V at the end of the positive contactor Relay P away from the power battery can be calculated through the voltage at the sampling point of the sampling circuit. vol-p , by setting V vol-p By comparing with the voltage of the power battery (i.e., battery pack), it can be determined whether the positive contactor Relay P is disconnected or adhered.

[0022] In this embodiment, in order to more reliably control the closing and opening of each switch, each switch adopts a relay switch, and the relay switch is a normally open switch. Figure 1 The controller shown controls the closing of each relay switch. Of course, as other implementations, each switch can also be an electronic switch. The switching devices selected for different application scenarios are different. The present invention does not limit the specific implementation of the switch, as long as the circuit can be turned on and off.

[0023] To further simplify the calculation process, in this embodiment, the first voltage divider resistor R1 and the second voltage divider resistor R2 have the same resistance value. In other embodiments, the first voltage divider resistor R1 and the second voltage divider resistor R2 may also have different resistance values.

[0024] In order to more accurately collect the voltage at the sampling point, in this embodiment, the sampling circuit is an ADC circuit, and the acquisition is completed by an ADC chip. Of course, the present invention does not limit the specific implementation of the sampling circuit, as long as the voltage at the sampling point can be collected.

[0025] The specific method for collecting and diagnosing the total voltage of the positive contactor is as follows:

[0026] When the circuit performs positive contactor diagnosis, the ground reference is set to the negative electrode of the battery pack (ie BATN), the positive electrode of the battery pack is BATP, and the voltage of the battery pack is:

[0027] V bat =BATP–BATN,

[0028] When this circuit is used for diagnosis, there is no limit on the number of positive contactors, and there can be multiple positive contactors.

[0029] 1) The controller controls the closing of the first switch SW3 and the second switch SW2, and the ADC circuit collects the voltage V at the sampling point adc .

[0030] 2) ADC circuit collects the voltage V adc Sent to the controller, the controller calculates according to Kirchhoff's current law. The calculation process is: Assume that the point to be measured is V x ,

[0031] (Vref –V adc ) / R1+(V x –V adc ) / R3=V adc / R2, where R1=R2;

[0032] Then we can conclude that: V x =2*R3*V adc / R2+V adc –V ref *R3 / R2;

[0033] At this time, when V x =V vol-p (Total voltage of positive contactor);

[0034] V vol-p =(2*R3 / R2+1)*V adc –(R3 / R2)*V ref .

[0035] 3) Compare V vol-p With V bat Size:

[0036] If (V bat –V vol-p ) / V bat If the value is less than 0.05, the positive contactor is judged to be stuck; otherwise, the positive contactor is judged to be disconnected. The 0.05 in the formula is a coefficient and can be adjusted according to actual conditions.

[0037] This embodiment collects and diagnoses the total voltage of the positive contactor. Of course, the detection branch can also be used alone for collecting and diagnosing the total voltage of the negative contactor. However, one end of the detection branch needs to be connected to the end of the negative contactor connected to other protection devices, and the other end needs to be connected to the positive output end of the power battery.

[0038] Example 2 of contactor diagnosis / total voltage acquisition circuit for vehicle power battery:

[0039] The design concept of the contactor diagnosis / total voltage acquisition circuit of the vehicle power battery proposed in this embodiment is the same as that in the embodiment 1, except that in this embodiment, not only the total voltage acquisition and diagnosis of the positive contactor Relay P can be performed, but also the total voltage acquisition and diagnosis of the negative contactor Relay N can be performed. The circuit can switch the detection of the positive contactor Relay P and the negative contactor Relay N by switching the switch. The specific circuit is as follows Figure 2As shown, the circuit includes a first detection branch and a second detection branch. The first detection branch detects the positive contactor Relay P. The circuit structure is basically the same as that in Example 1, except that the first detection branch also includes a fourth voltage-dividing resistor R4, which is connected in series between the third voltage-dividing resistor R3 and the first switch SW3.

[0040] The second detection branch detects the negative contactor Relay N. The first end of the second detection branch is connected to the end of the negative contactor Relay N (hereinafter referred to as the negative contactor) away from the power battery (the end away from the power battery here is the end of the negative contactor connected to other protection devices), and the second end of the detection branch is connected to the end of the positive contactor Relay P (hereinafter referred to as the positive contactor) close to the power battery (the end close to the power battery here is the positive output terminal of the power battery).

[0041] The second detection branch is provided with a fourth switch SW4 connected to the first end of the branch, a third switch SW1 connected to the second end of the branch, and a fifth voltage-dividing resistor R5; the first detection branch and the second detection branch share a reference voltage source V ref , a first voltage-dividing resistor R1 , a second voltage-dividing resistor R2 , a third voltage-dividing resistor R3 , a fourth switch SW4 , a fifth voltage-dividing resistor R5 , and the third voltage-dividing resistor R3 are sequentially connected in series.

[0042] The detection principle of the second detection branch is: close the fourth switch SW4 and the third switch SW1, and calculate the voltage V at the end of the negative contactor Relay P away from the power battery (i.e., battery pack) through the voltage at the sampling point of the sampling circuit. vol-n , by setting V vol-n By comparing with the voltage of the power battery, it can be determined whether the negative contactor Relay N is disconnected or adhered.

[0043] In this embodiment, in order to more reliably control the closing and opening of each switch, each switch adopts a relay switch, and the relay switch is a normally open switch. Figure 2 The controller shown controls the closing of each relay switch. Of course, as other implementations, each switch can also be an electronic switch. The switching devices selected for different application scenarios are different. The present invention does not limit the specific implementation of the switch, as long as the circuit can be turned on and off.

[0044] To further simplify the calculation process, in this embodiment, the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 have the same resistance value, and the fourth voltage-dividing resistor R4 and the fifth voltage-dividing resistor R5 have the same resistance value. In other embodiments, the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 may have different resistance values, and the fourth voltage-dividing resistor R4 and the fifth voltage-dividing resistor R5 may have different resistance values.

[0045] In order to more accurately collect the voltage at the sampling point, in this embodiment, the sampling circuit is an ADC circuit, and the acquisition is completed by an ADC chip. Of course, the present invention does not limit the specific implementation of the sampling circuit, as long as the voltage at the sampling point can be collected.

[0046] The following describes the method for collecting and diagnosing the total voltage of the positive and negative contactors.

[0047] When the circuit is performing positive contactor diagnosis, the ground reference is the negative electrode of the battery pack (i.e., BATN); when performing negative contactor diagnosis, the ground reference is the positive electrode of the battery pack (i.e., BATP); the voltage of the battery pack is:

[0048] V bat =BATP–BATN,

[0049] When this circuit is performing diagnosis, it can only diagnose the positive contactor or the negative contactor separately, and cannot diagnose both at the same time. However, the present invention does not limit the number of positive contactors or negative contactors, and there can be multiple positive contactors or negative contactors.

[0050] The method for collecting and diagnosing the total voltage of the positive contactor is as follows:

[0051] 1) The controller controls the closing of the first switch SW3 and the second switch SW2, and the opening of the fourth switch SW4 and the third switch SW1. The ADC circuit collects the voltage V at the sampling point. adc .

[0052] 2) ADC circuit collects the voltage V adc Sent to the controller, the controller calculates according to Kirchhoff's current law. The calculation process is: Assume that the point to be measured is V x ,

[0053] (V ref –V adc ) / R1+(V x –V adc ) / (R3+R4)=V adc / R2, where R1=R2;

[0054] Then we can conclude that: V x =2*(R3+R4)*V adc / R2+V adc –V ref *(R3+R4) / R2;

[0055] At this time, when V x =V vol-p (Total voltage of positive contactor);

[0056] V vol-p =(2*(R4+R3) / R2+1)*V adc –((R4+R3) / R2)*V ref .

[0057] 3) Compare V vol-p With V bat Size:

[0058] If (V bat –V vol-p ) / V bat If the value is less than 0.05, the positive contactor is judged to be stuck; otherwise, the positive contactor is judged to be disconnected. The 0.05 in the formula is a coefficient and can be adjusted according to actual conditions.

[0059] The method for collecting and diagnosing the total voltage of the negative contactor is as follows:

[0060] 1) The controller controls the closing of the fourth switch SW4 and the third switch SW1, and the opening of the first switch SW3 and the second switch SW2. The ADC circuit collects the voltage V at the sampling point. adc .

[0061] 2) ADC circuit collects the voltage V adc Sent to the controller, the controller calculates according to Kirchhoff's current law. The calculation process is: Assume that the point to be measured is V x ,

[0062] (V ref –V adc ) / R1=V adc / R2+(V adc +BATP–V x ) / (R3+R5), where R1=R2;

[0063] Then we can conclude that: (V ref –2V adc ) / R2=(V adc +BATP–V x ) / (R3+R5),

[0064] (R3+R5) / R2*V ref –2*(R3+R5) / R2*V adc –V adc=BATP–V x ,

[0065] At this time, when V x =V vol-n (total voltage of negative contactor), BATP=V bat ,

[0066] V vol-n =V bat +(2*(R5+R3) / R1+1)*V adc –(R5+R3) / R1*V ref .

[0067] 3) Compare V vol-n With V bat Size:

[0068] If (V bat –V vol-n ) / V bat >0.95, the negative contactor is judged to be stuck; otherwise, the negative contactor is judged to be disconnected. The 0.95 in the formula is a coefficient and can be adjusted according to actual conditions.

[0069] The above completes the total voltage collection and diagnosis of the positive and negative contactors. The voltage V = V at the battery pack connection end can also be calculated through the above total voltage collection. vol-p –V vol-n .

[0070] The above method is verified through simulation.

[0071] When performing simulation, the parameters selected are V bat =200V; R1=R2=1kΩ; R3=R4=R5=100kΩ; V ref = 2.5 V. In addition, the total voltage acquisition time of the positive and negative contactors and the voltage acquisition time of the battery pack need to increase the time interval t, t = 100 ms. Of course, the time interval t can be adjusted according to actual needs.

[0072] According to the above method, the total voltage acquisition and diagnosis of the positive contactor are simulated.

[0073] The actual simulation sampling obtains V adc =1.7456359V; V vol-p =200V;

[0074] According to the calculation formula of the positive contactor above:

[0075] V vol-p =401*1.7456359V–200*2.5V=700V–500V=200V;

[0076] Theoretical calculation is V vol-p =200V, the actual simulation result V vol-p =200V;

[0077] After judgment, (V bat –V vol-p ) / V bat =0, it can be determined that the positive contactor is stuck. In the actual simulation, the positive contactor is also in a stuck state, which can be determined that the theoretical derivation is consistent with the actual application.

[0078] According to the above method, the total voltage acquisition and diagnosis of the negative contactor are simulated.

[0079] The actual simulation sampling obtains V adc =0.74813V; V vol-n =0V;

[0080] According to the calculation formula of the negative contactor above:

[0081] V vol-n =200V+401*0.74813V–200*2.5V=200V+300V–500V=0V;

[0082] Theoretical calculation is V vol-n =0V, the actual simulation result V vol-n =0V;

[0083] After judgment, (V bat -V vol-n ) / V bat =1, it can be determined that the negative contactor is stuck. In the actual simulation, the negative contactor is also in a stuck state, which can be determined that the theoretical derivation is consistent with the actual application.

[0084] This circuit diagnoses contactor faults based on total voltage acquisition, improving the reliability of contactor diagnosis. This circuit not only enables contactor diagnosis but also acquires the total voltage of the contactor, greatly reducing the difficulty of measuring the contactor terminal voltage and saving costs.

Claims

1. A contactor diagnosis / total voltage acquisition circuit for a vehicle power battery, characterized in that: The contactor diagnosis / total voltage acquisition circuit includes a controller, a voltage sampling circuit and at least one detection branch, wherein the first end of the detection branch is connected to the end of the contactor to be detected that is away from the power battery, and the second end of the detection branch is connected to the end of the contactor not to be detected that is close to the power battery; the detection branch is provided with a first switch connected to the first end, a second switch connected to the second end, a first voltage divider resistor, a second voltage divider resistor, a third voltage divider resistor and a reference voltage source for providing a forward bias for the sampling point of the sampling circuit; the first switch, the third voltage divider resistor, the first voltage divider resistor, the reference voltage source and the second switch are connected in series in sequence, and the reference voltage source is connected to the first end of the contactor. A voltage source and a first voltage-dividing resistor are connected in series and then connected in parallel with the second voltage-dividing resistor; a sampling point of the voltage sampling circuit is connected to a series connection point of the first voltage-dividing resistor and the third voltage-dividing resistor, and the voltage sampling circuit is used to collect a voltage at the sampling point when the first switch and the second switch are closed, and send the sampling point voltage to a controller. The controller calculates a voltage at a terminal of the contactor to be detected that is away from the power battery based on the sampling point voltage, the reference voltage source voltage, and Kirchhoff's current law, and compares the voltage at the terminal of the contactor to be detected that is away from the power battery with the power battery pack voltage to determine whether the contactor to be detected is disconnected or stuck.

2. The contactor diagnosis / total voltage acquisition circuit for a vehicle power battery according to claim 1, characterized in that: The contactor diagnosis / total voltage acquisition circuit includes a first and a second detection branch. The first detection branch is used to detect the positive contactor, and the second detection branch is used to detect the negative contactor. The first end of the first detection branch is connected to the end of the positive contactor away from the power battery, and the second end of the first detection branch is connected to the end of the negative contactor close to the power battery; a first switch and a second switch are set in the first detection branch; the first end of the second detection branch is connected to the end of the negative contactor away from the power battery, and the second end of the second detection branch is connected to the end of the positive contactor close to the power battery. A third switch and a fourth switch are set in the second detection branch, the first end of the second detection branch is connected to one end of the fourth switch, and the other end of the fourth switch is connected to the third voltage dividing resistor, the second end of the second detection branch is connected to one end of the third switch, and the other end of the third switch is connected to the third voltage dividing resistor. One end is connected to a reference voltage source, and the voltage sampling circuit is used to collect a first voltage at a sampling point when the first switch and the second switch are closed and the third switch and the fourth switch are opened, and collect a second voltage at the sampling point when the third switch and the fourth switch are closed and the first switch and the second switch are opened, and send the first voltage or the second voltage to a controller, wherein the controller is used to calculate a voltage at an end of the positive contactor away from the power battery based on the first voltage, and compare the voltage at the end of the positive contactor away from the power battery with the voltage of the power battery pack, thereby determining whether the positive contactor is disconnected or stuck; and the controller is used to calculate a voltage at an end of the negative contactor away from the power battery based on the second voltage, and compare the voltage at the end of the negative contactor away from the power battery with the voltage of the power battery pack, thereby determining whether the negative contactor is disconnected or stuck.

3. The contactor diagnosis / total voltage acquisition circuit for a vehicle power battery according to claim 2, characterized in that: The first switch is connected in series with the third voltage-dividing resistor via the fourth voltage-dividing resistor, and the fourth switch is connected to the series connection point between the third voltage-dividing resistor and the fourth voltage-dividing resistor via the fifth voltage-dividing resistor.

4. The contactor diagnosis / total voltage acquisition circuit for a vehicle power battery according to claim 1 or 2, characterized in that: The first voltage-dividing resistor and the second voltage-dividing resistor have the same resistance value.

5. The contactor diagnosis / total voltage acquisition circuit for a vehicle power battery according to claim 1 or 2, characterized in that: The sampling circuit includes an ADC circuit.

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