Low-cost battery voltage isolation sampling circuit

Abstract

The utility model discloses a low-cost battery voltage isolation sampling circuit, which comprises a voltage-to-current circuit, an optical coupler isolation circuit, a current-to-voltage circuit, an amplification circuit and an ADC (Analog to Digital Converter) circuit which are connected in sequence, the voltage-to-current circuit is connected with the positive electrode and the negative electrode of a battery PACK, the voltage of the battery PACK is converted into a current signal through the voltage-to-current circuit, then a primary side current signal is transmitted to a secondary side through the optocoupler isolation circuit, the current signal is converted into a voltage signal through the current-to-voltage circuit, the voltage signal is amplified through the amplification circuit, and finally the voltage signal is transmitted to the ADC circuit. And isolation voltage sampling of the battery PACK is completed. According to the utility model, an auxiliary power supply is not needed to supply power to the primary high-voltage side of the optocoupler, only the power supply to the secondary low-voltage side is needed, the PACK voltage of the battery is converted into a current signal by improving the circuit, then the current signal is restored into a voltage signal at the secondary side of the optocoupler, and then the voltage signal is output through the amplifying circuit, so that the circuit is simple in structure and low in cost.

Description

Technical Field

[0001] This utility model relates to the field of isolated voltage sampling circuit technology, and in particular to a low-cost battery voltage isolated sampling circuit. Background Technology

[0002] In modern energy storage systems, the charging and discharging management of battery packs is extremely important, and enabling the energy storage system to monitor the battery pack voltage in real time is crucial and fundamental. Furthermore, since the battery pack is on the high-voltage side, while the ADC and MCU are on the low-voltage control side, electrical isolation is required according to safety regulations. Therefore, isolated voltage sampling technology based on the battery pack has emerged.

[0003] Patent 1 (CN 207703924 U - A Low-Cost DC Voltage Isolation Acquisition Circuit) proposes a DC voltage sampling technology that uses dual-channel optocouplers for isolation and signal transmission. However, due to the feedback signal to the second optocoupler input, the safety distance becomes more difficult to control, making it unsuitable for applications requiring higher isolation voltages. Patent 2 (CN 119556164A - A Vehicle BMS High-Voltage Sampling System Based on Isolated High-Voltage Sampling) proposes an isolated voltage sampling scheme based on an isolated operational amplifier module. This first requires powering the primary side VDD1. Since VDD1 is located on the high-voltage side of the battery, electrical isolation must also be considered when designing the auxiliary power supply. The most common method is to add an extra winding to the auxiliary power transformer and provide an additional power supply. This not only increases the design difficulty of the auxiliary power supply but also increases the cost.

[0004] The existing technology improves upon the technology proposed in Patent 2 by using a high-performance linear optocoupler. The battery PACK voltage is first divided by a resistor and then sent to this optocoupler. The optocoupler converts the single-ended signal into a differential signal, which is then amplified by a differential amplifier circuit before being sent to the ADC for isolated sampling. However, since both the primary and secondary sides of this high-performance linear optocoupler require power, and the primary side is the high-voltage side of the battery, even if the voltage amplitudes of the primary and secondary sides are the same, their power supplies must be separated for electrical isolation. This increases the design complexity and cost of the auxiliary power supply. Utility Model Content

[0005] The purpose of this invention is to provide a low-cost battery voltage isolation sampling circuit. Using a common linear optocoupler, only the low-voltage side of the secondary side of the optocoupler isolation circuit needs to be powered, while the high-voltage side of the primary side does not need to be powered. By improving the circuit, the battery PACK voltage is converted into a current signal, then restored to a voltage signal on the secondary side of the optocoupler, and then output through an amplification circuit. The circuit structure is simple and the cost is low.

[0006] To achieve the above objectives, this utility model provides the following solution:

[0007] A low-cost battery voltage isolation sampling circuit includes a voltage-to-current circuit, an optocoupler isolation circuit, a current-to-voltage circuit, an amplifier circuit, and an ADC circuit.

[0008] The voltage-to-current circuit includes a voltage input interface, a first resistor, and the primary side of an optocoupler isolation circuit arranged in series; the secondary side of the optocoupler isolation circuit is connected to the current-to-voltage circuit, the current-to-voltage circuit is connected to the amplifier circuit, and the output terminal of the amplifier circuit is connected to the ADC circuit.

[0009] The voltage input interface of the voltage-to-current circuit is used to connect to the positive and negative terminals of the battery pack. The battery pack voltage is converted into a current signal by the voltage-to-current circuit, and then the primary current signal is transmitted to the secondary side through the optocoupler isolation circuit. The current signal is converted into a voltage signal by the current-to-voltage circuit, and then the voltage signal is amplified by the amplifier circuit. Finally, it is transmitted to the ADC circuit to complete the isolation voltage sampling of the battery pack.

[0010] Furthermore, the primary side of the optocoupler isolation circuit is a light-emitting diode, and the secondary side is a phototransistor.

[0011] Furthermore, the current-to-voltage circuit includes a second resistor, one end of which is grounded and the other end is connected to the emitter of the phototransistor, and the collector of the phototransistor is connected to a DC power supply.

[0012] Furthermore, the amplifier circuit is a non-inverting amplifier circuit composed of a third resistor, a fourth resistor, a fifth resistor, and an operational amplifier;

[0013] One end of the third resistor is connected to one end of the second resistor, and the non-inverting input of the operational amplifier is connected to the other end of the second resistor;

[0014] The other end of the third resistor and one end of the fourth resistor are connected to the inverting input of the operational amplifier, the other end of the fourth resistor is connected to one end of the fifth resistor, and the other end of the fifth resistor is connected to the output of the operational amplifier.

[0015] Furthermore, the output of the operational amplifier is connected to the ADC circuit.

[0016] Furthermore, the output voltage V acquired by the ADC circuit OUT With battery pack voltage V PACK The mapping relationship is as follows:

[0017]

[0018] Among them, VF R1, R2, R3, R4, and R5 represent the forward voltage drop of the LED in the optocoupler isolation circuit, and R1, R2, R3, R4, and R5 represent the resistance values ​​of the first, second, third, fourth, and fifth resistors, respectively. CTR represents the current transfer ratio of the optocoupler isolation circuit.

[0019] According to the specific embodiments provided by this utility model, the low-cost battery voltage isolation sampling circuit provided by this utility model discloses the following technical effects:

[0020] The circuit structure is simple, including a voltage-to-current circuit, an optocoupler isolation circuit, a current-to-voltage circuit, an amplifier circuit, and an ADC circuit;

[0021] The acquisition principle is simple: the battery PACK voltage is converted into current through a voltage-to-current circuit, and then the current signal carrying the PACK voltage information is transmitted through the light-emitting diode and phototransistor of the optocoupler isolation circuit. After being transmitted to the secondary side of the optocoupler isolation circuit, the current signal is converted into a voltage signal, and then the voltage signal is amplified by the amplifier circuit and finally transmitted to the ADC circuit to complete the isolation voltage sampling of the battery PACK.

[0022] This invention addresses the problem of high design difficulty and cost of auxiliary power supply in existing dual-power supply solutions. It achieves isolated voltage sampling using ordinary linear optocouplers and operational amplifiers, and only the secondary side of the optocoupler isolation circuit needs to be powered, while the primary side (i.e., the high-voltage side of the battery pack) does not need to be powered. This reduces the design difficulty of the auxiliary power supply and lowers the overall cost. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the low-cost battery voltage isolation sampling circuit structure of this utility model;

[0025] Figure 2 This is a flowchart illustrating the low-cost battery voltage isolation sampling circuit of this invention. Detailed Implementation

[0026] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0027] This invention provides a low-cost battery voltage isolation sampling circuit. The key feature is the use of a common linear optocoupler, which eliminates the need for a separate power supply to the primary side. The battery PACK voltage is converted into a current signal through a voltage-to-current circuit, and then restored to a voltage signal on the secondary side of the optocoupler isolation circuit. Finally, the signal is output through an amplifier circuit. The circuit structure is simple and the cost is low.

[0028] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1 As shown, this utility model embodiment provides a low-cost battery voltage isolation sampling circuit, including a voltage-to-current circuit, an optocoupler isolation circuit, a current-to-voltage circuit, an amplifier circuit, and an ADC circuit.

[0030] The voltage-to-current circuit includes a voltage input interface, a first resistor R1, and the primary side of an optocoupler isolation circuit U1 connected in series; the secondary side of the optocoupler isolation circuit U1 is connected to the current-to-voltage circuit, the current-to-voltage circuit is connected to the amplifier circuit, and the output terminal of the amplifier circuit is connected to the ADC circuit.

[0031] The voltage input interface of the voltage-to-current circuit is used to connect to the positive and negative terminals of the battery pack.

[0032] The primary side of the optocoupler isolation circuit U1 is a light-emitting diode, and the secondary side is a phototransistor.

[0033] The current-to-voltage circuit includes a second resistor R2, one end of which is grounded and the other end is connected to the emitter of the phototransistor. The collector of the phototransistor is connected to the DC power supply VCC.

[0034] The amplifier circuit is a non-inverting amplifier circuit composed of the third resistor R3, the fourth resistor R4, the fifth resistor R5, and the operational amplifier U2.

[0035] One end of the third resistor R3 is connected to one end of the second resistor R2, and the non-inverting input of the operational amplifier U2 is connected to the other end of the second resistor R2;

[0036] The other end of the third resistor R3 and one end of the fourth resistor R4 are connected to the inverting input of the operational amplifier U2. The other end of the fourth resistor R4 is connected to one end of the fifth resistor R5, and the other end of the fifth resistor R5 is connected to the output terminal of the operational amplifier U2. The output terminal of the operational amplifier U2 is connected to the ADC circuit.

[0037] To improve the voltage sampling accuracy on the DC battery PACK side, it is recommended to use high-precision (0.1% accuracy) resistors for R1 to R5, and optocouplers with high current transfer ratio (CTR) accuracy for the optocoupler isolation circuit. At the same time, when configuring the resistor values, the optocoupler must be operated in the linear region rather than the saturation region. It is recommended to use a precision operational amplifier to reduce gain error.

[0038] like Figure 2 As shown, the operation of the low-cost battery voltage isolation sampling circuit is as follows:

[0039] The battery PACK voltage is converted into a current signal by a voltage-to-current circuit. Then, the primary current signal is transmitted to the secondary side through an optocoupler isolation circuit. The current signal is converted into a voltage signal by a current-to-voltage circuit. The voltage signal is then amplified by an amplifier circuit and finally transmitted to the ADC circuit to complete the isolated voltage sampling of the battery PACK.

[0040] The output voltage V acquired by the ADC circuit OUT With battery pack voltage V PACK The mapping relationship is as follows:

[0041]

[0042] Among them, V F R1, R2, R3, R4, and R5 represent the forward voltage drop of the LED in the optocoupler isolation circuit, and R1, R2, R3, R4, and R5 represent the resistance values ​​of the first, second, third, fourth, and fifth resistors, respectively. CTR represents the current transfer ratio of the optocoupler isolation circuit.

[0043] The derivation process of the above mapping relationship is as follows:

[0044] Assume the battery pack voltage is V. PACK The primary current of the optocoupler isolation circuit is I. F The secondary current of the optocoupler isolation circuit is I. C The current transfer ratio of the optocoupler isolation circuit is CTR, and the forward voltage drop of the light-emitting diode in the optocoupler isolation circuit is V. F The voltage across the second resistor R2 is V. IN The final output voltage to the ADC circuit is V. OUT ;

[0045] The battery PACK voltage is converted into a current signal through the first resistor R1 and the LED circuit of the optocoupler isolation circuit. Therefore, the primary current of the optocoupler isolation circuit is:

[0046] I F =(V PACK -V F ) / R1 (2)

[0047] The secondary current of the optocoupler isolation circuit is:

[0048] I C =I F *CTR (3)

[0049] The voltage across the second resistor R2 (which is the input of the subsequent operational amplifier) ​​is:

[0050] V IN =I C *R2 (4)

[0051] The final voltage output to the ADC circuit is:

[0052] V OUT =V IN *[1+(R4+R5) / R3] (5)

[0053] Substituting formula (2) into formula (3), then substituting formula (3) into formula (4), and finally substituting formula (4) into formula (5) yields the mapping relationship formula (1).

[0054] Among them, V F The CTR can be found in the technical manual of the selected optocoupler. The resistance values ​​of resistors R1 to R5 are fixed after the circuit is determined. According to the mapping formula (1), as long as V F The CTR and the resistance values ​​of resistors R1 to R5 are determined, and the unique battery PACK voltage corresponds to the unique voltage received by the ADC (i.e., V). OUT ), by detecting V OUT This allows for monitoring of the battery pack voltage, thus achieving the purpose of sampling the battery pack isolation voltage.

[0055] This document uses specific examples to illustrate the principles and implementation methods of this utility model. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this utility model. Furthermore, those skilled in the art will recognize that, based on the ideas of this utility model, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. A low-cost battery voltage isolation sampling circuit, characterized in that, include: Voltage-to-current circuit, optocoupler isolation circuit, current-to-voltage circuit, amplifier circuit and ADC circuit; The voltage-to-current circuit includes a voltage input interface, a first resistor, and the primary side of an optocoupler isolation circuit arranged in series; the secondary side of the optocoupler isolation circuit is connected to the current-to-voltage circuit, the current-to-voltage circuit is connected to the amplifier circuit, and the output terminal of the amplifier circuit is connected to the ADC circuit. The voltage input interface of the voltage-to-current circuit is used to connect to the positive and negative terminals of the battery pack. The battery pack voltage is converted into a current signal by the voltage-to-current circuit, and then the primary current signal is transmitted to the secondary side through the optocoupler isolation circuit. The current signal is converted into a voltage signal by the current-to-voltage circuit, and then the voltage signal is amplified by the amplifier circuit. Finally, it is transmitted to the ADC circuit to complete the isolation voltage sampling of the battery pack.

2. The low-cost battery voltage isolation sampling circuit according to claim 1, characterized in that, The primary side of the optocoupler isolation circuit is a light-emitting diode, and the secondary side is a phototransistor.

3. The low-cost battery voltage isolation sampling circuit according to claim 2, characterized in that, The current-to-voltage circuit includes a second resistor, one end of which is grounded and the other end is connected to the emitter of the phototransistor. The collector of the phototransistor is connected to a DC power supply.

4. The low-cost battery voltage isolation sampling circuit according to claim 3, characterized in that, The amplifier circuit is a non-inverting amplifier circuit composed of a third resistor, a fourth resistor, a fifth resistor, and an operational amplifier. One end of the third resistor is connected to one end of the second resistor, and the non-inverting input of the operational amplifier is connected to the other end of the second resistor; The other end of the third resistor and one end of the fourth resistor are connected to the inverting input of the operational amplifier, the other end of the fourth resistor is connected to one end of the fifth resistor, and the other end of the fifth resistor is connected to the output of the operational amplifier.

5. The low-cost battery voltage isolation sampling circuit according to claim 4, characterized in that, The output of the operational amplifier is connected to the ADC circuit.

6. The low-cost battery voltage isolation sampling circuit according to claim 5, characterized in that, The output voltage V acquired by the ADC circuit OUT With battery pack voltage V PACK The mapping relationship is as follows: Among them, V F R1, R2, R3, R4, and R5 represent the forward voltage drop of the LED in the optocoupler isolation circuit, and R1, R2, R3, R4, and R5 represent the resistance values ​​of the first, second, third, fourth, and fifth resistors, respectively. CTR represents the current transfer ratio of the optocoupler isolation circuit.

Images