A battery relay control circuit, method, and power supply circuit

Abstract

This invention relates to the field of power electronics technology, specifically to a battery relay control circuit, method, and power supply circuit. The battery relay control circuit includes: a battery voltage sampling circuit, with its input terminal connected to the end of the power switch near the pre-charging circuit, for acquiring the switching voltage on the pre-charging circuit side of the power switch; a bus voltage sampling circuit, with its input terminal connected to the BUS bus on the bus capacitor side, for acquiring the bus capacitor voltage; and a comparator, with its first input terminal connected to the bus voltage sampling circuit and its second input terminal connected to the battery voltage sampling circuit. The comparator compares the switching voltage with the bus capacitor voltage. When the absolute difference between the switching voltage and the bus capacitor voltage is greater than the pull-in voltage threshold, the comparator outputs a signal indicating that the relay can be pulled in, thereby avoiding the problem of difficulty in determining a fixed threshold due to large battery voltage fluctuations.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a battery relay control circuit, method, and power supply circuit. Background Technology

[0002] In industrial vehicles such as electric forklifts, relays are built into the electronic control system as core power switches. A typical connection is as follows: one end is directly connected to the positive terminal of the battery (BAT+), and the other end is connected to the bus capacitor inside the electronic control system. When the system is powered on, the bus capacitor must first be pre-charged through a pre-charging circuit. Only after the bus voltage rises to a certain level can the controller close the relay to prevent damage to the contacts from a large surge current.

[0003] The core condition for a relay to close safely is that the voltage difference between its two contacts (i.e., the pull-in voltage) must be less than its permissible switching voltage. However, the contacts of the relay connected to the battery remain energized when the device is off. To ensure safety, the voltage at these contacts is not directly detected within the electronic control unit. Existing technology typically uses the bus voltage detection method to indirectly determine this: the software sets a fixed charging threshold; when the bus voltage charges to this threshold, the pull-in voltage is considered to have dropped to a safe range, and the microcontroller (MCU) then sends a drive signal to close the relay.

[0004] This existing technology has significant drawbacks: First, the battery voltage itself has a fluctuation range, causing the actual pull-in voltage across the relay to fluctuate accordingly. For battery systems with a wide voltage range, if the bus charging threshold set by the software is too low, the actual pull-in voltage may still be higher than the safe switching voltage when the battery voltage is high, leading to a risk of relay closure. If it is set too high, a longer pre-charging time is required to reach the threshold when the battery voltage is low, extending the system startup time. Second, during this process, the MCU needs to continuously sample and judge the bus voltage to respond quickly when the threshold is reached, which consumes valuable MCU processing resources. Summary of the Invention

[0005] To address the technical problems of difficulty in setting software thresholds and high computational load in the comparison process, this application provides a battery relay control circuit, method, and power supply circuit, wherein the battery relay control circuit includes: The battery voltage sampling circuit has its input terminal connected to the end of the power switch closest to the pre-charging circuit, and is used to collect the switching voltage on the pre-charging circuit side of the power switch. The bus voltage sampling circuit, with its input terminal connected to the BUS bus on the bus capacitor side, is used to acquire the bus capacitor voltage at the bus capacitor terminal; and The comparator has its first input terminal connected to the bus voltage sampling circuit and its second input terminal connected to the battery voltage sampling circuit. The comparator is used to compare the switching voltage with the bus capacitor voltage. When the absolute difference between the switching voltage and the bus capacitor voltage is greater than the pull-in voltage threshold, the output terminal of the comparator sends a relay pull-in signal.

[0006] The circuit described above directly detects the voltage difference across relay K1 using hardware and compares the voltage difference with the pull-in voltage threshold, thus avoiding the problem of difficulty in determining a fixed threshold due to large fluctuations in battery voltage.

[0007] In some embodiments, the battery voltage sampling circuit includes: a Zener diode and a first resistor connected in series between the power switch and the second input terminal of the comparator, and a second resistor grounding the second input terminal of the comparator; The Zener diode is connected to the power switch, and the first resistor is connected to the second input terminal of the comparator and the second resistor.

[0008] The Zener diode generates a stable voltage drop, which serves as the basis for the relay's pull-in voltage threshold. This threshold is used to determine whether the relay meets the pull-in conditions. Regardless of changes in battery voltage, the relay's pull-in conditions can be flexibly adjusted. This ensures that the voltage difference between the two contacts is always below the safety standard when the relay is pulled in, and also reduces the charging time of the bus capacitor, ensuring the circuit responds promptly to system startup.

[0009] In some embodiments, the bus voltage sampling circuit includes a third resistor and a fourth resistor connected in series. One end of the third resistor is connected to the BUS bus on the bus capacitor side, and the other end is connected to the fourth resistor and the first input terminal of the comparator. The fourth resistor is grounded.

[0010] This direct voltage divider method not only has a simple circuit structure and fewer components, which helps reduce hardware costs and circuit complexity, but also avoids the errors and delays that may be caused by complex signal conditioning circuits.

[0011] In some embodiments, the voltage division ratio of the first resistor and the second resistor is the same as the voltage division ratio of the third resistor and the fourth resistor. This ensures that the bus capacitor voltage sampled by the bus voltage sampling circuit is comparable to the switching voltage sampled by the battery voltage sampling circuit.

[0012] In some embodiments, the battery relay control circuit further includes a logic unit, the first input of which is connected to the MCU controller, and the second input of which is connected to the output of the comparator; The AND logic unit is configured such that when the comparator outputs a relay that can be activated and the MCU controller issues a relay activation signal, the output of the AND logic unit issues a relay activation command.

[0013] By configuring the logic unit, a crucial hardware safety safeguard is added to the engagement of the battery relay.

[0014] In some embodiments, the battery relay control circuit further includes a hysteresis circuit, one end of which is connected to the second input terminal of the comparator, and the other end of which is connected to the output terminal of the logic unit.

[0015] Hysteresis circuits can effectively suppress noise and voltage fluctuations in the input signal by introducing a positive feedback mechanism, thus preventing the comparator from frequently switching near the pull-in voltage threshold.

[0016] The battery relay control method provided in this application includes the following steps: Obtain the battery voltage and bus capacitor voltage; When the absolute difference between the battery voltage and the bus capacitor voltage is less than the pull-in voltage threshold, a signal is issued that the relay can be pulled in.

[0017] By using the absolute difference between the battery voltage and the bus capacitor voltage as the basis for determining whether the relay is engaged, the technical problem of difficulty in determining the threshold when relying solely on the bus capacitor voltage is avoided.

[0018] The above-mentioned battery relay control method also includes the following steps: After a relay can be activated signal is issued, the relay can be activated signal and ANDed with the MCU instruction. When the MCU instruction is to activate the relay, a relay activation instruction is issued.

[0019] By introducing AND operation logic, the relay activation signal determined by the hardware level is logically ANDed with the relay activation command issued by the MCU. Only when both conditions are met simultaneously, that is, when the hardware determination condition is met and the MCU issues a clear activation command, is the relay activation command finally issued. This forms a dual protection mechanism of hardware safety determination and software command control, which further improves the reliability and safety of relay activation control and avoids the risk of malfunction that may be caused by a single control source.

[0020] The power supply circuit provided in this application includes: Battery; Bus capacitors, and A relay connected in series between the battery and the bus capacitor, and A pre-charging circuit connected in parallel with the relay, and A power switch connected in series between the battery and the pre-charge circuit, and The battery relay control circuit described above; The battery relay control circuit is connected in parallel with the pre-charging circuit.

[0021] The technical effects and advantages of the invention are as follows: By directly detecting the voltage difference across relay K1 through hardware circuitry and comparing it directly with the pull-in voltage threshold, the problem of difficulty in determining a fixed threshold due to large battery voltage fluctuations is avoided. Simultaneously, by directly comparing the switching voltage V_KSI sampled by the battery voltage sampling circuit and the bus capacitor voltage V_BUS sampled by the bus voltage sampling circuit through hardware circuitry, the comparison process is simplified. The judgment logic is decoupled from the MCU software and automatically implemented by the hardware circuitry, significantly reducing the sampling and judgment tasks of the MCU and freeing up MCU resources. Attached Figure Description

[0022] Figure 1 This is an electrical schematic diagram of a power supply circuit in the prior art.

[0023] Figure 2 This is the electrical schematic diagram of the battery relay control circuit of the present invention.

[0024] Figure 3 This is an electrical schematic diagram of one embodiment of the battery relay control circuit of the present invention.

[0025] Figure 4 This is a schematic flowchart of the battery relay control method of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] refer to Figure 1 The power circuit of an electric forklift typically includes: a battery, a pre-charging circuit, a relay K1, a power switch K2, and a bus capacitor. The relay K1 is connected in series between the battery's output terminal BAT+ and the bus capacitor to connect or disconnect the BUS bus between the battery's output terminal BAT+ and the bus capacitor. The pre-charging circuit is connected in parallel across the two ends of the relay K1, and its on / off state is controlled by the power switch.

[0028] When the vehicle is powered on, the power switch is closed, and the battery charges the bus capacitor through the pre-charging circuit. When the voltage of the bus capacitor is close to the battery voltage, relay K1 is energized, connecting the BUS bus between the battery and the bus capacitor. During normal vehicle operation, relay K1 remains energized, and the battery provides a stable DC power supply to subsequent electrical equipment such as the motor controller and DC-DC converter through the BUS bus.

[0029] Conventional power supply circuits typically include a sampling circuit on the bus capacitor side of relay K1. This sampling circuit transmits the bus capacitor voltage to the MCU controller. The MCU controller compares the bus capacitor voltage with a preset voltage threshold to determine if the activation condition has been met, thus controlling relay K1 to activate. However, determining a suitable voltage threshold is difficult for batteries with a wide voltage range. On one hand, if the voltage threshold is set too low, the voltage difference between the relay K1 contacts may exceed the safe voltage during actual activation. On the other hand, if the voltage threshold is set too high, a longer pre-charging time is required for the bus capacitor voltage to reach the set threshold when the battery voltage is low (e.g., a decrease in battery power leading to a drop in battery output voltage). This undoubtedly prolongs the system startup time. Furthermore, the continuous sampling and evaluation of the bus capacitor voltage during charging consumes significant MCU controller resources.

[0030] refer to Figure 2 To address the technical problems of difficult threshold setting and complex comparison process in existing relay control schemes, this invention provides a battery relay control circuit, including: a battery voltage sampling circuit, a bus voltage sampling circuit, and a comparator U1.

[0031] The input terminal of the battery voltage sampling circuit is connected to the end of the power switch K2 closest to the pre-charge circuit. It is used to collect the switching voltage V_KSI on the pre-charge circuit side of the power switch K2. When the power switch K2 is closed, the switching voltage V_KSI is approximately equal to the battery output voltage V_BAT. The input terminal of the bus voltage sampling circuit is connected to the BUS bus on the bus capacitor side to collect the bus capacitor voltage V_BUS at the bus capacitor terminal. The first input terminal of comparator U1 is connected to the bus voltage sampling circuit, and the second input terminal is connected to the battery voltage sampling circuit. Comparator U1 is used to compare the switching voltage V_KSI with the bus capacitor voltage V_BUS. When the absolute difference between the switching voltage and the bus capacitor voltage is greater than the pull-in voltage threshold, the output terminal of comparator U1 sends a relay pull-in signal (high-level signal), indicating that relay K1 can be pulled in.

[0032] Compared to existing technologies, the battery relay control circuit described above has the advantage of directly detecting the voltage difference across relay K1 via hardware circuitry and directly comparing this voltage difference with the pull-in voltage threshold. This avoids the problem of difficulty in determining a fixed threshold due to large battery voltage fluctuations. Simultaneously, by directly comparing the switching voltage V_KSI sampled by the battery voltage sampling circuit and the bus capacitor voltage V_BUS sampled by the bus voltage sampling circuit via hardware circuitry, the comparison process is simplified. The judgment logic is decoupled from the MCU software and automatically implemented by the hardware circuitry, significantly reducing the MCU's sampling and judgment tasks and freeing up MCU resources.

[0033] In some embodiments, the first and second input terminals of comparator U1 refer to its non-inverting and inverting input terminals, respectively. Specifically, as shown below... Figure 2 As shown, the first input terminal is the non-inverting input terminal, and the second input terminal is the inverting input terminal. In other circuit topologies, these two can be interchanged. Figure 2 The topology shown is only one implementation of this application and is not intended to limit this application.

[0034] Specifically, in some embodiments, reference is made to Figure 3 The battery voltage sampling circuit mentioned above includes a Zener diode ZD and a first resistor R1 connected in series between the power switch K2 and the second input terminal of the comparator U1, and a second resistor R2 grounding the second input terminal of the comparator U1. The Zener diode ZD is connected to the power switch K2, and the first resistor R1 is connected to the second input terminal of the comparator U1 and the second resistor R2.

[0035] At this time, the voltage at the second input terminal of comparator U1 is the voltage after being divided by the Zener diode ZD and the first resistor R1, that is: V_R1=(V_KSI-V_ZD)*R2 / (R1+R2) In this formula, V_R1 represents the voltage at the second input terminal of comparator U1, V_KSI is the switching voltage when power switch K2 is closed, V_ZD is the stable voltage drop formed by Zener diode ZD after reverse breakdown, and R1 and R2 are the resistance values ​​of the first and second resistors, respectively. This formula clearly shows that the voltage at the second input terminal of comparator U1 is jointly determined by the switching voltage V_KSI, the Zener diode voltage V_ZD, and the resistance values ​​of the two voltage divider resistors. This achieves indirect sampling and conversion of the battery voltage, providing an accurate voltage reference for subsequent determination of the relay's activation condition.

[0036] When the power switch K2 is closed, since the switching voltage V_KSI is approximately equal to the battery output voltage V_BAT, the voltage at the second output terminal of comparator U1 has a stable voltage drop compared to the battery output voltage V_BAT, namely: V_ZD*R2 / (R1+R2). This voltage drop can be used as the relay's pull-in voltage threshold during the charging process of the bus capacitor to determine whether the relay meets the pull-in condition. Regardless of changes in the battery voltage, the pull-in condition of relay K1 can be flexibly adjusted, thereby ensuring that the voltage difference between the two contacts when the relay is pulled in is always below the safety standard. Furthermore, it can reduce the charging time of the bus capacitor and ensure the circuit's timely response to system startup.

[0037] The voltage divider circuit formed by the first resistor R1 and the second resistor R2 divides the stable voltage across the Zener diode ZD to obtain a reference voltage that matches the input range of comparator U1. The resistance values ​​of the first resistor R1 and the second resistor R2 can be flexibly configured according to the Zener diode ZD's voltage regulation value and the input characteristics of comparator U1 in practical applications. This ensures that the reference voltage obtained after voltage division accurately reflects changes in battery voltage and is reliably compared with the bus capacitor voltage V_BUS sampled by the bus voltage sampling circuit in comparator U1.

[0038] Specifically, in some embodiments, reference is made to Figure 3 The bus voltage sampling circuit mentioned above includes a third resistor R3 and a fourth resistor R4 connected in series. One end of the third resistor R3 is connected to the BUS bus on the bus capacitor side, and the other end is connected to the fourth resistor R4 and the first input terminal of the comparator U1. The fourth resistor R4 is grounded.

[0039] At this moment, the voltage at the first input terminal of comparator U1 is equal to: V_R3 = V_BUS * R4 / (R3 + R4) In the formula, V_BUS is the bus capacitor voltage.

[0040] By employing a series voltage divider structure consisting of the third resistor R3 and the fourth resistor R4, the voltage signal can be directly obtained from the BUS bus on the bus capacitor side. Through precise resistor parameter matching, the higher bus capacitor voltage V_BUS is proportionally reduced to a sampling voltage V_R3 suitable for the input range of comparator U1. This direct voltage divider method not only simplifies the circuit structure and reduces the number of components, thus lowering hardware costs and circuit complexity, but also avoids errors and delays that may arise from complex signal conditioning circuits. Furthermore, the resistor parameters can be flexibly set according to the actual bus voltage range and the comparator's input requirements, ensuring that the sampling voltage V_R3 accurately and linearly reflects the changes in the bus capacitor voltage V_BUS. This provides a precise input signal basis for comparator U1 to perform stable and reliable voltage comparisons, ensuring the accuracy and timeliness of the comparison results.

[0041] To ensure that the voltages at the first and second input terminals of comparator U1 accurately reflect the relationship between the bus capacitor voltage V_BUS and the switching voltage V_KSI, the voltage division ratio of the first resistor R1 and the second resistor R2 must be consistent with the voltage division ratio of the third resistor R3 and the fourth resistor R4, that is: R2 / (R1+R2)=R4 / (R3+R4) This ensures that the bus capacitor voltage V_BUS sampled by the bus voltage sampling circuit and the switching voltage V_KSI sampled by the battery voltage sampling circuit are comparable.

[0042] Furthermore, the battery relay control circuit of this embodiment also includes a logic unit U2, whose first input terminal is connected to the MCU controller and its second input terminal is connected to the output terminal of the comparator U1; The AND logic unit U2 is configured to issue a relay activation command at its output when the comparator U1 outputs a high-level signal and the MCU controller issues a relay activation signal.

[0043] This application adds a crucial hardware safety layer to the battery relay's activation by configuring the logic unit U2. Specifically, only when comparator U1 determines that the bus capacitor voltage V_BUS and the switching voltage V_KSI meet a preset comparability condition (usually meaning the two voltages are close to reduce the inrush current when the relay activates) and outputs a high-level signal, and simultaneously the MCU controller issues a relay activation signal based on the overall system status, can both inputs of the logic unit U2 be simultaneously high-level. Only then will its output issue a relay activation command, driving the relay to operate. This design effectively avoids the risks that may exist if relying solely on software control. For example, if the MCU controller erroneously issues an activation signal due to program abnormalities or interference, because comparator U1 does not output a high level, the logic unit U2 cannot output an activation command, thus preventing the relay from activating under inappropriate voltage conditions and protecting the safety and stability of the relay and the entire circuit system.

[0044] Furthermore, the battery relay control circuit of this embodiment also includes a hysteresis circuit, one end of which is connected to the second input terminal of the comparator U1, and the other end is connected to the output terminal of the logic unit U2.

[0045] The hysteresis circuit introduces a positive feedback mechanism, allowing the comparator U1's threshold voltage (i.e., pull-in voltage threshold) to have two different levels: an upper threshold and a lower threshold. When the bus capacitor voltage V_BUS gradually rises and reaches the upper threshold, comparator U1 outputs a high level; conversely, when the bus capacitor voltage V_BUS decreases, comparator U1 only flips to a low level output when the voltage falls below the lower threshold. This hysteresis characteristic effectively suppresses noise and voltage fluctuations in the input signal, preventing frequent switching actions of the comparator near the pull-in voltage threshold, thus ensuring the stability of the relay's pull-in and release, and further improving the overall control circuit's anti-interference capability.

[0046] In summary, the battery relay control circuit provided in this application successfully solves the technical problems of difficult software threshold setting and large computational load in the comparison process. It cleverly uses the stable voltage difference formed by the Zener diode as the relay's pull-in voltage threshold, and compares the voltage at the power switch with the bus capacitor voltage instead of the battery voltage. When the difference between the two is less than the pull-in voltage threshold, the relay is determined to be able to pull in. This avoids the technical problem of being difficult to adapt to a wide range of batteries due to a fixed voltage threshold, and effectively expands the application range of the battery relay control circuit.

[0047] This application also provides a power supply circuit, including the above-described battery relay control circuit.

[0048] Based on the above-described battery relay control circuit, this application also provides a battery relay control method, see reference. Figure 4 This includes the following steps: S1. Obtain the battery voltage and bus capacitor voltage; S2. When the absolute difference between the battery voltage and the bus capacitor voltage is less than the pull-in voltage threshold, a signal is issued that the relay can be pulled in.

[0049] By using the absolute difference between the battery voltage and the bus capacitor voltage as the basis for determining whether the relay is engaged, the technical problem of difficulty in determining the threshold when relying solely on the bus capacitor voltage is avoided. Furthermore, it addresses the essence of relay engagement control requirements, namely ensuring that the voltage difference between the two contacts is within a safe range when the relay is engaged. This ensures that the relay engagement action is performed under safe voltage conditions, guaranteeing the accuracy and adaptability of relay engagement judgment in a wide range of battery voltage input scenarios. Consequently, it effectively improves the overall performance and application flexibility of battery relay control.

[0050] Furthermore, the above method also includes the following steps: S3. After the relay can be activated signal is issued, the relay can be activated signal and the MCU instruction are ANDed. When the MCU instruction is to activate the relay, the relay activation instruction is issued.

[0051] By introducing AND operation logic, the relay activation signal determined by the hardware level is logically ANDed with the relay activation command issued by the MCU. Only when both conditions are met simultaneously, that is, when the hardware determination condition is met and the MCU issues a clear activation command, is the relay activation command finally issued. This forms a dual protection mechanism of hardware safety determination and software command control, which further improves the reliability and safety of relay activation control and avoids the risk of malfunction that may be caused by a single control source.

[0052] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery relay control circuit, characterized in that, include: The battery voltage sampling circuit has its input terminal connected to the end of the power switch closest to the pre-charging circuit, and is used to collect the switching voltage on the pre-charging circuit side of the power switch. The bus voltage sampling circuit has its input terminal connected to the BUS bus on the bus capacitor side, and is used to collect the bus capacitor voltage at the bus capacitor terminal. as well as The comparator has its first input terminal connected to the bus voltage sampling circuit and its second input terminal connected to the battery voltage sampling circuit. The comparator is used to compare the switching voltage with the bus capacitor voltage. When the absolute difference between the switching voltage and the bus capacitor voltage is greater than the pull-in voltage threshold, the output terminal of the comparator sends a relay pull-in signal.

2. The circuit according to claim 1, characterized in that, The battery voltage sampling circuit includes: a Zener diode and a first resistor connected in series between the power switch and the second input terminal of the comparator, and a second resistor grounding the second input terminal of the comparator; The Zener diode is connected to the power switch, and the first resistor is connected to the second input terminal of the comparator and the second resistor.

3. The circuit according to claim 2, characterized in that, The bus voltage sampling circuit includes a third resistor and a fourth resistor connected in series. One end of the third resistor is connected to the BUS bus on the bus capacitor side, and the other end is connected to the fourth resistor and the first input terminal of the comparator. The fourth resistor is grounded.

4. The circuit according to claim 3, characterized in that, The voltage division ratio of the first resistor and the second resistor is the same as that of the third resistor and the fourth resistor.

5. The circuit according to claim 1, characterized in that, The battery relay control circuit also includes a logic unit, whose first input terminal is connected to the MCU controller and its second input terminal is connected to the output terminal of the comparator. The AND logic unit is configured such that when the comparator outputs a relay that can be activated and the MCU controller issues a relay activation signal, the output of the AND logic unit issues a relay activation command.

6. The circuit according to claim 5, characterized in that, The battery relay control circuit also includes a hysteresis circuit, one end of which is connected to the second input terminal of the comparator, and the other end is connected to the output terminal of the logic unit.

7. A battery relay control method, characterized in that, Includes the following steps: Obtain the battery voltage and bus capacitor voltage; When the absolute difference between the battery voltage and the bus capacitor voltage is less than the pull-in voltage threshold, a signal is issued that the relay can be pulled in.

8. The method according to claim 7, characterized in that, Also includes: After a relay can be activated signal is issued, the relay can be activated signal and ANDed with the MCU instruction. When the MCU instruction is to activate the relay, a relay activation instruction is issued.

9. A power supply circuit, characterized in that, include: Battery; Bus capacitors, and A relay connected in series between the battery and the bus capacitor, and A pre-charging circuit connected in parallel with the relay, and A power switch connected in series between the battery and the pre-charge circuit, and The battery relay control circuit according to any one of claims 1-6; The battery relay control circuit is connected in parallel with the pre-charging circuit.

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