Control circuit using switching power supply chip to drive disengagement mechanism

Abstract

The invention discloses a control circuit for driving a disconnecting mechanism by a switching power supply chip, which comprises an MCU (Microprogrammed Control Unit) chip and the switching power supply chip, and is characterized in that the switching power supply chip is connected between the MCU chip and the disconnecting mechanism; the switching power supply chip comprises a switching tube Q1, a switching tube Q2, a switching tube Q3, a switching tube Q4, a buck-boost control logic module, a current sampling operational amplifier, a voltage comparison module and an operational amplifier. The invention discloses a control circuit for driving a disconnecting mechanism by using a switching power supply chip. The chip has a fault protection function of short circuit to the ground or a power supply; the total grid charge of the internal Mosfet is small, high-frequency control is supported, power consumption is low, an operational amplifier is internally integrated, load current is collected in real time, follow current is achieved through an internal body diode, dependence on an external circuit is reduced, system design is simplified, and cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the control technology of a disengaging mechanism, and particularly relates to a control circuit for driving a disengaging mechanism with a switching power supply chip. Background Art

[0002] The disengaging mechanism is applied to the opening and closing between the motor and the wheel of a new energy hybrid vehicle. When the motor needs to work, the disengaging mechanism is controlled to enter the closed state to connect with the wheel. When the motor does not need to work, the disengaging mechanism is controlled to enter the disengaged state to disconnect from the wheel. The actuator of the disengaging mechanism is a solenoid valve. Since the coil resistance value of the solenoid valve is extremely small and changes with temperature, constant current control is generally achieved by detecting the coil current to realize the on-off of the disengaging unit.

[0003] 1. Solution 1, as Figure 1 shown, is a low-side drive solution based on an independent NMOS. The disengaging mechanism is between point A and point B. The MCU samples the current magnitude through an operational amplifier and a sampling resistor, and then outputs a PWM wave through proportional-integral control to control the on and off of the Mosfet, realizing constant current control. The control circuit does not add a fault diagnosis circuit. If a short circuit to ground or a short circuit to the power supply occurs at point A or point B, fault protection and fault status recording cannot be performed, and there are certain reliability risks in the system.

[0004] 2. Solution 2, as Figure 2 shown, is a high-side drive chip solution with a protection function. The control method is the same as that of Solution 1,

[0005] and fault protection can be provided. However, the high-side drive chips on the current market are not designed specifically for driving the disengaging mechanism, and the total gate charge (Qg) of the integrated MOS inside is too large. When the required frequency of the disengaging unit becomes higher, the switching loss becomes larger, and the chip will turn off the output due to overheat protection.

[0006] Both of the above two drive solutions require the operational amplifier of the external circuit to sample the load current in real time, so as to adjust the duty cycle of the output switch and realize the constant current control of the disengaging mechanism; both solutions also require an external diode to play a freewheeling role when the disengaging unit is disconnected. This not only increases the complexity of software design but also increases the hardware cost.

[0007] Therefore, in view of the above problems, further improvements are made. Summary of the Invention

[0008] The main purpose of the present invention is to provide a control circuit that drives a disconnect mechanism using a switching power supply chip. Compared with Solution 1, the chip has a fault protection function for short circuit to ground or power supply; compared with Solution 2, the chip is designed specifically for switching power supply, and the total gate charge (Qg) of the internal Mosfet is small, supports high-frequency control, and consumes less power. Compared with Solutions 1 and 2, the switching power supply chip has an operational amplifier integrated inside, which recovers the load current in real time and uses the internal body diode for continuous current flow. It not only reduces the dependence on external circuits, but also simplifies system design and reduces costs. The chip has its own constant current mode control output, and the MCU only needs to pass I 2 C bus to adjust the target current value, and simultaneously reduce the software development work.

[0009] To achieve the above objectives, the present invention provides a control circuit that drives a disconnection mechanism using a switching power supply chip, characterized in that it includes an MCU chip and a switching power supply chip, wherein the switching power supply chip is connected between the MCU chip and the disconnection mechanism, and the switching power supply chip includes a switch tube Q1, a switch tube Q2, a switch tube Q3, a switch tube Q4, a buck-boost control logic module, a current sampling operational amplifier, a voltage comparison module, and an operational amplifier, wherein:

[0010] The drain of the switch tube Q1 is connected to the power supply voltage Vbat, and the source of the switch tube Q1 is electrically connected to the drain of the switch tube Q2, the source of the switch tube Q2 is electrically connected to the drain of the switch tube Q3, and the source of the switch tube Q3 is electrically connected to the drain of the switch tube Q4, the source of the switch tube Q4 is connected to the voltage output terminal VOUT, and the voltage output terminal VOUT is connected to the input inductor of the disconnect mechanism, and the disconnect mechanism is grounded through the resistor R1;

[0011] Assume that the two ends of the disconnect mechanism are points A and B, respectively, the end of the resistor R1 closest to the disconnect mechanism is point C, the source of the switch Q2 is point D, and points C and D form the same network. When the disconnect unit is disconnected, the current generated by the inductor coil is freewheeled by the body diodes of the switches Q3 and Q4. The current loop is A→B→C→D→body diode of switch Q3→body diode of switch Q4→A, where:

[0012] The positive input terminal and the negative input terminal of the current sampling amplifier are respectively connected to the two ends of the resistor R1. When the external load is short-circuited to the ground, the OCP overcurrent protection is triggered through the current sampling amplifier.

[0013] The positive input terminal of the voltage comparison module is electrically connected to the source electrode of the switching transistor Q4, and the negative input terminal is connected to the reference voltage VREF. When the external load is short-circuited to the power supply, it will be compared with the reference voltage VREF through the voltage output terminal VOUT, triggering the OVP overvoltage protection of the chip. Once the overvoltage or overcurrent protection is triggered, the chip will immediately turn off the output to achieve fault protection;

[0014] The operational amplifier is connected between the current sampling operational amplifier and the MCU chip. The operational amplifier feeds back the analog signal of the load current in real time to the MCU chip through the IMON pin for the real-time load current collected by the current sampling operational amplifier; during the startup process, when the required current of the load is less than the preset target current value, the switching power supply chip outputs a constant voltage, and the current gradually increases to the target value. When the load current reaches the target setting value, the switching power supply chip switches from the constant voltage mode to the constant current mode. In the constant current mode, the switching power supply chip maintains the output current within the preset current demand value range by reducing the output voltage.

[0015] As a further preferred technical solution of the above technical solution, the switching power supply chip further includes a register, and the register is electrically connected to the MCU chip, where:

[0016] The MCU chip is connected to the register through the I 2 C bus, thereby dynamically adjusting the target current value. During the startup process of the release mechanism, the MCU chip configures a larger target current value through the I 2 C bus. After the output voltage of the switching power supply chip is gradually established, subsequently the MCU chip configures a smaller target current value through the I 2 C bus, and through output dynamic adjustment, the current curve required by the release mechanism is realized.

[0017] As a further preferred technical solution of the above technical solution, for the switching power supply chip:

[0018] In the buck-boost mode, the switching transistors Q1, Q2, Q3, and Q4 switch alternately;

[0019] In the buck mode, Q4 is normally open, Q1 is normally closed, and Q2 and Q3 switch alternately;

[0020] In the boost mode, Q1 is normally open, Q4 is normally closed, and Q2 and Q3 switch alternately.

[0021] As a further preferred technical solution of the above technical solution, for the switching power supply chip:

[0022] When the switching power supply chip operates in the constant voltage mode, VOUT is the preset voltage; when the switching power supply chip operates in the constant current mode, VOUT is the product of the preset current and the resistance value of the solenoid valve.

[0023] When the supply voltage Vbat is greater than VOUT, the switching power supply chip operates in the buck mode; when the supply voltage Vbat is less than VOUT, the switching power supply chip operates in the boost mode; when Vbat is approximately equal to VOUT, the power supply operates in the buck-boost mode.

[0024] As a further preferred technical solution of the above technical solution, an inductor L1 is connected between the drain of the switching transistor Q2 and the source of the switching transistor Q3.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. The switching power supply chip has built-in over-temperature, short-circuit to ground or power supply and other fault protection functions, improving system reliability.

[0027] 2. The Qg of the internal MOS of the switching power supply is small, suitable for high-frequency operation, reducing power consumption and improving overall efficiency.

[0028] 3. The chip has a built-in constant current mode, uses an internal operational amplifier, and uses the internal body diode for freewheeling. The software control requirements for the MCU chip are reduced, the software development workload is reduced, the cost is reduced, and the board area of the circuit design is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic diagram of an existing low-side drive solenoid valve control scheme.

[0030] Figure 2 is a schematic diagram of an existing high-side drive solenoid valve control scheme.

[0031] Figure 3 is a schematic diagram of the control scheme for driving a solenoid valve using the switching power supply chip of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles defined in the following description can be applied to other embodiments, variations, improvements, equivalent solutions, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0033] In the preferred embodiment of the present invention, those skilled in the art should note that the disengagement mechanism and the like involved in the present invention can be regarded as the prior art.

[0034] Preferred embodiment.

[0035] As Figure 3 shown, the present invention discloses a control circuit for driving a disengaging mechanism with a switching power supply chip, including an MCU chip and a switching power supply chip. The switching power supply chip is connected between the MCU chip and the disengaging mechanism. The switching power supply chip includes a switching transistor Q1, a switching transistor Q2, a switching transistor Q3, a switching transistor Q4, a buck-boost control logic module, a current sampling operational amplifier, a voltage comparison module, and an operational amplifier, where:

[0036] The drain of the switching transistor Q1 is connected to the supply voltage Vbat, and the source of the switching transistor Q1 is electrically connected to the drain of the switching transistor Q2. The source of the switching transistor Q2 and the drain of the switching transistor Q3 are electrically connected, and the source of the switching transistor Q3 and the drain of the switching transistor Q4 are electrically connected. The source of the switching transistor Q4 is connected to the voltage output terminal VOUT, and the voltage output terminal VOUT is connected to the input inductor of the disengaging mechanism (i.e., the load) (for providing a driving current to the disengaging unit; when the current output by VOUT reaches the working threshold of the disengaging mechanism, the actuating mechanism of the disengaging unit forms a power-on loop, and the armature inside it generates a displacement under the action of electromagnetic force and maintains the suction state, so that the disengaging unit maintains the connection state; when the current output by VOUT is lower than the working threshold or in a no-output state, the power-on loop of the disengaging mechanism is disconnected, and the disengaging unit returns to the initial position under the action of the reset element, resulting in the disconnection state being released). The disengaging mechanism is grounded through the resistor R1;

[0037] Let the two ends of the disengaging mechanism be point A and point B respectively, and the end of the resistor R1 close to the disengaging mechanism be point C, and the source of the switching transistor Q2 be point D. Points C and D are the same network; when the disengaging unit is disconnected, the current generated by the inductor coil continues to flow through the body diodes of the switching transistor Q3 and the switching transistor Q4, and the current loop is A→B→C→D→the body diode of the switching transistor Q3→the body diode of the switching transistor Q4→A (for the freewheeling loop, the inductive load will generate an induced electromotive force, and the direction of the induced electromotive force is opposite to the direction of the voltage applied across it. When the inductive load suddenly loses power, the induced electromotive force still exists. Since the induced electromotive force is opposite to the original voltage direction, there was the original voltage to cancel it when there was no power outage, and there is no voltage to cancel the induced electromotive force after power outage, and this induced electromotive force may damage the components in the circuit. With the freewheeling loop, the current direction in the loop is exactly forward-conductive with the body diode, and the current of the induced electromotive force can be released), where:

[0038] The positive input terminal and the negative input terminal of the current sampling operational amplifier are respectively connected to both ends of the resistor R1. When the external load is shorted to ground, through the current sampling operational amplifier, OCP overcurrent protection will be triggered (after the short to ground, the load current will increase and be compared with the maximum current value set inside the chip. After the chip internally samples that the load current exceeds the set value, OCP overcurrent protection will be triggered);

[0039] The positive input terminal of the voltage comparison module is electrically connected to the source electrode of the switching transistor Q4 and the negative input terminal is connected to the reference voltage VREF. When the external load is shorted to the power supply, it will be compared with the reference voltage VREF through the voltage output terminal VOUT (it is worth mentioning that here the voltage output terminal VOUT will be connected to the voltage comparison module through a voltage dividing resistor, and the voltage VFB after passing through the voltage dividing resistor is compared with VREF to judge the voltage of VOUT), triggering the OVP overvoltage protection of the chip (after shorting to the power supply, Vout will increase, and after voltage division, it is compared with the reference voltage VREF. If it exceeds the reference voltage, OVP protection will be triggered). Once overvoltage or overcurrent protection is triggered, the chip will immediately turn off the output to achieve fault protection;

[0040] The operational amplifier is connected between the current sampling operational amplifier and the MCU chip. The operational amplifier feeds back the analog signal of the load current collected by the current sampling operational amplifier to the MCU chip in real time through the IMON pin; during the startup process, when the required current of the load (i.e., the release mechanism) is less than the preset target current value, the switching power supply chip outputs a constant voltage, and the current gradually increases to the target value. When the load current reaches the target set value, the switching power supply chip switches from the constant voltage (CV) mode to the constant current (CC) mode. In the constant current mode, the switching power supply chip maintains the output current within the preset current demand value range by reducing the output voltage.

[0041] Specifically, the switching power supply chip further includes a register, and the register is electrically connected to the MCU chip, where:

[0042] The MCU chip is connected to the register through the I 2 C bus, thereby dynamically adjusting the target current value (in the initial startup stage of the release mechanism, due to the need to overcome the spring force, friction, and inertia, a large startup current is required to generate magnetic force. When the release unit is in place, only a small holding current is required to maintain its position). During the startup process of the release mechanism, the MCU chip configures a larger target current value through the I 2 C bus. After the output voltage of the switching power supply chip is gradually established (sufficient to maintain a large current output for a period of time), subsequently the MCU chip passes through the I 2The C bus configures a smaller target current value, which is dynamically adjusted through the output to achieve the current curve required by the release mechanism (the target current value can be dynamically adjusted according to the requirements of the selected release mechanism).

[0043] More specifically, for the switching power supply chip:

[0044] In the buck-boost mode, the switching transistors Q1, Q2, Q3, and Q4 switch alternately;

[0045] In the buck mode, Q4 is always on, Q1 is always off, and Q2 and Q3 switch alternately (the alternation of Q2 / Q3 means that when Q2 is conducting, Q3 is off, and when Q2 is off, Q3 is conducting);

[0046] In the boost mode, Q1 is always on, Q4 is always off, and Q2 and Q3 switch alternately.

[0047] Furthermore, for the switching power supply chip:

[0048] When the switching power supply chip operates in the constant voltage mode, VOUT is a preset voltage; when the switching power supply chip operates in the constant current mode, VOUT is the product of the preset current and the resistance value of the solenoid valve;

[0049] When the supply voltage Vbat is greater than VOUT, the switching power supply chip operates in the buck mode; when the supply voltage Vbat is less than VOUT, the switching power supply chip operates in the boost mode; when Vbat is approximately equal to VOUT, the power supply operates in the buck-boost mode.

[0050] Even further, an inductor L1 is connected between the drain of the switching transistor Q2 and the source of the switching transistor Q3.

[0051] It is worth mentioning that the technical features such as the release mechanism involved in this invention patent application should be regarded as the prior art. The specific structures, working principles, and possible control methods and spatial arrangement methods of these technical features can be selected conventionally in the art and should not be regarded as the invention points of this invention patent. This invention patent will not be further specifically elaborated.

[0052] For those skilled in the art, it is still possible to modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A control circuit for driving a disengaging mechanism with a switching power supply chip, characterized in that, It includes an MCU chip and a switching power supply chip. The switching power supply chip is connected between the MCU chip and the release mechanism. The switching power supply chip includes a switching transistor Q1, a switching transistor Q2, a switching transistor Q3, a switching transistor Q4, a buck-boost control logic module, a current sampling operational amplifier, a voltage comparison module, and an operational amplifier, where: The drain of the switching transistor Q1 is connected to the supply voltage Vbat, and the source of the switching transistor Q1 is electrically connected to the drain of the switching transistor Q2. The source of the switching transistor Q2 and the drain of the switching transistor Q3 are electrically connected, and the source of the switching transistor Q3 and the drain of the switching transistor Q4 are electrically connected. The source of the switching transistor Q4 is connected to the voltage output terminal VOUT, and the voltage output terminal VOUT is connected to the input inductor of the release mechanism. The release mechanism is grounded through a resistor R1. Let the two ends of the release mechanism be point A and point B respectively, and the end of the resistor R1 close to the release mechanism be point C. The source of the switching transistor Q2 is point D. Point C and point D are in the same network. When the release unit is disconnected, the current generated by the inductor coil continues to flow through the body diodes of the switching transistor Q3 and the switching transistor Q4. The current loop is A→B→C→D→the body diode of the switching transistor Q3→the body diode of the switching transistor Q4→A, where: The positive input terminal and the negative input terminal of the current sampling operational amplifier are respectively connected to both ends of the resistor R1. When the external load is shorted to ground, the OCP overcurrent protection will be triggered through the current sampling operational amplifier. The positive input terminal of the voltage comparison module is electrically connected to the source of the switching transistor Q4, and the negative input terminal is connected to the reference voltage VREF. When the external load is shorted to the power supply, it will compare through the voltage output terminal VOUT and the reference voltage VREF to trigger the OVP overvoltage protection of the chip. Once the overvoltage or overcurrent protection is triggered, the chip will immediately turn off the output to achieve fault protection. The operational amplifier is connected between the current sampling operational amplifier and the MCU chip. The operational amplifier feeds back the analog signal of the load current to the MCU chip in real time through the IMON pin with the real-time load current collected by the current sampling operational amplifier. During the startup process, when the required current of the load is less than the preset target current value, the switching power supply chip outputs a constant voltage, and the current gradually increases to the target value. When the load current reaches the target setting value, the switching power supply chip switches from the constant voltage mode to the constant current mode. In the constant current mode, the switching power supply chip reduces the output voltage to maintain the output current within the preset current demand value range.

2. The control circuit for driving a disengaging mechanism with a switching power supply chip according to claim 1, characterized in that The switching power supply chip further includes a register, and the register is electrically connected to the MCU chip, where: The MCU chip is connected to the register through the I 2 C bus, so as to dynamically adjust the target current value. During the startup process of the release mechanism, the MCU chip configures a relatively large target current value through the I 2 C bus. After the output voltage of the switching power supply chip is gradually established, subsequently, the MCU chip configures a relatively small target current value through the I 2 C bus, and realizes the current curve required by the release mechanism through output dynamic adjustment.

3. The control circuit for driving the disengaging mechanism with a switching power supply chip according to claim 2, wherein For the switching power supply chip: In the buck-boost mode, the switching transistors Q1, Q2, Q3, and Q4 switch alternately. In the buck mode, Q4 is normally open, Q1 is normally closed, and Q2 and Q3 switch alternately. In the boost mode, Q1 is normally open, Q4 is normally closed, and Q2 and Q3 switch alternately.

4. The control circuit for driving a disengaging mechanism with a switching power supply chip according to claim 3, wherein For the switching power supply chip: When the switching power supply chip operates in the constant voltage mode, VOUT is the preset voltage; when the switching power supply chip operates in the constant current mode, VOUT is the product of the preset current and the resistance value of the solenoid valve. When the supply voltage Vbat is greater than VOUT, the switching power supply chip operates in the buck mode; when the supply voltage Vbat is less than VOUT, the switching power supply chip operates in the boost mode; when Vbat is approximately equal to VOUT, the power supply operates in the buck-boost mode.

5. The control circuit for driving the disengaging mechanism with a switching power supply chip according to claim 4, characterized in that, An inductor L1 is connected between the drain of the switching transistor Q2 and the source of the switching transistor Q3.

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