PWM-based constant-current constant-voltage heating pad control circuit and control method
Through the PWM-based constant current constant pressure heating pad control circuit, the problem of the inability to dynamically adjust the temperature and lack of protection in the prior art is solved, and the constant current constant voltage output of the heating pad is realized, which improves the energy conversion efficiency and system stability of the battery pack, and reduces noise interference and safety hazards.
Patent Information
- Application Number
- CN202510809109.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-17
- Publication Date
- 2025-08-26
AI Technical Summary
The existing battery heating methods cannot achieve dynamic temperature regulation and lack overcurrent protection, resulting in inefficiency and safety hazards.
The constant current and constant voltage heating pad control circuit based on PWM is adopted, including asynchronous buck circuit, gate driving circuit, voltage control driving circuit and PWM control circuit. The MOS tube is controlled through the MCU chip to realize dynamic regulation of the heating pad current and soft current limit protection.
The constant current and constant voltage output of the heating pad is realized, the energy conversion efficiency is improved, the battery pack life is extended, the system stability and safety is improved, noise interference is reduced, and control accuracy and system reliability are improved.
Smart Images
Figure CN120547710A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium batteries, in particular to a PWM-based constant current and constant voltage heating pad control circuit and a control method. Background Art
[0002] Low temperatures can affect the battery's chemical reaction rate, leading to a decrease in capacity, increased internal resistance, and even potential damage. Therefore, heating the battery is essential. There are many heating methods. Most resistance heating pads use voltage control, but the heating power is fixed, making it impossible to dynamically adjust the temperature of the heating pad itself and lacking an overcurrent protection mechanism. Conventional linear voltage regulation solutions are inefficient and can cause severe heating of the MOS tube. Summary of the Invention
[0003] In order to solve the problems raised in the above background technology, the present invention provides a PWM-based constant current and constant voltage heating pad control circuit, including an asynchronous buck circuit, a gate drive circuit, a voltage control drive circuit, a PWM control circuit, and an MCU chip. The asynchronous buck circuit is provided with an LCSG_DriveA0 port, an LCSG_DriveB0 port, a HEAT+ heating pad positive electrode port, a P+ power supply positive electrode port, a HEAT- heating pad negative electrode port, and a VSamp port; the gate drive circuit is provided with a HEAT_OFF port, an LCSG_DriveA0 port, an LCSG_DriveB0 port, and a CON_PWM port; the voltage control drive circuit is provided with a CL_PWM port and a REF_PWM port; the PWM control circuit is provided with a C ON_PWM port, VRef port, VSamp port; the LCSG_DriveA0 port and LCSG_DriveB0 port of the asynchronous buck circuit are connected to the LCSG_DriveA0 port and LCSG_DriveB0 port of the gate drive circuit in sequence, the VSamp port of the asynchronous buck circuit is connected to the VSamp port of the PWM control circuit, the CON_PWM port of the gate drive circuit is connected to the CON_PWM port of the PWM control circuit, the REF_PWM port of the voltage control drive circuit is connected to the VRef port of the PWM control circuit, one PE pin of the MCU chip is connected to the HEAT_OFF port of the gate drive circuit, and the other PE pin of the MCU chip is connected to the CL_PWM port of the voltage control drive circuit.
[0004] The HEAT-heating pad negative electrode port of the asynchronous buck circuit is respectively connected to one end of the capacitor C1, one end of the capacitor C2, one end of the capacitor C3, one end of the capacitor C4, and one end of the inductor L1. The other end of the capacitor C1, the other end of the capacitor C2, and the other end of the capacitor C3 are combined to connect the HEAT+heating pad positive electrode port and the P+ power supply positive electrode port. The other end of the capacitor C4 is connected to one end of the resistor R1. The other end of the resistor R1 and the other end of the inductor L1 are combined and respectively connected to one end of the resistor R2, one end of the resistor R3, the drain of the MOS tube Q1, and the MOS The drain of tube Q1, one end of resistor R7, one end of resistor R8, the anode of diode D1, the anode of diode D2, the anode of diode D3, the anode of diode D5, the other end of resistor R2, the other end of resistor R3 are connected together to one end of capacitor C8, the other end of resistor R7, the other end of resistor R8 are connected together to one end of capacitor C7, the cathode of diode D1, the cathode of diode D2, the cathode of diode D3, the cathode of diode D5, and the other end of capacitor C7 are connected together to the positive terminal of HEAT+ heating pad and the positive terminal of P+ power supply, MOS tube The gate of Q1 is connected to one end of resistor R9, one end of resistor R12, and one end of resistor R13 respectively. The other end of resistor R12 is connected to the anode of diode D5. The cathode of diode D5 and the other end of resistor R13 are combined and connected to the LCSG_DriveA0 port. The gate of MOS tube Q2 is connected to one end of resistor R6, one end of resistor R10, and one end of resistor R11 respectively. The other end of resistor R10 is connected to the anode of diode D6. The cathode of diode D6 and the other end of resistor R11 are combined and connected to the LCSG_DriveB0 port. The source of the MOS transistor Q1 is respectively connected to the other end of the resistor R9, the other end of the resistor R6, the source of the MOS transistor Q2, the other end of the capacitor C8, one end of the capacitor C5, one end of the capacitor C6, one end of the capacitor C10, the VSamp port, one end of the sampling resistor R4, and one end of the sampling resistor R5. The other end of the capacitor C5, the other end of the capacitor C6, and the other end of the capacitor C10 are combined and connected to the positive electrode port HEAT+ of the heating pad and the positive electrode port P+ of the power supply. The other end of the sampling resistor R4 and the other end of the sampling resistor R5 are combined and connected to the negative electrode of the power supply and the power ground.
[0005] The CON_PWM port of the gate drive circuit is respectively connected to the anode of the diode Q23 and the base of the transistor Q21, the cathode of the diode Q23 is respectively connected to the anode of the diode Q22, one end of the resistor R23, and the emitter of the transistor Q21, the collector of the transistor Q21 is grounded, the other end of the resistor R23 is respectively connected to the cathode of the diode Q22, one end of the capacitor C43, pin 2 of the gate drive chip U2, and pin 4 of the gate drive chip U2, the other end of the capacitor C43 is grounded, pins 8 and 1 of the gate drive chip U2 are combined to connect to the HEAT_OFF port, and pin 3 of the gate drive chip U2 is connected to the The pin is grounded, pin 7 of the gate driver chip U2 is connected to one end of the resistor R22, and the other end of the resistor R22 is connected to the LCSG_DriveA0 port, pin 5 of the gate driver chip U2 is connected to one end of the resistor R21, and the other end of the resistor R21 is connected to the LCSG_DriveB0 port, pin 6 of the gate driver chip U2 is respectively connected to one end of the capacitor C41, one end of the capacitor C42, and one end of the inductor L2, the other end of the capacitor C41 and the other end of the capacitor C42 are combined to ground, the other end of the inductor L2 is connected to the voltage 12V_TL494+, and the gate driver chip U2 uses model UCC27524D.
[0006] The voltage control drive circuit includes a voltage follower U5, which adopts the model LM358. Pin 8 of the voltage follower U5 is respectively connected to one end of the capacitor C40, one end of the capacitor C28, and one end of the resistor R59. The other end of the resistor R59 is connected to the voltage 12V-TL494+, the other end of the capacitor C40 and the other end of the capacitor C28 are combined and grounded, pin 7 of the voltage follower U5 is connected to pin 6 of the voltage follower U5, pin 5 of the voltage follower U5 is grounded, pin 4 of the voltage follower U5 is grounded, pin 1 of the voltage follower U5 and pin 2 of the voltage follower U5 are combined and connected to the REF_PWM port, and pin 3 of the voltage follower U5 is connected to the resistor R5 8, the other end of the resistor R58 is respectively connected to one end of the resistor R57 and one end of the capacitor C33, the other end of the capacitor C33 is grounded, the other end of the resistor R57 is respectively connected to one end of the resistor R56 and one end of the capacitor C32, the other end of the capacitor C32 is grounded, the other end of the resistor R57 is respectively connected to one end of the resistor R54 and the emitter of the photoelectric coupler Q5, the collector of the photoelectric coupler Q5 is connected to one end of the capacitor C33, one end of the capacitor C39, and the voltage 12V_PWM+, the negative electrode of the photoelectric coupler Q5 is connected to one end of the capacitor C31 and ground, the positive electrode of the photoelectric coupler Q5 is respectively connected to the other end of the capacitor C31 and one end of the resistor R55, and the other end of the resistor R55 is connected to the CL_PWM port.
[0007] The PWM control circuit includes a PWM chip U3, which adopts a model TL494. Pin 1 of the PWM chip U3 is respectively connected to one end of a resistor R37, one end of a capacitor C9, and one end of a capacitor C24. The other end of the resistor R37 is connected to the VSamp port, and the other end of the capacitor C24 and the other end of the capacitor C9 are combined and grounded. Pin 2 of the PWM chip U3 is connected to the VRef port. Pin 3 of the PWM chip U3 is respectively connected to one end of a resistor R38 and one end of a resistor R39. The other end of the resistor R39 is connected to one end of a capacitor C21. The other end of the capacitor C21 and the other end of the resistor R38 are combined and connected to the VRef port. Pin 5 of the PWM chip U3 is connected to one end of a capacitor C23, and the other end of the capacitor C23 is grounded. Pin 6 of the PWM chip U3 is connected to one end of a resistor R45, and the other end of the resistor R45 is grounded. Pin 7 of the PWM chip U3 and pin 13 of the PWM chip U3 are combined and grounded. Pin 8 of the PWM chip U3 and pin 11 of the PWM chip U3 are combined to connect to the voltage 12V_TL494+. Pin 8 of the PWM chip U3 and pin 11 of the PWM chip U3 are combined and connected to the CON_PWM port and one end of the resistor R43, and the other end of the resistor R43 is grounded. Pin 12 of the PWM chip U3 is respectively connected to one end of the capacitor C19, one end of the capacitor C18 and the voltage 12V_TL494+. The other end of the capacitor C19 and the other end of the capacitor C18 are combined and grounded. Pin 15 of the PWM chip U3 is connected to one end of the resistor R42. Pin 4 of the PWM chip U3 is respectively connected to one end of the capacitor C22 and one end of the resistor R44, and the other end of the resistor R44 is grounded. Pin 14 of the PWM chip U3 is respectively connected to one end of the capacitor C15, the other end of the capacitor C22 and the other end of the resistor R42, and the other end of the capacitor C15 is grounded. Pin 16 of the PWM chip U3 is connected to one end of the resistor R41, and the other end of the resistor R41 is grounded.
[0008] The MCU chip is provided with a plurality of PE pins, and the MCU chip adopts a GD32 series chip.
[0009] A control method for a PWM-based constant current and constant voltage heating pad control circuit, comprising any one of the PWM-based constant current and constant voltage heating pad control circuits described in claims 1-6, the control method comprising the following steps: S1, presetting a target current value, and the MCU chip outputting a PWM signal with a corresponding duty cycle according to the target current value; S2, the PWM signal passes through a voltage-controlled drive circuit, is isolated by a photoelectric coupler of the voltage-controlled drive circuit, and is filtered by a second-order RC composed of a resistor R56, a capacitor C32, a resistor R57, and a capacitor C33, and a set value Vset is obtained by voltage division and transmitted to the PWM chip. The calculation formula is as follows: ; S3. When the current passes through the sampling resistors R4 and R5, a voltage drop is generated. The voltage drop is used as the sampling value Vsample and the current sampling signal is output and transmitted to the PWM chip. The calculation formula is as follows: ; S4. The error amplifier of the PWM chip obtains the set value Vset and the sampling value Vsample and adjusts them through the compensation network. The error amplifier of the PWM chip outputs the feedback voltage V3. S5. The real-time sawtooth wave Vcc of the oscillator in the PWM chip is obtained. The PWM chip compares the feedback voltage V3 with the sawtooth wave Vcc. The sawtooth wave Vcc outputs the PWM duty cycle signal. If the feedback voltage V3 is greater than the sawtooth wave Vcc, the output PWM duty cycle signal is at a high level; if the feedback voltage V3 is less than or equal to the sawtooth wave Vcc, the output PWM duty cycle signal is at a low level. S6. The adjusted PWM duty cycle signal drives the MOS tube of the asynchronous buck circuit. By controlling the MOS tube, the average current of the heating pad is adjusted to reach the set value. When the received PWM duty cycle signal is at a high level, the MOS tube is turned on, and when the received PWM duty cycle signal is at a low level, the MOS tube is turned off.
[0010] Compared with the existing technology, the present invention realizes dynamic regulation of the current of the heating pad, ensures constant current and constant voltage output to both ends of the heating pad, improves energy conversion efficiency, and extends battery life; realizes dynamic current limiting through real-time current sampling and feedback control, realizes a soft current limiting protection mechanism, avoids MOS tube breakdown or battery thermal runaway, and significantly improves system stability and safety; by adjusting the sampling resistor to be suitable for heating pads with different resistance values, the compatibility of the circuit is improved; adopts optocoupler isolation and voltage follower structure to effectively suppress noise interference and improve control accuracy; the unidirectional conduction of the diode can effectively prevent the risk of direct conduction, and improve the reliability of the system integrated design. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 This is the circuit diagram of the asynchronous buck circuit; Figure 2 is a circuit diagram of a gate drive circuit; Figure 3 This is a circuit diagram of a voltage-controlled drive circuit; Figure 4 This is the circuit diagram of the PWM control circuit; Figure 5 This is a schematic diagram of the current flow of the constant current and constant voltage heating pad control circuit; DETAILED DESCRIPTION
[0012] The present invention will be further described below with reference to the accompanying drawings.
[0013] A PWM-based constant current and constant voltage heating pad control circuit includes an asynchronous buck circuit, a gate drive circuit, a voltage control drive circuit, a PWM control circuit, and an MCU chip. The asynchronous buck circuit is provided with an LCSG_DriveA0 port, an LCSG_DriveB0 port, a HEAT+ heating pad positive electrode port, a P+ power supply positive electrode port, a HEAT- heating pad negative electrode port, and a VSamp port; the gate drive circuit is provided with a HEAT_OFF port, an LCSG_DriveA0 port, an LCSG_DriveB0 port, and a CON_PWM port; the voltage control drive circuit is provided with a CL_PWM port and a REF_PWM port; the PWM control circuit is provided with a CON_PWM port and a VRef port , VSamp port; the LCSG_DriveA0 port and LCSG_DriveB0 port of the asynchronous buck circuit are connected to the LCSG_DriveA0 port and LCSG_DriveB0 port of the gate drive circuit in sequence, the VSamp port of the asynchronous buck circuit is connected to the VSamp port of the PWM control circuit, the CON_PWM port of the gate drive circuit is connected to the CON_PWM port of the PWM control circuit, the REF_PWM port of the voltage control drive circuit is connected to the VRef port of the PWM control circuit, one PE pin of the MCU chip is connected to the HEAT_OFF port of the gate drive circuit, and the other PE pin of the MCU chip is connected to the CL_PWM port of the voltage control drive circuit.
[0014] like Figure 1The negative terminal of the HEAT-heating pad of the asynchronous buck circuit is connected to one end of the capacitor C1, one end of the capacitor C2, one end of the capacitor C3, one end of the capacitor C4, and one end of the inductor L1. The other end of the capacitor C1, the other end of the capacitor C2, and the other end of the capacitor C3 are connected to the positive terminal of the HEAT+heating pad and the positive terminal of the P+power supply. The other end of the capacitor C4 is connected to one end of the resistor R1. The other end of the resistor R1 and the other end of the inductor L1 are connected to one end of the resistor R2, one end of the resistor R3, the drain of the MOS tube Q1, and the drain of the MOS tube Q1. The drain of 1, one end of the resistor R7, one end of the resistor R8, the anode of the diode D1, the anode of the diode D2, the anode of the diode D3, the anode of the diode D5, the other end of the resistor R2, the other end of the resistor R3 are combined to connect to one end of the capacitor C8, the other end of the resistor R7, the other end of the resistor R8 are combined to connect to one end of the capacitor C7, the cathode of the diode D1, the cathode of the diode D2, the cathode of the diode D3, the cathode of the diode D5, and the other end of the capacitor C7 are combined and connected to the positive terminal of the HEAT+ heating pad and the positive terminal of the P+ power supply, the MOS tube Q The gate of MOS tube Q1 is respectively connected to one end of resistor R9, one end of resistor R12, and one end of resistor R13. The other end of resistor R12 is connected to the anode of diode D5. The cathode of diode D5 and the other end of resistor R13 are combined and connected to the LCSG_DriveA0 port. The gate of MOS tube Q2 is respectively connected to one end of resistor R6, one end of resistor R10, and one end of resistor R11. The other end of resistor R10 is connected to the anode of diode D6. The cathode of diode D6 and the other end of resistor R11 are combined and connected to the LCSG_DriveB0 port. The source of the MOS transistor Q1 is respectively connected to the other end of the resistor R9, the other end of the resistor R6, the source of the MOS transistor Q2, the other end of the capacitor C8, one end of the capacitor C5, one end of the capacitor C6, one end of the capacitor C10, the VSamp port, one end of the sampling resistor R4, and one end of the sampling resistor R5. The other end of the capacitor C5, the other end of the capacitor C6, and the other end of the capacitor C10 are combined and connected to the positive electrode port HEAT+ of the heating pad and the positive electrode port P+ of the power supply. The other end of the sampling resistor R4 and the other end of the sampling resistor R5 are combined and connected to the negative electrode of the power supply and the power ground.
[0015] like Figure 2The CON_PWM port of the gate drive circuit is connected to the anode of the diode Q23 and the base of the transistor Q21 respectively. The cathode of the diode Q23 is connected to the anode of the diode Q22, one end of the resistor R23, and the emitter of the transistor Q21. The collector of the transistor Q21 is grounded. The other end of the resistor R23 is connected to the cathode of the diode Q22, one end of the capacitor C43, pin 2 of the gate drive chip U2, and pin 4 of the gate drive chip U2. The other end of the capacitor C43 is grounded. Pins 8 and 1 of the gate drive chip U2 are combined and connected to the HEAT_OFF port. Pin 3 of the gate drive chip U2 is connected to the Grounded, pin 7 of the gate drive chip U2 is connected to one end of the resistor R22, and the other end of the resistor R22 is connected to the LCSG_DriveA0 port. Pin 5 of the gate drive chip U2 is connected to one end of the resistor R21, and the other end of the resistor R21 is connected to the LCSG_DriveB0 port. Pin 6 of the gate drive chip U2 is respectively connected to one end of the capacitor C41, one end of the capacitor C42, and one end of the inductor L2. The other end of the capacitor C41 and the other end of the capacitor C42 are combined and grounded. The other end of the inductor L2 is connected to the voltage 12V_TL494+. The gate drive chip U2 uses model UCC27524D.
[0016] like Figure 3 The voltage control drive circuit includes a voltage follower U5. The voltage follower U5 adopts the model LM358. Pin 8 of the voltage follower U5 is respectively connected to one end of the capacitor C40, one end of the capacitor C28, and one end of the resistor R59. The other end of the resistor R59 is connected to the voltage 12V-TL494+. The other end of the capacitor C40 and the other end of the capacitor C28 are combined and grounded. Pin 7 of the voltage follower U5 is connected to pin 6 of the voltage follower U5, pin 5 of the voltage follower U5 is grounded, pin 4 of the voltage follower U5 is grounded, pin 1 of the voltage follower U5 and pin 2 of the voltage follower U5 are combined and connected to the REF_PWM port, and pin 3 of the voltage follower U5 is connected to the resistor R58. One end of the resistor R58 is respectively connected to one end of the resistor R57 and one end of the capacitor C33, the other end of the capacitor C33 is grounded, the other end of the resistor R57 is respectively connected to one end of the resistor R56 and one end of the capacitor C32, the other end of the capacitor C32 is grounded, the other end of the resistor R57 is respectively connected to one end of the resistor R54 and the emitter of the photoelectric coupler Q5, the collector of the photoelectric coupler Q5 is connected to one end of the capacitor C33, one end of the capacitor C39, and the voltage 12V_PWM+, the negative electrode of the photoelectric coupler Q5 is connected to one end of the capacitor C31 and ground, the positive electrode of the photoelectric coupler Q5 is respectively connected to the other end of the capacitor C31 and one end of the resistor R55, and the other end of the resistor R55 is connected to the CL_PWM port.
[0017] like Figure 4The PWM control circuit includes a PWM chip U3. The PWM chip U3 adopts the model TL494. Pin 1 of the PWM chip U3 is respectively connected to one end of the resistor R37, one end of the capacitor C9, and one end of the capacitor C24. The other end of the resistor R37 is connected to the VSamp port. The other end of the capacitor C24 and the other end of the capacitor C9 are combined and grounded. Pin 2 of the PWM chip U3 is connected to the VRef port. Pin 3 of the PWM chip U3 is respectively connected to one end of the resistor R38 and one end of the resistor R39. The other end of the resistor R39 is connected to one end of the capacitor C21. The other end of the capacitor C21 and the other end of the resistor R38 are combined and connected to the VRef port. Pin 5 of the PWM chip U3 is connected to one end of the capacitor C23. The other end of the capacitor C23 is grounded. Pin 6 of the PWM chip U3 is connected to one end of the resistor R45. The other end of the resistor R45 is grounded. Pin 7 of the PWM chip U3 and pin 13 of the PWM chip U3 are combined and grounded. Pin 8 and pin 11 of the PWM chip U3 are combined to connect to the voltage 12V_TL494+. Pin 8 of the PWM chip U3 and pin 11 of the PWM chip U3 are combined and connected to the CON_PWM port and one end of the resistor R43 respectively. The other end of the resistor R43 is grounded. Pin 12 of the PWM chip U3 is respectively connected to one end of the capacitor C19, one end of the capacitor C18 and the voltage 12V_TL494+. The other end of the capacitor C19 and the other end of the capacitor C18 are combined to ground. Pin 15 of the PWM chip U3 is connected to one end of the resistor R42. Pin 4 of the PWM chip U3 is respectively connected to one end of the capacitor C22 and one end of the resistor R44. The other end of the resistor R44 is grounded. Pin 14 of the PWM chip U3 is respectively connected to one end of the capacitor C15, the other end of the capacitor C22 and the other end of the resistor R42. The other end of the capacitor C15 is grounded. Pin 16 of the PWM chip U3 is connected to one end of the resistor R41, and the other end of the resistor R41 is grounded.
[0018] There are several PE pins on the MCU chip, and the MCU chip adopts the GD32 series chip.
[0019] The control method includes the following steps: S1, preset the target current value, and the MCU chip outputs a PWM signal with a corresponding duty cycle according to the target current value; S2, the PWM signal passes through the voltage control drive circuit, is isolated by the optocoupler of the voltage control drive circuit, and is filtered by the second-order RC composed of resistor R56, capacitor C32 and resistor R57, capacitor C33. After voltage division, the set value Vset is obtained and transmitted to the PWM chip. The calculation formula is as follows: ; S3. When the current passes through the sampling resistors R4 and R5, a voltage drop is generated. The voltage drop is used as the sampling value Vsample and the current sampling signal is output and transmitted to the PWM chip. The calculation formula is as follows: ; S4. The error amplifier of the PWM chip obtains the set value Vset and the sampling value Vsample, adjusts and outputs the feedback voltage V3 through the compensation network; S5. The real-time sawtooth wave Vcc of the oscillator in the PWM chip is obtained. The range of the sawtooth wave Vcc is 0.3V-3V. The PWM chip compares the feedback voltage V3 with the sawtooth wave Vcc. The sawtooth wave Vcc outputs a PWM duty cycle signal. If the feedback voltage V3 is greater than the sawtooth wave Vcc, the output PWM duty cycle signal is at a high level; if the feedback voltage V3 is less than or equal to the sawtooth wave Vcc, the output PWM duty cycle signal is at a low level; S6. The adjusted PWM duty cycle signal drives the MOS tube of the asynchronous buck circuit. By controlling the MOS tube, the average current of the heating pad is adjusted to reach the set value. When the received PWM duty cycle signal is at a high level, the MOS tube is turned on, and when the received PWM duty cycle signal is at a low level, the MOS tube is turned off.
[0020] Assume that the duty cycle of the PWM signal output by the MCU chip is 10%. The signal is converted into a DC voltage after optocoupler isolation and second-order RC filtering. The converted DC voltage value is 1.2V. After voltage division, the voltage division ratio is 1 / 50, and the set value Vset is 24mV, which is sent to pin 2 of the PWM chip TL494. TL494 adjusts the voltage of pin 1 to be close to the set value Vset according to the voltage received at pin 2, and sets the sampling resistor to 5 milliohms. If the voltage of pin 1 is adjusted to 24mV, the current passing through the sampling resistor is 4.8A. The current passing through the heating pad is 4.8A, and the output voltage is adjusted.
[0021] When the PWM duty cycle signal is at a high level, the current starts from the P+ power supply positive terminal, flows to the HEAT+ heating pad positive terminal, then flows out from the heating pad negative terminal, passes through inductor L1, MOS transistor Q2, MOS transistor Q1, sampling resistor R4 and sampling resistor R5, and finally reaches the P- power supply negative terminal. When the PWM duty cycle signal is at a low level, the current starts from inductor L1, passes through diode D1, diode D2, diode D3, diode D4, returns to the P+ power supply positive terminal, then flows out from the HEAT+ heating pad positive terminal, out from the HEAT- heating pad negative terminal, and then returns to inductor L1.
[0022] This system integrates PWM chip control and current sampling functions into a compact circuit, improving system stability and reliability. At high input voltages (e.g., 60V), system efficiency and energy conversion efficiency are increased to over 90%, saving over 40% energy compared to traditional linear regulation solutions and extending battery life. The TL494 PWM chip automatically adjusts the PWM duty cycle based on real-time current, implementing "soft current limiting" protection to prevent MOSFET breakdown or battery thermal runaway, enhancing system safety.
Claims
1. A PWM-based constant current and constant voltage heating pad control circuit, including an asynchronous buck circuit, a gate drive circuit, a voltage control drive circuit, a PWM control circuit, and an MCU chip, characterized in that: The asynchronous buck circuit is provided with LCSG_DriveA0 port, LCSG_DriveB0 port, HEAT+ heating pad positive port, P+ power supply positive port, HEAT- heating pad negative port, VSamp port; the gate drive circuit is provided with HEAT_OFF port, LCSG_DriveA0 port, LCSG_DriveB0 port, CON_PWM port; the voltage control drive circuit is provided with CL_PWM port, REF_PWM port; the PWM control circuit is provided with CON_PWM port, VRef port, VSamp port; the LCSG_ The DriveA0 port and LCSG_DriveB0 port are connected to the LCSG_DriveA0 port and LCSG_DriveB0 port of the gate drive circuit respectively, the VSamp port of the asynchronous buck circuit is connected to the VSamp port of the PWM control circuit, the CON_PWM port of the gate drive circuit is connected to the CON_PWM port of the PWM control circuit, the REF_PWM port of the voltage control drive circuit is connected to the VRef port of the PWM control circuit, one PE pin of the MCU chip is connected to the HEAT_OFF port of the gate drive circuit, and the other PE pin of the MCU chip is connected to the CL_PWM port of the voltage control drive circuit.
2. A PWM-based constant current and constant voltage heating pad control circuit according to claim 1, characterized in that: The HEAT-heating pad negative electrode port of the asynchronous buck circuit is respectively connected to one end of the capacitor C1, one end of the capacitor C2, one end of the capacitor C3, one end of the capacitor C4, and one end of the inductor L1. The other end of the capacitor C1, the other end of the capacitor C2, and the other end of the capacitor C3 are combined to connect the HEAT+heating pad positive electrode port and the P+ power supply positive electrode port. The other end of the capacitor C4 is connected to one end of the resistor R1. The other end of the resistor R1 and the other end of the inductor L1 are combined and respectively connected to one end of the resistor R2, one end of the resistor R3, the drain of the MOS tube Q1, and the MOS The drain of tube Q1, one end of resistor R7, one end of resistor R8, the anode of diode D1, the anode of diode D2, the anode of diode D3, the anode of diode D5, the other end of resistor R2, the other end of resistor R3 are connected together to one end of capacitor C8, the other end of resistor R7, the other end of resistor R8 are connected together to one end of capacitor C7, the cathode of diode D1, the cathode of diode D2, the cathode of diode D3, the cathode of diode D5, and the other end of capacitor C7 are connected together to the positive terminal of HEAT+ heating pad and the positive terminal of P+ power supply, MOS tube The gate of Q1 is connected to one end of resistor R9, one end of resistor R12, and one end of resistor R13 respectively. The other end of resistor R12 is connected to the anode of diode D5. The cathode of diode D5 and the other end of resistor R13 are combined and connected to the LCSG_DriveA0 port. The gate of MOS tube Q2 is connected to one end of resistor R6, one end of resistor R10, and one end of resistor R11 respectively. The other end of resistor R10 is connected to the anode of diode D6. The cathode of diode D6 and the other end of resistor R11 are combined and connected to the LCSG_DriveB0 port. The source of the MOS transistor Q1 is respectively connected to the other end of the resistor R9, the other end of the resistor R6, the source of the MOS transistor Q2, the other end of the capacitor C8, one end of the capacitor C5, one end of the capacitor C6, one end of the capacitor C10, the VSamp port, one end of the sampling resistor R4, and one end of the sampling resistor R5. The other end of the capacitor C5, the other end of the capacitor C6, and the other end of the capacitor C10 are combined and connected to the positive electrode port HEAT+ of the heating pad and the positive electrode port P+ of the power supply. The other end of the sampling resistor R4 and the other end of the sampling resistor R5 are combined and connected to the negative electrode of the power supply and the power ground.
3. A PWM-based constant current and constant voltage heating pad control circuit according to claim 1, characterized in that: The CON_PWM port of the gate drive circuit is respectively connected to the anode of the diode Q23 and the base of the transistor Q21, the cathode of the diode Q23 is respectively connected to the anode of the diode Q22, one end of the resistor R23, and the emitter of the transistor Q21, the collector of the transistor Q21 is grounded, the other end of the resistor R23 is respectively connected to the cathode of the diode Q22, one end of the capacitor C43, pin 2 of the gate drive chip U2, and pin 4 of the gate drive chip U2, the other end of the capacitor C43 is grounded, pins 8 and 1 of the gate drive chip U2 are combined to connect to the HEAT_OFF port, and pin 3 of the gate drive chip U2 is connected to the The pin is grounded, pin 7 of the gate driver chip U2 is connected to one end of the resistor R22, and the other end of the resistor R22 is connected to the LCSG_DriveA0 port, pin 5 of the gate driver chip U2 is connected to one end of the resistor R21, and the other end of the resistor R21 is connected to the LCSG_DriveB0 port, pin 6 of the gate driver chip U2 is respectively connected to one end of the capacitor C41, one end of the capacitor C42, and one end of the inductor L2, the other end of the capacitor C41 and the other end of the capacitor C42 are combined to ground, the other end of the inductor L2 is connected to the voltage 12V_TL494+, and the gate driver chip U2 uses model UCC27524D.
4. The PWM-based constant current and constant voltage heating pad control circuit according to claim 1, characterized in that: The voltage control drive circuit includes a voltage follower U5, which adopts the model LM358. Pin 8 of the voltage follower U5 is respectively connected to one end of the capacitor C40, one end of the capacitor C28, and one end of the resistor R59. The other end of the resistor R59 is connected to the voltage 12V-TL494+, the other end of the capacitor C40 and the other end of the capacitor C28 are combined and grounded, pin 7 of the voltage follower U5 is connected to pin 6 of the voltage follower U5, pin 5 of the voltage follower U5 is grounded, pin 4 of the voltage follower U5 is grounded, pin 1 of the voltage follower U5 and pin 2 of the voltage follower U5 are combined and connected to the REF_PWM port, and pin 3 of the voltage follower U5 is connected to the resistor R5 8, the other end of the resistor R58 is respectively connected to one end of the resistor R57 and one end of the capacitor C33, the other end of the capacitor C33 is grounded, the other end of the resistor R57 is respectively connected to one end of the resistor R56 and one end of the capacitor C32, the other end of the capacitor C32 is grounded, the other end of the resistor R57 is respectively connected to one end of the resistor R54 and the emitter of the photoelectric coupler Q5, the collector of the photoelectric coupler Q5 is connected to one end of the capacitor C33, one end of the capacitor C39, and the voltage 12V_PWM+, the negative electrode of the photoelectric coupler Q5 is connected to one end of the capacitor C31 and ground, the positive electrode of the photoelectric coupler Q5 is respectively connected to the other end of the capacitor C31 and one end of the resistor R55, and the other end of the resistor R55 is connected to the CL_PWM port.
5. The PWM-based constant current and constant voltage heating pad control circuit according to claim 1, characterized in that: The PWM control circuit includes a PWM chip U3, which adopts a model TL494. Pin 1 of the PWM chip U3 is respectively connected to one end of a resistor R37, one end of a capacitor C9, and one end of a capacitor C24. The other end of the resistor R37 is connected to the VSamp port, and the other end of the capacitor C24 and the other end of the capacitor C9 are combined and grounded. Pin 2 of the PWM chip U3 is connected to the VRef port. Pin 3 of the PWM chip U3 is respectively connected to one end of a resistor R38 and one end of a resistor R39. The other end of the resistor R39 is connected to one end of a capacitor C21. The other end of the capacitor C21 and the other end of the resistor R38 are combined and connected to the VRef port. Pin 5 of the PWM chip U3 is connected to one end of a capacitor C23, and the other end of the capacitor C23 is grounded. Pin 6 of the PWM chip U3 is connected to one end of a resistor R45, and the other end of the resistor R45 is grounded. Pin 7 of the PWM chip U3 and pin 13 of the PWM chip U3 are combined and grounded. Pin 8 of the PWM chip U3 and pin 11 of the PWM chip U3 are combined to connect to the voltage 12V_TL494+. Pin 8 of the PWM chip U3 and pin 11 of the PWM chip U3 are combined and connected to the CON_PWM port and one end of the resistor R43, and the other end of the resistor R43 is grounded. Pin 12 of the PWM chip U3 is respectively connected to one end of the capacitor C19, one end of the capacitor C18 and the voltage 12V_TL494+. The other end of the capacitor C19 and the other end of the capacitor C18 are combined and grounded. Pin 15 of the PWM chip U3 is connected to one end of the resistor R42. Pin 4 of the PWM chip U3 is respectively connected to one end of the capacitor C22 and one end of the resistor R44, and the other end of the resistor R44 is grounded. Pin 14 of the PWM chip U3 is respectively connected to one end of the capacitor C15, the other end of the capacitor C22 and the other end of the resistor R42, and the other end of the capacitor C15 is grounded. Pin 16 of the PWM chip U3 is connected to one end of the resistor R41, and the other end of the resistor R41 is grounded.
6. The PWM-based constant current and constant voltage heating pad control circuit according to claim 1, characterized in that: The MCU chip is provided with a plurality of PE pins, and the MCU chip adopts a GD32 series chip.
7. A control method for a PWM-based constant current and constant voltage heating pad control circuit, comprising any one of claims 1 to 6, wherein: The control method includes the following steps: S1, preset the target current value, and the MCU chip outputs a PWM signal with a corresponding duty cycle according to the target current value; S2, the PWM signal passes through the voltage control drive circuit, is isolated by the optocoupler of the voltage control drive circuit, and is filtered by the second-order RC composed of resistor R56, capacitor C32 and resistor R57, capacitor C33. After voltage division, the set value Vset is obtained and transmitted to the PWM chip. The calculation formula is as follows: ； S3. When the current passes through the sampling resistors R4 and R5, a voltage drop is generated. The voltage drop is used as the sampling value Vsample and the current sampling signal is output and transmitted to the PWM chip. The calculation formula is as follows: ； S4. The error amplifier of the PWM chip obtains the set value Vset and the sampling value Vsample, adjusts and outputs the feedback voltage V3 through the compensation network; S5. The real-time sawtooth wave Vcc of the oscillator in the PWM chip is obtained, and the PWM chip compares the feedback voltage V3 with the sawtooth wave Vcc. The sawtooth wave Vcc outputs the PWM duty cycle signal. If the feedback voltage V3 is greater than the sawtooth wave Vcc, the output PWM duty cycle signal is at a high level; if the feedback voltage V3 is less than or equal to the sawtooth wave Vcc, the output PWM duty cycle signal is at a low level; S6. The adjusted PWM duty cycle signal drives the MOS tube of the asynchronous buck circuit. By controlling the MOS tube, the average current of the heating pad is adjusted to reach the set value. When the received PWM duty cycle signal is at a high level, the MOS tube is turned on, and when the received PWM duty cycle signal is at a low level, the MOS tube is turned off.