Application method of voltage stabilizing circuit in 24VEPS circuit system

Abstract

The invention belongs to the technical field of automobile electric power steering, and relates to an application method of a voltage stabilizing circuit in a 24VEPS circuit system, which comprises the following steps of: 1, after EMC (Electro Magnetic Compatibility) filtering, judging whether the current input voltage is less than or equal to the preset maximum output voltage; 2, when it is judged that the input voltage is larger than the preset maximum output voltage, entering the step 3, and otherwise, entering the step 4; 3, reducing and stabilizing the power output voltage to a safe voltage range; 4, the output voltage is transmitted to a power management module for processing after passing through a synchronous rectification MOS tube, a feedback regulation circuit and a protection circuit; by adding the voltage stabilizing circuit, the voltage range is always controlled within the system safety voltage range; the power management module of the 24VEPS system is safer and more efficient, the compatibility of related electronic components of the power management module is expanded, and the cost output of the whole product can be effectively reduced on the basis of improving the product performance.

Description

Technical Field

[0001] This invention belongs to the field of automotive electric power steering technology, specifically relating to a method for applying a voltage regulator circuit in a 24VEPS circuit system. Background Technology

[0002] As automotive electronics technology evolves towards higher power and higher efficiency, 24V electric power steering (EPS) systems are widely used in commercial vehicles, large passenger vehicles, and new energy vehicles due to their advantages of higher power transmission efficiency and lower line loss. As a core safety component of a vehicle, the EPS system places stringent requirements on the stability of the power supply, dynamic response speed, and environmental adaptability of its control unit, sensors, and actuators, directly affecting steering accuracy and driving safety.

[0003] According to requirements, on-board DC-DC step-down regulator circuits must meet the following standards: efficiency ≥92% (E1 level), output ripple ≤5%, electromagnetic compatibility (EMC) compliance, and stable operation within an extreme temperature range of -40℃ to 125℃. However, the power supply for the 24VEPS system comes from the vehicle's power battery, and its output voltage is prone to wide fluctuations of 18V to 36V due to battery aging, sudden load changes, or charge-discharge cycles. Traditional DC-DC step-down circuits are difficult to adapt to this characteristic.

[0004] The LM5085-Q, an automotive-grade synchronous buck regulator chip from Texas Instruments, features a wide input voltage range of 4.5V to 75V, ultra-fast transient response, and AEC-Q100 Level 1 certification, perfectly matching the extreme operating conditions of automobiles. It integrates a high-voltage bias regulator and a PFET gate driver, supporting programmable switching frequency and 100% duty cycle operation, effectively simplifying circuit structure and reducing losses. However, its current applications are concentrated in general fields such as automotive infotainment systems and LED drivers. It lacks specific design adaptation for the dynamic load characteristics, EMC requirements, and functional safety requirements of 24V EPS systems. Its peripheral circuit parameters, filtering topology, and protection mechanisms are not precisely matched to the power requirements of EPS systems, preventing its core performance advantages from being fully realized and making it difficult to directly apply to 24V EPS systems.

[0005] Therefore, a suitable DC-DC buck regulator circuit is needed to address the shortcomings of existing solutions in terms of wide voltage compatibility, dynamic response, efficiency, and EMC. Summary of the Invention

[0006] The present invention aims to solve the problem that the large fluctuation range of the power supply voltage of the 24VEPS system affects the normal operation of EPS, and to improve the performance of 24VEPS.

[0007] This invention provides the following technical solution: a method for applying a voltage regulator circuit in a 24VEPS circuit system, comprising the following steps: Step 1: During the initialization phase after system power-on, after EMC filtering, the filtered voltage is supplied to the synchronous buck regulator chip for processing. It determines whether the current input voltage is less than or equal to the preset maximum output voltage, that is, whether the input voltage exceeds the withstand voltage range of the subsequent circuit. Step 2: If the input voltage is determined to be greater than the preset maximum output voltage, proceed to Step 3; if the input voltage is determined to be less than or equal to the preset maximum output voltage, proceed to Step 4. Step 3: The power output voltage is stepped down and regulated to a safe voltage range by using a synchronous buck regulator chip and a low on-resistance synchronous rectifier MOSFET, combined with a high-frequency alloy inductor in the BUCK circuit, and then proceeds to Step 4. Step 4: After passing through the synchronous rectification MOSFET, feedback regulation circuit, and protection circuit, the output voltage is sent to the power management module for processing.

[0008] Preferably, the synchronous buck regulator chip is model LM5085-Q.

[0009] More preferably, the circuit components of the voltage regulator circuit include: synchronous buck regulator chip U1, diodes D1 and D2, capacitors C1 to C5, C26 to C28, resistors R1, R2, R4, R5, R6, common mode inductor L1, inductor L2, and transistor M1.

[0010] The voltage regulator circuit is connected as follows: Diode D1 is connected to the two power supplies of the DC-DC converter; the anode of diode D1 is connected to pin 4 of common-mode inductor L1; pin 3 of common-mode inductor L1 is grounded; pins 1 and 2 of common-mode inductor L1 are connected to the two ends of capacitor C3; one end of capacitor C3 is grounded and the other end is connected to power supply VSUP; capacitors C4 and C5 are connected in parallel, with one end grounded and the other end connected to power supply VSUP; one end of resistor R4 is connected to pin 1 of common-mode inductor L1, and the other end of resistor R4 is connected to pin 2 of synchronous buck regulator chip U1; pins 4 and 9 of synchronous buck regulator chip U1 are grounded; pins 7 and 8 of synchronous buck regulator chip U1 are connected to the two ends of capacitor C1; the two ends of capacitor C2 and resistor R2 are connected in parallel... Connect pins 1 and 8 of the synchronous buck regulator chip U1. Connect the two ends of resistor R1 to pins 5 and 8 of the synchronous buck regulator chip U1 respectively. Connect pin 6 of the synchronous buck regulator chip U1 to the gate of transistor M1. Connect pin 5 of the synchronous buck regulator chip U1 to the drain of transistor M1. Connect the source of transistor M1 to ground after connecting diode D3 in series. Connect the source of transistor M1 to pin 3 of the synchronous buck regulator chip U1 after connecting inductor L2 and capacitor C26 in series. Connect the two ends of resistor R5 to the two ends of capacitor C26. Connect the two ends of resistor R6 and capacitor C27 in series to the two ends of resistor R5 respectively. Connect the two ends of capacitor C28 to the two ends of capacitor C27 respectively. Connect one end of capacitor C28 to ground and the other end of capacitor C28 to VST.

[0011] More preferably, the EMC filter circuit in step one consists of a common-mode inductor L1, an X capacitor C1, and Y capacitors C2 / C3.

[0012] Preferably, in step two, when it is determined that the input voltage is greater than the preset maximum output voltage, the input voltage received by the subsequent circuit is clamped without changing the subsequent circuit, and then step three is performed.

[0013] Preferably, in step three, the BUCK circuit uses a single-transistor non-isolated DC-DC converter with an output voltage lower than the input voltage. The single transistor is a freewheeling diode. The non-isolation method means that the input and output are in the same closed-loop circuit, without the use of transformer components for isolation.

[0014] Preferably, in step three, when the synchronous buck regulator chip-based buck DC-DC controller employs comparator and monostable multivibrator control, the output voltage feedback is compared with the internal reference voltage. When the feedback voltage is lower than the reference value, transistor Q1 turns on, and the on-time is determined by the input voltage and the programming resistor. After turning on, transistor Q1 remains off until the feedback voltage falls below the reference value again, at which point transistor Q1 turns on again, entering the next conduction cycle. The output voltage is set by the feedback resistor. The formula for calculating the regulated output voltage is: VOUT = 1.25V x (RFB2+ RFB1) / RFB1 (1) In equation (1): VOUT is the output voltage of the BUCK circuit composed of a synchronous buck regulator chip, a synchronous rectifier MOSFET with low on-resistance, and a high-frequency alloy inductor; 1.25V is the internal reference voltage of the synchronous buck regulator chip; RFB1 and RFB2 are the feedback adjustment circuit resistors of the FB pin on the synchronous buck regulator chip.

[0015] The beneficial effects of this invention are: This invention, based on the LM5085-Q chip, significantly improves the power supply stability of 24V EPS systems. Through an optimized synchronous buck architecture and high-precision feedback network, the output voltage ripple is controlled within 50mV, and the voltage recovery time during load surges does not exceed 10μs, perfectly adapting to the dynamic operating characteristics of EPS systems with frequent start-stop cycles. The circuit conversion efficiency reaches 92%-95%, greatly reducing power losses, thus reducing onboard energy consumption and improving the range of hybrid / electric vehicle EPS systems. Thanks to automotive-grade component selection and EMC-optimized design, the circuit can operate stably in extreme temperature ranges from -40℃ to 125℃, and its electromagnetic compatibility meets ISO7637-2 standards, fully satisfying the environmental adaptability requirements of complex automotive operating conditions. Furthermore, leveraging the high integration of the LM5085-Q chip, the peripheral circuit structure is simplified, reducing the number of components. This reduces circuit size and production costs while facilitating integration with EPS systems, combining performance improvement with practicality and economy. Attached Figure Description

[0016] Fig. 1 This is a flowchart illustrating the application method of a voltage regulator circuit in a 24VEPS circuit system according to the present invention; Fig. 2 This is a schematic diagram of the step-down voltage regulator circuit based on LM5085-Q according to the present invention. Detailed Implementation

[0017] The related technologies of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figs. 1-2 As shown, the application method of a voltage regulator circuit in a 24VEPS circuit system according to this embodiment includes: Step 1: After the system is powered on, during the system initialization phase, the filtered voltage is supplied to the LM5085-Q chip after EMC filtering. The LM5085-Q chip then regulates the voltage to determine if the current input voltage is less than or equal to the preset maximum output voltage, i.e., whether the input voltage exceeds the withstand voltage range of subsequent circuits. Step 2: If the input voltage is determined to be greater than the preset maximum output voltage, that is, if the input voltage exceeds the withstand voltage range of the subsequent circuit, proceed to Step 3; if the input voltage is determined to be less than or equal to the preset maximum output voltage, that is, if the input voltage does not exceed the withstand voltage range of the subsequent circuit, proceed to Step 4. Step 3: The power output voltage is stepped down and regulated to a safe voltage range by using an LM5085-Q synchronous rectifier MOSFET with a high-frequency alloy inductor in a BUCK circuit. Then proceed to Step 4. Step 4: After passing through the synchronous rectification MOSFET, feedback regulation circuit, and protection circuit, the output voltage is sent to the power management module for further processing.

[0019] Furthermore, the EMC filter circuit in step one consists of a common-mode inductor L1, an X capacitor C1, and Y capacitors C2 / C3, which meets the ISO 7637-2 electromagnetic compatibility standard.

[0020] Furthermore, if the input voltage in step two exceeds the withstand voltage range of the subsequent circuit, then clamping the input voltage received by the subsequent circuit is the optimal solution without changing the subsequent circuit, and then proceed to step three.

[0021] Furthermore, in step three, the BUCK circuit composed of an LM5085-Q, a low on-resistance synchronous rectifier MOSFET, and a high-frequency alloy inductor constitutes a single-transistor non-isolated DC-DC converter with an output voltage lower than the input voltage. Here, "single-transistor" refers to a freewheeling diode, and "non-isolated" means that the input and output are in the same closed-loop circuit, without any transformer components separating them.

[0022] Furthermore, in step three, the LM5085-Q step-down DC-DC controller employs a control scheme based on a comparator and a monostable multivibrator. Its output voltage feedback is compared with an internal reference voltage (1.25V). When the feedback voltage is lower than the reference value, transistor Q1 will conduct, with the conduction time determined by the input voltage and the programming resistor (RT). After conduction, Q1 remains off until the feedback voltage falls below the reference value again, at which point Q1 will conduct again, entering the next conduction cycle. The output voltage is set by the feedback resistor. The formula for calculating the regulated output voltage is as follows: VOUT = 1.25V x (RFB2+ RFB1) / RFB1 (1) In formula (1): VOUT is the output voltage of a BUCK circuit consisting of an LM5085-Q synchronous rectifier MOSFET with low on-resistance and a high-frequency alloy inductor. 1.25V is the internal reference voltage of the LM5085-Q; RFB1 and RFB2 are the feedback regulation circuit resistors for the FB pin on the LM5085-Q.

[0023] Example

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following description is provided in conjunction with the appendix of the present invention. Figs. 1-2 The technical solutions in the embodiments of the present invention will be described in complete and clear form as follows: like Fig. 2 As shown in the figure, this invention discloses an application of a voltage regulator circuit based on LM5085-Q in a 24VEPS system. The aim is to effectively protect the 24VEPS system and improve its stability and reliability in the event of sudden power supply fluctuations.

[0025] like Fig. 1 After the system is powered on, during the system initialization phase, the filtered voltage is supplied to the LM5085-Q chip after EMC filtering, and then processed by the voltage regulation circuit built by the LM5085-Q.

[0026] After system power is supplied, the input voltage is filtered by EMC and then connected to the LM5085-Q. When the voltage at the EN pin reaches the chip enable threshold (1.25V), the chip starts working. The LM5085-Q's internal PWM controller adjusts the drive signal at the PGATE pin based on the output voltage signal acquired by the FB pin, controlling the on and off times of the MOSFET. Through the energy storage and release of the inductor and the action of the freewheeling diode, the input voltage is contained within the set voltage range, ensuring that the output voltage does not exceed the set maximum voltage, thus protecting the circuit. The formula for calculating the regulated output voltage is as follows: VOUT = 1.25V x (RFB2+ RFB1) / RFB1 (1) In formula (1): VOUT is the output voltage of a BUCK circuit consisting of an LM5085-Q synchronous rectifier MOSFET with low on-resistance and a high-frequency alloy inductor. 1.25V is the internal reference voltage of the LM5085-Q; RFB1 and RFB2 are the feedback regulation circuit resistors for the FB pin on the LM5085-Q.

[0027] Table 1 below shows the test results of the LM5085-Q-based voltage regulator circuit in a 24VEPS system:

[0028] like Fig. 2 The figure shown is a specific embodiment of the present invention, wherein the resistance values ​​of RFB1 and RFB2 and the VOUT voltage are shown in Table 2 below:

[0029] In summary, the voltage regulator circuit solution built using the LM5085-Q chip in this invention demonstrates significant advantages in 24VEPS system applications. Its core innovation lies in the deep integration of automotive-grade power management chips with dynamic response optimization technology, achieving system-level reliability enhancement through a triple protection mechanism: First, a dual-stage EMC filtering architecture (common-mode inductor + X / Y capacitor combination) effectively suppresses conducted interference, meeting the CISPR 25 Class 5 standard in actual testing; second, adaptive voltage clamping technology maintains output voltage fluctuations within ±2% even when the input voltage surges to 36V; finally, relying on the chip's built-in over-temperature protection (OTP) and over-current protection (OCP) functions, combined with an external watchdog circuit, forms a redundant protection system.

[0030] Engineering verification data shows that this solution exhibits superior dynamic performance in bench tests: when the EPS motor load suddenly increases from no-load to full-load (0-8A / 10ms), the output voltage recovery time is only 8.3μs, a 62% improvement over traditional solutions; the output voltage accuracy remains within ±1.5% across the entire temperature range of -40℃ to 125℃; and the circuit conversion efficiency reaches 94.2% under typical operating conditions (14V input / 12V output), a 3.7 percentage point improvement over competing solutions. Real-vehicle road testing has verified that this solution can reduce the EPS system failure rate to 0.03 times / thousand hours, significantly better than the industry average of 0.15 times / thousand hours.

[0031] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for applying a voltage regulator circuit in a 24VEPS circuit system, characterized in that, Includes the following steps: Step 1: During the initialization phase after system power-on, after EMC filtering, the filtered voltage is supplied to the synchronous buck regulator chip for processing to determine whether the current input voltage is less than or equal to the preset maximum output voltage. Step 2: If the input voltage is determined to be greater than the preset maximum output voltage, proceed to Step 3; if the input voltage is determined to be less than or equal to the preset maximum output voltage, proceed to Step 4. Step 3: The power output voltage is stepped down and regulated to a safe voltage range by using a synchronous buck regulator chip and a low on-resistance synchronous rectifier MOSFET, combined with a high-frequency alloy inductor in the BUCK circuit, and then proceeds to Step 4. Step 4: After passing through the synchronous rectification MOSFET, feedback regulation circuit, and protection circuit, the output voltage is sent to the power management module for processing.

2. The method for applying a voltage regulator circuit in a 24VEPS circuit system according to claim 1, characterized in that, The synchronous buck regulator chip is model LM5085-Q.

3. The method for applying a voltage regulator circuit in a 24VEPS circuit system according to claim 2, characterized in that, The circuit components of the voltage regulator circuit include: synchronous buck regulator chip U1, diodes D1 and D2, capacitors C1 to C5, C26 to C28, resistors R1, R2, R4, R5, R6, common mode inductor L1, inductor L2, and transistor M1. The circuit connection of the voltage regulator circuit is as follows: the two ends of diode D1 are connected to the two power supplies of DC-DC input respectively, and the positive terminal of diode D1 is connected to pin 4 of common-mode inductor L1; pin 3 of common-mode inductor L1 is grounded, and pins 1 and 2 of common-mode inductor L1 are connected to the two ends of capacitor C3 respectively; one end of capacitor C3 is grounded and the other end is connected to power supply VSUP; capacitors C4 and C5 are connected in parallel, with one end grounded and the other end connected to power supply VSUP; one end of resistor R4 is connected to pin 1 of common-mode inductor L1, and the other end of resistor R4 is connected to pin 2 of synchronous buck regulator chip U1; pins 4 and 9 of synchronous buck regulator chip U1 are grounded, and pins 7 and 8 of synchronous buck regulator chip U1 are connected to the two ends of capacitor C1 respectively; the two ends of capacitor C2 and resistor R2 are connected in parallel... Do not connect pins 1 and 8 of the synchronous buck regulator chip U1. Connect the two ends of resistor R1 to pins 5 and 8 of the synchronous buck regulator chip U1 respectively. Connect pin 6 of the synchronous buck regulator chip U1 to the gate of transistor M1. Connect pin 5 of the synchronous buck regulator chip U1 to the drain of transistor M1. Connect the source of transistor M1 to ground after connecting diode D3 in series. Connect the source of transistor M1 to pin 3 of the synchronous buck regulator chip U1 after connecting inductor L2 and capacitor C26 in series. Connect the two ends of resistor R5 to the two ends of capacitor C26. Connect the two ends of resistor R6 and capacitor C27 in series to the two ends of resistor R5 respectively. Connect the two ends of capacitor C28 to the two ends of capacitor C27 respectively. Connect one end of capacitor C28 to ground and the other end of capacitor C28 to VST.

4. The method for applying a voltage regulator circuit in a 24VEPS circuit system according to claim 3, characterized in that, The EMC filter circuit in step one consists of a common-mode inductor L1, an X capacitor C1, and Y capacitors C2 / C3.

5. The method for applying a voltage regulator circuit in a 24VEPS circuit system according to claim 1, characterized in that, In step two, when the input voltage is determined to be greater than the preset maximum output voltage, the input voltage received by the subsequent circuit is clamped without changing the subsequent circuit, and then step three is performed.

6. The method for applying a voltage regulator circuit in a 24VEPS circuit system according to claim 1, characterized in that, In step three, the BUCK circuit uses a single-transistor non-isolated DC-DC converter with an output voltage lower than the input voltage. The single transistor is a freewheeling diode. The non-isolation method means that the input and output are in the same closed-loop circuit, without the use of transformer components for isolation.

7. The method for applying a voltage regulator circuit in a 24VEPS circuit system according to claim 1, characterized in that, In step three, when the synchronous buck regulator chip-based DC-DC controller uses comparator and monostable multivibrator control, the output voltage feedback is compared with the internal reference voltage. When the feedback voltage is lower than the reference value, transistor Q1 turns on, and the on-time is determined by the input voltage and the programming resistor. After turning on, transistor Q1 remains off until the feedback voltage falls below the reference value again, at which point transistor Q1 turns on again, entering the next conduction cycle. The output voltage is set by the feedback resistor. The formula for calculating the regulated output voltage is: VOUT = 1.25V x (RFB2+ RFB1) / RFB1 (1) In equation (1): VOUT is the output voltage of the BUCK circuit composed of a synchronous buck regulator chip, a synchronous rectifier MOSFET with low on-resistance, and a high-frequency alloy inductor; 1.25V is the internal reference voltage of the synchronous buck regulator chip; RFB1 and RFB2 are the feedback adjustment circuit resistors of the FB pin on the synchronous buck regulator chip.

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