Motor driving circuit based on pre-charging and multi-path flyback power supply

Abstract

A motor driving circuit based on pre-charging and multipath flyback power supplies belongs to the field of motor driving, and comprises high-voltage DC input terminals, a pre-charging buffer unit, a multipath isolation power supply conversion unit and a motor driving unit, the pre-charging buffer unit is connected between the input terminals, current-limiting charging is carried out on a bus capacitor through a pre-charging resistor, and the multipath isolation power supply conversion unit is connected with the motor driving unit. The power-on impact current is suppressed; the multi-path isolation power supply conversion unit adopts flyback topology, bus voltage is converted and isolated into multi-path independent low-voltage direct-current power supplies, a closed-loop voltage stabilizing circuit is configured for at least one path of output, and the motor driving unit obtains driving power from a bus capacitor and obtains a control power supply from the multi-path isolation power supplies, so that efficient and reliable driving of a motor is realized; according to the invention, the problems of high-voltage power-on impact and multi-path isolation power supply are solved, and high reliability, high integration and strong anti-interference capability are realized.

Description

Technical Field

[0001] This utility model is a motor drive circuit based on pre-charge and multi-channel flyback power supply, belonging to the field of motor drive. Background Technology

[0002] High-voltage motor drive systems are widely used in modern industrial automation, new energy vehicles, servo drives, and other fields. These systems typically use a high-voltage DC bus for power supply, and their core circuits generally include: a high-voltage DC bus for powering the power inverter bridge, a low-voltage auxiliary power supply for powering the control and sensing circuits, and an inverter and controller for executing motor drive. However, this architecture faces two prominent challenges in practical applications:

[0003] First, to stabilize the bus voltage and filter ripple, a large-capacity support capacitor must be connected in parallel at the bus end. At the moment of system power-on, this capacitor is equivalent to a short circuit, drawing a huge instantaneous surge current from the high-voltage power supply. This current spike not only stresses the power supply itself but may also damage the bus capacitor, contactor, and subsequent power devices (such as IGBTs or MOSFETs), affecting system reliability. To address this issue, existing technologies often employ a simple soft-start circuit consisting of a pre-charge resistor and a contactor. However, such solutions may suffer from problems such as the resistor not being effectively bypassed after pre-charging, leading to continuous losses, or they may lack precise voltage detection and logic control, resulting in insufficient reliability during the pre-charging process and remaining a risk.

[0004] Secondly, different functional modules on the driver board (such as microcontrollers, gate driver chips, operational amplifiers, communication interfaces, etc.) require multiple isolated and stable low-voltage power supplies (e.g., ±15V, +5V, +24V, etc.). Traditional solutions typically use multiple independent isolated DC-DC modules or complex multi-output switching power supplies. The former results in bulky circuits, high costs, and complex wiring; the latter often suffers from poor cross-regulation, complex design, and low reliability when achieving multiple high-precision isolated outputs. Utility Model Content

[0005] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide a motor drive circuit based on pre-charge and multi-channel flyback power supply, so as to solve the technical problem that the existing technology lacks a highly integrated, safe and reliable motor drive circuit that can safely and shocklessly establish a high-voltage bus and then efficiently and compactly generate all the isolated low-voltage power supplies required by the system.

[0006] To achieve the above objectives, this utility model is implemented through the following technical solution: a motor drive circuit based on pre-charge and multi-channel flyback power supply, which includes a high-voltage DC input terminal;

[0007] A pre-charge buffer unit is connected between the high-voltage DC input terminals. It includes a pre-charge resistor and a bus capacitor. The pre-charge resistor is used to limit the current charging of the bus capacitor to suppress the power-on inrush current.

[0008] A multi-channel isolated power conversion unit, the input terminal of which is connected to the bus capacitor, is used to convert and isolate the bus voltage into multiple independent low-voltage DC power supplies;

[0009] The motor drive unit has its power bus terminal connected to the bus capacitor to obtain drive power, and its control power terminal connected to each output terminal of the multi-channel isolated power conversion unit to obtain operating power.

[0010] Furthermore, the precharge buffer unit includes a control drive module, a power execution module, and a current detection module. The control drive module responds to an external precharge enable signal and drives the power execution module to operate. The power execution module is used to connect or disconnect the precharge resistor from the main power circuit to perform current-limited charging of the bus capacitor. The current detection module is used to monitor the voltage of the bus capacitor and generate a feedback signal.

[0011] Furthermore, the control drive module includes an optocoupler PC2 and a MOSFET FET2. The anode of the input side of the optocoupler PC2 is connected to the precharge enable signal through a resistor R58, and its cathode is connected to the control signal ground. The collector of the output side of the optocoupler PC2 is connected to the drive power supply, and its emitter is connected to the gate of the MOSFET FET2 through a resistor R59. The source of the MOSFET FET2 is grounded, and its drain is connected to one end of the coil of the power relay in the power execution module.

[0012] Furthermore, the power execution module includes a dual-winding coupled inductor L1, a power relay RY2, and a pre-charge resistor. The first winding of the dual-winding coupled inductor L1 is connected between the high-voltage input terminals, and its second winding is connected between the positive and negative terminals of the bus. The contacts of the power relay RY2 are connected in series between the second winding and the pre-charge resistor, and the pre-charge resistor is connected in series between the contacts of the power relay RY2 and the positive terminal of the bus capacitor.

[0013] Furthermore, the current detection module includes a current sensor IC7, which is connected in series in the charging circuit of the pre-charging resistor to detect the charging current flowing through the pre-charging resistor. The power supply pin of its output terminal is connected to a low-voltage power supply, and its signal output terminal outputs a feedback signal proportional to the charging current through a resistor R68.

[0014] Furthermore, the multi-channel isolated power conversion unit is a flyback switching power supply, which includes a current-mode PWM controller, a power switching transistor, and a high-frequency isolation transformer. The current-mode PWM controller controls the switching of the power switching transistor according to the feedback signal. The primary winding of the high-frequency isolation transformer is connected to the bus capacitor through the power switching transistor, and its secondary winding contains at least two independent windings.

[0015] Furthermore, after passing through their respective rectifier and filter circuits, the multiple secondary windings output multiple isolated DC power supplies with different voltages. The DC power supplies include at least a power supply for the interface and drive, a power supply for the analog circuit, and a power supply for the digital circuit.

[0016] Furthermore, the multi-channel isolated power conversion unit also includes a closed-loop voltage regulator circuit, which includes a three-terminal adjustable shunt reference source connected to any output and an optocoupler, used to isolate and feed back the output voltage error signal to the current-mode PWM controller on the primary side.

[0017] Furthermore, the motor drive unit includes a microcontroller, a drive circuit, and a three-phase inverter bridge. The DC side of the three-phase inverter bridge is connected to the bus capacitor to obtain drive power. The power supply terminals of the microcontroller and the drive circuit are respectively connected to the corresponding output terminals of the multi-channel isolated power conversion unit to obtain operating power, thereby supplying power to different functional modules of the drive circuit.

[0018] The beneficial effects of this utility model are:

[0019] This application achieves overall performance optimization through the coordinated operation of a pre-charge buffer unit, a multi-channel isolated power supply conversion unit, and a motor drive unit. The pre-charge buffer unit accurately detects the charging current using a Hall sensor, indirectly and reliably determining the pre-charge completion point. The multi-channel isolated power supply conversion unit, based on a single-channel flyback topology and a multi-winding transformer, efficiently and compactly achieves the conversion from a single high voltage to multiple isolated low voltages, and ensures the accuracy and stability of each output voltage through closed-loop voltage regulation. The motor drive unit benefits from the high-quality energy provided by the first two units, with its power section directly drawing power from the stable bus, and its control section being independently powered by the isolated multi-channel power supply. This significantly enhances the anti-interference capability and operational reliability while improving the system's power density and efficiency. Attached Figure Description

[0020] Other features, objects, and advantages of this invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0021] Figure 1This is a schematic diagram of the pre-charging circuit in a motor drive circuit based on pre-charging and multi-channel flyback power supply according to the present invention.

[0022] Figure 2 This is a schematic diagram of the structure of a multi-channel isolated power supply conversion unit in a motor drive circuit based on pre-charge and multi-channel flyback power supply according to this utility model. Detailed Implementation

[0023] To make the technical means, creative features, objectives and effects of this utility model easier to understand, the present utility model will be further described below in conjunction with specific embodiments.

[0024] This utility model is achieved through the following technical solution, which consists of a high-voltage DC input terminal, a pre-charge buffer unit, a multi-channel isolated power conversion unit, and a motor drive unit:

[0025] 1. Pre-charge buffer unit: The pre-charge buffer unit is connected between the high voltage DC input terminals and includes a pre-charge resistor and a bus capacitor. It is used to perform current-limited charging of the bus capacitor through the pre-charge resistor to suppress the power-on inrush current.

[0026] Reference Figure 1 As shown, the unit can be divided into three cooperating sub-modules in terms of circuit structure: control drive module, power execution module and current detection module.

[0027] 11. Control and drive module:

[0028] This module is responsible for receiving the low-voltage enable signal from the main controller (such as an MCU), isolating and amplifying it to drive the power execution device on the high-voltage side. Its core consists of an optocoupler PC2 and a MOSFET FET2.

[0029] The pre-charge enable signal (typically +5V) is connected to the anode (pin 1) of the LED on the input side of the optocoupler PC2 via a current-limiting resistor R58, and its cathode (pin 2) is connected to the controller signal ground. When the enable signal is valid, the LED inside the optocoupler PC2 conducts and emits light. On the output side, the collector (pin 4) of the phototransistor in the optocoupler PC2 is connected to the drive power supply (+24V), and the emitter (pin 3) is connected to the gate of the N-channel MOSFET FET2 via a drive resistor R59. The source of the MOSFET FET2 is connected to the power ground (DCM), and its drain is directly connected to one end (pin 1) of the coil of the power relay RY2 in the power execution module.

[0030] In addition, a network consisting of resistor R61 and capacitor C49 is connected in parallel between the gate and source of FET2 to regulate the drive speed and suppress oscillation. A freewheeling diode D19 is connected in reverse parallel across the coil of relay RY2 to absorb the induced electromotive force spike generated when the coil is de-energized and protect MOSFET FET2.

[0031] 12. Power Execution Module:

[0032] This module is responsible for controlling the connection and removal of the pre-charging resistor. During the pre-charging phase, the pre-charging resistor is connected to the main power circuit to limit the inrush current to the bus capacitor. After pre-charging is completed, the pre-charging resistor is disconnected from the main circuit and bypassed, thereby safely ending the pre-charging process. It mainly consists of a dual-winding coupled inductor L1, a power relay RY2, and pre-charging resistors (DR1, DR2).

[0033] The first winding (pins 1-2) of the dual-winding coupled inductor L1 is connected in series between the positive (P+) and negative (N1) terminals of the high-voltage DC input, and the second winding (pins 3-4) is connected between the positive (P) and negative (N) terminals of the busbar inside the system. The normally open contact (pins 3-4) of the power relay RY2 is connected in series between the output terminal (pin 4) of the second winding and one end of the pre-charge resistor (DR1, DR2). The other end of the pre-charge resistor (DR1, DR2) is connected to the positive terminal (point P) of the busbar support capacitor.

[0034] On the input side, a capacitor C52 is connected in parallel across the first winding (pins 1-2) to form an input differential mode filter. On the bus side, a capacitor C51 is connected in parallel across the second winding (pins 3-4) to form a bus differential mode filter. Between the high-voltage DC input terminals (P+ and N1), capacitors C50 and C54 are also connected in parallel as common-mode filters or auxiliary filters at the input. Inside the system, between the buses (P and N), multiple voltage equalization or bleedering resistors (R62, R63, R64, R65, R66) are connected in parallel to equalize the bus capacitor voltage and release residual charge after power failure.

[0035] When the coil of power relay RY2 is not energized, its normally open contacts open, and the pre-charge resistors (DR1, DR2) are connected to the main power circuit. High-voltage DC current flows out from the positive terminal P+, sequentially through the first and second windings of the dual-winding coupled inductor L1, and then through the pre-charge resistors DR1 / DR2 for current limiting, charging the bus support capacitor (represented by C53). Finally, the current returns through the negative terminal N of the bus, forming a complete charging circuit. In this process, the pre-charge resistors play a crucial role in limiting the inrush current.

[0036] When the bus capacitor voltage approaches the input voltage and the charging current approaches zero, the pre-charge stage ends. The control circuit energizes the RY2 coil, its normally open contact closes, bypassing the pre-charge resistor from the main circuit, and the system enters normal operation mode.

[0037] 13. Current detection module:

[0038] This module is used to monitor the charging current in real time during the pre-charging process. It determines whether the bus capacitor has finished charging by detecting the charging current. Its core is a high-performance Hall effect current sensor IC7 (such as IC6921).

[0039] The current sensor IC7 has a current via connected in series in the charging circuit from the pre-charge resistors (DR1, DR2) to the bus capacitor, so that the entire charging current flows through the sensor. Its power supply pin (VCC) is connected to the +5V low-voltage power supply, its ground pin (GND) is connected to the signal ground, and its analog voltage output pin outputs a feedback signal VIpn that is precisely proportional to the real-time charging current through resistor R68. In order to improve the signal quality, an RC low-pass filter network consisting of capacitor C56 and resistor R69 is connected in parallel between the signal output terminal and ground to suppress high-frequency interference noise.

[0040] At the moment the pre-charge process begins, the charging current flowing through the pre-charge resistor is at its maximum due to the low voltage of the bus capacitor. Consequently, the amplitude of the Vipn signal output by sensor IC7 is also at a high level. As charging progresses, the voltage across the bus capacitor continuously rises, and the difference between it and the input voltage decreases, causing the charging current to decay exponentially. The amplitude of the Vipn signal output by sensor IC7 also decreases synchronously. The system's main controller (such as an MCU) continuously samples the Vipn signal through its internal analog-to-digital converter (ADC). When the signal value drops to a pre-set threshold close to zero current, it can determine that the bus capacitor voltage is close to the input voltage and the charging current has approached zero, thus marking the completion of the pre-charge process. Subsequent operations (such as disconnecting the pre-charge circuit) can then be safely performed.

[0041] The workflow of the pre-charged buffer unit is briefly described as follows:

[0042] After the system is powered on, the main controller keeps the pre-charge enable signal in an invalid state. At this time, the optocoupler PC2 in the control drive module is turned off, the MOSFET FET2 is turned off, and the coil of the power relay RY2 is de-energized, with its normally open contact in the open position. In this state, the high-voltage DC input performs current-limited charging on the bus capacitor bank (C50, C54, etc.) through the path formed by the pre-charge resistors (DR1, DR2), and the bus voltage slowly rises from zero. During the charging process, the Hall effect current sensor IC7 connected in series in the circuit detects the current flowing through the pre-charge resistor in real time and outputs an analog voltage signal VIpn proportional to it. The main controller continuously samples the VIpn signal through its internal ADC channel. When the signal value drops to a preset threshold (corresponding to the charging current approaching zero, indicating that the bus voltage is close to the input voltage), the main controller determines that the pre-charge is complete and then issues a valid pre-charge enable signal. This signal turns on the optocoupler PC2, which in turn drives the MOSFET FET2 to turn on, energizing the coil of the power relay RY2, and closing its normally open contact. After the contacts are closed, the pre-charge resistors (DR1, DR2) are bypassed from the main power circuit, the pre-charge process ends safely, the system enters normal operation mode, and subsequent circuits (such as the multi-channel isolated power conversion unit and the motor drive unit) can be put into normal operation.

[0043] 2. Multi-channel isolated power conversion unit: The input terminal of the multi-channel isolated power conversion unit is connected to the bus capacitor, and is used to convert and isolate the bus voltage into multiple independent low-voltage DC power supplies;

[0044] Reference Figure 2 As shown, this unit adopts a flyback switching power supply topology and uses a current-mode PWM controller as the core control device (for example, a dedicated chip of model UC2844M can be used). The controller receives the isolation feedback signal from the secondary side and dynamically adjusts the duty cycle of its output PWM pulse, thereby precisely controlling the turn-on and turn-off timing of the power switching transistor (usually MOSFET). The power switching transistor drives the primary winding of the high-frequency isolation transformer to convert the DC bus voltage into high-frequency alternating energy stored in the transformer core.

[0045] To achieve multiple independent outputs, the high-frequency isolation transformer has multiple electrically isolated secondary windings. Each secondary winding constitutes an independent energy output channel. These outputs include: a +24V power supply, mainly used for relay and external interface driving; a symmetrical ±15V power supply, for analog circuits such as analog operational amplifiers and sensors; and a +5V (or +3.3V) power supply, for digital circuits such as microcontrollers, digital logic chips, and communication modules. This design achieves power supply isolation between different functional modules, effectively avoiding mutual interference.

[0046] To ensure the high accuracy and stability of at least one critical output voltage (typically a +5V digital power supply), the multi-channel isolated power conversion unit also includes a closed-loop voltage regulator circuit. The closed-loop voltage regulator circuit includes a three-terminal adjustable shunt reference source connected to any output and an optocoupler, which is used to isolate and feed back the output voltage error signal to the current-mode PWM controller on the primary side. The controller adjusts the duty cycle of the switching transistor in real time, thereby forming a complete and isolated voltage closed loop, which dynamically compensates for changes in input voltage and load, ensuring the long-term accuracy and stability of the critical output voltage.

[0047] 3. Motor drive unit: The power bus terminal of the motor drive unit is connected to the bus capacitor to obtain drive power, and its control power supply terminal is connected to each output terminal of the multi-channel isolated power conversion unit to obtain working power.

[0048] To achieve effective separation of high and low voltage power supplies, the motor drive unit includes a microcontroller, a drive circuit, and a three-phase inverter bridge. The DC side of the three-phase inverter bridge is connected to the bus capacitor to obtain drive power. The power supply terminals of the microcontroller and the drive circuit are respectively connected to the corresponding output terminals of the multi-channel isolated power conversion unit to obtain operating power, thereby supplying power to different functional modules of the drive circuit.

[0049] This application achieves overall performance optimization through the coordinated operation of a pre-charge buffer unit, a multi-channel isolated power supply conversion unit, and a motor drive unit. The pre-charge buffer unit accurately detects the charging current using a Hall sensor, indirectly and reliably determining the pre-charge completion point. The multi-channel isolated power supply conversion unit, based on a single-channel flyback topology and a multi-winding transformer, efficiently and compactly achieves the conversion from a single high voltage to multiple isolated low voltages, and ensures the accuracy and stability of each output voltage through closed-loop voltage regulation. The motor drive unit benefits from the high-quality energy provided by the first two units, with its power section directly drawing power from the stable bus, and its control section being independently powered by the isolated multi-channel power supply. This significantly enhances the anti-interference capability and operational reliability while improving the system's power density and efficiency.

[0050] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. It will be apparent to those skilled in the art that this utility model is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or basic characteristics of this utility model. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this utility model is defined by the appended claims rather than the foregoing description, and thus all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this utility model. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0051] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A motor drive circuit based on pre-charge and multi-path flyback power supply, characterized in that: It includes high-voltage DC input terminals; A pre-charge buffer unit is connected between the high-voltage DC input terminals, which includes a pre-charge resistor and a bus capacitor, and is used to limit the charging current of the bus capacitor through the pre-charge resistor to suppress the power-on inrush current; A multi-path isolated power conversion unit, the input of which is connected to the bus capacitor, is used to convert and isolate the bus voltage into multiple independent low-voltage DC power supplies; A motor drive unit, the power bus end of which is connected to the bus capacitor to obtain driving power, and the control power end of which is connected to each output end of the multi-path isolated power conversion unit to obtain working power.

2. The motor drive circuit based on pre-charge and multi-path flyback power supply according to claim 1, characterized in that: The pre-charge buffer unit includes a control drive module, a power execution module, and a current detection module. The control drive module responds to an external pre-charge enable signal and drives the power execution module to act. The power execution module is used to connect or disconnect the pre-charge resistor to the main power loop to limit the charging current of the bus capacitor. The current detection module is used to monitor the voltage of the bus capacitor and generate a feedback signal.

3. The motor drive circuit based on pre-charge and multi-path flyback power supply according to claim 2, characterized in that: The control drive module includes a photoelectric coupler PC2 and a MOSFET tube FET2. The anode of the input side of the photoelectric coupler PC2 is connected to the pre-charge enable signal through a resistor R58, and the cathode is connected to the control signal ground. The collector of the output side of the photoelectric coupler PC2 is connected to the driving power supply, and the emitter is connected to the gate of the MOSFET tube FET2 through a resistor R59. The source of the MOSFET tube FET2 is grounded, and the drain is connected to one end of the coil of the power relay in the power execution module.

4. The motor drive circuit based on pre-charge and multi-path flyback power supply according to claim 2, characterized in that: The power execution module includes a double-winding coupled inductor L1, a power relay RY2, and a pre-charge resistor. The first winding of the double-winding coupled inductor L1 is connected between the high-voltage input terminals, and the second winding is connected between the positive and negative poles of the bus. The contacts of the power relay RY2 are connected in series between the second winding and the pre-charge resistor. The pre-charge resistor is connected in series between the contacts of the power relay RY2 and the positive pole of the bus capacitor.

5. The motor drive circuit based on pre-charge and multi-path flyback power supply according to claim 2, characterized in that: The current detection module includes a current sensor IC7, which is connected in series in the charging loop of the pre-charge resistor to detect the charging current flowing through the pre-charge resistor. The power pin of the output end is connected to a low-voltage power supply, and the signal output end outputs a feedback signal proportional to the charging current through a resistor R68.

6. The motor drive circuit based on pre-charge and multi-path flyback power supply according to claim 1, characterized in that: The multi-path isolated power conversion unit is a flyback switching power supply, which includes a current mode PWM controller, a power switch tube, and a high-frequency isolation transformer. The current mode PWM controller controls the on-off of the power switch tube according to the feedback signal. The primary winding of the high-frequency isolation transformer is connected to the bus capacitor through the power switch tube, and the secondary winding contains at least two independent windings.

7. The motor drive circuit based on pre-charge and multi-path flyback power supply according to claim 6, characterized in that: Multiple secondary windings output multiple isolated and voltage-different DC power supplies through respective rectifier and filter circuits. The DC power supplies include at least power supplies for interface and drive, power supplies for analog circuits, and power supplies for digital circuits.

8. The motor drive circuit based on pre-charge and multi-path flyback power supply according to claim 7, characterized in that: The multi-path isolated power conversion unit further comprises a closed-loop voltage stabilizing circuit, which comprises a three-terminal adjustable shunt reference source connected to any one of the output paths and an optoelectronic coupler for isolating and feeding back an output voltage error signal to the current-mode PWM controller of the primary side.

9. The motor drive circuit based on pre-charge and multi-path flyback power supply according to claim 1, characterized in that: The motor driving unit comprises a microcontroller, a driving circuit and a three-phase inverter bridge, the DC side of the three-phase inverter bridge is connected to the bus capacitor to obtain driving power, the power supply end of the microcontroller and the power supply end of the driving circuit are respectively connected to the corresponding output end of the multi-path isolated power conversion unit to obtain working power, thereby supplying power to different functional modules of the driving circuit.

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