Capacitor pre-charging control circuit based on power converter
By adopting constant current output technology based on power converter in the capacitor precharge control circuit, the existing capacitor precharge control circuit has solved the problems of large size, heavy weight, high cost, low efficiency and short service life, and achieved more efficient and economical capacitor precharge control.
Patent Information
- Application Number
- CN202510128333.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-05
- Publication Date
- 2025-04-25
AI Technical Summary
The existing capacitor precharge control circuit has problems such as large size, heavy weight, high cost, low efficiency and short service life. Especially in electric drive control systems such as new energy vehicles, it is necessary to improve to ensure the stable operation of the motor controller.
The capacitance precharge control circuit based on the power converter is adopted to charge the bus capacitor through the constant current output of the DCDC power converter, and the control unit is used to control the off state of the main switch to realize the constant current output of the power converter.
Capacitor pre-charge control with small size, light weight, low cost, high efficiency and long service life is realized, which shortens the pre-charge time, reduces energy loss, and improves the stability and reliability of the system.
Smart Images
Figure CN119891763A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of electrical control technology, and in particular to a capacitor pre-charging control circuit based on a power converter. Background Art
[0002] In the field of motor control, in most electric drive control systems, including new energy vehicles, a large-capacity bus capacitor needs to be connected in parallel to the DC input of the motor controller to ensure the stable operation of the motor controller. At the initial moment when the motor controller is powered on, the voltage on the bus capacitor is usually 0V, which is equivalent to a short circuit for the power supply system. If the power switch is turned on directly, it will cause instantaneous large current and cause damage to the power supply system, switch elements, or the bus capacitor itself. Therefore, a pre-charge control circuit is required to charge the bus capacitor to a voltage close to the power supply system before turning on the power switch.
[0003] The prior art uses pre-charging resistors and pre-charging switches for pre-charging control. Pre-charging resistors consume a lot of energy, are usually large in size, heavy in weight, high in cost, low in efficiency, require a long pre-charging time, and the number of pre-charging power-ups within a certain period of time is limited. In addition, if the pre-charging switch uses a mechanical switch, it is also large in size, heavy in weight, high in cost, and the service life of the mechanical switch is short.
[0004] Therefore, it is necessary to improve the existing pre-charge control circuit. Summary of the invention
[0005] In view of this, it is necessary to provide a capacitor pre-charging control circuit based on a power converter, which can achieve the purpose of small size, light weight, low cost, high efficiency, short pre-charging time and long service life of the bus capacitor pre-charging control circuit.
[0006] In order to achieve the above object, the present invention provides a capacitor pre-charge control circuit based on a power converter, comprising: A DCDC power converter, a first end of which is connected to a bus capacitor, and a second end of which is connected to a power battery, wherein the DCDC power converter has a controllable constant current output; A first main switch, two contacts of which are connected in parallel to two ends of the DCDC power converter; A second main switch, two contacts of which are connected to the power battery and the bus capacitor respectively; A control unit is connected to the first coil of the first main switch and the second coil of the second main switch, and is used to control the on and off states of the first main switch and the second main switch to achieve constant current output of the DCDC power converter.
[0007] In some possible implementations, the DCDC power converter includes a PWM controller, electronic switches Q1 and Q2, a power inductor L1, a current sampling resistor RS1, an input capacitor C1, an output capacitor C2, an input anti-reverse diode D1, and an output anti-reverse diode D2; The PWM controller and the control unit, the gate of the electronic switch Q1 and the gate of the electronic switch Q2; The drain of the electronic switch Q1 is connected to the cathode of the input anti-reverse diode D1 and the first end of the input capacitor C1, the anode of the input anti-reverse diode D1 is connected to the power battery, and the second end of the input capacitor C1 is grounded; The source of the electronic switch Q1 is connected to the first end of the current sampling resistor RS1, and the second end of the current sampling resistor RS1 is connected to the drain of the electronic switch Q2 and the first end of the power inductor L1; The second end of the power inductor L1 is connected to the positive electrode of the output anti-reverse diode D2 and the first end of the output capacitor C2, the negative electrode of the output anti-reverse diode D2 is connected to the bus capacitor, and the second end of the output capacitor C2 is connected to the bus capacitor and the source of the electronic switch Q2.
[0008] In some possible implementations, the control unit is used to start or shut down the PWM controller to start or stop the pre-charge output of the power module.
[0009] In some possible implementations, the PWM controller is a buck controller with an output constant current regulation function.
[0010] In some possible implementations, the electronic switches Q1 and Q2 are NMOS tubes or IGBTs.
[0011] In some possible implementations, for a selected PWM controller, the output current of the power converter mainly depends on the resistance of the current sampling resistor RS1 .
[0012] In some possible implementations, the output current value of the power converter is determined by the capacitance value of the bus capacitor CX1, the voltage value of the power supply system, the pre-charge preset voltage value, the pre-charge time and cost factors.
[0013] In some possible implementations, if the capacitance value of the bus capacitor CX1, the power supply system voltage value, and the pre-charge preset voltage value are fixed, the pre-charge time depends on the output current of the power converter. The larger the pre-charge current, the shorter the pre-charge time.
[0014] The beneficial effects of the present invention are as follows: the present invention uses the constant current output of the power converter to charge the bus capacitor. Compared with the prior art method of using a pre-charging resistor to limit the current to charge the capacitor, the present invention has the advantages of small size, light weight, low cost, high efficiency and long service life. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.
[0016] Figure 1 It is a circuit structure diagram of a capacitor pre-charge control circuit in the prior art; Figure 2 A circuit structure diagram of a first embodiment of a capacitor pre-charge control circuit based on a power converter provided by the present invention; Figure 3 A circuit structure diagram of a second embodiment of a capacitor pre-charging control circuit based on a power converter provided by the present invention; Figure 4 This is an example diagram comparing the pre-charging curves of the present invention and the prior art. DETAILED DESCRIPTION
[0017] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.
[0018] The descriptions of "first", "second", etc. involved in the embodiments of the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the technical features defined as "first" or "second" may explicitly or implicitly include at least one of the features.
[0019] The "embodiment" provided herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.
[0020] Before describing the specific embodiments, the technical defects of the prior art are described in detail. Figure 1 , Figure 1The circuit structure diagram of the capacitor pre-charge control circuit in the prior art.
[0021] In the field of motor control, most electric drive control systems including new energy vehicles (such as Figure 1 The DC input of the motor controller needs to be connected in parallel with a large bus capacitor (such as Figure 1 CX1) to smooth the DC bus voltage, reduce noise, provide energy reserves, and mitigate current fluctuations to ensure that the motor controller can operate stably and efficiently.
[0022] At the initial moment when the motor controller is powered on, the voltage on the bus capacitor CX1 is usually 0V, which has a negative impact on the power supply system (such as Figure 1 If you directly turn on the power switch (such as Figure 1 The main switches 1 and 2 in the figure may cause a large charging current of the bus capacitor CX1 by the power supply system at the moment of turning on the switch. This large current may cause damage to the power supply system, switch components, or the bus capacitor CX1 itself.
[0023] The function of the pre-charge control circuit is to charge the bus capacitor to a voltage close to the power supply system voltage to reduce the instantaneous current when it is turned on and avoid damage to the device.
[0024] In the prior art, the pre-charging circuit usually includes a pre-charging resistor and a pre-charging switch. The function of the pre-charging resistor is to limit the charging current of the bus capacitor CX1 by the power supply system. The function of the pre-charging switch is to control the on-off of the pre-charging circuit. Usually, before turning on the power supply switch (main switch 1 and main switch 2), the pre-charging circuit will be turned on first. After the power supply system charges the bus capacitor CX1 to a voltage close to the power supply system through the pre-charging resistor, the power supply main switch 1 will be turned on.
[0025] The pre-charge resistor is usually a high-power resistor, which is large in size, heavy in weight and high in cost. In addition, since the pre-charge resistor consumes power and generates heat during the pre-charge process, in order to prevent the temperature rise from being too high and damaging the pre-charge resistor, the number of pre-charge power-ups within a certain period of time is limited.
[0026] The pre-charge switch can be a mechanical switch (such as a relay) or an electronic switch (such as a MOS tube, IGBT, etc.). Mechanical switches are large in size, heavy in weight, high in cost, and have a short service life.
[0027] In addition, during the pre-charging process, the energy consumed by the pre-charging resistor through heat generation is equivalent to the charging energy of the bus capacitor, and the energy loss during pre-charging is as high as more than 50%.
[0028] Therefore, the circuit using such a pre-charging resistor and a pre-charging switch for pre-charging control is large in size, heavy in weight, high in cost, low in efficiency, and short in service life.
[0029] In order to overcome the above defects, the present invention provides a capacitor pre-charge control circuit based on a power converter, see Figure 2 , the circuit comprises: A DCDC power converter, a first end of which is connected to a bus capacitor, and a second end of which is connected to a power battery, wherein the DCDC power converter has a controllable constant current output; A first main switch (i.e., main switch 1), two contacts of which are connected in parallel to two ends of the DCDC power converter; A second main switch (i.e., main switch 2), two contacts of which are connected to the power battery and the bus capacitor respectively; A control unit is connected to the first coil of the first main switch and the second coil of the second main switch, and is used to control the on and off states of the first main switch and the second main switch to achieve constant current output of the DCDC power converter.
[0030] Preferably, the constant current output DCDC power converter can receive a control signal from the system control unit to perform switch control, and optionally, can also perform regulation control on its output current.
[0031] In some embodiments of the present invention, see Figure 3 , the DCDC power converter includes a PWM controller, electronic switches Q1 and Q2, a power inductor L1, a current sampling resistor RS1, an input capacitor C1, an output capacitor C2, an input anti-reverse diode D1 and an output anti-reverse diode D2; The PWM controller and the control unit, the gate of the electronic switch Q1 and the gate of the electronic switch Q2; The drain of the electronic switch Q1 is connected to the cathode of the input anti-reverse diode D1 and the first end of the input capacitor C1, the anode of the input anti-reverse diode D1 is connected to the power battery, and the second end of the input capacitor C1 is grounded; The source of the electronic switch Q1 is connected to the first end of the current sampling resistor RS1, and the second end of the current sampling resistor RS1 is connected to the drain of the electronic switch Q2 and the first end of the power inductor L1; The second end of the power inductor L1 is connected to the positive electrode of the output anti-reverse diode D2 and the first end of the output capacitor C2, the negative electrode of the output anti-reverse diode D2 is connected to the bus capacitor, and the second end of the output capacitor C2 is connected to the bus capacitor and the source of the electronic switch Q2.
[0032] Wherein, the control unit is used to start or shut down the PWM controller to start or stop the pre-charge output of the power module; In some embodiments of the present invention, the PWM controller is a buck controller with an output constant current regulation function. Preferably, a synchronous buck controller can be used to further improve the working efficiency of the power converter. For this PWM controller, by controlling the feedback (i.e., voltage feedback loop) of the output voltage of the power converter, it also has the function of regulating and controlling the output voltage of the power converter. In the embodiment of the present invention, since it only involves feedback regulation of the output current of the power converter, a constant current output is performed, and the output voltage of the power converter can eventually be as close to the voltage of the power supply system as possible. Therefore, when applied, the voltage feedback loop of the PWM controller is open-loop processed (i.e., there is no voltage feedback loop).
[0033] In some embodiments of the present invention, the electronic switches Q1 and Q2 are NMOS tubes or IGBTs. In addition, if the PWM controller is a non-synchronous buck controller, the electronic switch Q2 can be replaced by a diode.
[0034] In some embodiments of the present invention, for a selected PWM controller, the output current of the power converter mainly depends on the resistance of the current sampling resistor RS1. Optionally, RS1 can also be placed at the output end, and even the equivalent resistance of the power inductor L1 itself can be used to achieve current collection and feedback control.
[0035] During operation, after the control unit starts the power converter, the input power from the power supply system (such as a power battery) is controlled by the PWM controller to switch the electronic switches Q1 and Q2, and the power is stored and released through the power inductor L1, the input capacitor C1, and the output capacitor C2, so that the power converter outputs a constant current according to the set current value, charges the bus capacitor CX1, and allows the voltage of the bus capacitor CX1 to gradually rise and eventually approach the power supply system voltage.
[0036] In some embodiments of the present invention, the output current value of the power converter is determined by the capacitance value of the bus capacitor CX1, the voltage value of the power supply system, the pre-charge preset voltage value, the pre-charge time and cost factors.
[0037] In some embodiments of the present invention, for a set system, after the capacitance value of the bus capacitor CX1, the power supply system voltage value, and the pre-charge preset voltage value are fixed, the pre-charge time mainly depends on the set pre-charge current (the output current of the power converter). The larger the pre-charge current, the shorter the pre-charge time required.
[0038] Generally, the shorter the pre-charging time is, the better. For the existing control technology of pre-charging resistors and pre-charging switches, if the pre-charging time needs to be shortened, it is necessary to reduce the resistance of the pre-charging resistor, increase the power of the pre-charging resistor, and increase the pre-charging switch. Through the power converter of the present invention, the purpose of increasing the pre-charging current to shorten the pre-charging time can be achieved more economically and simply.
[0039] In addition, compared with the energy efficiency of less than 50% of the existing pre-charging control technology, the efficiency of the power converter in the present invention can usually reach more than 90%, which greatly reduces the energy loss in the pre-charging process.
[0040] Since the power converter has high efficiency, low energy loss and low temperature rise, the number of pre-charge power-ups within a certain period of time is not limited.
[0041] In order to understand the pre-charging situation of the present invention and the prior art, please refer to Figure 4 For the existing pre-charging technology based on pre-charging resistors and pre-charging switches, the voltage of the bus capacitor CX1 increases exponentially. For the pre-charging technology of the present invention, the voltage of the bus capacitor CX1 increases linearly. When the voltage of the bus capacitor CX1 rises to the pre-charging preset voltage, the pre-charging is considered to be completed.
[0042] Regarding the pre-charging time, compared with the existing pre-charging technology (such as Figure 4 The present invention can achieve the purpose of shortening the pre-charging time more economically and simply (e.g. Figure 4 Medium pre-charge duration t1).
[0043] In summary, the beneficial effects of the present invention are as follows: the present invention uses the constant current output of the power converter to charge the bus capacitor, which has the advantages of small size, light weight, low cost, high efficiency and long service life compared to the prior art method of using pre-charging resistors to limit current to charge the capacitor.
[0044] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.
Claims
1. A capacitor pre-charge control circuit based on a power converter, characterized in that: include: A DCDC power converter, a first end of which is connected to a bus capacitor, and a second end of which is connected to a power battery, wherein the DCDC power converter has a controllable constant current output; A first main switch, two contacts of which are connected in parallel to two ends of the DCDC power converter; A second main switch, two contacts of which are connected to the power battery and the bus capacitor respectively; A control unit is connected to the first coil of the first main switch and the second coil of the second main switch, and is used to control the on and off states of the first main switch and the second main switch to achieve constant current output of the DCDC power converter.
2. The capacitor pre-charge control circuit based on the power converter according to claim 1, characterized in that: The DCDC power converter includes a PWM controller, electronic switches Q1 and Q2, a power inductor L1, a current sampling resistor RS1, an input capacitor C1, an output capacitor C2, an input anti-reverse diode D1, and an output anti-reverse diode D2; The PWM controller and the control unit, the gate of the electronic switch Q1 and the gate of the electronic switch Q2; The drain of the electronic switch Q1 is connected to the cathode of the input anti-reverse diode D1 and the first end of the input capacitor C1, the anode of the input anti-reverse diode D1 is connected to the power battery, and the second end of the input capacitor C1 is grounded; The source of the electronic switch Q1 is connected to the first end of the current sampling resistor RS1, and the second end of the current sampling resistor RS1 is connected to the drain of the electronic switch Q2 and the first end of the power inductor L1; The second end of the power inductor L1 is connected to the positive electrode of the output anti-reverse diode D2 and the first end of the output capacitor C2, the negative electrode of the output anti-reverse diode D2 is connected to the bus capacitor, and the second end of the output capacitor C2 is connected to the bus capacitor and the source of the electronic switch Q2.
3. The capacitor pre-charge control circuit based on the power converter according to claim 2, characterized in that: The control unit is used to start or shut down the PWM controller to start or stop the pre-charge output of the power module.
4. The capacitor pre-charge control circuit based on the power converter according to claim 2, characterized in that: The PWM controller is a buck controller with an output constant current regulation function.
5. The capacitor pre-charge control circuit based on the power converter according to claim 2, characterized in that: The electronic switches Q1 and Q2 are NMOS tubes or IGBTs.
6. The capacitor pre-charge control circuit based on the power converter according to claim 2, characterized in that: For the selected PWM controller, the output current of the power converter mainly depends on the resistance value of the current sampling resistor RS1.
7. The capacitor pre-charge control circuit based on the power converter according to claim 2, characterized in that: The output current value of the power converter is determined by the capacitance value of the bus capacitor CX1, the voltage value of the power supply system, the pre-charge preset voltage value, the pre-charge time and cost factors.
8. The capacitor pre-charge control circuit based on the power converter according to claim 7, characterized in that: If the capacitance value of the bus capacitor CX1, the voltage value of the power supply system and the pre-charge preset voltage value are fixed, the pre-charge time depends on the output current of the power converter. The larger the pre-charge current, the shorter the pre-charge time.