Active and passive hybrid filter circuit of direct current bus

Abstract

The embodiment of the invention relates to the technical field of direct current power supply, and discloses an active and passive hybrid filter circuit of a direct current bus. Comprising a passive filtering module, an active filtering module and a power supply module, and the power supply module is used for providing electric energy for the active filtering module; the passive filtering module is used for filtering interference signals on the direct-current bus by adopting a passive device; and the active filtering module is used for detecting current on the direct current bus by adopting an active device, outputting reverse injection current to the direct current bus and inhibiting interference signals on the direct current bus. The passive filtering module adopts CLC or LCLC filtering to suppress alternating current interference on the direct current bus, and the active filtering module adopts a current detection and current injection mode to offset direct current interference on the direct current bus, so that the direct current stability of the direct current bus is improved, and specified requirements are met.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of direct current power supply, and in particular to an active-passive hybrid filter circuit of a direct current bus. Background Art

[0002] In the field of high-power conversion, such as electric vehicles, photovoltaics, and energy storage, a DC power supply is used to provide power to the converter. In electric vehicles, the battery pack provides 400V DC or 800V DC to the electric drive system. In the process of converting DC power to AC power, the electric drive system will generate interference signals, affecting the stability of the DC power.

[0003] At present, passive filtering is basically used to filter interference signals on the DC bus. If the class 4 and class 5 limits of EMI conducted interference are met, a large inductor is required to filter out the low-frequency AC interference on the DC bus. The cost of selecting a large inductor is an increase in volume, weight and cost.

[0004] Therefore, how to filter and suppress the interference on the DC bus and reduce the weight, volume, and cost is a problem that needs to be solved urgently. Summary of the invention

[0005] The purpose of the embodiments of the present invention is to at least provide an active-passive hybrid filter circuit for a DC bus, which can at least solve the interference problem on the DC bus and at least reduce the AC and DC interference signals on the DC bus.

[0006] To solve the above technical problems, at least one embodiment of the present application provides an active-passive hybrid filter circuit for a DC bus, comprising a passive filtering module, an active filtering module and a power supply module, wherein the power supply module is used to provide power to the active filtering module; the passive filtering module is used to filter the interference signal on the DC bus using passive devices; the active filtering module is used to detect the current on the DC bus using active devices, and output a reverse injection current to the DC bus, so as to suppress the interference signal on the DC bus.

[0007] The embodiment of the present application provides an active-passive hybrid filter circuit for a DC bus. Compared with the prior art, it uses a passive filter module to filter the AC interference signal on the DC bus, and uses an active filter module to inject a reverse current into the negative pole of the DC bus to offset the DC interference signal. Therefore, the interference problem on the DC bus is solved and the stability of the DC signal on the DC bus is ensured.

[0008] In addition, the passive filtering module includes: a first-stage LC filtering unit, which includes a common-mode filtering circuit and a differential-mode filtering circuit to filter the common-mode interference signal and the differential-mode interference signal on the DC bus.

[0009] In addition, the common-mode filtering circuit includes: a first coil, a first capacitor and a second capacitor, the first coil is arranged around the DC bus, one end of the first capacitor is connected to the positive pole of the DC bus, and the other end is connected to the ground (PE), one end of the second capacitor is connected to the negative pole of the DC bus, and the other end is connected to the ground (PE), which is used to suppress the common-mode interference between the positive and negative poles of the DC bus.

[0010] In addition, the differential mode filter circuit includes: a third capacitor, one end of which is connected to the positive electrode of the DC bus, and the other end is connected to the negative electrode of the DC bus, for suppressing differential mode interference between the positive and negative electrodes of the DC bus.

[0011] In addition, the active-passive hybrid filter circuit of the DC bus further includes: a second-stage LC filter unit, the second-stage LC filter unit has the same structure as the first-stage LC filter unit, and the two-stage filter units are used to suppress interference signals in different frequency ranges; the second-stage LC filter unit is arranged at one end close to the load, and is used to suppress the resonance formed by the LC filter unit and the load capacitor and filter the AC interference signal on the DC bus; the first-stage LC filter unit is arranged at one end close to the active filter module, and is used to perform impedance matching with the active filter module.

[0012] In addition, the active-passive hybrid filter circuit of the DC bus also includes: a second-stage C filter unit, the second-stage C filter unit includes three capacitors, and a capacitor is respectively arranged between the DC bus, between the positive pole of the DC bus and the earth (PE), and between the negative pole of the DC bus and the earth (PE); the second-stage C filter unit is arranged at one end close to the load, and is used to filter the AC interference signal on the DC bus; the first-stage LC filter unit is arranged at one end close to the active filter module, and is used to perform impedance matching with the active filter module.

[0013] In addition, the active filtering module includes an induction unit and an active filtering unit connected in sequence, the induction unit is used to sense the current on the DC bus, and the active filtering unit is used to amplify and reverse the induced current of the induction unit to obtain a reverse injection current, which is input into the DC bus to suppress the interference signal on the DC bus, thereby achieving the cancellation of the DC interference signal on the DC bus.

[0014] In addition, the induction unit includes an induction coil wrapped around the DC bus and used to sense the current on the DC bus; the active filtering unit includes: a current sampling circuit and an amplifying and inverting circuit connected in sequence, the current sampling circuit is used to convert the induced current signal of the induction unit into a voltage signal, and the amplifying and inverting circuit is used to amplify and invert the voltage signal to obtain a reverse injection current signal, which is used to offset the DC interference signal on the DC bus.

[0015] In addition, the amplifying reverse circuit includes: a first-stage amplifying reverse subcircuit and a second-stage amplifying subcircuit connected in sequence, the input end of the first-stage amplifying reverse subcircuit is connected to the output end of the current sampling circuit, and its output end is connected to the input end of the second-stage amplifying subcircuit, and the output end of the second-stage amplifying subcircuit is fed back to the input end of the first-stage amplifying reverse subcircuit; the first-stage amplifying reverse subcircuit is used to amplify the voltage signal once, and the second-stage amplifying subcircuit is used to amplify the voltage signal a second time and convert it into current to obtain an amplified reverse current, and feed the amplified reverse voltage back to the first-stage amplifying reverse subcircuit. The current on the induced DC bus is converted into voltage, amplified and reversed, and a reverse injection current is obtained, which is used to input into the negative pole of the DC bus to offset the DC interference signal on the DC bus and improve the stability of the DC.

[0016] In addition, the power supply module includes: an EMI filter unit, a power conversion unit, and a filter output unit connected in sequence. The EMI filter unit and the filter output unit are used for EMI filtering. The power conversion unit is used to convert the first power supply voltage into the second power supply voltage, boost and filter the power supply, thereby improving the power supply stability of the active filter module. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0018] Figure 1 is a schematic structural diagram of an active-passive hybrid filter circuit provided according to an embodiment of the present invention;

[0019] Figure 2 is a schematic structural diagram of an active filter unit provided according to an embodiment of the present invention;

[0020] Figure 3 is a schematic structural diagram of a power module provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, it can be understood by those skilled in the art that in the embodiments of the present invention, many technical details are provided to enable readers to better understand the present invention. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present invention can be implemented.

[0022] Embodiment 1:

[0023] The embodiment of the present invention relates to an active-passive hybrid filter circuit of a DC bus, comprising a passive filter module, an active filter module and a power supply module, wherein the power supply module is used to provide electric energy to the active filter module; the passive filter module is used to filter interference signals on the DC bus by using passive devices; the active filter module is used to detect the current on the DC bus by using active devices, and output a reverse injection current to the DC bus, so as to suppress the interference signals on the DC bus.

[0024] The embodiment of the present application provides an active-passive hybrid filter circuit for a DC bus. Compared with the prior art, it uses a passive filter module to filter the AC interference signal on the DC bus, and uses an active filter module to inject a reverse current into the negative pole of the DC bus to offset the DC interference signal. Therefore, the interference problem on the DC bus is solved and the stability of the DC signal on the DC bus is ensured.

[0025] The following is a detailed description of the implementation details of an active-passive hybrid filter circuit for a DC bus in this embodiment. The following content is only provided for easy understanding of the implementation details and is not necessary for implementing this solution.

[0026] An embodiment of the present invention provides an active-passive hybrid filter circuit for a DC bus, comprising: a passive filter module, an active filter module and a power supply module, wherein the passive filter module and the active filter module are used to detect the resonance on the DC bus and offset the resonance on the DC bus, and the power supply module is used to provide electric energy to the active filter module.

[0027] The passive filtering module includes a two-stage LC filtering unit for suppressing common-mode interference signals and differential-mode interference signals of different frequencies.

[0028] The two-stage filter units have the same structure, including a common-mode filter circuit and a differential-mode filter circuit. The common-mode filter circuit is used to suppress common-mode interference on the DC bus, and the differential-mode filter circuit is used to suppress differential-mode interference on the DC bus.

[0029] The first-stage filtering unit is arranged at one end close to the load, and is used to suppress interference on the load side. The first-stage filtering unit includes a first common-mode filtering circuit and a first differential-mode filtering circuit.

[0030] The first common mode filter circuit includes a first coil, a first capacitor and a second capacitor. The first coil is disposed around the DC bus to suppress resonance in a first frequency range.

[0031] One end of the first capacitor is connected to the positive pole of the DC bus, and the other end is connected to the earth PE. One end of the second capacitor is connected to the negative pole of the DC bus, and the other end is connected to the earth PE. The first capacitor and the second capacitor are used to suppress common mode interference in the second frequency range.

[0032] The resonance in the first frequency range is formed between the first capacitor, the second capacitor and the load capacitor.

[0033] The first differential mode filter circuit includes a third capacitor, one end of the third capacitor is connected to the positive electrode of the DC bus, and the other end of the third capacitor is connected to the negative electrode of the DC bus, and is used to suppress differential mode interference in the second frequency range.

[0034] The second-stage filtering unit is arranged at one end close to the active filtering module and is used for impedance matching with the active filtering module. It includes a second common-mode filtering circuit and a second differential-mode filtering circuit.

[0035] The second common mode filter circuit includes a second coil, a fourth capacitor and a fifth capacitor. The second coil is arranged around the DC bus and is used for impedance matching with the active filter module to ensure that the source impedance is greater than the load impedance at low frequency.

[0036] One end of the fourth capacitor is connected to the positive pole of the DC bus, and the other end is connected to the earth PE. One end of the fifth capacitor is connected to the negative pole of the DC bus, and the other end is connected to the earth PE. The fourth capacitor and the fifth capacitor are used to suppress common mode interference in the third frequency range.

[0037] The second differential mode filter circuit includes a sixth capacitor, one end of the sixth capacitor is connected to the positive electrode of the DC bus, and the other end is connected to the negative electrode of the DC bus, and is used to suppress differential mode interference in the third frequency range.

[0038] In another specific embodiment of the present application, the passive filtering module includes a C filtering unit and an LC filtering unit. The difference between the C filtering unit and the LC filtering unit is that the C filtering unit includes a capacitor, that is, the coil reserved capacitor is cancelled in the LC filtering unit. In particular, when the first capacitor, the second capacitor and the load capacitor do not form resonance, a combination of the C filtering unit and the LC filtering unit is used to perform passive filtering.

[0039] Specifically, the C filter circuit in the C filter unit includes three capacitors, which are respectively arranged between the DC bus, between the positive pole of the DC bus and the earth PE, and between the negative pole of the DC bus and the earth PE. The negative pole of the car battery is connected to the earth PE.

[0040] The active filter module includes an induction unit and an active filter unit connected in sequence. The induction unit is used to sense the current on the DC bus. The active filter unit is used to amplify and reverse the induced current of the induction unit to obtain a reverse injection current, which is input into the DC bus to suppress the noise interference signal on the DC bus.

[0041] The induction unit comprises an induction coil for inducing current on the DC bus.

[0042] The active filter unit comprises a current sampling circuit and an amplifying inverting circuit which are connected in sequence.

[0043] The current sampling circuit is connected to the sensing unit and is used to convert the current signal of the sensing unit into a voltage signal. The amplifying and inverting circuit is used to amplify and invert the voltage signal and output it to the DC bus to offset the noise interference on the DC bus.

[0044] The current sampling circuit includes a first filter capacitor and a sampling resistor. One end of the first filter capacitor is connected to one end of the induction coil, and the other end is connected to one end of the sampling resistor. The other end of the sampling resistor is connected to the other end of the induction coil. The two ends of the sampling resistor serve as two output ends of the current sampling circuit.

[0045] The amplifying and inverting circuit comprises: a first-stage amplifying and inverting sub-circuit and a second-stage amplifying and inverting sub-circuit connected in sequence, and is used for amplifying and inverting the voltage at both ends of the sampling circuit.

[0046] The first-stage amplifying reverse subcircuit is used to amplify the voltage signal once, and the second-stage amplifying subcircuit is used to amplify and reverse the voltage signal amplified for the first time, obtain an amplified reverse voltage, convert it into an amplified reverse current, and feed it back to the first-stage amplifying reverse subcircuit.

[0047] The first-stage amplification reverse subcircuit includes an amplifier and its peripheral circuits, the positive input end of the amplifier is connected to one end of the second resistor, the other end of the second resistor is connected to one end of the sampling resistor and one end of the filter capacitor, the negative input end of the amplifier is connected to one end of the third resistor, one end of the fourth resistor, and one end of the second capacitor, and the other end of the third resistor is connected to the other end of the sampling resistor. The other end of the fourth resistor and the other end of the second capacitor are connected to the output end of the second amplification circuit, and the output end of the amplifier is connected to the input end of the second-stage amplification subcircuit. The second capacitor is connected between the negative input end and the output end, which resists the self-excited resonance of the first-stage amplification reverse subcircuit and enhances the loop stability.

[0048] The second-stage amplifier sub-circuit adopts a class AB power amplifier circuit, including two diodes and two transistors. The cathode of the first diode and the anode of the second diode are connected to the output end of the amplifier, the anode of the first diode is connected to one end of the fifth resistor and the control electrode of the first NPN transistor, the other end of the fifth resistor and the input electrode of the first NPN transistor are connected to the power supply end, the output electrode of the first NPN transistor is connected to one end of the seventh resistor, and the other end of the seventh resistor serves as the output end of the second-stage amplifier sub-circuit, and is connected to the other end of the fourth resistor, the other end of the second capacitor, and the other end of the eighth resistor.

[0049] The cathode of the second diode is connected to one end of the sixth resistor and the control electrode of the second PNP transistor. The other end of the sixth resistor and the output electrode of the second PNP transistor are grounded. The input electrode of the second PNP transistor is connected to one end of the eighth resistor. The other end of the eighth resistor serves as the output end of the second-stage amplifier sub-circuit and is connected to the other end of the fourth resistor, the other end of the second capacitor, and the other end of the seventh resistor.

[0050] The output end of the second-stage amplifier subcircuit is connected to one end of the ninth resistor, the other end of the ninth resistor is connected to one end of the third capacitor, and the other end of the third capacitor serves as the output end of the active filter unit and is used to be connected to the negative pole of the DC bus.

[0051] The first-stage amplifying reverse subcircuit amplifies and reverses the voltage across the sampling resistor, and the second-stage amplifying subcircuit performs secondary amplification on the output of the first-stage amplifying reverse subcircuit and feeds it back to the first-stage amplifying reverse subcircuit to improve output stability and convert the amplified reverse voltage into an amplified reverse current.

[0052] The power module includes an EMI filter unit, a power conversion unit, and a filter output unit connected in sequence. The EMI filter unit is used to eliminate the EMI interference of the power conversion unit on the first power supply, the power conversion unit is used to convert the first power supply voltage into the second power supply voltage, and the filter output unit is used to resist the interference of the load circuit from affecting the first power supply.

[0053] The EMI filtering unit includes two magnetic beads and a first common-mode filtering coil, wherein one end of the first magnetic bead is connected to the power supply end of the first power supply, and the other end is connected to one end of the fourth capacitor and the first end of the first common-mode filtering coil, one end of the second magnetic bead is connected to the ground end of the first power supply, and the other end is connected to the other end of the fourth capacitor and the second end of the first common-mode filtering coil, the third end of the first common-mode filtering coil is connected to the first end of the input side of the power conversion unit and one end of the fifth capacitor, and the fourth end of the first common-mode filtering coil is connected to the second end of the input side of the power conversion unit and the other end of the fifth capacitor, wherein the first common-mode filtering coil includes two coils, wherein the first end and the third end are the two ends of one coil, and the second end and the fourth end are the two ends of another coil.

[0054] The power conversion unit includes a power conversion chip. The power conversion chip has a spread spectrum function, which can reduce the external interference of the chip itself.

[0055] The filter output unit also adopts an EMI filter structure to resist the interference of the power module from affecting the first power supply, and includes two magnetic beads and a second common mode filter coil.

[0056] One end of the third magnetic bead is connected to the first end of the output side of the power conversion chip, and the other end is connected to one end of the sixth capacitor and the first end of the second common-mode filter coil. One end of the fourth magnetic bead is connected to the second end of the output side of the power conversion chip, and the other end is connected to the other end of the sixth capacitor and the second end of the second common-mode filter coil. The third end of the second common-mode filter coil is connected to one end of the seventh capacitor and serves as the positive output end of the power module, that is, the power end of the second power supply. The fourth end of the second common-mode filter coil is connected to the other end of the seventh capacitor and serves as the negative output end of the power module, that is, the ground end of the second power supply.

[0057] The present embodiment provides an active-passive hybrid filter circuit for a DC bus, which adopts a passive filter module, an active filter module and a power supply module. Since the passive filter module can suppress the AC interference signal on the DC bus, the active filter module offsets the DC interference signal by injecting reverse current, and the power supply module can provide electric energy to the active filter module through voltage conversion, the interference problem on the DC bus is solved and the DC stability on the DC bus is guaranteed.

[0058] Embodiment 2

[0059] The embodiment of the present invention is a detailed description of the above embodiment 1, see Figure 1 and Figure 3 .

[0060] In this specific embodiment, the voltage on the DC bus of the battery pack used in the electric vehicle is 400V high voltage, and the input voltage of the power module powered by the battery is 12V. The voltages of different values ​​in other application scenarios are similar and will not be repeated.

[0061] In this embodiment, an active-passive hybrid filter circuit of a DC bus is provided. Figure 1 As shown, it includes an active filtering module and a passive filtering module. The active filtering module includes an induction coil CT and an active filtering unit. The passive filtering module includes a two-stage LC filtering unit.

[0062] The first-stage LC filter unit is located on a side close to the active filter module and is used to suppress AC interference signals on the high-voltage DC bus. It includes coil L2, capacitor C9, capacitor C10 and capacitor C8. Coil L2, capacitor C9 and capacitor C10 form a common-mode filter circuit for common-mode filtering, and capacitor C8 is used for differential-mode filtering.

[0063] The coil L2 is wound around the high-voltage DC bus, one end of the capacitor C9 is connected to the positive electrode of the high-voltage DC bus, and the other end thereof is connected to the earth PE, and one end of the capacitor C10 is connected to the negative electrode of the high-voltage DC bus, and the other end thereof is connected to the earth PE.

[0064] The coil L2 and the active filter module are used to perform impedance matching adjustment to ensure that the source impedance is greater than the load impedance at low frequencies and that the active filter module can work normally and stably.

[0065] The second-stage LC filter unit is located on the side close to the load and is used to suppress the AC interference signal on the high-voltage DC bus. It includes coil L1, capacitor C12, capacitor C13 and capacitor C11. Coil L1, capacitor C12 and capacitor C13 form a common-mode filter circuit for common-mode filtering, and capacitor C11 is used for differential-mode filtering.

[0066] The coil L1 is wound around the high-voltage DC bus, one end of the capacitor C12 is connected to the positive electrode of the high-voltage DC bus, and the other end thereof is connected to the earth PE, and one end of the capacitor C13 is connected to the negative electrode of the high-voltage DC bus, and the other end thereof is connected to the earth PE.

[0067] The coil L1 is used to suppress the resonance in the first frequency range, and the resonance in the first frequency range is generated by the capacitor C12, the capacitor C13 and the load capacitor.

[0068] In a specific embodiment of the present application, capacitors C9 and C10 are large-capacity capacitors with a capacitance value ranging from nF level, such as between 1nF and 10nF, for suppressing common-mode interference signals above 30MHz.

[0069] Capacitor C8 also adopts a large-capacity capacitor, and its capacitance value ranges from nF level, such as between 1uF and 100uF, and is mainly used to suppress differential mode interference signals above 30MHz.

[0070] The first frequency is 1 MHz, and capacitors C12 and C13 are large-capacity capacitors with capacitance values ​​ranging from nF level, such as between 68nF and 330nF, for suppressing common-mode interference signals below 30MHz.

[0071] Capacitor C11 also adopts a large-capacity capacitor, and its capacitance value ranges from uF level, such as between 1uF and 4.7uF, and is mainly used to suppress differential mode interference signals below 30MHz.

[0072] In another specific embodiment of the present application, the second-stage LC filter unit has no coil and only includes a capacitor C, and the connection method of the capacitor remains unchanged.

[0073] The induction coil CT in the active filter module is also wrapped around the high-voltage DC bus. The active filter module uses current detection and current reverse injection to offset the DC interference signal on the high-voltage DC bus.

[0074] The ideal calculation formula for insertion loss of current detection and current reverse injection is as follows:

[0075]

[0076] Where IL is the insertion loss, ZS is the source impedance, ZL is the load impedance, and G is the active filter gain.

[0077] Ideally, when the source impedance is much larger than the load impedance, the larger the G, the greater the insertion loss.

[0078] Active filter units, such as Figure 2 As shown, one end of the capacitor C1 is connected to one end of the induction coil CT, and the other end is connected to one end of the resistor R1 and one end of the resistor R2. The other end of the resistor R1 is connected to the other end of the induction coil CT and one end of the resistor R3.

[0079] The current sampling circuit includes capacitor C1 and resistor R1. The current on the high-voltage DC bus is sensed by the induction coil CT, and after coupling and filtering by capacitor C1, an induced voltage is generated at both ends of resistor R1 and input into the amplifying reverse circuit.

[0080] The first-stage amplification and inversion subcircuit includes an amplifier U1 and peripheral circuits, and is used to amplify and invert the sampled voltage across the resistor R1.

[0081] The other end of the resistor R2 is connected to the positive input of the amplifier U1, the other end of the resistor R3 is connected to the negative input of the amplifier U1, one end of the resistor R4, and one end of the capacitor C2, and the output of the amplifier U1 is connected to the input of the second stage amplifier circuit.

[0082] The second-stage amplifier subcircuit adopts a class AB power amplifier circuit, including an NPN transistor Q1 and a PNP transistor Q2. The cathode of the diode D1 and the anode of the diode D2 are connected to the output end of the amplifier U1, the anode of the diode D1 is connected to the base of the NPN transistor Q1 and one end of the resistor R5, the other end of the resistor R5 and the collector of the transistor Q1 are connected to the power supply end of the DC 24V power supply, and the emitter of the transistor Q1 is connected to one end of the resistor R7; the cathode of the diode D2 is connected to the base of the PNP transistor Q2 and one end of the resistor R6, the other end of the resistor R6 and the collector of the transistor Q2 are connected to the ground end of the DC 24V power supply, and the emitter of the transistor Q2 is connected to one end of the resistor R8.

[0083] The other end of the resistor R7 and the other end of the resistor R8 are connected together as the output end and feedback node of the second-stage amplifier sub-circuit, and are connected to the other end of the resistor R4, the other end of the capacitor C2, and one end of the resistor R9. One end of the resistor R9 is connected to one end of the capacitor C3. The other end of the capacitor C3, as the output end of the active filter unit, is connected to the negative electrode of the DC bus.

[0084] Connecting the feedback node to the output of the class AB amplifier is conducive to more stable feedback. Capacitor C2 is set to suppress self-oscillation and enhance loop stability.

[0085] After the sampling voltage is amplified by the amplifier U1, when it is higher than a certain value, such as a positive voltage, the diode D2 is turned on, the transistor Q2 is turned on, and a negative voltage is output through the resistor R8, and a current flowing through the resistor R9 and the capacitor C3 is output; when it is lower than a certain value, such as a negative voltage, the diode D1 is turned on, the transistor Q1 is turned on, and a positive voltage is output through the resistor R7, and a current flowing through the resistor R9 and the capacitor C3 is output.

[0086] The induction coil CT induces the common-mode current I1, generates an induced common-mode voltage on the resistor R1, and the operational amplifier U1 reversely amplifies the induced voltage. Finally, through a class AB power amplifier, the current I2 is injected into the main loop of the high-voltage DC bus.

[0087] The main function of the active filter module adopts a first-order operational amplifier to ensure the stability of the loop and avoid the possibility of phase delay and poor stability caused by using multiple orders.

[0088] At the same time, in order to suppress the high-frequency oscillation problem, a capacitor C2 is added between the operational amplifier feedback, and the capacitance of capacitor C2 is between 10pF and 1nF. The main function of capacitor C2 includes reducing the gain of the frequency band above 30MHz to ensure that the operational amplifier U1 will not self-oscillate at high frequencies.

[0089] The current flowing out from the output end of the active filter unit flows into the negative pole of the DC bus. Because it is opposite to the sampling current, it enters the ground (PE) through capacitors C13 and C10 on the one hand, and enters the ground (PE) through capacitors C8, C9, C11, and C12 on the other hand, offsetting the DC interference on the negative and positive poles of the DC bus and improving the stability of the DC bus current.

[0090] Power modules, such as Figure 3 As shown, it is used to convert 12V DC voltage into 24V DC voltage.

[0091] The EMI filtering unit is close to the first power supply 12V and is used to protect the power conversion chip from EMI interference to the first power supply. It includes magnetic beads L5 and L6, capacitors C4 and C5, and a common mode filtering coil Lcm1.

[0092] One end of the magnetic bead L5 is connected to the power supply end of the 12V power supply through the fuse, and the other end is connected to one end of the capacitor C4 and the first end of the common mode filter coil Lcm1; one end of the magnetic bead L6 is connected to the ground GND end of the 12V power supply, and the other end is connected to the other end of the capacitor C4 and the second end of the common mode filter coil Lcm1, the third end of the common mode filter coil Lcm1 is connected to one end of the capacitor C5 and the first end of the input side of the boost chip, and the fourth end of the common mode filter coil Lcm1 is connected to the other end of the capacitor C5 and the second end of the input side of the boost chip.

[0093] The power conversion unit includes a boost chip or a buck chip, depending on the specific situation, and is not limited to using only a boost chip. In this specific embodiment, a boost chip is used to convert a 12V voltage into a 24V voltage.

[0094] In a specific embodiment of the present application, the boost chip or the buck chip has a spread spectrum function, which can spread the switching frequency to reduce the interference it generates to the external power supply.

[0095] The filter output unit also adopts an EMI filter structure, which is the same as the EMI filter unit structure, and is used to suppress the influence of the interference of the entire circuit on the first power supply. It includes magnetic beads L3, magnetic beads L4, capacitors C6, capacitors C7 and common mode filter coil Lcm2.

[0096] One end of the magnetic bead L3 is connected to the first end of the output side of the boost chip, the other end of the magnetic bead L3 is connected to one end of the capacitor C6 and the first end of the common-mode filter coil Lcm2, one end of the magnetic bead L4 is connected to the second end of the output side of the boost chip, the other end of the magnetic bead L4 is connected to the other end of the capacitor C6 and the second end of the common-mode filter coil Lcm2; the third end of the common-mode filter coil Lcm2 is connected to one end of the capacitor C7, and serves as the positive output end of the filter output unit, outputting a 24V DC voltage; the fourth end of the common-mode filter coil Lcm2 is connected to the other end of the capacitor C7, and serves as the negative output end of the filter output unit, serving as the ground end of the 24V DC voltage.

[0097] Embodiment 3

[0098] An embodiment of the present invention further provides an active-passive hybrid filter for a DC bus, comprising an active-passive hybrid filter circuit for a DC bus as described in Embodiment 1 and Embodiment 2 of the present application, to suppress and offset interference on the DC bus and meet the CLASS 5 limit requirements.

[0099] It should be understood that the expressions "mechanism", "device", "component" and the like used in this application are only a method for distinguishing different components, elements, parts, portions or assemblies at different levels. However, if other words can achieve the same purpose, the word can be replaced by other expressions.

[0100] Those skilled in the art can understand that the above-mentioned embodiments are specific examples for realizing the present invention, and in practical applications, the technical features of the above-mentioned embodiments can be arbitrarily combined. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification, and various changes can be made in form and details without departing from the spirit and scope of the present invention.

Claims

1. An active-passive hybrid filter circuit for a DC bus, characterized in that: Including passive filter module, active filter module and power supply module, The power supply module is used to provide electric energy to the active filter module; The passive filtering module is used to filter the interference signal on the DC bus using passive devices; The active filter module is used to detect the current on the DC bus using active devices, and output a reverse injection current to the DC bus to suppress interference signals on the DC bus.

2. The active-passive hybrid filter circuit of a DC bus according to claim 1, characterized in that: The passive filtering module comprises: a first-stage LC filtering unit, wherein the first-stage LC filtering unit comprises a common-mode filtering circuit and a differential-mode filtering circuit.

3. The active-passive hybrid filter circuit of a DC bus according to claim 2, characterized in that: The common-mode filtering circuit comprises: a first coil, a first capacitor and a second capacitor, wherein the first coil is arranged around a DC bus, one end of the first capacitor is connected to a positive electrode of the DC bus and the other end is connected to the ground, and one end of the second capacitor is connected to a negative electrode of the DC bus and the other end is connected to the ground, for suppressing common-mode interference; The differential mode filter circuit comprises: a third capacitor, one end of which is connected to the positive electrode of the DC bus, and the other end of which is connected to the negative electrode of the DC bus, for suppressing differential mode interference.

4. The active-passive hybrid filter circuit of a DC bus according to claim 2, characterized in that: Also includes: The second-stage LC filter unit has the same structure as the first-stage LC filter unit. The two-stage filter units are used to suppress interference signals in different frequency ranges. The second stage LC filter unit is arranged at one end close to the load; The first-stage LC filter unit is arranged at one end close to the active filter module and is used for impedance matching with the active filter module.

5. The active-passive hybrid filter circuit of a DC bus according to claim 2, characterized in that: Also includes: The second-stage C filter unit includes three capacitors, one capacitor is respectively arranged between the DC bus, between the positive pole of the DC bus and the ground, and between the negative pole of the DC bus and the ground; The second stage C filter unit is arranged at one end close to the load; The first-stage LC filter unit is arranged at one end close to the active filter module and is used for impedance matching with the active filter module.

6. The active-passive hybrid filter circuit of a DC bus according to claim 1, characterized in that: The active filtering module includes an induction unit and an active filtering unit connected in sequence, the induction unit is used to sense the current on the DC bus, and the active filtering unit is used to amplify and reverse the induced current of the induction unit to obtain a reverse injection current, which is input into the DC bus to suppress the interference signal on the DC bus.

7. The active-passive hybrid filter circuit of a DC bus according to claim 6, characterized in that: The induction unit includes an induction coil wrapped around the DC bus; The active filter unit includes: a current sampling circuit and an amplifying and inverting circuit connected in sequence, wherein the current sampling circuit is used to convert the induced current signal of the induction unit into a voltage signal, and the amplifying and inverting circuit is used to amplify and invert the voltage signal to obtain a reverse injection current signal.

8. The active-passive hybrid filter circuit of a DC bus according to claim 7, characterized in that: The amplifying reverse circuit comprises: a first-stage amplifying reverse subcircuit and a second-stage amplifying subcircuit connected in sequence, the input end of the first-stage amplifying reverse subcircuit is connected to the output end of the current sampling circuit, the output end of the first-stage amplifying reverse subcircuit is connected to the input end of the second-stage amplifying subcircuit, and the output end of the second-stage amplifying subcircuit is fed back to the input end of the first-stage amplifying reverse subcircuit; The first-stage amplifying reverse subcircuit is used to amplify the voltage signal once, and the second-stage amplifying subcircuit is used to amplify the voltage signal a second time and convert it into current to obtain an amplified reverse current, and feed the amplified reverse voltage back to the first-stage amplifying reverse subcircuit.

9. The active-passive hybrid filter circuit of a DC bus according to claim 1, characterized in that: The power module comprises: an EMI filter unit, a power conversion unit and a filter output unit which are connected in sequence. The EMI filter unit and the filter output unit are used for EMI filtering, and the power conversion unit is used for converting a first power supply voltage into a second power supply voltage.

10. The active-passive hybrid filter circuit of a DC bus according to claim 9, characterized in that: The EMI filter unit and the filter output unit have the same structure, including two magnetic beads and a common mode filter coil, one end of a magnetic bead serves as the input end of the EMI filter unit, the two input ends of the common mode filter coil are respectively connected to the other end of a magnetic bead, the two output ends of the common mode filter coil serve as the output end of the EMI filter unit, a filter capacitor is arranged between the two input ends of the common mode filter coil, and a filter capacitor is arranged between the two output ends of the common mode filter coil.

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