Active electromagnetic interference filter, switching power supply and power equipment

Abstract

The invention discloses an active electromagnetic interference filter, a switching power supply and power equipment. The active electromagnetic interference filter is coupled to a positive power supply line and a negative power supply line between a power supply of the SMPS and the power conversion circuit. The filtering inductor of the sampling circuit of the active electromagnetic interference filter is coupled to the positive electrode power supply line and the negative electrode power supply line, and can filter EMI noise of the SMPS. The sampling circuit collects voltage signals of the dotted terminal of the filter inductor or two ports of any inductor winding, pure common-mode noise components can be obtained, and noise separation is not needed. The active electromagnetic interference filter does not need to additionally introduce a sampling device, and is simple in circuit, high in applicability and small in size. Common-mode noise components of the positive electrode power supply line and the negative electrode power supply line are injected into the ground line after being subjected to reverse-phase amplification through the integral amplifier, and common-mode EMI noise of the positive electrode power supply line and the negative electrode power supply line is restrained.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to an active electromagnetic interference filter, a switching power supply and a power device. Background Art

[0002] Switching mode power supply (SMPS) is a high-frequency power conversion device. The function of SMPS is to convert a voltage level into the voltage or current required by the user through different forms of architecture. SMPS has the advantages of small size, light weight, and high power density, and is widely used in industrial automation control, scientific research equipment, industrial control equipment, communication equipment, power equipment and other fields. However, when SMPS switches, it will generate rapidly changing switching current di / dt and switching voltage du / dt, thereby generating electromagnetic interference noise. The electromagnetic interference noise generated by SMPS will affect the normal operation of other devices inside it and other surrounding equipment. Summary of the invention

[0003] In order to solve the above problems, an active electromagnetic interference filter is provided in the embodiment of the present application. The active EMI filter has the advantages of small size, light weight, low power loss of the circuit, etc., and is more widely used in various fields. In addition, the present application also provides a switching power supply and power equipment corresponding to the active electromagnetic interference filter.

[0004] To this end, the following technical solutions are adopted in the embodiments of the present application:

[0005] In a first aspect, an embodiment of the present application provides an active electromagnetic interference filter, comprising: a sampling circuit, comprising a filter inductor, a first resistor, and a second resistor, the filter inductor being coupled to a positive power supply line and a negative power supply line, and being used to filter the electromagnetic interference noise of the electrical signals of the positive power supply line and the negative power supply line; the first resistor and the second resistor being respectively coupled to two ports of the filter inductor, and being used to collect voltage signals of the two ports of the filter inductor; an inverting amplifier circuit, coupled between the first resistor and the second resistor and a ground line, and being used to receive the voltage signal of the first resistor and the voltage signal of the second resistor, superimposing the voltage signal of the first resistor and the voltage signal of the second resistor, and inverting and amplifying the superimposed voltage signal.

[0006] In this embodiment, the active electromagnetic interference filter is generally coupled to the positive power supply line and the negative power supply line between the power supply of the SMPS and the power conversion circuit. The filter inductor of the sampling circuit of the active electromagnetic interference filter is coupled to the positive power supply line and the negative power supply line, which can filter the EMI noise of the SMPS. The sampling circuit collects the voltage signal of the same-name end of the filter inductor or the two ports of any inductor winding, and a pure common-mode noise component can be obtained without noise separation. The active electromagnetic interference filter does not require the introduction of additional sampling devices, the circuit is simple, the applicability is relatively strong, and the volume is relatively small. The noise components of the positive power supply line and the negative power supply line are inverted and amplified by the integral amplifier, and then injected into the ground line to suppress the EMI noise of the positive power supply line and the negative power supply line.

[0007] In one embodiment, the positive power supply line and the negative power supply line are coupled between a power supply source and a power conversion circuit, and are used to transmit an electrical signal of the power supply source to the power conversion circuit.

[0008] In this implementation, the active electromagnetic interference filter is coupled between the power supply of the SMPS and the power conversion circuit, and can filter the EMI noise of the power conversion circuit to avoid interference of the power conversion circuit on the SMPS.

[0009] In one embodiment, the sampling circuit also includes a jumper capacitor, which includes a first capacitor and a second capacitor, the first capacitor and the second capacitor are connected in series, and one end of the first capacitor is coupled to the positive power supply line of the power supply, and one end of the second capacitor is coupled to the negative power supply line of the power supply; a branch is drawn between the first capacitor and the second capacitor to construct a reference ground.

[0010] In this embodiment, the cross-over capacitor of the sampling circuit can isolate the noise generated by the power supply, and prevent the voltage input to the power conversion circuit from carrying noise. In addition, the branch between the two capacitors of the cross-over capacitor can construct a neutral point as a reference ground of the operational amplifier, so that the operational amplifier can work normally.

[0011] In one embodiment, the inverting integrating amplifier includes an operational amplifier and a third capacitor, the negative input terminal of the operational amplifier is coupled to the first resistor and the second resistor, the positive input terminal of the operational amplifier is coupled to a reference ground, and the output terminal of the operational amplifier is coupled to a ground line; the two ends of the third capacitor are respectively coupled to the negative input terminal of the operational amplifier and the output terminal of the operational amplifier.

[0012] In this implementation, the noise component input by the sampling circuit is inverted and amplified by an integrating amplifier and then injected into the ground line, thereby suppressing EMI noise.

[0013] In one implementation, the filter inductor is a common mode inductor or a differential mode inductor.

[0014] In this embodiment, when the filter inductor is a common mode inductor, the common mode EMI noise of the electrical signal generated by the power conversion circuit can be filtered out. When the filter inductor is a differential mode inductor, the differential mode EMI noise of the electrical signal generated by the power conversion circuit can be filtered out.

[0015] In one implementation, the jumper capacitor is coupled between the power supply and the filter inductor; or, the jumper capacitor is coupled between the filter inductor and the power conversion circuit.

[0016] In this implementation, the jumper capacitor can be coupled between the power supply and the filter inductor, or can be coupled between the filter inductor and the power conversion circuit, thereby improving the richness of the active electromagnetic interference filter design.

[0017] In one embodiment, the first resistor and the second resistor are respectively coupled to ports of two inductor windings in the filter inductor between the power supply and the filter inductor; or, the first resistor and the second resistor are respectively coupled to ports of two inductor windings in the filter inductor between the filter inductor and the power conversion circuit; or, the first resistor and the second resistor are respectively coupled to two ports of any one inductor winding in the filter inductor.

[0018] In this implementation, the first resistor and the second resistor may be coupled to the same-named ends of the filter inductor, or may be coupled to two ports of any inductor winding of the filter inductor T1, thereby improving the richness of the active electromagnetic interference filter design.

[0019] In one embodiment, it also includes: a compensation circuit coupled between the inverting amplifier circuit and the ground line, used to convert the voltage signal output by the inverting amplifier circuit into a current signal, and compensate for the phase shift of the voltage signal output by the inverting amplifier circuit.

[0020] In this embodiment, the compensation circuit is coupled between the inverting amplifier circuit and the ground line, converts the voltage signal output by the inverting amplifier circuit into a current signal, and injects it into the ground line. The compensation circuit can prevent other DC interference signals from affecting the normal operation of the operational amplifier.

[0021] In one embodiment, the compensation circuit includes a third resistor and a fourth capacitor, one end of the third resistor is coupled to the output end of the inverting amplifier circuit, the other end of the third resistor is coupled to one end of the fourth capacitor, and the other end of the fourth capacitor is coupled to the ground line.

[0022] In this embodiment, the third resistor converts the voltage signal output by the inverting amplifier circuit into a current signal. The fourth capacitor can compensate for the phase offset of the voltage signal output by the operational amplifier, isolate the output terminal of the operational amplifier from the ground line, and avoid other DC interference signals from affecting the normal operation of the operational amplifier.

[0023] In one embodiment, the method further includes: a linear impedance stabilization network coupled between the power supply and the sampling circuit, for isolating interference signals of the electrical signal of the power supply and providing a stable impedance for the electrical signal.

[0024] In this embodiment, the linear impedance stabilization network is coupled between the power supply and the sampling circuit to provide a specified stable line impedance within a set frequency range, which can prevent the power supply from being affected by various factors, making the impedance of the entire line unstable. The linear impedance stabilization network isolates the power supply from the subsequent circuit to ensure that the power received by the load is pure power. The linear impedance stabilization network filters the interference signal generated by the load.

[0025] In one implementation, the linear impedance stabilization network includes a first inductor, a second inductor, a fifth capacitor, a sixth capacitor, a fourth resistor and a fifth resistor, wherein the first inductor is coupled between the positive power supply line of the power supply and the sampling circuit, and the second inductor is coupled between the negative power supply line of the power supply and the sampling circuit; the fifth capacitor, the fourth resistor, the fifth resistor and the sixth capacitor are connected in series in sequence, and one end of the fifth capacitor is coupled between the first inductor and the sampling circuit, and one end of the sixth capacitor is coupled between the second inductor and the sampling circuit; a branch is drawn between the fourth resistor and the fifth resistor and coupled to a ground line.

[0026] In a second aspect, an embodiment of the present application provides a switching power supply, comprising: a power supply for providing an electrical signal, at least one power conversion circuit for converting the electrical signal into an electrical signal of a set power; and at least one active electromagnetic interference filter as may be implemented in the first aspect, respectively coupled to the power supply and the power conversion circuit, for suppressing electromagnetic interference noise of the electrical signal.

[0027] In a third aspect, an embodiment of the present application provides an electric device, including: at least one power component, at least one switching power supply as each of which may be implemented in the second aspect, and the at least one switching power supply is electrically connected to the at least one power component. The electric device can be an electric car, a charger, a charging pile, a laptop computer, a base station, a cabinet, and other equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The following is a brief introduction to the drawings required for describing the embodiments or prior art.

[0029] Figure 1 A schematic diagram of the architecture of an SMPS provided in an embodiment of the present application;

[0030] Figure 2 A schematic diagram of the architecture of an SMPS provided in an embodiment of the present application;

[0031] Figure 3 A circuit diagram of an active MEI filter provided in an embodiment of the present application;

[0032] Figure 4 A schematic diagram of the change between the voltage at the negative input terminal of the operational amplifier and the voltage at the output terminal of the operational amplifier provided in an embodiment of the present application;

[0033] Figure 5 This is a circuit diagram of an electric power device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0035] In the description of the present application, the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0036] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, a conflicting connection or an integrated connection. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0037] In the description of this application, the term "and / or" is a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " herein indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0038] In the description of this application, the terms "first" and "second" are used to distinguish different objects rather than to describe a specific order of objects. For example, a first response message and a second response message are used to distinguish different response messages rather than to describe a specific order of response messages.

[0039] In the embodiments of the present application, the words "in one embodiment" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "in one embodiment" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the words "in one embodiment" or "for example" is intended to present related concepts in a concrete way.

[0040] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0041] In order to suppress the electromagnetic interference (EMI) noise of SMPS from interfering with other devices or equipment, an EMI filter is set inside the SMPS. An EMI filter is an electronic circuit device used to suppress EMI, especially noise in power lines or control signal lines. The EMI filter can filter the switching current di / dt and switching voltage du / dt of the SMPS to prevent the SMPS from generating EMI noise.

[0042] EMI filters can be divided into passive EMI filters and active EMI filters. Passive EMI filters suppress the propagation of EMI noise by increasing the equivalent impedance of the conduction path. When the passive EMI filter increases the impedance, the volume and weight of the passive EMI filter will increase, and the power loss of the circuit will also increase, resulting in the inability of passive EMI filters to be applied to miniaturized devices. Active EMI filters suppress the propagation of EMI noise through steps such as signal sampling, feedback, and compensation. Compared with passive EMI filters, active EMI filters have the advantages of small size, light weight, and low circuit power loss, and are more widely used in various fields.

[0043] Figure 1 Schematic diagram of the architecture of an SMPS provided in an embodiment of the present application. Figure 1As shown, the SMPS includes a power supply end (supply), a load end (nonlinear load) and an active EMI filter (AEF). The power supply end and the load end are electrically connected through a power line. The input end and the output end of the active EMI filter are both electrically connected to the power line. Moreover, the input end of the active EMI filter is close to the load end. The output end of the active EMI filter is close to the power supply end.

[0044] When switching noise is generated at the power supply end, the sensor (sense) of the active EMI filter samples the switching noise signal of the power line through the input end. After the amplifier (amplifier) ​​of the active EMI filter performs inverse amplification on the interference signal of the power line, it injects the inverse amplified interference signal into the ground through the compensation circuit to achieve active filtering. The active EMI filter is based on the switching current i n Generate cancellation current i c On the power line, the noise signal at the power supply end is superimposed with the compensation signal to obtain the load current i l , in order to suppress the propagation of EMI noise.

[0045] The existing active EMI filter needs to introduce additional devices to construct the sampling network, which leads to defects such as a large number of devices and a large board area, resulting in poor applicability of the existing active EMI filter. In addition, the sampling amplitude of the existing active EMI filter is low, the active filter insertion loss gain is small, and the insertion loss optimization requires a series op amp, which makes the circuit complex.

[0046] In order to solve the defects of existing active filtering, the embodiments of the present application provide a new active EMI filter, SMPS and power equipment. The filter inductor of the active EMI filter is coupled between the power supply of the SMPS and the power conversion circuit, and a sampling circuit is introduced at the two ports of the filter inductor to obtain the voltage drop of the common-mode interference signal of the inductor winding of the filter inductor. The interference component collected by the sampling circuit is amplified by an integral amplifier through an inverting amplifier to suppress the EMI noise of the SMPS. The SMPS does not need to introduce additional sampling devices, the circuit is simple, the applicability is relatively strong, and the volume is relatively small. Moreover, the sampling of the filter inductor and the addition processing on the input side of the integral amplifier can effectively increase the sampling interference amplitude and improve the insertion loss gain of the active EMI filter.

[0047] Figure 2 Schematic diagram of the architecture of an SMPS provided in an embodiment of the present application. Figure 2As shown, SMPS200 may include a power supply 210, an active EMI filter 220, and a power conversion circuit 230. The power supply 210 and the power conversion circuit 230 may be electrically connected via a positive power supply line and a negative power supply line. The input end of the active EMI filter 220 is coupled to the positive power supply line and the negative power supply line. The output end of the active EMI filter 220 is coupled to a protective earth (PE).

[0048] The power supply 210 can be a battery, a mains system connected to an alternating current / direct current (AC / DC) converter, or other direct current source. The power supply 210 is used to provide direct current. The positive output terminal of the power supply 210 is coupled to the positive power supply line. The negative output terminal of the power supply 210 is coupled to the negative power supply line. Therefore, the positive power supply line can be defined as a live wire (L). The negative power supply line can be defined as a neutral wire (N). In an embodiment of the present application, the power supply 210 can transmit direct current to the power conversion circuit 230 via the live wire and the neutral wire.

[0049] The power conversion circuit 230 is used to convert the DC power output by the power supply 210 into electric energy of a set power, so that the SMPS 200 can provide electric energy for the load of the set power. Generally, the power of the electric energy output by the power supply 210 may be different from the rated power of the load, and the power conversion circuit 230 is provided inside the SMPS 200. The power conversion circuit 230 can convert the electric energy of the power supply 210 into the electric energy of the rated power of the load according to the rated power of the load, so that the SMPS 200 can provide electric energy for loads with different rated powers.

[0050] The active EMI filter 220 is coupled to the positive power supply line and the negative power supply line between the power supply 210 and the power conversion circuit 230. The active EMI filter 220 is used to suppress the EMI noise of the power conversion circuit 230. Figure 3 As shown, the active EMI filter 220 may include a sampling circuit 221 and an inverting amplifier circuit 222 .

[0051] The sampling circuit 221 is coupled to the live wire and the neutral wire between the power supply 210 and the power conversion circuit 230, and is used to collect the interference voltage generated by the power conversion circuit 230, and can filter out part of the EMI noise of the power conversion circuit 230. Figure 3As shown, the sampling circuit 221 includes a filter inductor T1, a cross-over capacitor, a first resistor R1 and a second resistor R2. The filter inductor T1 is coupled to the live wire and the neutral wire between the power supply 210 and the power conversion circuit 230. The filter inductor T1 is composed of two inductor windings. One inductor winding of the filter inductor T1 is coupled to the live wire. The other inductor winding of the filter inductor T1 is coupled to the neutral wire. The filter inductor T1 is used to suppress the EMI noise generated by the power conversion circuit 230. Optionally, the filter inductor T1 can be a common mode inductor. The common mode inductor can filter the common mode EMI noise of the electrical signal generated by the power conversion circuit 230. The filter inductor T1 can be a differential mode inductor. The differential mode inductor can filter the differential mode EMI noise of the electrical signal generated by the power conversion circuit 230.

[0052] The crossover capacitor is coupled between the live wire and the neutral wire. The crossover capacitor includes a first capacitor C1 and a second capacitor C2. The first capacitor C1 and the second capacitor C2 are connected in series, and one end of the first capacitor C1 is coupled to the live wire, and one end of the second capacitor C2 is coupled to the neutral wire. A branch is drawn between the first capacitor C1 and the second capacitor C2, and the branch can construct a neutral point as a reference point of the operational amplifier, so that the operational amplifier can work normally. The neutral point can also be called a "reference ground". -

[0053] like Figure 3 As shown, one end of the first capacitor C1 is coupled to the live line between the filter inductor T1 and the power conversion circuit 230. One end of the second capacitor C2 is coupled to the neutral line between the filter inductor T1 and the power conversion circuit 230. Optionally, one end of the first capacitor C1 can be coupled to the live line between the power supply 210 and the filter inductor T1. One end of the second capacitor C2 can be coupled to the neutral line between the power supply 210 and the filter inductor T1.

[0054] The first resistor R1 and the second resistor R2 are respectively coupled to the same-named ends of the filter inductor T1, or are respectively coupled to the two ports of any one of the inductor windings of the filter inductor T1. The first resistor R1 is coupled to one port of the filter inductor T1, and is used to collect the voltage drop of the interference signal of the inductor winding. The second resistor R2 is coupled to another port of the filter inductor T1, and is used to collect the voltage drop of the interference signal of the inductor winding. The voltages collected by the first resistor R1 and the second resistor R2 are the voltage drops of the common-mode interference signals on the two inductor windings of the filter inductor T1. Preferably, the resistance values ​​of the first resistor R1 and the second resistor R2 are the same.

[0055] like Figure 3As shown, the first resistor R1 is coupled to the live line between the power supply 210 and the filter inductor T1, and is located at a port of one inductor winding of the filter inductor T1. The second resistor R2 is coupled to the neutral line between the power supply 210 and the filter inductor T1, and is located at a port of another inductor winding of the filter inductor T1. That is, the first resistor R1 is coupled to port 1 of the filter inductor T1, and the second resistor R2 is coupled to port 3 of the filter inductor T1.

[0056] In one case, the first resistor R1 is coupled to the live line between the filter inductor T1 and the power conversion circuit 230, and is located at a port of one inductor winding of the filter inductor T1. The second resistor R2 is coupled to the neutral line between the filter inductor T1 and the power conversion circuit 230, and is located at a port of another inductor winding of the filter inductor T1. That is, the first resistor R1 is coupled to port 2 of the filter inductor T1, and the second resistor R2 is coupled to port 4 of the filter inductor T1.

[0057] In another case, the first resistor R1 and the second resistor R2 are respectively coupled to two ports of any one inductor winding of the filter inductor T1. That is, the first resistor R1 is coupled to port 1 of the filter inductor T1, and the second resistor R2 is coupled to port 2 of the filter inductor T1. Alternatively, the first resistor R1 is coupled to port 3 of the filter inductor T1, and the second resistor R2 is coupled to port 4 of the filter inductor T1.

[0058] In the embodiment of the present application, the filter inductor T1 of the sampling circuit 221 can be coupled to the live wire and the neutral wire between the power supply 210 and the power conversion circuit 230, and can filter the EMI noise of the power conversion circuit 230. The cross-capacitor of the sampling circuit 221 can construct a reference ground to provide input for the positive input terminal of the operational amplifier. The first resistor R1 and the second resistor R2 of the sampling circuit 221 are respectively coupled to the same-name ends of the filter inductor T1 or the two ports of any one of the inductor windings, and the voltage signals of the two ports of the filter inductor T1 are sampled by using the first resistor R1 and the second resistor R2, so that a pure common-mode interference component can be obtained without the need for noise separation. SMPS200 does not require the introduction of additional sampling devices, the circuit is simple, the applicability is relatively strong, and the volume is relatively small.

[0059] The inverting amplifier circuit 222 is coupled between the sampling circuit 221 and the ground line, and is used to amplify the voltage signal of the first resistor R1 and the voltage signal of the second resistor R2 of the sampling circuit 221, so that the phase of the voltage signal of the first resistor R1 and the voltage signal of the second resistor R2 is inverted. The inverting amplifier circuit 222 inputs the inverted amplified voltage signal to the ground line to offset the EMI noise generated by the power conversion circuit 230 and complete active filtering.

[0060] like Figure 3As shown, the inverting amplifier circuit 222 includes an operational amplifier (OPA) and a third capacitor C3. The negative input terminal of the OPA is coupled to the first resistor R1 and the second resistor R2. The negative input terminal of the OPA can receive a voltage signal after the first resistor R1 and the second resistor R2 are superimposed, which can effectively increase the amplitude of the sampling interference and increase the active filter insertion loss gain. The positive input terminal of the OPA is coupled to the reference ground. The output terminal of the OPA is coupled to the ground line. The two ends of the third capacitor C3 are respectively coupled to the negative input terminal of the OPA and the output terminal of the OPA.

[0061] OPA is an electronic integrated circuit containing multiple amplifier circuits. The input stage of OPA is a differential amplifier circuit with high input resistance and zero drift suppression capability. The intermediate stage of OPA mainly performs voltage amplification and has a high voltage amplification factor, and is generally composed of a common emitter amplifier circuit. The output stage of OPA is connected to the load and has the characteristics of strong load capacity and low output resistance.

[0062] In the embodiment of the present application, the OPA and the third capacitor C3 can form an integrating amplifier. The integrating amplifier can perform a mathematical operation of integration so that the output voltage changes with time in response to the input voltage. That is, the output voltage of the integrating amplifier is proportional to the integral of the input voltage at the negative input terminal.

[0063] In a possible implementation, when the negative input terminal of the integrating amplifier is input with voltage for the first time, the resistance of the third capacitor C3 can be considered very small, and the branch where the third capacitor C3 is located is equivalent to a short circuit. The total current i(t) passing through the first resistor R1 and the second resistor R2 is:

[0064]

[0065] Wherein, t represents time, U1 represents the voltage collected by the sampling circuit 220, and R=R1R2 / (R1+R2).

[0066] When the third capacitor C3 is short-circuited, no current flows into the negative input terminal of the OPA. There is no output at the output terminal of the OPA. At this time, the impedance of the third capacitor C3 is very small, and the ratio (C / R) of the third capacitor C3 to the resistor R is also very small, indicating that the voltage gain through the OPA is less than 1.

[0067] When the negative input terminal of the OPA continuously inputs voltage, the third capacitor C3 is continuously charged. The voltage U across the third capacitor C3 is C for:

[0068]

[0069] Wherein, C represents the capacitance of the third capacitor C3, Q C(t) represents the charge of the third capacitor C3.

[0070] The impedance of the third capacitor C3 increases slowly in proportion to the charging rate of the third capacitor C3. The charging rate of the third capacitor C3 is associated with the RC time constant. When there is a voltage across the third capacitor C3, the negative input terminal of the OPA generates an input voltage. The output voltage U0 of the OPA is:

[0071]

[0072] After the voltage between the two plates of the third capacitor C3 continues to increase, the charging current of the third capacitor C3 decreases as the impedance of the third capacitor C3 increases. The ratio (C / R) of the third capacitor C3 to the resistor R continues to increase, and the OPA generates a linearly increasing ramp output voltage. After the third capacitor C3 is charged, the output voltage at the output end of the OPA reaches stability. At this time, the ratio (C / R) of the third capacitor C3 to the resistor R is infinite, allowing the integrating amplifier to generate infinite gain.

[0073] like Figure 4 As shown, when the negative input terminal of the OPA just starts to input the voltage Vinput, the output voltage at the output terminal of the OPA is zero. When the negative input terminal of the OPA continues to input the voltage Vinput, the output voltage Voutput at the output terminal of the OPA continuously increases from 0 to the set voltage Vk, thereby delaying the phase of the input voltage. The rate k at which the output voltage Voutput at the output terminal of the OPA increases is determined by the third capacitor C3 and the resistor R. That is, k = 1 / RC. The user can change the values ​​of the third capacitor C3 and the resistor R to change the rate k at which the output voltage of the integrating amplifier increases.

[0074] In the embodiment of the present application, a filter inductor is coupled between the power supply 210 of SMPS200 and the power conversion circuit 230, and the voltage signals of the same-name end of the filter inductor or the two ports of any one of the inductor windings are directly collected, so that a pure common-mode noise component can be obtained without noise separation. SMPS200 does not need to introduce additional sampling devices, the circuit is simple, the applicability is relatively strong, and the volume is relatively small. The noise component of the internal circuit of SMPS200 is inverted and amplified by an integrating amplifier and then injected into the ground line to suppress the EMI noise of SMPS200.

[0075] In the embodiment of the present application, the active EMI filter 220 may further include a compensation circuit 223. The compensation circuit 223 is coupled between the inverting amplifier circuit 222 and the ground line, and is used to convert the voltage signal output by the inverting amplifier circuit 222 into a current signal and inject it into the ground line.

[0076] like Figure 3As shown, the compensation circuit 223 includes a third resistor R3 and a fourth capacitor C4. One end of the third resistor R3 is coupled to the output end of the inverting amplifier circuit 222. The other end of the third resistor R3 is coupled to one end of the fourth capacitor C4, and the other end of the fourth capacitor C4 is coupled to the ground line. The third resistor R3 is used to convert the voltage signal output by the inverting amplifier circuit 222 into a current signal. The fourth capacitor C4 can compensate for the phase offset of the voltage signal output by the OPA, isolate the output end of the OPA from the ground line, and avoid other DC interference signals from affecting the normal operation of the OPA.

[0077] In the embodiment of the present application, the active EMI filter 220 may further include a linear impedance stabilization network (LISN) 224 coupled between the power supply 210 and the sampling circuit 221, which is used to provide a specified stable line impedance within a set frequency range, so as to prevent the power supply 210 from being affected by various factors, making the impedance of the entire line unstable. The LISN 224 is also used to isolate the power supply 210 from the subsequent circuit to ensure that the electric energy received by the load is pure electric energy.

[0078] like Figure 3 As shown, the LISN 224 includes a first inductor L1, a second inductor L2, a fifth capacitor C5, a sixth capacitor C6, a fourth resistor R4 and a fifth resistor R5. The first inductor L1 is coupled to the live line between the power supply 210 and the sampling circuit 221. The second inductor L2 is coupled to the neutral line between the power supply 210 and the sampling circuit 221. The fifth capacitor C5, the fourth resistor R4, the fifth resistor R5 and the sixth capacitor C6 are sequentially connected in series between the live line and the neutral line. A branch is drawn between the fourth resistor R4 and the fifth resistor R5 to be grounded.

[0079] When the current signal output by the power supply 210 is in the low frequency band, the first inductor L1 and the second inductor L2 can be equivalent to a short circuit. The fifth capacitor C5 and the sixth capacitor C6 can be equivalent to an open circuit. The low frequency current will not flow into the two test resistors of the LISN 224, and will not affect the normal working point of the switching power supply.

[0080] When the current signal output by the power supply 210 is in the normal frequency band, the first inductor L1 and the second inductor L2 can be equivalent to an open circuit. The fifth capacitor C5 and the sixth capacitor C6 can be equivalent to a short circuit. The power supply 210 and the power conversion circuit 230 can also be equivalent to a short circuit and an open circuit, respectively. The EMI noise output by the power supply 210 directly flows into the two resistors of the LISN 224, so as to isolate the power supply 210 from the subsequent circuits to ensure that the electric energy received by the load is pure electric energy.

[0081] In the embodiment of the present application, SMPS200 can be applicable to vehicle-mounted components and complete machines, as well as traditional information and communication technology (ICT) equipment, power modules and other switching converters. During the switching process, the switch tube of the switching converter will generate a relatively high switching current di / dt and switching voltage du / dt, which is the main reason for the excessive conduction noise of the product. The SMPS 200 protected by this application can make up for the technical shortcomings of existing filtering technologies such as large volume and poor applicability of solutions, effectively reduce line conduction noise, and meet the requirements of relevant standards for electromagnetic compatibility (EMC). Among them, the MEC here refers to the ability of a device or system to operate in accordance with the requirements in its electromagnetic environment and not to produce intolerable electromagnetic disturbance to any device in its environment.

[0082] Figure 5 Schematic diagram of a circuit of an electric device provided in an embodiment of the present application. Figure 5 As shown, the power device includes SMPS200 and n power components. n is a positive integer greater than or equal to 1. The positive power supply line and the negative power supply line of SMPS200 are electrically connected to each power component respectively.

[0083] In the embodiment of the present application, the SMPS 200 of the power equipment can be as follows: Figure 2-Figure 4 and the SMPS200 described in the above corresponding protection scheme. SMPS200 provides electrical signals to filter EMI noise to each power component, so that each power component maintains stable and normal operation, and reduces the negative impact of EMI noise on the power equipment. Since the power equipment includes the SMPS200, the power equipment has all or at least part of the advantages of the SMPS200. The power equipment can be electric vehicles, chargers, charging piles, laptops, base stations, cabinets and other equipment. The power components can be electronic devices such as resistors, switch tubes, chips, fans, motors, etc.

[0084] The number of circuits, interconnection relationships, types of circuits, etc. of the SMPS200 provided in the embodiment of the present application are not limited to the above-mentioned embodiment, and all technical solutions implemented under the principle of the present application are within the protection scope of the present solution. Any one or more embodiments or diagrams in the specification, combined in an appropriate manner, are within the protection scope of the present solution.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application. Those skilled in the art should understand that, although the present application is described in detail with reference to the aforementioned embodiments, the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions in the embodiments of the present application.

Claims

1. An active electromagnetic interference filter, characterized in that: include: A sampling circuit (221), comprising a filter inductor (T1), a first resistor (R1) and a second resistor (R2), wherein the filter inductor is coupled to a positive power supply line and a negative power supply line, and is used to filter electromagnetic interference noise of electrical signals of the positive power supply line and the negative power supply line; The first resistor and the second resistor are respectively coupled to two ports of the filter inductor, and are used to collect voltage signals of the two ports of the filter inductor; An inverting amplifier circuit (222) is coupled between the first resistor, the second resistor and a ground line (PE), and is used to receive a voltage signal of the first resistor and a voltage signal of the second resistor, superimpose the voltage signal of the first resistor and the voltage signal of the second resistor, and invert and amplify the superimposed voltage signal.

2. The active electromagnetic interference filter according to claim 1, characterized in that: The positive power supply line and the negative power supply line are coupled between a power supply (210) and a power conversion circuit (230) and are used to transmit an electrical signal of the power supply to the power conversion circuit.

3. The active electromagnetic interference filter according to claim 1 or 2, characterized in that: The sampling circuit further includes a cross-over capacitor, wherein the cross-over capacitor includes a first capacitor (C1) and a second capacitor (C2). The first capacitor and the second capacitor are connected in series, and one end of the first capacitor is coupled to the positive power supply line of the power supply, and one end of the second capacitor is coupled to the negative power supply line of the power supply; a branch is drawn between the first capacitor and the second capacitor to construct a reference ground.

4. The active electromagnetic interference filter according to any one of claims 1 to 3, characterized in that: The inverting integrating amplifier comprises an operational amplifier (OPA) and a third capacitor (C3), the negative input terminal of the operational amplifier is coupled to the first resistor and the second resistor, the positive input terminal of the operational amplifier is coupled to a reference ground, and the output terminal of the operational amplifier is coupled to a ground line; two ends of the third capacitor are respectively coupled to the negative input terminal of the operational amplifier and the output terminal of the operational amplifier.

5. The active electromagnetic interference filter according to any one of claims 1 to 4, characterized in that: The filter inductor is a common mode inductor or a differential mode inductor.

6. The active electromagnetic interference filter according to any one of claims 1 to 5, characterized in that: The jumper capacitor is coupled between the power supply and the filter inductor; or, The jumper capacitor is coupled between the filter inductor and the power conversion circuit.

7. The active electromagnetic interference filter according to any one of claims 1 to 6, characterized in that: The first resistor and the second resistor are respectively coupled to ports of two inductor windings in the filter inductor between the power supply and the filter inductor; or, The first resistor and the second resistor are respectively coupled to ports of two inductor windings in the filter inductor between the filter inductor and the power conversion circuit; or, The first resistor and the second resistor are respectively coupled to two ports of any one inductor winding of the filter inductor.

8. The active electromagnetic interference filter according to any one of claims 1 to 7, characterized in that: Also includes: A compensation circuit (223) is coupled between the inverting amplifier circuit and the ground line, and is used to convert the voltage signal output by the inverting amplifier circuit into a current signal, and to compensate for the phase shift of the voltage signal output by the inverting amplifier circuit.

9. The active electromagnetic interference filter according to claim 8, characterized in that: The compensation circuit includes a third resistor (R3) and a fourth capacitor (C4), one end of the third resistor is coupled to the output end of the inverting amplifier circuit, the other end of the third resistor is coupled to one end of the fourth capacitor, and the other end of the fourth capacitor is coupled to the ground line.

10. The active electromagnetic interference filter according to any one of claims 1 to 9, characterized in that: Also includes: A linear impedance stabilization network (224) is coupled between the power supply and the sampling circuit and is used to isolate interference signals of the electrical signal of the power supply and provide a stable impedance for the electrical signal.

11. The active electromagnetic interference filter according to claim 10, characterized in that: The linear impedance stabilization network includes a first inductor (L1), a second inductor (L2), a fifth capacitor (C5), a sixth capacitor (C6), a fourth resistor (R4) and a fifth resistor (R5), The first inductor is coupled between the positive power supply line of the power supply and the sampling circuit, and the second inductor is coupled between the negative power supply line of the power supply and the sampling circuit; The fifth capacitor, the fourth resistor, the fifth resistor and the sixth capacitor are sequentially connected in series, and one end of the fifth capacitor is coupled between the first inductor and the sampling circuit, and one end of the sixth capacitor is coupled between the second inductor and the sampling circuit; A branch is drawn between the fourth resistor and the fifth resistor and is coupled to the ground line.

12. A switching power supply, characterized in that: include: Power supply, used to provide electrical signals, at least one power conversion circuit, used for converting the electrical signal into an electrical signal of set power; At least one active electromagnetic interference filter as described in any one of claims 1 to 11 is coupled to the power supply and the power conversion circuit respectively, and is used to suppress electromagnetic interference noise of the electrical signal.

13. An electric power device, characterized in that: include: at least one power component, At least one switching power supply as claimed in claim 12, wherein the at least one switching power supply is electrically connected to the at least one power component.

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