Switching power converter and its active electromagnetic interference filter circuit

Abstract

A switching power converter and its active electromagnetic interference (EMI) filter circuit are disclosed. The switching power converter includes: a power stage circuit including at least one transistor for switching an inductor to convert an input power supply to an output power supply; and an active EMI filter circuit including at least one amplifier, wherein the at least one amplifier is used to sense a noise input signal and amplify the noise input signal to generate a noise cancellation signal, wherein the noise input signal is related to switching noise generated when the power stage circuit switches, wherein the noise cancellation signal is injected into the input node of the switching power converter to suppress switching noise and thus reduce EMI, wherein the input power supply powers the power stage circuit via the input node.

Description

Technical Field

[0001] This invention relates to a switching power converter, and more particularly to a switching power converter that utilizes an active electromagnetic interference (AEF) filter circuit to reduce electromagnetic interference. The invention also relates to an active electromagnetic interference (EMI) filter circuit for avoiding electromagnetic interference (EMI) caused by power stage circuit switching in a switching power converter. Background Technology

[0002] Regarding the elimination of switching noise, related prior art using methods different from those of this invention includes: R. Goswami, S. Wang and Y. Chu, “Design of an active differential mode current filter for a boost power factor correction AC-DC converter”, 2015 IEEE Energy Conversion Congress and Exposition (ECCE), Montreal, QC, 2015, pp. 4375-4382.

[0003] With the increasing use of electronic devices in modern vehicles, electromagnetic interference (EMI) is becoming an increasingly challenging issue in switching power converters, especially in high-current applications. To reduce EMI noise and meet international standards (such as CISPR 25), existing technologies often employ methods such as... Figure 1 The passive electromagnetic interference filter 80 shown is used to mitigate electromagnetic interference generated by the prior art switching power converter 101. The passive electromagnetic interference filter 80 includes a filter inductor Lf, a filter capacitor Cf, and a resistor-capacitor damping circuit (including capacitor Cd and resistor Rd). However, the passive electromagnetic interference filter 80 requires the use of large inductors and large capacitors to achieve sufficient noise filtering effect, which will cause problems such as increased size and cost. Summary of the Invention

[0004] In one viewpoint, the present invention provides a switching power converter comprising: a power stage circuit including at least one transistor for switching an inductor to convert an input power supply into an output power supply; a switching controller for controlling the at least one transistor; and an active electromagnetic interference filter (AEF) circuit including at least one amplifier, wherein the at least one amplifier is configured to sense a noise input signal and amplify the noise input signal to generate a noise cancellation signal, wherein the noise input signal is related to switching noise generated when the power stage circuit switches, wherein the noise cancellation signal is injected into an input node of the switching power converter to suppress the switching noise and thereby reduce electromagnetic interference, wherein the input power supply supplies power to the power stage circuit via the input node.

[0005] In a preferred embodiment, the switching power converter further includes a sensing resistor, wherein a first end of the sensing resistor is coupled to the input node and a second end of the sensing resistor is coupled to the power stage circuit, wherein the noise input signal is generated based on a voltage across the sensing resistor.

[0006] In a preferred embodiment, the at least one amplifier includes an amplifier, wherein an inverting input of the amplifier is coupled to the second terminal of the sensing resistor via a first input capacitor, and a non-inverting input of the amplifier is coupled to the first terminal of the sensing resistor via a second input capacitor, thereby differentially coupling the alternating current component (AC component) of the noise input signal from the sensing resistor; wherein the noise cancellation signal is generated by an output of the amplifier, and wherein the noise cancellation signal is coupled to the first terminal of the sensing resistor via an injection capacitor, thereby injecting the AC component of the noise cancellation signal into the input node of the switching power converter.

[0007] In a preferred embodiment, the active electromagnetic interference filter circuit further includes a first input resistor and a second input resistor, which are respectively connected in series to the first input capacitor and the second input capacitor.

[0008] In a preferred embodiment, the at least one amplifier includes a first amplifier and a second amplifier, wherein an inverting input of the first amplifier is coupled to a first terminal of the sensing resistor via a first input capacitor, and a non-inverting input of the first amplifier is coupled to a second terminal of the sensing resistor via a second input capacitor, thereby differentially coupling the alternating current component (AC component) of the noise input signal from the sensing resistor; wherein an inverting input of the second amplifier is coupled to an output of the first amplifier via a DC blocking capacitor, wherein the noise cancellation signal is generated by an output of the second amplifier, and wherein the noise cancellation signal is coupled to the first terminal of the sensing resistor via an injection capacitor, thereby injecting the AC component of the noise cancellation signal into the input node of the switching power converter.

[0009] In a preferred embodiment, the inverting input of the first amplifier is further coupled to the first terminal of the sensing resistor via a first input resistor connected in parallel with the first input capacitor, and the non-inverting input of the first amplifier is further coupled to the second terminal of the sensing resistor via a second input resistor connected in parallel with the second input capacitor, thereby differentially coupling the AC component and DC component of the noise input signal from the sensing resistor.

[0010] In a preferred embodiment, an AC coupling ratio is higher than a DC coupling ratio, wherein the AC coupling ratio and the DC coupling ratio refer to the coupling ratio of the noise input signal to the inverting input terminal and the non-inverting input terminal of the first amplifier.

[0011] In a preferred embodiment, the switching power converter further includes a passive filter circuit coupled between the sensing resistor and the power stage circuit, wherein the passive filter circuit includes a filter inductor and a filter capacitor for further filtering the noise input signal.

[0012] In a preferred embodiment, the switching power converter further includes a passive filter circuit coupled between the input node and the power stage circuit, wherein the passive filter circuit includes a filter inductor and a filter capacitor for further filtering the noisy input signal.

[0013] In a preferred embodiment, the switching power converter further includes a buffer circuit comprising a buffer capacitor and a buffer resistor, wherein the buffer capacitor and the buffer resistor are connected in series to a switching node, wherein the switching node is coupled to one end of the inductor; wherein the at least one amplifier includes an amplifier configured as a non-inverting amplifier stage, wherein a non-inverting input terminal of the amplifier is coupled to the switching node via the buffer circuit and an input capacitor, wherein the input capacitor is coupled to a shared node to which the buffer capacitor and the buffer resistor are coupled, and a non-inverting input terminal of the amplifier is coupled to a ground node via a DC blocking capacitor, thereby coupling the AC component of the noise input signal from the sensing resistor; wherein the noise cancellation signal is generated by an output terminal of the amplifier and injected into the input node of the switching power converter via an injection capacitor.

[0014] In a preferred embodiment, the at least one transistor includes an upper-bridge transistor and / or a lower-bridge transistor coupled to each other at the switching node for switching one end of the inductor; wherein the noise input signal is related to a drain-source current of the upper-bridge transistor and / or a drain-source current of the lower-bridge transistor.

[0015] In a preferred embodiment, the switching power converter is configured to include at least one of the following: a. wherein the at least one amplifier includes a first amplifier configured as a non-inverting amplification stage, wherein a non-inverting input of the first amplifier is coupled to a first sensing element, wherein the first sensing element senses the drain-source current of the upper-bridge transistor via a first input capacitor, thereby coupling the AC component of the noise input signal from the first sensing element, and an inverting input of the first amplifier is coupled to a ground node via a first DC blocking capacitor; and / or b. wherein the at least one amplifier includes a second amplifier configured as an inverting amplification stage, wherein an inverting input of the second amplifier is coupled to a second sensing element, wherein the second sensing element senses the drain-source current of the lower-bridge transistor via a second input capacitor, thereby coupling the AC component of the noise input signal from the second sensing element, and a non-inverting input of the second amplifier is coupled to a DC voltage; wherein the noise cancellation signal is generated based on the first amplifier and / or the second amplifier. And injected into the input node of the switching power converter.

[0016] In a preferred embodiment, a first output signal generated by the first amplifier and a second output signal generated by the second amplifier are superimposed to generate the noise cancellation signal.

[0017] In a preferred embodiment, the at least one amplifier further includes a third amplifier configured as a non-inverting adder circuit, wherein a non-inverting input terminal of the third amplifier is coupled to an output terminal of the first amplifier via a second DC blocking capacitor, and is coupled to an output terminal of the second amplifier via a third DC blocking capacitor, such that the AC component of the first output signal is superimposed with the AC component of the second output signal; wherein the noise cancellation signal is generated by an output terminal of the third amplifier and injected into the input node of the switching power converter via an injection capacitor.

[0018] From another perspective, the present invention also provides an active electromagnetic interference (EMI) filter circuit for a switching power converter, wherein the switching power converter includes: a power stage circuit including at least one transistor for switching an inductor to convert an input power supply into an output power supply; the active EMI filter circuit includes: at least one amplifier; and a plurality of passive filtering elements coupled to the at least one amplifier; wherein the at least one amplifier is used to sense a noise input signal and amplify the noise input signal to generate a noise cancellation signal, wherein the noise input signal is related to a switching noise generated when the power stage circuit switches; wherein the noise cancellation signal is injected into an input node of the switching power converter to suppress the switching noise and thus reduce EMI; wherein the input power supply supplies power to the power stage circuit via the input node.

[0019] This invention proposes a switching power converter with an active electromagnetic interference (EMI) filter circuit. The switching power converter using the active EMI filter circuit according to this invention can significantly reduce size and cost.

[0020] The following detailed description through specific embodiments will make it easier to understand the purpose, technical content, features and effects achieved by the present invention. Attached Figure Description

[0021] Figure 1 This demonstrates a switching power converter based on existing technology.

[0022] Figure 2 A schematic diagram showing a preferred embodiment of the switching power converter of the present invention is displayed.

[0023] Figure 3 Displays the Fast Fourier Transform (FFT) frequency response plot obtained by the analyzer (coupled to the line impedance stabilization network 50).

[0024] Figure 4 A schematic diagram showing a preferred embodiment of the switching power converter of the present invention is displayed.

[0025] Figure 5 The display shows the fast Fourier transform frequency response measured by the analyzer (coupled to the line impedance stabilization network 50).

[0026] Figure 6 A schematic diagram showing a preferred embodiment of the switching power converter of the present invention is displayed.

[0027] Figure 7 The display shows the fast Fourier transform frequency response measured by the analyzer (coupled to the line impedance stabilization network 50).

[0028] Figure 8 A schematic diagram showing a preferred embodiment of the switching power converter of the present invention is displayed.

[0029] Figure 9 The display shows the fast Fourier transform frequency response measured by the analyzer (coupled to the line impedance stabilization network 50).

[0030] Figure 10 A schematic diagram showing a preferred embodiment of the switching power converter of the present invention is displayed.

[0031] Figure 11 The display shows the fast Fourier transform frequency response measured by the analyzer (coupled to the line impedance stabilization network 50).

[0032] Figure 12A A schematic diagram showing a preferred embodiment of the switching power converter of the present invention is displayed.

[0033] Figure 12B A schematic diagram showing a more specific embodiment of the switching power converter of the present invention is shown.

[0034] Figure 13 The display corresponds to Figure 8 , Figure 10 , Figure 12B The operation waveform diagram of the embodiment.

[0035] Figure 14 The display shows the fast Fourier transform frequency response measured by the analyzer (coupled to the line impedance stabilization network 50).

[0036] Figure 15 This table shows a noise comparison of the prior art and all the embodiments described above, based on the present invention, for switching power converters with different active electromagnetic interference filter (AEF) circuits.

[0037] Explanation of symbols in the diagram

[0038] 10: Power stage circuit

[0039] 101, 102, 104, 106, 108, 110, 112A, 112B: Switching power converters

[0040] 30, 32, 33, 34, 35: Active electromagnetic interference filter circuits

[0041] 310, 320, 330, 340, 350, 360: Amplifiers

[0042] 40: Buffer circuit

[0043] 50: Line Impedance Stabilization Network

[0044] 80: Passive Electromagnetic Interference Filter

[0045] 80': Passive filter circuit

[0046] 90: Battery

[0047] Cd: Capacitance

[0048] Cd': Damping capacitance

[0049] Cdc: DC blocking capacitor

[0050] Cdc1~Cdc4: DC blocking capacitors

[0051] Cf: Filter capacitor

[0052] CFB1, CFB2: Feedback capacitors

[0053] CIN: Input capacitance

[0054] CINJ: Injection Capacitor

[0055] CS1, CS2: Input capacitors

[0056] Csnub: Buffer capacitor

[0057] Fsw: Switching frequency

[0058] HG: Signal

[0059] IdsH: Drain-source current

[0060] IdsL: Drain-source current

[0061] Iin: Input current

[0062] I_inj: Noise cancellation signal

[0063] ILx: Inductor current

[0064] Iout: Output current

[0065] Lf, Lf': Filter inductors

[0066] LG: Signal

[0067] Lx: Inductance

[0068] NII: Input Node

[0069] NLx: Switch Node

[0070] Nsn: Shared Node

[0071] QH: Upper Bridge Transistor

[0072] QL: Lower-bridge transistor

[0073] Rd: Resistance

[0074] Rd': Damping resistance

[0075] Rfb1~Rfb3: Feedback resistors

[0076] Ri1, Ri2: Input resistance

[0077] Rs: Sensing resistance

[0078] Rs1, Rs2: Resistors

[0079] Rsnub: Buffer resistor

[0080] Tsw: Period

[0081] Vcomp: Compensation signal

[0082] VcsH: Sensing signal

[0083] VcsL: Sensing signal

[0084] Vin: Input voltage

[0085] VLx: Switching node voltage

[0086] Vnoise: Noise input signal

[0087] Vout: Output voltage

[0088] Vref: DC reference voltage Detailed Implementation

[0089] The accompanying drawings in this invention are all schematic and are mainly intended to show the coupling relationship between various circuits and the relationship between various signal waveforms. The circuits, signal waveforms and frequencies are not drawn to scale.

[0090] Figure 2This diagram illustrates a preferred embodiment of the switching power converter of the present invention. The switching power converter 102 includes a power stage circuit 10 and an active electromagnetic interference (EMI) filter circuit 30. The power stage circuit 10 includes at least one transistor for switching inductor Lx to convert input power to output power. The active EMI filter circuit 30 senses a noise input signal Vnoise, which is related to switching noise generated when the power stage circuit 10 switches (e.g., when switching transistor QH or transistor QL). The active EMI filter circuit 30 also amplifies the noise input signal Vnoise to generate a noise cancellation signal I_inj. In one embodiment, the noise cancellation signal I_inj is injected into the input node NII of the switching power converter 102 to suppress switching noise and thus reduce EMI. In this embodiment, the input power supplies the power stage circuit via the input node NII.

[0091] In one embodiment, for example, the input power supply may be provided by battery 90. The input power supply includes an input voltage Vin and an input current Iin. In one embodiment, the output power supply includes an output voltage Vout and provides an output current Iout to the load.

[0092] In one embodiment, the power stage circuit 10 includes an upper-bridge transistor QH and a lower-bridge transistor QL, used to switch the inductor Lx via control signals HG and LG. In this embodiment, the power stage circuit 10 is a buck converter; however, the present invention can also be applied to other types of switching converters, such as boost converters, buck-boost converters, flyback converters, etc.

[0093] It should be noted that the line impedance stabilization network (LISN) 50 is coupled between the input power supply and the input node NII, wherein the input power supply supplies power to the power stage circuit 10 via the input node NII. The line impedance stabilization network and analyzer are used to measure the level of switching noise caused by the power stage circuit 10 and the electromagnetic interference suppression effect achieved by the active electromagnetic interference filter circuit 30. It should be noted that in one embodiment, the line impedance stabilization network may be omitted, that is, the input power supply can be directly coupled to the input node NII in practical applications.

[0094] Specifically, in one embodiment, the active electromagnetic interference filter circuit 30 includes at least one amplifier, wherein the at least one amplifier is used to sense a noise input signal Vnoise and amplify the noise input signal Vnoise to generate a noise cancellation signal I_inj.

[0095] Please continue reading. Figure 2In this embodiment, the switching power converter 102 further includes a sensing resistor Rs, the first end of which is coupled to the input node NII, and the second end of which is coupled to the power stage circuit 10. The noise input signal Vnoise is generated based on the voltage across the sensing resistor Rs.

[0096] Please continue reading. Figure 2 In one embodiment, the active electromagnetic interference filter circuit 30 includes an amplifier 310, which cooperates with... Figure 2 The passive component shown is configured as a differential amplifier stage. Specifically, the inverting input of amplifier 310 is coupled to the second terminal of sensing resistor Rs via input capacitor CS1, and the non-inverting input of amplifier 310 is coupled to the first terminal of sensing resistor Rs via input capacitor CS2, thereby differentially coupling the alternating current component (AC component) of the noise input signal Vnoise from the sensing resistor Rs. In one embodiment, the active electromagnetic interference filter circuit 30 further includes input resistors Ri1 and Ri2, which are connected in series with input capacitors CS1 and CS2, respectively.

[0097] Please continue reading. Figure 2 In one embodiment, the noise cancellation signal I_inj is generated by the output of amplifier 310. In one embodiment, the noise cancellation signal I_inj is coupled to the first end of the sensing resistor Rs via an injection capacitor CINJ, thereby injecting the AC component of the noise cancellation signal I_inj into the input node NII of the switching power converter 102. In one embodiment, the at least one amplifier is used to make the phase of the noise cancellation signal I_inj opposite to the phase of the noise input signal Vnoise.

[0098] It should be noted that in this embodiment, the DC component of the noise input signal Vnoise is blocked by input capacitors CS1 and CS2, and the DC component of the output signal of amplifier 310 is blocked by injection capacitor CINJ. In one embodiment, feedback capacitor CFB1 and feedback resistor are connected in parallel between the output terminal and the inverting terminal of the feedback architecture, and feedback capacitor CFB2 and feedback resistor are connected in parallel from the non-inverting terminal to the DC reference voltage Vref.

[0099] Figure 3 The results are displayed by the analyzer (coupled to the line impedance stabilization network 50), corresponding to the measurements respectively. Figure 1 The existing technology and the Fast Fourier Transform (FFT) frequency response diagram of the switching power converter 102 are shown. It should be noted that, as Figure 3From the fundamental frequency to all higher harmonics, the switching power converter 102 using an active electromagnetic interference filter circuit can effectively improve the suppression of switching noise.

[0100] Figure 4 A schematic diagram showing a preferred embodiment of the switching power converter of the present invention is displayed. Figure 4 The switching power converter 104 in the middle is similar to Figure 2 The switching power converter 102 is described in this embodiment. In this embodiment, the switching power converter 104 includes amplifiers 320 and 330. Amplifier 320 is configured as a differential amplifier stage. The inverting input of amplifier 320 is coupled to a first terminal of sensing resistor Rs via an input resistor Ri1 and an input capacitor CS1 connected in parallel. The non-inverting input of amplifier 320 is coupled to a second terminal of sensing resistor Rs via an input resistor Ri2 and an input capacitor CS2 connected in parallel, thereby differentially coupling the AC and DC components of the noise input signal Vnoise to the sensing resistor Rs. In one embodiment, feedback resistor Rfb1 is coupled between the output and inverting input of amplifier 320 in the feedback architecture, and feedback resistor Rfb2 is coupled from the non-inverting input to the DC reference voltage Vref. In one embodiment, the impedance of feedback resistor Rfb1 is the same as that of feedback resistor Rfb2, and the impedance of input resistor Ri1 is the same as that of input resistor Ri2.

[0101] From one perspective, the input capacitors CS1 and CS2 of the switching power converter 104 can be configured as feedforward capacitors to prevent the AC component of the resistive network from being separated. In other words, the AC coupling ratio is higher than the DC coupling ratio, where the AC coupling ratio and DC coupling ratio refer to the coupling ratio of the noise input signal Vnoise to the inverting and non-inverting input terminals of the amplifier 320.

[0102] Please continue reading. Figure 4 Amplifier 330 is configured as a single-ended inverting amplifier. The inverting input of amplifier 330 is coupled to the output of amplifier 320 via a DC blocking capacitor Cdc, and the non-inverting input of amplifier 330 is coupled to a DC reference voltage Vref. A noise cancellation signal I_inj is generated from the output of amplifier 330 and is coupled to the first end of the sensing resistor Rs via an injection capacitor CINJ, thereby injecting the AC component of the noise cancellation signal I_inj into the input node NII of the switching power converter 104. A feedback resistor Rfb3 is coupled between the output and the inverting input of amplifier 330, thereby providing feedback control. It should be noted that in one embodiment, the amplifiers (e.g., amplifiers 310, 320, and 330) can be single-supply amplifiers, as can the following amplifiers.

[0103] Please continue reading. Figure 2 and Figure 4 The switching power converters 102 and 104 further include passive filter circuits 80'. In one embodiment, the passive filter circuit 80' is coupled between the sensing resistor Rs and the power stage circuit 10. The passive filter circuit 80' includes a filter inductor Lf', a damping capacitor Cd', and a damping resistor Rd', to further filter the noise input signal Vnoise. It should be noted that, compared with the prior art, the present invention, through the effect of the active electromagnetic interference filter circuit on reducing electromagnetic interference, can significantly reduce the inductance value of the filter inductor Lf' and the capacitance value of the damping capacitor Cd' required in the passive filter circuit 80', and the present invention can omit the prior art. Figure 1 The filter capacitors in the circuit can be used, thus saving costs. It should also be noted that the input capacitor CIN can be configured to be coupled to the connection node between the passive filter circuit 80' and the power stage circuit 10.

[0104] Figure 5 The results are displayed by the analyzer (coupled to the line impedance stabilization network 50), corresponding to the measurements respectively. Figure 1 The existing technology and the Fast Fourier Transform (FFT) frequency response diagram of the switching power converter 104 are shown. It should be noted that, as Figure 5 As shown in the diagram, from the fundamental frequency to all higher harmonics, the switching power converter 104 using an active electromagnetic interference filter circuit can effectively improve the suppression of switching noise.

[0105] Figure 6 This diagram illustrates a preferred embodiment of the switching power converter of the present invention. In one embodiment, the noise input signal Vnoise is related to the switching node NLx of the power stage.

[0106] The switching power converter 106 also includes a buffer circuit 40, which includes a buffer capacitor Csnub and a buffer resistor Rsnub, wherein the buffer capacitor Csnub and the buffer resistor Rsnub are connected in series to the switching node NLx, and the switching node NLx is coupled to one end of the inductor Lx.

[0107] In this embodiment, the amplifier 340 of the active electromagnetic interference filter circuit 32 is configured as a non-inverting amplifier stage. The non-inverting input terminal of the amplifier 340 is coupled to the switching node NLx via the buffer circuit 40 and an input capacitor CS1. The input capacitor CS1 is coupled to the shared node Nsn, which is coupled to the buffer capacitor Csnub and the buffer resistor Rsnub. The noise cancellation signal I_inj is generated by the output terminal of the amplifier 340. The noise cancellation signal I_inj is coupled to the input node NII via the injection capacitor CINJ. Specifically, the AC component of the noise cancellation signal I_inj is injected into the input node NII of the switching power converter 106.

[0108] Please continue reading. Figure 6 The switching power converter 106 also includes a passive filter circuit 80'. In one embodiment, the passive filter circuit 80' is coupled between the input node NII and the power stage circuit 10.

[0109] Figure 7 The results are displayed by the analyzer (coupled to the line impedance stabilization network 50), corresponding to the measurements respectively. Figure 1 The existing technology and the Fast Fourier Transform (FFT) frequency response diagram of the switching power converter 106 are shown. It should be noted that, as Figure 7 As shown in the diagram, from the fundamental frequency to all higher harmonics, the switching power converter 106 using an active electromagnetic interference filter circuit can effectively improve the suppression of switching noise.

[0110] Figure 8 A schematic diagram showing a preferred embodiment of the switching power converter of the present invention is displayed. Figure 10 A schematic diagram showing a preferred embodiment of the switching power converter of the present invention is displayed. Figure 12B This diagram illustrates a preferred embodiment of the switching power converter of the present invention. In the above embodiment, the power stage circuit 10 in the switching power converters 108, 110, and 112B each includes an upper-bridge transistor QH and a lower-bridge transistor QL, coupled to each other at a switching node NLx, for switching one end of the inductor Lx. In the above embodiment, the power stage circuit 10 is configured as a buck converter. In this embodiment, the noise input signal Vnoise is related to the drain-source current IdsH of the upper-bridge transistor QH and / or the drain-source current IdsL of the lower-bridge transistor QL.

[0111] Please see Figure 8The active electromagnetic interference filter circuit 33 includes an amplifier 340 configured as a non-inverting amplification stage. The non-inverting input of the amplifier 340 is coupled to a sensing element that senses the drain-source current IdsH of the upper-bridge transistor QH via an input capacitor CS1, thereby coupling the AC component of the noise input signal Vnoise from the sensing element through the input capacitor CS1. In one embodiment, the sensing element may be, for example, a current mirror, used to mirror a portion of the drain-source current IdsH, and a resistor Rs1 is used to convert the mirrored current into a sensing voltage related to the noise input signal Vnoise. In another embodiment, the sensing element may be, for example, a sensing resistor, connected in series with the upper-bridge transistor QH. The inverting input of the amplifier 340 is coupled to a ground node via a DC blocking capacitor Cdc1.

[0112] Please continue reading. Figure 8 The noise cancellation signal I_inj is generated at the output of amplifier 340 and coupled to input node NII via injection capacitor CINJ. Specifically, the AC component of the noise cancellation signal I_inj is injected into input node NII of the switching power converter 108.

[0113] Figure 9 The results are displayed by the analyzer (coupled to the line impedance stabilization network 50), corresponding to the measurements respectively. Figure 1 The existing technology and the Fast Fourier Transform (FFT) frequency response diagram of the switching power converter 108 are shown. It should be noted that, as Figure 9 As shown in the diagram, from the fundamental frequency to all higher harmonics, the switching power converter 108 using an active electromagnetic interference filter circuit can effectively improve the suppression of switching noise.

[0114] Please see Figure 10 The active electromagnetic interference filter circuit 34 includes an amplifier 350 configured as an inverting amplifier stage. The inverting input of the amplifier 350 is coupled to a sensing element that senses the drain-source current IdsL of the lower-bridge transistor QL via an input capacitor CS2, thereby coupling the AC component of the noise input signal Vnoise from the sensing element through the input capacitor CS2. In one embodiment, the sensing element may be, for example, a current mirror, used to mirror a portion of the drain-source current IdsL, and a resistor Rs2 is used to convert the mirrored current into a sensing voltage related to the noise input signal Vnoise. In another embodiment, the sensing element may be, for example, a sensing resistor, connected in series with the lower-bridge transistor QL. The non-inverting input of the amplifier 350 is coupled to a DC reference voltage Vref.

[0115] Please continue reading. Figure 10The noise cancellation signal I_inj is generated at the output of amplifier 350 and coupled to input node NII via injection capacitor CINJ. Specifically, the AC component of the noise cancellation signal I_inj is injected into input node NII of the switching power converter 110.

[0116] Figure 11 The results are displayed by the analyzer (coupled to the line impedance stabilization network 50), corresponding to the measurements respectively. Figure 1 The existing technology and the Fast Fourier Transform (FFT) frequency response diagram of the switching power converter 110 are shown. It should be noted that, as Figure 11 As shown in the diagram, from the fundamental frequency to all higher harmonics, the switching power converter 110 using an active electromagnetic interference filter circuit can effectively improve the suppression of switching noise.

[0117] Figure 12A This diagram illustrates a preferred embodiment of the switching power converter of the present invention. The switching power converter 112A is a combination of switching power converters 108 and 110. In one embodiment, as... Figure 12A As shown, the outputs of amplifiers 340 and 350 are added together and then injected into the input node N1I of the switching power converter 112A via the injection capacitor CINJ.

[0118] Figure 12B The display corresponds to Figure 12A A more specific embodiment diagram is shown.

[0119] Please continue reading. Figure 12B The active electromagnetic interference filter circuit 35 of the switching power converter 112B includes an amplifier 360, which is configured as a non-inverting adder circuit. The non-inverting input of amplifier 360 is coupled to the output of amplifier 340 via a DC blocking capacitor Cdc2, and to the output of amplifier 350 via a DC blocking capacitor Cdc3, such that the AC component of the output signal generated by the output of amplifier 340 and the AC component of the output signal generated by the output of amplifier 350 are superimposed and amplified by amplifier 360. The inverting input of amplifier 360 is coupled to a ground node via a DC blocking capacitor Cdc4.

[0120] Please continue reading. Figure 12B The noise cancellation signal I_inj is generated at the output of amplifier 360 and coupled to input node NII via injection capacitor CINJ. Specifically, the AC component of the noise cancellation signal I_inj is injected into input node NII of the switching power converter 112B.

[0121] Figure 13 The display corresponds to Figure 8 , Figure 10 , Figure 12B The operating waveforms of the embodiment are shown below. The first waveform shows the waveform of the switching node voltage VLx at the switching node NLx. The second waveform shows the waveform of the sensing signal VcsH, which is related to the inductor current ILx and sensed based on the drain-source current IdsH of the upper-bridge transistor QH. The third waveform shows the waveform of the sensing signal VcsL, which is related to the inductor current ILx and sensed based on the drain-source current IdsL of the lower-bridge transistor QL. The fourth waveform shows the waveform of the noise input signal Vnoise. The fifth waveform shows the waveform of the noise cancellation signal I_inj, obtained by superimposing and amplifying the sensing signals VcsH and VcsL, where the DC component is blocked by an injection capacitor (e.g., CINJ). The sixth waveform shows the waveform of the compensation signal Vcomp, which is the noise input signal Vnoise canceled by the noise cancellation signal I_inj. The level of the compensation signal Vcomp is significantly lower than that of the noise input signal Vnoise. It should be noted that the switching frequency of the switching power converter according to the present invention is Fsw, and Tsw is the period corresponding to the switching frequency Fsw, where Fsw=1 / Tsw.

[0122] Figure 14 The results are displayed by the analyzer (coupled to the line impedance stabilization network 50), corresponding to the measurements respectively. Figure 1 The existing technology and the Fast Fourier Transform (FFT) frequency response diagram of the switching power converter 112B are shown. It should be noted that, as... Figure 14 As shown in the diagram, the switching power converter 112B using an active electromagnetic interference filter circuit can effectively improve the suppression of switching noise, from the fundamental frequency to all higher harmonics.

[0123] Figure 15 This table displays a noise comparison of prior art (without active electromagnetic interference filter circuit) and all the embodiments described above, based on the present invention, a switching power converter with different active electromagnetic interference filter circuits (AEF). For example... Figure 15 As shown, all embodiments of the present invention achieve significant improvements compared to the prior art.

[0124] The present invention has been described above with reference to preferred embodiments. However, the above description is only intended to facilitate understanding of the invention by those skilled in the art and is not intended to limit the broadest scope of the invention. The described embodiments are not limited to individual application and can also be used in combination. For example, two or more embodiments can be used in combination, and some components of one embodiment can be used to replace corresponding components in another embodiment. Furthermore, within the same spirit of the invention, those skilled in the art can conceive of various equivalent changes and combinations. For example, the phrase "processing or calculating based on a signal or generating an output result" in the present invention is not limited to the signal itself, but also includes, when necessary, performing voltage-to-current conversion, current-to-voltage conversion, and / or proportional conversion on the signal, and then processing or calculating based on the converted signal to generate an output result. Therefore, within the same spirit of the invention, those skilled in the art can conceive of various equivalent changes and combinations, and there are many combinations, which will not be listed here. Therefore, the scope of the present invention should cover the above and all other equivalent changes.

Claims

1. A switching power converter, characterized in that, Include: A power stage circuit includes at least one transistor for switching an inductor to convert an input power supply into an output power supply; A switching controller is used to control the at least one transistor; An active electromagnetic interference (EMI) filter circuit includes at least one amplifier, wherein the at least one amplifier is configured to sense a noise input signal and amplify the noise input signal to generate a noise cancellation signal, wherein the noise input signal is related to switching noise generated during switching of the power stage circuit, wherein the noise cancellation signal is injected into an input node of the switching power converter to suppress the switching noise and thus reduce EMI, wherein the input power supply supplies power to the power stage circuit via the input node; and The switching power converter also includes a buffer circuit, which includes a buffer capacitor and a buffer resistor. The buffer capacitor and the buffer resistor are connected in series to a switching node, and the switching node is coupled to one end of the inductor. The at least one amplifier includes an amplifier configured as a non-inverting amplification stage, wherein a non-inverting input of the amplifier is coupled to the switching node via the buffer circuit and an input capacitor, wherein the input capacitor is coupled to a shared node coupled to the buffer capacitor and the buffer resistor, and a non-inverting input of the amplifier is coupled to a ground node via a DC blocking capacitor, thereby coupling the AC component of the noise input signal from the buffer circuit; The noise cancellation signal is generated at one output of the amplifier and injected into the input node of the switching power converter via an injection capacitor.

2. The switching power converter as described in claim 1, wherein, It also includes a passive filter circuit, wherein the passive filter circuit is coupled between the input node and the power stage circuit, and wherein the passive filter circuit includes a filter inductor and a filter capacitor for further filtering the noisy input signal.

3. An active electromagnetic interference filter circuit for a switching power converter, wherein the switching power converter comprises: A power stage circuit, including at least one transistor, for switching an inductor to convert an input power supply into an output power supply, characterized in that the active electromagnetic interference filter circuit comprises: At least one amplifier; Multiple passive filtering elements are coupled to the at least one amplifier; The at least one amplifier is used to sense a noise input signal and amplify the noise input signal to generate a noise cancellation signal, wherein the noise input signal is related to switching noise generated when the power stage circuit switches, wherein the noise cancellation signal is injected into an input node of the switching power converter to suppress the switching noise and thus reduce electromagnetic interference, wherein the input power supply supplies power to the power stage circuit via the input node; and A buffer circuit, wherein the buffer circuit includes a buffer capacitor and a buffer resistor, wherein the buffer capacitor and the buffer resistor are connected in series and coupled to a switching node, wherein the switching node is coupled to one end of the inductor. The at least one amplifier includes an amplifier configured as a non-inverting amplification stage, wherein a non-inverting input of the amplifier is coupled to the switching node via the buffer circuit and an input capacitor, wherein the input capacitor is coupled to a shared node coupled to the buffer capacitor and the buffer resistor, and a non-inverting input of the amplifier is coupled to a ground node via a DC blocking capacitor, thereby coupling the AC component of the noise input signal from the buffer circuit; The noise cancellation signal is generated at one output of the amplifier and injected into the input node of the switching power converter via an injection capacitor.

4. The active electromagnetic interference filter circuit as described in claim 3, wherein, The switching power converter also includes a passive filter circuit, which is coupled between the input node and the power stage circuit. The passive filter circuit includes a filter inductor and a filter capacitor to further filter the noisy input signal.

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