A three-level boost circuit and switching power supply

Abstract

The utility model provides a kind of three-level boost circuit and switching power supply, the three-level boost circuit includes: input EMI filter, three-level boost converter and cross connection capacitor unit, the three-level boost converter includes bus capacitor series connection unit, the cross connection capacitor unit is respectively with the midpoint of the input EMI filter, the bus capacitor series connection unit electrically connected.The utility model increases cross connection capacitor unit after the midpoint of bus capacitor series connection unit and input EMI filter, can make input transmission due to the oscillation frequency point left shift caused by parasitic parameter, make the oscillation frequency point move to the frequency range of higher peak limit, to be able to make the effect that full-range input transmission more easily satisfy limit requirement, ensure that circuit meets EMI standard.

Description

Technical Field

[0001] This utility model relates to the field of circuit technology, and in particular to a three-level boost circuit and a switching power supply. Background Technology

[0002] Three-level boost circuits are widely used in high-power, high-voltage applications. Compared to traditional two-level boost circuits, they allow the use of low-voltage power transistors and small-sized inductors to achieve high-voltage output.

[0003] When a three-level boost circuit is applied to a DC input, at least one EMI (electromagnetic interference) filter is typically added at the input to suppress EMI noise generated within the circuit. Without effective filtering, this noise will radiate through the input lines, affecting other circuits and potentially failing to meet EMI standards. Furthermore, practical three-level boost circuits contain numerous parasitic parameters, such as parasitic capacitance of inductors, parasitic capacitance and inductance of switching transistors, and parasitic capacitance and inductance of diodes. These parasitic parameters can form resonant circuits in the circuit, causing high-frequency oscillations at certain specific frequencies. These oscillations, superimposed on the noise generated by the switching transistors themselves, result in insufficient or excessive input conduction margin at the oscillation frequency during EMC (electromagnetic compatibility) testing, preventing the circuit from adequately meeting EMI requirements. Utility Model Content

[0004] This invention provides a three-level boost circuit and a switching power supply, aiming to solve the problem in related technologies where the oscillation peak value caused by the parasitic parameters of the boost circuit exceeds the limit, making the circuit unable to meet EMI requirements.

[0005] To solve the above-mentioned technical problems, the first aspect of this utility model provides a three-level boost circuit, including: an input EMI filter, a three-level boost converter, and a bridging capacitor unit. The three-level boost converter includes a bus capacitor series unit, and the bridging capacitor unit is electrically connected to the midpoint of the input EMI filter and the bus capacitor series unit, respectively.

[0006] Furthermore, the bridging capacitor unit includes a first bridging capacitor, and the input EMI filter includes an output capacitor series unit. The first bridging capacitor is electrically connected to the midpoint of the output capacitor series unit and the bus capacitor series unit, respectively.

[0007] Furthermore, the three-level boost circuit also includes a first bridging resistor, which is connected in series with the first bridging capacitor.

[0008] Furthermore, the bridging capacitor unit includes a first bridging capacitor and a second bridging capacitor. The first bridging capacitor is electrically connected to the positive output terminal of the input EMI filter and the midpoint of the series bus capacitor unit, respectively. The second bridging capacitor is electrically connected to the negative output terminal of the input EMI filter and the midpoint of the series bus capacitor unit, respectively.

[0009] Furthermore, the three-level boost circuit also includes a first bridging resistor and a second bridging resistor, wherein the first bridging resistor is connected in series with the first bridging capacitor, and the second bridging resistor is connected in series with the second bridging capacitor.

[0010] Furthermore, the input EMI filter also includes an input capacitor series unit and at least one common-mode inductor. The output terminals of the common-mode inductor are electrically connected to the output capacitor series unit, and the input terminals of the common-mode inductor are electrically connected to the input capacitor series unit.

[0011] Furthermore, the input EMI filter includes a first Y capacitor and a second Y capacitor, the first Y capacitor being electrically connected at a midpoint to the output capacitor series unit, and the second Y capacitor being electrically connected at a midpoint to the input capacitor series unit.

[0012] Furthermore, the three-level boost converter also includes a first inductor, a second inductor, a first diode, a second diode, and a series connection unit of a switching transistor; one end of the first inductor, the anode of the first diode, and one end of the series connection unit of the switching transistor are interconnected; one end of the second inductor, the cathode of the first diode, and the other end of the series connection unit of the switching transistor are interconnected; the cathode of the first diode and the anode of the second diode are respectively electrically connected to the series connection unit of the bus capacitor; the midpoint of the series connection unit of the switching transistor is electrically connected to the midpoint of the series connection unit of the bus capacitor.

[0013] The second aspect of this utility model provides a switching power supply, including the three-level boost circuit as described in the first aspect of this utility model.

[0014] As can be seen from the above description, by adding a bridging capacitor unit between the midpoint of the bus capacitor series unit and the input EMI filter, this application can reduce the oscillation frequency caused by parasitic parameters in the input conduction, that is, the oscillation frequency is in a frequency range with a higher peak limit, thereby making it easier for the input conduction across the entire range to meet the limit requirements and ensuring that the circuit complies with EMI standards. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a three-level boost circuit according to an embodiment of the present invention; Figure 2 This is the schematic diagram of a three-level boost circuit without a bridging capacitor. Figure 3 This is a schematic diagram of the conduction test results of the input voltage Vin+ of a three-level boost circuit without a bridging capacitor. Figure 4 This is a schematic diagram of the conduction test results of the input voltage Vin+ of the first three-level boost circuit according to an embodiment of this utility model; Figure 5 This is a circuit diagram of the first type of three-level boost circuit according to an embodiment of this utility model; Figure 6 This is a circuit diagram of the second type of three-level boost circuit according to an embodiment of this utility model; Figure 7 This is a schematic diagram of the conduction test results of the input voltage Vin+ of the second type of three-level boost circuit according to an embodiment of this utility model; Figure 8 This is a circuit diagram of the third type of three-level boost circuit according to an embodiment of this utility model; Figure 9 This is a circuit diagram of the fourth type of three-level boost circuit according to an embodiment of this utility model. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. Throughout the description, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model. Furthermore, the technical features involved in the various embodiments of the present utility model described below can be combined with each other as long as they do not conflict with each other.

[0017] In related technologies, there is a problem that the oscillation peak value caused by the parasitic parameters of the boost circuit exceeds the limit, making the circuit unable to meet the EMI requirements well. Therefore, this utility model embodiment provides a three-level boost circuit.

[0018] like Figure 1 The diagram shown is a structural schematic of a three-level boost circuit provided in an embodiment of the present invention. The three-level boost circuit includes: an input EMI filter 100, a three-level boost converter 200, and a bridging capacitor unit 300. The three-level boost converter 200 includes a bus capacitor series unit 210. The bridging capacitor unit 300 is electrically connected to the midpoint of the input EMI filter 100 and the bus capacitor series unit 210, respectively.

[0019] In practical circuits, power devices such as inductors, switching transistors, and diodes possess parasitic parameters. These parasitic parameters can form resonant circuits, generating high-frequency oscillations at specific frequencies. These high-frequency oscillations are superimposed on the electromagnetic interference noise generated by the switching transistors in the main circuit, thus affecting the input and output conduction characteristics. In EMC testing, if the level of conducted interference at the oscillation frequency point approaches or exceeds a preset limit, it will lead to insufficient margin or exceeding the limit, thereby affecting the electromagnetic compatibility of the equipment. For example, when using... Figure 2 When the three-level boost circuit without a bridging capacitor is shown, the input conduction test results corresponding to the input voltage Vin+ are as follows: Figure 3 As shown, the input conducted signal test measures the electromagnetic interference level on the input transmission line, typically expressed in decibels and microvolts (dBµV). These values ​​reflect the interference intensity at different frequencies. The blue curve represents the variation of the quasi-resonant value at different frequencies, and the green curve represents the variation of the average electromagnetic interference level at different frequencies. The limit corresponding to the quasi-resonant value is the red line (i.e., CE_AC Mains_Class A_QP in the figure), and the limit corresponding to the average resonant value is the green line (i.e., CE_AC Mains_Class A_AV in the figure). Due to the influence of parasitic parameters of the three-level boost circuit, a high-frequency resonant peak appears in the input conducted signal near 600kHz, resulting in a resonant margin (green line) of less than 3dB.

[0020] In this embodiment, by adding a bridging capacitor unit 300 between the midpoint of the bus capacitor series unit 210 and the input EMI filter 100, the oscillation frequency point caused by parasitic parameters in the input conduction can be shifted to the left. For example... Figure 4 The input conduction test results corresponding to the input voltage Vin+ show that the frequency corresponding to the resonant peak has shifted to the left to around 200kHz. Since the peak value limit is higher in the frequency range of 150 to 500kHz, it is easier to meet EMI limits for input conduction across the entire range, which is beneficial for improving the circuit's EMC performance.

[0021] like Figure 5 The diagram shown is the circuit schematic of the first type of three-level boost circuit provided in this embodiment. Please refer to [link / reference]. Figure 1 and Figure 5 The bridging capacitor unit 300 includes a first bridging capacitor C9, and the input EMI filter 100 includes an output capacitor series unit. The first bridging capacitor C9 is electrically connected to the midpoint of the output capacitor series unit and the bus capacitor series unit 210, respectively.

[0022] In this embodiment, the bridging capacitor unit 300 includes a bridging capacitor connected between the midpoint of the output capacitor series unit and the midpoint of the bus capacitor series unit 210. The bridging capacitor can be a type of capacitor such as an aluminum electrolytic capacitor, and its value can be selected based on the noise frequency type (e.g., high-frequency or low-frequency noise), or by using simulation tools to verify the impact of different capacitor values ​​on circuit performance to determine a suitable value. The output capacitor series unit in the input EMI filter 100 can be used to smooth the power output and reduce power fluctuations, while the bus capacitor series unit 210 can be used to stabilize circuit performance, improve efficiency, and ensure the quality of the output voltage.

[0023] Adding the bridging capacitor C9 shifts the oscillation frequency point caused by parasitic parameters in the input conduction result to the left, that is, moves the oscillation frequency point to a frequency range higher than the peak and quasi-peak limits. This makes it easier for the full-range input conduction to meet the limit requirements, ensuring that the circuit meets EMI requirements. For example... Figure 4 The input voltage Vin+ input conduction test results show that the resonant peak frequency shifts to the left to around 200kHz, and the resonant margin (green line) is greater than 5dB.

[0024] like Figure 6 The diagram shown is the circuit schematic of the second type of three-level boost circuit provided in this embodiment. Please refer to [link / reference]. Figure 6 The three-level boost circuit also includes a first bridging resistor R1, which is connected in series with a first bridging capacitor C9.

[0025] In this embodiment, a bridging resistor R1 can also be connected in series with the bridging capacitor C9, such as... Figure 7 The input conduction test results corresponding to the input voltage Vin+ shown show that after adding the bridging resistor R1, the amplitude of the resonance peak of the input conduction near 200kHz is significantly reduced, and the resonance margin (green line) is greater than 10dB, which can further increase the input conduction margin.

[0026] like Figure 8 The diagram shown is the circuit schematic of the third type of three-level boost circuit provided in this embodiment. Please refer to [link / reference]. Figure 8 The bridging capacitor unit 300 includes a first bridging capacitor C9 and a second bridging capacitor C10. The first bridging capacitor C9 is electrically connected to the positive output terminal of the input EMI filter 100 and the midpoint of the bus capacitor series unit 210, respectively. The second bridging capacitor C10 is electrically connected to the negative output terminal of the input EMI filter 100 and the midpoint of the bus capacitor series unit 210, respectively.

[0027] In this embodiment, the bridging capacitor unit 300 may further include two bridging capacitors, each connected between the output terminal of the input EMI filter 100 and the midpoint of the bus capacitor series unit 210. The principle of this structure is the same as that of the bridging capacitor unit 300 containing a single bridging capacitor connected between the midpoint of the output capacitor series unit and the midpoint of the bus capacitor series unit 210, and will not be repeated here.

[0028] like Figure 9 The diagram shown is the circuit schematic of the third type of three-level boost circuit provided in this embodiment. Please refer to [link / reference]. Figure 9 The three-level boost circuit also includes a first bridging resistor R1 and a second bridging resistor R2. The first bridging resistor R1 is connected in series with the first bridging capacitor C9, and the second bridging resistor R2 is connected in series with the second bridging capacitor C10.

[0029] In this embodiment, when the bridging capacitor unit 300 includes two bridging capacitors, each can also be connected in series with a bridging resistor to further optimize the amplitude of the resonance peak. The principle of this structure is the same as that of the bridging capacitor unit 300 including a single bridging capacitor, where the single bridging capacitor is connected between the midpoint of the output capacitor series unit and the midpoint of the bus capacitor series unit 210, and will not be described again here.

[0030] Further, please see Figures 1 to 9 The output capacitor series unit includes a first X capacitor C3 and a second X capacitor C4; the first X capacitor C3 and the second X capacitor C4 are connected in series, and the common connection terminal of the first X capacitor C3 and the second X capacitor C4 is the midpoint of the output capacitor series unit. The two ends of the output capacitor series unit are electrically connected to the two input ends of the three-level boost converter 200.

[0031] Further, please see Figures 1 to 9 The input EMI filter 100 also includes an input capacitor series unit and at least one common-mode inductor L3. The output terminals of the common-mode inductor L3 are electrically connected to the output capacitor series unit, and the input terminals of the common-mode inductor L3 are electrically connected to the input capacitor series unit. The input capacitor series unit includes a third X capacitor C6 and a fourth X capacitor C7; the third X capacitor C6 and the fourth X capacitor C7 are connected in series, and the two ends of the input capacitor series unit are electrically connected to the two ends of an external power supply circuit.

[0032] Further, please see Figures 1 to 9 The input EMI filter 100 also includes a first Y capacitor C5 and a second Y capacitor C8. The first Y capacitor C5 is electrically connected to the midpoint of the output capacitor series unit, and the second Y capacitor C8 is electrically connected to the midpoint of the input capacitor series unit.

[0033] In this embodiment, the input EMI filter 100 includes a common-mode inductor L3, an input capacitor series unit, an output capacitor series unit, a first Y capacitor C5, a second Y capacitor C8, an input capacitor series unit including a third X capacitor C6 and a fourth X capacitor C7, and an output capacitor series unit including a first X capacitor C3 and a second X capacitor C4. X capacitors C6 and C7 are connected in series to the positive and negative input terminals of the input EMI filter 100, and the midpoint of the series connection of X capacitors C6 and C7 is connected to the PE (ground) via the second Y capacitor C8. X capacitors C3 and C4 are connected in series to the positive and negative output terminals of the input EMI filter 100, and the midpoint of the series connection of X capacitors C3 and C4 is connected to the PE via the first Y capacitor C5. One side of the common-mode inductor L3 is connected to the positive input terminal and the positive output terminal of the input EMI filter 100, and the other side of the common-mode inductor L3 is connected to the negative input terminal and the negative output terminal of the input EMI filter 100. The input EMI filter 100 can be used to suppress high-frequency stray signals and electromagnetic interference on signal transmission lines, reduce the interference of the equipment to the outside world, improve its own anti-interference ability, and maintain the working stability of the circuit.

[0034] Further, please see Figures 1 to 9 The bus capacitor series unit 210 includes a first bus capacitor C1 and a second bus capacitor C2 connected in series, and the common connection terminal of the first bus capacitor C1 and the second bus capacitor C2 is the midpoint of the bus capacitor series unit 210.

[0035] Further, please see Figures 1 to 9 The three-level boost converter 200 also includes a first inductor L1, a second inductor L2, a first diode D1, a second diode D2, and a series switching transistor unit; one end of the first inductor L1, the anode of the first diode D1, and one end of the series switching transistor unit are interconnected; one end of the second inductor L2, the cathode of the first diode D1, and the other end of the series switching transistor unit are interconnected; the cathode of the first diode D1 and the anode of the second diode D2 are respectively electrically connected to the series bus capacitor unit 210; the midpoint of the series switching transistor unit is electrically connected to the midpoint of the series bus capacitor unit 210.

[0036] Further, please see Figures 1 to 9 The series-connected switching transistor unit includes a first switching transistor Q1 and a second switching transistor Q2. The first terminal of the first switching transistor Q1 is electrically connected to a first inductor L1 and a first diode D1, respectively. The second terminal of the first switching transistor Q1 is electrically connected to the first terminal of the second switching transistor Q2 and the bus capacitor series-connected unit 210, respectively. The second terminal of the second switching transistor Q2 is electrically connected to a second inductor L2 and a second diode D2, respectively. The third terminals of both the first switching transistor Q1 and the second switching transistor Q2 are used for electrical connection to an external control circuit. The first switching transistor Q1 and the second switching transistor Q2 can be either a MOSFET or an IGBT.

[0037] In this embodiment, the three-level boost converter 200 includes inductors L1 and L2, switching transistors Q1 and Q2, diodes D1 and D2, and bus capacitors C1 and C2. One end of inductor L1 is connected to the positive output terminal of the input EMI filter 100, and the other end is connected to the drain of the switching transistor (e.g., a MOSFET) Q1 and the anode of diode D1. One end of inductor L2 is connected to the negative output terminal of the input EMI filter 100, and the other end is connected to the source of the switching transistor (e.g., a MOSFET) Q2 and the cathode of diode D2. The source of switching transistor Q1 and the drain of switching transistor Q2 are connected in series. The cathode of diode D1 is connected to one end of bus capacitor C1 to the positive output terminal, and the anode of diode D2 is connected to one end of bus capacitor C2 to the negative output terminal. The other ends of bus capacitors C1 and C2 are connected in series to the midpoint of the series connection between the source of switching transistor Q1 and the drain of switching transistor Q2. The inductors can be used to store energy, reduce fluctuations and ripples in the output voltage, and provide a smoother DC output. Switching transistors are used to control the flow of current, periodically turning them on and off to regulate the output voltage. Diodes are used to control the direction of current flow, ensuring that current flows in only one direction. Bus capacitors are used to smooth the voltage, prevent voltage fluctuations, and stabilize the power supply. By configuring inductors, switching transistors, diodes, and bus capacitors, voltage conversion can be stabilized.

[0038] Furthermore, the switching transistors in this embodiment can be synchronously turned on and off, or they can be interleaved. When switching transistors Q1 and Q2 are turned on at different times, the ripple of the inductor current and the bus ripple current can be reduced, further improving the amplitude of the input conduction.

[0039] The three-level boost circuit provided in this embodiment of the invention, by connecting a capacitor unit across the midpoint of the series capacitor unit on the bus and the input EMI filter, can shift the resonant peak frequency caused by the parasitic parameters of the main circuit to a higher limit frequency range, such as 150 to 500 kHz, during input conduction testing, thereby meeting the conduction amplitude limit requirements. Furthermore, by connecting a bridging resistor in series with the bridging capacitor, the amplitude of the resonant point after the frequency reduction can be further limited, increasing the input conduction margin. Additionally, if the three-level boost topology is followed by a DC-DC main topology, a significant amount of common-mode interference is usually added to the bus. When a Y capacitor is connected to the midpoint of the series capacitor X at the filter output, a bridging capacitor is added between the midpoint of the bus capacitor and the midpoint of the input series capacitor. This bridging capacitor provides a common-mode path for the common-mode noise on the bus, effectively reducing the electromagnetic interference from the subsequent DC-DC topology.

[0040] This utility model embodiment also provides a switching power supply, which includes the above-described three-level boost circuit.

[0041] It should be noted that the various embodiments in this utility model are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0042] It should also be noted that, in the present invention, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0043] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined in the present invention may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-level boost circuit, characterized in that, include: The system includes an input EMI filter, a three-level boost converter, and a bridging capacitor unit. The three-level boost converter includes a bus capacitor series unit, and the bridging capacitor unit is electrically connected to the midpoint of the input EMI filter and the bus capacitor series unit, respectively.

2. The three-level boost circuit according to claim 1, characterized in that, The bridging capacitor unit includes a first bridging capacitor, and the input EMI filter includes an output capacitor series unit. The first bridging capacitor is electrically connected to the midpoint of the output capacitor series unit and the bus capacitor series unit, respectively.

3. The three-level boost circuit according to claim 2, characterized in that, It also includes a first bridging resistor, which is connected in series with the first bridging capacitor.

4. The three-level boost circuit according to claim 1, characterized in that, The bridging capacitor unit includes a first bridging capacitor and a second bridging capacitor. The first bridging capacitor is electrically connected to the positive output terminal of the input EMI filter and the midpoint of the series bus capacitor unit, respectively. The second bridging capacitor is electrically connected to the negative output terminal of the input EMI filter and the midpoint of the series bus capacitor unit, respectively.

5. The three-level boost circuit according to claim 4, characterized in that, It also includes a first bridging resistor and a second bridging resistor, wherein the first bridging resistor is connected in series with the first bridging capacitor, and the second bridging resistor is connected in series with the second bridging capacitor.

6. The three-level boost circuit according to claim 2, characterized in that, The input EMI filter further includes an input capacitor series unit and at least one common-mode inductor. The output terminals of the common-mode inductor are electrically connected to the output capacitor series unit, and the input terminals of the common-mode inductor are electrically connected to the input capacitor series unit.

7. The three-level boost circuit according to claim 6, characterized in that, The input EMI filter further includes a first Y capacitor and a second Y capacitor. The first Y capacitor is electrically connected at a midpoint to the output capacitor series unit, and the second Y capacitor is electrically connected at a midpoint to the input capacitor series unit.

8. The three-level boost circuit according to any one of claims 1 to 7, characterized in that, The three-level boost converter also includes a first inductor, a second inductor, a first diode, a second diode, and a series connection unit of a switching transistor; One end of the first inductor, the anode of the first diode, and one end of the series-connected switching transistor unit are interconnected; one end of the second inductor, the cathode of the first diode, and the other end of the series-connected switching transistor unit are interconnected; the cathode of the first diode and the anode of the second diode are respectively electrically connected to the series-connected bus capacitor unit; the midpoint of the series-connected switching transistor unit is electrically connected to the midpoint of the series-connected bus capacitor unit.

9. The three-level boost circuit according to claim 8, characterized in that, The switching transistors in the series switching transistor unit include any of the following: MOSFETs and IGBTs.

10. A switching power supply, characterized in that, Includes the three-level boost circuit as described in any one of claims 1 to 9.

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