Surge absorption circuit, frequency converter without electrolytic capacitor and air conditioner

Abstract

The utility model discloses a surge absorption circuit, no electrolytic capacitor frequency converter and air conditioner, no electrolytic capacitor frequency converter includes rectifier circuit, first filter circuit and inverter circuit, first filter circuit includes film capacitor, rectifier circuit's alternating current end is used for inputting alternating current, and inverter circuit is used for the inverter circuit. The direct-current end of the rectifying circuit is connected with the input end of the first filter circuit, the two ends of the thin-film capacitor serve as the output end of the first filter circuit and are connected with the direct-current end of the inverter circuit, and the alternating-current end of the inverter circuit is used for being connected with a load. Wherein the surge absorption circuit comprises a resistance sub-circuit and a discharge tube, and the resistance sub-circuit and the discharge tube are connected in series between the two ends of the direct current end of the rectification circuit. The surge absorption circuit can clamp the bus residual voltage of the DC side of the rectification circuit below a specified value when lightning surge occurs in the frequency converter without the electrolytic capacitor, so that the rectification circuit can be effectively prevented from being damaged, and the working safety and reliability of the frequency converter without the electrolytic capacitor are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of frequency converters, in particular to a surge absorption circuit, a frequency converter without electrolytic capacitors and an air conditioner. Background Art

[0002] When a lightning surge occurs in an inverter system without electrolytic capacitors, the lightning surge current will enter through the input end of the three-phase uncontrolled rectifier, causing the rectifier DC (Direct Current) side bus to pump. The residual voltage generated may be higher than the value that the rectifier can withstand, which can easily cause damage to the rectifier. Utility Model Content

[0003] The utility model aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the purpose of the utility model is to provide a surge absorption circuit, an electrolytic capacitor-free inverter and an air conditioner, so that when a lightning surge occurs in the electrolytic capacitor-free inverter, the bus residual voltage on the DC side of the rectifier circuit is clamped below a specified value, thereby avoiding damage to the rectifier circuit when a lightning surge occurs, and improving the safety and reliability of the electrolytic capacitor-free inverter.

[0004] To achieve the above-mentioned purpose, the first aspect of the utility model proposes a surge absorption circuit for an electrolytic capacitor-free inverter, wherein the electrolytic capacitor-free inverter comprises a rectifier circuit, a first filter circuit and an inverter circuit, wherein the first filter circuit comprises a thin film capacitor, the AC end of the rectifier circuit is used to input AC power, the DC end of the rectifier circuit is connected to the input end of the first filter circuit, the two ends of the thin film capacitor serve as the output ends of the first filter circuit, and are connected to the DC end of the inverter circuit, and the AC end of the inverter circuit is used to connect a load; wherein the surge absorption circuit comprises: a resistor subcircuit and a discharge tube, wherein the resistor subcircuit and the discharge tube are connected in series between the two ends of the DC end of the rectifier circuit.

[0005] In addition, the surge absorption circuit of the utility model may also have the following additional technical features:

[0006] In some examples, the resistor subcircuit includes: a first resistor, a first end of the first resistor is connected to a first end of a DC end of the rectifier circuit, a second end of the first resistor is connected to a first end of the discharge tube, and a second end of the discharge tube is connected to the other end of the DC end of the rectifier circuit.

[0007] In some examples, the first resistor is a varistor.

[0008] In some examples, the varistor is a varistor with an operating voltage of 820V, and the discharge tube is a discharge tube with an operating voltage of 1200V.

[0009] To achieve the above-mentioned purpose, the second aspect of the utility model proposes a non-electrolytic capacitor inverter, comprising: a rectifier circuit, a first filter circuit and an inverter circuit, and a surge absorption circuit according to the above-mentioned first aspect; wherein, the first filter circuit comprises a thin film capacitor, the AC end of the rectifier circuit is used to input AC power, the DC end of the rectifier circuit is connected to the input end of the first filter circuit, the two ends of the thin film capacitor serve as the output ends of the first filter circuit, and are connected to the DC end of the inverter circuit, the AC end of the inverter circuit is used to connect a load, and the surge absorption circuit is connected between the two ends of the DC end of the rectifier circuit.

[0010] In addition, the electrolytic capacitor-free frequency converter of the utility model may also have the following additional technical features:

[0011] In some examples, the first filter circuit further includes: a reactor, wherein a first end of the reactor is respectively connected to one end of the DC end of the rectifier circuit and a first end of the surge absorption circuit, a second end of the reactor is respectively connected to a first end of the thin film capacitor and one end of the DC end of the inverter circuit, and a second end of the thin film capacitor is respectively connected to the other end of the DC end of the rectifier circuit, a second end of the surge absorption circuit, and the other end of the DC end of the inverter circuit.

[0012] In some examples, the electrolytic capacitor-free inverter further includes: a second filter circuit, wherein an input end of the second filter circuit is used to input the alternating current, and an output end of the second filter circuit is connected to an alternating current end of the rectifier circuit.

[0013] In some examples, the rectifier circuit is a three-phase bridge diode rectifier circuit.

[0014] In some examples, the inverter circuit is a three-phase bridge inverter bridge.

[0015] To achieve the above-mentioned object, the third aspect of the present invention provides an air conditioner, characterized in that it comprises: the electrolytic capacitor-free inverter according to the second aspect.

[0016] The utility model provides a surge absorption circuit, an electrolytic capacitor-free frequency converter and an air conditioner. By connecting a resistor circuit and a discharge tube in series between the two ends of the DC end of the rectifier circuit of the electrolytic capacitor-free frequency converter, the bus residual voltage on the DC side of the rectifier circuit can be clamped below a specified value when a lightning surge occurs in the electrolytic capacitor-free frequency converter, thereby effectively avoiding damage to the rectifier circuit and improving the safety and reliability of the operation of the electrolytic capacitor-free frequency converter.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description and in part will become apparent from the following description or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of an electrolytic capacitor-free frequency converter according to an embodiment of the utility model;

[0019] Figure 2 This is a system topology diagram of an electrolytic capacitor-free frequency converter according to an embodiment of the utility model;

[0020] Figure 3 This is a waveform diagram of the power-on instant of an embodiment of the utility model;

[0021] Figure 4 This is a surge test waveform diagram of an embodiment of the utility model;

[0022] Figure 5 This is a surge test waveform diagram of an embodiment of the utility model;

[0023] Figure 6 This is a diagram of the surge residual pressure selection process of an embodiment of the utility model. DETAILED DESCRIPTION

[0024] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0025] The surge absorption circuit, the electrolytic capacitor-free inverter and the air conditioner according to the embodiments of the present utility model are described below with reference to the accompanying drawings.

[0026] Figure 1 It is a structural schematic diagram of an electrolytic capacitor-free frequency converter according to an embodiment of the utility model.

[0027] like Figure 1 As shown, the electrolytic capacitor-free inverter 100 includes: a rectifier circuit 101, a first filter circuit 103 and an inverter circuit 104, the first filter circuit 103 includes a thin film capacitor C, the AC end of the rectifier circuit 101 is used to input AC power, the DC end of the rectifier circuit 101 is connected to the input end of the first filter circuit 103, the two ends of the thin film capacitor C serve as the output ends of the first filter circuit 103, connected to the DC end of the inverter circuit 104, and the AC end of the inverter circuit 104 is used to connect the load; the surge absorption circuit 102 includes: a resistor sub-circuit 1021 and a discharge tube GD, the resistor sub-circuit 1021 and the discharge tube GD are connected in series between the two ends of the DC end of the rectifier circuit 101.

[0028] Specifically, when the electrolytic capacitor-free inverter is powered on or a lightning surge occurs, if the bus voltage phase angle is exactly 90 degrees, theoretically the bus voltage may be pumped up to nearly 1300V, thereby causing the bus residual voltage to exceed the specified value that the rectifier circuit 101 can withstand. For this reason, the utility model connects a surge absorption circuit 102 in parallel on the rear-stage DC output side of the rectifier circuit 101 of the electrolytic capacitor-free inverter 100 to clamp the bus residual voltage below the specified value, thereby effectively avoiding damage to the rectifier circuit 101 and improving the safety and reliability of the operation of the electrolytic capacitor-free inverter 100.

[0029] In some embodiments of the present invention, Figure 2 As shown, the resistor subcircuit 1021 includes: a first resistor R1, a first end of the first resistor R1 is connected to a first end of the DC end of the rectifier circuit 101, a second end of the first resistor R1 is connected to a first end of the discharge tube GD, and a second end of the discharge tube GD is connected to the other end of the DC end of the rectifier circuit 101.

[0030] Among them, Figure 2 As shown, the first resistor R1 may be a varistor.

[0031] Specifically, a varistor is a voltage-limiting protection device. When the voltage applied to the varistor is lower than its threshold, the current flowing through it is extremely small, which is equivalent to a resistor with infinite resistance, that is, a switch in the open state; when the voltage applied to the varistor exceeds its threshold, the current flowing through it surges, which is equivalent to a resistor with infinite resistance, that is, a switch in the closed state. By utilizing the nonlinear characteristics of the varistor, when an overvoltage appears between the two poles of the varistor, the varistor can clamp the voltage to a relatively fixed voltage value, thereby protecting the subsequent circuit. The discharge tube GD is a high-voltage protection element. If the voltage at both ends of it is higher than its protection specification value, a short circuit will occur inside it and absorb the input overvoltage. Figure 2 In the surge absorption circuit 102 shown, the positions of the varistor and the discharge tube GD are exemplary, and the varistor and the discharge tube GD may be exchanged.

[0032] Figure 3 The waveform diagram of the input voltage, bus voltage and discharge tube voltage of the non-electrolytic capacitor inverter 100 at the moment of power-on is shown after the surge absorption circuit 102 is set. Figure 3 At the moment when the inverter 100 without electrolytic capacitor is powered on, the bus voltage is randomly pumped up to 1242V, but the two ends of the discharge tube GD are always under voltage and are not turned on. Figure 4 , Figure 5 The waveforms of input voltage, bus voltage and discharge tube GD current when different surge tests are performed on the non-electrolytic capacitor inverter 100 are shown respectively. Figure 4When a surge occurs, the bus voltage pump rises to 1630V, a short circuit occurs inside the discharge tube GD, and the current of the discharge tube GD reaches 1870A to absorb the input overvoltage and clamp the residual voltage of the bus; see Figure 5 When a surge occurs, the bus voltage pump rises to 1570V, a short circuit occurs inside the discharge tube GD, and the current of the discharge tube GD reaches 1760A to absorb the input overvoltage and clamp the residual voltage of the bus.

[0033] In some embodiments of the present invention, the varistor may be a 821 varistor (with an operating voltage of 820V), and the discharge tube GD may be a 122 discharge tube (with an operating voltage of 1200V).

[0034] Specifically, in order to make the bus residual voltage of the non-electrolytic capacitor inverter 100 less than the maximum allowable value specified in the specification, not only the surge residual voltage is considered when selecting, but also the surge absorption circuit 102 does not operate at the moment of power-on and when the non-electrolytic capacitor inverter 100 is operating normally. To this end, the utility model selects 821 varistor and 122 discharge tube, wherein 821 varistor and 122 discharge tube not only meet the surge residual voltage requirements, but also the 821 varistor operates at the lower limit of accuracy 657V, and the discharge tube GD operates at the lower limit of accuracy 960V, 657V+960V=1617V>1200Vmax, which satisfies the moment of power-on and when the non-electrolytic capacitor inverter is operating normally, and the surge absorption circuit 102 does not operate. Table 1 below shows the surge residual voltage satisfaction, power-on overvoltage action, and abnormal overvoltage action during operation corresponding to different varistor and discharge tube GD selections.

[0035] Table 1

[0036]

[0037] Among them, the operating voltage of the 102 discharge tube is 1000V, the operating voltage of the 152 discharge tube is 1500V, and the operating voltage of the 681 varistor is 680V.

[0038] Based on the surge absorption circuit 102 of the above embodiment, the utility model also proposes an electrolytic capacitor-free frequency converter.

[0039] See also Figure 1 , Figure 2The electrolytic capacitor-free inverter 100 includes: a rectifier circuit 101, a first filter circuit 103 and an inverter circuit 104, and the surge absorption circuit 102 of the above embodiment; wherein, the first filter circuit 103 includes a film capacitor C, the AC end of the rectifier circuit 101 is used to input AC power, the DC end of the rectifier circuit 101 is connected to the input end of the first filter circuit 103, the two ends of the film capacitor C serve as the output ends of the first filter circuit 103, and are connected to the DC end of the inverter circuit 104, the AC end of the inverter circuit 104 is used to connect the load, and the surge absorption circuit 102 is connected between the two ends of the DC end of the rectifier circuit 101.

[0040] Therefore, by connecting the surge absorption circuit 102 in parallel on the DC output side of the rectifier circuit 101 of the electrolytic capacitor-free inverter 100, the bus residual voltage can be clamped below the specified value, thereby effectively avoiding damage to the rectifier circuit 101 and improving the safety and reliability of the operation of the electrolytic capacitor-free inverter 100.

[0041] In some embodiments of the present invention, the rectifier circuit 101 may be a three-phase bridge diode rectifier circuit, which is used to convert AC into unidirectional pulsating DC. The inverter circuit 104 may be a three-phase bridge inverter bridge, which corresponds to the rectifier circuit 101 and realizes the conversion of the input DC voltage by controlling the conduction and disconnection of the switch devices in the three-phase bridge inverter bridge, thereby outputting the required AC voltage and frequency.

[0042] Among them, the switching device can be an IGBT (insulated gate bipolar transistor) tube, which is the core device of power control and power conversion. It is a composite fully controlled voltage-driven power semiconductor device composed of BJT (bipolar transistor) and MOS (insulated gate field effect transistor). It has the characteristics of high input impedance and low on-state voltage drop, and can achieve high-efficiency power regulation; it has high-speed switching characteristics and can complete switching operations in a short time, so it can be used in high-frequency circuits, thereby improving the performance of the system; it has the characteristics of low on-state loss, and can use low control voltage to switch high current levels, and has stronger conductivity and safety.

[0043] In some embodiments of the present invention, see Figure 2 The first filter circuit 103 also includes: a reactor Ldc, a first end of the reactor Ldc is respectively connected to one end of the DC end of the rectifier circuit 101 and a first end of the surge absorption circuit 102, a second end of the reactor Ldc is respectively connected to a first end of the film capacitor C and one end of the DC end of the inverter circuit 104, a second end of the film capacitor C is respectively connected to the other end of the DC end of the rectifier circuit 101, a second end of the surge absorption circuit 102, and the other end of the DC end of the inverter circuit 104.

[0044] Specifically, since the alternating current is rectified into pulsating direct current, such a direct current power supply cannot be directly used as a power supply for electronic circuits because it contains large AC ripples. The first filter circuit 103 can greatly reduce such AC ripple components, making the rectified voltage waveform smoother.

[0045] Among them, the main purpose of the reactor Ldc is to limit the AC component superimposed on the DC current to a certain specified value, maintain the continuity of the rectified current, reduce the high-frequency ripple value of the current, improve the input power factor, and suppress the harmonics generated by the rectifier circuit 101. The characteristics of the film capacitor C include: no polarity, no distinction between positive and negative poles, can be connected to the circuit at will; high insulation impedance, can withstand higher voltages without breakdown or leakage; excellent frequency characteristics, can maintain a stable capacitance value within a wide frequency range; small dielectric loss, can effectively reduce distortion when transmitting signals, especially where precise signal transmission is required; small temperature coefficient, the amplitude of capacitance value change with temperature is small, suitable for use in environments with large temperature changes, with good stability and reliability.

[0046] In some embodiments of the present invention, see Figure 2 The electrolytic capacitor-free inverter 100 further includes: a second filter circuit 105 , an input end of the second filter circuit 105 is used to input alternating current, and an output end of the second filter circuit 105 is connected to an alternating current end of the rectifier circuit 101 .

[0047] Specifically, the second filter circuit 105 may include an AC reactor, a current fuse, a differential mode X capacitor, a common mode Y capacitor, a varistor, and a discharge tube, etc., thereby reducing the influence of conducted interference between the non-electrolytic capacitor inverter 100 and the power grid, reducing the lightning strike damage suffered by the non-electrolytic capacitor inverter 100, and improving the reliability of the non-electrolytic capacitor inverter 100. In addition, by simultaneously providing the second filter circuit 105 and the surge absorption circuit 102 in the non-electrolytic capacitor inverter 100, the damage of the rectifier circuit 101 can be better avoided.

[0048] The utility model also provides an air conditioner.

[0049] Figure 6 It is a structural block diagram of an air conditioner according to an embodiment of the utility model.

[0050] like Figure 6 As shown, the air conditioner 600 includes the electrolytic capacitor-free inverter 100 of the above embodiment.

[0051] The surge absorption circuit, electrolytic capacitor-free inverter and air conditioner of the utility model embodiment can clamp the bus residual voltage on the DC side of the rectifier circuit below a specified value when a lightning surge occurs in the electrolytic capacitor-free inverter and the second filter circuit cannot meet actual needs, by connecting a varistor and a discharge tube in series between the two ends of the rectifier circuit of the electrolytic capacitor-free inverter. This can effectively avoid damage to the rectifier circuit and improve the safety and reliability of the operation of the electrolytic capacitor-free inverter.

[0052] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0053] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention 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 invention.

[0054] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present utility model, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0055] In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0056] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0057] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations of the present invention. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A surge absorption circuit, characterized in that: Used in an electrolytic capacitor-free frequency converter, the electrolytic capacitor-free frequency converter comprises a rectifier circuit, a first filter circuit and an inverter circuit, the first filter circuit comprises a thin film capacitor, the AC end of the rectifier circuit is used to input AC power, the DC end of the rectifier circuit is connected to the input end of the first filter circuit, the two ends of the thin film capacitor serve as the output ends of the first filter circuit, and are connected to the DC end of the inverter circuit, and the AC end of the inverter circuit is used to connect a load; Wherein, the surge absorption circuit comprises: a resistor subcircuit and a discharge tube, and the resistor subcircuit and the discharge tube are connected in series between two ends of the DC end of the rectifier circuit.

2. The surge absorption circuit according to claim 1, characterized in that: The resistor subcircuit includes: a first resistor, a first end of the first resistor is connected to a first end of the DC end of the rectifier circuit, a second end of the first resistor is connected to a first end of the discharge tube, and a second end of the discharge tube is connected to the other end of the DC end of the rectifier circuit.

3. The surge absorption circuit according to claim 2, characterized in that: The first resistor is a varistor.

4. The surge absorption circuit according to claim 3, characterized in that: The varistor adopts a varistor with an operating voltage of 820V, and the discharge tube adopts a discharge tube with an operating voltage of 1200V.

5. An electrolytic capacitor-free frequency converter, characterized in that: include: A rectifier circuit, a first filter circuit and an inverter circuit, and a surge absorption circuit according to any one of claims 1 to 4; Among them, the first filtering circuit includes a thin film capacitor, the AC end of the rectifier circuit is used to input AC power, the DC end of the rectifier circuit is connected to the input end of the first filtering circuit, the two ends of the thin film capacitor serve as the output ends of the first filtering circuit, and are connected to the DC end of the inverter circuit, the AC end of the inverter circuit is used to connect to the load, and the surge absorption circuit is connected between the two ends of the DC end of the rectifier circuit.

6. The electrolytic capacitor-free frequency converter according to claim 5, characterized in that: The first filter circuit also includes: a reactor, a first end of the reactor is respectively connected to one end of the DC end of the rectifier circuit and the first end of the surge absorption circuit, a second end of the reactor is respectively connected to the first end of the film capacitor and one end of the DC end of the inverter circuit, a second end of the film capacitor is respectively connected to the other end of the DC end of the rectifier circuit, the second end of the surge absorption circuit, and the other end of the DC end of the inverter circuit.

7. The electrolytic capacitor-free frequency converter according to claim 5, characterized in that: The electrolytic capacitor-free frequency converter further includes: a second filter circuit, wherein an input end of the second filter circuit is used to input the alternating current, and an output end of the second filter circuit is connected to an alternating current end of the rectifier circuit.

8. The electrolytic capacitor-free frequency converter according to claim 5, characterized in that: The rectifier circuit is a three-phase bridge diode rectifier circuit.

9. The electrolytic capacitor-free frequency converter according to claim 5, characterized in that: The inverter circuit is a three-phase bridge inverter bridge.

10. An air conditioner, characterized in that: include: An electrolytic capacitor-free frequency converter according to any one of claims 5 to 9.

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