Peak voltage absorption circuit and flyback power supply

Abstract

The utility model relates to a peak voltage absorption circuit and a flyback power supply, and the peak voltage absorption circuit comprises an absorption loop. The absorption loop comprises a first resistor group, an absorption capacitor and a voltage clamping conduction unit; a first connecting end of the voltage clamping conduction unit is connected with a peak voltage end, and a second connecting end of the voltage clamping conduction unit is connected with the first resistor group; the other end, not connected with the voltage clamping conduction unit, of the first resistor group is connected with the absorption capacitor; the other end of the absorption capacitor not connected with the first resistor group is connected with a direct-current voltage end; when the voltage clamping conduction unit is conducted, the first resistor group charges the absorption capacitor. According to the flyback power supply, the problems that when the peak voltage in the flyback power supply is too high, the energy loss of the absorption circuit is large, and the absorption effect is poor are solved, and the current stress and EMI radiation of the diode are remarkably reduced.

Description

Technical Field

[0001] This application relates to the field of flyback power supplies, and in particular to a spike voltage absorption circuit and a flyback power supply. Background Technology

[0002] In high-frequency switching circuits such as switching power supplies, voltage spikes are a critical concern. Voltage spikes typically arise during switching due to the interaction between parasitic inductances (such as transformer leakage inductance and PCB trace inductance) and parasitic capacitances (such as the gate-source capacitance and junction capacitance of the switching transistor) within the circuit, creating a resonance effect that leads to drastic fluctuations in voltage and current. At the moment the switching transistor turns off, because the current cannot immediately drop to zero, the parasitic inductance induces a high back electromotive force, which is superimposed on the power supply voltage, resulting in a very large voltage spike. This voltage spike may exceed the rated voltage of the switching device, causing device breakdown or reducing its lifespan.

[0003] In existing technologies, peak absorption circuits are commonly used to suppress voltage spikes. The main function of a peak absorption circuit is to absorb and dissipate transient energy generated during switching, clamping voltage spikes within a safe level and thus protecting power semiconductor devices from damage. In flyback switching power supplies, the RCD peak absorption circuit is a common and practical circuit form. An RCD circuit consists of a resistor (R), a capacitor (C), and a diode (D). Through the energy storage of the capacitor and the conduction path of the diode, it can effectively absorb voltage spikes. Although RCD peak absorption circuits are widely used in flyback switching power supplies, some technical problems still exist. For example, the selection of the capacitor and the resistance value directly affect the peak voltage absorption effect. If the capacitor is too small, it may not be able to absorb a large amount of energy in a short time, resulting in an excessively high voltage spike; while if the capacitor is too large, it may affect the circuit's startup and dynamic response performance. Furthermore, the resistance value also needs careful consideration; too large or too small a value may lead to poor absorption. Meanwhile, traditional RCD peak absorption circuits often generate some energy loss when absorbing peak voltages, which not only reduces the efficiency of the circuit but may also increase the difficulty of heat dissipation.

[0004] Currently, no effective solution has been proposed to address the problem of high energy loss and poor absorption effect in the absorption circuit when the peak voltage in the flyback power supply is too high. Utility Model Content

[0005] This application provides a spike voltage absorption circuit and a flyback power supply to at least solve the problem in the related art that when the spike voltage in the flyback power supply is too high, the absorption circuit has large energy loss and poor absorption effect.

[0006] In a first aspect, embodiments of this application provide a spike voltage absorption circuit, including an absorption loop;

[0007] The absorption circuit includes a first resistor group, an absorption capacitor, and a voltage clamping conduction unit;

[0008] The first connection terminal of the voltage clamping conduction unit is connected to the peak voltage terminal, and the second connection terminal of the voltage clamping conduction unit is connected to the first resistor group;

[0009] The other end of the first resistor group, which is not connected to the voltage clamping conduction unit, is connected to the absorption capacitor; the other end of the absorption capacitor, which is not connected to the first resistor group, is connected to the DC voltage terminal; wherein, when the voltage clamping conduction unit is turned on, the first resistor group charges the absorption capacitor.

[0010] In some embodiments, the first resistor group includes a plurality of first resistors, and the first resistors are connected in parallel.

[0011] In some embodiments, the absorption circuit further includes a second resistor group; the second resistor group is connected in parallel across the two ends of the absorption capacitor, and one end of the second resistor group is connected to the DC voltage terminal.

[0012] In some embodiments, the equivalent resistance value of the second resistor group is less than the equivalent resistance value of the first resistor group.

[0013] In some embodiments, the spike voltage absorption circuit further includes a switching transistor; one end of the switching transistor is connected to the spike voltage terminal, and the other end is connected to the voltage clamping conduction unit.

[0014] In some embodiments, when the switch is turned off, the voltage clamping conduction unit is turned on when the voltage generated at the spike voltage terminal is higher than the spike voltage threshold.

[0015] In some embodiments, the voltage clamping conduction unit includes a first conductor and a second conductor; the first conductor and the second conductor are connected in parallel.

[0016] In some embodiments, the conduction direction of the voltage clamping conduction unit is from the first connection terminal to the second connection terminal.

[0017] In some embodiments, the voltage rating of the absorption capacitor is higher than the maximum voltage of the DC voltage terminal.

[0018] Secondly, embodiments of this application provide a flyback power supply, including the spike voltage absorption circuit described in any of the first aspects above.

[0019] Compared to related technologies, the spike voltage absorption circuit and flyback power supply provided in this application replace the existing simple absorption circuit by connecting a resistor group in series in the spike voltage charging circuit and setting an absorption capacitor. This solves the problem that the absorption circuit has large energy loss and poor absorption effect when the spike voltage in the flyback power supply is too high, and significantly reduces diode current stress and EMI radiation.

[0020] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0021] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0022] Figure 1 This is a block diagram of the absorption loop structure of the spike voltage absorption circuit according to this application;

[0023] Figure 2 This is a peak voltage absorption circuit diagram according to a preferred embodiment of this application. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application. Furthermore, it is understood that although the efforts made in such a development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, modifications to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0025] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0026] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms “a,” “an,” “an,” “the,” and similar words used in this application do not indicate quantity limitation and may indicate singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or devices. The terms “connected,” “linked,” “coupled,” and similar words used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. “Multiple” used in this application means two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. The terms “first,” “second,” “third,” etc., used in this application are merely to distinguish similar objects and do not represent a specific ordering of the objects.

[0027] This embodiment provides a spike voltage absorption circuit, including an absorption loop;

[0028] Figure 1 The block diagram of the absorption circuit structure of the spike voltage absorption circuit according to this application is as follows: Figure 1 As shown, the absorption circuit 10 includes an absorption capacitor 11, a first resistor group 12, and a voltage clamping conduction unit 13;

[0029] The first connection terminal of the voltage clamping conduction unit 13 is connected to the peak voltage terminal, and the second connection terminal of the voltage clamping conduction unit 13 is connected to the first resistor group.

[0030] The other end of the first resistor group 12, which is not connected to the voltage clamping conduction unit, is connected to an absorption capacitor; the other end of the absorption capacitor 11, which is not connected to the first resistor group, is connected to a DC voltage terminal; wherein, when the voltage clamping conduction unit 13 is turned on, the first resistor group 12 charges the absorption capacitor 11. The voltage clamping conduction unit 13 refers to a specific circuit module or component used to limit (or "clamp") the voltage signal in a circuit within a predetermined safe range. The voltage clamping conduction unit typically contains one or more nonlinear elements (such as diodes, transistors, or Zener diodes) and possibly linear elements (such as resistors and capacitors), which work together to achieve voltage clamping control.

[0031] The absorption circuit is a circuit module composed of a first resistor group, an absorption capacitor, and a voltage clamping conduction unit. It is used to absorb the peak voltage energy generated when the flyback power supply switch is turned off. Through the synergistic effect of the resistor and capacitor, the energy of the peak voltage is converted into heat energy or stored and then released, so as to avoid the voltage peak from damaging the switch and other components.

[0032] The first resistor group is a resistor network composed of multiple resistors connected in series between the voltage clamping conduction unit and the absorption capacitor. By reducing the equivalent resistance value through multiple resistors, the peak value of the current spike is reduced, thereby reducing the current stress on the diode and lowering the cost of using high-current diodes. The introduction of the first resistor group also slows down the rate of current change, reducing high-frequency electromagnetic interference (RE radiation), and some of the spike energy is directly dissipated by the resistors. The absorption capacitor is connected in parallel between the first resistor group and the DC voltage terminal; for example, a 10nF capacitor can be selected. It absorbs the energy of the voltage spike when the switch is turned off, preventing voltage overshoot. The voltage clamping conduction unit can be a diode, connected between the voltage spike terminal and the first resistor group. When the voltage spike exceeds the DC voltage terminal, it conducts, forming an energy absorption path.

[0033] Traditional flyback power supply spike absorption circuits consist of a diode, an absorption capacitor, and a discharge resistor. When the switching transistor is turned off, a spike voltage Vpk is generated on the primary side of the transformer. If Vpk > Vin, the diode conducts, and the spike current directly charges the absorption capacitor. However, since the circuit relies solely on the diode's on-resistance (which is extremely small), the current is extremely high, requiring the use of a high-voltage, high-current diode, resulting in high cost. Furthermore, the instantaneous rate of change of current di / dt is extremely high, causing high-frequency radiation. Simultaneously, almost all the spike energy is stored in the capacitor, and the discharge resistor must rapidly release energy when conducting, leading to high power stress. This application proposes connecting a first resistor group in series in the charging circuit. By setting a smaller equivalent resistance value for the first resistor group, the peak charging current is significantly reduced. The charging current decays exponentially over time, thereby greatly reducing di / dt and suppressing EMI radiation. When the switching transistor is turned off, the peak voltage is turned on through the voltage clamping conduction unit, and the current flows through the first resistor group to charge the absorption capacitor. The first resistor group shares the peak energy, reducing the power demand of the discharge resistor. This solves the problem of large energy loss and poor absorption effect of the absorption circuit when the peak voltage is too high in the flyback power supply, and significantly reduces diode current stress and EMI radiation.

[0034] In some embodiments, the first resistor group includes a plurality of first resistors, and the first resistors are connected in parallel.

[0035] In this system, one end of each resistor is connected to the second connection terminal of the voltage clamping conduction unit, and the other end is connected to the absorption capacitor. When the switching transistor is turned off, the voltage spike is turned on through the voltage clamping conduction unit, and current flows through the first resistor group to charge the absorption capacitor. For example, the first resistor group consists of multiple resistors connected in parallel (such as R7~R7). 12 The components (model 180KΩ) are connected in parallel, and the formula for calculating the total equivalent resistance is as follows:

[0036] R eq = 1 / (1 / R7+1 / R8+......+1 / R) 12 );

[0037] In the above formula, R eq This represents the equivalent resistance of the first resistance group. When all resistances are the same (180KΩ), the equivalent resistance decreases significantly to 30KΩ when six are connected in parallel. The current formula is as follows:

[0038] i charge =(V pk -V in ) / R eq ;

[0039] In the above formula, V pk The peak voltage is the voltage spike generated on the primary side of the transformer when the switching transistor is turned off; V in This is a DC voltage, derived from the output of the rectifier bridge; i charge This is the charging current, which is the current that charges the absorption capacitor through the first resistor group when the switching transistor is turned off.

[0040] This embodiment reduces the equivalent resistance of the first resistor group by using parallel resistors, thereby significantly reducing the peak value of the charging current. The parallel resistors also slow down the current change rate (di / dt) of the charging circuit, thereby reducing high-frequency radiation (RE radiation), meeting the compliance requirements of EMI-sensitive scenarios (such as high-frequency switching power supplies), and improving system stability.

[0041] In some embodiments, the absorption circuit further includes a second resistor group; the second resistor group is connected in parallel across the two ends of the absorption capacitor, and one end of the second resistor group is connected to the DC voltage terminal.

[0042] The second resistor group consists of multiple parallel second resistors (e.g., R1 to R6, 33Ω). One end of each second resistor is connected to the positive terminal of the absorption capacitor, and the other end is connected to the DC voltage terminal. The total equivalent resistance after parallel connection is:

[0043] R eq2 =1 / (1 / R1+1 / R2+......+1 / R6);

[0044] In the above formula, R eq2 This is the equivalent resistance value of the second resistance group. If all six resistors are 33Ω, then the equivalent resistance is 5.5Ω.

[0045] When the switching transistor is turned on, the absorption capacitor discharges to the DC voltage terminal through the second resistor group, and the discharge current is:

[0046] i discharge =(V c -V in ) / R eq2 ;

[0047] In the above formula, V C This is the voltage across the absorption capacitor; V in This is a DC voltage, derived from the output of the rectifier bridge; i discharge This is the discharge current.

[0048] This embodiment significantly shortens the discharge time constant of the absorption capacitor by using the low equivalent resistance value of the second resistor group, avoiding the impact of residual capacitor voltage on the peak absorption effect in the next cycle and improving circuit stability. Rapid discharge prevents the absorption capacitor voltage from gradually increasing due to multiple charge-discharge cycles (voltage accumulation), thereby reducing the capacitor's withstand voltage requirement. After the peak energy is partially consumed by the first resistor group, the remaining energy is converted into heat energy by the second resistor group during discharge. The power is distributed by multiple resistors in parallel (each resistor only needs to withstand about 0.067mJ), avoiding local overheating. The first resistor group limits the charging current (reducing diode losses), and the second resistor group quickly releases energy (reducing capacitor energy storage time), synergistically optimizing overall efficiency. Compared to traditional discharge resistors (single resistors) that need to withstand all energy, have high power density, and are prone to failure, this solution reduces the risk of single-point failure through parallel design.

[0049] In some embodiments, the equivalent resistance value of the second resistance group is smaller than the equivalent resistance value of the first resistance group.

[0050] In the flyback power supply circuit, the main function of the spike voltage absorption circuit is to absorb and dissipate the spike energy generated when the switching transistor is turned off. This energy can be dissipated through the first and second resistor groups. By setting the equivalent resistance value to be smaller than that of the first resistor group (i.e., the equivalent resistance value of the second resistor group is smaller), the second resistor group plays a greater role in dissipating the spike energy, thereby reducing the burden on the first resistor group. This makes the energy distribution of the entire circuit more reasonable, avoids excessive power stress on any part of the resistors, and improves the reliability and stability of the circuit. Furthermore, when the switching transistor is turned off, a spike voltage is generated. This spike voltage needs to be absorbed by the diode and the absorption capacitor C2. The diode will bear a large reverse current, i.e., current stress. If the equivalent resistance value of the second resistor group is large, then when the spike voltage occurs, the charging current through the diode will also be large, thus increasing the current stress on the diode. Therefore, by setting the equivalent resistance value of the second resistor group to be smaller, the charging current is limited, thereby reducing the current stress on the diode.

[0051] In some embodiments, the spike voltage absorption circuit further includes a switching transistor; one end of the switching transistor is connected to the spike voltage terminal, and the other end is connected to the voltage clamping conduction unit.

[0052] In flyback power supply circuits, the switching transistor typically serves as the main switching device, controlling the power supply's switching state. In spike voltage absorption circuits, one end of the switching transistor (usually the drain or collector) is connected to the circuit section that may generate spike voltages; this section is the spike voltage terminal. The other end of the switching transistor (source or emitter) is connected to a voltage clamping conduction unit via certain components. The voltage clamping conduction unit can be primarily composed of diodes, used to clamp and absorb the spike voltage. By connecting one end of the switching transistor to the spike voltage terminal and the other end to the voltage clamping conduction unit, it is ensured that spike voltages generated when the switching transistor is turned off can be quickly absorbed and clamped, protecting other components in the circuit from damage by the spike voltage and improving the circuit's reliability and stability.

[0053] In some embodiments, when the switch is turned off and the voltage generated at the spike voltage terminal is higher than the spike voltage threshold, the voltage clamping conduction unit is turned on.

[0054] The peak voltage threshold is a preset voltage value used to determine whether a peak voltage is too high and needs to be absorbed by the absorption circuit. It is typically set based on the specific requirements of the circuit and the voltage withstand capability of the components. When the peak voltage exceeds the set threshold, the voltage clamping conduction unit activates. This unit primarily consists of diodes, which, as conducting elements, conduct under the influence of the peak voltage, allowing the voltage spike to be applied to the absorption capacitor. The absorption capacitor then stores and absorbs the energy of the peak voltage, thereby reducing its impact on the circuit. By setting the peak voltage threshold, when the peak voltage is too high, the voltage clamping conduction unit can conduct in a timely manner, clamping the peak voltage to a safe level, thus protecting other components in the circuit from damage.

[0055] In some embodiments, the voltage clamping conduction unit includes a first conduction body and a second conduction body; the first conduction body and the second conduction body are connected in parallel.

[0056] In this circuit, the first and second conducting elements are two parallel-connected conducting components that jointly handle the current flow when a voltage spike occurs. Furthermore, the number of conducting elements is not limited to two; multiple elements can be used. The parallel structure enhances conductivity, ensuring a rapid response under high-voltage transients. The first and second conducting elements can be two diodes with identical or similar electrical characteristics, such as forward voltage drop and reverse breakdown voltage. Choosing a parallel connection increases the redundancy of the conduction path, improving circuit reliability. Even if one diode fails, the other can continue operating, ensuring that voltage spikes are effectively absorbed.

[0057] In some embodiments, the conduction direction of the voltage clamping conduction unit is from the first connection terminal to the second connection terminal.

[0058] In this circuit, the first connection terminal of the voltage clamping conduction unit may be connected to the drain or collector of the switching transistor, i.e., the peak voltage terminal. The second connection terminal is connected to one end of an absorption capacitor, and the other end of the absorption capacitor is connected to a DC voltage terminal. With this connection method, when a peak voltage is generated, if the peak voltage value is higher than the forward conduction voltage of the voltage clamping conduction unit, the voltage clamping conduction unit will conduct, allowing current to flow from the first connection terminal to the second connection terminal, and then into the absorption capacitor; the reverse flow is not allowed. This embodiment, by setting the conduction direction of the voltage clamping conduction unit to be from the first connection terminal to the second connection terminal, ensures that the current can flow in a predetermined direction, thereby ensuring that the peak voltage can be quickly absorbed and clamped to a safe level when it is generated. This helps protect other components in the circuit from damage by the peak voltage, improving the reliability and stability of the circuit.

[0059] In some embodiments, the voltage rating of the absorption capacitor is higher than the maximum voltage at the DC voltage terminal.

[0060] In this embodiment, the maximum voltage value at the DC voltage terminal is measured or estimated, and a capacitor with a withstand voltage higher than this maximum voltage value is selected as the absorption capacitor to ensure that the capacitor will not be damaged when subjected to peak voltage. When designing the circuit, a suitable capacitance range can be preset based on the expected peak voltage magnitude, the circuit's switching frequency, and the required energy absorption capacity. A specific capacitance value within this preset range can then be selected as the capacitance value of the absorption capacitor C2. This embodiment, by selecting an absorption capacitor with an appropriate capacitance value, ensures that the peak voltage generated when the switching transistor is turned off can be quickly absorbed, avoiding damage to the circuit; the absorption capacitor's withstand voltage value is higher than the maximum voltage at the DC voltage terminal, ensuring the capacitor's safety during long-term operation and improving the overall circuit reliability.

[0061] The embodiments of this application will be described and illustrated below through preferred embodiments.

[0062] Figure 2 This is a peak voltage absorption circuit diagram according to a preferred embodiment of this application, such as... Figure 2 As shown, Vin is the output voltage terminal of the rectifier bridge, with a voltage range of 310V; one end of D1 (i.e., the first conductor mentioned above) and D2 (i.e., the second conductor mentioned above), model S3M, is connected in series with Q1 (i.e., the switching transistor mentioned above), mainly to prevent the Vin voltage from passing through R1~R6, C2, R7~R 12 Backflow to Q1; R7~R 12 One end of the first resistor group (i.e., the above-mentioned first resistor group, model number 180KΩ) is connected in series with D1 and D2, mainly used to limit the charging current of C2 (i.e., the above-mentioned absorption capacitor); one end of R1 to R6 (i.e., the above-mentioned second resistor group, model number 33Ω) is connected to Vin, mainly used to consume the energy stored in C2; one end of C2 (model number 10nF) is connected to Vin, mainly used to absorb the energy of peak voltage; R1 to R6 are connected in parallel with C2.

[0063] First, when Q1 is turned off, a very high spike voltage V will be generated on the primary side of the transformer. pk When V pk When the voltage is higher than 310V, D1 and D2 conduct, and power flows through R7 to R8. 12 C1 is charged, thus attenuating the peak voltage.

[0064] At this time, the charging current is

[0065] The peak current flowing through D1 and D2 is

[0066] R7~R 12 The peak current flowing through D1 and D2 was greatly attenuated.

[0067] R7~R in one cycle 12 The energy consumed is: W = i charge 2 ×R2×f sw (J).

[0068] Secondly, when Q1 is turned on, C2 discharges through R1 to R6, releasing C2 energy.

[0069] In this preferred embodiment, R7~R are connected in series. 12 The peak current during capacitor C2 charging is limited, and the current values ​​of diodes D1 and D2 are reduced; the di / dt change rate of the C2 charging circuit is reduced, thereby reducing EMI generation; some of the peak energy is consumed in resistor R2, thereby reducing the power stress on R1.

[0070] This embodiment also provides a flyback power supply, including a spike voltage absorption circuit as described above.

[0071] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0072] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A spike voltage absorbing circuit characterized by comprising: The absorption circuit comprises a first resistance group, an absorption capacitor and a voltage clamping conduction unit. The first connection end of the voltage clamping conduction unit is connected to a spike voltage end, and the second connection end of the voltage clamping conduction unit is connected to the first resistance group. The other end of the first resistance group not connected to the voltage clamping conduction unit is connected to the absorption capacitor, and the other end of the absorption capacitor not connected to the first resistance group is connected to a direct current voltage end. When the voltage clamping conduction unit is turned on, the first resistance group charges the absorption capacitor.

2. The spike voltage sink circuit of claim 1, wherein, The first resistance group comprises a plurality of first resistances, and each of the first resistances is connected in parallel.

3. The spike voltage sink circuit of claim 1, wherein, The absorption circuit further comprises a second resistance group, which is connected in parallel across the absorption capacitor, and one end of the second resistance group is connected to the direct current voltage end.

4. The spike voltage sink circuit of claim 3, wherein, The equivalent resistance value of the second resistance group is smaller than the equivalent resistance value of the first resistance group.

5. The spike voltage sucking circuit according to claim 1, wherein The spike voltage absorption circuit further comprises a switch tube, one end of which is connected to the spike voltage end, and the other end of which is connected to the voltage clamping conduction unit.

6. The spike voltage sink circuit of claim 5, wherein, When the switch tube is turned off and the voltage generated by the spike voltage end is higher than a spike voltage threshold, the voltage clamping conduction unit is turned on.

7. The spike voltage sucking circuit according to claim 1, wherein The voltage clamping conduction unit comprises a first conduction body and a second conduction body, which are connected in parallel.

8. The spike voltage sucking circuit according to claim 1, wherein The conduction direction of the voltage clamping conduction unit is from the first connection end to the second connection end.

9. The spike voltage sucking circuit according to claim 1, wherein The withstand voltage value of the absorption capacitor is higher than the maximum voltage of the direct current voltage end.

10. A flyback power supply characterized by comprising: The spike voltage absorption circuit comprises the spike voltage absorption circuit according to any one of claims 1 to 9.

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