Flyback converter

Abstract

The flyback converter comprises a transformer, a first switch tube and a second switch tube, and the first switch tube and the second switch tube are connected in series and then connected between an input end and a reference ground. The first capacitor and the leakage inductor of the transformer form a resonant circuit when the second switching tube is switched on; and the adjusting module adjusts the resonance period of the resonance circuit according to the output voltage of the flyback converter, and the resonance period and the output voltage are in a negative correlation relationship. According to the flyback converter provided by the utility model, when low-voltage output is switched, the resonance period of the resonance circuit can be synchronously adjusted, so that the resonance period is increased, thereby reducing resonance current, reducing conduction loss and improving efficiency.

Description

Technical Field

[0001] The utility model belongs to the technical field of power electronics, and in particular relates to a flyback converter. Background Art

[0002] Asymmetric half-bridge flyback converter (AHB) and active clamp flyback converter (ACF) are suitable for applications with a wide range of output voltages. The resonant capacitor and leakage inductance in the asymmetric half-bridge flyback converter and active clamp flyback converter will form a resonant circuit during the freewheeling period. Among them, the resonant capacitor is generally a polypropylene film capacitor, and the capacitance of the film capacitor does not change much with the voltage, so the resonant period of the resonant circuit is basically unchanged. However, when the output of the asymmetric half-bridge flyback converter and the active clamp flyback converter is switched from high voltage to low voltage, if the resonant period remains unchanged, it will cause the resonant current to be too large and the secondary current to be too large, resulting in large conduction losses and reduced efficiency. Utility Model Content

[0003] In order to solve the technical problem that the resonance period of the asymmetric half-bridge flyback converter and the active clamp flyback converter in the prior art cannot follow the output change, the utility model proposes a flyback converter, comprising:

[0004] transformer;

[0005] A first switch tube and a second switch tube, wherein the first switch tube and the second switch tube are connected in series and connected between an input terminal and a reference ground;

[0006] A first capacitor, wherein the first capacitor and the leakage inductance of the transformer form a resonant circuit when the second switch tube is turned on;

[0007] The regulating module regulates the resonance period of the resonant circuit according to the output voltage of the flyback converter, wherein the resonance period is negatively correlated with the output voltage.

[0008] Furthermore, the regulating module regulates the total inductance of the resonant circuit, and the total inductance of the resonant circuit is negatively correlated with the output voltage.

[0009] Furthermore, the regulating module regulates the total capacitance value of the resonant circuit, and the total capacitance value of the resonant circuit is negatively correlated with the output voltage.

[0010] Preferably, the regulating module comprises a plurality of regulating inductors, and the regulating module adjusts the number of the regulating inductors connected to the resonant circuit according to the output voltage.

[0011] Preferably, the regulating module includes a second capacitor, the second capacitor is connected in parallel with the first capacitor, and the capacitance of the second capacitor is negatively correlated with the voltage.

[0012] Preferably, the regulating module comprises a plurality of regulating capacitors, and the regulating module regulates the number of the regulating capacitors connected to the resonant circuit according to the output voltage.

[0013] Preferably, a plurality of the regulating inductors connected in parallel are connected in the resonant circuit, each of the regulating inductors is connected in series with a control switch, and as the output voltage increases, the number of the regulating inductors connected to the resonant circuit increases.

[0014] Preferably, a plurality of the regulating inductors connected in series are connected in the resonant circuit, each of the regulating inductors is connected in parallel with a control switch, and as the output voltage increases, the number of the regulating inductors connected to the resonant circuit decreases.

[0015] Preferably, a plurality of the regulating capacitors connected in parallel are connected in the resonant circuit, each of the regulating capacitors is connected in series with a control switch, and as the output voltage increases, the number of the regulating capacitors connected to the resonant circuit decreases.

[0016] Preferably, a plurality of the regulating capacitors connected in series are connected in the resonant circuit, and after each regulating capacitor is connected in parallel with a control switch, as the output voltage increases, the number of the regulating capacitors connected to the resonant circuit increases.

[0017] The flyback converter proposed in the utility model controls the resonance period to be negatively correlated with the output voltage, so after the flyback converter switches from high voltage output to low voltage output, the resonance period will become larger, thereby reducing the resonance current and the secondary current, thereby reducing the conduction loss and improving the efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a structural diagram of the asymmetric half-bridge flyback converter proposed by the utility model;

[0019] Figure 2 This is a structural diagram of the active clamp flyback converter proposed by the utility model;

[0020] Figure 3 A first partial circuit diagram of the regulating module;

[0021] Figure 4 The second partial circuit structure diagram of the regulating module;

[0022] Figure 5 This is the third partial circuit structure diagram of the regulating module;

[0023] Figure 6 This is a circuit diagram of the fourth part of the regulating module;

[0024] Figure 7The fifth partial circuit structure diagram of the regulating module;

[0025] Figure 8 This is the overall structure diagram of the adjustment module. DETAILED DESCRIPTION

[0026] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively with reference to the relevant drawings. The drawings provide preferred embodiments of the present invention. However, the present invention can be implemented in different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0027] In existing flyback converters, the capacitance of the resonant capacitor generally does not change with the change of voltage, so the resonant period of the resonant circuit is basically unchanged. Therefore, after the flyback converter switches from high-voltage output to low-voltage output, the resonant period remains unchanged, which will lead to excessive resonant current and secondary current, resulting in large conduction losses.

[0028] In order to solve the above problems, Figure 1 and Figure 2 As shown, the utility model provides a flyback converter, comprising:

[0029] Transformer T;

[0030] A first switch tube Q1 and a second switch tube Q2, which are connected in series between the input terminal and a reference ground;

[0031] A first capacitor Cr, the first capacitor Cr, the second switch tube Q2, and the leakage inductance Lr of the transformer form a resonant circuit;

[0032] The regulating module regulates the resonance period of the resonant circuit according to the output voltage of the flyback converter, so that the resonance period is negatively correlated with the output voltage.

[0033] It can be seen from this that the flyback converter proposed in the present invention controls the resonant period to be negatively correlated with the output voltage, so after the flyback converter switches from high-voltage output to low-voltage output, the resonant period will become larger, thereby reducing the resonant current and the secondary current, thereby reducing the conduction loss and improving the efficiency.

[0034] In the first embodiment, the regulating module regulates the resonance period by regulating the total capacitance of the resonance circuit, and controls the total capacitance of the resonance circuit to be negatively correlated with the output voltage to achieve a negative correlation between the resonance period and the output voltage.

[0035] In the second embodiment, the regulating module regulates the resonance period by regulating the total inductance of the resonance circuit, and controls the total inductance of the resonance circuit to be negatively correlated with the output voltage, thereby achieving a negative correlation between the resonance period and the output voltage.

[0036] In the first embodiment, if Figure 3 As shown, preferably, the adjustment module includes a second capacitor C2, the second capacitor C2 is connected in parallel with the first capacitor Cr, the capacitance of the first capacitor Cr does not change with the voltage, such as a film capacitor, and the capacitance of the second capacitor C2 is negatively correlated with the voltage, such as an MLCC capacitor. Thus, the first capacitor Cr establishes a basic capacitance value, and is used with the second capacitor C2 with a smaller capacitance value to adjust the total capacitance of the resonant capacitor under different output voltages, so as to adapt to a wide range of outputs at a lower cost. It should be noted that in other embodiments, the first capacitor Cr can be directly set to a capacitor whose capacitance is negatively correlated with the voltage, such as an MLCC capacitor, to meet the needs of adjusting the resonant period. However, this requires setting the capacitance of the first capacitor Cr to be very large, which will lead to problems of large capacitor size and high cost.

[0037] In the first embodiment, if Figure 4 As shown, the regulating module includes regulating capacitors Cr1 to Crn, each of which is connected in series with a control switch and then connected in parallel with the first capacitor Cr. The capacitance of the first capacitor Cr and the regulating capacitors Cr1 to Crn does not change with the voltage. Specifically, Figure 8 As shown, when the first switch tube Q1 is turned off and the second switch tube Q2 is turned on, the sampling module in the regulation module obtains the voltage Vcr across the primary winding, thereby obtaining the output voltage information (or the output voltage information can be obtained through the auxiliary winding). The switch control circuit in the regulation module controls the on-off of the control switches S1-Sn according to the output voltage information, so that as the output voltage increases, the number of regulation capacitors connected in parallel with the first capacitor Cr decreases, thereby achieving a negative correlation between the resonant period and the output voltage. Or, as Figure 5 As shown, the regulating module includes a plurality of regulating capacitors Cr1 to Cr n , adjusting capacitor Cr1 to adjusting capacitor Cr n After being connected in parallel with a control switch, they are connected in series with the first capacitor Cr. The first capacitor Cr, the regulating capacitor Cr1 to the regulating capacitor Cr nThe capacitance value does not change with voltage. When the first switch tube Q1 is turned off and the second switch tube Q2 is turned on, the sampling module in the regulation module obtains the voltage Vcr across the primary winding, thereby obtaining the output voltage information. The switch control circuit in the regulation module controls the on and off of the control switches S1-Sn according to the output voltage information, so that as the output voltage increases, the number of regulating capacitors connected in series with the first capacitor Cr increases, thereby achieving a negative correlation between the resonant period and the output voltage. It should be noted that Figure 4 The figure shows that the multiple regulating capacitors connected in parallel are connected in parallel with the first capacitor, but this is only for illustration, and the multiple regulating capacitors connected in parallel can also be connected in series with the first capacitor. In fact, it is only necessary to connect the regulating capacitors to the resonant circuit.

[0038] In the second embodiment, if Figure 6 As shown, the regulating module includes regulating inductors Lr1 to Lr n , adjust the inductance Lr1 to adjust the inductance Lr n Each of them is connected in series with a control switch and then connected in parallel with the leakage inductor Lr. When the first switch tube Q1 is turned off and the second switch tube Q2 is turned on, the sampling module in the regulation module obtains the voltage Vcr across the primary winding, thereby obtaining the output voltage information. The switch control circuit in the regulation module controls the on and off of the control switches S1-Sn according to the output voltage information, so that as the output voltage increases, the number of regulating inductors connected in parallel with the leakage inductor Lr increases, thereby achieving a negative correlation between the resonant period and the output voltage. Or, as Figure 7 As shown, the regulating module includes a plurality of regulating inductors Lr1 to Lr n , adjust the inductance Lr1 to adjust the inductance Lr n Each of them is connected in parallel with a control switch and then connected in series with the leakage inductor Lr. When the first switch tube Q1 is turned off and the second switch tube Q2 is turned on, the sampling module in the regulation module obtains the voltage Vcr across the primary winding, thereby obtaining the output voltage information. The switch control circuit in the regulation module controls the on and off of the control switches S1-Sn according to the output voltage information, so that as the output voltage increases, the number of regulating inductors connected in series with the leakage inductor Lr decreases, thereby achieving a negative correlation between the resonant period and the output voltage. It should be noted that Figure 6 and Figure 7 The diagram shows that the multiple parallel-connected regulating inductors are connected in series or in parallel with the leakage inductor. However, this is only a diagram. In practice, the leakage inductor is not an inductor device actually connected in the circuit. When setting the regulating inductor, it is impossible to accurately determine the connection relationship between the regulating inductor and the leakage inductor. Figure 6 and Figure 7 What is actually shown is that the inductor can be adjusted to connect to the resonant circuit.

[0039] In summary, the flyback converter proposed in the present invention controls the resonant period to be negatively correlated with the output voltage, so after the flyback converter switches from high-voltage output to low-voltage output, the resonant period will become larger, thereby reducing the resonant current and the secondary current, thereby reducing the conduction loss, improving efficiency, and adapting to a wide range of output.

[0040] It should be noted that the specific implementation and corresponding illustrations given are merely a way of describing the implementation method of the utility model, and do not limit the specific structure of the implementation scheme of the utility model. Various changes or modifications can be made to these implementation schemes without departing from the principle and essence of the utility model, but these changes and modifications are all within the scope of protection of the utility model.

[0041] Although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated. If the content is not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0042] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. A flyback converter, comprising: transformer; A first switch tube and a second switch tube, wherein the first switch tube and the second switch tube are connected in series and connected between an input terminal and a reference ground; A first capacitor, wherein the first capacitor and the leakage inductance of the transformer form a resonant circuit when the second switch tube is turned on; It is characterized by further comprising: The regulating module regulates the resonance period of the resonant circuit according to the output voltage of the flyback converter, wherein the resonance period is negatively correlated with the output voltage.

2. The flyback converter according to claim 1, characterized in that: The regulating module regulates the total inductance of the resonant circuit, and the total inductance of the resonant circuit is negatively correlated with the output voltage.

3. The flyback converter according to claim 1 or 2, characterized in that: The regulating module regulates the total capacitance value of the resonant circuit, and the total capacitance value of the resonant circuit is negatively correlated with the output voltage.

4. The flyback converter according to claim 2, characterized in that: The regulating module includes a plurality of regulating inductors, and the regulating module regulates the number of the regulating inductors connected to the resonant circuit according to the output voltage.

5. The flyback converter according to claim 3, characterized in that: The regulating module includes a second capacitor, which is connected in parallel with the first capacitor, and the capacitance of the second capacitor is negatively correlated with the voltage.

6. The flyback converter according to claim 3, characterized in that: The regulating module includes a plurality of regulating capacitors, and the regulating module regulates the number of the regulating capacitors connected to the resonant circuit according to the output voltage.

7. The flyback converter according to claim 4, characterized in that: A plurality of regulating inductors connected in parallel are connected in the resonant circuit, each regulating inductor is connected in series with a control switch, and as the output voltage increases, the number of regulating inductors connected to the resonant circuit increases.

8. The flyback converter according to claim 4, characterized in that: A plurality of regulating inductors connected in series are connected in the resonant circuit, each regulating inductor is connected in parallel with a control switch, and as the output voltage increases, the number of regulating inductors connected to the resonant circuit decreases.

9. The flyback converter according to claim 6, characterized in that: A plurality of regulating capacitors connected in parallel are connected in the resonant circuit, each regulating capacitor is connected in series with a control switch, and as the output voltage increases, the number of regulating capacitors connected to the resonant circuit decreases.

10. The flyback converter according to claim 6, characterized in that: A plurality of regulating capacitors connected in series are connected in the resonant circuit, each regulating capacitor is connected in parallel with a control switch, and as the output voltage increases, the number of regulating capacitors connected to the resonant circuit increases.

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