Combined active clamp drive flyback circuit

Abstract

The application relates to a combined active clamp drive flyback circuit, which comprises a primary winding unit and an auxiliary winding unit. An input end of the primary winding unit is adapted to electrically connect a positive voltage end of a direct-current voltage, and an output end is adapted to be grounded. The primary winding unit comprises a primary winding, a clamping circuit and a main switch. The primary winding is connected in series with the main switch, and the clamping circuit is connected in parallel with the primary winding. The clamping circuit comprises a clamping capacitor, a clamping switch and a clamping diode, which are connected in series. A control end of the main switch is applied with a synchronous driving signal. The primary windings at all levels are controlled in phase and share a magnetic core. The auxiliary winding unit comprises an auxiliary winding, a D0 diode and an auxiliary clamping capacitor. One end of the auxiliary winding is connected in series with the D0 diode to output a voltage, and the other end is connected with one end of the auxiliary clamping capacitor. Through the active clamp technology, the voltage stress of the switch tube is reduced, and soft switching is realized to improve the efficiency.

Description

Technical Field

[0001] This application relates to the field of flyback circuit technology, and in particular to a combined active clamp drive flyback circuit. Background Technology

[0002] Flyback converters are widely used in small and medium power supply systems due to their simple circuit structure, low cost, and high core utilization. However, as power electronics technology develops towards medium and high voltage input, high frequency, and high reliability, traditional flyback circuits have gradually exposed the following problems: At the moment the main switching device turns off, the transformer leakage inductance and the switch parasitic capacitance resonate, generating a high-amplitude voltage spike. The spike voltage superimposed on the input voltage causes a sharp increase in voltage stress on the switching transistor, which can easily damage the device if it exceeds its rated withstand voltage. The spike energy is dissipated through the RC absorption circuit, significantly increasing switching losses and limiting the improvement of circuit efficiency. Utility Model Content

[0003] To address the problem of low efficiency in traditional circuits, this invention provides a combined active clamp drive flyback circuit, comprising: a primary winding unit and an auxiliary winding unit; The input terminal of the primary winding unit is suitable for electrical connection to the positive voltage terminal of DC voltage, and the output terminal is suitable for grounding. The primary winding unit includes a primary winding, a clamping circuit and a main switch. The primary winding is connected in series with the main switch, and the clamping circuit is connected in parallel with the primary winding. The clamping circuit includes a clamping capacitor, a clamping switch and a clamping diode. The clamping capacitor, the clamping switch and the clamping diode are connected in series. The control terminal of the main switch applies a synchronous drive signal. The primary windings of each stage are controlled in phase and share a common magnetic core. The auxiliary winding unit includes an auxiliary winding, a D0 diode, and an auxiliary clamping capacitor. One end of the auxiliary winding is connected in series with the D0 diode to output voltage, and the other end is connected to one end of the auxiliary clamping capacitor.

[0004] In one possible implementation, the primary winding unit is multi-stage, with each stage of the primary winding unit connected in parallel; The input terminal of the primary winding unit in the first stage is suitable for electrical connection to the positive voltage terminal of DC voltage, and the output terminal of the primary winding unit in the last stage is grounded.

[0005] One possible implementation also includes: voltage equalizing capacitors; The voltage equalizing capacitor is connected in parallel with the primary winding; The voltage equalizing capacitors at each stage are connected in series.

[0006] In one possible implementation, the main switch is a MOSFET, the inlet of the main switch is the drain of the MOSFET, the outlet of the main switch is the source of the MOSFET, and the control terminal of the main switch is the gate of the MOSFET.

[0007] One possible implementation also includes a driving circuit; The driving circuit includes an input unit, a driving unit, and a driving transformer; The input unit is suitable for receiving PWM signals; The driving unit is an IXDF604 chip, which is electrically connected to the input unit; The drive transformer includes a drive primary winding and a drive auxiliary winding. The drive primary winding shares a common magnetic core with the drive primary winding, and the drive primary winding is electrically connected to the drive unit. The drive auxiliary winding is electrically connected to the clamping switch and / or the main switch.

[0008] In one possible implementation, the input unit includes an input diode, an input resistor, an input capacitor, an output diode, an output resistor, and an output capacitor; The input diode is connected in parallel with the input resistor, the input capacitor is connected in series with the input diode and the input resistor, and the current of the input diode is directed towards the driving unit. The input unit is adapted to receive PWM signals. The output diode is connected in parallel with the output resistor, the output capacitor is connected in series with the output diode and the output resistor, and the current flow of the output diode is away from the driving unit. The input unit is suitable for outputting PWM signals.

[0009] In one possible implementation, the drive transformer includes a first drive transformer and a second drive transformer; The primary winding of the first driving transformer is connected in series with the driving unit and the input diode. One end of the auxiliary driving winding of the first driving transformer is electrically connected to the gate of the clamping switch, and the other end is electrically connected to the source of the clamping switch. The primary winding of the second driving transformer is connected in series with the driving unit and the output diode. One end of the auxiliary driving winding of the second driving transformer is electrically connected to the gate of the main switch, and the other end is electrically connected to the source of the main switch.

[0010] The beneficial effects of the combined active clamp drive flyback circuit in this application embodiment are as follows: In this specific embodiment, active clamping technology is used to achieve soft switching and improve efficiency. By reducing the voltage stress on the switching transistor, input series technology can be reduced under the same derating conditions, improving reliability and reducing switching losses to improve efficiency. Specifically, the clamping circuit is connected in parallel with the primary winding to achieve active clamping. When the main switch is turned off, the clamping switch is turned on, absorbing leakage inductance energy and storing it in the clamping capacitor, suppressing voltage spikes, and recovering energy at the same time.

[0011] Other features and aspects of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0012] The accompanying drawings, which are included in and form part of this specification, illustrate exemplary embodiments, features, and aspects of this application together with the specification and serve to explain the principles of this application.

[0013] Figure 1 This diagram illustrates the main structure of a combined active clamp flyback circuit according to an embodiment of this application. Figure 2 This diagram shows the main structure of the combined active clamping drive circuit according to an embodiment of this application. Detailed Implementation

[0014] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0015] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model or simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0016] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0017] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0018] Furthermore, to better illustrate this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented without certain specific details. In some instances, methods, means, components, and circuits well-known to those skilled in the art have not been described in detail in order to highlight the main points of this application.

[0019] like Figure 1 As shown, the combined active clamp drive flyback circuit of this application embodiment includes: a primary winding unit and an auxiliary winding unit. The input terminal of the primary winding unit is suitable for electrical connection to the positive voltage terminal of DC voltage, and the output terminal is suitable for grounding. The primary winding unit includes a primary winding, a clamping circuit and a main switch. The primary winding is connected in series with the main switch, and the clamping circuit is connected in parallel with the primary winding. The clamping circuit includes a clamping capacitor, a clamping switch and a clamping diode. The clamping capacitor, clamping switch and clamping diode are connected in series. The control terminal of the main switch applies a synchronous drive signal. Each stage of the primary winding is controlled in phase and has a common magnetic core. The auxiliary winding unit includes an auxiliary winding, a D0 diode and an auxiliary clamping capacitor. One end of the auxiliary winding is connected in series with the D0 diode to output voltage, and the other end is connected to one end of the auxiliary clamping capacitor.

[0020] In this specific embodiment, active clamping technology is used to improve efficiency through soft switching. By reducing the voltage stress on the switching transistor, input series technology can be reduced under the same derating conditions, improving reliability and reducing switching losses to improve efficiency. Specifically, the clamping circuit is connected in parallel with the primary winding to achieve active clamping. When the main switch is turned off, the clamping switch is turned on, absorbing leakage inductance energy and storing it in the clamping capacitor to suppress voltage spikes and recover energy.

[0021] In one specific embodiment, the primary winding unit is multi-stage, with each stage of the primary winding unit connected in parallel. The input terminal of the first-stage primary winding unit is suitable for electrical connection to the positive voltage terminal of DC voltage, and the output terminal of the last-stage primary winding unit is grounded.

[0022] For details, please refer to Figure 1 It features a two-stage primary winding unit with a multi-stage parallel structure. The first stage is connected to a positive DC voltage, and the last stage is grounded. Each primary winding unit bears a portion of the input voltage's shared voltage stress. This expands the input voltage range and overcomes the voltage limitation of a single-stage flyback inverter. In one specific embodiment, the circuit further includes: a voltage-equalizing capacitor connected in parallel with the primary winding, and voltage-equalizing capacitors at each stage connected in series. The addition of voltage-equalizing capacitors, connected in parallel with each stage of the primary winding and in series with each stage, forms a voltage divider network. This forces a balance of the terminal voltages of the multi-stage primary windings, resolving the voltage unevenness caused by parameter differences when multiple stages are connected in parallel, preventing damage from single-stage overvoltage, suppressing voltage fluctuations, and enhancing the long-term stability of the circuit.

[0023] In one specific embodiment, the main switch is a MOSFET, the inlet of the main switch is the drain of the MOSFET, the outlet of the main switch is the source of the MOSFET, and the control terminal of the main switch is the gate of the MOSFET.

[0024] In this specific embodiment, the main switch uses a MOS field-effect transistor, with the drain as the on-current input terminal, the source as the output terminal, and the gate as the control terminal. MOS transistors have fast switching speeds, which are suitable for the high-frequency requirements of flyback circuits, and their low on-resistance reduces conduction losses and improves efficiency.

[0025] In one specific embodiment, a drive circuit is also included. The drive circuit includes an input unit, a drive unit, and a drive transformer. The input unit is adapted to receive PWM signals. The drive unit is an IXDF604 chip and is electrically connected to the input unit. The drive transformer includes a primary drive winding and a secondary drive winding. The primary drive winding and the secondary drive winding share a common magnetic core, and the primary drive winding is electrically connected to the drive unit. The secondary drive winding is electrically connected to a clamping switch and / or a main switch.

[0026] In this specific embodiment, the input unit receives the PWM signal, the IXDF604 driver chip enhances the signal driving capability, and the drive transformer transmits the drive signal through magnetic coupling isolation. Its primary winding and auxiliary winding share a common magnetic core, connecting to a clamping switch and / or the main switch to achieve electrical isolation between the high-voltage and low-voltage sides. This electrical isolation prevents high-voltage interference from the main circuit to the control circuit, improving system reliability. The IXDF604 chip provides sufficient drive current to ensure rapid switching, and the magnetic isolation adapts to multi-level high-voltage environments, ensuring drive signal synchronization.

[0027] In one specific embodiment, the input unit includes an input diode, an input resistor, an input capacitor, an output diode, an output resistor, and an output capacitor. The input diode is connected in parallel with the input resistor, and the input capacitor is connected in series with the input diode and the input resistor. The current of the input diode is directed towards the driving unit, and the input unit is suitable for receiving PWM signals. The output diode is connected in parallel with the output resistor, and the output capacitor is connected in series with the output diode and the output resistor. The current of the output diode is directed away from the driving unit, and the input unit is suitable for outputting PWM signals.

[0028] In this specific embodiment, the input unit comprises an input diode, an input resistor, and an input capacitor connected in series. The diode faces forward towards the drive unit to suppress overshoot and noise in the PWM signal. The output unit is similar to the input unit, with the diode facing forward away from the drive unit to optimize the signal quality output to the drive transformer. This filters out high-frequency noise, improves the stability of the drive signal, avoids abnormal voltage impacts on the drive chip, extends its lifespan, ensures steep rise / fall times of the drive signal, and optimizes the on / off characteristics of the switching devices.

[0029] In one specific embodiment, the drive transformer includes a first drive transformer and a second drive transformer. The primary drive winding of the first drive transformer is connected in series with the drive unit and the input diode. One end of the auxiliary drive winding of the first drive transformer is electrically connected to the gate of the clamping switch, and the other end is electrically connected to the source of the clamping switch. The primary drive winding of the second drive transformer is connected in series with the drive unit and the output diode. One end of the auxiliary drive winding of the second drive transformer is electrically connected to the gate of the main switch, and the other end is electrically connected to the source of the main switch.

[0030] In this specific embodiment, see Figure 2 The drive transformers are divided into a first drive transformer T3 (driving clamp switches S2 / S4) and a second drive transformer T4 (driving main switches S1 / S3). The primary winding of T3 is connected in series with the drive unit and the input diode, and the auxiliary winding is connected to the gate-source of the clamp switch. The primary winding of T4 is connected in series with the drive unit and the output diode, and the auxiliary winding is connected to the gate-source of the main switch, achieving independent isolated drive. This ensures the synchronization of the clamp switch and the main switch, adapts to the precise timing of active clamping, avoids drive interference between different switches, improves the control accuracy of multi-stage circuits, and customizes the drive signal to reduce switching losses due to the characteristic differences between the clamp switch and the main switch.

[0031] Among them, see Figure 1 The first stage: Power supply → Body diode D1 of the main switch (anode → cathode, freewheeling) → Drain of the main switch → Buffer capacitor C1 of the main switch (charging) → Primary winding. The second stage: Body diode D1 of the main switch (anode → cathode, freewheeling) → Drain of the main switch → Buffer capacitor C1 of the main switch (charging) → Primary winding. The third stage: Vin → Clamping capacitor → Clamping switch (conducting, drain → source) → Drain of the clamping switch → D1 of the main switch (reverse turn-off) → Primary winding → Vin / 2 power supply → Vin (forming a circuit). The fourth stage: After the clamping switch turns off, the clamping capacitor begins to charge, inductors Lr1 and Lm1 resonate with C1 of the main switch, and the body diode D1 of the main switch is pre-conducted.

[0032] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A combined active clamp drive flyback circuit, characterized in that, include: Primary winding unit and auxiliary winding unit; The input terminal of the primary winding unit is suitable for electrical connection to the positive voltage terminal of DC voltage, and the output terminal is suitable for grounding. The primary winding unit includes a primary winding, a clamping circuit and a main switch. The primary winding is connected in series with the main switch, and the clamping circuit is connected in parallel with the primary winding. The clamping circuit includes a clamping capacitor, a clamping switch and a clamping diode. The clamping capacitor, the clamping switch and the clamping diode are connected in series. The control terminal of the main switch applies a synchronous drive signal. The primary windings of each stage are controlled in phase and share a common magnetic core. The auxiliary winding unit includes an auxiliary winding, a D0 diode, and an auxiliary clamping capacitor. One end of the auxiliary winding is connected in series with the D0 diode to output voltage, and the other end is connected to one end of the auxiliary clamping capacitor.

2. The combined active clamp drive flyback circuit according to claim 1, characterized in that, The primary winding unit is multi-stage, and the primary winding units of each stage are connected in parallel; The input terminal of the primary winding unit in the first stage is suitable for electrical connection to the positive voltage terminal of DC voltage, and the output terminal of the primary winding unit in the last stage is grounded.

3. The combined active clamp drive flyback circuit according to claim 2, characterized in that, Also includes: Voltage equalizing capacitor; The voltage equalizing capacitor is connected in parallel with the primary winding; The voltage equalizing capacitors at each stage are connected in series.

4. The combined active clamp drive flyback circuit according to claim 1, characterized in that, The main switch is a MOSFET, the inlet of the main switch is the drain of the MOSFET, the outlet of the main switch is the source of the MOSFET, and the control terminal of the main switch is the gate of the MOSFET.

5. The combined active clamp drive flyback circuit according to claim 1, characterized in that, It also includes the drive circuit; The driving circuit includes an input unit, a driving unit, and a driving transformer; The input unit is suitable for receiving PWM signals; The driving unit is an IXDF604 chip, which is electrically connected to the input unit; The drive transformer includes a drive primary winding and a drive auxiliary winding. The drive primary winding shares a common magnetic core with the drive primary winding, and the drive primary winding is electrically connected to the drive unit. The drive auxiliary winding is electrically connected to the clamping switch and / or the main switch.

6. The combined active clamp drive flyback circuit according to claim 5, characterized in that, The input unit includes: an input diode, an input resistor, an input capacitor, an output diode, an output resistor, and an output capacitor; The input diode is connected in parallel with the input resistor, the input capacitor is connected in series with the input diode and the input resistor, and the current of the input diode is directed towards the driving unit. The input unit is adapted to receive PWM signals. The output diode is connected in parallel with the output resistor, the output capacitor is connected in series with the output diode and the output resistor, and the current flow of the output diode is away from the driving unit. The input unit is suitable for outputting PWM signals.

7. The combined active clamp drive flyback circuit according to claim 6, characterized in that, The drive transformer includes a first drive transformer and a second drive transformer; The primary winding of the first driving transformer is connected in series with the driving unit and the input diode. One end of the auxiliary driving winding of the first driving transformer is electrically connected to the gate of the clamping switch, and the other end is electrically connected to the source of the clamping switch. The primary winding of the second driving transformer is connected in series with the driving unit and the output diode. One end of the auxiliary driving winding of the second driving transformer is electrically connected to the gate of the main switch, and the other end is electrically connected to the source of the main switch.

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