Efficient self-driven clamping circuit

Abstract

The utility model provides a high-efficiency self-driven clamping circuit, and belongs to the technical field of electronic circuits. Comprising a transformer T1, and a primary winding pin 2 of the transformer T1 and a drain electrode of a main switching tube Q2 are connected to a node 6; a pin 1 of the primary winding and one end of the clamping capacitor C1 are connected to a node 7, and the other end of the clamping capacitor C1 is connected with a drain electrode of the clamping tube Q1 and used for absorbing and storing leakage inductance peak energy. According to the utility model, through cooperation of the transformer T1, the clamping tube Q1, the clamping capacitor C1, the damping resistor R1 and other elements, the purpose of accurate and stable clamping of peak voltage under a high-power working condition is realized, and through the self-driving circuit composed of the capacitor C3, the Zener diode ZD1, the diode D2 and the capacitor C2, the effect of simplifying the circuit control structure is achieved, and the reliability of the circuit is improved. In addition, by means of a driving control circuit composed of a clamping capacitor C1, a resistor R2 and a capacitor C2, the effect of improving the energy utilization efficiency is achieved.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuit technology, and in particular to a high-efficiency self-driven clamping circuit. Background Technology

[0002] In the operation of a flyback switching power supply topology, transformer leakage inductance is unavoidable. When the switching transistor enters the off state, based on the principle of electromagnetic induction, a sharp increase in the rate of change of current occurs. At this instant, the energy previously stored in the transformer leakage inductance is rapidly released, generating a high-amplitude reverse spike voltage. Without effective clamping measures, the combined voltage of this reverse spike voltage, along with the input voltage and reflected voltage, is very likely to far exceed the reverse breakdown voltage threshold of the switching transistor. This will undoubtedly cause severe electrical stress on the switching transistor, greatly threatening the reliability and stability of the switching transistor and even the entire flyback switching power supply topology.

[0003] However, in applications with relatively low power levels, RCD clamping circuits have become the most widely used clamping solution due to their low cost and effective clamping of voltage spikes. However, when the power increases to 150W or higher, the proportionally increasing leakage inductance energy due to the continuous increase in primary-side current highlights the limitations of RCD clamping circuits. Their clamping capability becomes insufficient when faced with the significantly increased leakage inductance energy, making it difficult to meet the precise and stable clamping requirements for voltage spikes under high-power conditions. In contrast, while active clamping circuits can theoretically handle clamping tasks in high-power scenarios, their complex circuit structure involves sophisticated control strategies and multiple control components. This not only significantly increases the difficulty of circuit design and debugging but also leads to higher costs, limiting their widespread adoption in practical applications. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide a high-efficiency self-driven clamping circuit, which solves the problems of existing RCD clamping circuits, which are difficult to meet the clamping requirements of accurate and stable peak voltage under high power conditions when the power is increased to 150W or above, traditional clamping circuits usually require an additional drive signal to control the clamping tube, and traditional circuits usually dissipate the energy as heat through resistors when dealing with leakage inductance peak energy, resulting in a lot of energy waste.

[0005] Technical Solution: To achieve the above objectives, this utility model is implemented through the following technical solution: A high-efficiency self-driven clamping circuit, comprising: a transformer T1, wherein the primary winding pin 2 of the transformer T1 is connected to the drain of the main switching transistor Q2 at node 6; the primary winding pin 1 is connected to one end of the clamping capacitor C1 at node 7, and the other end of the clamping capacitor C1 is connected to the drain of the clamping transistor Q1, for absorbing and storing leakage inductance spike energy.

[0006] In a further embodiment, the damping resistor R1 is connected at one end to the source of the clamping transistor Q1 at node 4 and at the other end to node 6. The damping resistor R1 is used to dampen the current oscillation and detect the clamping current, converting it into a pulse voltage to drive Q1.

[0007] In a further embodiment, the self-driven circuit is used for automatic control of the clamping process. The self-driven circuit includes a capacitor C3 and a Zener diode ZD1. One end of the capacitor C3 is connected to the cathode of the Zener diode ZD1 at node 3, and the other end of the capacitor C3 is connected to the other end of the damping resistor R1 at node 6. The anode of the Zener diode ZD1 is connected to node 4 to stabilize the voltage of the self-driven circuit.

[0008] In a further embodiment, diode D2, the anode of which is connected to node 3 and the cathode of which is connected to the gate of clamping transistor Q1 at node 2, is used to guide the drive current generated by the self-driven circuit to the gate of clamping transistor Q1.

[0009] In a further embodiment, capacitor C2, with one end connected to node 2 and the other end connected to node 4, is used to buffer and store the gate current of clamping transistor Q1.

[0010] In a further embodiment, resistor R2, which is connected in parallel with capacitor C2, is connected at both ends to node 2 and node 4 respectively. Resistor R2 is used to ensure that clamping transistor Q1 is reliably turned off.

[0011] In a further embodiment, diode D1, which is connected in parallel with damping resistor R1, has its anode connected to node 4 and its cathode connected to node 6. Diode D1 is used to clamp reverse voltage.

[0012] In another embodiment, capacitor C4 and bridge rectifier BR are connected, with the positive terminal of capacitor C4 connected to the positive terminal of bridge rectifier BR at node 7 and the negative terminal of capacitor C4 connected to the negative terminal of bridge rectifier BR at node 8, so as to achieve filtering and rectification of the output voltage.

[0013] In a further embodiment, resistor R2 and capacitor C2 form a drive control circuit for precise control of the charging and discharging process of clamping capacitor C1, ensuring effective handling of leakage inductance spike energy.

[0014] In a further embodiment, diode D1 and damping resistor R1 form a reverse voltage clamping circuit to clamp the reverse voltage generated by the primary winding of transformer T1.

[0015] Beneficial effects: 1. Through the cooperation of components such as transformer T1, clamping transistor Q1, clamping capacitor C1, and damping resistor R1, the purpose of precise and stable clamping of peak voltage under high power conditions is achieved. Compared with the traditional RCD clamping circuit, it can better protect circuit components and significantly enhance circuit stability and reliability, ensuring stable operation of the circuit under high power conditions. It utilizes the characteristic of transformer T1 generating back electromotive force when the main switch Q2 is turned off, so that clamping capacitor C1 can accurately absorb and store leakage inductance peak energy. Damping resistor R1 guides energy to charge clamping capacitor C1, and works with diode D1 to limit voltage when the current is reversed, effectively dealing with the significantly increased leakage inductance energy under high power.

[0016] 2. The self-driven circuit, composed of capacitor C3, Zener diode ZD1, diode D2, and capacitor C2, uses capacitor C3 to store electrical energy, Zener diode ZD1 to stabilize the voltage, and diode D2 to guide the current direction. The components work closely together. During circuit operation, it automatically provides suitable driving conditions for clamping transistor Q1, thereby eliminating the dependence on external driving signals. Ultimately, it simplifies the circuit control structure, reduces circuit complexity, and reduces instability factors introduced by external driving signals.

[0017] 3. With the help of the driving control circuit composed of clamping capacitor C1, resistor R2 and capacitor C2, clamping capacitor C1 first absorbs and stores the leakage inductance spike energy. Resistor R2 and capacitor C2 then control the charging and discharging process of clamping capacitor C1 to reasonably manage and allocate the stored energy, thereby achieving effective energy recovery and reuse; thus improving energy utilization efficiency. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a circuit diagram for a high-efficiency self-driven clamping circuit.

[0020] Figure 2 This is the timing diagram for a high-efficiency self-driven clamping circuit.

[0021] Figure 3Simulation diagram of a high-efficiency self-driven clamping circuit.

[0022] Figure 4 Voltage waveform diagram across the main switch S1

[0023] Figure 5 The gate voltage waveform diagram of clamping transistor Q1 Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions in this utility model are described clearly and completely. Obviously, the described embodiments are only some, not all, of the embodiments in this utility model. All other embodiments obtained by those skilled in the art based on the embodiments in this utility model without creative effort are within the scope of protection of this utility model.

[0025] This application provides a high-efficiency self-driven clamping circuit, solving the technical problems of existing RCD clamping circuits, which struggle to meet the precise and stable clamping requirements for peak voltages under high-power conditions (above 150W), require additional drive signals to control the clamping transistor, and waste energy by dissipating leakage inductance spikes as heat through resistors. In practical applications, this circuit achieves good clamping performance, adaptability to higher power circuits, self-drive of the clamping transistor Q1, simple circuit control (no additional clamping signal required), high clamping efficiency, low energy loss, and allows leakage inductance energy to be returned to the transformer.

[0026] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0027] Reference Figure 1-5 A high-efficiency self-driven clamping circuit includes: a transformer T1, wherein the primary winding pin 2 of the transformer T1 is connected to the drain of the main switching transistor Q2 at node 6; the primary winding pin 1 is connected to one end of the clamping capacitor C1 at node 7, and the other end of the clamping capacitor C1 is connected to the drain of the clamping transistor Q1, for absorbing and storing leakage inductance spike energy.

[0028] The back electromotive force generated in the primary winding of transformer T1 at the moment the main switch Q2 is turned off, and the absorption and storage of leakage inductance spike energy by clamping capacitor C1, that is, when the main switch Q2 is turned off, the primary winding of transformer T1 generates a back electromotive force. This phenomenon provides the basic conditions for energy conversion and processing in the subsequent circuit, and is the starting point for energy change and regulation of the entire circuit. The clamping capacitor C1 is connected between node 7 and clamping transistor Q1. By connecting the negative terminal to node 7 and the positive terminal to the drain of clamping transistor Q1, it can effectively absorb and store the leakage inductance spike energy generated during circuit operation, avoiding excessive voltage surges caused by leakage inductance spike energy in the circuit, protecting other components in the circuit, enhancing the stability of the circuit when handling leakage inductance spike energy, ensuring that the circuit can operate safely and stably under different operating conditions, and providing a relatively stable energy environment for subsequent circuit operation; at the same time, it lays the foundation for the entire circuit to achieve efficient clamping function.

[0029] The damping resistor R1 is connected at one end to the source of the clamping transistor Q1 at node 4 and at the other end to node 6. The damping resistor R1 is used to dampen the current oscillation and detect the clamping current, converting it into a pulse voltage to drive Q1.

[0030] At the instant the main switch Q2 is turned off, the energy flow is guided to ensure that the leakage inductance energy can charge the clamping capacitor C1 in an orderly manner, avoiding disorderly energy surges. Simultaneously, when the current reverses, the voltage is limited within a certain range through cooperation with diode D1 to prevent excessive reverse voltage. This ensures the circuit remains stable under complex current and voltage changes, improving the circuit's adaptability and stability to voltage fluctuations. This achieves the effect of guiding leakage inductance energy to charge the clamping capacitor C1 when the main switch Q2 is turned off, and limiting the voltage in cooperation with diode D1 when the current reverses.

[0031] The self-driven circuit is used for automatic control of the clamping process. The self-driven circuit includes a capacitor C3 and a Zener diode ZD1. One end of the capacitor C3 is connected to the cathode of the Zener diode ZD1 at node 3, and the other end of the capacitor C3 is connected to the other end of the damping resistor R1 at node 6. The anode of the Zener diode ZD1 is connected to node 4 to stabilize the voltage of the self-driven circuit.

[0032] By connecting capacitor C3 and Zener diode ZD1 to the corresponding node in a specific connection method, capacitor C3 stores charge and Zener diode ZD1 plays a voltage stabilizing role. Together, they maintain the voltage of the self-driven circuit within a relatively stable range, preventing voltage fluctuations from affecting the normal driving of clamping transistor Q1. This provides stable and reliable driving conditions for clamping transistor Q1, ensuring the stability and reliability of the self-driven circuit and improving the adaptability of the entire clamping circuit under different operating conditions.

[0033] Diode D2, the anode of which is connected to node 3, and the cathode of which is connected to the gate of clamping transistor Q1 at node 2, is used to guide the drive current generated by the self-driven circuit to the gate of clamping transistor Q1.

[0034] By utilizing its own unidirectional conductivity, the current generated by the self-driven circuit is accurately guided to the gate of the clamping transistor Q1, ensuring the correct flow of the driving current and avoiding reverse current flow. This ensures the normal driving of the gate of the clamping transistor Q1, enabling the clamping transistor Q1 to be accurately turned on according to the signal of the self-driven circuit. This helps to realize the automatic control of the clamping process and ensures the reliability and stability of the operation of the clamping transistor Q1.

[0035] Capacitor C2, with one end connected to node 2 and the other end connected to node 4, is used to buffer and store the gate current of clamping transistor Q1.

[0036] When current flows through the gate of clamp transistor Q1, capacitor C2 can buffer the current to prevent a sudden surge of current from impacting the gate of clamp transistor Q1. At the same time, it stores a certain amount of electrical energy. When the circuit state changes or the drive current fluctuates, it can provide continuous current support for clamp transistor Q1, ensuring that the conduction state of clamp transistor Q1 is more stable. Thus, it achieves the effect of buffering and storing the gate current of clamp transistor Q1.

[0037] Resistor R2 is connected in parallel with capacitor C2. The two ends of resistor R2 are connected to node 2 and node 4 respectively. Resistor R2 is used to ensure that clamping transistor Q1 is reliably turned off.

[0038] By connecting it in parallel with capacitor C2 at a specific node, the gate voltage and current of clamping transistor Q1 are optimized and adjusted to ensure that when clamping transistor Q1 needs to be turned off, its turn-off state can be achieved quickly and stably, avoiding circuit abnormalities such as leakage current and malfunctions caused by incomplete or unstable turn-off. This improves the stability and working accuracy of the entire circuit and ensures the reliability and stability of the circuit during long-term operation.

[0039] Diode D1 is connected in parallel with damping resistor R1. The anode of diode D1 is connected to node 4, and the cathode of diode D1 is connected to node 6. Diode D1 is used to clamp reverse voltage.

[0040] Utilizing the unidirectional conductivity of the diode, it quickly conducts when reverse voltage occurs. Together with the parallel damping resistor R1, it limits the amplitude of the reverse voltage, preventing the reverse voltage from causing breakdown damage to semiconductor devices in the circuit (such as switching transistors, diodes, etc.). This ensures that the circuit can safely and stably cope with reverse voltage changes during the switching process of the main switching transistor Q2, maintain the normal operating state of the circuit, and reduce the probability of failure caused by reverse voltage.

[0041] Capacitor C4 and bridge rectifier BR are connected together. The positive terminal of capacitor C4 is connected to the positive terminal of the output of bridge rectifier BR at node 7, and the negative terminal of capacitor C4 is connected to the negative terminal of the output of bridge rectifier BR at node 8, so as to achieve filtering and rectification of the output voltage.

[0042] The bridge rectifier BR converts the input AC power into DC power, while capacitor C4, through its own energy storage and discharge characteristics, smooths the rectified DC voltage, removing ripple and noise components. This provides a stable and clean DC power supply for subsequent electrical equipment or circuits, meeting their requirements for power stability and quality, improving the power supply performance of the entire circuit system, and ensuring that devices connected to the power output can work normally and stably without being affected by power fluctuations.

[0043] The resistor R2 and capacitor C2 form a drive control circuit, which is used to precisely control the charging and discharging process of the clamping capacitor C1, and ensure effective handling of leakage inductance spike energy.

[0044] By matching the parameters of resistor R2 and capacitor C2 and working together, the charging and discharging rate and charge of clamping capacitor C1 can be precisely adjusted according to the actual working conditions of the circuit. This ensures that the absorption, storage and release of leakage inductance spike energy are carried out in the best possible condition, maximizing energy utilization efficiency, enhancing clamping effect, effectively protecting the circuit from the harm of spike energy, and optimizing the overall performance of the circuit while reducing unnecessary energy loss and voltage fluctuations.

[0045] The diode D1 and the damping resistor R1 form a reverse voltage clamping circuit, which is used to clamp the reverse voltage generated by the primary winding of transformer T1.

[0046] This circuit enables a rapid response when a reverse voltage occurs during circuit operation. By using the rapid conduction of diode D1 and the current-limiting effect of damping resistor R1, the reverse voltage is limited to a safe range, preventing damage to various components in the circuit. This ensures that the circuit can maintain a stable operating state and normal voltage level even in complex electrical environments, especially when the current direction changes frequently, thereby reducing the risk of failure caused by reverse voltage.

[0047] During operation, when the main switch Q2 is turned on, current flows through the primary winding of transformer T1, storing electrical energy. After the main switch Q2 is turned off, due to the leakage inductance of the transformer, the leakage inductance energy begins to be released. The resulting current flows through the damping resistor R1, generating a voltage drop across R1. This voltage drop is coupled to the Zener diode ZD1 via capacitor C3 for voltage limiting. After voltage limiting, the voltage across capacitor C2 is used to charge capacitor C2. As the charging process continues, the voltage across capacitor C2 becomes sufficient to turn on the clamping transistor Q1. At this point, the clamping transistor Q1, the clamping capacitor C1, and the damping resistor R1 form a circuit. Utilizing the connection between the clamping capacitor C1, R1, and the body diode of Q1, and taking advantage of the characteristic that the capacitor voltage cannot change abruptly, the voltage spike generated by the leakage inductance at the primary winding of transformer T1 during the release of leakage inductance energy is controlled. The voltage is clamped to stabilize it at a certain level. When the leakage inductance energy is released and the current flowing through the damping resistor R1 begins to reverse, some of the energy across the clamping capacitor C1 is returned to the primary winding of transformer T1. Then, when the voltage across the damping resistor R1 becomes negative, diode D1 conducts to clamp the voltage at around -1V. At the same time, capacitor C3 discharges after being forward-conducted by ZD1 under the negative voltage, and the voltage across capacitor C2 gradually decreases to 0V under the discharge effect of resistor R2, causing clamping transistor Q1 to turn off, completing one working cycle. Before the main switch Q2 turns on again, the energy interaction between capacitors C1, C2, C3 and the primary winding of transformer T1 in the circuit is in a stable state, waiting for the next turn-off of the main switch Q2 to repeat the above working process.

[0048] The figures shown in the accompanying drawings are illustrative and are intended only to more intuitively demonstrate the key structure and connection relationships of the efficient self-driven clamping circuit of this invention. In practical applications, the appearance and size of the device can be adjusted and optimized according to specific needs.

[0049] This utility model encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this utility model. To provide the public with a thorough understanding of this utility model, specific details have been described in detail in the above preferred embodiments; however, those skilled in the art can fully understand this utility model even without these detailed descriptions. Furthermore, to avoid unnecessary confusion regarding the essence of this utility model, well-known methods, processes, procedures, components, and circuits have not been described in detail.

[0050] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A high-efficiency self-driven clamping circuit, characterized in that, include: Transformer T1, wherein the primary winding pin 2 of transformer T1 is connected to the drain of the main switch Q2 at node 6; The primary winding pin 1 is connected to one end of the clamping capacitor C1 at node 7, and the other end of the clamping capacitor C1 is connected to the drain of the clamping transistor Q1 to absorb and store the leakage inductance spike energy.

2. The high-efficiency self-driven clamping circuit according to claim 1, characterized in that, Also includes: The damping resistor R1 is connected at one end to the source of the clamping transistor Q1 at node 4 and at the other end to node 6. The damping resistor R1 is used to dampen the current oscillation and detect the clamping current, converting it into a pulse voltage to drive Q1.

3. The high-efficiency self-driven clamping circuit according to claim 2, characterized in that, It also includes a self-driving circuit: the self-driving circuit is used for automatic control of the clamping process. The self-driving circuit includes a capacitor C3 and a Zener diode ZD1. One end of the capacitor C3 is connected to the cathode of the Zener diode ZD1 at node 3, and the other end of the capacitor C3 is connected to the other end of the damping resistor R1 at node 6. The anode of the Zener diode ZD1 is connected to node 4 to stabilize the voltage of the self-driving circuit.

4. The high-efficiency self-driven clamping circuit according to claim 3, characterized in that, The self-driven circuit also includes: Diode D2, the anode of which is connected to node 3, and the cathode of which is connected to the gate of clamping transistor Q1 at node 2, is used to guide the drive current generated by the self-driven circuit to the gate of clamping transistor Q1.

5. The high-efficiency self-driven clamping circuit according to claim 4, characterized in that, The self-driven circuit also includes: Capacitor C2, with one end connected to node 2 and the other end connected to node 4, is used to buffer and store the gate current of clamping transistor Q1.

6. The high-efficiency self-driven clamping circuit according to claim 5, characterized in that, Also includes: Resistor R2 is connected in parallel with capacitor C2. The two ends of resistor R2 are connected to node 2 and node 4 respectively. Resistor R2 is used to ensure that clamping transistor Q1 is reliably turned off.

7. The high-efficiency self-driven clamping circuit according to claim 3, characterized in that, Also includes: Diode D1 is connected in parallel with damping resistor R1. The anode of diode D1 is connected to node 4, and the cathode of diode D1 is connected to node 6. Diode D1 is used to clamp reverse voltage.

8. The high-efficiency self-driven clamping circuit according to claim 1, characterized in that, Also includes: Capacitor C4 and bridge rectifier BR are connected together. The positive terminal of capacitor C4 is connected to the positive terminal of the output of bridge rectifier BR at node 7, and the negative terminal of capacitor C4 is connected to the negative terminal of the output of bridge rectifier BR at node 8, so as to achieve filtering and rectification of the output voltage.

9. The high-efficiency self-driven clamping circuit according to claim 6, characterized in that: The resistor R2 and capacitor C2 form a drive control circuit, which is used to precisely control the charging and discharging process of the clamping capacitor C1, and ensure effective handling of leakage inductance spike energy.

10. The high-efficiency self-driven clamping circuit according to claim 7, characterized in that: The diode D1 and the damping resistor R1 form a reverse voltage clamping circuit, which is used to clamp the reverse voltage generated by the primary winding of transformer T1.

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