Active clamping lossless absorption circuit for synchronous rectification of switching power supply

Abstract

The invention discloses an active clamping lossless absorption circuit for synchronous rectification of a switching power supply, which relates to the technical field of power electronics and comprises a full-wave rectification active clamping lossless absorption circuit. The full-wave rectification active clamping lossless absorption circuit comprises a first peak voltage absorption circuit, a first voltage conversion circuit, a first rectifier tube, a second rectifier tube, a first inductor and a first transformer, and the peak voltage absorption circuit can absorb reverse recovery energy on the rectifier tubes to eliminate voltage peaks. The voltage conversion circuit can carry out voltage conversion on energy absorbed by the voltage absorption circuit, peak energy is completely transmitted to the output end of the rectification circuit in a lossless mode after voltage conversion, voltage peaks and oscillation on a rectification tube in the rectification circuit of the switching power supply are restrained, and meanwhile the voltage peak energy is completely transmitted to the output. The switching power supply efficiency is improved.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to an active clamping lossless absorption circuit for synchronous rectification of a switching power supply. Background Art

[0002] As electronic devices increasingly shift toward miniaturization and higher efficiency, miniaturization and efficiency of switching power supplies, as essential power supply components, have become increasingly important. In switching power supplies, heat sinks occupy a significant portion of the device's volume. Improving the efficiency of switching power supplies not only saves energy but also reduces the size of these heat sinks, thereby miniaturizing the overall device. Synchronous rectification is a commonly used efficiency-enhancing technology in switching power supplies. By replacing traditional diodes with low-on-resistance switching elements like MOSFETs for rectification, energy losses during the rectification process can be significantly reduced, improving the overall efficiency of the power supply.

[0003] However, in practical applications, synchronous rectifier MOSFETs face several operational challenges. First, due to the presence of a parasitic body diode, the MOSFET generates a large current surge during reverse recovery, resulting in voltage spikes between the MOSFET's Ds terminals that far exceed the nominal nominal voltage. These excessive voltage spikes can damage the rectifier and reduce power supply reliability. To address this issue, rectifiers with higher voltage ratings are typically selected. However, for a given volume, high-voltage rectifiers have a higher on-resistance, which reduces power supply efficiency. Second, transformer leakage inductance can also cause voltage spikes between the MOSFET's Ds terminals. To address these issues, numerous circuits have been designed to mitigate the excessive voltage spikes caused by the rectifiers. However, existing snubber circuits generate losses and heat during the discharge process, which not only reduces power supply efficiency but also limits miniaturization. Common snubber circuits include RC snubbers and RCD snubbers. While these circuits share similar principles, RC snubbers are less efficient and generate significant heat. While RCD snubbers mitigate some of the shortcomings of RC snubbers, they still present certain losses and heat generation issues.

[0004] In summary, the existing absorption circuit cannot fully meet the requirements of the switching power supply in terms of high efficiency and miniaturization. Summary of the Invention

[0005] The purpose of this application is to overcome the existing technical defects and provide an active clamping lossless absorption circuit for synchronous rectification of a switching power supply. The peak voltage absorption circuit can absorb the reverse recovery energy on the rectifier tube to eliminate the voltage spike. The voltage conversion circuit can convert the energy absorbed by the voltage absorption circuit into voltage. After the voltage conversion, the peak energy is completely transferred to the output end of the rectifier circuit without loss, thereby suppressing the voltage spike and oscillation on the rectifier tube in the switching power supply rectifier circuit, and at the same time transferring all the voltage spike energy to the output, thereby improving the efficiency of the switching power supply.

[0006] The purpose of this application is achieved through the following technical solutions: In a first aspect, the present application proposes an active clamp lossless absorption circuit for synchronous rectification of a switching power supply, the circuit comprising a full-wave rectifier active clamp lossless absorption circuit, the full-wave rectifier active clamp lossless absorption circuit comprising a first peak voltage absorption circuit, a first voltage conversion circuit, a first rectifier tube, a second rectifier tube, a first inductor, and a first transformer, the first transformer comprising a first winding and a second winding connected to the first winding, the first peak voltage absorption circuit comprising a first diode, a second diode, and a first capacitor, the first voltage conversion circuit comprising a third switching tube, a second inductor, a third diode, and a second capacitor; The positive end of the first winding is connected to the anode of the second diode and the drain of the second rectifier tube, the cathode of the second diode is respectively connected to the cathode of the first diode, one end of the first capacitor and the drain of the third switch tube, the source of the second rectifier tube is respectively connected to the other end of the first capacitor, the source of the first rectifier tube, the anode of the third diode and one end of the second capacitor, and the other end of the second inductor is respectively connected to the cathode of the third diode and the source of the third switch tube; The negative end of the first winding is connected to one end of the first inductor, and the other end of the first inductor is connected to the other end of the second capacitor and one end of the second inductor respectively; The negative end of the second winding is connected to the drain of the first rectifier tube and the anode of the first diode.

[0007] In one possible implementation, the circuit further includes a full-bridge rectifier active clamp lossless absorption circuit, the full-bridge rectifier active clamp lossless absorption circuit including a fourth rectifier tube, a fifth rectifier tube, a sixth rectifier tube, and a seventh rectifier tube, a second peak voltage absorption circuit, a second voltage conversion circuit, and a third inductor, the second peak voltage absorption circuit including a fourth diode and a third capacitor, and the second voltage conversion circuit including an eighth switching tube, a fourth inductor, a fifth diode, and a fourth capacitor; The drain of the fourth rectifier is respectively connected to the drain of the fifth rectifier, the anode of the fourth diode, and one end of the third inductor; the source of the fourth rectifier is respectively connected to the drain of the sixth rectifier; the source of the sixth rectifier is respectively connected to the source of the seventh rectifier, one end of the third capacitor, the anode of the fifth diode, and one end of the fourth capacitor; The source of the fifth rectifier tube is connected to the drain of the seventh rectifier tube, the other end of the third capacitor is respectively connected to the cathode of the fourth diode and the drain of the eighth switching tube, the source of the eighth switching tube is respectively connected to the cathode of the fifth diode and one end of the fourth inductor, and the other end of the fourth inductor is respectively connected to the other end of the fourth capacitor and the other end of the third inductor.

[0008] In one possible implementation, the circuit further includes a forward output rectifier active clamp lossless absorption circuit, the forward output rectifier active clamp lossless absorption circuit including a third peak voltage absorption circuit, a third voltage conversion circuit, a ninth rectifier tube, a tenth freewheeling tube, and a fifth inductor, the third peak voltage absorption circuit including a fifth capacitor and a sixth diode, and the third voltage conversion circuit including an eleventh switching tube, a sixth inductor, a seventh diode, and a sixth capacitor; The source of the ninth rectifier tube is respectively connected to the source of the tenth freewheeling tube, one end of the fifth capacitor, the anode of the seventh diode and one end of the sixth capacitor; the drain of the tenth freewheeling tube is respectively connected to the anode of the sixth diode and one end of the fifth inductor; the cathode of the sixth diode is respectively connected to the other end of the fifth capacitor and the drain of the eleventh switching tube; the source of the eleventh switching tube is respectively connected to one end of the sixth inductor and the cathode of the seventh diode; the other end of the sixth inductor is connected to the other end of the fifth inductor and the sixth capacitor.

[0009] In a possible implementation, the negative end of the first winding is connected to the positive end of the second winding.

[0010] In a possible implementation, the first peak voltage absorption circuit is used to absorb reverse recovery energy on the first rectifier tube and the second rectifier tube to eliminate voltage spikes; The first voltage conversion circuit is used to convert the energy absorbed by the first peak voltage absorption circuit into voltage, and transfer all the energy to the second capacitor.

[0011] In one possible embodiment, the full-bridge rectifier active clamping lossless absorption circuit also includes a second transformer, the positive end of the fourth winding of the second transformer is connected to the source of the fifth rectifier tube and the drain of the seventh rectifier tube, and the negative end of the fourth winding of the second transformer is connected to the source of the fourth rectifier tube and the drain of the sixth rectifier tube.

[0012] In a possible implementation, the second peak voltage absorption circuit is used to absorb reverse recovery energy on the fourth rectifier tube, the fifth rectifier tube, the sixth rectifier tube, and the seventh rectifier tube to eliminate voltage spikes; The second voltage conversion circuit is used to convert the energy absorbed by the second peak voltage absorption circuit into voltage, and transfer all the energy to the fourth capacitor.

[0013] In one possible embodiment, the forward output rectifier active clamping lossless absorption circuit also includes a third transformer, the positive end of the sixth winding of the third transformer is connected to the drain of the tenth freewheeling tube, and the negative end of the sixth winding of the third transformer is connected to the drain of the ninth rectifier tube.

[0014] In a possible implementation, the third peak voltage absorption circuit is used to absorb the reverse recovery energy on the ninth rectifier tube and the ninth rectifier tube to eliminate the voltage spike; The third voltage conversion circuit is used to convert the energy absorbed by the third peak voltage absorption circuit into voltage, and transfer all the energy to the sixth capacitor.

[0015] The above-mentioned main solution of this application and its various further options can be freely combined to form multiple solutions, all of which are solutions that can be adopted and protected by this application. Moreover, in this application, (non-conflicting options) can also be freely combined with each other and with other options. After understanding the solution of this application, those skilled in the art will understand that there are many combinations based on existing technology and common knowledge, all of which are technical solutions to be protected by this application, and this is not an exhaustive list.

[0016] The present application discloses an active clamping lossless absorption circuit for synchronous rectification of a switching power supply, which includes a full-wave rectifier active clamping lossless absorption circuit. The full-wave rectifier active clamping lossless absorption circuit includes a first peak voltage absorption circuit, a first voltage conversion circuit, a first rectifier tube, a second rectifier tube, a first inductor and a first transformer. The peak voltage absorption circuit can absorb reverse recovery energy on the rectifier tube to eliminate voltage spikes. The voltage conversion circuit can perform voltage conversion on the energy absorbed by the voltage absorption circuit. After voltage conversion, the peak energy is completely transferred to the output end of the rectifier circuit without loss, thereby suppressing voltage spikes and oscillations on the rectifier tube in the switching power supply rectifier circuit and transferring all the voltage spike energy to the output, thereby improving the efficiency of the switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A schematic diagram of a full-wave rectifier active clamping lossless absorption circuit proposed in an embodiment of the present application is shown.

[0019] Figure 2 Schematic diagram of the full-bridge rectifier active clamp lossless absorption circuit proposed in the embodiment of the present application Figure 3A schematic diagram of a forward output rectifier active clamp lossless absorption circuit proposed in an embodiment of the present application is shown.

[0020] Reference numerals: first rectifier tube - Q1; second rectifier tube - Q2; third switch tube - Q3; fourth rectifier tube - Q4; fifth rectifier tube - Q5; sixth rectifier tube - Q6; seventh rectifier tube - Q7; eighth switch tube - Q8; ninth rectifier tube - Q9; tenth freewheeling tube - Q10; eleventh switch tube - Q11; first diode - D1; second diode - D2; third diode - D3; fourth diode - D4; fifth diode - D5; sixth diode - D6; seventh diode - D7; first capacitor -C1; second capacitor -C2; third capacitor -C3; fourth capacitor -C4; fifth capacitor -C5; sixth capacitor -C6; first inductor -L1; second inductor -L2; third inductor -L3; fourth inductor -L4; fifth inductor -L5; sixth inductor -L6; first transformer T1; second transformer T2; third transformer T3; first winding -N2; second winding -N3; ​​third winding -N4; fourth winding -N5; fifth winding -N6; sixth winding -N7; first primary winding -N1. DETAILED DESCRIPTION

[0021] The following describes the embodiments of the present application through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0022] Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of this application.

[0023] Commonly used snubber circuits in existing technology include RC and RCD snubber circuits. While the principles of these circuits are similar, RC snubber circuits are less efficient than RCD snubber circuits and generate significant heat. Consequently, numerous circuits have been developed to address the issue of excessively high voltage spikes in rectifier tubes. However, the discharge process in existing snubber circuits generates heat and loss, which reduces power supply efficiency and limits their miniaturization.

[0024] In order to solve the above-mentioned technical problems, an embodiment of the present application proposes an active clamping lossless absorption circuit for synchronous rectification of a switching power supply, which can suppress the voltage spikes and oscillations on the rectifier tube in the switching power supply rectification circuit, and at the same time transfer all the voltage spike energy to the output, thereby improving the efficiency of the switching power supply. It is described in detail below.

[0025] This application proposes an active clamp lossless absorption circuit for synchronous rectification of a switching power supply. The circuit includes a full-wave rectification active clamp lossless absorption circuit. Please refer to Figure 1 , Figure 1 A schematic diagram of a full-wave rectifier active clamp lossless absorption circuit proposed in an embodiment of the present application is shown. The full-wave rectifier active clamp lossless absorption circuit includes a first peak voltage absorption circuit, a first voltage conversion circuit, a first rectifier tube Q1, a second rectifier tube Q2, a first inductor L1, and a first transformer T1. The first transformer T1 includes a first winding N2 and a second winding N3 connected to the first winding N2. The first peak voltage absorption circuit includes a first diode D1, a second diode D2, and a first capacitor C1. The first voltage conversion circuit includes a third switch tube Q3, a second inductor L2, a third diode D3, and a second capacitor C2. The positive end of the first winding N2 is connected to the anode of the second diode D2 and the drain of the second rectifier Q2. The cathode of the second diode D2 is respectively connected to the cathode of the first diode D1, one end of the first capacitor C1, and the drain of the third switch Q3. The source of the second rectifier Q2 is respectively connected to the other end of the first capacitor C1, the source of the first rectifier Q1, the anode of the third diode D3, and one end of the second capacitor C2, and is grounded GND. The other end of the second inductor L2 is respectively connected to the cathode of the third diode D3 and the source of the third switch Q3.

[0026] The negative end of the first winding N2 is connected to one end of the first inductor L1, and the other end of the first inductor L1 is connected to the other end of the second capacitor C2 and one end of the second inductor L2 respectively; The negative end of the second winding N3 is connected to the drain of the first rectifier Q1 and the anode of the first diode D1.

[0027] The first transformer T1 converts the input AC voltage into the required lower or higher AC voltage. It comprises a first primary winding N1, a first winding N2, and a second winding N3. One end of the first primary winding N1 is connected to the power input, and the other end is grounded. The secondary coil consists of two windings (first winding N2 and second winding N3), each connected to two rectifiers: the first rectifier Q1 and the second rectifier Q2. These two rectifiers, using MOSFETs or other types of transistors, convert the AC voltage generated by the transformer's secondary coil into a pulsating DC voltage. The first inductor L1, the output filter inductor, and the second capacitor C2 combine to filter the rectified pulsating DC voltage, resulting in a smoother and more stable DC output.

[0028] The first diode D1 and second diode D2 in the first spike voltage absorption circuit provide a path for the reverse recovery energy of the corresponding first rectifier Q1 or second rectifier Q2 when they are turned off, thereby preventing the generation of voltage spikes. The first capacitor C1 is used to store the reverse recovery energy transferred through the first diode D1 and second diode D2, and also helps limit the amplitude of the voltage spike.

[0029] In the first voltage conversion circuit, the third switch Q3 is periodically turned on and off under a specific control signal, transferring the energy stored in the first capacitor C1 to the second capacitor C2 via the second inductor L2. The second inductor L2, the third diode D3, and the third switch Q3 form a simple DC-DC converter that can effectively transfer the energy in the first capacitor C1 to the second capacitor C2 while ensuring the stability of the output voltage.

[0030] The negative end of the first winding N2 is connected to the positive end of the second winding N3.

[0031] The first peak voltage absorption circuit is used to absorb the reverse recovery energy of the first rectifier tube Q1 and the second rectifier tube Q2 to eliminate the voltage spike; The first voltage conversion circuit is used to convert the energy absorbed by the first peak voltage absorption circuit into voltage, and transfer all the energy to the second capacitor C2.

[0032] The first peak voltage absorption circuit absorbs the reverse recovery energy generated by the first and second rectifiers Q1, Q2 during switching operations, preventing this energy from causing voltage spikes and protecting sensitive components in the circuit from damage. The first voltage conversion circuit transfers the energy absorbed by the first peak voltage absorption circuit and stored in the first capacitor C1 to the second capacitor C2 through an efficient conversion mechanism, ensuring that this energy is not wasted and helping to improve the efficiency of the entire circuit.

[0033] When the first rectifier Q1 or the second rectifier Q2 is turned off for some reason, their reverse recovery energy is transferred to the first capacitor C1 through the first diode D1 or the second diode D2. The first capacitor C1 acts as a buffer, absorbing this energy and preventing voltage spikes. At the appropriate time, the third switch Q3 is activated and turned on. At this time, the energy in the first capacitor C1 is transferred to the second capacitor C2 through the second inductor L2. During this process, the third diode D3 ensures unidirectional current flow, preventing energy backflow. As the energy in the first capacitor C1 is gradually transferred to the second capacitor C2, the voltage of the first capacitor C1 decreases until it approaches the voltage level of the second capacitor C2. When this process is complete, the third switch Q3 is turned off, and the remaining current in the second inductor L2 continues to charge the second capacitor C2 through the third diode D3 until all the energy is transferred to the second capacitor C2, completing the complete energy conversion and utilization.

[0034] In the full-wave rectifier active clamp lossless absorption circuit, when the voltage on the second winding N3 changes from positive to zero, the driving voltage of the first rectifier Q1 becomes low and the first rectifier Q1 is turned off. The diode of the first rectifier Q1 is turned on to provide a freewheeling path for the first inductor L1. When the voltage on the second winding N3 becomes negative, the diode of the first rectifier Q1 reversely recovers. The reverse recovery energy charges the first capacitor C1 through the first diode D1. The first capacitor C1 limits the peak value and rising rate of the voltage between the DS poles of the first rectifier Q1. After the voltage on the first capacitor C1 reaches the peak value, it remains unchanged due to the lack of a discharge circuit. At this time, the driving voltage of the third switch tube Q3 changes from zero to a high level, the third switch tube Q3 is turned on, the third diode D3 is turned off, the first capacitor C1 charges the second capacitor C2 through the second inductor L2, and the discharge voltage of the first capacitor C1 decreases. When the voltage of the first capacitor C1 drops close to the voltage of the second capacitor C2, the driving voltage of the third switch tube Q3 becomes zero, and the third switch tube Q3 is turned off. The current of the second inductor L2 passes through the second capacitor C2 and the third diode D3 to form a freewheeling path, charging the second capacitor C2. When the current of the second inductor L2 becomes zero, the energy conversion process ends, and the peak energy is completely transferred to the output second capacitor C2. When the voltage on the first winding N2 changes from negative to zero, the driving voltage of the second rectifier Q2 becomes low and the second rectifier Q2 is turned off. The diode of the second rectifier Q2 is turned on to provide a freewheeling path for the first inductor L1. When the voltage on the first winding N2 becomes positive, the diode of the second rectifier Q2 reverse recovers, and the reverse recovery energy charges the first capacitor C1 through the second diode D2. The first capacitor C1 limits the peak value and rising rate of the voltage between the DS poles of the second rectifier Q2. After the voltage on the first capacitor C1 reaches the peak value, it remains unchanged due to the lack of a discharge circuit. At this point, the driving voltage of the third switch tube Q3 changes from zero to a high level, turning on the third switch tube Q3 and cutting off the third diode D3. The first capacitor C1 charges the second capacitor C2 through the second inductor L2, causing the discharge voltage of the first capacitor C1 to drop. When the voltage of the first capacitor C1 drops close to the voltage of the second capacitor C2, the driving voltage of the third switch tube Q3 becomes zero, and the third switch tube Q3 turns off. The current of the second inductor L2 forms a freewheeling path through the second capacitor C2 and the third diode D3, charging the second capacitor C2. When the current of the second inductor L2 reaches zero, the energy conversion process ends, and the peak energy is fully transferred to the second capacitor C2. The coordinated operation of the first peak voltage absorption circuit and the first voltage conversion circuit not only effectively protects the key components in the circuit from damage caused by voltage spikes, but also achieves efficient energy recovery and utilization, improving the overall performance of the system.

[0035] This application proposes an active clamp lossless absorption circuit for synchronous rectification of switching power supply, including a full-bridge rectifier active clamp lossless absorption circuit. Please refer to Figure 2 , Figure 2A schematic diagram of a full-bridge rectifier active clamp lossless absorption circuit proposed in an embodiment of the present application is shown. The full-bridge rectifier active clamp lossless absorption circuit includes a fourth rectifier tube Q4, a fifth rectifier tube Q5, a sixth rectifier tube Q6, and a seventh rectifier tube Q7, a second peak voltage absorption circuit, a second voltage conversion circuit, and a third inductor L3. The second peak voltage absorption circuit includes a fourth diode D4 and a third capacitor C3. The second voltage conversion circuit includes an eighth switch tube Q8, a fourth inductor L4, a fifth diode D5, and a fourth capacitor C4. The drain of the fourth rectifier Q4 is respectively connected to the drain of the fifth rectifier Q5, the anode of the fourth diode D4, and one end of the third inductor L3. The source of the fourth rectifier Q4 is connected to the drain of the sixth rectifier Q6. The source of the sixth rectifier Q6 is respectively connected to the source of the seventh rectifier Q7, one end of the third capacitor C3, the anode of the fifth diode D5, and one end of the fourth capacitor C4. The source of the sixth rectifier Q6 is also grounded GND. The source of the fifth rectifier Q5 is connected to the drain of the seventh rectifier Q7. The other end of the third capacitor C3 is respectively connected to the cathode of the fourth diode D4 and the drain of the eighth switch tube Q8. The source of the eighth switch tube Q8 is respectively connected to the cathode of the fifth diode D5 and one end of the fourth inductor L4. The other end of the fourth inductor L4 is respectively connected to the other end of the fourth capacitor C4 and the other end of the third inductor L3.

[0036] The fourth rectifier Q4, the fifth rectifier Q5, the sixth rectifier Q6 and the seventh rectifier Q7 form a full-bridge rectifier bridge. The drains of the fourth rectifier Q4 and the fifth rectifier Q5 are connected, and the sources of the sixth rectifier Q6 and the seventh rectifier Q7 are connected.

[0037] The second peak voltage absorption circuit includes a fourth diode D4 and a third capacitor C3. The anode of the fourth diode D4 is connected to the drains of the fourth rectifier Q4 and the fifth rectifier Q5, and the cathode is connected to one end of the third capacitor C3.

[0038] The second voltage conversion circuit includes an eighth switching tube Q8, a fourth inductor L4, a fifth diode D5 and a fourth capacitor C4. The drain of the eighth switching tube Q8 is connected to the other end of the third capacitor C3, the source is connected to the cathode of the fifth diode D5 and one end of the fourth inductor L4, the other end of the fourth inductor L4 is connected to the other end of the fourth capacitor C4, and the third inductor L3 is connected to the drains of the fourth rectifier tube Q4 and the fifth rectifier tube Q5.

[0039] After the input AC power is transformed by the transformer, it is rectified into DC power by the full-bridge rectifier circuit. When the rectifier tube is turned off, a spike voltage is generated. This spike voltage is absorbed by the second spike voltage absorption circuit (the fourth diode D4 and the third capacitor C3). The absorbed energy is converted and stored by the second voltage conversion circuit to achieve lossless absorption.

[0040] In a possible embodiment, the full-bridge rectifier active clamp lossless absorption circuit further includes a second transformer T2, the positive end of the fourth winding N5 of the second transformer T2 is connected to the source of the fifth rectifier tube Q5 and the drain of the seventh rectifier tube Q7, and the negative end of the fourth winding N5 of the second transformer T2 is connected to the source of the fourth rectifier tube Q4 and the drain of the sixth rectifier tube Q6.

[0041] The third winding N4 and the fourth winding N5 are two windings of the second transformer T2. The third winding N4 is the primary winding and the fourth winding N5 is the secondary winding. The second transformer T2 forms a full-bridge rectifier circuit with the fourth rectifier Q4, the fifth rectifier Q5, the sixth rectifier Q6 and the seventh rectifier Q7 respectively. Current passes through the two windings of the transformer. When the upper end voltage of the fourth winding N5 is positive and the lower end voltage is negative, the fifth rectifier Q5 and the sixth rectifier Q6 are turned on at the same time, the fourth rectifier Q4 and the seventh rectifier Q7 are turned off, the drain voltage of the fifth rectifier Q5 is positive, and the source voltage of the sixth rectifier Q6 is negative. When the upper end voltage of the fourth winding N5 is negative and the lower end voltage is positive, the fourth rectifier Q4 and the seventh rectifier Q7 are turned on at the same time, the fifth rectifier Q5 and the sixth rectifier Q6 are turned off, the drain voltage of the fourth rectifier Q4 is positive, and the source voltage of the seventh rectifier Q7 is negative, thereby realizing full-wave rectification.

[0042] In a possible implementation, the second peak voltage absorption circuit is used to absorb reverse recovery energy on the fourth rectifier tube Q4, the fifth rectifier tube Q5, the sixth rectifier tube Q6, and the seventh rectifier tube Q7 to eliminate voltage spikes; The second voltage conversion circuit is used to convert the energy absorbed by the second peak voltage absorption circuit into voltage, and transfer all the energy to the fourth capacitor C4.

[0043] In the second peak voltage absorption circuit, when the rectifier is turned off, a peak voltage is generated. This peak voltage is absorbed by an absorption circuit consisting of a fourth diode D4 and a third capacitor C3 and stored in the third capacitor C3. In the second voltage conversion circuit, the energy stored in the absorption circuit is converted to the required voltage through the combination of the eighth switching tube Q8, the fourth inductor L4, and the fifth diode D5, and then transferred to the fourth capacitor C4, ensuring efficient energy utilization.

[0044] The full-bridge rectifier active clamp lossless absorption circuit is mainly used to effectively absorb and process spike voltage during the rectification process, while converting and storing the absorbed energy to improve the efficiency and stability of the system.

[0045] This application proposes an active clamp lossless absorption circuit for synchronous rectification of switching power supply, and also includes a forward output rectification active clamp lossless absorption circuit. Please refer to Figure 3 , Figure 3 A schematic diagram of a forward output rectifier active clamp lossless absorption circuit proposed in an embodiment of the present application is shown. The forward output rectifier active clamp lossless absorption circuit includes a third peak voltage absorption circuit, a third voltage conversion circuit, a ninth rectifier tube Q9, a tenth freewheeling tube Q10, and a fifth inductor L5. The third peak voltage absorption circuit includes a fifth capacitor C5 and a sixth diode D6. The third voltage conversion circuit includes an eleventh switching tube Q11, a sixth inductor L6, a seventh diode D7, and a sixth capacitor C6. The source of the ninth rectifier tube Q9 is respectively connected to the source of the tenth freewheeling tube Q10, one end of the fifth capacitor C5, the anode of the seventh diode D7, one end of the sixth capacitor C6 and is grounded GND. The drain of the tenth freewheeling tube Q10 is respectively connected to the anode of the sixth diode D6 and one end of the fifth inductor L5. The cathode of the sixth diode D6 is respectively connected to the other end of the fifth capacitor C5 and the drain of the eleventh switching tube Q11. The source of the eleventh switching tube Q11 is respectively connected to one end of the sixth inductor L6 and the cathode of the seventh diode D7. The other end of the sixth inductor L6 is connected to the other end of the fifth inductor L5 and the sixth capacitor C6.

[0046] The forward output rectifier active clamp lossless absorption circuit also includes a third transformer T3, the positive end of the sixth winding N7 of the third transformer T3 is connected to the drain of the tenth freewheeling tube Q10, and the negative end of the sixth winding N7 of the third transformer T3 is connected to the drain of the ninth rectifier tube Q9.

[0047] The fifth winding N6 and the sixth winding N7 are the two windings of the third transformer T3. The fifth winding N6 is the primary winding, and the sixth winding N7 is the secondary winding. When the transformer primary winding is connected to the power supply, the secondary winding generates an AC voltage. During the positive half-cycle, the ninth rectifier Q9 is turned on, and current flows through the ninth rectifier Q9 and the fifth inductor L5 to the sixth capacitor C6, charging the sixth capacitor C6. During the negative half-cycle, the ninth rectifier Q9 is turned off, and the tenth freewheeling diode Q10 is turned on. Current continues to flow through the fifth inductor L5 and the tenth freewheeling diode Q10 to the sixth capacitor C6, maintaining a stable output voltage.

[0048] When the tenth freewheeling tube Q10 is turned off, a spike voltage is generated on the tenth freewheeling tube Q10 due to the parasitic inductance and the reverse recovery current of the body diode of the tenth freewheeling tube Q10. The spike voltage charges the fifth capacitor C5 through the sixth diode D6, thereby absorbing the spike voltage and protecting other components in the circuit from damage.

[0049] When the third voltage conversion circuit is operating, the energy stored in the fifth capacitor C5 is converted to a suitable voltage via the eleventh switch Q11, the sixth inductor L6, and the seventh diode D7 to charge the sixth capacitor C6. When the eleventh switch Q11 is on, the energy in the fifth capacitor C5 is transferred to the sixth capacitor C6 via the eleventh switch Q11 and the sixth inductor L6. When the eleventh switch Q11 is off, the seventh diode D7 is turned on, and the current in the sixth inductor L6 forms a freewheeling loop through the seventh diode D7, charging the sixth capacitor C6. The energy absorbed by the peak voltage absorption circuit is effectively converted and transferred to the sixth capacitor C6, improving the efficiency and stability of the entire circuit.

[0050] The third peak voltage absorption circuit is used to absorb the reverse recovery energy on the ninth rectifier tube Q9 and the tenth freewheeling tube Q10 to eliminate the voltage spike; the third voltage conversion circuit is used to convert the energy absorbed by the third peak voltage absorption circuit into voltage and transfer all the energy to the sixth capacitor C6.

[0051] The third peak voltage absorption circuit absorbs the reverse recovery energy on the ninth rectifier tube Q9 and the tenth freewheeling tube Q10 to eliminate voltage spikes. When the tenth freewheeling tube Q10 is turned off, a spike voltage is generated on these tubes due to the parasitic inductance and the reverse recovery current of the body diode of the tenth freewheeling tube Q10. The spike voltage charges the fifth capacitor C5 through the sixth diode D6, thereby absorbing the spike voltage and protecting other components in the circuit from damage.

[0052] When the eleventh switch Q11 of the third voltage conversion circuit is turned on, the energy in the fifth capacitor C5 is transferred to the sixth capacitor C6 via the eleventh switch Q11 and the sixth inductor L6. When the eleventh switch Q11 is turned off, the seventh diode D7 is turned on, and the current in the sixth inductor L6 forms a freewheeling loop through the seventh diode D7, charging the sixth capacitor C6. The energy absorbed by the peak voltage absorption circuit is effectively converted and transferred to the sixth capacitor C6, improving the efficiency and stability of the entire circuit.

[0053] Compared with the prior art, the embodiments of the present application have the following beneficial effects: First, it can effectively suppress the oscillation voltage spike on the rectifier tube in the switching power supply rectifier circuit and suppress it to a lower level.

[0054] Second, the absorbed voltage spike energy is converted through the voltage conversion circuit and transmitted to the output end without loss.

[0055] Third, by losslessly absorbing and transmitting voltage spike energy, the overall efficiency of the switching power supply is greatly improved.

[0056] Fourth, since the energy loss of the absorption circuit is greatly reduced, the heat generated by the switching power supply is significantly reduced.

[0057] Therefore, this application discloses an active clamping lossless absorption circuit for synchronous rectification of a switching power supply. This circuit suppresses the oscillating voltage spike on the rectifier tube in the switching power supply rectification circuit to a relatively low level. At the same time, the voltage conversion circuit transfers all the energy of the oscillating voltage spike to the output, achieving a lossless absorption effect, greatly improving the efficiency of the switching power supply and reducing the heat generation of the switching power supply. At the same time, the circuit structure is simple, the device does not require heat dissipation measures, and the reliability is high.

[0058] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. An active clamp lossless absorption circuit for synchronous rectification of a switching power supply, characterized in that: The circuit includes a full-wave rectifier active clamp lossless absorption circuit, the full-wave rectifier active clamp lossless absorption circuit includes a first peak voltage absorption circuit, a first voltage conversion circuit, a first rectifier tube, a second rectifier tube, a first inductor and a first transformer, the first transformer includes a first winding and a second winding connected to the first winding, the first peak voltage absorption circuit includes a first diode, a second diode, and a first capacitor, and the first voltage conversion circuit includes a third switch tube, a second inductor, a third diode, and a second capacitor; The positive end of the first winding is connected to the anode of the second diode and the drain of the second rectifier tube, the cathode of the second diode is respectively connected to the cathode of the first diode, one end of the first capacitor and the drain of the third switch tube, the source of the second rectifier tube is respectively connected to the other end of the first capacitor, the source of the first rectifier tube, the anode of the third diode and one end of the second capacitor, and the other end of the second inductor is respectively connected to the cathode of the third diode and the source of the third switch tube; The negative end of the first winding is connected to one end of the first inductor, and the other end of the first inductor is connected to the other end of the second capacitor and one end of the second inductor respectively; The negative end of the second winding is connected to the drain of the first rectifier tube and the anode of the first diode.

2. The active clamp lossless absorption circuit according to claim 1, characterized in that: The circuit also includes a full-bridge rectifier active clamp lossless absorption circuit, the full-bridge rectifier active clamp lossless absorption circuit includes a fourth rectifier tube, a fifth rectifier tube, a sixth rectifier tube and a seventh rectifier tube, a second peak voltage absorption circuit, a second voltage conversion circuit, and a third inductor, the second peak voltage absorption circuit includes a fourth diode and a third capacitor, and the second voltage conversion circuit includes an eighth switch tube, a fourth inductor, a fifth diode and a fourth capacitor; The drain of the fourth rectifier is respectively connected to the drain of the fifth rectifier, the anode of the fourth diode and one end of the third inductor, the source of the fourth rectifier is connected to the drain of the sixth rectifier, and the source of the sixth rectifier is respectively connected to the source of the seventh rectifier, one end of the third capacitor, the anode of the fifth diode and one end of the fourth capacitor; The source of the fifth rectifier is connected to the drain of the seventh rectifier, the other end of the third capacitor is respectively connected to the cathode of the fourth diode and the drain of the eighth switch tube, the source of the eighth switch tube is respectively connected to the cathode of the fifth diode and one end of the fourth inductor, and the other end of the fourth inductor is respectively connected to the other end of the fourth capacitor and the other end of the third inductor.

3. The active clamp lossless absorption circuit according to claim 1, characterized in that: The circuit also includes a forward output rectifier active clamp lossless absorption circuit, the forward output rectifier active clamp lossless absorption circuit includes a third peak voltage absorption circuit, a third voltage conversion circuit, a ninth rectifier tube, a tenth freewheeling tube and a fifth inductor, the third peak voltage absorption circuit includes a fifth capacitor and a sixth diode, and the third voltage conversion circuit includes an eleventh switch tube, a sixth inductor, a seventh diode and a sixth capacitor; The source of the ninth rectifier tube is respectively connected to the source of the tenth freewheeling tube, one end of the fifth capacitor, the anode of the seventh diode and one end of the sixth capacitor, the drain of the tenth freewheeling tube is respectively connected to the anode of the sixth diode and one end of the fifth inductor, the cathode of the sixth diode is respectively connected to the other end of the fifth capacitor and the drain of the eleventh switch tube, the source of the eleventh switch tube is respectively connected to one end of the sixth inductor and the cathode of the seventh diode, and the other end of the sixth inductor is connected to the other end of the fifth inductor and the sixth capacitor.

4. The active clamp lossless absorption circuit according to claim 1, characterized in that: The negative end of the first winding is connected to the positive end of the second winding.

5. The active clamp lossless absorption circuit according to claim 1, characterized in that: The first peak voltage absorption circuit is used for absorbing the reverse recovery energy on the first rectifier tube and the second rectifier tube to eliminate the voltage spike; The first voltage conversion circuit is used to convert the energy absorbed by the first peak voltage absorption circuit into voltage, and transfer all the energy to the second capacitor.

6. The active clamp lossless absorption circuit according to claim 2, characterized in that: The full-bridge rectifier active clamp lossless absorption circuit also includes a second transformer, the positive end of the fourth winding of the second transformer is connected to the source of the fifth rectifier tube and the drain of the seventh rectifier tube, and the negative end of the fourth winding of the second transformer is connected to the source of the fourth rectifier tube and the drain of the sixth rectifier tube.

7. The active clamp lossless absorption circuit according to claim 2, characterized in that: The second peak voltage absorption circuit is used for absorbing the reverse recovery energy on the fourth rectifier tube, the fifth rectifier tube, the sixth rectifier tube and the seventh rectifier tube to eliminate the voltage spike; The second voltage conversion circuit is used to convert the energy absorbed by the second peak voltage absorption circuit into voltage, and transfer all the energy to the fourth capacitor.

8. The active clamp lossless absorption circuit according to claim 3, characterized in that: The forward output rectifier active clamp lossless absorption circuit also includes a third transformer, the positive end of the sixth winding of the third transformer is connected to the drain of the tenth freewheeling tube, and the negative end of the sixth winding of the third transformer is connected to the drain of the ninth rectifier tube.

9. The active clamp lossless absorption circuit according to claim 3, characterized in that: The third peak voltage absorption circuit is used for absorbing the reverse recovery energy on the ninth rectifier tube and the tenth freewheeling tube to eliminate the voltage spike; The third voltage conversion circuit is used to convert the energy absorbed by the third peak voltage absorption circuit into voltage, and transfer all the energy to the sixth capacitor.

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