Synchronous rectification control circuit and device

Abstract

The present application relates to a kind of synchronous rectification control circuit and device, circuit includes resonant circuit, transformer, rectifier circuit, current transformer, signal conversion circuit and signal comparison circuit;Signal comparison circuit includes first comparison circuit and second comparison circuit;Through the corresponding level signal of first comparison circuit and second comparison output is driven to rectifier circuit work.Compared with the related art, the synchronous rectification control circuit and synchronous rectification control device provided in the embodiment of the present application, by signal conversion circuit and signal comparison circuit, to the voltage signal output by current transformer is converted and compared, so that in different operating modes, signal conversion circuit outputs different voltage values, then signal comparison circuit compares according to different voltage values, to determine the conduction and shutdown of MOS tube in rectifier circuit, the synchronous rectification control circuit of the present application not only avoids the misoperation, and it is simple to realize, no delay, high reliability, low cost.

Description

Technical Field

[0001] This invention relates to the field of power supply technology, and in particular to a synchronous rectification control circuit and device. Background Technology

[0002] As power modules become increasingly powerful, such as communication power modules or data center power modules, the industry has higher and higher requirements for the efficiency of power modules. Synchronous rectification technology is being adopted more and more. Currently, MOSFETs with low on-resistance are usually used to replace traditional rectifier diodes.

[0003] While existing synchronous rectification schemes each have their own characteristics, they also have their own shortcomings. For example, comparing the voltage across the CT sampling resistor with zero voltage (or a very small level) to determine the turn-on and turn-off of the MOSFET is a simple method, but it is prone to malfunctions because the comparison level is too small. Summary of the Invention

[0004] This invention provides a synchronous rectification control circuit and device to at least solve the technical defects in the related art that are prone to malfunctions in synchronous rectification technology.

[0005] In a first aspect, embodiments of the present invention provide a synchronous rectification control circuit, the circuit including a resonant circuit, a transformer, a rectifier circuit, a current transformer, a signal conversion circuit, and a signal comparison circuit;

[0006] The resonant circuit is connected between the power supply and the primary winding of the transformer, and its control terminal is connected to a first driving signal and a second driving signal, respectively. The first end of the secondary winding of the transformer is connected to the tail end of the primary winding of the current transformer through the rectifier circuit, and the first end of the primary winding of the current transformer is connected to the tail end of the secondary winding of the transformer. The secondary winding of the current transformer is connected to the signal conversion circuit, and the input terminal of the signal comparison circuit is connected to the output terminal of the signal conversion circuit. The output terminal of the signal comparison circuit is connected to the control terminal of the rectifier circuit.

[0007] The signal comparison circuit includes a first comparison circuit and a second comparison circuit; the first driving signal and the second driving signal control the first comparison circuit and the second comparison circuit to output corresponding level signals, and the level signals drive the rectifier circuit to work. The level signals include a first level signal output by the first comparison circuit and a second level signal output by the second comparison circuit.

[0008] In some embodiments, the signal conversion circuit includes a first sampling resistor, a second sampling resistor, a first diode, and a second diode;

[0009] Wherein, the first end of the secondary winding of the current transformer is connected to the first end of the first sampling resistor, the tail end of the secondary winding of the current transformer, the cathode of the first diode, and the anode of the second diode are grounded, the second end of the first sampling resistor is coupled to the anode of the first diode and the cathode of the second diode, and the second sampling resistor is connected between the first end and the tail end of the secondary winding of the current transformer; the connection point of the first sampling resistor and the second sampling resistor is the output terminal of the signal conversion circuit;

[0010] When the first driving signal is high and the second driving signal is low, the first diode is turned on and the second diode is turned off, and the signal conversion circuit outputs a positive voltage; when the first driving signal is low and the second driving signal is high, the first diode is turned off and the second diode is turned on, and the signal conversion circuit outputs a negative voltage.

[0011] The first comparator circuit includes a first switching transistor, a second switching transistor, a third diode, a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor;

[0012] In this circuit, the emitter of the first switching transistor is grounded, the collector is connected to the power supply through the fifth resistor, and the base is connected to the power supply through the sixth and fourth resistors; the emitter of the second switching transistor is connected to the output terminal of the signal conversion circuit, the collector is connected to the power supply through the third resistor, and the base is connected to the power supply through the fourth resistor; the anode of the third diode is connected to the collector of the second switching transistor, and the cathode of the third diode is grounded through the second resistor; the cathode of the third diode serves as the output terminal of the first comparator circuit, outputting the first level signal.

[0013] When the first driving signal is high and the second driving signal is low, the first comparator circuit outputs a high level; when the first driving signal is low and the second driving signal is high, the first comparator circuit outputs a low level.

[0014] In some embodiments, the second comparator circuit includes a third switch, a fourth switch, a fourth diode, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, and an eleventh resistor;

[0015] In this circuit, the emitter of the third switching transistor is connected to the output of the signal conversion circuit, the collector is connected to the power supply through the tenth resistor, and the base is connected to the power supply through the eleventh and ninth resistors; the emitter of the fourth switching transistor is grounded, the collector is connected to the power supply through the eighth resistor, and the base is connected to the power supply through the ninth resistor; the anode of the fourth diode is connected to the collector of the fourth switching transistor, and the cathode of the fourth diode is grounded through the seventh resistor; the cathode of the fourth diode serves as the output of the second comparator circuit, outputting the second level signal.

[0016] When the first driving signal is high and the second driving signal is low, the second comparator circuit outputs a low level; when the first driving signal is low and the second driving signal is high, the second comparator circuit outputs a high level.

[0017] In some embodiments, the resonant circuit is a full-bridge resonant circuit or a half-bridge resonant circuit.

[0018] Preferably, when the resonant circuit is a full-bridge resonant circuit, it includes a first full-bridge circuit, a first capacitor, and a first inductor; wherein,

[0019] The first full-bridge circuit includes a first MOSFET, a second MOSFET, a third MOSFET, and a fourth MOSFET. The first and second MOSFETs are connected in series between the positive and negative terminals of the power supply, and the third and fourth MOSFETs are connected in series between the positive and negative terminals of the power supply. The first terminal of the first capacitor is connected to the connection point of the first and second MOSFETs, the second terminal of the first capacitor is connected to the first terminal of the first inductor, the second terminal of the first inductor is connected to the beginning of the primary winding of the transformer, and the end of the primary winding of the transformer is connected to the connection point of the third and fourth MOSFETs. The first and fourth MOSFETs are respectively connected to a first drive signal, and the second and third MOSFETs are respectively connected to a second drive signal.

[0020] In some embodiments, the rectifier circuit is a full-bridge rectifier circuit or a half-bridge rectifier circuit.

[0021] Preferably, when the rectifier circuit is a full-bridge rectifier circuit, it includes a second full-bridge circuit and a second capacitor; wherein,

[0022] The second full-bridge circuit includes a fifth MOSFET, a sixth MOSFET, a seventh MOSFET, and an eighth MOSFET. The fifth and seventh MOSFETs are connected in series and then in parallel with the second capacitor. The sixth and eighth MOSFETs are connected in series and then in parallel with the second capacitor. The two ends of the second capacitor serve as the output terminals of the circuit. The first end of the secondary winding of the transformer is connected to the connection point of the fifth and seventh MOSFETs. The first end of the primary winding of the current transformer is connected to the connection point of the sixth and eighth MOSFETs. The fifth and eighth MOSFETs are respectively connected to the level signals output by the first comparator circuit, and the sixth and seventh MOSFETs are respectively connected to the level signals output by the second comparator circuit.

[0023] Preferably, the full-bridge rectifier circuit further includes four diodes, each of which is connected in parallel with a MOSFET.

[0024] Secondly, embodiments of the present invention provide a synchronous rectification control device, including the synchronous rectification control circuit as described in any of the preceding embodiments.

[0025] Compared to related technologies, the synchronous rectification control circuit and synchronous rectification control device provided in this invention convert and compare the voltage signal output by the current transformer through a signal conversion circuit and a signal comparison circuit composed of simple electronic components. This allows the signal conversion circuit to output different voltage values ​​under different operating modes (first mode, second mode, and third mode). Then, the signal comparison circuit compares the different voltage values ​​and outputs a corresponding level signal according to the comparison result to determine the conduction and cutoff of the MOSFET in the rectification circuit. The synchronous rectification control circuit of this invention not only avoids malfunctions but is also simple to implement, has no delay, high reliability, and low cost, making it suitable for high-frequency and high-power-density applications. Attached Figure Description

[0026] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0027] Figure 1 This is a partial circuit structure diagram of a rectifier circuit according to an embodiment of the present invention;

[0028] Figure 2(a) is a circuit diagram of the first comparison circuit of a signal comparison circuit according to an embodiment of the present invention;

[0029] Figure 2(b) is a circuit diagram of the second comparison circuit of a signal comparison circuit according to an embodiment of the present invention;

[0030] Figure 3 This is a circuit diagram of a resonant circuit according to an embodiment of the present invention;

[0031] Figure 4 This is a circuit schematic diagram of a rectifier circuit according to an embodiment of the present invention;

[0032] Figure 5(a) is a schematic diagram of the working principle of a rectifier circuit according to an embodiment of the present invention in the first mode;

[0033] Figure 5(b) is a schematic diagram of the working principle of the rectifier circuit in the second mode according to an embodiment of the present invention;

[0034] Figure 5(c) is a schematic diagram of the working principle of the rectifier circuit in the third mode according to an embodiment of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments provided by this invention without inventive effort are within the scope of protection of this invention. Furthermore, it is understood that although the efforts made in such a development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this invention, some design, manufacturing, or production modifications based on the technical content disclosed in this invention are merely conventional technical means and should not be construed as insufficient disclosure of the invention.

[0036] In this invention, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention may be combined with other embodiments without conflict.

[0037] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "a," "an," "an," "the," and similar words used in this invention do not indicate quantity limitation and may indicate singular or plural. The terms "comprising," "including," "having," and any variations thereof used in this invention are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or devices. The terms "connected," "linked," "coupled," and similar words used in this invention are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "A plurality" in this invention means two or more. "And / or" describes the relationship between related objects, indicating that three relationships may exist; for example, "A and / or B" can represent: A alone, A and B simultaneously, and B alone. The terms "first," "second," and "third" used in this invention are merely to distinguish similar objects and do not represent a specific ordering of the objects.

[0038] The synchronous rectification control circuit provided by this invention includes a resonant circuit, a transformer, a rectifier circuit, a current transformer, a signal conversion circuit, and a signal comparison circuit. For example... Figure 1 As shown, the resonant circuit (resonant circuit topology) is connected between the power supply and the primary winding of transformer TX1, and the control terminal of the resonant circuit is connected to the first drive signal driver1 and the second drive signal driver2; the first end of the secondary winding S1 of transformer TX1 is connected to the tail end of the primary winding P2 of current transformer TX2 through a rectifier circuit, and the first end of the primary winding P2 of current transformer TX2 is connected to the tail end of the secondary winding S1 of transformer TX1; the secondary winding S2 of current transformer TX2 is connected to the signal conversion circuit, and the input terminal of the signal comparison circuit is connected to the output terminal sam of the signal conversion circuit; the output terminal of the signal comparison circuit is connected to the control terminal of the rectifier circuit.

[0039] Specifically, the signal comparison circuit includes a first comparison circuit and a second comparison circuit. In this embodiment of the invention, a first driving signal and a second driving signal are used to control the first comparison circuit and the second comparison circuit to output corresponding level signals. These level signals drive the rectifier circuit to operate. The level signals of this invention include a first level signal output by the first comparison circuit and a second level signal output by the second comparison circuit. For example, when the first driving signal is high and the second driving signal is low, the first comparison circuit outputs a high level and the second comparison circuit outputs a low level to drive the rectifier circuit to operate; when the first driving signal is low and the second driving signal is high, the first comparison circuit outputs a low level and the second comparison circuit outputs a high level to drive the rectifier circuit to operate.

[0040] Preferably, the signal conversion circuit of one embodiment of the present invention includes a first sampling resistor, a second sampling resistor, a first diode, and a second diode. (See reference) Figure 1 The first end of the secondary winding S2 of current transformer TX2 is connected to the first end of the first sampling resistor R1. The tail end of the secondary winding S2 of current transformer TX2, the cathode of the first diode D1, and the anode of the second diode D2 are grounded. The second end of the first sampling resistor R1 is coupled to the anode of the first diode D1 and the cathode of the second diode D2. The second sampling resistor R0 is connected between the first and tail ends of the secondary winding S2 of current transformer TX2. The connection point sam of the first sampling resistor R1 and the second sampling resistor R0 is the output terminal of the signal conversion circuit. When the first driving signal is high and the second driving signal is low, the first diode D1 is turned on and the second diode D2 is turned off, and the signal conversion circuit outputs a positive voltage. When the first driving signal is low and the second driving signal is high, the first diode D1 is turned off and the second diode D2 is turned on, and the signal conversion circuit outputs a negative voltage.

[0041] In a preferred embodiment, the first comparator circuit includes a first switch, a second switch, a third diode, a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. Referring to Figure 2(a), the emitter of the first switch Q1 is grounded, its collector is connected to the power supply Vcc through the fifth resistor R5, and its base is connected to the power supply Vcc through the sixth resistor R6 and the fourth resistor R4; the emitter of the second switch Q2 is connected to the output terminal sam of the signal conversion circuit, its collector is connected to the power supply Vcc through the third resistor R3, and its base is connected to the power supply through the fourth resistor R4; the anode of the third diode D3 is connected to the collector of the second switch Q2, and the cathode of the third diode D3 is grounded through the second resistor R2; the cathode of the third diode D3 serves as the output terminal of the first comparator circuit, outputting a first level signal SR1 (high / low level).

[0042] Referring to Figure 2(b), the second comparator circuit includes a third switch Q3, a fourth switch Q4, a fourth diode D4, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, and an eleventh resistor R11. The emitter of the third switch Q3 is connected to the output terminal sam of the signal conversion circuit; its collector is connected to the power supply Vcc through the tenth resistor R10; and its base is connected to the power supply through the eleventh resistor R11 and the ninth resistor R9. The emitter of the fourth switch Q4 is grounded; its collector is connected to the power supply Vcc through the eighth resistor R8; and its base is connected to the power supply Vcc through the ninth resistor R9. The anode of the fourth diode D4 is connected to the collector of the fourth switch Q4; and the cathode of the fourth diode D4 is grounded through the seventh resistor R7. The cathode of the fourth diode D4 serves as the output terminal of the second comparator circuit, outputting a second level signal SR2 (high / low level).

[0043] In this embodiment of the invention, the resonant circuit is a full-bridge resonant circuit or a half-bridge resonant circuit. (See reference...) Figure 3 When the resonant circuit is a full-bridge resonant circuit, it includes a first full-bridge circuit, a first capacitor C1, and a first inductor L1. The first full-bridge circuit includes a first MOSFET S1, a second MOSFET S2, a third MOSFET S3, and a fourth MOSFET S4. MOSFETs S1 and S2 are connected in series between the positive and negative terminals of power supply V2, and MOSFETs S3 and S4 are also connected in series between the positive and negative terminals of power supply V2. The first terminal of the first capacitor C1 is connected to the connection point of the first MOSFET S1 and the second MOSFET S2, and the second terminal of the first capacitor C1 is connected to the first terminal of the first inductor L1. The second terminal of the first inductor L1 is connected to the beginning of the primary winding P1 of transformer TX1, and the end of the primary winding P1 of transformer TX1 is connected to the connection point of the third MOSFET S3 and the fourth MOSFET S4. MOSFETs S1 and S4 are respectively connected to the first drive signal driver1, and MOSFETs S2 and S3 are respectively connected to the second drive signal driver2. Figure 3 In this context, diodes D5, D6, D7, and D8 can be the body diodes of their respective MOSFETs, or they can be additional diodes.

[0044] refer to Figure 4 The rectifier circuit can be a full-bridge rectifier circuit or a half-bridge rectifier circuit. When the rectifier circuit is a full-bridge rectifier circuit, it includes a second full-bridge circuit and a second capacitor C2. The full-bridge rectifier circuit also includes four diodes (D9, D10, D11, D12), each of which is connected in parallel with a MOSFET. Figure 4The diodes in the circuit can be the body diodes of their corresponding MOSFETs or additional diodes. The second full-bridge circuit includes a fifth MOSFET S5, a sixth MOSFET S6, a seventh MOSFET S7, and an eighth MOSFET S8. MOSFETs S5 and S7 are connected in series and then in parallel with the second capacitor C2. MOSFETs S6 and S8 are connected in series and then in parallel with the second capacitor C2. The two ends of the second capacitor C2 serve as the output terminals of the circuit, outputting a rectified voltage V0. The first end of the secondary winding S1 of transformer TX1 is connected to the connection point of the fifth MOSFET S5 and the seventh MOSFET S7. The first end of the primary winding P2 of current transformer TX2 is connected to the connection point of the sixth MOSFET S6 and the eighth MOSFET S8. MOSFETs S5 and S8 are respectively connected to the first level signal SR1 output by the first comparator circuit, and the sixth and seventh MOSFETs are respectively connected to the second level signal SR2 output by the second comparator circuit.

[0045] The operation of the rectifier circuit of the present invention is as follows: Figures 5(a)-5(c) As shown in Figure 5(a), specifically, when the first drive signal driver1 is high and the second drive signal driver2 is low (first mode), the first MOSFET S1 and the fourth MOSFET S4 are turned on. The body diodes (D9 and D12) of the fifth and eighth MOSFETs in the rectifier circuit are turned on, and the current does not pass through the fifth and eighth MOSFETs. In the figure, the body diodes (D9 and D12), the secondary winding S1 of the transformer, and the primary winding P2 of the current transformer form a current loop. After the secondary winding S2 of the current transformer TX2 senses the current, the first diode D1 is turned on. At this time, the output voltage V of the current conversion circuit is V. sam =i*R1+V F , where V F Let i be the forward voltage drop of the first diode D1, and i be the secondary current of the current transformer TX2. In this embodiment, the second sampling resistor R0 is set to be much larger than the first sampling resistor R1. Therefore, the current flowing through the second sampling resistor R0 can be ignored in this invention. Since the output voltage V sam Because the voltage is high, the first switch Q1 of the first comparator circuit and the fourth switch Q4 of the second comparator circuit are turned on. Therefore, the first level signal SR1 output by the first comparator circuit is high, and the second level signal SR2 output by the second comparator circuit is low. After receiving the first level signal SR1 and the second level signal SR2, the rectifier circuit drives the fifth MOSFET S5 and the eighth MOSFET S8 in the rectifier circuit to turn on, and current flows through S5 and S8, thereby reducing losses. This invention can reduce the voltage V across the sixth resistor R6 by selecting a suitable sixth resistor R6. R6 The forward voltage drop V of the first diode D1 is less than that of the first diode. F .

[0046] When the first drive signal driver1 is low and the second drive signal driver2 is high (second mode), as shown in Figure 5(b), the second MOSFET S2 and the third MOSFET S3 are turned on. The body diodes (D10 and D11) of the sixth MOSFET S6 and the seventh MOSFET S7 in the rectifier circuit are turned on, and the current does not pass through the sixth MOSFET and the seventh MOSFET. In the figure, the body diodes (D10 and D11), the secondary winding S1 of the transformer, and the primary winding P2 of the current transformer form a current loop. After the secondary winding S2 of the current transformer TX2 senses the current, the second diode D2 is turned on. At this time, the output voltage V of the current conversion circuit is V. sam =(-i*R1-V F ), where V F Let be the forward voltage drop of the first diode D1, and i be the secondary current of the current transformer TX2. In this embodiment of the invention, the second sampling resistor R0 is set to be much larger than the first sampling resistor R1, thereby ignoring the current flowing through the second sampling resistor R0. Since the output voltage V... sam Because the voltage is low, the second switch Q2 and the third switch Q3 of the first comparator circuit are turned on. Therefore, the first level signal SR1 output by the first comparator circuit is low, and the second level signal SR2 output by the second comparator circuit is high. After receiving the first level signal SR1 and the second level signal SR2, the rectifier circuit drives the sixth MOSFET S5 and the seventh MOSFET S8 in the rectifier circuit to turn on, and current flows through S6 and S7, thereby reducing losses. This invention can reduce the voltage V across the eleventh resistor R11 by selecting a suitable eleventh resistor R11. R11 Less than the forward voltage drop of the second diode D2 -V F .

[0047] When the operating frequency of the resonant circuit is lower than the resonant frequency (third mode), as shown in Figure 5(c), regardless of whether the first drive signal driver1 is high and the second drive signal driver2 is low; or whether the second drive signal driver2 is high and the first drive signal driver1 is low, the secondary winding of the transformer has no current for a portion of a switching cycle. At this time, V sam ≈0. Due to the effect of the sixth resistor R6, the second switch Q2 of the first comparator circuit will be turned on. Due to the effect of the eleventh resistor R11, the fourth switch Q4 of the second comparator circuit will be turned on. At this time, the first level signal SR1 and the second level signal SR2 are both low level. Therefore, the four MOSFETs (S5, S8, S6, S7) in the rectifier circuit are all turned off, thereby achieving the purpose of preventing the output current from flowing back.

[0048] The rectifier circuit of this application converts and compares the voltage signal output by the current transformer through a signal conversion circuit and a signal comparison circuit composed of simple electronic components. This allows the signal conversion circuit to output different voltage values ​​under different operating modes (first mode, second mode, and third mode). Then, the signal comparison circuit compares the different voltage values ​​and outputs a corresponding level signal according to the comparison result to determine the conduction and cutoff of the MOSFET in the rectifier circuit. The synchronous rectification control circuit of this invention not only avoids malfunctions but is also simple to implement, has no delay, high reliability, low cost, and is suitable for high-frequency and high-power-density applications.

[0049] In another embodiment of the present invention, a synchronous rectification control device is provided, including the synchronous rectification control circuit as described in any of the preceding embodiments.

[0050] It should be noted that the above modules can be functional modules or program modules, and can be implemented through software or hardware. For modules implemented through hardware, the above modules can reside in the same processor; or the above modules can be located in different processors in any combination.

[0051] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementations, and will not be repeated here.

[0052] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0053] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A synchronous rectification control circuit, characterized in that, The circuit includes a resonant circuit, a transformer, a rectifier circuit, a current transformer, a signal conversion circuit, and a signal comparison circuit. The resonant circuit is connected between the power supply and the primary winding of the transformer, and its control terminal is connected to a first driving signal and a second driving signal, respectively. The first end of the secondary winding of the transformer is connected to the tail end of the primary winding of the current transformer through the rectifier circuit, and the first end of the primary winding of the current transformer is connected to the tail end of the secondary winding of the transformer. The secondary winding of the current transformer is connected to the signal conversion circuit, and the input terminal of the signal comparison circuit is connected to the output terminal of the signal conversion circuit. The output terminal of the signal comparison circuit is connected to the control terminal of the rectifier circuit. The signal comparison circuit includes a first comparison circuit and a second comparison circuit; the first driving signal and the second driving signal control the first comparison circuit and the second comparison circuit to output corresponding level signals, and the level signals drive the rectifier circuit to work. The level signals include a first level signal output by the first comparison circuit and a second level signal output by the second comparison circuit. The first comparator circuit includes a first switching transistor, a second switching transistor, a third diode, a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. The emitter of the first switching transistor is grounded, its collector is connected to a power supply via the fifth resistor, and its base is connected to a power supply via the sixth and fourth resistors. The emitter of the second switching transistor is connected to the output terminal of the signal conversion circuit, its collector is connected to a power supply via the third resistor, and its base is connected to a power supply via the fourth resistor. The anode of the third diode is connected to the collector of the second switching transistor, and the cathode of the third diode is grounded via the second resistor. The cathode of the third diode serves as the output terminal of the first comparator circuit, outputting the first level signal.

2. The circuit according to claim 1, characterized in that, The signal conversion circuit includes a first sampling resistor, a second sampling resistor, a first diode, and a second diode; Wherein, the first end of the secondary winding of the current transformer is connected to the first end of the first sampling resistor, the tail end of the secondary winding of the current transformer, the cathode of the first diode, and the anode of the second diode are grounded, the second end of the first sampling resistor is coupled to the anode of the first diode and the cathode of the second diode, and the second sampling resistor is connected between the first end and the tail end of the secondary winding of the current transformer; the connection point of the first sampling resistor and the second sampling resistor is the output terminal of the signal conversion circuit; When the first driving signal is high and the second driving signal is low, the first diode is turned on and the second diode is turned off, and the signal conversion circuit outputs a positive voltage; when the first driving signal is low and the second driving signal is high, the first diode is turned off and the second diode is turned on, and the signal conversion circuit outputs a negative voltage.

3. The circuit according to claim 1, characterized in that, When the first driving signal is high and the second driving signal is low, the first comparator circuit outputs a high level; when the first driving signal is low and the second driving signal is high, the first comparator circuit outputs a low level.

4. The circuit according to claim 1, characterized in that, The second comparator circuit includes a third switch, a fourth switch, a fourth diode, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, and an eleventh resistor; In this circuit, the emitter of the third switching transistor is connected to the output of the signal conversion circuit, the collector is connected to the power supply through the tenth resistor, and the base is connected to the power supply through the eleventh and ninth resistors; the emitter of the fourth switching transistor is grounded, the collector is connected to the power supply through the eighth resistor, and the base is connected to the power supply through the ninth resistor; the anode of the fourth diode is connected to the collector of the fourth switching transistor, and the cathode of the fourth diode is grounded through the seventh resistor; the cathode of the fourth diode serves as the output of the second comparator circuit, outputting the second level signal. When the first driving signal is high and the second driving signal is low, the second comparator circuit outputs a low level; when the first driving signal is low and the second driving signal is high, the second comparator circuit outputs a high level.

5. The circuit according to claim 1, characterized in that, The resonant circuit is a full-bridge resonant circuit or a half-bridge resonant circuit.

6. The circuit according to claim 5, characterized in that, When the resonant circuit is a full-bridge resonant circuit, it includes a first full-bridge circuit, a first capacitor, and a first inductor; wherein, The first full-bridge circuit includes a first MOSFET, a second MOSFET, a third MOSFET, and a fourth MOSFET. The first and second MOSFETs are connected in series between the positive and negative terminals of the power supply, and the third and fourth MOSFETs are connected in series between the positive and negative terminals of the power supply. The first terminal of the first capacitor is connected to the connection point of the first and second MOSFETs, the second terminal of the first capacitor is connected to the first terminal of the first inductor, the second terminal of the first inductor is connected to the beginning of the primary winding of the transformer, and the end of the primary winding of the transformer is connected to the connection point of the third and fourth MOSFETs. The first and fourth MOSFETs are respectively connected to a first drive signal, and the second and third MOSFETs are respectively connected to a second drive signal.

7. The circuit according to claim 1, characterized in that, The rectifier circuit is a full-bridge rectifier circuit or a half-bridge rectifier circuit.

8. The circuit according to claim 7, characterized in that, When the rectifier circuit is a full-bridge rectifier circuit, it includes a second full-bridge circuit and a second capacitor; wherein, The second full-bridge circuit includes a fifth MOSFET, a sixth MOSFET, a seventh MOSFET, and an eighth MOSFET. The fifth and seventh MOSFETs are connected in series and then in parallel with the second capacitor. The sixth and eighth MOSFETs are connected in series and then in parallel with the second capacitor. The two ends of the second capacitor serve as the output terminals of the circuit. The first end of the secondary winding of the transformer is connected to the connection point of the fifth and seventh MOSFETs. The first end of the primary winding of the current transformer is connected to the connection point of the sixth and eighth MOSFETs. The fifth and eighth MOSFETs are respectively connected to the level signals output by the first comparator circuit, and the sixth and seventh MOSFETs are respectively connected to the level signals output by the second comparator circuit.

9. The circuit according to claim 8, characterized in that, The full-bridge rectifier circuit also includes four diodes, each of which is connected in parallel with a MOSFET.

10. A synchronous rectification control device, characterized in that, Includes the synchronous rectification control circuit as described in any one of claims 1 to 9.

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