Active rectifier circuit, control method thereof and isolated power supply

Abstract

The active rectification circuit, the control method thereof and the isolated power supply, the active rectification circuit comprising an active rectification module, a sampling processing module, a delay control module and a drive control module; the first input end of the sampling processing module is connected with the first end of the secondary coil of the transformer, the second input end of the sampling processing module is connected with the second end of the secondary coil of the transformer, the first output end of the sampling processing module outputs a first frequency signal, the second output end outputs a second frequency signal, and the third output end outputs a third frequency signal; the delay control module is used for determining the delay time of the second frequency signal according to the first frequency signal and the third frequency signal, and outputting a delay processing signal from the output end thereof; the output end of the drive control module is connected with the control end of the active rectification module, and the drive control module is used for outputting a drive control signal according to the delay processing signal and the second frequency signal. The scheme takes into account EMI radiation and rectification efficiency.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of electronic technology, and in particular to an active rectifier circuit, its control method, and an isolated power supply. Background Technology

[0002] With the development of electronic technology, isolated power supplies have been widely adopted to ensure system safety and reliability.

[0003] On the one hand, as isolated power supplies develop towards miniaturization and high power density, their internal power switching frequencies are constantly increasing (reaching tens or even hundreds of MHz), making the isolated power supply chip itself a strong source of electromagnetic interference (EMI). On the other hand, driven by the pursuit of high efficiency, the rectifier circuit of isolated power supplies is shifting from traditional passive diode rectification to active MOSFET rectification. Passive rectification, composed of diodes, has good circuit symmetry and stable common-mode voltage, resulting in excellent EMI performance. However, its large diode forward voltage drop leads to low efficiency, severely restricting the energy efficiency of the entire power supply system. Active rectification uses MOSFETs instead of diodes, resulting in a lower forward voltage drop and significantly improving efficiency (especially under low voltage conditions). However, its control circuit is susceptible to changes in switching timing due to process, voltage, and temperature fluctuations, leading to unstable fluctuations in the primary and secondary common-mode voltages, exacerbating the aforementioned dipole radiation problem, and resulting in poor EMI performance. Therefore, existing technologies face a dilemma: passive rectification can achieve good EMI performance but sacrifices efficiency; active rectification can achieve high efficiency but deteriorates EMI performance. Currently, there is a lack of isolated power supply rectification solutions that can address both high rectification efficiency and low electromagnetic interference (especially low dipole radiation) from the circuit architecture level. Summary of the Invention

[0004] This invention provides an active rectifier circuit, its control method, and an isolated power supply to solve the problem of incompatibility between high rectification efficiency and low electromagnetic interference.

[0005] According to one aspect of the present invention, an active rectifier circuit is provided, comprising: an active rectifier module, a sampling processing module, a delay control module, and a drive control module;

[0006] The first input terminal of the active rectifier module is connected to the first terminal of the secondary coil of the transformer, and the second input terminal of the active rectifier module is connected to the second terminal of the secondary coil of the transformer. The active rectifier module is used to output rectified voltage.

[0007] The first input terminal of the sampling processing module is connected to the first terminal of the secondary coil of the transformer, the second input terminal of the sampling processing module is connected to the second terminal of the secondary coil of the transformer, and the first output terminal of the sampling processing module outputs a first frequency signal, the second output terminal outputs a second frequency signal, and the third output terminal outputs a third frequency signal.

[0008] The first input terminal of the delay control module is connected to the first output terminal of the sampling processing module, the second input terminal of the delay control module is connected to the second output terminal of the sampling processing module, and the third input terminal of the delay control module is connected to the third output terminal of the sampling processing module. The delay control module is used to determine the delay time of the second frequency signal based on the first frequency signal and the third frequency signal, and output the delay processing signal from its own output terminal.

[0009] The first input terminal of the drive control module is connected to the second output terminal of the sampling processing module, the second input terminal of the drive control module is connected to the output terminal of the delay control module, and the output terminal of the drive control module is connected to the control terminal of the active rectifier module. The drive control module is used to output a drive control signal according to the delay processing signal and the second frequency signal.

[0010] Optionally, the sampling processing module includes a sampling processing unit and an oscillator. The first input terminal of the sampling processing unit is connected to the first terminal of the secondary coil of the transformer, the second input terminal of the sampling processing unit is connected to the second terminal of the secondary coil of the transformer, the first output terminal of the sampling processing unit is connected to the first input terminal of the delay control module, the second output terminal of the sampling processing unit is connected to the second input terminal of the delay control module, and the output terminal of the oscillator is connected to the third input terminal of the delay control module.

[0011] Optionally, the delay control module includes a first conversion unit, a second conversion unit, and a voltage-controlled delay unit;

[0012] The input terminal of the first conversion unit is connected to the first output terminal of the sampling processing module, and the output terminal of the first conversion unit is connected to the first input terminal of the voltage-controlled delay unit. The first conversion unit is used to convert the first frequency signal into a first voltage signal.

[0013] The input terminal of the second conversion unit is connected to the third output terminal of the sampling processing module, and the output terminal of the second conversion unit is connected to the second input terminal of the voltage-controlled delay unit. The second conversion unit is used to convert the third frequency signal into a second voltage signal.

[0014] The third input terminal of the voltage-controlled delay unit is connected to the second output terminal of the sampling processing module, and the output terminal of the voltage-controlled delay unit is connected to the second input terminal of the drive control module. The voltage-controlled delay unit is used to control the delay time of the second frequency signal according to the first voltage signal and the second voltage signal, and output the delay processing signal.

[0015] Optionally, the drive control module includes a logic control unit and a drive unit. The first input terminal of the logic control unit serves as the first input terminal of the drive control module, and the second input terminal of the logic control unit serves as the second input terminal of the drive control module. The logic control unit is used to output a switching signal according to the delay processing signal and the second frequency signal.

[0016] The drive unit is used to output the drive control signal according to the switch signal.

[0017] Optionally, the driving unit includes a first driving subunit and a second driving subunit. The input terminal of the first driving subunit is connected to the first output terminal of the logic control unit, and the output terminal of the first driving subunit outputs a first driving control signal and a second driving control signal. The input terminal of the second driving subunit is connected to the second output terminal of the logic control unit, and the output terminal of the second driving subunit outputs a third driving control signal and a fourth driving control signal.

[0018] Optionally, the active rectifier module includes a first transistor, a second transistor, a third transistor, and a fourth transistor. The control electrode of the first transistor is connected to a first drive control signal. The first electrode of the first transistor and the first electrode of the third transistor are connected. The second electrode of the first transistor is connected to the first terminal of the secondary coil of the transformer. The control electrode of the second transistor is connected to a second drive control signal. The first electrode of the second transistor is connected to the second terminal of the secondary coil of the transformer. The second electrode of the second transistor is connected to the second electrode of the fourth transistor. The first electrode of the fourth transistor is connected to the first terminal of the secondary coil of the transformer. The control electrode of the fourth transistor is connected to a fourth drive control signal. The control electrode of the third transistor is connected to a third drive control signal. The second electrode of the third transistor is connected to the second terminal of the secondary coil of the transformer.

[0019] The channel type of the first transistor is different from that of the second transistor, and the channel type of the third transistor is different from that of the fourth transistor.

[0020] According to another aspect of the present invention, a control method for an active rectifier circuit is provided, the active rectifier circuit including an active rectifier module, a sampling processing module, a delay control module, and a drive control module;

[0021] The control method for the active rectifier circuit includes:

[0022] The sampling and processing module is controlled to sample the voltage at the first end of the transformer secondary coil and the voltage at the second end of the transformer secondary coil, and output a first frequency signal, a second frequency signal and a third frequency signal.

[0023] The delay control module determines the delay time of the second frequency signal based on the first frequency signal and the third frequency signal, and outputs a delay processing signal.

[0024] The drive control module outputs a drive control signal based on the delay processing signal and the second frequency signal;

[0025] The active rectifier module is controlled to rectify the voltage at the first end of the transformer secondary coil and the voltage at the second end of the transformer secondary coil according to the drive control signal, and outputs the rectified voltage.

[0026] Optionally, the first frequency signal and the second frequency signal are inverse signals of each other;

[0027] The turn-on signal of the drive control signal is obtained based on the rising edge of the second frequency signal, and the turn-off signal of the drive control signal is obtained based on the rising edge of the delay processing signal.

[0028] Optionally, controlling the active rectifier module to rectify the voltage at the first terminal of the transformer secondary coil and the voltage at the second terminal of the transformer secondary coil according to the drive control signal, and outputting a rectified voltage includes:

[0029] When the falling edge of the voltage at the first terminal of the transformer secondary coil or the voltage at the second terminal of the transformer secondary coil is detected, the active rectifier module is controlled to operate in active rectification mode, and before the rising edge of the corresponding voltage arrives, the active rectifier module is controlled to operate in passive rectification mode.

[0030] According to another aspect of the present invention, an isolated power supply is provided, the isolated power supply including the active rectifier circuit provided in any embodiment of the present invention.

[0031] The technical solution provided in this invention sample and process the voltages at the first and second terminals of the transformer secondary coil using a sampling processing module, and outputs a first frequency signal, a second frequency signal, and a third frequency signal. A delay control module compares the received first and third frequency signals to determine whether the delay function of the delay control module needs adjustment, thereby adjusting the delay time of the second frequency signal. This results in the formation and output of a delay processing signal. The drive control module generates a drive control signal for driving the active rectifier module based on the delay processing signal and the second frequency signal. The active rectifier module adaptively adjusts the conduction time of its transistors according to the drive control signal to rectify the output voltage of the transformer secondary coil. Compared to existing technologies, this solution, based on changes in the transformer terminal voltage frequency (changes in operating conditions), uses adaptive delay control to adjust the conduction time (or turn-off time) of the transistors inside the active rectifier module. This allows the delay time to dynamically track changes in the operating conditions at the transmitting end (transformer primary coil side), thereby optimizing the drive timing. This improves the robustness of rectification, reduces EMI radiation, and increases rectification efficiency.

[0032] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A schematic diagram of an active rectifier circuit provided for the prior art;

[0035] Figure 2 This is a schematic diagram of an active rectifier circuit provided in an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of another active rectifier circuit provided in an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of another active rectifier circuit provided in an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of another active rectifier circuit provided in an embodiment of the present invention;

[0039] Figure 6 A waveform diagram of an active rectifier circuit provided in an embodiment of the present invention;

[0040] Figure 7 A waveform diagram of another active rectifier circuit provided in an embodiment of the present invention;

[0041] Figure 8 A waveform diagram of another active rectifier circuit provided in an embodiment of the present invention;

[0042] Figure 9 A flowchart of a control method for an active rectifier circuit provided in an embodiment of the present invention. Detailed Implementation

[0043] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0044] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0045] Figure 1 A schematic diagram of an active rectifier circuit provided for reference in the prior art. Figure 1The active rectifier circuit consists of a first transistor MP1, a second transistor MN1, a third transistor MP2, a fourth transistor MN2, a first comparator CMP1, and a second comparator CMP2. Traditional active rectification often uses comparators to compare zero-crossing points to provide the gate control signal (i.e., the drive control signal). When VSP - VSN > |VtP|, the first transistor MP1 is turned on. Simultaneously, when VSN < 0, the first comparator CMP1 turns on the second transistor MN1, charging Viso using VSP. Here, VSP is the voltage at the first terminal of the transformer secondary coil 100, VSN is the voltage at the second terminal of the transformer secondary coil 100, Viso is the rectified voltage, and VtP is the threshold voltage of either the first transistor MP1 or the third transistor MP2. When VSP swings above zero, the first comparator CMP1 turns off the second transistor MN1. In the next half-cycle of the AC input, the third transistor MP2 and the fourth transistor MN2 turn on in a similar manner, achieving active rectification.

[0046] Ideally, the second transistor MN1 (or the fourth transistor MN2) would turn on (or turn off) once immediately after VSN (or VSP) swings below (or above) 0. However, due to the propagation delay of the comparator and gate driver, the P-transistors and N-transistors do not actually turn on (or turn off) simultaneously, causing fluctuations in the common-mode level at the rectifier and generating electromagnetic interference. Furthermore, as the rectification frequency gradually increases (tens of MHz), the comparator struggles to respond promptly; its propagation delay can exceed 1 / 10 of the rectification cycle, resulting in passive rectification for an extended period and severely limiting rectification efficiency.

[0047] To address the aforementioned problems, embodiments of the present invention provide an active rectifier circuit. Figure 2 This is a schematic diagram of an active rectifier circuit provided in an embodiment of the present invention, with reference to... Figure 2 The active rectifier circuit includes: an active rectifier module 200, a sampling processing module 300, a delay control module 400, and a drive control module 500.

[0048] The first input terminal of the active rectifier module 200 is connected to the first terminal of the secondary coil 100 of the transformer, and the second input terminal of the active rectifier module 200 is connected to the second terminal of the secondary coil 100 of the transformer. The active rectifier module 200 is used to output a rectified voltage Viso. The voltage VSP at the first terminal and the voltage VSN at the second terminal of the secondary coil 100 of the transformer are both alternating signals. The active rectifier module 200 can respond to the drive control signal VS5 output by the drive control module 500 to rectify the alternating signals, thereby outputting the rectified voltage Viso.

[0049] The first input terminal of the sampling processing module 300 is connected to the first terminal of the transformer secondary coil 100, and the second input terminal is connected to the second terminal of the transformer secondary coil 100. The first output terminal of the sampling processing module 300 outputs a first frequency signal VS1, the second output terminal outputs a second frequency signal VS2, and the third output terminal outputs a third frequency signal VS3. The sampling processing module 300 samples the voltage VSP at the first terminal and the voltage VSN at the second terminal of the transformer secondary coil 100, and converts VSP and VSN into signals that can be processed by subsequent circuit modules. The first frequency signal VS1 is the power stage frequency signal after processing VSP and VSN by the sampling processing module 300, the second frequency signal VS2 is the transformer terminal voltage frequency signal, and the third frequency signal VS3 is a reference frequency signal. Here, the first frequency signal VS1 and the second frequency signal VS2 can be inverted signals for easier reception and processing by subsequent circuits.

[0050] The first input terminal of the delay control module 400 is connected to the first output terminal of the sampling processing module 300, the second input terminal of the delay control module 400 is connected to the second output terminal of the sampling processing module 300, and the third input terminal of the delay control module 400 is connected to the third output terminal of the sampling processing module 300. The delay control module 400 is used to determine the delay time of the second frequency signal VS2 based on the first frequency signal VS1 and the third frequency signal VS3, and outputs the delay processing signal VS4 from its own output terminal.

[0051] The first input terminal of the drive control module 500 is connected to the second output terminal of the sampling processing module 300, the second input terminal of the drive control module 500 is connected to the output terminal of the delay control module 400, and the output terminal of the drive control module 500 is connected to the control terminal of the active rectifier module 200. The drive control module 500 is used to output the drive control signal VS5 according to the delay processing signal VS4 and the second frequency signal VS2.

[0052] The technical solution provided in this embodiment of the invention samples the voltage VSP at the first end and the voltage VSN at the second end of the transformer secondary coil 100 using a sampling processing module 300, and outputs a first frequency signal VS1, a second frequency signal VS2, and a third frequency signal VS3. A delay control module 400 compares the received first frequency signal VS1 and third frequency signal VS3 to determine whether the delay function of the delay control module needs adjustment, thereby adjusting the delay time of the second frequency signal VS2, and forming and outputting a delay processing signal VS4. A drive control module 500 generates a drive control signal VS5 for driving the active rectifier module 200 based on the delay processing signal VS4 and the second frequency signal VS2. The active rectifier module 200 adaptively adjusts the conduction time of its transistors according to the drive control signal VS5 to rectify the output voltage of the transformer secondary coil 100. Compared to existing technologies, this solution uses adaptive delay control to adjust the conduction (or turn-off) duration of the transistors inside the active rectifier module 200 based on the changes in the transformer terminal voltage frequency (changes in operating conditions). This allows the delay time to dynamically track the changes in operating conditions at the transmitter (transformer primary coil side), thereby optimizing the drive timing. This improves the robustness of rectification, reduces EMI radiation, and enhances rectification efficiency.

[0053] Figure 3 This is a schematic diagram of another active rectifier circuit provided in an embodiment of the present invention, referred to... Figure 3 Based on the above embodiments, optionally, the sampling processing module 300 includes a sampling processing unit 301 and an oscillator 302. The first input terminal of the sampling processing unit 301 is connected to the first terminal of the secondary coil 100 of the transformer, the second input terminal of the sampling processing unit 301 is connected to the second terminal of the secondary coil 100 of the transformer, the first output terminal of the sampling processing unit 301 is connected to the first input terminal of the delay control module 400, the second output terminal of the sampling processing unit 301 is connected to the second input terminal of the delay control module 400, and the output terminal of the oscillator 302 is connected to the third input terminal of the delay control module 400.

[0054] The oscillator 302 is used to generate a third frequency signal VS3, and uses the third frequency signal VS3 as a reference frequency signal for delay adjustment. The third frequency signal VS3 has a fixed frequency.

[0055] The sampling processing unit 301 is used to sample the voltage VSP at the first terminal and the voltage VSN at the second terminal of the transformer secondary coil 100, and output a first frequency signal VS1 and a second frequency signal VS2. For example, the sampling processing unit 301 may include a Schmitt trigger and a level conversion circuit. The Schmitt trigger samples the falling edges of the voltage VSP at the first terminal and the voltage VSN at the second terminal of the transformer secondary coil 100, and controls the level conversion circuit to convert the power stage voltage signal into a power stage frequency signal (a digital signal that can be processed by the control stage).

[0056] Figure 4 This is a schematic diagram of another active rectifier circuit provided in an embodiment of the present invention, referred to... Figure 4 Based on the above embodiments, optionally, the delay control module 400 includes a first conversion unit 401, a second conversion unit 402, and a pressure-controlled delay unit 403.

[0057] The input terminal of the first conversion unit 401 is connected to the first output terminal of the sampling processing module 300 (i.e., connected to the first output terminal of the sampling processing unit 301), and the output terminal of the first conversion unit 401 is connected to the first input terminal of the voltage-controlled delay unit 403. The first conversion unit 401 is used to convert the first frequency signal VS1 into a first voltage signal V1. The input terminal of the second conversion unit 402 is connected to the third output terminal of the sampling processing module 300 (i.e., connected to the output terminal of the oscillator 302), and the output terminal of the second conversion unit 402 is connected to the second input terminal of the voltage-controlled delay unit 403. The second conversion unit 402 is used to convert the third frequency signal VS3 into a second voltage signal V2.

[0058] The first conversion unit 401 and the second conversion unit 402 can both be frequency-to-voltage circuits to convert the frequency information in the first frequency signal VS1 and the third frequency signal VS3 into voltage signals so that the voltage-controlled delay unit 403 can recognize and process them.

[0059] The third input terminal of the voltage-controlled delay unit 403 is connected to the second output terminal of the sampling processing module 300, and the output terminal of the voltage-controlled delay unit 403 is connected to the second input terminal of the drive control module 500. The voltage-controlled delay unit 403 is used to control the delay time of the second frequency signal VS2 according to the first voltage signal V1 and the second voltage signal V2, and outputs the delay processing signal VS4. For example, the voltage-controlled delay unit 403 is set to have a preset delay time. When the voltage-controlled delay unit 403 detects that the first voltage signal V1 and the second voltage signal V2 are the same, it indicates that the sampling frequency is the same as the local oscillation frequency (the first frequency signal VS1 and the third frequency signal VS3 are the same), and the operating conditions of the transformer transmitter and receiver are the same. At this time, there is no need to adjust the delay time of the voltage-controlled delay unit 403. When the voltage-controlled delay unit 403 detects a difference between the first voltage signal V1 and the second voltage signal V2, it indicates that the sampling frequency is different from the local oscillation frequency (the first frequency signal VS1 is different from the third frequency signal VS3), and the operating conditions at the transformer's transmitting and receiving ends are different. In this case, the delay time of the voltage-controlled delay unit 403 needs to be adjusted. For example, if the first frequency signal VS1 is lower than the third frequency signal VS3, the delay time generated by the voltage-controlled delay unit 403 becomes longer; if the first frequency signal VS1 is higher than the third frequency signal VS3, the delay time generated by the voltage-controlled delay unit 403 becomes shorter.

[0060] Figure 5 This is a schematic diagram of another active rectifier circuit provided in an embodiment of the present invention, referred to... Figure 5 Based on the above embodiments, optionally, the drive control module 500 includes a logic control unit 501 and a drive unit. The first input terminal of the logic control unit 501 serves as the first input terminal of the drive control module 500, and the second input terminal of the logic control unit 501 serves as the second input terminal of the drive control module 500. The logic control unit 501 is used to output a switching signal according to the delay processing signal VS4 and the second frequency signal VS2; the drive unit is used to output a drive control signal VS5 according to the switching signal.

[0061] The driving unit includes a first driving subunit 502 and a second driving subunit 503. The input terminal of the first driving subunit 502 is connected to the first output terminal of the logic control unit 501, and the output terminal of the first driving subunit 502 outputs a first driving control signal VG1 and a second driving control signal VG2. The input terminal of the second driving subunit 503 is connected to the second output terminal of the logic control unit 501, and the output terminal of the second driving subunit 503 outputs a third driving control signal VG3 and a fourth driving control signal VG4 (that is, the driving control signal VS5 includes the first driving control signal VG1, the second driving control signal VG2, the third driving control signal VG3 and the fourth driving control signal VG4).

[0062] The active rectifier module 200 includes a first transistor MP1, a second transistor MN1, a third transistor MP2, and a fourth transistor MN2. The control electrode of the first transistor MP1 is connected to a first drive control signal VG1. The first electrode of the first transistor MP1 is connected to the first electrode of the third transistor MP2. The second electrode of the first transistor MP1 is connected to the first terminal of the secondary coil 100 of the transformer. The control electrode of the second transistor MN1 is connected to a second drive control signal VG2. The first electrode of the second transistor MN1 is connected to the second terminal of the secondary coil 100 of the transformer. The second electrode of the second transistor MN1 is connected to the second electrode of the fourth transistor MN2. The first electrode of the fourth transistor MN2 is connected to the first terminal of the secondary coil 100 of the transformer. The control electrode of the fourth transistor MN2 is connected to a fourth drive control signal VG4. The control electrode of the third transistor MP2 is connected to a third drive control signal VG3. The second electrode of the third transistor MP2 is connected to the second terminal of the secondary coil 100 of the transformer.

[0063] In this configuration, the channel type of the first transistor MP1 differs from that of the second transistor MN1, and the channel type of the third transistor MP2 differs from that of the fourth transistor MN2. For example, the first transistor MP1 and the third transistor MP2 are both P-type transistors, while the second transistor MN1 and the fourth transistor MN2 are both N-type transistors. The first transistor MP1 and the second transistor MN1 belong to the same group, and the third transistor MP2 and the fourth transistor MN2 belong to the same group.

[0064] Optionally, the first capacitor C1 is used to filter the rectified voltage Viso.

[0065] Figure 6 A waveform diagram of an active rectifier circuit provided in an embodiment of the present invention, combined with... Figure 5 and Figure 6 Taking the voltage VSP at the first terminal of the secondary coil 100 of the transformer as an example, the specific working principle of this circuit is as follows:

[0066] The sampling processing unit 301 processes the sampled voltage VSP at the first terminal of the transformer secondary coil 100 to obtain a first frequency signal VS1, and inverts the first frequency signal VS1 to obtain a second frequency signal VS2. The first conversion unit 401 converts the first frequency signal VS1 into a first voltage signal V1, and the second conversion unit 402 converts the third frequency signal VS3 output by the oscillator 302 into a second voltage signal V2. The voltage-controlled delay unit 403 compares the first voltage signal V1 and the second voltage signal V2 (that is, compares the first frequency signal VS1 and the third frequency signal VS3), and determines the delay time according to the frequency relationship between the first voltage signal V1 and the second voltage signal V2. The voltage-controlled delay unit 403 delays the second frequency signal VS2 according to the determined delay time to obtain a delayed processing signal VS4. The logic control unit 501 performs logical operations on the delayed processing signal VS4 and the second frequency signal VS2. Based on the rising edge of the second frequency signal VS2, it obtains the turn-on signal of the fourth transistor MN2, and based on the rising edge of the delayed processing signal VS4, it obtains the turn-off signal of the fourth transistor MN2, thus forming the switching signal corresponding to the fourth transistor MN2. This switching signal is then driven through multiple stages by the second driving subunit 503 to generate a fourth driving control signal VG4 with driving capability. The third driving control signal VG3 corresponding to the third transistor MP2 is obtained simply by inverting the fourth driving control signal VG4. Based on the waveforms of the fourth driving control signal VG4 and the voltage VSP at the first terminal of the transformer secondary coil 100, it can be seen that when the falling edge of the voltage VSP at the first terminal of the transformer secondary coil 100 is detected, the active rectifier module 200 is controlled to operate in active rectification mode, and before the rising edge of the voltage VSP at the first terminal of the transformer secondary coil 100 arrives, the active rectifier module 200 is controlled to operate in passive rectification mode.

[0067] Optionally, the generation principles of the first drive control signal VG1 and the second drive control signal VG2 are similar to those of the third drive control signal VG3 and the fourth drive control signal VG4, and will not be repeated here.

[0068] In this embodiment, the logic control unit 501 integrates PWM synchronization and non-overlap protection circuits to ensure that the first transistor MP1 and the fourth transistor MN2 do not conduct simultaneously, and the second transistor MN1 and the third transistor MP2 do not conduct simultaneously. When all four transistors are off, the active rectifier module 200 can be considered as a passive rectifier circuit composed of body diodes corresponding to the four transistors, and the active rectifier circuit operates in passive rectification mode. When the first transistor MP1 and the second transistor MN1 are on, and the third transistor MP2 and the fourth transistor MN2 are off, or when the third transistor MP2 and the fourth transistor MN2 are on, and the first transistor MP1 and the second transistor MN1 are off, the active rectifier module 200 operates in active rectification mode.

[0069] Figure 7 This is a waveform diagram of another active rectifier circuit provided in an embodiment of the present invention. Figure 8 This is a waveform diagram of another active rectifier circuit provided in an embodiment of the present invention. VSP-1 and VSP-1' are both voltages at the first end of the transformer secondary coil 100 without using the delay control module 400, and VSP-1 and VSP-1' correspond to different frequencies; VSP-2 and VSP-2' are both voltages at the first end of the transformer secondary coil 100 with the delay control module 400 used; VG4 is the fourth drive control signal with the delay control module 400 used, and VG4' is the fourth drive control signal without using the delay control module 400. Figure 7 As shown, when the system operates in its initial state, i.e., the transmitter and receiver have the same process, voltage, temperature, and other conditions, and their frequencies are consistent, the delay control module 400 does not need to adjust the delay. The active rectifier circuit operates in normal mode, i.e., it detects the falling edge of the voltage VSP at the first terminal of the transformer secondary coil 100, turns on the corresponding pair of transistors, keeps them on for a fixed period of time, and then turns them off. Then, it detects the falling edge of the voltage VSN at the second terminal of the transformer secondary coil 100, and turns on another pair of transistors. In this state, the process, voltage, and temperature parameters of the transmitter and receiver fluctuate simultaneously, and the delay control module 400 will follow the fluctuations to achieve efficient active rectification within the cycle. Furthermore, there is a situation where the four body diodes alternately conduct, meaning that when the transformer current commutates, the rectifier side will operate in a more symmetrical passive rectification state (as shown in the red dashed box), resulting in lower EMI radiation interference.

[0070] like Figure 8 As shown, when the frequency of power conversion changes due to variations in the operating voltage at the transmitting end, the drive signal on the rectifier side, which does not use the delay control module 400 in this embodiment, will not change (e.g., Figure 8 VG4' in Figure 7(The same as VG4' in the original text). This means that when the transmitter frequency decreases, the receiver delay is relatively short, resulting in a long period of passive rectification (as shown in the red dashed box of VSP-1'), which greatly reduces the system efficiency. When the transmitter frequency increases, the receiver delay will be relatively long, and the rectifier will not be able to turn off in advance, causing increased radiated electromagnetic interference. When the delay is too long, the rectifier will be unable to turn off because the MOS transistor is forced to turn on by the logic circuit, causing timing errors and causing load power to flow back. In this embodiment, the rectifier side of the delay control module 400 will track the frequency change of the transmitter. When the transmitter frequency increases, the delay time is reduced (i.e., the transistor turns off earlier), and when the transmitter frequency decreases, the delay time is increased (i.e., the transistor turns off later, as shown in the red dashed box of VSP-1'). Figure 8 The high level of VG4 in the diode is longer, thus achieving overcompensated active rectification. In this case, the rectification efficiency is higher because the conduction time of the body diode is shorter.

[0071] The technical solution provided in this invention uses a delay control module 400 to replace the original comparator scheme. Simplifying the signal link improves circuit reliability and robustness. Furthermore, the delay time setting enables overcompensation of active rectification under varying transformer operating conditions, ensuring strict symmetry of the transformer terminal voltage signal during current commutation, thereby suppressing common-mode voltage fluctuations and significantly improving EMI immunity. In addition, by adaptively adjusting the delay time based on the frequency change of the voltage across the transformer secondary coil 100, the corresponding transistor's on (or off) state can dynamically track changes in the transmitter's operating conditions, effectively reducing the conduction time of the transistor's body diode and improving rectification efficiency while reducing EMI radiation.

[0072] Optionally, embodiments of the present invention also provide a control method for an active rectifier circuit, applicable to the active rectifier circuits provided in any of the above embodiments. Figure 9 A flowchart of a control method for an active rectifier circuit provided in an embodiment of the present invention is shown below. Figure 9 The control method includes:

[0073] S110: The control sampling and processing module samples the voltage at the first end of the transformer secondary coil and the voltage at the second end of the transformer secondary coil, and outputs a first frequency signal, a second frequency signal and a third frequency signal.

[0074] S120: The delay control module determines the delay time of the second frequency signal based on the first frequency signal and the third frequency signal, and outputs the delay processing signal.

[0075] S130, the control drive control module outputs drive control signals based on the delay processing signal and the second frequency signal.

[0076] S140: The active rectifier module rectifies the voltage at the first end of the transformer secondary coil and the voltage at the second end of the transformer secondary coil according to the drive control signal, and outputs the rectified voltage.

[0077] The technical solution provided by this invention uses adaptive delay control to control the conduction duration (or turn-off duration) of the transistors inside the active rectifier module 200 based on the change in transformer terminal voltage frequency (change in operating conditions). This allows the delay time to dynamically track the change in operating conditions at the transmitting end (transformer primary coil side), thereby optimizing the drive timing. This improves the robustness of rectification, reduces EMI radiation, and enhances rectification efficiency.

[0078] Optionally, step S140 specifically includes:

[0079] When the falling edge of the voltage at the first terminal of the transformer secondary coil or the second terminal of the transformer secondary coil is detected, the active rectifier module is controlled to operate in active rectification mode, and before the rising edge of the corresponding voltage arrives, the active rectifier module is controlled to operate in passive rectification mode.

[0080] The specific working principle of this step can be found in [reference needed]. Figure 6 The relevant descriptions will not be repeated here.

[0081] Optionally, embodiments of the present invention also provide an isolated power supply, which includes the active rectifier circuit provided in any embodiment of the present invention. Therefore, the isolated power supply also has the beneficial effects described in any of the above embodiments.

[0082] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0083] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. An active rectifier circuit, characterized in that, Includes: an active rectification module, a sampling and processing module, a delay control module, and a drive control module; The first input terminal of the active rectifier module is connected to the first terminal of the secondary coil of the transformer, and the second input terminal of the active rectifier module is connected to the second terminal of the secondary coil of the transformer. The first input terminal of the sampling processing module is connected to the first terminal of the secondary coil of the transformer, the second input terminal of the sampling processing module is connected to the second terminal of the secondary coil of the transformer, and the first output terminal of the sampling processing module outputs a first frequency signal, the second output terminal outputs a second frequency signal, and the third output terminal outputs a third frequency signal. The first input terminal of the delay control module is connected to the first output terminal of the sampling processing module, the second input terminal of the delay control module is connected to the second output terminal of the sampling processing module, and the third input terminal of the delay control module is connected to the third output terminal of the sampling processing module. The delay control module is used to determine the delay time of the second frequency signal based on the first frequency signal and the third frequency signal, and output the delay processing signal from its own output terminal. The first input terminal of the drive control module is connected to the second output terminal of the sampling processing module, the second input terminal of the drive control module is connected to the output terminal of the delay control module, and the output terminal of the drive control module is connected to the control terminal of the active rectifier module. The drive control module is used to output a drive control signal according to the delay processing signal and the second frequency signal. The active rectifier module is used to rectify the voltage at the first terminal of the transformer secondary coil and the voltage at the second terminal of the transformer secondary coil according to the drive control signal, and output the rectified voltage.

2. The active rectifier circuit according to claim 1, characterized in that, The sampling processing module includes a sampling processing unit and an oscillator. The first input terminal of the sampling processing unit is connected to the first terminal of the secondary coil of the transformer, the second input terminal of the sampling processing unit is connected to the second terminal of the secondary coil of the transformer, the first output terminal of the sampling processing unit is connected to the first input terminal of the delay control module, the second output terminal of the sampling processing unit is connected to the second input terminal of the delay control module, and the output terminal of the oscillator is connected to the third input terminal of the delay control module.

3. The active rectifier circuit according to claim 1, characterized in that, The delay control module includes a first conversion unit, a second conversion unit, and a voltage-controlled delay unit; The input terminal of the first conversion unit is connected to the first output terminal of the sampling processing module, and the output terminal of the first conversion unit is connected to the first input terminal of the voltage-controlled delay unit. The first conversion unit is used to convert the first frequency signal into a first voltage signal. The input terminal of the second conversion unit is connected to the third output terminal of the sampling processing module, and the output terminal of the second conversion unit is connected to the second input terminal of the voltage-controlled delay unit. The second conversion unit is used to convert the third frequency signal into a second voltage signal. The third input terminal of the voltage-controlled delay unit is connected to the second output terminal of the sampling processing module, and the output terminal of the voltage-controlled delay unit is connected to the second input terminal of the drive control module. The voltage-controlled delay unit is used to control the delay time of the second frequency signal according to the first voltage signal and the second voltage signal, and output the delay processing signal.

4. The active rectifier circuit according to claim 1, characterized in that, The drive control module includes a logic control unit and a drive unit. The first input terminal of the logic control unit serves as the first input terminal of the drive control module, and the second input terminal of the logic control unit serves as the second input terminal of the drive control module. The logic control unit is used to output a switching signal according to the delay processing signal and the second frequency signal. The drive unit is used to output the drive control signal according to the switch signal.

5. The active rectifier circuit according to claim 4, characterized in that, The driving unit includes a first driving subunit and a second driving subunit. The input terminal of the first driving subunit is connected to the first output terminal of the logic control unit, and the output terminal of the first driving subunit outputs a first driving control signal and a second driving control signal. The input terminal of the second driving subunit is connected to the second output terminal of the logic control unit, and the output terminal of the second driving subunit outputs a third driving control signal and a fourth driving control signal.

6. The active rectifier circuit according to any one of claims 1-5, characterized in that, The active rectifier module includes a first transistor, a second transistor, a third transistor, and a fourth transistor. The control electrode of the first transistor is connected to a first drive control signal. The first electrode of the first transistor and the first electrode of the third transistor are connected. The second electrode of the first transistor is connected to the first terminal of the secondary coil of the transformer. The control electrode of the second transistor is connected to a second drive control signal. The first electrode of the second transistor is connected to the second terminal of the secondary coil of the transformer. The second electrode of the second transistor is connected to the second electrode of the fourth transistor. The first electrode of the fourth transistor is connected to the first terminal of the secondary coil of the transformer. The control electrode of the fourth transistor is connected to a fourth drive control signal. The control electrode of the third transistor is connected to a third drive control signal. The second electrode of the third transistor is connected to the second terminal of the secondary coil of the transformer. The channel type of the first transistor is different from that of the second transistor, and the channel type of the third transistor is different from that of the fourth transistor.

7. A control method for an active rectifier circuit, characterized in that, The active rectifier circuit includes an active rectifier module, a sampling processing module, a delay control module, and a drive control module; The control method for the active rectifier circuit includes: The sampling and processing module is controlled to sample the voltage at the first end of the transformer secondary coil and the voltage at the second end of the transformer secondary coil, and output a first frequency signal, a second frequency signal and a third frequency signal. The delay control module determines the delay time of the second frequency signal based on the first frequency signal and the third frequency signal, and outputs a delay processing signal. The drive control module outputs a drive control signal based on the delay processing signal and the second frequency signal; The active rectifier module is controlled to rectify the voltage at the first end of the transformer secondary coil and the voltage at the second end of the transformer secondary coil according to the drive control signal, and outputs the rectified voltage.

8. The control method for the active rectifier circuit according to claim 7, characterized in that, The first frequency signal and the second frequency signal are inverse signals of each other; The turn-on signal of the drive control signal is obtained based on the rising edge of the second frequency signal, and the turn-off signal of the drive control signal is obtained based on the rising edge of the delay processing signal.

9. The control method for the active rectifier circuit according to claim 7, characterized in that, The control of the active rectifier module to rectify the voltage at the first terminal and the voltage at the second terminal of the transformer secondary coil according to the drive control signal, and to output the rectified voltage includes: When the falling edge of the voltage at the first terminal of the transformer secondary coil or the voltage at the second terminal of the transformer secondary coil is detected, the active rectifier module is controlled to operate in active rectification mode, and before the rising edge of the corresponding voltage arrives, the active rectifier module is controlled to operate in passive rectification mode.

10. An isolated power supply, characterized in that, Includes the active rectifier circuit as described in any one of claims 1-6.

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