Control device, control method for isolated converter and isolated converter

Abstract

This application discloses a control device, control method, and isolated converter for an isolated converter. The isolated converter includes a transformer, a primary switching transistor, and a secondary rectifier transistor. The control device includes a secondary control circuit, an isolation module, and a primary control circuit. The secondary control circuit sends a first handshake signal to the primary control circuit at a first frequency when the supply voltage of the secondary control circuit rises to a first threshold. The first handshake signal instructs the primary switching transistor to stop switching. Within a first detection window after sending the first handshake signal, the state of the primary switching transistor is detected. The start time of the first detection window is greater than the sum of the first transmission time and one switching cycle of the primary switching transistor. The first transmission time is the time when the first handshake signal is sent. Using this solution, the accuracy of the primary control circuit's judgment of the handshake signal from the secondary control circuit can be guaranteed, improving the stability of the system operation.

Description

Technical Field

[0001] This application relates to the field of switching power supplies, specifically to a control device, control method, and isolated converter for an isolated converter. Background Technology

[0002] In small and medium power supply systems with high reliability and high dynamic performance requirements, isolated converters such as flyback converters, forward converters, and LLC (Inductor-Inductor-Capacitor) resonant converters have become the mainstream choice for industrial control, medical equipment, new energy charging, and power supply of smart terminals due to their electrical isolation characteristics.

[0003] In isolated converters, digital isolation communication technology can be used to achieve efficient feedback transmission. The secondary control circuit transmits information to the primary control circuit through handshake signals. However, current handshake communication processes are prone to false detections, leading to incorrect handshake communication judgments and thus affecting the stability of the system. Summary of the Invention

[0004] This application provides a control device, control method, and isolated converter for an isolated converter, so as to ensure the accuracy of the handshake signal judgment of the primary control circuit to the secondary control circuit and improve the stability of the system operation.

[0005] On one hand, embodiments of this application provide a control device for an isolated converter, the isolated converter including a transformer, a primary switching transistor, and a secondary rectifier transistor, the control device including: a secondary control circuit, an isolation module, and a primary control circuit; the secondary control circuit and the primary control circuit communicate through the isolation module; The secondary control circuit is configured to send a first handshake signal to the primary control circuit at a first frequency when the supply voltage of the secondary control circuit rises to a first threshold. The first handshake signal is used to instruct the primary switch to stop switching. The secondary control circuit also detects the state of the primary switch within a first detection window after sending the first handshake signal. The start time of the first detection window is greater than the sum of the first sending time point and one switching cycle of the primary switch. The first sending time point is the time point at which the first handshake signal is sent.

[0006] Optionally, the end time of the first detection window is less than the sum of the first transmission time point and twice the switching cycle of the primary switch.

[0007] Optionally, the secondary control circuit is further configured to resend the first handshake signal if the primary switch is not continuously detected to stop switching within the first detection window.

[0008] Optionally, the secondary control circuit is further configured to send a second handshake signal to the primary control circuit at a second frequency when the primary switch is detected to stop switching, the second handshake signal being used to instruct the primary switch to perform a switching action, and to detect the state of the primary switch within a second detection window after sending the second handshake signal.

[0009] Optionally, the start time of the second detection window is the second transmission time point; the second transmission time point is the time point at which the second handshake signal is transmitted; and the end time of the second detection window is greater than the sum of the second transmission time point and the maximum allowable turn-on time of the primary switch.

[0010] Optionally, the end time of the second detection window is the sum of the second transmission time and K times the maximum allowable turn-on time of the primary switch tube, where K is any value between 1.1 and 1.3.

[0011] Optionally, the secondary control circuit continuously detects the voltage across the secondary rectifier diode to determine the state of the primary switching diode.

[0012] Optionally, the secondary control circuit is further configured to send a first handshake signal to the primary control circuit at the first frequency after detecting that the primary switch has spontaneously turned on a set number of times after the power supply voltage rises to a first threshold, and when the power supply voltage rises to a second threshold or the output voltage rises to a third threshold.

[0013] Optionally, the secondary control circuit is further configured to determine that the handshake is complete when the primary switch is detected to be turned on within the second detection window, and the primary control circuit performs feedback control.

[0014] Optionally, the secondary control circuit is further configured to re-initiate handshake communication if, under the feedback control of the primary control circuit, the primary switching transistor is detected to have not performed a switching action within a third time period.

[0015] On the other hand, embodiments of this application also provide a control method for an isolated converter, the isolated converter including a transformer, a primary switching transistor, and a secondary rectifier transistor, the control method including: When the supply voltage of the secondary control circuit rises to a first threshold, a first handshake signal is sent to the primary control circuit at a first frequency. The first handshake signal is used to instruct the primary switch to stop switching. Within a first detection window after sending the first handshake signal, the state of the primary switch is detected; wherein, the start time of the first detection window is greater than the sum of the first sending time point and one switching cycle of the primary switch, and the first sending time point is the time point when the first handshake signal is sent.

[0016] Optionally, the end time of the first detection window is less than the sum of the first transmission time point and twice the switching cycle of the primary switch.

[0017] Optionally, the method further includes: retransmitting the first handshake signal if the primary switch tube is not continuously detected to stop switching within the first detection window.

[0018] Optionally, the method further includes: when the primary switch is detected to stop switching, sending a second handshake signal to the primary control circuit at a second frequency, the second handshake signal being used to instruct the primary switch to perform a switching action, and detecting the state of the primary switch within a second detection window after sending the second handshake signal.

[0019] Optionally, the start time of the second detection window is the second transmission time point; the second transmission time point is the time point at which the second handshake signal is transmitted; and the end time of the second detection window is greater than the sum of the second transmission time point and the maximum allowable turn-on time of the primary switch.

[0020] On the other hand, embodiments of this application also provide an isolated converter, the isolated converter including a control device for the isolated converter.

[0021] The control device, control method, and isolated converter provided in this application embodiment set a first detection window for the first handshake signal. When the supply voltage of the secondary control circuit rises to a first threshold, the first handshake signal is sent to the primary control circuit at a first frequency to instruct the primary switch to stop switching. Within the first detection window after sending the first handshake signal, the state of the primary switch is detected. By setting the start time of the first detection window to be greater than the sum of the first transmission time and one switching cycle of the primary switch, and the first transmission time being the time point for sending the first handshake signal, misjudgment of the first handshake can be effectively avoided.

[0022] Furthermore, if the primary switch is not continuously detected to stop switching within the first detection window, the reliability of the handshake signal transmission can be ensured by retransmitting the first handshake signal.

[0023] Furthermore, a second detection window is set for the second handshake signal. When the primary switch is detected to have stopped switching, a second handshake signal is sent to the primary control circuit at a second frequency to instruct the primary switch to perform a switching action. Within the second detection window following the sending of the second handshake signal, the state of the primary switch is detected. By setting the start and end times of the second detection window, the duration of the second detection window is made longer than the maximum allowable on-time of the primary switch, thereby effectively preventing missed detection of the second handshake signal. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a structure of an isolated converter control device provided in an embodiment of this application; Figure 2 This is a schematic diagram of the timing relationship between the first handshake signal and the PWM signal in an embodiment of this application; Figure 3 This is a waveform diagram of the relevant signals during the handshake process in the embodiments of this application; Figure 4 This is a flowchart of an isolated converter control method provided in an embodiment of this application; Figure 5 This is another flowchart of the isolated converter control method provided in the embodiments of this application; Figure 6 This is another flowchart of the isolated converter control method provided in the embodiments of this application; Figure 7 This is another flowchart of the isolated converter control method provided in the embodiments of this application. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] In the prior art, after the secondary control module of the switching power supply sends the first handshake signal, it determines whether the primary-side main control power transistor should stop switching by judging whether the voltage value at the connection point between the primary and secondary rectifier diodes meets a preset condition after a first duration. The first duration is used to ensure that the primary control module has sufficient time to control the primary-side main control power transistor to stop switching. Since the primary control module is simultaneously controlling the primary-side main control power transistor to switch when it receives the first handshake signal, the turn-off of the primary-side main control power transistor may be due to receiving the first handshake signal or due to the PWM signal turn-off of the primary control module. Consequently, even if the secondary control module detects that the voltage value at the connection point does not meet the preset condition after the first duration, it cannot determine whether it is caused by the first handshake signal or by the PWM signal turn-off of the primary control module 101, resulting in a misjudgment of the handshake.

[0028] Therefore, embodiments of this application provide a control device, control method, and isolated converter for an isolated converter. After sending a first handshake signal, the secondary control circuit can avoid misjudging the first handshake by detecting the state of the primary switch within a reasonably set first detection window. Furthermore, after sending a second handshake signal, the secondary control circuit can avoid missing the second handshake by detecting the state of the primary switch within a reasonably set second detection window. The first handshake signal is used to instruct the primary switch to stop switching, and the second handshake signal is used to instruct the primary switch to perform a switching action.

[0029] like Figure 1 The diagram shown is a structural schematic of a control device for an isolated converter provided in an embodiment of this application.

[0030] To clearly describe the control device 100, in Figure 1 The example is a flyback converter, and the transformer T, primary switch M1, and secondary rectifier M2 in the flyback converter are also shown. Figure 1 The resistor R, capacitor C, and diode D in the circuit form an RCD absorption circuit.

[0031] In the initial stage of system startup, the primary control circuit 103 is powered on and started. At this time, the primary control circuit 103 and the secondary control circuit 101 have not established communication. The primary switching transistor M1 usually runs spontaneously with a fixed switching cycle Ts.

[0032] After the secondary control circuit 101 is powered on, it sends a first handshake signal. At the same time, the primary control circuit 103 is also generating a PWM signal in real time to control the primary switching transistor M1. The timing of the first handshake signal sent by the secondary control circuit 101 is not synchronized with the timing of the PWM signal sent by the primary control circuit 103. The PWM signal may be sent before, simultaneously with, or after the handshake signal transmission time. Figure 2As shown. In the first operating condition, the PWM signal (denoted as PWM1 signal) is ahead of the transmission time of the first handshake signal. In the second operating condition, the PWM signal (denoted as PWM2 signal) is synchronized with the transmission time of the first handshake signal. In the third operating condition, the PWM signal (denoted as PWM3 signal) is behind the transmission time of the first handshake signal.

[0033] In the first operating condition, after the PWM1 signal controls the primary switch M1 to turn off, the secondary winding Ns of the transformer and the body diode of the secondary rectifier M2 continue to flow, and the drain-source voltage Vds of the secondary rectifier M2 is negative. Subsequently, the primary control circuit 103 receives the first handshake signal and instructs the primary switch M1 to turn off again. However, at this time, the primary switch M1 is already in the off state, and the drain-source voltage Vds does not change any further. The secondary control circuit 101 cannot distinguish whether the current turn-off of the primary switch M1 is caused by the first handshake signal (controlled turn-off after successful handshake) or by the PWM1 signal (normal switching action) by detecting the drain-source voltage Vds, thus leading to a misjudgment of the handshake.

[0034] Furthermore, even if the primary switch M1 is controlled to stop switching for a sufficient period of time as in the prior art, the internal circuit logic may make an error due to the decrease in power supply voltage (because the primary switch stops supplying energy) during this period, which may also result in handshake failure. Moreover, the excessively long judgment time will increase the total handshake time, which is not conducive to the normal operation of the system.

[0035] In the second operating condition, the turn-off edge of PWM2 almost coincides with the arrival time of the first handshake signal. The change in drain-source voltage Vds may be caused by either of them. The secondary control circuit 101 also cannot distinguish the cause-and-effect relationship, which poses a risk of misjudgment.

[0036] In the third operating condition, the first handshake signal arrives first, instructing the primary switch M1 to turn off. Subsequently, when the PWM3 signal arrives, the primary switch M1 is already off. In this case, the change in drain-source voltage Vds detected on the secondary side occurs after the handshake signal, resulting in a low risk of misjudgment. However, if the PWM3 signal has a very short delay, the waveform of the drain-source voltage Vds may be superimposed and distorted, leading to some uncertainty.

[0037] To address the aforementioned issues, this application embodiment sets a suitable first detection window. After the secondary control circuit sends the first handshake signal, it detects the state of the primary switching transistor within the first detection window, thus avoiding misjudgment of the first handshake.

[0038] Example 1

[0039] Reference Figure 1The control device 100 includes a secondary control circuit 101, an isolation module 102, and a primary control circuit 103. The secondary control circuit 101 and the primary control circuit 103 communicate through the isolation module 102.

[0040] After the system is powered on, the primary switching transistor M1 operates automatically with a fixed switching cycle Ts. The secondary control circuit 101 can be powered by the output voltage or the auxiliary winding. The secondary control circuit 101 monitors its supply voltage in real time. When the supply voltage rises to a first threshold (e.g., 3.3V or 5V, depending on the chip process), the secondary control circuit 101 determines that it has the ability to operate normally and begins to communicate with the primary control circuit 103.

[0041] The secondary control circuit 101 then sends a first handshake signal to the primary control circuit 103 at a first frequency (e.g., a lower frequency of 1Hz to 10Hz to avoid interference). This first handshake signal is typically lower than the normal operating frequency of the isolated converter. The first handshake signal is transmitted to the primary control circuit 103 through the isolation module 102 to instruct the primary switch M1 to stop switching, thereby switching the system from a spontaneous operation state to a controlled shutdown state.

[0042] In this embodiment, the secondary control circuit 101 detects the state of the primary switch M1 within the first detection window after sending the first handshake signal. The state detection of the primary switch M1 can be achieved, for example, by detecting the waveform characteristics of the voltage across the secondary rectifier M2, and this embodiment is not limited to this approach. Taking a MOSFET as an example, the voltage across the secondary rectifier M2 is the drain-source voltage of the secondary rectifier M2.

[0043] The start time of the first detection window is configured to be greater than the sum of the first transmission time point and one time the switching cycle of the primary switch M1. The first transmission time point is the time point when the first handshake signal is transmitted. For example, if the first transmission time point is T0 and the switching cycle of the primary switch M1 in the current operating mode is Ts, then the opening time of the first detection window is T_start1 > T0 + Ts.

[0044] In the first stage of the handshake process, after the secondary control circuit 101 sends the first handshake signal, the primary control circuit 103 receives the first handshake signal at a time that differs from the PWM signal. The primary side main control power transistor may be turned off by receiving the first handshake signal or by the PWM signal of the primary control module being turned off.

[0045] If the first detection window opens too early, for example, in the range of T0 to T0+Ts, the secondary control circuit 101 may mistakenly identify the mutual inductance coupling waveform generated by the normal switching action of the primary switch M1 (such as the voltage drop on the secondary rectifier M2) as caused by the first handshake signal, thus causing misjudgment.

[0046] By setting the start time of the first detection window to be greater than T0+Ts, that is, delaying detection until at least one complete switching cycle, it is ensured that the primary switch M1 has completely completed one switching cycle after receiving the stop command. Only if the primary switch M1 continues to switch at this time does it truly indicate that the handshake has failed or the primary control circuit 103 has not responded correctly.

[0047] As can be seen, by setting the first detection window as described above, it is possible to reliably avoid misjudgments of the handshake response caused by the normal switching action of the primary switching transistor, thereby improving the accuracy of handshake detection.

[0048] Furthermore, the end time T_end1 of the first detection window can be configured to be less than the sum of the first transmission time T0 and twice the switching period of the primary switch M1, i.e., T_end1 < T0 + 2Ts. By limiting the end time of the first detection window to less than T0 + 2Ts, not only is it possible to avoid other interferences introduced by an excessively long window, such as noise caused by sudden changes in secondary load, but it also speeds up the handshake judgment and improves the handshake response.

[0049] In some embodiments, the secondary control circuit 101 is further configured to retransmit the first handshake signal if the primary switch 103 is not continuously detected to stop switching within the first detection window. It should be noted that this retransmission process can continue multiple times until successful or the maximum number of retries is reached, after which a protection state is entered. By introducing a retry mechanism, the secondary control circuit 101 can automatically overcome transient interference or brief unready states on the primary side. Each retry follows the timing constraints of the first detection window (start time > T0 + Ts, end time < T0 + 2Ts), thus each retry has the same fault tolerance capability. By introducing a retry mechanism, the probability of a successful handshake is significantly improved, and the reliable startup capability of the system in harsh electromagnetic environments is enhanced.

[0050] In the initial stage of system power-on, in some cases, even if the supply voltage of the secondary control circuit 101 has reached the first threshold (e.g., 3.3V), it may not be stable yet, affecting the transmission of the first handshake signal and causing handshake failure or system malfunction. Therefore, in some embodiments, the secondary control circuit 101 may also send the first handshake signal to the primary control circuit 103 at a first frequency after detecting that the supply voltage has risen to the first threshold, detecting that the primary switch M1 has spontaneously turned on a set number of times, and that the supply voltage has risen to the second threshold or the output voltage Vo has risen to the third threshold.

[0051] By adding the condition that the primary switch automatically turns on a set number of times and the supply voltage rises to a second threshold or the output voltage Vo rises to a third threshold, the secondary control circuit 101 can perform handshake communication under stable power supply conditions. This avoids handshake failure or system malfunction caused by unstable power supply to the secondary control circuit 101. Simultaneously, it ensures that the secondary control circuit 101 itself has sufficient energy margin to complete the entire handshake process, preventing abnormal interruption of the handshake process due to voltage drops when the power supply is insufficient. This embodiment ensures the reliability of the handshake and improves the smoothness and success rate of system startup.

[0052] Example 2

[0053] Based on Embodiment 1, the secondary control circuit 101 is further configured to send a second handshake signal to the primary control circuit 103 at a second frequency when the primary switch M1 is detected to stop switching, so as to instruct the primary switch to perform a switching action, and to detect the state of the primary switch M1 within a second detection window after sending the second handshake signal.

[0054] The second frequency differs from the first frequency and is typically the normal operating frequency of the isolated converter, such as tens to hundreds of kHz. The second handshake signal is used to instruct the primary switch M1 to restart its switching action.

[0055] Within the second detection window after sending the second handshake signal, the secondary control circuit 101 re-detects the state of the primary switch M1 to confirm whether the primary control circuit 103 has correctly responded to the second handshake signal. Preferably, the secondary control circuit 101 can detect whether the voltage across the secondary rectifier M2 is high or negative within the second detection window to determine the state of the primary switch M1.

[0056] In some embodiments, the start time of the second detection window is the second transmission time point T1, that is, the time point at which the second handshake signal is sent; the end time T_end2 of the second detection window is configured to be greater than the sum of the second transmission time point T1 and the maximum allowable turn-on time Ton_max of the primary switch M1, that is: T_end2 > T1 + Ton_max, and the maximum allowable turn-on time Ton_max of the primary switch M1 is preferably a preset fixed value.

[0057] In the second stage of the handshake process, the secondary control circuit 101 sends a second handshake signal to instruct the primary switch M1 to resume its switching action, and hopes to detect an on-time event within a reasonable time. However, due to factors such as transmission delay and soft start, the actual on-time of the primary switch M1 fluctuates randomly. If the end time of the second detection window, T_end2, is less than or equal to T1 + Ton_max, the delayed response event of the primary switch M1 will be excluded from this window, causing the secondary control circuit 101 to miss the second handshake and mistakenly judge it as a handshake failure. In this embodiment, the second detection window is set to T_end2 > T1 + Ton_max, making it wide enough to ensure that the presence of a high or negative voltage across the secondary rectifier M2 can be detected. When the secondary control circuit 101 correctly detects a high or negative voltage across the secondary rectifier M2 within the second detection window, it determines that the second handshake is successful, thereby solving the problem of missed handshake detection in response delay scenarios.

[0058] Furthermore, considering the signal transmission delay, isolation module response deviation, internal logic processing time of the primary control circuit, and soft-start time in the actual circuit, the end time T_end2 of the second detection window is set to the sum of K times the second transmission time T1 and the maximum allowable turn-on time Ton_max of the primary switch M1, i.e.: T_end2 = T1 + K×Ton_max. Preferably, K is any value between 1.1 and 1.3. This margin design can reliably cover the above-mentioned engineering errors, while avoiding the system waiting too long in fault conditions due to an excessively long window, thus improving the robustness of the handshake process under abnormal operating conditions.

[0059] In some embodiments, the secondary control circuit 101 is further configured to determine that the handshake is complete when the primary switch M1 is detected to be turned on (i.e., changing from the on state to the off state, or detecting the on state) within the second detection window, and the primary control circuit 103 performs feedback control. That is, after the handshake is completed, the system enters the normal operating state. The primary control circuit 103 no longer executes a special handshake protocol, but performs closed-loop feedback control based on the feedback signal (e.g., voltage or current error signal) transmitted by the secondary control circuit 101 through the isolation module 102, adjusting the duty cycle or frequency of the primary switch M1 to stabilize the output voltage or current.

[0060] Furthermore, in some embodiments, the secondary control circuit 101 is also used to re-initiate the handshake judgment if, under the feedback control of the primary control circuit 103, the primary switch M1 is detected to have not performed a switching action within a third time period (e.g., no switching event for more than 1 ms or 10 switching cycles). By automatically re-entering the handshake communication when no switching action of the primary switch is detected within the third time period, the system can recover from abnormal states without a complete power-off restart, thereby significantly improving the system's fault tolerance and user experience.

[0061] It should be noted that in the above embodiments, the secondary control circuit 101 can determine the state of the primary switching transistor M1 by continuously detecting the voltage across the secondary rectifier transistor M2.

[0062] To better understand the two handshake processes described above Figure 3 This is a waveform diagram of the relevant signals during the handshake process in the embodiments of this application.

[0063] Simultaneously refer to Figure 1 and Figure 3 The complete working process of the control circuit 100 is as follows: 1. Secondary Power-On Monitoring: When the system powers on, the primary control circuit 103 spontaneously generates a PWM signal to drive the primary switching transistor M1 to switch, and the secondary power supply voltage gradually increases. The secondary control circuit 1 monitors the secondary power supply voltage, and when it reaches the first threshold, it initiates handshake communication.

[0064] 2. First handshake phase (stop switch): The secondary control circuit 101 sends a first handshake signal at a first frequency and checks whether the primary switch M1 has stopped within the first detection window of [T0+Ts, T0+2Ts). If it has not stopped, it retryes.

[0065] 3. Second handshake phase (restore switch): After confirming that the primary switch M1 is stopped, a second handshake signal is sent at the second frequency, and the primary switch M1 is checked for whether it is turned on within the second detection window of [T1, T1+1.2×Ton_max].

[0066] 4. Feedback control phase: After the handshake is completed, normal closed-loop feedback control begins.

[0067] Accordingly, this application embodiment also provides an isolated converter, which includes the control device 100 of the isolated converter described above. The isolated converter can be any of the following: flyback converter, forward converter, LLC resonant converter, isolated full-bridge converter, or isolated half-bridge converter.

[0068] Accordingly, embodiments of this application also provide a control method for an isolated converter, such as... Figure 4 The diagram shown is a flowchart of this control method, which includes the following steps: Step 401: When the supply voltage of the secondary control circuit rises to the first threshold, a first handshake signal is sent to the primary control circuit at a first frequency. The first handshake signal is used to instruct the primary switch to stop switching.

[0069] Step 402: Within the first detection window after sending the first handshake signal, detect the state of the primary switch; wherein, the start time of the first detection window is greater than the sum of the first sending time point and one switching cycle of the primary switch, and the first sending time point is the time point when the first handshake signal is sent.

[0070] In some embodiments, the end time of the first detection window is less than the sum of the first transmission time point and twice the switching period of the primary switch.

[0071] The control method of the isolated converter in this embodiment sets the start time of the first detection window to be greater than the sum of the first transmission time point and one switching cycle of the primary switch, that is, the detection is started only after a delay of at least one complete switching cycle. This can reliably avoid misjudgment of handshake response caused by normal switching action of the primary switch and improve the accuracy of handshake detection.

[0072] like Figure 5 The diagram shown is another flowchart of a control method for an isolated converter provided in this application, including the following steps: Step 501: When the supply voltage of the secondary control circuit rises to the first threshold, a first handshake signal is sent to the primary control circuit at a first frequency. The first handshake signal is used to instruct the primary switch to stop switching.

[0073] Step 502: Within the first detection window after sending the first handshake signal, detect the state of the primary switch; wherein, the start time of the first detection window is greater than the sum of the first sending time point and one switching cycle of the primary switch, and the first sending time point is the time point when the first handshake signal is sent.

[0074] Step 503: When it is detected that the primary switch has stopped switching, a second handshake signal is sent to the primary control circuit at a second frequency. The second handshake signal is used to instruct the primary switch to perform a switching action.

[0075] Step 504: Within the second detection window after sending the second handshake signal, detect the state of the primary switch transistor.

[0076] In some embodiments, the start time of the second detection window is the second transmission time point; the second transmission time point is the time point at which the second handshake signal is transmitted; and the end time of the second detection window is greater than the sum of the second transmission time point and the maximum allowable turn-on time of the primary switch.

[0077] The control method of the isolated converter in this embodiment sets the start time of the first detection window to be greater than the sum of the first transmission time point and one time the switching cycle of the primary switch, that is, it delays for at least one complete switching cycle before starting detection, and sets the end time of the second detection window to be greater than the sum of the second transmission time point and the maximum allowable turn-on time of the primary switch. This not only avoids misjudgment of handshake response caused by normal switching action of the primary switch, but also solves the problem of missed handshake detection in response delay scenarios.

[0078] In some embodiments, a retry mechanism can also be introduced to further increase the probability of a successful handshake and enhance the system's reliable startup capability in harsh electromagnetic environments. The following section combines... Figure 6 Please provide a detailed explanation.

[0079] like Figure 6 The diagram shown is another flowchart of a control method for an isolated converter provided in this application, including the following steps: Step 601: The power supply voltage of the secondary control circuit rises to the first threshold.

[0080] Step 602: The secondary control circuit detects that the primary self-starting has reached the set number of times.

[0081] Step 603: The power supply voltage of the secondary control circuit rises to the second threshold, or the system output voltage rises to the third threshold.

[0082] Step 604: The secondary control circuit sends a first handshake signal to the primary control circuit at a first frequency to stop the primary switch from turning on, and enables the first detection window after sending the signal.

[0083] Step 605: The secondary control circuit determines whether the primary switch has not been spontaneously turned on within the first detection window; if so, proceed to step 606; otherwise, return to step 604 and resend the first handshake signal to the primary control circuit at the first frequency.

[0084] Step 606: The secondary control circuit sends a second handshake signal to the primary control circuit at a second frequency to enable the primary switch at the second frequency and then enables the second detection window.

[0085] Step 607: The secondary control circuit determines whether the primary switch is not detected to be turned on within the second detection window; if so, proceed to step 608; otherwise, return to step 606 and resend the second handshake signal to the primary control circuit at the second frequency.

[0086] Step 608: The initial handshake is complete. Accordingly, the system enters normal operating mode.

[0087] like Figure 7 The diagram shown is another flowchart of a control method for an isolated converter provided in this application, including the following steps: Steps 701 to 708, and Figure 6 Steps 601 to 608 are the same as shown, and will not be repeated here.

[0088] Step 709: After the initial handshake is completed, the primary and secondary control circuits operate normally.

[0089] Step 710: The primary control circuit detects whether the primary switching transistor has not performed a switching action within the third time period; if so, proceed to step 711; otherwise, return to step 709.

[0090] Step 711: Initial and secondary communication is interrupted. The communication flag is pulled low to restart the handshake communication. Then, return to step 702.

[0091] By automatically re-entering the handshake communication when no switching action of the primary switch is detected within the third time period, the system can recover from abnormal states without a complete power outage and restart, thereby significantly improving the system's fault tolerance and user experience.

[0092] In the description of the embodiments of this application, unless otherwise expressly specified and limited, ordinal numbers, such as "first" and "second," are used only to distinguish and describe related objects, and should not be construed as indicating or implying the relative importance or order between related objects. Furthermore, ordinal numbers do not represent the number of related objects.

[0093] In the description of the embodiments in this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. Other quantifiers are similar.

[0094] The terms "or" and "and / or" used in this application are used to describe the relationship between related objects, indicating a non-exclusive inclusion. For example, "A and / or B" can include: "A alone", "B alone", or "A with B". Additionally, the character " / " in this document indicates that the preceding and following related objects are in an "or" relationship.

[0095] In the several embodiments provided in this application, it should be understood that the disclosed apparatus can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for example, the division of modules is merely a logical functional division, and there may be other division methods in actual implementation, which this application does not limit.

[0096] In the embodiments of this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0097] Furthermore, the functional modules in the various embodiments of this application can be integrated into one processing unit, or they can be separate physical units, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware and software functional units.

[0098] Although embodiments of this application have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting this application. Any person skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments without departing from the spirit and scope of this application.

Claims

1. A control device for an isolated converter including a transformer, a primary switching transistor and a secondary rectifying transistor, characterized by, The control device includes: a secondary control circuit, an isolation module, and a primary control circuit; the secondary control circuit and the primary control circuit communicate through the isolation module. The secondary control circuit is configured to send a first handshake signal to the primary control circuit at a first frequency when the supply voltage of the secondary control circuit rises to a first threshold. The first handshake signal is used to instruct the primary switch to stop switching. The secondary control circuit also detects the state of the primary switch within a first detection window after sending the first handshake signal. The start time of the first detection window is greater than the sum of the first sending time point and one switching cycle of the primary switch. The first sending time point is the time point at which the first handshake signal is sent.

2. The control device of the isolated converter according to claim 1, characterized in that, The end time of the first detection window is less than the sum of the first transmission time point and twice the switching cycle of the primary switch.

3. The control device for the isolated converter according to claim 2, characterized in that, The secondary control circuit is also used to resend the first handshake signal if the primary switch does not continuously stop switching action within the first detection window.

4. The control device for the isolated converter according to claim 1, characterized in that, The secondary control circuit is further configured to send a second handshake signal to the primary control circuit at a second frequency when the primary switch is detected to have stopped switching. The second handshake signal is used to instruct the primary switch to perform a switching action, and to detect the state of the primary switch within a second detection window after sending the second handshake signal.

5. The control device of the isolated converter according to claim 4, characterized in that, The start time of the second detection window is the second transmission time point; the second transmission time point is the time point at which the second handshake signal is transmitted; the end time of the second detection window is greater than the sum of the second transmission time point and the maximum allowable turn-on time of the primary switch.

6. The control device for the isolated converter according to claim 5, characterized in that, The end time of the second detection window is the sum of the second transmission time and K times the maximum allowable turn-on time of the primary switch tube, where K is any value between 1.1 and 1.

3.

7. The control device of an isolated converter according to any one of claims 1 to 6, characterized in that, The secondary control circuit continuously monitors the voltage across the secondary rectifier diode to determine the state of the primary switching diode.

8. The control device for the isolated converter according to any one of claims 1 to 6, characterized in that, The secondary control circuit is further configured to send a first handshake signal to the primary control circuit at the first frequency after detecting that the primary switch has spontaneously turned on a set number of times after the power supply voltage rises to a first threshold, and when the power supply voltage rises to a second threshold or the output voltage rises to a third threshold.

9. The control device for the isolated converter according to any one of claims 4 to 6, characterized in that, The secondary control circuit is also used to determine that the handshake is complete when the primary switch is detected to be turned on within the second detection window, and the primary control circuit performs feedback control.

10. The control device for the isolated converter according to claim 9, characterized in that, The secondary control circuit is also used to re-initiate handshake communication if, under the feedback control of the primary control circuit, the primary switch does not perform a switching action within a third time period.

11. A control method of an isolated converter including a transformer, a primary switching transistor and a secondary rectifying transistor, characterized by, The control method includes: When the supply voltage of the secondary control circuit rises to a first threshold, a first handshake signal is sent to the primary control circuit at a first frequency. The first handshake signal is used to instruct the primary switch to stop switching. Within the first detection window after sending the first handshake signal, the state of the primary switch is detected; wherein, the start time of the first detection window is greater than the sum of the first sending time point and one switching cycle of the primary switch, and the first sending time point is the time point when the first handshake signal is sent.

12. The control method of an isolated converter according to claim 11, wherein The end time of the first detection window is less than the sum of the first transmission time point and twice the switching cycle of the primary switch.

13. The control method of an isolated converter according to claim 12, wherein The method further includes: If the primary switch does not continuously stop switching action within the first detection window, the first handshake signal is resent.

14. The control method of an isolated converter according to claim 11, wherein, The method further includes: If the primary switch is detected to have stopped switching, a second handshake signal is sent to the primary control circuit at a second frequency. The second handshake signal is used to instruct the primary switch to perform a switching action. The state of the primary switch is detected within a second detection window after the second handshake signal is sent.

15. The control method of an isolated converter according to claim 14, wherein The start time of the second detection window is the second transmission time point; the second transmission time point is the time point at which the second handshake signal is transmitted; the end time of the second detection window is greater than the sum of the second transmission time point and the maximum allowable turn-on time of the primary switch.

16. An isolated converter, comprising: The isolated converter includes a control device for an isolated converter as described in any one of claims 1 to 10.

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