Control circuit of isolated switching converter and control method thereof
By designing control circuits in an isolated switch converter, we ensure that the synchronous rectifier tube is in a shutdown state before the main switch tube is turned on, solving the problem of the circuit through the primary and secondary side, and improving the safety performance and reliability of the equipment.
Patent Information
- Application Number
- CN202311708806.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-12
- Publication Date
- 2025-06-13
AI Technical Summary
Existing isolation switch converters are prone to problems of the primary and secondary circuit penetration, resulting in insufficient safety performance and reliability.
A control circuit is designed to ensure that the synchronous rectification tube is in the off state before the main switch tube is turned on, thereby avoiding the commonality between the primary and secondary edges.
It effectively prevents the penetration of the primary and secondary circuits from being passed through, and improves the safety performance and reliability of the isolated switch converter.
Smart Images
Figure CN120150488A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of electronic circuits, and particularly to a control circuit and a control method for an isolated switching converter. Background Art
[0002] With the rapid development of large-scale and very large-scale integrated circuits, miniaturized and highly efficient isolated switching converters are widely used in various power supply systems. The isolated switching converter generally includes a primary circuit and a secondary circuit. By controlling the on and off of the power switch in the primary circuit, a constant output of the secondary circuit is achieved. Moreover, during the operation of the isolated switching converter, it is necessary to interlock the drives of the power switch tube in the primary circuit and the synchronous rectifier tube in the secondary circuit to prevent the drives of the primary circuit and the secondary circuit from being common. However, in practical applications, for example, there may be a possibility of mis-conduction of the synchronous rectifier tube in the secondary circuit, resulting in the problem of common conduction between the primary circuit and the secondary circuit.
[0003] Therefore, it is necessary to provide a control circuit and a control method for preventing the penetration between the primary circuit and the secondary circuit to improve the safety performance and reliability of the isolated switching converter. Summary of the Invention
[0004] The purpose of the present invention is to provide a control circuit for an isolated switching converter to solve the problem that the existing isolated switching converter is prone to penetration between the primary circuit and the secondary circuit.
[0005] To solve the above technical problems, the present invention provides a control circuit for controlling an isolated switching converter, where the isolated switching converter includes a primary circuit, a secondary circuit, and a transformer coupled between the primary circuit and the secondary circuit; wherein, the control circuit includes: a primary controller having an output terminal electrically connected to the control terminal of the main switch tube in the primary circuit for outputting a control signal of the main switch tube; a primary controller having an output terminal electrically connected to the control terminal of the synchronous rectifier tube in the secondary circuit for outputting a control signal of the synchronous rectifier tube; wherein, after receiving an inquiry signal from the secondary controller, the primary controller sends a feedback signal to the secondary controller, and the secondary controller keeps the synchronous rectifier tube off according to the feedback signal, and the primary controller controls the main switch tube in the primary circuit to turn on after the synchronous rectifier tube is turned off.
[0006] Optionally, the secondary controller is used to receive the output voltage of the switching converter and send the inquiry signal when the output voltage of the switching converter is lower than a preset voltage.
[0007] Optionally, the secondary side controller is further configured to send a first indication signal to the primary side controller after controlling the synchronous rectifier tube to turn off according to the feedback signal, so as to indicate the primary side controller to control the main switch tube to turn on.
[0008] Optionally, the primary side controller is configured to control the main switch tube to turn on at a predetermined time after sending out the feedback signal, and the predetermined time is later than the turn-off time of the synchronous rectifier tube.
[0009] Optionally, the primary side controller is further configured to send a second indication signal when the main switch tube turns off, so as to indicate the secondary side controller to control the synchronous rectifier tube to turn on.
[0010] Optionally, the secondary side controller is further configured to detect the voltage signal of the secondary side winding, and control the synchronous rectifier tube to turn on when the voltage signal of the secondary side winding drops to a preset value when the main switch tube turns off.
[0011] Optionally, the secondary side controller is further configured to detect the secondary side current of the secondary side circuit, and control the synchronous rectifier tube to turn off when it detects that the secondary side current drops to a first preset current during the turn-on process of the synchronous rectifier tube.
[0012] Optionally, the secondary side controller is further configured to detect the output voltage of the switching converter in real time during the turn-on process of the synchronous rectifier tube, and send an inquiry signal for preparing to enter the next switching cycle to the primary side controller after the output voltage of the switching converter drops to a preset voltage, and control the synchronous rectifier tube to turn off after receiving the feedback signal from the primary side controller.
[0013] Optionally, the secondary side controller includes a first logic control module, a first sending module and a first receiving module. Wherein, the first output end of the first logic control module is electrically connected to the control end of the synchronous rectifier tube for providing a control signal to the synchronous rectifier tube; the second output end of the first logic control module is electrically connected to the first sending module for sending out the generated signal through the first sending module; and, the first input end of the first logic control module is electrically connected to the first receiving module for receiving a signal from the primary side controller through the first receiving module.
[0014] Optionally, the primary controller includes a second logic control module, a second receiving module, and a second transmitting module. Among them, the input end of the second logic control module is connected to the second receiving module and is configured to receive signals from the secondary controller through the second receiving module; the first output end of the second logic control module is electrically connected to the control end of the main switch tube and is configured to provide a control signal to the main switch tube; and the second output end of the second logic control module is electrically connected to the second transmitting module and is configured to transmit the generated signals through the second transmitting module.
[0015] Optionally, the control circuit further includes: at least one isolator, coupled between the primary controller and the secondary controller, configured to enable the signals of the secondary controller to be transmitted to the primary controller through the isolator, and the signals of the primary controller to be transmitted to the secondary controller through the isolator.
[0016] Optionally, a first isolator and a second isolator are provided in the control circuit. Both the first isolator and the second isolator are coupled between the primary controller and the secondary controller. The first isolator is configured to couple the signals from the secondary controller to the primary controller, and the second isolator is configured to couple the signals from the primary controller to the secondary controller.
[0017] The present invention also provides a control method for an isolated switch converter. The isolated switch converter includes a primary circuit, a secondary circuit, and a transformer coupled between the primary circuit and the secondary circuit. The control method includes: the secondary controller sending an interrogation signal to the primary controller; after receiving the interrogation signal, the primary controller sending a feedback signal to the secondary controller; the secondary controller receiving the feedback signal and providing a turn-off signal to the synchronous rectifier tube in the secondary circuit to control the synchronous rectifier tube to remain turned off; and after the synchronous rectifier tube is turned off, the primary controller providing a turn-on signal to the main switch tube in the primary circuit to control the main switch tube to turn on.
[0018] Optionally, the secondary controller receives the output voltage of the switch converter and sends the interrogation signal when the output voltage of the switch converter is lower than a preset voltage.
[0019] Optionally, after the secondary controller controls the synchronous rectifier tube to turn off according to the feedback signal, it further sends a first indication signal to the primary controller, and the primary controller controls the main switch tube to turn on according to the first indication signal.
[0020] Optionally, after a predetermined time from sending out the feedback signal, the primary controller provides a turn-on signal to the main switching transistor to control the main switching transistor to turn on, and the predetermined time is later than the turn-off time of the synchronous rectifier transistor.
[0021] Optionally, when the main switching transistor is turned off, the primary controller also sends a second indication signal, and the secondary controller provides a turn-on signal to the synchronous rectifier transistor according to the second indication signal to control the synchronous rectifier transistor to turn on.
[0022] Optionally, the secondary controller detects the voltage signal of the secondary winding, and when the voltage signal of the secondary winding drops to a preset value when the main switching transistor is turned off, provides a turn-on signal to the synchronous rectifier transistor to control the synchronous rectifier transistor to turn on.
[0023] Optionally, the secondary controller also detects the secondary current of the secondary circuit, and during the turn-on process of the synchronous rectifier transistor, when it detects that the secondary current drops to a first preset current, controls the synchronous rectifier transistor to turn off.
[0024] Optionally, during the turn-on process of the synchronous rectifier transistor, the secondary controller also real-time detects the output voltage of the switching converter, and after the output voltage of the switching converter drops to a preset voltage, sends an inquiry signal for preparing to enter the next switching cycle to the primary controller, and controls the synchronous rectifier transistor to turn off after receiving the feedback signal from the primary controller.
[0025] In the control circuit for an isolated switching converter provided by the present invention, before preparing to turn on the main switching transistor in the primary circuit, the secondary controller is preferentially used to send an inquiry signal to the primary controller, and when the primary controller confirms being in a preparation state, sends a feedback signal to the secondary controller, so that the secondary controller can control the synchronous rectifier transistor to be in an off state according to the feedback signal, and then the primary controller is used to control the main switching transistor to turn on. That is, in the control circuit and its control method provided by the present invention, when preparing to turn on the main switching transistor, through the information interaction between the primary side and the secondary side, it is ensured that after the synchronous rectifier transistor is turned off, the main switching transistor is then turned on, avoiding the problem of mis-conduction of the synchronous rectifier transistor when the main switching transistor is turned on, which may cause the penetration between the primary side and the secondary side, and effectively reducing the risk of common conduction between the primary side and the secondary side.
[0026] In addition, based on the control circuit provided by the present invention, in practical applications, a magnetic coupling isolator, a capacitive coupling isolator, a digital isolator, etc. can be selected as the isolator between the primary controller and the secondary controller, so as to use the isolator to realize the two-way communication between the primary side and the secondary side, which is beneficial to improving the response speed and reducing the system power consumption. Description of the Drawings
[0027] Figure 1Schematic diagram of an isolated switch converter coupled with a control circuit in an embodiment of the present invention.
[0028] Figure 2 Waveform diagram of key signals of an isolated switch converter coupled with a control circuit in an embodiment of the present invention in discontinuous conduction mode.
[0029] Figure 3 Waveform diagram of key signals of an isolated switch converter coupled with a control circuit in an embodiment of the present invention in continuous conduction mode.
[0030] Figure 4 Another waveform diagram of key signals of an isolated switch converter coupled with a control circuit in an embodiment of the present invention in continuous conduction mode. Detailed implementation manners
[0031] The following further details a control circuit and a control method of an isolated switch converter proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise scales, only for conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention. Additionally, it should be noted that the "time", "on-time length", and "on-time" referred to in this specification are all time periods, that is, the length of a period of time; "moment", "when...", and "turn-off moment" are all time points, that is, the moment when an event occurs; "valid level" and "high level" indicate that a level that can be detected and judged as valid indicates that a certain component or module performs corresponding actions; "invalid level" and "low level" indicate that a level that can be detected and judged as invalid or a level that cannot be detected indicates that a certain component or module performs corresponding actions; "signal" can represent some specific electrical / magnetic signals, which can be represented by specific waveforms, or can represent some information transmitted in a circuit, which can be represented by specific values.
[0032] Figure 1 Schematic diagram of an isolated switch converter coupled with a control circuit in an embodiment of the present invention. As Figure 1 shown, the isolated switch converter includes a primary circuit, a secondary circuit, and a transformer T1 coupled between the primary circuit and the secondary circuit and providing electrical isolation. Among them, the primary circuit and the secondary circuit are electrically isolated and are respectively connected to different grounding terminals. The transformer T1 includes a primary winding W1 and a secondary winding W2. The primary circuit is coupled to the primary winding W1 of the transformer T1, and the secondary circuit is coupled to the secondary winding W2 of the transformer T1.
[0033] Continue to refer to Figure 1As shown, the control circuit includes a primary controller 200 and a secondary controller 100. Among them, the primary controller 200 has an output terminal, and the output terminal of the primary controller 200 is electrically connected to the control terminal of the main switch tube G1 in the primary circuit, and is used to output the control signal PWM of the main switch tube G1 to control the switching state of the main switch tube G1. And, the secondary controller 100 has an output terminal, and the output terminal of the secondary controller 100 is electrically connected to the control terminal of the synchronous rectifier tube SR in the secondary circuit, and is used to output the control signal of the synchronous rectifier tube SR to control the switching state of the synchronous rectifier tube SR. That is, the primary controller 200 can be used to control the switching state of the main switch tube G1, and the secondary controller 100 can be used to control the switching state of the synchronous rectifier tube SR.
[0034] In one example, the primary circuit may include an input capacitor Cbus and a main switch tube G1. The first end of the input capacitor Cbus is coupled to the primary winding W1 of the transformer T1, and the second end of the input capacitor Cbus is connected to the ground terminal of the primary circuit; and, the main switch tube G1 can be, for example, a power switch tube, the drain of the power switch tube is connected to the primary winding W1 of the transformer T1, the source of the power switch tube is connected to the ground terminal of the primary circuit, and the gate of the power switch tube is connected to the primary controller 200 for receiving the control signal PWM of the main switch tube G1.
[0035] In one example, the secondary circuit may include a synchronous rectifier tube SR and an output capacitor Cout. The first end of the output capacitor Cout is coupled to the secondary winding W2 of the transformer T1 and is connected to the load, and the second end of the output capacitor Cout is connected to the ground terminal of the secondary circuit. The synchronous rectifier tube SR is, for example, a power switch tube, the drain of the power switch tube is connected to the secondary winding W2 of the transformer T1, the source of the power switch tube is connected to the ground terminal of the secondary circuit, and the gate of the power switch tube is connected to the secondary controller 100 for receiving the control signal of the synchronous rectifier tube SR.
[0036] In addition, the secondary controller 100 in this embodiment can also be coupled to the secondary winding W2 of the transformer T1 for obtaining the voltage signal Forward of the secondary winding W2 of the transformer T1. In a specific example, the secondary controller 100 can sense the voltage signal Forward of the secondary winding W2 to reflect the switching state of the main switch tube G1 in the primary circuit. For example, when the voltage signal Forward of the secondary winding W2 drops to a preset value, it means that the main switch tube G1 is in the off state. Further, the secondary controller 100 can also be used to detect the output voltage Vout of the switching converter. In an optional solution, the time node for the switching converter to enter a new switching cycle can be controlled according to the output voltage Vout. For example, when the output voltage Vout is lower than the preset voltage, it indicates that the circuit is ready to enter the next switching cycle.
[0037] In the control circuit provided by this embodiment, the primary controller 200 and the secondary controller 100 perform information interaction to ensure that the synchronous rectifier SR is in the off state before the main switch tube G1 is turned on; similarly, it can ensure that the synchronous rectifier SR is turned on after the main switch tube G1 is turned off, effectively solving the problem common to the primary side and the secondary side.
[0038] Specifically, when preparing to enter a new switching cycle, the primary controller 200 is used to receive the inquiry signal request1_0 sent from the secondary controller 100 and start a self-detection operation to enter a preparatory state (the self-detection operation may include, for example: checking whether the main switch tube G1 in the primary circuit is turned off to ensure that the main switch tube G1 is in the off state; and ensuring that each module in the primary controller 200 is in a preparatory state, etc.). For example Figures 2 - 4 as shown in, at time t1, the secondary controller 100 sends the inquiry signal request1_0 ( Figures 2 - 4 the first pulse of the Request1 waveform shown in, and the following signals such as request1_1 are similarly postponed) to the primary controller 200.
[0039] In an optional solution, the secondary controller 100 is further used to receive the output voltage Vout of the switching converter and send the inquiry signal request1_0 when the output voltage Vout of the switching converter is lower than a preset voltage to prepare to enter a new switching cycle, so as to ensure the stability of the output voltage Vout.
[0040] Moreover, the primary controller 200 can control the main switch tube G1 in the primary circuit to turn on after confirming that the synchronous rectifier SR is turned off, so as to enter a new switching cycle. That is, the process of the primary controller 200 controlling the main switch tube G1 in the primary circuit to turn on to enter a new switching cycle may include: after receiving the inquiry signal request1_0, the primary controller 200 starts a self-detection operation, and after the self-detection operation is completed, sends a feedback signal request2_0 to the secondary controller 100 to indicate that the primary controller 200 has entered the preparatory state; the secondary controller 100 controls the synchronous rectifier SR to turn off according to the feedback signal request2_0 (the secondary controller 100 can specifically provide a turn-off signal to the synchronous rectifier SR according to the feedback signal request2_0. At this time, if the current state of the synchronous rectifier SR is the on state, the synchronous rectifier SR is controlled to turn off under this turn-off signal; if the current state of the synchronous rectifier SR should be the off state, the synchronous rectifier SR can be ensured to remain off under this turn-off signal), and then, the primary controller 200 controls the main switch tube G1 in the primary circuit to turn on. For example Figure 2As shown in the figure, at time t2, the primary controller 200 completes the self-detection operation and sends a feedback signal request2_0 to the secondary controller 100. The secondary controller 100 provides a turn-off signal to the synchronous rectifier SR to ensure that the synchronous rectifier SR remains off. Also, Figure 3 and Figure 4 In the example of, at time t2, the primary controller 200 completes the self-detection operation and sends a feedback signal request2_0 ( Figures 2 - 4 the first pulse of the Request2 waveform shown in, and the signals such as request2_1 are similarly extended in sequence), and the secondary controller 100 controls the synchronous rectifier SR to turn off according to the feedback signal request2_0.
[0041] Among them, the primary controller 200 ensures a way to control the main switch G1 to turn on after the synchronous rectifier SR is turned off. For specific examples, please refer to the following.
[0042] In the first example, after the secondary controller 100 ensures that the synchronous rectifier SR remains off, it is also used to send a first indication signal request1_1 to the primary controller 200 to indicate that the primary controller 200 controls the main switch G1 in the primary circuit to turn on according to the first indication signal request1_1. That is, in this example, the primary controller 200 controls the turn-on timing of the main switch G1 based on the first indication signal request1_1. When the primary controller 200 receives the first indication signal request1_1, it means that the synchronous rectifier SR has been confirmed to be off. At this time, controlling the main switch G1 to turn on can effectively avoid the problem of commonality between the primary and secondary sides. For example Figure 2 and Figure 3 As shown in, at time t3, after the secondary controller 100 ensures that the synchronous rectifier SR remains off, it sends a first indication signal request1_1 to the primary controller 200, so that the primary controller 200 controls the main switch G1 in the primary circuit to turn on according to the first indication signal request1_1.
[0043] It should be noted that when the secondary controller 100 generates the inquiry signal request1_0, it can generate the inquiry signal request1_0 based on the output voltage Vout of the switching converter being lower than the preset voltage. On this basis, after the secondary controller 100 receives the feedback signal request2_0 and turns off the synchronous rectifier SR, it can directly send the first indication signal request1_1.
[0044] In the second example, the primary controller 200 can control the main switching transistor G1 in the primary circuit to turn on at a predetermined time after sending out the feedback signal request2_0. The predetermined time mentioned here is later than the turn-off time of the synchronous rectifier SR, so as to ensure that the main switching transistor G1 is turned on after the synchronous rectifier SR is turned off. That is, in this example, the primary controller 200 reserves the time for the secondary controller 100 to control the synchronous rectifier SR to turn off after sending out the feedback signal request2_0, and then controls the main switching transistor G1 to turn on, which can also effectively avoid the problem of commonality between the primary side and the secondary side. For example Figure 4 As shown in, at time t1, the primary controller 200 sends out the feedback signal request2_0, and controls the main switching transistor G1 to turn on until time t3, while the synchronous rectifier SR turns off at a time earlier than t3 (i.e., time t2).
[0045] Furthermore, after the main switching transistor G1 is turned on, the primary current Ipri in the primary circuit can be gradually increased. In a specific example, after the primary current Ipri rises to a second preset current, the primary controller 200 can control the main switching transistor G1 to turn off. And, after confirming that the main switching transistor G1 is turned off, the secondary controller 100 can control the synchronous rectifier SR in the secondary circuit to turn on. For example Figures 2 - 4 As shown in, at time t4, the primary current Ipri rises to the second preset current, thereby controlling the main switching transistor G1 to turn off and controlling the synchronous rectifier SR to turn on at time t5.
[0046] Among them, the way for the secondary controller 100 to ensure that it can control the synchronous rectifier SR to turn on after the main switching transistor G1 is turned off can be specifically referred to the following examples.
[0047] In one example, the primary controller 200 is further configured to send a second indication signal request2_1 when the main switching transistor G1 is turned off, to instruct the secondary controller 100 to control the synchronous rectifier SR to turn on after receiving the second indication signal request2_1. That is, in this example, the secondary controller 100 controls the turn-on timing of the synchronous rectifier SR based on the second indication signal request2_1. When the secondary controller 100 receives the second indication signal request2_1, it means that the main switching transistor G1 has been confirmed to be turned off. At this time, controlling the synchronous rectifier SR to turn on can effectively avoid the problem of commonality between the primary side and the secondary side. For example Figures 2 - 4 As shown in, at time t4, the primary current Ipri rises to the second preset current, thereby controlling the main switching transistor G1 to turn off and sending the second indication signal request2_1. The secondary controller 100 can delay until time t5 to control the synchronous rectifier SR to turn on.
[0048] In another example, the secondary side controller 100 can also detect the voltage signal Forward of the secondary side winding W2, and when the voltage signal Forward of the secondary side winding W2 drops to a preset value due to the turn-off of the main switch tube G1, control the synchronous rectifier tube SR to turn on. That is, in this example, the secondary side controller 100 independently detects the voltage signal Forward of the secondary side winding W2. When the voltage signal Forward of the secondary side winding W2 drops to the preset value, it means that the main switch tube G1 has been turned off. At this time, controlling the synchronous rectifier tube SR to turn on can also effectively avoid the problem of commonality between the primary side and the secondary side.
[0049] In a specific example, after the synchronous rectifier tube SR is turned on, the secondary side controller 100 can still detect the output voltage Vout of the switching converter in real time, and determine whether to prepare to enter the next switching cycle according to the output voltage Vout of the switching converter. When the output voltage Vout of the switching converter is lower than the preset voltage, the secondary side controller 100 sends an interrogation signal request1_0 to the primary side controller 200, and after receiving the feedback signal request2_0 from the primary side controller 200, provides a turn-off signal to the synchronous rectifier tube SR to prepare to enter the next switching cycle.
[0050] It should be noted that the control circuit provided by the present disclosure can be applied to a controlled isolated switching converter in continuous conduction mode, and can also be applied to a controlled isolated switching converter in discontinuous conduction mode.
[0051] Continue to refer to Figure 1 , and a specific structure of one of the control circuits will be described in detail.
[0052] As Figure 1 shown, the secondary side controller 100 may specifically include a first logic control module, a first sending module, and a first receiving module.
[0053] Among them, the first output terminal of the first logic control module is electrically connected to the control terminal of the synchronous rectifier tube SR, and is used to provide a control signal to the synchronous rectifier tube SR. The second output terminal of the first logic control module is electrically connected to the first sending module, and is used to send out the generated signal through the first sending module. For example, the first logic control module can generate an interrogation signal request1_0 and send it out through the first sending module.
[0054] The first input terminal of the first logic control module is electrically connected to the first receiving module, and is used to receive the signal request2 from the primary controller 200 through the first receiving module. For example, the feedback signal request2_0 from the primary controller 200 can be received through the first receiving module, so that the first logic control module provides a turn-off signal to the synchronous rectifier tube SR after receiving the feedback signal request2_0 to control the synchronous rectifier tube SR to turn off; and, the second indication signal request2_1 from the primary controller 200 can also be received through the first receiving module, so that the first logic control module can generate a turn-on signal for the synchronous rectifier tube SR according to the second indication signal request2_1.
[0055] In an optional solution, after the first logic control module ensures that the synchronous rectifier tube SR remains off according to the feedback signal request2_0, it can also be used to generate a first indication signal request1_1 and send it to the primary controller 200 through the first sending module to instruct the primary controller 200 to control the main switch tube G1 to turn on.
[0056] In a further solution, the first logic control module further has a second input terminal, and its second input terminal can be electrically connected to the output terminal of the secondary winding W2 of the transformer T1 for obtaining the voltage signal Forward of the secondary winding W2. In a specific example, the first logic control module can be used to generate a turn-on signal for the synchronous rectifier tube SR according to the voltage signal Forward. For example, the turn-on signal for the synchronous rectifier tube SR can be generated after detecting that the voltage signal Forward drops to a preset value after the main switch tube G1 turns off. In this embodiment, the first logic control module further has a third input terminal, and its third input terminal is further used to receive the output voltage Vout of the switching converter. In an example, the first logic control module can use the output voltage Vout as the timing for generating the inquiry signal request1_0. For example, the inquiry signal request1_0 can be generated when the output voltage Vout is lower than the preset voltage.
[0057] Continue to refer to Figure 1 As shown, the primary controller 200 specifically includes a second logic control module, a second receiving module, and a second sending module.
[0058] Among them, the input end of the second logic control module is connected to the second receiving module, and is used to receive the signal request1 from the secondary side controller 100 through the second receiving module. For example, the inquiry signal request1_0, the first indication signal request1_1, etc. from the secondary side controller 100 can be received through the second receiving module. The first output end of the second logic control module is electrically connected to the control end of the main switch tube G1, and is used to provide the control signal PWM to the main switch tube G1. Among them, the second logic control module can provide a turn-on signal to the main switch tube G1 after receiving the first indication signal request1_1, for example. The second output end of the second logic control module is electrically connected to the second sending module, and is used to send the generated information to the second sending module and send it out by using the second sending module. For example, the second logic control module can generate a feedback signal request2_0 after completing the self-detection operation and send it out by this second sending module; and, the second logic control module can generate a second indication signal request2_1 after turning off the main switch tube G1 and send it out by this second sending module.
[0059] In a specific example, the control circuit further includes an isolator. The isolator is coupled between the primary side controller 200 and the secondary side controller 100, and is used to isolate the primary side controller 200 and the secondary side controller 100, and enable the secondary side controller 100 and the primary side controller 200 to achieve information intercommunication through the isolator. That is, the signal of the secondary side controller 100 can be transmitted to the primary side controller 200 through the isolator, and the signal of the primary side controller 200 can be transmitted to the secondary side controller 100 through the isolator.
[0060] In one example, the control circuit can be provided with only one isolator, and both the primary side controller 200 and the secondary side controller 100 achieve information intercommunication through the same isolator. In another example, for example Figure 1 As shown, the control circuit can be provided with a first isolator and a second isolator. The first isolator is used to couple the signal request1 from the secondary side controller 100 to the primary side controller 200, and the second isolator is used to couple the signal request2 from the primary side controller 200 to the secondary side controller 100. It should be recognized that in other examples, only one isolator can also be provided, and this isolator can be multiplexed in different time periods to achieve the signal transmission from the secondary side controller 100 to the primary side controller 200 and the signal transmission from the primary side controller 200 to the secondary side controller 100. Among them, the first isolator and the second isolator are, for example, magnetic coupling isolators, capacitive coupling isolators, or digital isolators, etc.
[0061] Based on the control circuit described above, the control method of the isolated switch converter provided by the present invention will be further described in detail by listing three examples below.
[0062] <Example 1>
[0063] In this example, taking the operation of an isolated switch converter in discontinuous conduction mode (DCM) as an example, the process of entering a complete switching cycle is explained. Specifically, it can be based on Figure 1 combined with Figure 2 the key signal waveform diagram shown. It should be noted that Figure 2 Request1 in Figure 2 is used to represent the signal from the secondary controller 100, and
[0064] At time t1, the secondary controller 100 can send an interrogation signal request1_0 to the primary controller 200 through the first isolator to prepare to enter a new switching cycle. As described above, the secondary controller 100 can send the interrogation signal request1_0 when the output signal Vout of the switch converter it detects drops to a preset voltage. Also, after receiving the interrogation signal request1_0, the primary controller 200 performs a self-detection operation to enter a preparatory state.
[0065] At time t2, the primary controller 200 completes the self-detection operation and is in a preparatory state. At this time, it can send a feedback signal request2_0 to the secondary controller 100 through the second isolator; after receiving the feedback signal request2_0, the secondary controller 100 checks whether the synchronous rectifier tube SR is off and ensures that the synchronous rectifier tube SR is in the off state. In this embodiment, after receiving the feedback signal request2_0, the secondary controller 100 still maintains the off state of the synchronous rectifier tube SR.
[0066] At time t3, after the secondary controller 100 ensures that the synchronous rectifier tube SR is in the off state, it sends a first indication signal request1_1 to the primary controller 200 through the first isolator to instruct the primary controller 200 to control the main switch tube G1 to turn on. In a specific example, the secondary controller 100 can directly send the first indication signal request1_1 to the primary controller 200 after ensuring that the synchronous rectifier tube SR is in the off state.
[0067] At time t4, as the main switch tube G1 turns on, the primary current Ipir of the primary circuit gradually increases. When the primary current Ipir increases to the second preset current, the primary controller 200 controls the main switch tube G1 to turn off and sends a second indication signal request2_1 through the second isolator.
[0068] At time t5, after the secondary controller 100 receives the second indication signal request2_1 indicating that the main switch tube G1 has turned off, it controls the synchronous rectifier tube SR to turn on.
[0069] At time t6, as the main switch G1 turns off and the synchronous rectifier SR turns on, the secondary current Isec in the secondary circuit gradually decreases. After the demagnetization of the secondary circuit is completed, the secondary controller 100 controls the synchronous rectifier SR to turn off.
[0070] In this way, one switching cycle is completed. Also, when the output voltage Vout of the switching converter is lower than the preset voltage, the secondary controller 100 can continue to send an inquiry signal request1_0 to the primary controller 200 to prepare for entering the next switching cycle.
[0071] <Example 2>
[0072] In this example, taking the operation of an isolated switching converter in continuous conduction mode (CCM) as an example, the process of entering a complete switching cycle is explained. Specifically, it can be combined with Figure 1 on the basis of Figure 3 the key signal waveform diagram shown. It should be noted that Figure 3 Request1 in Figure 3 is used to represent the signal from the secondary controller 100, and
[0073] At time t1, the secondary controller 100 can send an inquiry signal request1_0 to the primary controller 200 through the first isolator to prepare for entering a new switching cycle. In this embodiment, the secondary controller 100 can send the inquiry signal request1_0 when it detects that the output signal Vout of the switching converter drops to the preset voltage. Also, after receiving the inquiry signal request1_0, the primary controller 200 performs a self-detection operation to enter the standby state.
[0074] At time t2, the primary controller 200 completes the self-detection operation and is in the standby state. At this time, it can send a feedback signal request2_0 to the secondary controller 100 through the second isolator, and the secondary controller 100 turns off the synchronous rectifier SR according to the feedback signal request2_0.
[0075] At time t3, after turning off the synchronous rectifier SR, the secondary controller 100 sends a first indication signal request1_1 to the primary controller 200 through the first isolator to instruct the primary controller 200 to control the main switch G1 to turn on.
[0076] At time t4, with the turn-on of the main switch G1, the primary current Ipir of the primary circuit gradually increases. When the primary current Ipir increases to the second preset current, the primary controller 200 controls the main switch G1 to turn off and sends a second indication signal request2_1 through the second isolator.
[0077] At time t5, after receiving the second indication signal request2_1, the secondary controller 100 controls the synchronous rectifier SR to conduct.
[0078] At time t6, during the turn-on process of the synchronous rectifier SR, the secondary controller 100 also continuously detects the output voltage Vout of the switching converter and sends an inquiry signal request1_0 to prepare to enter the next switching cycle when the output voltage Vout drops to the preset voltage. After receiving this inquiry signal request1_0, the primary controller 200 performs a self-detection operation.
[0079] At time t7, the primary controller 200 completes the self-detection operation and is in a standby state, and sends a feedback signal request2_0 to the secondary controller 100. The secondary controller 100 receives the feedback signal request2_0 and turns off the synchronous rectifier SR. Thus, the current switching cycle ends, and then enters the next switching cycle.
[0080] <Example 3>
[0081] The difference from Example 1 and Example 2 is that the turn-on timing of the main switch G1 in this example is to turn on at a predetermined time after the primary controller 200 sends out the feedback signal request2_0; while the turn-on timing of the main switch G1 in Example 1 and Example 2 is to turn on after the first indication signal request1_1 sent out by the secondary controller 100.
[0082] Specifically, it can be combined on the basis of Figure 1 with the key signal waveform diagram shown in Figure 4 It should be noted that Figure 4 still takes the continuous conduction mode (CCM) as an example for illustration, and Request1 in it is used to represent the signal from the secondary controller 100, Figure 4 and Request2 in
[0083] At time t1 and time t2, the same as Figure 3The example shown is similar. That is, the secondary side controller 100 sends an interrogation signal request1_0 to the primary side controller 200 through a first isolator to prepare to enter a new switching cycle. Among them, the secondary side controller 100 specifically sends the interrogation signal request1_0 when the output signal Vout of the switching converter it detects drops to a preset voltage. And, after receiving the interrogation signal request1_0, the primary side controller 200 performs a self-detection operation to enter a preparation state, and sends a feedback signal request2_0 to the secondary side controller 100 through a second isolator. The secondary side controller 100 turns off the synchronous rectifier tube SR according to the feedback signal request2_0.
[0084] At time t3, after the primary side controller 200 delays for a predetermined time after sending the feedback signal request2_0, it controls the main switching tube G1 to conduct. It should be recognized that the predetermined time after sending the feedback signal request2_0 is later than the turn-off time of the synchronous rectifier tube SR, specifically as Figure 4 shown, the synchronous rectifier tube SR turns off at time t2, and the main switching tube G1 turns on at time t3.
[0085] At time t4 and time t5, similar to the Figure 3 example shown, that is, as the primary side current Ipir of the primary side circuit gradually increases, and when the primary side current Ipir increases to a second preset current, the primary side controller 200 controls the main switching tube G1 to turn off, and sends a second indication signal request2_1 through the second isolator. Then, after receiving the second indication signal request2_1, the secondary side controller 100 controls the synchronous rectifier tube SR to conduct.
[0086] After that, repeat the above-mentioned time t1 and time t2 to end the current switching cycle and prepare to enter the next switching cycle.
[0087] It should be noted that the various embodiments in this specification are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. The systems disclosed in the embodiments correspond to the methods disclosed in the embodiments, and the relevant parts can be referred to each other. Although the present invention has been disclosed above with preferred embodiments, the above embodiments are not intended to limit the present invention. For any person skilled in the art, without departing from the scope of the technical solution of the present invention, many possible changes and modifications can be made to the technical solution of the present invention by using the above-disclosed technical content, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belong to the scope of protection of the technical solution of the present invention.
[0088] It should also be understood that, unless otherwise specified or indicated, the terms "first", "second", "third", etc. in the specification are only used to distinguish the various components, elements, steps, etc. in the specification, rather than to represent the logical relationship or sequential relationship, etc. between the various components, elements, steps. In addition, it should also be recognized that the singular forms "a" and "an" used herein and in the appended claims include plural referents unless the context clearly dictates otherwise. For example, a reference to "a step" or "a device" means a reference to one or more steps or devices and may include sub-steps as well as sub-devices. All conjunctions used should be understood in their broadest sense.
Claims
1. A control circuit for controlling an isolated switching converter, the isolated switching converter including a primary circuit, a secondary circuit, and a transformer coupled between the primary circuit and the secondary circuit, characterized in that, the control circuit includes: a primary controller having an output terminal electrically connected to a control terminal of a main switch tube in the primary circuit for outputting a control signal of the main switch tube; a secondary controller having an output terminal electrically connected to a control terminal of a synchronous rectifier tube in the secondary circuit for outputting a control signal of the synchronous rectifier tube; wherein, after receiving an inquiry signal from the secondary controller, the primary controller detects the state of the main switch tube, and sends a feedback signal to the secondary controller when the main switch tube is turned off; the secondary controller controls the synchronous rectifier tube to turn off according to the feedback signal, and the primary controller controls the main switch tube in the primary circuit to turn on after the synchronous rectifier tube is turned off.
2. The control circuit according to claim 1, characterized in that, the secondary controller is configured to receive an output voltage of the switching converter, and send the inquiry signal when the output voltage of the switching converter is lower than a preset voltage.
3. The control circuit according to claim 1, characterized in that, after controlling the synchronous rectifier tube to turn off according to the feedback signal, the secondary controller is further configured to send a first indication signal to the primary controller to indicate the primary controller to control the main switch tube to turn on.
4. The control circuit according to claim 1, characterized in that, the primary controller is configured to control the main switch tube to turn on at a predetermined time after sending out the feedback signal, and the predetermined time is later than the turn-off time of the synchronous rectifier tube.
5. The control circuit according to claim 1, characterized in that, when the main switch tube is turned off, the primary controller is further configured to send a second indication signal to indicate the secondary controller to control the synchronous rectifier tube to turn on.
6. The control circuit according to claim 1, characterized in that, the secondary controller is further configured to detect a voltage signal of a secondary winding of the transformer, and control the synchronous rectifier tube to turn on when the voltage signal of the secondary winding drops to a preset value when the main switch tube is turned off.
7. The control circuit according to claim 1, characterized in that, the secondary controller is further configured to detect a secondary current of the secondary circuit, and control the synchronous rectifier tube to turn off when it detects that the secondary current drops to a first preset current during the turn-on process of the synchronous rectifier tube.
8. The control circuit according to claim 1, characterized in that, the secondary controller includes a first logic control module, a first sending module, and a first receiving module; wherein, a first output terminal of the first logic control module is electrically connected to a control terminal of the synchronous rectifier tube for providing a control signal to the synchronous rectifier tube; a second output terminal of the first logic control module is electrically connected to the first sending module for sending the generated signal to the primary controller through the first sending module; and, The first input terminal of the first logic control module is electrically connected to the first receiving module, and is used to receive a signal from the primary controller through the first receiving module.
9. The control circuit according to claim 1, wherein, the primary controller includes a second logic control module, a second receiving module, and a second transmitting module; wherein, the input terminal of the second logic control module is connected to the second receiving module, and is used to receive a signal from the secondary controller through the second receiving module; the first output terminal of the second logic control module is electrically connected to the control terminal of the main switch tube, and is used to provide a control signal to the main switch tube; and, the second output terminal of the second logic control module is electrically connected to the second transmitting module, and is used to transmit the generated signal to the secondary controller through the second transmitting module.
10. The control circuit according to claim 1, wherein, the control circuit further includes: an isolator, coupled between the primary controller and the secondary controller, and is used to enable the signals of the secondary controller and the primary controller to be transmitted to each other through the isolator.
11. The control circuit according to claim 1, wherein, a first isolator and a second isolator are provided in the control circuit, both the first isolator and the second isolator are coupled between the primary controller and the secondary controller, the first isolator is used to couple the signal from the secondary controller to the primary controller, and the second isolator is used to couple the signal from the primary controller to the secondary controller.
12. A control method for an isolated switch converter, the isolated switch converter includes a primary circuit, a secondary circuit, and a transformer coupled between the primary circuit and the secondary circuit, wherein, the control method includes: sending an interrogation signal from the secondary controller to the primary controller; after the primary controller receives the interrogation signal, detecting the state of the main switch tube, and sending a feedback signal to the secondary controller when the main switch tube is turned off; the secondary controller receives the feedback signal, and provides a turn-off signal to the synchronous rectifier tube in the secondary circuit to control the synchronous rectifier tube to turn off; and, after the synchronous rectifier tube is turned off, the primary controller provides a turn-on signal to the main switch tube in the primary circuit to control the main switch tube to turn on.
13. The control method according to claim 12, wherein, the secondary controller receives the output voltage of the switch converter, and sends the interrogation signal when the output voltage of the switch converter is lower than a preset voltage.
14. The control method according to claim 12, wherein, after the secondary controller controls the synchronous rectifier tube to turn off according to the feedback signal, it further sends a first indication signal to the primary controller, and the primary controller controls the main switch tube to turn on according to the first indication signal.
15. The control method according to claim 12, wherein, After a predetermined time after sending out the feedback signal, the primary controller provides a turn-on signal to the main switch to control the turn-on of the main switch, and the predetermined time is later than the turn-off time of the synchronous rectifier tube.
16. The control method according to claim 12, wherein, when the main switch is turned off, the primary controller also sends a second indication signal, and the secondary controller provides a turn-on signal to the synchronous rectifier tube according to the second indication signal to control the turn-on of the synchronous rectifier tube.
17. The control method according to claim 12, wherein, the secondary controller detects the voltage signal of the secondary winding of the transformer, and when the voltage signal of the secondary winding drops to a preset value when the main switch is turned off, provides a turn-on signal to the synchronous rectifier tube to control the turn-on of the synchronous rectifier tube.
18. The control method according to claim 12, wherein, the secondary controller also detects the secondary current of the secondary circuit, and during the turn-on process of the synchronous rectifier tube, when it detects that the secondary current drops to a first preset current, provides a turn-off signal to the synchronous rectifier tube in the secondary circuit to control the turn-off of the synchronous rectifier tube.
19. An isolated switch converter, wherein, it includes the control circuit according to any one of claims 1-11.