Flyback converter topology circuit and control method and related control device thereof
By using bidirectional working switches and triangular carrier modulation technologies in flyback converters, zero voltage activation of the primary switch is solved, and the switching tube is high energy loss in flyback converters is extended, and the equipment life is reduced and maintenance is reduced. cost.
Patent Information
- Application Number
- CN202411397762.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-08
- Publication Date
- 2025-01-10
AI Technical Summary
In flyback converters, it is difficult to switch the switch tube under zero voltage or zero current conditions, resulting in large energy loss, high heat loss and high maintenance costs.
A bidirectional working switch is used as a secondary side switch, and the current and inductor storage energy is monitored in real time, the dead time range is determined, and the switching state of the primary and secondary side switches is controlled by triangular carrier modulation to achieve zero voltage activation of the primary side switch.
It reduces the stress and energy loss of the switch tube during the switching process, extends the service life of the flyback converter, reduces the circuit maintenance cost, and improves efficiency.
Smart Images
Figure CN119298674A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of electronic circuits, and in particular to a flyback converter topology circuit, a control method thereof, and a related control device. Background Art
[0002] With the continuous development of electronic technology, switching power supplies are increasingly used in various electronic devices. In switching power supplies, flyback converters are a common topology structure that is widely used because of their simple structure and low cost.
[0003] Soft switching technology is a technology that improves power efficiency by optimizing switching action and reducing energy loss during the switching process. Ideally, soft switching enables the switch tube to switch under zero voltage or zero current conditions, thereby greatly reducing switching losses. At present, in conventional flyback converters, diodes are usually used as switch tubes, and the switching action of the switch tube is driven by software control signals. Since the diode has a forward voltage drop when it is forward-conducted, it is difficult for the switch tube in the flyback converter to switch under ideal zero voltage or zero current conditions. The energy loss during the switching process is large, the stress that the switch tube needs to bear and the resulting heat loss are also large, the switch tube is easily damaged, and the maintenance cost of the circuit is high.
[0004] Therefore, how to reduce the stress borne by the switch tube in the flyback converter during the switching process becomes a problem that needs to be solved. Summary of the invention
[0005] Based on the above problems, the present application provides a flyback converter topology circuit and a control method and a related control device, which can reduce the stress borne by the switch tube in the flyback converter during the switching process.
[0006] The embodiments of the present application disclose the following technical solutions:
[0007] In a first aspect, an embodiment of the present application provides a flyback converter topology circuit, the circuit comprising: a first inductor, a primary switch, a second inductor and a secondary switch;
[0008] The secondary side switch is a bidirectional working switch;
[0009] The first inductor and the primary switch are connected in series to form a first loop; the second inductor and the secondary switch are connected in series to form a second loop; the first inductor and the second inductor share the same iron core.
[0010] Optionally, the circuit further includes: a first capacitor connected in parallel to both ends of the primary switch.
[0011] Optionally, the circuit further includes: a first output capacitor connected in parallel across the first inductor, and a second output capacitor connected in parallel across the second inductor.
[0012] In a second aspect, an embodiment of the present application provides a method for controlling a flyback converter, the method being used to control the flyback converter topology circuit described in any one of the embodiments of the first aspect, the method comprising:
[0013] Real-time monitoring of a first current in the first loop and a second current in the second loop;
[0014] Based on the first current and the second current, determining a dead time range in which both the primary switch and the secondary switch are turned off; the dead time range includes: a first dead time range from the moment when the secondary switch is turned off to the moment when the energy stored in the second inductor is completely consumed, and a second dead time range from the moment when the primary switch is turned off to the moment when the second current reaches a maximum current;
[0015] Based on the dead time range, the switching states of the primary switch and the secondary switch are controlled by triangular carrier modulation.
[0016] Optionally, determining a dead time range in which both the primary switch and the secondary switch are turned off based on the first current and the second current includes:
[0017] Calculating the energy stored in the second inductor during the secondary switch turning on process based on the second maximum reverse current and the inductance value of the second inductor;
[0018] Based on the energy stored in the second inductor and the first maximum reverse current, calculate the moment when the energy stored in the second inductor is completely consumed;
[0019] The time interval from the moment when the secondary switch is turned off to the moment when the energy stored in the second inductor is completely consumed is determined as the first dead time range.
[0020] Optionally, controlling the switching states of the primary switch and the secondary switch based on the dead time range and triangular carrier modulation includes:
[0021] When the secondary switch is turned on, if the second current reaches a second maximum reverse current, controlling the secondary switch to be turned off;
[0022] When both the primary switch and the secondary switch are turned off, if the first current reaches a preset reference current, the primary switch is controlled to be turned on outside the dead time range; the reference current is: the current in the first loop when the energy stored in the second inductor is completely consumed;
[0023] When the primary switch is turned on, if the first current reaches a first maximum current, controlling the primary switch to be turned off;
[0024] In a case where both the primary switch and the secondary switch are turned off, if the second current reaches a second maximum current, then outside the dead time range, the secondary switch is controlled to be turned on.
[0025] Optionally, controlling the primary switch to turn on includes:
[0026] In a time interval from when the energy stored in the second inductor is completely consumed to when the first current reaches a zero-crossing point, the primary switch is controlled to be turned on.
[0027] In a third aspect, an embodiment of the present application provides a control device for a flyback converter, the device being used to control the flyback converter topology circuit described in any one of the embodiments of the first aspect, the device comprising: a monitoring module, a determination module and a control module;
[0028] The monitoring module is used to monitor the first current in the first loop and the second current in the second loop in real time;
[0029] The determination module is used to determine a dead time range in which both the primary switch and the secondary switch are turned off based on the first current and the second current; the dead time range includes: from the time when the primary switch is turned off to the time when the second current reaches the maximum current, and from the time when the secondary switch is turned off to the time when the energy stored in the second inductor is completely consumed;
[0030] The control module is used to control the switching states of the primary switch and the secondary switch through triangular carrier modulation based on the dead time range.
[0031] In a fourth aspect, an embodiment of the present application provides a control device for a flyback converter, the device being used to control the flyback converter topology circuit described in any one of the implementations of the first aspect, the device comprising: a memory and a processor;
[0032] The memory is used to store program codes and transmit the program codes to the processor;
[0033] The processor is used to execute the steps of the flyback converter control method described in any implementation of the second aspect according to the instructions in the program code.
[0034] Compared with the prior art, this application has the following beneficial effects:
[0035] The embodiment of the present application provides a flyback converter topology circuit, which includes: a first inductor, a primary switch, a second inductor and a secondary switch; wherein the secondary switch is a bidirectional working switch; the first inductor and the primary switch are connected in series to form a first loop; the second inductor and the secondary switch are connected in series to form a second loop; the first inductor and the second inductor are connected to the same iron core. Thus, by using a bidirectional working switch as a secondary switch, it can be maintained in a reverse conduction state for a period of time, so that it can be controlled to turn on after the primary switch voltage drops to 0, realizing zero voltage turn-on of the primary switch, reducing the stress that the switch tube needs to bear and the energy loss generated during the switching process, extending the service life of the flyback converter, reducing the circuit maintenance cost, and improving the efficiency of the flyback converter. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0037] Figure 1 A flyback converter topology circuit structure diagram provided in an embodiment of the present application;
[0038] Figure 2 Another flyback converter topology circuit structure diagram provided in an embodiment of the present application;
[0039] Figure 3 A flow chart of a control method for a flyback converter provided in an embodiment of the present application;
[0040] Figure 4 A control timing diagram of a flyback converter provided in an embodiment of the present application;
[0041] Figure 5 A schematic diagram of a triangular carrier control principle of a flyback converter provided in an embodiment of the present application;
[0042] Figure 6 A schematic diagram of a control device for a flyback converter provided in an embodiment of the present application;
[0043] Figure 7 A structural diagram of a control device of a flyback converter provided in an embodiment of the present application. DETAILED DESCRIPTION
[0044] The flyback converter topology circuit, control method and related control device provided in the present application can be used in the field of electronic circuits. The above is only an example and does not limit the application field of the flyback converter topology circuit, control method and related control device provided in the present application.
[0045] The terms "first", "second", "third" and "fourth" etc. in the specification, claims and drawings of this application are used to distinguish different objects rather than to limit a specific order.
[0046] In the embodiments of the present application, the words "as an example" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "as an example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the words "as an example" or "for example" is intended to present the relevant concepts in a specific way.
[0047] The terms used in the implementation section of this application are only used to explain the specific embodiments of this application and are not intended to limit this application.
[0048] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0049] See also Figure 1 , which is a structure diagram of a flyback converter topology circuit provided in an embodiment of the present application, and the circuit includes: a first inductor L1, a primary switch Q1, a second inductor L2 and a secondary switch Q2.
[0050] The first inductor L1 and the primary switch Q1 are connected in series to form a first loop; the second inductor L2 and the secondary switch Q2 are connected in series to form a second loop; the first inductor L1 and the second inductor L2 share the same iron core. The number of turns of the first inductor L1 is N1, and the number of turns of the second inductor L2 is N2.
[0051] The secondary switch Q2 is a bidirectional working switch, for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor). Therefore, after the current passes through zero, the switch tube can still maintain a conduction time, and the current can flow through the secondary switch Q2 in the reverse direction.
[0052] Since the input and output voltages of the primary switch Q1 and the secondary switch Q2 are different, different types of switch tubes can be selected as the primary switch Q1 and the secondary switch Q2 based on actual needs. Even different types of switch tubes can be selected as the primary switch Q1 and the secondary switch Q2. For example, MOSFET can be used as the primary switch Q1 and IGBT can be used as the secondary switch Q2.
[0053] In this embodiment, it is assumed that both the primary switch Q1 and the secondary switch Q2 are MOSFETs. Figure 1 , D Q1 is the parasitic diode of the primary switch Q1, C Q1 is the parasitic capacitance of the primary switch Q1, D Q2 is the parasitic diode of the secondary switch Q2, C Q2 is the parasitic capacitance of the secondary switch Q2.
[0054] Optionally, in the embodiment of the present application, a first freewheeling diode may be connected in parallel at both ends of the primary switch Q1, and / or a second freewheeling diode may be connected in parallel at both ends of the secondary switch Q2. Thus, even if the selected primary switch Q1 and the secondary switch Q2 do not have parasitic diodes, the reverse current may flow in the loop through the freewheeling diode, thereby maintaining the reverse conduction of the loop for a period of time.
[0055] For example, a freewheeling diode may be connected in parallel at both ends of one of the primary switch Q1 and the secondary switch Q2, or a freewheeling diode may be connected in parallel at both ends of the primary switch Q1 and the secondary switch Q2, so that the switch with freewheeling diodes connected in parallel at both ends may be a bidirectional working switch without a parasitic diode.
[0056] When the primary switch Q1 is in the on state, the current flows through the first inductor L1, the first inductor L1 stores energy, and the current in the first loop increases; when the primary switch Q1 is turned off, the energy stored in the first inductor L1 is transferred to the second loop through the second inductor L2, the current in the first loop decreases, and the current in the second loop increases; after the current in the second loop reaches the maximum value, the secondary switch Q2 is turned on, the current in the second loop continues to decrease, and increases in the reverse direction after crossing zero, and after a time T1, the reverse current reaches the maximum; when the reverse current in the second loop reaches the maximum, the secondary switch Q2 is turned off, at this time, the primary switch Q1 is also in the off state, and the energy stored in the second inductor L2 is transferred to the first inductor L1, the reverse current in the first loop first gradually increases, and after reaching the maximum value, it gradually decreases within the T2 time period.
[0057] Soft switching technology can introduce zero voltage or zero current state during the on and off process of the switch tube, thereby reducing switching losses. In this embodiment, since a bidirectional working switch is used as the secondary switch, the zero voltage switching (Zero-Voltage Switching, ZVS) of the primary switch Q1 can be achieved through the control strategy, thereby significantly reducing switching losses.
[0058] Specifically, the primary switch Q1 can be turned on after the charge in the parasitic capacitor connected in parallel between the drain and source of the primary switch Q1 is completely drained away, thereby achieving zero-voltage turning-on of the primary switch Q1, which can reduce the stress that the switch tube needs to bear and the energy loss generated during the switching process, extend the service life of the flyback converter, reduce the circuit maintenance cost, and improve the efficiency of the flyback converter.
[0059] In the embodiment of the present application, the flyback converter topology circuit includes a first inductor, a primary switch, a second inductor and a secondary switch; wherein the secondary switch is a bidirectional working switch; the first inductor and the primary switch are connected in series to form a first loop; the second inductor and the secondary switch are connected in series to form a second loop; the first inductor and the second inductor are connected to the same iron core. Thus, by using a bidirectional working switch as a secondary switch, it can be maintained in a reverse conduction state for a period of time, so that it can be controlled to turn on after the voltage of the primary switch drops to 0, realizing zero voltage turn-on of the primary switch, reducing the stress that the switch tube needs to bear and the energy loss generated during the switching process, extending the service life of the flyback converter, reducing the circuit maintenance cost, and improving the efficiency of the flyback converter.
[0060] See also Figure 2 , this figure is a structure diagram of another flyback converter topology circuit provided in an embodiment of the present application, the circuit includes: a first inductor L1, a primary switch Q1, a first capacitor C1, a first output capacitor Cs, a second inductor L2, a secondary switch Q2 and a second output capacitor Co.
[0061] Among them, the primary switch Q1 and the secondary switch Q2 are bidirectional working switches; the first output capacitor Cs is connected in parallel to the first inductor L1 and the two ends of the primary switch Q1, and the first capacitor C1 is connected in parallel to the two ends of the primary switch Q1 to form a first loop; the second output capacitor Co is connected in parallel to the second inductor L2 and the two ends of the secondary switch Q2 to form a second loop; the first inductor L1 and the second inductor L2 share the same iron core. The number of turns of the first inductor L1 is N1, and the number of turns of the second inductor L2 is N2. The first output capacitor C s Can provide voltage U s , the second output capacitor C o Can provide voltage U o .
[0062] In this embodiment, a first capacitor C1 is connected in parallel at both ends of the primary switch Q1. The first capacitor C1 and the parasitic capacitor C1 of the primary switch Q1 are connected in parallel. Q1 They can form a resonant circuit together with the first inductor L1 to increase the total resonant capacitance value in the first circuit, thereby reducing the voltage stress and voltage spike when the primary switch Q1 is turned off, reducing switching losses and improving circuit reliability.
[0063] Optionally, based on the same principle, a first capacitor C1 can be connected in parallel across the primary switch Q1, while a second capacitor can be connected in parallel across the secondary switch Q2, so as to better achieve zero-voltage turn-on of the switch tube in high-frequency power density and high-efficiency application scenarios.
[0064] In addition, the first output capacitor Cs and the second output capacitor Co can absorb ripples in the output voltage to make the output voltage more stable; when the load in the loop changes, the output capacitor can provide a temporary current supply to maintain the stability of the output voltage.
[0065] See also Figure 3 , which is a flow chart of a control method for a flyback converter provided in an embodiment of the present application, the method is used to control the flyback converter topology circuit provided in any of the above embodiments, the method comprising:
[0066] S301: monitor a first current in a first loop and a second current in a second loop in real time.
[0067] As an example, the first current in the first loop and the second current in the second loop can be respectively monitored in real time by devices such as current sensors, Hall effect integrated chips, resistor shunts, or electromagnetic induction sensors.
[0068] S302: Determine a dead time range in which both the primary switch and the secondary switch are turned off based on the first current and the second current.
[0069] Triangular Carrier Modulation is a commonly used control technology for power electronic converters, especially in pulse width modulation (PWM) inverters. This technology uses a triangular wave as a carrier signal and compares it with one or more reference signals. When the triangular wave crosses the reference signal, the switching action is triggered, thereby determining the turn-on and turn-off moments of the switching device.
[0070] In the process of controlling the flyback converter, the turn-on and turn-off times of the primary switch and the secondary switch need to be determined by triangle wave modulation technology, which may cause the primary switch and the secondary switch to be turned on at the same time, and the first circuit and the second circuit are turned on at the same time, causing current shock and even damaging the switch tube. To avoid this situation, it is necessary to set the dead time range in which both the primary switch and the secondary switch are turned off, so as to ensure the safe operation of the flyback converter.
[0071] The method provided in this embodiment is applied to the flyback converter topology circuit provided in any of the above embodiments. Since a bidirectional working switch is used as a secondary switch in the flyback converter, it can be maintained in a reverse conduction state for a period of time, so that it can be controlled to turn on after the primary switch voltage drops to 0, thereby achieving zero-voltage turning on of the primary switch, reducing the stress that the switch tube needs to bear and the energy loss generated during the switching process, extending the service life of the flyback converter, reducing the circuit maintenance cost, and improving the efficiency of the flyback converter.
[0072] See also Figure 4 , which is a control timing diagram of a flyback converter provided in an embodiment of the present application, wherein V GS-Q1 is the gate drive voltage of the primary switch Q1, V GS-Q2 is the gate drive voltage of the secondary switch Q2, a high level indicates that the switch is turned on, and a low level indicates that the switch is turned off; I1 is the first current, and I2 is the second current.
[0073] As an example, the second maximum reverse current I 2MIN and the inductance value L2 of the second inductor, calculate the energy stored in the second inductor during the secondary switch opening process; based on the energy E2 stored in the second inductor and the first maximum reverse current I 1MIN , calculate the time t5 when the energy stored in the second inductor is completely consumed after being transferred to the first inductor; determine the time interval from the secondary switch off time t3 to the time t5 when the energy stored in the second inductor is completely consumed as the first dead time range T d In addition, the time interval from the time t8 when the primary switch Q1 is turned off to the time t9 when the second current reaches the maximum current can be determined as the second dead zone range T d1 .
[0074] Specifically, in the flyback converter, the number of turns of the first inductor is N1, and the number of turns of the second inductor is N2. Since the first inductor and the second inductor share the same core, L1 / L2=(N1 / N2) 2 , I 1MIN =I 2MIN (N1 / N2); and because soft switching is required, I 2MIN The charge Q in the parasitic capacitance of the primary switch Q1 can be completely CQ1 Take all away, so I 1MIN 2 L1≥UsQ CQ1 +UoQ CQ2 , where Q CQ2 is the charge in the parasitic capacitance of the secondary switch Q2.
[0075] Therefore, through theoretical calculation and derivation, we can get:
[0076] The second inductor stores energy for a period of time T1 = L2I 2MIN / U o ;
[0077] The first current when the energy stored in the second inductor is completely consumed
[0078]
[0079] Thus, the time period T2 from the beginning of energy consumption in the first loop to the complete consumption of energy stored in the second inductor can be obtained as follows: L1(I 1MIN -T RV ) / Us, and the time period T from when the energy stored in the second inductor is completely consumed to when the first current reaches the zero crossing point RV =L1I RV / Us, and the time t7 when the first current reaches the zero-crossing point, the time t5 when the energy stored in the second inductor is completely consumed can be obtained.
[0080] Among them, T2 <T d <T2+T RV .
[0081] Alternatively, if Figure 4 The primary switch Q1 can be turned on at any time during the period from t5 to t7. The first dead time range is T d It can be flexibly adjusted within the range of t3 to t5 to t7 according to actual needs. For example, the first dead time range T dIt can be the period from t3 to t5, the period from t3 to t6, or the period from t3 to t7. Since the current level is low near the zero crossing point, the noise has a greater impact on the accuracy of the current monitoring result, and the time window for executing the switch tube opening action is very narrow, making it difficult to achieve soft shutdown. Therefore, by adjusting the first dead time range, the opening operation of the primary switch Q1 can be avoided near the zero crossing point, thereby ensuring that the soft switching of the primary switch Q1 can be achieved, effectively reducing the loss generated during the switching process, and improving the efficiency of the flyback converter.
[0082] The secondary switch Q2 can be turned on at any time within the period of t9 to t10, wherein t10 can be set according to actual needs. For example, it can be set that the time interval between the time t9 at which the second current reaches the maximum current and the preset time length is t10, wherein t10 is after t9. The second dead time range T d1 It can be flexibly adjusted within the range of t8 to t9 to t10 according to actual needs. For example, the second dead time range T d1 It can be the period from t8 to t9 or the period from t8 to t10.
[0083] Specifically, see Figure 5 , which is a schematic diagram of a triangular carrier control principle of a flyback converter provided in an embodiment of the present application, wherein V GS_Q1 is the gate-source voltage of the primary switch, V DS-Q1 is the drain-source voltage of the primary switch, V GS_Q2 is the gate-source voltage of the secondary switch, V DS-Q2 is the drain-source voltage of the secondary switch, i p is the drain current of the primary switch, i s is the source current of the secondary switch. Taking the semicircular modulation wave as the reference signal, when the current triangle wave, the carrier wave, intersects with the semicircular modulation wave, a driving signal that controls the switch tube to turn on or off will be generated.
[0084] Therefore, by modulating the reference signal into a curve, the circuit can have a weaker ability to extract the charge stored in the capacitor in the opposite circuit during the period close to the input voltage zero crossing such as stage 1 and stage 3, and the current does not cross zero and reverse during the switching process, thereby reducing current stress; and during the period close to the peak value such as stage 2, the current in the circuit will also increase, and soft switching can be fully realized by the method provided in any embodiment of the present application, thereby effectively reducing losses and improving efficiency.
[0085] S303: Based on the dead time range, control the switching states of the primary switch and the secondary switch through triangular carrier modulation.
[0086] As an example, by adjusting the dead time range and triangular carrier modulation, it is possible to achieve:
[0087] When the secondary switch is turned on, if the second current reaches the second maximum reverse current, the secondary switch is controlled to be turned off; at this time, it can be considered that the drain-source parasitic capacitance of the secondary switch is fully charged.
[0088] When both the primary switch and the secondary switch are turned off, if the first current reaches a preset reference current, the primary switch is controlled to turn on outside the dead time range; wherein the reference current is the current in the first loop when the energy stored in the second inductor is completely consumed. It is understandable that at different stages of the switching cycle, energy is transferred between the inductor and the capacitor, and the energy stored in the second inductor is determined by the amount of charge stored in the capacitor in the second loop.
[0089] When the primary switch is turned on, if the first current reaches the first maximum current, the primary switch is controlled to be turned off.
[0090] When both the primary switch and the secondary switch are turned off, if the second current reaches the second maximum current, the secondary switch is controlled to be turned on outside the dead time range.
[0091] Optionally, in order to avoid a large current spike, a fixed frequency control method is used in this embodiment to control the on and off of the switch tube.
[0092] Therefore, in this embodiment, based on the flyback converter using a bidirectional working switch as a secondary switch, the switch tube is controlled by using triangular carrier modulation coordinated with current control. After all the energy stored in the second inductor is transferred to the first inductor and is completely consumed, that is, the charge in the parasitic capacitor in parallel between the drain and source of the primary switch Q1 is completely drawn out, and the primary switch voltage drops to 0, it is controlled to turn on again, thereby achieving zero voltage turning on of the primary switch, reducing the stress that the switch tube needs to bear and the energy loss generated during the switching process, extending the service life of the flyback converter, reducing the circuit maintenance cost, and improving the efficiency of the flyback converter.
[0093] See also Figure 6 , this figure is a schematic diagram of a control device of a flyback converter provided in an embodiment of the present application. The device is applied to the flyback converter topology circuit provided in any of the above embodiments. The device includes: a monitoring module 601, a determination module 602 and a control module 603.
[0094] A monitoring module 601, configured to monitor in real time a first current in the first loop and a second current in the second loop;
[0095] The determination module 602 is used to determine the dead time range in which both the primary switch and the secondary switch are turned off based on the first current and the second current; the dead time range includes: from the time when the primary switch is turned off to the time when the second current reaches the maximum current, and from the time when the secondary switch is turned off to the time when the energy stored in the second inductor is completely consumed;
[0096] The control module 603 is used to control the switching states of the primary switch and the secondary switch through triangular carrier modulation based on the dead time range.
[0097] Therefore, in this embodiment, based on the flyback converter using a bidirectional working switch as a secondary switch, the switch tube is controlled by using triangular carrier modulation coordinated with current control. After all the energy stored in the second inductor is transferred to the first inductor and is completely consumed, that is, the charge in the parasitic capacitor in parallel between the drain and source of the primary switch Q1 is completely drawn out, and the primary switch voltage drops to 0, it is controlled to turn on again, thereby achieving zero voltage turning on of the primary switch, reducing the stress that the switch tube needs to bear and the energy loss generated during the switching process, extending the service life of the flyback converter, reducing the circuit maintenance cost, and improving the efficiency of the flyback converter.
[0098] Optionally, the determination module 602 is specifically used to: calculate the energy stored in the second inductor during the process of turning on the secondary switch based on the second maximum reverse current and the inductance value of the second inductor; calculate the moment when the energy stored in the second inductor is completely consumed based on the energy stored in the second inductor and the first maximum reverse current; and determine the time interval from the moment when the secondary switch is turned off to the moment when the energy stored in the second inductor is completely consumed as the first dead time range.
[0099] Optionally, the control module is specifically used to: when the secondary switch is turned on, if the second current reaches the second maximum reverse current, control the secondary switch to be turned off; when both the primary switch and the secondary switch are turned off, if the first current reaches a preset reference current, control the primary switch to be turned on outside the dead time range; the reference current is: the current in the first loop when the energy stored in the second inductor is completely consumed; when the primary switch is turned on, if the first current reaches the first maximum current, control the primary switch to be turned off; when both the primary switch and the secondary switch are turned off, if the second current reaches the second maximum current, control the secondary switch to be turned on outside the dead time range.
[0100] Optionally, controlling the primary switch to turn on is specifically: controlling the primary switch to turn on in a time interval from when the energy stored in the second inductor is completely consumed to when the first current reaches a zero-crossing point.
[0101] See also Figure 7, which is a structural diagram of a control device of a flyback converter provided in an embodiment of the present application, and the device includes: a memory 701 and a processor 702.
[0102] Memory 701: used to store program codes and transmit the program codes to the processor.
[0103] Processor 702: used for executing the steps of the above-mentioned flyback converter control method according to the instructions in the program code.
[0104] In addition, the present application also provides a computer-readable storage medium, which stores computer instructions. When the computer instructions are executed on the control device of the flyback converter, the control device of the flyback converter executes the steps of the above-mentioned flyback converter control method.
[0105] It should be noted that each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments. The device and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components indicated as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.
[0106] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.
Claims
1. A flyback converter topology circuit, characterized in that: The circuit comprises: a first inductor, a primary switch, a second inductor and a secondary switch; The secondary side switch is a bidirectional working switch; The first inductor and the primary switch are connected in series to form a first loop; the second inductor and the secondary switch are connected in series to form a second loop; the first inductor and the second inductor share the same iron core.
2. The circuit according to claim 1, characterized in that The circuit further includes: a first freewheeling diode connected in parallel to both ends of the primary switch.
3. The circuit according to claim 1, characterized in that The circuit further includes: a first capacitor connected in parallel to both ends of the primary switch.
4. The circuit according to claim 1, characterized in that The circuit further includes: a first output capacitor connected in parallel to both ends of the first inductor, and a second output capacitor connected in parallel to both ends of the second inductor.
5. A control method for a flyback converter, characterized in that: The method is used to control the flyback converter topology circuit according to any one of claims 1 to 4, and the method comprises: Real-time monitoring of a first current in the first loop and a second current in the second loop; Based on the first current and the second current, determining a dead time range in which both the primary switch and the secondary switch are turned off; the dead time range includes: a first dead time range from the moment when the secondary switch is turned off to the moment when the energy stored in the second inductor is completely consumed, and a second dead time range from the moment when the primary switch is turned off to the moment when the second current reaches a maximum current; Based on the dead time range, the switching states of the primary switch and the secondary switch are controlled by triangular carrier modulation.
6. The method according to claim 5, characterized in that The determining, based on the first current and the second current, a dead time range in which both the primary switch and the secondary switch are turned off includes: Calculating the energy stored in the second inductor during the secondary switch turning on process based on the second maximum reverse current and the inductance value of the second inductor; Based on the energy stored in the second inductor and the first maximum reverse current, calculate the moment when the energy stored in the second inductor is completely consumed; The time interval from the moment when the secondary switch is turned off to the moment when the energy stored in the second inductor is completely consumed is determined as the first dead time range.
7. The method according to claim 5, characterized in that The controlling the switch states of the primary switch and the secondary switch based on the dead time range and the triangular carrier modulation includes: When the secondary switch is turned on, if the second current reaches a second maximum reverse current, controlling the secondary switch to be turned off; When both the primary switch and the secondary switch are turned off, if the first current reaches a preset reference current, the primary switch is controlled to be turned on outside the dead time range; the reference current is: the current in the first loop when the energy stored in the second inductor is completely consumed; When the primary switch is turned on, if the first current reaches a first maximum current, controlling the primary switch to be turned off; In a case where both the primary switch and the secondary switch are turned off, if the second current reaches a second maximum current, then outside the dead time range, the secondary switch is controlled to be turned on.
8. The method according to claim 7, characterized in that The controlling the primary switch to turn on includes: In a time interval from when the energy stored in the second inductor is completely consumed to when the first current reaches a zero-crossing point, the primary switch is controlled to be turned on.
9. A control device for a flyback converter, characterized in that: The device is used to control the flyback converter topology circuit according to any one of claims 1 to 4, and the device comprises: a monitoring module, a determination module and a control module; The monitoring module is used to monitor the first current in the first loop and the second current in the second loop in real time; The determination module is used to determine a dead time range in which both the primary switch and the secondary switch are turned off based on the first current and the second current; the dead time range includes: from the time when the primary switch is turned off to the time when the second current reaches the maximum current, and from the time when the secondary switch is turned off to the time when the energy stored in the second inductor is completely consumed; The control module is used to control the switching states of the primary switch and the secondary switch through triangular carrier modulation based on the dead time range.
10. A control device for a flyback converter, characterized in that: The device is used to control the flyback converter topology circuit according to any one of claims 1 to 4, and the device comprises: a memory and a processor; The memory is used to store program codes and transmit the program codes to the processor; The processor is used to execute the steps of the flyback converter control method according to any one of claims 5 to 8 according to the instructions in the program code.