A control method and control device for an asymmetric half-bridge flyback circuit

Abstract

The embodiment of the present invention provides a control method and control device for an asymmetric half-bridge flyback circuit. The working mode of the asymmetric half-bridge flyback circuit includes an enhanced power mode; the asymmetric half-bridge flyback circuit includes an energy storage tube and a freewheeling tube; the control method includes the following steps: obtaining a power parameter, the power parameter can characterize the output power of the asymmetric half-bridge flyback circuit; comparing the power parameter with the preset power parameter; when the power parameter is greater than the preset power parameter, controlling the asymmetric half-bridge flyback circuit to enter the enhanced power mode; in the enhanced power mode, controlling the conduction time of the energy storage tube to be positively correlated with the loop compensation amount or controlling the conduction time of the freewheeling tube to be negatively correlated with the loop compensation amount; wherein the loop compensation amount is positively correlated with the output power. The control method can improve the output power of the asymmetric half-bridge flyback circuit without changing the hardware circuit parameter design.

Description

Technical Field

[0001] The present invention relates to the field of switch power supply control, and in particular to a control method and a control device for an asymmetric half-bridge flyback circuit. Background Art

[0002] With the development of consumer electronics applications, people's requirements for device charging are constantly increasing. The asymmetric half-bridge flyback circuit is shown in Figure 1. It has been favored in recent years because of its simple structure, low cost, ability to achieve ZVS (zero voltage switching) and adaptability to a wide output voltage range. However, in order to fully utilize the topological advantages of the asymmetric half-bridge flyback circuit, generally, its control strategy is to make the topology work in DCM (discontinuous mode), CRM (critical mode) or a combination of CRM / DCM. In this way, for applications where the power supply needs to provide a large power in a short time, if the asymmetric half-bridge flyback circuit is designed directly based on the required maximum power, the size of the transformer will increase, and under most working conditions, the system is in a non-CRM working mode, which greatly reduces the efficiency.

[0003] Therefore, how to further improve the maximum output power of the asymmetric half-bridge flyback circuit is a technical problem that needs to be solved. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a control method and a control device for an asymmetric half-bridge flyback circuit. The control method adds an enhanced power mode, and through control, the circuit can operate in the enhanced power mode, thereby increasing the input current of the circuit and further improving the output power of the circuit.

[0005] This application adopts the following technical solutions:

[0006] A control method for an asymmetric half-bridge flyback circuit, wherein the working mode of the asymmetric half-bridge flyback circuit includes an enhanced power mode; the asymmetric half-bridge flyback circuit includes an energy storage tube and a freewheeling tube; the control method includes the following steps:

[0007] Acquiring a power parameter, where the power parameter can characterize the output power of the asymmetric half-bridge flyback circuit;

[0008] Comparing the power parameter with a preset power parameter;

[0009] When the power parameter is greater than the preset power parameter, the asymmetric half-bridge flyback circuit is controlled to enter an enhanced power mode; the power parameter includes one or more of a loop compensation amount, a current parameter, and a conduction time of the energy storage tube; the preset power parameter includes one or more of a preset loop compensation amount, a preset current parameter, and a preset conduction time of the energy storage tube;

[0010] In the enhanced power mode, the conduction time of the energy storage tube is controlled to be positively correlated with the loop compensation amount, or the conduction time of the freewheeling tube is controlled to be negatively correlated with the loop compensation amount; wherein the loop compensation amount is positively correlated with the output power.

[0011] The control method compares the power parameter with the preset power parameter, and enters the enhanced power mode when the power parameter is greater than the preset power parameter; after entering the enhanced power mode, the conduction time of the freewheeling tube or the conduction time of the energy storage tube is further controlled according to the loop compensation amount, so that the circuit can continue to operate in the enhanced power mode, increase the input current of the circuit, and thus help to improve the output power of the circuit.

[0012] A control device for an asymmetric half-bridge flyback circuit, comprising:

[0013] A power judgment module, used to judge whether the asymmetric half-bridge flyback circuit needs to enter an enhanced power mode according to a power parameter characterizing the output power of the asymmetric half-bridge flyback circuit and a preset power parameter; the power parameter includes one or more of a loop compensation amount, a current parameter, and a conduction time of the energy storage tube; the preset power parameter includes one or more of a preset loop compensation amount, a preset current parameter, and a preset conduction time of the energy storage tube;

[0014] A control unit is used to control the conduction time of the energy storage tube to be positively correlated with the loop compensation amount or to control the conduction time of the freewheeling tube to be negatively correlated with the loop compensation amount when the asymmetric half-bridge flyback circuit enters the enhanced power mode; wherein the loop compensation amount is positively correlated with the output power of the asymmetric half-bridge flyback circuit.

[0015] The power judgment module of the control device can determine whether it is necessary to enter the enhanced power mode according to the power parameters and the preset power parameters. The control unit is used to control the conduction time of the freewheeling tube or the conduction time of the energy storage tube according to the loop compensation amount after entering the enhanced power mode, so that the circuit can continue to operate in the enhanced power mode, increase the input current of the circuit, and thus help to improve the output power of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work, but they should fall within the scope of protection of this application.

[0017] Figure 1 A schematic diagram of an asymmetric half-bridge flyback circuit in the prior art;

[0018] Figure 2 A flow chart of a control method for an asymmetric half-bridge flyback circuit provided in an embodiment of the present application;

[0019] Figure 3 This is a schematic diagram of the control waveform for controlling the conduction time of the energy storage tube after adding EPM (enhanced power mode);

[0020] Figure 4 This is a schematic diagram of the control waveform for controlling the conduction time of the freewheeling tube after adding EPM;

[0021] Figure 5 The freewheeling tube conduction time and V comp Schematic diagram of the corresponding curve;

[0022] Figure 6 A schematic diagram of the working mode of the asymmetric half-bridge flyback circuit disclosed in this application;

[0023] Figure 7 Under EPM, the peak current command value and the freewheeling tube conduction time are respectively comp The corresponding first curve diagram;

[0024] Figure 8 Under EPM, the peak current command value and the freewheeling tube conduction time are respectively comp The corresponding schematic diagram of the second curve;

[0025] Fig. 9 Under EPM, the peak current command value and the freewheeling tube conduction time are respectively comp The corresponding schematic diagram of the third curve;

[0026] Fig.10 Under EPM, the peak current command value and the freewheeling tube conduction time are respectively comp The corresponding schematic diagram of the fourth curve;

[0027] Fig.11 A schematic diagram of a control device for an asymmetric half-bridge flyback circuit provided in an embodiment of the present application;

[0028] Fig.12 This is a schematic diagram of a power judgment module;

[0029] Fig.13 A schematic diagram of a timing unit and a storage unit of a control device. DETAILED DESCRIPTION

[0030] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0031] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. Electrical connection mainly refers to the transmission of signals, including direct electrical connection and indirect electrical connection.

[0033] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0034] Figure 1 The asymmetric half-bridge flyback circuit shown in the figure includes an energy storage tube Q1, a freewheeling tube Q2, a leakage inductance Lr, an excitation inductance Lm, a resonant capacitor Cr and a transformer T; the first end of the energy storage tube Q1 is connected to the input voltage V in The high potential end is electrically connected, the second end is electrically connected to the first end of the freewheeling tube Q2, and the second end of the freewheeling tube Q2 is electrically connected to the input voltage V in The low potential end is electrically connected; the resonant unit of the asymmetric half-bridge flyback circuit includes a leakage inductor Lr, an excitation inductor Lm, and a resonant capacitor Cr connected in series; one end of the resonant unit is electrically connected to the first end of the freewheeling tube Q2, and the other end is electrically connected to the second end of the freewheeling tube; the primary winding of the transformer is connected in parallel with the excitation inductor Lm, and the secondary winding of the transformer and the secondary circuit constitute a secondary unit. The energy storage tube Q1 and the freewheeling tube Q2 are mutually exclusive and turned on. When the energy storage tube Q1 is turned on, the excitation inductor is excited, and the excitation inductor current I Lm Generally, during most of the time when the freewheeling tube Q2 is turned on, the excitation inductor is demagnetized and the excitation inductor current I Lm Reduce until it is reduced to 0; by further controlling the conduction time of the freewheeling tube, the circuit can be operated in discontinuous mode and realize zero voltage switching of Q1 to meet the output power and system efficiency requirements. It should be noted that the leakage inductance Lr and the excitation inductance Lm are only schematic diagrams on the circuit schematic, and do not necessarily include the device. It can be realized by the design of the transformer T, and of course it can also be realized by inductance, and this application does not limit this.

[0035] In the asymmetric half-bridge flyback circuit, the on-time control of the energy storage tube Q1 can be controlled by peak current control or constant on-time control. The general principle of peak current control is to adjust the loop compensation value V of the asymmetric half-bridge flyback circuit according to the peak current control value. comp The peak current command value V corresponding to the peak current control is generated cspk_ref ; Sampling to obtain the characterization of the excitation inductance current I Lm The current sampling signal V cs ; Then use the comparator to calculate the peak current command value V cspk_ref and the current sampling signal V cs When the current sampling signal V cs Reach the peak current command value V cspk_ref When the control signal G is generated to close the energy storage tube Q1 Q1_rst The general principle of constant on-time control is to use the loop compensation value V comp The on-time target value T corresponding to the constant on-time control is generated ref ; and calculate the conduction time of the energy storage tube Q1 through the timing unit, and compare this time with the conduction time target value T ref When the timing reaches the on-time target value, a control signal G is generated to turn off the energy storage tube Q1. Q1_rst .

[0036] The on-time control of the freewheeling tube Q2 can be calculated based on the unbalanced coefficient control and the inductor induced voltage formula. The general principle of unbalanced coefficient control is to combine the energy storage tube to achieve zero voltage switching (ZVS) requirements, generate a compensation coefficient based on the volt-second balance relationship to be satisfied when the excitation inductor is excited and demagnetized, and compensate for the on-time of Q2; and the on-time of Q2 can be determined by the volt-second balance relationship under the charging and discharging of the excitation inductor. Calculating the on-time of Q2 using the inductor induced voltage formula is equivalent to calculating it based on the volt-second balance relationship of the charging and discharging of the excitation inductor, such as the following relationship:

[0037]

[0038] Among them, T on_Q2 Indicates the conduction time of the freewheeling tube Q2, V cspk is the peak current sampling value of the excitation inductance Lm, R CS is the current sampling resistor value, L m is the value of the excitation inductance Lm, V aux is the auxiliary winding voltage of transformer T, N aux is the number of turns of the auxiliary winding, N p is the number of turns of the primary side of the transformer.

[0039] In order to improve the output power of the above-mentioned asymmetric half-bridge flyback circuit, the embodiment of the present application provides a control method, which enables the asymmetric half-bridge flyback circuit to operate in an enhanced power mode, thereby increasing its output power, which is particularly suitable for applications that require a large power supply in a short time, such as power tools and printers. In order to adapt to higher power application scenarios, if the circuit is designed directly based on the required maximum power, the size of the transformer will increase, and under most operating conditions, the system is in a non-high-power operation mode, which will greatly reduce the overall efficiency of the circuit.

[0040] To solve the above problems, the control method provided in the present application enables the asymmetric half-bridge flyback circuit to operate in an enhanced power mode, which can provide a greater output power. By controlling the enhanced power mode, the output power of the circuit can be increased without changing the hardware circuit parameter design; specifically, Figure 2 As shown, the control method includes the following steps:

[0041] Step S1: obtaining a power parameter, where the power parameter can characterize the output power of the asymmetric half-bridge flyback circuit;

[0042] Step S2: Compare the above power parameter with the preset power parameter;

[0043] Step S3: Entering enhanced power mode: When the power parameter is greater than the preset power parameter, it means that the required output power becomes larger, and the conventional control method of the asymmetric half-bridge flyback circuit can no longer meet the output power requirement. At this time, the asymmetric half-bridge flyback circuit is controlled to enter the enhanced power mode to increase the output power;

[0044] Step S4: Enhanced power mode control: In the enhanced power mode, control the conduction time T of the energy storage tube on_Q1 and loop compensation V comp Positive correlation or control of the conduction time T of the freewheeling tube on_Q2 and loop compensation V comp Negative correlation; among them, the loop compensation amount V comp Positively correlated with output power.

[0045] In this embodiment, Figure 3 As shown, the EPM flag is high, indicating that it has entered EPM (Extended Power Mode). That is, the circuit works in the enhanced power mode, by controlling the on-time T of the energy storage tube. on_Q1 and loop compensation V comp Positive correlation, that is, the loop compensation amount V comp Increase, T on_Q1 becomes longer, at this time the excitation time of the excitation inductance becomes longer, if the demagnetization time is controlled (equivalent to T on_Q2) remains unchanged, the current of the excitation inductor after demagnetization will not reach 0, and the asymmetric half-bridge flyback circuit works in the enhanced power mode. Similarly, by controlling the on-time T of the freewheeling tube on_Q2 and loop compensation V comp Negative correlation, that is, the loop compensation amount V comp Increase, T on_Q2 becomes shorter, and the demagnetization time of the excitation inductor becomes shorter. If the excitation control mode remains unchanged, the current after the excitation inductor is demagnetized will not reach 0. At this time, the asymmetric half-bridge flyback circuit also works in the enhanced power mode.

[0046] The working modes of the asymmetric half-bridge flyback circuit also include hiccup mode, intermittent mode and critical mode; these three modes are also collectively referred to as non-EPM working modes. The control method of the asymmetric half-bridge flyback circuit provided in the embodiment of the present application enables the circuit to add a new working mode: EPM (enhanced power mode) to increase the output power of the circuit. In the non-EPM working mode, Q1 and Q2 are controlled to be turned on alternately. The hiccup mode mainly corresponds to the deep light load condition; the intermittent mode mainly corresponds to the light load and medium load conditions, and the intermittent mode can also be called the valley conduction mode; the critical mode mainly corresponds to the heavy load condition. In the non-EPM working mode, the freewheeling tube can be controlled by one or more parameters in the unbalance coefficient, volt-second balance, valley number or switching frequency, and the energy storage tube can be controlled according to peak current control or constant conduction time control.

[0047] It should be noted that the positive correlation / negative correlation in this article follows the basic principle of the scientific variable method, which means that when other parameters remain roughly unchanged, the two parameters are positively correlated / negatively correlated. comp Positive correlation with output power refers to the relationship when the input parameters of the circuit (such as input voltage) remain roughly unchanged; ignoring smaller parameter fluctuations or interference in actual application.

[0048] In a specific embodiment, the power parameter may be the loop compensation amount V comp , Current parameter V cs , the conduction time of the energy storage tube T on_Q1 One or more of; correspondingly, the preset power parameter includes a preset loop compensation amount V comp_epm , preset current parameter V cs_epm And the preset conduction time T of the energy storage tube on_ epm One or more of the following. Among them, the current parameter V cs Characterizing the magnetizing inductor current I of an asymmetric half-bridge flyback circuit Lm ,like Figure 1As shown, it can be obtained by sampling the resistor Rcs; the output power corresponding to the preset power parameter is greater than or equal to the output power of the asymmetric half-bridge flyback circuit working in the critical mode. When the acquired power parameter is greater than the corresponding preset power parameter, it indicates that the output power corresponding to the asymmetric half-bridge flyback circuit working in the critical mode cannot meet the required output power requirement, and the circuit is controlled to enter the enhanced power mode. In this embodiment, it can be determined whether the circuit needs to enter the EPM on a switching cycle by switching cycle. The condition for entering the EPM can be one of the following conditions or a random combination of the following conditions, which is not limited in this application.

[0049] 1. V comp >V comp_epm ;

[0050] 2. V cs >V cs_epm ;

[0051] 3. T on_Q1 >T on _epm ;

[0052] In one embodiment, in order to implement control in the enhanced power mode, the control method is further configured to include the following steps:

[0053] Record the critical on-time; the critical on-time is the on-time of the freewheeling tube Q2 when the asymmetric half-bridge flyback circuit works in the critical mode;

[0054] When the power parameter is greater than the preset power parameter and enters the enhanced power mode, the conduction time T of the freewheeling tube is controlled. on_Q2 Less than or equal to the critical conduction time, and controls the conduction time T of the energy storage tube Q1 on_Q1 and loop compensation V comp Positive correlation; in this way, the circuit can continue to work in the enhanced power mode; until the required output power becomes smaller, and after exiting the enhanced power mode, the non-EPM working mode control is performed according to the output power.

[0055] Further, in one embodiment, the enhanced power mode includes a first control mode;

[0056] In the first control mode, the conduction time of the freewheeling tube is controlled to be fixed to the critical conduction time T Q2_CRM ;

[0057] When the peak current is used to control the energy storage tube Q1, the conduction time of the energy storage tube in step S4 is positively correlated with the loop compensation amount, including the steps of controlling the peak current command value V cspk_ref and loop compensation V comp Positive correlation.

[0058] In this embodiment, as the output power increases, the loop compensation amount V comp As T increases, the on-time of Q1 increases, while the on-time of Q2 is Q2_CRM Therefore, the current of the excitation inductor is not 0 after demagnetization, and the circuit enters the enhanced power mode. The schematic waveform is shown in Figure 3. The conduction time T of the freewheeling tube is on_ Q2 Fixed to T Q2_CRM , as the load power increases, V comp Slowly increasing, V cspk_ref When the EPM flag is high, the circuit enters EPM, and the conduction time of Q2 is T Q2_reg Decision; T Q2_reg It is the Q2 conduction time recorded in the non-EPM working mode and updated in each switching cycle. It is generally the critical conduction time T when the asymmetric half-bridge flyback circuit works in the critical mode. Q2_CRM . After that, as the energy increases further, V cspk_ref The amplitude of is getting higher and higher. After the excitation inductance is demagnetized, the current is not 0 and is getting larger and larger. At this time, the circuit is in the deep power enhancement mode.

[0059] When the energy storage tube Q1 is controlled by adopting a constant on-time, the on-time of the energy storage tube in step S4 is positively correlated with the loop compensation amount, including the steps of controlling the on-time target value T of the energy storage tube on_ref is positively correlated with the loop compensation amount. Similarly, in this embodiment, as the output power increases, the loop compensation amount V comp becomes larger, the on-time target value T of Q1 on_ref The on-time of Q1 will increase continuously, and the on-time of Q2 will be increased by T Q2_CRM It is determined that the current is not zero after the excitation inductance is demagnetized, and the circuit enters the enhanced power mode.

[0060] It should be noted that, in some embodiments, the circuit does not necessarily need to switch from the critical mode to the enhanced power mode. Therefore, the conduction time T of the freewheeling tube in the enhanced power mode is on_ Q2 It is not necessarily the critical conduction time T Q2_CRM , which is the Q2 conduction time T recorded in non-enhanced power mode Q2_reg Specifically, whether to update can be determined based on the EPM flag: in each switching cycle, when the EPM flag is 1, the Q2 conduction time T recorded by the storage unit Q2_reg When the EPM flag is 0, the storage unit will update the recorded value to the on-time T of Q2 in the latest switching cycle. Q2_regIf the EPM flag is always 0, the on-time recorded in the storage unit will be continuously updated until the EPM flag is 1, according to the on-time T of Q2 in the latest switching cycle Q2_reg (ie, the conduction time of the freewheeling tube recorded in the storage unit) sets the conduction time of the freewheeling tube.

[0061] In another embodiment, when the power parameter is greater than the preset power parameter and the enhanced power mode is entered, in order to implement control in the enhanced power mode, setting the control method includes the following steps:

[0062] Record the critical conduction parameter; the critical conduction parameter represents the conduction time of the energy storage tube Q1 when the asymmetric half-bridge flyback circuit works in the critical mode. Among them, the critical conduction parameter can be the peak current command value or the conduction time target value T of the energy storage tube. ref ;

[0063] When entering the enhanced power mode, the above critical conduction parameters are controlled to increase or remain unchanged, and the conduction time T of the freewheeling tube is controlled on_Q2 and loop compensation V comp In this way, the circuit can continue to work in the enhanced power mode until the required output power becomes smaller and exits the enhanced power mode, and then controls the non-EPM working mode according to the output power.

[0064] Further, in one embodiment, the enhanced power mode includes a second control mode;

[0065] In the second control mode, the conduction time T of the freewheeling tube is controlled on_ Q2 and loop compensation V comp Negative correlation; that is, after entering the enhanced power mode, the on-time of Q2 is no longer calculated based on the unbalanced coefficient control and the inductor induced voltage formula, but is mainly determined by the loop compensation amount V comp Decide.

[0066] When a constant conduction time is used to control the energy storage tube, the critical conduction parameter is the conduction time target value T of the energy storage tube. ref The target value of the conduction time of the energy storage tube in the second control mode is equal to the maximum conduction time target value of the energy storage tube in the critical mode. In this embodiment, as the output power increases, the loop compensation amount V comp becomes larger, the conduction time T of Q2 on_Q2 The on-time of Q1 is still controlled by the on-time target value corresponding to the critical mode. In this way, the current is not zero after the excitation inductance is demagnetized, and the circuit enters the enhanced power mode.

[0067] When the peak current is used to control the energy storage tube, the critical conduction parameter is the peak current command value; the peak current command value in the second control mode is equal to the maximum peak current command value in the critical mode.

[0068] like Figure 4 As shown, in this embodiment, as the output power increases, the loop compensation amount V comp becomes larger, the conduction time T of Q2 on_Q2 The on-time control of Q1 is still controlled by the corresponding peak current command value in the critical mode. cspk_ref , so that the current of the excitation inductor is not 0 after demagnetization, and the circuit automatically enters the enhanced power mode. In this embodiment, although the enhanced power mode can be entered, the maximum value of the peak current of the inductor current I Lm_MAX Basically, it remains unchanged, so the requirement for transformer saturation current will not increase and there is no need to redesign the transformer.

[0069] In this embodiment, by setting the conduction time T of the freewheeling tube on_ Q2 and loop compensation V comp Negative correlation, which helps to reduce the size of magnetic components and reduce the V cspk_ref The maximum value requirement, that is, the requirement for transformer saturation current is reduced, but the output power is increased by increasing the switching frequency. Figure 5 As shown, construct T Q2_reg_proc Curve, T Q2_reg_proc The curve represents the conduction time T of the freewheeling tube on_ Q2 The maximum value is T Q2_reg , T Q2_reg is the Q2 conduction time recorded and updated in each switching cycle in the non-EPM working mode; and the conduction time of the freewheeling tube T on_ Q2 With V comp The increase and continuous decrease of Q2 can increase the switching frequency and increase the output power. It should be noted that this curve is only a schematic representation of a Q2 conduction time T on_Q2 With V comp There is a negative correlation between them. Q2_reg_min A protection mechanism is set up so that the conduction time of the freewheeling tube is set with a corresponding minimum conduction time T Q2_reg_min , V comp After exceeding a certain range, as V comp With continuous improvement, the on-time of the freewheeling tube is finally kept constant at the minimum on-time, thereby avoiding unlimited increase in the switching frequency and helping to enhance system reliability.

[0070] In the enhanced power mode, according to the loop compensation amount V comp V cspk_ref and T on_Q2These two control modes can be used alone or in combination to improve the output power of the system. Figure 7-10 As shown:

[0071] like Figure 7 As shown, after entering EPM, V cspk_ref Can be used with V comp The Q2 on-time is T of the latest Q2 on-time recorded in the non-EPM working mode. Q2_reg Decide and keep it.

[0072] like Figure 8 As shown, after entering EPM, V cspk_ref No longer changes, and Q2 conduction time T on_Q2 According to T Q2_reg_proc Curve adjustment, T Q2_reg_proc The starting value is determined by the most recent Q2 on-time T recorded in non-EPM mode. Q2_reg Decision, with V comp Increase, T on_Q2 decreases, that is, the two are negatively correlated.

[0073] like Fig. 9 As shown, after entering EPM, V cspk_ref You can first follow V comp Continue to increase, Q2 conduction time according to T Q2_reg Keep unchanged, V cspk_ref Increase to the set maximum value V cspk_ref_max remains unchanged; thereafter, as V comp Further increase, V cspk_ref no longer changes, but the conduction time of Q2 is based on T Q2_reg_proc Curve adjustment.

[0074] like Fig.10 As shown, after entering EPM, V cspk_ref It can remain unchanged first, and the conduction time of Q2 is based on T Q2_reg_proc Curve adjustment, as the output power further increases, T Q2_reg_pro Reach the set minimum value T Q2_reg_min When V cspk_ref With V comp Continues to increase, but the Q2 on-time remains at T Q2_reg_min .

[0075] like Figure 6As shown, the working modes of the asymmetric half-bridge flyback circuit provided in the embodiment of the present application include not only the hiccup mode, the discontinuous mode and the critical mode, but also a new working mode: the enhanced power mode. The entry and control of the enhanced power mode refer to the aforementioned embodiment. As the output power continues to increase, the working mode of the asymmetric half-bridge flyback circuit gradually switches between the hiccup mode, the discontinuous mode, the critical mode and the enhanced power mode.

[0076] Based on the above-mentioned control method of an asymmetric half-bridge flyback circuit, the embodiment of the present application also provides a control device of an asymmetric half-bridge flyback circuit, such as Fig.11 As shown, including:

[0077] The power judgment module 11 is used to judge whether the asymmetric half-bridge flyback circuit needs to enter the enhanced power mode according to the power parameter characterizing the output power of the asymmetric half-bridge flyback circuit and the preset power parameter. When the acquired power parameter is greater than the preset power parameter, the EPM is entered, that is, the asymmetric half-bridge flyback circuit works in the enhanced power mode.

[0078] The control unit 12 is used to control the conduction time T of the energy storage tube when the asymmetric half-bridge flyback circuit enters the enhanced power mode. on_Q1 and loop compensation V comp Positive correlation or control of the conduction time T of the freewheeling tube on_Q2 and loop compensation V comp Negative correlation; among them, the loop compensation amount V comp The principle of the control device can be referred to the above control method embodiment, and the present application will not elaborate on it here.

[0079] Further, such as Fig.12 As shown, the power determination module 11 includes a first comparator 111, a second comparator 112, a third comparator 113 and an OR gate 114;

[0080] The comparison terminals of the first comparator 111, the second comparator 112 and the third comparator 113 are respectively used to receive the loop compensation value V comp , Current parameter V cs And the conduction time of the energy storage tube T on_Q1 ; Loop compensation amount V comp , Current parameter V cs And the conduction time of the energy storage tube T on_Q1 is the power parameter;

[0081] The reference terminals of the first comparator 111, the second comparator 112 and the third comparator 113 are respectively used to receive the preset loop compensation value V comp_epm , preset current parameter V cs_epm And the preset conduction time T of the energy storage tubeon_epm ; Preset loop compensation amount V comp_epm , preset current parameter V cs_epm And the preset conduction time T of the energy storage tube on_epm is the preset power parameter; among which, the current parameter V cs Characterizes the excitation inductor current of the asymmetric half-bridge flyback circuit; the output power corresponding to the preset power parameter is greater than the output power of the asymmetric half-bridge flyback circuit working in the critical mode.

[0082] The output ends of the first comparator 111, the second comparator 112 and the third comparator 113 are electrically connected to the input end of the OR gate 114 respectively. The OR gate 114 determines whether it is necessary to enter the enhanced power mode according to the comparison results of the first comparator 111, the second comparator 112 and the third comparator 113. Specifically, the reference end of the comparator is the reverse input end, and the comparison end is the in-phase input end. When the power parameter is greater than the corresponding preset power parameter, the corresponding comparator outputs a high level; when there is a comparator outputting a high level, the corresponding OR gate input end will obtain a high level. At this time, the OR gate outputs a high level, that is, the EPM flag is 1, and it is determined that it is necessary to enter the EPM working mode. When the power parameters are all less than the corresponding preset power parameters, the three comparators all output a low level. At this time, the OR gate input ends are all low levels. At this time, the OR gate outputs a low level, that is, when the EPM flag is 0, there is no need to enter the EPM. Of course, in some cases, only one or two comparators can be used to generate the EPM flag to determine whether it is necessary to enter the EPM. When only one comparator is used, the OR gate may not be used and the comparator output may be directly used as the EPM flag.

[0083] Further, such as Fig.13 As shown, the control device further includes a timing unit 114 and a storage unit 113. The timing unit 114 is used to calculate the time according to the control signal G of Q2. Q2 The on-time of Q2 is timed; the storage unit is used to record the on-time T of the freewheeling tube in the previous switching cycle in the non-enhanced power mode. Q2_reg Specifically, according to the EPM flag, in each switching cycle, when EPM is 1, the Q2 on-time recorded in the storage unit will no longer be updated; when EPM is 0, the storage unit will update the recorded value to the latest Q2 on-time. If EPM is always 0, the on-time T recorded in the storage unit Q2_reg After entering the enhanced power mode, the on-time of Q2 is no longer calculated based on the unbalanced coefficient control and the inductor induced voltage formula, but is calculated based on the loop compensation value V comp and the conduction time T recorded by the storage unit 113 Q2_regDecision. It should be noted that the control unit 12 can also be used to execute other method steps in the embodiment of the aforementioned asymmetric half-bridge flyback circuit control method to achieve the above control process. Specifically, the control device can be composed of analog devices, digital devices, or a combination of multiple control modes composed of discrete devices, or an integrated circuit. The control device can also be integrated in an existing asymmetric half-bridge flyback circuit control chip to increase the output power of the circuit, so that the circuit has a wider range of applications.

[0084] The above disclosure is only the preferred embodiment of the present application, and cannot be used to limit the scope of rights of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this specification are still within the scope covered by the present application.

Claims

1. A control method for an asymmetric half-bridge flyback circuit, characterized in that: The working mode of the asymmetric half-bridge flyback circuit includes an enhanced power mode; the asymmetric half-bridge flyback circuit includes an energy storage tube and a freewheeling tube; the control method includes the following steps: Acquiring a power parameter, where the power parameter can characterize the output power of the asymmetric half-bridge flyback circuit; Comparing the power parameter with a preset power parameter; the power parameter includes one or more of a loop compensation amount, a current parameter, and a conduction time of the energy storage tube; the preset power parameter includes one or more of a preset loop compensation amount, a preset current parameter, and a preset conduction time of the energy storage tube; When the power parameter is greater than the preset power parameter, controlling the asymmetric half-bridge flyback circuit to enter the enhanced power mode; In the enhanced power mode, the conduction time of the energy storage tube is controlled to be positively correlated with the loop compensation amount, or the conduction time of the freewheeling tube is controlled to be negatively correlated with the loop compensation amount; wherein the loop compensation amount is positively correlated with the output power.

2. The control method according to claim 1, characterized in that: The following steps are also included: Recording the critical on-time; the critical on-time is the on-time of the freewheeling tube when the asymmetric half-bridge flyback circuit operates in the critical mode; When entering the enhanced power mode, the conduction time of the freewheeling tube is controlled to be less than or equal to the critical conduction time, and the conduction time of the energy storage tube is controlled to be positively correlated with the loop compensation amount.

3. The control method according to claim 2, characterized in that: The enhanced power mode includes a first control mode; In the first control mode, the conduction time of the freewheeling tube is controlled to be fixed to the critical conduction time; When the peak current is used to control the energy storage tube, the conduction time of the energy storage tube is controlled to be positively correlated with the loop compensation amount, including the steps of: controlling the peak current command value to be positively correlated with the loop compensation amount; When the energy storage tube is controlled by adopting a constant on-time, the on-time of the energy storage tube is positively correlated with the loop compensation amount, including the steps of controlling the on-time target value of the energy storage tube to be positively correlated with the loop compensation amount.

4. The control method according to claim 1, characterized in that: The following steps are involved: Recording a critical conduction parameter; the critical conduction parameter represents the conduction time of the energy storage tube when the asymmetric half-bridge flyback circuit operates in a critical mode; When entering the enhanced power mode, the critical conduction parameter is controlled to increase or remain unchanged, and the conduction time of the freewheeling tube is controlled to be negatively correlated with the loop compensation amount.

5. The control method according to claim 4, characterized in that: The enhanced power mode includes a second control mode; In the second control mode, the conduction time of the freewheeling tube is controlled to be negatively correlated with the loop compensation amount; When the energy storage tube is controlled by using the peak current, the critical conduction parameter is the peak current command value; The peak current command value in the second control mode is equal to the maximum peak current command value in the critical mode; When the energy storage tube is controlled by a constant conduction time, the critical conduction parameter is the conduction time target value of the energy storage tube; the conduction time target value of the energy storage tube in the second control mode is equal to the maximum conduction time target value of the energy storage tube in the critical mode.

6. The control method according to any one of claims 1 to 5, characterized in that: The current parameter represents the excitation inductance current of the asymmetric half-bridge flyback circuit; the output power corresponding to the preset power parameter is greater than or equal to the output power of the asymmetric half-bridge flyback circuit operating in a critical mode.

7. The control method according to claim 1, characterized in that: The working modes of the asymmetric half-bridge flyback circuit also include hiccup mode, discontinuous mode and critical mode; in the enhanced power mode, the conduction time of the freewheeling tube is set to a minimum conduction time; the control method also includes the steps of: In the non-enhanced power mode, the conduction time of the freewheeling tube is recorded and updated, and the conduction time of the freewheeling tube in the enhanced power mode is determined at least according to the conduction time of the freewheeling tube recorded in the non-enhanced power mode.

8. A control device for an asymmetric half-bridge flyback circuit, characterized in that: include: A power judgment module, used to judge whether the asymmetric half-bridge flyback circuit needs to enter an enhanced power mode according to a power parameter characterizing the output power of the asymmetric half-bridge flyback circuit and a preset power parameter; the power parameter includes one or more of a loop compensation amount, a current parameter, and a conduction time of the energy storage tube; the preset power parameter includes one or more of a preset loop compensation amount, a preset current parameter, and a preset conduction time of the energy storage tube; A control unit is used to control the conduction time of the energy storage tube to be positively correlated with the loop compensation amount or to control the conduction time of the freewheeling tube to be negatively correlated with the loop compensation amount when the asymmetric half-bridge flyback circuit enters the enhanced power mode; wherein the loop compensation amount is positively correlated with the output power of the asymmetric half-bridge flyback circuit.

9. The control device according to claim 8, characterized in that: The power judgment module includes a first comparator and / or a second comparator and / or a third comparator; the power judgment module also includes an OR gate; Wherein, the comparison terminal of the first comparator is used to receive the loop compensation amount; the loop compensation amount is the power parameter; The reference terminal of the first comparator is used to receive the preset loop compensation amount; the preset loop compensation amount is the preset power parameter; The comparison terminal of the second comparator is used to receive the current parameter; the current parameter is the power parameter; the current parameter represents the excitation inductance current of the asymmetric half-bridge flyback circuit; The reference terminal of the second comparator is used to receive the preset current parameter; the preset current parameter is the preset power parameter; The comparison end of the third comparator is used to receive the conduction time of the energy storage tube; the conduction time of the energy storage tube is the power parameter; The reference end of the third comparator is used to receive the preset conduction time of the energy storage tube; the preset conduction time of the energy storage tube is the preset power parameter; The output ends of the first comparator and / or the second comparator and / or the third comparator are electrically connected to the input ends of the OR gate respectively, and the OR gate determines whether it is necessary to enter the enhanced power mode according to the comparison results of the first comparator and / or the second comparator and / or the third comparator; The output power corresponding to the preset power parameter is greater than the output power of the asymmetric half-bridge flyback circuit operating in a critical mode.

10. The control device according to claim 8, characterized in that: It also includes a storage unit, which is used to record the conduction time of the freewheeling tube in a previous switching cycle in the non-enhanced power mode.

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