Voltage-second balance control circuit, method, chip and power supply equipment
By using a volt-second balance control circuit in the asymmetric half-bridge flyback converter, the shutdown time of the second primary switch tube is adjusted, and the problem of excessive negative excitation current caused by error in the prior art is solved, and the efficiency of the converter is improved.
Patent Information
- Application Number
- CN202510370394.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-26
- Publication Date
- 2025-07-29
AI Technical Summary
There are sampling errors and calculation errors in the volt-second balance control scheme of existing asymmetric half-bridge flyback converters, resulting in excessive negative excitation current, affecting the efficiency of the converter.
The volt-second balance control circuit is adopted, including the volt-second balance module and the primary control module. The volt-second balance time is determined based on the volt-second balance principle, and the turn-off time of the second primary switch tube is adjusted under preset conditions to achieve bidirectional adjustment of volt-second balance, avoiding the shutdown time caused by calculation errors later than the zero-crossing point of the excitation current.
Reduce the negative excitation current and improve the efficiency of the asymmetric half-bridge flyback converter.
Smart Images
Figure CN120389622A_ABST
Abstract
Description
Technical Field
[0001] Embodiments of the present disclosure relate to the field of integrated circuit technologies, and particularly to a volt-second balance control circuit, method, chip, and power supply device. Background Art
[0002] In the volt-second balance control scheme of an asymmetrical half-bridge flyback converter, first, a volt-second balance moment is determined based on the excitation voltage, demagnetization voltage, and conduction duration of the first primary switch tube. Then, the moment obtained by delaying the volt-second balance moment by a certain time is used as the turn-off moment of the second primary switch tube.
[0003] However, in the existing control scheme, there are certain sampling errors and calculation errors in the process of determining the volt-second balance moment, resulting in the calculated volt-second balance moment being much later than the actual zero-crossing moment of the excitation current. As a result, even if the calculated volt-second balance moment is used as the turn-off moment of the second primary switch tube, there is still a large negative excitation current, thus affecting the efficiency of the asymmetrical half-bridge flyback converter. Summary of the Invention
[0004] The present disclosure provides a volt-second control circuit, method, chip, and power supply device, which can achieve bidirectional adjustment of volt-second balance, reduce negative excitation current, and improve the efficiency of an asymmetrical half-bridge flyback converter.
[0005] In a first aspect, the present disclosure provides a volt-second balance control circuit applied to an asymmetrical half-bridge flyback converter. The asymmetrical half-bridge flyback converter includes: a primary power loop and a secondary power loop, the primary power loop and the secondary power loop are coupled, and the primary power loop includes a primary winding and a first primary switch tube and a second primary switch tube connected in series between a voltage input terminal and the ground.
[0006] The volt-second balance control circuit includes: a volt-second balance module and a primary control module. The input terminal of the volt-second balance module is connected to the sampling point of the primary power loop, and the output terminal of the volt-second balance module is connected to the control terminal of the primary power loop through the primary control module.
[0007] The volt-second balance module is configured to determine a volt-second balance moment based on the volt-second balance principle according to the excitation voltage, demagnetization voltage, and excitation duration of the primary power loop in the current switching cycle.
[0008] The primary control module is configured to, in response to the first primary switch tube satisfying a preset condition, when the first turn-off moment is later than the volt-second balance moment, determine that the second turn-off moment is earlier than the first turn-off moment, and when the first turn-off moment is not later than the volt-second balance moment, determine that the second turn-off moment is earlier than the volt-second balance moment.
[0009] Wherein, the preset condition is to achieve zero-voltage turn-on in the current switching period, the first turn-off moment is the turn-off moment of the second primary switch in the current switching period, and the second turn-off moment is the turn-off moment of the second primary switch in the next switching period.
[0010] In some embodiments of the present disclosure, the primary control module is further configured to, in response to the first primary switch not satisfying the preset condition, determine that the second turn-off moment is later than the first turn-off moment.
[0011] In some embodiments of the present disclosure, the volt-second balance control circuit further includes a primary sampling module, and the input end of the volt-second balance module is connected to the sampling point of the primary power circuit through the primary sampling module.
[0012] The primary sampling module is configured to sample the voltage at the sampling point to obtain a sampled voltage signal. The volt-second balance module is further configured to, in the current switching period, determine the voltage of the sampled voltage signal at the turn-on moment of the first primary switch to obtain a turn-on voltage. The primary control module is further configured to compare the turn-on voltage with a first preset voltage to determine whether the first primary switch satisfies the preset condition.
[0013] In some embodiments of the present disclosure, the primary control module includes an adjustment signal unit and a time adjustment unit.
[0014] The adjustment signal unit is configured to generate a first adjustment signal in response to the turn-on voltage being greater than the first preset voltage; generate a second adjustment signal in response to the turn-on voltage being less than the first preset voltage when the first turn-off moment is later than the volt-second balance moment, and generate a third adjustment signal when the first turn-off moment is not later than the volt-second balance moment.
[0015] The time adjustment unit is configured to, according to the first adjustment signal, extend the first turn-off moment by a preset duration to obtain the second turn-off moment; according to the second adjustment signal, advance the first turn-off moment by the preset duration to obtain the second turn-off moment; according to the third adjustment signal, advance the volt-second balance moment by the preset duration to obtain the second turn-off moment.
[0016] In some embodiments of the present disclosure, the time adjustment unit includes a first current source, a second current source, a first switch, a second switch, a comparator, and a capacitor. The output terminal of the first current source is connected to the first plate of the capacitor, the positive input terminal of the comparator, and the input terminal of the second current source through the first switch. The output terminal of the second current source is grounded through the second switch. The second plate of the capacitor is grounded. The input terminal of the first current source is connected to an external power supply. The negative input terminal of the comparator is configured to receive a second preset voltage. The control terminal of the first switch is connected to the control terminal of the first primary switch tube. The control terminal of the second switch is connected to the control terminal of the second primary switch tube.
[0017] The first current source is configured to generate a first current according to the excitation voltage and generate an adjustment current according to an adjustment signal, so as to provide a charging current to the capacitor. The charging current is the sum of the first current and the adjustment current. The adjustment signal is any one of the first adjustment signal, the second adjustment signal, and the third adjustment signal.
[0018] The second current source is configured to generate a second current according to the demagnetization voltage. The comparator is configured to generate a turn-off indication signal to indicate the generation of a turn-off signal of the second primary switch tube when the voltage across the capacitor is less than the second preset voltage in the conduction state of the second primary switch tube.
[0019] In some embodiments of the present disclosure, the volt-second balance module is further configured to determine the voltage of the sampling voltage signal after the conduction moment of the first primary switch tube in the current switching period to obtain the excitation voltage, determine the voltage of the sampling voltage signal at the conduction moment of the second primary switch tube to obtain the demagnetization voltage, and determine the conduction duration of the first primary switch tube to obtain the excitation duration.
[0020] In some embodiments of the present disclosure, the primary sampling module includes a first primary sampling unit and a second primary sampling unit. The sampling points include a first sampling point and a second sampling point. The input terminal of the first primary sampling unit is connected to the first sampling point. The input terminal of the second primary sampling unit is connected to the second sampling point. The output terminals of the first primary sampling unit and the second primary sampling unit are connected to the input terminal of the volt-second balance module.
[0021] The first primary sampling unit is configured to sample the voltage of the first sampling point to obtain a first sampling voltage signal. The second primary sampling unit is configured to sample the voltage of the second sampling point to obtain a second sampling voltage signal.
[0022] The volt-second balance module is further configured to, in the current switching cycle, determine the voltage of the first sampled voltage signal at the conduction moment of the first primary switching tube to obtain the conduction voltage, determine the voltage of the first sampled voltage signal after the conduction moment of the first primary switching tube to obtain the excitation voltage, and determine the voltage of the second sampled voltage signal at the conduction moment of the second primary switching tube to obtain the demagnetization voltage.
[0023] In some embodiments of the present disclosure, the volt-second balance module is further configured to determine the product of the excitation voltage and the excitation duration, determine the ratio of the product to the demagnetization voltage as the demagnetization duration, and determine the volt-second balance moment according to the demagnetization duration.
[0024] In a second aspect, the present disclosure provides a volt-second balance control method applied to an asymmetrical half-bridge flyback converter. The asymmetrical half-bridge flyback converter includes a primary power loop and a secondary power loop. The primary power loop and the secondary power loop are coupled. The primary power loop includes a primary winding, a first primary switching tube, and a second primary switching tube connected in series between a voltage input terminal and the ground.
[0025] The method includes:
[0026] In the current switching cycle, based on the volt-second balance principle, determine the volt-second balance moment according to the excitation voltage, demagnetization voltage, and excitation duration of the primary power loop; in response to the first primary switching tube satisfying a preset condition, when the first turn-off moment is later than the volt-second balance moment, determine that the second turn-off moment is earlier than the first turn-off moment; in response to the first primary switching tube satisfying a preset condition, when the first turn-off moment is not later than the volt-second balance moment, determine that the second turn-off moment is earlier than the volt-second balance moment.
[0027] Wherein, the preset condition is zero-voltage turn-on in the current switching cycle. The first turn-off moment is the turn-off moment of the second primary switching tube in the current switching cycle, and the second turn-off moment is the turn-off moment of the second primary switching tube in the next switching cycle.
[0028] In a third aspect, the present disclosure provides a chip including any of the volt-second balance control circuits provided in the first aspect.
[0029] In a fourth aspect, the present disclosure provides a power supply device including an asymmetrical half-bridge flyback converter and any of the volt-second balance control circuits provided in the first aspect.
[0030] In the technical solution of the present disclosure, a volt-second balance control circuit is provided, which includes a volt-second balance module and a primary control module. In the current switching cycle, based on the volt-second balance principle, the volt-second balance module determines the volt-second balance moment according to the excitation voltage, demagnetization voltage, and excitation duration of the primary power circuit. When the first primary switch satisfies the preset condition, the primary control module determines that the second turn-off moment is ahead of the first turn-off moment when the first turn-off moment is later than the volt-second balance moment, and determines that the second turn-off moment is ahead of the volt-second balance moment when the first turn-off moment is not later than the volt-second balance moment. The volt-second balance moment can be used as the turn-off reference moment of the second primary switch. Whether the turn-off moment of the second primary switch is ahead of or behind the turn-off reference moment, the turn-off moment of the second primary switch can be adaptively adjusted to achieve bidirectional regulation of volt-second balance, which can avoid the turn-off moment of the second primary switch being later than the zero-crossing point of the excitation current due to calculation errors, thereby reducing the negative excitation current and improving the efficiency of the asymmetrical half-bridge flyback converter. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. It should be understood that the following described drawings only relate to some embodiments of the present disclosure and do not limit the present disclosure, where:
[0032] Figure 1 FIG. 9 is a schematic structural diagram of a control circuit of an asymmetrical half-bridge flyback converter provided in the prior art.
[0033] Figure 2 FIG. 13 is a schematic diagram of the working waveforms of an asymmetrical half-bridge flyback converter provided in the prior art.
[0034] Figure 3 FIG. 17 is a schematic structural diagram of a volt-second balance control circuit of an asymmetrical half-bridge flyback converter provided in an embodiment of the present disclosure.
[0035] Figure 4 FIG. 21 is a schematic structural diagram of another volt-second balance control circuit of an asymmetrical half-bridge flyback converter provided in an embodiment of the present disclosure.
[0036] Figure 5 FIG. 25 is a schematic diagram of the working waveforms of an asymmetrical half-bridge flyback converter provided in an embodiment of the present disclosure.
[0037] Figure 6 FIG. 29 is a schematic diagram of the working waveforms of another asymmetrical half-bridge flyback converter provided in an embodiment of the present disclosure.
[0038] Figure 7 FIG. 33 is a schematic diagram of the working waveforms of yet another asymmetrical half-bridge flyback converter provided in an embodiment of the present disclosure.
[0039] Figure 8 Schematic circuit diagram of a time adjustment unit provided by an embodiment of the present disclosure.
[0040] Figure 9 Schematic flowchart of a volt-second balance control method provided by an embodiment of the present disclosure. Detailed implementation manners
[0041] In order to make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are some but not all of the embodiments of the present disclosure. All other embodiments obtained by those skilled in the art without creative efforts based on the described embodiments of the present disclosure also fall within the scope of protection of the present disclosure.
[0042] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the subject matter of the present disclosure belongs. Further, it will be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the specification and the relevant art, and will not be interpreted in an idealized or overly formal form unless expressly defined otherwise herein. As used herein, the statement of connecting two or more parts together shall mean that these parts are directly joined together or joined through one or more intermediate components.
[0043] Referring to "embodiments" in the present disclosure means that specific features, structures, or characteristics described in connection with the embodiments may be included in at least one embodiment of the present application. The phrase "embodiment" appearing in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described in the present disclosure may be combined with other embodiments.
[0044] In addition, terms such as "first", "second", etc. in the specification and claims of the present disclosure or in the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order, and may explicitly or implicitly include one or more of such features.
[0045] The term "and / or" in the present disclosure is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: the existence of A, the simultaneous existence of A and B, and the existence of B. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.
[0046] In the description of the present disclosure, unless otherwise specified, the meanings of "multiple" and "at least two" refer to more than two (including two). Similarly, "multiple groups" and "at least two groups" refer to more than two groups (including two groups).
[0047] To enable those skilled in the art to better understand the solution of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.
[0048] Figure 1 FIG. 1 is a schematic structural diagram of a control circuit of an asymmetric half-bridge flyback converter provided in the prior art, as Figure 1 shown, the asymmetric half-bridge flyback converter 10 includes an input capacitor Cin, a first primary switch Q1, a second primary switch Q2, a resonant inductor Lr, a primary winding Np, a resonant capacitor Cr, and a sampling resistor Rs.
[0049] Among them, the first plate of the input capacitor Cin is connected to the voltage input terminal and the first end of the first primary switch Q1. The second end of the first primary switch Q1 is connected to the first end of the resonant inductor Lr and the first end of the second primary switch Q2. The second end of the resonant inductor Lr is connected to the power ground PGND through the primary winding Np, the resonant capacitor Cr, and the sampling resistor Rs. The second end of the second primary switch Q2 is connected to the power ground PGND.
[0050] The asymmetric half-bridge flyback converter 10 further includes an auxiliary winding Naux, a first auxiliary sampling resistor R1, and a second auxiliary sampling resistor R2. Among them, the first end of the auxiliary winding Naux is connected to the first end of the first auxiliary sampling resistor R1. The second end of the auxiliary winding Naux is connected to the power ground PGND. The second end of the first auxiliary sampling resistor R1 is connected to the power ground PGND through the second auxiliary sampling resistor R2.
[0051] The asymmetric half-bridge flyback converter 10 further includes a secondary winding Ns, an output capacitor Cout, and a secondary switch Q3. Among them, the first end of the secondary winding Ns is connected to the voltage output terminal and the first plate of the output capacitor Cout. The second end of the secondary winding Ns is connected to the first end of the secondary switch Q3. The second end of the secondary switch Q3 and the second plate of the output capacitor Cout are connected to the signal ground SGND.
[0052] The primary control circuit 20 includes a primary driver 21, a primary controller 22, a volt-second balance unit 23, and a primary sampling unit 24. The input end of the primary sampling unit 24 is connected to the connection point of the first auxiliary sampling resistor R1 and the second auxiliary sampling resistor R2. The output end of the primary sampling unit 24 is connected to the input end of the primary driver 21 through the volt-second balance unit 23 and the primary controller 22. The two output ends of the primary driver 21 are respectively connected to the control ends of the first primary switch Q1 and the second primary switch Q2.
[0053] Figure 2 A schematic diagram of the working waveform of an asymmetrical half-bridge flyback converter provided for the prior art is shown in Figure 2 As shown, the asymmetrical half-bridge flyback converter 10 operates in the Critical Conduction Mode (CrM), and the first primary switch Q1 and the second primary switch Q2 conduct alternately.
[0054] The primary sampling unit 24 can continuously sample the voltage at the connection point of the first auxiliary sampling resistor R1 and the second auxiliary sampling resistor R2 during the alternating conduction of the first primary switch Q1 and the second primary switch Q2 to obtain the auxiliary voltage signal Vaux.
[0055] When the first primary control signal VQ1 is at a high level, the first primary switch Q1 conducts, and the magnetizing current Imag increases. The volt-second balance unit 23 can determine the magnetizing voltage of the asymmetrical half-bridge flyback converter and the conduction duration of the first primary switch Q1 based on the auxiliary voltage signal Vaux. When the second primary control signal VQ2 is at a high level, the second primary switch Q2 conducts, and the magnetizing current Imag linearly decreases. The volt-second balance unit 23 can determine the demagnetizing voltage of the asymmetrical half-bridge flyback converter based on the auxiliary voltage signal Vaux.
[0056] The volt-second balance unit 23 can also calculate the volt-second balance moment according to the magnetizing voltage, the demagnetizing voltage, and the conduction duration of the first primary switch Q1, and delay the volt-second balance moment for a period of time as the turn-off moment of the second primary switch Q2. Obviously, the turn-off moment of the second primary switch Q2 is later than the volt-second balance moment.
[0057] There is a sampling error in the working process of the primary sampling unit 24, and there is a calculation error in the working process of the volt-second balance unit 23, resulting in the volt-second balance moment calculated by the volt-second balance unit 23 being much later than the actual zero-crossing point of the magnetizing current Imag, as shown in Figure 2 As shown. Then, even if the turn-off moment of the second primary switch Q2 is adjusted forward to the volt-second balance moment, the negative current of the magnetizing current Imag is still too large, resulting in too large circulating power of the asymmetrical half-bridge flyback converter, thereby affecting the efficiency of the asymmetrical half-bridge flyback converter.
[0058] In view of this, the present disclosure provides a volt-second balance control circuit for an asymmetrical half-bridge flyback converter, including a volt-second balance module and a primary control module. The volt-second balance module determines the volt-second balance moment based on the volt-second balance principle according to the excitation voltage, demagnetization voltage, and excitation duration of the primary power loop in the current switching cycle. When the first primary switch meets the preset conditions, the primary control module determines that the second turn-off moment is earlier than the first turn-off moment when the first turn-off moment is later than the volt-second balance moment, and determines that the second turn-off moment is earlier than the volt-second balance moment when the first turn-off moment is not later than the volt-second balance moment. The volt-second balance moment can be used as the turn-off reference moment of the second primary switch. Whether the turn-off moment of the second primary switch is earlier or later than the turn-off reference moment, the turn-off moment of the second primary switch can be adaptively adjusted to achieve bidirectional regulation of volt-second balance, which can avoid the turn-off moment of the second primary switch being later than the zero-crossing point of the excitation current due to calculation errors, thereby reducing the negative excitation current and improving the efficiency of the asymmetrical half-bridge flyback converter.
[0059] The technical solutions will be described in detail below with several specific embodiments.
[0060] Figure 3 FIG. is a schematic structural diagram of a volt-second control circuit for an asymmetrical half-bridge flyback converter provided by an embodiment of the present disclosure. As Figure 3 shown, the asymmetrical half-bridge flyback converter 100 includes a primary power loop 110 and a secondary power loop 120, and the primary power loop 110 and the secondary power loop 120 are coupled.
[0061] Among them, the primary power loop 110 includes a first primary switch Q1, a second primary switch Q2, and a primary winding Np. The first primary switch Q1 and the second primary switch Q2 are connected in series between the voltage input terminal and the power ground PGND.
[0062] Exemplarily, as Figure 3 shown, the primary power loop 110 further includes a resonant inductor Lr, a resonant capacitor Cr, an input capacitor Cin, a sampling resistor Rs, an auxiliary winding Naux, a first auxiliary sampling resistor R1, and a second auxiliary sampling resistor R2. The first end of the auxiliary winding Naux is connected to the power ground PGND through the first auxiliary sampling resistor R1 and the second auxiliary sampling resistor R2 in sequence, and the second end of the auxiliary winding Naux is connected to the power ground PGND. Among them, the connection point of the first auxiliary sampling resistor R1 and the second auxiliary sampling resistor R2 is the sampling point of the primary power loop 110.
[0063] The first electrode plate of the input capacitor Cin is the voltage input terminal. The voltage input terminal is successively connected to the power ground PGND through the first primary switching transistor Q1 and the second primary switching transistor Q2. The connection point of the first primary switching transistor Q1 and the second primary switching transistor Q2 is successively connected to the power ground PGND through the resonant inductor Lr, the primary winding Np, the resonant capacitor Cr, and the sampling resistor Rs. The second electrode plate of the input capacitor Cin is connected to the power ground PGND. Among them, the control terminals of the first primary switching transistor Q1 and the second primary switching transistor Q2 constitute the control terminal of the primary power circuit 110.
[0064] The secondary power circuit 120 includes a secondary winding Ns, an output capacitor Cout, and a secondary switching transistor Q3. The first electrode plate of the output capacitor Cout is the voltage output terminal. The second electrode plate of the output capacitor Cout is connected to the signal ground SGND. The secondary winding Ns is coupled with the primary winding Np and is also coupled with the auxiliary winding Naux.
[0065] As Figure 3 shown, the first end of the secondary winding Ns is connected to the voltage output terminal through the secondary switching transistor Q3, and the second end of the secondary winding Ns is connected to the second electrode plate of the output capacitor Cout. Alternatively, the first end of the secondary winding Ns is connected to the first electrode plate of the output capacitor Cout, and the second end of the secondary winding Ns is connected to the signal ground SGND through the secondary switching transistor Q3, as Figure 4 shown. Figure 4 This is a schematic structural diagram of a volt-second control circuit for another asymmetrical half-bridge flyback converter provided by an embodiment of the present disclosure.
[0066] Continuing to refer to Figure 3 , the volt-second balance control circuit 200 includes a volt-second balance module 210 and a primary control module 220. For example, the primary control module 220 is an asymmetrical half-bridge (AHB) controller. The input terminal of the volt-second balance module 210 is connected to the sampling point of the primary power circuit 110, and the output terminal of the volt-second balance module 210 is connected to the control terminal of the primary power circuit 110 through the primary control module 220.
[0067] The volt-second balance module 210 is configured to, in the current switching period, based on the volt-second balance principle, according to the excitation voltage V mag 、demagnetization voltage V dem and excitation duration T mag , determine the volt-second balance moment t'. The primary control module 220 is configured to, when the first primary switching transistor Q1 meets the preset conditions, when the first turn-off moment is later than the volt-second balance moment t', determine that the second turn-off moment t2 is ahead of the first turn-off moment t1, and when the first turn-off moment t1 is not later than the volt-second balance moment t', determine that the second turn-off moment t2 is ahead of the volt-second balance moment t'.
[0068] Wherein, the preset condition is to achieve zero-voltage turn-on in the current switching period. The first turn-off moment t1 is the turn-off moment of the second primary switch Q2 in the current switching period, and the second turn-off moment t2 is the turn-off moment of the second primary switch Q2 in the next switching period.
[0069] Exemplarily, as Figure 3 shown, the volt-second balance control circuit 200 further includes a primary sampling module 230 and a primary driving module 240. The input end of the volt-second balance module 210 is connected to the sampling point of the primary power loop 110 through the primary sampling module 230, and the output end of the primary control module 220 is respectively connected to the control ends of the first primary switch Q1 and the second primary switch Q2 through the primary driving module 240.
[0070] The primary sampling module 230 can sample the voltage of the sampling point of the primary power loop 110 during the alternating conduction of the first primary switch Q1 and the second primary switch Q2 to obtain a first sampling voltage signal Vzcd, as Figure 5 shown. Figure 5 This is a schematic diagram of the working waveform of an asymmetric half-bridge flyback converter provided by the embodiment of the present disclosure.
[0071] Continue to refer to Figure 5 , the asymmetric half-bridge flyback converter operates in CrM. The current switching period is from time T0 to time T1, and the next switching period is from time T1 to time T2.
[0072] In the current switching period, the first primary control signal VQ1 flips from a low level to a high level at time T0. Time T0 is the conduction time of the first primary switch Q1 in the current switching period. At time T0, the volt-second balance module 210 can determine the voltage of the first sampling voltage signal Vzcd, and this voltage is the conduction voltage V turnon .
[0073] In the current switching period, after time T0, the first primary switch Q1 continuously remains in a stable conduction state until the first primary control signal VQ1 flips to a low level. After time T0 and until the moment when the first primary control signal VQ1 flips to a low level, the volt-second balance module 210 can determine the voltage of the first sampling voltage signal Vzcd, and this voltage is the excitation voltage V mag .
[0074] In the current switching period, at the moment when the second primary control signal VQ1 flips from a low level to a high level, that is, at the conduction moment of the second primary switch Q2, the volt-second balance module 210 can determine the voltage of the first sampling voltage signal Vzcd, and this voltage is the demagnetization voltage V dem .
[0075] Thus, the volt-second balance module 230 can determine the voltage of the first sampled voltage signal Vzcd at the conduction moment of the first primary switch Q1 in the current switching cycle to obtain the conduction voltage V turnon , and determine the voltage of the first sampled voltage signal Vzcd after the conduction moment of the first primary switch Q1 to obtain the exciting voltage V mag , and determine the voltage of the first sampled voltage signal Vzcd at the conduction moment of the second primary switch Q2 to obtain the demagnetizing voltage V dem .
[0076] It should be noted that in practical applications, the primary sampling module 230 can be a single sampling unit, as Figure 3 shown, or the primary sampling module 230 can include two sampling units, as Figure 4 shown.
[0077] Exemplarily, as Figure 4 shown, the asymmetrical half-bridge flyback converter 100 further includes a first capacitor voltage sampling resistor R3 and a second capacitor voltage sampling resistor R4. The connection point of the resonant capacitor Cr and the primary winding Np is connected to the power ground PGND through the first capacitor voltage sampling resistor R3 and the second capacitor voltage sampling resistor R4.
[0078] The sampling points include a first sampling point and a second sampling point. Among them, the first sampling point is the connection point of the first auxiliary sampling resistor R1 and the second auxiliary sampling resistor R2, and the second sampling point is the connection point of the first capacitor voltage sampling resistor R3 and the second capacitor voltage sampling resistor R4.
[0079] The primary sampling module 230 includes a first primary sampling unit 231 and a second primary sampling unit 232. The input end of the first primary sampling unit 231 is connected to the first sampling point, the input end of the second primary sampling unit 232 is connected to the second sampling point, and the output ends of the first primary sampling unit 231 and the second primary sampling unit 232 are connected to the input end of the volt-second balance module 220.
[0080] The first primary sampling unit 231 can sample the voltage of the first sampling point to obtain the first sampled voltage signal Vzcd, and the second primary sampling unit 232 can sample the voltage of the second sampling point to obtain the second sampled voltage signal Vcr, as Figure 6 shown, Figure 6 which is a schematic diagram of the working waveform of another asymmetrical half-bridge flyback converter provided by the present disclosure.
[0081] Continue to refer to Figure 6 , the asymmetrical half-bridge flyback converter operates in CrM, the current switching cycle is from the moment T0 to the moment T1, and the next switching cycle is from the moment T1 to the moment T2.
[0082] In the current switching period, the first primary control signal VQ1 flips from a low level to a high level at time T0. Time T0 is the conduction time of the first primary switch Q1 in the current switching period. At time T0, the volt-second balance module 210 can determine the voltage of the first sampled voltage signal Vzcd, and this voltage is the conduction voltage V turnon 。
[0083] In the current switching period, after time T0, the first primary switch Q1 remains in a stable conduction state until the first primary control signal VQ1 flips to a low level. From time T0 until the time when the first primary control signal VQ1 flips to a low level, the volt-second balance module 210 can determine the voltage of the first sampled voltage signal Vzcd, and this voltage is the excitation voltage V mag 。
[0084] In the current switching period, at the moment when the second primary control signal VQ1 flips from a low level to a high level, that is, at the conduction time of the second primary switch Q2, the volt-second balance module 210 can determine the voltage of the second sampled voltage signal Vcr, and this voltage is the demagnetization voltage V dem 。
[0085] In this way, the volt-second balance module 230 can, in the current switching period, determine the voltage of the first sampled voltage signal Vzcd at the conduction time of the first primary switch Q1 to obtain the conduction voltage V turnon and determine the voltage of the first sampled voltage signal Vzcd after the conduction time of the first primary switch Q1 to obtain the excitation voltage V mag and determine the voltage of the second sampled voltage signal Vcr at the conduction time of the second primary switch Q2 to obtain the demagnetization voltage V dem 。
[0086] Exemplarily, continue to refer to Figure 5 and Figure 6 In the current switching period, after the first primary control signal VQ1 flips to a low level, that is, after the first primary switch Q1 turns off, the volt-second balance module 210 can calculate the time difference between the turn-off time of the first primary switch Q1 and time T0 to obtain the conduction duration of the first primary switch Q1 in the current switching period, which is also the excitation duration T mag 。
[0087] In this way, in the current switching period, the volt-second balance module 210 can determine the conduction duration of the first primary switch Q1 to obtain the excitation duration T mag 。
[0088] Exemplarily, the volt-second balance module 210 can calculate the product of the excitation voltage V mag and the excitation duration T mag Vmag *T mag , then calculate the product V mag *T mag and the demagnetization voltage V dem of the ratio V mag *T mag / V dem , and determine the ratio V mag *T mag / V dem as the demagnetization duration T dem , that is, T dem =V mag *T mag / V dem , finally delay the demagnetization duration T dem at the conduction moment of the second primary switch Q2 to obtain the volt-second balance moment t'.
[0089] In this way, the volt-second balance module 210 can determine the product V mag and the excitation duration T mag of the excitation voltage V mag *T mag , and determine the ratio V mag *T mag and the demagnetization voltage V dem of the ratio V mag *T mag / V dem as the demagnetization duration T dem , and determine the volt-second balance moment t' according to the demagnetization duration T dem .
[0090] In the current switching cycle, when the drain-source voltage Vds of the first primary switch Q1 is zero at the conduction moment of the first primary switch Q1, the first primary switch Q1 realizes zero-voltage turn-on in the current switching cycle, that is, the first primary switch Q1 meets the preset conditions. The primary control module 220 responds to the first primary switch Q1 meeting the preset conditions and judges whether the turn-off moment of the second primary switch Q2 in the current switching cycle, that is, the first turn-off moment t1, is later than the volt-second balance moment t'.
[0091] When it is determined that the first turn-off moment t1 is later than the volt-second balance moment t', the primary control module 220 responds to the first turn-off moment t1 being later than the volt-second balance moment t' and advances the first turn-off moment t1 by a preset duration Δt to obtain the turn-off moment of the second primary switch Q2 in the next switching cycle, that is, the second turn-off moment t2, then t2 = t1 - Δt.
[0092] When it is determined that the first turn-off time t1 is earlier than the volt-second balance time t', in response to the first turn-off time t1 being earlier than the volt-second balance time t', the primary control module 220 advances the volt-second balance time t' by a preset duration Δt to obtain a second turn-off time t2, that is, t2 = t' - Δt.
[0093] Exemplarily, Figure 7 FIG. 5 is a schematic diagram of the working waveforms of another asymmetrical half-bridge flyback converter provided by an embodiment of the present disclosure. As Figure 7 shown, the asymmetrical half-bridge flyback converter operates in CrM. The current switching period is from time T0 to time T1, and the next switching period is from time T1 to time T2.
[0094] When it is determined that the first turn-off time t1 is equal to the volt-second balance time t', in response to the first turn-off time t1 being equal to the volt-second balance time t', the primary control module 220 advances the volt-second balance time t' by a preset duration Δt to obtain a second turn-off time t2, then t2 = t' - Δt.
[0095] In summary, taking the volt-second balance time t' as the turn-off reference time of the second primary switch Q2, whether the turn-off time of the second primary switch Q2 is ahead of or lagging behind the turn-off reference time, the turn-off time of the second primary switch Q2 can be adaptively adjusted to achieve bidirectional regulation of volt-second balance, and it can avoid the turn-off time of the second primary switch Q2 being later than the zero-crossing point of the exciting current due to calculation errors, thereby reducing the negative exciting current and further improving the efficiency of the asymmetrical half-bridge flyback converter 100.
[0096] In some embodiments, the primary control module 220 is further configured to determine that the second turn-off time t2 is later than the first turn-off time t1 in response to the first primary switch Q1 not meeting the preset conditions.
[0097] Exemplarily, in the current switching period, when the drain-source voltage Vds of the first primary switch Q1 is greater than zero at the conduction time of the first primary switch Q1, the first primary switch Q1 does not achieve zero-voltage turn-on in the current switching period, that is, the first primary switch Q1 does not meet the preset conditions. In response to the first primary switch Q1 not meeting the preset conditions, the primary control module 220 delays the first turn-off time t1 by a preset duration Δt to obtain a second turn-off time t2, that is, t2 = t1 + Δt.
[0098] In some embodiments, the volt-second balance module 210 is further configured to compare the conduction voltage V turnon with a first preset voltage Vth1 to determine whether the first primary switch Q1 meets the preset conditions.
[0099] Exemplarily, referring to Figures 5 to 7, at time T0, the voltage of the first sampling voltage signal Vzcd is related to the drain-source voltage Vds of the first primary switch Q1, that is, the conduction voltage V turnon is related to the drain-source voltage Vds of the first primary switch Q1 at time T1. Therefore, based on the conduction voltage V turnon it is possible to determine whether the first primary switch Q1 achieves zero-voltage turn-on.
[0100] When the conduction voltage V turnon is greater than the first preset voltage Vth1, that is, V turnon > Vth1, the first primary switch Q1 does not achieve zero-voltage turn-on, that is, the first primary switch Q1 does not meet the preset condition. When the conduction voltage V turnon is less than the first preset voltage Vth1, that is, V turnon < Vth1, the first primary switch Q1 achieves zero-voltage turn-on, that is, the first primary switch Q1 meets the preset condition.
[0101] In some embodiments, the primary control module 220 includes an adjustment signal unit and a time adjustment unit. The output end of the adjustment signal unit is connected to the input end of the time adjustment unit.
[0102] The adjustment signal unit is configured to generate a first adjustment signal in response to the conduction voltage V turnon being greater than the first preset voltage Vth1; and generate a second adjustment signal in response to the conduction voltage V turnon being less than the first preset voltage Vth1 when the first turn-off time t1 is later than the volt-second balance time t', and generate a third adjustment signal when the first turn-off time t1 is not later than the volt-second balance time t'.
[0103] The time adjustment unit is configured to extend the first turn-off time t1 by a preset duration Δt according to the first adjustment signal to obtain a second turn-off time t2; advance the first turn-off time by the preset duration Δt according to the second adjustment signal to obtain a second turn-off time t2; and advance the volt-second balance time t' by the preset duration Δt according to the third adjustment signal to obtain a second turn-off time t2.
[0104] Exemplarily, Figure 8 is a circuit schematic diagram of a time adjustment unit provided by an embodiment of the present disclosure. As Figure 8 shown, the time adjustment unit includes a first current source IB1, a second current source IB2, a first switch K1, a second switch K2, a comparator CMP, and a capacitor C.
[0105] Among them, the output terminal of the first current source IB1 is connected to the first electrode plate of the capacitor C, the positive input terminal of the comparator CMP, and the input terminal of the second current source IB2 through the first switch K1. The output terminal of the second current source IB2 is grounded through the second switch K2. The second electrode plate of the capacitor C is grounded. The input terminal of the first current source IB1 is connected to an external power supply.
[0106] The inverting input terminal of the comparator CMP is used to receive the second preset voltage Vth2. The control terminal of the first switch K1 is connected to the control terminal of the first primary switch tube Q1. The control terminal of the second switch K2 is connected to the control terminal of the second primary switch tube Q2.
[0107] The first current source IB1 is controlled by the excitation voltage V mag , and can generate the first current I mag according to the excitation voltage V charge . It is also controlled by the adjustment signal output by the adjustment signal unit and generates an adjustment current I' according to the adjustment signal. Therefore, the first current source IB1 can output the current I charge + I'. The second current source IB2 is controlled by the demagnetization voltage V dem , and can generate the second current I dem according to the demagnetization voltage V discharge .
[0108] When the first primary switch tube Q1 is turned on, the second primary switch tube Q2 is turned off. The first switch K1 is closed and the second switch K2 is turned off. The first current source IB1 provides a charging current I charge + I' to the capacitor C to charge the capacitor C. When the first primary switch tube Q1 is turned off, the second primary switch tube Q2 is turned on. The first switch K1 is turned off and the second switch K2 is closed. The second current source IB2 provides the second current I discharge to the capacitor C to discharge the capacitor C.
[0109] During the discharge process of the capacitor C, that is, in the on state of the second primary switch tube Q2, the comparator CMP can compare the voltage across the capacitor C with the second preset voltage Vth2. For example, the preset voltage Vth can be 0. When the voltage across the capacitor C is greater than the second preset voltage Vth2, the comparator CMP outputs a high-level signal. As the discharge process continues, the voltage across the capacitor C continues to decrease. When the voltage across the capacitor C decreases to less than the second preset voltage Vth2, the output of the comparator CMP flips to a low-level signal, that is, a turn-off indication signal is generated to indicate the generation of a turn-off signal for the second primary switch tube Q2.
[0110] Exemplarily, in the current switching cycle, the charging current of the capacitor C is I charge + I'. When the conduction voltage V turnonWhen it is greater than the first preset voltage Vth1, the adjustment signal unit generates a first adjustment signal. In the next switching period, according to the first adjustment signal, the first current source IB1 increases the preset current ΔI on the basis of the charging current I charge +I’, and adjusts the charging current to I charge +I’+ΔI, and charges the capacitor C.
[0111] Compared with the current switching period, the charging current of the capacitor C in the next switching period increases by the preset current ΔI. Therefore, the discharge duration of the capacitor C increases by the preset duration Δt, that is, the second turn-off moment t2 = t1 + Δt.
[0112] On the basis of the above embodiment, when the conduction voltage V turnon is less than the first preset voltage Vth1 and the first turn-off moment t1 is later than the volt-second balance moment t’, the adjustment signal unit generates a second adjustment signal. In the next switching period, according to the second adjustment signal, the first current source IB1 decreases the preset current ΔI on the basis of the charging current I charge +I’, and adjusts the charging current to I charge +I’-ΔI, and charges the capacitor C.
[0113] Compared with the current switching period, the charging current of the capacitor C in the next switching period decreases by the preset current ΔI. Therefore, the discharge duration of the capacitor C decreases by the preset duration Δt, that is, the second turn-off moment t2 = t1 - Δt.
[0114] On the basis of the above embodiment, when the conduction voltage V turnon is less than the first preset voltage Vth1 and the first turn-off moment t1 is not later than the volt-second balance moment t’, the adjustment signal unit generates a third adjustment signal. In the next switching period, according to the third adjustment signal, the first current source IB1 decreases the preset current ΔI on the basis of the first current I charge and adjusts the charging current to I charge -ΔI, and charges the capacitor C.
[0115] Compared with the charging current I charge , the charging current of the capacitor C in the next switching period decreases by the preset current ΔI. Therefore, the discharge duration of the capacitor C decreases by the preset duration Δt on the basis of the demagnetization duration, that is, the second turn-off moment t2 = t’ - Δt.
[0116] Figure 9 It is a schematic flowchart of a volt-second balance control method provided by an embodiment of the present disclosure. Figure 9 The shown embodiment is applicable to any volt-second balance control circuit 200 provided by the present disclosure. The specific steps of the volt-second balance control method include:
[0117] S101. Based on the volt-second balance principle, at the current switching cycle, determine the volt-second balance moment according to the exciting voltage, demagnetizing voltage, and exciting duration of the primary power circuit.
[0118] Exemplarily, first, the volt-second balance module determines the product V mag of the exciting voltage and the exciting duration T mag , then, determines the ratio V mag *T mag of the product V mag *T mag to the demagnetizing voltage V dem as the demagnetizing duration T mag *T mag / V dem , and finally, determines the volt-second balance moment t' according to the demagnetizing duration T dem . dem
[0119] In some embodiments, before S101, it further includes:
[0120] The primary sampling module samples the voltage at the sampling point of the primary power circuit to obtain a sampling voltage signal; the primary control module, at the current switching cycle, determines the voltage of the sampling voltage signal at the conduction moment of the first primary switch to obtain the conduction voltage, determines the voltage of the sampling voltage signal after the conduction moment of the first primary switch Q1 to obtain the exciting voltage, determines the voltage of the sampling voltage signal at the conduction moment of the second primary switch to obtain the demagnetizing voltage, and determines the conduction duration of the first primary switch to obtain the exciting duration.
[0121] In some other embodiments, before S101, it further includes:
[0122] The first primary sampling unit samples the voltage at the first sampling point to obtain a first sampling voltage signal, and the second primary sampling unit samples the voltage at the second sampling point to obtain a second sampling voltage signal. The primary control module, at the current switching cycle, determines the voltage of the first sampling voltage signal at the conduction moment of the first primary switch to obtain the conduction voltage, determines the voltage of the first sampling voltage signal after the conduction moment of the first primary switch to obtain the exciting voltage, determines the voltage of the second sampling voltage signal at the conduction moment of the second primary switch to obtain the demagnetizing voltage, and determines the conduction duration of the first primary switch to obtain the exciting duration.
[0123] S102. In response to the first primary switch satisfying a preset condition, when the first turn-off moment is later than the volt-second balance moment, determine that the second turn-off moment is earlier than the first turn-off moment. [[ID=*]]
[0124] Among them, the preset condition is to achieve zero-voltage turn-on in the current switching cycle. The first turn-off moment is the turn-off moment of the second primary switch in the current switching cycle, and the second turn-off moment is the turn-off moment of the second primary switch in the next switching cycle.
[0125] Exemplarily, in the current switching cycle, when the drain-source voltage of the first primary switch is zero at the turn-on moment of the first primary switch, the first primary switch achieves zero-voltage turn-on in the current switching cycle, that is, the first primary switch meets the preset condition. In response to the first primary switch meeting the preset condition, the primary control module determines whether the turn-off moment of the second primary switch in the current switching cycle, that is, the first turn-off moment, is later than the volt-second balance moment.
[0126] When it is determined that the first turn-off moment is later than the volt-second balance moment, in response to the first turn-off moment being later than the volt-second balance moment, the primary control module advances the first turn-off moment by a preset duration to obtain the turn-off moment of the second primary switch in the next switching cycle, that is, the second turn-off moment.
[0127] S103, in response to the first primary switch meeting the preset condition, when the first turn-off moment is not later than the volt-second balance moment, it is determined that the second turn-off moment is ahead of the volt-second balance moment.
[0128] Exemplarily, when it is determined that the first turn-off moment is earlier than the volt-second balance moment, in response to the first turn-off moment being earlier than the volt-second balance moment, the primary control module advances the volt-second balance moment by a preset duration to obtain the second turn-off moment.
[0129] When it is determined that the first turn-off moment is equal to the volt-second balance moment, in response to the first turn-off moment being equal to the volt-second balance moment, the primary control module advances the volt-second balance moment by a preset duration to obtain the second turn-off moment.
[0130] In the embodiments of the present disclosure, in the current switching cycle, based on the volt-second balance principle, according to the excitation voltage, demagnetization voltage, and excitation duration of the primary power circuit, the volt-second balance moment is determined. In response to the first primary switch meeting the preset condition, when the first turn-off moment is later than the volt-second balance moment, it is determined that the second turn-off moment is ahead of the first turn-off moment. When the first turn-off moment is not later than the volt-second balance moment, it is determined that the second turn-off moment is ahead of the volt-second balance moment. The volt-second balance moment can be used as the turn-off reference moment of the second primary switch. Whether the turn-off moment of the second primary switch is ahead of or behind the turn-off reference moment, the turn-off moment of the second primary switch can be adaptively adjusted to achieve bidirectional adjustment of volt-second balance, and it can avoid the turn-off moment of the second primary switch being later than the zero-crossing point of the excitation current due to calculation errors, thereby reducing the negative excitation current and improving the efficiency of the asymmetrical half-bridge flyback converter.
[0131] In some embodiments, the volt-second balance control method further includes:
[0132] S104. When the first primary switch does not meet the preset conditions, it is determined that the second turn-off time is later than the first turn-off time.
[0133] Exemplarily, in the current switching cycle, when the drain-source voltage of the first primary switch is greater than zero at the conduction time of the first primary switch, the first primary switch does not achieve zero-voltage turn-on in the current switching cycle, that is, the first primary switch does not meet the preset conditions. In response to the first primary switch not meeting the preset conditions, the primary control module delays the first turn-off time by a preset duration to obtain the second turn-off time.
[0134] In some embodiments, before S102, it further includes:
[0135] S201. Compare the conduction voltage with the first preset voltage to determine whether the first primary switch meets the preset conditions.
[0136] Exemplarily, when the conduction voltage is greater than the first preset voltage, the first primary switch does not achieve zero-voltage turn-on, that is, the first primary switch does not meet the preset conditions. When the conduction voltage is less than the first preset voltage, the first primary switch achieves zero-voltage turn-on, that is, the first primary switch meets the preset conditions.
[0137] In some embodiments, as a specific description of a possible implementation manner when executing S104, it is as follows:
[0138] The adjustment signal unit generates a first adjustment signal in response to the conduction voltage being greater than the first preset voltage. The time adjustment unit extends the first turn-off time by a preset duration according to the first adjustment signal to obtain the second turn-off time.
[0139] Exemplarily, in the next switching cycle, the first current source generates a first current according to the excitation voltage, and according to the first adjustment signal, increases the adjustment current of the current switching cycle by a preset current to obtain a new adjustment current, so as to provide a charging current to the capacitor. The charging current is the sum of the first current and the new adjustment current. The second current source generates a second current according to the demagnetization voltage to provide a discharge current to the capacitor.
[0140] Compared with the current switching cycle, the charging current of the capacitor C in the next switching cycle increases by a preset current. Therefore, the discharge duration of the capacitor C increases by a preset duration, that is, the second turn-off time is the first turn-off time extended by a preset duration.
[0141] In some embodiments, as a specific description of a possible implementation manner when executing S102, it is as follows:
[0142] The adjustment signal unit generates a second adjustment signal in response to the conduction voltage being less than the first preset voltage, and when the first turn-off moment is later than the volt-second balance moment, the time adjustment unit advances the first turn-off moment by a preset duration according to the second adjustment signal to obtain the second turn-off moment.
[0143] Exemplarily, in the next switching cycle, the first current source generates a first current according to the exciting voltage, and according to the second adjustment signal, reduces the adjustment current of the current switching cycle by a preset current to obtain a new adjustment current, so as to provide a charging current for the capacitor, and the charging current is the sum of the first current and the new adjustment current. The second current source generates a second current according to the demagnetizing voltage to provide a discharging current for the capacitor.
[0144] Compared with the current switching cycle, the charging current of the capacitor C in the next switching cycle is reduced by a preset current, so the discharging duration of the capacitor C is reduced by a preset duration, that is, the second turn-off moment is the first turn-off moment advanced by a preset duration.
[0145] In some embodiments, as a specific description of a possible implementation manner when executing S103, it is as follows:
[0146] The adjustment signal unit generates a third adjustment signal in response to the conduction voltage being less than the first preset voltage, and when the first turn-off moment is not later than the volt-second balance moment, the time adjustment unit advances the volt-second balance moment by a preset duration according to the third adjustment signal to obtain the second turn-off moment.
[0147] Exemplarily, in the next switching cycle, the first current source generates a first current according to the exciting voltage, and generates an adjustment current according to the third adjustment signal to provide a charging current for the capacitor, and the charging current is the sum of the first current and the adjustment current. The second current source generates a second current according to the demagnetizing voltage to provide a discharging current for the capacitor.
[0148] Compared with the charging current in the volt-second balance state, the charging current of the capacitor C in the next switching cycle is reduced by a preset current, so the discharging duration of the capacitor C is reduced by a preset duration on the basis of the demagnetizing duration, that is, the second turn-off moment is the volt-second balance moment advanced by a preset duration.
[0149] The present disclosure also provides a chip, including a volt-second balance control circuit 200. The chip has the corresponding functional modules and beneficial effects of the volt-second balance control circuit 200, which will not be elaborated here.
[0150] The present disclosure also provides a power supply device, including a half-bridge flyback converter 100 and a volt-second balance control circuit 200. The power supply device has the corresponding functional modules and beneficial effects of the volt-second balance control circuit 200, which will not be elaborated here.
[0151] Unless the context clearly indicates otherwise, the singular forms of words used in this specification and the appended claims include the plural, and vice versa. Thus, when referring to the singular, the corresponding plural of the term is generally included. Similarly, the terms "comprising" and "including" shall be interpreted as inclusive rather than exclusive. Likewise, the term "including" and "or" shall be interpreted as inclusive, unless such an interpretation is explicitly prohibited herein. Where the term "exemplary" is used herein, the "exemplary" is merely illustrative and should not be considered exclusive or extensive.
[0152] The above has described several embodiments of the present disclosure in detail. However, it is obvious that those skilled in the art can make various modifications and variations to the embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. The protection scope of the present disclosure is defined by the appended claims.
Claims
1. A volt-second balance control circuit, characterized in that, Applied to an asymmetrical half-bridge flyback converter, the asymmetrical half-bridge flyback converter includes: a primary power loop and a secondary power loop, the primary power loop and the secondary power loop are coupled, the primary power loop includes a primary winding, a first primary switch tube and a second primary switch tube connected in series between a voltage input terminal and the ground; The volt-second balance control circuit includes: a volt-second balance module and a primary control module, the input end of the volt-second balance module is connected to the sampling point of the primary power loop, and the output end of the volt-second balance module is connected to the control end of the primary power loop through the primary control module; The volt-second balance module is configured to, in the current switching cycle, based on the volt-second balance principle, determine the volt-second balance moment according to the excitation voltage, demagnetization voltage and excitation duration of the primary power loop; The primary control module is configured to, in response to the first primary switch tube satisfying a preset condition, when the first turn-off moment is later than the volt-second balance moment, determine that the second turn-off moment is earlier than the first turn-off moment, and when the first turn-off moment is not later than the volt-second balance moment, determine that the second turn-off moment is earlier than the volt-second balance moment; Wherein, the preset condition is to achieve zero-voltage turn-on in the current switching cycle, the first turn-off moment is the turn-off moment of the second primary switch tube in the current switching cycle, and the second turn-off moment is the turn-off moment of the second primary switch tube in the next switching cycle.
2. The volt-second balance control circuit according to claim 1, wherein The primary control module is further configured to, in response to the first primary switch tube not satisfying the preset condition, determine that the second turn-off moment is later than the first turn-off moment.
3. The volt-second balance control circuit according to claim 2, wherein, The volt-second balance control circuit further includes a primary sampling module, and the input end of the volt-second balance module is connected to the sampling point of the primary power loop through the primary sampling module; The primary sampling module is configured to sample the voltage at the sampling point to obtain a sampled voltage signal; The volt-second balance module is further configured to, in the current switching cycle, determine the voltage of the sampled voltage signal at the conduction moment of the first primary switch tube to obtain a conduction voltage; The primary control module is further configured to compare the conduction voltage with a first preset voltage to determine whether the first primary switch tube satisfies the preset condition.
4. The volt-second balance control circuit according to claim 3, wherein The primary control module includes an adjustment signal unit and a time adjustment unit; The adjustment signal unit is configured to, in response to the conduction voltage being greater than the first preset voltage, generate a first adjustment signal; in response to the conduction voltage being less than the first preset voltage, when the first turn-off moment is later than the volt-second balance moment, generate a second adjustment signal, and when the first turn-off moment is not later than the volt-second balance moment, generate a third adjustment signal; The time adjustment unit is configured to extend the first turn-off moment by a preset duration according to the first adjustment signal to obtain the second turn-off moment; advance the first turn-off moment by the preset duration according to the second adjustment signal to obtain the second turn-off moment; and advance the volt-second balance moment by the preset duration according to the third adjustment signal to obtain the second turn-off moment.
5. The volt-second balance control circuit according to claim 4, characterized in that, The time adjustment unit includes a first current source, a second current source, a first switch, a second switch, a comparator, and a capacitor; The output terminal of the first current source is connected to the first plate of the capacitor, the positive input terminal of the comparator, and the input terminal of the second current source through the first switch. The output terminal of the second current source is grounded through the second switch. The second plate of the capacitor is grounded. The input terminal of the first current source is connected to an external power supply. The negative input terminal of the comparator is configured to receive a second preset voltage. The control terminal of the first switch is connected to the control terminal of the first primary switch tube. The control terminal of the second switch is connected to the control terminal of the second primary switch tube; The first current source is configured to generate a first current according to the excitation voltage and generate an adjustment current according to an adjustment signal to provide a charging current to the capacitor. The charging current is the sum of the first current and the adjustment current. The adjustment signal is any one of the first adjustment signal, the second adjustment signal, and the third adjustment signal; The second current source is configured to generate a second current according to the demagnetization voltage; The comparator is configured to generate a turn-off indication signal to indicate the generation of a turn-off signal for the second primary switch tube when the voltage across the capacitor is less than the second preset voltage in the conduction state of the second primary switch tube.
6. The volt-second balance control circuit according to claim 3, characterized in that, The volt-second balance module is further configured to determine the voltage of the sampling voltage signal after the conduction moment of the first primary switch tube in the current switching period to obtain the excitation voltage, determine the voltage of the sampling voltage signal at the conduction moment of the second primary switch tube to obtain the demagnetization voltage, and determine the conduction duration of the first primary switch tube to obtain the excitation duration.
7. The volt-second balance control circuit according to claim 6, wherein The primary sampling module includes a first primary sampling unit and a second primary sampling unit, and the sampling points include a first sampling point and a second sampling point; The input terminal of the first primary sampling unit is connected to the first sampling point. The input terminal of the second primary sampling unit is connected to the second sampling point. The output terminals of the first primary sampling unit and the second primary sampling unit are connected to the input terminal of the volt-second balance module; The first primary sampling unit is configured to sample the voltage of the first sampling point to obtain a first sampling voltage signal; The second primary sampling unit is configured to sample the voltage of the second sampling point to obtain a second sampling voltage signal; The volt-second balance module is further configured to, in the current switching cycle, determine the voltage of the first sampled voltage signal at the conduction moment of the first primary switch tube to obtain the conduction voltage, determine the voltage of the first sampled voltage signal after the conduction moment of the first primary switch tube to obtain the excitation voltage, and determine the voltage of the second sampled voltage signal at the conduction moment of the second primary switch tube to obtain the demagnetization voltage.
8. The volt-second balance control circuit according to any one of claims 1-7, characterized in that, The volt-second balance module is further configured to determine the product of the excitation voltage and the excitation duration, determine the ratio of the product to the demagnetization voltage as the demagnetization duration, and determine the volt-second balance moment according to the demagnetization duration.
9. A volt-second balance control method, characterized in that, Applied to an asymmetrical half-bridge flyback converter, the asymmetrical half-bridge flyback converter includes: a primary power loop and a secondary power loop, the primary power loop and the secondary power loop are coupled, and the primary power loop includes a primary winding and a first primary switch tube and a second primary switch tube connected in series between the voltage input terminal and the ground. The method includes: In the current switching cycle, based on the volt-second balance principle, determine the volt-second balance moment according to the excitation voltage, demagnetization voltage, and excitation duration of the primary power loop. In response to the first primary switch tube satisfying a preset condition, when the first turn-off moment is later than the volt-second balance moment, determine that the second turn-off moment is earlier than the first turn-off moment. In response to the first primary switch tube satisfying a preset condition, when the first turn-off moment is not later than the volt-second balance moment, determine that the second turn-off moment is earlier than the volt-second balance moment. Wherein, the preset condition is zero-voltage turn-on in the current switching cycle, the first turn-off moment is the turn-off moment of the second primary switch tube in the current switching cycle, and the second turn-off moment is the turn-off moment of the second primary switch tube in the next switching cycle.
10. A chip, characterized in that, It includes the volt-second balance control circuit according to any one of claims 1-8.
11. A power supply device, characterized in that, It includes an asymmetrical half-bridge flyback converter and the volt-second balance control circuit according to any one of claims 1-8.