Asymmetric half-bridge flyback converter and input voltage detection method thereof

Abstract

The present invention discloses an asymmetric half-bridge flyback converter and an input voltage detection method thereof, the detection method comprising: sampling a predetermined parameter of the asymmetric half-bridge flyback converter during the conduction period of a first switch tube and performing sampling and holding to obtain a first sampling signal; sampling a predetermined parameter of the asymmetric half-bridge flyback converter during the conduction period of a second switch tube to obtain a second sampling signal; and obtaining a voltage detection signal representing input voltage information according to the first sampling signal and the second sampling signal. The present invention can realize functions such as input voltage protection or input voltage compensation without adding additional peripheral devices and control chip pins, and the technical solution is simple and the operation is convenient and flexible.

Description

Technical Field

[0001] The present invention relates to the technical field of asymmetric half-bridge flyback converters, and in particular to an asymmetric half-bridge flyback converter and an input voltage detection method thereof. Background Art

[0002] With the rapid development of power electronics, the application of switching converters is becoming more and more extensive, especially people have put forward more requirements for high power density, high reliability and small size switching converters. Generally, traditional low-power switching converters are implemented using flyback topology, which has the advantages of simple structure and low cost; however, ordinary flyback topology is a hard switch and cannot recover leakage inductance energy, thus limiting the efficiency and volume of small and medium power converters. In order to meet the development trend of miniaturization, lightweight and modularization of power converters, soft switching technology has become one of the hot spots of power electronics technology. "Soft switching" refers to zero voltage switching (ZVS) or zero current switching. It uses the principle of resonance to make the switch tube voltage (or current) of the switching converter change according to the sine (or quasi-sine) law. When the voltage passes through zero, the device is turned on (or when the current naturally passes through zero, the device is turned off), and the switching loss is zero, thereby improving the efficiency and switching frequency of the converter and reducing the volume of the transformer and inductor. Although soft switching technology can achieve miniaturization and modularization of power converters, many circuits, such as LLC, become very complex, which increases the cost of small and medium-power converters and is often not conducive to commercial competition. The asymmetric half-bridge flyback converter (AHB) has two switches on the primary side of the transformer, which can be provided in a half-bridge configuration and driven by different pulse width modulation (PWM) signals for the two switches. The inductor of the asymmetric half-bridge flyback converter is divided to form a transformer, so that the voltage ratio is doubled based on the winding ratio of the transformer, and it also has the additional advantage of isolation. At the same time, under the condition that the number and complexity of components are close to those of ordinary flyback converters, it can realize zero voltage turn-on of two switch tubes, recover leakage inductance energy, and easily realize self-driven synchronous rectification, which effectively improves efficiency while reducing the size of the transformer, becoming a better application solution.

[0003] A conventional flyback converter, whether a fixed-frequency flyback converter, a quasi-resonant flyback converter (QR), or an active clamp flyback converter (AFC), can detect the input voltage through an auxiliary winding detection method, that is, when the main switch is on, the voltage across the auxiliary winding represents the magnitude of the input voltage, thereby detecting the input voltage and realizing related functions such as input voltage protection or input voltage compensation of the flyback converter system.

[0004] However, due to the differences between the topology of the asymmetric half-bridge flyback converter and the topology of the traditional flyback converter, the commonly used topology of the asymmetric half-bridge flyback converter is as follows: Figure 1a and Figure 1b As shown in Figure 2, the voltage waveform on the auxiliary winding of the asymmetric half-bridge flyback converter is as follows: Figure 2 As shown in the Vaux curve, it can be seen that if the same input voltage detection method as the traditional flyback converter is used in the topology of the asymmetric half-bridge flyback converter, it is impossible to accurately and directly detect the input voltage information of the system.

[0005] Therefore, it is necessary to provide an improved technical solution to overcome the above technical problems existing in the prior art. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides an asymmetric half-bridge flyback converter and an input voltage detection method thereof, which can realize functions such as input voltage protection or input voltage compensation without adding additional peripheral devices and control chip pins. The technical solution is simple and the operation is convenient and flexible.

[0007] According to a first aspect of the present disclosure, an asymmetric half-bridge flyback converter and an input voltage detection method thereof are provided. The asymmetric half-bridge flyback converter includes a first switch tube and a second switch tube constituting a half bridge, a transformer and a controller. The input voltage detection method includes:

[0008] During the conduction period of the first switch tube, a predetermined parameter of the asymmetric half-bridge flyback converter is sampled and sampled and held to obtain a first sampling signal;

[0009] sampling predetermined parameters of the asymmetric half-bridge flyback converter during the conduction period of the second switch tube to obtain a second sampling signal;

[0010] A voltage detection signal representing input voltage information is obtained according to the first sampling signal and the second sampling signal.

[0011] Optionally, obtaining a voltage detection signal representing input voltage information according to the first sampling signal and the second sampling signal includes:

[0012] An absolute value of the first sampling signal and an absolute value of the second sampling signal are added together to obtain a voltage detection signal proportional to the input voltage.

[0013] Optionally, the voltage detection signal is in direct proportion to the input voltage.

[0014] Optionally, the transformer comprises a primary winding, a secondary winding and an auxiliary winding, and the predetermined parameter is a voltage representing the voltage across any winding of the transformer;

[0015] The first sampling signal is a first voltage signal corresponding to the sampling during the conduction period of the first switch tube, and the second sampling signal is a second voltage signal corresponding to the sampling during the conduction period of the second switch tube.

[0016] Optionally, the predetermined parameter is the voltage across the auxiliary winding.

[0017] Optionally, the predetermined parameter is the voltage division of the voltage across the auxiliary winding in the transformer.

[0018] Optionally, the predetermined parameter is a current flowing through a voltage detection pin of a controller of the asymmetric half-bridge flyback converter.

[0019] The first sampling signal is a first current signal corresponding to the sampling during the conduction period of the first switch tube, and the second sampling signal is a second current signal corresponding to the sampling during the conduction period of the second switch tube.

[0020] The voltage detection pin of the controller is connected to one end of the auxiliary winding in the transformer via a resistor element, and the other end of the auxiliary winding is connected to a reference ground.

[0021] Optionally, after obtaining the voltage detection signal representing the input voltage information, the method further includes:

[0022] An input voltage protection operation and / or an input voltage compensation operation is performed on the asymmetric half-bridge flyback converter based on the voltage detection signal.

[0023] According to a second aspect of the present disclosure, an asymmetric half-bridge flyback converter and an input voltage detection method thereof are provided, comprising: a transformer including a primary winding, a secondary winding and an auxiliary winding;

[0024] A first switch tube and a second switch tube connected in series between an input voltage input terminal and a reference ground;

[0025] an excitation inductor connected between the drain of the second switch tube and the same-name end of the primary winding;

[0026] a first capacitor connected between a reference ground and the opposite-name end of the primary winding; and

[0027] a controller connected to the first switch tube, the second switch tube and the auxiliary winding respectively,

[0028] Wherein, the controller comprises:

[0029] A first control unit is configured to provide a first driving signal for controlling the first switch tube to be turned on / off;

[0030] A second control unit is configured to provide a second driving signal for controlling the second switch tube to be turned on / off;

[0031] The input voltage detection module is configured to sample predetermined parameters of the asymmetric half-bridge flyback converter during the conduction period of the first switch tube and the conduction period of the second switch tube respectively, and the input voltage detection module is also configured to obtain a voltage detection signal representing the input voltage information based on the two sampling results.

[0032] Optionally, the input voltage detection module includes:

[0033] a sampling and holding unit, configured to sample and hold predetermined parameters of the asymmetric half-bridge flyback converter during the conduction period of the first switch tube, and output a first sampling signal according to the sampling result;

[0034] a sampling unit, configured to sample predetermined parameters of the asymmetric half-bridge flyback converter during the conduction period of the second switch tube, and output a second sampling signal according to the sampling result;

[0035] An operation unit is connected to the sampling and holding unit and the sampling unit respectively, and is configured to receive the first sampling signal and the second sampling signal, and add the absolute value of the first sampling signal and the absolute value of the second sampling signal to obtain a voltage detection signal that is proportional to the input voltage.

[0036] Optionally, the predetermined parameter is the voltage across any winding in the transformer.

[0037] Optionally, the predetermined parameter is the voltage across the auxiliary winding.

[0038] Optionally, the predetermined parameter is a voltage division of a voltage across an auxiliary winding in the transformer, and the asymmetric half-bridge flyback converter further includes:

[0039] A first resistor and a second resistor are connected in series between a first end and a second end of the auxiliary winding, and a connection node between the first resistor and the second resistor is connected to a voltage detection pin of the controller.

[0040] Optionally, the predetermined parameter is a current flowing through a voltage detection pin of a controller of the asymmetric half-bridge flyback converter, and the asymmetric half-bridge flyback converter further includes:

[0041] a third resistor, the third resistor being connected between a voltage detection pin of the controller and a first end of an auxiliary winding in the transformer, and a second end of the auxiliary winding being connected to a reference ground;

[0042] A third switch tube, the third switch tube is connected between the voltage detection pin of the controller and a reference ground;

[0043] The third control unit is connected to the control end of the third switch tube, and is used to control the third switch tube to be turned on during the conduction period of the first switch tube and the second switch tube.

[0044] Optionally, the predetermined parameter is the voltage across the auxiliary winding, and the asymmetric half-bridge flyback converter further includes:

[0045] A first capacitor forms a loop with the auxiliary winding through a first conductive element. When the first switch tube is turned on, the first conductive element is turned on.

[0046] The second capacitor, the first capacitor, the second conductive element and the second capacitor form a loop with the auxiliary winding, and the second conductive element is turned on during the conduction period of the second switch tube.

[0047] The beneficial effects of the present invention are as follows: the present invention samples the current size or voltage size on the voltage detection pin of the controller during the first switch tube conduction period and the second switch tube conduction period, and obtains voltage value information or current value information proportional to the input voltage by adding the two sampling results, thereby realizing the detection of the input voltage. In this process, functions such as input voltage protection or input voltage compensation can be realized without adding additional peripheral devices and control chip pins. The technical solution is simple and the operation is convenient and flexible.

[0048] It should be noted that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1a A schematic diagram of the circuit structure of an existing asymmetric half-bridge flyback converter is shown;

[0050] Figure 1b A schematic diagram of the circuit structure of another existing asymmetric half-bridge flyback converter is shown;

[0051] Figure 2 The timing waveform diagram of the existing asymmetric half-bridge flyback converter in the critical mode (BCM mode) is shown;

[0052] Figure 3 A schematic diagram of the circuit structure of an asymmetric half-bridge flyback converter provided according to the first embodiment of the present disclosure is shown;

[0053] Figure 4 A schematic diagram of the circuit structure of an asymmetric half-bridge flyback converter provided according to a second embodiment of the present disclosure is shown;

[0054] Figure 5 A schematic diagram of the circuit structure of an asymmetric half-bridge flyback converter provided according to a third embodiment of the present disclosure is shown;

[0055] Figure 6 A structural block diagram of an input voltage detection module provided according to an embodiment of the present disclosure is shown;

[0056] Figure 7 A flow chart of an input voltage detection method for an asymmetric half-bridge flyback converter provided according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0057] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0058] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

[0059] Figure 1a and Figure 1b The circuit structures of two existing asymmetric half-bridge flyback converters are shown respectively. Figure 1a and 1b As shown, Figure 1a The upper switch tube Q2 is the second switch tube, and the lower switch tube Q1 is the first switch tube; Figure 1b The upper switch tube Q1 is the first switch tube, and the lower switch tube Q2 is the second switch tube. The working principles of the two circuits are basically the same, except that the winding positions are different. Figure 1b Take the working waveform of the critical mode (BCM mode) as an example. Figure 2 As shown, Vgs_Q1 and Vgs_Q2 are driving signal waveforms of the first switch tube Q1 and the second switch tube Q2 respectively; i Lm is the excitation current waveform on the primary winding Np; Vaux is the voltage across the auxiliary winding Na; Vds_Q1 is the drain-source voltage of the first switch tube.

[0060] refer to Figure 2 , Figure 1b The operating principle of the asymmetric half-bridge flyback converter shown in is as follows:

[0061] During the time period t0-t1, the second control signal Vgs_Q1 is at a high level, and the first switch tube Q1 is turned on. During this time period, the energy at the input end of the input voltage Vin excites the transformer TR through the loop of the first switch tube Q1, the excitation inductor Lm, the primary winding Np and the first capacitor Cr. The excitation current i Lm First, it decreases linearly from negative to zero and then increases linearly. In this process, the magnetizing inductor Lm, the transformer TR and the first capacitor Cr store energy, and the secondary rectifier diode D1 is negatively cut off.

[0062] At time t1 , the second control signal Vgs_Q1 changes to a low level, and the first switch tube Q1 is turned off.

[0063] During the time period t1-t2, the first switch tube Q1 is in the off state, and the second switch tube Q2 is not turned on yet. This time period is the dead time. During this dead time, because the excitation inductance Lm and the primary winding Np need to continue current, the junction capacitance C1 of the first switch tube Q1, the junction capacitance C2 of the second switch tube Q2, the first capacitor Cr, the excitation inductance Lm and the primary winding Np resonate, extracting the energy of the junction capacitance C2 of the second switch tube Q2, causing the drain-source voltage Vds_Q2 of the second switch tube Q2 to drop, while charging the junction capacitance C1 of the first switch tube Q1, and the drain-source voltage Vds_Q1 of the first switch tube Q1 rises. At the same time, during this time period, the voltage Vaux on the auxiliary winding Na starts to rise from a negative voltage.

[0064] At time t2, the junction capacitance voltage of the first switch tube Q1 reaches the maximum, and the junction capacitance voltage of the second switch tube Q2 is reduced to zero voltage. At this time, the first control signal Vgs_Q2 becomes high level, and the second switch tube Q2 is turned on, so that the zero voltage turn-on of the second switch tube Q2 can be achieved. At the same time, the voltage Vaux across the auxiliary winding Na also reaches the maximum.

[0065] During the time period t2-t3, in the secondary side of the asymmetric half-bridge flyback converter, the rectifier diode D1 is forward-conducted, and the energy stored in the primary side of the transformer TR begins to be released to the secondary side, and the excitation current i Lm Linear decrease.

[0066] At time t3, this time is the initial turn-off time of the asymmetric half-bridge flyback converter, and at time t3, the excitation current i Lm It decreases linearly to near zero current.

[0067] During the time period t3-t4, the second switch tube Q2 is delayed on, and the magnetizing inductor Lm and the first capacitor Cr resonate during this time period. The energy stored in the first capacitor Cr is also released to the secondary side through the forward excitation process. The magnetizing current i Lm Going into negative direction.

[0068] At time t4, the second driving signal Vgs_Q2 received by the gate of the second switch tube Q2 changes to a low level, and the second switch tube Q2 is turned off.

[0069] During the time period t4-t5, the first switch tube Q1 and the second switch tube Q2 are both in the off state because the excitation current i Lm The excitation inductance Lm and the primary winding Np need to continue the current, so the junction capacitance C1 of the first switch tube Q1, the junction capacitance C2 of the second switch tube Q2, the first capacitor Cr, the excitation inductance Lm and the primary winding Np resonate, extracting the energy of the junction capacitance C1 of the first switch tube Q1, and the drain-source voltage Vds_Q1 of the first switch tube Q1 decreases, while charging the junction capacitance C2 of the second switch tube Q2, and the drain-source voltage Vds_Q1 of the second switch tube Q2 increases. At the same time, the voltage Vaux across the auxiliary winding Na decreases linearly.

[0070] At time t5, the voltage Vaux across the auxiliary winding Na drops to the minimum, and at the same time, the junction capacitance voltage of the second switch tube Q2 reaches the maximum, the junction capacitance voltage of the first switch tube Q1 is drawn to zero voltage, and the second control signal Vgs_Q1 becomes high level, realizing the zero voltage turn-on of the first switch tube Q1. This completes a cycle, and then continues to work repeatedly according to the same working process.

[0071] In principle, the asymmetric half-bridge flyback converter in the BCM mode controls the second switch tube Q2 to be turned on for an additional period of time (such as t ZVS ), generating a negative excitation current i Lm , thereby achieving zero voltage turn-on of the first switch tube Q1.

[0072] Based on the working principle of the transformer TR, it can be known that the voltage across the primary winding Np, the voltage across the secondary winding Ns, and the voltage Vaux across the auxiliary winding Na in the transformer TR have a certain proportional relationship with each other. From the working principle of the asymmetric half-bridge flyback converter, it can be known that the voltage across the primary winding Np, or the voltage across the secondary winding Ns, or the voltage Vaux across the auxiliary winding Na in the transformer TR will change with the on / off conditions of the first switch tube Q1 and the second switch tube Q2, and during the on period of the first switch tube Q1 and the on period of the second switch tube Q2, the voltage Vaux across the auxiliary winding Na is maintained at the minimum value and the maximum value respectively.

[0073] like Figure 3 , Figure 4 and Figure 5As shown, in the present disclosure, the asymmetric half-bridge flyback converter includes: a transformer TR including a primary winding Np, a secondary winding Ns and an auxiliary winding Na, a first switch tube Q1 and a second switch tube Q2 constituting a half bridge, an excitation inductor Lm, a first capacitor Cr and a controller 100.

[0074] Among them, the drain of the first switch tube Q1 is connected to the input terminal of the input voltage Vin, and the gate of the first switch tube Q1 is connected to the controller 100; the drain of the second switch tube Q2 is connected to the source of the first switch tube Q1, the source of the second switch tube Q2 is connected to the reference ground, the gate of the second switch tube Q2 is connected to the controller 100, and the capacitor C1 and the capacitor C2 are the junction capacitances of the first switch tube Q1 and the second switch tube Q2 respectively. In the same switching cycle, the first switch tube Q1 and the second switch tube Q2 are turned on in time to transfer the input voltage Vin from the primary side of the transformer TR to the secondary side. In a possible embodiment, the first switch tube Q1 and the second switch tube Q2 are both NMOS field effect transistors.

[0075] One end of the excitation inductor Lm is connected to the drain of the second switch tube Q2, and the other end of the excitation inductor Lm is connected to the same-name end of the primary winding Np; one end of the first capacitor Cr is connected to the opposite-name end of the primary winding Np, and the other end of the first capacitor Cr is connected to the reference ground. In this embodiment, the first capacitor Cr is a resonant capacitor.

[0076] The secondary side of the asymmetric half-bridge flyback converter includes: a rectifier diode D1 and an output capacitor Co. The anode of the rectifier diode D1 is connected to the opposite end of the secondary winding Ns, and the cathode of the rectifier diode D1 is connected to the output end of the asymmetric half-bridge flyback converter; the positive electrode of the output capacitor Co is connected to the output end of the asymmetric half-bridge flyback converter, and the negative electrode of the output capacitor Co is connected to the reference ground. At the same time, the same end of the secondary winding Ns is also connected to the reference ground. Further, the output end of the asymmetric half-bridge flyback converter is connected to the load, and the load receives the electric energy (such as voltage and current) converted by the asymmetric half-bridge flyback converter. In some instances, the electric energy converted by the asymmetric half-bridge flyback converter also passes through a filter before reaching the load. In some instances, the filter is a subcomponent of the asymmetric half-bridge flyback converter, an external component of the asymmetric half-bridge flyback converter, and / or a subcomponent of the load. In any case, the load can use the filtered or unfiltered electric energy from the asymmetric half-bridge flyback converter to perform a function. Optionally, the load may include, but is not limited to, computing devices and related components such as microprocessors, electrical components, circuits, laptop computers, desktop computers, tablet computers, mobile phones, batteries, speakers, lighting units, automotive / marine / aircraft / train related components, motors, transformers, or any other type of electrical device and / or circuit that receives voltage or current from a flyback converter.

[0077] The controller 100 includes: a first control unit 110, a second control unit 120 and an input voltage detection module 130. The first control unit 110 is connected to the gate of the first switch tube Q1, the second control unit 120 is connected to the gate of the second switch tube Q2, and the input voltage detection module 130 is connected to the auxiliary winding Na via the voltage detection pin Vs of the controller 100.

[0078] The first control unit 110 is configured to provide a first drive signal Vgs_Q1 to the gate of the first switch tube Q1 for controlling the on / off of the first switch tube Q1. For example, the first control unit 110 is configured to sample the voltage across any winding in the transformer TR (preferably the voltage Vaux across the auxiliary winding Na) in each switching cycle, and generate a turn-on signal for controlling the first switch tube Q1 to turn on after a predetermined time delay from the zero-crossing moment of the voltage Vaux across the auxiliary winding Na from high to low, i.e., the first drive signal Vgs_Q1 in a high level state. Optionally, the predetermined delayed time can be set to be equal to the resonant cycle time of the asymmetric half-bridge flyback converter multiplied by x, wherein x includes but is not limited to one of 1 / 5, 9 / 40, 1 / 4, 7 / 24, and 1 / 3, and at the same time, x can also be any real value in the range of 1 / 5 to 1 / 3, preferably 1 / 4.

[0079] The second control unit 120 is configured to provide a second driving signal Vgs_Q2 to the gate of the second switch tube Q2 for controlling the on / off of the second switch tube Q2. For example, the second control unit 120 can be configured to determine the initial turn-off time of the second switch tube Q2 according to the integral of the preset parameters of the asymmetric half-bridge flyback converter over time in the BCM mode (critical mode) of the asymmetric half-bridge flyback converter, that is, Figure 2 At the moment t3 in the figure, and after a certain time delay from the moment t3, the second control unit 120 outputs a turn-off signal for controlling the second switch tube Q2 to be turned off, that is, a low-level second drive signal Vgs_Q2 to the gate of the second switch tube Q2. Alternatively, the second control unit 120 can be configured to output the second drive signal Vgs_Q2 with a corresponding control timing to the gate of the second switch tube Q2 according to the sampling result of the specific parameters of the asymmetric half-bridge flyback converter in the DCM mode (discontinuous mode) of the asymmetric half-bridge flyback converter, so as to control the number of times the second switch tube Q2 is turned on in one switching cycle.

[0080] The input voltage detection module 130 is configured to sample predetermined parameters of the asymmetric half-bridge flyback converter during the conduction period of the first switch tube Q1 and the conduction period of the second switch tube Q2, respectively. At the same time, the input voltage detection module 130 is also configured to obtain a voltage detection signal representing the input voltage information based on the two sampling results.

[0081] Further, refer to Figure 6 The input voltage detection module 130 includes: a sampling and holding unit 131 , a sampling unit 132 and a calculation unit 133 .

[0082] The sampling and holding unit 131 is configured to: Figure 2 The predetermined parameters of the asymmetric half-bridge flyback converter are sampled and held during the time period t0-t1 in the embodiment, and a first sampling signal is output according to the sampling result.

[0083] The sampling unit 132 is configured to: Figure 2 The method samples the predetermined parameters of the asymmetric half-bridge flyback converter (in the time period t2-t3 or the time period t2-t4), and outputs a second sampling signal according to the sampling result.

[0084] The operation unit 133 is connected to the sampling and holding unit 131 and the sampling unit 132 respectively. The operation unit 133 is configured to receive the first sampling signal and the second sampling signal, and add the absolute value of the received first sampling signal and the absolute value of the second sampling signal to obtain a voltage detection signal that is proportional to the input voltage Vin.

[0085] Exemplarily, if the voltage detection pin Vs of the controller 100 in the asymmetric half-bridge flyback converter can withstand negative voltage, then in some embodiments, the predetermined parameter of the asymmetric half-bridge flyback converter is a voltage representing the voltage across any winding in the transformer TR. At this time, the first sampling signal is a corresponding first voltage signal obtained by sampling during the conduction period of the first switch tube Q1, and the second sampling signal is a corresponding second voltage signal obtained by sampling during the conduction period of the second switch tube Q2. Exemplarily, taking the predetermined parameter as a voltage Vaux representing the voltage across the auxiliary winding Na as an example, at this time, the voltage detection pin Vs of the controller 100 can be directly connected to one end of the auxiliary winding Na, and at the same time, the other end of the auxiliary winding Na is connected to the reference ground.

[0086] In other embodiments, the predetermined parameter of the symmetrical half-bridge flyback converter is the voltage division of the voltage across any winding in the transformer TR. For example, taking the predetermined parameter as the voltage division of the voltage Vaux across the auxiliary winding Na as an example, at this time, reference Figure 3 , the asymmetric half-bridge flyback converter further includes: a first resistor R1 and a second resistor R2. The first resistor R1 and the second resistor R2 are connected in series between the opposite-name end and the same-name end of the auxiliary winding Na, and the connection node of the first resistor R1 and the second resistor R2 is connected to the voltage detection pin Vs of the controller 100. It should be noted that when Figure 3 After the connection relationship between the opposite-name end and the same-name end of the auxiliary winding Na is interchanged, the technical solution disclosed in the present invention is also applicable.

[0087] That is to say, in the present disclosure, the voltage across the auxiliary winding Na can be sampled by the voltage detection pin Vs of the controller 100 after being divided by the first resistor R1 and the second resistor R2, or the voltage across the auxiliary winding Na can be directly sampled by the voltage detection pin Vs of the controller 100.

[0088] Based on the aforementioned Figure 2 and Figure 3 As described above, if the predetermined parameter is the voltage Vaux across the auxiliary winding Na in the transformer TR, then during the conduction period of the first switch tube Q1, the first sampling signal (denoted as Vaux1) obtained after sampling and holding is as follows:

[0089] Vaux1=-(Na / Np)*(Vin-Vc) (1),

[0090] During the conduction period of the second switch tube Q2, the second sampling signal (denoted as Vaux2) obtained after sampling is as follows:

[0091] Vaux2=(Na / Np)*Vc (2),

[0092] Wherein, Na is the number of turns of the auxiliary winding, Np is the number of turns of the primary winding, Vin is the input voltage, and Vc is the voltage across the first capacitor Cr.

[0093] Furthermore, based on formula (1) and formula (2), it can be known that the voltage detection signal (denoted as Vina) obtained by adding the absolute value of the first sampling signal Vaux1 and the absolute value of the second sampling signal Vaux2 by the operation unit 133 is as follows:

[0094] Vina=|Vaux1|+|Vaux2|=(Na / Np)*(Vin-Vc)+(Na / Np)*Vc,

[0095] After simplification, we can get:

[0096]

[0097] That is to say, the operation unit 133 will eventually output a voltage value that is proportional to the input voltage Vin. When the input voltage Vin changes, the voltage value will also change accordingly. Therefore, by detecting the voltage value output by the operation unit 133, the input voltage Vin can be detected equivalently, thereby providing a basis for subsequent protection operations and / or compensation operations on the input voltage Vin.

[0098] Alternatively, when the predetermined parameter of the asymmetric half-bridge flyback converter is a voltage Vaux representing the voltage across the auxiliary winding Na in the transformer TR, the following may also be used: Figure 4 The rectifier circuit shown in the figure is Figure 4 , at this time, the asymmetric half-bridge flyback converter further includes: a first capacitor C3, a second capacitor C4, a first conductive element D2 and a second conductive element D3. Among them, the first capacitor C3 forms a first loop with the auxiliary winding Na through the first conductive element D2, and the first capacitor C3, the second conductive element D3 and the second capacitor C4 form a second loop with the auxiliary winding Na. Based on the working principle of the auxiliary winding Na in the asymmetric half-bridge flyback converter, it can be known that during the conduction period of the first switch tube Q1, the first conductive element D2 is turned on; during the conduction period of the second switch tube Q2, the second conductive element D3 is turned on.

[0099] Optionally, both the first conductive member D2 and the second conductive member D3 can be selected as diodes. In this case, the second capacitor C4 is connected between the voltage detection pin Vs of the controller and the reference ground, one end of the first capacitor C3 is connected to the opposite end of the auxiliary winding Na, the other end of the first capacitor C3 is connected to the anode of the second conductive member D3, the cathode of the second conductive member D3 is connected to the voltage detection pin Vs of the controller, the anode of the first conductive member D2 is connected to the reference ground, and the cathode of the first conductive member D2 is connected to the anode of the second conductive member D3. Alternatively, the first conductive member D2 and the second conductive member D3 can also be selected as other switch elements controlled by the driving voltage, as long as the first conductive member D2 is turned on and the second conductive member D3 is turned off during the conduction period of the first switch tube Q1; the second conductive member D3 is turned on and the first conductive member D2 is turned off during the conduction period of the second switch tube Q2.

[0100] Further, based on Figure 4 It can be seen that in this embodiment, during the conduction period of the first switch tube Q1, the voltage across the first capacitor C3 (denoted as V_C3) is as follows:

[0101] V_C3=(Na / Np)*(Vin-Vc) (4),

[0102] During the conduction period of the second switch tube Q2, the voltage Vaux across the auxiliary winding Na is as follows:

[0103] Vaux=(Na / Np)*Vc (5),

[0104] Furthermore, based on Figure 4 From the working principle of the circuit, it can be seen that during the conduction period of the second switch tube Q2, the voltage across the second capacitor C4 (denoted as V_C4) is as follows:

[0105] V_C4=V_C3+Vaux=(Na / Np)*(Vin-Vc) (6),

[0106] Wherein, Na is the number of turns of the auxiliary winding, Np is the number of turns of the primary winding, Vin is the input voltage, and Vc is the voltage across the first capacitor Cr.

[0107] That is to say, the voltage across the second capacitor C4 during the conduction period of the second switch tube Q2 is the sum of the voltage across the auxiliary winding Na during the conduction period of the first switch tube Q1 and the conduction period of the second switch tube Q2. Figure 4 In the circuit structure shown, the input voltage Vin of the circuit can be equivalently obtained by sampling the voltage across the second capacitor C4 during the conduction period of the second switch tube Q2.

[0108] In some other embodiments, the predetermined parameter of the asymmetric half-bridge flyback converter is the current flowing through the voltage detection pin Vs of the controller 100 of the asymmetric half-bridge flyback converter. This solution can be applied to controller chips whose pins do not support negative voltage. In this case, the first sampling signal is the corresponding first current signal obtained by sampling during the conduction period of the first switch tube Q1, and the second sampling signal is the corresponding second current signal obtained by sampling during the conduction period of the second switch tube Q2. At this time, reference Figure 5 The asymmetric half-bridge flyback converter further includes: a third resistor RFB1, a third switch tube Q3 and a third control unit 140. The third resistor RFB1 is connected between the voltage detection pin Vs of the controller 100 and the opposite-name end of the auxiliary winding Na, and the same-name end of the auxiliary winding Na is connected to the reference ground; the third switch tube Q3 is connected between the voltage detection pin Vs of the controller 100 and the reference ground; and the third control unit 140 is connected to the control end of the third switch tube Q3, and is used to control the third switch tube Q3 to be turned on during the conduction period of the first switch tube Q1 and the second switch tube Q2.

[0109] Optionally, in this embodiment, the third switch tube Q3 may be integrated inside the controller 100 or may be disposed outside the controller 100, which is not limited in the present invention. In a possible embodiment, the third switch tube Q3 is an NMOS field effect transistor.

[0110] Further, based on Figure 5 It can be seen that in this embodiment, during the conduction period of the first switch tube Q1, the first sampling signal (denoted as Is1) obtained after sampling and holding is as follows:

[0111]

[0112] During the conduction period of the second switch tube Q2, the second sampling signal (denoted as Is2) obtained after sampling is as follows:

[0113]

[0114] Wherein, Na is the number of turns of the auxiliary winding, Np is the number of turns of the primary winding, Vin is the input voltage, Vc is the voltage across the first capacitor Cr, and RFB1 is the resistance value of the third resistor.

[0115] Furthermore, based on formula (7) and formula (8), it can be known that the voltage detection signal obtained by adding the absolute value of the first sampling signal Is1 and the absolute value of the second sampling signal Is2 by the operation unit 133 is as follows:

[0116]

[0117] After simplification, we can get:

[0118]

[0119] That is to say, the operation unit 133 will eventually output a current value that is proportional to the input voltage Vin. When the input voltage Vin changes, the current value will also change accordingly. Therefore, by detecting the current value output by the operation unit 133, the input voltage Vin can be detected equivalently, thereby providing a basis for subsequent protection and / or compensation functions of the input voltage Vin.

[0120] It should be noted that the sampling and holding unit 131 and the sampling unit 132 are used in the above embodiments to sample the first sampling signal and the second sampling signal respectively. However, in the present disclosure, only one sampling unit can be set in the input voltage detection module 130, and it can be configured to sample the predetermined parameter by the sampling unit during the conduction period of the first switch tube Q1, and transmit the sampling result to the register or buffer for buffering after the first switch tube Q1 is turned off. During the conduction period of the second switch tube Q2, the sampling unit also samples the predetermined parameter, and then, it is only necessary to simultaneously transmit the buffered signal and the signal sampled during the conduction period of the second switch tube Q2 to the operation unit 133 for addition operation. In this way, resources can be saved and production costs can be reduced.

[0121] In addition, the parameters of the asymmetric half-bridge flyback converter targeted by the first control unit 110, the second control unit 120 and the input voltage detection module 130 in their respective working processes may be the same parameters or different parameters. Also, when the first control unit 110, the second control unit 120 and the input voltage detection module 130 need to sample a certain parameter of the asymmetric half-bridge flyback converter in their respective working processes, the same sampling unit and / or sampling and holding unit may be used for sampling, that is, a common sampling unit and / or sampling and holding unit that can be called by the first control unit 110, the second control unit 120 and the input voltage detection module 130 in time sharing or at the same time is set in the controller 100 to reduce the volume of the controller and reduce the manufacturing cost. Similarly, respective sampling units and / or sampling and holding units may also be set in the first control unit 110, the second control unit 120 and the input voltage detection module 130 to avoid mutual interference between the units or modules and improve the accuracy and reliability of the system operation. The specific selection may be made reasonably according to the actual situation, and the present disclosure does not limit this.

[0122] refer to Figure 7 , Figure 7 A flowchart showing an input voltage detection method for an asymmetric half-bridge flyback converter according to an embodiment of the present disclosure is shown. The input voltage detection method can be used in the aforementioned Figures 3 to 6 The asymmetric half-bridge flyback converter described in the previous section can also be applied to the Figure 3 and Figure 5 In the asymmetric half-bridge flyback converter structure, the like-name ends of the auxiliary winding Na are opposite.

[0123] like Figure 7 As shown, in the present disclosure, the input voltage detection method of the flyback converter includes executing steps S01 to S03.

[0124] Specifically, in step S01, a predetermined parameter of the asymmetric half-bridge flyback converter is sampled and sampled and held during the conduction period of the first switch tube to obtain a first sampling signal.

[0125] In step S02, a predetermined parameter of the asymmetric half-bridge flyback converter is sampled during the conduction period of the second switch tube to obtain a second sampling signal.

[0126] In some embodiments, the predetermined parameter is a voltage across any winding in the transformer TR. Preferably, the voltage across the auxiliary winding Na is used. For example, the predetermined parameter is a voltage across the auxiliary winding Na. Then, the predetermined parameter of the asymmetric half-bridge flyback converter is sampled during the conduction period of the first switch tube Q1 (e.g., Figure 2The voltage across the auxiliary winding Na is sampled and held by the sampling and holding unit 131 in the input voltage detection module 130 during the t0-t1 time period. And, the predetermined parameter of the asymmetric half-bridge flyback converter is sampled during the conduction period of the second switch tube Q2 (e.g. Figure 2 The sampling unit 132 in the input voltage detection module 130 samples the voltage across the auxiliary winding Na during the time period t2-t3 or the time period t2-t4 in FIG. 1 . The specific sampling results can be referred to in the foregoing Figure 6 It is understandable that, at this time, the first sampling signal is the corresponding first voltage signal obtained by sampling during the conduction period of the first switch tube Q1, and the second sampling signal is the corresponding second voltage signal obtained by sampling during the conduction period of the second switch tube Q2.

[0127] In some other embodiments, the predetermined parameter is a voltage division characterizing the voltage across any winding in the transformer TR, wherein the predetermined parameter is preferably a voltage division characterizing the voltage across the auxiliary winding Na. Exemplarily, taking the predetermined parameter as the voltage division characterizing the voltage across the auxiliary winding Na as an example, further, sampling the predetermined parameter of the asymmetric half-bridge flyback converter during the conduction period of the first switch tube is during the conduction period of the first switch tube Q1 (e.g. Figure 2 In the time period t0-t1 in the input voltage detection module 130, the sampling and holding unit 131 is used to detect the input voltage. Figure 3 The voltage at the connection node of the first resistor R1 and the second resistor R2 is sampled and held. And, the predetermined parameter of the asymmetric half-bridge flyback converter is sampled during the conduction period of the second switch tube Q2 (e.g. Figure 2 The sampling unit 132 in the input voltage detection module 130 is used to detect the voltage in the time period t2-t3 or the time period t2-t4. Figure 3 The voltage at the connection node between the first resistor R1 and the second resistor R2 is sampled.

[0128] In some other embodiments, the predetermined parameter is the current flowing through the voltage detection pin Vs of the controller 100 of the asymmetric half-bridge flyback converter. Further, the predetermined parameter of the asymmetric half-bridge flyback converter is sampled during the conduction period of the first switch tube Q1 (e.g. Figure 2 In the time period t0-t1 in the input voltage detection module 130, the sampling and holding unit 131 is used to detect the input voltage. Figure 5 The current flowing into the voltage detection pin Vs of the controller 100 is sampled and held. Also, the predetermined parameter of the asymmetric half-bridge flyback converter is sampled during the conduction period of the second switch tube Q2 (e.g. Figure 2 The sampling unit 132 in the input voltage detection module 130 is used to detect the voltage in the time period t2-t3 or the time period t2-t4. Figure 5 The current flowing out of the voltage detection pin Vs of the controller 100 is sampled. The specific sampling results can be referred to the above Figure 6 It is understandable that, at this time, the first sampling signal is the corresponding first current signal obtained by sampling during the conduction period of the first switch tube Q1, and the second sampling signal is the corresponding second current signal obtained by sampling during the conduction period of the second switch tube Q2.

[0129] In step S03 , a voltage detection signal representing input voltage information is obtained according to the first sampling signal and the second sampling signal.

[0130] In this embodiment, obtaining a voltage detection signal representing input voltage information according to the first sampling signal and the second sampling signal includes: adding the absolute value of the first sampling signal and the absolute value of the second sampling signal to obtain a voltage detection signal proportional to the input voltage. Further, it can be seen from the above formula (3) and / or formula (6) and / or formula (9) that the voltage detection signal is in direct proportion to the input voltage Vin.

[0131] Furthermore, after obtaining the voltage detection signal representing the input voltage information, the method further includes: performing an input voltage protection operation and / or an input voltage compensation operation on the asymmetric half-bridge flyback converter based on the voltage detection signal.

[0132] Specifically, when the predetermined parameter is the voltage across any winding in the transformer TR or the predetermined parameter is the voltage division of the voltage across any winding in the transformer TR, the operation unit 133 can be used to add the absolute value of the first sampling signal and the absolute value of the second sampling signal to obtain a voltage value proportional to the input voltage Vin. Then, based on the voltage value, the protection operation and / or compensation operation of the input voltage Vin can be realized. Figure 6 The description of is not repeated here. Wherein, k is the voltage division coefficient. When k is equal to 1, it means that the voltage across any winding in the transformer TR is directly sampled; when k is less than 1, it means that the voltage across any winding in the transformer TR is first divided and then sampled.

[0133] When the predetermined parameter is the current flowing through the voltage detection pin Vs of the controller 100 of the asymmetric half-bridge flyback converter, the operation unit 133 can be used to add the absolute value of the first sampling signal and the absolute value of the second sampling signal to obtain a current value proportional to the input voltage Vin. Then, based on the current value, the protection operation and / or compensation operation of the input voltage Vin can be realized. Figure 6 The description is not repeated here.

[0134] In summary, in the present disclosure, by sampling the current or voltage on the voltage detection pin of the controller during the first switch tube conduction period and the second switch tube conduction period, and adding the absolute values ​​of the two sampling results to obtain voltage value information or current value information proportional to the input voltage, equivalent detection of the input voltage is achieved. In this process, functions such as input voltage protection or input voltage compensation can be achieved without adding additional peripheral devices and control chip pins, and the technical solution is simple and the operation is convenient and flexible.

[0135] Finally, it should be noted that: Obviously, the above embodiments are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the scope of protection of the present invention.

Claims

1. A method for detecting an input voltage of an asymmetric half-bridge flyback converter, wherein the asymmetric half-bridge flyback converter comprises a first switch tube and a second switch tube constituting a half-bridge, a transformer and a controller, wherein: The input voltage detection method comprises: During the conduction period of the first switch tube, a predetermined parameter of the asymmetric half-bridge flyback converter is sampled and sampled and held to obtain a first sampling signal; sampling predetermined parameters of the asymmetric half-bridge flyback converter during the conduction period of the second switch tube to obtain a second sampling signal; performing an addition operation on the absolute value of the first sampling signal and the absolute value of the second sampling signal to obtain a voltage detection signal representing input voltage information, Wherein, the predetermined parameter is a voltage representing the voltage across any winding in the transformer; Alternatively, the predetermined parameter is the voltage division of the voltage across the auxiliary winding in the transformer; Alternatively, the predetermined parameter is a current flowing through a voltage detection pin of a controller of the asymmetric half-bridge flyback converter.

2. The input voltage detection method according to claim 1, wherein: Acquiring a voltage detection signal representing input voltage information according to the first sampling signal and the second sampling signal includes: The absolute value of the first sampling signal and the absolute value of the second sampling signal are added together to obtain a voltage detection signal proportional to the input voltage.

3. The input voltage detection method according to claim 2, wherein: The voltage detection signal is in direct proportion to the input voltage.

4. The input voltage detection method according to claim 1, wherein: The transformer comprises a primary winding, a secondary winding and an auxiliary winding. When the predetermined parameter is a voltage representing the voltage across any winding of the transformer, The first sampling signal is a first voltage signal corresponding to the sampling during the conduction period of the first switch tube, and the second sampling signal is a second voltage signal corresponding to the sampling during the conduction period of the second switch tube.

5. The input voltage detection method according to claim 1, wherein: When the predetermined parameter is the current flowing through the voltage detection pin of the controller of the asymmetric half-bridge flyback converter, The first sampling signal is a first current signal corresponding to the sampling during the conduction period of the first switch tube, and the second sampling signal is a second current signal corresponding to the sampling during the conduction period of the second switch tube. The voltage detection pin of the controller is connected to one end of the auxiliary winding in the transformer via a resistor element, and the other end of the auxiliary winding is connected to a reference ground.

6. The input voltage detection method according to any one of claims 1 to 5, wherein: After obtaining the voltage detection signal representing the input voltage information, the method further includes: An input voltage protection operation and / or an input voltage compensation operation is performed on the asymmetric half-bridge flyback converter based on the voltage detection signal.

7. An asymmetric half-bridge flyback converter, wherein: include: A transformer consisting of a primary winding, a secondary winding and an auxiliary winding. A first switch tube and a second switch tube connected in series between the input voltage input terminal and the reference ground, and a controller connected to the first switch tube, the second switch tube and the auxiliary winding respectively, Wherein, the controller comprises: A first control unit is configured to provide a first driving signal for controlling the first switch tube to be turned on and off; A second control unit is configured to provide a second driving signal for controlling the second switch tube to be turned on and off; An input voltage detection module is configured to sample predetermined parameters of the asymmetric half-bridge flyback converter during the first switch tube conduction period and the second switch tube conduction period, and the input voltage detection module is further configured to add the absolute values ​​of the two sampling results to obtain a voltage detection signal representing the input voltage information. The predetermined parameter is the voltage across any winding in the transformer; Alternatively, the predetermined parameter is the voltage division of the voltage across the auxiliary winding in the transformer; Alternatively, the predetermined parameter is a current flowing through a voltage detection pin of a controller of the asymmetric half-bridge flyback converter.

8. The asymmetric half-bridge flyback converter according to claim 7, wherein: The input voltage detection module comprises: a sampling and holding unit, configured to sample and hold predetermined parameters of the asymmetric half-bridge flyback converter during the conduction period of the first switch tube, and output a first sampling signal according to the sampling result; a sampling unit, configured to sample predetermined parameters of the asymmetric half-bridge flyback converter during the conduction period of the second switch tube, and output a second sampling signal according to the sampling result; An operation unit is connected to the sampling and holding unit and the sampling unit respectively, and is configured to receive the first sampling signal and the second sampling signal, and add the absolute value of the first sampling signal and the absolute value of the second sampling signal to obtain a voltage detection signal that is proportional to the input voltage.

9. The asymmetric half-bridge flyback converter according to claim 7, wherein: When the predetermined parameter is the voltage division of the voltage across the auxiliary winding in the transformer, the asymmetric half-bridge flyback converter further includes: A first resistor and a second resistor are connected in series between a first end and a second end of the auxiliary winding, and a connection node between the first resistor and the second resistor is connected to a voltage detection pin of the controller.

10. The asymmetric half-bridge flyback converter according to any one of claims 7 and 8, wherein: When the predetermined parameter is a current flowing through a voltage detection pin of a controller of the asymmetric half-bridge flyback converter, the asymmetric half-bridge flyback converter further includes: a third resistor, the third resistor being connected between a voltage detection pin of the controller and a first end of an auxiliary winding in the transformer, and a second end of the auxiliary winding being connected to a reference ground; A third switch tube, the third switch tube is connected between the voltage detection pin of the controller and a reference ground; The third control unit is connected to the control end of the third switch tube, and is used to control the third switch tube to be turned on during the conduction period of the first switch tube and the second switch tube.

11. The asymmetric half-bridge flyback converter according to claim 8, wherein: When the predetermined parameter is the voltage across the auxiliary winding, the asymmetric half-bridge flyback converter further includes: A first capacitor forms a loop with the auxiliary winding through a first conductive element. When the first switch tube is turned on, the first conductive element is turned on. The second capacitor, the first capacitor, the second conductive element and the second capacitor form a loop with the auxiliary winding, and the second conductive element is turned on during the conduction period of the second switch tube.

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