Control circuit and control method and power apparatus of asymmetrical half-bridge flyback converter

Abstract

A control circuit and control method for a resonant power conversion circuit are disclosed. This method can be used to turn off the first switch of the resonant power conversion circuit at an appropriate time before the transformer completes demagnetization, based on the resonant current information in the resonant circuit of the primary side circuit of the resonant power conversion circuit under low output voltage conditions. This reduces the resonant energy in the resonant circuit, thereby reducing power loss caused by resonance and improving the operating efficiency of the resonant power conversion circuit.

Description

Technical Field

[0001] The embodiments of the present invention relate to electronic circuits, and more specifically, to a control circuit and a control method of a resonant power conversion circuit. Prior Art

[0002] Traditional power conversion circuits convert input power into output power that meets the requirements and provide it to the load. Resonant power conversion circuits further reduce the switching loss of the circuit through soft switching technology, thereby greatly improving the circuit efficiency.

[0003] As a type of resonant power conversion circuit, the asymmetric half-bridge flyback converter has the advantages of simple structure, high efficiency, and a wide output voltage range, so it has been used more and more widely. However, it is precisely because the output voltage range of the asymmetric half-bridge flyback converter is large, and because it works under the rated output voltage condition, that is, the working condition where the output voltage is close to the upper limit value, the circuit loss is large. In order to optimize the working efficiency under the rated output voltage condition, its efficiency under low output voltage conditions is usually sacrificed. Summary of the invention

[0004] The present invention provides a control circuit for optimizing the circuit efficiency of a resonant power conversion circuit under low output voltage working conditions. The control circuit and control method of the resonant power conversion circuit of the present invention select appropriate timing to cut off the corresponding switch of the resonant power conversion circuit under certain output voltage conditions to reduce circuit resonance, thereby reducing circuit power loss and improving efficiency.

[0005] According to an embodiment of the present invention, a control circuit of an asymmetric half-bridge flyback converter is provided, wherein the asymmetric half-bridge flyback converter comprises a first switch, a second switch, a transformer and a resonant capacitor. The control circuit comprises an input end and an output end. The input end receives resonant current information, wherein the resonant current information is related to a resonant current flowing through a resonant circuit, and wherein the resonant circuit comprises a primary winding of a transformer and a resonant capacitor. The output end outputs a first control signal based on the resonant current information to control the first switch to be turned off.

[0006] According to an embodiment of the present invention, a power supply device is provided, comprising an asymmetric half-bridge flyback converter and a control circuit. The asymmetric half-bridge flyback converter comprises a first switch, a second switch, a transformer and a resonant capacitor, wherein the first switch and the second switch are coupled in series between an input terminal and a primary side reference ground terminal, the transformer comprises a primary winding and a secondary winding, and the resonant circuit comprises a primary winding and a resonant capacitor. The control circuit receives resonant current information related to a resonant current flowing through the resonant circuit, and based on the resonant current information, outputs a first control signal to control the first switch to be turned off.

[0007] According to an embodiment of the present invention, a control method of a resonant power conversion circuit is provided. The resonant power conversion circuit includes a first switch, a second switch, a transformer and a resonant capacitor. The control method includes: controlling the first switch and the second switch in the resonant power conversion circuit to adjust the energy transfer from the primary winding to the secondary winding of the transformer of the resonant power conversion circuit, wherein the resonant circuit of the resonant power conversion circuit includes the primary winding and the resonant capacitor; receiving resonant current information related to the resonant current flowing through the resonant circuit; and controlling the first switch to be turned off based on the resonant current information. Simple diagram description

[0008] In order to better understand the present invention, the present invention will be described in detail according to the following drawings:

[0009] [Figure 1] is a schematic diagram of the structure of an existing asymmetric half-bridge flyback converter 10;

[0010] [Figure 2] is a schematic diagram of the waveform of part of the signal when the output voltage Vout of the asymmetric half-bridge flyback converter 10 is small;

[0011] [Figure 3] is a schematic diagram of the circuit structure of a power supply device 30 according to an embodiment of the present invention;

[0012] [Figure 4] is a schematic diagram of the circuit structure of a power supply device 40 according to an embodiment of the present invention;

[0013] [Figure 5] is a schematic diagram of waveforms of some signals of a power supply device 40 according to an embodiment of the present invention;

[0014] [Figure 6] is a schematic diagram of the circuit structure of a power supply device 60 according to another embodiment of the present invention;

[0015] [Figure 7] is a schematic diagram of the circuit structure of a power supply device 70 according to another embodiment of the present invention;

[0016] [Figure 8] is a schematic diagram of the circuit structure of a power supply device 80 according to another embodiment of the present invention;

[0017] [Figure 9] is a schematic diagram of the circuit structure of a resonant power conversion circuit 90 according to an embodiment of the present invention;

[0018] [Figure 10] is a schematic diagram of the circuit structure of a resonant power conversion circuit 100 according to an embodiment of the present invention;

[0019] [Figure 11] is a schematic diagram of the circuit structure of a resonant power conversion circuit 110 according to an embodiment of the present invention;

[0020] [Figure 12] is a schematic diagram of the circuit structure of a resonant power conversion circuit 120 according to an embodiment of the present invention;

[0021] [Figure 13] is a schematic diagram of the circuit structure of a power supply device 130 according to an embodiment of the present invention;

[0022] [FIG. 14] is a schematic diagram of waveforms of some signals of the power supply device 130 according to an embodiment of the present invention;

[0023] [Figure 15] is a schematic diagram of the circuit structure of a power supply device 150 according to an embodiment of the present invention;

[0024] [ Fig. 16 ] is a flow chart of a control method 160 of a resonant power conversion circuit according to an embodiment of the present invention. Implementation

[0025] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described here are only for illustration and are not intended to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to a person skilled in the art that these specific details are not necessary to implement the present invention. In other examples, in order to avoid confusing the present invention, well-known circuits, materials or methods are not specifically described.

[0026] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment," "in an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any appropriate combination and / or subcombination. In addition, it should be understood by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale. The same reference numerals indicate the same elements. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] FIG. 1 is a schematic diagram of the structure of an existing asymmetric half-bridge flyback converter 10. In FIG. 1 , the first switch 141 and the second switch 142 are turned on in turn under the control of the first control signal G1 and the second control signal G2, respectively, to convert the input voltage Vin of the asymmetric half-bridge flyback converter 10 into an output voltage Vout and provide it to the load 130. The first control signal G1 and the second control signal G2 are usually PWM signals (Pulse Width Modulation). By adjusting the pulse widths of the first control signal G1 and the second control signal G2, the asymmetric half-bridge flyback converter 10 can adapt to different input and output conditions. Usually, in order to optimize efficiency, the first switch 141 is controlled to be turned off after the transformer 150 is demagnetized. The demagnetization time of the transformer 150 is related to the peak value of the resonant current Ir flowing through the primary winding 151 of the transformer 150 and the output voltage Vout. When the output voltage Vout of the asymmetric half-bridge flyback converter 10 has a large range, for example, in some applications, the output voltage Vout ranges from 5V to 48V. In this case, since the energy loss of the circuit is the largest when the asymmetric half-bridge flyback converter 10 operates under the output voltage condition of 48V, the design of the demagnetization time of the asymmetric half-bridge flyback converter 10 gives priority to the application environment where the output voltage Vout is 48V. In this case, when the output voltage Vout of the asymmetric half-bridge flyback converter 10 is small, its circuit efficiency will be poor.

[0028] FIG2 is a waveform diagram of some signals when the output voltage Vout of the asymmetric half-bridge flyback converter 10 is small. As shown in FIG2, when the first switch 141 is turned off and the second switch 142 is turned on, corresponding to the time period t10-t11, the input voltage Vin charges the primary winding 151 of the transformer 150, the resonant current Ir rises, and the primary winding 151 stores energy. When the first switch 141 is turned on and the second switch 142 is turned off, corresponding to the time period t11-t12, the resonant current Ir decreases, and the energy of the primary winding 151 is transferred to the secondary winding 152, generating a current Is flowing through the secondary winding 152. Since the output voltage Vout is small, the primary winding 151 of the transformer 150 is demagnetized at time t12, and the first switch 141 is turned off at time t12. However, before time t12, the leakage inductance Lr of the primary winding 151 of the transformer 150 and the resonant capacitor Cr form a resonant circuit, and the resonant current Ir in the resonant circuit oscillates multiple times, causing energy loss and reducing circuit efficiency.

[0029] FIG3 is a schematic diagram of the circuit structure of a power supply device 30 according to an embodiment of the present invention. As shown in FIG3, the power supply device 30 includes a resonant power conversion circuit 320 and a control circuit 310 for controlling the resonant power conversion circuit 320. The resonant power conversion circuit 320 includes a first switch 341, a second switch 342, a transformer 350, a resonant capacitor Cr and other components. The transformer 350 includes a primary winding 351 and a secondary winding 352.

[0030] It should be understood that the resonant power conversion circuit 320 includes but is not limited to an asymmetric half-bridge flyback conversion circuit, and may also be an LLC circuit, for example. The control circuit 310 may be implemented in any form, such as a digital circuit or an analog circuit, or a digital-analog hybrid circuit. The control circuit 310 may be presented in the form of an independent chip, or may be implemented by a suitable processor loading a corresponding program.

[0031] As shown in FIG3 , the resonant power conversion circuit 320 receives an input voltage Vin. The transformer 350 includes a magnetically coupled primary winding 351 and a secondary winding 352. The primary winding 351 stores energy through the input voltage Vin and transfers the energy to the secondary winding 352, thereby generating an output voltage Vout. In the resonant power conversion circuit 320, a circuit directly or indirectly electrically connected to the primary winding 351 is referred to as a primary side circuit 361, and a circuit directly or indirectly electrically connected to the secondary winding 352 is referred to as a secondary side circuit 362.

[0032] During the operation of the power supply device 30, the control circuit 310 outputs one or more control signals 308 (such as PWM signals, etc.) for controlling the on and off of the corresponding switches 341 and 342 of the resonant power conversion circuit 320, so that the resonant power conversion circuit 320 provides a suitable output voltage Vout to the load 160.

[0033] The first switch 341 and the second switch 342 may be coupled in series. The control circuit 310 controls the first switch 341 and the second switch 342 to be alternately turned on and off, so that the first switch 341 and the second switch 342 appear alternately in the resonant circuit including the primary winding 351, and transfer energy from the primary winding 351 to the secondary winding 352. The alternating on and off of the first switch 341 and the second switch 342 causes the change of the current amplitude flowing through the primary winding 351, thereby storing energy in the primary winding 351. After receiving the energy transferred by the primary winding 351, the secondary winding 352 converts it into an output voltage Vout and provides it to the load 160.

[0034] The first switch 341 and the second switch 342 can be implemented by any suitable controllable switch, such as a field effect transistor, a bipolar transistor, etc.

[0035] In an embodiment of the present invention, the primary side circuit 361 of the resonant power conversion circuit 320 generates a resonant current Ir. The control circuit 310 converts the resonant current Ir into a first signal Vr through the current detection circuit 340, and controls the turn-off of the first switch 341 based on the first signal Vr. In one embodiment, the first signal Vr is a voltage signal, the resonant current Ir is a current signal, and the first signal Vr is converted from the resonant current Ir, and the two have similar waveforms. The following will describe in detail how the first signal Vr assists in controlling the on-time of the first switch 341, thereby improving the circuit efficiency of the resonant power conversion circuit 320 when the output voltage Vout is low. In some embodiments of the present invention, the information of the resonant current Ir can also be estimated through some parameter information of a specific application, so that the estimated information of the resonant current Ir can also assist in controlling the on-time of the first switch 341.

[0036] It should be understood that the resonant power conversion circuit of the present invention may adopt any applicable topology. For example, in some embodiments of the present invention, the resonant power conversion circuit adopts an asymmetric half-bridge flyback topology. In other embodiments, the resonant power conversion circuit of the present invention may also adopt other suitable topologies, such as LLC circuits, etc.

[0037] FIG4 is a schematic diagram of the circuit structure of a power supply device 40 according to an embodiment of the present invention. As shown in FIG4 , the power supply device 40 includes a resonant power conversion circuit 420 and a control circuit 410 for controlling the resonant power conversion circuit 420. The resonant power conversion circuit 420 has an asymmetric half-bridge flyback topology, including a first switch 441, a second switch 442, a resonant capacitor Cr, a transformer 150, a secondary switch 443 and an output capacitor Co. The transformer 150 includes a primary winding 151 and a secondary winding 152, wherein the inductor Lr shown in the figure is the leakage inductance of the primary winding 151. In other embodiments, the inductor Lr can also be implemented by an independent inductor device, or can also be the superposition of an independent inductor device and the leakage inductance of the primary winding 151. It should be understood that the primary winding 151 and the devices electrically coupled to the primary winding 151 (switches 441, 442, resonant capacitor Cr and other devices not shown in the figure) constitute the primary side circuit 461, and the secondary winding 152 and the devices electrically coupled to the secondary winding 152 (switch 443, output capacitor Co and other devices not shown in the figure) constitute the secondary side circuit 462.

[0038] In the embodiment of FIG. 4 , the first switch 441, the second switch 442 and the third switch 443 are implemented by MOSFET (metal oxide semiconductor field effect transistor). The first switch 441 includes a gate G, a drain D, a source S, a body diode D1 and a source-drain capacitor C1. The second switch 442 includes a gate G, a drain D, a source S, a body diode D2 and a source-drain capacitor C2. The third switch 443 includes a gate G, a drain D, a source S, a body diode D3 and a source-drain capacitor C3. It should be understood that the body diodes corresponding to each switch are parasitic diodes.

[0039] In the embodiment of FIG. 4 , the control circuit 410 includes a driver 417 and a driver 418, which are respectively used to drive a first switch 441 and a second switch 442. The driver 417 and the driver 418 are used to receive control signals of the first switch 441 and the second switch 442, and after amplifying the driving capability of the corresponding control signals, they are respectively used to provide the gates of the first switch 441 and the second switch 442 to control the on and off of the first switch 441 and the second switch 442. The drain D of the second switch 442 is coupled to the input terminal 203 to receive the input voltage Vin, and the source S is coupled to the switch terminal 204. The drain D of the first switch 441 is coupled to the switch terminal 204, and the source S is coupled to the primary side reference ground terminal 201. The first switch 441 and the second switch 442 are coupled to one end of the primary winding 151 of the transformer 150 through the switch terminal 204. The other end of the primary winding 151 of the transformer 150 is coupled to one end of the resonant capacitor Cr. The other end of the resonant capacitor Cr is coupled to the primary-side reference ground terminal 201 .

[0040] In some embodiments of the present invention, the resonant power conversion circuit 420 has a resonant circuit, including an inductor Lr and a resonant capacitor Cr, which is coupled between the switch terminal 204 and the primary side reference ground terminal 201. In other words, the primary winding 151 and the resonant capacitor Cr are coupled in series between the switch terminal 204 and the primary side reference ground terminal 201.

[0041] In the embodiment of FIG. 4 , the drivers 417 and 418 are integrated into the control circuit 410. In some embodiments, the driver 417 and the first switch 441 are integrated together, and the driver 418 and the second switch 442 are integrated together. It should be understood that the drivers 417, 418, switches 441, 442 and the control circuit 410 can be integrated into a single chip or multiple chips in any suitable combination.

[0042] As shown in the embodiment of FIG. 4 , the secondary winding 152 of the transformer 150 is coupled between the output terminal 206 and the secondary switch 443. That is, the secondary winding 152 and the secondary switch 443 are coupled in series between the output terminal 206 and the secondary side reference ground terminal 202. In the embodiment of FIG. 4 , the secondary switch 443 is implemented by a MOSFET, and the control signal 210 of the gate thereof can be provided by the control circuit 410 or by other control circuits. In some embodiments, the secondary switch 443 can also be implemented by a diode.

[0043] The output capacitor Co is coupled between the output terminal 206 and the secondary-side reference ground terminal 202 .

[0044] As mentioned above, the primary winding 151 of the transformer 150 is located in the resonant circuit, which includes the inductor Lr, the resonant capacitor Cr and the primary winding 151. The control circuit 410 outputs the first control signal 308-1 and the second control signal 308-2 to control the first switch 441 and the second switch 442 respectively, so that the switching frequency of the first switch 441 and the second switch 442 is equal to or close to the resonant frequency of the resonant circuit. The first switch 441 and the second switch 442 are switched on and off alternately. When the first switch 441 is turned off and the second switch 442 is turned on, the resonant circuit stores energy; when the first switch 441 is turned on and the second switch 442 is turned off, the energy of the resonant circuit is transferred from the primary winding 151 to the secondary winding 152.

[0045] As mentioned above, the information of the resonant current Ir flowing through the resonant circuit is provided to the control circuit 410 in the form of the first signal Vr, and participates in the control of the resonant power conversion circuit 420. In the embodiment of FIG4 , the control circuit 410 includes a zero-crossing detection circuit 415 and a counting circuit 416.

[0046] The zero-crossing detection circuit 415 receives the first signal Vr, detects the zero-crossing event indicating that the resonant current Ir crosses the zero point from positive to negative by detecting the first signal Vr, and outputs the zero-crossing detection signal 104 indicating the zero-crossing event. In one embodiment, the first signal Vr is a voltage signal, and its waveform is consistent with the waveform of the resonant current Ir. Therefore, the zero-crossing point of the first signal Vr corresponds to the zero-crossing point of the resonant current Ir. In some embodiments, it is assumed that the direction of the resonant current Ir shown in FIG. 4 is the positive direction, that is, the resonant current Ir flows from the switch terminal 204 to the resonant inductor Lr. In some other embodiments, when the resonant current Ir flows from the resonant inductor Lr to the switch terminal 204, the direction of the resonant current Ir is the negative direction.

[0047] In one embodiment, the zero-crossing detection circuit 415 includes a comparison circuit. During the operation of the circuit, the comparison circuit compares the first signal Vr with a zero-crossing threshold value Vt equal to or close to zero, and outputs a zero-crossing indication signal 10​​4 based on the comparison result of the first signal Vr and the zero-crossing threshold value Vt. In one embodiment, when the first signal Vr drops to the zero-crossing threshold value Vt, the zero-crossing detection circuit 415 detects a zero-crossing event. The zero-crossing indication signal 10​​4 in different states indicates different comparison results of the first signal Vr and the zero-crossing threshold value Vt. For example, the first state (such as a rising edge) of the zero-crossing detection signal 104 indicates that the first signal Vr drops to the zero-crossing threshold value Vt, and the second state (such as a falling edge) of the zero-crossing detection signal 104 indicates that the first signal Vr rises to the zero-crossing threshold value Vt. In one embodiment, when the first signal Vr drops from 0.5V to 0V, the zero-crossing detection signal 104 generates a rising edge, and when the first signal Vr rises from -0.5V to 0V, the zero-crossing detection signal 104 generates a falling edge.

[0048] The counting circuit 416 receives the zero-crossing detection signal 104 and counts the number of zero-crossing events based on the zero-crossing detection signal 104. In some embodiments, the counting circuit 416 counts the number of first states of the zero-crossing detection signal 104 to obtain the number of zero-crossing events. In some embodiments, when the number of zero-crossing events reaches a set number, the output control signal 106 controls the driver 417 to turn off the first switch 441.

[0049] Fig. 5 is a waveform diagram of some signals of a power supply device 40 according to an embodiment of the present invention. The working principle of the power supply device 40 of the present invention is described below in conjunction with Fig. 4 and Fig. 5 .

[0050] In FIG. 5 , the high level state of the control signals 308 - 1 and 308 - 2 corresponds to the on state of the first switch 441 and the second switch 442 , respectively, and the low level state corresponds to the off state of the first switch 441 and the second switch 442 , respectively.

[0051] As shown in FIG. 5 , at time t20, the first switch 441 is in the off state, the second switch 442 is turned on, the primary winding 151 is connected to the input voltage Vin through the second switch 442, and the resonant current Ir flowing through the primary winding 151 increases.

[0052] At time t21, the resonant current Ir reaches a peak value, the second switch 442 is turned off, and the first switch 441 is turned on. It should be understood that in order to avoid direct conduction between the first switch 441 and the second switch 442, thereby damaging the circuit components, a dead time is set between the turning off of the second switch 442 and the turning on of the first switch 441, that is, the time during which the first switch 441 and the second switch 442 are both in the off state. Because the dead time is short, for the sake of simplicity of description and clarity of illustration, this period is not explicitly shown in FIG5. Similarly, a dead time is also set during the period between the turning off of the first switch 441 and the turning on of the second switch 442. When the second switch 442 is turned off and the first switch 441 is turned on, the current Ir begins to decrease, and the resonant circuit composed of the inductor Lr and the resonant capacitor Cr begins to oscillate, and its resonant period Tr is , where Lr in the formula represents the inductance of the inductor Lr, and Cr in the formula represents the capacitance of the resonant capacitor Cr.

[0053] At time t22, the first signal Vr drops to the zero-crossing threshold value Vt. As mentioned above, the waveform of the first signal Vr is consistent with the waveform of the resonant current Ir. Therefore, in FIG5 , the first signal Vr and the resonant current Ir are represented by the same waveform. It should be understood that the resonant current Ir is a current signal, and the first signal Vr can be a voltage signal. Therefore, the two are not equal in actual value. The waveforms of the first signal Vr and the resonant current Ir in FIG5 are only for illustration, and are used to illustrate the working principle of the circuit of the present invention. The value of the zero-crossing threshold value Vt is close to zero. Therefore, the moment when the first signal Vr drops to the zero-crossing threshold value Vt corresponds to the moment when the resonant current Ir crosses the zero point from positive to negative. At this time, the zero-crossing detection signal 104 output by the zero-crossing detection circuit 415 jumps from a low level to a high level, generating a rising edge. The counting circuit 416 is triggered by the rising edge of the zero-crossing detection signal 104, that is, after the counting circuit 416 detects the rising edge of the zero-crossing detection signal 104, it counts once.

[0054] After time t22, the resonant current Ir oscillates downward to the negative maximum value and then begins to oscillate upward until time t23, when the resonant current Ir crosses the zero point from negative to positive, corresponding to the first signal Vr crossing the zero-crossing threshold Vt from negative to positive, causing the zero-crossing detection signal 104 to jump from a high level to a low level.

[0055] At time t24, the resonant current Ir crosses zero again from positive to negative, the first signal Vr crosses the zero-crossing threshold Vt from positive to negative, and the zero-crossing detection signal 104 jumps from a low level to a high level. After the counting circuit 416 detects the rising edge of the zero-crossing detection signal 104, it counts again. At this time, the counting circuit 416 detects two rising edges of the zero-crossing detection signal 104, and the total count number is 2, reaching the preset count number, and the counting circuit 416 outputs the control signal 106, and the control signal 106 outputs the first control signal 308-1 through the driver 417 to turn off the first switch 441.

[0056] Compared with the prior art, in the embodiment of the present invention, the first switch 441 is turned off when the resonant current Ir crosses the zero point from top to bottom for the second time, which reduces the current oscillation in the resonant circuit, thereby reducing the power loss and improving the circuit efficiency. When the first switch 441 is turned off, the resonant circuit is composed of the inductor Lr, the resonant capacitor Cr and the source-drain capacitor C1 of the first switch 441. In other words, after the first switch 441 is turned off, the source-drain capacitor C1 of the first switch 441 participates in the resonant circuit. After the first switch 441 is turned off, the negative resonant current Ir charges the source-drain capacitor C1. Since the capacitance value of the source-drain capacitor C1 is small, the voltage of the switch end 204 is quickly pulled up. Therefore, the resonant current Ir starts to oscillate upward when it oscillates downward to a smaller negative value (i.e., a smaller absolute value), so the oscillation amplitude of the resonant current Ir is reduced, thereby reducing the circuit power loss and improving the efficiency.

[0057] At time t25, the demagnetization of the transformer 150 is completed.

[0058] At time t26, the second switch 442 is turned on again, a new switching cycle of the resonant power conversion circuit 420 begins, and the working process is repeated, which will not be repeated here.

[0059] In some embodiments of the present invention, it is an approximate approach to make the first signal Vr pass through the zero-crossing threshold Vt to correspond to the resonant current Ir passing through the zero point. By adjusting the value of the zero-crossing threshold Vt to make it close to zero, the accuracy of circuit control can be adjusted. However, it should be understood that in actual circuits, due to the non-ideal characteristics of circuit components and the existence of circuit delays, the turn-off time of the first switch 441 does not accurately correspond to the time when the resonant current passes through the zero point from positive to negative, and there is a certain error between the two.

[0060] Meanwhile, it should be understood that the first switch 441 is turned off at the moment when the resonant current Ir crosses the zero point from positive to negative for the second time in the embodiment of the present invention for illustrative purposes. A person skilled in the art may set the first switch 441 to be turned off when the resonant current Ir crosses the zero point from positive to negative for the third or fourth time, or any other time, according to the needs of practical applications.

[0061] FIG6 is a schematic diagram of the circuit structure of a power supply device 60 according to another embodiment of the present invention. As shown in FIG6 , the power supply device 60 includes a resonant power conversion circuit 620 and a control circuit 610 for controlling the resonant power conversion circuit 620. The resonant power conversion circuit 620 has an asymmetric half-bridge flyback topology, including a first switch 441, a second switch 442, a resonant capacitor Cr, a transformer 170, a secondary switch 443 and an output capacitor Co. The transformer 170 includes a primary winding 171, a secondary winding 172 and an auxiliary winding 173, wherein the inductor Lr shown in the figure is the leakage inductance of the primary winding 171. In other embodiments, the inductor Lr can also be implemented by an independent inductor device, or can also be a superposition of an independent inductor device and the leakage inductance of the primary winding 171. The auxiliary winding 173 is magnetically coupled with the primary winding 171 and the secondary winding 172.

[0062] In the embodiment of FIG. 6 , the auxiliary winding 173 provides an output voltage feedback signal Va, i.e., an auxiliary winding voltage Va, which is used to characterize the output voltage Vout of the resonant power conversion circuit 620. The value of the output voltage feedback signal Va is proportional to the output voltage Vout, and the proportionality coefficient is determined by the turns ratio of the auxiliary winding 173 to the secondary winding 172, i.e., Va:Vout=N 173:N 172. In other words, Va=Vout×(N 173 / N 172), where N 173 is the number of turns of the auxiliary winding 173, and N 172 is the number of turns of the secondary winding 172. A person skilled in the art can determine the turns ratio of the auxiliary winding 173 to the secondary winding 172 according to the specific circuit application parameters and the required value of the output voltage feedback signal Va. In some embodiments, the output voltage feedback signal Va can also be divided by a voltage divider circuit, and the divided voltage signal is then provided to the control circuit 610.

[0063] In the embodiment of FIG6 , the control circuit 610 includes a zero-crossing detection circuit 415, a counting circuit 416 and an enabling circuit 660. The working principles of the zero-crossing detection circuit 415 and the counting circuit 416 are as described above.

[0064] After receiving the output voltage feedback signal Va, the control circuit 610 provides the output voltage feedback signal Va to the enabling circuit 660. The enabling circuit 660 detects the output voltage feedback signal Va, and shields the control signal 106 when the output voltage feedback signal Va indicates that the output voltage Vout is above a certain value, such as 5V. Otherwise, the control signal 106 can control the first control signal 308-1 to turn off the first switch 441 through the driver 417, that is, enable the first control signal 308-1 to turn off the first switch 441. It should be understood that the enabling circuit 660 enables or disables the action of the first control signal 308-1 to turn off the first switch 441 at the moment when the resonant current Ir crosses the zero point from positive to negative for the second time based on the value of the output voltage feedback signal Va, and the action of the first control signal 308-1 to turn off the first switch 441 at the moment when the resonant current Ir crosses the zero point from positive to negative for the second time is based on the control signal 106. Therefore, enabling or disabling the first control signal 308-1 to implement this action can be achieved by shielding the control signal 106. That is, by shielding the control signal 106, the first control signal 308-1 can be disabled or enabled to turn off the first switch 441 when the resonant current Ir crosses the zero point from positive to negative for the second time. In some embodiments, the control signal 106 can be a data, and whether the data affects the first control signal 308-1 is determined according to the output voltage feedback signal Va detected by the enabling circuit 660.

[0065] In the embodiment of FIG6 , the enabling circuit 660 includes an output voltage detection circuit 661 and a shielding circuit 662. The output voltage detection circuit 661 receives the output voltage feedback signal Va and outputs a shielding signal 107. The shielding circuit 662 receives the shielding signal 107 and determines whether to shield the control signal 106 based on the shielding signal 107.

[0066] In one embodiment, the output voltage detection circuit 661 includes a comparison circuit. The comparison circuit receives the output voltage feedback signal Va, compares it with a shielding threshold Vtb, and outputs a shielding signal 107 according to the comparison result. In one embodiment, the control signal 106 works when the output voltage Vout is less than 5V. In this embodiment, if the ratio of the output voltage feedback signal Va to the output voltage Vout is 1:5, the shielding threshold Vtb is 1V. When the output voltage feedback signal Va is less than 1V, the control signal 106 is provided to the driver 417, otherwise, the control signal 106 is shielded, and does not affect the control of the first switch 441 by the first control signal 308-1.

[0067] In one embodiment, the shielding circuit 662 includes a switch. The switch is controlled by the shielding signal 107. When the shielding signal 107 indicates that the output voltage Vout is less than the corresponding threshold value, that is, when the output voltage feedback signal Va is less than the shielding threshold value Vtb, the switch is turned on, and the control signal 106 can be provided to the driver 417 through the shielding circuit 662. Otherwise, the switch is turned off, and the control signal 106 is shielded by the shielding circuit 662 and cannot act on the driver 417.

[0068] It should be understood that the enabling circuit 660 may also shield the control signal 106 in other ways, such as by a program or a digital circuit. The control signal 106 may also be shielded by disabling the circuit, such as disabling the counting circuit 416 and / or the zero-crossing detection circuit 415, so that they cannot provide the control signal 106.

[0069] It should be known to those skilled in the art that the auxiliary winding voltage Va feeds back the magnitude of the output voltage Vout during the conduction period of the secondary switch 443, but other than that, the auxiliary winding voltage Va does not represent the output voltage Vout. A commonly used method in the prior art is to sample and hold the auxiliary winding voltage Va during the conduction period of the secondary switch 443. Since this method is relatively common and well known to those skilled in the art, the structure and corresponding description of this part of the sampling and holding circuit are omitted in the embodiment of the present invention. It should be understood that the output voltage feedback signal Va mentioned in the embodiment of the present invention is a processed circuit signal of the feedback output voltage Vout. At the same time, it should be understood that detecting the output voltage Vout through the auxiliary winding 173 in FIG6 is a way to obtain information about the output voltage Vout. Other methods, such as estimating through a digital circuit, can also obtain information about the output voltage Vout.

[0070] In the embodiment of FIG. 6 , when the output voltage Vout is greater than the corresponding threshold value, the control signal 106 is shielded and does not implement control of the first switch 441. It should be understood that the shielding control signal 106 can affect the first switch 441 in many ways, for example, the shielding signal 107 can be used to disable the counting circuit 416 or the zero-crossing detection circuit 415, or the shielding signal 107 can be used to shield the zero-crossing detection signal 104. In some embodiments of the present invention, the function of the enabling circuit 660 is to enable the control signal 106 to work under certain output voltage conditions, such as when the output voltage Vout is less than 5 volts, and to prohibit working under other output voltage conditions, such as when the output voltage Vout is greater than or equal to 5 volts.

[0071] In the embodiment of FIG. 6 , the working principles of the zero-crossing detection circuit 415 and the counting circuit 416 are consistent with those in the embodiment of FIG. 5 , and will not be described in detail here.

[0072] FIG7 is a schematic diagram of a circuit structure of a power supply device 70 according to another embodiment of the present invention. As shown in FIG7, the power supply device 70 includes a resonant power conversion circuit 720 and a control circuit 410 for controlling the resonant power conversion circuit 720. The resonant power conversion circuit 720 has an asymmetric half-bridge topology, including a first switch 741, a second switch 742, a resonant capacitor Cr, a transformer 150, a secondary switch 443 and an output capacitor Co.

[0073] Compared with the embodiment shown in FIG. 4 , the structure of the primary side circuit of the resonant power conversion circuit 720 shown in FIG. 7 is slightly different. In FIG. 7 , the first switch 741 is located at the high side, and the second switch 742 is located at the low side. Specifically, the drain D of the first switch 741 is coupled to the input terminal 203 to receive the input voltage Vin, and the source S is coupled to the switch terminal 204. The drain D of the second switch 742 is coupled to the switch terminal 204, and the source S is coupled to the primary side reference ground terminal 201. The drain D of the first switch 741 is coupled to one end of the primary winding 151 of the transformer 150. The other end of the primary winding 151 of the transformer 150 is coupled to one end of the resonant capacitor Cr. The other end of the resonant capacitor Cr is coupled to the switch terminal 204.

[0074] In the embodiment of FIG. 7 , the control circuit 410 includes a driver 417 and a driver 418, which are respectively used to drive a first switch 741 and a second switch 742. The driver 417 outputs a first control signal 308-1 for controlling the first switch 741, and the driver 418 outputs a second control signal 308-2 for controlling the second switch 742. When the first switch 741 is turned off and the second switch 742 is turned on, the resonant circuit stores energy; when the first switch 741 is turned on and the second switch 742 is turned off, the energy of the resonant circuit is transferred from the primary winding 151 to the secondary winding 152.

[0075] It should be understood that in the embodiment of FIG. 7, although the positions of the first switch 741 and the second switch 742 are just opposite to the first switch 441 and the second switch 442 in the embodiment of FIG. 4, the same thing is that when the first switch 441 / 741 is turned on, the primary winding 151 transfers energy to the secondary winding 152; when the second switch 442 / 742 is turned on, the primary winding 151 stores energy. That is, in the embodiment of the present invention, the first switch corresponds to a switch that forms a resonant circuit in the primary side circuit after closing to generate current oscillation, and the second switch corresponds to a switch that stores energy in the primary winding after closing. Accordingly, the driver 417 outputs the first control signal 308-1 for driving the first switch 741, and the driver 418 outputs the second control signal 308-2 for driving the second switch 742.

[0076] The working principle of the power supply device 70 is similar to that of the power supply device 40, and the waveforms of some of its signals (control signals 308-1, 308-2, the first signal Vr, the resonant current Ir and the zero-crossing detection signal 104) are also shown in FIG. 5, so they are not described again here.

[0077] FIG8 is a schematic diagram of a circuit structure of a power supply device 80 according to another embodiment of the present invention. As shown in FIG8 , the power supply device 80 includes a resonant power conversion circuit 820 and a control circuit 610 for controlling the resonant power conversion circuit 820. The resonant power conversion circuit 820 has an asymmetric half-bridge flyback topology, including a first switch 741, a second switch 742, a resonant capacitor Cr, a transformer 170, a secondary switch 443, and an output capacitor Co.

[0078] Compared with the embodiment shown in FIG4 , in the primary side circuit of the resonant power conversion circuit 720 shown in FIG8 , the first switch 741 is located at the high side, and the second switch 742 is located at the low side. Specifically, the drain D of the first switch 741 is coupled to the input terminal 203 to receive the input voltage Vin, and the source S is coupled to the switch terminal 204. The drain D of the second switch 742 is coupled to the switch terminal 204, and the source S is coupled to the primary side reference ground terminal 201. The first switch 741 and the second switch 742 are coupled to one end of the primary winding 171 of the transformer 170 through the switch terminal 204. The other end of the primary winding 171 of the transformer 170 is coupled to one end of the resonant capacitor Cr. The other end of the resonant capacitor Cr is coupled to the primary side reference ground terminal 201.

[0079] In the embodiment of FIG8 , the control circuit 610 includes a driver 417 and a driver 418, which are respectively used to drive a first switch 741 and a second switch 742. The driver 417 outputs a first control signal 308-1 for controlling the first switch 741, and the driver 418 outputs a second control signal 308-2 for controlling the second switch 742. When the first switch 741 is turned off and the second switch 742 is turned on, the resonant circuit stores energy; when the first switch 741 is turned on and the second switch 742 is turned off, the energy of the resonant circuit is transferred from the primary winding 171 to the secondary winding 172.

[0080] In the embodiment of FIG8 , the control circuit 610 includes a zero-crossing detection circuit 415, a counting circuit 416, and an enabling circuit 660. The working principles of the zero-crossing detection circuit 415, the counting circuit 416, and the enabling circuit 660 are as described above and will not be described in detail here.

[0081] FIG9 is a schematic diagram of the circuit structure of a resonant power conversion circuit 90 according to an embodiment of the present invention. Compared with the resonant power conversion circuit 420 shown in FIG4 , the resonant power conversion circuit 90 further includes a current detection resistor Rcs, which is coupled in series with the resonant capacitor Cr and the primary winding 151, that is, between the detection terminal 901 and the primary side reference ground terminal 201, and is located in the resonant circuit through which the resonant current Ir flows. When the resonant current Ir flows through the current detection resistor Rcs, a first signal Vr is generated on the current detection resistor Rcs, that is, the detection terminal 901 provides the first signal Vr, and the value of the first signal Vr is Vr=Ir×Rcs, that is, the value of the first signal Vr is in direct proportion to the value of the resonant current Ir, and the value of the proportionality coefficient is the resistance value of the current detection resistor Rcs. The first signal Vr is provided to the control circuit 410 or 610 as described above, and becomes the control basis for controlling the first switch of the corresponding circuit.

[0082] FIG10 is a schematic diagram of the circuit structure of a resonant power conversion circuit 100 according to an embodiment of the present invention. Compared with the resonant power conversion circuit 420 shown in FIG4 , the resonant power conversion circuit 100 further includes a current detection circuit 920, which has an input end coupled to one end of the resonant capacitor Cr, namely the resonant capacitor end 101, and an output end providing a first signal Vr. The current detection circuit 920 includes a capacitor Cs, a resistor Ra, and a filter circuit 190. The capacitor Cs and the resistor Ra are coupled in series between the resonant capacitor end 101 and the primary side reference ground end 201. When the circuit is working, the resonant current Ir flows through the resonant capacitor Cr and the capacitor Cs, wherein the magnitude of the current Ics flowing through the capacitor Cs is related to the capacitance of the resonant capacitor Cr and the capacitor Cs, and is In this formula, Ics represents the value of current Ics, Ir represents the value of resonant current Ir, Cs represents the capacitance of capacitor Cs, and Cr represents the capacitance of resonant capacitor Cr. It can be seen that the value of current Ics is proportional to the value of resonant current Ir, and the proportionality coefficient is Cs / (Cr+Cs). When current Ics flows through resistor Ra, voltage Ics×Ra is generated on resistor Ra, where Ra represents the resistance of resistor Ra. Substituting into the above formula, the voltage is , the voltage is filtered by the filter circuit 190 to generate the first signal Vr, that is, From this formula, we can see that the value of the first signal Vr is proportional to the value of the resonant current Ir, and the proportionality coefficient is By properly selecting the resistance of the resistor Ra and the capacitance of the capacitor Cs, the required value of the first signal Vr can be obtained. The first signal Vr is provided to the control circuit 410 or 610 as described above, and becomes the control basis for controlling the first switch of the corresponding circuit.

[0083] In some embodiments of the present invention, the current detection circuit 920 is integrated into the control circuit 410 or the control circuit 610 .

[0084] FIG11 is a schematic diagram of the circuit structure of a resonant power conversion circuit 110 according to an embodiment of the present invention. Compared with the resonant power conversion circuit 720 shown in FIG7 , the resonant power conversion circuit 110 further includes a current detection resistor Rcs and a current detection circuit 130. The current detection resistor Rcs is coupled in series with the resonant capacitor Cr and the primary winding 151, and is located between the detection terminal 209 and the switch terminal 204 in the resonant circuit through which the resonant current Ir flows. When the resonant current Ir flows through the current detection resistor Rcs, a voltage is generated on the current detection resistor Rcs. The voltage detection circuit 130 has two input terminals respectively coupled to the two ends of the current detection resistor Rcs, and generates a first signal Vr based on the voltage across the two ends of the current detection resistor Rs. In one embodiment, the voltage detection circuit 130 includes a differential amplifier circuit, and the value of the first signal Vr is proportional to the value of the resonant current Ir, and the proportionality coefficient is Rcs×A1, where A1 is the amplification coefficient of the differential amplifier circuit. The first signal Vr is provided to the control circuit 410 or 610 as described above, and becomes the control basis for controlling the first switch of the corresponding resonant power conversion circuit. In some embodiments of the present invention, the voltage detection circuit 130 is integrated into the control circuit 410 or the control circuit 610.

[0085] FIG12 is a schematic diagram of the circuit structure of a resonant power conversion circuit 120 according to an embodiment of the present invention. Compared with the resonant power conversion circuit 720 shown in FIG7 , the resonant power conversion circuit 120 further includes a current detection circuit 920, which has an input end coupled to one end of the resonant capacitor Cr, namely the resonant capacitor end 701, and an output end providing a first signal Vr. The current detection circuit 920 includes a capacitor Cs, a resistor Ra, and a filter circuit 190. The capacitor Cs and the resistor Ra are coupled in series between the resonant capacitor end 701 and the primary side reference ground end 201. When the circuit is working, the resonant current Ir flows through the resonant capacitor Cr and the capacitor Cs, wherein the magnitude of the current Ics flowing through the capacitor Cs is related to the capacitance of the resonant capacitor Cr and the capacitor Cs, and is In this formula, Ics represents the value of current Ics, Ir represents the value of resonant current Ir, Cs represents the capacitance of capacitor Cs, and Cr represents the capacitance of resonant capacitor Cr. It can be seen that the absolute value of current Ics is proportional to the absolute value of resonant current Ir, and the proportionality coefficient is Cs / (Cr+Cs). When current Ics flows through resistor Ra, voltage Ics×Ra is generated on resistor Ra, where Ra represents the resistance of resistor Ra. Substituting into the above formula, the voltage is , the voltage is filtered by the filter circuit 190 to generate the first signal Vr, that is, From this formula, we can see that the value of the first signal Vr is proportional to the value of the resonant current Ir, and the proportionality coefficient is By properly selecting the resistance of the resistor Ra and the capacitance of the capacitor Cs, the required value of the first signal Vr can be obtained. The first signal Vr is provided to the control circuit 410 or 610 as described above, and becomes the control basis for controlling the first switch of the corresponding circuit.

[0086] FIG13 is a schematic diagram of the circuit structure of a power supply device 130 according to an embodiment of the present invention. As shown in FIG13 , the power supply device 130 includes a resonant power conversion circuit 1320 and a control circuit 1310 for controlling the resonant power conversion circuit 1320. The resonant power conversion circuit 1320 has an asymmetric half-bridge flyback topology, including a first switch 441, a second switch 442, a resonant capacitor Cr, a transformer 150, a secondary switch 443, and an output capacitor Co. The transformer 150 includes a primary winding 151 and a secondary winding 152, wherein the inductor Lr shown in the figure is the leakage inductance of the primary winding 151. In other embodiments, the inductor Lr can also be implemented by an independent inductor device, or can also be the superposition of an independent inductor device and the leakage inductance of the primary winding 151. It should be understood that the primary winding 151 and the devices electrically coupled to the primary winding 151 (switches 441, 442, resonant capacitor Cr and other devices not shown in the figure) constitute the primary side circuit 1361, and the secondary winding 152 and the devices electrically coupled to the secondary winding 152 (switch 443, output capacitor Co and other devices not shown in the figure) constitute the secondary side circuit 1362.

[0087] In the embodiment of FIG13, during the period when the first switch 441 is turned on and the second switch 442 is turned off, the information of the resonant current Ir flowing through the resonant circuit is estimated by the capacitance of the resonant capacitor Cr and the inductance of the inductor Lr. Wherein, the mark 133 in FIG13 represents the capacitance information of the resonant capacitor Cr, and the mark 134 represents the inductance information of the inductor Lr, and the capacitance information of the resonant capacitor Cr and the inductance information of the inductor Lr are provided to the control circuit 1310 in the form of data. In some embodiments, the capacitance information of the resonant capacitor Cr and the inductance information of the inductor Lr can also be provided to the control circuit 1310 in the form of signals.

[0088] The control circuit 1310 includes a resonance period calculation circuit 315 and a duration control circuit 316. The resonance period calculation circuit 315 includes a memory unit 315S, which is used to store the capacitance information 133 of the resonance capacitor Cr and the inductance information 134 of the inductance Lr. The period calculation circuit 315 calculates the resonance period Tr of the resonance circuit of the resonance power conversion circuit 1320 by the capacitance of the resonance capacitor Cr and the inductance of the inductance Lr, and obtains the resonance period information 103 including the resonance period Tr information. The duration control circuit 316 receives the resonance period information 103, and based on the length of the resonance period Tr, outputs a control signal 105 for controlling the conduction duration of the first switch 441. The duration control circuit 316 starts at the conduction moment of the first switch 441, and after a duration of 1.1 to 1.4 times the resonance period Tr, outputs a control signal 105 for controlling the first switch 441 to be turned off. In one embodiment, the control signal 105 controls the first control signal 308-1 to turn off the first switch 441 through the driver 417. In one embodiment, the duration control circuit 316 further receives the first control signal 308-1 to determine the moment when the first switch 441 is turned on. It should be understood that other signals for indicating the conduction moment of the first switch 441 (for example, an intermediate signal of a part of the circuit for generating the first control signal 308-1 in the control circuit 1310) can also be used in the embodiment of the present invention as one of the references for calculating the turn-off moment of the first switch 441. In one embodiment, the control circuit 1310 controls the first switch 441 to be turned off after 1.25 times of the resonance period Tr from the time when the first switch 441 is turned on. Ideally, the time node corresponding to 1.25 times of the resonance period Tr from the time when the first switch 441 is turned on is the time when the resonance current Ir crosses the zero point from positive to negative for the second time. However, due to the non-ideal characteristics of actual circuit elements and the existence of circuit delay, the time when the resonance current Ir crosses the zero point from positive to negative for the second time does not accurately correspond to the time when 1.25 times of the resonance period Tr is passed from the time when the first switch 441 is turned on. Therefore, in actual applications, those skilled in the art can choose to turn off the first switch 441 at the time node corresponding to 1.1 to 1.4 times of the resonance period Tr from the time when the first switch 441 is turned on according to the actual application circuit. That is to say, the time duration of 1.1 to 1.4 times of the resonance period Tr after the first switch 441 is turned on represents the time when the resonance current Ir crosses the zero point from positive to negative for the second time.

[0089] In some embodiments, the duration of the resonance period Tr may be obtained by other methods. For example, in some applications, the length of the resonance period Tr is preset, and the capacitance of the resonance capacitor Cr and the inductance of the inductor Lr are determined by the preset resonance period Tr. In these embodiments, the preset resonance period Tr may be directly stored in the memory unit 315S or the control circuit 1310 may receive data including the information of the resonance period Tr through the interface circuit.

[0090] Fig. 14 is a waveform diagram of some signals of the power supply device 130 according to an embodiment of the present invention. The working principle of the power supply device 130 of the present invention is described below in conjunction with Fig. 13 and Fig. 14 .

[0091] In FIG. 14 , the high level states of the control signals 308 - 1 and 308 - 2 correspond to the on-states of the first switch 441 and the second switch 442 , respectively, and the low level states correspond to the off-states of the first switch 441 and the second switch 442 , respectively.

[0092] As shown in FIG. 14 , at time t30, the first switch 441 is in the off state, the second switch 442 is turned on, the primary winding 151 is connected to the input voltage Vin through the second switch 442, and the current Ir flowing through the primary winding 151 increases.

[0093] At time t31, the current Ir reaches a peak value, the second switch 442 is turned off, and the first switch 441 is turned on. It should be understood that in order to avoid direct conduction between the first switch 441 and the second switch 442 and damage to the circuit components, a dead time is set between the turning off of the second switch 442 and the turning on of the first switch 441, that is, the time when the first switch 441 and the second switch 442 are both in the off state. Because the dead time is short, for the sake of simplicity and clarity of the illustration, this period is not explicitly shown in Figure 14. Similarly, a dead time is also set during the period when the first switch 441 is turned off and the second switch 442 is turned on. When the second switch 442 is turned off and the first switch 441 is turned on, the current Ir begins to decrease, and the resonant circuit composed of the inductor Lr and the resonant capacitor Cr begins to oscillate, and its resonant period Tr is , where Lr in the formula represents the inductance of the inductor Lr, and Cr in the formula represents the capacitance of the resonant capacitor Cr.

[0094] At time t32, the conduction time of the first switch 441 reaches 1.25 times of the resonance period Tr, and the control signal 105 generates a pulse. The pulse controls the first control signal 308-1 through the driver 417 to turn off the first switch 441.

[0095] At time t33, the demagnetization of the transformer 150 is completed.

[0096] At time t34, the second switch 442 is turned on again, a new switching cycle of the resonant power conversion circuit 1320 begins, and the working process is repeated, which will not be repeated here.

[0097] The control circuit 1310 of the embodiment of the present invention is not only applicable to the resonant power conversion circuit in which the first switch 441 is located on the low side as shown in Figure 13, but is also applicable to the resonant power conversion circuit in which the first switch 741 is located on the high side as shown in Figure 8.

[0098] FIG15 is a schematic diagram of the circuit structure of a power supply device 150 according to an embodiment of the present invention. As shown in FIG15 , the power supply device 150 includes a resonant power conversion circuit 1520 and a control circuit 1510 for controlling the resonant power conversion circuit 1520. The resonant power conversion circuit 1520 has an asymmetric half-bridge flyback topology, including a first switch 441, a second switch 442, a resonant capacitor Cr, a transformer 170, a secondary switch 443 and an output capacitor Co. The transformer 170 includes a primary winding 171, a secondary winding 172 and an auxiliary winding 173, wherein the inductor Lr shown in the figure is the leakage inductance of the primary winding 171. In other embodiments, the inductor Lr can also be implemented by an independent inductor device, or can also be a superposition of an independent inductor device and the leakage inductance of the primary winding 171. The auxiliary winding 173 is magnetically coupled with the primary winding 171 and the secondary winding 172.

[0099] In the embodiment of FIG. 15 , the auxiliary winding 173 provides an output voltage feedback signal Va, which is used to characterize the output voltage Vout of the resonant power conversion circuit 1520. The value of the output voltage feedback signal Va is proportional to the output voltage Vout, and the proportionality coefficient is determined by the turns ratio of the auxiliary winding 173 to the secondary winding 172, that is, Va:Vout=N 173:N 172. In other words, Va=Vout×(N 173 / N 172), where N 173 is the number of turns of the auxiliary winding 173, and N 172 is the number of turns of the secondary winding 172. A person skilled in the art can determine the turns ratio of the auxiliary winding 173 to the secondary winding 172 according to the specific circuit application parameters and the required value of the output voltage feedback signal Va. In some embodiments, the output voltage feedback signal Va can also be divided by a voltage divider circuit, and the divided voltage signal is then provided to the control circuit 1510.

[0100] In the embodiment of FIG15 , the control circuit 1510 includes a resonance period calculation circuit 315, a duration control circuit 316, and an enabling circuit 660. The circuit structures and working principles of the resonance period calculation circuit 315, the duration control circuit 316, and the enabling circuit 660 are as described above and will not be described in detail here.

[0101] After receiving the output voltage feedback signal Va, the control circuit 1510 provides the output voltage feedback signal Va to the enabling circuit 660. The enabling circuit 660 detects the output voltage feedback signal Va, and shields the control signal 105 when the output voltage feedback signal Va indicates that the output voltage Vout is above a certain value, such as 5V; otherwise, the control signal 105 can be enabled to generate the first control signal 308-1 through the driver 417 to control the turn-off of the first switch 441.

[0102] In the embodiment of FIG. 15 , when the output voltage Vout is greater than the corresponding threshold value, the control signal 105 is shielded and the control of the first switch 441 is not implemented, that is, the first control signal 308-1 is not output through the driver 417 to turn off the first switch 441. It should be understood that the enabling circuit 660 enables or disables the first control signal 308-1 to turn off the first switch 441 at the moment when the resonant current Ir crosses the zero point from positive to negative for the second time based on the value of the output voltage feedback signal Va, and the action basis of the first control signal 308-1 to turn off the first switch 441 at the moment when the resonant current Ir crosses the zero point from positive to negative for the second time is the control signal 105. Therefore, enabling or disabling the first control signal 308-1 to implement this action can be achieved by shielding the control signal 105. That is, by shielding the control signal 105, the first control signal 308-1 can be disabled or enabled to turn off the first switch 441 at the moment when the resonant current Ir crosses the zero point from positive to negative for the second time. In some embodiments, the control signal 105 may be a data, and whether the data affects the first control signal 308-1 is determined according to the output voltage feedback signal Va detected by the enabling circuit 660. It should be understood that there are many ways to shield the influence of the control signal 105 on the first switch 441, for example, the shielding signal 107 can be used to disable the duration control circuit 316 or the resonance period calculation circuit 315, or both. In some embodiments of the present invention, the function of the enabling circuit 660 is to make the control signal 105 work under certain output voltage conditions, for example, when the output voltage Vout is less than 5 volts, and prohibit the operation under other output voltage conditions, for example, when the output voltage Vout is greater than or equal to 5 volts. The embodiment of the present invention shows that the enabling circuit 660 achieves the purpose of making the control signal 105 work under certain output voltage conditions by isolating or passing the control signal 105. It should be understood that other ways, such as disabling the duration control circuit 316 and / or the resonance period calculation circuit 315, so that it cannot provide the control signal 105, can also achieve the purpose of shielding the control signal 105.

[0103] The working principles of the resonance period calculation circuit 315 and the duration control circuit 316 are as described above, and will not be described in detail here. In some embodiments, the resonance period calculation circuit 315 and the duration control circuit 316 are implemented by digital circuits or programs. In these embodiments, some of the connections and signals in Figures 13 and 15 do not necessarily exist in reality, and can be implemented in the form of data and links. For example, the resonance period information 103 therein can be data including information of the resonance period Tr, and the data may exist in a register or other memory unit and can be read. In other words, the embodiment of the present invention is only used to illustrate the working principle of the circuit. According to the working principle of the circuit of the embodiment of the present invention provided in this specification, various forms of circuits can be derived to implement the embodiment of the present invention.

[0104] The control circuits 1310 and 1510 of the embodiments of the present invention are not only applicable to the resonant power conversion circuit in which the first switch 441 is located on the low side as shown in Figures 13 and 15, but are also applicable to the resonant power conversion circuit in which the first switch 741 is located on the high side as shown in Figure 8.

[0105] It should be understood that the control circuit in the embodiment of the present invention can be implemented in the form of a digital circuit or a program. Therefore, the circuit connection structures and signals in the control circuit do not necessarily exist in reality. For example, the control signal 106 can be a piece of information that exists in the form of data. At the same time, some input terminals and output terminals in the present invention can be pins of an actual chip or ports of a circuit, or interfaces for data transmission. For example, the control circuit is used to receive resonant current information related to the resonant current flowing through the resonant circuit, and can be a pin of a chip for receiving a voltage or current signal representing the resonant current, or for receiving a signal representing the value of the leakage inductance and resonant capacitance of the primary winding of the transformer; it can also be a data interface for receiving information representing the leakage inductance and resonant capacitance of the primary winding of the transformer, or data of the resonant current information.

[0106] FIG16 is a flow chart of a control method 160 of a resonant power conversion circuit according to an embodiment of the present invention. The resonant power conversion circuit includes each resonant power conversion circuit in the aforementioned embodiments. The resonant power conversion circuit includes a first switch, a second switch, a transformer, and a resonant capacitor. The first switch and the second switch are coupled in series between the input terminal and the primary side reference ground terminal. When the first switch is turned on, the resonant capacitor and the resonant inductor of the resonant power conversion circuit resonate. The resonant inductor may be the leakage inductance of the primary winding of the resonant power conversion circuit, or may be the inductance provided by a separate inductor element, or a combination of the two. The control method 160 includes: step 1601, controlling the first switch and the second switch in the resonant power conversion circuit to adjust the energy transfer from the primary winding to the secondary winding of the transformer of the resonant power conversion circuit, wherein the resonant circuit of the resonant power conversion circuit includes the primary winding and the resonant capacitor; step 1602, receiving resonant current information related to the resonant current flowing through the resonant circuit; and step 1603, based on the resonant current information, controlling the first switch to be turned off.

[0107] In one embodiment, the control method 160 further includes step 1604, detecting the output voltage of the resonant power conversion circuit, and when the output voltage is lower than a set value, controlling the first switch to turn off based on the resonant current information.

[0108] In one embodiment, the resonant current information includes an actual value of the resonant current, and step 1603 includes: detecting a zero-crossing event indicating that the resonant current crosses a zero point from positive to negative; and when the number of zero-crossing events reaches a set number, controlling the first switch to turn off.

[0109] In one embodiment, the resonant current information includes the resonant period of the resonant circuit during the period when the first switch is turned on and the second switch is turned off, and controlling the first switch to turn off based on the resonant current information includes turning off the first switch when the turn-on time of the first switch reaches between 1.1 and 1.4 times the resonant period.

[0110] In one embodiment, the resonant current information includes the resonant period of the resonant circuit during the period when the first switch is turned on and the second switch is turned off, and controlling the first switch to turn off based on the resonant current information includes turning off the first switch when the turn-on time of the first switch reaches 1.25 times the resonant period.

[0111] In one embodiment, the resonant current information includes a leakage inductance value of the primary winding of the transformer and a capacitance value of a resonant capacitor in the resonant circuit, wherein step 1603 includes: calculating a resonant period of the resonant circuit based on the leakage inductance value and the capacitance value of the resonant capacitor; and based on the resonant period, turning off the first switch when the on-time of the first switch reaches between 1.1 and 1.4 times of the resonant period.

[0112] In one embodiment, the resonant current information includes the leakage inductance value of the primary winding of the transformer and the capacitance value of the resonant capacitor in the resonant circuit, wherein the step 1603 includes: calculating the resonant period of the resonant circuit based on the leakage inductance value and the capacitance value of the resonant capacitor; and based on the resonant period, turning off the first switch when the on-time of the first switch reaches 1.25 times of the resonant period.

[0113] Although the present invention has been described with reference to several typical embodiments, it should be understood that the terms used are illustrative and exemplary rather than restrictive. Since the present invention can be implemented in a variety of forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the attached patent claims, so all changes and modifications that fall within the scope of the patent claims or their equivalents should be covered by the attached patent claims.

[0114] 10: Asymmetric half-bridge flyback converter 30,40,60,70,80,130: Power supply 101,701: Resonant capacitor end 103: Resonance cycle information 104: Zero-crossing detection signal 105,106,210: control signal 107: Shield signal 133: Capacitance information 134: Sensitivity information 141,341,741: First switch 142,342,742: Second switch 150,170,350: Transformer 151: Primary winding 152: Secondary winding 171,351: Primary winding 172,352: Secondary winding 173: Auxiliary winding 190:Filter circuit 160: Load 201: Primary side reference ground 202: Secondary side reference ground terminal 203: Input terminal 204: switch end 206: Output 308: Control signal 308-1, G1: first control signal 308-2, G2: Second control signal 310,410,610,1310,1510: Control circuit 315: Resonance period calculation circuit 315S:Memory unit 316: Duration control circuit 90,100,110,120,320,420,620,720,820,1320,1520: Resonant power conversion circuit 340,920: Current detection circuit 361,461,1361: Primary side circuit 362,462,1362: Secondary side circuit 415: Zero-crossing detection circuit 416: Counting circuit 417,418:Drive 441,442: Switch 443: Secondary switch 660: enabling circuit 661: Output voltage detection circuit 662: Shielding Circuit 209,901: Detection terminal 1601~1603: Method Vout: output voltage Vin: Input voltage Co: output capacitance Cr: resonant capacitor Lr: Inductance G: Gate D: Drain S: Source D1, D2, D3: body diode C1, C2, C3: Source-drain capacitors Ir: Resonant current Is,Ics: current VR: First Signal Va: output voltage feedback signal Vtb: shielding threshold Rcs: Current detection resistor Cs: Capacitance Ra: Resistance

Claims

1. A control circuit for an asymmetric half-bridge flyback converter, the asymmetric half-bridge flyback converter comprising a first switch, a second switch, a transformer, and a resonant capacitor, the control circuit comprising: An input terminal receives resonant current information, wherein the resonant current information is related to a resonant current flowing through a resonant circuit, and wherein the resonant circuit includes a primary winding of the transformer and the resonant capacitor; and an output terminal outputs a first control signal based on the resonant current information, wherein the first control signal controls the first switch to turn off when the number of zero-crossing events of the resonant current crossing zero from positive to negative reaches a set number.

2. The control circuit as claimed in claim 1 further includes an output voltage detection circuit, which receives an output voltage feedback signal characterizing an output voltage of the asymmetric half-bridge flyback converter, and based on the output voltage feedback signal, masks or enables the first control signal.

3. The control circuit as claimed in claim 2, wherein the output voltage detection circuit receives the output voltage feedback signal from an auxiliary winding magnetically coupled to the transformer.

4. The control circuit as claimed in claim 1, wherein the resonant current information includes a first signal characterizing the actual value of the resonant current.

5. The control circuit as described in claim 4, further comprising: A zero-crossing detection circuit receives the first signal characterizing the actual value of the resonant current, detects the zero-crossing event indicating that the resonant current crosses zero from positive to negative based on the first signal, and outputs a zero-crossing detection signal indicating the zero-crossing event. And a counting circuit, which receives the zero-crossing detection signal and counts the number of zero-crossing events based on the zero-crossing detection signal; wherein the first control signal controls the first switch to turn off when the number of zero-crossing events reaches the set number.

6. A control circuit for an asymmetric half-bridge flyback converter, the asymmetric half-bridge flyback converter comprising a first switch, a second switch, a transformer, and a resonant capacitor, the control circuit comprising: An input terminal receives resonant current information, wherein the resonant current information is related to a resonant current flowing through a resonant circuit, and wherein the resonant circuit includes a primary winding of the transformer and a resonant capacitor, wherein the resonant current information includes a resonant period of the resonant circuit; and an output terminal outputs a first control signal based on the resonant current information, wherein the first control signal turns off the first switch when a conduction duration of the first switch reaches between 1.1 and 1.4 times the resonant period.

7. A control circuit for an asymmetric half-bridge flyback converter, the asymmetric half-bridge flyback converter comprising a first switch, a second switch, a transformer, and a resonant capacitor, the control circuit comprising: An input terminal receives resonant current information, wherein the resonant current information is related to a resonant current flowing through a resonant circuit, and wherein the resonant circuit includes a primary winding of the transformer and a resonant capacitor, wherein the resonant current information includes an inductance value of a resonant inductor and a capacitance value of the resonant capacitor in the resonant circuit; an output terminal outputs a first control signal based on the resonant current information; a resonant period calculation circuit calculates the resonant period based on the inductance value of the resonant inductor and the capacitance value of the resonant capacitor; and a duration control circuit outputs the first control signal to turn off the first switch when the conduction duration of the first switch reaches between 1.1 and 1.4 times the resonant period, based on the resonant period.

8. A power supply device for an asymmetric half-bridge flyback converter, comprising: The asymmetric half-bridge flyback converter includes a first switch, a second switch, a transformer, and a resonant capacitor. The first switch and the second switch are connected in series and coupled to an input terminal and a primary-side reference ground terminal. The transformer includes a primary winding and a secondary winding. A control circuit receives resonant current information and, based on the resonant current information, outputs a first control signal to control the first switch to turn off. The resonant current information is related to a resonant current flowing through a resonant circuit, and the resonant circuit includes the primary winding and the resonant capacitor. The first control signal controls the first switch to turn off when the number of zero-crossing events of the resonant current crossing zero from positive to negative reaches a predetermined number.

9. The power supply device as claimed in claim 8, wherein the control circuitry comprises: An output voltage detection circuit receives an output voltage feedback signal characterizing an output voltage of the asymmetric half-bridge flyback converter from an auxiliary winding magnetically coupled to the transformer, and based on the output voltage feedback signal, shields or enables the first control signal.

10. The power supply device as claimed in claim 8, wherein the resonant current information includes a first signal characterizing the resonant current, and the control circuitry includes: A zero-crossing detection circuit receives the first signal characterizing the resonant current, detects the zero-crossing event indicating that the resonant current crosses zero from positive to negative based on the first signal, and outputs a zero-crossing detection signal indicating the zero-crossing event. And a counting circuit, which receives the zero-crossing detection signal and counts the number of zero-crossing events based on the zero-crossing detection signal; wherein the first control signal controls the first switch to turn off when the number of zero-crossing events reaches the set number.

11. A power supply device for an asymmetric half-bridge flyback converter, comprising: The asymmetric half-bridge flyback converter includes a first switch, a second switch, a transformer, and a resonant capacitor. The first switch and the second switch are connected in series and coupled to an input terminal and a primary-side reference ground terminal. The transformer includes a primary winding and a secondary winding. A control circuit receives resonant current information and, based on the resonant current information, outputs a first control signal to control the first switch to turn off. The resonant current information is related to a resonant current flowing through a resonant circuit, and the resonant circuit includes the primary winding and the resonant capacitor. The resonant current information includes a resonant period of the resonant circuit. The first control signal turns off the first switch when the on-time of the first switch reaches between 1.1 and 1.4 times the resonant period.

12. A power supply device for an asymmetric half-bridge flyback converter, comprising: The asymmetric half-bridge flyback converter includes a first switch, a second switch, a transformer, and a resonant capacitor. The first switch and the second switch are connected in series and coupled to an input terminal and a primary-side reference ground terminal. The transformer includes a primary winding and a secondary winding. A control circuit receives resonant current information and, based on the resonant current information, outputs a first control signal to control the first switch to turn off. The resonant current information is related to a resonant current flowing through a resonant circuit, and the resonant circuit includes the primary winding and the resonant capacitor. The resonant current information includes the inductance value of a resonant inductor and the capacitance value of the resonant capacitor in the resonant circuit. The control circuit includes: a resonant period calculation circuit that calculates a resonant period based on the inductance value of the resonant inductor and the capacitance value of the resonant capacitor; and a duration control circuit that, based on the resonant period, outputs the first control signal to turn off the first switch when the conduction duration of the first switch reaches between 1.1 and 1.4 times the resonant period.

13. A control method for an asymmetric half-bridge flyback converter, the asymmetric half-bridge flyback converter comprising a first switch, a second switch, a transformer, and a resonant capacitor, the control method comprising: Controlling the first switch and the second switch to regulate the energy transfer from a primary winding to a secondary winding of the transformer, wherein a resonant circuit includes the primary winding and the resonant capacitor; receiving resonant current information related to a resonant current flowing through the resonant circuit; and based on the resonant current information, controlling the first switch to turn off when the number of zero-crossing events of the resonant current crossing zero from positive to negative reaches a predetermined number.

14. The control method as described in claim 13 further includes: The output voltage of the asymmetric half-bridge flyback converter is detected, and when the output voltage is lower than a set value, the first switch is turned off based on the resonant current information.

15. The control method as claimed in claim 13, wherein the resonant current information includes the actual value of the resonant current.

16. A control method for an asymmetric half-bridge flyback converter, the asymmetric half-bridge flyback converter comprising a first switch, a second switch, a transformer, and a resonant capacitor, the control method comprising: The first switch and the second switch are controlled to regulate the energy transfer from a primary winding to a secondary winding of the transformer, wherein a resonant circuit includes the primary winding and the resonant capacitor; a resonant current information related to a resonant current flowing through the resonant circuit is received, wherein the resonant current information includes a resonant period of the resonant circuit, and the first switch is turned off when a conduction duration of the first switch reaches between 1.1 and 1.4 times the resonant period.

17. A control method for an asymmetric half-bridge flyback converter, the asymmetric half-bridge flyback converter comprising a first switch, a second switch, a transformer, and a resonant capacitor, the control method comprising: The system controls the first switch and the second switch to regulate energy transfer from a primary winding to a secondary winding of the transformer, wherein a resonant circuit includes the primary winding and the resonant capacitor; receives resonant current information related to a resonant current flowing through the resonant circuit, wherein the resonant current information includes an inductance value of a resonant inductor and a capacitance value of the resonant capacitor in the resonant circuit; calculates a resonant period based on the inductance value of the resonant inductor and the capacitance value of the resonant capacitor; and, based on the resonant period, turns off the first switch when a conduction duration of the first switch reaches between 1.1 and 1.4 times the resonant period.

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