Control circuit and control method of resonance power conversion circuit

Abstract

The invention discloses a control circuit and a control method of a resonant power conversion circuit. The method can be used for turning off a first switch of the resonance power conversion circuit at a proper moment before demagnetization of a transformer based on resonance current information in a resonance loop in a primary side circuit of the resonance power conversion circuit under the condition of low output voltage of the resonance power conversion circuit, so that resonance energy in the resonance loop is reduced, and the demagnetization efficiency is improved. Therefore, the power loss caused by resonance is reduced, and the working efficiency of the resonance power conversion circuit is improved.

Description

Technical Field

[0001] Embodiments of the present invention relate to electronic circuits, and more particularly, to a control circuit and a control method for a resonant power conversion circuit. Background Art

[0002] Traditional power conversion circuits convert input power into output power that meets the requirements and supply it to a load. Resonant power conversion circuits further reduce the switching losses of the circuits through soft switching technology, thus 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 increasingly widely used. However, precisely because the output voltage range of the asymmetric half-bridge flyback converter is large, and when it operates under the rated output voltage condition, that is, the operating condition where the output voltage is close to the upper limit value, the circuit losses are large. To optimize the operating efficiency under the rated output voltage condition, the efficiency under the low output voltage condition 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 operating conditions. The control circuit and the control method of the resonant power conversion circuit of the present invention select an appropriate time to turn off the corresponding switch of the resonant power conversion circuit under a certain output voltage condition to reduce circuit resonance, thereby reducing circuit power losses and improving efficiency.

[0005] According to an embodiment of the present invention, a control circuit for a resonant power conversion circuit is proposed, which is suitable for controlling a first switch and a 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. The primary winding and the resonant capacitor are arranged in the resonant loop of the resonant power conversion circuit. The control circuit includes: an input terminal for receiving resonant current information related to the resonant current flowing through the resonant loop; and an output terminal for outputting a first control signal to control the first switch to turn off based on the resonant current information.

[0006] According to an embodiment of the present invention, a power supply device is proposed, which includes: a resonant power conversion circuit including a first switch and a second switch connected in series between an input voltage and a primary side reference ground terminal, a transformer, and a resonant capacitor, wherein the transformer includes a primary winding and a secondary winding, and the primary winding and the resonant capacitor are arranged in the resonant loop of the resonant power conversion circuit; and a control circuit for receiving resonant current information related to the resonant current flowing through the resonant loop and outputting a first control signal to control the first switch to turn off based on the resonant current information.

[0007] According to an embodiment of the present invention, a control method for a resonant power conversion circuit is provided, including: controlling a first switch and a second switch in the resonant power conversion circuit to adjust the energy transfer from the primary winding to the secondary winding of a transformer in the resonant power conversion circuit, wherein the primary winding and a resonant capacitor are arranged in a resonant loop of the resonant power conversion circuit; receiving resonant current information related to a resonant current flowing through the resonant loop; and based on the resonant current information, controlling the first switch to turn off. Description of the Drawings

[0008] For a better understanding of the present invention, the present invention will be described in detail with reference to the following drawings:

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

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

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

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

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

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

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

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

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

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

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

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

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

[0022] Figure 14 Schematic diagram of the waveforms of some signals of the power supply device 130 according to an embodiment of the present invention;

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

[0024] Figure 16 Schematic diagram of the flow of the control method 160 of the resonant power conversion circuit according to an embodiment of the present invention. Detailed implementation manners

[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 illustrative purposes and are not used to limit the present invention. In the following description, in order to provide a thorough understanding of the present invention, a large number of specific details are set forth. However, it will be apparent to those of ordinary skill in the art that: the present invention does not have to be practiced with these specific details. In other instances, well-known circuits, materials, or methods have not been described in detail to avoid obscuring the present invention.

[0026] Throughout the specification, the reference to "one embodiment", "an embodiment", "one example" or "an example" means that: the specific features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the present invention. Thus, the phrases "in one embodiment", "in an embodiment", "one example" or "an example" appearing throughout the specification do not necessarily all refer to the same embodiment or example. In addition, the specific features, structures, or characteristics may be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. In addition, those of ordinary skill in the art should understand that the drawings provided herein are for illustrative purposes only and are not necessarily drawn to scale. The same reference numerals indicate the same elements. The term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0027] Figure 1 Schematic diagram of the structure of the existing asymmetric half-bridge flyback converter 10. Figure 1In it, the first switch 141 and the second switch 142 are alternately turned on under the control of the first control signal G1 and the second control signal G2 respectively, converting the input voltage Vin of the asymmetric half-bridge flyback converter 10 into an output voltage Vout to be supplied 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-output conditions. Usually, for optimizing efficiency, the first switch 141 is controlled to turn off after the transformer 150 demagnetizes. 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 range of the output voltage Vout of the asymmetric half-bridge flyback converter 10 is relatively large, for example, in some applications, the output voltage Vout ranges from 5 volts to 48 volts. 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 48 volts, therefore, 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 48 volts. In this case, when the output voltage Vout of the asymmetric half-bridge flyback transformer 10 is relatively small, its circuit efficiency will be relatively poor.

[0028] Figure 2 It is a schematic waveform diagram of some signals when the output voltage Vout of the asymmetric half-bridge flyback converter 10 is relatively small. As Figure 2 shown, 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, and 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 relatively small, at the moment t12, the primary winding 151 of the transformer 150 just finishes demagnetizing, and the first switch 141 is turned off at the moment t12. However, before the moment 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 this resonant circuit generates multiple oscillations, causing energy loss and reducing the circuit efficiency.

[0029] Figure 3 It is a schematic circuit diagram of the power supply device 30 according to an embodiment of the present invention. As Figure 3As shown, 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 components such as a first switch 341, a second switch 342, a transformer 350, and a resonant capacitor Cr. 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. For example, it can also be an LLC circuit. The control circuit 310 can be implemented in any form, such as a digital circuit, an analog circuit, or a digital-analog hybrid circuit. The control circuit 310 can be presented in the form of an independent chip or can be implemented by a suitable processor loading a corresponding program.

[0031] As Figure 3 shown, 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, the circuit directly or indirectly electrically connected to the primary winding 351 is called the primary side circuit 361, and the circuit directly or indirectly electrically connected to the secondary winding 352 is called the 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.) to control the on / 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 130.

[0033] The first switch 341 and the second switch 342 can be coupled in series. The control circuit 310 controls the first switch 341 and the second switch 342 to alternately turn on and off, so that the first switch 341 and the second switch 342 alternately appear in the current loop including the primary winding 351, and transfer energy from the primary winding 351 to the secondary winding 352. The alternating on / off of the first switch 341 and the second switch 342 causes a change in the amplitude of the current flowing through the primary winding 351, thereby storing energy in the primary winding 351. After the secondary winding 352 receives the energy transferred from the primary winding 351, it converts it into an output voltage Vout and provides it to the load 130.

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

[0035] In an embodiment of the present invention, a 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 a 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 they 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 relatively low. In some embodiments of the present invention, through some parameter information of a specific application, the information of the resonant current Ir can also be estimated, and thus the information of the estimated resonant current Ir can also be used to 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 can 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 can also adopt a symmetric half - bridge flyback topology, such as an LLC circuit, etc.

[0037] Figure 4 is a schematic circuit diagram of a power supply device 40 according to an embodiment of the present invention. As Figure 4 shown, 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 and includes 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, where the inductance Lr shown in the figure is the leakage inductance of the primary winding 151. In other embodiments, the inductance 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 Figure 4In the embodiment, the first switch 441, the second switch 442, and the third switch 443 are implemented by MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The first switch 441 includes a gate terminal G, a drain terminal D, a source terminal S, a body diode D1, and a source-drain capacitance C1. The second switch 442 includes a gate terminal G, a drain terminal D, a source terminal S, a body diode D2, and a source-drain capacitance C2. The third switch 443 includes a gate terminal G, a drain terminal D, a source terminal S, a body diode D3, and a source-drain capacitance C3. It should be understood that the body diodes corresponding to the respective switches are parasitic diodes.

[0039] In Figure 4 the embodiment, the control circuit 410 includes drivers 417 and 418, which are respectively used to drive the first switch 441 and the second switch 442. The drivers 417 and 418 are used to receive the control signals of the first switch 441 and the second switch 442, and after amplifying the driving capabilities of the corresponding control signals, they are respectively used to provide to the gate terminals 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 terminal D of the second switch 442 is coupled to the input terminal 203 to receive the input voltage Vin, and the source terminal S is coupled to the switching terminal 204. The drain terminal D of the first switch 441 is coupled to the switching terminal 204, and the source terminal 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 switching terminal 204. The other end of the primary winding 151 of the transformer 150 is coupled to one end of the resonant capacitance Cr. The other end of the resonant capacitance 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 path, including an inductor Lr and a resonant capacitance Cr, which are coupled between the switching terminal 204 and the primary side reference ground terminal 201. That is to say, the primary winding 151 and the resonant capacitance Cr are serially coupled between the switching terminal 204 and the primary side reference ground terminal 201.

[0041] In Figure 4 the embodiment, 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 or multiple chips in any applicable combination form.

[0042] As Figure 4As shown in the embodiment, the secondary winding 152 of the transformer 150 is coupled between the output terminal 206 and the secondary switch 443. That is to say, the secondary winding 152 and the secondary switch 443 are serially coupled between the output terminal 206 and the secondary side reference ground terminal 202. In Figure 4 the embodiment, the secondary switch 443 is implemented by a MOSFET, and the control signal 210 of its gate terminal can be provided by the control circuit 410, or can be provided 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 described above, the primary winding 151 of the transformer 150 is located in the resonant circuit, and the resonant circuit includes an inductor Lr, a resonant capacitor Cr, and the primary winding 151. The control circuit 410 outputs a first control signal 308-1 and a second control signal 308-2 to control the first switch 441 and the second switch 442 respectively, so that the switching frequencies of the first switch 441 and the second switch 442 are equal to or approximate to the resonant frequency of the resonant circuit. The first switch 441 and the second switch 442 are alternately turned on and off. 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 described above, the information of the resonant current Ir flowing through the resonant circuit is provided to the control circuit 410 in the form of a first signal Vr to participate in the control of the resonant power conversion circuit 420. In Figure 4 the embodiment, 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 and detects the zero-crossing point of the resonant current Ir by detecting the first signal Vr. 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 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 Vt equal to or approximate to zero, so as to obtain a zero-crossing detection signal 104 for characterizing the zero-crossing point of the first signal Vr.

[0047] Based on the detection of the zero-crossing point of the first signal Vr, the zero-crossing detection circuit 415 outputs a zero-crossing detection signal 104. The signal state of the zero-crossing detection signal 104 can characterize the zero-crossing point of the first signal Vr. In one embodiment, the zero-crossing point of the first signal Vr includes both the event that the first signal Vr crosses the zero point from positive to negative and the event that the first signal Vr crosses the zero point from negative to positive. The zero-crossing detection signal 104 corresponds to the event that the first signal Vr crosses the zero point from positive to negative and the event that the first signal Vr crosses the zero point from negative to positive with different signal states. The counting circuit 416 receives the zero-crossing detection signal 104. The signal state in the zero-crossing detection signal 104 corresponding to the first signal Vr crossing the zero point from positive to negative is the counting object of the counting circuit 416.

[0048] The counting circuit 416 receives the zero-crossing detection signal 104 and counts the signal state in the zero-crossing detection signal 104 corresponding to the first signal Vr crossing the zero point from positive to negative. After the number of occurrences of this signal state reaches a set number of times, it outputs a control signal 106 to control the driver 417 to turn off the first switch 441.

[0049] Figure 5 It is a waveform schematic diagram of partial signals of the 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 will be described below in conjunction with Figure 4 and Figure 5 to illustrate.

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

[0051] As Figure 5 shown, at the moment t20, the first switch 441 is in the off state, the second switch 442 is 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 rises.

[0052] At the moment t21, the current Ir reaches the 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 a direct connection between the first switch 441 and the second switch 442 and damage the circuit devices, a dead time is set between the turn-off of the second switch 442 and the turn-on of the first switch 441, that is, the time when both the first switch 441 and the second switch 442 are in the off state. Because this dead time is short, for the sake of concise description and clear illustration, Figure 5This time period is not explicitly shown in [the relevant content]. 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. After the second switch 442 is turned off and the first switch 441 is turned on, the current Ir starts to decrease, and the resonant circuit composed of the inductor Lr and the resonant capacitor Cr starts to oscillate, and its resonant period Tr is where Lr in the formula represents the inductance value of the inductor Lr, and Cr in the formula represents the capacitance value of the resonant capacitor Cr.

[0053] At time t22, the first signal Vr drops to the zero-crossing threshold Vt. As described above, the waveform of the first signal Vr is consistent with the waveform of the resonant current Ir. Therefore, in Figure 5 the first signal Vr and the resonant current Ir are represented by the same waveform. It should be understood that the current Ir is a current signal, and the first signal Vr can be a voltage signal. Therefore, they are not equal in actual values. Figure 5 In [the relevant content], the waveforms of the first signal Vr and the resonant current Ir are only for illustration to explain the working principle of the circuit of the present invention. The value of the zero-crossing threshold Vt is close to zero. Therefore, the moment when the first signal Vr drops to the zero-crossing threshold 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 starts to oscillate upward until at time t23, 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, changing from a high level to a low level.

[0055] At time t24, the resonant current Ir crosses the zero point from positive to negative again, 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 number of counting times is 2, reaching the preset number of counting times. The counting circuit 416 outputs a control signal 106, and this control signal 106 outputs a first control signal 308-1 through the driver 417 to turn off the first switch 441.

[0056] Compared with the prior art, in the embodiments 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, reducing the current oscillation in the resonant circuit, thereby reducing power loss and improving circuit efficiency. After the first switch 441 is turned off, the resonant circuit is composed of the inductor Lr, the resonant capacitor Cr, and the source-drain capacitance C1 of the first switch 441. When the resonant current Ir crosses the zero point from top to bottom and the first switch 441 is turned off, the energy of the resonant circuit drops to the lowest, and the oscillation amplitude of the resonant current Ir decreases, thereby reducing the circuit power loss and improving the efficiency.

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

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

[0059] In some embodiments of the present invention, it is an approximate method that the first signal Vr crossing the zero-crossing threshold Vt corresponds to the resonant current Ir crossing the zero point. By adjusting the value of the zero-crossing threshold Vt to be close to zero, the accuracy of circuit control can be adjusted. However, it should be understood that in an actual circuit, due to the non-ideal characteristics of circuit devices and the existence of circuit delay, the turn-off moment of the first switch 441 does not exactly correspond to the moment when the resonant current crosses the zero point from positive to negative, and there is a certain error between the two.

[0060] Meanwhile, it should be understood that the description of turning 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 the embodiments of the present invention is for illustrative purposes. Those of ordinary skill in the art can, according to the needs of actual applications, set to turn off the first switch 441 when the resonant current Ir crosses the zero point from positive to negative for the third time, the fourth time, or any other arbitrary time.

[0061] Figure 6 FIG. is a schematic circuit diagram of a power supply device 60 according to another embodiment of the present invention. As Figure 6 shown, 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 and includes 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, where 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 the superposition of an independent inductor device and the leakage inductance of the primary winding 171. The auxiliary winding 173 is magnetically coupled to the primary winding 171 and the secondary winding 172.

[0062] In Figure 6 the embodiment, the auxiliary winding 173 provides an output voltage feedback signal Va, that is, the 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 turn ratio of the auxiliary winding 173 to the secondary winding 172, that is, Va:Vout = N 173 :N 172 . That is to say, 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. Those of ordinary skill in the art can determine the turn ratio of the auxiliary winding 173 to the secondary winding 172 according to the specific circuit application parameters and the value of the required output voltage feedback signal Va. In some embodiments, the output voltage feedback signal Va can also be divided by a voltage dividing circuit, and then the divided voltage signal is provided to the control circuit 610.

[0063] In Figure 6 the embodiment, 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 enable circuit 660. The enable circuit 660 detects the output voltage feedback signal Va, and when the output voltage feedback signal Va indicates that the output voltage Vout is above a certain value, such as 5V, it shields the control signal 106. 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, enables the first control signal 308-1 to turn off the first switch 441. It should be understood that the enable circuit 660 enables or disables the operation of the first control signal 308-1 to turn off the first switch 441 at the moment when the resonant current Ir crosses zero from positive to negative for the second time based on the value of the output voltage feedback signal Va, and the operation of the first control signal 308-1 to turn off the first switch 441 at the moment when the resonant current Ir crosses zero 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 perform this operation can be achieved by shielding the control signal 106. That is to say, by whether to shield the control signal 106, 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 zero from positive to negative for the second time. In some embodiments, the control signal 106 can be a piece of data, and whether this data affects the first control signal 308-1 is determined according to the output voltage feedback signal Va detected by the enable circuit 660.

[0065] In Figure 6 an embodiment, the enable 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 the shielding signal 107 according to the comparison result. In one embodiment, the control signal 106 operates 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 value of 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 opening 441 by the first control signal 308-1.

[0067] In one embodiment, the shielding circuit 662 includes a switch. The switch is controlled by a 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 pass through the shielding circuit 662 and be provided to the driver 417. 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 can also shield the control signal 106 in other ways, such as by a program or a digital circuit to implement the shielding function. The control signal 106 can also be shielded by disabling the circuit, for example, the counting circuit 416 and / or the zero-crossing detection circuit 415 can be disabled so that they cannot provide the control signal 106.

[0069] Those of ordinary skill in the art should know that the auxiliary winding voltage Va reflects the magnitude of the output voltage Vout during the conduction of the secondary switch 443, and besides this, the auxiliary winding voltage Va does not represent the output voltage Vout. The commonly used method in the prior art is to sample and hold the auxiliary winding voltage Va during the conduction of the secondary switch 443. Since this method is relatively common and well-known to those of ordinary skill in the art, the structure of the sampling and holding circuit and the corresponding description are omitted in the embodiments of the present invention. It should be understood that the output voltage feedback signal Va mentioned in the embodiments of the present invention is the circuit signal of the processed feedback output voltage Vout. At the same time, it should be understood that Figure 6 detecting the output voltage Vout through the auxiliary winding in [the text] is a way to obtain information about the output voltage Vout. Other ways, such as estimating through a digital circuit, can also obtain information about the output voltage Vout.

[0070] In Figure 6 the embodiment, when the output voltage Vout is greater than the corresponding threshold value, the control signal 106 is shielded and does not control the first switch 441. It should be understood that there are many ways to shield the influence of the control signal 106 on the first switch 441. For example, the counting circuit 416 or the zero-crossing detection circuit 415 can be disabled by using the shielding signal 107, or the zero-crossing detection signal 104 can be shielded by using the shielding signal 107. In some embodiments of the present invention, the function of the enabling circuit 660 is to make the control signal 106 work under certain output voltage conditions. For example, when the output voltage Vout is less than 5 volts, and prohibited from working under other output voltage conditions, such as when the output voltage Vout is greater than or equal to 5 volts.

[0071] Figure 6 In the embodiment, the working principles of the zero-crossing detection circuit 415 and the counting circuit 416 are the same as Figure 5This is consistent with the embodiments and will not be elaborated here.

[0072] Figure 7 FIG. is a schematic circuit diagram of a power supply device 70 according to another embodiment of the present invention. As Figure 7 described, 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 and includes 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 Figure 4 the embodiment shown, Figure 7 the structure of the primary side circuit of the resonant power conversion circuit 720 shown is slightly different. In Figure 7 it, the first switch 741 is located on the high side and the second switch 742 is located on 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 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.

[0074] In Figure 7 the embodiment, the control circuit 410 includes drivers 417 and 418 for driving the first switch 741 and the second switch 742 respectively. 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 Figure 7 the embodiment, although the positions of the first switch 741 and the second switch 742 are exactly opposite to those in Figure 4The first switch 441 and the second switch 442 in the embodiments are opposite, but the same 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 to say, in the embodiments of the present invention, the first switch corresponds to the switch that forms a resonant circuit in the primary side circuit and generates current oscillation after closing, and the second switch corresponds to the switch that stores energy in the primary winding after closing. Correspondingly, the driver 417 outputs a first control signal 308-1 to drive the first switch 741, and the driver 418 outputs a second control signal 308-2 to drive 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 as Figure 5 shown, so they will not be elaborated here.

[0077] Figure 8 FIG. is a schematic circuit diagram of a power supply device 80 according to another embodiment of the present invention. As Figure 8 shown, 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 and includes 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 Figure 4 embodiment shown, Figure 8 in the primary side circuit of the resonant power conversion circuit 720 shown, the first switch 741 is located on the high side and the second switch 742 is located on 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 switching terminal 204. The drain D of the second switch 742 is coupled to the switching 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 switching 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 Figure 8In an embodiment, the control circuit 610 includes drivers 417 and 418, which are respectively used to drive the first switch 741 and the second switch 742. The driver 417 outputs a first control signal 308-1 to control the first switch 741, and the driver 418 outputs a second control signal 308-2 to control 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 Figure 8 In an embodiment, 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 elaborated here.

[0081] Figure 9 FIG. is a schematic circuit diagram of a resonant power conversion circuit 90 according to an embodiment of the present invention. Compared with Figure 4 the shown resonant power conversion circuit 420, the resonant power conversion circuit 90 further includes a current detection resistor Rcs, which is serially coupled 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] Figure 10 FIG. is a schematic circuit diagram of a resonant power conversion circuit 100 according to an embodiment of the present invention. Compared with Figure 4 the shown resonant power conversion circuit 420, the resonant power conversion circuit 100 further includes a current detection circuit 920, which has an input terminal coupled to one end of the resonant capacitor Cr, that is, the resonant capacitor terminal 101, and has an output terminal providing a first signal Vr. The current detection circuit 920 includes a capacitor Cs, a resistor Ra, and a filtering circuit 190. The capacitor Cs and the resistor Ra are serially coupled between the resonant capacitor terminal 101 and the primary side reference ground terminal 201. When the circuit is operating, the resonant current Ir flows through the resonant capacitor Cr and the capacitor Cs, and the magnitude of the current Ics flowing through the capacitor Cs is related to the capacitance values 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 value of capacitor Cs, and Cr represents the capacitance value of resonant capacitor Cr. It can be seen therefrom 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, a voltage Ics×Ra is generated across resistor Ra, where Ra represents the resistance value of resistor Ra. Substituting into the foregoing formula gives the voltage After being filtered by filter circuit 190, this voltage generates a first signal Vr, that is As can be seen from this formula, the value of the first signal Vr is in a proportional relationship with the value of the resonant current Ir, and the proportionality coefficient is By reasonably selecting the resistance value of resistor Ra and the capacitance value of capacitor Cs, the desired value of the first signal Vr can be obtained. This first signal Vr is provided to the control circuit 410 or 610 as described above, serving as 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] Figure 11 FIG. 13 is a schematic circuit diagram of a resonant power conversion circuit 110 according to an embodiment of the present invention. Compared with Figure 7 the shown resonant power conversion circuit 720, 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 serially coupled with the resonant capacitor Cr and the primary winding 151, between the detection terminal 209 and the switch terminal 204, and is located in the resonant loop through which the resonant current Ir flows. When the resonant current Ir flows through the current detection resistor Rcs, a voltage is generated across the current detection resistor Rcs. The voltage detection circuit 130 has two input terminals respectively coupled to both ends of the current detection resistor Rcs, and generates a first signal Vr based on the voltage across the current detection resistor Rs. In one embodiment, the voltage detection circuit 130 includes a differential amplifier circuit. The value of the first signal Vr is in a proportional relationship with 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. This first signal Vr is provided to the control circuit 410 or 610 as described above, serving as 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] Figure 12 FIG. 14 is a schematic circuit diagram of a resonant power conversion circuit 120 according to an embodiment of the present invention. Compared with Figure 7Compared with the resonant power conversion circuit 720 shown, the resonant power conversion circuit 120 further includes a current detection circuit 920, having an input terminal coupled to one end of the resonant capacitor Cr, i.e., the resonant capacitor terminal 701, and having an output terminal 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 serially coupled between the resonant capacitor terminal 701 and the primary side reference ground terminal 201. When the circuit is operating, the resonant current Ir flows through the resonant capacitor Cr and the capacitor Cs, and the magnitude of the current Ics flowing through the capacitor Cs is related to the capacitance values of the resonant capacitor Cr and the capacitor Cs, and is In this formula, Ics represents the value of the current Ics, Ir represents the value of the resonant current Ir, Cs represents the capacitance value of the capacitor Cs, and Cr represents the capacitance value of the resonant capacitor Cr. It can be seen therefrom that the absolute value of the current Ics is proportional to the absolute value of the resonant current Ir, and the proportionality coefficient is Cs / (Cr + Cs). When the current Ics flows through the resistor Ra, a voltage Ics×Ra is generated across the resistor Ra, where Ra represents the resistance value of the resistor Ra, and substituting the foregoing formula gives the voltage as This voltage is filtered by the filter circuit 190 to generate the first signal Vr, that is As can be seen from this formula, the value of the first signal Vr is proportional to the value of the resonant current Ir, and the proportionality coefficient is By reasonably selecting the resistance value of the resistor Ra and the capacitance value of the capacitor Cs, the desired 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] Figure 13 FIG. is a schematic circuit diagram of a power supply device 130 according to an embodiment of the present invention. As Figure 13As shown, 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 and includes 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, and the inductance Lr shown in the figure is the leakage inductance of the primary winding 151. In other embodiments, the inductance 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 Figure 13 an embodiment, 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 value of the resonant capacitor Cr and the inductance value of the inductance Lr. Among them, Figure 13 the mark 133 in represents the capacitance value information of the resonant capacitor Cr, the mark 134 represents the inductance value information of the inductance Lr, and the capacitance value information of the resonant capacitor Cr and the inductance value information of the inductance Lr are provided to the control circuit 1310 in the form of data. In some embodiments, the capacitance value information of the resonant capacitor Cr and the inductance value information of the inductance Lr can also be provided to the control circuit 1310 in the form of signals.

[0088] The control circuit 1310 includes a resonant period calculation circuit 315 and a duration control circuit 316. The resonant period calculation circuit 315 includes a storage unit 315S for storing the capacitance value information 133 of the resonant capacitor Cr and the inductance value information 134 of the inductance Lr. The period calculation circuit 315 calculates the resonant period Tr of the resonant circuit of the resonant power conversion circuit 1320 based on the capacitance value of the resonant capacitor Cr and the inductance value of the inductance Lr, and obtains a resonant period information 103 including the resonant period Tr information. Among them, The duration control circuit 316 receives the resonance period information 103 and outputs a control signal 105 based on the length of the resonance period Tr to control the conduction duration of the first switch 441. Among them, the duration control circuit 316 starts from the conduction moment of the first switch 441 and outputs a control signal 105 to control the turning off of the first switch 441 after a duration of 1.1 to 1.4 times the resonance period Tr. 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 conduction moment of the first switch 441. It should be understood that other signals indicating the conduction moment of the first switch 441 (such as intermediate signals of some circuits in the control circuit 1310 for generating the first control signal 308-1) can also be used in the embodiments of the present invention as one of the references for calculating the turning-off moment of the first switch 441. In one embodiment, the control circuit 1310 starts from the conduction moment of the first switch 441 and controls the turning off of the first switch 441 after a duration of 1.25 times the resonance period Tr. Ideally, the time node corresponding to the moment when the resonance current Ir crosses zero from positive to negative for the second time is the moment after a duration of 1.25 times the resonance period Tr starting from the conduction moment of the first switch 441. However, due to the non-ideal characteristics of actual circuit components and the existence of circuit delay, the moment when the resonance current Ir crosses zero from positive to negative for the second time does not exactly correspond to the moment after a duration of 1.25 times the resonance period Tr starting from the conduction moment of the first switch 441. Therefore, in practical applications, those of ordinary skill in the art can select the time node corresponding to the moment after a duration of 1.1 to 1.4 times the resonance period Tr starting from the conduction moment of the first switch 441 to turn off the first switch 441 according to the actual application circuit conditions. That is to say, the duration of 1.1 to 1.4 times the resonance period Tr starting from the conduction moment of the first switch 441 represents the moment when the resonance current Ir crosses zero from positive to negative for the second time.

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

[0090] Figure 14 It is a waveform schematic diagram of some signals of the power supply device 130 according to an embodiment of the present invention. The following is combined with Figure 13 and Figure 14to illustrate the working principle of the power supply device 130 of the present invention.

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

[0092] As Figure 14 shown, at time t30, the first switch 441 is in the off-state, the second switch 442 is 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 rises.

[0093] At time t31, the current Ir reaches the peak value, the second switch 442 turns off, and the first switch 441 turns on. It should be understood that to avoid a direct connection between the first switch 441 and the second switch 442 and damage the circuit components, a dead time is set between the turn-off of the second switch 442 and the turn-on of the first switch 441, that is, the time when both the first switch 441 and the second switch 442 are in the off-state. Because this dead time is short, for the sake of concise description and clear illustration, Figure 14 this period is not explicitly shown in the same. Similarly, a dead time is also set during the turn-off of the first switch 441 and the turn-on of the second switch 442. After the second switch 442 turns off and the first switch 441 turns on, the current Ir starts to decrease, and the resonant circuit composed of the inductor Lr and the resonant capacitor Cr starts to oscillate, and its resonant period Tr is

[0094] where Lr in the formula represents the inductance value of the inductor Lr, and Cr in the formula represents the capacitance value of the resonant capacitor Cr.

[0095] At time t32, the conduction duration of the first switch 441 reaches 1.25 times the resonant period Tr, and the control signal 105 generates a pulse. This pulse will control the first control signal 308-1 through the driver 417 to turn off the first switch 441.

[0096] At time t33, the demagnetization of the transformer 150 ends.

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

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

[0098] Figure 15 Schematic diagram of the circuit structure of the power supply device 150 according to an embodiment of the present invention. As Figure 15 shown, 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 and includes 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, where 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 the superposition of an independent inductor device and the leakage inductance of the primary winding 171. The auxiliary winding 173 is magnetically coupled to the primary winding 171 and the secondary winding 172.

[0099] In Figure 15 the embodiment, the auxiliary winding 173 provides an output voltage feedback signal Va for characterizing 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 turn ratio of the auxiliary winding 173 to the secondary winding 172, that is, Va:Vout = N 173 :N 172 . That is to say 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. Those of ordinary skill in the art can determine the turn ratio of the auxiliary winding 173 to the secondary winding 172 according to the specific circuit application parameters and the value of the required output voltage feedback signal Va. In some embodiments, the output voltage feedback signal Va can also be divided by a voltage dividing circuit, and then the divided voltage signal is provided to the control circuit 1510.

[0100] In Figure 15 the embodiment, the control circuit 1510 includes a resonant period calculation circuit 315, a duration control circuit 316, and an enable circuit 660. The circuit structures and working principles of the resonant period calculation circuit 315, the duration control circuit 316, and the enable circuit 660 are as described above and will not be elaborated here.

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

[0102] In Figure 15 In the embodiment, when the output voltage Vout is greater than the corresponding threshold, 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 enable 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 zero 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 zero from positive to negative for the second time is based on the control signal 105. Therefore, enabling or disabling the first control signal 308-1 to perform this action can be achieved by shielding the control signal 105. That is to say, by whether to shield 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 zero from positive to negative for the second time. In some embodiments, the control signal 105 can be a piece of data, and whether this data affects the first control signal 308-1 is determined according to the output voltage feedback signal Va detected by the enable 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 resonant period calculation circuit 315, or both at the same time. In some embodiments of the present invention, the function of the enable circuit 660 is to make the control signal 105 work under certain output voltage conditions, such as when the output voltage Vout is less than 5 volts, and prohibit it from working under other output voltage conditions, such as when the output voltage Vout is greater than or equal to 5 volts. The embodiments of the present invention show that the enable circuit 660 achieves the purpose of making the control signal 105 work under certain output voltage conditions by isolating or through the control signal 105. It should be understood that other methods, such as disabling the duration control circuit 316 and / or the resonant period calculation circuit 315, etc., so that they 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 elaborated 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, Figure 13 and Figure 15 Some of the connections and signals therein do not necessarily actually exist and can be implemented in the form of data and links. For example, the resonance period information 103 can be data including information on the resonance period Tr, and this data may exist in a register or other storage unit for reading. That is to say, the embodiments of the present invention are only for illustrating the working principle of the circuit. Based on the working principle of the circuit of the embodiments of the present invention provided in this specification, various forms of circuits can be derived to implement the embodiments of the present invention.

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

[0105] It should be understood that the control circuit in the embodiments 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 actually exist. For example, the control signal 106 can be an information existing in the form of data. At the same time, some of the input terminals and output terminals in the present invention can be either the pins of an actual chip or the ports of a circuit, or interfaces for data transmission. For example, the control circuit is used to receive resonance current information related to the resonance current flowing through the resonance circuit, which can be the pin of a chip for receiving a voltage or current signal representing the resonance current, or a signal representing the values of the leakage inductance of the primary winding of the transformer and the resonance capacitor; it can also be a data interface for receiving information representing the leakage inductance of the primary winding of the transformer and the resonance capacitor, or data of the resonance current information.

[0106] Figure 16Schematic flow diagram of a control method 160 for 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 foregoing embodiment. The resonant power conversion circuit includes a first switch and a second switch serially coupled between an input voltage and a 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 an inductance provided by a separate inductance element, or a combination of both. 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 primary winding and the resonant capacitor are disposed in the resonant loop of the resonant power conversion circuit; Step 1602, receiving resonant current information related to the resonant current flowing through the resonant loop; and Step 1603, based on the resonant current information, controlling the first switch to turn 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, performing the action of controlling the first switch to turn off based on the resonant current information.

[0108] In one embodiment, the resonant current information includes the actual value of the resonant current. Step 1603 includes: detecting a zero-crossing event in which the resonant current crosses zero from positive to negative; and when the resonant current crosses zero from positive to negative for the second time, controlling the first switch to turn off.

[0109] In one embodiment, the resonant current information includes the resonant period of the resonant loop during the conduction of the first switch and the second switch. Controlling the first switch to turn off based on the resonant current information includes turning off the first switch when the conduction duration of the first switch reaches 1.1 to 1.4 times the resonant period.

[0110] In one embodiment, the resonant current information includes the resonant period of the resonant loop during the conduction of the first switch and the second switch. Controlling the first switch to turn off based on the resonant current information includes turning off the first switch when the conduction duration of the first switch reaches 1.25 times the resonant period.

[0111] 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 loop. Wherein, Step 1603 includes: calculating the resonant period of the resonant loop 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 conduction duration of the first switch reaches 1.1 to 1.4 times 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 turning off the first switch when the conduction duration of the first switch reaches 1.25 times the resonant period based on the resonant period.

[0113] Although the present invention has been described with reference to several exemplary embodiments, it should be understood that the terms used are illustrative and exemplary rather than restrictive. Since the present invention can be embodied in many 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 broadly construed within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A control circuit for a resonant power conversion circuit, suitable for controlling a first switch and a second switch in the resonant power conversion circuit to regulate the energy transfer from the primary winding to the secondary winding of a transformer in the resonant power conversion circuit, wherein the primary winding and the resonant capacitor are arranged in a resonant loop of the resonant power conversion circuit, and the control circuit comprises: an input terminal for receiving resonant current information related to a resonant current flowing through the resonant loop; and an output terminal for outputting a first control signal to control the first switch to turn off based on the resonant current information.

2. The control circuit according to claim 1, further comprising an output voltage detection circuit for receiving an output voltage feedback signal representing the output voltage of the resonant power conversion circuit and masking or enabling the first control signal based on the output voltage feedback signal.

3. The control circuit according to claim 2, wherein the output voltage detection circuit receives the output voltage feedback signal from an auxiliary winding magnetically coupled to the primary winding.

4. The control circuit according to claim 1, wherein the resonant current information includes a first signal representing an actual value of the resonant current.

5. The control circuit according to claim 4, further comprises: a zero-crossing detection circuit for receiving the first signal representing the actual value of the resonant current, detecting a zero-crossing event of the resonant current crossing zero from positive to negative based on the first signal, and outputting a zero-crossing detection signal representing the zero-crossing point of the resonant current from positive to negative; and a counting circuit for receiving the zero-crossing detection signal and counting the moment when the resonant current crosses zero from positive to negative based on the zero-crossing detection signal; wherein the first control signal controls the first switch to turn off at the moment when the resonant current crosses zero from positive to negative for the second time.

6. The control circuit according to claim 1, wherein the resonant current information includes a resonant period of the resonant loop during a period when the first switch in the resonant power conversion circuit is on and the second switch is off.

7. The control circuit according to claim 6, wherein the first control signal turns off the first switch when the conduction duration of the first switch reaches between 1.1 and 1.4 times the resonant period.

8. The control circuit according to claim 1, wherein the resonant current information includes the inductance value of a resonant inductor and the capacitance value of a resonant capacitor in the resonant loop.

9. The control circuit according to claim 8, further comprises: a resonant period calculation circuit for calculating 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 for outputting the first control signal to turn off the first switch based on the resonant period when the conduction duration of the first switch reaches between 1.1 and 1.4 times the resonant period.

10. A power supply device, comprises: a resonant power conversion circuit including a transformer, a resonant capacitor, and a first switch and a second switch connected in series between an input voltage and a primary side reference ground terminal, wherein the transformer includes a primary winding and a secondary winding, and the primary winding and the resonant capacitor are arranged in a resonant loop of the resonant power conversion circuit; and A control circuit receives resonant current information related to a resonant current flowing through a resonant circuit, and based on the resonant current information, outputs a first control signal to control the first switch to turn off.

11. The power supply device according to claim 10, wherein the control circuit comprises: An output voltage detection circuit receives an output voltage feedback signal representing the output voltage of the resonant power conversion circuit from an auxiliary winding magnetically coupled to the primary winding of the transformer, and based on the output voltage feedback signal, shields or enables the first control signal.

12. The power supply device according to claim 10, wherein the resonant current information includes a first signal representing the resonant current, and the control circuit comprises: A zero-crossing detection circuit receives the first signal representing the resonant current, and based on the first signal, detects a zero-crossing event where the resonant current crosses zero from positive to negative, and outputs a zero-crossing detection signal representing the zero-crossing point of the resonant current from positive to negative; and A counting circuit receives the zero-crossing detection signal, and based on the zero-crossing detection signal, counts the moment when the resonant current crosses zero from positive to negative; wherein the first control signal controls the first switch to turn off at the moment when the resonant current crosses zero from positive to negative for the second time.

13. The power supply device according to claim 10, wherein the resonant current information includes the resonant period of the resonant circuit during the conduction of the first switch and the turn-off of the second switch, and the first control signal turns off the first switch when the conduction duration of the first switch reaches between 1.1 and 1.4 times the resonant period.

14. The power supply device according to claim 10, wherein the resonant current information includes the inductance value of the resonant inductor and the capacitance value of the resonant capacitor in the resonant circuit, and the control circuit comprises: 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, based on the resonant period, outputs a first control signal to turn off the first switch when the conduction duration of the first switch reaches between 1.1 times and 1.4 times the resonant period.

15. A control method for a resonant power conversion circuit, comprising: 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 in the resonant power conversion circuit, wherein the primary winding and the resonant capacitor are disposed in the resonant circuit of the resonant power conversion circuit; 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.

16. The control method according to claim 15, further comprises: Detecting the output voltage of the resonant power conversion circuit, and when the output voltage is lower than a set value, performing the action of controlling the first switch to turn off based on the resonant current information.

17. The control method according to claim 15, wherein the resonant current information includes the actual value of the resonant current, and the controlling the first switch to turn off based on the resonant current information comprises: Detecting a zero-crossing event where the resonant current crosses zero from positive to negative; and Controlling the first switch to turn off when the resonant current crosses zero from positive to negative for the second time.

18. The control method according to claim 15, wherein the resonant current information includes the resonant period of the resonant circuit during the conduction of the first switch and the cutoff of the second switch, and the control of turning off the first switch based on the resonant current information includes turning off the first switch when the conduction duration of the first switch reaches 1.1 to 1.4 times the resonant period.

19. The control method according to claim 15, wherein the resonant current information includes the inductance value of the resonant inductor and the capacitance value of the resonant capacitor in the resonant circuit, and the control of turning off the first switch based on the resonant current information includes: calculating the resonant period based on the inductance value of the resonant inductor and the capacitance value of the resonant capacitor; and turning off the first switch based on the resonant period when the conduction duration of the first switch reaches 1.1 to 1.4 times the resonant period.

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