Switching power supply circuit and control method thereof

Abstract

The invention discloses a switching power supply circuit and a control method thereof. The switching power supply circuit comprises an input end, a primary side first bridge arm, a primary side second bridge arm, a primary side third bridge arm, a first resonant cavity, a second resonant cavity, a third resonant cavity, a secondary side first rectifying circuit, a secondary side second rectifying circuit and a secondary side third rectifying circuit. By adopting a three-phase three-level frequency multiplication control method, the input gain of a primary side is reduced by half, so that the turn ratio can be reduced by half when the transformer is designed, and the cost of the transformer is further reduced; therefore, the effect of replacing a 1200V SiC switch tube with a conventional 650V Si switch tube can be realized, and the driving cost is reduced while the cost of the switch tube is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit technology, and in particular to a switching power supply circuit and its control method. Background Technology

[0002] The 21st century is the era of electrical intelligence, and power electronics technology plays a vital role in all aspects of life. Switching power supplies are an indispensable branch of power electronics technology, playing a crucial role in various fields, including industrial control, intelligent transportation, smart grids, smart healthcare, new energy, the Internet of Things, and communications. Currently, the application of switching power supplies is increasingly focused on high-power and wide-range (input / output) applications, such as charging piles. The industry's largest charging pile has reached a power of 900kW, while charging power supplies have achieved 60kW per module.

[0003] Such high-power power supplies all employ a two-stage structure: PFC + DC-DC converter. Their inputs are all three-phase, resulting in an 800V high-voltage input voltage for the DC-DC stage after PFC. Commonly used DC-DC solutions include half-bridge LLC, full-bridge LLC, three-phase LLC, and hysteresis full-bridge topologies. However, each switch in these solutions requires a voltage rating exceeding 800V. Conventional high-power Si switches have a voltage rating of 650V, which is insufficient for 800V input applications. To meet 800V input requirements, 1200V SiC switches must be used. However, 1200V SiC switches are currently more expensive, and they also require negative voltage turn-off, necessitating a matching driver IC, which is also costly.

[0004] Furthermore, Si switches can be driven by transformers, significantly reducing costs. By employing a frequency multiplication control method, the input gain on the primary side is already reduced by half, which also allows for a 50% reduction in the turns ratio during transformer design, further lowering transformer costs. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to provide a switching power supply circuit and its control method, which can at least partially solve the shortcomings of the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a switching power supply circuit, the switching power supply circuit comprising: an input terminal, a primary side first bridge arm, a primary side second bridge arm, a primary side third bridge arm, a first resonant cavity, a second resonant cavity, a third resonant cavity, a secondary side first rectifier circuit, a secondary side second rectifier circuit, and a secondary side third rectifier circuit;

[0008] The positive input terminals of the first primary bridge arm, the second primary bridge arm, and the third primary bridge arm are all connected to the positive input terminal of the switching power supply, and the negative input terminals of the first primary bridge arm, the second primary bridge arm, and the third primary bridge arm are all connected to the negative input terminal of the switching power supply.

[0009] The midpoint of the first primary bridge arm is electrically connected to the first end of the first resonant cavity, the midpoint of the second primary bridge arm is electrically connected to the first end of the second resonant cavity, and the midpoint of the third primary bridge arm is electrically connected to the first end of the third resonant cavity; the first end of the primary winding of the first transformer of the first resonant cavity, the first end of the primary winding of the second transformer of the second resonant cavity, and the first end of the primary winding of the third transformer of the third resonant cavity are electrically connected together.

[0010] The first end of the secondary winding of the first transformer is electrically connected to the midpoint of the secondary first rectifier circuit, the first end of the secondary winding of the second transformer is electrically connected to the midpoint of the secondary second rectifier circuit, the first end of the secondary winding of the third transformer is electrically connected to the midpoint of the secondary third rectifier circuit, and the second end of the secondary winding of the first transformer is electrically connected together with the second end of the secondary winding of the second transformer and the second end of the secondary winding of the third transformer.

[0011] The positive output terminals of the first secondary rectifier circuit, the second secondary rectifier circuit, and the third secondary rectifier circuit are all connected to the positive output terminal of the switching power supply, and the negative output terminals of the first secondary rectifier circuit, the second secondary rectifier circuit, and the third secondary rectifier circuit are all connected to the negative output terminal of the switching power supply.

[0012] Optionally, the secondary-side first rectifier circuit includes a first switching transistor and a second switching transistor. The first terminal of the first switching transistor is connected to the positive output terminal of the switching power supply. The second terminal of the first switching transistor is connected to the first terminal of the second switching transistor and the first terminal of the secondary winding of the first transformer, respectively. The second terminal of the second switching transistor is connected to the negative output terminal of the switching power supply.

[0013] Optionally, the secondary-side first rectifier circuit includes a first bridge arm and a second bridge arm. The first bridge arm includes a first switching transistor and a second switching transistor, and the second bridge arm includes a first switching transistor and a second switching transistor. The first terminal of the first switching transistor in the first bridge arm is connected to the first terminal of the first switching transistor in the second bridge arm and a switching power supply, respectively. At the positive output terminal, the second terminal of the first switch transistor of the first bridge arm of the secondary first rectifier circuit is connected to the first terminal of the second switch transistor of the first bridge arm of the secondary first rectifier circuit and the first terminal of the secondary winding of the first transformer, respectively. The second terminal of the first switch transistor of the second bridge arm of the secondary first rectifier circuit is connected to the first terminal of the second switch transistor of the second bridge arm of the secondary first rectifier circuit and the second terminal of the secondary winding of the first transformer, respectively. The second terminals of the second switch transistor of the first bridge arm of the secondary first rectifier circuit and the second terminal of the second switch transistor of the second bridge arm of the secondary first rectifier circuit are both connected to the negative output terminal of the switching power supply.

[0014] In a second aspect, the present invention also provides a control method for the switching power supply circuit described in the first aspect, the control method comprising:

[0015] The primary drive signal frequencies of the switching transistors in the first, second, and third primary bridge arms are set to be the same.

[0016] In the first bridge arm, the second bridge arm, or the third bridge arm of the primary side, the first switch and the fourth switch are driven in a complementary manner, and the second switch and the third switch are driven in a complementary manner.

[0017] The primary drive signals of the corresponding positions of the switching transistors in the primary first bridge arm, the primary second bridge arm, and the primary third bridge arm are set to have a phase difference of 120°.

[0018] Optionally, the control method further includes:

[0019] The secondary drive signal frequencies of the switching transistors in the first, second, and third secondary rectifier circuits are the same, and the secondary drive signal is twice the primary drive signal.

[0020] The switching transistors in the secondary-side first rectifier circuit, the secondary-side second rectifier circuit, or the secondary-side third rectifier circuit are configured to drive each other complementaryly.

[0021] The secondary drive signal of the first switch in the first secondary rectifier circuit is set to be in phase with the primary drive signal of the first switch in the first primary bridge arm. The secondary drive signal of the switch in the corresponding position of the second secondary rectifier circuit lags behind the secondary drive signal of the switch in the corresponding position of the first secondary rectifier circuit by 240°. The secondary drive signal of the switch in the corresponding position of the third secondary rectifier circuit lags behind the secondary drive signal of the switch in the corresponding position of the first secondary rectifier circuit by 120°.

[0022] Optionally, in the primary side first bridge arm, the primary side second bridge arm, or the primary side third bridge arm, the duty cycle of the first switch is 75%, and the duty cycle of the second switch is 75%.

[0023] Optionally, in the first, second, or third primary bridge arm, the primary-side drive signal of the first switch is made to lag the primary-side drive signal of the second switch by 180°.

[0024] Optionally, the control method further includes:

[0025] The secondary drive signal frequencies of the switching transistors in the first, second, and third secondary rectifier circuits are the same, and the secondary drive signal is twice the primary drive signal.

[0026] The switching transistors in the same bridge arm of the secondary first rectifier circuit, the secondary second rectifier circuit, or the secondary third rectifier circuit are configured to drive each other complementaryly.

[0027] The secondary-side drive signal of the first switch transistor in the secondary-side first rectifier circuit is set to be in phase with the primary-side drive signal of the first switch transistor in the primary-side first bridge arm.

[0028] In the secondary-side first rectifier circuit, the driving signal of the first switch in the first bridge arm is the same as the driving signal of the second switch in the second bridge arm, and the driving signal of the second switch in the first bridge arm is the same as the driving signal of the first switch in the second bridge arm; the secondary-side driving signal of the switch in the corresponding position of the secondary-side second rectifier circuit lags behind the secondary-side driving signal of the switch in the corresponding position of the secondary-side first rectifier circuit by 240°, and the secondary-side driving signal of the switch in the corresponding position of the secondary-side third rectifier circuit lags behind the secondary-side driving signal of the switch in the corresponding position of the secondary-side first rectifier circuit by 120°.

[0029] Optionally, the duty cycle of the switching transistors in the secondary-side first rectifier circuit, the secondary-side second rectifier circuit, and the secondary-side third rectifier circuit is 50%.

[0030] Thirdly, the present invention also provides a switching power supply circuit, the switching power supply circuit comprising: an input terminal, a primary side first bridge arm, a primary side second bridge arm, a primary side third bridge arm, a first resonant cavity, a second resonant cavity, a third resonant cavity, a secondary side first rectifier circuit, a secondary side second rectifier circuit, and a secondary side third rectifier circuit;

[0031] The positive input terminals of the first primary bridge arm, the second primary bridge arm, and the third primary bridge arm are all connected to the positive input terminal of the switching power supply, and the negative input terminals of the first primary bridge arm, the second primary bridge arm, and the third primary bridge arm are all connected to the negative input terminal of the switching power supply.

[0032] The midpoint of the first bridge arm of the primary side is electrically connected to the first end of the first resonant cavity, the midpoint of the second bridge arm of the primary side is electrically connected to the first end of the second resonant cavity, and the midpoint of the third bridge arm of the primary side is electrically connected to the first end of the third resonant cavity; the first end of the primary winding of the first transformer of the first resonant cavity, the first end of the primary winding of the second transformer of the second resonant cavity, and the first end of the primary winding of the third transformer of the third resonant cavity are electrically connected together.

[0033] The first terminal of the first winding of the secondary side of the first transformer is electrically connected to the first terminal of the first switching transistor of the first rectifier circuit on the secondary side, and the second terminal of the first switching transistor of the first rectifier circuit on the secondary side is electrically connected to the positive output terminal of the switching power supply. Similarly, the first terminal of the second winding of the secondary side of the first transformer is electrically connected to the first terminal of the second switching transistor of the first rectifier circuit on the secondary side, and the second terminal of the second switching transistor of the second rectifier circuit on the secondary side is electrically connected to the positive output terminal of the switching power supply. The first end of the second winding of the secondary side of the second transformer is electrically connected to the first end of the second switching transistor of the second rectifier circuit on the secondary side, and the second end of the second switching transistor of the second rectifier circuit on the secondary side is electrically connected to the positive output terminal of the switching power supply; the first end of the first winding of the secondary side of the third transformer is electrically connected to the first end of the first switching transistor of the third rectifier circuit on the secondary side, and the second end of the first switching transistor of the third rectifier circuit on the secondary side is electrically connected to the positive output terminal of the switching power supply; the first end of the second winding of the secondary side of the third transformer is electrically connected to the first end of the second switching transistor of the third rectifier circuit on the secondary side, and the second end of the second switching transistor of the third rectifier circuit on the secondary side is electrically connected to the positive output terminal of the switching power supply.

[0034] Fourthly, the present invention further provides a control method for a switching power supply circuit as described in the third aspect, the control method comprising:

[0035] The primary drive signal frequencies of the switching transistors in the first, second, and third primary bridge arms are set to be the same.

[0036] In the first bridge arm, the second bridge arm, or the third bridge arm of the primary side, the first switch and the fourth switch are driven in a complementary manner, and the second switch and the third switch are driven in a complementary manner.

[0037] The primary drive signal phase difference of the corresponding positions of the switching transistors in the primary first bridge arm, the primary second bridge arm, and the primary third bridge arm is set to 120°.

[0038] The secondary drive signal frequencies of the switching transistors in the first, second, and third secondary rectifier circuits are the same, and the secondary drive signal is twice the primary drive signal.

[0039] The switching transistors in the secondary-side first rectifier circuit, the secondary-side second rectifier circuit, or the secondary-side third rectifier circuit are configured to drive each other complementaryly.

[0040] The secondary drive signal of the first switch in the first secondary rectifier circuit is set to be in phase with the primary drive signal of the first switch in the first primary bridge arm. The secondary drive signal of the switch in the corresponding position of the second secondary rectifier circuit lags behind the secondary drive signal of the switch in the corresponding position of the first secondary rectifier circuit by 240°. The secondary drive signal of the switch in the corresponding position of the third secondary rectifier circuit lags behind the secondary drive signal of the switch in the corresponding position of the first secondary rectifier circuit by 120°.

[0041] The beneficial effects of this invention are as follows:

[0042] This invention employs a three-phase, three-level frequency multiplication control method, which reduces the input gain of the primary side by half, allowing the transformer turns ratio to be reduced by half during design, further reducing transformer costs. This enables the use of conventional 650V Si switching transistors to replace 1200V SiC switching transistors, significantly reducing switching transistor costs while also lowering drive costs. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the first embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of the second embodiment of the present invention;

[0045] Figure 3 This is a schematic diagram of the third embodiment of the present invention;

[0046] Figure 4 This is a timing diagram of the driving signals according to the first embodiment of the present invention;

[0047] Figure 5 This is a timing diagram of the driving signals according to the second embodiment of the present invention;

[0048] Figure 6 This is a timing diagram of the driving signals according to the third embodiment of the present invention;

[0049] Figure 7 This is the voltage waveform of the three-level three-phase LLC frequency multiplication control resonant cavity of the present invention;

[0050] Figure 8 The voltage waveform of the two-level three-phase LLC resonant cavity of this invention is shown. Detailed Implementation

[0051] The present invention and its beneficial effects will be further described in detail below with reference to specific embodiments and accompanying drawings. However, the specific embodiments of the present invention are not limited thereto.

[0052] First Embodiment

[0053] Figure 1 This is a schematic diagram of the first embodiment of the present invention, which includes an input terminal 110, a primary side first bridge arm 120, a primary side second bridge arm 130, a primary side third bridge arm 140, a first resonant cavity 150, a second resonant cavity 160, a third resonant cavity 170, a secondary side first rectifier circuit 180, a secondary side second rectifier circuit 190, and a secondary side third rectifier circuit 200.

[0054] Input terminal 110 includes:

[0055] One end of the input power supply 111 is electrically connected to the positive terminal of the input capacitor 112, and the other end is connected to ground. The negative terminal of the input capacitor 112 is electrically connected to the positive terminal of the input capacitor 113, with the connection point being O. The negative terminal of the input capacitor 113 is connected to ground.

[0056] The first bridge arm 120 on the original side includes:

[0057] The cathode of diode 121 is electrically connected to the source of the first switching transistor 124 in the first bridge arm of the primary side; the anode of diode 121 is electrically connected to the cathode of diode 122, with the connection point being O; the anode of diode 122 is electrically connected to the source of the third switching transistor 126 in the first bridge arm of the primary side; one end of clamping capacitor 123 is electrically connected to the source of the first switching transistor 124 in the first bridge arm of the primary side, and the other end is electrically connected to the source of the third switching transistor 126 in the first bridge arm of the primary side; the drain of the first switching transistor 124 in the first bridge arm of the primary side is connected to the input... The positive terminal of power supply 111 is electrically connected. The source of the first switch transistor 124 of the first bridge arm of the primary side is electrically connected to the drain of the second switch transistor 125 of the first bridge arm of the primary side. The source of the second switch transistor 125 of the first bridge arm of the primary side is electrically connected to the drain of the third switch transistor 126 of the first bridge arm of the primary side. The connection point is the midpoint A of the first bridge arm of the primary side. The source of the third switch transistor 126 of the first bridge arm of the primary side is electrically connected to the drain of the fourth switch transistor 127 of the first bridge arm of the primary side. The source of the fourth switch transistor 127 of the first bridge arm of the primary side is electrically connected to the input ground.

[0058] The original second bridge arm 130 includes:

[0059] The cathode of diode 131 is electrically connected to the source of the first switching transistor 134 in the second primary-side bridge arm; the anode of diode 131 is electrically connected to the cathode of diode 132, with the connection point being O; the anode of diode 132 is electrically connected to the source of the third switching transistor 136 in the second primary-side bridge arm; one end of clamping capacitor 133 is electrically connected to the source of the first switching transistor 134 in the second primary-side bridge arm, and the other end is electrically connected to the source of the third switching transistor 136 in the second primary-side bridge arm; the drain of the first switching transistor 134 in the second primary-side bridge arm is connected to the input... The positive terminal of power supply 111 is electrically connected. The source of the first switch transistor 134 of the second bridge arm of the primary side is electrically connected to the drain of the second switch transistor 135 of the second bridge arm of the primary side. The source of the second switch transistor 135 of the second bridge arm of the primary side is electrically connected to the drain of the third switch transistor 136 of the second bridge arm of the primary side. The connection point is the midpoint A of the second bridge arm of the primary side. The source of the third switch transistor 136 of the second bridge arm of the primary side is electrically connected to the drain of the fourth switch transistor 137 of the second bridge arm of the primary side. The source of the fourth switch transistor 137 of the second bridge arm of the primary side is electrically connected to the input ground.

[0060] The original third bridge arm 140 includes:

[0061] The cathode of diode 141 is electrically connected to the source of the first switching transistor 144 in the third primary-side bridge arm; the anode of diode 141 is electrically connected to the cathode of diode 142, with the connection point being O; the anode of diode 142 is electrically connected to the source of the first switching transistor 146 in the third primary-side bridge arm; one end of clamping capacitor 143 is electrically connected to the source of the first switching transistor 144 in the third primary-side bridge arm, and the other end is electrically connected to the source of the third switching transistor 146 in the third primary-side bridge arm; the drain of the first switching transistor 144 in the third primary-side bridge arm is connected to the input... The positive terminal of power supply 111 is electrically connected. The source of the first switch transistor 144 of the third bridge arm of the primary side is electrically connected to the drain of the second switch transistor 145 of the third bridge arm of the primary side. The source of the second switch transistor 145 of the third bridge arm of the primary side is electrically connected to the drain of the third switch transistor 146 of the third bridge arm of the primary side. The connection point is the midpoint A of the second bridge arm of the primary side. The source of the third switch transistor 146 of the third bridge arm of the primary side is electrically connected to the drain of the fourth switch transistor 147 of the third bridge arm of the primary side. The source of the fourth switch transistor 147 of the third bridge arm of the primary side is electrically connected to the input ground.

[0062] The first resonant cavity 150 includes:

[0063] One end of the resonant inductor 151 is electrically connected to the midpoint A of the first bridge arm of the primary side, and the other end is electrically connected to one end of the resonant capacitor 152. The other end of the resonant capacitor 152 is electrically connected to one end of the primary winding 153 of the first transformer. The other end of the primary winding 153 of the first transformer is electrically connected to one end of the primary winding 163 of the second transformer and one end of the primary winding 173 of the third transformer, forming point N. One end of the secondary winding 154 of the first transformer is electrically connected to the source of the switching transistor 181 of the first bridge arm of the secondary side, and the other end is electrically connected to one end of the secondary winding 164 of the second transformer and one end of the secondary winding 174 of the third transformer.

[0064] The second resonant cavity 160 includes:

[0065] One end of the resonant inductor 161 is electrically connected to the midpoint B of the second bridge arm of the primary side, and the other end is electrically connected to one end of the resonant capacitor 162. The other end of the resonant capacitor 162 is electrically connected to one end of the primary winding 163 of the second transformer. One end of the secondary winding 164 of the second transformer is electrically connected to the source of the secondary second bridge arm switching transistor 191.

[0066] The third resonant cavity 170 includes:

[0067] One end of the resonant inductor 171 is electrically connected to the midpoint C of the third bridge arm of the primary side, and the other end is electrically connected to one end of the resonant capacitor 172. The other end of the resonant capacitor 172 is electrically connected to one end of the primary winding 173 of the third transformer. One end of the secondary winding 174 of the third transformer is electrically connected to the source of the secondary third bridge arm switching transistor 201.

[0068] The secondary-side first rectifier circuit 180 includes:

[0069] The drain of the first switching transistor 181 in the secondary first rectifier circuit is electrically connected to the positive terminal of the output capacitor 203; the source of the first switching transistor 181 in the secondary first rectifier circuit is electrically connected to the drain of the second switching transistor 182 in the secondary first rectifier circuit; and the source of the second switching transistor 182 in the secondary first rectifier circuit is electrically connected to the negative terminal of the output capacitor 203.

[0070] The second rectifier circuit on the secondary side, number 190, includes:

[0071] The drain of the first switching transistor 191 in the secondary side second rectifier circuit is electrically connected to the positive terminal of the output capacitor 203; the source of the first switching transistor 191 in the secondary side second rectifier circuit is electrically connected to the drain of the second switching transistor 192 in the secondary side second rectifier circuit; and the source of the second switching transistor 192 in the secondary side second rectifier circuit is electrically connected to the negative terminal of the output capacitor 203.

[0072] The 200th secondary-side third rectifier circuit includes:

[0073] The drain of the first switching transistor 201 in the secondary third rectifier circuit is electrically connected to the positive terminal of the output capacitor 203. The source of the first switching transistor 201 in the secondary third rectifier circuit is electrically connected to the drain of the second switching transistor 202 in the secondary third rectifier circuit. The source of the second switching transistor 202 in the secondary third rectifier circuit is electrically connected to the negative terminal of the output capacitor 203. The negative terminal of the output capacitor 203 is electrically connected to the output ground.

[0074] The working principle of the schematic diagram of the first embodiment of the present invention is as follows:

[0075] like Figure 4 As shown, the drive signals of the first switch 124 and the fourth switch 127 of the first bridge arm on the primary side are complementary signals. The duty cycle of the signal of the first switch 124 is 75%, and the duty cycle of the signal of the fourth switch 127 is 25%, with a dead time. The drive signals of the second switch 125 and the third switch 126 of the first bridge arm on the primary side are complementary signals. The duty cycle of the signal of the second switch 125 is 75%, and the duty cycle of the signal of the third switch 126 is 25%, with a dead time. The drive signal of the second switch 125 lags behind the drive signal of the first switch 124 by 180 degrees, and the drive signal of the third switch 126 lags behind the drive signal of the fourth switch 127 by 180 degrees.

[0076] The drive signals of the first switch 134 and the fourth switch 137 of the second bridge arm on the primary side are complementary signals. The duty cycle of the signal of the first switch 134 is 75%, and the duty cycle of the signal of the fourth switch 137 is 25%, with a dead time. The drive signals of the second switch 135 and the third switch 136 of the second bridge arm on the primary side are complementary signals. The duty cycle of the signal of the second switch 135 is 75%, and the duty cycle of the signal of the third switch 136 is 25%, with a dead time. The drive signal of the second switch 135 lags behind the drive signal of the first switch 134 by 180 degrees, and the drive signal of the third switch 136 lags behind the drive signal of the fourth switch 137 by 180 degrees.

[0077] The drive signals of the first switch 144 and the fourth switch 147 of the third bridge arm on the primary side are complementary signals, with the duty cycle of the first switch 144 being 75% and the duty cycle of the fourth switch 147 being 25%, and both having a dead time. The drive signals of the second switch 145 and the third switch 146 of the third bridge arm on the primary side are also complementary signals, with the duty cycle of the second switch 145 being 75% and the duty cycle of the third switch 146 being 25%, and both having a dead time. The drive signal of the second switch 145 lags behind the drive signal of the first switch 144 by 180 degrees, and the drive signal of the third switch 146 lags behind the drive signal of the fourth switch 147 by 180 degrees.

[0078] The drive signals of all switches in the second primary arm lag behind the drive signals of the corresponding switches in the first primary arm by 120 degrees.

[0079] The drive signals of all switches in the third arm of the primary side lag behind the drive signals of the corresponding switches in the second arm of the primary side by 120 degrees.

[0080] The drive signal of the first switch 181 in the secondary-side first rectifier circuit and the drive signal of the second switch 182 in the secondary-side first rectifier circuit are complementary signals, both with a 50% duty cycle and a dead time; the first switch 181 in the secondary-side first rectifier circuit is in phase with the first switch 124 in the primary-side first bridge arm, but the switching frequency of the secondary-side first rectifier circuit is twice that of the primary-side first bridge arm.

[0081] The drive signal of the first switch 191 in the secondary second rectifier circuit and the drive signal of the second switch 192 in the secondary second rectifier circuit are complementary signals, both with a 50% duty cycle and a dead time; the drive signal of the switch in the secondary second rectifier circuit has the same frequency as the drive signal of the corresponding switch in the secondary first rectifier circuit, and the drive signal of the switch in the secondary second rectifier circuit lags behind the drive signal of the corresponding switch in the secondary first rectifier circuit by 240 degrees.

[0082] The drive signal of the first switch 201 in the secondary third rectifier circuit is complementary to the drive signal of the second switch 202 in the secondary third rectifier circuit. Both have a 50% duty cycle and a dead time. The drive signal of the switch in the secondary third rectifier circuit has the same frequency as the drive signal of the corresponding switch in the secondary first rectifier circuit. The drive signal of the switch in the secondary third rectifier circuit lags behind the drive signal of the corresponding switch in the secondary first rectifier circuit by 120 degrees.

[0083] like Figure 4 As shown, taking the first bridge arm as an example, for the four switching transistors of the first bridge arm, only two switching transistors are turned on simultaneously each time, while the other two switching transistors are turned off. The turn-on sequence is as follows: Figure 4 As shown:

[0084] When the first switch tube 124 and the second switch tube 125 of the first bridge arm on the primary side are turned on, the third switch tube 126 and the fourth switch tube 127 of the primary side are turned off.

[0085] When the first switch tube 124 of the first bridge arm on the primary side and the third switch tube 126 on the primary side are turned on, the second switch tube 125 and the fourth switch tube 127 on the primary side are turned off.

[0086] When the first switch tube 124 and the second switch tube 125 of the first bridge arm on the primary side are turned on, the third switch tube 126 and the fourth switch tube 127 of the primary side are turned off.

[0087] When the second switch tube 125 and the fourth switch tube 127 of the first bridge arm on the primary side are turned on, the first switch tube 124 and the third switch tube 126 of the primary side are turned off.

[0088] The voltage across each of the two switched transistors that are turned off is only half of the input voltage, so a low-voltage switched transistor can be used instead of a high-voltage switched transistor.

[0089] by Figure 1 and Figure 4 To explain the working principle of halving the input voltage gain under frequency multiplication control:

[0090] like Figure 4 As shown, assume the input voltage is V. inAt time t1-t2, the first switch 124 and the third switch 126 of the first bridge arm are turned on, the second switch 135 and the fourth switch 137 of the second bridge arm are turned on, and the first switch 144 and the second switch 145 of the third bridge arm are turned on. At this time, the corresponding midpoint voltage of the first bridge arm is... Voltage at the midpoint of the second bridge arm The voltage at the midpoint of the third bridge arm is V. C =V in Therefore, the voltage applied across the first resonant cavity is V. AN =V A -V N The voltage applied between the second resonant cavities is V. BN =V B -V N The voltage applied across the third resonant cavity is V. CN =V C -V N According to the KVL theorem, V AN +V BN +V CN =0, the t1-t2 stage can be calculated. Therefore, at this stage Therefore, the amplitude of the resonant cavity is A four-level square wave, such as Figure 7 As shown. The same analytical method can be used to calculate the resonant cavity amplitude of a two-level three-phase LLC. Four-level square wave such as Figure 8 As shown, this means that the input voltage gain of a three-level three-phase LLC frequency multiplier control is half that of a two-level three-phase LLC.

[0091] Second Embodiment

[0092] Figure 2 This is a schematic diagram of the second embodiment of the present invention, which includes an input terminal 210, a primary side first bridge arm 220, a primary side second bridge arm 230, a primary side third bridge arm 240, a first resonant cavity 250, a second resonant cavity 260, a third resonant cavity 270, a secondary side first rectifier circuit 280, a secondary side second rectifier circuit 290, and a secondary side third rectifier circuit 300.

[0093] The input terminal 210 includes:

[0094] One end of the input power supply 211 is electrically connected to the positive terminal of the input capacitor 212, and the other end is connected to ground. The negative terminal of the input capacitor 212 is electrically connected to the positive terminal of the input capacitor 213, with the connection point being O. The negative terminal of the input capacitor 213 is connected to ground.

[0095] The first bridge arm 220 on the original side includes:

[0096] The cathode of diode 221 is electrically connected to the source of the first switch 224 in the first bridge arm of the primary side; the anode of diode 221 is electrically connected to the cathode of diode 222, with the connection point being O; the anode of diode 222 is electrically connected to the source of the third switch 226 in the first bridge arm of the primary side; one end of clamping capacitor 223 is electrically connected to the source of the first switch 224 in the first bridge arm of the primary side, and the other end is electrically connected to the source of the third switch 226 in the first bridge arm of the primary side; the drain of the first switch 224 in the first bridge arm of the primary side is connected to the input... The positive terminal of power supply 211 is electrically connected. The source of the first switch 224 of the first bridge arm of the primary side is electrically connected to the drain of the second switch 225 of the first bridge arm of the primary side. The source of the second switch 225 of the first bridge arm of the primary side is electrically connected to the drain of the third switch 226 of the first bridge arm of the primary side. The connection point is the midpoint A of the first bridge arm of the primary side. The source of the third switch 226 of the first bridge arm of the primary side is electrically connected to the drain of the fourth switch 227 of the first bridge arm of the primary side. The source of the fourth switch 227 of the first bridge arm of the primary side is electrically connected to the input ground.

[0097] The original second bridge arm 230 includes:

[0098] The cathode of diode 231 is electrically connected to the source of the first switching transistor 234 in the second primary arm of the primary side; the anode of diode 231 is electrically connected to the cathode of diode 232, with the connection point being O; the anode of diode 232 is electrically connected to the source of the third switching transistor 236 in the second primary arm of the primary side; one end of clamping capacitor 233 is electrically connected to the source of the first switching transistor 234 in the second primary arm of the primary side, and the other end is electrically connected to the source of the third switching transistor 236 in the second primary arm of the primary side; the drain of the first switching transistor 234 in the second primary arm of the primary side is connected to the input... The positive terminal of power supply 211 is electrically connected. The source of the first switch 234 of the second bridge arm of the primary side is electrically connected to the drain of the second switch 235 of the second bridge arm of the primary side. The source of the second switch 235 of the second bridge arm of the primary side is electrically connected to the drain of the third switch 236 of the second bridge arm of the primary side. The connection point is the midpoint A of the second bridge arm of the primary side. The source of the third switch 236 of the second bridge arm of the primary side is electrically connected to the drain of the fourth switch 237 of the second bridge arm of the primary side. The source of the fourth switch 237 of the second bridge arm of the primary side is electrically connected to the input ground.

[0099] The original third bridge arm 240 includes:

[0100] The cathode of diode 241 is electrically connected to the source of the first switching transistor 244 in the third bridge arm of the primary side; the anode of diode 241 is electrically connected to the cathode of diode 242, with the connection point being O; the anode of diode 242 is electrically connected to the source of the first switching transistor 246 in the third bridge arm of the primary side; one end of clamping capacitor 243 is electrically connected to the source of the first switching transistor 244 in the third bridge arm of the primary side, and the other end is electrically connected to the source of the third switching transistor 246 in the third bridge arm of the primary side; the drain of the first switching transistor 244 in the third bridge arm of the primary side is connected to the input... The positive terminal of power supply 211 is electrically connected. The source of the first switch transistor 244 of the third bridge arm of the primary side is electrically connected to the drain of the second switch transistor 245 of the third bridge arm of the primary side. The source of the second switch transistor 245 of the third bridge arm of the primary side is electrically connected to the drain of the third switch transistor 246 of the third bridge arm of the primary side. The connection point is the midpoint A of the second bridge arm of the primary side. The source of the third switch transistor 246 of the third bridge arm of the primary side is electrically connected to the drain of the fourth switch transistor 247 of the third bridge arm of the primary side. The source of the fourth switch transistor 247 of the third bridge arm of the primary side is electrically connected to the input ground.

[0101] The first resonant cavity 250 includes:

[0102] One end of the resonant inductor 251 is electrically connected to the midpoint A of the first bridge arm of the primary side, and the other end is electrically connected to one end of the resonant capacitor 252. The other end of the resonant capacitor 252 is electrically connected to one end of the primary winding 253 of the first transformer. The other end of the primary winding 253 of the first transformer is electrically connected to one end of the primary winding 263 of the second transformer and one end of the primary winding 273 of the third transformer, forming point N. One end of the secondary winding 254 of the first transformer is electrically connected to the source of the switching transistor 281 of the first rectifier circuit on the secondary side, and the other end of the secondary winding 254 of the first transformer is electrically connected to the source of the switching transistor 283 of the first rectifier circuit on the secondary side.

[0103] The second resonant cavity 260 includes:

[0104] One end of the resonant inductor 261 is electrically connected to the midpoint B of the second bridge arm of the primary side, and the other end is electrically connected to one end of the resonant capacitor 262. The other end of the resonant capacitor 262 is electrically connected to one end of the primary winding 263 of the second transformer. One end of the secondary winding 264 of the second transformer is electrically connected to the source of the secondary rectifier circuit switch 291, and the other end of the secondary winding 264 of the second transformer is electrically connected to the source of the secondary rectifier circuit switch 293.

[0105] The third resonant cavity 270 includes:

[0106] One end of the resonant inductor 271 is electrically connected to the midpoint C of the third bridge arm of the primary side, and the other end is electrically connected to one end of the resonant capacitor 272. The other end of the resonant capacitor 272 is electrically connected to one end of the primary winding 273 of the third transformer. One end of the secondary winding 274 of the third transformer is electrically connected to the source of the switching transistor 301 of the first rectifier circuit on the secondary side, and the other end of the secondary winding 274 of the third transformer is electrically connected to the source of the switching transistor 303 of the first rectifier circuit on the secondary side.

[0107] The secondary-side first rectifier circuit 280 includes:

[0108] The drain of the first switch 281 in the first bridge arm of the secondary rectifier circuit is electrically connected to the positive terminal of the output capacitor 295; the source of the first switch 281 in the first bridge arm of the secondary rectifier circuit is electrically connected to the drain of the second switch 282 in the first bridge arm of the secondary rectifier circuit; the source of the second switch 282 in the first bridge arm of the secondary rectifier circuit is electrically connected to the output ground; the drain of the first switch 283 in the second bridge arm of the secondary rectifier circuit is electrically connected to the positive terminal of the output capacitor 295; the source of the first switch 283 in the second bridge arm of the secondary rectifier circuit is electrically connected to the drain of the second switch 284 in the second bridge arm of the secondary rectifier circuit; the source of the fourth switch 284 in the second bridge arm of the secondary rectifier circuit is electrically connected to the output ground.

[0109] The secondary-side second rectifier circuit 290 includes:

[0110] The drain of the first switch 291 in the first bridge arm of the secondary rectifier circuit is electrically connected to the positive terminal of the output capacitor 295; the source of the first switch 291 in the first bridge arm of the secondary rectifier circuit is electrically connected to the drain of the second switch 292 in the first bridge arm of the secondary rectifier circuit; the source of the second switch 292 in the first bridge arm of the secondary rectifier circuit is electrically connected to the output ground; the drain of the first switch 293 in the second bridge arm of the secondary rectifier circuit is electrically connected to the positive terminal of the output capacitor 295; the source of the first switch 293 in the second bridge arm of the secondary rectifier circuit is electrically connected to the drain of the second switch 294 in the second bridge arm of the secondary rectifier circuit; the source of the second switch 294 in the second bridge arm of the secondary rectifier circuit is electrically connected to the output ground.

[0111] The secondary-side third rectifier circuit 300 includes:

[0112] The drain of the first switch 301 in the first bridge arm of the secondary-side third rectifier circuit is electrically connected to the positive terminal of the output capacitor 295; the source of the first switch 301 in the first bridge arm of the secondary-side third rectifier circuit is electrically connected to the drain of the second switch 302 in the first bridge arm of the secondary-side third rectifier circuit; the source of the second switch 302 in the first bridge arm of the secondary-side third rectifier circuit is electrically connected to the output ground; the drain of the first switch 303 in the second bridge arm of the secondary-side third rectifier circuit is electrically connected to the positive terminal of the output capacitor 295; the source of the first switch 303 in the second bridge arm of the secondary-side third rectifier circuit is electrically connected to the drain of the second switch 304 in the second bridge arm of the secondary-side third rectifier circuit; the source of the second switch 304 in the second bridge arm of the secondary-side third rectifier circuit is electrically connected to the output ground.

[0113] The working principle of the schematic diagram of the second embodiment of the present invention is as follows:

[0114] like Figure 5As shown, the drive signals of the first switch 224 and the fourth switch 227 of the first bridge arm on the primary side are complementary signals. The duty cycle of the signal of the first switch 224 is 75%, and the duty cycle of the signal of the fourth switch 227 is 25%, with a dead time. The drive signals of the second switch 225 and the third switch 226 of the first bridge arm on the primary side are complementary signals. The duty cycle of the signal of the second switch 225 is 75%, and the duty cycle of the signal of the third switch 226 is 25%, with a dead time. The drive signal of the second switch 225 lags behind the drive signal of the first switch 224 by 180 degrees, and the drive signal of the third switch 226 lags behind the drive signal of the fourth switch 227 by 180 degrees.

[0115] The drive signals of the first switch 234 and the fourth switch 237 of the second bridge arm on the primary side are complementary signals. The duty cycle of the signal of the first switch 234 is 75%, and the duty cycle of the signal of the fourth switch 237 is 25%, with a dead time. The drive signals of the second switch 235 and the third switch 236 of the second bridge arm on the primary side are complementary signals. The duty cycle of the signal of the second switch 235 is 75%, and the duty cycle of the signal of the third switch 236 is 25%, with a dead time. The drive signal of the second switch 235 lags behind the drive signal of the first switch 234 by 180 degrees, and the drive signal of the third switch 236 lags behind the drive signal of the fourth switch 237 by 180 degrees.

[0116] The drive signals of the first switch 244 and the fourth switch 247 of the third bridge arm on the primary side are complementary signals. The duty cycle of the signal of the first switch 244 is 75%, and the duty cycle of the signal of the fourth switch 247 is 25%, with a dead time. The drive signals of the second switch 245 and the third switch 246 of the third bridge arm on the primary side are complementary signals. The duty cycle of the signal of the second switch 245 is 75%, and the duty cycle of the signal of the third switch 246 is 25%, with a dead time. The drive signal of the second switch 245 lags behind the drive signal of the first switch 244 by 180 degrees, and the drive signal of the third switch 246 lags behind the drive signal of the fourth switch 247 by 180 degrees.

[0117] The drive signals of all switches in the second primary arm lag behind the drive signals of the corresponding switches in the first primary arm by 120 degrees.

[0118] The drive signals of all switches in the third arm of the primary side lag behind the drive signals of the corresponding switches in the second arm of the primary side by 120 degrees.

[0119] The drive signal of the first switch 281 of the first bridge arm of the secondary rectifier circuit is complementary to the drive signal of the second switch 282 of the first bridge arm of the secondary rectifier circuit. Both have a 50% duty cycle and a dead time. The drive signals of the first switch 281 of the first bridge arm of the secondary rectifier circuit are the same as those of the second switch 284 of the second bridge arm of the secondary rectifier circuit. The drive signals of the second switch 282 of the first bridge arm of the secondary rectifier circuit are the same as those of the first switch 283 of the second bridge arm of the secondary rectifier circuit. The first switch 281 of the first bridge arm of the secondary rectifier circuit is in phase with the first switch 224 of the first bridge arm of the primary side. However, the switching frequency of the secondary rectifier circuit is twice that of the primary side first bridge arm.

[0120] The drive signal of the first switch 291 of the first bridge arm of the secondary-side second rectifier circuit is complementary to the drive signal of the second switch 292 of the first bridge arm of the secondary-side second rectifier circuit. Both have a 50% duty cycle and a dead time. The drive signals of the first switch 291 of the first bridge arm of the secondary-side second rectifier circuit are the same as those of the second switch 294 of the second bridge arm of the secondary-side second rectifier circuit. The drive signals of the second switch 292 of the first bridge arm of the secondary-side second rectifier circuit are the same as those of the first switch 293 of the first bridge arm of the secondary-side second rectifier circuit. The drive signals of the switches in the secondary-side second rectifier circuit have the same frequency as the drive signals of the corresponding switches in the secondary-side first rectifier circuit. The drive signals of the switches in the secondary-side second rectifier circuit lag the drive signals of the corresponding switches in the secondary-side first rectifier circuit by 240 degrees.

[0121] The drive signal of the first switch 301 of the first bridge arm of the secondary-side third rectifier circuit is complementary to the drive signal of the second switch 302 of the first bridge arm of the secondary-side third rectifier circuit. Both have a 50% duty cycle and a dead time. The drive signals of the first switch 301 of the first bridge arm of the secondary-side third rectifier circuit are the same as those of the second switch 304 of the second bridge arm of the secondary-side third rectifier circuit. The drive signals of the second switch 302 of the first bridge arm of the secondary-side third rectifier circuit are the same as those of the first switch 303 of the second bridge arm of the secondary-side third rectifier circuit. The drive signals of the switches in the secondary-side third rectifier circuit have the same frequency as the drive signals of the corresponding switches in the secondary-side first rectifier circuit. The drive signals of the switches in the secondary-side third rectifier circuit lag the drive signals of the corresponding switches in the secondary-side first rectifier circuit by 120 degrees.

[0122] Third Embodiment

[0123] Figure 3This is a schematic diagram of the third embodiment of the present invention, which includes an input terminal 310, a primary side first bridge arm 320, a primary side second bridge arm 330, a primary side third bridge arm 340, a first resonant cavity 350, a second resonant cavity 360, a third resonant cavity 370, a secondary side first rectifier circuit 380, a secondary side second rectifier circuit 390, and a secondary side third rectifier circuit 400.

[0124] The input terminal 310 includes:

[0125] One end of the input power supply 311 is electrically connected to the positive terminal of the input capacitor 312, and the other end is connected to ground. The negative terminal of the input capacitor 312 is electrically connected to the positive terminal of the input capacitor 313, with the connection point being O. The negative terminal of the input capacitor 313 is connected to ground.

[0126] The first bridge arm 320 on the original side includes:

[0127] The cathode of diode 321 is electrically connected to the source of the first switching transistor 324 in the first bridge arm of the primary side; the anode of diode 321 is electrically connected to the cathode of diode 322, with the connection point being O; the anode of diode 322 is electrically connected to the source of the third switching transistor 326 in the first bridge arm of the primary side; one end of clamping capacitor 223 is electrically connected to the source of the first switching transistor 324 in the first bridge arm of the primary side, and the other end is electrically connected to the source of the third switching transistor 326 in the first bridge arm of the primary side; the drain of the first switching transistor 324 in the first bridge arm of the primary side is connected to the input... The positive terminal of power supply 211 is electrically connected. The source of the first switch transistor 324 of the first bridge arm of the primary side is electrically connected to the drain of the second switch transistor 325 of the first bridge arm of the primary side. The source of the second switch transistor 325 of the first bridge arm of the primary side is electrically connected to the drain of the third switch transistor 326 of the first bridge arm of the primary side. The connection point is the midpoint A of the first bridge arm of the primary side. The source of the third switch transistor 326 of the first bridge arm of the primary side is electrically connected to the drain of the fourth switch transistor 327 of the first bridge arm of the primary side. The source of the fourth switch transistor 327 of the first bridge arm of the primary side is electrically connected to the input ground.

[0128] The original second bridge arm 330 includes:

[0129] The cathode of diode 331 is electrically connected to the source of the first switch 334 in the second primary-side bridge arm; the anode of diode 331 is electrically connected to the cathode of diode 332, with the connection point being O; the anode of diode 332 is electrically connected to the source of the third switch 336 in the second primary-side bridge arm; one end of clamping capacitor 233 is electrically connected to the source of the first switch 334 in the second primary-side bridge arm, and the other end is electrically connected to the source of the third switch 336 in the second primary-side bridge arm; the drain of the first switch 334 in the second primary-side bridge arm is connected to the input... The positive terminal of power supply 211 is electrically connected. The source of the first switch transistor 334 of the second bridge arm of the primary side is electrically connected to the drain of the second switch transistor 335 of the second bridge arm of the primary side. The source of the second switch transistor 335 of the second bridge arm of the primary side is electrically connected to the drain of the third switch transistor 336 of the second bridge arm of the primary side. The connection point is the midpoint A of the second bridge arm of the primary side. The source of the third switch transistor 336 of the second bridge arm of the primary side is electrically connected to the drain of the fourth switch transistor 337 of the second bridge arm of the primary side. The source of the fourth switch transistor 337 of the second bridge arm of the primary side is electrically connected to the input ground.

[0130] The original third bridge arm 340 includes:

[0131] The cathode of diode 341 is electrically connected to the source of the first switching transistor 344 in the third primary-side bridge arm; the anode of diode 341 is electrically connected to the cathode of diode 342, with the connection point being O; the anode of diode 342 is electrically connected to the source of the first switching transistor 346 in the third primary-side bridge arm; one end of clamping capacitor 243 is electrically connected to the source of the first switching transistor 344 in the third primary-side bridge arm, and the other end is electrically connected to the source of the third switching transistor 346 in the third primary-side bridge arm; the drain of the first switching transistor 344 in the third primary-side bridge arm is connected to the input... The positive terminal of power supply 211 is electrically connected. The source of the first switch transistor 344 of the third bridge arm of the primary side is electrically connected to the drain of the second switch transistor 345 of the third bridge arm of the primary side. The source of the second switch transistor 345 of the third bridge arm of the primary side is electrically connected to the drain of the third switch transistor 346 of the third bridge arm of the primary side. The connection point is the midpoint A of the second bridge arm of the primary side. The source of the third switch transistor 346 of the third bridge arm of the primary side is electrically connected to the drain of the fourth switch transistor 347 of the third bridge arm of the primary side. The source of the fourth switch transistor 347 of the third bridge arm of the primary side is electrically connected to the input ground.

[0132] The first resonant cavity 350 includes:

[0133] One end of the resonant inductor 351 is electrically connected to the midpoint A of the first bridge arm of the primary side, and the other end is electrically connected to one end of the resonant capacitor 352. The other end of the resonant capacitor 352 is electrically connected to one end of the primary winding 353 of the first transformer. The other end of the primary winding 353 of the first transformer is electrically connected to one end of the primary winding 363 of the second transformer and one end of the primary winding 373 of the third transformer, forming point N. One end of the first winding 354 of the secondary side of the first transformer is electrically connected to the drain of the first switching transistor 381 of the first rectifier circuit on the secondary side, and the other end of the first winding 354 of the secondary side of the first transformer is electrically connected to the positive output terminal. One end of the second winding 355 of the secondary side of the first transformer is electrically connected to the drain of the second switching transistor 382 of the first rectifier circuit on the secondary side, and the other end of the second winding 355 of the secondary side of the first transformer is electrically connected to the positive output terminal.

[0134] The second resonant cavity 360 includes:

[0135] One end of the resonant inductor 361 is electrically connected to the midpoint B of the second bridge arm of the primary side, and the other end is electrically connected to one end of the resonant capacitor 362. The other end of the resonant capacitor 362 is electrically connected to one end of the primary winding 363 of the second transformer. One end of the first winding 364 of the secondary side of the second transformer is electrically connected to the drain of the first switching transistor 391 of the second rectifier circuit on the secondary side, and the other end of the first winding 364 of the secondary side of the second transformer is electrically connected to the positive output terminal. One end of the second winding 365 of the secondary side of the second transformer is electrically connected to the drain of the second switching transistor 392 of the second rectifier circuit on the secondary side, and the other end of the second winding 365 of the secondary side of the second transformer is electrically connected to the positive output terminal.

[0136] The third resonant cavity 370 includes:

[0137] One end of the resonant inductor 371 is electrically connected to the midpoint C of the third bridge arm of the primary side, and the other end is electrically connected to one end of the resonant capacitor 372. The other end of the resonant capacitor 372 is electrically connected to one end of the primary winding 373 of the third transformer. One end of the first winding 374 of the secondary side of the third transformer is electrically connected to the drain of the first switching transistor 401 of the third rectifier circuit on the secondary side, and the other end of the first winding 374 of the secondary side of the third transformer is electrically connected to the positive output terminal. One end of the second winding 375 of the secondary side of the third transformer is electrically connected to the drain of the second switching transistor 402 of the third rectifier circuit on the secondary side, and the other end of the second winding 375 of the secondary side of the third transformer is electrically connected to the positive output terminal.

[0138] The secondary-side first rectifier circuit 380 includes:

[0139] The source of the first switching transistor 381 in the secondary side first rectifier circuit is electrically connected to the negative terminal of the output capacitor 393, and the source of the second switching transistor 384 in the secondary side first rectifier circuit is electrically connected to the negative terminal of the output capacitor 393.

[0140] The secondary-side second rectifier circuit 390 includes:

[0141] The source of the first switching transistor 391 in the secondary side second rectifier circuit is electrically connected to the negative terminal of the output capacitor 393, and the source of the second switching transistor 392 in the secondary side second rectifier circuit is electrically connected to the negative terminal of the output capacitor 393.

[0142] The secondary-side third rectifier circuit 400 includes:

[0143] The source of the first switching transistor 401 in the secondary third rectifier circuit is electrically connected to the negative terminal of the output capacitor 393, and the source of the second switching transistor 402 in the secondary third rectifier circuit is electrically connected to the negative terminal of the output capacitor 393.

[0144] The working principle of the schematic diagram of the third embodiment of the present invention is as follows:

[0145] like Figure 6 As shown, the drive signals of the primary side first bridge arm switches 324 and 327 are complementary signals, with the duty cycle of switch 324 being 75% and the duty cycle of switch 327 being 25%, and both having a dead time. The drive signals of the primary side first bridge arm switches 325 and 326 are also complementary signals, with the duty cycle of switch 325 being 75% and the duty cycle of switch 326 being 25%, and both having a dead time. The drive signal of switch 325 lags behind the drive signal of switch 324 by 180 degrees, and the drive signal of switch 326 lags behind the drive signal of switch 327 by 180 degrees.

[0146] The drive signals of the primary side second bridge arm switches 334 and 337 are complementary signals, with the duty cycle of switch 334 being 75% and the duty cycle of switch 337 being 25%, and both having a dead time. The drive signals of the primary side first bridge arm switches 335 and 336 are complementary signals, with the duty cycle of switch 335 being 75% and the duty cycle of switch 336 being 25%, and both having a dead time. The drive signal of switch 335 lags behind the drive signal of switch 334 by 180 degrees, and the drive signal of switch 336 lags behind the drive signal of switch 337 by 180 degrees.

[0147] The drive signals of the primary side third bridge arm switches 344 and 347 are complementary signals, with the duty cycle of switch 344 being 75% and the duty cycle of switch 347 being 25%, and both having a dead time. The drive signals of the primary side first bridge arm switches 345 and 346 are complementary signals, with the duty cycle of switch 345 being 75% and the duty cycle of switch 346 being 25%, and both having a dead time. The drive signal of switch 345 lags behind the drive signal of switch 344 by 180 degrees, and the drive signal of switch 346 lags behind the drive signal of switch 347 by 180 degrees.

[0148] The drive signals of all switches in the second primary arm lag behind the drive signals of the corresponding switches in the first primary arm by 120 degrees.

[0149] The drive signals of all switches in the third arm of the primary side lag behind the drive signals of the corresponding switches in the second arm of the primary side by 120 degrees.

[0150] The drive signal of the first switch 381 in the secondary rectifier circuit is complementary to the drive signal of the second switch 382 in the secondary rectifier circuit. Both have a 50% duty cycle and a dead time. The first switch 381 in the secondary rectifier circuit is in phase with the first bridge arm switch 324 in the primary side, but the switching frequency of the switch in the secondary rectifier circuit is twice that of the switch in the primary side.

[0151] The drive signal of the first switch 391 in the secondary-side second rectifier circuit and the drive signal of the second switch 392 in the secondary-side second rectifier circuit are complementary signals, both with a 50% duty cycle and a dead time; the drive signal of the switch in the secondary-side second rectifier circuit has the same frequency as the drive signal of the corresponding switch in the secondary-side first rectifier circuit, and the drive signal of the switch in the secondary-side second rectifier circuit lags behind the drive signal of the corresponding switch in the secondary-side first rectifier circuit by 240 degrees.

[0152] The drive signal of the first switch 401 in the secondary third rectifier circuit is complementary to the drive signal of the second switch 402 in the secondary third rectifier circuit. Both have a 50% duty cycle and a dead time. The drive signal of the switch in the secondary third rectifier circuit has the same frequency as the drive signal of the corresponding switch in the secondary first rectifier circuit. The drive signal of the switch in the secondary third rectifier circuit lags behind the drive signal of the corresponding switch in the secondary first rectifier circuit by 120 degrees.

[0153] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limitations on the present invention. For those skilled in the art, several equivalent substitutions, improvements and modifications can be made without departing from the spirit and scope of the present invention. These equivalent substitutions, improvements and modifications should also be regarded as the protection scope of the present invention. Here, the embodiments will not be repeated. The protection scope of the present invention should be determined by the scope defined in the claims.

Claims

1. A switching power supply circuit, characterized in that, The switching power supply circuit includes: an input terminal, a primary side first bridge arm, a primary side second bridge arm, a primary side third bridge arm, a first resonant cavity, a second resonant cavity, a third resonant cavity, a secondary side first rectifier circuit, a secondary side second rectifier circuit, and a secondary side third rectifier circuit; The positive input terminals of the first primary bridge arm, the second primary bridge arm, and the third primary bridge arm are all connected to the positive input terminal of the switching power supply, and the negative input terminals of the first primary bridge arm, the second primary bridge arm, and the third primary bridge arm are all connected to the negative input terminal of the switching power supply. The midpoint of the first primary bridge arm is electrically connected to the first end of the first resonant cavity, the midpoint of the second primary bridge arm is electrically connected to the first end of the second resonant cavity, and the midpoint of the third primary bridge arm is electrically connected to the first end of the third resonant cavity; the first end of the primary winding of the first transformer of the first resonant cavity, the first end of the primary winding of the second transformer of the second resonant cavity, and the first end of the primary winding of the third transformer of the third resonant cavity are electrically connected together. The first end of the secondary winding of the first transformer is electrically connected to the midpoint of the secondary first rectifier circuit, the first end of the secondary winding of the second transformer is electrically connected to the midpoint of the secondary second rectifier circuit, the first end of the secondary winding of the third transformer is electrically connected to the midpoint of the secondary third rectifier circuit, and the second end of the secondary winding of the first transformer is electrically connected together with the second end of the secondary winding of the second transformer and the second end of the secondary winding of the third transformer. The positive output terminals of the first secondary rectifier circuit, the second secondary rectifier circuit, and the third secondary rectifier circuit are all connected to the positive output terminal of the switching power supply, and the negative output terminals of the first secondary rectifier circuit, the second secondary rectifier circuit, and the third secondary rectifier circuit are all connected to the negative output terminal of the switching power supply.

2. The switching power supply circuit according to claim 1, characterized in that: The secondary-side first rectifier circuit includes a first switching transistor and a second switching transistor. The first terminal of the first switching transistor is connected to the positive output terminal of the switching power supply. The second terminal of the first switching transistor is connected to the first terminal of the second switching transistor and the first terminal of the secondary winding of the first transformer, respectively. The second terminal of the second switching transistor is connected to the negative output terminal of the switching power supply.

3. The switching power supply circuit according to claim 1, characterized in that: The secondary-side first rectifier circuit includes a first bridge arm and a second bridge arm. The first bridge arm includes a first switching transistor and a second switching transistor. The second bridge arm includes a first switching transistor and a second switching transistor. The first terminal of the first switching transistor is connected to the first terminal of the first switching transistor in the second bridge arm and the positive input of the switching power supply. At the output terminal, the second terminal of the first switch transistor of the first bridge arm of the secondary rectifier circuit is connected to the first terminal of the second switch transistor of the first bridge arm of the secondary rectifier circuit and the first terminal of the secondary winding of the first transformer, respectively. The second terminal of the first switch transistor of the second bridge arm of the secondary rectifier circuit is connected to the first terminal of the second switch transistor of the second bridge arm of the secondary rectifier circuit and the second terminal of the secondary winding of the first transformer, respectively. The second terminals of the second switch transistor of the first bridge arm of the secondary rectifier circuit and the second terminal of the second switch transistor of the second bridge arm of the secondary rectifier circuit are both connected to the negative output terminal of the switching power supply.

4. A control method applied to the switching power supply circuit according to claim 2 or 3, characterized in that, The control method includes: The primary drive signal frequencies of the switching transistors in the first, second, and third primary bridge arms are set to be the same. In the first bridge arm, the second bridge arm, or the third bridge arm of the primary side, the first switch and the fourth switch are driven in a complementary manner, and the second switch and the third switch are driven in a complementary manner. The primary drive signals of the corresponding positions of the switching transistors in the primary first bridge arm, the primary second bridge arm, and the primary third bridge arm are set to have a phase difference of 120°.

5. The control method according to claim 4, characterized in that: The control method further includes: The secondary drive signal frequencies of the switching transistors in the first, second, and third secondary rectifier circuits are the same, and the secondary drive signal is twice the primary drive signal. The switching transistors in the secondary-side first rectifier circuit, the secondary-side second rectifier circuit, or the secondary-side third rectifier circuit are configured to drive each other complementaryly. The secondary drive signal of the first switch in the first secondary rectifier circuit is set to be in phase with the primary drive signal of the first switch in the first primary bridge arm. The secondary drive signal of the switch in the corresponding position of the second secondary rectifier circuit lags behind the secondary drive signal of the switch in the corresponding position of the first secondary rectifier circuit by 240°. The secondary drive signal of the switch in the corresponding position of the third secondary rectifier circuit lags behind the secondary drive signal of the switch in the corresponding position of the first secondary rectifier circuit by 120°.

6. The control method according to claim 4, characterized in that: In the primary side first bridge arm, the primary side second bridge arm, or the primary side third bridge arm, the duty cycle of the first switch is 75%, and the duty cycle of the second switch is 75%.

7. The control method according to claim 4, characterized in that: In the primary side first bridge arm, the primary side second bridge arm, or the primary side third bridge arm, the primary side drive signal of the first switch is delayed by 180° from the primary side drive signal of the second switch.

8. The control method according to claim 4, characterized in that: The control method further includes: The secondary drive signal frequencies of the switching transistors in the first, second, and third secondary rectifier circuits are the same, and the secondary drive signal is twice the primary drive signal. The switching transistors in the same bridge arm of the secondary first rectifier circuit, the secondary second rectifier circuit, or the secondary third rectifier circuit are configured to drive each other complementaryly. The secondary-side drive signal of the first switch transistor in the secondary-side first rectifier circuit is set to be in phase with the primary-side drive signal of the first switch transistor in the primary-side first bridge arm. In the secondary-side first rectifier circuit, the driving signal of the first switch in the first bridge arm is the same as the driving signal of the second switch in the second bridge arm, and the driving signal of the second switch in the first bridge arm is the same as the driving signal of the first switch in the second bridge arm; the secondary-side driving signal of the switch in the corresponding position of the secondary-side second rectifier circuit lags behind the secondary-side driving signal of the switch in the corresponding position of the secondary-side first rectifier circuit by 240°, and the secondary-side driving signal of the switch in the corresponding position of the secondary-side third rectifier circuit lags behind the secondary-side driving signal of the switch in the corresponding position of the secondary-side first rectifier circuit by 120°.

9. The control method according to claim 5 or 8, characterized in that: The duty cycle of the switching transistors in the first, second, and third secondary rectifier circuits is 50%.

10. A switching power supply circuit, characterized in that, The switching power supply circuit includes: an input terminal, a primary side first bridge arm, a primary side second bridge arm, a primary side third bridge arm, a first resonant cavity, a second resonant cavity, a third resonant cavity, a secondary side first rectifier circuit, a secondary side second rectifier circuit, and a secondary side third rectifier circuit; The positive input terminals of the first primary bridge arm, the second primary bridge arm, and the third primary bridge arm are all connected to the positive input terminal of the switching power supply, and the negative input terminals of the first primary bridge arm, the second primary bridge arm, and the third primary bridge arm are all connected to the negative input terminal of the switching power supply. The midpoint of the first bridge arm of the primary side is electrically connected to the first end of the first resonant cavity, the midpoint of the second bridge arm of the primary side is electrically connected to the first end of the second resonant cavity, and the midpoint of the third bridge arm of the primary side is electrically connected to the first end of the third resonant cavity; the first end of the primary winding of the first transformer of the first resonant cavity, the first end of the primary winding of the second transformer of the second resonant cavity, and the first end of the primary winding of the third transformer of the third resonant cavity are electrically connected together. The first terminal of the first winding of the secondary side of the first transformer is electrically connected to the first terminal of the first switching transistor of the first rectifier circuit on the secondary side, and the second terminal of the first switching transistor of the first rectifier circuit on the secondary side is electrically connected to the positive output terminal of the switching power supply. Similarly, the first terminal of the second winding of the secondary side of the first transformer is electrically connected to the first terminal of the second switching transistor of the first rectifier circuit on the secondary side, and the second terminal of the second switching transistor of the second rectifier circuit on the secondary side is electrically connected to the positive output terminal of the switching power supply. The first end of the second winding of the secondary side of the second transformer is electrically connected to the first end of the second switching transistor of the second rectifier circuit on the secondary side, and the second end of the second switching transistor of the second rectifier circuit on the secondary side is electrically connected to the positive output terminal of the switching power supply; the first end of the first winding of the secondary side of the third transformer is electrically connected to the first end of the first switching transistor of the third rectifier circuit on the secondary side, and the second end of the first switching transistor of the third rectifier circuit on the secondary side is electrically connected to the positive output terminal of the switching power supply; the first end of the second winding of the secondary side of the third transformer is electrically connected to the first end of the second switching transistor of the third rectifier circuit on the secondary side, and the second end of the second switching transistor of the third rectifier circuit on the secondary side is electrically connected to the positive output terminal of the switching power supply.

11. A control method applied to the switching power supply circuit as described in claim 10, characterized in that, The control method includes: The primary drive signal frequencies of the switching transistors in the first, second, and third primary bridge arms are set to be the same. In the first bridge arm, the second bridge arm, or the third bridge arm of the primary side, the first switch and the fourth switch are driven in a complementary manner, and the second switch and the third switch are driven in a complementary manner. The primary drive signal phase difference of the corresponding positions of the switching transistors in the primary first bridge arm, the primary second bridge arm, and the primary third bridge arm is set to 120°. The secondary drive signal frequencies of the switching transistors in the first, second, and third secondary rectifier circuits are the same, and the secondary drive signal is twice the primary drive signal. The switching transistors in the secondary-side first rectifier circuit, the secondary-side second rectifier circuit, or the secondary-side third rectifier circuit are configured to drive each other complementaryly. The secondary drive signal of the first switch in the first secondary rectifier circuit is set to be in phase with the primary drive signal of the first switch in the first primary bridge arm. The secondary drive signal of the switch in the corresponding position of the second secondary rectifier circuit lags behind the secondary drive signal of the switch in the corresponding position of the first secondary rectifier circuit by 240°. The secondary drive signal of the switch in the corresponding position of the third secondary rectifier circuit lags behind the secondary drive signal of the switch in the corresponding position of the first secondary rectifier circuit by 120°.

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