Isolated single-stage AC / DC converter, control method and related devices

Abstract

This application discloses an isolated single-stage AC / DC converter, a control method, and related devices. The converter includes a controller, a primary-side circuit, a resonant cavity, and a secondary-side circuit. The first terminal of the primary-side circuit is connected to an AC source, the second terminal of the primary-side circuit is connected to the first terminal of the resonant cavity, and the second terminal of the resonant cavity is connected to the secondary-side circuit. The primary-side circuit includes a bidirectional switching bridge arm. The upper arm of the bidirectional switching bridge arm includes two switching transistors connected in series, and the lower arm of the bidirectional switching bridge arm includes two switching transistors connected in series. The controller is configured to, within a preset range where the AC voltage is at zero-crossing, control at least one normally conducting transistor in the blocking transistors to turn off after all the freewheeling transistors are turned on, so that the current in the resonant cavity, in both positive and negative directions, flows through the switching transistors or their anti-parallel diodes. This provides an effective freewheeling path within the preset range where the AC voltage is at zero-crossing, reducing the stress on the switching transistors.

Description

Technical Field

[0001] This application relates to the field of rectification and conversion technology, specifically to an isolated single-stage AC / DC converter, control method, and related devices. Background Technology

[0002] An isolated single-stage AC / DC converter includes a primary circuit, a transformer, and a secondary circuit. The first terminal of the primary circuit is connected to an AC source, the second terminal of the primary circuit is connected to the primary winding of the transformer, the secondary winding of the transformer is connected to the first terminal of the secondary circuit, and the second terminal of the secondary circuit is connected to a DC source or load.

[0003] In actual operation, in order to prevent the upper and lower arms of the primary circuit from being directly connected and causing the AC source to be short-circuited, there is a dead time between the upper and lower arm switches. For example, there is a dead time delay between the lower arm switch being turned off and the upper arm switch being turned on.

[0004] However, during the dead time, when the AC source switches at the zero-crossing point, the switching transistor in the primary circuit lacks a freewheeling path, causing stress problems in the switching transistor. Summary of the Invention

[0005] In a first aspect of this application, an isolated single-stage AC / DC converter is provided, comprising: a controller, a primary-side circuit, a resonant cavity, and a secondary-side circuit;

[0006] The first end of the primary circuit is used to connect to an AC source, the second end of the primary circuit is connected to the first end of the resonant cavity, and the second end of the resonant cavity is connected to the secondary circuit. The primary circuit includes a bidirectional switching bridge arm, the upper bridge arm of the bidirectional switching bridge arm includes two switching transistors connected in series, and the lower bridge arm of the bidirectional switching bridge arm includes two switching transistors connected in series.

[0007] The controller is configured to control at least one normally conducting transistor in the blocking transistor to turn off after all the freewheeling transistors are turned on when the AC voltage is within a preset range of zero crossing points, so that the current in the resonant cavity freewheels through the switching transistor or the anti-parallel diode of the switching transistor in both positive and negative directions; when the freewheeling transistor is the switching transistor of the upper bridge arm, the blocking transistor is the switching transistor of the lower bridge arm; when the freewheeling transistor is the switching transistor of the lower bridge arm, the blocking transistor is the switching transistor of the upper bridge arm.

[0008] One possible implementation is that the primary-side circuit includes two bidirectional switching bridge arms connected in parallel, or the primary-side circuit includes one bidirectional switching bridge arm and one capacitor bridge arm.

[0009] The secondary circuit includes a full-bridge circuit or a half-bridge circuit, and the secondary circuit includes a switching transistor.

[0010] One possible implementation is that, when the primary-side circuit includes a first bidirectional switch bridge arm and a second bidirectional switch bridge arm connected in parallel, the upper arm of the first bidirectional switch bridge arm includes a first switch and a second switch connected in series, and the lower arm of the first bidirectional switch bridge arm includes a third switch and a fourth switch connected in series; the upper arm of the second bidirectional switch bridge arm includes a fifth switch and a sixth switch connected in series, and the lower arm of the second bidirectional switch bridge arm includes a seventh switch and an eighth switch connected in series.

[0011] The freewheeling diode includes a first switching diode, a second switching diode, a fifth switching diode, and a sixth switching diode. The blocking diode includes a normally open diode and a high-frequency switching diode. The normally open diode in the blocking diode includes a third switching diode and a seventh switching diode. The high-frequency switching diode in the blocking diode includes a fourth switching diode and an eighth switching diode.

[0012] One possible implementation is that, when the primary-side circuit includes a first bidirectional switch bridge arm and a second bidirectional switch bridge arm connected in parallel, the upper arm of the first bidirectional switch bridge arm includes a first switch and a second switch connected in series, and the lower arm of the first bidirectional switch bridge arm includes a third switch and a fourth switch connected in series; the upper arm of the second bidirectional switch bridge arm includes a fifth switch and a sixth switch connected in series, and the lower arm of the second bidirectional switch bridge arm includes a seventh switch and an eighth switch connected in series.

[0013] The freewheeling diode includes a third switch, a fourth switch, a seventh switch, and an eighth switch. The blocking diode includes a normally open diode and a high-frequency switch. The normally open diode in the blocking diode includes a first switch and a fifth switch. The high-frequency switch in the blocking diode includes a second switch and a sixth switch.

[0014] In one possible implementation, the controller is also used to alternately control the switching transistors of the upper and lower bridge arms as freewheeling transistors within a preset range of different zero-crossing points of the AC voltage.

[0015] In one possible implementation, the controller is also configured to control the switching transistor of the secondary circuit to turn off within a preset range, based on the turn-off time of the high-frequency switching transistor in the blocking transistor or the turn-off time of the normally-conducting transistor in the blocking transistor.

[0016] This application also provides a power supply device, including any of the above-mentioned isolated single-stage AC / DC converters.

[0017] This application also provides a control method for an isolated single-stage AC / DC converter, the converter including: a primary circuit, a resonant cavity and a secondary circuit; the primary circuit includes a bidirectional switching bridge arm, the upper bridge arm of the bidirectional switching bridge arm includes two switches connected in series, and the lower bridge arm of the bidirectional switching bridge arm includes two switches connected in series.

[0018] The method includes:

[0019] When the AC voltage is within the preset range of zero crossing, at least one normally conducting tube in the control blocking tube is turned off after all the freewheeling tubes are turned on, so that the current in the resonant cavity can be freewheeled through the switching tube or the anti-parallel diode of the switching tube in both the positive and negative directions.

[0020] When the freewheeling diode is the switching diode of the upper bridge arm, the blocking diode is the switching diode of the lower bridge arm; when the freewheeling diode is the switching diode of the lower bridge arm, the blocking diode is the switching diode of the upper bridge arm.

[0021] One possible implementation method further includes: controlling the switching transistor of the secondary circuit to turn off based on the turn-off time of the high-frequency switching transistor in the blocking transistor or the turn-off time of the normally-conducting transistor in the blocking transistor within a preset range.

[0022] This application also provides a controller for performing the methods described above.

[0023] The isolated single-stage AC / DC converter provided in this application, when the AC voltage is within a preset range of zero crossing, has at least one normally conducting transistor in the blocking transistor turn off after all the freewheeling transistors are turned on. Because at least one normally conducting transistor in the blocking transistor is on during the dead time, it can cooperate with the freewheeling transistor to provide a freewheeling path for both the positive and negative currents in the resonant cavity. This allows the current in the resonant cavity to freewheel through the switching transistors or their anti-parallel diodes in both positive and negative directions, instead of freewheeling from the junction capacitance of the switching transistors. This reduces the stress on each switching transistor and enables a smooth transition from normal operation to zero-crossing freewheeling state, allowing the energy in the resonant cavity to decay to zero without incurring additional hardware costs. Attached Figure Description

[0024] Figure 1 A schematic diagram of a first type of isolated single-stage AC / DC converter provided in the embodiments of this application;

[0025] Figure 2 A schematic diagram of a second isolated single-stage AC / DC converter provided in the embodiments of this application;

[0026] Figure 3 A schematic diagram of the switching timing in the first type of isolated single-stage AC / DC converter provided in this application embodiment;

[0027] Figure 4 A schematic diagram of the switching timing in a second type of isolated single-stage AC / DC converter provided in this application embodiment;

[0028] Figure 5 A schematic diagram of the switching timing in a third type of isolated single-stage AC / DC converter provided in this application embodiment;

[0029] Figure 6 A schematic diagram of a third type of isolated single-stage AC / DC converter provided in the embodiments of this application;

[0030] Figure 7 A schematic diagram of the switching timing in the fourth isolated single-stage AC / DC converter provided in this application embodiment;

[0031] Figure 8 A flowchart illustrating a first type of control method for an isolated single-stage AC / DC converter provided in this application embodiment;

[0032] Figure 9 This is a schematic diagram of a controller provided in an embodiment of this application. Detailed Implementation

[0033] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0034] In related technologies, the switching transistors of isolated single-stage AC / DC converters may experience significant stress during the dead time in the transition freewheeling range due to the lack of a freewheeling path.

[0035] In order to reduce the stress borne by the switching transistor during the dead time, the first aspect of the present application provides an isolated single-stage AC / DC converter that can provide a new freewheeling path for the switching transistor and reduce the voltage stress borne by the switching transistor.

[0036] See Figure 1 The figure is a schematic diagram of the first isolated single-stage AC / DC converter provided in the embodiments of this application.

[0037] The isolated single-stage AC / DC converter provided in this application includes a controller 40, a primary-side circuit 10, a resonant cavity 20, and a secondary-side circuit 30. The resonant cavity 20 includes a resonant inductor L. pr Resonant capacitor C pr And transformers, where the transformer is taken as an ideal transformer, the inductance of the primary winding of the transformer is equivalent to the magnetizing inductance L. m .

[0038] The first terminal of the primary circuit 10 is used to connect to the AC source V. ac The second end of the primary circuit 10 is connected to the first end of the resonant cavity 20, and the second end of the resonant cavity 20 is connected to the secondary circuit 30. The primary circuit 10 includes a bidirectional switching bridge arm, the upper bridge arm of which includes two switching transistors connected in series, and the lower bridge arm of which includes two switching transistors connected in series.

[0039] The controller 40 is configured to control at least one normally conducting transistor in the blocking transistor to turn off after all the freewheeling transistors are turned on when the AC voltage of the AC source is within a preset range of zero crossing points, so that the current in the resonant cavity can freewheel through the switching transistor or the anti-parallel diode of the switching transistor in both positive and negative directions; wherein, when the freewheeling transistor is the switching transistor of the upper bridge arm, the blocking transistor is the switching transistor of the lower bridge arm; when the freewheeling transistor is the switching transistor of the lower bridge arm, the blocking transistor is the switching transistor of the upper bridge arm.

[0040] The anti-parallel diode of the switching transistor can be a parasitic diode of the switching transistor or an external diode; this application does not impose specific limitations on the embodiments thereof.

[0041] The embodiments of this application do not specifically limit the structure of the primary circuit 10 and the secondary circuit 30. Some possible implementations include the primary circuit 10 including two bidirectional switching bridge arms connected in parallel, or the primary circuit 10 including one bidirectional switching bridge arm and one capacitor bridge arm; the secondary circuit 30 includes a full-bridge circuit or a half-bridge circuit, and the secondary circuit 30 includes a switching transistor, that is, the secondary circuit 30 includes a controllable full-bridge circuit or a controllable half-bridge circuit.

[0042] To enable those skilled in the art to fully understand the control logic of controller 40, the following will be used as an example. Figure 1 The primary circuit 10 of the provided isolated single-stage AC / DC converter includes two parallel bidirectional switching bridge arms as an example for illustration.

[0043] See Figure 2 This figure is a schematic diagram of a second type of isolated single-stage AC / DC converter provided in an embodiment of this application.

[0044] Figure 2 In the provided isolated single-stage AC / DC converter, when the primary-side circuit 10 includes a first bidirectional switching bridge arm and a second bidirectional switching bridge arm connected in parallel, the upper bridge arm of the first bidirectional switching bridge arm includes a first switching transistor Q connected in series. p1 Second switch Q p2 The lower arm of the first bidirectional switching bridge arm includes a third switch Q connected in series. p3 and the fourth switch Q p4 The upper arm of the second bidirectional switching bridge arm includes a fifth switching transistor Q connected in series. p5 and the sixth switch Q p6 The lower arm of the second bidirectional switching bridge arm includes a seventh switch Q connected in series. p7 and the eighth switch Q p8 The anti-parallel diodes of the two series-connected switching transistors are either top-to-top or back-to-back, meaning the anti-parallel diodes of the two switching transistors are in opposite directions, thus providing a freewheeling path.

[0045] In the exchange source V ac During the positive half-cycle of the AC voltage, the first switching transistor Q...p1 The third switch Q p3 Fifth switch Q p5 and the seventh switch Q p7 Normally on, second switching transistor Q p2 The fourth switch Q p4 The sixth switch Q p6 and the eighth switch Q p8 High-frequency switching. To meet the dead-time requirements, the sixth switch Q... p6 The eighth switch Q needs to be used. p8 Turn-off is completed before conduction, in the eighth switch Q p8 It will be turned on again after being turned off.

[0046] This application does not specifically limit the choice of freewheeling or blocking transistors. For ease of explanation, the freewheeling transistor will be used as the first switching transistor Q below. p1 Second switch Q p2 Fifth switch Q p5 and the sixth switch Q p6 The blocking transistor is the third switching transistor Q. p3 The fourth switch Q p4 The seventh switch Q p7 and the eighth switch Q p8 Let's take an example to illustrate.

[0047] Controller 40 is configured to operate at AC source V ac When the AC voltage switches from the positive half-cycle to the zero-crossing point of the negative half-cycle, the third switch Q is controlled. p3 and the seventh switch Q p7 At least one switching transistor, in the first switching transistor Q p1 Second switch Q p2 Fifth switch Q p5 and the sixth switch Q p6 Turn off the circuit only after all circuits are connected.

[0048] One possible implementation, for example, is that the controller can be located at the first switching transistor Q. p1 Second switch Q p2 Fifth switch Q p5 and the sixth switch Q p6 After the first preset time period when all transistors are turned on, the seventh switch Q is then controlled. p7 Turn off. Due to the sixth switch Q p6 and the eighth switch Q p8 During the dead time when all switches are in the off state, the seventh switch Q p7 When the resonant cavity 20 is in the conducting state, and the current in the resonant cavity 20 is in the positive direction, the current in the resonant cavity 20 can pass through the first switching transistor Q. p1 Second switch Q p2The sixth switch Q p6 The anti-parallel diode and the fifth switch Q p5 Freewheeling; When the current in resonant cavity 20 is in the negative direction, because the voltage across the resonant inductor is higher than the voltage of the AC source, the current in resonant cavity 20 cannot flow through the third switch Q. p3 and the fourth switch Q p4 The current in resonant cavity 20 can be transmitted through the eighth switch Q. p8 Anti-parallel diode, seventh switch Q p7 Second switch Q p2 and the first switching transistor Q p1 Freewheeling. Therefore, during the dead time, the current in the resonant cavity 20 freewheels through the switching transistor or its anti-parallel diode in both the positive and negative directions.

[0049] After the dead time ends, the first switch Q p1 Second switch Q p2 Fifth switch Q p5 and the sixth switch Q p6 When all are turned on, both the positive and negative currents of resonant cavity 20 can pass through the fifth switch Q. p5 The sixth switch Q p6 Second switch Q p2 and the first switching transistor Q p1 Full-bridge circuit freewheeling.

[0050] This application does not specifically limit the time of the first preset time period, which can be selected according to the actual situation.

[0051] The above embodiments of this application use the example of the current in the resonant cavity 20 switching from positive to negative as an example. The control logic provided in the embodiments of this application is also applicable to the case where the current in the resonant cavity 20 switches from negative to positive, and will not be repeated here.

[0052] The isolated single-stage AC / DC converter provided in this application embodiment has a controller that controls at least one normally conducting transistor in the blocking transistor to turn off after all the freewheeling transistors are turned on when the AC voltage of the AC source is within a preset range of zero crossing. Since at least one normally conducting transistor in the blocking transistor is on during the dead time, the freewheeling transistor can provide a freewheeling path for the positive current of the resonant cavity during the dead time. The freewheeling transistor and the normally conducting transistor in the blocking transistor can jointly provide a freewheeling path for the negative current of the resonant cavity. This allows the current in the resonant cavity to freewheel through the switching transistors or their anti-parallel diodes in both positive and negative directions, instead of freewheeling from the junction capacitance of the switching transistors. This reduces the stress on each switching transistor and enables a smooth transition of the isolated single-stage AC / DC converter from normal operation to zero-crossing freewheeling state, allowing the energy in the resonant cavity to decay to zero without incurring additional hardware costs.

[0053] The following is combined Figure 2 The switching timing of each switch in the provided isolated single-stage AC / DC converter further explains the control logic of the controller 40. This application embodiment does not specifically limit the selection of the freewheeling diode; it first focuses on selecting the first switch Q. p1 Second switch Q p2 Fifth switch Q p5 and the sixth switch Q p6 This will be introduced using a freewheeling tube as an example.

[0054] See Figure 3 The figure is a schematic diagram of the switching timing of the first type of isolated single-stage AC / DC converter provided in the embodiments of this application.

[0055] Figure 3 In the provided embodiment, the freewheeling diode includes a first switching transistor Q. p1 Second switch Q p2 Fifth switch Q p5 and the sixth switch Q p6 The high-frequency switching transistor includes the second switching transistor Q. p2 The fourth switch Q p4 The sixth switch Q p6 and the eighth switch Q p8 The blocking transistor includes a normally-conducting transistor and a high-frequency switching transistor. The normally-conducting transistor in the blocking transistor includes a third switching transistor Q. p3 and the seventh switch Q p7 The high-frequency switching transistor in the blocking transistor includes the fourth switching transistor Q. p4 and the eighth switch Q p8 . Figure 3 The interval within the dashed box represents the transition freewheeling interval where the AC voltage of the AC source transitions from the positive half-cycle to the negative half-cycle.

[0056] Figure 3 Continue with the exchange source V ac The following is an example of switching AC voltage from the positive half-cycle to the negative half-cycle.

[0057] Controller 40 is configured to switch the first transistor Q within a preset range when the AC voltage is at the zero-crossing point. p1 and the fifth switch Q p5 Normally on; at the third time t3, the eighth switch Q p8 The switch changes from on to off; at the fourth time t4, the sixth switch Q... p6 The switch changes from off to on; in the sixth switch Q p6 After the switch changes from off to on, the third switch Q... p3 and the seventh switch Q p7The switch changes from being on to being off. The time interval between the third time t3 and the fourth time t4 is the period of the sixth switch Q. p6 and the eighth switch Q p8 Dead time when all are in a shutdown state. Figure 3 With the third switch Q p3 At the fifth moment t5, the transistor changes from on to off, and the seventh switch Q... p7 Taking the change from on to off at time t6 as an example, the time interval between time t5 (fifth time) and time t4 (fourth time) can be equal to or unequal to the time interval between time t6 (sixth time) and time t4 (fourth time). That is, the third switch Q... p3 With the seventh switch Q p7 The transistors can switch from on to off simultaneously, or they can switch from on to off at different times. The turn-off times can be the same or different, but the turn-off time must be within the range of the sixth switch Q. p6 After changing from off to on, the first preset time period mentioned above includes the time period between the fourth time t4 and the fifth time t5, and the time period between the fourth time t4 and the sixth time t6.

[0058] Before the first moment t1, the second switch Q p2 and the eighth switch Q p8 Turn off, fourth switch Q p4 and the sixth switch Q p6 Conduction. To prevent a direct connection between the upper and lower bridge arms, the second switch Q... p2 The fourth switch Q needs to be used. p4 After being turned off, the eighth switch Q is turned on. p8 The sixth switch Q needs to be used. p6 After being turned off, it is turned on again. Therefore, controller 40 is configured so that at the first moment t1, the fourth switch Q... p4 and the sixth switch Q p6 The switch changes from on to off; at the second time t2, the second switch Q... p2 and the eighth switch Q p8 The circuit changes from off to on. To establish a freewheeling path for the negative current in resonant cavity 20, the sixth switch Q needs to be turned on. p6 Similarly, to avoid a direct connection between the upper and lower bridge arms, the sixth switch Q... p6 The eighth switch Q needs to be used. p8 It is turned on after being turned off.

[0059] Therefore, controller 40 is configured so that at the third time t3, the eighth switch Q... p8 The switch changes from on to off; at the fourth time t4, the sixth switch Q... p6 It changes from off to on. For Figure 3 The switching timing shown indicates that when the current in resonant cavity 20 is negative, the seventh switch Q...p7 The anti-parallel diode is reverse-biased. To construct a freewheeling path for the negative current in resonant cavity 20, the seventh switch Q needs to be reverse-biased. p7 The circuit remains on. Therefore, during the dead time, when the current in the resonant cavity 20 is in the positive direction, the current in the resonant cavity 20 can pass through the first switch Q. p1 Second switch Q p2 The sixth switch Q p6 The anti-parallel diode and the fifth switch Q p5 Freewheeling; When the current in resonant cavity 20 is in the negative direction, because the voltage across the resonant inductor is higher than the voltage of the AC source, the negative current in resonant cavity 20 cannot flow through the third switch Q. p3 and the fourth switch Q p4 The negative current in resonant cavity 20 can be transmitted through the eighth switch Q. p8 Anti-parallel diode, seventh switch Q p7 Second switch Q p2 and the first switching transistor Q p1 Continuous streaming.

[0060] See Figure 4 The figure is a schematic diagram of the switching timing in the second type of isolated single-stage AC / DC converter provided in the embodiments of this application.

[0061] Figure 3 The switching timing shown is based on the dead time between the third time t3 and the fourth time t4 for the second switching transistor Q. p2 The sixth switch Q is turned on. p6 Let's take shutdown as an example. Figure 4 The switching timing shown indicates that during the dead time between the third time t3 and the fourth time t4, the second switching transistor Q... p2 Turn off, sixth switch Q p6 Let's take conduction as an example.

[0062] At this time, the forward current of the resonant cavity 20 can pass through the fourth switch Q. p4 Anti-parallel diode, third switch Q p3 The sixth switch Q p6 and the fifth switch Q p5 Freewheeling; the negative current in resonant cavity 20 can pass through the fifth switch Q. p5 The sixth switch Q p6 Second switch Q p2 The anti-parallel diode and the first switching transistor Q p1 Continuous streaming.

[0063] Therefore, controller 40 is configured to activate the third switch Q at the fifth time t5. p3The switch changes from on to off at the sixth time t6, and the seventh switch Q... p7 It changes from being on to being off. Thus, regardless of the second switch Q... p2 and the sixth switch Q p6 Regarding the timing of the operation, during the dead time between the third time t3 and the fourth time t4, both the negative current and the positive current of resonant cavity 20 have freewheeling loops. After the sixth time t6, all four blocking transistors are turned off and all four freewheeling transistors are turned on, disconnecting resonant cavity 20 from the AC source. Both the positive current and the negative current of resonant cavity 20 can then flow through the fifth switching transistor Q. p5 The sixth switch Q p6 Second switch Q p2 and the first switching transistor Q p1 Full-bridge circuit freewheeling.

[0064] Due to the AC source V ac When the AC voltage switches from the positive half-cycle to the negative half-cycle, both the positive current and the negative current of the resonant cavity 20 have freewheeling loops, which allows the energy in the resonant cavity 20 to decay to zero, thus reducing the stress on the switching transistor.

[0065] The following embodiments of this application select the third switch Q. p3 The fourth switch Q p4 The seventh switch Q p7 and the eighth switch Q p8 This will be introduced using a freewheeling tube as an example.

[0066] See Figure 5 The figure is a schematic diagram of the switching timing of the third type of isolated single-stage AC / DC converter provided in the embodiments of this application.

[0067] Figure 5 In the provided embodiment, the freewheeling diode includes a third switching transistor Q. p3 The fourth switch Q p4 The seventh switch Q p7 and the eighth switch Q p8 The high-frequency switching transistor includes the second switching transistor Q. p2 The fourth switch Q p4 The sixth switch Q p6 and the eighth switch Q p8 The blocking transistor includes a normally-conducting transistor and a high-frequency switching transistor. The normally-conducting transistor in the blocking transistor includes the first switching transistor Q. p1 and the fifth switch Q p5 The high-frequency switching transistor in the blocking transistor includes the second switching transistor Q. p2 and the sixth switch Q p6 . Figure 5The interval within the dashed box represents the transition freewheeling interval where the AC voltage of the AC source transitions from the positive half-cycle to the negative half-cycle.

[0068] Figure 5 Continue with the exchange source V ac The following is an example of switching AC voltage from the positive half-cycle to the negative half-cycle.

[0069] Controller 40 is configured to activate the third switch Q within a preset range when the AC voltage is at its zero-crossing point. p3 and the seventh switch Q p7 Normally on; at the third time t3, the second switch Q... p2 The switch changes from on to off; at the fourth time t4, the fourth switch Q... p4 From off to on; the fourth switch Q p4 After changing from off to on, the first switch Q p1 and the fifth switch Q p5 The switch changes from being on to being off. The time interval between the third time t3 and the fourth time t4 is the period of the sixth switch Q. p6 and the eighth switch Q p8 Dead time when all are in a shutdown state.

[0070] To establish a freewheeling path for the negative current in resonant cavity 20, the fourth switch Q needs to be turned on. p4 Similarly, to avoid a direct connection between the upper and lower bridge arms, the fourth switch Q... p4 A second switch Q is required p2 After being turned off, it is turned on again. Therefore, controller 40 is configured so that at the third time t3, the second switch Q... p2 The switch changes from on to off; at the fourth time t4, the fourth switch Q... p4 The switch changes from off to on; in the fourth switch Q p4 After changing from off to on, the first switch Q p1 and the fifth switch Q p5 It changes from being on to being off. Figure 4 With the first switching transistor Q p1 At the fifth moment t5, the transistor changes from on to off, and the fifth switch Q... p5 Taking the change from on to off at time t6 as an example, the time interval between time t5 (fifth time) and time t4 (fourth time) can be equal to or unequal to the time interval between time t6 (sixth time) and time t4 (fourth time). That is, the first switch Q... p1 and the fifth switch Q p5 The shutdown time can be the same or different.

[0071] Thus, during the time interval between the third time t3 and the fourth time t4, the forward current of the resonant cavity 20 can pass through the fourth switch Q. p4Anti-parallel diode, third switch Q p3 The seventh switch Q p7 and the eighth switch Q p8 Freewheeling, the negative current in resonant cavity 20 can pass through the seventh switch Q. p7 The eighth switch Q p8 Second switch Q p2 The anti-parallel diode and the first switching transistor Q p1 Continued flow. Due to AC source V ac When the AC voltage switches from the positive half-cycle to the negative half-cycle, both the positive and negative currents in resonant cavity 20 have freewheeling loops, allowing the energy in resonant cavity 20 to decay to zero, thus reducing the stress on the switching transistor. After the fifth moment t5, all four blocking transistors are turned off, and all four freewheeling transistors are turned on. Resonant cavity 20 is disconnected from the AC source, and both the positive and negative currents in resonant cavity 20 can now flow through the third switching transistor Q. p3 The fourth switch Q p4 The seventh switch Q p7 and the eighth switch Q p8 Continuous streaming.

[0072] In one possible implementation, the controller 40 is further configured to alternately control the switching transistors of the upper and lower bridge arms as freewheeling transistors within a preset range of different zero-crossing points of the AC voltage. For example, the controller 40 can select the first switching transistor Q when the AC voltage transitions from the positive half-cycle to the negative half-cycle in each cycle of the AC voltage. p1 Second switch Q p2 Fifth switch Q p5 and the sixth switch Q p6 As a freewheeling diode, the third switching transistor Q can be selected when the AC voltage transitions from the negative half-cycle to the positive half-cycle. p3 The fourth switch Q p4 The seventh switch Q p7 and the eighth switch Q p8 The full-bridge circuit is used as a freewheeling diode.

[0073] Figure 3 , Figure 4 and Figure 5 The isolated single-stage AC / DC converters provided in the embodiments all take the primary-side circuit 10 as an example, which includes two bidirectional switching bridge arms connected in parallel. The primary-side circuit 10 may also include one bidirectional switching bridge arm and one capacitor bridge arm. The following description is in conjunction with the accompanying drawings.

[0074] See Figure 6 This figure is a schematic diagram of a third type of isolated single-stage AC / DC converter provided in an embodiment of this application.

[0075] Figure 6In the provided isolated single-stage AC / DC converter, the primary-side circuit 10 includes a bidirectional switching bridge arm and a capacitor bridge arm. The upper arm of the bidirectional switching bridge arm includes a first switching transistor Q connected in series. p1 Second switch Q p2 The lower arm of the bidirectional switching bridge arm includes a third switch Q connected in series. p3 and the fourth switch Q p4 The upper arm of the capacitor bridge includes a first capacitor C1, and the lower arm of the capacitor bridge includes a second capacitor C2.

[0076] See Figure 7 The figure is a schematic diagram of the switching timing in the fourth type of isolated single-stage AC / DC converter provided in the embodiments of this application.

[0077] Figure 7 Continue with the exchange source V ac The following is an example of switching AC voltage from the positive half-cycle to the negative half-cycle.

[0078] Figure 7 In the provided embodiment, the freewheeling diode includes a first switching transistor Q. p1 Second switch Q p2 The high-frequency switching transistor includes the second switching transistor Q. p2 and the fourth switch Q p4 The normally open transistor in the blocking transistor includes the third switching transistor Q. p3 The high-frequency switching transistor in the blocking transistor includes the fourth switching transistor Q. p4 . Figure 7 The interval within the dashed box represents the transition freewheeling interval where the AC voltage of the AC source transitions from the positive half-cycle to the negative half-cycle.

[0079] Controller 40 is configured to switch the first transistor Q within a preset range when the AC voltage is at the zero-crossing point. p1 Normally on; at the third time t3, the fourth switch Q p4 The switch changes from on to off; at the fourth time t4, the second switch Q... p2 The switch changes from off to on; at the fifth moment t5, the third switch Q... p3 The transistor changes from being on to being off. The time interval between the third time t3 and the fourth time t4 is the period of the second switch Q. p2 and the fourth switch Q p4 Dead time when all are in a shutdown state.

[0080] Before the first moment t1, the fourth switch Q p4 Turn off, second switch Q p2 Conduction. To prevent a direct connection between the upper and lower bridge arms, the fourth switch Q... p4 A second switch Q is required p2After being turned off, it is turned on again. Therefore, controller 40 is configured so that at the first moment t1, the second switch Q... p2 The switch changes from on to off; at the second time t2, the fourth switch Q... p4 The circuit changes from off to on. To establish a freewheeling path for the negative current in the resonant cavity 20, the second switch Q needs to be turned on. p2 Similarly, to avoid a direct connection between the upper and lower bridge arms, the second switch Q... p2 The fourth switch Q needs to be used. p4 After being turned off, it is turned on again. Therefore, controller 40 is configured so that at the third time t3, the fourth switch Q is turned on. p4 The switch changes from on to off; at the fourth time t4, the second switch Q... p2 It changes from being off to being on.

[0081] To construct a freewheeling path for the forward current in resonant cavity 20, the third switch Q needs to be made... p3 The circuit remains on. Therefore, controller 40 is configured so that at time t5, the third switch Q remains on. p3 The circuit changes from on to off, so that during the time interval between the third time t3 and the fourth time t4, the forward current of the resonant cavity 20 can pass through the fourth switch Q. p4 Anti-parallel diode, third switch Q p3 The second capacitor C2 freewheels; the negative current of the resonant cavity 20 can pass through the first capacitor C1 and the second switch Q. p2 The anti-parallel diode and the first switching transistor Q p1 Freewheeling. After the fifth moment t5, both blocking transistors are turned off and both freewheeling transistors are turned on. Both the positive and negative currents of the resonant cavity 20 can pass through the first switching transistor Q. p1 Second switch Q p2 Continuous streaming.

[0082] The isolated single-stage AC / DC converter provided in this application embodiment controls the switching of multiple switching transistors according to a timing sequence. After all the freewheeling transistors are turned on, the normally-conducting transistor in the blocking transistor is turned off after a first preset time period. During the dead time, the freewheeling transistor and the normally-conducting transistor in the blocking transistor are turned on simultaneously, which can provide a freewheeling circuit for the positive current and the negative current of the resonant cavity, thus reducing the stress on the switching transistors.

[0083] In one possible implementation, in order to prevent the energy of the resonant cavity 20 from increasing during the dead time of the switching between the upper and lower bridge arms, the isolated single-stage AC / DC converter provided in this application embodiment is further configured to control the switching of the secondary circuit 30 to turn off within a preset range according to the turn-off time of the high-frequency switching transistor in the blocking transistor or the turn-off time of the normally-on transistor in the blocking transistor, thereby preventing the energy of the secondary circuit 30 from being transferred to the resonant cavity 20.

[0084] This application does not specifically limit the exact time when the switching transistor in the secondary circuit is turned off, as long as it can achieve the effect of preventing the energy transfer of the resonant cavity to the secondary circuit. For example, the switching transistor in the secondary circuit 30 can be turned off within a preset time before the turn-off time of the high-frequency switching transistor in the blocking transistor or within a preset time after the turn-off time of the high-frequency switching transistor in the blocking transistor, or it can be turned off within a preset time before the turn-off time of the normally-continuous transistor in the blocking transistor or within a preset time after the turn-off time of the normally-continuous transistor in the blocking transistor.

[0085] Based on any of the isolated single-stage AC / DC converters provided in the above embodiments, this application also provides a power supply device, which is an inverter, a charging pile, or an on-board charger, etc.

[0086] The power supply device provided in this application includes the isolated single-stage AC / DC converter and other components (such as AC switches, DC switches, etc.). It can provide a freewheeling path for both the positive and negative currents of the resonant cavity during the dead time of the switching between the upper and lower bridge arms. This enables a smooth transition of the isolated single-stage AC / DC converter from normal operation to zero-crossing freewheeling state, allowing the energy in the resonant cavity to decay to zero, reducing the stress on each switching transistor, and eliminating the need for additional hardware costs.

[0087] Based on the isolated single-stage AC / DC converter provided in the above embodiments, this application also provides a control method for the isolated single-stage AC / DC converter.

[0088] The control method for an isolated single-stage AC / DC converter provided in this application embodiment is applicable to any of the above-mentioned isolated single-stage AC / DC converters. The isolated single-stage AC / DC converter includes: a primary-side circuit, a resonant cavity, and a secondary-side circuit; the resonant cavity includes a resonant inductor, a resonant capacitor, and a transformer; the first terminal of the primary-side circuit is connected to an AC source, the second terminal of the primary-side circuit is connected to the first terminal of the resonant cavity, and the second terminal of the resonant cavity is connected to the secondary-side circuit; the primary-side circuit includes a bidirectional switching bridge arm, the upper bridge arm of which includes two switches connected in series, and the lower bridge arm of which includes two switches connected in series.

[0089] See Figure 8 The figure is a flowchart of the control method for the first isolated single-stage AC / DC converter provided in the embodiments of this application.

[0090] The method includes:

[0091] S901: When the AC voltage is within a preset range of zero crossing, at least one normally conducting transistor in the blocking transistor is turned off after all the freewheeling transistors are turned on, so that the current in the resonant cavity freewheels through the switching transistor or the anti-parallel diode of the switching transistor in both positive and negative directions; when the freewheeling transistor is the switching transistor of the upper bridge arm, the blocking transistor is the switching transistor of the lower bridge arm; when the freewheeling transistor is the switching transistor of the lower bridge arm, the blocking transistor is the switching transistor of the upper bridge arm.

[0092] For example, the controller determines whether the converter is within the preset range of the AC voltage zero-crossing point based on the AC voltage of the AC source. If the converter is within the preset range of the AC voltage zero-crossing point, the controller controls at least one normally open tube in the blocking tube to turn off after all the freewheeling tubes are turned on, so that the current in the resonant cavity can be freewheeled through the switching tube or the anti-parallel diode of the switching tube in both positive and negative directions.

[0093] The control method for an isolated single-stage AC / DC converter provided in this application involves controlling at least one normally-conducting transistor in the blocking transistors to turn off after all the freewheeling transistors are turned on, when the AC voltage is within a preset range of zero crossing. Since at least one normally-conducting transistor in the blocking transistors is on during the dead time, it can cooperate with the freewheeling transistors to allow the current in the resonant cavity to freewheel through the switching transistors or their anti-parallel diodes in both positive and negative directions. This method enables a smooth transition of the isolated single-stage AC / DC converter from normal operation to zero-crossing freewheeling state, allowing the energy in the resonant cavity to decay to zero and reducing the stress on each switching transistor.

[0094] In one possible implementation, the method further includes: within a preset range, controlling the switching transistor of the secondary circuit to turn off based on the turn-off time of the high-frequency switching transistor in the blocking transistor or the turn-off time of the normally-conducting transistor in the blocking transistor, thereby preventing the energy of the resonant cavity from being transferred to the secondary circuit.

[0095] Based on the isolated single-stage AC / DC converter provided in the above embodiments, this application also provides another control method for an isolated single-stage AC / DC converter. The control method for an isolated single-stage AC / DC converter provided in this application is applicable to any of the above-described isolated single-stage AC / DC converters. The isolated single-stage AC / DC converter includes: a primary-side circuit, a resonant cavity, and a secondary-side circuit; the resonant cavity includes a resonant inductor, a resonant capacitor, and a transformer; a first terminal of the primary-side circuit is connected to an AC source, a second terminal of the primary-side circuit is connected to the first terminal of the resonant cavity, and a second terminal of the resonant cavity is connected to the secondary-side circuit; the primary-side circuit includes a bidirectional switching bridge arm, the upper arm of which includes two switches connected in series, and the lower arm of which includes two switches connected in series.

[0096] The controller provided in this application embodiment may include software to implement the control methods described above. Alternatively, the controller provided in this application embodiment may include hardware to implement the control methods described above. Or, the controller provided in this application embodiment may include both software and hardware, using a combination of software and hardware to execute the control methods described above.

[0097] In one possible implementation, see Figure 9 This figure is a schematic diagram of a controller provided in an embodiment of this application.

[0098] The controller may include a memory 1011 and a processor 1012. The processor 1012 can be connected to the primary-side circuit and the secondary-side circuit, and can drive the various switching transistors in the primary-side circuit and the secondary-side circuit. The memory may be random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (Electronic Programmable ROM), registers, hard disk, removable disk, etc.

[0099] The memory 1011 can store computer instructions. When the computer instructions stored in the memory 1011 are executed by the processor 1012, the processor 1012 can be used to execute the control method of the isolated single-stage AC / DC converter. The memory 1011 can also store data, such as information like the dead time involved in the above embodiments.

[0100] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape) or a semiconductor medium (e.g., solid-state disk (SSD)).

[0101] This application also provides a readable storage medium for storing the methods provided in the above embodiments. Examples include random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (EPROM), registers, hard disks, removable disks, or any other form of storage medium in the art.

[0102] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0103] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An isolated single-stage AC / DC converter, characterized in that, include: Controller, primary circuit, resonant cavity, and secondary circuit; The first end of the primary circuit is used to connect to an AC source, the second end of the primary circuit is connected to the first end of the resonant cavity, and the second end of the resonant cavity is connected to the secondary circuit; the primary circuit includes a bidirectional switching bridge arm, the upper bridge arm of the bidirectional switching bridge arm includes two switching transistors connected in series, and the lower bridge arm of the bidirectional switching bridge arm includes two switching transistors connected in series. The controller is configured to, when the AC voltage is within a preset range of zero crossing points, control at least one normally conducting transistor in the blocking transistor to turn off after all the freewheeling transistors are turned on, so that the current in the resonant cavity, whether in the positive or negative direction, is freewheeled through the switching transistor or the anti-parallel diode of the switching transistor; when the freewheeling transistor is the switching transistor of the upper bridge arm, the blocking transistor is the switching transistor of the lower bridge arm; when the freewheeling transistor is the switching transistor of the lower bridge arm, the blocking transistor is the switching transistor of the upper bridge arm.

2. The converter according to claim 1, characterized in that, The primary-side circuit includes two bidirectional switch bridge arms connected in parallel, or the primary-side circuit includes one bidirectional switch bridge arm and one capacitor bridge arm. The secondary circuit includes a full-bridge circuit or a half-bridge circuit, and the secondary circuit includes a switching transistor.

3. The converter according to claim 2, characterized in that, When the primary-side circuit includes a first bidirectional switch bridge arm and a second bidirectional switch bridge arm connected in parallel, the upper bridge arm of the first bidirectional switch bridge arm includes a first switch and a second switch connected in series, and the lower bridge arm of the first bidirectional switch bridge arm includes a third switch and a fourth switch connected in series; the upper bridge arm of the second bidirectional switch bridge arm includes a fifth switch and a sixth switch connected in series, and the lower bridge arm of the second bidirectional switch bridge arm includes a seventh switch and an eighth switch connected in series. The freewheeling diode includes the first switching diode, the second switching diode, the fifth switching diode, and the sixth switching diode; the blocking diode includes the normally-continuous diode and the high-frequency switching diode; the normally-continuous diode in the blocking diode includes the third switching diode and the seventh switching diode; and the high-frequency switching diode in the blocking diode includes the fourth switching diode and the eighth switching diode.

4. The converter according to claim 2, characterized in that, When the primary-side circuit includes a first bidirectional switch bridge arm and a second bidirectional switch bridge arm connected in parallel, the upper bridge arm of the first bidirectional switch bridge arm includes a first switch and a second switch connected in series, and the lower bridge arm of the first bidirectional switch bridge arm includes a third switch and a fourth switch connected in series; the upper bridge arm of the second bidirectional switch bridge arm includes a fifth switch and a sixth switch connected in series, and the lower bridge arm of the second bidirectional switch bridge arm includes a seventh switch and an eighth switch connected in series. The freewheeling diode includes the third switch, the fourth switch, the seventh switch, and the eighth switch; the blocking diode includes the normally-continuous diode and the high-frequency switch; the normally-continuous diode in the blocking diode includes the first switch and the fifth switch; and the high-frequency switch in the blocking diode includes the second switch and the sixth switch.

5. The converter according to any one of claims 1-4, characterized in that, The controller is also configured to alternately control the switching transistor of the upper bridge arm and the switching transistor of the lower bridge arm as the freewheeling transistor within a preset range of different zero crossing points of the AC voltage.

6. The converter according to claim 3 or 4, characterized in that, The controller is further configured to control the switching transistor of the secondary circuit to turn off within the preset range, based on the turn-off time of the high-frequency switching transistor in the blocking transistor or the turn-off time of the normally-continuous transistor in the blocking transistor.

7. A power supply device, characterized in that, Includes the isolated single-stage AC / DC converter as described in any one of claims 1-6.

8. A control method for an isolated single-stage AC / DC converter, characterized in that, The converter includes: a primary-side circuit, a resonant cavity, and a secondary-side circuit; the primary-side circuit includes a bidirectional switching bridge arm, the upper bridge arm of the bidirectional switching bridge arm includes two switching transistors connected in series, and the lower bridge arm of the bidirectional switching bridge arm includes two switching transistors connected in series. The method includes: When the AC voltage is within a preset range of zero crossing, at least one normally conducting tube in the control blocking tube is turned off after all the freewheeling tubes are turned on, so that the current in the resonant cavity can be freewheeled through the switching tube or the anti-parallel diode of the switching tube in both positive and negative directions. When the freewheeling diode is the switching diode of the upper bridge arm, the blocking diode is the switching diode of the lower bridge arm; when the freewheeling diode is the switching diode of the lower bridge arm, the blocking diode is the switching diode of the upper bridge arm.

9. The method according to claim 8, characterized in that, Also includes: Within the preset range, the switching transistor of the secondary circuit is turned off according to the turn-off time of the high-frequency switching transistor in the blocking transistor or the turn-off time of the normally-continuous transistor in the blocking transistor.

10. A controller, characterized in that, Used to perform the method of claim 8 or 9.

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