Series-parallel switching Buck circuit based on adjustable staggered phase-shifting three levels and method of series-parallel switching Buck circuit

Abstract

The invention relates to the technical field of power electronic application, in particular to a series-parallel connection switching Buck circuit based on adjustable staggered phase-shifting three levels and a method of the series-parallel connection switching Buck circuit. According to the circuit, series-parallel connection switching of two Buck circuits is achieved through three switches, each Buck circuit uses two IGBT switch tubes and one fly-wheel diode, the switching frequency can be equivalently improved in two working modes, therefore, current ripples are reduced, the dynamic response is improved, and the size of a filter element is reduced; the two IGBT switching tubes used by the two Buck circuits are subjected to phase interleaving control, so that current ripples are partially offset, the equivalent ripple frequency is doubled, and the problem of meeting the scene requirement of constant power output in a wide voltage range of the charger under the condition of low-voltage large-current output is solved.

Description

Technical Field

[0001] The present application relates to the technical field of power electronics applications, and in particular, to a series-parallel switching Buck circuit and method based on adjustable interleaved phase-shifted three-level Background Art

[0002] The three-level Buck circuit is a DC-DC buck converter that can convert the input high-voltage DC signal into a low-voltage DC signal. The three-level Buck circuit usually consists of a switching tube, an inductor, a freewheeling diode, and a load. Through the coordinated operation of the switching tube, inductor, and diode, the DC buck is efficiently achieved. The output DC current of the related three-level Buck circuit is restricted by the current-carrying capacity of its switching device and output inductor, and the external characterization is a constant current source characteristic. On the premise that the circuit topology remains unchanged, its working mode is fixed, and it cannot solve the problem of enabling the circuit to switch between series and parallel working modes without changing the circuit topology; in addition, its maximum output power is only positively correlated with the voltage, and it cannot achieve low-voltage and large-current output, thus unable to meet the scenario requirements of constant power output in a wide voltage range of the charger. Summary of the Invention

[0003] To overcome the problems existing in the related art, an embodiment of the present application provides a series-parallel switching Buck circuit and method based on adjustable interleaved phase-shifted three-level to solve the problem of meeting the scenario requirements of constant power output in a wide voltage range of the charger under the condition of low-voltage and large-current output.

[0004] The series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level provided by the embodiment of the present application includes:

[0005] A first Buck circuit, including a first capacitor, a first switch controller, a first coupled inductor, a first freewheeling diode, and a load. The first end of the first capacitor is connected to the first end of the first switch controller. The second end of the first capacitor is connected to the input end of the first freewheeling diode and the negative electrode side of the DC output of the load. The second end of the first switch control is connected to the output end of the first freewheeling diode and the same-name end of the first coupled inductor. The non-same-name end of the first coupled inductor is connected to the positive electrode side of the DC output of the load. The first coupled inductor and the load are connected in series and then connected in parallel with the first freewheeling diode. The first switch controller includes a first switching tube and a first auxiliary switching tube;

[0006] The second Buck circuit includes a second capacitor, a second switch controller, a second coupled inductor, and a second freewheeling diode. The first end of the second capacitor is connected to the positive electrode side of the DC output of the load and the output end of the second freewheeling diode. The negative electrode side of the DC output of the load is connected to the same-name end of the second coupled inductor. The second end of the second capacitor is connected to the second end of the second switch controller. The first end of the second switch controller is connected to the input end of the second freewheeling diode and the non-same-name end of the second coupled inductor. The second coupled inductor and the load are connected in series and then connected in parallel with the second freewheeling diode. The second switch controller includes a second switch tube and a second auxiliary switch tube;

[0007] A first switch for controlling the series connection of the first capacitor and the second capacitor is provided between the first capacitor and the second capacitor;

[0008] A second switch is directly provided between the second end of the first capacitor and the negative electrode side of the DC output of the load;

[0009] A third switch is provided between the first end of the second capacitor and the positive electrode side of the DC output of the load.

[0010] Further, when the first switch is closed and the second switch and the third switch are open, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in the series operation mode, and the duty cycle range of the series operation mode is 0 - 100%; when the first switch is open and the second switch and the third switch are closed, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in the parallel operation mode, and the duty cycle range of the parallel operation mode is 0 - 50%.

[0011] Further, when the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in the series operation mode, the first switch tube and the first auxiliary switch tube are synchronously turned on, the second switch tube and the second auxiliary switch tube are synchronously turned on, and at least one of the first switch tube and the first auxiliary switch tube is phase-shifted 180 degrees from at least one of the second switch tube and the second auxiliary switch tube.

[0012] Further, when the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in the parallel operation mode, the first switch tube and the first auxiliary switch tube are turned on with a 180-degree phase difference, the second switch tube and the second auxiliary switch tube are turned on with a 180-degree phase difference, and the first switch tube is synchronous with the second switch tube, and the first auxiliary switch tube is synchronous with the second auxiliary switch tube.

[0013] On the other hand, an embodiment of the present application provides a series-parallel switching method applied to the above-mentioned series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level. The method includes:

[0014] Determine the operating mode of the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level according to the closed states of the first switch, the second switch, and the third switch;

[0015] Perform interleaved phase-shift control on the first switch controller and the second switch controller according to the operating mode.

[0016] Further, performing interleaved phase-shift control on the first switch controller and the second switch controller according to the operating mode includes:

[0017] If the operating mode is the series operating mode, control is performed according to the rule that the first switch tube and the first auxiliary switch tube are turned on synchronously, the second switch tube and the second auxiliary switch tube are turned on synchronously, and at least one of the first switch tube and the first auxiliary switch tube is phase-shifted by 180 degrees from at least one of the second switch tube and the second auxiliary switch tube;

[0018] If the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in the parallel operating mode, control is performed according to the rule that the first switch tube and the first auxiliary switch tube are turned on with a 180-degree phase shift, the second switch tube and the second auxiliary switch tube are turned on with a 180-degree phase shift, and the first switch tube is synchronous with the second switch tube, and the first auxiliary switch tube is synchronous with the second auxiliary switch tube.

[0019] Further, determining the operating mode of the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level according to the closed states of the first switch, the second switch, and the third switch includes:

[0020] When the first switch is closed and the second switch and the third switch are open, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in the series operating mode, and the duty cycle range of the series operating mode is 0 - 100%;

[0021] When the first switch is open and the second switch and the third switch are closed, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in the parallel operating mode, and the duty cycle range of the parallel operating mode is 0 - 50%.

[0022] Advantages of this application: By controlling the three switches set in the two Buck circuits, the series-parallel switching of the bridge arm is realized on the premise of keeping the circuit topology unchanged; at the same time, since two switch tubes are connected in parallel in both Buck circuits, by interleaved control of the four switch tubes, the switching frequency and inductance in the two operating modes can be improved, thus solving the problem of meeting the scene requirements of constant power output in the wide voltage range of the charger in the case of low-voltage and large-current output.

[0023] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. Description of the Drawings

[0024] The drawings herein are incorporated into and form a part of the specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0025] Figure 1 It is a circuit diagram provided by an embodiment of the present application based on a series-parallel switching Buck circuit with adjustable interleaved phase-shifted three-level;

[0026] Figure 2 It is a circuit diagram of the series operation mode provided by an embodiment of the present application based on a series-parallel switching Buck circuit with adjustable interleaved phase-shifted three-level;

[0027] Figure 3 It is a schematic diagram of the driving waveform logic of the series operation mode provided by an embodiment of the present application based on a series-parallel switching Buck circuit with adjustable interleaved phase-shifted three-level;

[0028] Figure 4 It is a schematic diagram of the commutation loop with a duty cycle less than 50% in the series operation mode provided by an embodiment of the present application based on a series-parallel switching Buck circuit with adjustable interleaved phase-shifted three-level;

[0029] Figure 5 It is a schematic diagram of the commutation loop with a duty cycle greater than 50% in the series operation mode provided by an embodiment of the present application based on a series-parallel switching Buck circuit with adjustable interleaved phase-shifted three-level;

[0030] Figure 6 It is a schematic diagram of the current waveform on the resistor in the series operation mode provided by an embodiment of the present application based on a series-parallel switching Buck circuit with adjustable interleaved phase-shifted three-level;

[0031] Figure 7 It is a circuit diagram of the parallel operation mode provided by an embodiment of the present application based on a series-parallel switching Buck circuit with adjustable interleaved phase-shifted three-level;

[0032] Figure 8 It is a schematic diagram of the driving waveform logic of the parallel operation mode provided by an embodiment of the present application based on a series-parallel switching Buck circuit with adjustable interleaved phase-shifted three-level;

[0033] Figure 9 It is a schematic diagram of the commutation loop of the parallel operation mode provided by an embodiment of the present application based on a series-parallel switching Buck circuit with adjustable interleaved phase-shifted three-level;

[0034] Figure 10 It is a schematic diagram of the current waveform on the resistor in the parallel operation mode provided by an embodiment of the present application based on a series-parallel switching Buck circuit with adjustable interleaved phase-shifted three-level;

[0035] Figure 11 It is a schematic flowchart of an embodiment of the series - parallel switching method of the present application. Detailed implementation manners

[0036] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0037] It should be noted that although the functional modules are divided in the device schematic diagram and the logical sequence is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order from the module division in the device or the sequence in the flowchart.

[0038] Figure 1 It is a circuit diagram provided by an embodiment of the series - parallel switching Buck circuit based on adjustable interleaved phase - shifted three - level of the present application. The circuit includes a first Buck circuit and a second Buck circuit. Among them, the first Buck circuit includes a first capacitor C1, a first switch controller, a first coupled inductor L1, a first free - wheeling diode D1 and a load. The first end of the first capacitor C1 is connected to the first end of the first switch controller. The second end of the first capacitor C1 is connected to the input end of the first free - wheeling diode D1 and the negative electrode side of the DC output of the load. The second end of the first switch control is connected to the output end of the first free - wheeling diode D1 and the same - name end of the first coupled inductor L1. The non - same - name end of the first coupled inductor L1 is connected to the positive electrode side of the DC output of the load. The first coupled inductor L1 and the load are connected in series and then in parallel with the first free - wheeling diode D1. The first switch controller includes a first switch tube S1 and a first auxiliary switch tube S2; the second Buck circuit includes a second capacitor C2, a second switch controller, a second coupled inductor L2, a second free - wheeling diode D2. The first end of the second capacitor C2 is connected to the positive electrode side of the DC output of the load and the output end of the second free - wheeling diode D2. The negative electrode side of the DC output of the load is connected to the same - name end of the second coupled inductor L2. The second end of the second capacitor C2 is connected to the second end of the second switch controller. The first end of the second switch controller is connected to the input end of the second free - wheeling diode D2 and the non - same - name end of the second coupled inductor L2. The second coupled inductor L2 and the load are connected in series and then in parallel with the second free - wheeling diode D2. The second switch controller includes a second switch tube S3 and a second auxiliary switch tube S4; a first switch KM1 for controlling their series connection is arranged between the first capacitor C1 and the second capacitor C2; a second switch KM2 is arranged between the second end of the first capacitor C1 and the negative electrode side of the DC output of the load; a third switch KM3 is arranged between the first end of the second capacitor C2 and the positive electrode side of the DC output of the load. S1 - S4 are IGBTs.

[0039] Specifically, when KM1 is closed and KM2 and KM3 are opened, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level of the present application is in Figure 2 the series operating mode shown, that is, the series connection of the first Buck circuit and the second Buck circuit is realized. The wave generation logic of the series operating mode is: the first switching tube and the first auxiliary switching tube are synchronously turned on, the second switching tube and the second auxiliary switching tube are synchronously turned on, and at least one of the first switching tube and the first auxiliary switching tube is phase-shifted by 180 degrees interleaved with at least one of the second switching tube and the second auxiliary switching tube. As Figure 3 shown, the wave generation logic is that S1 and S2 are synchronously turned on, S3 and S4 are synchronously turned on, S1 and S2 are phase-shifted by 180 degrees interleaved with S3 and S4 (duty cycle control range 0-100%), its switching frequency is f, then the inductor current ripple frequency is 2f. Assuming that the single-sided inductance of the reactor is m, and the series inductance of the inductor L is 2m.

[0040] When the duty cycle is less than 50%, S1, S2 and S3, S4 are alternately turned on, and the commutation circuits of the switching states of S1, S2, S3, S4 being 1100, 0000 and 0011 are respectively as Figure 4 shown in the left, middle and right in, and the output is 3 levels ( ). When the duty cycle is greater than 50%, S1 and S2, S3 and S4 are alternately turned on, and the commutation circuits of the switching states of S1, S2, S3, S4 being 1100, 1111 and 0011 are respectively as Figure 5 shown in the left, middle and right in, and the output is 3 levels ( ). Through the analysis of Figure 4 and Figure 5 , it can be known that the current ripple frequency on the inductor is 2f (f is the switching frequency), the two windings of the reactor are in series. Assuming that the current flowing through the reactor is , the number of turns of each coil of the reactor is N (ignoring the leakage magnetic flux of the reactor), the magnetomotive force of the reactor core is: , and the current waveform flowing through the reactor is as Figure 6 .

[0041] Specifically, when KM1 is opened and KM2 and KM3 are closed, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level of the present application is in Figure 7 the parallel operating mode shown, that is, the parallel connection of the first Buck circuit and the second Buck circuit is realized. The wave generation logic of the parallel operating mode is: the first switching tube and the first auxiliary switching tube are phase-shifted by 180 degrees to conduct, the second switching tube and the second auxiliary switching tube are phase-shifted by 180 degrees to conduct, and the first switching tube is synchronous with the second switching tube, and the first auxiliary switching tube is synchronous with the second auxiliary switching tube. As Figure 8As shown, S1 and S2 conduct alternately with a 180-degree phase shift, S3 and S4 conduct alternately with a 180-degree phase shift, S1 and S3 conduct synchronously, S2 and S4 conduct synchronously, and the duty cycle is 0 - 50%. In the parallel operation mode: if the switching frequency is f, the inductor ripple frequency in the parallel state is still 2f. Since S1 and S3 conduct synchronously, the change trends of the parallel currents flowing through the two sets of coils of the reactor are the same. The superimposed changing magnetic fluxes induced in the reactor core ensure that the inductance of the single-sided reactor is 2m, thus ensuring that the ripple current on the reactor is the same as that in the series operation condition. When the switching states of S1, S2, S3, and S4 are 1010, 0000, and 0101, the commutation circuits are respectively as shown in Figure 9 the left, middle, and right in the figure, and the output is three-level ( ). Thus, the current ripple frequency on the inductor is 2f (f is the switching frequency). The reactor (i.e., the coupling capacitor) is composed of two windings in parallel. Assuming that the currents flowing through the two windings of the reactor are respectively and , the two-winding currents are made consistent through current closed-loop control, that is: (ignoring the leakage flux of the reactor), and the magnetomotive force of the reactor core is: , and the current waveform flowing through the reactor is as shown in Figure 10 . Therefore, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level provided in this application can be controlled with reference to Table 1 below. In this application, both the first Buck circuit and the second Buck circuit use two IGBT switching tubes, which can not only equivalently increase the switching frequency in two working modes, thereby reducing the current ripple and improving the dynamic response, but also reduce the volume of the filtering components. For the phase interleaved control of S1, S2, S3, and S4, the phase difference of 180° is superimposed at the output end. Due to the phase interleaving, the current ripple is partially cancelled, making the equivalent ripple frequency double (2f). Since the frequency is increased, the change rate of the inductor current is faster, and the ripple is smaller under the same inductor value. If the same ripple is maintained, the inductor can be reduced by about 50%, improving the power density.

[0042] Table 1 - Switching Conduction Comparison Relationship in Series-Parallel Working Modes

[0043]

[0044] Figure 11 is a method applied to the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level provided in the above embodiment. As shown in the figure, the method includes step S101 and step S102.

[0045] Step S101: Determine the working mode of the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level by controlling the first switch, the second switch, and the third switch;

[0046] Step S102: Perform interleaved phase-shift control on the first switch controller and the second switch controller according to the working mode.

[0047] Specifically, the closed states of the first switch, the second switch, and the third switch include: the first switch is closed and the second switch and the third switch are open; the first switch is open and the second switch and the third switch are closed.

[0048] In the embodiment of the present application, by controlling the first switch, the second switch, and the third switch to perform series-parallel switching, low-voltage and high-current output can be achieved through series-parallel switching, and a wide-range constant power range can be realized.

[0049] In some embodiments, step S102 further includes: if the working mode is a series working mode, then control is performed according to the rule that the first switching tube and the first auxiliary switching tube are synchronously turned on, the second switching tube and the second auxiliary switching tube are synchronously turned on, and at least one of the first switching tube and the first auxiliary switching tube is phase-shifted by 180 degrees interleaved with at least one of the second switching tube and the second auxiliary switching tube; if the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in a parallel working mode, then control is performed according to the rule that the first switching tube and the first auxiliary switching tube are turned on with a 180-degree interleaving, the second switching tube and the second auxiliary switching tube are turned on with a 180-degree interleaving, and the first switching tube is synchronized with the second switching tube, and the first auxiliary switching tube is synchronized with the second auxiliary switching tube.

[0050] In some embodiments, step S101 further includes: when the first switch is closed and the second switch and the third switch are open, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in a series working mode, and the duty cycle range of the series working mode is 0-100%; when the first switch is open and the second switch and the third switch are closed, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in a parallel working mode, and the duty cycle range of the parallel working mode is 0-50%.

[0051] The above is a specific description of the preferred embodiment of the present application, but the present application is not limited to the above embodiments. Those skilled in the art can also make various equivalent deformations or substitutions without departing from the spirit of the present application, and these equivalent deformations or substitutions are all included in the scope defined by the claims of the present application.

Claims

1. A series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level, characterized in that: include: A first Buck circuit includes a first capacitor, a first switch controller, a first coupling inductor, a first freewheeling diode and a load, wherein a first end of the first capacitor is connected to a first end of the first switch controller, a second end of the first capacitor is connected to an input end of the first freewheeling diode and a negative electrode side of a DC output of the load, a second end of the first switch controller is connected to an output end of the first freewheeling diode and a same-name end of the first coupling inductor, a non-same-name end of the first coupling inductor is connected to a positive electrode side of a DC output of the load, the first coupling inductor and the load are connected in series and then connected in parallel with the first freewheeling diode, and the first switch controller includes a first switch tube and a first auxiliary switch tube; A second Buck circuit includes a second capacitor, a second switch controller, a second coupling inductor, and a second freewheeling diode, wherein a first end of the second capacitor is connected to a DC output positive electrode side of the load and an output end of the second freewheeling diode, a DC output negative electrode side of the load is connected to a same-name end of the second coupling inductor, a second end of the second capacitor is connected to a second end of the second switch controller, a first end of the second switch controller is connected to an input end of the second freewheeling diode and a non-same-name end of the second coupling inductor, the second coupling inductor is connected in series with the load and then connected in parallel with the second freewheeling diode, and the second switch controller includes a second switch tube and a second auxiliary switch tube; A first switch is provided between the first capacitor and the second capacitor to control the two to be connected in series; A second switch is directly disposed between the second end of the first capacitor and the DC output negative electrode side of the load; A third switch is provided between the first end of the second capacitor and the DC output positive electrode side of the load.

2. The Buck circuit based on adjustable interleaved phase shifting three-level series-parallel switching according to claim 1 is characterized in that: When the first switch is closed and the second switch and the third switch are opened, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in a series operation mode, and the duty cycle range of the series operation mode is 0-100%; When the first switch is opened and the second switch and the third switch are closed, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in a parallel working mode, and the duty cycle range of the parallel working mode is 0-50%.

3. The Buck circuit based on adjustable interleaved phase shifting three-level series-parallel switching according to claim 2 is characterized in that: The wave generation logic of the series working mode is: the first switch tube and the first auxiliary switch tube are turned on synchronously, the second switch tube and the second auxiliary switch tube are turned on synchronously, and at least one of the first switch tube and the first auxiliary switch tube is staggered with at least one of the second switch tube and the second auxiliary switch tube by 180 degrees.

4. The series-parallel switching Buck circuit based on adjustable interleaved phase shifting three-level according to claim 2 is characterized in that: When the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in the parallel working mode, the first switch tube and the first auxiliary switch tube are turned on 180 degrees staggered, the second switch tube and the second auxiliary switch tube are turned on 180 degrees staggered, and the first switch tube is synchronized with the second switch tube, and the first auxiliary switch tube is synchronized with the second auxiliary switch tube.

5. A series-parallel switching method, characterized in that: The method applied to the adjustable interleaved phase-shifted three-level series-parallel switching Buck circuit according to any one of claims 1 to 4 comprises: Determine the working mode of the adjustable interleaved phase-shifted three-level series-parallel switching Buck circuit according to the closed states of the first switch, the second switch and the third switch; The first switch controller and the second switch controller are subjected to staggered phase shift control according to the working mode.

6. The method according to claim 5, characterized in that The interleaving phase-shifting control of the first switch controller and the second switch controller according to the working mode includes: If the working mode is the series working mode, the control is performed according to the rule that the first switch tube and the first subsidiary switch tube are synchronously turned on, the second switch tube and the second subsidiary switch tube are synchronously turned on, and at least one of the first switch tube and the first subsidiary switch tube is staggered with at least one of the second switch tube and the second subsidiary switch tube by 180 degrees; If the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in the parallel working mode, it is controlled according to the rule that the first switch tube and the first auxiliary switch tube are turned on 180 degrees staggered, the second switch tube and the second auxiliary switch tube are turned on 180 degrees staggered, and the first switch tube is synchronized with the second switch tube, and the first auxiliary switch tube is synchronized with the second auxiliary switch tube.

7. The method according to claim 5, characterized in that The step of determining the operating mode of the adjustable interleaved phase-shifted three-level series-parallel switching Buck circuit according to the closed states of the first switch, the second switch, and the third switch includes: When the first switch is closed and the second switch and the third switch are opened, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in a series operation mode, and the duty cycle range of the series operation mode is 0-100%; When the first switch is opened and the second switch and the third switch are closed, the series-parallel switching Buck circuit based on adjustable interleaved phase-shifted three-level is in a parallel working mode, and the duty cycle range of the parallel working mode is 0-50%.

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