DCDC circuit

Abstract

The DCDC circuit comprises a first switching tube, a second switching tube, an energy storage inductor and a switching circuit, the control ends of the first switch tube and the second switch tube receive control signals respectively, the first end of the first switch tube is connected with the second end of the second switch tube and the first end of the energy storage inductor, and the second end of the first switch tube is connected with the first end of the switching circuit. The second end of the energy storage inductor is connected with the second end of the switching circuit, the third end of the switching circuit is connected with the anode of the first power supply, the fourth end is connected with the anode of the second power supply, and the first end of the second switching tube is connected with the cathodes of the first power supply and the second power supply; when the switching circuit works in a first switching state, the DCDC circuit works as a BOOST circuit; and when the switching circuit works in a second switching state, the DCDC circuit works as a BUCK circuit. The DCDC circuit is low in device cost and simple and convenient in control process.

Description

Technical Field

[0001] The present invention relates to the field of converters, and more particularly to a DC-DC circuit. Background Art

[0002] Existing buck-boost circuits are generally as Figure 1 shown, which includes four (groups) of high-frequency switching transistors Q1 to Q4 and a storage inductor 1. By controlling the on-off combinations of different high-frequency switching transistors, the buck (BUCK) mode or the boost (BOOST) mode can be achieved. Therefore, it not only requires at least four high-frequency switching transistors, but also requires precise control of the timing of these four high-frequency switching transistors to prevent cross conduction in order to achieve the BUCK mode or the BOOST mode. Therefore, not only is the device cost high, but the control process is also complex. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a DC-DC circuit with low device cost and simple control process in view of the above-mentioned defects of the prior art.

[0004] The technical solution adopted by the present invention to solve its technical problems is to construct a DC-DC circuit, including: a first switching transistor, a second switching transistor, a storage inductor, and a switching circuit; the control terminals of the first switching transistor and the second switching transistor respectively receive control signals, the first end of the first switching transistor is connected to the second end of the second switching transistor and the first end of the storage inductor, the second end of the first switching transistor is connected to the first end of the switching circuit, the second end of the storage inductor is connected to the second end of the switching circuit, the third end of the switching circuit is connected to the positive pole of the first power supply, the fourth end is connected to the positive pole of the second power supply, and the first end of the second switching transistor is connected to the positive pole of the first power supply and the negative pole of the second power supply;

[0005] When the switching circuit operates in the first switching state, the second switching transistor serves as the main switching transistor, the first switching transistor serves as the freewheeling switching transistor, and the DC-DC circuit operates as a BOOST circuit;

[0006] When the switching circuit operates in the second switching state, the first switching transistor serves as the main switching transistor, the second switching transistor serves as the freewheeling switching transistor, and the DC-DC circuit operates as a BUCK circuit.

[0007] In the DC-DC circuit of the present invention, the switching circuit includes two-loop switching circuits. Among them, one-loop switching circuit includes a first switching device and a third switching device, the other-loop switching circuit includes a second switching device and a fourth switching device, or both the one-loop switching circuit and the other-loop switching circuit include single-pole single-throw relays.

[0008] In the DCDC circuit of the present invention, when the first loop switching circuit includes the first switching device and the third switching device, and the other loop switching circuit includes the second switching device and the fourth switching device, it specifically includes:

[0009] The first end of the first switching device is connected to the positive pole of the first power supply, the second end is connected to the second end of the energy storage inductor and the first end of the second switching device; the first end of the third switching device is connected to the positive pole of the first power supply, the second end is connected to the second end of the first switching tube and the first end of the fourth switching device; the second ends of the second switching tube and the fourth switching device are respectively connected to the positive pole of the second power supply;

[0010] When the switching circuit operates in the first switching state, the second switching tube serves as the main switching tube, the first switching tube serves as the freewheeling switching tube, and the DCDC circuit operates as a BOOST circuit, including: when the first switching device and the fourth switching device are turned on and the second switching tube serves as the main switching tube and is turned on, the DCDC circuit operates as a BOOST circuit in the inductor energy storage stage; when the first switching device and the fourth switching device are turned on and the first switching tube serves as the freewheeling switching tube and is turned on, the DCDC circuit operates as a BOOST circuit in the inductor freewheeling stage;

[0011] When the switching circuit operates in the second switching state, the first switching tube serves as the main switching tube, the second switching tube serves as the freewheeling switching tube, and the DCDC circuit operates as a BUCK circuit, including: when the second switching device and the third switching device are turned on and the first switching tube serves as the main switching tube and is turned on, the DCDC circuit operates as a BUCK circuit in the inductor energy storage stage; when the second switching device and the third switching device are turned on and the second switching tube serves as the freewheeling switching tube and is turned on, the DCDC circuit operates as a BUCK circuit in the inductor freewheeling stage.

[0012] In the DCDC circuit of the present invention, when the DCDC circuit operates as a BOOST circuit, the input-output voltage relationship is Vout / Vin = 1 / (1 - D1), where Vout represents the output voltage between the positive pole and the negative pole of the second power supply, Vin represents the input voltage between the positive pole and the negative pole of the first power supply, and D1 represents the duty cycle of the second switching tube;

[0013] When the DCDC circuit operates as a BUCK circuit, the relationship between the input and output voltages is Vout / Vin = D2, where Vout represents the output voltage between the positive and negative terminals of the second power supply, Vin represents the input voltage between the positive and negative terminals of the first power supply, and D2 represents the duty cycle of the first switching transistor.

[0014] In the DCDC circuit of the present invention, the first loop switching circuit further includes a first single-pole single-throw relay and a third single-pole single-throw relay, and the second loop switching circuit further includes a second single-pole single-throw relay and a fourth single-pole single-throw relay; the first single-pole single-throw relay is connected in parallel between the first and second ends of the first switching device, the second single-pole single-throw relay is connected in parallel between the first and second ends of the second switching device, the third single-pole single-throw relay is connected in parallel between the first and second ends of the third switching device, and the fourth single-pole single-throw relay is connected in parallel between the first and second ends of the fourth switching device; the single-pole single-throw relay is attracted when the corresponding switching device is turned on.

[0015] In the DCDC circuit of the present invention, the first loop switching circuit further includes a first single-pole double-throw relay, and the second loop switching circuit further includes a second single-pole double-throw relay; the moving contact of the first single-pole double-throw relay is connected to the second end of the first switching device, the first end of the second switching device, and the second end of the energy storage inductor, the first stationary contact of the first single-pole double-throw relay is connected to the positive terminal of the first power supply and the first stationary contact of the second single-pole double-throw relay, the second stationary contact of the first single-pole double-throw relay is connected to the positive terminal of the second power supply and the second stationary contact of the second single-pole double-throw relay, and the moving contact of the second single-pole double-throw relay is connected to the second end of the first switching transistor; the single-pole double-throw relay switches between the first and second stationary contacts when the corresponding switching device is turned on.

[0016] In the DCDC circuit of the present invention, the first switching device, the second switching device, and the fourth switching device are silicon controlled rectifier diodes, and the third switching device is a diode; or the first switching device, the second switching device, the third switching device, and the fourth switching device are all silicon controlled rectifier diodes;

[0017] The first end of the switching device is the anode of the diode, and the second end of the switching device is the cathode of the diode.

[0018] In the DCDC circuit of the present invention, the first switching device, the second switching device, the third switching device, and the fourth switching device are all switching transistors, and the control terminals of the switching transistors receive control signals; the first ends of the first switching device and the fourth switching device are the second ends of the switching transistors, and the second ends of the first switching device and the fourth switching device are the first ends of the switching transistors; the first ends of the second switching device and the third switching device are the first ends of the switching transistors, and the second ends of the second switching device and the third switching device are the second ends of the switching transistors.

[0019] In the DCDC circuit of the present invention, the two-loop switching circuit includes a first single-pole double-throw relay and a second single-pole double-throw relay;

[0020] The moving contact of the first single-pole double-throw relay is connected to the second end of the energy storage inductor, the first stationary contact is connected to the positive electrode of the second power supply, and the second stationary contact is connected to the positive electrode of the first power supply;

[0021] The moving contact of the second single-pole double-throw relay is connected to the second end of the first switching transistor, the second stationary contact is connected to the positive electrode of the second power supply, and the first stationary contact is connected to the positive electrode of the first power supply;

[0022] When the switching circuit operates in the first switching state, the second switching transistor serves as the main switching transistor, and the first switching transistor serves as the freewheeling switching transistor. The DCDC circuit operates as a BOOST circuit, including: when the moving contacts of the first single-pole double-throw relay and the second single-pole double-throw relay are both connected to their second stationary contacts and the second switching transistor serves as the main switching transistor and conducts, the DCDC circuit operates as a BOOST circuit in the inductor energy storage stage; when the moving contacts of the first single-pole double-throw relay and the second single-pole double-throw relay are both connected to their second stationary contacts and the first switching transistor serves as the freewheeling switching transistor and conducts, the DCDC circuit operates as a BOOST circuit in the inductor freewheeling stage;

[0023] When the switching circuit operates in the second switching state, the first switching transistor serves as the main switching transistor, and the second switching transistor serves as the freewheeling switching transistor. The DCDC circuit operates as a BUCK circuit, including: when the moving contacts of the first single-pole double-throw relay and the second single-pole double-throw relay are both connected to their first stationary contacts and the first switching transistor serves as the main switching transistor and conducts, the DCDC circuit operates as a BUCK circuit in the inductor energy storage stage; when the moving contacts of the first single-pole double-throw relay and the second single-pole double-throw relay are both connected to their first stationary contacts and the second switching transistor serves as the freewheeling switching transistor and conducts, the DCDC circuit operates as a BUCK circuit in the inductor freewheeling stage.

[0024] In the DCDC circuit of the present invention, when the DCDC circuit operates as a BOOST circuit, the input-output voltage relationship is Vout / Vin = 1 / (1 - D1), where Vout represents the output voltage between the positive and negative terminals of the second power supply, Vin represents the input voltage between the positive and negative terminals of the first power supply, and D1 represents the duty cycle of the second switching transistor;

[0025] When the DCDC circuit operates as a BUCK circuit, the input-output voltage relationship is Vout / Vin = D2, where Vout represents the output voltage between the positive and negative terminals of the second power supply, Vin represents the input voltage between the positive and negative terminals of the first power supply, and D2 represents the duty cycle of the first switching transistor.

[0026] Implementing the DCDC circuit of the present invention, a switching circuit is used to replace two high-frequency switching transistors in the existing design. When the switching circuit operates in the first switching state, the second switching transistor serves as the main switching transistor, and the first switching transistor serves as the freewheeling switching transistor, and the DCDC circuit operates as a BOOST circuit; when the switching circuit operates in the second switching state, the first switching transistor serves as the main switching transistor, and the second switching transistor serves as the freewheeling switching transistor, and the DCDC circuit operates as a BUCK circuit. Therefore, only by controlling the timing switching of the switching circuit and the two switching transistors can the BUCK mode or the BOOST mode be realized respectively. Therefore, the device cost is low, and at the same time, because the number of controlled switching transistors is reduced, the control instructions are reduced, and thus the control process is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0028] Figure 1 is the circuit diagram of a prior art BUCK-BOOST circuit;

[0029] Figure 2 is the principle block diagram of a preferred embodiment of the DCDC circuit of the present invention;

[0030] Figure 3 The circuit diagram of a preferred embodiment of the DCDC circuit of the present invention;

[0031] Figure 4 is Figure 3 the modal diagram when the DCDC circuit shown operates in the Ton inductor energy storage stage in the BOOST mode;

[0032] Figure 5 is Figure 3 the modal diagram when the DCDC circuit shown operates in the Toff inductor freewheeling mode in the BOOST mode;

[0033] Figure 6 is Figure 3 The modal diagram when the DCDC circuit shown operates in the Ton inductive energy storage stage in BUCK mode;

[0034] Figure 7 is Figure 3 The modal diagram when the DCDC circuit shown operates in the Toff inductive energy storage stage in BUCK mode;

[0035] Figure 8 The circuit diagram of another preferred embodiment of the DCDC circuit of the present invention;

[0036] Figure 9 The circuit diagram of another preferred embodiment of the DCDC circuit of the present invention;

[0037] Figure 10 The circuit diagram of another preferred embodiment of the DCDC circuit of the present invention;

[0038] Figure 11 The circuit diagram of another preferred embodiment of the DCDC circuit of the present invention;

[0039] Figure 12A The mode diagram when the DCDC circuit of another preferred embodiment of the present invention operates in BOOST mode;

[0040] Figure 12B The mode diagram when the DCDC circuit of another preferred embodiment of the present invention operates in BUCK mode. Specific embodiments

[0041] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention 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 invention and are not used to limit the present invention.

[0042] Figure 2 is the principle block diagram of a preferred embodiment of the DCDC circuit of the present invention. As Figure 2As shown, the DCDC circuit of the present invention includes: a first switching transistor Q1, a second switching transistor Q2, a storage inductor L, and a switching circuit 10; the control terminals of the first switching transistor Q1 and the second switching transistor Q2 respectively receive control signals, the first terminal of the first switching transistor Q1 is connected to the second terminal of the second switching transistor Q2 and the first terminal of the storage inductor L, the second terminal of the first switching transistor Q1 is connected to the first terminal C of the switching circuit 10, the second terminal of the storage inductor L is connected to the second terminal B of the switching circuit 10, the third terminal A of the switching circuit 10 is connected to the positive electrode of the first power supply, the fourth terminal D is connected to the positive electrode of the second power supply, and the first terminal of the second switching transistor Q2 is connected to the positive electrode of the first power supply and the negative electrode of the second power supply.

[0043] When the switching circuit 10 operates in the first switching state, the second switching transistor Q2 serves as the main switching transistor, the first switching transistor Q1 serves as the freewheeling switching transistor, and the DCDC circuit operates as a BOOST circuit. When the switching circuit 10 operates in the second switching state, the first switching transistor Q1 serves as the main switching transistor, the second switching transistor Q2 serves as the freewheeling switching transistor, and the DCDC circuit operates as a BUCK circuit.

[0044] In a preferred embodiment of the present invention, the switching circuit 10 can adopt any suitable switching devices and their combined structures, such as relays (such as single-pole single-throw relays, single-pole double-throw relays, double-pole double-throw relays, etc.), diodes (such as ordinary diodes, thyristor diodes), switching transistors (such as MOS transistors, IGBT transistors, triodes), etc.

[0045] In a preferred embodiment of the present invention, the switching circuit includes two-loop switching circuits. Among them, one-loop switching circuit includes a first switching device and a third switching device, and the other-loop switching circuit includes a second switching device and a fourth switching device, or both the one-loop switching circuit and the other-loop switching circuit include single-pole single-throw relays. In a further preferred embodiment of the present invention, the one-loop switching circuit further includes a first single-pole single-throw relay and a third single-pole single-throw relay, and the other-loop switching circuit further includes a second single-pole single-throw relay and a fourth single-pole single-throw relay; or the one-loop switching circuit further includes a first single-pole double-throw relay, and the other-loop switching circuit further includes a second single-pole double-throw relay.

[0046] In a preferred embodiment of the present invention, the switching circuit includes a first switching device, a second switching device, a third switching device, and a fourth switching device; a first end of the first switching device is connected to the positive electrode of the first power supply, a second end of the first switching device is connected to a second end of the energy storage inductor and a first end of the second switching device; a first end of the third switching device is connected to the positive electrode of the first power supply, a second end of the third switching device is connected to a second end of the first switching tube and a first end of the fourth switching device; second ends of the second switching tube and the fourth switching device are respectively connected to the positive electrode of the second power supply; when the switching circuit operates in a first switching state, the second switching tube serves as a main switching tube, the first switching tube serves as a freewheeling switching tube, and the DCDC circuit operates as a BOOST circuit, including: when the first switching device and the fourth switching device are turned on and the second switching tube serves as a main switching tube and is turned on, the DCDC circuit operates as a BOOST circuit in an inductor energy storage stage; when the first switching device and the fourth switching device are turned on and the first switching tube serves as a freewheeling switching tube and is turned on, the DCDC circuit operates as a BOOST circuit in an inductor freewheeling stage; when the switching circuit operates in a second switching state, the first switching tube serves as a main switching tube, the second switching tube serves as a freewheeling switching tube, and the DCDC circuit operates as a BUCK circuit, including: when the second switching device and the third switching device are turned on and the first switching tube serves as a main switching tube and is turned on, the DCDC circuit operates as a BUCK circuit in an inductor energy storage stage; when the second switching device and the third switching device are turned on and the second switching tube serves as a freewheeling switching tube and is turned on, the DCDC circuit operates as a BUCK circuit in an inductor freewheeling stage.

[0047] In another preferred embodiment of the present invention, the switching circuit includes a first single-pole double-throw relay and a second single-pole double-throw relay; the moving contact of the first single-pole double-throw relay is connected to the second end of the energy storage inductor, the first stationary contact is connected to the positive electrode of the second power supply, and the second stationary contact is connected to the positive electrode of the first power supply; the moving contact of the second single-pole double-throw relay is connected to the second end of the first switching tube, the second stationary contact is connected to the positive electrode of the second power supply, and the first stationary contact is connected to the positive electrode of the first power supply; when the switching circuit operates in the first switching state, the second switching tube serves as the main switching tube, the first switching tube serves as the freewheeling switching tube, and the DCDC circuit operates as a BOOST circuit, including: when the moving contacts of the first single-pole double-throw relay and the second single-pole double-throw relay are both connected to their second stationary contacts and the second switching tube serves as the main switching tube and conducts, the DCDC circuit operates as a BOOST circuit in the inductor energy storage stage; when the moving contacts of the first single-pole double-throw relay and the second single-pole double-throw relay are both connected to their second stationary contacts and the first switching tube serves as the freewheeling switching tube and conducts, the DCDC circuit operates as a BOOST circuit in the inductor freewheeling stage; when the switching circuit operates in the second switching state, the first switching tube serves as the main switching tube, the second switching tube serves as the freewheeling switching tube, and the DCDC circuit operates as a BUCK circuit, including: when the moving contacts of the first single-pole double-throw relay and the second single-pole double-throw relay are both connected to their first stationary contacts and the first switching tube serves as the main switching tube and conducts, the DCDC circuit operates as a BUCK circuit in the inductor energy storage stage; when the moving contacts of the first single-pole double-throw relay and the second single-pole double-throw relay are both connected to their first stationary contacts and the second switching tube serves as the freewheeling switching tube and conducts, the DCDC circuit operates as a BUCK circuit in the inductor freewheeling stage.

[0048] Implementing the DCDC circuit of the present invention, a switching circuit is used to replace two high-frequency switching tubes in the existing design. When the switching circuit operates in the first switching state, the second switching tube serves as the main switching tube, the first switching tube serves as the freewheeling switching tube, and the DCDC circuit operates as a BOOST circuit; when the switching circuit operates in the second switching state, the first switching tube serves as the main switching tube, the second switching tube serves as the freewheeling switching tube, and the DCDC circuit operates as a BUCK circuit. Therefore, only by controlling the timing switching of the switching circuit and the two switching tubes can the BUCK mode or the BOOST mode be realized respectively. Therefore, the device cost is low, and at the same time, because the number of controlled switching tubes is reduced, the control instructions are reduced, and thus the control process is simple.

[0049] Figure 3 Circuit diagram of a preferred embodiment of the DCDC circuit of the present invention. Combined Figures 2 - 3As shown in the figure, the DCDC circuit of the present invention includes: a first switching transistor Q1, a second switching transistor Q2, a storage inductor L, and a switching circuit 10; the control terminals of the first switching transistor Q1 and the second switching transistor Q2 respectively receive control signals, the first terminal of the first switching transistor Q1 is connected to the second terminal of the second switching transistor Q2 and the first terminal of the storage inductor L, the second terminal of the first switching transistor Q1 is connected to the first terminal C of the switching circuit 10, the second terminal of the storage inductor L is connected to the second terminal B of the switching circuit 10, the third terminal A of the switching circuit 10 is connected to the positive electrode of the first power supply, the fourth terminal D is connected to the positive electrode of the second power supply, and the first terminal of the second switching transistor Q2 is connected to the positive electrode of the first power supply and the negative electrode of the second power supply.

[0050] As Figure 3 shown, the switching circuit 10 includes a first switching device, a second switching device, a third switching device, and a fourth switching device. In Figure 3 the preferred embodiment shown, the first switching device, the second switching device, and the fourth switching device are respectively silicon controlled rectifier diodes D1, D2, and D4, and the third switching device is a diode D3. The first switching transistor Q1 and the second switching transistor are MOS transistors or IGBT transistors. The gate of the MOS transistor or the gate of the IGBT transistor receives the control signal. In this preferred embodiment, the first terminals of the first switching transistor Q1 and the second switching transistor Q2 are the drains of the MOS transistors, and the second terminals are the sources of the MOS transistors.

[0051] As Figure 3 shown, the anode of the silicon controlled rectifier diode D1 is connected to the positive electrode of the first power supply, the cathode is connected to the second terminal of the storage inductor L and the anode of the silicon controlled rectifier diode D2; the anode of the diode D3 is connected to the positive electrode of the first power supply, the cathode is connected to the source of the first switching transistor Q1 and the anode of the silicon controlled rectifier diode D4; the drain of the first switching transistor Q1 is connected to the first terminal of the storage inductor L and the source of the second switching transistor Q2, and the drain of the second switching transistor Q2 is connected to the negative electrode of the first power supply and the negative electrode of the second power supply. The cathodes of the silicon controlled rectifier diode D2 and the silicon controlled rectifier diode D4 are respectively connected to the positive electrode of the second power supply.

[0052] In Figure 3 the preferred embodiment shown, the DCDC circuit further includes an input capacitor C1 and an output capacitor C2. The input capacitor C1 is connected between the positive electrode of the first power supply and the negative electrode of the first power supply, and the output capacitor C2 is connected between the positive electrode of the second power supply and the negative electrode of the second power supply.

[0053] When the switching circuit 10 operates in the first switching state, the second switching transistor Q2 serves as the main switching transistor, the first switching transistor Q1 serves as the freewheeling switching transistor, and the DCDC circuit operates as a BOOST circuit, including: when the thyristor diode D1 and the thyristor diode D4 are conducting and the second switching transistor Q2 is conducting as the main switching transistor, the DCDC circuit operates as a BOOST circuit in the inductor energy storage stage; when the thyristor diode D1 and the thyristor diode D4 are conducting and the first switching transistor Q1 is conducting as the freewheeling switching transistor, the DCDC circuit operates as a BOOST circuit in the inductor freewheeling stage. When the switching circuit 10 operates in the second switching state, the first switching transistor Q1 serves as the main switching transistor, the second switching transistor Q2 serves as the freewheeling switching transistor, and the DCDC circuit operates as a BUCK circuit, including: when the thyristor diode D2 and the diode D3 are conducting and the first switching transistor Q1 is conducting as the main switching transistor, the DCDC circuit operates as a BUCK circuit in the inductor energy storage stage; when the thyristor diode D2 and the diode D3 are conducting and the second switching transistor Q2 is conducting as the freewheeling switching transistor, the DCDC circuit operates as a BUCK circuit in the inductor freewheeling stage.

[0054] When the DCDC circuit operates as a BOOST circuit, the input-output voltage relationship is Vout / Vin = 1 / (1 - D1), where Vout represents the output voltage between the positive and negative terminals of the second power supply, Vin represents the input voltage between the positive and negative terminals of the first power supply, and D1 represents the duty cycle of the second switching transistor Q2; when the DCDC circuit operates as a BUCK circuit, the input-output voltage relationship is Vout / Vin = D2, where Vout represents the output voltage between the positive and negative terminals of the second power supply, Vin represents the input voltage between the positive and negative terminals of the first power supply, and D2 represents the duty cycle of the first switching transistor Q1.

[0055] Figure 4 is Figure 3 The modal diagram when the shown DCDC circuit operates in the Ton inductor energy storage stage in the BOOST mode. Figure 5 is Figure 3 The modal diagram when the shown DCDC circuit operates in the Toff inductor freewheeling mode in the BOOST mode. Figure 6 is Figure 3 The modal diagram when the shown DCDC circuit operates in the Ton inductor energy storage stage in the BUCK mode. Figure 7 is Figure 3 The modal diagram when the shown DCDC circuit operates in the Toff inductor energy storage stage in the BUCK mode. The following will be combined with Figures 3 - 7The principle of the DCDC circuit of the present invention is described as follows.

[0056] As Figure 4 shown, when the silicon-controlled diode D1 and the silicon-controlled diode D4 are turned on and the second switching transistor Q2 is turned on as the main switching transistor, the current flows from the positive pole of the first power supply through the silicon-controlled diode D1 and the second switching transistor Q2 in the forward direction through the energy storage inductor L. The energy storage inductor stores energy, and the DCDC circuit operates as a BOOST circuit in the Ton inductor energy storage stage. As Figure 5 shown, when the silicon-controlled diode D1 and the silicon-controlled diode D4 are turned on and the first switching transistor Q1 is turned on as the freewheeling switching transistor, the energy storage inductor L freewheels in the forward direction. The freewheeling current reaches the positive pole of the second power supply through the first switching transistor Q1 and the silicon-controlled diode D2. The DCDC circuit operates as a BOOST circuit in the Toff inductor freewheeling stage. At this time, if the duty ratio of the second switching transistor Q2 is D1, then the input-output voltage relationship is Vout / Vin = 1 / (1 - D1), where Vout represents the output voltage between the positive pole and the negative pole of the second power supply, Vin represents the input voltage between the positive pole and the negative pole of the first power supply, and D1 represents the duty ratio of the second switching transistor Q2.

[0057] As Figure 6 shown, when the silicon-controlled diode D2 and the diode D3 are turned on and the first switching transistor Q1 is turned on as the main switching transistor, the current flows from the positive pole of the first power supply through the diode D3 and the first switching transistor Q1 in the forward direction through the energy storage inductor L. The energy storage inductor stores energy, and the DCDC circuit operates as a BUCK circuit in the Ton inductor energy storage stage. As Figure 7 shown, when the silicon-controlled diode D2 and the diode D3 are turned on and the second switching transistor Q2 is turned on as the freewheeling switching transistor, the energy storage inductor L freewheels in the forward direction. The freewheeling current reaches the positive pole of the second power supply through the second switching transistor Q2 and the silicon-controlled diode D2. The DCDC circuit operates as a BUCK circuit in the Toff inductor freewheeling stage. At this time, if the duty ratio of the first switching transistor Q1 is D2, then the input-output voltage relationship is Vout / Vin = D2, where Vout represents the output voltage between the positive pole and the negative pole of the second power supply, Vin represents the input voltage between the positive pole and the negative pole of the first power supply, and D2 represents the duty ratio of the first switching transistor Q1.

[0058] To implement the DCDC circuit of the present invention, a switching circuit is used to replace two high-frequency switching transistors in the existing design. When the switching circuit operates in the first switching state, the second switching transistor serves as the main switching transistor, and the first switching transistor serves as the freewheeling switching transistor, and the DCDC circuit operates as a BOOST circuit; when the switching circuit operates in the second switching state, the first switching transistor serves as the main switching transistor, and the second switching transistor serves as the freewheeling switching transistor, and the DCDC circuit operates as a BUCK circuit. Therefore, only by controlling the timing switching of the switching circuit and the two switching transistors can the BUCK mode or the BOOST mode be respectively achieved. Therefore, the circuit structure is simple, the device cost is low, and the control process is simple.

[0059] Figure 8 It is a circuit diagram of another preferred embodiment of the DCDC circuit of the present invention. Figure 8 The illustrated embodiment is similar to Figure 3 the illustrated embodiment, and the only difference is that, in Figure 8 the illustrated preferred embodiment, the first switching device, the second switching device, the third switching device, and the fourth switching device are respectively thyristor diodes D1 to D4, and its principle is the same as Figure 3 that, and will not be elaborated here.

[0060] Figure 9 It is a circuit diagram of another preferred embodiment of the DCDC circuit of the present invention. Figure 9 The illustrated embodiment is similar to Figure 3 the illustrated embodiment, and the only difference is that the first switching device, the second switching device, the third switching device, and the fourth switching device are respectively constructed by switching transistors, and the DCDC circuit further includes filter inductors L1, L2 and filter capacitors C3, C4. As described above, when using switching transistors, the first ends of the first switching device and the fourth switching device are the second ends of the switching transistors, and the second ends of the first switching device and the fourth switching device are the first ends of the switching transistors; the first ends of the second switching device and the third switching device are the first ends of the switching transistors, and the second ends of the second switching device and the third switching device are the second ends of the switching transistors.

[0061] That is, the first switching device and the fourth switching device are in the same direction, the second switching device and the third switching device are in the same direction, while the first switching device and the third switching device are in the opposite direction, and the second switching device and the fourth switching device are in the opposite direction.

[0062] That is, as Figure 9 shown, in Figure 9In the preferred embodiment shown, the first switching device, the second switching device, the third switching device, and the fourth switching device are MOS transistors Q1, MOS transistor Q2, MOS transistor Q3, and MOS transistor Q4, respectively. As Figure 9 shown, the gates of the MOS transistors Q1, Q2, Q3, and Q4 receive control signals. The drain of the MOS transistor Q1 is connected to the second end of the energy storage inductor and the drain of the MOS transistor Q2. The source of the MOS transistor Q1 and the drain of the MOS transistor Q3 are connected to the positive pole of the first power supply through the filter inductor L1. The source of the MOS transistor Q3 is connected to the source of the main switching transistor Q5 and the source of the MOS transistor Q2. The source of the MOS transistor Q2 and the drain of the MOS transistor Q4 are connected to the positive pole of the second power supply through the filter inductor L2. The first end of the filter capacitor C3 is connected to the source of the MOS transistor Q1 and the drain of the MOS transistor Q3, and the second end is connected to the negative pole of the first power supply. The first end of the filter capacitor C4 is connected to the source of the MOS transistor Q2 and the drain of the MOS transistor Q4, and the second end is connected to the negative pole of the second power supply.

[0063] In Figure 9 the preferred embodiment shown, the switching circuit is constructed with MOS transistors, so it can work bidirectionally, that is, the voltage can be output from the positive pole and negative pole of the first power supply to the positive pole and negative pole of the second power supply, or from the positive pole and negative pole of the second power supply to the positive pole and negative pole of the first power supply. The process and principle are similar to those of the Figure 3 embodiment shown, and will not be repeated here.

[0064] Figure 10 is the circuit diagram of another preferred embodiment of the DCDC circuit of the present invention. Figure 9 The embodiment shown is similar to the Figure 8 embodiment shown. The difference is only that the switching circuit 10 further includes a single-pole single-throw relay S1, a single-pole single-throw relay S2, a single-pole single-throw relay S3, and a single-pole single-throw relay S4. The single-pole single-throw relay S1 is connected in parallel between the anode and cathode of the thyristor diode D1. The single-pole single-throw relay S2 is connected in parallel between the anode and cathode of the thyristor diode D2. The single-pole single-throw relay S3 is connected in parallel between the anode and cathode of the thyristor diode D3. The single-pole single-throw relay S4 is connected in parallel between the anode and cathode of the thyristor diode D4. The single-pole single-throw relay is attracted when the corresponding thyristor diode conducts, thereby reducing the conduction loss.

[0065] Figure 11 is the circuit diagram of another preferred embodiment of the DCDC circuit of the present invention. Figure 11 The embodiment shown is similar to the Figure 10The illustrated embodiment is similar, except that the switching circuit 10 uses two single-pole double-throw relays instead of Figure 10 the four single-pole single-throw relays in. As Figure 11 shown, the switching circuit 10 further includes a single-pole double-throw relay S1 and a single-pole double-throw relay S2; the moving contact of the single-pole double-throw relay S1 is connected to the cathode of the thyristor diode D1, the anode of the thyristor diode D2, and the second end of the energy storage inductor L, the first stationary contact of the single-pole double-throw relay S1 is connected to the positive pole of the first power supply, the anode of the thyristor diode D1, the anode of the thyristor diode D3, and the first stationary contact of the single-pole double-throw relay S2, the second stationary contact of the single-pole double-throw relay S1 is connected to the positive pole of the second power supply and the second stationary contact of the single-pole double-throw relay S2, and the moving contact of the single-pole double-throw relay S2 is connected to the second end of the first switching transistor Q1. When the corresponding thyristor diodes are turned on, the single-pole double-throw relays S1 to S2 switch between the first stationary contact and the second stationary contact, thereby reducing the conduction loss. The principle is similar to that of the Figure 10 illustrated embodiment, and will not be elaborated here.

[0066] Figure 12A FIG. is the mode diagram of the DCDC circuit of another preferred embodiment of the present invention operating in the BOOST mode. Figure 12B FIG. is the mode diagram of the DCDC circuit of another preferred embodiment of the present invention operating in the BUCK mode. In Figures 12A - 12B the illustrated preferred embodiment, the DCDC circuit of the present invention includes: a first switching transistor Q1, a second switching transistor Q2, an energy storage inductor L, and a switching circuit 10; the control terminals of the first switching transistor Q1 and the second switching transistor Q2 respectively receive control signals, the first end of the first switching transistor Q1 is connected to the second end of the second switching transistor Q2 and the first end of the energy storage inductor L, the second end of the first switching transistor Q1 is connected to the first end C of the switching circuit 10, the second end of the energy storage inductor L is connected to the second end B of the switching circuit 10, the third end A of the switching circuit 10 is connected to the positive pole of the first power supply, the fourth end D is connected to the positive pole of the second power supply, and the first end of the second switching transistor Q2 is connected to the positive pole of the first power supply and the negative pole of the second power supply.

[0067] As Figures 12A - 12B shown, the switching circuit 10 includes a single-pole double-throw relay S1 and a single-pole double-throw relay S2. The moving contact of the single-pole double-throw relay S1 is connected to the second end of the energy storage inductor L, the first stationary contact is connected to the positive pole of the second power supply, and the second stationary contact is connected to the positive pole of the first power supply; the moving contact of the single-pole double-throw relay S2 is connected to the second end of the first switching transistor Q1, the second stationary contact is connected to the positive pole of the second power supply, and the first stationary contact is connected to the positive pole of the first power supply.

[0068] When the switching circuit 10 operates in the first switching state, the second switching transistor Q2 serves as the main switching transistor, the first switching transistor Q1 serves as the freewheeling switching transistor, and the DCDC circuit operates as a BOOST circuit; when the switching circuit 10 operates in the second switching state, the first switching transistor Q1 serves as the main switching transistor, the second switching transistor Q2 serves as the freewheeling switching transistor, and the DCDC circuit operates as a BUCK circuit.

[0069] Its specific principle is the same as that of Figure 3 the shown DCDC circuit. Specifically, as Figure 12A shown, when the moving contacts of the single-pole double-throw relay S1 and the single-pole double-throw relay S2 are both connected to their second stationary contacts and the second switching transistor Q2 serves as the main switching transistor and conducts, the DCDC circuit operates as a BOOST circuit in the inductor energy storage stage; when the moving contacts of the single-pole double-throw relay S1 and the single-pole double-throw relay S2 are both connected to their second stationary contacts and the first switching transistor Q1 serves as the freewheeling switching transistor and conducts, the DCDC circuit operates as a BOOST circuit in the inductor freewheeling stage.

[0070] As Figure 12B shown, when the moving contacts of the single-pole double-throw relay S1 and the single-pole double-throw relay S2 are both connected to their first stationary contacts and the first switching transistor Q1 serves as the main switching transistor and conducts, the DCDC circuit operates as a BUCK circuit in the inductor energy storage stage; when the moving contacts of the single-pole double-throw relay S1 and the single-pole double-throw relay S2 are both connected to their first stationary contacts and the second switching transistor Q2 serves as the freewheeling switching transistor and conducts, the DCDC circuit operates as a BUCK circuit in the inductor freewheeling stage.

[0071] As described above, when the DCDC circuit operates as a BOOST circuit, the input-output voltage relationship is Vout / Vin = 1 / (1 - D1), where Vout represents the output voltage between the positive electrode and the negative electrode of the second power supply, Vin represents the input voltage between the positive electrode and the negative electrode of the first power supply, and D1 represents the duty cycle of the second switching transistor Q2; when the DCDC circuit operates as a BUCK circuit, the input-output voltage relationship is Vout / Vin = D2, where Vout represents the output voltage between the positive electrode and the negative electrode of the second power supply, Vin represents the input voltage between the positive electrode and the negative electrode of the first power supply, and D2 represents the duty cycle of the first switching transistor Q1.

[0072] In this preferred embodiment, only two relays and two switching tubes are used to respectively implement the BUCK mode or the BOOST mode. Therefore, the circuit structure is simpler, the device cost is lower, and the control process is more convenient.

[0073] For the DCDC circuit implementing the present invention, a switching circuit is used to replace the two high-frequency switching tubes in the existing design. When the switching circuit operates in the first switching state, the second switching tube serves as the main switching tube, and the first switching tube serves as the freewheeling switching tube, and the DCDC circuit operates as a BOOST circuit; when the switching circuit operates in the second switching state, the first switching tube serves as the main switching tube, and the second switching tube serves as the freewheeling switching tube, and the DCDC circuit operates as a BUCK circuit. Therefore, only by controlling the timing switching of the switching circuit and the two switching tubes can the BUCK mode or the BOOST mode be respectively implemented. Therefore, the device cost is low, and at the same time, since the number of controlled switching tubes is reduced, the control instructions are reduced, thus making the control process simple.

[0074] Although the present invention is illustrated by specific embodiments, those skilled in the art should understand that various transformations and equivalent substitutions can be made to the present invention without departing from the scope of the present invention. Additionally, various modifications can be made to the present invention for specific situations or materials without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims of the present invention.

[0075] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A DCDC circuit, characterized in that: include: A first switch tube, a second switch tube, an energy storage inductor and a switching circuit; the control ends of the first switch tube and the second switch tube receive control signals respectively, the first end of the first switch tube is connected to the second end of the second switch tube and the first end of the energy storage inductor, the second end of the first switch tube is connected to the first end of the switching circuit, the second end of the energy storage inductor is connected to the second end of the switching circuit, the third end of the switching circuit is connected to the positive electrode of the first power supply, the fourth end is connected to the positive electrode of the second power supply, and the first end of the second switch tube is connected to the positive electrode of the first power supply and the negative electrode of the second power supply; When the switching circuit works in the first switching state, the second switch tube serves as the main switch tube, the first switch tube serves as the freewheeling switch tube, and the DCDC circuit works as a BOOST circuit; When the switching circuit operates in the second switching state, the first switch tube serves as a main switch tube, the second switch tube serves as a freewheeling switch tube, and the DCDC circuit operates as a BUCK circuit.

2. The DCDC circuit according to claim 1, characterized in that: The switching circuit includes two-loop switch circuits; wherein one loop switch circuit includes a first switch device and a third switch device, and the other loop switch circuit includes a second switch device and a fourth switch device; or one loop switch circuit and the other loop switch circuit both include a single-pole single-throw relay.

3. The DCDC circuit according to claim 2, characterized in that: When the one-loop switch circuit includes the first switch device and the third switch device, and the other-loop switch circuit includes the second switch device and the fourth switch device, the method specifically includes: The first end of the first switch device is connected to the positive electrode of the first power supply, and the second end is connected to the second end of the energy storage inductor and the first end of the second switch device; the first end of the third switch device is connected to the positive electrode of the first power supply, and the second end is connected to the second end of the first switch tube and the first end of the fourth switch device; the second end of the second switch tube and the second end of the fourth switch device are respectively connected to the positive electrode of the second power supply; When the switching circuit works in the first switching state, the second switch tube serves as the main switch tube, the first switch tube serves as the freewheeling switch tube, and the DCDC circuit works as a BOOST circuit, including: when the first switch device and the fourth switch device are turned on and the second switch tube serves as the main switch tube, the DCDC circuit works in the inductive energy storage stage as a BOOST circuit; when the first switch device and the fourth switch device are turned on and the first switch tube serves as the freewheeling switch tube, the DCDC circuit works in the inductive freewheeling stage as a BOOST circuit; When the switching circuit operates in the second switching state, the first switch tube serves as the main switch tube, the second switch tube serves as the freewheeling switch tube, and the DCDC circuit operates as a BUCK circuit, including: when the second switch device and the third switch device are turned on and the first switch tube is turned on as the main switch tube, the DCDC circuit operates in the inductive energy storage stage as a BUCK circuit; when the second switch device and the third switch device are turned on and the second switch tube is turned on as the freewheeling switch tube, the DCDC circuit operates in the inductive freewheeling stage as a BUCK circuit.

4. The DCDC circuit according to claim 2, characterized in that: When the DCDC circuit works as a BOOST circuit, the input-output voltage relationship is Vout / Vin=1 / (1-D1), where Vout represents the output voltage between the positive electrode of the second power supply and the negative electrode of the second power supply, Vin represents the input voltage between the positive electrode of the first power supply and the negative electrode of the first power supply, and D1 represents the duty cycle of the second switch tube; When the DCDC circuit works as a BUCK circuit, the input-output voltage relationship is Vout / Vin=D2, where Vout represents the output voltage between the positive electrode of the second power supply and the negative electrode of the second power supply, Vin represents the input voltage between the positive electrode of the first power supply and the negative electrode of the first power supply, and D2 represents the duty cycle of the first switch tube.

5. The DCDC circuit according to claim 3, characterized in that: The one-loop switch circuit further includes a first single-pole single-throw relay and a third single-pole single-throw relay, and the other-loop switch circuit further includes a second single-pole single-throw relay and a fourth single-pole single-throw relay; the first single-pole single-throw relay is connected in parallel between the first end and the second end of the first switch device, the second single-pole single-throw relay is connected in parallel between the first end and the second end of the second switch device, the third single-pole single-throw relay is connected in parallel between the first end and the second end of the third switch device, and the fourth single-pole single-throw relay is connected in parallel between the first end and the second end of the fourth switch device; the single-pole single-throw relay is energized when the corresponding switch device is turned on.

6. The DCDC circuit according to claim 3, characterized in that: The one-loop switch circuit further includes a first single-pole double-throw relay, and the other-loop switch circuit further includes a second single-pole double-throw relay; the moving contact of the first single-pole double-throw relay is connected to the second end of the first switching device, the first end of the second switching device and the second end of the energy storage inductor, the first static contact of the first single-pole double-throw relay is connected to the positive electrode of the first power supply and the first static contact of the second single-pole double-throw relay, the second static contact of the first single-pole double-throw relay is connected to the positive electrode of the second power supply and the second static contact of the second single-pole double-throw relay, and the moving contact of the second single-pole double-throw relay is connected to the second end of the first switch tube; when the corresponding switching device is turned on, the single-pole double-throw relay switches between the first static contact and the second static contact.

7. The DCDC circuit according to any one of claims 2 to 6, characterized in that: The first switch device, the second switch device and the fourth switch device are thyristor diodes, and the third switch device is a diode; or the first switch device, the second switch device, the third switch device and the fourth switch device are all thyristor diodes; The first end of the switch device is the anode of the diode, and the second end of the switch device is the cathode of the diode.

8. The DCDC circuit according to any one of claims 2 to 6, characterized in that: The first switch device, the second switch device, the third switch device and the fourth switch device are all switch tubes, and the control end of the switch tube receives a control signal; the first end of the first switch device and the fourth switch device is the second end of the switch tube, and the second end of the first switch device and the fourth switch device is the first end of the switch tube; the first end of the second switch device and the third switch device is the first end of the switch tube, and the second end of the second switch device and the third switch device is the second end of the switch tube.

9. The DCDC circuit according to claim 2, characterized in that: The two-loop switch circuit includes a first single-pole double-throw relay and a second single-pole double-throw relay; The moving contact of the first single-pole double-throw relay is connected to the second end of the energy storage inductor, the first static contact is connected to the positive electrode of the second power supply, and the second static contact is connected to the positive electrode of the first power supply; The moving contact of the second single-pole double-throw relay is connected to the second end of the first switch tube, the second static contact is connected to the positive electrode of the second power supply, and the first static contact is connected to the positive electrode of the first power supply; When the switching circuit works in the first switching state, the second switch tube serves as the main switch tube, the first switch tube serves as the freewheeling switch tube, and the DCDC circuit works as a BOOST circuit, including: when the moving contacts of the first single-pole double-throw relay and the second single-pole double-throw relay are both connected to their second static contacts and the second switch tube is turned on as the main switch tube, the DCDC circuit works in the inductive energy storage stage as a BOOST circuit; when the moving contacts of the first single-pole double-throw relay and the second single-pole double-throw relay are both connected to their second static contacts and the first switch tube is turned on as the freewheeling switch tube, the DCDC circuit works in the inductive freewheeling stage as a BOOST circuit; When the switching circuit operates in the second switching state, the first switch tube serves as the main switch tube, the second switch tube serves as the freewheeling switch tube, and the DCDC circuit operates as a BUCK circuit, including: when the moving contacts of the first single-pole double-throw relay and the second single-pole double-throw relay are both connected to their first static contacts and the first switch tube is turned on as the main switch tube, the DCDC circuit operates in the inductive energy storage stage as a BUCK circuit; when the moving contacts of the first single-pole double-throw relay and the second single-pole double-throw relay are both connected to their first static contacts and the second switch tube is turned on as the freewheeling switch tube, the DCDC circuit operates in the inductive freewheeling stage as a BUCK circuit.

10. The DCDC circuit according to claim 9, characterized in that: When the DCDC circuit works as a BOOST circuit, the input-output voltage relationship is Vout / Vin=1 / (1-D1), where Vout represents the output voltage between the positive electrode of the second power supply and the negative electrode of the second power supply, Vin represents the input voltage between the positive electrode of the first power supply and the negative electrode of the first power supply, and D1 represents the duty cycle of the second switch tube; When the DCDC circuit works as a BUCK circuit, the input-output voltage relationship is Vout / Vin=D2, where Vout represents the output voltage between the positive electrode of the second power supply and the negative electrode of the second power supply, Vin represents the input voltage between the positive electrode of the first power supply and the negative electrode of the first power supply, and D2 represents the duty cycle of the first switch tube.

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