A method for improving LLC reverse gain with center-tapped transformer based on external phase shift

Abstract

The present invention relates to the technical field of converters, and discloses a method for boosting the reverse gain of a center-tapped transformer LLC based on external phase shift. This gain boosting method is implemented through the primary circuit of the transformer and the secondary circuit of the transformer. The primary circuit includes the first winding N of the transformer P1 and the leakage inductance L of the first winding K1 , the second primary winding N P2 and the leakage inductance L of the second winding K2 , the power transistor Q1 and its internal diode and parasitic capacitance, the power transistor Q2 and its internal diode and parasitic capacitance, the input capacitor C in and the DC voltage source U in ; the secondary circuit includes the secondary winding N of the transformer s , the resonant capacitor C r . The method for boosting the reverse gain of a center-tapped transformer LLC based on external phase shift according to the present invention can not only solve the problem that the converter cannot meet the gain requirement in a specific occasion, but also achieve soft switching, ensure high gain and high efficiency at the same time. Compared with the existing methods for boosting the reverse gain, the control of this solution is simple and does not require frequency conversion adjustment.

Description

Technical Field

[0001] The invention relates to the technical field of converters, in particular to an LLC reverse gain enhancement method with a center-tapped transformer based on external phase shift. Background Art

[0002] LLC resonant converter is widely used in the field of battery energy storage due to its soft switching, high efficiency and bidirectional operation in the full load range. However, in actual operation, the transformer leakage inductance cannot be ignored, resulting in a voltage drop in the leakage inductance, which leads to a decrease in the gain of LLC in reverse operation at the open-loop resonance point. At present, there are several methods for improving the reverse operation gain of LLC with a center-tapped transformer: (1) Control the turn-on timing of the power tube after the resonant current is too negative, so that the resonant tank stores energy to improve the gain. However, this method will increase the stress of the power tube and is not suitable for high-power occasions. (2) The overlapping duty cycle method is used in the output full-bridge measurement. In a certain period of time, the upper tube or the lower tube of the two bridge arms is turned on at the same time, so that the resonant tank stores energy to improve the gain. However, this method cannot achieve soft switching in the full load, so the efficiency is not high; therefore, there is an urgent need for a reverse gain improvement method of LLC with a center-tapped transformer based on external phase shift to solve the above technical problems. Summary of the invention

[0003] The object of the present invention is to provide a method for increasing the reverse gain of a center-tapped LLC transformer based on external phase shifting. The method for increasing the gain is implemented by a primary circuit of the transformer and a secondary circuit of the transformer. The primary circuit includes a first winding N of the transformer. P1 And the first winding leakage inductance L K1 , the primary second winding N P2 And the second winding leakage inductance L K2 , power tube Q 1 Its internal diode and parasitic capacitance, power tube Q 2 And the internal diode and parasitic capacitance, input capacitance C in and DC voltage source U in ; The secondary circuit includes the secondary winding N of the transformer s , resonant capacitor C r , resonant inductor L r , magnetizing inductance L m , and full bridge circuit (Q 3 ~Q 6 ), filter capacitor C o and load R o The LLC reverse gain enhancement method with a center-tapped transformer based on external phase shifting comprises the following steps:

[0004] Step 1: The external phase shift control signal of the present invention, Q 2 , Q 3 , Q6 After the tubes are turned on together for T(1-d) / 2 time, Q 2 Tube shut off;

[0005] Step 2: After a short dead time, turn on Q 1 Tube, Q 1 Tube and Q 3 Tube, Q 6 The tubes are turned on together for Td / 2 time and then turned off Q 3 Tube and Q 6 Tube;

[0006] Step 3: After a short dead time, turn on Q 4 Tube and Q 5 Tube, Q 1 Tube and Q 4 Tube, Q 5 After the tubes are turned on together for T(1-d) / 2 time, Q 1 Tube shut off;

[0007] Step 4: After a short dead time, Q 2 Tube opened, Q 2 Tube and Q 4 Tube, Q 5 After the tubes are turned on for Td time, Q 4 Tube and Q 5 Tube shut off;

[0008] Step 5: After a short dead time, turn on Q 3 Tube and Q 6 Tube, at this time Q 2 Tube, Q 3 Tube and Q 6 The tube is turned on and return to step 1.

[0009] Preferably, the primary circuit connection relationship is: power tube Q 1 The drain and input DC source U in The negative terminal and input capacitor C in The negative pole of the power tube Q 1 The drain of the first winding is connected to the leakage inductance, the other end of the leakage inductance is connected to the same-name end of the first winding, and the opposite-name end of the first winding and the same-name end of the second winding are connected to the input DC source U in The positive terminal and input capacitor C in The positive pole is connected.

[0010] Preferably, the power tube Q 2 The drain and input DC source U in The negative terminal and input capacitor C in The negative pole of the power tube Q 2The drain is connected to the leakage inductance of the second winding, and the other end of the leakage inductance is connected to the opposite end of the second winding.

[0011] Preferably, the secondary circuit connection is as follows: the secondary winding N of the transformer s The same-name terminal and the resonant capacitor C r and resonant inductor L r Connect the power tube Q in series 3 source and Q 4 The drain of the transformer secondary winding N s The opposite end of the power tube Q 5 The source and power tube Q 6 The drain is connected.

[0012] Preferably, the excitation inductance L m Connected in parallel to the secondary winding N s At both ends, the power tube Q 3 and Q 5 The source of the input capacitor is connected to the positive terminal of the load resistor R o The upper end is connected to the power tube Q 4 and Q 6 The source of the input capacitor is connected to the negative terminal of the input capacitor, and the load resistor R o The lower end is connected.

[0013] Compared with the prior art, the present invention has the following beneficial effects: the LLC reverse gain enhancement method with a center-tapped transformer based on external phase shifting can not only solve the problem that the converter cannot meet the gain requirements in specific occasions, but also realize soft switching, ensuring high gain while achieving high efficiency. Compared with the existing method for enhancing reverse gain, this scheme is simple to control and does not require frequency conversion adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0015] Figure 1 It is the LLC reverse topology diagram of the present invention;

[0016] Figure 2 This is the LLC external phase shift timing diagram of the present invention;

[0017] Figure 3 This is a simulation diagram of LLC external phase shift of the present invention. DETAILED DESCRIPTION

[0018] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should also be noted that, for ease of description, only the parts related to the invention are shown in the accompanying drawings. The different types of section lines in the drawings in the embodiments of the present invention are not marked according to the national standard, nor are there any requirements for the materials of the components, but are used to distinguish the cross-sectional views of the components in the drawings.

[0019] See also Figure 1-3 A method for increasing the reverse gain of a center-tapped LLC transformer based on external phase shifting is implemented by a transformer primary circuit and a transformer secondary circuit. The primary circuit includes a transformer first winding N P1 And the first winding leakage inductance L K1 , the primary second winding N P2 And the second winding leakage inductance L K2 , power tube Q 1 Its internal diode and parasitic capacitance, power tube Q 2 And the internal diode and parasitic capacitance, input capacitance C in and DC voltage source U in ; The secondary circuit includes the secondary winding N of the transformer s , resonant capacitor C r , resonant inductor L r , magnetizing inductance L m , and full bridge circuit (Q 3 ~Q 6 ), filter capacitor C o and load R o The LLC reverse gain enhancement method with a center-tapped transformer based on external phase shifting comprises the following steps:

[0020] Step 1: The external phase shift control signal of the present invention, Q 2 , Q 3 , Q 6 After the tubes are turned on together for T(1-d) / 2 time, Q 2 Tube shut off;

[0021] Step 2: After a short dead time, turn on Q 1 Tube, Q 1 Tube and Q 3 Tube, Q 6 The tubes are turned on together for Td / 2 time and then turned off Q 3 Tube and Q 6 Tube;

[0022] Step 3: After a short dead time, turn on Q 4 Tube and Q 5 Tube, Q 1 Tube and Q4 Tube, Q 5 After the tubes are turned on together for T(1-d) / 2 time, Q 1 Tube shut off;

[0023] Step 4: After a short dead time, Q 2 Tube opened, Q 2 Tube and Q 4 Tube, Q 5 After the tubes are turned on for Td time, Q 4 Tube and Q 5 Tube shut off;

[0024] Step 5: After a short dead time, turn on Q 3 Tube and Q 6 Tube, at this time Q 2 Tube, Q 3 Tube and Q 6 The tube is turned on and return to step 1.

[0025] Among them, the connection relationship of the primary circuit is: power tube Q 1 The drain and input DC source U in The negative terminal and input capacitor C in The negative pole of the power tube Q 1 The drain of the first winding is connected to the leakage inductance, the other end of the leakage inductance is connected to the same-name end of the first winding, and the opposite-name end of the first winding and the same-name end of the second winding are connected to the input DC source U in The positive terminal and input capacitor C in The positive pole is connected.

[0026] Among them, the power tube Q 2 The drain and input DC source U in The negative terminal and input capacitor C in The negative pole of the power tube Q 2 The drain is connected to the leakage inductance of the second winding, and the other end of the leakage inductance is connected to the opposite end of the second winding.

[0027] Among them, the secondary circuit connection is: the secondary winding N of the transformer s The same-name terminal and the resonant capacitor C r and resonant inductor L r Connect the power tube Q in series 3 the source and Q 4 The drain of the transformer secondary winding N s The opposite end of the power tube Q 5 The source and power tube Q 6 The drain is connected.

[0028] Among them, the excitation inductance L m Connected in parallel to the secondary winding N sAt both ends, the power tube Q 3 and Q 5 The source of the input capacitor is connected to the positive terminal of the load resistor R o The upper end of the power tube Q 4 and Q 6 The source of the input capacitor is connected to the negative terminal of the input capacitor, and the load resistor R o The lower end is connected.

[0029] It should be noted that the LLC topology is Figure 1 As shown, it includes a transformer primary circuit and a transformer secondary circuit. The primary circuit includes the transformer first winding N P1 And the first winding leakage inductance L K1 , the primary second winding N P2 And the second winding leakage inductance L K2 , power tube Q 1 Its internal diode and parasitic capacitance, power tube Q 2 And the internal diode and parasitic capacitance, input capacitance C in and DC voltage source U in The connection relationship of the primary circuit is: Power tube Q 1 The drain and input DC source U in The negative terminal and input capacitor C in The negative pole of the power tube Q 1 The drain of the first winding is connected to the leakage inductance, the other end of the leakage inductance is connected to the same-name end of the first winding, and the opposite-name end of the first winding and the same-name end of the second winding are connected to the input DC source U in The positive terminal and input capacitor C in The positive pole of the power tube Q 2 The drain and input DC source U in The negative terminal and input capacitor C in The negative pole of the power tube Q 2 The drain is connected to the leakage inductance of the second winding, and the other end of the leakage inductance is connected to the opposite end of the second winding. The secondary circuit includes a transformer secondary winding N s , resonant capacitor C r , resonant inductor L r , magnetizing inductance L m , and full bridge circuit (Q 3 ~Q 6 ), filter capacitor C o and load R o The secondary circuit connection is: the secondary winding N s The same-name terminal and the resonant capacitor C r and resonant inductor L r Connect the power tube Q in series 3 the source and Q 4 The drain of the transformer secondary winding Ns The opposite end of the power tube Q 5 The source and power tube Q 6 The drain of the excitation inductor L m Connected in parallel to the secondary winding N s Both ends. Power tube Q 3 and Q 5 The source of the input capacitor is connected to the positive terminal of the load resistor R o The upper end of the power tube Q 4 and Q 6 The source of the input capacitor is connected to the negative terminal of the input capacitor, and the load resistor R o The external phase shift control signal of the present invention, i.e. the switching timing is: ①Q 2 , Q 3 , Q 6 After the tubes are turned on together for T(1-d) / 2 time, Q 2 ②Tube is turned off; ②After a short dead time, Q is turned on 1 Tube, Q 1 Tube and Q 3 Tube, Q 6 The tubes are turned on together for Td / 2 time and then turned off Q 3 Tube and Q 6 ③ After a short dead time, open Q 4 Tube and Q 5 Tube, Q 1 Tube and Q 4 Tube, Q 5 After the tubes are turned on together for T(1-d) / 2 time, Q 1 4. After a short dead time, Q 2 Tube opened, Q 2 Tube and Q 4 Tube, Q 5 After the tubes are turned on for Td time, Q 4 Tube and Q 5 5. After a short dead time, turn on Q 3 Tube and Q 6 Tube, at this time Q 2 Tube, Q 3 Tube and Q 6 The tube is turned on and the process returns to step ①. The detailed power tube timing diagram is as follows: Figure 2 The main boost principle of this method is to store energy in the resonant tank at the input end during the phase shift period to achieve boost. The specific simulation waveform is shown in Figure 3The simulation parameters are: phase shift angle 5% (d=0.05T), switching frequency 300kHz, input voltage 3.2V, output voltage 40.9V, transformer turns ratio 1:1:12, resonant inductance 2.5uH, resonant capacitance 99.9nF, excitation inductance 25.2uH, and total power 200W.

[0030] The contents not described in detail in this specification belong to the prior art known to professionals in this field.

[0031] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in this application (but not limited to) by each other.

Claims

1. A method for increasing the reverse gain of a center-tapped LLC transformer based on external phase shifting, wherein the method is implemented by a transformer primary circuit and a transformer secondary circuit, wherein the primary circuit includes a transformer first winding N P1 And the first winding leakage inductance L K1 , the primary second winding N P2 and the second winding leakage inductance L K2 , power tube Q1 and its internal diode and parasitic capacitance, power tube Q2 and its internal diode and parasitic capacitance, input capacitor C in and DC voltage source U in ; The secondary circuit includes the secondary winding N of the transformer s , resonant capacitor C r , resonant inductor L r , magnetizing inductance L m , and full bridge circuit Q3, Q4, Q5, Q6, output capacitor C o and load R o The source of the power tube Q1 is connected to the negative electrode of the input DC source Uin, the negative electrode of the input capacitor Cin, and the source of the power tube Q2. The drain of the power tube Q1 is connected to the first winding N p1 The source of the power tube Q2 is connected to the negative electrode of the input DC source Uin, the negative electrode of the input capacitor Cin, and the source of the power tube Q1. The drain of the power tube Q2 is connected to the second winding N p2 The leakage inductance is connected, the same-name end of the secondary winding Ns of the transformer is connected in series with the resonant capacitor Cr and the resonant inductor Lr to the source of the power tube Q3 and the drain of Q4, the opposite-name end of the secondary winding Ns of the transformer is connected to the source of the power tube Q5 and the drain of the power tube Q6, the drains of the power tubes Q3 and Q5 are connected to the positive electrode of the output capacitor and the positive electrode of the load resistor Ro, the sources of the power tubes Q4 and Q6 are connected to the negative electrode of the output capacitor and the negative electrode of the load resistor Ro, the excitation inductor L m Connected in parallel to the secondary winding N s At both ends, the drains of the power tubes Q3 and Q5 are connected to the positive electrode of the output capacitor and the upper end of the load resistor Ro, the sources of the power tubes Q4 and Q6 are connected to the negative electrode of the output capacitor and the lower end of the load resistor Ro, the positive electrode of the input capacitor Cin is connected to the positive electrode of the input DC source Uin and the center tap of the primary winding of the transformer, the negative electrode of the input capacitor Cin is connected to the negative electrode of the input DC source Uin, the source of the power tube Q1, and the source of the power tube Q2, and there is no electrical connection with the secondary circuit, which is characterized by: The LLC reverse gain enhancement method with a center-tapped transformer based on external phase shifting comprises the following steps: Step 1: External phase shift control signal, Q2, Q3, Q6 are turned on together for T(1-d) / 2 time, and then Q2 is turned off; Step 2: After a short dead time, turn on Q1, Q3 and Q6 together for Td / 2 time, then turn off Q3 and Q6; Step 3: After a short dead time, turn on Q4 and Q5. After Q1, Q4 and Q5 are turned on for T(1-d) / 2, Q1 is turned off. Step 4: After a short dead time, Q2 is turned on. After Q2, Q4 and Q5 are turned on together for Td / 2 time, Q4 and Q5 are turned off. Step 5: After a short dead time, turn on Q3 and Q6. At this time, Q2, Q3 and Q6 are turned on, and the process returns to step 1.

2. A method for improving LLC reverse gain based on external phase shift with center-tapped transformer according to claim 1, characterized in that: The connection relationship of the primary circuit is: the source of the power tube Q1 and the input DC source U in The negative pole of the input capacitor C in The negative electrode of the power tube Q1 is connected to the source of the power tube Q2, the drain of the power tube Q1 is connected to the leakage inductance of the first winding Np1, the other end of the leakage inductance is connected to the same-name end of the first winding, the opposite-name end of the first winding and the same-name end of the second winding are connected to the positive electrode of the input DC source Uin and the positive electrode of the input capacitor Cin.

3. A method for improving LLC reverse gain based on external phase shift with center-tapped transformer according to claim 1, characterized in that: The source of the power tube Q2 is connected to the negative electrode of the input DC source Uin, the negative electrode of the input capacitor Cin, and the source of the power tube Q1. The drain of the power tube Q2 is connected to the leakage inductance of the second winding Np2, and the other end of the leakage inductance is connected to the opposite end of the second winding.

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