LLC DC-DC converter based on dynamic reconstruction of main circuit

Abstract

The utility model discloses an LLC DC-DC converter based on dynamic reconstruction of a main circuit, a reconstruction switch T1, a reconstruction switch T2 and a boost inductor Lb are added into the main circuit of the LLC DC-DC converter, when an input power supply Vin is a high-voltage DC power supply, the reconstruction switch T1 is turned on and is kept normally open, and when the input power supply Vin is a high-voltage DC power supply, the reconstruction switch T2 is turned off and is kept normally open; the main circuit topology is an LLC resonant circuit of the LLC DC-DC isolation converter; when the input power supply Vin is a low-voltage direct-current power supply, the reconfiguration switch T2 is turned on and is kept normally open, and the low-voltage direct-current power supply obtains high direct-current bus voltage through the Boost circuit; according to the utility model, the LLC resonance circuit and the Boost circuit are integrated to adapt to different types of input power supplies, so that a plurality of circuits are prevented from being needed when power supplies with different voltage levels are used for supplying power, and the complexity of a main circuit is reduced; and a multi-stage converter main circuit is changed into a single-stage converter main circuit, so that the energy transfer stage number is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of power electronic converters, and specifically relates to an LLC DC-DC converter based on dynamic reconstruction of a main circuit, which is suitable for power conversion in a DC transmission network where the DC input power supply voltage difference is more than ten times. Background Art

[0002] As a clean energy, electric energy is fully and deeply applied to all fields of production and life in today's rapidly developing human society. DC converters are widely used in industry, energy, electricity, transportation and other fields. It is of great practical significance to study DC converters with strong applicability, high efficiency, soft switching, integration and electrical isolation. LLC DC converters are widely used in many fields such as new energy vehicles, LED drivers, and communication power supplies due to their advantages such as electrical isolation and soft switching.

[0003] The output-input voltage gain of LLC under conventional PFM (pulse frequency modulation) control has a narrow variation range, usually 0.8-2.5, and its application range is limited. In order to overcome this problem, researchers have made improvements in the topology and control strategy, which can widen the voltage gain range to 2-3 times the original, so that the LLC topology can be used in situations such as a wider input voltage range. For situations where the input voltage varies over an ultra-wide range (the highest voltage is several times more than the lowest voltage), such as when hundreds of volts of DC power grids and tens of volts of batteries are used as power supplies, it is often necessary to add a conversion circuit at the input end to stabilize the wide range input voltage at a uniform bus voltage before performing LLC conversion. In this way, the number of energy conversion stages increases, affecting the system conversion efficiency. At the same time, more conversion stages also mean that more components and multi-level control schemes are required, making the system complex. Utility Model Content

[0004] The purpose of the utility model is to provide an LLC DC-DC converter based on dynamic reconstruction of the main circuit in view of the above problems existing in the prior art.

[0005] The above-mentioned purpose of the utility model is achieved by the following technical means:

[0006] An LLC DC-DC converter based on dynamic reconstruction of the main circuit includes an input power supply V in , resonant inductor L r , resonant capacitor C r , and a high-frequency transformer T, and also includes a reconstruction switch T1, a reconstruction switch T2, a boost inductor L b , half-bridge switch S1, half-bridge switch S2, synchronous rectifier switch SR1, and synchronous rectifier switch SR2; input power supply V inThe positive electrode is connected to one end of the reconstruction switch T1 and one end of the reconstruction switch T2, and the other end of the reconstruction switch T1 is connected to one end of the half-bridge switch S1 and the bus capacitor C b The other end of the reconstruction switch T2 is connected to the boost inductor L b The other end of the half-bridge switch S1 is connected to the boost inductor L b The other end of the resonant inductor L r and one end of the half-bridge switch S2, and the other end of the half-bridge switch S2 is connected to the diode D I The positive electrode and bus capacitance C b The other end of the resonant capacitor C r One end of the diode D I The negative terminal is connected to the input power supply V in The negative connection of the resonant inductor L r The other end of the high-frequency transformer T is connected to the same-name end of the primary winding, and the opposite-name end of the primary winding of the high-frequency transformer T is connected to the resonant capacitor C r The other end is connected to the excitation inductance L of the high-frequency transformer T m Connected in parallel at both ends of the primary winding of the high-frequency transformer T.

[0007] As described above, the same-name end of the first secondary winding of the high-frequency transformer T is connected to one end of the synchronous rectifier switch SR1, and the opposite-name end of the first secondary winding of the high-frequency transformer T is connected to the same-name end of the second secondary winding of the high-frequency transformer T, and the load resistor R L The other end of the synchronous rectifier switch SR1 is connected to the load resistor R L The other end of the synchronous rectification switch SR2 is connected to the opposite end of the second secondary winding of the high-frequency transformer T.

[0008] As mentioned above, the input power supply V in It is a high voltage DC power supply or a low voltage DC power supply.

[0009] As described above, the reconstruction switch T1 , the reconstruction switch T2 , the half-bridge switch S1 , the half-bridge switch S2 , the synchronous rectification switch SR1 , and the synchronous rectification switch SR2 are all NMOS tubes.

[0010] Compared with the prior art, the utility model has the following beneficial effects:

[0011] (1) The utility model integrates the LLC resonant circuit and the Boost circuit into one, and changes the main circuit topology of the LLC DC-DC converter by turning on and off the reconstruction switch T1 and the reconstruction switch T2 during operation to adapt to different types of input power supplies, thereby avoiding the need for multiple sets of circuits when power supplies with different voltage levels are used, and reducing the complexity of the main circuit of the LLC DC-DC converter.

[0012] (2) The utility model changes the main circuit of a multi-stage converter that realizes the same function into a single-stage converter main circuit, reducing the number of energy transfer stages. It can overcome the problem that when the input voltage changes over a wide range, multi-stage conversion is required, resulting in complex system solutions and reduced efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the structure of the circuit of the utility model;

[0014] Figure 2 It is an equivalent topological structure diagram of the circuit of the utility model when the input power supply is a high voltage DC power supply;

[0015] Figure 3 When the input power supply is a high voltage DC power supply, the switch tube drive waveform and the main current waveform (where v GT1 To reconstruct the drive signal of switch T1, v GT2 To reconstruct the drive signal of switch T2, v GS1 is the driving signal of the half-bridge switch S1, v GS2 is the driving signal of the half-bridge switch S2, i Lr is the resonant current, i R1 is the synchronous rectification current of the first secondary winding of the high-frequency transformer T, i R2 is the synchronous rectification current of the second secondary winding of the high-frequency transformer T);

[0016] Figure 4 It is an equivalent topological structure diagram of the circuit of the utility model when the input power supply is a low-voltage DC power supply;

[0017] Figure 5 When the input power supply is a low voltage DC power supply, the switch tube drive waveform and the main current waveform (where i Lm is the current flowing through the magnetizing inductance L m The excitation current, i b is the current flowing through the boost inductor). DETAILED DESCRIPTION

[0018] In order to facilitate those skilled in the art to understand and implement the present invention, the present invention is further described in detail below in conjunction with embodiments. The embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0019] Embodiment 1:

[0020] An LLC DC-DC converter based on dynamic reconstruction of the main circuit includes an input power supply V in , Reconstruction switch T1, Reconstruction switch T2, Boost inductor L b , half-bridge switch S1, half-bridge switch S2, bus capacitor C b , resonant inductor L r , Excitation inductance L m , resonant capacitor C r , high frequency transformer T, synchronous rectification switch SR1, synchronous rectification switch SR2, and filter capacitor C f .

[0021] Input power V in The positive electrode is connected to one end of the reconstruction switch T1 and one end of the reconstruction switch T2, and the other end of the reconstruction switch T1 is connected to one end of the half-bridge switch S1 and the bus capacitor C b The other end of the reconstruction switch T2 is connected to the boost inductor L b The other end of the half-bridge switch S1 is connected to the boost inductor L b The other end of the resonant inductor L r and one end of the half-bridge switch S2, and the other end of the half-bridge switch S2 is connected to the diode D I The positive electrode and bus capacitance C b The other end of the resonant capacitor C r One end of the diode D I The negative pole of the input power supply V in The negative connection of the resonant inductor L r The other end of the high-frequency transformer T is connected to the same-name end of the primary winding, and the opposite-name end of the primary winding of the high-frequency transformer T is connected to the resonant capacitor C r The other end is connected to the excitation inductance L of the high-frequency transformer T m Connected in parallel at both ends of the primary winding of the high-frequency transformer T.

[0022] The same-name end of the first secondary winding of the high-frequency transformer T is connected to one end of the synchronous rectifier switch SR1, and the opposite-name end of the first secondary winding of the high-frequency transformer T is connected to the same-name end of the second secondary winding of the high-frequency transformer T and the filter capacitor C f One end of the load resistor R L One end of the synchronous rectifier switch SR1 is connected to the filter capacitor C f The other end of the load resistor R L The other end of the synchronous rectification switch SR2 is connected to the opposite end of the second secondary winding of the high-frequency transformer T.

[0023] The high frequency transformer T adopts the same polarity connection mode (that is, the primary winding, the first secondary winding and the second secondary winding adopt the same polarity connection mode).

[0024] In this embodiment, the reconstruction switch T1, the reconstruction switch T2, the half-bridge switch S1, the half-bridge switch S2, the synchronous rectification switch SR1, and the synchronous rectification switch SR2 are all NMOS transistors.

[0025] The circuit of the utility model is the main circuit of LLC DC-DC converter. The input power supply V in It can be a high voltage DC power supply (such as a DC grid of hundreds of volts) or a low voltage DC power supply (such as a battery of tens of volts):

[0026] like Figure 2 As shown, when the input power V in When the power supply is a high voltage DC power supply, the reconstruction switch T1 is turned on and remains on, the reconstruction switch T2 remains off, and the reconstruction switch T2 and the boost inductor L b The branch is disconnected, and the circuit topology becomes the LLC resonant circuit of the LLC DC-DC isolation converter. The boost inductor L b Without connecting to the LLC resonant circuit, the half-bridge switch S1 and the half-bridge switch S2 work in a high-frequency complementary conduction state. The half-bridge switch S1 and the half-bridge switch S2 are sensitive to the input power supply V in High-frequency modulation is performed, and then transmitted to the secondary winding of the high-frequency transformer T (including the first secondary winding and the second secondary winding) through the primary winding of the high-frequency transformer T, and finally converted into a DC output through the synchronous rectification switch SR1 and the synchronous rectification switch SR2, completing the isolated DC / DC conversion and obtaining a stable output DC voltage.

[0027] The LLC resonant circuit controls the output voltage V through the switching frequency of the half-bridge switch S1 and the half-bridge switch S2. o and power, when the switching frequency increases, the output voltage V o and power reduction; when the switching frequency is reduced, the output voltage V o and power increase;

[0028] When the half-bridge switch S1 is turned on and the half-bridge switch S2 is turned off, the input power supply V in , reconstruction switch T1, half-bridge switch S1, resonant inductor L r , Excitation inductance L m , resonant capacitor C r , and the primary winding of the high-frequency transformer T form the positive half-cycle resonant circuit of the LLC resonant circuit. Under the action of the input high voltage, the current flows through the resonant inductor L r The resonant current i LrThe positive direction increases (the positive direction is from the midpoint of the half-bridge arm formed by the half-bridge switch S1 and the half-bridge switch S2 through the resonant inductor L r It flows to the primary winding of the high-frequency transformer T) in a sinusoidal shape and supplies the resonant capacitor C r Charging; Excitation inductance L m The two ends are clamped to the output voltage through the high-frequency transformer T, and the excitation inductor L m The voltage across the two ends can be considered constant during one switching cycle of the half-bridge switch S1 (or half-bridge switch S2), so the current flowing through the magnetizing inductor L m The excitation current i Lm Increases linearly. The resonant current i Lr For resonance formation, the resonant current i Lr The increase rate is higher than the excitation current i Lm , resonant current i Lr With the excitation current i Lm The difference i T It flows to the primary winding of the high-frequency transformer T and is converted into output DC power through the synchronous rectifier tube SR1 on the secondary side of the high-frequency transformer T.

[0029] When the half-bridge switch S2 is turned on and the half-bridge switch S1 is turned off, the half-bridge switch S2 and the resonant inductor L r , Excitation inductance L m , resonant capacitor C r , and the primary winding of the high-frequency transformer T form the negative half-cycle resonant circuit of the LLC resonant circuit, and the input power supply V in The negative half-cycle resonant loop is not connected to the LLC resonant circuit, and the resonant current i Lr Decreases rapidly, and when it drops to zero, the resonant capacitance C r The voltage charged is reversely discharged, and the resonant current i Lr The reverse resonance increases. The resonant current i Lr With the excitation current i Lm The difference i T It flows to the primary winding of the high-frequency transformer T and is converted into output DC power through the synchronous rectifier tube SR2 on the secondary side of the high-frequency transformer T.

[0030] from Figure 3 As can be seen, the high voltage DC power supply is used as the input power supply V in When the drive signal v of the reconstructed switch T1 is GT1 Continuously high level, reconstructing the drive signal v of switch T2 GT2 The drive signal v of the half-bridge switch S1 is continuously low (the reconstruction switch T1 and the reconstruction switch T2 are both high and turned on). GS1 and the driving signal v of the half-bridge switch S2 GS2 Perform high frequency switching so that the resonant current i Lr In binary resonance (resonant inductor Lr and resonant capacitor C r ) and three-element resonance (resonant inductor L r , Excitation inductance L m and resonant capacitor C r ), these two resonant currents are both part of the sine waveform, the difference is the resonant period is different.

[0031] like Figure 4 As shown, when the input power V in When the power supply is low voltage DC, the reconstruction switch T2 is turned on and remains on, the reconstruction switch T1 remains off, and the reconstruction switch T2 and the boost inductor L b The branch formed is connected to the input power supply V of the LLC resonant circuit in The positive electrode and the midpoint of the half-bridge arm formed by the half-bridge switch S1 and the half-bridge switch S2 are connected to the input power supply V in , bus capacitance C b , half-bridge switch S1, and half-bridge switch S2 form a Boost circuit. The low-voltage DC power supply obtains a high DC bus voltage through the Boost circuit, and then undergoes high-frequency modulation through half-bridge switch S1 and half-bridge switch S2. Then, it is transmitted to the first secondary winding and the second secondary winding of the high-frequency transformer T through the primary winding of the high-frequency transformer T, and finally converted into a DC output through the synchronous rectification switch SR1 and the synchronous rectification switch SR2, completing the isolated DC / DC conversion and obtaining a stable output DC voltage. Functional reuse of half-bridge switch S1 and half-bridge switch S2:

[0032] The half-bridge switch S2 is used as the switch of the negative half-cycle resonant circuit of the LLC resonant circuit, and as the switch of the charging circuit of the Boost boost circuit: When the half-bridge switch S2 is turned on, the input power supply V in , boost inductor L b , and half-bridge switch S2 form the charging circuit of the Boost circuit, and the input power supply V in The boost inductor L is connected to the half-bridge switch S2. b Charging; half-bridge switch S2, resonant inductor L r , Excitation inductance L m , resonant capacitor C r , and the primary winding of the high-frequency transformer T constitute a resonant circuit of the negative half-cycle of LLC resonance.

[0033] The half-bridge switch S1 is used as the switch tube of the positive half-cycle resonant circuit of the LLC resonant circuit, and as the freewheeling diode of the discharge circuit of the Boost boost circuit: When the half-bridge switch S1 is turned on, the input power supply V in , boost inductor L b , half-bridge switch S1, and bus capacitor C bThe boost inductor L constitutes the discharge loop of the Boost circuit. b The stored energy is transferred to the bus capacitor C through the half-bridge switch S1. b Charging, while input power V in Also for the bus capacitance C b Charging, thereby obtaining a higher DC bus voltage; input power supply V in , boost inductor L b , half-bridge switch S1, resonant inductor L r , Excitation inductance L m , resonant capacitor C r , and the primary winding of the high-frequency transformer T constitute a resonant circuit of the LLC resonance positive half cycle.

[0034] from Figure 5 As can be seen, the low voltage DC power supply is used as the input power supply V in When the drive signal v of the reconstructed switch T1 is GT1 The drive signal v of switch T2 is reconstructed. GT2 During half of the switching cycle of the half-bridge switch S1 (or half-bridge switch S2), the resonant current i Lr With the excitation current i Lm The waveform is the same for part of the time and different for part of the time. In the intervals with different waveforms, the excitation current i Lm Linear.

[0035] The utility model solves the problem of requiring a set of converters for high voltage input and low voltage input respectively through dynamic reconstruction of the LLC resonant circuit, reduces the complexity of the circuit system, and is very suitable for DC power transmission occasions.

[0036] It should be noted that the embodiments described in the present invention are merely examples of the spirit of the present invention. Those skilled in the art of the present invention may make various modifications or additions to the embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the attached claims.

Claims

1. An LLC DC-DC converter based on dynamic reconstruction of the main circuit, comprising an input power supply V in , resonant inductor L r , resonant capacitor C r , and a high-frequency transformer T, characterized in that, Also includes a reconstruction switch T1, a reconstruction switch T2, a boost inductor L b , half-bridge switch S1, half-bridge switch S2, synchronous rectifier switch SR1, and synchronous rectifier switch SR2; input power supply V in The positive electrode is connected to one end of the reconstruction switch T1 and one end of the reconstruction switch T2, and the other end of the reconstruction switch T1 is connected to one end of the half-bridge switch S1 and the bus capacitor C b The other end of the reconstruction switch T2 is connected to the boost inductor L b The other end of the half-bridge switch S1 is connected to the boost inductor L b The other end of the resonant inductor L r and one end of the half-bridge switch S2, and the other end of the half-bridge switch S2 is connected to the diode D I The positive electrode and bus capacitance C b The other end of the resonant capacitor C r One end of the diode D I The negative pole of the input power supply V in The negative connection of the resonant inductor L r The other end of the high-frequency transformer T is connected to the same-name end of the primary winding, and the opposite-name end of the primary winding of the high-frequency transformer T is connected to the resonant capacitor C r The other end is connected to the excitation inductance L of the high-frequency transformer T m Connected in parallel at both ends of the primary winding of the high-frequency transformer T.

2. According to claim 1, an LLC DC-DC converter based on dynamic reconstruction of the main circuit is characterized in that: The same-name end of the first secondary winding of the high-frequency transformer T is connected to one end of the synchronous rectifier switch SR1, and the opposite-name end of the first secondary winding of the high-frequency transformer T is connected to the same-name end of the second secondary winding of the high-frequency transformer T and the load resistor R L The other end of the synchronous rectifier switch SR1 is connected to the load resistor R L The other end of the synchronous rectification switch SR2 is connected to the opposite end of the second secondary winding of the high-frequency transformer T.

3. The LLC DC-DC converter based on dynamic reconstruction of the main circuit according to claim 2, characterized in that: The input power supply V in It is a high voltage DC power supply or a low voltage DC power supply.

4. The LLC DC-DC converter based on dynamic reconstruction of the main circuit according to claim 3, characterized in that: The reconstruction switch T1, the reconstruction switch T2, the half-bridge switch S1, the half-bridge switch S2, the synchronous rectification switch SR1, and the synchronous rectification switch SR2 are all NMOS tubes.

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