Structure for inhibiting output voltage ripples of LLC resonant converter

Abstract

The invention belongs to the technical field of switching power supplies, and provides a structure for suppressing output voltage ripples of an LLC resonant converter, which comprises a direct-current power supply, a direct-current bus capacitor C1, a half-bridge arm I, a resonant inductor L1, a resonant capacitor C2, a transformer T1, a full-wave first rectifier bridge, an output capacitor C4, a half-bridge arm II, a resonant inductor L2, a resonant capacitor C3, a transformer T2 and a full-wave second rectifier bridge. The upper ends of the half-bridge arm I, the half-bridge arm II and the direct-current bus capacitor C1 are connected with the positive electrode of the direct-current power supply, and the lower ends are connected with the negative electrode of the direct-current power supply; the non-dotted terminal of the transformer T1 is connected with the negative electrode of the direct-current power supply. According to the technical scheme, the single-half-bridge LLC resonant converter is connected in parallel on the basis of a traditional single-half-bridge LLC, and the capacity is increased, wherein the secondary sides of the two LLC transformers adopt full-wave rectification. In addition, odd harmonics of the output voltage are eliminated through carrier phase shifting, the ripple amplitude is weakened, and the output precision is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of switching power supplies, and in particular relates to a structure for suppressing output voltage ripple of an LLC resonant converter. Background Art

[0002] With the large-scale application of power electronics, the demand for power supplies with high power density, high efficiency, low ripple, low electromagnetic interference, good dynamic performance and high reliability in various fields is also increasing, such as in aerospace power supply, communication power supply, server power supply, electric vehicle charging and precision instruments. Among them, the LLC resonant conversion topology uses inductor and capacitor resonance to achieve soft switching. Compared with the traditional hard switching power supply topology, it significantly improves the power density and reduces electromagnetic interference, but its output ripple is still too large, which limits its application in the field of high-precision power supply. Therefore, it is very important to further study the output accuracy of the LLC resonant converter output voltage.

[0003] Due to the capacity limitation of current high-frequency switching devices, the power of traditional single half-bridge LLC resonant high-power switching power supply is limited, and the output voltage ripple is large when the load is heavy, resulting in the power supply accuracy unable to meet the requirements in high-precision power supply occasions, limiting the application of LLC resonant power supply. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] The technical problem to be solved by the present invention is: the capacity limitation of the current high-frequency switching devices leads to the power limitation of the traditional single half-bridge LLC resonant high-power switching power supply, and the output voltage ripple is large when the load is heavy, resulting in the power supply accuracy unable to meet the requirements in high-precision power supply occasions, limiting the application of LLC resonant power supply.

[0006] (II) Technical solution

[0007] In order to solve the above technical problems, the present invention provides a structure for suppressing the output voltage ripple of an LLC resonant converter, including a DC power supply, a DC bus capacitor C1, a half-bridge arm 1, a resonant inductor L1, a resonant capacitor C2, a transformer T1, a full-wave first rectifier bridge, an output capacitor C4, a half-bridge arm 2, a resonant inductor L2, a resonant capacitor C3, a transformer T2, and a full-wave second rectifier bridge;

[0008] The upper end of the half bridge arm 1, the half bridge arm 2 and the DC bus capacitor C1 are connected to the positive electrode of the DC power supply, and the lower end is connected to the negative electrode of the DC power supply; the non-same-name end of the transformer T1 is connected to the negative electrode of the DC power supply;

[0009] The resonant inductor L1 is connected in series with the resonant capacitor C2, and is connected in series between the half-bridge arm T1 and the same-name end of the transformer; the resonant inductor L2 is connected in series with the resonant capacitor C3, and is connected in series between the half-bridge arm 1 and the same-name end of the transformer T2; the non-same-name end of the transformer T2 is connected to the negative pole of the DC power supply;

[0010] The same-name end of the secondary side of transformer T1 is connected to the midpoint of the first bridge arm of the full-wave first rectifier bridge, and the non-same-name end of the secondary side of transformer 1 is connected to the midpoint of the second bridge arm of the full-wave first rectifier bridge;

[0011] The same-name end of the secondary side of the transformer T2 is connected to the midpoint of the first bridge arm of the full-wave second rectifier bridge, and the non-same-name end of the secondary side of the transformer T2 is connected to the midpoint of the second bridge arm of the full-wave second rectifier bridge;

[0012] The upper ends of the full-wave first rectifier bridge and the full-wave second rectifier bridge are connected to the upper end of the output capacitor C4, and the lower ends of the full-wave second rectifier bridge and the full-wave second rectifier bridge are connected to the upper end of the output capacitor C4.

[0013] Furthermore, the first half bridge arm is composed of switch tubes K1 and K2.

[0014] Furthermore, the second half bridge arm is composed of switch tubes K3 and K4.

[0015] Furthermore, the full-wave first rectifier bridge is composed of 4 diodes.

[0016] Furthermore, the full-wave second rectifier bridge is composed of 4 diodes.

[0017] Furthermore, the phase of half bridge arm one leads that of half bridge arm two by π / 2.

[0018] Furthermore, the phase of half bridge arm one lags behind half bridge arm two by π / 2.

[0019] (III) Beneficial effects

[0020] Compared with the prior art, the present invention has the following beneficial effects: a single half-bridge LLC resonant converter is connected in parallel on the basis of the traditional single half-bridge LLC (the secondary sides of the two LLC transformers adopt full-wave rectification) to increase the capacity. In addition, the odd harmonics of the output voltage are eliminated by carrier phase shifting, the ripple amplitude is weakened, and the output accuracy is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of parallel half-bridge LLC resonant topology. DETAILED DESCRIPTION

[0022] In order to make the purpose, content, and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the accompanying drawings and examples.

[0023] The present embodiment provides a parallel half-bridge LLC resonant topology structure, which includes: a DC power supply 1, a DC bus capacitor C1, a half-bridge arm 2 (composed of switch tubes K1 and K2), a resonant inductor L1, a resonant capacitor C2, a transformer T1, a first rectifier bridge 4 (composed of 4 diodes), an output capacitor C4, a half-bridge arm 2 3 (composed of switch tubes K3 and K4), a resonant inductor L2, a resonant capacitor C3, a transformer T2, and a second rectifier bridge 5 (also composed of 4 diodes).

[0024] Connect the upper ends of half bridge arm 1, half bridge arm 2 3, and DC bus capacitor C1 to the positive electrode of DC power supply 1, and the lower ends to the negative electrode of DC power supply 1, and the non-same-name end of transformer T1 to the negative electrode of DC power supply 1;

[0025] The resonant inductor L1 and the resonant capacitor C2 are connected in series and connected in series between the half bridge arm T1 and the same-name end of the transformer, and the resonant inductor L2 and the resonant capacitor C3 are connected in series and connected in series between the half bridge arm 1 and the same-name end of the transformer T2, and the non-same-name end of the transformer T2 is connected to the negative electrode of the DC power supply 1;

[0026] The same-name end of the secondary side of transformer T1 is connected to the midpoint of the first bridge arm of the full-wave first rectifier bridge 4, and the non-same-name end of the secondary side of transformer 1 is connected to the midpoint of the second bridge arm of the full-wave first rectifier bridge 4;

[0027] The same-name end of the secondary side of the transformer T2 is connected to the midpoint of the first bridge arm of the full-wave second rectifier bridge 5, and the non-same-name end of the secondary side of the transformer T2 is connected to the midpoint of the second bridge arm of the full-wave second rectifier bridge 5;

[0028] The upper ends of the full-wave first rectifier bridge 4 and the full-wave second rectifier bridge 5 are connected to the upper end of the output capacitor C4, and the lower ends of the full-wave second rectifier bridge 5 and the full-wave second rectifier bridge 5 are connected to the upper end of the output capacitor C4;

[0029] Based on the above hardware connection, the present invention provides a driving method for half-bridge arm 1 2 and half-bridge arm 2 3. Since the DC component of the resonant circuit composed of a single half-bridge LLC, which is composed of a resonant inductor, a resonant capacitor, a half-bridge arm LLC and a transformer, cannot be transmitted to the output side through the transformer (i.e., there is no DC component on the secondary side of the transformer), the harmonics of the output voltage after full-wave rectification of the secondary side AC voltage of the transformer through the rectifier bridge arm are mainly integer harmonics of 2 times the frequency of the secondary side AC voltage of the transformer. In addition, since the two full-wave rectifier bridges are connected in parallel, when the driving signal of the half-bridge arm 1 is ahead of or behind the half-bridge arm 2 by π / 2, the odd harmonics of the output voltage V0 can be eliminated, thereby suppressing the ripple amplitude of the output voltage and improving the accuracy.

[0030] The implementation scheme is described based on the topological structure of the attached figure, wherein the parameters of the components of the two half-bridge LLC resonant converters are kept consistent, and the implementation is carried out in the form of open-loop control, and the closed-loop control is the same. The output V0 is modulated by variable switching frequency.

[0031] The specific implementation is as follows:

[0032] Considering the soft switching operating frequency range, the operating frequency range is first calculated. The maximum operating frequency is generated by the resonant inductor and the resonant capacitor, as shown in Equation 1.

[0033]

[0034] The minimum operating frequency is determined by the resonant inductance, resonant capacitance and the transformer's magnetizing inductance L. m Produced as shown in formula (2).

[0035]

[0036] After the frequency range is determined, the duty cycle of PWM is fixed to 50%, the upper and lower switches in the same bridge arm are turned on complementarily, and the phase of half bridge arm one leads half bridge arm two by π / 2, and vice versa.

[0037] The present invention improves the power output power of the power supply by connecting two half-bridge LLC resonant conversion power supplies in parallel through input and output, compared with a single half-bridge arm LLC resonant power supply. By shifting the carrier phase of the two half-bridge arms and utilizing the harmonic frequency multiplication effect of full-wave rectification, the odd harmonics of the output voltage are eliminated, the output voltage ripple amplitude is reduced (the output voltage ripple amplitude of a single half-bridge arm is reduced by about 2 / 3 within the operating frequency of the LLC resonant converter), the output capacitor life is increased, and the output voltage accuracy is significantly improved.

[0038] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A structure for suppressing output voltage ripple of an LLC resonant converter, characterized in that: It includes a DC power supply, a DC bus capacitor C1, a half bridge arm 1, a resonant inductor L1, a resonant capacitor C2, a transformer T1, a full-wave first rectifier bridge, an output capacitor C4, a half bridge arm 2, a resonant inductor L2, a resonant capacitor C3, a transformer T2, and a full-wave second rectifier bridge; The upper end of the half bridge arm 1, the half bridge arm 2 and the DC bus capacitor C1 are connected to the positive electrode of the DC power supply, and the lower end is connected to the negative electrode of the DC power supply; the non-same-name end of the transformer T1 is connected to the negative electrode of the DC power supply; The resonant inductor L1 is connected in series with the resonant capacitor C2, and is connected in series between the half-bridge arm T1 and the same-name end of the transformer; the resonant inductor L2 is connected in series with the resonant capacitor C3, and is connected in series between the half-bridge arm 1 and the same-name end of the transformer T2; the non-same-name end of the transformer T2 is connected to the negative pole of the DC power supply; The same-name end of the secondary side of transformer T1 is connected to the midpoint of the first bridge arm of the full-wave first rectifier bridge, and the non-same-name end of the secondary side of transformer 1 is connected to the midpoint of the second bridge arm of the full-wave first rectifier bridge; The same-name end of the secondary side of the transformer T2 is connected to the midpoint of the first bridge arm of the full-wave second rectifier bridge, and the non-same-name end of the secondary side of the transformer T2 is connected to the midpoint of the second bridge arm of the full-wave second rectifier bridge; The upper ends of the full-wave first rectifier bridge and the full-wave second rectifier bridge are connected to the upper end of the output capacitor C4, and the lower ends of the full-wave second rectifier bridge and the full-wave second rectifier bridge are connected to the upper end of the output capacitor C4.

2. The structure for suppressing output voltage ripple of LLC resonant converter according to claim 1, characterized in that: Half bridge arm 1 is composed of switch tubes K1 and K2.

3. The structure for suppressing output voltage ripple of LLC resonant converter according to claim 1, characterized in that: The second half bridge arm is composed of switch tubes K3 and K4.

4. The structure for suppressing output voltage ripple of LLC resonant converter according to claim 1, characterized in that: The full-wave first rectifier bridge consists of 4 diodes.

5. The structure for suppressing output voltage ripple of LLC resonant converter according to claim 1, characterized in that: The full-wave second rectifier bridge consists of 4 diodes.

6. The structure for suppressing output voltage ripple of LLC resonant converter according to claim 1, characterized in that: The phase of half bridge arm one leads half bridge arm two by π / 2.

7. The structure for suppressing output voltage ripple of LLC resonant converter according to claim 1, characterized in that: The phase of half bridge arm one lags half bridge arm two by π / 2.

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