Bridgeless single-stage wide-input soft switching resonant power supply conversion device

Abstract

According to the bridgeless single-stage wide-input soft switching resonant power supply conversion device provided by the utility model, three MOS tubes are arranged in a Buck-Boost circuit, so that one MOS tube can be multiplexed as an upper tube Q3 of an LLC circuit. Meanwhile, the voltage stress is equal to the input voltage, so that the type selection of the MOS tube is more favorable, a 500V MOS tube with high cost performance can be selected, and two power diodes are omitted in a main loop, so that the cost of the power semiconductor device can be reduced. Meanwhile, the working principle of the LLC circuit part is completely the same as that of a conventional LLC circuit, and Q3 and Q4 can realize ZVS in a full-load range, so that the circuit has obvious advantages in thermal design and efficiency, and is more convenient for product development in practical application.

Description

Technical Field

[0001] This utility model relates to power converters, and more particularly to a bridgeless single-stage wide-input soft-switching resonant power converter. Background Technology

[0002] With the rapid development of semiconductor technology, fourth-generation LED light sources have been widely adopted and used. Compared with traditional light sources, LEDs have many unparalleled advantages, such as long lifespan, high efficiency, low power consumption, high brightness, and small size, making their application in the lighting field particularly prominent. An LED lighting system consists of two parts: the LED driver and the LED luminaire, with the LED driver being the core component. High-efficiency, energy-saving, high-power LED drivers have become an important research direction in the industry.

[0003] High frequency and miniaturization are important design parameters for switching power supplies. If the power supply operates in hard-switching mode, increasing its switching frequency will result in significant switching losses, reducing the system's conversion efficiency. Therefore, soft-switching technology, which aims to reduce switching losses, has become a major research hotspot in the field of power electronics.

[0004] Resonant converters, including series, parallel, and series-parallel resonant converters, are common soft-switching converters. With proper design, resonant converters can achieve zero-voltage turn-on of the switching transistors and zero-current turn-off of the secondary rectifier diodes over a wide load range, thereby reducing switching losses and improving efficiency. The AC-DC converter uses a Buck-Boost topology, operating in discontinuous mode and automatically implementing PFC (Power Factor Correction). It is a single-switch, low-order boost-and-slow converter circuit that allows for adjustable DC bus voltage, reducing stress on the downstream LLC switching transistors and capacitors.

[0005] There are two main technical solutions in the existing technology: 1. High-power is a two-stage solution, with the first stage Boost achieving power factor correction and voltage regulation, and the second stage DC-DC (isolated and non-isolated topology) achieving output voltage regulation (and electrical isolation, etc.). This solution is technically mature, but the system is complex, costly, and inefficient. 2. Low-power is a single-stage PFC flyback solution, which achieves both input power factor correction and output voltage regulation in a single stage. It is mainly used in low-power LED driver power supplies. This solution is technically mature, simple, low-cost, and efficient, but the output has obvious power frequency ripple (which can cause LED flickering), a narrow input voltage range, and lacks a bus capacitor, which can lead to lightning surge problems. Utility Model Content

[0006] The main technical problem to be solved by this utility model is to provide a bridgeless single-stage wide-input soft-switching resonant power converter that simplifies the circuit, reduces the size, increases the power density, and reduces the cost.

[0007] To solve the above-mentioned technical problems, this utility model provides a bridgeless single-stage wide-input soft-switching resonant power converter, including a Buck-Boost circuit and an LLC circuit; the Buck-Boost circuit includes three switching transistors Q1, Q2, and Q3, and one of the switching transistors Q3 is multiplexed as the upper transistor of the LLC circuit.

[0008] In a preferred embodiment: the switching transistors Q3 and Q1 are simultaneously turned on or off, or the switching transistors Q3 and Q2 are simultaneously turned on or off.

[0009] In a preferred embodiment, the LLC circuit further includes a lower transistor Q4, which has the opposite state to Q3.

[0010] In a preferred embodiment: the switching transistors Q1, Q2, upper transistor Q3 and lower transistor Q4 are controlled by PWM or PFM respectively.

[0011] In a preferred embodiment, a bridgeless rectifier is also included, with its AC input connected to an AC power supply and its DC output connected to a high-frequency transformer T1 via the Buck-Boost circuit and the LLC circuit.

[0012] In a preferred embodiment: the opposite terminals of the secondary winding of the high-frequency transformer T1 are respectively connected to the anodes of diodes D4 and D5, the cathodes of diodes D4 and D5 are connected to each other and grounded through electrolytic capacitor C2, and the cathodes of diodes D4 and D5 are also connected to the same terminals of the secondary winding through load R1.

[0013] In a preferred embodiment: one end of the primary winding of the high-frequency transformer T1 is connected to a resonant circuit consisting of an inductor Lr and a capacitor Cr connected in series.

[0014] In a preferred embodiment: the resonant frequency of the resonant circuit is Lm is the magnetizing inductance.

[0015] In a preferred embodiment: the switching transistors Q1, Q2, upper transistor Q3 and lower transistor Q4 are power MOSFETs.

[0016] Compared with the prior art, the technical solution of this utility model has the following beneficial effects:

[0017] This invention provides a bridgeless single-stage wide-input soft-switching resonant power converter. Three MOSFETs are incorporated into the Buck-Boost circuit, allowing one MOSFET to be reused as the upper transistor Q3 in the LLC circuit. Simultaneously, the voltage stress equals the input voltage, providing a greater advantage in MOSFET selection, enabling the use of cost-effective 500V MOSFETs. Two fewer power diodes are also eliminated in the main circuit, reducing the cost of power semiconductor devices. Furthermore, the LLC circuit operates on the same principle as a conventional LLC circuit. Q3 and Q4 achieve Zero-Switching (ZVS) across the entire load range, offering significant advantages in thermal design and efficiency, and facilitating product development for practical applications. Attached Figure Description

[0018] Figure 1 This is a circuit diagram of a preferred embodiment of the present invention;

[0019] Figure 2 This is a timing diagram of a preferred embodiment of the present invention;

[0020] Figures 3-10 Equivalent circuit diagrams of preferred embodiments of the utility model in various modes. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0022] In the description of this utility model, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed", "equipped with", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0024] refer to Figure 1 This example provides a bridgeless single-stage wide-input soft-switching resonant power converter. It integrates the Buck-Boost circuit with the LLC circuit, reusing MOSFET Q3, which serves as both the switch for the Buck-Boost circuit and the upper transistor of the LLC circuit. Q1 to Q4 are power MOSFETs, where Q1 and Q2 are input rectifier MOSFETs, Q3 is the switch for the Buck-Boost circuit and also the upper transistor of the LLC circuit, and Q4 is the lower transistor of the LLC circuit. For control, Q1, Q2, Q3, and Q4 employ PWM / PFM control. Q1 and Q2 operate during the positive and negative half-cycles of the AC signal, respectively. Q3 is simultaneously turned on and off with either Q1 or Q2, and Q4's drive is complementary to Q3. D1 to D2 are AC input rectifier diodes, which, together with Q1 and Q2, form a bridgeless rectifier to rectify the AC input into pulsating DC. D4 to D5 are power diodes used to rectify the high-frequency AC voltage of the secondary winding of T1 into DC. L1 and Lr are high-frequency inductors, C1 and C2 are electrolytic capacitors, Cr is a high-frequency capacitor, and D3 is a Buck-Boost freewheeling diode. T1 is a high-frequency transformer, and the corresponding terminals of its primary winding Np and secondary windings Ns1 and Ns2 are in the same direction.

[0025] In terms of control, Q1, Q2, Q3, and Q4 employ PWM / PFM control. Q1 and Q2 operate during the positive and negative half-cycles of the AC circuit, respectively. Q3 is simultaneously turned on and off with either Q1 or Q2, and Q4's drive is complementary to Q3's. D1-D2 are AC input rectifier diodes, which, together with Q1 and Q2, form a bridgeless rectifier to rectify the AC input into pulsating DC. D4-D5 are power diodes used to rectify the high-frequency AC voltage of the secondary winding of T1 into DC. L1 and Lr are high-frequency inductors, C1 and C2 are electrolytic capacitors, and Cr is a high-frequency capacitor. T1 is a high-frequency transformer.

[0026] In this embodiment, the Buck-Boost circuit operates in discontinuous mode. The circuit's operating state is symmetrical within the positive and negative cycles of the AC power supply frequency. This explanation uses the positive half-cycle as an example; the negative half-cycle will not be detailed here. Figure 2 For the corresponding key waveform, Figures 3 to 10 Half-cycle 8-mode equivalent diagram.

[0027] The operation is divided into the following 8 modes:

[0028] Mode 1 [t0~t1]: Before t0, the current i in inductor L1 L The voltage has dropped to 0. Simultaneously, because the body diode of Q3 is conducting, at time t0, Q3 is turned on with zero voltage, and Q1 is turned on with zero current. in The Buck-Boost inductor L1 is charged through MOSFETs Q1 and Q3, and the current i in inductor L1 is... L With slope u in / L1 increases linearly. Simultaneously, the DC bus capacitor C1 provides energy to the LLC circuit through the MOSFET Q3. During this stage, the resonant inductor L in the LLC circuit... r Resonant capacitor C r Participating in resonance, the resonant frequency is The secondary diode D5 conducts, charging the output capacitor C2 and supplying power to the output load R1. Simultaneously, it clamps the primary winding of the transformer, so the magnetizing inductance of transformer T1 does not participate in resonance during this stage. Magnetizing current i Lm With slope nV o / L m Linear increase.

[0029] Mode 2 [t1~t2]: At time t1, the resonant current equals the magnetizing current. At this time, the current in the secondary diode D5 drops to zero and it turns off. The primary winding of the transformer is no longer clamped by the output voltage, and the magnetizing inductor participates in the resonance. The resonant frequency is... MOSFETs Q1 and Q3 remain on, and the current i in inductor L1... L It continues to increase linearly.

[0030] Mode 3 [t2~t3]: At time t2, MOSFETs Q1 and Q3 are turned off, entering the dead time. Inductor L1 begins to discharge, and its current i L The DC bus capacitor C1 is charged through the power diode D3, and the current i in the inductor L1 is... L The linear decrease occurs. The magnetizing inductance Lm, resonant inductance Lr, and resonant capacitance Cr form a series resonant circuit, with the resonant frequency... At resonance, the resonant current charges the junction capacitance of MOSFET Q3, while the junction capacitance of MOSFET Q4 discharges, until the voltage across the junction capacitance of MOSFET Q4 drops to 0. During this stage, the resonant current is still equal to the magnetizing current, and the secondary diode remains off.

[0031] Mode 4 [t3~t4]: At time t3, the resonant current flows entirely through the body diode of MOSFET Q4, and MOSFET Q4 satisfies the zero-voltage turn-on condition. During this stage, the resonant inductor Lr and resonant capacitor Cr move at the resonant frequency... Resonance occurs, and the resonant current exceeds the magnetizing current, causing the secondary diode D4 to conduct. The voltage across the transformer's primary winding is clamped at -nVo, and the magnetizing current flows at a slope of nVo. o / L m The current increases linearly. During this phase, the current i in inductor L1... L Continue to decrease.

[0032] Mode 5 [t4~t5]: At time t4, the current iL in the inductor L of the Buck-Boost circuit drops to zero. MOSFET Q4 continues to conduct, and the resonant inductor Lr and resonant capacitor Cr continue to conduct at the resonant frequency. When there is resonance, the resonant current is greater than the excitation current, and the secondary diode D4 conducts.

[0033] Mode 6 [t5~t6]: At time t5, the current in Lr is equal to the current in Lm, the secondary rectifier diode D4 is turned off with zero current, the output voltage no longer clamps the transformer, Lm becomes a free resonant inductor and participates in the resonance. The magnetizing inductance Lm, the resonant inductance Lr, and the resonant capacitor Cr form a series resonant circuit with a resonant frequency of During resonance, due to the large excitation inductance Lm, the resonance period is very large. During this stage, the resonant current is consistent with the excitation current and is approximately constant.

[0034] Mode 7 [t6~t7]: At time t6, MOSFET Q4 is turned off. Entering the dead time, similar to Mode 6, the magnetizing inductor Lm, resonant inductor Lr, and resonant capacitor Cr operate at the resonant frequency. During resonance, the resonant current is still equal to the magnetizing current, and the secondary rectifier diode is turned off. The resonant current discharges the junction capacitance of MOSFET Q3 and charges the junction capacitance of MOSFET Q4 until the voltage across the junction capacitance of MOSFET Q2 drops to 0.

[0035] In this simple substitution, the input AC power supply can be changed from two-phase AC to three-phase AC. The inductor Lr in Embodiment 1 can also be integrated into the transformer T1, and the MOSFET Q1 can be adjusted from the DC negative terminal side to the DC positive terminal side. The rectifier diode D6 of the transformer secondary winding can also be replaced with a MOSFET to achieve synchronous rectification of the output, etc. As long as the Buck-Boost circuit of the power conversion device includes three MOSFETs, Q1, Q2, and Q3, where Q1 and Q2 are bridgeless rectifier MOSFETs and the switching transistor Q3 is reused as the upper transistor of the LLC circuit, any other modifications are considered simple substitutions of this embodiment.

[0036] The above description is only a preferred embodiment of the present utility model, but the design concept of the present utility model is not limited thereto. Any non-substantial modifications made to the present utility model by those skilled in the art within the scope of the technology disclosed in the present utility model using this concept shall be deemed as an infringement of the protection scope of the present utility model.

Claims

1. A bridgeless single-stage wide-input soft-switching resonant power converter, characterized in that: It includes a Buck-Boost circuit and an LLC circuit; the Buck-Boost circuit includes three switching transistors Q1, Q2, and Q3, and one of the switching transistors Q3 is multiplexed as the upper transistor of the LLC circuit.

2. The bridgeless single-stage wide-input soft-switching resonant power converter according to claim 1, characterized in that: The switching transistors Q3 and Q1 are simultaneously turned on or off, or the switching transistors Q3 and Q2 are simultaneously turned on or off.

3. The bridgeless single-stage wide-input soft-switching resonant power converter according to claim 2, characterized in that: The LLC circuit also includes a lower transistor Q4, which has the opposite state to Q3.

4. The bridgeless single-stage wide-input soft-switching resonant power converter according to claim 3, characterized in that: The switching transistors Q1, Q2, upper transistor Q3, and lower transistor Q4 are controlled by PWM or PFM, respectively.

5. A bridgeless single-stage wide-input soft-switching resonant power converter according to any one of claims 1-4, characterized in that: It also includes a bridgeless rectifier, whose AC input is connected to an AC power supply, and whose DC output is connected to a high-frequency transformer T1 through the Buck-Boost circuit and LLC circuit.

6. The bridgeless single-stage wide-input soft-switching resonant power converter according to claim 5, characterized in that: The opposite terminals of the secondary winding of the high-frequency transformer T1 are connected to the anodes of diodes D4 and D5, respectively. The cathodes of diodes D4 and D5 are connected to each other and grounded through electrolytic capacitor C2. The cathodes of diodes D4 and D5 are also connected to the same terminals of the secondary winding through load R1.

7. The bridgeless single-stage wide-input soft-switching resonant power converter according to claim 5, characterized in that: One end of the primary winding of the high-frequency transformer T1 is connected to a resonant circuit consisting of an inductor Lr and a capacitor Cr connected in series.

8. The bridgeless single-stage wide-input soft-switching resonant power converter according to claim 7, characterized in that: The resonant frequency of the resonant circuit is Lm is the magnetizing inductance.

9. The bridgeless single-stage wide-input soft-switching resonant power converter according to claim 3, characterized in that: The switching transistors Q1, Q2, upper transistor Q3, and lower transistor Q4 are all power MOSFETs.

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