Single-stage bridgeless conversion apparatus integrating buck-boost circuit and AHB flyback circuit

Abstract

Provided in the present invention is a single-stage bridgeless conversion apparatus integrating a buck-boost circuit and an AHB flyback circuit. The apparatus comprises a bridgeless buck-boost circuit and an AHB flyback circuit, wherein the buck-boost circuit comprises three switch transistors Q1, Q2, Q3, and one of the switch transistors Q3 is reused as an upper transistor of the AHB flyback circuit. In the single-stage bridgeless conversion apparatus integrating the buck-boost circuit and the AHB flyback circuit, the voltage stress on the switch transistor Q3 can be significantly reduced, and the increased stress on the switch transistors Q1, Q2 is equal to an input voltage, and thus the type selection of switch transistors is more favorable, and cost-effective switch transistors with 500 V can be selected; and two power diodes are also removed from a main loop, such that the costs of power semiconductor devices can be reduced. In addition, the operating principle of the AHB flyback circuit portion is identical to that of a conventional AHB flyback circuit, Q3 and Q4 can achieve ZVS within the entire load range, and a secondary-side rectifier diode achieves ZCS; therefore, the gain variation range is large, and wide-voltage input / output can be achieved.

Description

A single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits Technical Field

[0001] This invention relates to power converters, and more particularly to a single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits. 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] The most mainstream technical solutions currently are: 1. High-power two-stage system: The first stage, Boost converter, achieves power factor correction and voltage regulation, while the second stage, DC-DC converter (isolated / non-isolated topology), achieves output voltage regulation (and electrical isolation, etc.). This solution is technically mature, but the system is complex, costly, and inefficient. 2. Low-power single-stage PFC flyback converter: A single-stage flyback converter simultaneously achieves input power factor correction and output voltage regulation. It is mainly used in low-power LED driver power supplies. This solution is technically mature, simple, low-cost, and efficient, but it has obvious power frequency ripple (which can cause LED flickering), a narrow input voltage range, and lacks a bus capacitor, leading to lightning surge problems. Summary of the Invention

[0006] The main technical problem to be solved by the present invention is to provide a single-stage bridgeless converter that integrates Buck-Boost and AHB flyback circuits, which simplifies the circuit, reduces the size, increases power density, and reduces cost.

[0007] To address the aforementioned technical problems, this invention provides a single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits, comprising a bridgeless Buck-Boost circuit and an AHB flyback 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 AHB flyback circuit.

[0008] In a preferred embodiment, the AHB flyback circuit further includes a lower transistor Q4.

[0009] In a preferred embodiment: the switching transistors Q1 or Q2 are simultaneously turned on and off with the upper transistor Q3, and the state is opposite to that of the lower transistor Q4.

[0010] In a preferred embodiment: the bridgeless Buck-Boost circuit further includes AC input rectifier diodes D1 and D2; the AC input rectifier diodes D1 and D2 and the switching transistors Q1 and Q2 rectify the AC input into pulsating DC.

[0011] In a preferred embodiment: the AC input terminals of the AC input rectifier diodes D1 and D2 are connected to an AC power supply, and the DC output terminals are connected to a high-frequency transformer T1 through a Buck-Boost circuit and an AHB flyback circuit.

[0012] In a preferred embodiment: the bridgeless Buck-Boost circuit further includes a freewheeling diode D3, and the AHB flyback circuit further includes a rectifier diode D4, which is used to rectify the high-frequency AC voltage of the secondary winding of the high-frequency transformer T1 into DC.

[0013] 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, the cathodes of diodes D4 are interconnected and grounded through electrolytic capacitor C2, and the cathodes of diodes D4 are also connected to the same terminals of the secondary winding through load R1.

[0014] In a preferred embodiment: the primary winding Np of the high-frequency transformer T1 is in the same direction as the corresponding terminals of the secondary windings Ns1 and Ns2.

[0015] 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.

[0016] In a preferred embodiment: the resonant frequency of the resonant circuit is Lm is the magnetizing inductance.

[0017] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0018] This invention provides a single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits. The voltage stress on switch Q3 can be significantly reduced, while the increased stress on switches Q1 and Q2 equals the input voltage. Therefore, switch selection is more advantageous, allowing for the selection of cost-effective 500V switches. Two fewer power diodes are also eliminated in the main circuit, thus reducing the cost of power semiconductor devices. Furthermore, the operating principle of the AHB flyback circuit is exactly the same as that of a conventional AHB flyback circuit. Q3 and Q4 achieve ZVS across the entire load range, and the secondary rectifier diodes achieve ZCS. The wide gain range enables wide input and output voltage, offering significant advantages in thermal design and efficiency, and facilitating product development for practical applications. Attached Figure Description

[0019] Figure 1 is a circuit diagram of a preferred embodiment of the present invention;

[0020] Figure 2 is a timing diagram of a preferred embodiment of the present invention;

[0021] Figures 3-9 show the equivalent circuit diagrams of the preferred embodiments of the invention in various modes. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "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 invention can be understood according to the specific circumstances.

[0025] Referring to Figure 1, this example provides a single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits, including a bridgeless Buck-Boost circuit and an AHB flyback circuit. The Buck-Boost circuit includes three switching transistors Q1, Q2, and Q3, with one of the switching transistors, Q3, being multiplexed as the upper transistor of the AHB flyback circuit. Q1 to Q6 are power MOSFETs, where Q1, Q2, and Q3 are the switching transistors of the Buck-Boost circuit, Q3 is the upper transistor of the AHB flyback circuit, and Q4 is the lower transistor of the AHB flyback circuit. For control, Q1 to Q4 use PWM / PFM control. Q1 and Q2 operate during the positive and negative half-cycles of the AC signal, respectively, and Q1 (or Q2) and Q4 are simultaneously turned on and off, with Q1 (or Q2) and Q3 driving complementaryly. D1 to D2 are AC input rectifier diodes, which, together with Q1 and Q2, rectify the AC input into pulsating DC. D3-D4 are power diodes, with D3 being the freewheeling diode for the Buck-Boost circuit and D4 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, with its primary winding Np and secondary winding Ns1 and Ns2 having the same polarity in the same direction.

[0026] In this embodiment, the bridgeless 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. The positive half-cycle is used as an example; the negative half-cycle will not be detailed here. Figure 2 shows the corresponding key waveforms, and Figures 3 to 9 are equivalent diagrams of the seven modes during the positive half-cycle.

[0027] 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 has zero voltage, and Q1 is turned on with zero current. in The Buck-Boost inductor L1 is charged by switches 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 AHB flyback circuit through the switching transistor Q3. During this stage, the secondary-side rectifier diode D4 in the AHB flyback circuit is reverse-biased and cut off, storing the input energy in Lm and Lr, and the magnetizing current i Lm Equal to the resonant current i Lr The voltage rises linearly. At this time, the output capacitor C2 supplies power to the output load R1.

[0028] Mode 2 [t1~t2]: At time t1, Q1 and Q3 are turned off, entering the dead time. The current in inductor L1 reaches its maximum and begins to discharge. 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 excitation current i decreases linearly. Lm The junction capacitance of Q3 is charged, and the junction capacitance of Q4 is discharged until the voltage across the junction capacitance of Q4 drops to zero. At this time, the output capacitor C2 continues to supply power to the output load R1.

[0029] Mode 3 [t2~t3]: At time t2, the resonant current i Lr All current flows through the body diode of switching transistor Q4, satisfying the zero-voltage turn-on condition, and Q4 is turned on. The secondary rectifier diode D4 is also turned on, transferring the energy stored in Lm to the secondary side to charge output capacitor C2 and supply power to output load R1. Simultaneously, the voltage across the primary winding of the transformer is clamped at -nVo, and the magnetizing current i... Lm As the linear decrease occurs, the resonant inductor Lr and the resonant capacitor Cr begin to resonate.

[0030] Mode 4 [t3~t4]: At time t3, the current i in the inductor L of the Buck-Boost circuit. L The current drops to zero. Q4 continues to conduct, and the resonant inductor Lr and resonant capacitor Cr continue to resonate, with the resonant current i... Lr Greater than the excitation current i Lm The secondary diode D4 continues to conduct.

[0031] Mode 5 [t4~t5]: At time t4, 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 primary winding of 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.

[0032] Mode 6 [t5~t6]: At time t5, Q4 is turned off, entering the dead time. Excitation current iLm Charge the junction capacitance of Q4 and discharge the junction capacitance of Q3 until the voltage across the junction capacitance of Q3 drops to zero.

[0033] The above description is merely a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention by those skilled in the art within the scope of the technology disclosed in the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention. Industrial applicability

[0034] This invention provides a single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits. The voltage stress on switch Q3 can be significantly reduced, while the increased stress on switches Q1 and Q2 equals the input voltage. Therefore, switch selection is more advantageous, allowing for the selection of cost-effective 500V switches. Two fewer power diodes are also eliminated in the main circuit, thus reducing the cost of power semiconductor devices. Furthermore, the operating principle of the AHB flyback circuit is exactly the same as that of a conventional AHB flyback circuit. Q3 and Q4 achieve ZVS across the entire load range, and the secondary rectifier diodes achieve ZCS. The wide gain range enables wide input and output voltage, offering significant advantages in thermal design and efficiency, and facilitating product development for practical applications.

Claims

1. A single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits, characterized in that: It includes a bridgeless Buck-Boost circuit and an AHB flyback 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 AHB flyback circuit.

2. The single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits according to claim 1, characterized in that: The AHB flyback circuit also includes the lower transistor Q4.

3. A single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits according to claim 2, characterized in that: Switch Q1 or Q2 is turned on and off simultaneously with the upper switch Q3, and the state is opposite to that of the lower switch Q4.

4. A single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits according to claim 3, characterized in that: The bridgeless Buck-Boost circuit also includes AC input rectifier diodes D1 and D2; the AC input rectifier diodes D1 and D2, together with the switching transistors Q1 and Q2, rectify the AC input into pulsating DC.

5. A single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits according to claim 4, characterized in that: The AC input terminals of the AC input rectifier diodes D1 and D2 are connected to the AC power supply, and the DC output terminals are connected to the high-frequency transformer T1 through the Buck-Boost circuit and the AHB flyback circuit.

6. A single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits according to claim 5, characterized in that: The bridgeless Buck-Boost circuit also includes a freewheeling diode D3, and the AHB flyback circuit also includes a rectifier diode D4, which is used to rectify the high-frequency AC voltage of the secondary winding of the high-frequency transformer T1 into DC.

7. A single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits according to claim 6, characterized in that: The opposite terminals of the secondary winding of the high-frequency transformer T1 are respectively connected to the anodes of diodes D4, the cathodes of diodes D4 are interconnected and grounded through electrolytic capacitor C2, and the cathodes of diodes D4 are also connected to the same terminals of the secondary winding through load R1.

8. A single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits according to claim 7, characterized in that: The primary winding Np of the high-frequency transformer T1 is in the same direction as the corresponding terminals of the secondary windings Ns1 and Ns2.

9. A single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits according to claim 8, 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.

10. A single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits according to claim 9, characterized in that: The resonant frequency of the resonant circuit is Lm is the magnetizing inductance.

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