Single-stage bridgeless conversion device integrated with Buck-Boost and AHB flyback circuits

Abstract

The utility model provides a single-stage bridgeless conversion device integrated with a Buck-Boost circuit and an AHB flyback circuit. The single-stage bridgeless conversion device is characterized by comprising a bridgeless Buck-Boost circuit and an AHB flyback circuit, the Buck-Boost circuit comprises three switching tubes Q1, Q2 and Q3, and one of the switching tubes Q3 is multiplexed as an upper tube of the AHB flyback circuit. According to the single-stage bridgeless conversion device integrated with the Buck-Boost and AHB flyback circuits, the voltage stress of the switch tube Q3 can be obviously reduced, and the stress of the added switch tubes Q1 and Q2 is equal to the input voltage, so that the type selection of the switch tubes is more favorable, a 500V switch tube with high cost performance can be selected, two power diodes are reduced in a main loop, and the cost performance of the main loop is improved. Therefore, the cost of the power semiconductor device can be reduced. Meanwhile, the working principle of the AHB flyback circuit part is completely the same as that of a conventional AHB flyback circuit, Q3 and Q4 can realize ZVS in a full-load range, a secondary side rectifier diode realizes ZCS, the gain change range is large, and wide voltage input and output can be realized.

Description

Technical Field

[0001] The utility model relates to a power converter, in particular to a single-stage bridge-less conversion device integrating a Buck-Boost circuit and an AHB flyback circuit. Background Art

[0002] With the rapid development of semiconductor technology, the fourth-generation electric light source LED has been widely promoted and used. Compared with traditional electric light sources, LEDs have many incomparable advantages, such as long life, high efficiency, low power consumption, high brightness, small size, etc. Therefore, their application in the lighting field is particularly prominent. The LED lighting system consists of two parts: an LED driver power supply and an LED lamp, and its core is the LED driver power supply. High-efficiency and energy-saving high-power LED driver power supplies have become an important research direction in the industry.

[0003] High frequency and miniaturization are important indicators in the design of current switching power supplies. If the driver power supply operates in the hard-switching mode, the increase in its switching frequency will generate a large switching loss, reducing the conversion efficiency of the system. Therefore, soft-switching technology aimed at reducing switching losses has also become an important research hotspot in the field of power electronics research.

[0004] Resonant converters, including series, parallel, and series-parallel resonant converters, etc., are all common soft-switching converters. Through reasonable design, resonant converters can achieve zero-voltage turn-on of switching tubes and zero-current turn-off of secondary rectifier diodes within a wide load range, thereby reducing switching tube losses and improving efficiency. The AC-DC conversion adopts the Buck-Boost topology, and the circuit operates in the discontinuous mode, automatically realizing the PFC function. It is a single-switch low-order step-up / step-down converter circuit that can increase or decrease the intermediate DC bus voltage, reducing the stress on the LLC switching tubes and capacitors at the subsequent stage.

[0005] The current most mainstream technical solutions are as follows: 1. For high power, it is a two-stage type. The first stage Boost is used to achieve power factor correction and voltage stabilization, and the second stage DCDC (isolated or non-isolated topology) is used to achieve output voltage stabilization (and electrical isolation, etc.). This solution has mature technology, but the system is complex, the cost is high, and the efficiency is low; 2. For low power, it is a single-stage PFC flyback, which simultaneously realizes input power factor correction and output voltage stabilization through a single-stage flyback. It is mainly applied to low-power LED driver power supplies. This solution has mature technology, a simple system, low cost, and high efficiency. However, there are obvious power frequency ripples in the output (which will cause LED lights to flicker), the input voltage range is narrow, and the lack of a bus capacitor brings lightning surge problems. Summary of the Utility Model

[0006] The main technical problem to be solved by the utility model is to provide a single-stage bridge-less conversion device integrating a Buck-Boost circuit and an AHB flyback circuit, which simplifies the circuit, reduces the volume, improves the power density, and reduces the cost.

[0007] To solve the above technical problems, the present utility model provides a single-stage bridge-less conversion device integrating a Buck-Boost circuit and an AHB flyback circuit, which includes a bridge-less Buck-Boost circuit and an AHB flyback circuit; the Buck-Boost circuit includes three switching tubes Q1, Q2, and Q3, and one of the switching tubes Q3 is multiplexed as the upper tube of the AHB flyback circuit.

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

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

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

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

[0012] In a preferred embodiment: the bridge-less Buck-Boost circuit further includes a freewheeling diode D3, and the AHB flyback circuit further includes a rectifier diode D4, and the rectifier diode D4 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-named ends of the secondary winding of the high-frequency transformer T1 are respectively connected to the anodes of the diodes D4, the cathodes of the diodes D4 are connected to each other and grounded through an electrolytic capacitor C2, and the cathodes of the diodes D4 are also connected to the same-named end of the secondary winding through a load R1.

[0014] In a preferred embodiment: the same-named ends of the primary winding Np of the high-frequency transformer T1 and the secondary windings Ns1, Ns2 are in the same direction.

[0015] In a preferred embodiment: one end of the primary winding of the high-frequency transformer T1 is connected to a resonant circuit composed 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 exciting inductance.

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

[0018] The utility model provides a single-stage bridgeless conversion device integrating a Buck-Boost circuit and an AHB flyback circuit. The voltage stress of the switching transistor Q3 can be significantly reduced. The stress of the added switching transistors Q1 and Q2 is equal to the input voltage. Therefore, it is more advantageous in the selection of switching transistors, and a 500V switching transistor with high cost performance can be selected. There are also two fewer power diodes in the main circuit, so the cost of power semiconductor devices can be reduced. At the same time, the working principle of the AHB flyback circuit part is exactly the same as that of the conventional AHB flyback circuit. Q3 and Q4 can achieve ZVS within the full load range, and the secondary rectifier diode achieves ZCS. The gain change range is large, and wide-voltage input and output can be realized, which has obvious advantages in thermal design and efficiency and is more convenient for product development in practical applications. Description of the Drawings

[0019] Figure 1 is the circuit diagram of the preferred embodiment of the utility model;

[0020] Figure 2 is the timing diagram of the preferred embodiment of the utility model;

[0021] Figures 3 - 9 The equivalent circuit diagrams of the preferred embodiment of the utility model in each mode. Detailed Embodiments

[0022] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the drawings in the embodiments of the present utility model; obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0023] In the description of the present utility model, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "top / bottom end", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation of the present utility model. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0024] In the description of the present utility model, it should be noted that unless otherwise clearly specified and defined, terms such as "installation", "provided with", "sheathed / connected", "connection", etc. should be understood in a broad sense. For example, "connection" can be wall-mounted connection, detachable connection, or integral connection, can be mechanical connection, can also be electrical connection, can be directly connected, or can be indirectly connected through an intermediate medium, and can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific situations.

[0025] Reference Figure 1 , this embodiment provides a single-stage bridgeless conversion device integrating a Buck-Boost and an AHB flyback circuit, including a bridgeless Buck-Boost circuit and an AHB flyback circuit; the Buck-Boost circuit includes three switching tubes Q1, Q2, and Q3, and one of the switching tubes Q3 is multiplexed as the upper tube of the AHB flyback circuit. Q1~Q6 are power MOS tubes. Among them, Q1, Q2, and Q3 are the switching tubes of the Buck-Boost, Q3 is the upper tube of the AHB flyback circuit, and Q4 is the lower tube of the AHB flyback circuit. In terms of control, Q1~Q4 adopt PWM\PFM control. Q1 and Q2 work in the positive and negative half-cycles of the AC respectively. Q1 (or Q2) and Q4 are turned on and off simultaneously, and the driving of Q1 (or Q2) and Q3 is complementary. D1~D2 are AC input rectifier diodes, which, together with Q1 and Q2, rectify the AC input into pulsating DC. D3~D4 are power diodes, where D3 is the freewheeling diode of the Buck-Boost circuit, and D4 is 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, and the homonymous ends of its primary winding Np and secondary windings Ns1 and Ns2 are in the same direction.

[0026] In this embodiment, the bridgeless Buck-Boost circuit operates in the discontinuous mode. During the positive and negative cycles of the power frequency of the AC power supply, the working states of the circuit are symmetrical. Here, the positive half-cycle is taken as an example for illustration, and the negative half-cycle will not be elaborated one by one. Figure 2 are the corresponding key waveforms. Figures 3 to 9 are the equivalent diagrams of 7 modes in the positive half-cycle.

[0027] Mode 1 [t0~t1]: Before t0, the current i L of the inductor L1 has dropped to 0. At the same time, since the body diode of Q3 is conducting, at the moment of t0, Q3 has zero voltage and Q1 is turned on with zero current. u in charges the Buck-Boost inductor L1 through the switching tubes Q1 and Q3, and the current i L of the inductor L1 increases with a slope of u in / L1 increases linearly. At the same time, the DC bus capacitor C1 supplies energy to the AHB flyback circuit through the switching transistor Q3. During this stage, the secondary rectifier diode D4 in the AHB flyback circuit is reverse-biased and cut off, and the input energy is stored in Lm and Lr, and the exciting current i Lm is equal to the resonant current i Lr , and rises linearly. At this time, the output capacitor C2 supplies power to the output load R1.

[0028] Mode 2 [t1~t2]: At the moment of t1, Q1 and Q3 are turned off, and enter the dead time. The current of the inductor L1 reaches the maximum and starts to discharge. Its current i L charges the DC bus capacitor C1 through the power diode D3, and the current i L of the inductor L1 decreases linearly. The exciting current i Lm charges the junction capacitance of Q3 and discharges the junction capacitance of Q4 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 the moment of t2, the resonant current i Lr flows entirely through the body diode of the switching transistor Q4, and the switching transistor Q4 meets the zero-voltage turn-on condition. At this time, Q4 conducts. The secondary rectifier diode D4 conducts, and the energy stored in Lm is transferred to the secondary side, charges the output capacitor C2 and supplies power to the output load R1. At the same time, the voltage across the primary winding of the transformer is clamped at -nVo, and the exciting current i Lm decreases linearly, and the resonant inductor Lr and the resonant capacitor Cr start to resonate.

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

[0031] Mode 5 [t4~t5]: At the moment of t4, the current in Lr is equal to the current in Lm, and the secondary rectifier diode D4 turns off with zero current. The output voltage no longer clamps the primary winding of the transformer, and Lm becomes a free resonant inductor and participates in the resonance. The exciting inductor Lm, the resonant inductor Lr, and the resonant capacitor Cr form a series resonant circuit and resonate at the resonant frequency Since the exciting inductor Lm is very large, the resonant period is very large, and the resonant current is consistent with the exciting current during this stage and is approximately a constant value.

[0032] Mode 6 [t5~t6]: At the moment of t5, Q4 is turned off, and enter the dead time. The exciting 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] As described above, only the preferred specific embodiments of the present invention are provided, but the design concept of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention who makes non-substantive modifications to the present invention using this concept shall fall within the scope of infringement of the protection of the present invention.

Claims

1. A single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits, characterized in that: It comprises a bridgeless Buck-Boost circuit and an AHB flyback circuit; the Buck-Boost circuit comprises three switch tubes Q1, Q2 and Q3, and one of the switch tubes Q3 is multiplexed as the upper tube 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 further includes a lower tube Q4.

3. The single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits according to claim 2, characterized in that: The switch tube Q1 or Q2 and the switch tube Q3 are turned on and off at the same time, and the state is opposite to that of the lower tube Q4.

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

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

6. The single-stage bridgeless converter integrating Buck-Boost and AHB flyback circuits according to claim 5, characterized in that: 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 a DC voltage.

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

8. The 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 has the same direction as the like-named ends of the secondary windings Ns1 and Ns2.

9. The 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. The 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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