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

Abstract

The utility model provides a single-stage conversion device integrated with a Buck-Boost circuit and an AHB flyback circuit. The single-stage conversion device is characterized in that the single-stage conversion device comprises the Buck-Boost circuit and the AHB flyback circuit; the Buck-Boost circuit comprises two switch tubes Q1 and Q2, and one switch tube Q2 is multiplexed as an upper tube of the AHB flyback circuit. The single-stage conversion device integrated with the Buck-Boost and AHB flyback circuits is small in stress, has obvious advantages in thermal design and efficiency, and is more convenient for product development in practical application.

Description

Technical Field

[0001] The utility model relates to a power converter, in particular to a single-stage conversion device integrating a Buck-Boost 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. An LED lighting system includes an LED driving power supply and an LED lamp, and its core is the LED driving power supply. High-efficiency and energy-saving high-power LED driving power supplies have become an important research direction in the industry.

[0003] High frequency and miniaturization are important indicators in the current design of switching power supplies. If the driving 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, the 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, a resonant converter can achieve zero-voltage turn-on of the switching tube and zero-current turn-off of the secondary rectifier diode within a wide load range, thereby reducing the switching tube loss and improving the 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 tube and capacitor at the subsequent stage.

[0005] There are mainly two technical solutions in the prior art: 1. For high power, it is a two-stage type. The first stage Boost realizes power factor correction and voltage regulation, and the second stage DCDC (isolated or non-isolated topology) realizes output voltage regulation (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 regulation by a single-stage flyback. It is mainly applied to low-power LED driving 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 present utility model is to provide a single-stage conversion device integrating a Buck-Boost and an AHB flyback circuit, which has small stress and obvious advantages in thermal design and efficiency, and is more convenient for product development in practical applications.

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

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

[0009] In a preferred embodiment: the AHB flyback circuit further includes a lower tube Q3, and the state of Q3 is opposite to that of Q1 and Q2.

[0010] In a preferred embodiment: the switching tubes Q1, Q2 and the upper tube Q3 are controlled by PWM or PFM.

[0011] In a preferred embodiment: it further includes a rectifier bridge, whose AC input terminal is connected to an AC power supply, and the DC output terminal is connected to a high-frequency transformer T1 through the Buck-Boost circuit and the AHB flyback circuit.

[0012] In a preferred embodiment: the two ends of the secondary winding of the high-frequency transformer T1 are connected through a diode D6 and a resistor R1; the resistor R1 is connected in parallel with a capacitor C2.

[0013] 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.

[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 tubes Q1, Q2 and the upper tube Q3 are power MOS tubes.

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

[0017] The utility model provides a single-stage conversion device integrating a Buck-Boost circuit and an AHB flyback circuit. Two MOS transistors are arranged in the Buck-Boost circuit, which are reused as the upper transistor Q2 of the AHB flyback circuit. The voltage stress of the switching transistor Q2 can be significantly reduced, and the stress of the added switching transistor Q1 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. Q2 and Q3 can achieve ZVS within the full load range, with a large gain change range, enabling wide voltage input and output. At the same time, there are obvious advantages in thermal design and efficiency, which is more convenient for product development in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the circuit diagram of the preferred embodiment of the present utility model;

[0019] Figure 2 is the timing diagram of the preferred embodiment of the present utility model;

[0020] Figures 3 - 9 is the equivalent circuit diagram of the preferred embodiment of the present utility model in each mode;

[0021] Figure 10 is the alternative scheme diagram of the preferred embodiment of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying 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 making 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 should not 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 a wall-mounted connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be directly connected or indirectly connected through an intermediate medium. It 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 circumstances.

[0025] Reference Figure 1 , this embodiment provides a single-stage conversion device integrating a Buck-Boost circuit and an AHB flyback circuit, including a rectifier bridge, a Buck-Boost circuit, an AHB flyback circuit, a high-frequency transformer T1, and a load R1;

[0026] Among them, the rectifier bridge is a full-bridge rectifier, including four diodes D1, D2, D3, and D4; the AC input terminal of the rectifier bridge is connected to an AC power supply, and the DC output terminal outputs pulsating direct current. Among them, the positive pole of the DC output is connected to the cathode of diode D5, and the anode of diode D5 is connected to one end of the primary winding of the high-frequency transformer T1; the negative pole of the DC output is connected to the other end of the primary winding of the high-frequency transformer T1 through the switching tube Q1, the high-frequency capacitor Cr, and the inductor Lr.

[0027] The cathode of the diode D5 is also connected to the anode of the diode D5 through the inductor L1 and the electrolytic capacitor C1; the same-named ends of the inductor L1 and the electrolytic capacitor C1 are also connected to the high-frequency capacitor Cr through the switching tube Q2, and the anode of the diode D5 is also connected to the high-frequency capacitor Cr through the switching tube Q3.

[0028] One end of the secondary winding is connected to the other end through the diode D6 and the resistor R1, and the resistor R1 is connected in parallel with the capacitor C2.

[0029] The switching tubes Q1, Q2, and Q3 are respectively power MOS tubes. For the above single-stage conversion device integrating a Buck-Boost circuit and an AHB flyback circuit, by integrating the Buck-Boost circuit and the AHB flyback circuit together and reusing the MOS tube Q2, the switching tube Q2 is both the switching tube of the Buck-Boost circuit and the upper tube of the AHB flyback circuit at the same time.

[0030] In terms of control, Q1, Q2, and Q3 adopt PWM\PFM control. Q1 and Q2 are turned on and off simultaneously, and Q3 is complementary to the drive of Q1\Q2. D5 and D6 are power diodes, which are used to rectify the high-frequency AC voltage of the secondary winding of T1 into direct current. 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.

[0031] When working, it is divided into the following six modes:

[0032] Mode 1 [t0~t1]: Before t0, the current i of inductor L1 L has dropped to 0. At the same time, due to the conduction of the body diode of Q2, at the moment of t0, Q2 is at zero voltage and Q1 is turned on with zero current. u in charges the Buck - Boost inductor L1 through the switching transistors Q1 and Q2. The current i of inductor L1 L increases linearly with a slope of u in / L1. At the same time, the DC - bus capacitor C1 supplies energy to the AHB flyback circuit through the switching transistor Q2. During this stage, the secondary rectifier diode D6 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.

[0033] Mode 2 [t1~t2]: At the moment of t1, Q1 and Q2 are turned off and enter the dead - time. The current of inductor L1 reaches the maximum and starts to discharge. Its current i L charges the DC - bus capacitor C1 through the power diode D5. The current i of inductor L1 L decreases linearly. The exciting current i Lm charges the junction capacitance of Q2 and discharges the junction capacitance of Q3 until the voltage across the junction capacitance of Q3 drops to zero. At this time, the output capacitor C2 continues to supply power to the output load R1.

[0034] Mode 3 [t2~t3]: At the moment of t2, the resonant current i Lr flows entirely through the body diode of the switching transistor Q3. The switching transistor Q3 meets the zero - voltage turn - on condition, and at this time Q3 is turned on. The secondary rectifier diode D6 is turned on, and the energy stored in Lm is transferred to the secondary side, charging the output capacitor C2 and supplying 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.

[0035] Mode 4 [t3~t4]: At the moment of t3, the current i of the inductor L in the Buck - Boost circuit L drops to zero. Q3 continues to conduct, and 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 D6 continues to conduct.

[0036] Mode 5 [t4~t5]: At time t4, the current in Lr is equal to the current in Lm, and the secondary rectifier diode D6 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 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 remains consistent with the exciting current in this stage and is approximately a constant value.

[0037] Mode 6 [t5~t6]: At time t5, Q3 turns off and enters the dead time. The exciting current i Lm charges the junction capacitance of Q3 and discharges the junction capacitance of Q2 until the voltage across the junction capacitance of Q2 drops to zero, as shown in Figure 9 .

[0038] As a simple replacement for this embodiment, Figure 1 the diode D6 in Figure 10 can also be changed to the

[0039] The above is only a preferred specific embodiment of the present invention, 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 converter integrating Buck-Boost and AHB flyback circuits, characterized in that: It includes a Buck-Boost circuit and an AHB flyback circuit; the Buck-Boost circuit includes two switch tubes Q1 and Q2, and one of the switch tubes Q2 is multiplexed as the upper tube of the AHB flyback circuit.

2. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 1, characterized in that: The switch tubes Q1 and Q2 are turned on or off at the same time.

3. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 2, characterized in that: The AHB flyback circuit further includes a lower tube Q3, and the state of Q3 is opposite to that of Q1 and Q2.

4. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 3, characterized in that: The switch tubes Q1, Q2 and the lower tube Q3 are controlled by PWM or PFM.

5. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to any one of claims 1 to 4, characterized in that: It also includes a rectifier bridge, whose AC input end is connected to an AC power supply, and whose DC output end is connected to a high-frequency transformer T1 through the Buck-Boost circuit and the AHB flyback circuit.

6. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 5, characterized in that: The two ends of the secondary winding of the high-frequency transformer T1 are connected via a diode D6 and a resistor R1; the resistor R1 is connected in parallel with the capacitor C2.

7. The single-stage converter integrating Buck-Boost and AHB flyback circuits 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 single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 7, characterized in that: The resonant frequency of the resonant circuit is Lm is the magnetizing inductance.

9. The single-stage converter integrating Buck-Boost and AHB flyback circuits according to claim 3, characterized in that: The switch tubes Q1, Q2 and the lower tube Q3 are power MOS tubes.

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