Single-stage conversion device integrating buck-boost circuit and AHB flyback circuit

Abstract

The present invention provides a single-stage conversion device integrating a Buck-Boost circuit and an AHB flyback circuit, comprising a Buck-Boost circuit and an AHB flyback circuit. The Buck-Boost circuit comprises two switching transistors, i.e., Q1 and Q2, and one of the switching transistors, i.e., Q2, is reused as an upper transistor of the AHB flyback circuit. The single-stage conversion device integrating a Buck-Boost circuit and an AHB flyback circuit involves small stress, offering obvious advantages in thermal design and efficiency, thereby facilitating product development in practical applications.

Description

A single-stage conversion device integrating buck-boost and AHB flyback circuits TECHNICAL FIELD

[0001] The present invention relates to power converters, and in particular to a single-stage conversion device integrating buck-boost and AHB flyback circuits. BACKGROUND

[0002] With the rapid development of semiconductor technology, the fourth generation of electric light source LED has been widely promoted and used. Compared with traditional electric light source, LED has many incomparable advantages, such as long service life, high efficiency, low power consumption, high brightness, small size and other advantages, so it is particularly prominent in the application of lighting field. LED lighting system includes LED driving power and LED lamp two parts, and the core is LED driving power. High-efficiency and energy-saving high-power LED driving power becomes an important research direction in the industry.

[0003] High frequency and miniaturization are important indicators of current switching power supply design. If the driving power works in hard switching mode, the increase of switching frequency will generate a lot of switching loss, which reduces the conversion efficiency of the system. Therefore, the soft switching technology aiming at reducing switching loss has also become an important research hotspot in the field of power electronics.

[0004] Resonant converters, including series, parallel, series-parallel resonant converters, etc. are common soft switching converters. Resonant converter can realize zero voltage turn-on of switching tube and zero current turn-off of secondary side rectifier diode in a wide load range through reasonable design, thereby reducing switching tube loss and improving efficiency. AC-DC conversion adopts Buck-Boost topology, and the circuit works in discontinuous mode to automatically realize PFC function. It is a single-switch low-order boost-buck converter circuit, which realizes intermediate DC bus voltage boost-buck, and reduces the stress of LLC switching tube and capacitor in the later stage.

[0005] There are mainly two technical solutions in the prior art: 1. High power is two-stage, which realizes power factor correction and voltage stabilization by the first stage Boost, and realizes output voltage stabilization (and electrical isolation, etc.) by the second stage DCDC (isolated or non-isolated topology). This scheme is mature in technology, but the system is complex, the cost is high, and the efficiency is low; 2. Small power single-stage PFC flyback, which realizes input power factor correction and output voltage stabilization by single-stage flyback, mainly applied to small power LED driving power. This scheme is mature in technology, the system is simple, the cost is low, and the efficiency is high, but the output has obvious power frequency ripple (which will cause LED lamp flicker), the input voltage range is narrow, and the lack of bus capacitor causes lightning surge problem. SUMMARY

[0006] The present application aims to provide a single-stage conversion device integrating Buck-Boost and AHB flyback circuits, which has small stress, obvious advantages in thermal design and efficiency, and is more convenient for product development in practical application.

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

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

[0009] In a preferred embodiment, the AHB flyback circuit further comprises a lower tube Q3, and the state of the Q3 is opposite to that of the 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, a rectifier bridge is further included, the AC input end of which is connected to an AC power supply, and the DC output end is connected to a high-frequency transformer T1 through the Buck-Boost circuit and the AHB flyback circuit.

[0012] In a preferred embodiment, two ends of the secondary winding of the high-frequency transformer T1 are connected through a diode D6 and a resistor R1; and 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 resonance loop composed of a series-connected inductor Lr and capacitor Cr.

[0014] In a preferred embodiment, the resonance frequency of the resonance loop is Lm is the excitation 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 scheme of the present application has the following beneficial effects:

[0017] The application provides a single-stage conversion device integrating Buck-Boost and AHB flyback circuits, two MOS transistors are arranged in the Buck-Boost circuit, so as to reuse the upper transistor Q2 of the AHB flyback circuit. The voltage stress of the switch transistor Q2 can be obviously reduced, the stress of the added switch transistor Q1 is equal to the input voltage, so the selection of the switch transistor is more favorable, and a 500V switch transistor with high cost performance can be selected, two power diodes are also saved in the main circuit, so 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 the conventional AHB flyback circuit, Q2 and Q3 can realize ZVS in the full load range, the gain change range is large, wide voltage input and output can be realized, and obvious advantages are obtained in the thermal design and efficiency, and the product development in the actual application is more convenient. BRIEF DESCRIPTION OF DRAWINGS

[0018] Fig. 1 is a circuit diagram of the preferred embodiment of the application;

[0019] Fig. 2 is a timing diagram of the preferred embodiment of the application;

[0020] Figs. 3-9 are equivalent circuit diagrams of the preferred embodiment of the application in various modes;

[0021] Fig. 10 is an alternative scheme of the preferred embodiment of the application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0023] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom end" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance. In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "provided with", "sleeved / connected", "connected" and the like should be broadly understood, for example, "connected" can be wall-mounted connection, can also be detachable connection, or integral connection, can be mechanical connection, can also be electrical connection, can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements, and the specific meaning of the above terms in the present application can be understood according to the specific circumstances by those skilled in the art.

[0024] Referring to FIG. 1, the present example provides a single-stage conversion device integrating Buck-Boost and AHB flyback circuits, including a rectifier bridge, a Buck-Boost circuit, an AHB flyback circuit, a high-frequency transformer T1 and a load R1;

[0025] The rectifier bridge is a full-bridge rectifier, including four diodes D1, D2, D3 and D4. The AC input end of the rectifier bridge is connected to an AC power supply, and the DC output end outputs pulsating DC. The positive DC output end is connected to the cathode of diode D5, and the anode of diode D5 is connected to one end of the primary winding of high-frequency transformer T1. The negative DC output end is connected to the other end of the primary winding of high-frequency transformer T1 through switch tube Q1, high-frequency capacitor Cr and inductor Lr.

[0026] The cathode of diode D5 is also connected to the anode of diode D5 through inductor L1 and electrolytic capacitor C1. The same end of inductor L1 and electrolytic capacitor C1 is also connected to high-frequency capacitor Cr through switch tube Q2. The anode of diode D5 is also connected to high-frequency capacitor Cr through switch tube Q3.

[0027] One end of the secondary winding is connected to the other end through diode D6 and resistor R1, and resistor R1 is connected in parallel with capacitor C2.

[0028] The switch tubes Q1, Q2 and Q3 are power MOS tubes. The above-mentioned single-stage conversion device integrating Buck-Boost and AHB flyback circuits reuses MOS tube Q2 by integrating Buck-Boost circuit and AHB flyback circuit together, so that MOS tube Q2 is both the switch tube of Buck-Boost circuit and the upper tube of AHB flyback circuit.

[0029] In control, Q1, Q2, Q3 use PWM\PFM control, Q1, Q2 are turned on and turned off at the same time, Q3 is driven complementarily with Q1\Q2. D5, D6 are power diodes, used to rectify the high-frequency alternating voltage of the secondary winding of T1 into direct current. L1, Lr are high-frequency inductors, C1, C2 are electrolytic capacitors, and Cr is a high-frequency capacitor. T1 is a high-frequency transformer.

[0030] When working, it is divided into the following 6 modes:

[0031] Mode 1 [t0-t1]: Before t0, the current i L of the inductor L1 has dropped to 0, and at the same time, since the body diode of Q2 is turned on, at t0, Q2 is zero voltage, Q1 is zero current, and u in is turned on. The switch tube Q1, Q2 charges the Buck-Boost inductor L1, and the current i L of the inductor L1 increases linearly with the slope u in / L1. At the same time, the DC bus capacitor C1 provides energy for the AHB flyback circuit through the switch tube 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. The magnetizing current i Lm is equal to the resonant current i Lr , and linearly rises. At this time, the output capacitor C2 supplies power to the output load R1.

[0032] Mode 2 [t1-t2]: At t1, Q1 and Q2 are turned off, and enter the dead time. The inductor L1 current reaches the maximum and begins to discharge. Its current i L charges the DC bus capacitor C1 through the power diode D5, and the current i L of the inductor L1 decreases linearly. The magnetizing current i Lm charges the junction capacitor of Q2 and discharges the junction capacitor of Q3 until the voltage across the junction capacitor of Q3 drops to zero. At this time, the output capacitor C2 continues to supply power to the output load R1.

[0033] Mode 3 [t2-t3]: At t2, the resonant current i Lr flows through the body diode of the switch tube Q3, and the switch tube Q3 meets the zero-voltage turn-on condition, at which time Q3 is turned on. The secondary rectifier diode D6 is turned on, 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 magnetizing current i Lm linearly decreases, and the resonant inductor Lr and the resonant capacitor Cr begin to resonate.

[0034] Mode 4 [t3-t4]: at t3, the current i of the inductor L in the Buck-Boost circuit L to zero. Q3 continues to be turned on, and the resonant inductor Lr and the resonant capacitor Cr continue to resonate, and the resonant current i Lr is greater than the excitation current i Lm The secondary diode D6 continues to be turned on.

[0035] Mode 5 [t4-t5]: at t4, the current in Lr is equal to the current in Lm, the secondary rectifier diode D6 is turned off with zero current, and the output voltage is no longer clamped to the primary winding of the transformer, and Lm becomes a free resonant inductor and participates in the resonance, and the excitation inductor Lm, the resonant inductor Lr and the resonant capacitor Cr form a series resonant circuit, and the resonant frequency is equal to the resonant frequency

[0036] Mode 6 [t5-t6]: at t5, Q3 is turned off and enters a dead time. The excitation current i Lm charges the junction capacitor of Q3 and discharges the junction capacitor of Q2, until the voltage across the junction capacitor of Q2 drops to zero, as shown in Fig. 9.

[0037] As a simple replacement of this embodiment, the diode D6 in Fig. 1 can also be replaced by the position placed in Fig. 10.

[0038] The above is only a preferred specific embodiment of the present application, but the design concept of the present application is not limited thereto, and any person skilled in the art can make non-essential changes to the present application within the technical scope disclosed by the present application, and such changes shall be deemed to fall within the scope of protection of the present application. Industrial applicability

[0039] The present application provides a single-stage conversion device integrating Buck-Boost and AHB flyback circuits, two MOS transistors are arranged in the Buck-Boost circuit, so that the upper transistor Q2 of the AHB flyback circuit is reused. The voltage stress of the switch transistor Q2 can be significantly reduced, and the stress of the added switch transistor Q1 is equal to the input voltage, so the selection of the switch transistor is more advantageous, and a 500V switch transistor with high cost performance can be selected, and two power diodes are also saved 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, and Q2 and Q3 can realize ZVS in the full load range, the gain change range is large, wide voltage input and output can be realized, and there are obvious advantages in thermal design and efficiency, which is more convenient for product development in practical application.

Claims

1. A single-stage converter integrating Buck-Boost and AHB flyback circuits, characterized by: 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 upper tube Q3 are controlled by PWM or PFM.

5. A single-stage converter integrating a Buck-Boost and an AHB flyback circuit 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 the AC power supply, and whose DC output end is connected to the 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 upper tube Q3 are power MOS tubes.

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