Single-stage bridgeless conversion device integrating Buck-Boost circuit and full-bridge LCC circuit

Abstract

The utility model provides a single-stage bridgeless conversion device integrating a Buck-Boost circuit and a full-bridge LCC circuit. The single-stage bridgeless conversion device comprises the bridgeless Buck-Boost circuit and the full-bridge LCC 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 full-bridge LCC circuit. The Buck-Boost circuit is provided with three MOS (Metal Oxide Semiconductor) tubes, so that one MOS tube can be multiplexed as a switch tube Q3 of the LCC circuit. The MOS tubes Q1 and Q2 serve as input rectification MOS tubes to replace diodes, the loss can be obviously reduced, the efficiency can be improved, meanwhile, the voltage stress is equal to the input voltage, the MOS tubes can select 500V MOS tubes with high cost performance, two power diodes are omitted in a main loop, and meanwhile the full-bridge LCC can achieve higher power output and can be wider in application range.

Description

Technical Field

[0001] The utility model relates to a power converter, in particular to a single-stage bridge-less conversion device integrating Buck-Boost and full-bridge LCC circuits. 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., so their application in the lighting field is particularly prominent. The LED lighting system includes two parts: 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 design of current 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, 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, the 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 LCC switching tube and capacitor at the rear 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 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, but 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. Content 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 Buck-Boost and full-bridge LCC circuits, 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 bridgeless conversion device integrating Buck-Boost and full-bridge LCC circuits, including a bridgeless Buck-Boost circuit and a full-bridge LCC 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 full-bridge LCC circuit.

[0008] In a preferred embodiment: the LCC circuit further includes an upper tube Q4, lower tubes Q5, and Q6.

[0009] In a preferred embodiment: switching tube Q1 or Q2 is turned on and off simultaneously with switching tubes Q3 and lower tube Q5, and has a state opposite to that of upper tube Q4 and lower tube Q6.

[0010] In a preferred embodiment: the bridgeless Buck-Boost circuit further includes AC input rectifier diodes D1, D2; the AC input rectifier diodes D1, D2 and 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 LCC circuit.

[0012] In a preferred embodiment: the bridgeless Buck-Boost circuit further includes a freewheeling diode D3, and the full-bridge LCC circuit further includes rectifier diodes D4, D5, and the rectifier diodes D4, D5 are 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 non-polar ends 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 an electrolytic capacitor C2, and the cathodes of diodes D4 and D5 are also connected to the polar end of the secondary winding through a load R1.

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

[0015] In a preferred embodiment: a capacitor Cp is connected between the two ends of the primary winding of the high-frequency transformer T1, and the capacitor Cp is connected to an inductor Lr and a capacitor Cs.

[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 bridge-less conversion device integrating Buck-Boost and full-bridge LCC circuits. Three MOS transistors are arranged in the Buck-Boost circuit, so that one of the MOS transistors can be reused as the switching transistor Q3 of the LCC circuit. MOS transistors Q1 and Q2 are used as input rectifying MOS transistors to replace diodes, the loss can be significantly reduced and the efficiency can be improved. At the same time, the voltage stress is equal to the input voltage, so it is more advantageous in the selection of MOS transistors, and 500V MOS transistors with high cost performance can be selected. Two power diodes are less in the main circuit. At the same time, the full-bridge LCC can achieve a larger power output and has a wider application range. At the same time, the working principle of the LCC circuit part is exactly the same as that of the conventional LCC circuit. The switching transistors Q3 to Q6 can achieve ZVS within a certain range, and 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 utility model;

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

[0020] Figures 3 - 10 The equivalent circuit diagrams of the preferred embodiment of the utility model in each mode. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] 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 creative efforts shall fall within the protection scope of the present utility model.

[0022] 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 understood as a limitation of the present utility model. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0023] 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, and 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 situations.

[0024] Reference Figure 1 , this embodiment provides a single-stage bridgeless conversion device integrating Buck-Boost and full-bridge LCC circuits, including a bridgeless Buck-Boost circuit and a full-bridge LCC circuit; the Buck-Boost circuit includes three switching tubes Q1, Q2, Q3, and one of the switching tubes Q3 is multiplexed as the upper tube of the full-bridge LCC circuit. Q1~Q6 are power MOS tubes. Among them, Q1, Q2, Q3 are the switching tubes of Buck-Boost, Q3, Q4 are the upper tubes of the full-bridge LCC circuit, and Q5, Q6 are the lower tubes of the full-bridge LCC circuit. In terms of control, Q1~Q6 adopt PWM\PFM\phase-shift control. Q1 and Q2 work in the positive and negative half-cycles of AC respectively. Q1 (or Q2), Q3, and Q5 conduct and turn off simultaneously. Q1 (or Q2)\Q3\Q5 and Q4\Q6 are driven complementarily. D1~D2 are AC input rectifier diodes, which rectify the AC input into pulsating DC together with Q1 and Q2. D3~D5 are power diodes. Among them, D3 is the freewheeling diode of the Buck-Boost circuit, and D4 and D5 are 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 Cs and Cp are high-frequency capacitors. T1 is a high-frequency transformer, and the same-named ends of its primary winding Np and secondary windings Ns1 and Ns2 are in the same direction.

[0025] The Buck-Boost circuit works in the discontinuous mode, and the LCC circuit works in the ZVS region. During the positive and negative cycles of the AC power supply power frequency, the working states of the circuit are symmetrical. Here, the positive half-cycle is taken as an example for description, and the negative half-cycle will not be elaborated one by one. Figure 2 are the corresponding key waveforms. Figures 3 to 10 are the equivalent diagrams of 8 modes in the positive half-cycle.

[0026] Mode 1 [t0~t1]: Before t0, the current i of inductor L1 L has dropped to 0. At the same time, since the body diodes of Q3 and Q5 are conducting, at the moment of t0, Q3 and Q5 are turned on with zero voltage, Q1 is turned on with zero current, and u in charges the Buck-Boost inductor L1 through MOS tubes Q1 and Q3, and the current i of inductor L1L Increases linearly with a slope of u in / L1. At this time, the parallel resonance capacitor C in the LCC circuit p The voltage is equal to -nVo, and the secondary diode D4 conducts. Cp charges the output capacitor C2 through the transformer T1 and supplies power to the output load R1. When the voltage on the parallel resonance capacitor C p Is less than -nVo, the current of D4 naturally drops to 0 to achieve ZCS turn-off. At this time, the bus capacitor C1 supplies power to the series resonance capacitor Cs, the resonance inductor Lr, and the parallel resonance capacitor C through the MOS transistors Q3 and Q5 p Stores energy, and the output capacitor C2 supplies power to the output load R1.

[0027] Mode 2 [t1 to t2]: At the moment t1, the MOS transistors Q1, Q3, and Q5 continue to conduct, and the current i of the inductor L1 L Continues to increase linearly. At this time, the parallel resonance capacitor C p The voltage is equal to nVo, and the secondary diode D5 conducts. Cp charges the output capacitor C2 through the transformer T1 and supplies power to the output load R1.

[0028] Mode 3 [t2 to t3]: At the moment t2, the MOS transistors Q1, Q3, and Q5 turn off and enter the dead time. The current i of the inductor L1 L Reaches the maximum and starts to discharge, and its current i L Charges the DC bus capacitor C1 through the power diode D3, and the current i of the inductor L1 L Decreases linearly. At this time, the parallel resonance capacitor C p The voltage is equal to nVo, and the secondary diode D5 conducts. In the resonance circuit, the resonance current iLr remains continuous, charges the junction capacitors of the MOS transistors Q3 and Q5, and discharges the junction capacitors of the MOS transistors Q4 and Q6 until the voltage across the junction capacitors of the MOS transistors Q4 and Q6 drops to 0.

[0029] Mode 4 [t3 to t4]: At the moment t3, all the resonance current flows through the body diodes of the MOS transistors Q4 and Q6, and the MOS transistors Q4 and Q6 meet the zero-voltage turn-on condition. During this stage, the current i of the inductor L1 L Continues to decrease linearly, and the parallel resonance capacitor C p The voltage is equal to nVo, the secondary diode D5 conducts, and Cp charges the output capacitor C2 through the transformer T1 and supplies power to the output load R1.

[0030] Mode 5 [t4 to t5]: At the moment t4, the MOS transistors Q4 and Q6 continue to conduct, and the voltage on the parallel resonance capacitor C p Is less than nVo, the current of D5 naturally drops to 0 to achieve ZCS turn-off, and the output capacitor C2 supplies power to the output load R1.

[0031] Mode 6 [t5 - t6]: At time t5, the current i of inductor L1 L drops to 0, and MOS transistors Q4 and Q6 continue to conduct. During this stage, the parallel resonant capacitor C p voltage is equal to -nVo, the secondary diode D4 conducts, and Cp charges the output capacitor C2 through the transformer T1 and supplies power to the output load R1.

[0032] Mode 7 [t6 - t7]: At time t6, MOS transistors Q4 and Q6 turn off. Entering the dead time, during this stage, the parallel resonant capacitor C p voltage is equal to -nVo, and the secondary diode D4 conducts. In the resonant circuit, the resonant current iLr remains continuous, charges the junction capacitors of MOS transistors Q4 and Q6, and discharges the junction capacitors of MOS transistors Q3 and Q5 until the voltage across the junction capacitors of MOS transistors Q3 and Q5 drops to 0.

[0033] As described above, it is only the 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 - substantial 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 bridge-less conversion device integrating Buck-Boost and full-bridge LCC circuits, characterized in that: It includes a bridge-less Buck-Boost circuit and a full-bridge LCC circuit; the Buck-Boost circuit includes three switching transistors Q1, Q2, Q3, and one of the switching transistors Q3 is multiplexed as the upper transistor of the full-bridge LCC circuit.

2. The single-stage bridge-less conversion device integrating Buck-Boost and full-bridge LCC circuits according to claim 1, characterized in that: The LCC circuit further includes an upper transistor Q4, lower transistors Q5, Q6.

3. The single-stage bridge-less conversion device integrating Buck-Boost and full-bridge LCC circuits according to claim 2, characterized in that: The switching transistor Q1 or Q2 is turned on and off simultaneously with the switching transistor Q3 and the lower transistor Q5, and has an opposite state to the upper transistor Q4 and the lower transistor Q6.

4. The single-stage bridge-less conversion device integrating Buck-Boost and full-bridge LCC circuits according to claim 3, characterized in that: The bridge-less Buck-Boost circuit further includes AC input rectifier diodes D1, D2; the AC input rectifier diodes D1, D2 and the switching transistors Q1, Q2 rectify the AC input into a pulsating DC.

5. The single-stage bridge-less conversion device integrating Buck-Boost and full-bridge LCC circuits according to claim 4, characterized in that: The AC input terminals of the AC input rectifier diodes D1, D2 are connected to an AC power supply, and the DC output terminals are connected to a high-frequency transformer T1 through the Buck-Boost circuit and the LCC circuit.

6. The single-stage bridge-less conversion device integrating Buck-Boost and full-bridge LCC circuits according to claim 5, characterized in that: The bridge-less Buck-Boost circuit further includes a freewheeling diode D3, and the full-bridge LCC circuit further includes rectifier diodes D4, D5. The rectifier diodes D4, D5 are used to rectify the high-frequency AC voltage of the secondary winding of the high-frequency transformer T1 into DC.

7. The single-stage bridge-less conversion device integrating Buck-Boost and full-bridge LCC 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 anodes of the diodes D4 and D5. The cathodes of the diodes D4 and D5 are connected to each other and grounded through an electrolytic capacitor C2. The cathodes of the diodes D4 and D5 are also connected to the same-named end of the secondary winding through a load R1.

8. The single-stage bridge-less conversion device integrating Buck-Boost and full-bridge LCC circuits according to claim 7, characterized in that: The same-named ends of the primary winding Np and the secondary windings Ns1, Ns2 of the high-frequency transformer T1 are in the same direction.

9. The single-stage bridge-less conversion device integrating Buck-Boost and full-bridge LCC circuits according to claim 8, characterized in that: A capacitor Cp is connected between the two ends of the primary winding of the high-frequency transformer T1, and the capacitor Cp is connected to an inductor Lr and a capacitor Cs.

Images