Single-stage bridgeless conversion device integrating buck-boost circuit and full-bridge LCC circuit

Abstract

The present invention provides a single-stage bridgeless conversion device integrating a Buck-Boost circuit and a full-bridge LCC circuit, the single-stage bridgeless conversion device comprising a bridgeless Buck-Boost circuit and a full-bridge LCC circuit. The Buck-Boost circuit comprises three switching transistors Q1, Q2 and Q3, wherein one of the switching transistors, i.e. Q3, is reused as a high-side transistor of the full-bridge LCC circuit. The provision of the three MOS transistors in the Buck-Boost circuit allows one of the MOS transistors to be reused as the high-side transistor Q3 of the LCC circuit; the MOS transistors Q1 and Q2 are used as input rectifying MOS transistors to replace diodes, such that the loss can be obviously reduced and the efficiency can be improved; in addition, the voltage stress is equal to an input voltage, such that cost-effective 500 V MOS transistors can be selected; moreover, two power diodes are omitted in a main circuit, and the full-bridge LCC can achieve higher power output, thus making the application range wider.

Description

A single-stage bridgeless conversion device integrating Buck-Boost and full-bridge LCC circuits TECHNICAL FIELD

[0001] The present application relates to a power converter, in particular to a single-stage bridgeless conversion device integrating Buck-Boost and full-bridge LCC 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 has become 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 LCC switching tube and capacitor in the latter stage.

[0005] The current most mainstream technical solution: 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 at the same time by single-stage flyback, mainly applied to small power LED driving power. This scheme is mature in technology, simple in system, low in cost and high in efficiency, 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 bridgeless conversion device integrating Buck-Boost and full-bridge LCC circuits, which simplifies the circuit, reduces the volume, improves the power density and lowers the cost.

[0007] To solve the above technical problems, the present application provides a single-stage bridgeless conversion device integrating Buck-Boost and full-bridge LCC circuits, which comprises a bridgeless Buck-Boost circuit and a 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.

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

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

[0010] In a preferred embodiment, the bridgeless Buck-Boost circuit further comprises alternating current (AC) input rectifier diodes D1 and D2; the AC input rectifier diodes D1 and D2 and the switching tubes Q1 and Q2 rectify the AC input into pulsating direct current (DC).

[0011] In a preferred embodiment, the AC input ends of the AC input rectifier diodes D1 and 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 comprises a freewheeling diode D3, and the full-bridge LCC circuit further comprises rectifier diodes D4 and D5, which 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 opposite-phase 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, and the cathodes of the diodes D4 and D5 are further connected to the same-phase ends of the secondary winding through a load R1.

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

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

[0016] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0017] The present application provides a single-stage bridgeless 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 upper transistor Q3 of the LCC circuit. The MOS transistors Q1 and Q2 are used as input rectification MOS transistors to replace diodes, so that 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 the selection of the MOS transistors is more advantageous, and a 500V MOS transistor with high cost performance can be selected. Two power diodes are saved in the main circuit, and the full-bridge LCC can realize larger power output, so the application range can be more widely. At the same time, the working principle of the LCC circuit part is exactly the same as that of the conventional LCC circuit, and the switching transistors Q3-Q6 can realize ZVS in a certain range, so that the heat design and efficiency will have obvious advantages, and the product development in practical application will be more convenient. BRIEF DESCRIPTION OF DRAWINGS

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

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

[0020] Figs. 3-10 are equivalent circuit diagrams of the preferred embodiment of the present application in various modes. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0022] 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" and "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0023] In the description of the present application, it should be noted that unless otherwise expressly specified and limited, the terms "mounting", "provided with", "sleeved / connected", "connected" and the like should be understood in a broad sense, 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 those skilled in the art can understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0024] Referring to FIG. 1, the present example 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, wherein 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, Q2 work in the positive and negative half cycles of AC respectively, Q1(or Q2), Q3, Q5 are simultaneously turned on and off, Q1(or Q2)\Q3\Q5 and Q4\Q6 are driven complementarily. D1-D2 are AC input rectifier diodes, which, together with Q1, Q2, rectify the AC input to pulsed DC. D3-D5 are power diodes, wherein D3 is the freewheeling diode of the Buck-Boost circuit, and D4, D5 are used to rectify the high-frequency AC voltage of the secondary winding of T1 to DC. L1, Lr are high-frequency inductors, C1, C2 are electrolytic capacitors, Cs, Cp are high-frequency capacitors. T1 is a high-frequency transformer, and the same-named ends of the primary winding Np and the secondary windings Ns1, Ns2 are in the same direction.

[0025] The Buck-Boost circuit works in discontinuous mode, and the LCC circuit works in ZVS zone. In the positive and negative cycles of the AC power frequency, the working state of the circuit is symmetrical, and here the positive half cycle is taken as an example for illustration, and the negative half cycle is not described one by one. FIG. 2 is the corresponding key waveform, and FIGS. 3-10 are the eight mode equivalent diagrams of the positive half cycle.

[0026] 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 diodes of Q3, Q5 are turned on, at t0, Q3, Q5 are zero-voltage turned on, Q1 is zero-current turned on, and u in The MOS tubes Q1, Q3 charge the Buck-Boost inductor L1, and the current i L of the inductor L1 increases with a slope u in / L1 linearly increases. At this time, the parallel resonant capacitor C p The voltage is equal to -nVo, the secondary diode D4 is turned on, Cp charges the output capacitor C2 through the transformer T1 and supplies power to the output load R1. When the voltage on the parallel resonant capacitor C p is less than -nVo, the D4 current naturally drops to 0 to achieve ZCS turn-off, at this time the bus capacitor C1 charges the series resonant capacitor Cs and the resonant inductor Lr and the parallel resonant capacitor C p stores energy, and the output capacitor C2 supplies power to the output load R1.

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

[0028] Mode 3 [t2-t3]: At t2, MOS tubes Q1, Q3, Q5 are turned off, and a dead time is entered. The current i L of the inductor L1 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 L of the inductor L1 linearly decreases. At this time, the parallel resonant capacitor C p The voltage is equal to nVo, the secondary diode D5 is turned on. In the resonant circuit, the resonant current iLr remains continuous, charging the MOS tubes Q3, Q5 junction capacitors, and discharging the MOS tubes Q4, Q6 junction capacitors, until the MOS tubes Q4, Q6 junction capacitors drop to 0.

[0029] Mode 4 [t3-t4]: At t3, the resonant current flows through the body diode of the MOS tubes Q4, Q6, and the MOS tubes Q4, Q6 meet the zero-voltage turn-on condition. In this phase, the current i L of the inductor L1 continues to linearly decrease, and the voltage on the parallel resonant capacitor C p The voltage is equal to nVo, the secondary diode D5 is turned on, Cp charges the output capacitor C2 through the transformer T1 and supplies power to the output load R1.

[0030] Mode 5 [t4-t5]: At t4, the MOS tubes Q4, Q6 continue to be turned on, and the voltage on the parallel resonant capacitor C p is less than nVo, the D5 current 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 t5, the current iL Drop to 0, MOS Q4, Q6 continue to conduct, in this phase, parallel resonance capacitor C p The voltage is equal to -nVo, the secondary diode D4 is turned on, Cp through the transformer T1 is charged for the output capacitor C2 and power supply for the output load R1.

[0032] Mode 7 [t6~t7]: at t6 time, MOS Q4, Q6 are turned off. Enter the dead time, this stage, parallel resonance capacitor C p The voltage is equal to -nVo, the secondary diode D4 is turned on. In the resonant circuit, the resonant current iLr keeps continuous, the MOS Q4, Q6 junction capacitor is charged, the MOS Q3, Q5 junction capacitor is discharged, until the MOS Q3, Q5 junction capacitor voltage drops to 0.

[0033] The above, only for the preferred specific embodiments of the present application, but the design concept of the present application is not limited to this, any skilled in the art of the technical range disclosed by the present application, using this concept of the present application is not substantial change, all belong to the infringement of the scope of the present application. Industrial applicability

[0034] The application provides a single-stage bridgeless conversion device of Buck-Boost and full-bridge LCC circuit, three MOS transistors are arranged in the Buck-Boost circuit, so that one of the MOS transistors can be multiplexed as the upper transistor Q3 of the LCC circuit. The MOS transistors Q1 and Q2 are used as input rectification MOS transistors to replace diodes, so that the loss can be obviously reduced and the efficiency is improved, and the voltage stress is equal to the input voltage, so that the selection of the MOS transistors is more favorable, and a 500V MOS transistor with high cost performance can be selected. Two power diodes are saved in the main circuit, meanwhile, the full-bridge LCC can realize larger power output, and the application range can be more widely. Meanwhile, the working principle of the LCC circuit part is exactly the same as that of the conventional LCC circuit, the switching transistors Q3-Q6 can realize ZVS in a certain range, and the heat design and efficiency are obviously superior, so that the product development in practical application is more convenient, and the application has good industrial applicability.

Claims

1. A single stage bridgeless converter combining Buck-Boost and full bridge LCC circuits, characterized by: The bridgeless Buck-Boost circuit and the 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.

2. A single stage bridgeless converter incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 1, wherein: The LCC circuit further includes upper tube Q4, lower tubes Q5, Q6.

3. A single stage bridgeless converter combining Buck-Boost and full bridge LCC circuits as claimed in claim 2, wherein: The switching tube Q1 or Q2 is simultaneously turned on and turned off with the upper tube Q3 and the lower tube Q5, and the state is opposite to that of the upper tube Q4 and the lower tube Q6.

4. A single stage bridgeless converter incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 3, wherein: The bridgeless 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 to pulsed DC.

5. A single stage bridgeless converter incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 4, wherein: The AC input end of the AC input rectifier diodes D1, D2 is connected to the AC power supply, and the DC output end is connected to the high-frequency transformer T1 through the Buck-Boost circuit and the LCC circuit.

6. A single stage bridgeless converter incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 5, wherein: The bridgeless Buck-Boost circuit further includes a freewheeling diode D3, and the full-bridge LCC circuit further includes rectifier diodes D4, D5, which are used to rectify the high-frequency AC voltage of the secondary winding of the high-frequency transformer T1 to DC.

7. A single stage bridgeless converter incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 6, wherein: The antiphase 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 electrolytic capacitor C2, and the cathodes of diodes D4 and D5 are also connected to the same phase end of the secondary winding through the load R1.

8. A single stage bridgeless converter incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 7, wherein: The same phase ends of the primary winding Np and the secondary windings Ns1, Ns2 of the high-frequency transformer T1 are in the same direction.

9. A single stage bridgeless converter incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 8, wherein: The 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 the inductor Lr and the capacitor Cs.

Images