Single-stage bridgeless conversion apparatus integrating buck-boost circuit and full-bridge LLC circuit

Abstract

Provided in the present application is a single-stage bridgeless conversion apparatus integrating a buck-boost circuit and a full-bridge LLC circuit, the apparatus comprising a bridgeless buck-boost circuit and a full-bridge LLC circuit, wherein the buck-boost circuit comprises three switch transistors (Q1, Q2, Q3), and one of the switch transistors (Q3) is reused as an upper transistor of the full-bridge LLC circuit. Three MOS transistors are provided in the buck-boost circuit, such that one of the MOS transistors can be reused as an upper transistor of the LLC circuit. The MOS transistors (Q1, Q2) are used as input rectifier MOS transistors to replace diodes, such that the loss can be significantly reduced and the efficiency can be improved, and the voltage stress is equal to an input voltage. Therefore, cost-effective MOS transistors with 500 V can be selected as the MOS transistors, two power diodes are removed from a main loop, and the full-bridge LLC can also achieve a larger power output, thus implementing a wider application range.

Description

A single-stage bridgeless converter integrating buck-boost and full-bridge LLC circuits TECHNICAL FIELD

[0001] The present invention relates to power converters, and in particular to a single-stage bridgeless converter integrating buck-boost and full-bridge LLC 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. The 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] 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, 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 LLC circuits, which simplifies the circuit, reduces the size, 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 LLC circuits, which comprises a bridgeless Buck-Boost circuit and a full-bridge LLC circuit.

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

[0009] In a preferred embodiment, the switch 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, and the AC input rectifier diodes D1 and D2 and the switch 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 LLC circuit.

[0012] In a preferred embodiment, the bridgeless Buck-Boost circuit further comprises a freewheeling diode D3, and the full-bridge LLC 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, one end of the primary winding of the high-frequency transformer T1 is connected to a resonance loop composed of a serially connected inductor Lr and capacitor Cr.

[0016] In a preferred embodiment: the resonant frequency of the resonant circuit is Lm is the magnetizing inductance.

[0017] In a preferred embodiment: the switch tubes Q1, Q2, upper tubes Q3, Q4 and lower tubes Q5, Q6 are power MOS tubes respectively.

[0018] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0019] The present application provides a single-stage bridgeless conversion device integrating Buck-Boost and full-bridge LLC circuits. Three MOS tubes are arranged in the Buck-Boost circuit, so that one of the MOS tubes can be reused as the upper tube Q3 of the LLC circuit. The MOS tubes Q1 and Q2 are used as input rectification MOS tubes instead of diodes, so that the loss can be significantly reduced and the efficiency is improved, and the voltage stress is equal to the input voltage, so that the selection of the MOS tube is more advantageous, and a 500V MOS tube with high cost performance can be selected. Two power diodes are saved in the main circuit, and the full-bridge LLC can realize larger power output, so that the application range can be more widely. At the same time, the working principle of the LLC circuit part is exactly the same as that of the conventional LLC circuit, and the switch tubes Q3-Q6 can realize ZVS in the full load range, so that there will be obvious advantages in thermal design and efficiency, and it is more convenient for product development in practical application. BRIEF DESCRIPTION OF DRAWINGS

[0020] Fig. 1 is a circuit diagram of a preferred embodiment of the present application;

[0021] Fig. 2 is a timing diagram of a preferred embodiment of the present application;

[0022] Figs. 3-10 are equivalent circuit diagrams of the preferred embodiment of the present application in various modes;

[0023] Figs. 11-12 are alternative circuit diagrams of the preferred embodiment of the present application. DETAILED DESCRIPTION

[0024] 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 a part of the embodiments of the present application, but 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 fall within the scope of protection of the present application.

[0025] 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.

[0026] 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 those skilled in the art can understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0027] Referring to FIG. 1, the present example provides a single-stage bridgeless conversion device integrating Buck-Boost and full-bridge LLC circuits, including a bridgeless Buck-Boost circuit and a full-bridge LLC 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 LLC 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 LLC circuit, and Q5, Q6 are the lower tubes of the full-bridge LLC circuit. In 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, and Cr is a high-frequency capacitor. T1 is a high-frequency transformer, and the same name ends of the primary winding Np and the secondary winding Ns1, Ns2 are in the same direction.

[0028] In the present embodiment, the bridgeless Buck-Boost circuit works in discontinuous mode. 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.

[0029] Mode 1 [t0~t1]: Before t0, the current i of the inductor L1 has dropped to 0, and at the moment t0, Q3 and Q5 are turned on with zero voltage and Q1 is turned on with zero current because the body diodes of Q3 and Q5 are turned on. At this moment, u L = 0, and at the moment t0, Q3 and Q5 are turned on with zero voltage and Q1 is turned on with zero current because the body diodes of Q3 and Q5 are turned on. At this moment, u in The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u L = 0, and at the moment t0, Q3 and Q5 are turned on with zero voltage and Q1 is turned on with zero current because the body diodes of Q3 and Q5 are turned on. At this moment, u in The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u r The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u r The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u Lm The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u o The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u m The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u

[0030] Mode 2 [t1~t2]: At the moment t1, the resonant current is equal to the magnetizing current, at which time the secondary-side diode D5 current drops to zero and is turned off, and the primary winding of the transformer is no longer clamped by the output voltage, so the magnetizing inductance participates in resonance, and the resonant frequency is The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u L The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u

[0031] Mode 3 [t2~t3]: At the moment t2, MOS tubes Q1, Q3 and Q5 are turned off, and a dead time is entered. The inductor L1 begins to discharge, and the current i of the inductor L1 linearly decreases at a slope of L The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u L The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u The inductor L1 is charged through MOS tubes Q1 and Q3, and the current i of the inductor L1 linearly increases at a slope of u

[0032] Mode 4 [t3~t4]: At the moment t3, the resonant current flows through the body diodes of MOS tubes Q4 and Q6, and MOS tubes Q4 and Q6 meet the zero-voltage turn-on condition. In this stage, the resonant inductor L r and the resonant capacitor C r resonate at a resonant frequency of The resonant inductor Lr and the resonant capacitor Cr form a series resonant circuit, and the resonant current is in phase with the voltage across the resonant inductor Lr. The resonant current is greater than the magnetizing current, and the secondary diode D4 is turned on. o / L m The linear rise. In this stage, the current i L continues to decrease.

[0033] Mode 5 [t4-t5]: at t4, the current iL of the inductor L in the Buck-Boost circuit drops to zero. The MOS transistors Q4 and Q6 continue to be turned on, and the resonant inductor Lr and the resonant capacitor Cr continue to resonate at the resonant frequency The resonant inductor Lr and the resonant capacitor Cr form a series resonant circuit, and the resonant current is in phase with the voltage across the resonant inductor Lr. The resonant current is greater than the magnetizing current, and the secondary diode D4 is turned on.

[0034] Mode 6 [t5-t6]: at t5, the current in Lr is equal to the current in Lm, the secondary rectifier diode D4 is turned off with zero current, and the output voltage is no longer clamped to the transformer. Lm becomes a free resonant inductor and participates in the resonance. The magnetizing inductor Lm, the resonant inductor Lr, and the resonant capacitor Cr form a series resonant circuit, and the resonant frequency The resonant inductor Lr and the resonant capacitor Cr form a series resonant circuit, and the resonant current is in phase with the voltage across the resonant inductor Lr. The resonant current is greater than the magnetizing current, and the secondary diode D4 is turned on.

[0035] Mode 7 [t6-t7]: at t6, the MOS transistors Q4 and Q6 are turned off. The dead time is entered, and the magnetizing inductor Lm, the resonant inductor Lr, and the resonant capacitor Cr resonate at the resonant frequency The resonant inductor Lr and the resonant capacitor Cr form a series resonant circuit, and the resonant current is in phase with the voltage across the resonant inductor Lr. The resonant current is greater than the magnetizing current, and the secondary diode D4 is turned on.

[0036] The simple replacement of the embodiment is shown in FIGS. 11 and 12. The resonant inductor Lr can also be placed in the secondary winding of the transformer T1, and the AC rectifier diodes D1 and D2 can also be replaced by MOS transistors.

[0037] The above description is only a preferred embodiment of the present application, but the design concept of the present application is not limited thereto. Any skilled person 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 not be regarded as departing from the scope of the present application. Industrial applicability

[0038] The application provides a single-stage bridgeless conversion device integrating Buck-Boost and full-bridge LLC circuits, 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 LLC 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 the selection of the MOS transistor is more favorable, and a 500V MOS transistor with high cost performance can be selected, two power diodes are saved in the main circuit, the full-bridge LLC can realize larger power output, and the application range can be wider. Meanwhile, the working principle of the LLC circuit part is exactly the same as that of the conventional LLC circuit, the switching transistors Q3-Q6 can realize ZVS in the full-load range, and there are obvious advantages in thermal design and efficiency, and the product development in practical application is more convenient.

[0039] .

Claims

1. A single-stage bridgeless converter integrating Buck-Boost and full-bridge LLC circuits, characterized by: The bridgeless Buck-Boost circuit and the full-bridge LLC circuit; the Buck-Boost circuit comprises three switching tubes Q1, Q2 and Q3, and one of the switching tubes Q3 is multiplexed as the upper tube of the full-bridge LLC circuit.

2. A single-stage bridgeless converter integrated Buck-Boost and full-bridge LLC circuit according to claim 1, characterized in that: The LLC circuit further comprises upper tube Q4 and lower tubes Q5 and Q6.

3. The single-stage bridgeless converter of claim 2, wherein: 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 is opposite to that of the upper tube Q4 and the lower tube Q6.

4. The single-stage bridgeless converter of claim 3, wherein: The bridgeless Buck-Boost circuit further comprises 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 to pulsed DC.

5. The single-stage bridgeless converter of claim 4, wherein: The AC input end of the AC input rectifier diodes D1 and 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 LLC circuit.

6. The single-stage bridgeless converter of claim 5, wherein: The bridgeless Buck-Boost circuit further comprises a freewheeling diode D3, and the full-bridge LLC 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 to DC.

7. The single-stage bridgeless converter of claim 6, wherein: 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 the electrolytic capacitor C2, and the cathodes of the diodes D4 and D5 are also connected to the same-phase end of the secondary winding through the load R1.

8. The single-stage bridgeless converter of claim 7, wherein: 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.

9. The single-stage bridgeless converter of claim 8, wherein: 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 a capacitor Cr.

10. The single-stage bridgeless converter of claim 9, wherein: The resonance frequency of the resonance circuit is Lm is the magnetizing inductance.

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