Single-stage bridgeless conversion apparatus integrating buck-boost and half-bridge LCC circuits

Abstract

Provided in the present invention are a single-stage bridgeless conversion apparatus integrating Buck-Boost and half-bridge LCC circuits. The single-stage bridgeless conversion apparatus comprises a bridgeless Buck-Boost circuit and a half-bridge LCC circuit. The Buck-Boost circuit comprises three switch transistors Q1, Q2 and Q3, wherein the switch transistor Q3 is shared as a high-side transistor of the half-bridge LCC circuit. In the single-stage bridgeless conversion apparatus integrating Buck-Boost and half-bridge LCC circuits, the voltage stress on the MOS transistor Q3 can be remarkably reduced, while the stress on the added MOS transistors Q1 and Q2 is equal to an input voltage, such that favorable conditions are provided for MOS transistor selection, cost-effective 500 V MOS transistors can be selected, and two power diodes are also omitted from a main circuit, thus reducing the costs of power semiconductor devices. In addition, the operating principle of the LCC circuit part is exactly the same as that of a conventional LCC circuit, wherein Q3 and Q4 can achieve ZVS within a certain range and a secondary rectifier diode achieves ZCS, thereby offering significant advantages in thermal design and efficiency, and better facilitating product development in practical applications.

Description

A single-stage bridgeless conversion device integrating buck-boost and half-bridge LCC circuits TECHNICAL FIELD

[0001] The present application relates to power converters, and in particular to a single-stage bridgeless conversion device integrating buck-boost and half-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 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 LCC switching tube and capacitor in the latter stage.

[0005] The most mainstream technical solution at present: 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 half-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 half-bridge LCC circuits, which comprises a bridgeless Buck-Boost circuit and a half-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 the upper tube of the half-bridge LCC circuit.

[0008] In a preferred embodiment, the LCC circuit further comprises a lower tube Q4.

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

[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 half-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, 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 scheme of the present application has the following beneficial effects:

[0017] The application provides a single-stage bridgeless conversion device integrating a Buck-Boost and a half-bridge LCC circuit, the voltage stress of the MOS tube Q3 can be obviously reduced, the stress of the increased MOS tubes Q1 and Q2 is equal to the input voltage, so the MOS tube selection is more favorable, a 500V MOS tube with high cost performance can be selected, and two power diodes are also saved in the main circuit, so the cost of the power semiconductor device can be saved. Meanwhile, the working principle of the LCC circuit part is exactly the same as that of a conventional LCC circuit, Q3 and Q4 can realize ZVS in a certain range, and the secondary side rectification diode realizes ZCS, so obvious advantages are obtained in thermal design and efficiency, and product development in 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. 3-10 are equivalent circuit diagrams of the preferred embodiment of the application in various modes. DETAILED DESCRIPTION

[0021] 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 some of the embodiments of the application, rather than all the embodiments of the application, and all other embodiments obtained by those skilled in the art without creative efforts based on the embodiments in the application fall within the protection scope of the application.

[0022] In the description of the 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 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 application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0023] In the description of the 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 understood in a broad sense, for example, "connected" can be wall-mounted connection, can be detachable connection, or integral connection, can be mechanical connection, can be electrical connection, can be direct connection, can be indirect connection through an intermediate medium, or can be the communication between two elements, and those skilled in the art can understand the specific meaning of the above terms in the application according to the specific circumstances.

[0024] Referring to FIG. 1, the present example provides a single-stage bridgeless Buck-Boost and half-bridge LCC circuit, including a bridgeless Buck-Boost circuit and a half-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 half-bridge LCC circuit. Q1-Q6 are power MOS tubes, wherein Q1, Q2, and Q3 are the switching tubes of the Buck-Boost, Q3 is the upper tube of the half-bridge LCC circuit, and Q4 is the lower tube of the half-bridge LCC circuit. Control, Q1-Q4 use PWM\PFM, Q1 and Q2 work in the positive and negative half cycles of AC respectively, Q1(or Q2) and Q4 are simultaneously turned on and off, and Q1(or Q2) and Q3 are driven complementarily. D1-D2 are AC input rectifier diodes, which, together with Q1 and 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 and D5 are used to rectify the high-frequency AC voltage of the secondary winding of T1 to DC. L1 and Lr are high-frequency inductors, C1 and C2 are electrolytic capacitors, and Cr and Cs 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 and Ns2 are in the same direction.

[0025] In the present embodiment, the bridgeless Buck-Boost circuit works in the discontinuous mode, and the LCC circuit works in the ZVS zone. In the positive and negative cycles of the AC power supply, 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 diode of Q3 is turned on, at t0, Q3 is turned on with zero voltage, Q1 is turned on with zero current, and u in The MOS tubes Q1 and Q3 charge the Buck-Boost inductor L1, and the current i L of the inductor L1 increases linearly with the slope u in / L1. At this time, the parallel resonant capacitor C p in the LCC circuit has a voltage 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 u in The MOS tube Q3 charges the series resonant capacitor Cs, the resonant inductor Lr, and the parallel resonant capacitor C pThe output capacitor C2 stores energy and supplies power to the output load R1.

[0027] Mode 2 [t1-t2]: At time t1, MOSFET Q1, Q3 continue to conduct, the inductor current i 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-t3]: At time t2, MOSFET Q1, Q3 are turned off, and a dead time is entered. The inductor current i L reaches the maximum and begins to discharge, and its current i L charges the DC bus capacitor C1 through the power diode D3, and the inductor current i 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 resonant circuit, the resonant current iLr remains continuous, charging the MOSFET Q3 junction capacitor and discharging the MOSFET Q4 junction capacitor until the voltage across the MOSFET Q4 junction capacitor drops to 0.

[0029] Mode 4 [t3-t4]: At time t3, the resonant current flows entirely through the body diode of MOSFET Q4, and MOSFET Q4 meets the zero-voltage turn-on condition. In this phase, the inductor current i L continues to decrease linearly, and 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.

[0030] Mode 5 [t4-t5]: At time t4, MOSFET Q4 continues to conduct, and the voltage across the parallel resonance capacitor C p is less than nVo, and 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 time t5, the inductor current i L drops to 0, and MOSFET Q4 continues to conduct. In this phase, the parallel resonance capacitor C 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.

[0032] Mode 7 [t6-t7]: At time t6, MOSFET Q4 is turned off. A dead time is entered, and in this phase, the parallel resonance capacitor C pThe voltage is equal to -nVo, and the secondary diode D4 is turned on. In the resonant circuit, the resonant current iLr keeps continuous, the MOS tube Q4 junction capacitor is charged, the MOS tube Q3 junction capacitor is discharged, and the voltage across the MOS tube Q3 junction capacitor is reduced to 0.

[0033] The above description is only a preferred embodiment of the present application, but the design concept of the present application is not limited thereto, and any skilled person in the art can make non-essential changes to the present application within the scope of the present application, which is an infringement of the protection scope of the present application. Industrial applicability

[0034] The present application provides a single-stage bridgeless conversion device integrated with Buck-Boost and half-bridge LCC circuit, the voltage stress of MOS tube Q3 can be significantly reduced, the stress of added MOS tubes Q1 and Q2 is equal to the input voltage, so the selection of MOS tube is more favorable, and a 500V MOS tube 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 saved. At the same time, the working principle of the LCC circuit part is exactly the same as that of the conventional LCC circuit, Q3 and Q4 can realize ZVS within a certain range, and the secondary rectifier diode realizes ZCS, which has obvious advantages in thermal design and efficiency, and is more convenient for product development in practical application, and has good industrial applicability.

Claims

1. A single stage bridgeless converter integrating Buck-Boost and half bridge LCC circuit, characterized in that: The circuit comprises a bridgeless Buck-Boost circuit and a half-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 the upper tube of the half-bridge LCC circuit.

2. A single stage bridgeless converter integrating Buck-Boost and half bridge LCC circuit as claimed in claim 1, wherein: The LCC circuit further comprises a lower tube Q4.

3. A single stage bridgeless converter integrating Buck-Boost and half bridge LCC circuit as claimed in claim 2, wherein: The switching tubes Q1 or Q2 are turned on and turned off at the same time as the upper tube Q3, and the state of the lower tube Q4 is opposite to that of the switching tubes Q1 or Q2.

4. A single stage bridgeless converter integrating Buck-Boost and half bridge LCC circuit as claimed in 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. A single stage bridgeless converter integrating Buck-Boost and half bridge LCC circuit as claimed in claim 4, wherein: 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.

6. A single stage bridgeless converter integrating Buck-Boost and half bridge LCC circuit as claimed in claim 5, wherein: The bridgeless Buck-Boost circuit further comprises a freewheeling diode D3, and the half-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 to DC.

7. A single stage bridgeless converter integrating Buck-Boost and half bridge LCC circuit as claimed in 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 an electrolytic capacitor C2, and the cathodes of the diodes D4 and D5 are further connected to the same-phase end of the secondary winding through a load R1.

8. A single stage bridgeless converter integrating Buck-Boost and half bridge LCC circuit as claimed in 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. A single stage bridgeless converter integrating Buck-Boost and half bridge LCC circuit as claimed in claim 8, wherein: 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.

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