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

Abstract

The present invention provides a single-stage wide-input soft-switching resonant power conversion device integrating a Buck-Boost circuit and a half-bridge LCC circuit, comprising a Buck-Boost circuit and a half-bridge LCC circuit. The Buck-Boost circuit comprises two switching transistors Q1 and Q2, and the switching transistor Q2 also functions as an upper transistor of the half-bridge LCC circuit. The single-stage wide-input soft-switching resonant power conversion device has low stress, exhibits significant advantages in thermal design and efficiency, and makes product development in practical applications easier.

Description

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

[0001] The present invention relates to power converters, and in particular to a single-stage 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 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 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 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 conversion device integrating Buck-Boost and half-bridge LCC circuits, which comprises a Buck-Boost circuit and a half-bridge LCC circuit; the Buck-Boost circuit comprises two switching tubes Q1 and Q2, and one of the switching tubes Q2 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 Q3.

[0009] In a preferred embodiment, the states of the switching tubes Q1 and Q2 are the same, and opposite to the state of the lower tube Q3.

[0010] In a preferred embodiment, the Buck-Boost circuit further comprises alternating current (AC) input rectifier diodes D1, D2, D3, and D4; the AC input rectifier diodes D1, D2, D3, and D4 rectify the AC input to pulsating direct current (DC).

[0011] In a preferred embodiment, the AC input ends of the AC input rectifier diodes D1, D2, D3, and D4 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 Buck-Boost circuit further comprises a freewheeling diode D5, and the half-bridge LCC circuit further comprises rectifier diodes D6 and D7, which are used to rectify the high-frequency AC voltage of the secondary winding of the high-frequency transformer T1 to DC.

[0013] In a preferred embodiment, the non-identical name ends of the secondary winding of the high-frequency transformer T1 are respectively connected to the anodes of the diodes D6 and D7, the cathodes of the diodes D6 and D7 are connected to each other and grounded through an electrolytic capacitor C2, and the cathodes of the diodes D6 and D7 are further connected to the identical name end of the secondary winding through a load R1.

[0014] In a preferred embodiment, the identical name 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 conversion device integrating a Buck-Boost and a half-bridge LCC circuit, the voltage stress of the MOS tube Q2 can be obviously reduced, the stress of the increased MOS tube Q1 is equal to the input voltage, so the MOS tube selection is more favorable, and a 500V MOS tube with high cost performance can be selected, two power diodes are less in the main circuit, so the cost of the power semiconductor device can be reduced. Meanwhile, the working principle of the LCC circuit part is exactly the same as that of the conventional LCC circuit, Q2 and Q3 can realize ZVS in a certain range, and the secondary side rectification diode realizes ZCS, which has obvious advantages in thermal design and efficiency, and is more convenient for product development in practical application. 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 belong to 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 descriptive purposes 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 broadly understood, for example, "connected" can be wall-mounted connection, can be detachable connection, or integrally connected, can be mechanical connection, can be electrical connection, can be directly connected, can be indirectly connected through an intermediate medium, 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 conversion device integrating Buck-Boost and half-bridge LCC circuits, including a Buck-Boost circuit and a half-bridge LCC circuit; the Buck-Boost circuit includes two switching tubes Q1 and Q2, and one of the switching tubes Q2 is multiplexed as the upper tube of the half-bridge LCC circuit. Q1-Q3 are power MOS tubes, wherein Q1 and Q2 are the switching tubes of the Buck-Boost, Q2 is the upper tube of the half-bridge LCC circuit, and Q3 is the lower tube of the half-bridge LCC circuit. For control, Q1-Q3 use PWM\PFM, Q1 and Q2 are simultaneously turned on and turned off, and Q3 is driven complementarily with Q1\Q2. D1-D4 are AC input rectifier diodes for rectifying AC input to pulsed DC. D6 and D7 are power diodes, wherein D5 is the Buck-Boost circuit freewheeling diode, and D6 and D7 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, Cs and Cp are high-frequency capacitors, and D5 is the Buck-Boost freewheeling diode. T1 is a high-frequency transformer, and the same-named ends of the primary winding Np and the secondary windings Ns1 and Ns2 of T1 are in the same direction.

[0025] In the present embodiment, the Buck-Boost circuit operates in the discontinuous mode, and the LCC circuit operates in the ZVS zone. Within the positive and negative cycles of the AC power supply operating frequency, the working state of the circuit is symmetrical. Here, the positive half cycle is taken as an example for illustration, and the negative half cycle is not described in detail. 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 Q2 is turned on, at t0, Q2 is turned on with zero voltage, Q1 is turned on with zero current, and u in The MOS tubes Q1 and Q2 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, and the secondary diode D6 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 D6 current naturally drops to 0 to achieve ZCS turn-off. At this time, the bus capacitor C1 stores energy for the series resonant capacitor Cs, the resonant inductor Lr, and the parallel resonant capacitor C p through the MOS tube Q2, and the output capacitor C2 supplies power to the output load R1.

[0027] Mode 2 [t1-t2]: At t1, MOS Q1, Q2 continue to conduct, the inductor L1 current i L continues to increase linearly. At this time, the parallel resonance capacitor C p The voltage is equal to nVo, the secondary diode D7 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 t2, MOS Q1, Q2 turn off, enter dead time. The inductor L1 current i L reaches the maximum and begins to discharge, its current i L charges the DC bus capacitor C1 through the power diode D5, the inductor L1 current i L decreases linearly. At this time, the parallel resonance capacitor C p The voltage is equal to nVo, the secondary diode D7 conducts. In the resonant circuit, the resonant current iLr remains continuous, charging the MOS Q2 junction capacitor, discharging the MOS Q3 junction capacitor, until the MOS Q3 junction capacitor voltage drops to 0.

[0029] Mode 4 [t3-t4]: At t3, the resonant current flows entirely through the MOS Q3 body diode, and the MOS Q3 meets the zero-voltage turn-on condition. In this phase, the inductor L1 current i L continues to decrease linearly, and the parallel resonance capacitor C p The voltage is equal to nVo, the secondary diode D7 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 t4, MOS Q3 continues to conduct, and the parallel resonance capacitor C p The voltage on the above is less than nVo, D7 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 inductor L1 current i L drops to 0, and the MOS Q3 continues to conduct. In this phase, the parallel resonance capacitor C p The voltage is equal to -nVo, the secondary diode D6 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 t6, MOS Q3 turns off. Enter dead time, in this phase, the parallel resonance capacitor C pThe voltage is equal to -nVo, and the secondary diode D6 is turned on. In the resonant circuit, the resonant current iLr keeps continuous, the MOS tube Q3 junction capacitor is charged, the MOS tube Q2 junction capacitor is discharged, and the voltage across the MOS tube Q2 junction capacitor is reduced to 0.

[0033] The above is only the 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 conversion device integrated with Buck-Boost and half-bridge LCC circuit, the voltage stress of MOS tube Q2 can be significantly reduced, the stress of MOS tube Q1 is increased and 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, two power diodes are saved in the main circuit, so the cost of power semiconductor devices can be reduced. At the same time, the working principle of the LCC circuit part is exactly the same as that of the conventional LCC circuit, Q2 and Q3 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 conversion device integrating a Buck-Boost and half bridge LCC circuit, characterized by: The Buck-Boost circuit includes two switching tubes Q1 and Q2, and one of the switching tubes Q2 is multiplexed as the upper tube of the half-bridge LCC circuit.

2. A single stage conversion apparatus integrating Buck-Boost and half bridge LCC circuit as claimed in claim 1, wherein: The LCC circuit further includes a lower tube Q3.

3. A single stage conversion apparatus integrating Buck-Boost and half bridge LCC circuit as claimed in claim 2, wherein: The states of the switching tubes Q1 and Q2 are the same, and opposite to the state of the lower tube Q3.

4. A single stage conversion apparatus integrating a Buck-Boost and half bridge LCC circuit as claimed in claim 3, characterized in that: The Buck-Boost circuit further includes AC input rectifier diodes D1, D2, D3 and D4.

5. A single stage conversion apparatus integrating a Buck-Boost and half bridge LCC circuit as claimed in claim 4, characterized in that: The AC input ends of the AC input rectifier diodes D1, D2, D3 and D4 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 conversion apparatus integrating Buck-Boost and half bridge LCC circuit as claimed in claim 4, wherein: The Buck-Boost circuit further includes a freewheeling diode D5, and the half-bridge LCC circuit further includes rectifier diodes D6 and D7, which are used to rectify the high-frequency AC voltage of the secondary winding of the high-frequency transformer T1 into DC.

7. A single stage conversion apparatus integrating a Buck-Boost and half bridge LCC circuit as claimed in claim 6, characterized in that: The antiphase ends of the secondary winding of the high-frequency transformer T1 are respectively connected to the anodes of the diodes D6 and D7, the cathodes of the diodes D6 and D7 are connected to each other and grounded through an electrolytic capacitor C2, and the cathodes of the diodes D6 and D7 are further connected to the same-phase end of the secondary winding through a load R1.

8. A single stage conversion apparatus integrating a Buck-Boost and half bridge LCC circuit as claimed in claim 7, characterized in that: 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 conversion apparatus integrating Buck-Boost and half bridge LCC circuit as claimed in claim 6, 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.

Images