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

Abstract

The present invention provides a single-stage conversion device integrating a Buck-Boost circuit and a full-bridge LCC circuit, comprising the Buck-Boost circuit and the full-bridge LCC circuit. The Buck-Boost circuit comprises two switch transistors Q1 and Q2, and the switch transistor Q2 among the switch transistors is reused as a high-side transistor of the full-bridge LCC circuit. In the single-stage conversion device integrating the Buck-Boost circuit and the full-bridge LCC circuit, the voltage stress of the MOS transistor Q2 may be significantly reduced, and the increased stress of the MOS transistor Q1 is equal to an input voltage. Therefore, the type selection of an MOS transistor is more favorable, and a cost-effective 500V MOS transistor may be selected; and two power diodes are removed in a main loop, while the full-bridge LCC can achieve higher power output, widening the application range. In addition, the operating principle of the LCC circuit portion is exactly the same as that of conventional LCC circuits. Q2-Q5 can achieve ZVS within a certain range, providing obvious advantages in thermal design and efficiency, thereby facilitating product development in practical applications.

Description

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

[0001] The present application relates to power converter, especially to a single-stage conversion device integrating Buck-Boost and full-bridge LCC circuit. BACKGROUND

[0002] With the rapid development of semiconductor technology, the fourth generation of electric light source LED has been widely used. Compared with the traditional electric light source, LED has many incomparable advantages, such as long 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 produce 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 converter, including series, parallel, series-parallel resonant converter, 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 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 conversion device integrating Buck-Boost and full-bridge LCC circuits, which comprises a Buck-Boost circuit and a full-bridge LCC circuit; the Buck-Boost circuit comprises two switching tubes Q1 and Q2, and one of the switching tubes Q2 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 Q3, lower tubes Q4 and Q5.

[0009] In a preferred embodiment, the states of the switching tubes Q1 and Q2 are the same as that of the lower tube Q4, and opposite to that of the upper tube Q3 and the lower tube Q5.

[0010] In a preferred embodiment, the Buck-Boost circuit further comprises AC input rectifier diodes D1, D2, D3 and D4; the AC input rectifier diodes D1, D2, D3 and D4 rectify the AC input into pulsating 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 full-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 into DC.

[0013] In a preferred embodiment, the non-identical 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 ends of the secondary winding through a load R1.

[0014] In a preferred embodiment, the identical 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 capacitor Cp, an inductor Lr and a capacitor Cr connected in series.

[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 conversion device integrating Buck-Boost and full-bridge LCC circuits, the voltage stress of MOS tube Q2 can be significantly reduced, the stress of the added MOS tube Q1 is equal to the input voltage, so the selection of 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, full-bridge LCC can realize larger power output, and the application range can be more extensive. At the same time, the working principle of the LCC circuit part is exactly the same as that of the conventional LCC circuit, Q2-Q5 can realize ZVS in a certain range, and there will be obvious advantages in thermal design and efficiency, which 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 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 some 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 fall 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 limiting the present 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 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 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 the communication between 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 conversion device integrating Buck-Boost and full-bridge LCC circuits, including a Buck-Boost circuit and a full-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 full-bridge LCC circuit. Q1-Q5 are power MOS tubes, wherein Q1 and Q2 are the switching tubes of the Buck-Boost, Q2 and Q3 are the upper tubes of the full-bridge LCC circuit, and Q4 and Q5 are the lower tubes of the full-bridge LCC circuit. For control, Q1-Q6 adopt PWM\PFM\phase shift control, Q1, Q2 and Q4 are simultaneously turned on and turned off, and Q3\Q5 and Q1\Q2\Q4 are driven complementarily. D1-D4 are AC input rectifier diodes for rectifying AC input to pulsed DC. D6 and D7 are power diodes, wherein D5 is the freewheeling diode of the Buck-Boost circuit, 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, and Cs and Cr are high-frequency capacitors. T1 is a high-frequency transformer, and the same name ends of the primary winding Np and the secondary windings Ns1 and Ns2 are in the same direction.

[0025] In the present embodiment, the Buck-Boost circuit works in discontinuous mode, and the LCC circuit works in ZVS zone. Within the positive and negative cycles of the AC power supply operating 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 Q2 and Q4 are turned on, at t0, Q2 and Q4 are zero-voltage turned on, Q1 is zero-current turned on, 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 pThe voltage is equal to -nVo, the secondary diode D6 is on, Cp charges the output capacitor C2 through the transformer T1 and supplies 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 charges the series resonant capacitor Cs and the resonant inductor Lr through the MOS tube Q2, Q4 and the parallel resonant capacitor C p stores energy, the output capacitor C2 supplies the output load R1.

[0027] Mode 2 [t1-t2]: At t1, MOS tubes Q1, Q2, Q4 continue to be on, the inductor L1 current i L continues to linearly increase. At this time, the parallel resonant capacitor C p The voltage is equal to nVo, the secondary diode D7 is on, Cp charges the output capacitor C2 through the transformer T1 and supplies the output load R1.

[0028] Mode 3 [t2-t3]: At t2, MOS tubes Q1, Q2, Q4 are off, entering the dead time. The inductor L1 current i L reaches the maximum and starts to discharge, its current i L charges the DC bus capacitor C1 through the power diode D5, the inductor L1 current i L linearly decreases. At this time, the parallel resonant capacitor C p The voltage is equal to nVo, the secondary diode D7 is on. In the resonant circuit, the resonant current iLr keeps continuous, charging the MOS tube Q2, Q4 junction capacitor, discharging the MOS tube Q3, Q5 junction capacitor, until the MOS tube Q3, Q5 junction capacitor voltage drops to 0.

[0029] Mode 4 [t3-t4]: At t3, the resonant current flows through the body diode of MOS tubes Q3, Q5, MOS tubes Q3, Q5 meet the zero-voltage turn-on condition. In this stage, the inductor L1 current i L continues to linearly decrease, and the parallel resonant capacitor C p The voltage is equal to nVo, the secondary diode D7 is on, Cp charges the output capacitor C2 through the transformer T1 and supplies the output load R1.

[0030] Mode 5 [t4-t5]: At t4, MOS tubes Q3, Q5 continue to be on, the voltage on the parallel resonant capacitor C p is less than nVo, the D7 current naturally drops to 0 to achieve ZCS turn-off, and the output capacitor C2 supplies the output load R1.

[0031] Mode 6 [t5-t6]: At t5, the inductor L1 current i LDrop to 0, MOS tube Q3, Q5 continue to turn on, in this stage, parallel resonant capacitor C p The voltage is 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.

[0032] Mode 7 [t6-t7]: at t6, MOS tube Q3, Q5 is off. Enter the dead time, this stage, parallel resonant capacitor C p The voltage is equal to -nVo, and the secondary diode D6 is turned on. In the resonant circuit, the resonant current iLr remains continuous, the MOS tube Q3, Q5 junction capacitor is charged, and the MOS tube Q2, Q4 junction capacitor is discharged until the MOS tube Q2, Q4 junction capacitor voltage drops 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 to this, any person skilled in the art within the scope of the present application disclosed by the technical range, using this concept to make non-essential changes to the present application, all belong to the act of infringing the scope of protection of the present application. Industrial applicability

[0034] The present application provides a single-stage conversion device of Buck-Boost and full-bridge LCC circuit, the voltage stress of MOS tube Q2 can be significantly reduced, the stress of added MOS tube Q1 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, two power diodes are less 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, Q2-Q5 can realize ZVS in a certain range, and there is obvious advantage in thermal design and efficiency, which is more convenient for product development in practical application, and has good industrial applicability.

Claims

1. A single stage conversion device combining Buck-Boost and full bridge LCC circuits, 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 full-bridge LCC circuit.

2. A single stage conversion device incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 1, characterized in that: The LCC circuit further includes upper tube Q3, lower tubes Q4 and Q5.

3. A single stage conversion device incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 2, wherein: The states of the switching tubes Q1 and Q2 are the same as that of the lower tube Q4, and are opposite to that of the upper tube Q3 and the lower tube Q5.

4. A single stage conversion device incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 3, wherein: The Buck-Boost circuit further includes AC input rectifier diodes D1, D2, D3 and D4.

5. A single stage conversion device incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 4, wherein: 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 device incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 4, wherein: The Buck-Boost circuit further includes a freewheeling diode D5, and the full-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 device incorporating Buck-Boost and full bridge LCC circuits 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 homonymous end of the secondary winding through a load R1.

8. A single-stage conversion device incorporating Buck-Boost and full-bridge LCC circuits as claimed in claim 7, characterized in that: The homonymous 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 device incorporating Buck-Boost and full bridge LCC circuits as claimed in claim 6, characterized in that: One end of the primary winding of the high-frequency transformer T1 is connected to a resonance loop composed of a capacitor Cp, an inductor Lr and a capacitor Cr connected in series.

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