Single-stage wide input soft switching resonant power supply conversion apparatus

Abstract

Provided is a single-stage wide input soft switching resonant power supply conversion apparatus, which is characterized in that: said apparatus comprises a buck-boost circuit and an LLC circuit; the buck-boost circuit comprises two switch transistors Q1 and Q2, where the switching transistor Q2 is also used as an upper transistor of the LLC circuit. The described single-stage wide input soft switching resonant power supply conversion apparatus is subject to low stress, has significant advantages in thermal design and efficiency, and better facilitates product development in practical applications.

Description

Single-stage wide input soft-switching resonant power converter Technical Field

[0001] The present invention relates to a power converter, in particular to a single-stage wide-input soft-switching resonant power converter. Background Art

[0002] With the rapid development of semiconductor technology, fourth-generation LEDs (electric light sources) have been widely promoted and adopted. Compared with traditional electric light sources, LEDs offer many incomparable advantages, such as long life, high efficiency, low power consumption, high brightness, and compact size. Therefore, their application in the lighting field is particularly prominent. LED lighting systems consist of two components: the LED driver and the LED lamp, with the LED driver being the core. High-efficiency, energy-saving, and high-power LED drivers have become a key research direction in the industry.

[0003] High frequency and miniaturization are currently key design criteria for switching power supplies. If the driver operates in hard-switching mode, increasing the switching frequency will result in significant switching losses, reducing system efficiency. Therefore, soft-switching technology, designed to reduce switching losses, has become a key research focus in power electronics.

[0004] Resonant converters, including series, parallel, and series-parallel resonant converters, are common soft-switching converters. Properly designed, resonant converters can achieve zero-voltage turn-on of the switch and zero-current turn-off of the secondary-side rectifier diode over a wide load range, thereby reducing switch losses and improving efficiency. The AC-DC converter utilizes a Buck-Boost topology, operating in discontinuous mode and automatically implementing PFC. This single-switch, low-order, step-up / step-down converter circuit achieves variable intermediate DC bus voltage, reducing stress on the subsequent LLC switch and capacitors.

[0005] There are two main technical solutions in the existing technology: 1. High-power two-stage type, with the first stage Boost achieving power factor correction and voltage regulation, and the second stage DCDC (isolated non-isolated topology) achieving output voltage regulation (and electrical isolation, etc.). This solution is technically mature, but the system is complex, costly, and inefficient. 2. Low-power single-stage PFC flyback, using a single-stage flyback to simultaneously achieve input power factor correction and output voltage regulation, is mainly used in low-power LED driver power supplies. This solution is technically mature, simple, low-cost, and highly efficient, but has significant power frequency ripple at the output (which can cause LED lights to flicker), a narrow input voltage range, and a lack of busbar capacitance that causes lightning surges. Summary of the Invention

[0006] The main technical problem to be solved by the present invention is to provide a single-stage wide-input soft-switching resonant power conversion device with low stress, obvious advantages in thermal design and efficiency, and more convenient for product development in practical applications.

[0007] In order to solve the above technical problems, the present invention provides a single-stage wide-input soft-switching resonant power conversion device, including a Buck-Boost circuit and an LLC circuit; the Buck-Boost circuit includes two switching tubes Q1 and Q2, and one of the switching tubes Q2 is reused as the upper tube of the LLC circuit.

[0008] In a preferred embodiment, the switch tubes Q1 and Q2 are turned on or off at the same time.

[0009] In a preferred embodiment, the LLC circuit further includes a lower tube Q3 , and the state of Q3 is opposite to that of Q1 and Q2 .

[0010] In a preferred embodiment, the switch tubes Q1, Q2 and the lower tube Q3 are controlled by PWM or PFM.

[0011] In a preferred embodiment, a rectifier bridge is further included, wherein the AC input end thereof is connected to the AC power supply, and the DC output end thereof is connected to the high-frequency transformer T1 through the Buck-Boost circuit and the LLC circuit.

[0012] In a preferred embodiment, the primary winding Np of the high-frequency transformer T1 and the like-named ends of the secondary windings Ns1 and Ns2 have the same direction.

[0013] In a preferred embodiment: the opposite-name ends of the secondary windings Ns1 and Ns2 are connected to the anodes of diodes D6 and D7 respectively, the cathodes of diodes D6 and D7 are connected to each other and grounded through the electrolytic capacitor C2, and are connected to the same-name ends of the secondary windings Ns1 and Ns2 through the load R1.

[0014] In a preferred embodiment, the switch tubes Q1, Q2 and the bottom tube Q3 are power MOS tubes.

[0015] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0016] The present invention provides a single-stage, wide-input, soft-switching resonant power converter. Two MOS transistors are incorporated into the Buck-Boost circuit. This significantly reduces the voltage stress of MOS transistor Q2, which is reused as the LLC circuit. The stress of the added MOS transistor Q1 is equal to the input voltage, making MOS transistor selection more advantageous. Cost-effective 500V MOS transistors can be selected. Two power diodes are also eliminated from the main circuit, reducing the cost of power semiconductor devices. Furthermore, the operating principle of the LLC circuit is identical to that of a conventional LLC circuit. Q2 and Q3 can achieve zero-voltage switching (ZVS) across the full load range, offering significant advantages in thermal design and efficiency, and facilitating product development for practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG1 is a circuit diagram of a preferred embodiment of the present invention;

[0018] FIG2 is a timing diagram of a preferred embodiment of the present invention;

[0019] 3 to 10 are equivalent circuit diagrams of the preferred embodiment of the present invention in various modes;

[0020] 11-14 are simple replacement circuit diagrams of a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "set / connected", "connected", etc. should be understood in a broad sense. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] Referring to FIG1 , this embodiment provides a single-stage wide-input soft-switching resonant power converter, including a rectifier bridge, a Buck-Boost circuit, an LLC circuit, a high-frequency transformer T1, and a load R1.

[0025] The rectifier bridge is a full-bridge rectifier, comprising four diodes D1, D2, D3, and D4. The bridge's AC input is connected to an AC power source, while its DC output outputs pulsating DC power. The DC output's positive terminal is connected to the cathode of diode D5, whose anode is connected to one end of the primary-side Np of high-frequency transformer T1. The DC output's negative terminal is connected to the other end of the primary-side Np of high-frequency transformer T1 via switch Q1, high-frequency capacitor Cr, and inductor Lr.

[0026] The cathode of the diode D5 is also connected to the anode of the diode D5 through the inductor L1 and the electrolytic capacitor C1; the same-name ends of the inductor L1 and the electrolytic capacitor C1 are also connected to the high-frequency capacitor Cr through the switch tube Q2, and the anode of the diode D5 is also connected to the high-frequency capacitor Cr through the switch tube Q3.

[0027] The opposite-name ends of the secondary windings Ns1 and Ns2 are connected to the anodes of diodes D6 and D7 respectively, and the cathodes of diodes D6 and D7 are connected to each other and grounded through the electrolytic capacitor C2, and are connected to the same-name ends of the secondary windings Ns1 and Ns2 through the load R1.

[0028] The primary winding Np of the high-frequency transformer T1 and the like-named terminals of the secondary windings Ns1 and Ns2 are in the same direction. The switching transistors Q1, Q2, and Q3 are each power MOS transistors. The single-stage, wide-input, soft-switching resonant power converter integrates the Buck-Boost circuit with the LLC circuit, reusing the MOS transistor Q2. This allows the MOS transistor Q2 to function as both the Buck-Boost circuit's switching transistor and the LLC circuit's high-side transistor.

[0029] Q1, Q2, and Q3 utilize PWM / PFM control, with Q1 and Q2 switching on and off simultaneously. Q3's drive is complementary to Q1 and Q2. D5, D6, and D7 are power diodes used to rectify the high-frequency AC voltage on T1's secondary winding into DC. L1 and Lr are high-frequency inductors, C1 and C2 are electrolytic capacitors, and Cr is a high-frequency capacitor. T1 is a high-frequency transformer, with its primary winding Np and the same-named terminals of the secondary windings Ns1 and Ns2 aligned in the same direction.

[0030] The working mode is divided into the following 7 modes:

[0031] Mode 1 [t0~t1]: Before t0, the current i of inductor L1 is L It has dropped to 0. At the same time, since the body diode of Q2 is turned on, at time t0, Q2 is turned on with zero voltage and zero current, and Q1 is turned on with zero current. in The Buck-Boost inductor L1 is charged through MOS tubes Q1 and Q2. The current i L With slope u in / L1 increases linearly. At the same time, the DC bus capacitor C1 provides energy to the LLC circuit through the MOS tube Q2. At this stage, the resonant inductor L in the LLC circuit r , resonant capacitor C r Participate in resonance, the resonant frequency is The secondary diode D7 is turned on, charging the output capacitor C2 and supplying power to the output load R1. It also clamps the primary winding of the transformer, so the magnetizing inductance of the transformer T1 does not participate in the resonance at this stage. Lm With slope nV o / L m Linear increase.

[0032] Mode 2 [t1~t2]: At t1, the resonant current is equal to the excitation current. At this time, the current of the secondary diode D8 drops to zero and turns off. The primary winding of the transformer is no longer clamped by the output voltage, and the excitation inductance participates in the resonance. The resonant frequency is MOS tubes Q1 and Q2 are still conducting, and the current i L Continue to increase linearly.

[0033] Mode 3 [t2~t3]: At t2, MOS tubes Q1 and Q2 are turned off and enter the dead time. Inductor L1 begins to discharge, and its current i L The DC bus capacitor C1 is charged through the power diode D5, and the current i L The excitation inductance Lm, the resonant inductance Lr, and the resonant capacitor Cr form a series resonant circuit with a resonant frequency of Resonance, the resonant current charges the junction capacitance of MOS tube Q2 and discharges the junction capacitance of MOS tube Q3 until the voltage across the junction capacitance of MOS tube Q3 drops to 0. At this stage, the resonant current is still equal to the excitation current, and the secondary diode continues to be turned off.

[0034] Mode 4 [t3~t4]: At t3, the resonant current flows through the body diode of MOS transistor Q3, and MOS transistor Q3 meets the zero voltage turn-on condition. In this stage, the resonant inductor Lr and the resonant capacitor Cr are at the resonant frequency. Resonance, the resonant current is greater than the excitation current, the secondary diode D6 is turned on. The voltage across the primary winding of the transformer is clamped at -nVo, and the excitation current is at a slope of nV o / L m In this stage, the current i L Continue to decrease.

[0035] Mode 5 [t4-t5]: At t4, the current iL of the inductor L in the Buck-Boost circuit drops to zero. The MOS tube Q3 continues to conduct, and the resonant inductor Lr and the resonant capacitor Cr continue to resonate at the resonant frequency. Resonance, the resonant current is greater than the excitation current, and the secondary side diode D6 is turned on.

[0036] Mode 6 [t5-t6]: At t5, the current in Lr is equal to the current in Lm, the secondary rectifier diode D6 is turned off with zero current, the output voltage no longer clamps the transformer, Lm becomes a free resonant inductor and participates in the resonance, the excitation inductor Lm, the resonant inductor Lr, and the resonant capacitor Cr form a series resonant circuit with the resonant frequency Resonance: Since the excitation inductance Lm is very large, the resonance period is very large. The resonant current is consistent with the excitation current in this stage and is approximately a constant value.

[0037] Mode 7 [t6~t7]: At t6, MOS tube Q3 is turned off. Entering the dead time, as in mode 6, the excitation inductance Lm, resonant inductance Lr, and resonant capacitor Cr are at the resonant frequency. Resonance: At this stage, the resonant current is still equal to the excitation current, and the secondary rectifier diode is turned off. The resonant current discharges the junction capacitance of MOS transistor Q2 and charges the junction capacitance of MOS transistor Q3 until the voltage across the junction capacitance of MOS transistor Q2 drops to 0.

[0038] As shown in Figures 11-14, as a simple replacement for this embodiment, the input AC power source can be changed from two-phase AC to three-phase AC. The inductor Lr in Example 1 can also be integrated into the transformer T1, and the MOS transistor Q1 can be adjusted from the negative DC side in Example 1 to the positive DC side. The rectifier diodes D6 and D7 on the secondary winding of the transformer can also be replaced with MOS transistors to achieve output synchronous rectification. As long as the Buck-Boost circuit of the power converter includes two switching transistors Q1 and Q2, and one of the switching transistors Q2 is reused as the high-side transistor of the LLC circuit, any modification of the other components is a simple replacement of this embodiment.

[0039] The above is only a preferred specific embodiment of the present invention, but the design concept of the present invention is not limited to this. Any technician familiar with this technical field who uses this concept to make non-substantial changes to the present invention within the technical scope disclosed by the present invention shall be deemed to infringe the scope of protection of the present invention. Industrial Applicability

[0040] The present invention provides a single-stage, wide-input, soft-switching resonant power converter. Two MOS transistors are incorporated into the Buck-Boost circuit. This significantly reduces the voltage stress of the MOS transistor Q2, which is reused as the LLC circuit. The stress of the added MOS transistor Q1 is equal to the input voltage, making MOS transistor selection more advantageous. Cost-effective 500V MOS transistors can be selected. Two power diodes are also eliminated from the main circuit, reducing the cost of power semiconductor devices. Furthermore, the operating principle of the LLC circuit is identical to that of a conventional LLC circuit. Q2 and Q3 can achieve zero-voltage switching (ZVS) over the full load range, offering significant advantages in thermal design and efficiency. This facilitates product development for practical applications and demonstrates excellent industrial applicability.

Claims

1. Single-stage wide input soft switching resonant power conversion device, characterized in that: It includes a Buck-Boost circuit and an LLC circuit; the Buck-Boost circuit includes two switch tubes Q1 and Q2, and one of the switch tubes Q2 is multiplexed as the upper tube of the LLC circuit.

2. The single-stage wide input soft switching resonant power conversion device according to claim 1, characterized in that: The switch tubes Q1 and Q2 are turned on or off at the same time.

3. The single-stage wide input soft switching resonant power conversion device according to claim 2, characterized in that: The LLC circuit further includes a lower tube Q3, and the state of Q3 is opposite to that of Q1 and Q2.

4. The single-stage wide input soft switching resonant power conversion device according to claim 3 is characterized in that: The switch tubes Q1, Q2 and the lower tube Q3 are controlled by PWM or PFM.

5. The single-stage wide input soft switching resonant power conversion device according to any one of claims 1 to 4, characterized in that: It also includes a rectifier bridge, whose AC input end is connected to an AC power supply, and whose DC output end is connected to a high-frequency transformer T1 through the Buck-Boost circuit and the LLC circuit.

6. The single-stage wide input soft-switching resonant power conversion device according to claim 5, characterized in that: The primary winding Np of the high-frequency transformer T1 has the same direction as the like-named ends of the secondary windings Ns1 and Ns2.

7. The single-stage wide input soft switching resonant power conversion device according to claim 7, characterized in that: The opposite ends of the secondary windings Ns1 and Ns2 are connected to the anodes of diodes D6 and D7 respectively, the cathodes of diodes D6 and D7 are connected to each other and grounded through the electrolytic capacitor C2, and are connected to the same ends of the secondary windings Ns1 and Ns2 through the load R1.

8. The single-stage wide input soft-switching resonant power conversion device according to claim 5, characterized in that: The switch tubes Q1, Q2 and the lower tube Q3 are power MOS tubes.

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