CN108235509A - A kind of single-stage LED drive circuit of integrated decompression Cuk and LLC circuits - Google Patents

Abstract

The invention relates to a single-stage LED driving circuit integrating a step-down Cuk and an LLC circuit. Including single-phase AC input power supply V _in , first power diode D ₁ , second power diode D ₂ , third power diode D ₃ , fourth power diode D ₄ , fifth power diode D ₅ , sixth power diode D ₆ , seventh power diode D ₇ , eighth power diode D _s1 , ninth power diode D _s2 , first power switch S ₁ , second power switch S ₂ , high frequency capacitor C ₁ , bus capacitor C _bus , output Capacitor C _o , resonant capacitor C _r , Cuk inductance L ₁ , Cuk inductance L ₂ , resonant inductance L _r , high frequency transformer T (including primary winding Np, secondary winding Ns1, secondary winding Ns2), LED light load. The invention proposes a single-stage LED driving circuit integrating step-down Cuk and LLC converter, which is oriented to high-voltage input applications, realizes high power factor and soft switching conversion, and improves the performance-price ratio of the LED driving circuit.

Description

A single-stage LED driver circuit integrating step-down Cuk and LLC circuits

technical field

The invention relates to a single-stage LED drive circuit integrating step-down Cuk and LLC circuits, which is applied to AC high-voltage input occasions. Power factor and soft switching conversion.

Background technique

Lighting appliances above 25 watts need to meet a series of mandatory related standards, such as IEC555-2, IEC1000-3-2 and other standards. Therefore, the power factor correction (Power Factor Correction—PFC) technology has become a key technology in the field of LED driving circuits. In the case of high-voltage AC input, research on high-efficiency step-down PFC circuits has become a hot spot.

The switching tube of the LLC resonant converter can work in the soft switching mode, and its switching loss can be kept at a very low level, and it has been widely used in medium and high power LED drive systems. Generally, the efficiency of an independent LLC resonant converter is above 90%. The traditional AC input LED drive power usually adopts a two-stage structure, the front stage is a power factor correction circuit, and the latter stage is a DC-DC conversion circuit. The driving power supply of the two-stage structure needs to adopt two sets of independent control systems respectively, so its cost is high and its reliability is poor. In recent years, more and more scholars have begun to pay attention to single-stage LED drive power. The single-stage circuit multiplexes the switching tubes of the two-stage circuit and integrates them into a single stage, which reduces the number of switching tubes and only requires a set of control systems, which improves reliability and reduces costs. It has important theoretical significance and engineering application value .

In addition, compared with the traditional step-down Buck active power factor correction circuit, the step-down Cuk circuit has filter inductors at the input and output ends, so the input and output current ripple and electromagnetic interference are reduced, and the efficiency of the step-down converter is improved. efficiency and power factor and reduce THD.

Contents of the invention

The purpose of the present invention is to provide a single-stage LED driving circuit integrating step-down Cuk and LLC circuits, so that the circuit can achieve high efficiency, high power factor, reduce the DC bus voltage, and improve the performance and price ratio of the driving circuit.

In order to achieve the above object, the technical solution of the present invention is: a single-stage LED drive circuit integrating step-down Cuk and LLC circuit, including single-phase AC input power supply V _in , first power diode D ₁ , second power diode D ₂ , the third power diode D ₃ , the fourth power diode D ₄ , the fifth power diode D ₅ , the sixth power diode D ₆ , the seventh power diode D ₇ , the eighth power diode D _s1 , the ninth power diode D _s2 , First power switch tube S ₁ , second power switch tube S ₂ , high frequency capacitor C ₁ , bus capacitor C _bus , output capacitor C _o , resonant capacitor C _r , Cuk inductance L ₁ , Cuk inductance L ₂ , resonant inductance L _r , high-frequency transformer T, LED lamp load; the cathode of the first power diode _D1 is connected to the cathode of the third power diode _D3 and one end of the Cuk inductance _L1 , and the cathode of the second power diode _D2 is connected to One end of the single-phase AC input power supply V _in is connected to the anode of the first power diode _D1 , and the anode of the second power diode _D2 is connected to one end of the high-frequency capacitor _C1 , the anode of the fourth power diode _D4 , and the anode of the second power diode D1. The source of the second power switch tube _S2 is connected to the anode of the sixth power diode _D6 , and the other end of the single-phase AC input power supply v _in is connected to the anode of the third power diode _D3 and the anode of the fourth power diode _D4. The cathode is connected, and the other end of the Cuk inductance _L1 is connected with one end of the Cuk inductance _L2 , the positive end of _{the bus} capacitor Cbus, the drain of the second power switch tube _S1 , and one end of the resonant inductance _Lr , so The other end of the Cuk inductance L ₂ is connected to the cathode of the fifth power diode D ₅ and the other end of the high frequency capacitor C ₁ , and the negative end of the bus capacitor C _bus is connected to the anode of the seventh power diode D ₇ and the fifth power The anode of the diode _D5 is connected to the cathode of the sixth power diode _D6 , the source of the first power switch _S1 is connected to the drain of the second power switch _S2 , the cathode of the seventh power diode _D7 and the resonance One end of the capacitor C _r is connected, the other end of the resonant inductance L _r is connected with the end of the same name of the primary winding N p of the high-frequency transformer T, and the other end of the resonant capacitor C _r is connected to the primary winding N _p of the high-frequency transformer T. The opposite end of the side winding N _p is connected; the opposite end of the secondary winding N _s1 of the high frequency transformer T is connected with the same end of the secondary winding N _s2 of the high frequency transformer T, the negative end of the output capacitor C _o and One end of the LED lamp load is connected, the same-named end of the secondary winding N _s1 of the high-frequency transformer T is connected to the anode of the eighth power diode D _s1 , and the opposite name of the secondary winding N _s2 of the high-frequency transformer T is The terminal is connected to the anode of the ninth power diode D _s2 , the cathode of the eighth power diode D _s1 is connected to the cathode of the ninth power diode D _s2 , the positive terminal of the output capacitor C _o and the other terminal of the LED lamp load.

In an embodiment of the present invention, the Cuk inductor L ₁ , the Cuk inductor L ₂ , the fifth power diode D ₅ , the seventh power diode D ₇ , the second power switch tube S ₂ , the high frequency capacitor C ₁ , and the bus capacitor C _bus forms a step-down Cuk circuit; the first power switch S ₁ , the second power switch S ₂ , the seventh power diode D ₇ , the sixth power diode D ₆ , the output capacitor C _o , the resonant capacitor C _r , Resonant inductor L _r , high frequency transformer T, eighth power diode D _s1 , ninth power diode D _s2 , and LED light load constitute an LLC circuit; the step-down Cuk circuit can work in DCM mode, BCM mode or CCM mode, and the LLC circuit Work in the ZVS area.

In an embodiment of the present invention, the first power diode D ₁ , the second power diode D ₂ , the third power diode D ₃ , and the fourth power diode D ₄ are rectifier diodes, and the fifth power diode D ₅ , The sixth power diode D ₆ , the seventh power diode D ₇ , the eighth power diode D _s1 , and the ninth power diode D _s2 are fast recovery diodes.

In an embodiment of the present invention, the first power switch tube S ₁ and the second power switch tube S ₂ are power MOSFET tubes, and a PFM control method is adopted.

In an embodiment of the present invention, the resonant capacitor C _r and the high frequency capacitor C ₁ are high frequency capacitors; the bus capacitor C _bus and the output capacitor C _o are electrolytic capacitors.

In an embodiment of the present invention, the resonant inductance L _r is formed by a leakage inductance, or is an independent inductance.

In an embodiment of the present invention, the working mode of the circuit is as follows:

Assume that the step-down Cuk circuit works in DCM mode, the LLC circuit works in the f _r1 < f _s < f _r region, and f _s is the switching tube frequency; in the positive and negative periods of the AC power supply frequency, the working state of the circuit is symmetrical. Take the positive half cycle of power frequency as an example, and the negative half cycle is similar;

(1) When the input voltage V _in is less than the DC bus voltage V _Cbus :

Mode 1[t ₀ <t<t ₁ ]: the switch tube S ₁ is turned off, the switch tube S ₂ is turned on with zero current, the input voltage V _in is less than the DC bus voltage V _Cbus , at this time the rectifier bridge is in the disconnected state, and the front stage The step-down Cuk circuit does not work, and the DC bus capacitor C _bus provides energy to the subsequent LLC; at this stage, the resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s1 is turned on; the voltage at both ends of the primary winding of the transformer is clamped at nV _o , and the excitation current rises linearly with a slope of nV _o /L _m ;

Mode 2[t ₁ <t<t ₂ ]: switch tube S ₁ is turned off, switch tube S ₂ is turned on, the input voltage V _in is less than the DC bus voltage V _Cbus , the pre-stage step-down Cuk circuit does not work, and the DC bus capacitor C _{The bus} provides energy to the subsequent LLC; at this time, the resonant current is equal to the excitation current, and the secondary diode D _s1 is turned off at zero current; the primary winding of the transformer is no longer clamped by the output voltage, and the excitation inductance L _m and the resonant inductance L _r , the resonant capacitor C _r participates in the resonance, at this stage, the resonant frequency is Due to the large excitation inductance, the resonance period is very large, and the resonance current is consistent with the excitation current at this stage, which is approximately a constant value;

Mode 3[t ₂ <t<t ₃ ]: The switching tubes S ₁ and S ₂ are turned off and enter the dead time; at this stage, the resonant frequency is The resonant current is greater than the excitation current, and the secondary side diode D _s2 is turned on; part of the resonant current charges the junction capacitance of the switch tube _S2 ; part of the resonant current discharges the junction capacitance of the switch tube _S1 until both ends of the junction capacitance of the switch tube _S1 The voltage is zero; after that, all the resonant current flows through the body diode of the switch tube _S1 , preparing for the zero-voltage turn-on of the switch tube _S1 ;

Mode 4[t ₃ <t<t ₄ ]: switching tube S ₁ is turned on at zero voltage, switching tube S ₂ is turned off, the input voltage V _in is less than the DC bus voltage V _Cbus , at this time the rectifier bridge is in the disconnected state, the front The step-down Cuk circuit does not work, at this stage, the resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s2 is turned on; the voltage at both ends of the primary winding of the transformer is clamped at -nV _o , and the excitation current rises linearly with a slope of nV _o /L _m ;

Mode 5[t ₄ <t<t ₅ ]: The switch tube S ₁ is still on; at this time, the resonant current is equal to the excitation current, and the secondary diode D _s2 is turned off at zero current; the primary winding of the transformer is no longer The output voltage is clamped, the excitation inductance L _m , the resonant inductance L _r , and the resonant capacitor C _r participate in the resonance. At this stage, the resonant frequency is Due to the large excitation inductance, the resonance period is very large, and the resonance current is consistent with the excitation current at this stage, which is approximately a constant value;

Mode 6[t ₅ <t<t ₆ ]: switch tube S ₁ is cut off, at this stage, the resonant frequency is The resonant current is greater than the excitation current, the secondary diode D _s1 is turned on; the voltage across the junction capacitance of the switch tube S ₁ is equal to the DC bus voltage, and the diode D ₇ is turned on to prepare for the zero-current turn-on of the switch tube S ₂ ;

(2) When the input voltage V _in is greater than the DC bus voltage V _Cbus :

Mode 1a[t ₀ <t<t ₁ ]: switch tube S ₁ is turned off, switch tube S ₂ is turned on with zero current, the input voltage V _in is greater than the DC bus voltage V _Cbus , the pre-stage step-down Cuk circuit works, and the Cuk inductor current i _L1 and i _L2 rise linearly with the slope (V _in -V _cbus )/L ₁ , and the step-down Cuk stage current i _cuk is greater than the LLC stage current i _r , and the step-down Cuk stage transfers part of the input energy to the subsequent LLC, and part of it Charge the bus capacitor C _bus ; at the same time, the LLC resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s1 is turned on; the voltage at both ends of the primary winding of the transformer is clamped at nV _o , and the excitation current rises linearly with a slope of nV _o /L _m ;

Mode 1b[t ₀ <t<t ₁ ]: switch tube S ₁ is turned off, switch tube S ₂ is turned on, the input voltage V _in is greater than the DC bus voltage V _Cbus , the pre-stage step-down Cuk circuit works, and the Cuk inductor current i _L1 , i _L2 rises linearly with the slope (V _in -V _cbus )/L ₁ , and the step-down Cuk level current i _cuk is smaller than the LLC level current i _r , the bus capacitor C _bus is in the discharge state; at the same time, the LLC resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s1 is turned on; the voltage at both ends of the primary winding of the transformer is clamped at nV _o , and the excitation current rises linearly with a slope of nV _o /L _m ;

Mode 2[t ₁ <t<t ₂ ]: switch tube S ₁ is turned off, switch tube S ₂ is turned on, the input voltage V _in is greater than the DC bus voltage V _Cbus , the pre-stage step-down Cuk circuit works, and the Cuk inductor current i _L1 、i _L2 continues to rise linearly with the slope (V _in -V _cbus )/L ₁ ; at this time, the resonant current is equal to the excitation current, and the secondary diode D _s1 is turned off at zero current; the primary winding of the transformer is no longer driven by the output voltage Clamping, the excitation inductance L _m , the resonant inductance L _r , and the resonant capacitor C _r participate in the resonance. At this stage, the resonant frequency is Due to the large excitation inductance, the resonance period is very large, and the resonance current is consistent with the excitation current at this stage, which is approximately a constant value;

Mode 3[t ₂ <t<t ₃ ]: Switch tubes S ₁ and S ₂ are turned off and enter dead time; Cuk inductor current i _L1 and i _L2 freewheel; at this stage, the resonant frequency is The resonant current is greater than the excitation current, and the secondary side diode D _s2 is turned on; part of the resonant current charges the junction capacitance of the switch tube _S2 ; part of the resonant current discharges the junction capacitance of the switch tube _S1 until both ends of the junction capacitance of the switch tube _S1 The voltage is zero; after that, all the resonant current flows through the body diode of the switch tube _S1 , preparing for the zero-voltage turn-on of the switch tube _S1 ;

Mode 4[t ₃ <t<t ₄ ]: switching tube S ₁ turns on at zero voltage, switching tube S ₂ turns off; Cuk inductor current i _L1 and i _L2 continue to flow; at this stage, the resonant inductor L _r , resonant Capacitor C _r at the resonant frequency Resonance, the resonant current is greater than the excitation current, the secondary diode D _s2 is turned on; the voltage at both ends of the primary winding of the transformer is clamped at -nV _o , and the excitation current rises linearly with a slope of nV _o /L _m ;

Mode 5[t ₄ <t<t ₅ ]: Switch tube S ₁ is still on; Cuk inductor current i _L1 and i _L2 freewheeling ends; at this stage, resonant inductance L _r and resonant capacitor C _r are at the resonant frequency Resonance, the resonant current is greater than the excitation current, the secondary diode D _s2 is turned on; the voltage at both ends of the primary winding of the transformer is clamped at -nV _o , and the excitation current rises linearly with a slope of nV _o /L _m ;

Mode 6[t ₅ <t<t ₆ ]: The switch tube S ₁ is still on; at this time, the resonant current is equal to the excitation current, and the secondary diode D _s2 is turned off at zero current; the primary winding of the transformer is no longer The output voltage is clamped, the excitation inductance L _m , the resonant inductance L _r , and the resonant capacitor C _r participate in the resonance. At this stage, the resonant frequency is Due to the large excitation inductance, the resonance period is very large, and the resonance current is consistent with the excitation current at this stage, which is approximately a constant value;

Mode 7[t ₆ <t<t ₇ ]: switch tube S ₁ is cut off, at this stage, the resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s1 is turned on; the voltage across the junction capacitance of the switch tube S ₁ is equal to the DC bus voltage, and the diode D ₇ is turned on, preparing for the zero-current turn-on of the switch tube S ₂ .

Compared with the prior art, the present invention has the following beneficial effects:

1. The present invention proposes an integrated step-down Cuk and LLC converter single-stage LED drive circuit, which only needs a set of control circuits, which can improve circuit reliability and reduce costs;

2. The input and output filter inductor of the present invention makes the input and output current pulsation small, which is beneficial to reduce ripple and EMI, improves the efficiency of the step-down converter and reduces THD.

3. The present invention can realize high power factor and lower DC bus voltage in the occasion of high-voltage AC input voltage.

Description of drawings

Fig. 1 is a schematic diagram of a single-stage LED driving circuit integrating step-down Cuk and llc circuits of the present invention.

Fig. 2 is the key waveform corresponding to the positive half cycle mode of the embodiment of the present invention.

Fig. 3 is an equivalent circuit diagram 1 of an integrated step-down Cuk and LLC converter single-stage LED drive circuit working stage according to a specific embodiment of the present invention.

Fig. 4 is an equivalent circuit diagram 2 of an integrated step-down Cuk and LLC converter single-stage LED drive circuit working stage according to a specific embodiment of the present invention.

Fig. 5 is an equivalent circuit diagram 3 of an integrated step-down Cuk and LLC converter single-stage LED drive circuit working stage according to a specific embodiment of the present invention.

Fig. 6 is an equivalent circuit diagram 4 of the working stage of a single-stage LED drive circuit of an integrated step-down Cuk and LLC converter according to a specific embodiment of the present invention.

Fig. 7 is an equivalent circuit diagram 5 of an integrated step-down Cuk and LLC converter single-stage LED drive circuit working stage according to a specific embodiment of the present invention.

Fig. 8 is an equivalent circuit diagram 6 of the working stage of a single-stage LED drive circuit of an integrated step-down Cuk and LLC converter according to a specific embodiment of the present invention.

Fig. 9 is an equivalent circuit diagram 7 of an integrated step-down Cuk and LLC converter single-stage LED drive circuit working stage according to a specific embodiment of the present invention.

Fig. 10 is the eighth equivalent circuit diagram of a single-stage LED drive circuit of an integrated step-down Cuk and LLC converter in a specific embodiment of the present invention.

Fig. 11 is an equivalent circuit diagram 9 of the working stage of a single-stage LED drive circuit of an integrated step-down Cuk and LLC converter according to a specific embodiment of the present invention.

Fig. 12 is an equivalent circuit diagram 10 of an integrated step-down Cuk and LLC converter single-stage LED drive circuit working stage according to a specific embodiment of the present invention.

Fig. 13 is the eleventh equivalent circuit diagram of a single-stage LED drive circuit of an integrated step-down Cuk and LLC converter in a specific embodiment of the present invention.

Fig. 14 is an equivalent circuit diagram 12 of an integrated step-down Cuk and LLC converter single-stage LED drive circuit working stage according to a specific embodiment of the present invention.

Fig. 15 is an equivalent circuit diagram 13 of a working stage of a single-stage LED driving circuit of an integrated step-down Cuk and LLC converter according to a specific embodiment of the present invention.

Fig. 16 is the fourteenth equivalent circuit diagram of a single-stage LED drive circuit of an integrated step-down Cuk and LLC converter in a specific embodiment of the present invention.

Detailed ways

The technical solution of the present invention will be specifically described below in conjunction with the accompanying drawings.

As shown in Fig. 1, this embodiment provides a single-stage LED drive circuit integrating step-down Cuk and LLC converter, including a single-phase AC input power supply v _in , a first power diode D ₁ , a second power diode D ₂ , The third power diode D ₃ , the fourth power diode D ₄ , the fifth power diode D ₅ , the sixth power diode D ₆ , the seventh power diode D ₇ , the eighth power diode D _s1 , the ninth power diode D _s2 , the A power switch tube S ₁ , a second power switch tube S ₂ , a high frequency capacitor C ₁ , a bus capacitor C _bus , an output capacitor C _o , a resonant capacitor C _r , a Cuk inductor L ₁ , a Cuk inductor L ₂ , and a resonant inductor L _r , High frequency transformer T, LED light load.

The cathode of the first power diode _D1 is connected to the cathode of the third power diode _D3 and one end of the Cuk inductor _L1 , the cathode of the second power diode _D2 is connected to one end of the single-phase AC input power supply v _in , the first The anode of a power diode _D1 is connected, the anode of the second power diode _D2 is connected to one end of the high frequency capacitor _C1 , the anode of the fourth power diode _D4 , the source of the second power switch _S2 and the first The anodes of the six power diodes D ₆ are connected, the other end of the single-phase AC input power supply v _in is connected with the anode of the third power diode D ₃ and the cathode of the fourth power diode D ₄ , the Cuk inductance L ₁ The other end is connected with one end of the Cuk inductance _L2 , the positive end of _{the bus} capacitor Cbus, the drain of the second power switch tube _S1 and one end of the resonant inductance _Lr , and the other end of the Cuk inductance _L2 is connected to the fifth power The cathode of the diode _D5 is connected to the other end of the high-frequency capacitor _C1 , and the negative end of the bus capacitor C _bus is connected to the anode of the seventh power diode _D7 , the anode of the fifth power diode _D5 , and the sixth power diode D ₆ , the source of the first power switch _S1 is connected to the drain of the second power switch _S2 , the cathode of the seventh power diode _D7 and one end of the resonant capacitor _Cr , the resonant The other end of the inductance L _r is connected to the end of the same name of the primary winding N _p of the high frequency transformer T, and the other end of the resonant capacitor C _r is connected to the end of the same name of the primary winding N _p of the high frequency transformer T The opposite end of the secondary winding N _s1 of the high frequency transformer T is connected with the end of the same name of the secondary winding N _s2 of the high frequency transformer T, the negative end of the output capacitor C _o and one end of the LED lamp load. The same-named end of the secondary winding N _s1 of the high-frequency transformer T is connected to the anode of the eighth power diode D _s1 , and the opposite-named end of the secondary winding N _s2 of the high-frequency transformer T is connected to the anode of the ninth power diode D _s2 The cathode of the eighth power diode D _s1 is connected to the cathode of the ninth power diode D _s2 , the positive end of the output capacitor C _o and the other end of the LED lamp load.

In this embodiment, the Cuk inductor L ₁ , the Cuk inductor L ₂ , the fifth power diode D ₅ , the seventh power diode D ₇ , the second power switch tube S ₂ , the high frequency capacitor C ₁ , and the bus capacitor C _bus Constitute a step-down Cuk circuit; the first power switch tube S ₁ , the second power switch tube S ₂ , the seventh power diode D ₇ , the sixth power diode D ₆ , the output capacitor C _o , the resonant capacitor C _r , and the resonant inductance L _r , high-frequency transformer T, eighth power diode D _s1 , ninth power diode D _s2 , and LED light load constitute an LLC circuit; the step-down Cuk circuit can work in DCM mode, BCM mode or CCM mode, and the LLC circuit works in ZVS area.

In this embodiment, the first power diode D ₁ , the second power diode D ₂ , the third power diode D ₃ , and the fourth power diode D ₄ are rectifier diodes, and the fifth power diode D ₅ , the sixth power diode The power diode D ₆ , the seventh power diode D ₇ , the eighth power diode D _s1 , and the ninth power diode D _s2 are fast recovery diodes.

In this embodiment, the first power switch tube S ₁ and the second power switch tube S ₂ are power MOSFET tubes, and a PFM control method is adopted.

In this embodiment, the resonant capacitor C _r and the high frequency capacitor C ₁ are high frequency capacitors; the bus capacitor C _bus and the output capacitor C _o are electrolytic capacitors.

In this embodiment, the resonant inductance _Lr may be formed by a leakage inductance, or may be an independent inductance;

In the present embodiment, in the single-stage LED driving circuit integrating step-down Cuk and LLC converter, the equivalent exciting inductance of the high-frequency transformer T is L _m .

In particular, as shown in FIG. 2 to FIG. 16 , this embodiment also provides a specific circuit working mode of a single-stage LED driving circuit integrating a step-down Cuk and an LLC converter.

Design the step-down Cuk circuit to work in DCM mode, and the LLC circuit to work in the f _r1 < f _s < f _r region, and f _s is the switching tube frequency. In the positive and negative cycles of the AC power supply frequency, the working state of the circuit is symmetrical. Here, the positive half cycle of the power frequency is taken as an example. The negative half cycle will not be described one by one. Figure 2 shows the corresponding key waveforms, and Figures 3 to 16 It is the equivalent diagram of 14 modes in the positive half cycle.

FIG. 3 to FIG. 8 are modal equivalent diagrams when the input voltage V _in in FIG. 2 is lower than the DC bus voltage V _Cbus .

Mode 1[t ₀ <t<t ₁ ]: As shown in Figure 3, the switch tube S ₁ is turned off, the switch tube S ₂ is turned on with zero current, the input voltage V _in is less than the DC bus voltage V _Cbus , and the rectifier bridge is disconnected at this time state, the front-stage step-down Cuk circuit does not work, and the DC bus capacitor C _bus provides energy to the rear-stage LLC. At this stage, the resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s1 is turned on. The voltage at both ends of the primary winding of the transformer is clamped at nV _o , and the excitation current rises linearly with a slope of nV _o /L _m .

Mode 2[t ₁ <t<t ₂ ]: As shown in Figure 4, the switch tube S ₁ is turned off, the switch tube S ₂ is turned on, the input voltage V _in is less than the DC bus voltage V _Cbus , the pre-stage step-down Cuk circuit does not work, The DC bus capacitor C _bus provides energy to the subsequent LLC. At this time, the resonant current is equal to the excitation current, and the secondary diode D _s1 is turned off with zero current. The primary winding of the transformer is no longer clamped by the output voltage, the excitation inductance L _m , the resonant inductance L _r , and the resonant capacitor C _r participate in the resonance. At this stage, the resonant frequency is Because the excitation inductance is very large, the resonance period is very large, and the resonance current is consistent with the excitation current at this stage, which is approximately a constant value.

Mode 3[t ₂ <t<t ₃ ]: As shown in Figure 5, the switching tubes S ₁ and S ₂ are turned off and enter the dead time. At this stage, the resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s2 is turned on. Part of the resonant current charges the junction capacitance of the switch _S2 ; part of the resonant current discharges the junction capacitance of the switch _S1 until the voltage across the junction capacitance of the switch _S1 is zero. Afterwards, all the resonant current flows through the body diode of the switch tube _S1 , preparing for the zero-voltage turn-on of the switch tube _S1 .

Mode 4[t ₃ <t<t ₄ ]: As shown in Figure 6, the switch tube S ₁ is turned on at zero voltage, the switch tube S ₂ is turned off, the input voltage V _in is less than the DC bus voltage V _Cbus , and the rectifier bridge is in the off state In the open state, the previous step-down Cuk circuit does not work. At this stage, the resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s2 is turned on. The voltage at both ends of the primary winding of the transformer is clamped at -nV _o , and the excitation current rises linearly with a slope of nV _o /L _m .

Mode 5[t ₄ <t<t ₅ ]: as shown in Figure 7, the switch tube S ₁ is still on. At this time, the resonant current is equal to the excitation current, and the secondary diode D _s2 is turned off with zero current. The primary winding of the transformer is no longer clamped by the output voltage, the excitation inductance L _m , the resonant inductance L _r , and the resonant capacitor C _r participate in the resonance. At this stage, the resonant frequency is Because the excitation inductance is very large, the resonance period is very large, and the resonance current is consistent with the excitation current at this stage, which is approximately a constant value.

Mode 6[t ₅ <t<t ₆ ]: as shown in Figure 8, the switching tube S ₁ is cut off, and at this stage, the resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s1 is turned on. The voltage across the junction capacitance of the switch tube _S1 is equal to the DC bus voltage, and the diode _D7 is turned on, preparing for the zero-current turn-on of the switch tube _S2 .

9 to 16 are modal equivalent diagrams when the input voltage V _in is greater than the DC bus voltage V _Cbus in FIG. 2 .

Mode 1a[t ₀ <t<t ₁ ]: as shown in Figure 9, the switch tube S ₁ is turned off, the switch tube S ₂ is turned on with zero current, the input voltage V _in is greater than the DC bus voltage V _Cbus , and the pre-stage step-down Cuk circuit works , the Cuk inductor current i _L1 , i _L2 rises linearly with the slope (V _in -V _cbus )/L ₁ , and the step-down Cuk stage current i _cuk is greater than the LLC stage current i _r , and the step-down Cuk stage transfers part of the input energy to the rear stage LLC, part of which charges the bus capacitor C _bus . Meanwhile, the LLC resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s1 is turned on. The voltage at both ends of the primary winding of the transformer is clamped at nV _o , and the excitation current rises linearly with a slope of nV _o /L _m .

Mode 1b[t ₀ <t<t ₁ ]: As shown in Figure 10, the switch tube S ₁ is turned off, the switch tube S ₂ is turned on, the input voltage V _in is greater than the DC bus voltage V _Cbus , the pre-stage step-down Cuk circuit works, and the Cuk The inductor currents i _L1 and i _L2 increase linearly with a slope of (V _in -V _cbus )/L ₁ , and the step-down Cuk stage current i _cuk is smaller than the LLC stage current _ir , and the bus capacitor C _bus is in a discharging state. Meanwhile, the LLC resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s1 is turned on. The voltage at both ends of the primary winding of the transformer is clamped at nV _o , and the excitation current rises linearly with a slope of nV _o /L _m .

Mode 2[t ₁ <t<t ₂ ]: As shown in Figure 11, the switch tube S ₁ is turned off, the switch tube S ₂ is turned on, the input voltage V _in is greater than the DC bus voltage V _Cbus , the pre-stage step-down Cuk circuit works, and the Cuk The inductor currents i _L1 and i _L2 continue to increase linearly with a slope of (V _in −V _cbus )/L ₁ . At this time, the resonant current is equal to the excitation current, and the secondary diode D _s1 is turned off with zero current. The primary winding of the transformer is no longer clamped by the output voltage, the excitation inductance L _m , the resonant inductance L _r , and the resonant capacitor C _r participate in the resonance. At this stage, the resonant frequency is Because the excitation inductance is very large, the resonance period is very large, and the resonance current is consistent with the excitation current at this stage, which is approximately a constant value.

Mode 3 [t ₂ <t<t ₃ ]: As shown in Figure 12, the switching tubes S ₁ and S ₂ are turned off and enter the dead time. Cuk inductor current i _L1 and i _L2 freewheel. At this stage, the resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s2 is turned on. Part of the resonant current charges the junction capacitance of the switch _S2 ; part of the resonant current discharges the junction capacitance of the switch _S1 until the voltage across the junction capacitance of the switch _S1 is zero. Afterwards, all the resonant current flows through the body diode of the switch tube _S1 , preparing for the zero-voltage turn-on of the switch tube _S1 .

Mode 4[t ₃ <t<t ₄ ]: as shown in Figure 13, the switch tube S ₁ is turned on with zero voltage, and the switch tube S ₂ is turned off. Cuk inductor current i _L1 and i _L2 continue to flow continuously. At this stage, the resonant inductor L _r and the resonant capacitor C _r are at the resonant frequency Resonant, the resonant current is greater than the excitation current, and the secondary diode D _s2 is turned on. The voltage at both ends of the primary winding of the transformer is clamped at -nV _o , and the excitation current rises linearly with a slope of nV _o /L _m .

Mode 5 [t ₄ <t<t ₅ ]: as shown in Figure 14, the switch tube S ₁ is still on. Cuk inductor current i _L1 , i _L2 freewheeling ends. At this stage, the resonant inductor L _r and the resonant capacitor C _r are at the resonant frequency Resonant, the resonant current is greater than the excitation current, and the secondary diode D _s2 is turned on. The voltage at both ends of the primary winding of the transformer is clamped at -nV _o , and the excitation current rises linearly with a slope of nV _o /L _m .

Mode 6[t ₅ <t<t ₆ ]: as shown in Figure 15, the switch tube S ₁ is still on. At this time, the resonant current is equal to the excitation current, and the secondary diode D _s2 is turned off with zero current. The primary winding of the transformer is no longer clamped by the output voltage, the excitation inductance L _m , the resonant inductance L _r , and the resonant capacitor C _r participate in the resonance. At this stage, the resonant frequency is Because the excitation inductance is very large, the resonance period is very large, and the resonance current is consistent with the excitation current at this stage, which is approximately a constant value.

Mode 7[t ₆ <t<t ₇ ]: as shown in Figure 16, the switching tube S ₁ is cut off, and at this stage, the resonant frequency is The resonant current is greater than the excitation current, and the secondary diode D _s1 is turned on. The voltage across the junction capacitance of the switch tube _S1 is equal to the DC bus voltage, and the diode _D7 is turned on, preparing for the zero-current turn-on of the switch tube _S2 .

The above are the preferred embodiments of the present invention, and all changes made according to the technical solution of the present invention, when the functional effect produced does not exceed the scope of the technical solution of the present invention, all belong to the protection scope of the present invention.

Claims (7)

1. a kind of single-stage LED drive circuit of integrated decompression Cuk and LLC circuits, it is characterised in that：Electricity is inputted including single phase ac Source V_in, the first power diode D₁, the second power diode D₂, third power diode D₃, the 4th power diode D₄, the 5th Power diode D₅, the 6th power diode D₆, the 7th power diode D₇, the 8th power diode D_s1, the 9th power diode D_s2, the first power switch tube S₁, the second power switch tube S₂, high frequency capacitance C₁, bus capacitor C_bus, output capacitance C_o, resonance electricity Hold C_r, Cuk inductance L₁, Cuk inductance L₂, resonant inductance L_r, high frequency transformer T, LED light load；The first power diode D₁ Cathode and third power diode D₃Cathode and Cuk inductance L₁One end be connected, the second power diode D₂Cathode With single phase ac input power V_inOne end, the first power diode D₁Anode be connected, the second power diode D₂ Anode and high frequency capacitance C₁One end, the 4th power diode D₄Anode, the second power switch tube S₂Source electrode and the 6th work( Rate diode D₆Anode be connected, the single phase ac input power v_inThe other end and third power diode D₃Sun Pole, the 4th power diode D₄Cathode be connected, the Cuk inductance L₁The other end and Cuk inductance L₂One end, busbar electricity Hold C_busAnode, the second power switch tube S₁Drain electrode and resonant inductance L_rOne end be connected, the Cuk inductance L₂The other end With the 5th power diode D₅Cathode, high frequency capacitance C₁The other end be connected, the bus capacitor C_busNegative terminal and the 7th Power diode D₇Anode, the 5th power diode D₅Anode and the 6th power diode D₆Cathode be connected, described One power switch tube S₁Source electrode and the second power switch tube S₂Drain electrode, the 7th power diode D₇Cathode and resonant capacitance C_r One end be connected, the resonant inductance L_rThe other end and high frequency transformer T primary side winding N_pSame Name of Ends be connected, institute State resonant capacitance C_rThe other end and high frequency transformer T primary side winding N_pDifferent name end be connected；The high frequency transformer T's Vice-side winding N_s1Different name end and high frequency transformer T vice-side winding N_s2Same Name of Ends, output capacitance C_oNegative terminal and LED light bear One end of load is connected, the vice-side winding N of the high frequency transformer T_s1Same Name of Ends and the 8th power diode D_s1Anode phase Connection, the vice-side winding N of the high frequency transformer T_s2Different name end and the 9th power diode D_s2Anode be connected, it is described 8th power diode D_s1Cathode and the 9th power diode D_s2Cathode, output capacitance C_oAnode and LED light load The other end be connected.

2. the single-stage LED drive circuit of a kind of integrated decompression Cuk according to claim 1 and LLC circuits, feature exist In：The Cuk inductance L₁, Cuk inductance L₂, the 5th power diode D₅, the 7th power diode D₇, the second power switch tube S₂、 High frequency capacitance C₁, bus capacitor C_busForm decompression Cuk circuits；First power switch tube S₁, the second power switch tube S₂, Seven power diode D₇, the 6th power diode D₆, output capacitance C_o, resonant capacitance C_r, resonant inductance L_r, high frequency transformer T, Eight power diode D_s1, the 9th power diode D_s2, LED light load form LLC circuits；Decompression Cuk circuits can be operated in Under DCM patterns, BCM patterns or CCM patterns, LLC circuits work in ZVS regions.

3. the single-stage LED drive circuit of a kind of integrated decompression Cuk according to claim 1 and LLC circuits, feature exist In：The first power diode D₁, the second power diode D₂, third power diode D₃, the 4th power diode D₄It is whole Flow diode, the 5th power diode D₅, the 6th power diode D₆, the 7th power diode D₇, the 8th power diode D_s1, the 9th power diode D_s2For fast recovery diode.

4. the single-stage LED drive circuit of a kind of integrated decompression Cuk according to claim 1 and LLC circuits, feature exist In：First power switch tube S₁, the second power switch tube S₂For power MOSFET tube, and use PFM control modes.

5. the single-stage LED drive circuit of a kind of integrated decompression Cuk according to claim 1 and LLC circuits, feature exist In：The resonant capacitance C_r, high frequency capacitance C₁For high frequency capacitance；The bus capacitor C_bus, output capacitance C_oFor electrolytic capacitor.

6. the single-stage LED drive circuit of a kind of integrated decompression Cuk according to claim 1 and LLC circuits, feature exist In：The resonant inductance L_rIt is made of leakage inductance or for separate inductor.

7. the single-stage LED drive circuit of a kind of integrated decompression Cuk according to claim 1 and LLC circuits, feature exist In：The operation mode of the circuit is as follows：

If decompression Cuk circuits are operated in DCM patterns, LLC circuits are operated in f_r1<f_s<f_rRegion, f_sFor switching tube frequency；It is exchanging In the positive negative cycle of power supply power frequency, the working condition of circuit is symmetrical, this illustrates for sentencing power frequency positive half period, negative half-cycle It is similar；

(1) as input voltage V_inLess than DC bus-bar voltage V_CbusDuring situation：

1 [t of mode₀<t<t₁]：Switching tube S₁Shutdown, switching tube S₂Zero current turning-on, input voltage V_inLess than DC bus-bar voltage V_Cbus, at this time rectifier bridge be off, prime decompression Cuk circuits do not work, dc-link capacitance C_busIt is carried to rear class LLC For energy；This stage, resonant frequency areResonance current is more than exciting current, secondary side diode D_s1Conducting；Become Depressor primary side winding both end voltage is clamped at nV_o, exciting current is with slope nV_o/L_mLinear rise；

2 [t of mode₁<t<t₂]：Switching tube S₁Shutdown, switching tube S₂It is open-minded, input voltage V_inLess than DC bus-bar voltage V_Cbus, it is preceding Grade decompression Cuk circuits do not work, dc-link capacitance C_busEnergy is provided to rear class LLC；At this point, resonance current and exciting current It is equal, secondary side diode D at this time_s1Zero-current switching；Transformer primary side winding is no longer clamped by output voltage, magnetizing inductance L_m、 Resonant inductance L_r, resonant capacitance C_rResonance is participated in, in this stage, resonant frequency isDue to magnetizing inductance Very big, so harmonic period is very big, resonance current is consistent in this stage with exciting current, is approximately steady state value；

3 [t of mode₂<t<t₃]：Switching tube S₁、S₂Shutdown, into dead time；This stage, resonant frequency are Resonance current is more than exciting current, secondary side diode D_s2Conducting；A resonance current part gives switching tube S₂Junction capacity charging；It is humorous An electric current part of shaking gives switching tube S₁Junction capacity electric discharge, until switching tube S₁Junction capacity both end voltage be zero；Later, resonance Electric current all flows through switching tube S₁Body diode, be switching tube S₁No-voltage open and prepare；

4 [t of mode₃<t<t₄]：Switching tube S₁No-voltage is connected, switching tube S₂Shutdown, input voltage V_inLess than DC bus-bar voltage V_Cbus, at this time rectifier bridge be off, prime decompression Cuk circuits do not work, in this stage, resonant frequency isResonance current is more than exciting current, secondary side diode D_s2Conducting；Transformer primary side winding both end voltage is by pincers Position is in-nV_o, exciting current is with slope nV_o/L_mLinear rise；

5 [t of mode₄<t<t₅]：Switching tube S₁Still it is connected；At this point, resonance current is equal with exciting current, secondary side diode at this time D_s2Zero-current switching；Transformer primary side winding is no longer clamped by output voltage, magnetizing inductance L_m, resonant inductance L_r, resonant capacitance C_r Resonance is participated in, in this stage, resonant frequency isSince magnetizing inductance is very big, so harmonic period is very Greatly, resonance current is consistent in this stage with exciting current, is approximately steady state value；

6 [t of mode₅<t<t₆]：Switching tube S₁Cut-off, in this stage, resonant frequency isResonance current is more than excitation Electric current, secondary side diode D_s1Conducting；Switching tube S₁Junction capacity both end voltage be equal to DC bus-bar voltage, diode D₇Conducting, For switching tube S₂Zero current turning-on is prepared；

(2) as input voltage V_inMore than DC bus-bar voltage V_CbusDuring situation：

Mode 1a [t₀<t<t₁]：Switching tube S₁Shutdown, switching tube S₂Zero current turning-on, input voltage V_inMore than DC bus-bar voltage V_Cbus, prime decompression Cuk circuit work, Cuk inductive currents i_L1、i_L2With slope (V_in-V_cbus)/L₁Linear rise, and it is depressured Cuk Grade electric current i_cukMore than LLC grades electric current i_r, an input energy part is transmitted to rear class LLC by Cuk grades of decompression, a part of to busbar electricity Hold C_busIt charges；Meanwhile LLC resonant frequencies areResonance current is more than exciting current, secondary side diode D_s1Conducting；Transformer primary side winding both end voltage is clamped at nV_o, exciting current is with slope nV_o/L_mLinear rise；

Mode 1b [t₀<t<t₁]：Switching tube S₁Shutdown, switching tube S₂It is open-minded, input voltage V_inMore than DC bus-bar voltage V_Cbus, it is preceding Grade decompression Cuk circuit work, Cuk inductive currents i_L1、i_L2With slope (V_in-V_cbus)/L₁Linear rise, and it is depressured Cuk grades of electric currents i_cukLess than LLC grades electric current i_r, bus capacitor C_busIn discharge condition；Meanwhile LLC resonant frequencies areResonance Electric current is more than exciting current, secondary side diode D_s1Conducting；Transformer primary side winding both end voltage is clamped at nV_o, exciting current With slope nV_o/L_mLinear rise；

2 [t of mode₁<t<t₂]：Switching tube S₁Shutdown, switching tube S₂It is open-minded, input voltage V_inMore than DC bus-bar voltage V_Cbus, it is preceding Grade decompression Cuk circuit work, Cuk inductive currents i_L1、i_L2With slope (V_in-V_cbus)/L₁Continue linear rise；At this point, resonance is electric Stream is equal with exciting current, at this time secondary side diode D_s1Zero-current switching；Transformer primary side winding is no longer clamped by output voltage, Magnetizing inductance L_m, resonant inductance L_r, resonant capacitance C_rResonance is participated in, in this stage, resonant frequency isBy Very big in magnetizing inductance, so harmonic period is very big, resonance current is consistent in this stage with exciting current, is approximately constant Value；

3 [t of mode₂<t<t₃]：Switching tube S₁、S₂Shutdown, into dead time；Cuk inductive currents i_L1、i_L2Afterflow；It is this stage, humorous Vibration frequency isResonance current is more than exciting current, secondary side diode D_s2Conducting；A resonance current part is opened Close pipe S₂Junction capacity charging；A resonance current part gives switching tube S₁Junction capacity electric discharge, until switching tube S₁Junction capacity two Terminal voltage is zero；Later, resonance current all flows through switching tube S₁Body diode, be switching tube S₁No-voltage open and do standard It is standby；

4 [t of mode₃<t<t₄]：Switching tube S₁No-voltage is open-minded, switching tube S₂Shutdown；Cuk inductive currents i_L1、i_L2Continue afterflow； This stage, resonant inductance L_r, resonant capacitance C_rWith resonant frequencyResonance, resonance current is more than exciting current, secondary Side diode D_s2Conducting；Transformer primary side winding both end voltage is clamped at-nV_o, exciting current is with slope nV_o/L_mOn linear It rises；

5 [t of mode₄<t<t₅]：Switching tube S₁Still it is connected；Cuk inductive currents i_L1、i_L2Afterflow terminates；In this stage, resonant inductance L_r, resonant capacitance C_rWith resonant frequencyResonance, resonance current are more than exciting current, secondary side diode D_s2Conducting； Transformer primary side winding both end voltage is clamped at-nV_o, exciting current is with slope nV_o/L_mLinear rise；

6 [t of mode₅<t<t₆]：Switching tube S₁Still it is connected；At this point, resonance current is equal with exciting current, secondary side diode at this time D_s2Zero-current switching；Transformer primary side winding is no longer clamped by output voltage, magnetizing inductance L_m, resonant inductance L_r, resonant capacitance C_r Resonance is participated in, in this stage, resonant frequency isSince magnetizing inductance is very big, so harmonic period is very Greatly, resonance current is consistent in this stage with exciting current, is approximately steady state value；

7 [t of mode₆<t<t₇]：Switching tube S₁Cut-off, in this stage, resonant frequency isResonance current is more than excitation Electric current, secondary side diode D_s1Conducting；Switching tube S₁Junction capacity both end voltage be equal to DC bus-bar voltage, diode D₇Conducting, For switching tube S₂Zero current turning-on is prepared.