Summary of the invention
The objective of the invention is to overcome the prior art above shortcomings, a kind of low voltage stress single-stage AC-DC converter based on the LLC series resonance be provided, its by the buck conversion stage and based on the DC-DC conversion stage of LLC series resonance in conjunction with and get.The present invention is achieved through the following technical solutions:
Based on the low voltage stress single-stage AC-DC converter of LLC series resonance, it comprises input filter circuit E, rectifier bridge Q, inductance L, first capacitor C, second capacitor C
r, the 3rd capacitor C
O, the first switching tube S
1, second switch pipe S
2, the first diode D
O1, the second diode D
O2With the 3rd diode D; Input filter circuit E and rectifier bridge Q constitute the input rectifying filter circuit; Inductance L, the first switching tube S
1, the 3rd diode D and first capacitor C constitute step-up/step-down circuit; The first diode D
O1, the second diode D
O2With the 3rd capacitor C
OConstitute output rectifier and filter; One end of inductance L is connected with the common cathode of the negative electrode of the 3rd diode D, rectifier bridge Q; One end of the other end of inductance L and capacitor C, the first switching tube S
1Drain electrode connect; The other end of first capacitor C is connected with the anode of the 3rd diode D, again with second switch pipe S
2Source electrode connect; The first switching tube S
1Source electrode be connected with the common anode of rectifier bridge Q, and then with second switch pipe S
2Drain electrode connect.
Above-mentioned low voltage stress single-stage AC-DC converter based on the LLC series resonance, the described first switching tube S
1With second switch pipe S
2All be integrated with body diode and body capacitance; Transformer T is integrated with leakage inductance L
rWith magnetizing inductance L
m
Above-mentioned low voltage stress single-stage AC-DC converter based on the LLC series resonance, the described first switching tube S
1, second switch pipe S
2, first capacitor C, second capacitor C
r, transformer T and leakage inductance L
rWith magnetizing inductance L
mConstitute LLC series-resonant inverting circuit; The shared first switching tube S of step-up/step-down circuit and LLC series-resonant inverting circuit
1
Above-mentioned low voltage stress single-stage AC-DC converter based on the LLC series resonance, the first switching tube S
1Drain electrode, an end of inductance L be connected with an end of first capacitor C; The first switching tube S
1Source electrode, second switch pipe S
2The drain electrode and second capacitor C
rAn end connect, and then be connected with the common anode of rectifier bridge Q; Second switch pipe S
2Source electrode, the other end and the leakage inductance L of first capacitor C
rAn end connect, and then be connected with the anode of the 3rd diode D; Second capacitor C
rThe other end be connected with the end of the same name of transformer T.
This circuit is by the control first switching tube S
1Thereby duty ratio make the discontinuous work of the electric current of inductance L realize the function that automatic power factor is proofreaied and correct, thereby the terminal voltage that realizes first capacitor C is simultaneously boosted or the voltage stress of step-down limit switch pipe at range of safety operation.This circuit is by the control first switching tube S
1With second switch pipe S
2Switching frequency regulate output voltage.This circuit adopts the LLC resonant technology to realize the soft switch of all power devices.The present invention realizes the input power factor correction, improves the adjustable range and the input ac voltage scope of application of output voltage, can reduce the voltage stress of switching tube, realizes the soft switch of all power devices, improves conversion efficiency.
Compared with prior art the present invention has following advantage and effect: the low voltage stress single-stage AC-DC converter based on the LLC series resonance of the present invention is realized the function that automatic power factor is proofreaied and correct with the electric current discontinuous conduction mode of inductance L.With inductance L, the first switching tube S
1, the 3rd diode D and first capacitor C constitute step-up/step-down circuit, when this circuit working during in decompression mode the terminal voltage of first capacitor C be lower than input voltage V
InAmplitude, thereby can reduce by first capacitor C, the first switching tube S
1With second switch pipe S
2Voltage stress.The first switching tube S
1With second switch pipe S
2, first capacitor C and second capacitor C
r, transformer T and the integrated leakage inductance L of T
rWith magnetizing inductance L
mConstitute LLC series-resonant inverting circuit, realize the soft switch of all switching tubes.Step-up/step-down circuit and LLC series-resonant inverting circuit common switch pipe S
1The present invention realizes the input power factor correction, and realizes boosting and buck functionality, has the wide output voltage adjustable range, uses less switching tubes, the efficient height, and cost is low, can be used as the LCD power supply.
Embodiment
Below in conjunction with accompanying drawing embodiments of the present invention are further described.
Low voltage stress single-stage AC-DC converter based on the LLC series resonance comprises:
Input filter circuit E, rectifier bridge Q, inductance L, capacitor C and CO, two switching tube S
1And S
2, diode D, D
O1And D
O2, D
1And C
1Be respectively switching tube S
1Integrated body diode and body capacitance, D
2And C
2Be respectively switching tube S
2Integrated body diode and body capacitance, L
rAnd L
mBe respectively integrated leakage inductance of transformer T and magnetizing inductance;
Input filter circuit E and rectifier bridge Q constitute the input rectifying filter circuit;
Inductance L, switching tube S
1, diode D and capacitor C constitute step-up/step-down circuit;
Switching tube S
1And S
2, capacitor C and C
r, transformer T and the integrated leakage inductance L of T
rWith magnetizing inductance L
mConstitute LLC series-resonant inverting circuit;
Diode D
O1, D
O2And capacitor C
OConstitute output rectifier and filter.
With reference to figure 3, input ac power is powered to the AB end by filter circuit E and rectifier bridge Q, and the AB terminal voltage is a half-sinusoid.Inductance L, switching tube S
1, diode D and capacitor C constitute step-up/step-down circuit.Switching tube S
1And S
2, capacitor C and C
r, transformer T and the integrated leakage inductance L of T
rWith magnetizing inductance L
mConstitute LLC series-resonant inverting circuit.Diode D
O1, D
O2And capacitor C
OConstitute output rectifier and filter.Step-up/step-down circuit and LLC series-resonant inverting circuit common switch pipe S
1One end of inductance L is connected (A end) with the common cathode of the negative electrode of diode D, rectifier bridge Q.One end of the other end of inductance L and capacitor C, switching tube S
1Drain electrode connect.The anode of the other end of capacitor C, diode D, switching tube S
2Source electrode and leakage inductance L
rAn end connect.Switching tube S
1Source electrode, S
2Drain electrode, capacitor C
rAn end be connected with the common anode (B end) of rectifier bridge Q.Capacitor C
rThe other end be connected with the end of the same name of transformer T.The secondary side winding N of transformer T
1Different name end and N
2End of the same name connects, and is connected with negative pole of output end then.N
1End of the same name and diode D
O1Anode connect.N
2Different name end and diode D
O2Anode connect.D
O1Negative electrode and D
O2Negative electrode connect, be connected with output head anode then.D
1And C
1Be respectively switching tube S
1Integrated body diode and body capacitance, D
2And C
2Be respectively switching tube S
2Integrated body diode and body capacitance, L
rAnd L
mBe respectively integrated leakage inductance of transformer T and magnetizing inductance.
Fig. 4 a~Fig. 4 i has provided circuit working process of the present invention, and Fig. 5 has provided the work wave of the present invention in a switch periods, and Fig. 6 provides the main waveform of the present invention under the power frequency pattern.
(1) the circuit working process in a switch periods, respectively corresponding following each stage of Fig. 4 a~Fig. 4 i:
Stage 1 (t
0~t
1): and t
0Moment switching tube S
1And S
2Turn-off inductance L
mCurrent i L
mWith resonance current i
LrEquate transformer primary side current i
pBe zero, output is exported rectifier diode D by transformer isolation
O1And D
O2Instead end output capacitance C partially
ODischarge and powering load.Resonance current i
LrTo S
2Body capacitance C
2Charging is S simultaneously
1Body capacitance C
1Discharge.Work as C
1When discharge finishes, S
1On body diode D
1Conducting, stage 1 operating state finishes.
Stages 2 (t
1~t
2): t
1Constantly, S
2Turn-off body diode D
1Conducting is S
1The ZVS conducting create conditions.This moment i
p=i
Lr-i
Lm, inductance L
mBack electromotive force V
LmRise gradually.t
2 'Moment V
Lm=nV
O, export rectifier diode D this moment
O1Conducting, transformer primary side voltage is clamped at nV
O, L
mIn this voltage lower linear charging, do not participate in resonance.As resonance current i
LrRise at 0 o'clock, stages 2 operating state finishes.
Stages 3 (t
2~t
3): S
1Added gate electrode drive signals 2 o'clock stages, at t
2Constantly, resonance current i
LrBy negative timing, the S of becoming
1Forward conduction, inductance L is at input voltage V
ABThe lower linear charging, output rectifier diode D
O1Conducting, transformer primary side voltage is clamped at nV
O, L
mIn this voltage lower linear charging, do not participate in resonance, energy is delivered to V by capacitor C
OWork as i
LmEqual resonance current i
LrThe time, the stage 3 finishes.
Stages 4 (t
3~t
4): t
3Constantly, i
LmEqual resonance current i
Lr, L
mParticipate in resonance, output rectifier diode D
O1Instead end output capacitance C partially
ODischarge and powering load.Inductance L continues at input voltage V
ABThe lower linear charging.
Stages 5 (t
4~t
5): t
4Constantly, S
1And S
2Turn-off output rectifier diode D
O1And D
O2Instead end output capacitance C partially
ODischarge and powering load, resonance current i
LrTo body capacitance C
1Charging is body capacitance C simultaneously
2Discharge.Inductance L is at voltage (V
AB-V
C1) charging down.Work as C
2When discharge finishes, S
2On body diode D
2Conducting, stages 5 operating state finishes.
Stages 6 (t
5~t
6): t
5Constantly, body diode D
2Conducting is S
2The ZVS conducting create conditions.Inductance L is at voltage V
CFollowing discharge is also charged to capacitor C.This moment i
p=i
Lr-i
Lm, inductance L
mBack electromotive force V
LmRise gradually.t
6 'Moment V
Lm=-nV
O, export rectifier diode D this moment
O2Conducting, transformer primary side voltage is clamped at-nV
O, L
mThe reverse linear charging does not participate in resonance under this voltage.As resonance current i
LrDrop at 0 o'clock, stages 6 operating state finishes.
Stages 7 (t
6~t
7): S
2Added gate electrode drive signals 6 o'clock stages, at t
6Constantly, resonance current i
LrWhen just becoming negative, S
2Forward conduction, output rectifier diode D
O2Conducting, transformer primary side voltage is clamped at-nV
O, L
mReverse linear charging under this voltage does not participate in resonance, the resonance current L that flows through
mWith the transformer primary side, deliver power to V
OInductance L is at voltage V
CFollowing continuation discharge is also given storage capacitor C
dCharging is as inductive current i
LWhen dropping to zero, D instead ends partially, and the stage 7 finishes.
Stages 8 (t
7~t
8): t
7Constantly, inductive current i
LWhen dropping to zero, D instead ends partially, and resonance current continues the L that flows through
mWith the transformer primary side, deliver power to V
OWork as i
LmEqual resonance current i
LrThe time, the stage 8 finishes.
Stages 9 (t
8~t
9): t
8Constantly, i
LmEqual resonance current i
Lr, L
mParticipate in resonance, output rectifier diode D
O2Instead end output capacitance C partially
ODischarge and powering load.
(2) operation principle of buck conversion stage
t
2~t
4The stage inductance is at input voltage V
ABThe lower linear charging, the increment of electric current is:
D wherein
ONBe switching tube S
1The conducting duty ratio, T is a switch periods.
t
4~t
5The stage inductance is at input voltage (V
AB-V
C1) the lower linear charging, the increment of electric current is:
t
5~t
6The stage inductance is at input voltage V
CThe lower linear discharge, the increment of electric current is:
D wherein
OFFIt is the duty ratio of inductance L discharge.
When circuit working in inductive current i
LDuring discontinuous mode, Δ i is arranged
L1+ Δ i
L2=| Δ i
L3|.Because t
4~t
5Time in stage is very short, this stage current i
LIncrement can ignore, can get thus
V
ABAmplitude equal power supply V
InAmplitude, therefore
Work as D as can be known by formula (5)
OND
OFFThe time, V
CV
InWork as D
ON<D
OFFThe time, V
C<V
InCan carry out initial adjustment to the terminal voltage of capacitor C by the control duty ratio, and reduce duty ratio D
ONEffectively the terminal voltage of control capacitance C is lower than the input voltage amplitude, thereby has reduced switching tube S
1And S
2Voltage stress.
(3) input power factor correction principle
Because inductive current i
LIntermittently, at MOSFET pipe S
1Each conducting phase i
LCurrent peak and this conducting phase input voltage V
CAB(V
CAB=| V
In|) mean value proportional, again because the average voltage of each conducting phase is a sinusoidal variations, so the peak value of input current also is a sinusoidal variations.And the inductive current pulse always starts from scratch, so their mean value also is sinusoidal variations, as shown in Figure 6.All alternating current pulses have been formed waveform and have been comprised 50 or first-harmonic and the switching frequency component of 60Hz frequency, through L
In, C
InFilter circuit E gets Sinusoidal Input Currents i
Lin