CN102355130A - Double-tube Buck-Boost type PFC (Power Factor Correction) converter based on one-cycle control - Google Patents

Abstract

The invention discloses a double-tube Buck-Boost type PFC (Power Factor Correction) converter based on one-cycle control, a bridge rectification circuit is then connected with a BOCBB type double-tube Buck-Boost converter; one path of output signal of a PI (proportion integral) adjuster is sent to a noninverting input end of a comparator, the other path of output signal is superposed with a sampling signal of input current and then is sent to a resettable integrator, an output end of the resettable integrator is connected with an inverting input end of the comparator, an output end of the comparator is connected with an RS (remote sensing) trigger, one end of the RS trigger is connected with a reset switch of the resettable integrator, and a Q-end output signal of the RS trigger simultaneously drives two switching tubes of the BOCBB type double-tube Buck-Boost converter after passing by a driving circuit. The converter disclosed by the invention not only can realize output voltage raising and reducing control, but also can improve a network side power factor, reduces the distortion factor of network entry current, has the advantages of simple structure, high system efficiency and the like and is convenient to control.

Description

Two-tube Buck-Boost type pfc converter based on monocycle control

Technical field

The present invention relates to a kind of pfc converter, be specifically related to a kind of two-tube Buck-Boost type pfc converter based on monocycle control.

Background technology

Equipments application is increasingly extensive in recent years.These equipment overwhelming majority will adopt direct current supply, so rectifying device becomes requisite part in the power electronic product.The simplest rectifying device is to be realized by diode rectifier bridge and very big filter capacitor, and its output is nonadjustable direct voltage.Because the rectifier diode angle of flow is very little, so electrical network only provides energy to load in the sub-fraction of each power frequency period the time, and its input current waveform comprises abundant high order harmonic.

Current harmonics brings a series of harm for system itself and electromagnetic environment on every side, and particularly to the harm of electric power system, communication system, instrument and meter, these harm mainly show the following aspects:

(1) harmonic components can influence the power supply quality of electric power system;

(2) harmonic components has increased the loss in transmission of electricity, distribution and the using electricity system;

(3) harmonic components influences the safety of electric power system;

(4) harmonic components can cause the misoperation of some important controls, protection and measurement mechanism;

(5) high order harmonic component interfere with communications system.

The main path that solves the power consumption equipment harmonic pollution has two kinds: the one, adopt passive filtering or active power filtering, and the 2nd, power electronic equipment is carried out reactive power compensation or or power factor correction.Power factor correction can also be divided into PPFC (Passive Power Factor Correction) (PPFC) and Active Power Factor Correction (APFC) two class methods.Passive PFC is simple in structure, cost is low, reliability is high, EMI (Electro-Magnetic Interference) is little, filter effect is also more remarkable etc.; Thereby be widely used; But also exist size, weight big; Be difficult to obtain High Power Factor (generally can bring up to about 0.9); Service behaviour is relevant with frequency, load variations and input voltage variation, and big shortcomings such as charging and discharging currents are arranged between inductance and electric capacity.Active type PFC adds a DC/DC switch converters between rectifier and load; The applied current feedback technique; The input current waveform is followed the tracks of exchanged input sinusoidal voltage waveform; Can make input current waveform be approximately sinusoidal, thereby make input THD less than 5%, power factor can be brought up to more than 0.99; And can under the input voltage range of broad and broadband, work; Volume, weight are little, and it is constant that output voltage can keep, and therefore are with a wide range of applications.

The basic circuit of pfc converter is made up of main circuit and control circuit two parts.The main circuit of common pfc converter has converters such as Buck, Boost, Buck-Boost, Cuk, flyback.Wherein, the Boost converter is the most extensive in practical application, because it has following special advantages: have the input filter inductance, so input current can be in continuous state, ripple is less, has reduced the requirement to filter circuit; The source electrode of power switch pipe (or emitter-base bandgap grading of bipolar transistor) current potential is always zero (being in earth potential), and therefore the driving to power tube is easy to realize; Output voltage and input voltage same polarity are convenient to control.Yet; The Boost converter can only be realized boosting (when 220V exchanged input, output DC was pressed in more than the 380V), often need be at back level cascaded buck converter in practical application; To mate the utilization voltage (generally lower) of back level equipment, make overall system efficiency decrease.

In addition, Chang Yong pfc converter control strategy mainly contains peak current control, Average Current Control, hysteresis current control etc.These control modes can both obtain excellent control effect, and just its control circuit all needs multiplier, have increased the complexity of control.

Summary of the invention

In order to overcome the problems referred to above, the invention provides a kind of two-tube Buck-Boost type pfc converter based on monocycle control (One-cycle Control).This pfc converter can be realized the control of output voltage buck, and low current distortion and High Power Factor, and does not adopt multiplier, makes the complexity of The whole control circuit reduce.

Technical solution of the present invention is:

Control based on single-cycle dual-tube Buck-Boost-type PFC converter, wherein: the bridge rectifier circuit connected with the high-frequency input capacitance, high-frequency input capacitance and BOCBB type? Double-barreled Buck-Boost Converter (Boost Level United Buck) connection, BOCBB double tube Buck-Boost converter output voltage followed by a sampling circuit, the output voltage sampling circuit is connected to the PI controller, PI regulator is connected to a reference voltage signal, PI regulator's output is divided into two , along with the comparator's inverting input terminal, another way to connect with the subtractor subtractor for BOCBB double tube Buck-Boost converter input current sampling signal and the output signal of the PI regulator can be reset after the operation input to the integrator, resettable integrator output and the inverting input terminal of the comparator output terminal connected to the RS flip-flop, RS flip-flop?

terminal and resettable integrator reset switch connection, RS flip-flop Q terminal and control BOCBB double tube Buck-Boost converter operating in the two switch drive circuit connections.

Said output voltage sampling circuit can have a lot of ways of realization.For example, the pressure sampling circuit that adopts two series resistances to form, the sampling point in the pressure sampling circuit between two series resistances is connected with pi regulator; Or be the pressure sampling circuit that two series resistances are formed, the sampling point in the pressure sampling circuit between two series resistances is connected with pi regulator; Or be two-tube Buck-Boost type pfc converter input circuit crosstalk resistance sampling or input circuit series direct current current Hall sensor sample.

The present invention is with the main circuit of the two-tube Buck-Boost converter of BOCBB type as pfc converter; And adopted nonlinear Control technology---the monocycle control technology of the novelty that Keyue M.Smedley proposes; Realized the correction of control of output voltage buck and input current waveform through single-stage converter; And cancelled the multiplier in traditional control method; Both reduce current distortion and improved power factor; Reduce the complexity of main circuit and control circuit again, improved system effectiveness.

Description of drawings

Fig. 1 is the electrical block diagram of one embodiment of the invention.

Fig. 2 is the circuit diagram of the two-tube Buck-Boost converter of BOCBB type.

Fig. 3 is the two-tube Buck-Boost converter of BOCBB type S ₁And S ₂While conducting state sketch map.

Fig. 4 is the two-tube Buck-Boost converter of BOCBB type S ₁And S ₂While off state sketch map.

Fig. 5 is a trailing edge modulation course of work theory analysis oscillogram.

Fig. 6 controls two-tube Buck-Boost type pfc converter artificial circuit figure the monocycle.

Fig. 7 is full load input voltage and input current simulation waveform.

Fig. 8 is input voltage, output voltage and the input inductance current simulations waveform of input voltage when uprushing.

The simulation waveform of input voltage, input inductance electric current and output voltage when Fig. 9 is load changing.

The simulation waveform of input voltage, output voltage and input inductance electric current when Figure 10 is underloading.

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is described further.

The two-tube Buck-Boost type pfc converter that is a kind of based on monocycle control shown in Figure 1.Among the figure, bridge rectifier and parallelly connected high frequency input capacitance C between two-tube Buck-Boost code converter is connected _InBe connected to the output voltage sample circuit behind the two-tube Buck-Boost type pfc converter; The output voltage sample circuit is connected with pi regulator; Pi regulator is connected to reference voltage signal; The output of pi regulator is divided into two-way; One the tunnel is connected with the in-phase input end of comparator; Another road is connected with subtracter; Subtracter is input to resetting integrator after to the input current sampled signal of two-tube Buck-Boost code converter and pi regulator output signal operation; Resetting integrator is connected with the inverting input of comparator; Comparator is connected with rest-set flip-flop, rest-set flip-flop

End is connected with the reset switch S of resetting integrator, and the Q of rest-set flip-flop end is connected with two switching tube S1, the drive circuit that S2 moves in controlling two-tube Buck-Boost code converter.

Said output voltage sampling circuit is the pressure sampling circuit that two series resistance R1, R2 form, and the sampling point in the pressure sampling circuit between two series resistances is connected with pi regulator.The input current of two-tube Buck-Boost code converter passes through resistance R _sSample.

Also have among Fig. 1: the electric capacity in inductance L 1, L2, capacitor C 1, C2, diode D1, D2, resistance R s, clock (CLK) the monocycle control circuit, resistance etc.

1, analysis of main circuit (as shown in Figure 2)

In order to simplify analysis, the special hypothesis as follows of doing:

1. S ₁And S ₂Open simultaneously or turn-off;

2. conduction voltage drop and the switching loss of ignoring device, not Considering Energy loss;

(1) S ₁And S ₂Conducting (as shown in Figure 3) simultaneously

Work as S ₁And S ₂During conducting simultaneously, D ₁And D ₂Not conducting, power supply V _gTo L ₁Charging, capacitor C ₁To L ₂Charging.At this moment, the pressure drop of bearing of each device two ends is following:

v _L1＝v _g；v _L2＝v _C1-V _o；

v _D1＝v _C1；v _D2＝v _C1。

(2) S ₁And S ₂Turn-off (as shown in Figure 4) simultaneously

Work as S ₁And S ₂When turn-offing simultaneously, D ₁And D ₂All conductings, L ₁, L ₂Release energy.At this moment, the pressure drop of bearing of each device two ends is following:

v _L1＝v _g-v _C1； $v_{L_2}=-V_o$ ；

v _S1＝v _C1；v _S2＝v _C1。

For inductance L ₁, L ₂, by " weber balance ":

v _gdT _s+(v _g-v _C1)(1-d)T _s＝0 (1)

(v _g-V _o)dT _s+(-V _o)(1-d)T _s＝0 (2)

Obtain output voltage V by formula (1) and (2) _oWith input voltage v _gBetween relation be:

$V_o=\frac{d}{1-d}{v}_g---\left(3\right)$

2, main circuit parameter design

Design objective is following:

Input voltage V _{In (RSM)}Be 90～270V;

Rated output voltage V _o=56V;

Peak power output P _o=150W;

Power factor PF >=0.99;

Efficiency eta＞0.9;

Switching frequency f _s=50kHz.

(1) inductance value design:

Inductance plays the effects such as transmission, storage and filtering of energy in the line, and has determined the high frequency ripple electric current total amount of input, therefore confirms inductance value according to the minimum principle of restriction current pulsation.Consider the poorest situation: power output is maximum, and input voltage is minimum.At this moment, input current is maximum, and ripple is also maximum, and in order to guarantee that the ripple of input current still meets the demands in this case, the design of inductance should be calculated at the minimum point of input voltage.

The peak value of input voltage:

$V_{\mathrm{in}\left(\mathrm{PK}\right)}=\sqrt{2}\×V_{\mathrm{in}\left(\mathrm{RSM}\right)}=\sqrt{2}\×90=127.279V---\left(4\right)$

The duty ratio of this moment is:

$d=\frac{V_o}{V_{\mathrm{in}\left(\mathrm{pk}\right)}+V_o}=\frac{56}{127.279+56}=0.3055---\left(5\right)$

The effective value of input current is:

$I_{\mathrm{in}\left(\mathrm{RMS}\right)}=\frac{P_o}{{\mathrm{\ηV}}_{\mathrm{in}\left(\mathrm{RMS}\right)}\mathrm{PF}}=\frac{150}{0.9\×90\×0.99}=1.871A---\left(6\right)$

The peak value of input current is:

$I_{\mathrm{in}\left(\mathrm{PK}\right)}=\sqrt{2}{I}_{\mathrm{in}\left(\mathrm{RMS}\right)}=\sqrt{2}\×1.871=2.645A---\left(7\right)$

The ripple peak-to-peak value is: the peak-to-peak value of ripple current is generally 20% of peak-peak input current in the inductance

That is:

ΔI _L＝0.2×I _in(PK)＝0.2×2.645＝0.529A (8)

Inductance value:

$L_1=\frac{{\mathrm{dT}}_s\×V_{\mathrm{in}\left(\mathrm{PK}\right)}}{\mathrm{\Δ}{I}_L}=\frac{0.3055\×20\×{10}^{-6}\×127.279}{0.529}=1.47\×{10}^{-3}H---\left(9\right)$

Get L ₁=1.5mH.

(2) the high frequency input capacitance chooses

The high frequency capacitance of input mainly be used for filtering input high frequency noise with improve the input ripple, the CALCULATION OF CAPACITANCE formula is following:

$C_{\mathrm{in}}=K_{{\mathrm{\ΔI}}_L}\frac{I_{\mathrm{in}\left(\mathrm{RMS}\right)}}{2\mathrm{\π}\×f_s\×r\×V_{\mathrm{in}\left(\mathrm{RMS}\right)}}=0.2\frac{1.871}{2\mathrm{\π}\×50\×{10}^3\×0.03\×90}=441.15\×{10}^{-9}F---\left(10\right)$

In the formula, Be the current ripples coefficient, generally get 10%-30%, (in this design, getting 20%), r is maximum high frequency voltage ripple coefficient (Δ V _In/ V _In), generally get 3%-9%, get 3% here.

Choose C _In=470nF.

(3) output capacitance Determination of Parameters

The factor that will consider when selecting output capacitance mainly contains: switching frequency ripple current, second harmonic ripple current, VD, output voltage ripple, hold time.The total current that flows through output capacitor is the effective value of switching frequency ripple current and the second harmonic of line current: select long-life, low resistance, the ability of leaking than large ripple current usually; The electrochemical capacitor of working range broad; And withstand voltage selection should leave sufficient surplus, to avoid overwork.

In the experience design, output capacitance C ₂Representative value be taken as every watt 1 μ F to 2 μ F.The maximum power of this converter is 150W, so get: C ₂=470 μ F.

3, control circuit operation principle

In order to carry out Analysis of Steady-State Performance, simplify derivation, the special work supposed as follows:

1. the ripple of inductive current can be ignored, and circuit operates in the CCM pattern;

2. switching frequency is much larger than the supply voltage frequency, and input voltage, electric current can be similar in the switch periods of several successive thinks constant, and circuit operates in quasi-stable state;

3. ignore the conduction voltage drop and the switching loss of switching device in the derivation, ignore effects of distribution parameters, not Considering Energy loss.

In the following theoretical derivation and analysis process, if no special instructions, such as the capital letter "V" represents the steady state volume, lowercase letters, such as "v" represents the time variable, add a dash as the letter "? " represents the average amount.

The controlled target of Single-phase PFC rectifier is: control suitable variable, making input current and input voltage all is that current waveform in full-wave rectifier and phase place are identical, and input impedance is a pure resistance, is expressed as with mathematical expression:

${\stackrel{\‾}{i}}_g=\frac{v_g}{R_e}---\left(11\right)$

In the formula, R _eThe equivalent input impedance of-Single-phase PFC rectifier, v _gThe input voltage of-Single-phase PFC rectifier.

During lower state, the output voltage V of Single-phase PFC rectifier _oWith input voltage v _gRelation be:

$v_g=\frac{V_o}{M\left(d\right)}---\left(12\right)$

The voltage transitions rate of M in the formula (d)---DC/DC converter (being the relational expression of duty ratio d).

To have in formula (12) the substitution formula (11):

${\stackrel{\‾}{i}}_g=\frac{V_o}{R_{e}M\left(d\right)}---\left(13\right)$

With formula (13) both sides with multiplication by constants R _S, R _SThe expression equivalent current detects resistance, can obtain:

$R_s{\stackrel{\‾}{i}}_g=\frac{V_o}{R_{e}M\left(d\right)}{R}_s---\left(14\right)$

If order:

$v_m=\frac{V_o{R}_s}{R_e}---\left(15\right)$

Then formula (14) can abbreviation be:

$R_s{\stackrel{\‾}{i}}_g=\frac{v_m}{M\left(d\right)}---\left(16\right)$

In the formula, v _mBe the input signal of integrator, be called modulation voltage.

Formula (15) is written as again:

$R_e=R_s\frac{V_o}{v_m}---\left(17\right)$

During stable state, output voltage V _oRemain unchanged, through changing modulation voltage v _mCan change equivalent resistance R _eThereby, realize control to input power.According to above-mentioned relation, modulation voltage v _mExport from pi regulator.When load and input voltage are constant, modulation voltage v _mConstant, the modulator output duty cycle is pressed the rule variation that governing equation (16) is confirmed.

For the two-tube Buck-Boost converter of BOCBB type, have

$M\left(d\right)=\frac{d}{1-d}---\left(18\right)$

After the substitution formula (16), put in order:

$v_m=d(R_s\stackrel{\‾}{i_g}+v_m)---\left(19\right)$

According to above governing equation, the two-tube Buck-Boost type pfc converter of design monocycle control, as shown in Figure 1.The output voltage sampled value and the reference voltage of two-tube Buck-Boost type pfc converter compare, and through pi regulator output, are modulation voltage v _mv _mAgain with the input current sampled signal of two-tube Buck-Boost code converter

Superpose, be input to resetting integrator.Resettable integrator output is the formula (19) equal to the right?

and?

are input to the comparator inverting input terminal and the inverting input, the comparator output terminal connected to the RS flip-flop, RS flip-flop?

terminal resettable integrator with reset switch S is connected, RS flip-flop Q terminal and control double-tube Buck-Boost Converter by the two switches S1, S2 action driving circuit connections.

Fig. 5 has provided trailing edge modulation course of work theory analysis waveform.Suppose that output voltage is stable, then v _mConstant.When one-period begins, Q=1, , switching tube is open-minded, and integrator is started working,

Beginning is linear rises, and inductive current is linear to rise; When v->=v+, the comparator output low level makes the rest-set flip-flop zero clearing,

Switching tube turn-offs, and integrator resets simultaneously, at this moment, and v _-＜v ₊, the rest-set flip-flop clear terminal is put height, and output Q=0 begins to repeat the work of last one-period up to the rising edge arrival of next clock pulse.

4, Circuit Design

(1) integrating circuit design

The integration reset circuit adopts reverse integral circuit and analog switch to realize; Integrator carries out integration to input signal when switch breaks off; Switch closure when the reset switch control end is received reset signal; Electric capacity is by the switch short circuit; Amplifier end of oppisite phase and in-phase end are empty short; Capacitor C is equivalent to short circuit ground connection, and integrator resets.

The integrator circuit parameter mainly is exactly the selection of resistance R and capacitor C among timeconstant=RC.According to the analysis of front, select the time constant of integrator to equal switch periods, then have:

τ＝RC＝T _s＝20us

(20)

According to above equality, can select resistance, capacitance parameter following:

R＝20KΩ，C＝1nF

Actual conditions when considering circuit working, R or C also need adjust slightly.But RC value and T _sBe more or less the same.

(2) current sense resistor design

If circuit gets into stable state, then

$I_g=\frac{P_o}{\mathrm{\η}{V}_g}=\frac{150}{0.9\×90}=1.852A---\left(21\right)$

$R_e=\frac{V_g}{I_g}=\frac{90}{1.852}=48.6\mathrm{\Ω}---\left(22\right)$

The input of integrator need be satisfied

$R_s{I}_g+V_m=R_s(I_g+\frac{V_o}{R_e})\≤12V---\left(23\right)$

R then _s≤4 Ω get R _s=2 Ω.

5, simulating, verifying

Two-tube Buck-Boost type pfc converter to based on monocycle control carries out emulation with Saber, and artificial circuit as shown in Figure 6.The circuit simulation parameter is following: input voltage: 220V; Output voltage: 56V; Switching frequency: 50kHz; Output capacitance: 470uF; Input inductance: 2mH; Load resistance: 20 Ω.

(1) specified input voltage and fully loaded

Specified input voltage and full load pfc converter input voltage and input inductance current waveform are as shown in Figure 7.The waveform of inductive current is sinusoidal wave, and keeps same-phase to change with input voltage waveform, has reached the purpose that input current is followed the tracks of input voltage.Therefore, can effectively reduce the high order harmonic component of input inductance electric current, improve system's net side power factor greatly based on the two-tube Buck-Boost type pfc converter of monocycle control.

(2) input voltage mutation and fully loaded

The waveform of input voltage, output voltage and the input inductance electric current of input voltage increase 20% suddenly and full load pfc converter as shown in Figure 8.As can be seen from the figure, after input voltage increased suddenly, input current reduced suddenly, and output voltage increases suddenly, but had crossed 8 cycles, and output voltage returns to initial value again.It is thus clear that the monocycle control technology can suppress the input voltage disturbance fast, obtains comparatively stable output voltage.

(3) specified input voltage and load changing

The waveform of input voltage, input inductance electric current and the output voltage of pfc converter as shown in Figure 9 when load suddenlyd change to 40 Ω by 20 Ω.Can find out that after load resistance increased suddenly, input current reduced suddenly, and output voltage increases suddenly, behind 10 cycles, output voltage returns to initial value.It is thus clear that the monocycle control technology also can effectively suppress load disturbance.Therefore, monocycle control has that dynamic response is fast, the advantage of strong robustness.

(4) specified input voltage and underloading

The input voltage of pfc converter, output voltage and input inductance current waveform when Figure 10 is 50% load.Can find out that the waveform of inductive current still keeps same-phase to change with input voltage waveform basically, and inductive current sine degree is very high.Therefore this converter can all be realized power factor correction in whole loading range.

Can know that by above each The simulation experiment result the two-tube Buck-Boost type pfc converter of monocycle control can be realized output buck and realize power factor correction effectively, and input voltage disturbance, load disturbance are all had the good restraining effect.

Claims (3)

1. two-tube Buck-Boost type pfc converter based on monocycle control; It is characterized in that: bridge rectifier is connected with the high frequency input capacitance; The high frequency input capacitance is connected with the two-tube Buck-Boost converter of BOCBB type; Be connected to the output voltage sample circuit behind the two-tube Buck-Boost converter of BOCBB type; The output voltage sample circuit is connected with pi regulator; Pi regulator is connected to reference voltage signal; The output of pi regulator is divided into two-way; One the tunnel is connected with the in-phase input end of comparator; Another road is connected with subtracter; Subtracter is input to resetting integrator after to the input current sampled signal of the two-tube Buck-Boost converter of BOCBB type and pi regulator output signal operation; The resetting integrator output is connected with the inverting input of comparator; Comparator output terminal is connected with rest-set flip-flop; The end of rest-set flip-flop is connected with the reset switch of resetting integrator, and the Q end of rest-set flip-flop is connected with the drive circuit that two switching tubes in controlling the two-tube Buck-Boost converter of BOCBB type move.

2. the two-tube Buck-Boost type pfc converter based on monocycle control according to claim 1; It is characterized in that: said output voltage sampling circuit is the pressure sampling circuit that two series resistances are formed, and the sampling point in the pressure sampling circuit between two series resistances is connected with pi regulator.

3. the two-tube Buck-Boost type pfc converter based on monocycle control according to claim 1 is characterized in that: said current sampling circuit is two-tube Buck-Boost type pfc converter input circuit crosstalk resistance sampling or input circuit series direct current current Hall sensor sample.

Images