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 converter based on single-cycle control. The bridge rectifier circuit is connected with a BOCBB type double-tube Buck-Boost converter; the output signal of the PI regulator is sent to the comparator in phase. The input terminal, the other channel and the sampling signal of the input current are superimposed, and then sent to the resettable integrator, the output terminal of the resettable integrator is connected to the inverting input terminal of the comparator, the output terminal of the comparator is connected to the RS flip-flop, and the RS flip-flop The end of the RS flip-flop is connected to the reset switch of the resettable integrator, and the output signal of the Q end of the RS flip-flop drives the two switch tubes of the BOCBB dual-tube Buck-Boost converter at the same time after passing through the driving circuit. The invention can not only realize the step-down control of the output voltage, but also improve the power factor of the network side, reduce the distortion factor of the current entering the network, and has the characteristics of simple structure, convenient control and high system efficiency.

Description

Dual-tube Buck-Boost PFC Converter Based on Single-Cycle Control

technical field

The invention relates to a PFC converter, in particular to a double-tube Buck-Boost type PFC converter based on single-cycle control. the

Background technique

In recent years, power electronic devices have been widely used. Most of these devices are powered by DC, so the rectifier has become an indispensable part of power electronic products. The simplest rectification device is realized by a diode rectifier bridge and a large filter capacitor, and its output is a non-adjustable DC voltage. Since the conduction angle of the rectifier diode is very small, the power grid only provides energy to the load in a small part of each power frequency cycle, and its input current waveform contains rich high-order harmonics. the

Current harmonics bring a series of hazards to the system itself and the surrounding electromagnetic environment, especially to the power system, communication system, and instrumentation. These hazards are mainly manifested in the following aspects:

(1) Harmonic components will affect the power supply quality of the power supply system;

(2) Harmonic components increase losses in power transmission, power distribution and power consumption systems;

(3) Harmonic components affect the safety of the power supply system;

(4) Harmonic components can cause malfunctions of some important control, protection and measurement devices;

(5) High-order harmonics interfere with the communication system. the

There are two main ways to solve the harmonic pollution of electrical equipment: one is to use passive filtering or active filtering, and the other is to perform reactive power compensation or power factor correction on power electronic devices. Power factor correction can also be divided into two types: passive power factor correction (PPFC) and active power factor correction (APFC). Passive PFC has simple structure, low cost, high reliability, small EMI (Electro-Magnetic Interference), and significant filtering effect, so it is widely used, but it also has large size and weight, and it is difficult to obtain high power factor (generally It can be increased to about 0.9), the working performance is related to the frequency, load change and input voltage change, there are disadvantages such as large charge and discharge current between the inductor and the capacitor. Active PFC is to add a DC/DC switching converter between the rectifier and the load, and apply current feedback technology to make the input current waveform track the AC input sinusoidal voltage waveform, which can make the input current waveform approximately sinusoidal, so that the input terminal The THD is less than 5%, the power factor can be increased to more than 0.99, and it can work in a wide input voltage range and wide frequency band. The volume and weight are small, and the output voltage can be kept constant, so it has wide application prospects. the

The basic circuit of the PFC converter consists of two parts, the main circuit and the control circuit. Common main circuits of PFC converters include converters such as Buck, Boost, Buck-Boost, Cuk, and flyback. Among them, the Boost converter is the most widely used in practical applications, because it has the following unique advantages: it has an input filter inductance, so the input current can be in a continuous state, and the ripple is small, which reduces the requirements for the filter circuit; the power switch tube The potential of the source (or the emitter of the bipolar transistor) is always zero (at the ground potential), so it is easy to drive the power tube; the output voltage and the input voltage have the same polarity, which is easy to control. However, the Boost converter can only achieve step-up (when the AC input is 220V, the output DC voltage is above 380V). generally lower), which reduces the efficiency of the entire system. the

In addition, commonly used PFC converter control strategies mainly include peak current control, average current control, and hysteresis current control. These control methods can achieve very good control effects, but their control circuits all need multipliers, which increases the complexity of the control. the

Contents of the invention

In order to overcome the above problems, the present invention provides a dual-tube Buck-Boost PFC converter based on one-cycle control. The PFC converter can realize output voltage step-down control, has low current distortion and high power factor, and does not use a multiplier, so that the complexity of the entire control circuit is reduced. the

Technical solution of the present invention is:

端与可复位积分器的复位开关连接，RS触发器的Q端与控制BOCBB型双管Buck-Boost变换器中的二个开关管动作的驱动电路连接。  A kind of double-tube Buck-Boost type PFC converter based on single-cycle control is characterized in that: a bridge rectifier circuit is connected with a high-frequency input capacitor, and the high-frequency input capacitor is connected with a BOCBB type double-tube Buck-Boost converter (Boost cascaded Buck) connection, the BOCBB type double-tube Buck-Boost converter is connected with an output voltage sampling circuit, the output voltage sampling circuit is connected with the PI regulator, the PI regulator is connected with a reference voltage signal, and the output terminal of the PI regulator is divided into two circuits, One path is connected to the non-inverting input terminal of the comparator, and the other path is connected to the subtractor. The subtractor inputs the input current sampling signal of the BOCBB type dual-tube Buck-Boost converter and the output signal of the PI regulator to the resettable integrator after calculation. The output terminal of the reset integrator is connected to the inverting input terminal of the comparator, the output terminal of the comparator is connected to the RS flip-flop, and the RS flip-flop

The terminal is connected to the reset switch of the resettable integrator, and the Q terminal of the RS flip-flop is connected to the drive circuit that controls the action of the two switching tubes in the BOCBB dual-tube Buck-Boost converter.

The output voltage sampling circuit may have many implementation forms. For example, a voltage-dividing sampling circuit composed of two series resistors is used, and the sampling point between the two series resistors in the voltage-dividing sampling circuit is connected to the PI regulator; or a voltage-dividing sampling circuit composed of two series resistors, the voltage-dividing sampling circuit The sampling point between the two series resistors in the circuit is connected to the PI regulator; or it is used for the sampling of the input circuit series resistance of the dual-tube Buck-Boost type PFC converter or the sampling of the input circuit series DC current Hall sensor. the

The present invention uses the BOCBB type double-tube Buck-Boost converter as the main circuit of the PFC converter, and adopts the novel nonlinear control technology proposed by Keyue M. Voltage-boost control and input current waveform correction, and cancel the multiplier in the traditional control method, which not only reduces the current distortion and improves the power factor, but also reduces the complexity of the main circuit and control circuit, and improves the system efficiency . the

Description of drawings

FIG. 1 is a schematic diagram of a circuit structure of an embodiment of the present invention. the

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

Fig. 3 is a schematic diagram of the BOCBB dual-tube Buck-Boost converter S ₁ and S ₂ being turned on at the same time.

Fig. 4 is a schematic diagram of the BOCBB dual-tube Buck-Boost converter S ₁ and S ₂ being turned off at the same time.

Figure 5 is a theoretical analysis waveform diagram of the falling edge modulation working process. the

Figure 6 is a simulation circuit diagram of a single-cycle control dual-tube Buck-Boost PFC converter. the

Figure 7 is the input voltage and input current simulation waveforms at full load. the

Figure 8 is the simulation waveform of the input voltage, output voltage and input inductor current when the input voltage suddenly increases. the

Figure 9 is the simulation waveform of the input voltage, input inductor current and output voltage when the load changes suddenly. the

Figure 10 is the simulation waveform of input voltage, output voltage and input inductor current at light load. the

Detailed ways

The present invention will be further described below in conjunction with drawings and embodiments. the

端与可复位积分器的复位开关S连接，RS触发器的Q端与控制双管Buck-Boost型变换器中的二个开关管S1、S2动作的驱动电路连接。  Figure 1 shows a dual-tube Buck-Boost PFC converter based on single-cycle control. In the figure, the high-frequency input capacitor C _in is connected in parallel between the bridge rectifier circuit and the dual-tube Buck-Boost converter, and the output voltage sampling circuit is connected after the dual-tube Buck-Boost PFC converter, and the output voltage sampling circuit is connected to the PI The regulator is connected, the PI regulator is connected to the reference voltage signal, the output of the PI regulator is divided into two circuits, one is connected to the non-inverting input of the comparator, and the other is connected to the subtractor, and the subtractor converts the dual-tube Buck-Boost The input current sampling signal of the device and the output signal of the PI regulator are input to the resettable integrator after operation, the resettable integrator is connected to the inverting input terminal of the comparator, the comparator is connected to the RS flip-flop, and the RS flip-flop

The terminal is connected to the reset switch S of the resettable integrator, and the Q terminal of the RS flip-flop is connected to the driving circuit that controls the action of the two switching tubes S1 and S2 in the dual-tube Buck-Boost converter.

The output voltage sampling circuit is a voltage-dividing sampling circuit composed of two series resistors R1 and R2, and the sampling point between the two series resistors in the voltage-dividing sampling circuit is connected to the PI regulator. The input current of the dual-tube Buck-Boost converter is sampled through the resistor R _s .

Also in Fig. 1: inductance L1, L2, capacitance C1, C2, diode D1, D2, resistance Rs, the capacitance in the clock (CLK) single-cycle control circuit, resistance etc. the

1. Main circuit analysis (as shown in Figure 2)

In order to simplify the analysis, the following assumptions are specially made:

①S ₁ and S ₂ are turned on or off at the same time;

② Ignore the conduction voltage drop and switching loss of the device, and do not consider the energy loss;

(1) S ₁ and S ₂ are turned on at the same time (as shown in Figure 3)

When _S1 and _S2 are turned on at the same time, _D1 and _D2 are not turned on, the power supply V _g charges to _L1 , and the capacitor _C1 charges to _L2 . At this time, the voltage drop across each device is as follows:

v _L1 =v _g ; v _L2 =v _C1 -V _o ;

v _D1 =v _C1 ; v _D2 =v _C1 .

(2) S ₁ and S ₂ are turned off at the same time (as shown in Figure 4)

When S ₁ and S ₂ are turned off at the same time, both D ₁ and D ₂ are turned on, and L ₁ and L ₂ release energy. At this time, the voltage drop across each device is as follows:

v _L1 =v _g -v _C1 ; $v_{L_2}=-V_o$ ;

v _S1 =v _C1 ; v _S2 =v _C1 .

For inductance L ₁ and L ₂ , from "volt-second balance", we get:

v _g dT _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)

The relationship between the output voltage V _o and the input voltage v _g is obtained from formulas (1) and (2):

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

2. Main circuit parameter design

The design indicators are as follows:

The input voltage Vin _(RSM) is 90~270V;

Rated output voltage V _o =56V;

Maximum output power P _o = 150W;

Power factor PF≥0.99;

Efficiency η>0.9;

The switching frequency f _s =50 kHz.

(1) Inductance design:

The inductance plays the role of energy transmission, storage and filtering in the circuit, and determines the total amount of high-frequency ripple current at the input end. Therefore, the inductance value is determined according to the principle of minimizing the current ripple. Consider the worst case: maximum output power, minimum input voltage. At this time, the input current is the largest, and the ripple is also the largest. In order to ensure that the ripple of the input current still meets the requirements in this case, the design of the inductor should be calculated at the point of the lowest input voltage. the

The peak value of the input voltage:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; PK</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; RSM</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 90</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 127.279</span>}\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

The duty cycle at this time is:

$\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; pk</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 56</span>}}{\mathrm{<span\; class="notranslate">\; 127.279</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 56</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.3055</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

The effective value of the input current is:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; RMS</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; \&eta;V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; RMS</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; PF</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 150</span>}}{\mathrm{<span\; class="notranslate">\; 0.9</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 90</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 0.99</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1.871</span>}\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

The peak value of the input current is:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; PK</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; RMS</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 1.871</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2.645</span>}\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

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

Right now:

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

Inductance value:

${\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; dT</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; PK</span>}<span\; class="notranslate">\; )</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 0.3055</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 20</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 127.279</span>}}{\mathrm{<span\; class="notranslate">\; 0.529</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1.47</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

Take L ₁ =1.5mH.

(2) Selection of high frequency input capacitor

The high-frequency capacitor at the input end is mainly used to filter the input high-frequency noise and improve the input ripple. The calculation formula of the capacitor is as follows:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{{\mathrm{<span\; class="notranslate">\; \&Delta;I</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; RMS</span>}<span\; class="notranslate">\; )</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; RMS</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.2</span>}\frac{\mathrm{<span\; class="notranslate">\; 1.871</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 50</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 0.03</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 90</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 441.15</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 9</span>}}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

In the formula, is the current ripple coefficient, generally 10%-30%, (20% in this design), r is the maximum high-frequency voltage ripple coefficient (ΔV _in /V _in ), generally 3%-9%, Take 3% here.

Choose C _in =470nF.

(3) Determination of output capacitor parameters

The main factors to be considered when selecting the output capacitor are: switching frequency ripple current, second harmonic ripple current, DC output voltage, output voltage ripple, and hold time. The total current flowing through the output capacitor is the effective value of the switching frequency ripple current and the second harmonic of the line current: usually choose an electrolytic capacitor with long life, low leakage resistance, ability to withstand large ripple current, and wide operating range, and There should be sufficient margin in the choice of withstand voltage to avoid overloading. the

In an empirical design, the typical value of the output capacitor _C2 is taken as 1μF to 2μF per watt. The maximum power of the converter is 150W, so take: C ₂ =470μF.

3. Working principle of the control circuit

In order to analyze the steady-state characteristics and simplify the derivation process, the following assumptions are specially made:

①The ripple of the inductor current can be ignored, and the circuit runs in CCM mode;

②The switching frequency is much higher than the frequency of the power supply voltage, the input voltage and current can be considered to be approximately constant in several consecutive switching cycles, and the circuit operates in a quasi-steady state;

③ During the derivation process, the conduction voltage drop and switching loss of switching devices are ignored, the influence of distribution parameters is ignored, and energy loss is not considered. the

In the following theoretical derivation and analysis process, unless otherwise specified, a capital letter such as "V" represents a steady-state quantity, a small letter such as "v" represents a time variable, and a horizontal line is added to the letter such as " " represents the average amount.

The control goal of the single-phase PFC rectifier is: to control the appropriate variables, so that the input current and the input voltage are both full-wave rectified waveforms with the same phase, and the input impedance is a pure resistance, which is expressed mathematically as:

${\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

In the formula, _Re - the equivalent input impedance of the single-phase PFC rectifier, v _g - the input voltage of the single-phase PFC rectifier.

In the steady state, the relationship between the output voltage V _o of the single-phase PFC rectifier and the input voltage v _g is:

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

In the formula, M(d)—the voltage conversion rate of the DC/DC converter (that is, the relational expression of the duty cycle d). the

Substituting formula (12) into formula (11):

${\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 13</span>}<span\; class="notranslate">\; )</span>$

Multiply both sides of formula (13) by the constant R _S , where R _S represents the equivalent current detection resistor, we can get:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

If order:

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 15</span>}<span\; class="notranslate">\; )</span>$

Then formula (14) can be simplified as:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 16</span>}<span\; class="notranslate">\; )</span>$

In the formula, v _m is the input signal of the integrator, which is called the modulation voltage.

Rewrite formula (15) as:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 17</span>}<span\; class="notranslate">\; )</span>$

In the steady state, the output voltage V _o remains unchanged, and the equivalent resistance _Re can be changed by changing the modulation voltage v _m , so as to realize the control of the input power. According to the above relationship, the modulation voltage v _m is output from the PI regulator. When the load and input voltage are constant, the modulation voltage v _m is constant, and the modulator output duty cycle changes according to the law determined by the control equation (16).

For the BOCBB double-tube Buck-Boost converter, there are

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 18</span>}<span\; class="notranslate">\; )</span>$

After substituting into formula (16), we can get:

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 19</span>}<span\; class="notranslate">\; )</span>$

进行叠加，输入到可复位积分器。可复位积分器的输出即为式(19)等号的右边 

和 

分别输入到比较器的同相输入端和反相输入端，比较器输出端与RS触发器连接，RS触发器的 

端与可复位积分器的复位开关S连接，RS触发器的Q端与控制双管Buck-Boost型变换器中的二个开关管S1、S2动作的驱动电路连接。  According to the above control equations, a dual-tube Buck-Boost PFC converter with single-cycle control is designed, as shown in Figure 1. The sampled value of the output voltage of the dual-tube Buck-Boost PFC converter is compared with the reference voltage, and is output by the PI regulator, which is the modulation voltage v _m . v _m and the input current sampling signal of the dual-tube Buck-Boost converter

are superimposed and input to a resettable integrator. The output of the resettable integrator is the right side of the equation (19)

and

Input to the non-inverting input terminal and inverting input terminal of the comparator respectively, the output terminal of the comparator is connected to the RS flip-flop, and the RS flip-flop

The terminal is connected to the reset switch S of the resettable integrator, and the Q terminal of the RS flip-flop is connected to the driving circuit that controls the action of the two switching tubes S1 and S2 in the dual-tube Buck-Boost converter.

开始线性上升，电感电流线性上升；当v-≥v+时，比较器输出低电平使RS触发器清零， 

开关管关断，同时积分器复位，此时，v_-＜v₊，RS触发器清零端置高，输出Q＝0，直到下一个时钟脉冲的上升沿到来开始重复上一周期的工作。  Figure 5 shows the theoretical analysis waveform of the falling edge modulation working process. Assuming that the output voltage has been stabilized, v _m does not change. At the beginning of a cycle, Q=1, , the switch tube is turned on, the integrator starts to work,

It starts to rise linearly, and the inductor current rises linearly; when v-≥v+, the comparator outputs a low level to clear the RS flip-flop,

The switch tube is turned off, and the integrator is reset at the same time. At this time, v _- <v ₊ , the reset terminal of the RS flip-flop is set high, and the output Q=0, until the rising edge of the next clock pulse arrives to repeat the work of the previous cycle.

4. Control circuit design

(1) Integral circuit design

The integral reset circuit is realized by a reverse integral circuit and an analog switch. When the switch is turned off, the integrator integrates the input signal. When the reset switch control terminal receives the reset signal, the switch closes, the capacitor is short-circuited by the switch, and the inverting terminal of the op amp and the non-inverting terminal are virtual short, the capacitor C is equivalent to a short circuit to ground, and the integrator is reset. the

The integrator circuit parameter is mainly the selection of the resistor R and the capacitor C in the time constant τ=RC. According to the previous analysis, if the time constant of the integrator is selected to be equal to the switching period, then:

τ = RC = T _s = 20us

(20)

According to the above equation, the resistance and capacitance parameters can be selected as follows:

R＝20KΩ, C＝1nF

Considering the actual situation when the circuit works, R or C needs to be adjusted slightly. But the RC value is not much different from T _s .

(2) Current detection resistor design

If the circuit enters a steady state, then

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{\mathrm{<span\; class="notranslate">\; \&eta;</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 150</span>}}{\mathrm{<span\; class="notranslate">\; 0.9</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 90</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1.852</span>}\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; one</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 90</span>}}{\mathrm{<span\; class="notranslate">\; 1.852</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 48.6</span>}\mathrm{<span\; class="notranslate">\; \&Omega;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; two</span>}<span\; class="notranslate">\; )</span>$

The input of the integrator needs to satisfy

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; 12</span>}\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; three</span>}<span\; class="notranslate">\; )</span>$

Then R _s ≤ 4Ω, R _s = 2Ω.

5. Simulation verification

Saber is used to simulate the dual-tube Buck-Boost PFC converter based on single-cycle control. The simulation circuit is shown in Figure 6. The circuit simulation parameters are as follows: input voltage: 220V; output voltage: 56V; switching frequency: 50kHz; output capacitance: 470uF; input inductance: 2mH; load resistance: 20Ω. the

(1) Rated input voltage and full load

Figure 7 shows the input voltage and input inductor current waveforms of the PFC converter at rated input voltage and full load. The waveform of the inductor current is a sine wave, and it keeps changing in phase with the waveform of the input voltage, so that the purpose of the input current tracking the input voltage is achieved. Therefore, the dual-tube Buck-Boost PFC converter based on single-cycle control can effectively reduce the high-order harmonics of the input inductor current and greatly improve the power factor of the system grid side. the

(2) The input voltage changes suddenly and is fully loaded

The waveforms of the input voltage, output voltage and input inductor current of the PFC converter are shown in Figure 8 when the input voltage suddenly increases by 20% and is fully loaded. It can be seen from the figure that when the input voltage suddenly increases, the input current decreases suddenly, while the output voltage suddenly increases, but after 8 cycles, the output voltage returns to the original value. It can be seen that the single-cycle control technology can quickly suppress the input voltage disturbance and obtain a relatively stable output voltage. the

(3) Rated input voltage and sudden change in load

The waveforms of the input voltage, input inductor current and output voltage of the PFC converter when the load changes from 20Ω to 40Ω are shown in Figure 9. It can be seen that when the load resistance increases suddenly, the input current decreases suddenly, while the output voltage increases suddenly. After 10 cycles, the output voltage returns to the original value. It can be seen that the single-cycle control technology can also effectively suppress the load disturbance. Therefore, single-cycle control has the advantages of fast dynamic response and strong robustness. the

(4) Rated input voltage and light load

Figure 10 shows the input voltage, output voltage and input inductor current waveforms of the PFC converter at 50% load. It can be seen that the waveform of the inductor current is still basically in phase with the input voltage waveform, and the sine degree of the inductor current is very high. Therefore, the converter can realize power factor correction in the whole load range. the

From the results of the above simulation experiments, it can be seen that the single-cycle controlled dual-tube Buck-Boost PFC converter can realize output step-down and effectively realize power factor correction, and has a good suppression effect on input voltage disturbance and load disturbance. the

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.

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