CN203039586U - Wide-load-range low-voltage stress flyback converter - Google Patents

Abstract

The utility model discloses a low-voltage stress flyback converter with a wide load range. A switch tube Q is connected in series between the switch tube _Q1 of the flyback power factor correction converter and the primary side winding 2 of the flyback transformer T. _2. The anode of the power diode _D6 is connected between the switching tube _Q1 and the switching tube _Q2 , and the cathode of the power diode _D6 is connected to terminal 1 of the primary winding of the flyback transformer T. Through the above design, the load capacity of the traditional flyback power factor converter is expanded. Under the premise of the same main circuit parameters, the utility model can increase the load range of the traditional flyback power factor corrector and reduce the voltage stress borne by the switch tube connected to the primary side winding of the transformer. At the same time, it can guarantee to obtain unity power factor in the whole input voltage range.

Description

A Low Voltage Stress Flyback Converter with Wide Load Range

technical field

The utility model relates to electric power control equipment, in particular to a control method and device for flyback power factor correction. the

Background technique

In recent years, power electronics technology has developed rapidly, and power supply technology, which is an important part of the power electronics field, has gradually become a hot spot in application and research. Switching power supply has established its mainstream position in the field of power supply because of its high efficiency and high power density, but there is a fatal weakness when it is connected to the power grid through a rectifier: the power factor is low (generally only 0.45 to 0.75), Moreover, a large number of current harmonics and reactive power will be generated in the grid to pollute the grid. There are two main methods for suppressing harmonics generated by switching power supplies: one is the passive method, that is, using passive filtering or active filtering circuits to bypass or eliminate harmonics; the other is the active method, that is, designing a new generation of high-performance rectifiers, which It has the characteristics of sine wave input current, low harmonic content and high power factor, that is, it has the function of power factor correction. The focus of research on switching power supply power factor correction is mainly the research of power factor correction circuit topology and the development of power factor correction control integrated circuits. Traditional active power factor correction circuits generally adopt Boost-boost topology, because Boost is easy to control, simple to drive, and the power factor can be close to 1, but Boost power factor correction has the disadvantage of high output voltage. In low-power applications, Buck-step-down topology and flyback converter are often used, but when the Buck circuit implements PFC, because when the input voltage is lower than the output voltage, no energy is transferred, the input current is 0, and the crossover distortion is serious . The flyback converter can transfer energy in the entire power frequency cycle, and its power factor and total harmonic distortion are better than the Buck converter. Flyback power factor correctors usually have two operating modes: discontinuous mode and critical continuous mode. The discontinuous mode flyback power factor corrector can obtain unity power factor, but its peak current is very large, which increases the conduction loss of the switch tube and affects the efficiency of the converter; the critical continuous mode flyback power factor corrector, its conduction The time is fixed in a power frequency cycle. Although the efficiency is higher than that of the discontinuous mode flyback power factor corrector, it cannot obtain unit power factor, and the power factor and total harmonic distortion are better than the discontinuous mode flyback power factor corrector. Difference. the

The technical scheme adopted in the utility model is proposed based on the method patent application proposed by the applicant in this patent application at the same time. the

Utility model content

The purpose of this utility model is to provide a novel flyback power factor correction converter, adopting the above method to make the flyback power factor correction converter obtain unit power factor, lower switching tube voltage stress and wider load range. the

The means that the utility model realizes the utility model purpose is:

A switch tube Q 2 is connected in series between the switch tube Q ₁ of the flyback power factor correction converter and the primary winding 2 terminal of the flyback transformer T, and the power diode D ₆ is connected between the switch tube _{Q 1 and} the switch tube Q ₂ The anode and the cathode of the power diode _D6 are connected to terminal 1 of the primary winding of the flyback transformer T.

In this way, the output voltage sampling composed of R ₁ and R ₂ samples the output voltage v _o (t) of the converter and then inputs it to the negative terminal of the operational amplifier, and the positive terminal of the operational amplifier inputs the reference voltage signal V _ref , after passing through the compensation network, the operational amplifier output a compensation control signal V _comp . The sawtooth wave output by the sawtooth generator and the compensation control signal V _comp are input to the positive terminal and the negative terminal of the comparator 1 respectively. The output signal of the comparator 1 is input to the half-bridge drive circuit after being passed through the RS-trigger 1, and then output to the switch tube Q ₁ after being amplified by the drive circuit. When the sawtooth wave voltage output by the sawtooth wave generator is greater than the compensation control signal V _comp , the switch tube _Q1 is turned off, and when the sawtooth wave voltage output by the sawtooth wave generator is less than the compensation control signal V _comp , the switch tube _Q1 is turned on; and set The fixed compensation network makes the cut-off frequency of the entire voltage control loop much lower than the power frequency, so the compensation control signal V _comp output by the operational amplifier remains unchanged in half the power frequency cycle. The input voltage v _in (t) and the load current i _o (t) signal are inversely input to the sine wave generating circuit, and the generated sine wave signal is input to the negative terminal of comparator 2, and the input signal of the positive terminal of comparator 2 is a flyback transformer The secondary output current signal i _L2 (t). The output signal of the comparator 2 and the output signal of the comparator 1 are input to the RS-flip-flop 2 through the OR gate, and its output is amplified by the half-bridge driving circuit and then output to the switch tube Q ₂ . It can be seen that the utility model method filed on the same day as the applicant of the present application can be realized conveniently and reliably by adopting the above device.

Compared with the prior art, the beneficial effects of the utility model are:

1. Compared with the traditional flyback power factor correction converter, the low voltage stress flyback power factor correction converter of the utility model with wide load range and its control can obtain unit power factor and smaller total harmonic distortion ; 2. Compared with the traditional flyback power factor correction converter, the low-voltage stress flyback power factor correction converter and its control of the wide load range of the utility model can be applied to more under the same main circuit parameter conditions A high-power power factor correction converter can obtain higher efficiency while obtaining the same high power factor. 3. Compared with the traditional flyback power factor correction converter, the low-voltage stress flyback power factor correction converter of the utility model with wide load range and its control can reduce the voltage stress on the switch tube and reduce the power consumption of the switch tube. The difficulty of selection, while reducing the cost of the converter and improving efficiency. the

Description of drawings

Figure 1 is a block diagram of a low voltage stress flyback power factor correction converter system with a wide load range. the

Figure 2 is the main waveform diagram of a traditional flyback power factor correction converter under 100W load power. the

Figure 3 is the main waveform diagram of the traditional flyback power factor correction converter under the load power of 200W. the

FIG. 4 is a main waveform diagram of Embodiment 1 of the present invention under a load power of 100W. the

FIG. 5 is a main waveform diagram of Embodiment 1 of the present invention under a load power of 200W. the

FIG. 6 is a schematic diagram of the circuit structure of Embodiment 2 of the present invention. the

Detailed ways

The utility model is described in further detail below through specific examples in conjunction with the accompanying drawings. the

Embodiment one

Figure 1 shows that a specific embodiment of the present invention is a topology and control method of a low-voltage stress flyback power factor correction converter with a wide load range, and its specific method is:

A switch tube Q 2 is connected in series between the switch tube Q ₁ of the traditional flyback power factor correction converter and the primary winding ₂ of the flyback transformer T, and a power diode D ₆ is connected between the switch tube Q ₁ and the switch tube Q ₂ The anode of the power diode _{D6 and} the cathode of the power diode D6 are connected to terminal 1 of the primary winding of the flyback transformer T.

The output voltage sampling composed of R ₁ and R ₂ samples the output voltage v _o (t) of the converter and inputs it to the negative terminal of the operational amplifier, and the positive terminal of the operational amplifier inputs the reference voltage signal V _ref , and the output of the operational amplifier is compensated after passing through the compensation network control signal V _comp . The sawtooth wave output by the sawtooth generator and the compensation control signal V _comp are input to the positive terminal and the negative terminal of the comparator 1 respectively. The output signal of the comparator 1 is input to the half-bridge drive circuit after being passed through the RS-trigger 1, and then amplified by the drive circuit and output to the switch tube Q ₁ . When the sawtooth wave voltage output by the sawtooth wave generator is greater than the compensation control signal V _comp , the switch tube _Q1 is turned off, and when the sawtooth wave voltage output by the sawtooth wave generator is less than the compensation control signal V _comp , the switch tube _Q1 is turned on; and set The fixed compensation network makes the cut-off frequency of the entire voltage control loop much lower than the power frequency, so the compensation control signal V _comp output by the operational amplifier remains unchanged in half the power frequency cycle. The input voltage v _in (t) and the load current i _o (t) signal are inversely input to the sine wave generating circuit, and the generated sine wave signal is input to the negative terminal of comparator 2, and the input signal of the positive terminal of comparator 2 is a flyback transformer The secondary output current signal i _L2 (t). The output signal of the comparator 2 and the output signal of the comparator 1 are input to the RS-flip-flop 2 through the OR gate, and its output is amplified by the half-bridge driving circuit and then output to the switch tube Q ₂ .

Utilize SIMetrix/SIMPLIS simulation software to carry out time-domain simulation on the traditional flyback power factor correction converter and the utility model embodiment 1 respectively, and the waveform of the simulation result is as follows:

Figure 2 is the time-domain simulation waveform of a traditional flyback power factor correction converter under a load power of 100W. From top to bottom, it shows the voltage stress waveform, output voltage waveform, input voltage waveform and input current waveform borne by the switching tube _Q1 . It can be seen from Figure 2 that the input current tracks the waveform of the input voltage very well, and the power supply has a very high power factor. At this time, the output voltage of the flyback power factor correction converter is stable at 48V, and the maximum voltage stress that the switching tube Q ₁ bears in the steady state is 300V.

Figure 3 is the time-domain simulation waveform of a traditional flyback power factor correction converter under a load power of 200W. From top to bottom, it is the voltage stress waveform, output voltage waveform, input voltage waveform and input current waveform borne by the switching tube _Q1 . It can be seen from Figure 3 that when the load power increases, the input current is distorted near the peak point, and the waveform of the input voltage cannot be tracked, which reduces the power factor of the power supply. At this time, the output voltage of the flyback power factor correction converter is stable at 48V, and the maximum voltage stress that the switching tube Q ₁ bears in the steady state is 450V.

Fig. 4 is the time-domain simulation waveform under 100W load power of embodiment one of the present utility model, is successively from top to bottom the voltage stress waveform that switch tube _Q2 bears, the voltage stress waveform that switch tube _Q1 bears, the output voltage waveform, Input voltage waveform and input current waveform. It can be seen from Figure 4 that the input current tracks the waveform of the input voltage very well, and the power supply has a very high power factor. At this time, the output voltage of the flyback power factor correction converter is stable at 48V, the maximum voltage stress of the switch tube _Q1 is 180V in the steady state, and the maximum voltage stress of the switch tube _Q1 is 140V in the steady state.

Fig. 5 is the time-domain simulation waveform under the load power of 200W of embodiment one of the present utility model, is successively from top to bottom the voltage stress waveform that switch tube _Q2 bears, the voltage stress waveform that switch tube _Q1 bears, the output voltage waveform, Input voltage waveform and input current waveform. It can be seen from Fig. 5 that when the load increases, the input current of Embodiment 1 of the present invention still tracks the waveform of the input voltage very well, and the power supply has a very high power factor. At this time, the output voltage of the flyback power factor correction converter is stable at 48V, the maximum voltage stress of the switch tube _Q1 is 200V in the steady state, and the maximum voltage stress of the switch tube _Q1 is 140V in the steady state.

It can be seen from Fig. 2 to Fig. 5 that the traditional flyback power factor correction converter cannot work normally under the load power of 200W; but under the same main circuit parameter conditions, the first embodiment of the utility model can operate under the load power of 100W and 200W , can realize that the input current tracks the waveform of the input voltage very well, has a high power factor, and the voltage stress of the switch tubes Q ₁ and Q ₂ is smaller than that of the switch tube Q ₁ in the traditional flyback power factor correction converter withstand voltage stress.

Example two

FIG. 6 shows that the difference between this example and the first example is that the power factor correction converter of the switching power supply is a forward converter. The control mode and working process are similar to the first embodiment. It can also be proved by simulation results that it can realize the purpose of the utility model. the

In addition to the switching power supply composed of the flyback power factor correction converter in the above embodiments, the utility model can also be used for the power factor switching power supply composed of isolated power factor correction converter circuits such as forward power factor correction converters. the

Claims (1)

1. A low-voltage stress flyback converter with a wide load range is characterized in that a switch tube is connected in series between the switching tube _Q1 of the flyback power factor correction converter and the primary side winding 2 ends of the flyback transformer T Q ₂ , the anode of the power diode D ₆ is connected between the switch tube Q ₁ and the switch tube Q ₂ , and the cathode of the power diode D ₆ is connected to terminal 1 of the primary winding of the flyback transformer T.

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