CN206099800U - High power factor AC‑DC constant current source power supply system based on ARM control - Google Patents

Abstract

The utility model discloses a high power factor AC DC constant current source electrical power generating system based on ARM control, constant current source electrical power generating system include EMI filter circuit, flyback converter circuit, auxiliary power circuit, input voltage sampling circuit, control circuit, output voltage sampling circuit and isolating driver circuit. The utility model discloses a ARM NULL is utilized to the single -stage structure, according to the power conservation principle, compiles the programmed algorithm, obtains different duty cycle pulse ripples under the input voltage of difference, and the control switch piping leads to and turn -offs, realizes the purpose of power factor correction and constant current output.

Description

High power factor AC-DC constant current source power supply system based on ARM control

technical field

The utility model relates to the technical field of switching power supplies, in particular to an AC-DC constant current source power supply system with high power factor.

Background technique

With the development of switching power supply technology and the wide application of power electronic products, more and more problems are presented to power supply engineers, such as how to improve power factor, reduce current harmonics and grid pollution, and improve power supply stability. With the deepening of research, passive power factor correction technology and active power factor correction technology have been developed rapidly. Passive power factor correction technology is implemented with passive components such as inductors and capacitors. The main advantages are: simplicity, low cost, high reliability, and low electromagnetic interference. Main disadvantages: large size, high weight, it is difficult to obtain a high power factor, and at the same time, the working performance is related to the change of the load condition and the change of the input voltage. Active power technology uses active devices to improve power factor. The advantages are: small size, light weight, and high power factor. The disadvantages are: the control circuit is complicated and the cost is high. At present, active power factor correction technology has been widely used in AC-DC switching power supply, and has a good development prospect.

Active power factor correction technology can be divided into single-stage structure and two-stage structure. The single-stage structure is simple in design and low in cost, but the power factor is low. The two-stage structure is complex in design, high in cost, but high in power factor. In order to better design a high power factor switching power supply with high comprehensive performance, the utility model adopts a single-stage structure, uses an ARM integrated chip, and writes a program algorithm according to the principle of power conservation to obtain different duty cycles under different input voltages. Compared with the pulse wave, the switching tube is controlled to be turned on and off, so as to realize the purpose of power factor correction and constant current output.

Utility model content

The purpose of this utility model is to provide a high power factor AC-DC constant current source power supply system based on ARM control, the system can obtain a higher power factor, reduce the output ripple voltage, and achieve the purpose of constant current output , and open-circuit protection of the constant current source.

The technical solution of the utility model is: high power factor AC-DC constant current source power supply system based on ARM control, characterized in that: the constant current source power supply system includes EMI filter circuit, flyback converter circuit, auxiliary power supply circuit, input voltage Sampling circuit, control circuit, output voltage sampling circuit and isolation drive circuit, where EMI filter circuit includes safety capacitor C1 and common mode inductor L1; flyback converter circuit includes resistor R1, capacitor C2, diode D2, transformer T1, rectifier diode D5, filter capacitor C3, switch tube VT; input voltage sampling circuit includes current limiting resistor R4, voltage divider resistors R5 and R6, DC blocking capacitor C4, voltage transformer, sampling resistor R7; control circuit includes ARM control chip and peripheral circuits; The output voltage sampling circuit includes sampling resistors R2 and R3; the isolation drive circuit includes isolation transformer T2, capacitors C6 and C7;

The system is powered by 220V, 50Hz AC. The EMI filter circuit composed of safety capacitor C1 and common mode inductor L1 filters out the interference signal in the power grid, and then connects the primary side of the transformer T1 and the auxiliary side of the flyback conversion circuit through the rectifier bridge D1. Power supply circuit, the auxiliary power supply generates two output voltages +5V and +12V;

The primary side of transformer T1 is connected to resistor R1 and capacitor C2, diode D2 absorbs the leakage inductance generated by transformer T1, the drain of switch tube VT is connected to the positive pole of diode D2 and the other end of transformer T1 inductance, the source of switch tube VT is grounded, and the secondary side of transformer T1 Connect the positive pole of the rectifier diode D5, the negative pole of the rectifier diode D5 is connected to the positive pole of the filter capacitor C3, and the negative pole of the filter capacitor C3 is grounded to supply power to the load RL;

One end of the current-limiting resistor R4 of the input voltage sampling circuit is connected to the EMI filter circuit, the other end is connected to the voltage transformer, the sampling resistor R7 is connected through the voltage transformer, the sampling resistor R7 is connected to the DC blocking capacitor C4, and the bias is added through the voltage dividing resistors R5 and R6 The voltage is sent to the EMI filter circuit to filter out the interference signal, and the filtered signal is then processed by the ARM control chip;

The sampling resistors R2 and R3 are connected in series to both ends of the filter capacitor C3, and the output voltage is sampled to the ARM control chip for processing;

The ARM control circuit is powered by the auxiliary power supply, and the generated variable duty cycle pulse is transmitted to the driver chip. The driver chip is connected to one end of the capacitor C7, and the other end is connected to the isolation pulse transformer T2. The isolation pulse transformer T2 is connected to the switch tube VT through the capacitor C6 to drive The signal is isolated and transmitted to the switch tube VT to control the on and off of the switch tube, thereby controlling the output voltage of the main road flyback converter and realizing the purpose of voltage control constant current.

Compared with the prior art, the utility model has the advantages of:

(1) The flyback converter topology is adopted, which is simple in design, low in cost and small in size.

(2) An independent power supply is used to supply power to the driver chip and the control chip, so that the power supply system is separated from the main circuit for easy maintenance.

(3) Use ARM for intelligent control. When the constant current source is short-circuited, the system samples and turns off the switch tube to protect the circuit.

(4) The input voltage and output voltage are sampled by AD, and the sampled data is substituted into the program to obtain pulse waves with different duty ratios, intelligently control the on and off of the switch tube, reduce the output voltage ripple, and improve the constant current stability Spend.

Description of drawings

Fig. 1 is the overall system schematic diagram of the utility model.

Figure 2 is a graph of power factor correction results using Simulink simulation.

Figure 3 is a graph of the output current results of the simulation of the whole machine circuit using Simulink.

Fig. 4 is a program flow chart of the utility model.

detailed description

The content of the utility model will be further described below in conjunction with the accompanying drawings and examples.

As shown in Figure 1, the 220V, 50Hz AC input voltage is passed through the EMI filter circuit, and the power is rectified by the rectifier bridge D1. After rectification, a DC pulse voltage is obtained, one of which is sent to the main circuit, and the other is sent to the auxiliary power supply to generate two auxiliary voltages. , +12V and +5V DC voltages are used to supply power for the system chip and control chip respectively. After the DC pulse voltage is sent to the main circuit, it is stepped down by the transformer T1. After being rectified and filtered by D5 and C3, it supplies power to the load. The system passes the sampling resistors R2 and R3 The output voltage is sampled to ARM, and the input voltage is obtained through a voltage transformer. The 220V voltage is connected to the current limiting resistor R4 after passing through the EMI electromagnetic anti-interference circuit. The resistor R4 converts the 220V voltage signal into a current signal, and converts it to R7 through the voltage transformer. , to form an AC voltage less than 2V. Since the ARM cannot sample negative voltages, it is necessary to superimpose a positive voltage bias on the AC voltage converted by the voltage transformer, so that the voltage range is within 0 to 3.3V. The superimposed positive bias voltage is generated by the auxiliary power supply. The +5V voltage is obtained by dividing the voltage by R5 and R6. Since the superimposed signal contains a large amount of DC and interference clutter, the superimposed voltage signal needs to be DC-blocked and filtered. The signal is isolated from DC by capacitor C5, and then passed through a low-pass filter circuit. Pass the input voltage signal to ARM, and then process the sampled data through the ARM program to generate pulses of different widths.

The flyback converter works in the DCM process. The primary inductance of the transformer T1 is energy conserved during the entire cycle of switch on and off. The energy stored in the inductance of the switch tube in one cycle is W _i = 1/2L ₁ I ² P, where W _i is the inductance Energy storage, L ₁ is the primary inductance, the peak current is I _P , then the average input power is P _i ＝[1/(2L ₁ )]D ² TU _m sin ² ω _o t, and the output power is P _o ＝U _o I _o , if the output power is equal to the input power, then the duty ratio D=1/(U _m sinω _o t)(2U _o I _o L ₁ /T) ^1/2 can be seen from the formula U _o , I _o , When L ₁ and T are fixed values, the input voltage is inversely proportional to the duty cycle, that is, a wide pulse wave is generated when the input pulse voltage is low, and a narrow pulse wave is generated when the input pulse voltage is high. The driving pulse passes through the driver chip and pulse The isolation transformer T2 controls the switch tube VT to make the whole system operate normally, reduce the output ripple voltage, and realize power factor correction and constant current output. Combined with the above design, Simulink is used to simulate the whole machine circuit. The experimental results are shown in Figure 2 It is the result of power factor correction. After the system stabilizes, the current waveform changes sinusoidally with the voltage, and the current and voltage waveforms are in the same phase, that is, the power factor is basically 1. As shown in Figure 3, the result shows that the output current ripple of the constant current source is only 56mA , the designed output current is 2.1A, then the constant current stability is ±1%, which is much higher than the current constant current stability ±5% on the market. The simulation results verify the integrity and feasibility of the design idea of the utility model.

Figure 4 is a program flow chart. After power-on, the entire system program is initialized, and the duty cycle D ₀ is given. After the system is running, the output voltage is sampled, and the output voltage result is read to determine whether there is a short circuit and improve the reliability of the system. If the system is short-circuited, the output duty cycle D is 0, and the switch tube is turned off. If it is judged not to be short-circuited, the program continues to run, and the sampling and conversion results of the input voltage and output voltage are substituted into the program formula to obtain the corresponding duty cycle pulse pair switch tube. Take control and the program runs normally.

Claims (1)

1. High power factor AC-DC constant current source power supply system based on ARM control, characterized in that: the constant current source power supply system includes EMI filter circuit, flyback converter circuit, auxiliary power supply circuit, input voltage sampling circuit, control circuit, Output voltage sampling circuit and isolation drive circuit, where the EMI filter circuit includes safety capacitor C1 and common mode inductor L1; the flyback converter circuit includes resistor R1, capacitor C2, diode D2, transformer T1, rectifier diode D5, filter capacitor C3, Switch tube VT; input voltage sampling circuit includes current limiting resistor R4, voltage dividing resistors R5 and R6, DC blocking capacitor C4, voltage transformer, sampling resistor R7; control circuit includes ARM control chip and peripheral circuits; output voltage sampling circuit includes sampling Resistors R2 and R3; the isolation drive circuit includes isolation transformer T2, capacitors C6 and C7; The system is powered by 220V, 50Hz alternating current. The EMI filter circuit composed of safety capacitor C1 and common mode inductor L1 filters out the interference signal in the power grid, and then connects the primary side of the transformer T1 of the flyback converter circuit through the rectifier bridge D1 and Auxiliary power supply circuit, the auxiliary power supply generates two output voltages +5V and +12V; The primary side of transformer T1 is connected to resistor R1 and capacitor C2, diode D2 absorbs the leakage inductance generated by transformer T1, the drain of switch tube VT is connected to the positive pole of diode D2 and the other end of transformer T1 inductance, the source of switch tube VT is grounded, and the secondary side of transformer T1 Connect the positive pole of the rectifier diode D5, the negative pole of the rectifier diode D5 is connected to the positive pole of the filter capacitor C3, and the negative pole of the filter capacitor C3 is grounded to supply power to the load RL; One end of the current-limiting resistor R4 of the input voltage sampling circuit is connected to the EMI filter circuit, the other end is connected to the voltage transformer, the sampling resistor R7 is connected through the voltage transformer, the sampling resistor R7 is connected to the DC blocking capacitor C4, and the bias is added through the voltage dividing resistors R5 and R6 The voltage is sent to the EMI filter circuit to filter out the interference signal, and the filtered signal is then processed by the ARM control chip; The sampling resistors R2 and R3 are connected in series to both ends of the filter capacitor C3, and the output voltage is sampled to the ARM control chip for processing; The ARM control circuit is powered by the auxiliary power supply, and the generated variable duty cycle pulse is transmitted to the driver chip. The driver chip is connected to one end of the capacitor C7, and the other end is connected to the isolation pulse transformer T2. The isolation pulse transformer T2 is connected to the switch tube VT through the capacitor C6 to drive The signal is isolated and transmitted to the switch tube VT to control the on and off of the switch tube, thereby controlling the output voltage of the main road flyback converter and realizing the purpose of voltage control constant current.