High voltage module principle?
Author:Populus tomentosa Time:2021-07-21 15:44 Browse(581)
High voltage distributed DC power supply
High voltage distributed DC power supply.

High voltage module principle?

high voltage distributed DC power supply is a new type of DC power supply equipment.
it is mainly used in small switching stations and user terminals to provide reliable uninterrupted power supply for secondary control lines (such as intelligent terminals such as microcomputer protection, indicator lights, analog indicators, etc.), so as to avoid the loss of protection function of microcomputer protection in case of AC power loss, It can also provide DC operation power supply for primary switching equipment (spring mechanism vacuum circuit breaker, permanent magnet mechanism vacuum circuit breaker, electric load switch, etc.) that meet the power requirements of the device.
wall mounted DC power supply.
wall mounted DC power supply is suitable for small switching station, power supply, power supply, etc The system of small user substation and small 10kV substation adopts the integrated design idea.
it is composed of rectifier module, monitoring module, step-down unit, power distribution unit and battery installation box; It has the characteristics of small volume, simple structure and independent system; The monitoring module adopts LCD Chinese character menu display, which has perfect functions of system monitoring and battery automation management. It has four remote interfaces to connect with the automation system, provides two communication interface options of RS232 and RS485, and three communication protocols of RTU, CDT and MODBUS.
micro DC operation power supply.
micro DC operation power supply is mainly used in substation, switching station, power supply and power supply It provides reliable DC power supply for primary switchgear (vacuum circuit breaker, vacuum contactor, load switch, etc.) and secondary control, protection and signal circuits (such as microcomputer protection, remote control unit RTU, load control device, indicator, analog indicator, intelligent instrument, etc.)   .      1. Introduction  .
   High voltage and low current low-power power supply is widely used in precision electronic systems such as copying equipment and medical instruments. At the same time, the power supply system is required to have the characteristics of light weight, fast response, good stability and high reliability It can be widely used in copying equipment, medical instruments and other precision electronic systems  .
     2. Circuit principle  .
     The principle block diagram of the system is shown in Figure 1. The input signal of the high-voltage power supply comes from the 220 V AC power supply.
after rectification and filtering, it drives the high-frequency transformer together with the output signal of the PWM pulse modulator. The high-voltage power supply obtained through the high-frequency transformer outputs the high-voltage DC after rectification and filtering. The output feedback signal is fed back to the pulse modulator after photoelectric isolation, By comparing with the reference voltage of the error amplifier in the pulse modulator, the output duty cycle of the pulse modulator is controlled to adjust the output voltage.
Fig. 1 system principle block diagram  .
     3. Key points of circuit design  .
     3.1 PWM control circuit  .
     The PWM modulator used in the system is a chip of SG3524 model [4].
the circuit is shown in Figure 2. A capacitor C2 is connected in parallel at the power signal inlet end of the chip to form a soft start circuit. The purpose of designing the soft start circuit is to prevent the chip from being impacted by the excessive current generated when the power is suddenly turned on,The voltage at both ends of the capacitor can't change abruptly. Its voltage increases gradually with the charging of the external power supply. After a period of time, the circuit enters the normal working state. This ensures that the input voltage is established slowly, The MOS power transistor is selected as the switching power transistor of the output circuit. Because the power transistor works at high frequency, it will produce oscillation. In order to eliminate the parasitic oscillation, the length of the connecting wire with each pin of the power transistor, especially the length of the grid lead, should be reduced as far as possible. If the length cannot be reduced, a small resistance can be connected in series, In the figure, R3 is not only the gate limiting current resistance of the power transistor, but also together with R4 to eliminate the parasitic oscillation of the power transistor  .
    2 PWM circuit diagram  .
     3.2 transformer drive circuit  .
     The driving circuit of high voltage transformer is shown in Figure 3.
Figure 3 driving circuit of high voltage transformer  .
     The power transistor is driven by the signal from SG3524 chip. The 11 pin and 14 pin single ended parallel output. When the SG3524 output is high, the power transistor turns on and stores energy in the inductor L; When the output voltage is low, the power transistor is cut off, which causes the current flowing through the inductor L to drop to zero suddenly, and l generates back EMF. The pulse voltage of the back EMF is applied to the input end of the high frequency transformer to drive the transformer to work. At the same time, the inductor L is used as the impedance matching element of the transformer  .
     The AC voltage output from high frequency transformer is rectified by diodes VD2 and VD3, then filtered by C2 to get high voltage output  .
     3.3 sampling feedback circuit  .
     In the feedback loop.
sampling of the output voltage signal,The method of parallel resistance at output end and series attenuation of high voltage through resistance is adopted  .
     R3, R4 and RW are voltage sampling feedback resistors. After isolation feedback, the voltage is input from pin 1 of SG3524 chip to control the duty cycle, and then adjust the output voltage to achieve the purpose of voltage stabilization. The principle of voltage stabilization is: if the output voltage is higher, the signal of sampling feedback is also higher, and the voltage is lower compared with the reference voltage of error amplifier in SG3524, resulting in the narrower width of duty cycle, It causes the output voltage to drop; RW is an adjustable resistor and the output voltage can be adjusted by adjusting RW  .
     4. Performance test  .
     The output voltage of the system is regulated by the sampling resistor RW.
changing the value of the variable resistor can change the output voltage. Figure 4 shows that the sampling resistor RW is 20K ω It can be seen from the figure that the response time of the output voltage rising from 0V to 5kV is about 0.5s, and the power system has a faster response speed. At the same time, it can be seen from the partial enlarged voltage waveform in figure (b) that the maximum voltage fluctuation is less than 5% when the output voltage is 5000v.
(a) output voltage response diagram     ( b) The voltage waveform is amplified locally.
Fig. 4 variable resistance is 20K ω Voltage output waveform diagram at the same time  .
     When RW is adjusted to 10K ω The output voltage is about 2500V as shown in Fig. 5. Compared with Fig. 4 (a), the response speed of the high-voltage power supply is improved, but the stability is basically unchanged. At the same time, it can be seen from Fig. 4 and Fig. 5 that the output voltage has a linear relationship with the regulating resistance, and the high-voltage power supply has good controllability.
the variable resistance in Fig. 5 is 10K ω Voltage output waveform diagram at the same time  .
     5. Conclusion  .
     A high-voltage switching power supply is designed and manufactured by using single ended flyback converter.
through the performance test of the power supply, it can be concluded that the high-voltage switching power supply has the advantages of small volume, good stability and fast response speed. It can be widely used in small power supply systems requiring high voltage and low current
Related topics