Research On Intrinsically Safe Switching Power Supply

Electrical devices in the dangerous environments such as mine, oil and natural gas, increasingly are designed to be intrinsically safe, power is the 'heart' of electrical devices, so it the essence of security design is the foundation of this system as a whole. This subject will mature switching power supply technology to the study of intrinsically safe circuits, a 18V/1A output intrinsic safety of switching power supply is designed based on the flyback converter. The power is small, low cost, electrical isolation for input and output, can achieve multi-channel intrinsic safety outputs for all kinds of electrical devices in the dangerous environments to provide different operating voltage.When capacitor shorts and inductance breakers, then produce the electric spark and focus on the release of energy, therefore, intrinsically safe switching power supply design should control their energy is not generated when the spark ignition of surrounding flammable gas mixture. Input rectifier filter circuit is a larger store of energy in the power system, therefore, this paper focuses on this part of the circuit, the security measures taken by the input filter capacitor in series with a small resistance, in order to reduce the capacitor short-circuit the instantaneous discharge current, thereby limiting the spark discharge energy, while the circuit also has a function of PFC. Spark discharge characteristics of the capacitor series resistance circuit when shorts is detail analyzed, the mathematical model is established, using MATLAB simulation software for the expression of simulation and input of the current wave of spectrum analysis to verify the method can effectively reduce capacitor the instantaneous discharge current, thereby reduce discharge energy to ensure that the intrinsically safe circuits; and verify the effect of series resistance had no significant effect on the filter, and a slight increase of power factor.The transformer of flyback converter is essentially an energy storage inductor, so the power takes another safety measure is to increase the operating frequency of switching power supply, reducing the stored energy of transformer.In the paper, the main circuit, over-current and over-voltage protection circuit of intrinsically safe switch power supply are designed, the important components of the calculation and selection of specific parameters are given, also for the PCB design, and ultimately produced a prototype of intrinsically safe switching power supply. The results show that the intrinsically safe switching power supply output is relatively stable, ripple voltage is small, it can basically meet the design requirements. Figure [51] table [7] reference [63]...