The device that can make a constant current in the circuit, such as dry cell, battery, DC generator, etc., is called DC power supply. DC power supply has positive and negative two electrodes, positive electrode potential is high, negative electrode potential is low; when the two electrodes are connected to the circuit, the DC power supply can maintain a constant potential difference between the two electrodes, so as to form a constant current in the external circuit from the positive electrode to the negative electrode. To maintain a constant potential difference between the two poles of the DC power supply must be made in the external circuit from the positive pole to flow to the negative pole of the positive charge, in the power supply against the direction of the electric field force, from the negative pole back to the positive pole to go. This process can not rely on electrostatic force, can only rely on some kind of electrostatic force and electrostatic force in the opposite direction of the "non-static force" to realize.
The role of AC-DC power modules
I, isolation
1, safety isolation: strong and weak power isolation \ IGBT isolation drive \ surge isolation protection \ lightning isolation protection (such as human contact with the isolation of medical electronic equipment protection)
2, noise isolation: (analog circuitry and digital circuitry isolation, isolation of strong and weak signals)
3, ground loops, the ground loop.
3, ground loop elimination: remote signal transmission \ distributed power supply system
Two, protection
Short-circuit protection, over-voltage protection, under-voltage protection, over-current protection, and other protections
Three, voltage conversion
Boost conversion \buck conversion \ AC/DC conversion (AC/DC, DC/AC) \ polarity conversion (positive and negative conversion) Single-supply and positive-negative power conversion, single-supply and multiple-supply conversion)
Four, voltage stabilization
AC utility power supply \remote DC power supply \distributed power supply system \battery power supply