The difference between switching power supply and linear power supply, the adjustment tube of the linear power regulator works in the state of amplification, so the heat is large, low efficiency, need to add a large volume of heat sink, but also need to also be a large volume of power frequency transformer, when to make multiple sets of voltage output transformer will be bigger.
The adjusting tube of the switching power supply works in the saturated and up state, so the calorific value is small, the efficiency is high (more than 75%) and the large volume transformer is eliminated. But the DC output of the switching power supply will be superimposed above the larger ripple, in the output end and connected to the regulator diode can be improved, in addition, because the switch tube work will produce a lot of peak pulse interference, but also need to be connected to the magnetic beads in the circuit to improve. Relatively speaking, linear power supply does not have the above defects, and its ripple can be made very small.
Linear power supply power devices working in linear state, because there is no switch intervention, is just like the water pipe has been in the water, if you have more, will leak out, this is what we often see some linear power Mos tube heat is very big, no shortage of electricity, all transformed into heat energy, therefore the conversion efficiency of linear power supply is very low, generally in 50% ~ 60%, And when the heat is high, the life of the component is bound to decrease, affecting the final use effect. The working mode of linear power supply, so that he must have a step-down device from high voltage to low voltage, the general is a transformer, after rectifying the output DC voltage. Disadvantages are large volume, bulky, low efficiency and large heat. Advantages: small ripple, good adjustment rate, small external interference, suitable for analog circuit, all kinds of amplifier, etc.
For power efficiency and installation volume requirements of the place with the best switching power supply, for electromagnetic interference and power supply purity requirements of the place (such as capacitance leakage detection) more linear power supply. In addition, when the need for isolation in the circuit is now most of the DC-DC to do the isolation part of the power supply (DC-DC from its working principle is the switching power supply). Also, the high frequency transformer used in switching power supply may be more troublesome to wind up.
The power components of the switching power supply work in the switching state. The frequency of the switching power supply is very fast. The frequency of the general switching power supply is 100~200KHz, and the module power supply is 300 ~ 500KHz. The bridge and the bridge over the main working principle is Mos tube conduction in turn, first Mos tube into the current through the bridge, use of coil storage function, the electricity agglomeration in coil, finally close Mos tube on the bridge, bridge under open Mos tube, coil and capacitance continued to external power supply, Mos tube, and then close the bridge opened on bridge let current into again, This is repeated, because to turn on and off the MOS tube, so called switching power supply. Advantages are small size, low loss, efficiency up to 80% ~ 90%. It is said that the best Vicor module in the United States up to 99%. The disadvantage is that the ripple is larger than the linear power supply, and the cost is higher.
