According to the working state regulator, and 95 datasheet
and often the power supply is divided into two categories: linear and 95 price
and switching power supply regulated power supply. Linear regulated power supply, adjust the tube is operating in the linear state of power supply. In the switching power supply is not in the same switch (in the switching power supply, in general, as the switch to adjust the tube) is working on and 95 suppliers
and off under two states: open: resistance is very small; off: great resistance.
switching power supply is a relatively new type of power. It has high efficiency, light weight, boost, buck, high output power and so on. However, due to state of the switch circuit, the noise is relatively large. Step-down switching power supply works as shown in Figure 24-45. Circuit by the switch K (the actual circuit for the transistor or FET), freewheeling diode VD, inductor L, filter capacitor C and other accessories. When the switch is closed, the power through the switch K, the inductor L to the load, and part of the energy stored in the inductor L and capacitor C,. As the self-inductance of the inductor L, connected to the switch, the current increases more slowly, that is, the output voltage value can not be immediately reached. After a certain time, switch off, because the role of self-inductance of the inductor L (the image can be compared to that in the inductor current has inertia), will maintain the same current in the circuit, which continues to flow from left to right. This current flows through the load from the ground return flow to the cathode diode VD, through diode VD, return to the Friends of the end of the inductor L to form a loop. And off by controlling the time switch is closed (ie, PWM: Pulse Width Modulation), can control the output voltage. If by detecting the output voltage to control the opening and closing time in order to maintain the output voltage constant, which achieved the purpose of regulation.
the switch is closed, the inductor stored energy; the switch off, the inductor releases energy, known as the energy storage inductor L inductance. During the switch off diode VD, is responsible for providing current to the inductor L channel, so called freewheeling diode diode VD.
in the actual switching power supply, switch K is replaced by the transistor or FET. When the switch opens, the current is very small; when the switch is closed, voltage is very small, so the heating power of U J will be small. This is the reason for the high efficiency switching power supply. Commonly used for switching power supply chip: TJA94, LM2575, LM2673, 34063,51414, etc.