Series DC regulated power supply

It can be seen that a regulated power supply usually consists of six parts: transformer, rectifier and filter, adjustment component
, comparison amplifier, reference power supply and sampling. Some regulated power supplies also have overload or short-circuit protection devices.
    The circuit uses transformer T to step down 220V to 10V. VD1~VD4 bridge rectification converts AC 10V into pulsating DC. After
filtering by capacitor c1, it then goes through the voltage stabilization, amplification and sampling links to make the adjustment tube VT2 work and output DC power Uo. is 6V. By adjusting the size of the sampling resistor RP , the output voltage U
can be changed . Changes within 6V, the output current Io of this circuit is 200mA.     Its voltage stabilization working process is: when the output voltage changes, it is "sampled" through the resistor divider. After comparing with the reference power supply, the amplifier amplifies the error signal and sends it to the base of the adjustment tube to adjust its tube voltage drop. , in order to achieve the purpose of stabilizing the output voltage. Generally speaking, the greater the magnification factor of the amplification link, the higher the stability.   Let’s analyze each one by referring to the stable-turn power supply block diagram shown in Figure 12-21a:   (1) Reference voltage The reference voltage should be a DC voltage with high stability. Otherwise, because the reference voltage value changes, even if U remains unchanged t It will also cause changes in the output voltage, affecting the stability of the output voltage .     at present. The reference voltage is often obtained by using a silicon voltage regulator tube, as shown in Figure 12-21b. The key to the voltage regulator tube circuit is to select a current-limiting resistor. Its resistance value should ensure that when the input voltage is minimum, the regulated voltage flows through The pipe current is not less than the minimum current to maintain a stable voltage.