DC Power Supply 2

Objectives

Ø Explain and analyze the operation of both half and full wave rectifiers 

Ø Explain and analyze filters and regulators and their characteristics  

RECTIFIER 

The SCR is the most important special semiconductor device. This device is popular for its Forward-Conducting and Reverse-blocking characteristics.

                SCR can be used in high-power devices. For example, in the central processing unit of the computer, the SCR is used in switch mode power supply (SMPS).

I–V Characteristics of the SCR

žAs -shown in Fig. 8-5, if the gate current is 0 mA, the critical voltage is higher, i.e., the SCR requires more voltage to switch to the conducting state.

ž          -But as the value of gate current increases, the critical voltage becomes lower, and the SCR      switches to the conducting state at a lower voltage.

ž           -At the higher gate current IG2, the SCR switches faster than at the lower gate current IG1,     because IG2 > IG1.

Simple Applications: 

ž                                 The SCR is the most important member of the thyristor family. The SCR is a capable power device as it can handle thousands of amperes and volts.

ž Generally the SCR is used in many applications such as in high power electronics, switches, power-control and conversion mode.

ž It is also used as surge protector.

ž Static Switch: The SCR is used as a switch for power-switching in various control circuits.

ž Power Control: Since the SCR can be turned on externally, it can be used to regulate the amount of power delivered to a load.

žSurge Protection:  In an SCR circuit, when the voltage rises beyond the threshold value, the SCR is turned on to dissipate the charge or voltage quickly.

žPower Conversion: The SCR is also used for high-power conversion and regulation. This includes conversion of power source from ac to ac, ac to dc and dc to ac.