zener diode as voltage regulator in hindi

ZENER DIODE AS VOLTAGE REGULATOR Regulation: The process of keeping constant voltage across load regardless of variation of input voltage or load current is called regulation. Zener diode is a specially designed diode which has ability to maintain constant voltage across load. Therefore zener diode can be used to provide constant voltage across load. Need for Regulation: Due to increase in the source voltage if the voltage and current across the load increases. Then the load may be damaged due to over heating To protect the load, zener diode is connected in parallel to the load RL in reverse fashion. This circuit shows, zener diode as shunt voltage regulator Vin is unregulated input voltage and Vo is regulated output voltage. Zener diode is reverse connected across the input voltage Vin whose variations are to be regulated. The resistor Rs is used to limit the reverse current through the zener diode to safer value. The voltage source Vin and resistor Rs are so selected that the diode operates in breakdown region. The diode voltage in this region, is called as zener voltage Vz , which is also voltage across RL The current through the diode is Iz , current through series resistor is Is and current through load resistor is IL As long as voltage across the load resistor RL is less than zener voltage VZ, diode does not conduct. When the supply voltage Vin increases and the voltage across the load resistor Vo becomes greater than or equal to zener breakdown voltage VZ Zener diode starts conducting Zener Regulator can be explained under following heads: Regulation with varying input voltage Vin Regulation with varying load resistance RL Regulation with varying input voltage Vin Regulation with varying input voltage Vin Regulation with varying input voltage Vin As the input voltage increases, Input current Is also increases, This increases the current through zener diode Iz without affecting the load current IL, With the increase in input current the voltage drop across resistor Rs will also increase, Thereby keeping the load voltage Vo constant WORKING: When Vin decreases As the input voltage decreases, Input current Is also decreases, This decreases the current through zener diode Iz without affecting the load current IL, With the decrease in input current the voltage drop across resistor Rs will also decrease, ThWORKING: When RL increases As the load resistance increases, Load current IL decreases, This increases the current through zener diode Iz As a result of this the input current IS and voltage drop across RS remains constant, Thereby keeping the load voltage Vo constant WORKING: When RL decreases As the load resistance decreases, Load current IL increases, This decreases the current through zener diode Iz As a result of this the input current IS and voltage drop across RS remains constant, Thereby keeping the load voltage Vo constant