Direction for [ Question No: 1 To 2 ] :
Read the passage below and answer the questions, that follows based on your understanding of the passage :
Many instruments require dc power of their operation. This power is available from a portable cell, however, the power output is low besides other problems. AC power is continuously and easily available, so it is convenient to use it. However, ac power must be converted into dc power.
The devices such as half-wave, full wave and bridge rectifiers convert bi-directional voltage to uni-directional voltage. However, the output has large ripple contents. Filters are used to reduce the ripple significantly. Various filters circuits and L, C, LC and CLC. The power supply with rectifier and filter is still unregulated.
The output of such power supplies varies with variations in a.c. mains voltage, load current and temperature.
In order to maintain the output at constant level, voltage or current regulation is necessary. This is obtained by using series or shunt feedback. In addition to regulation, the power supply also requires protection e.g. overload, over current or short circuit protection. Pre- regulation is also carried out to improve the stability.
Regulators can be designed by using discrete components. However, IC regulators are also available. These regulators have facilities like :
(i) voltage / current boosting
(ii) thermal shut-down
(iii) floating point to facilitate higher output voltage.
(iv) switching regulator to reduce the power dissipation.
