EasyElectronics

  ·          Basic Idea of SMPS   The regulated power supply, studied in the earlier section uses series regulators which are linear designed power supplies. Most of the energy supplied to them is wasted as heat. For small appliances it is acceptable, but for a PC power supply it is unacceptable. Thus, instead of using series pass element, switching regulator which produces large load currents with much less power dissipation is used. A switched-mode power supply (SMPS) is an electronic circuit that converts power using switching devices that are turned on and off at high frequencies, and storage components such as inductors or capacitors to supply power when the switching device is in its non-conduction state. SMPS uses a transistor switch and a closed feedback loop to produce D.C. output that is properly regulated. The basic idea of SMPS is as shown in fig. Working: Trains of pulses from pulse generator drives the base of t...

 Zener Diode as a Voltage Regulator Fig. Voltage regulator circuit using Zener diode The Zener diode is always connected in reverse biased in series in a voltage regulator circuit as shown in above fig. The Zener diode is selected with a Vz equal to the voltage desired across the load. The Zener diode acts as a ‘bypass valve’ through which more current flows when an increase in input voltage or a decrease in load current occurs, maintaining the voltage at the output nearly constant at Vz. The resistance Rs drops the excess voltage from the input to give the desired output; hence this circuit cannot compensate for input voltages smaller than desired output. The selection of R is made by using the following equation Rs= (Vin-Vout) / Iin Where, I = Iz + I L When R L is not connected,  I L =0 i.e. I= Iz = Iz(max) Therefore, Zener must be capable of passing all the current I through it. For Zener to be remaining in breakdown, Iz must not be permitted to fall below Iz(min) to work...

  ·          Rectifier with capacitor-filter –         Electronic filters are electronic circuits which performs the function of removing unwanted signal. –         Resistors, capacitors and inductors are used for the construction of filter circuits. –         As output of rectifier circuit contains some AC component, so to remove this unwanted AC component, capacitive filters are used. –         Capacitve filter circuit consists of a resistor and capacitor as shown in fig. –         The function of this filter is to remove AC component and give pure DC voltage. –         The output voltage of this filter still contains some AC component which is known as ripple. OR         Working: As we know the prope...

  Bridge Type Full wave Rectifier Above fig. shows a bridge rectifier, it is a commonly used circuit in power supplies. It consists of four diodes connected forming as a bridge circuit. The step down transformer lower the 230V/50Hz A.C. mains into desired value. The secondary of the transformer drives the bridge circuit formed by diodes D 1 , D 2 , D 3 and D 4 . The DC output is across R L . Working: During positive half cycle of input voltage (point A positive with respect to B), diodes D 1 , D 2 conduct and the current flows through load resistance R L developing a voltage drop across it.The path of the current flow at this time is A D 1 R L D 2 B   as shown by the dotted line During negative half cycle (point B positive with respect to point A) so, diode D 3 , D4 conducts and the current flows through R L as shown.The path of the current flow at this time is B D 3 R L D 4 A   as shown by the in the circuit above.   This produces a voltage drop...

  ·          Full wave Rectifier         Fig. shows the circuit of a full wave rectifier. The transformer used in this circuit is known as center tapped step down transformer.     Working: The voltage across secondary of the transformer is acting as the input of the full wave rectifier. During positive half cycle of input voltage (positive at point A) diode D1 becomes forward biased and current flows through diode D2, load resistance RL and center tapped transformer, producing a voltage drop across load During negative half cycle of input voltage, point B becomes positive with respect to point A makes D2 forward biased. The current through D2 and RL is shown by dotted line and arrow also flows in the direction   as that or D1 conduction. Thus during both the input cycles, rectified positive (DC) voltage across the load RL i...

  Half wave Rectifier Fig. Half wave Rectifier The line voltage 230 Volt 50 Hz is stepped down by using step down transformer and secondary of transformer voltage is given as output to the half wave rectifier using single diode. The load resistance R L is connected at the output where, we get the rectified D.C. Voltage. Working : During positive half cycle at point A of the input voltage, diode D1 becomes forward biased and current flows through the diode and load resistor R L producing a voltage drop across R L . The output voltage and current waveforms are shown in fig. During negative half cycle of the input voltage, D1 is reverse biased and no output voltage across the load R L . The D.C. voltage developed across the load R L is given by,   The undesired A.C. components present at D.C. output is known as ripples. Ripple Frequency of HWR is fr = fi = 50 Hz The effectiveness of a rectifier depends upon the magnitude of ...