ABSTRACT
Modern electronic devices and gadgets require a constant, unfluctuating power supply as per their design and manufacturing. This task is accomplished by Switched Mode Power Supply, in short, SMPS. It provides a constant dc output for the working of the device. Generally, in SMPS, a flyback converter topology is used. There are some disadvantages with this flyback topology like high RMS and peak currents in the design, high flux excursions in the inductor, low efficiency, high cost, complicated control of the converter, lower bandwidth due to a zero in the response of the converter, the current feedback loop used in current mode control needs slope compensation in cases where the duty cycle is above 50% etc. Due to this, we go for forward topology in SMPS. In the forward converter, the power switch is turned on and off quickly at the given frequency because the transformer cannot operate on dc. So the pulses have to be generated by the driver IC like SG 3524 and its output is used to drive the switch. The switch output (pulsating dc) is connected to transformer. So, the input is transferred to the secondary side of the transformer. In the secondary side, the rectifying and free wheeling actions take place and the ripple in the output is eliminated by the use of a large capacitance. The continuity in the circuit is maintained by the inductor so that a constant current is carried to the load from the rectifying and free wheeling actions. The load is resistive in nature and constant dc output is obtained. By varying the on- time and the duty cycle using potentiometer, the output voltage can be adjusted to the required level.
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