Many virtues are expected of electrical power converters. They must be highly efficient, occupy little volume, be cheap and light, and have a long service life with no failure. Often their output must be regulated to close tolerances, even though the input voltage may vary over a very wide range.The performance of the design depends on the accuracy of the feedback signal. The information must be transferred from the output of the power circuit to the controller in a way which provides effective isolation. There are several ways for isolating the feedback signal. One of them is by using an opto-coupler. Because of its disadvantages, (the short life, change in current transfer ratio with rise of temperature, and degradation in CTR (current transfer ratio) which occur with time), the opto-coupler is not always appropriate for use in a switch mode power supply. Another v/ay is through an auxiliary winding. Because of the the poor regulation caused by the overvoltage spikes due to leakage inductance and the loss of information in the transformer, this method is subject to inaccuracy. The output regulation achieved with this design, with the feedback signal isolated through the auxiliary winding, gave an error of 5%. A third way of feeding back an isolated signal is through the main transformer. It improves the load regulation by reducing the effect of leakage inductance. eliminating the overvoltage spikes by means of sample and hold technique. This method transmits information by using a switch in the secondary side. The output regulation achieved with this method gave an error of only 1.6%.The flyback converters are the most suitable. and the cheapest for low power . Their most significant feature is the need for only a single power magne tic element in the supply (no output filter inductor is required), and the simplicity by which a multiple output switching power supply may be realised. The most severe problem in the flyback converters is the leakage inductance. There are some techniques presented in this thesis which reduce the effect of leakage inductance (sandwich winding, sample and hold. and a switch in the secondary side). The output capacitor. with its equivalent series resistance. determines how fast the transient response is, and the amount of the output ripple voltage and care must be taken when selecting the output capacitor .The PWM control circuit uses a small number of discrete components and semi-conductors. It includes aIl the necessary functions in a single package with just addition of a few external components. The method of obtainning signal feedback through the main transformer requires the addition of some extra signalprocessing components. However, it is anticipated that the required functions could be incorporated in a specially designed integrated control circuits. The high volume of manufacture of low power nyback power supplies would justify the manufacture of dedicated integrated circuits. The subject of stability has received rouch attention. Ta achieve averall systero stability and adequate phase margin, the gain should cross the unit y at zero dB at the desired crossover at -20 dB/dec. The prototype supply was designed to have a good stability margin. The sampling methad was judged not to significantly .madify the conventional stability of the power supply. Since the error is less using the feedback through the main transformer method, we chose it to be the best impleroentation of the project. A circuit was built around this method and tested for maximum power level. The supply performed weIl. The ope ration could have been improved if a different type of transformer core had been chosen. Hawever, the higher leakage inductance and losses of the core actually used provided a good test of the feedback system. By using a core with lower losses, multiwires (to reduce the skin effect), uniforroly distribution of the windings around the entire core, a good winding arrangement, and good coupling the error could be reduced to 1% or less.For future work, a better attention could be given to the stability by operating the crossover point at larger bandwidth and achieving higher gain at 100 Hz, and greater attenuation at 100 kHz.