: In renewable dc-supply systems, batteries are usually required to back-up power for those electronic equipment that voltage levels are typically much lower than the dc-bus voltage. So Bidirectional converters for charging/discharging the batteries are required. To be bidirectional in these applications is in the flow of current. Bidirectional dc–dc converters is kind of converter that transfer the power between both dc sources in either direction. In these converters the direction of current can be reversed while the polarity of dc voltage of connected sources remains without change. These converters divide to isolated bidirectional converter and non-isolated bidirectional converter. At high power or at the cases that the difference level of voltage between input and output is high and you can’t use the common GND, the isolated bidirectional converter is highly recommended. Also these converters provide electrical isolation between the input and output sides, but because of the leakage inductance in the coupled inductor, they generally suffer from considerable switching loss and voltage stress on the switching devices. In comparison with base converters, providing soft-switching condition in bidirectional converter is more difficult. This is because in the bidirectional converter, the flow of current is two way and the converter has two main switches. So soft switching conditions should exist for both switches, in two modes of the operation.Several techniques which have been proposed for basic converters can expand to bidirectional converter to provide a soft switching. However pay attention that in these converters to prevent excessive increase in the number and complexity of circuit elements, it is desirable that use the same assistance elements to provide the soft switching for both the switches of converter. Also it is better Soft switching conditions for auxiliary switch converter has been provided. It is desirable that the auxiliary circuit does not impose additional stress voltage and current to converter switches and the control of converter should be simple. In order to reduce the switching losses and voltage stress problem for these converters numerous soft switching techniques has been presented that by using a switching auxiliary circuit or snubber circuit, solved the problems of unidirectional converter. For soft switching on both sides, auxiliary circuit must be used in both directions. At the first the topology of the bidirectional converter will be reviewed and in continue the analysis of the PWM circuit with soft switching conditions will be done. Then the proposed circuit will examine. Finally, conclusions and suggestions for further work are stated. Keywords : 1 - Switching Power Supply 2 - isolation Bidirectional converters 3 - zero voltage switching 4 - zero current switching