a power supply for a microwave range , which can control its own output voltage over a wide range of voltages by utilizing a voltage driving type switching element , and which includes a first transformer for driving a dc voltage , a switching element for driving the first transformer , a controller for supplying a switching signal which is pulse - width - modulated to the switching element , and a second transformer for transmitting the switching signal from the controller to the switching element . a buffer is coupled between the second transformer and the switching element for generating an amplified buffered switching signal , which maintains a constant dc voltage level and swing width so as to correctly drive the switching element .