This is the schematic diagram of 15W inverter circuit. The circuit is based PNP power transistor such us TIP32 and other similar transistors. This inverter is producing square wave, there may be some noticeable hum on audio units which powered using this inverter circuit. To reduce some of the hum, you may increase the value of the output capacito
r (. 47uf capacitor). The transformer will be a 24 Volt 2 ampere center tapped secondary.