Solar power supply system is made up of solar panels,solar controller,batteries. If the output is AC 220V or 110V,it need inverter. The action of each part is: Ⅰ, Solar panel：it is the hard core of solar power supply system. Its action is changing radiating power into electric energy or keeping in battery, or driving loads. Ⅱ, Solar controller：The action of controller is controlling running order of whole system. It can also avoid battery overcharging or over discharging. In some district, it has the action of temperature correction. Some other additive function such as light control switch,time control switch is selectable Ⅲ, Battery：Commonly we use lesd-acid battery. In micro system we can also use nickel-hydrogen battery,nickel-cadmium battery or lithium battery. Its action is storing electric energy and releasing when need. Ⅳ, Inverter：The output is 12VDC,24VDC,48VDC commonly in solar power supply system.。In order to supply electric energy to electric equipment of 220VAC，it has to change DC current into AC current.So it needs DC-AC inverter.