Improved wide input voltage range 1 kW solar inverter

In the case of low voltage (e.g. battery powered solar) inverter applications very high primary current values will occur. To improve the overall efficiency of the inverter and to reduce the input capacitor, a synchronized multi-phase PWM concept was chosen. This new solution will improve the disadvantage of parallel operation of output switches in the power stages in conventional converters with modern current sharing techniques. Due to the reduced current in each of the paralleled output stages the efficiency will increase significantly. The ripple of the input current is shared between the different stages, which can help to reduce the input capacitor. In addition, the resulting frequency rises with the number of used stages. This leads to a more silent (EMV) design. In this paper a 12 V/1 kW converter is described. Its power stage consists of four PWM half-bridges operating in parallel. Each output stage switches at 8 kHz with a phase delay of 45° to the previous one. The maximum peak current of each output stage is only about 50 A. So very cheap mass products can be used as power switches. The concept is well suited for solar and renewable energy as well as aerospace applications