System and method for initial configuration of photodectors in a multi-color flow cytometer to mitigate spectral compensation. The cooling apparatus includes a heat exchanging device for absorbing heat from heat-producing components. Thus, a power supply voltage converting circuit that can obtain a high current capacity on a small-area circuit scale, a control method thereof, a display apparatus having the power supply voltage converting circuit as a power supply circuit, and a portable terminal having the display apparatus are provided. The absence of inductive components eliminates electromagnetic interference generated by the circuit and avoids circuit components magnetically coupling to one another.