Two-input uninterruptible voltage converting device and method thereof

A two-input uninterruptible voltage converting device, comprising:

• a first conversion circuit, in which the first conversion circuit having a high-voltage DC (Direct Current) source, a main power transformer, an upper switch tube and a lower switch tube connected to a primary winding of the main power transformer, and a switch-type rectifying tube connected to a secondary winding of the main power transformer;
• and an output end of the switch-type rectifying tube taken as an intersection;
• a second conversion circuit, in which the second conversion circuit formed by a low-voltage DC source, an isolating diode and a low-voltage switch tube connected with each other in series in turn;
• an output end of the second conversion circuit connected to the intersection;
• the minimum allowable voltage of the low-voltage DC source being more than the rated output voltage of the device;
• and the maximum voltage of the low-voltage DC source being less than the voltage peak of the secondary winding of the main power transformer when the high-voltage DC is the minimum allowable value;
• an energy storage unit, in which the energy storage unit consisting of an inductance and a capacitance and directly connected between the intersection and a load end;
• a fly-wheel switch tube, in which the fly-wheel switch tube connected between the intersection and the ground;
• and
• a control unit, in which the control unit used for outputting first, second, third and fourth PWM (Pulse-Width Modulation) signals in phase to drive the upper switch tube, the lower switch tube, the switch-type rectifying tube and the low-voltage switch tube respectively to operate synchronously and outputting a fifth PWM signal in opposite phase with the first PWM signal to drive the fly-wheel switch tube to operate.