Contactless power transfer system and control method thereof

A contactless power transfer system, comprising:

• a coil configured to supply or receive power contactlessly via magnetic coupling;
• a bridge circuit having two direct current (DC) terminals and two alternating current (AC) terminals, the two AC terminals being respectively connected to two ends of the coil, the bridge circuit including a first circuit having two serially-connected switching arms each including a semiconductor switch and a diode in reverse parallel connection, and a second circuit having two serially-connected diodes;
• a smoothing capacitor connected between the two DC terminals of the bridge circuit, a load being connectable to either end of the smoothing capacitor;
• and
• a control device configured to generate drive signals to control the semiconductor switches of the bridge circuit, based on a DC output voltage of the bridge circuit and a current flowing through the coil, wherein
• a connection point of the two switching arms and a connection point of the two diodes form the two AC terminals of the bridge circuit,
• connection points of the first circuit and the second circuit form the DC terminals of the bridge circuit, and
• the drive signals include signals that put all of the semiconductor switches of the bridge circuit into an off condition during a period for which a power transfer to the coil is stopped, and that cause each of the semiconductor switches to carry out a switching action after a zero-crossing of the current of the coil is detected when power transfer to the coil is started.

A contactless power transfer system, comprising:

• a coil configured to supply or receive power contactlessly via magnetic coupling;
• a bridge circuit having two direct current (DC) terminals and two alternating current (AC) terminals, the two AC terminals being respectively connected to two ends of the coil, the bridge circuit including a first circuit having two serially-connected switching arms each including a semiconductor switch and a diode in reverse parallel connection, and a second circuit having two serially-connected resonant capacitors;
• a smoothing capacitor connected between the two DC terminals of the bridge circuit, a load being connectable to either end of the smoothing capacitor;
• and
• a control device configured to generate drive signals to control the semiconductor switches of the bridge circuit, based on a DC output voltage of the bridge circuit and a current flowing through the coil, wherein
• a connection point of the two switching arms and a connection point of the two resonant capacitors form the two AC terminals of the bridge circuit,
• connection points of the first circuit and the second circuit form the DC terminals of the bridge circuit, and
• the drive signals include signals that put all of the semiconductor switches of the bridge circuit into an off condition during a period for which a power transfer to the coil is stopped, and that cause each of the semiconductor switches to carry out a switching action after a zero-crossing of the current of the coil is detected when power transfer to the coil is started.