Patent ID: 8035361
Filing Date: 2011-10-11
Classification: H02M

Abstract:
1. A boost device for boosting an input voltage supplied by an external power source to an output voltage, comprising: a transformer having first, second, third and fourth windings each having a polarity end and a non-polarity end, said polarity end of said first winding being adapted to be coupled to the external power source and being coupled to said non-polarity end of said third winding, said non-polarity end of said first winding being coupled to said polarity end of said second winding, said polarity end of said third winding being coupled to said non-polarity end of said fourth winding; an output capacitor having a first terminal and a grounded second terminal, the output voltage being a voltage across said output capacitor; a first output diode having an anode coupled to said non-polarity end of said second winding of said transformer, and a cathode coupled to said first terminal of said output capacitor; a second output diode having an anode coupled to said polarity end of said fourth winding of said transformer, and a cathode coupled to said first terminal of said output capacitor; a first switch coupled between ground and a first common node between said non-polarity end of said first winding and said polarity end of said second winding; a second switch coupled between ground and a second common node between said polarity end of said third winding and said non-polarity end of said fourth winding; each of said first and second switches being operable to switch between an ON-state and an OFF-state, said first and second switches being operated alternately in the ON-state, duration of the ON-state of one of said first and second switches overlapping duration of the ON-state of the other one of said first and second switches; a first switching circuit coupled among said first common node, said anode of said first output diode and ground; and a second switching circuit coupled among said second common node, said anode of said second output diode and ground; wherein, when said first switch is in the ON-state and said second switch is in the OFF-state, said first switching circuit is operable to establish a ground path for said anode of said first output diode therethrough, and said second switching circuit is operable to disconnect said anode of said second output diode from said second common node and ground; wherein, when said first switch is in the OFF-state and said second switch is in the ON-state, said second switching circuit is operable to establish a ground path for said anode of said second output diode therethrough, and said first switching circuit is operable to disconnect said anode of said first output diode from said first common node and ground; and wherein, when said first and second switches are in the ON-state, said first switching circuit is operable to disconnect said anode of said first output diode from said first common node and ground, and said second switching circuit is operable to disconnect said anode of said second output diode from said second common node and ground.