| 摘要 |
A self-driven DC-DC converter (10) has a primary winding (20) of a power transfer (22) driven by a pair of complementary power transistors (Q1 and Q2). The base of each power transistor (Q1 or Q2) is alternatively driven by an associated base drive winding (40 or 42) of a current transformer (38), each of which develops a base drive current proportional to the primary current. Normally, one of the base drive windings (40 or 42) saturates to turn off its associated transistor (Q1 or Q2), which cause the polarity of the other base drive winding (40 or 42) to reverse and thereby turn on its associated power transistor (Q1 or Q2). An overcurrent protection circuit (70) senses excessive primary current resulting from an overload or short circuit on the secondary side of said power transformer (22) and clamps the voltage of one base drive winding (40 or 42) for a preselected time after its associated base drive winding (40 or 42) saturates to prevent the other base drive winding (40 or 42) from reversing polarity. After the preselected time has expired, the voltage clamp is removed, allowing the other base drive winding (40 or 42) to reverse polarity, enabling normal operation to resume. A second DC-DC converter (102) may be placed on the secondary side of said power transformer (22) to provide enhanced voltage regulation. |
