grizedale
Advanced Member level 3
Hi,
Is it right that the offline Half Bridge SMPS cannot provide short circuit protection by relying on its bias winding to collapse to zero volts in the event of an output short circuit ?
After all, supposing an output short circuit appeared......then the Vout would be zero volts....however, the secondary would not necessarily be zero volts, because the output inductor stands between it and the short circuit.
-But suppose the secondary winding did have zero volts across it and the primary started conducting.........well, then, in that case, the primary would also have zero volts across it, and the primary FET would be switching half the rail voltage into a short circuit....and bang....the fuse would blow.
...we dont want the fuse to blow every time theres an output short circuit......
...so therefore, we cannot rely on bias wionding collapse for providing short circuit protection, because, if the bias winding volts did go to zero, then the fuse would blow.
..so then, how must we provide output short circuit protection for an offline half-bridge?
Is it right that the offline Half Bridge SMPS cannot provide short circuit protection by relying on its bias winding to collapse to zero volts in the event of an output short circuit ?
After all, supposing an output short circuit appeared......then the Vout would be zero volts....however, the secondary would not necessarily be zero volts, because the output inductor stands between it and the short circuit.
-But suppose the secondary winding did have zero volts across it and the primary started conducting.........well, then, in that case, the primary would also have zero volts across it, and the primary FET would be switching half the rail voltage into a short circuit....and bang....the fuse would blow.
...we dont want the fuse to blow every time theres an output short circuit......
...so therefore, we cannot rely on bias wionding collapse for providing short circuit protection, because, if the bias winding volts did go to zero, then the fuse would blow.
..so then, how must we provide output short circuit protection for an offline half-bridge?
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