T
treez
Guest
Hello,
The attached Current Mode Synchronous Buck converter has a Current sense transformer (CST) to sense the hi-side FET current.
Because this is a Synchronous Buck, the current in the primary of the CST is sometimes AC..(eg when the Buck is lightly loaded)
With no-load on the Sync Buck output, it is “symmetrical” AC current in the CST primary, but when lightly loaded, it is non-symetrical AC current in the primary of the CST.
Do you know of a topology of CST that can ensure equal volt.seconds across the CST secondary through all these conditions of current flow in the CST? (ie to ensure reset of the CST under all conditions of current flow in the CST ..eg symmetrical AC, non-symmetrical AC, Unidirectional)
(When the Buck is fully loaded, the CST primary obviously has “unidirectional” current flow in its primary)
(the Buck is actually a Dual cascaded Buck, but that’s not central to the discussion)
Please find schematic and lightly loaded LTspice simulation attached.
The attached Current Mode Synchronous Buck converter has a Current sense transformer (CST) to sense the hi-side FET current.
Because this is a Synchronous Buck, the current in the primary of the CST is sometimes AC..(eg when the Buck is lightly loaded)
With no-load on the Sync Buck output, it is “symmetrical” AC current in the CST primary, but when lightly loaded, it is non-symetrical AC current in the primary of the CST.
Do you know of a topology of CST that can ensure equal volt.seconds across the CST secondary through all these conditions of current flow in the CST? (ie to ensure reset of the CST under all conditions of current flow in the CST ..eg symmetrical AC, non-symmetrical AC, Unidirectional)
(When the Buck is fully loaded, the CST primary obviously has “unidirectional” current flow in its primary)
(the Buck is actually a Dual cascaded Buck, but that’s not central to the discussion)
Please find schematic and lightly loaded LTspice simulation attached.
Attachments
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