Circuit for internal current limiting in a fast high side power

Details Circuit for internal current limiting in a fast high side power Circuit for internal current limiting in a fast high side power

1989-06-16

1991-05-21

DeBoer, Todd E.

Electricity: electrical systems and devices

Safety and protection of systems and devices

Voltage regulator protective circuits

361 86, 361 88, H02H 320

Patent

active

050180410

ABSTRACT:
A current limiting circuit (200, 300, 400) for instantaneously limiting the peak current of a fast high side power switch (212) or power FET has a reference switch (213) or FET, a first comparator (218), a current source I.sub.CL, control circuitry (209), and a clamping circuit (238). The reference FET (213) is smaller than the power FET (212). The first comparator compares the voltage drop across the power FET (212) and compares it with the voltage drop across the reference FET (213) and produces a signal COMPOUT which initiates the turn-off of the power FET (212) if the voltage drop across the power FET (212), caused by a load current flowing through it, is greater than or equal to the reference FET voltage drop induced by I.sub.CL. The clamp circuit (238), having diodes (D.sub.1, D.sub.2) and a tracking current source I'.sub.CL, disconnects the FETS (212, 213) from the comparator (218) when they are OFF. The circuit (200, 300, 400) may also have a second comparator (250) which protects the power switch (212) from a short circuit condition in the circuit (200, 300, 400).

REFERENCES:
patent: 4021701 (1977-05-01), Davies
patent: 4441136 (1984-04-01), Hampshire
patent: 4703390 (1987-10-01), Fay et al.
patent: 4819117 (1989-04-01), Brennan
A 30A 30V DMOS Motor Controller and Driver, I.E.E.E. International Solid State Circuits Conference, Digest of Technical Papers, pp. 192-193 and 365-366 (Feb. 18, 1988).

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