US 6,185,082 B2Granted

Protection circuit for a boost power converter

AssigneeSystem General Corp.

InventorTa-yung Yang

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Abstract

A protection circuit for a boost power converter provides input under-voltage protection and output over-voltage and over-current protection. The protection circuit includes a control power MOSFET connected in series between the ground of the boost power converter and the ground of the load. The arrangement of the circuit makes it easy to drive the gate of an N-channel power MOSFET and is ideal for current-limiting control, which utilizes the Rds-on of the MOSFET as a current sensing element. Neither a specific gate-driver nor a current sensing resistor is required, and thus high efficiency can be achieved. Furthermore, the slow slew-rate at the gate of the MOSFET provides a soft-start to the load. The protection circuit includes a temperature compensation circuitry to offset the variation of the Rds-on. A time delay circuit prevents the switching elements and protection elements from overload damage.

Claims7

Dependent claims

A protection circuit for a boost power converter comprising:

a transistor connected in series between a ground of said boost power converter and a ground of a load, said transistor having a source terminal, a drain terminal and a gate terminal, wherein the source terminal of said transistor is connected to the ground of said boost power converter, and the drain terminal of said transistor is connected to the ground of the load;
and
a control circuit having a first output coupled to the gate terminal of said transistor so as to shut-off said transistor, a second output coupled to a PWM controller of said boost power converter for current limiting, a first input coupled to the input of said boost power converter for sensing the input voltage of said boost power converter, and a second input coupled to the drain terminal of said transistor to sense a voltage drop across said transistor, wherein said voltage drop is produced by the current of the load to be protected and an on-state resistance, Rds-on, of said transistor.

Dependencies are inferred from the claim text.