Patent ID: 9739810
Date: 2017-08-22
CPC Classifications: G01R,H02M

Claim:
1. A circuit configured to measure a pulsed current through a pass transistor of a switching circuit in order to detect, independently of frequency and percentage of a duty cycle driving the switching circuit, if the current through the pass transistor has reached a threshold value, comprising: the pass transistor connected between a supply voltage and a load; a node for a reference voltage; and a circuit capable of comparing the reference voltage with a first voltage representing the pulsed current through the pass transistor during a first phase of the duty cycle of the switching circuit driving the switching circuit, while the pass transistor is ON, and of substituting the first voltage by the reference voltage during the remaining part of the duty cycle driving the switching circuit while the pass transistor is OFF, wherein the comparison detects independently of frequency and percentage of the duty cycle if an average current through the pass transistor has reached one or more threshold values over the duty cycle; wherein the circuit capable of comparing the reference voltage with a voltage representing the pulsed current through the pass transistor further comprises: a sense transistor connected between a supply voltage and a current source wherein the node for the reference voltage is deployed between the sense transistor and the current source and wherein the node for the reference voltage is connected to a second terminal of a second switch and to a second input of a comparator, wherein the sense transistor is matched to the pass transistor; said current source connected between ground and said sense transistor; a first switch, wherein a first terminal of the switch is connected to the load of the pass transistor and a second terminal of the switch is connected to a first input of the comparator and to a first terminal of the second switch; said second switch; and said comparator wherein its output is used to detect if the current through the pass transistor has reached a threshold; wherein the first switch is closed and the second switch is open during ON-time of the pass transistor and vice versa the first switch is open and the second switch is closed during OFF-time of the pass transistor.