Overcurrent protection circuit for low dropout linear voltage regulator

Abstract

The invention discloses an overcurrent protection circuit for a low dropout linear voltage regulator. The overcurrent protection circuit for the low dropout linear voltage regulator comprises a current sampling circuit, a current comparison circuit and an upward pull circuit, wherein the current sampling circuit samples gate-drain voltage of a power tube of the low dropout linear voltage regulator, and outputs a sampling current to the current comparison circuit, the current comparison circuit mirrors the sampling current through a current mirror, and then compares the sampling current with a current of a current source, and after output current value of the low dropout linear voltage regulator exceeds current protection threshold value, control voltage output by the current comparison circuit powers on the upward pull circuit, and the upward pull circuit pulls up gate end voltage of the power tube of the low dropout linear voltage regulator, and thereby limits increasing of the output current, and plays a part in overcurrent protection. The overcurrent protection circuit for the low dropout linear voltage regulator can effectively restrain channel length modulation effects of a current sampling tube in the current sampling circuit, decreases occurrence rate of the problem that deviation between value of the current sampled by the current sampling circuit and ideal value is overlarge, improves current sampling accuracy of the overcurrent protection circuit, and obtains accurate starting threshold value of the overcurrent protection circuit.

Description

technical field [0001] The invention belongs to the field of analog integrated circuit design, in particular to an overcurrent protection circuit for a low-dropout linear regulator LDO. Background technique [0002] With the advent of the information age, power management technology becomes more and more important. Low-dropout linear regulator LDO is more suitable for portable applications because of its small area, high power supply rejection ratio, micro power consumption, low noise, simple peripheral circuit, and good linear transient response and load transient response characteristics. in electronic products. [0003] When the load current is too large, especially when the output is short-circuited, since the output terminal is grounded, the power supply voltage is all added to both ends of the regulator tube, causing a large current to flow through the regulator tube. Low dropout linear regulator LDO regulator Very easily damaged. Therefore, in order to ensure the s...

AI Technical Summary

Problems solved by technology

When the current sampling tube M2 is connected to the low dropout linear regulator LDO power tube M P When the size of is taken according to a certain ratio, such as Even if the gate terminals of the two are connected so that their overdrive voltages are equal, if the drain-source voltage V of the two DS Due to the effect of channel length modulation, it can be seen from formula (1) that the currents flowing through the two are not mirrored according to the ratio of the set tube size, and the current sampled by the sampling tube M2 is the same as There is an error in the design value

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