Current sensor circuit inquiry?

hau30729

Current sensor circuit inquiry? [Copy link]

This is the current monitoring circuit seen when disassembling the Power on the computer host.

The questions are as follows:
(i) What is the possible purpose of this part of the LT431 circuit?
(ii) The reference circuit given in SPEC has a resistor at C29. What is the purpose of replacing it with a capacitor?

FP130A.pdf (314.4 KB, downloads: 11)

2019-12-20 09:40 上传

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文博东南

1.TL431 should be used as a comparator.

2. Here FP130A is directly used as a differential amplifier, and the capacitor has a simple filtering function.

hau30729

Wenbo Southeast published on 2019-12-29 20:55 1. TL431 should be used as a comparator. 2. FP130A is directly used as a differential amplifier, and the capacitor is a simple filter.

Comparator? Could you please tell me the operating principle?

文博东南

hau30729 posted on 2020-1-3 09:09 Comparator? Can you tell me the principle of operation?

For details, please refer to the manual. The 431 will compare the input of pin 2 with the internal 2.5V reference, and then control the current flowing from pin 3 to pin 1. In this case, if the voltage of pin 2 is greater than 2.5V, transistor Q1 will turn on.

hau30729

Wenbo Southeast published on 2020-1-3 19:09 For details, you can look at the manual. 431 will compare the input of pin 2 with the internal 2.5V reference, and then control the current flowing from pin 3 to pin 1. Here it is equivalent to if...

Got it, thanks.