Add Hysteresis to Window Comparator Circuit

[ghassan]

Hello,

I am unable to build a stable window comparator that accepts input voltage from 21 Volts DC till 30 Volts DC.

SO i think if the HYS was at 1V then it would fix the situation better.

When i add a capacitor 1uF or greater at the drain pin of "M2" , things get crazier .

Label "main_vin" without "R9":



I would like to build a window comparator similar to this IC http://cds.linear.com/docs/en/datasheet/4418f.pdf



Do you think it is safe to use a zener diode 6.2v as a regaulator from 24v supply or 30 vdc or greater!!! ?

I am looking for a fast start regualtor that is why i thought of using a zener diode . Your recommendation is appreciated.

By the way , resistor "R_MON1" or "R_MON2" shows that each comparator is dissipating continuous 16 mA which is bad for a battery .

Is there a fast comparator with low power dissipation ?

I appreciate your help.

[ghassan]

How to add hysteresis 1V ?

[danadak]

These might help -

https://www.maximintegrated.com/en/app-notes/index.mvp/id/3616

http://www.ti.com/lit/ug/tidu020a/tidu020a.pdf


https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-071j-introduction-to-electronics-signals-and-measurement-spring-2006/lecture-notes/24_op_amps3.pdf


Calc tool - http://sim.okawa-denshi.jp/en/compkeisan.htm



Regards, Dana.

[macboy]

Comparator U2 already have hysteresis, via R9 and R12, which provide feedback to the positive inputs. You can adjust those resistors to change the hysteresis (smaller R = more delta V).

Why label node main_Vin at two points in the circuit, instead of drawing the short connection between them? This makes it hard to read the schematic, because it is unusual and unexpected on such a small schematic.

[ghassan]

I have a problem and I would like it to get fixed . Zener Diodes D1 and D4 are acting as regulators and their output voltages raises when the input voltage at main power supply changes which is causing voltage references to change.

Is there any better solution with fast and stable regulation ?.

Do you prefer to use High Voltage Comparator instead of using 5v comparator since my power supply would be changing from 20VDC till 30VDC .

Your help is highly appreciated

[macboy]

Zener voltage always varies a little bit with changing current. You can try to pre-regulate with another zener stage before the 6.2 V one. Make the first stage, say, 12 V. This will vary a little bit too, but much less than the 20 to 30 V input voltage. This should provide a more stable input to the 6.2 V stage, which will then have a more stable output.