Timeline for Understanding current sense circuit
Current License: CC BY-SA 4.0
7 events
| when toggle format | what | by | license | comment | |
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| Feb 21 at 12:59 | vote | accept | Malte | ||
| Feb 13 at 15:22 | comment | added | Pete W | also note, your circuit has the "output" of the balance, which comes is the V at the top of R5, going into a PNP ... so it's all different after that. | |
| Feb 13 at 15:15 | comment | added | Pete W | @Malte - you can tune using the 30ohm. The 10k can in principle also be used, but that one should really be just to set the bias current (and thus power consumption. So it's probably easier to leave all those alone, and use the 30ohm. The turn-off condition is when the Vbe of Q3 falls below some nominal value, like maybe 450mV. (depends on what the output is going into of course, and Q3 temperature etc). Take a look at the links Tim Williams added in the comments, I think some of them have formulas. | |
| Feb 13 at 8:32 | comment | added | Malte | Thank you very much Pete, that already helps quite a bit. A few more questions if I may: - How would I set the balance point current in this circuit? Do I change the 10k resistor below Q1? And how can I calculate the resistance value for a given current. - How does the value of my sense resistor play into this, does it need to be selected to a certain max voltage drop for my maximum load current? If so, how does that correlate to the other resistance values in the circuit In general I'm trying to get a bit more of a mathematical understanding of how to size this circuit. | |
| Feb 12 at 21:47 | history | edited | Pete W | CC BY-SA 4.0 |
added 249 characters in body
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| Feb 12 at 21:37 | history | edited | Pete W | CC BY-SA 4.0 |
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| Feb 12 at 21:27 | history | answered | Pete W | CC BY-SA 4.0 |