| Electronics > Beginners |
| Foldback Current Limiting - an example |
| (1/1) |
| iMo:
Here is a small simulation with calculation of the resistors for a Foldback Current Limiting. Normally the current limiting with LM723 (or any other PSU with same current limiting wiring) works such the current flowing through the shorted output is aprox. I_limit = 0.7V/R_shunt With the Foldback Current Limiting the current during short is much lower, call it I_short. Thus we have I_limit and I_short. After the output current approaches I_limit, it starts to drop down to I_short. In the below example the I_short is aprox. 5x smaller than the I_limit. Below is, as an example, a simulation with an LM723 and the calculation. To find the right values is not straightforward, however. The Rshunt is a much higher value as you would expect, and the both currents depend on the Rshunt value and R4/R5 ratio as well. Excel sheet with the goal seeker is something which may help. The simulation shows the calculation fits pretty well, with larger deviations when k < 0.8 .. --- Code: --- I_limit I_short Calc: 41mA 8.5mA Sim: 39mA 8.7mA --- End code --- More on how it works here: http://www.eeeguide.com/foldback-current-limiting/ |
| ledtester:
FWIW, this lecture on the topic might also be helpful: |
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