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Self-initiated over-current protection control circuit using CH7555 and CD4013

Published on Apr 18 2011 // Protection Circuits

Self-initiated over-current protection control circuit using CH7555 and CD4013.

Shown for the self-initiated over-current protection control circuit. The circuit consists of sampling circuit BG1, RS flip-flop, one-shot (IC1, R2, C2 and IC2, R3, C3), D flip-flop and so on. When the sampling circuit is over the corresponding current flow after, BG1 saturated conduction, the RS flip-flop set. By the Q-side output high. The power level control device is disconnected. At the same time one-shot circuit IC1 (555) surface because ? pin is set low, the output pin high ? Pulse (t1 = 1.1R2C2) by reverse-phase, after a little delay added to the RS flip-flop, FF1 reset to restart the devices. Meanwhile IC2 pin 2 is low due to be set to generate one-shot delay (t2 = 1.1R3C3) pulse, the delay after the ICs are reset to IC3 to trigger monostable circuit IC1 becomes very narrow pulse .
  If the RS flip-flop in the reset period, still in the over-current condition, the FF1’s Q-side has remained high and continue to cut off the device. IC1 has been in a state set, and the FF1 of the R-side does not work. The control circuit of the phenomenon of over-current devices can not only cut off the power, and when returned to normal, but also start automatically, thus removing the trigger due to noise arising from the phenomenon of false power.