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SCR over-current protection circuit with the Hall components

2016-09-11 03:50  
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SCR over-current protection circuit with the Hall components
SCR over-current protection circuit with the Hall components
Related components PDF download: ULN302067L070 Here we introduce one kind of SCR over-current protection circuit that uses the Hall components as the sensor, it has the overheat protection function and the sound and light alarm function. The principle circuit is as shown in figure 1. The IC1 and IC2 are the Hall integrated circuit ULN3020, in the normal operation, their output port pins always have the low level voltage, D2 and D3 close, the SCR T1 is in the shutdown state, LED L4 does not light, the positive power supply form a loop through the R6, L1, IC4, R5, VT and the ground, if the base port of the control switch transistor VT has the high level voltage, it is in the conduction-status to open the zero-crossing trigger IC4 and also to trigger the two-way silicon T3, the load RL gets the power to work, their current will generate an alternating magnetic field in the magnetic circuit, if the peak value of the magnetic field intensity does not reach the two hall components' opening magnetic field strength, IC1 and IC2 will be maintained the original state.