active load circuit

Published:2011/5/24 5:15:00 Author:John | From:SeekIC

Q1 and Q2 constitute a Schmitt trigger. Constant current LED NSL4944 is regarded as load collector, providing output of 12V and 40mA. When the bulb is not conducting with Q2, most current of the light-emitting diode flows through the resistor with resistance of 100Ω. So the voltage in trigger circuit is limited to 2V. When the control signal saturates Q1, Q2 supplies the lamp with voltage of about 1V. Such plays a role of preheating and reducing voltage for starting. Q2 is conducted to light the bulb.



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