I am working on a LED (3 V/20 mA) torch circuit powered by 3.7 V/1000 mAh Lithium battery. Am planning to add discharge protection feature to this circuit. If battery voltage go down to 3.3 V the torch should cease operation. However I can not figure out how to do that. I have come across some circuits where they have used a 3.3 V zener diode and a transistor to turn the intended load on. However I couldn't validate the working of this circuit.
I tried simulations using circuit lab but voltage across zener is dropping after connecting to transistor base. Need help in figuring out this circuit. I have added a lamp with resistance of 25 ohms to simulate 7 LED's connecting in parallel in the below circuit. Any help will be much appreciated?