Low-Cost Voltage Regulated Circuit Design

I need a compact, low-cost circuit that automatically cuts off power when the supply voltage drops below 3.3V. The input voltage will range from 4V to 3.3V, and no additional or separate battery can be used — the circuit must work entirely from the same power source.

Requirements:

The circuit should completely turn off the output when the voltage falls below 3.3V — no dimming or gradual drop should occur; it must be either fully ON or fully OFF.

It should automatically turn back on when voltage rises above 3.3V (a small hysteresis is acceptable).

The entire circuit should cost around ₹30 or less.

Must use easily available components in India (transistors, MOSFETs, zener diodes, etc. — avoid costly or rare ICs).

Should work reliably with an input voltage up to 4V.

No extra power source or battery is allowed — it must run directly off the same 4V–3.3V supply.

Designed for low-current loads (you can specify, e.g., under 500 mA).

Should be simple, compact, and efficient.

Deliverables:

Circuit schematic

Component list with approximate cost

Short explanation of circuit operation