In this post we learn about a special circuit which can illuminate 24 high bright white LEDs from a single 9V PP3 battery, let's unravel the secret behind this amazing circuit.
Nine volt cells as the rating suggest, provides 9 volt output, but what about the current? A 9 volt PP3 battery will not provide more than 400 mAH of current,meaning any load consuming 400 mAH would last for 1 hour, well that's with an ideal battery, normally it would last not more than 20 minutes, and the battery would get flat.
How to illuminate 24 LEDs from a 9V Battery
Lighting white LEDs from a 9volt PP3 battery might look interesting but only as long the number of LEDs is below 10....and don't expect the battery to last more than an hour.
Imagine illuminating 24 high efficiency white LEDs with a couple 9 volt batteries and making it last for almost a day, now that's something that might intrigue you.
This become feasible only when a boost circuit, based on PWM is employed.
The present circuit is based exactly on the above principle, and thus it becomes feasible to keep 24 high bright LEDs lit from just two ordinary 9 volt batteries for almost a day.
The shown circuit for illuminating 24 white LEDs from two 9 volt batteries, utilizes the IC ZXSC400 from ZETEX which functions as a boost converter circuit and generates as high as 70 volts from a source of 18 volts.
The input of 18 volts to the circuit is derived by putting two 9 volt batteries in series.
D1 is a schotky diode having a high switching rate.
An externally applied PWM pulse input to the IC is used for controlling the brightness of the LEDs and thus helps in saving power.