In the supermarket, LED bulbs have started coming with battery backup. Recently I saw Panasonic 9W LED Light which has battery backup for roughly 2 hours. As always, I was curious about what goes inside, so I bought a few to use in my home and one extra to open and see from within.
The packaging looks like as shown in the images below. It’s a 9W 6500K LED Bulb. Manufactured in Maharashtra by Virtuoso Optoelectronics Private Limited. Maybe they are OEMs who manufacture for Panasonic.
As mentioned, it has various protection like Over temperature, Short circuit, Over-voltage, deep discharge of the battery, etc.
Lets us see what is there in the circuit. We need to open the Bulb to see that.
Once you open the plastic cover, you will find Aluminum PCB with around 21 white LEDs soldered.
4 wires are coming from within, which you need to de-solder to get further inside.
A metal plate between the LED PCB and the circuit inside protects and isolates it from heat.
Once you remove that plate, you will see another PCB which contains the primary electronics. This PCB has an LED driver circuit, Battery charger/protection circuit.
Mains AC is fed using two wires connected to the LED base. The AC then goes to a series fuse resistor that protects from high voltage spikes along with MOV(the blue colour component).
Then it goes to the EMI filter section, which consists of two polyester capacitors and inductor.
After the EMI filter, AC goes to bridge rectifier MB10F, a 4-Pin 1000V DC, 800mA Bridge rectifier IC.
AC gets converted to DC and goes to the LED driver circuit, designed using Si9752 LED driver IC from Shenzhen SI Semiconductors.
It’s a constant current LED driver. It has an inbuilt active Power Factor Correction circuit. The MOSFETs are 600V rated.
Cycle-by-cycle current limit, over temperature, LED short and open protection is built in.
Other than LED driver IC, a separate Battery charger and protection IC is used. It’s a 5-pin device, I could not find the part number on the internet. But it mainly handles the 3.7V battery charging and protects from deep discharge.
The battery used is a 3.7V single-cell battery with 1800mAH capacity.
I hope you found this teardown useful and learned something new!
If you have any feedback about the blog, you can share it in the comments below or contact me directly.
Read more exciting articles on Embedded Systems Design.