LED Lamp or Bulb with Flashlight option
This is another LED lamp from China, these people make nice lamps and also good designs of the plastic enclosure. Here by a clever enclosure design it is both a emergency mains bulb and Torch/Flashlight.
The price is low and they use a small sealed lead-acid battery worth 4.5 V and around 1 AHr. That means it could give an hour of performance at 1 A drain/usage. The voltage by the elapsed hour could be near 4. Here the battery failed, vibration or leakage; OR combination of both. The acid, very little or even corrosive vapor has eaten the copper wire of positive wire/junction. The Cut Red wire, broke circuit equilibrium and burnt the R? = 3.3K – 4.7k ?. The lamp failed all other parts intact.How it works ?
It uses a step-down cap, this is very tricky. It has to be a HV cap overrated and excellent quality. These caps not good enough. I am partially responsible for this cap idea spreading around. It was decades ago in relation to bringing down the cost of industrial. automation timers. The transformer had to go and smps solution too much; a resistor inefficient. I was triggered by the choke used in tubelights to bring down voltage after firing. So if L can be used, then even C for low currents, no heat wasted. The timer worked, successful sales. Idea/Concept became popular. This idea also misused by others to save cost. This design needs an Axial Polycarbonate/Polypropylene 630V/1KV cap for reliable operation.
Now this 18 LED array, has no current limit, is it not quite a problem. The chinese are innovative on saving cost, here its fine, but.many times we can sacrifice quality. In this design the LEDs drop around 3.3V and the Transistor 1 Volt as it is not driven to saturation. On full load the battery also deregulates, so it does manage to save itself. This transistor also serves as a mains detector along with the 1N4148. On mains failure the LED lamp turns on Automatically.
Another Lamp had a Burst out 100uF cap this means, surges or spikes are damaging the 1uF 400V Plastic cap used for current limit.
Recommendations to such Lamp Designers
Use Metalized Polypropylene MPP – rated for 440V AC continuous working. That means it must be rated like a Power Factor correction/saving capacitor. It may mean 1KV DC operation.
- Use an Axial 1uF polypropylene 630V DC or 440V AC Capacitor
- Sell it with a Marketing Advantage as Power Factor Compensation.
- Use two 2.2uF 630V DC Axial MPP, one on Live and the other on Neutral.
A house using Motors and Fans will have inductive elements, even tubelights that have chokes 50/60 Hz kind. This is compensated by capacitive loads. So each of these Capacitor LED lamps can be a Green Lighting and PF compensator.