Capacitive Power Supply For Led

How to calculate and deduce current voltage parameters in transformerless power supplies.

Capacitive power supply for led.

However with a capacitive type of power supply having peculiar features and with leds connected to it calculating current voltage drop and led resistor becomes a bit confusing. But it can be any load an electric motor a toaster an oven. Leds have a very steep voltage current relationship a small change in voltage can result in a very large change in current so much so that a common first approximation of a led is a component that maintains a fixed voltage for any forward current. Small changes in conditions either voltage of the power supply or temperature of the load result in small changes in the current.

For this project we chose to power an led. As per the required output voltage a suitable 0 5 watt zener diode used in this transformer power supply circuit. In the capacitive circuit c1 is labelled 225k 400v. The following transformerless or capacitive power supply circuit could be used as an led lamp circuit for illuminating minor led circuits safely such as small led bulbs or led string lights.

Led and the load. A 3mm red led used as a power on indicator and 1k 0 25 watt resistor protects the led. If an led peak current of 350 madc is required the sense resistor is calculated to be 3 6. 225k means 2 200 000 picofarad or 2 2 microfarad.

The wikipedia page also contains a photo of an led bulb with what to all appearances seems to be a capacitive supply. The idea was requested by mr. If we used a 2000µf it could power the led for double the time being that it can store more charge and if we used a 4000µf it could power the led for 4 times longer being that it has quadruple the charge capacity. There is no reference given as to who s led bulb this is but the text mentions a 1 2 uf capacitor providing 90 ma powering 48 white leds apparently divided into four branches of 12 that each use 20 ma.

These types of supplies are accepted by regulatory agencies provided the product is sealed and the consumer can not touch any connections. I already posted about transformerless power supplies in the article transformerless dc power supply here we will see how to design a capacitor dropper power supply. Capacitive transformer less power supply circuit diagram. Capacitive drop capacitive drop supplies have been used in many consumer products such as smoke detectors.

Capacitor power supplies are simple low cost and light weight solution for providing dc supplies to circuits which require low currents. The power supply is a very simple capacitive dropper that is extremely common on led lamps that use an array of ordinary 20ma style leds. Some of the power ratings of components in both capacitive and resistive circuits are too low.