The increased number of complaints from the readers regarding burning LEDs associated with my earlier posted transformerless 1 watt LED driver circuit, compelled me to solve the issue once for all. The power supply section of the circuit discussed here remains exactly identical to the previous configuration, except the inclusion of the "switch ON delay feature" which has been exclusively designed by me and added in the circuit for rectifying the burning LED problem (hopefully).The complaints that I kept on receiving were undoubtedly because of the initial switch ON surge which kept destroying the 1 watt LEDs connected at the output of the circuit.
The above problem is pretty common with all capacitive type of power supply, and the problems has created a lot of bad reputation to these types of power supplies.
Therefore normally many hobbyists and even engineers opt for lower values capacitors fearing the above consequence in case larger value capacitors are included.
However as far as I think, capacitive transformerless power supplies are superb cheap and compact AC to DC adapter circuits which requires little effort to build.
If the switch ON surge is tackled appropriately, these circuits would become spotless and could be used without the fear of any damage to the output load, especially an LED.
During switch ONs, the capacitor quite acts like a short for a few microseconds until it gets charged and only then it introduces the required reactance to the connected circuit so that the appropriate amount of current only reaches the circuit.
However the initial few micro second short condition across the capacitor inflicts huge surge to the connected vulnerable circuit and is sometimes enough for destroying the accompanied load.
The above situation can be effectively checked if the connected load is inhibited from responding to the initial switch-ON shock, or in other words we can eliminate the initial surge by keeping the load switched OFF until the safe period is reached.
This can be very easily achieved by adding a delay feature to the circuit. And that's exactly what I have included in this proposed surge protected hi-watt LED driver circuit.
The figure shows as usual an input capacitor, followed by a bridge rectifier, until here everything's pretty common capacitive power supply.
The next stage which includes the two 10 K resistors, two capacitors, transistor and the zener diode form the parts of the important delay timer circuit.
When power is switched ON, the two resistors and the capacitors restricts the transistor from conducting until both the capacitors get fully charged and allows the biasing voltage to reach the transistor base, illuminating the connected LED after a delay of about 2 seconds.
The zener is also responsible for prolonging the delay for two seconds.
The 1N4007 diode across one of rhe 10K resistors and the100 K resistor across one of the 470uF capacitors helps the capacitors discharge freely once the power is switched OFF so that the cycle can repeat enforcing the surge protection into action on each occasion.
More number of LEDs may be connected in series for increasing the power output, however the number may not exceed 25nos.
Therefore normally many hobbyists and even engineers opt for lower values capacitors fearing the above consequence in case larger value capacitors are included.
However as far as I think, capacitive transformerless power supplies are superb cheap and compact AC to DC adapter circuits which requires little effort to build.
If the switch ON surge is tackled appropriately, these circuits would become spotless and could be used without the fear of any damage to the output load, especially an LED.
During switch ONs, the capacitor quite acts like a short for a few microseconds until it gets charged and only then it introduces the required reactance to the connected circuit so that the appropriate amount of current only reaches the circuit.
However the initial few micro second short condition across the capacitor inflicts huge surge to the connected vulnerable circuit and is sometimes enough for destroying the accompanied load.
The above situation can be effectively checked if the connected load is inhibited from responding to the initial switch-ON shock, or in other words we can eliminate the initial surge by keeping the load switched OFF until the safe period is reached.
This can be very easily achieved by adding a delay feature to the circuit. And that's exactly what I have included in this proposed surge protected hi-watt LED driver circuit.
The figure shows as usual an input capacitor, followed by a bridge rectifier, until here everything's pretty common capacitive power supply.
The next stage which includes the two 10 K resistors, two capacitors, transistor and the zener diode form the parts of the important delay timer circuit.
When power is switched ON, the two resistors and the capacitors restricts the transistor from conducting until both the capacitors get fully charged and allows the biasing voltage to reach the transistor base, illuminating the connected LED after a delay of about 2 seconds.
The zener is also responsible for prolonging the delay for two seconds.
The 1N4007 diode across one of rhe 10K resistors and the100 K resistor across one of the 470uF capacitors helps the capacitors discharge freely once the power is switched OFF so that the cycle can repeat enforcing the surge protection into action on each occasion.
More number of LEDs may be connected in series for increasing the power output, however the number may not exceed 25nos.
can we connect only 2 or three 1 watt leds?
ReplyDeleteCan you use 10 watt LED @12volt or 100watt LED @32volt within this circuit?
ReplyDeleteckt is simple but powerfull. so I like this ckt.
ReplyDelete