G9 LED capsules in series

Thread Starter

Bhope691

Joined Oct 24, 2016
38
I have a simple circuit which comprises 10 G9 LED capsules in series connected to a power source. Each capsule is made up of the following circuit:

1617899719359.png

Each LED dissipates approx. 0.45W for a total power dissipation of approx. 4.5W. Total voltage drop across all the LEDs is 1619V using 2.8mA.

Can I create a circuit which combines all the LEDs together so I have one circuit (rather than the 10 LED mini circuits) that dissipates the 4.5W when a simple resistive load is attached rather than the LED chips? If so how and what would that circuit look like?
 

Ian0

Joined Aug 7, 2020
1,577
So the total current in the LED string is 33mA
The total voltage drop across the LEDs is about 18V
That makes the dissipation in the LEDs is about 600mW for each lamp.
The capacitor acts as a series impedance of about 6.8k
You can put more LEDs in series with the ones that are already there. The current will decrease a little.
You probably can't get 10 lots in series, but it may work with four or five.
 

DickCappels

Joined Aug 21, 2008
7,157
Just a quick note: It might save you some grief (damaged components) if you add some resistance, perhaps in the form of a fusible resistor in series with the AC line. That way if you happen to plug your light into the outlet during a peak in the AC cycle the current to initially charge the capacitors will be limited by the resistance.

You really need some sort of fuse in that thing which is why I mentioned a fusible resistor.
 

Ian0

Joined Aug 7, 2020
1,577
The presence of the fusible resistor makes the difference between the good ones and the ones that can burn your house down. Also, make sure it's a suitable capacitor - Class X with enough current rating. Don't try it with one rated 250V or 400V DC
 

Thread Starter

Bhope691

Joined Oct 24, 2016
38
Thanks for the replies, but I am actually after the answer to a different question.

Is it possible to combine the 10 LED capsule circuits so it is one circuit, which is equivalent to the 10 circuits, and what would it look like?
 

Yaakov

Joined Jan 27, 2019
2,362
Thanks for the replies, but I am actually after the answer to a different question.

Is it possible to combine the 10 LED capsule circuits so it is one circuit, which is equivalent to the 10 circuits, and what would it look like?
What do you mean by “one circuit” and “ten circuits”?
 

Ian0

Joined Aug 7, 2020
1,577
Thanks for the replies, but I am actually after the answer to a different question.

Is it possible to combine the 10 LED capsule circuits so it is one circuit, which is equivalent to the 10 circuits, and what would it look like?
You can put more LEDs in series with the ones that are already there. The current will decrease a little.
You probably can't get 10 lots in series, but it may work with four or five.
You could also put two strings in parallel, but you would need twice the capacitance, or otherwise you would get half the brightness.
 

Thread Starter

Bhope691

Joined Oct 24, 2016
38
What is "one circuit"?
A circuit that is the equivalent to the "ten circuits". So rather than using 10 LEDs I can use this "one circuit" which would act like I have 10 LEDs connected in series.

But I can use a simple resistive load rather than the LED chips as a load.
 

Yaakov

Joined Jan 27, 2019
2,362
A circuit that is the equivalent to the "ten circuits". So rather than using 10 LEDs I can use this "one circuit" which would act like I have 10 LEDs connected in series.

But I can use a simple resistive load rather than the LED chips as a load.
It is very hard to understand this description. Do you want to know the equivalent resistance of the all the LED lamps combined? Keep in mind that LEDs are not linear with respect to current vs. voltage so a resistor can't really substitute as a load for the full range of applied voltages.
 

Thread Starter

Bhope691

Joined Oct 24, 2016
38
Hopefully this is a little more clear.

I have 10 G9 LED capsules connected in series, where each capsule has the circuit in the OP. So essentially the whole circuit looks like:

Figure 1

Where the V's are the voltage drops across each diode. (i.e V1 - V2, V3 - V4 etc we neglect the voltage drop across all the other components). As an example V1 = 1600, V2 = 1440V. Each LED drops approx, 160V (so V1 - V2 = 160, V3 - V4 = 160 etc upto V19 - V20 = 160V.) V1 = 1600, V20 = 0.

What I am looking for is a circuit that (potentially? - is it possible?) looks like:

Figure 2

Where V1 - V20 is the same value as the V1 - V20 in the first image. i.e V1 = 1600, V20 = 0.
 

Thread Starter

Bhope691

Joined Oct 24, 2016
38
See post #2
Ok thanks, I get it now.

Yes, but why? If you want the same power then there won't be any significant saving of space.
I wan't the power source to supply that amount of power. I can't replicate that amount of power with just a resistive load. I can only replicate that power output with the LED capsules. So I wanted to see if there was a specific circuit I could make (with my very limited electronics experience) that could draw that amount of power from the source.
 

Alec_t

Joined Sep 17, 2013
11,981
I can't replicate that amount of power with just a resistive load.
You could. But to do it safely it would be better to use a step-down transformer (to provide mains isolation) with a 4.5W resistive load. To get 4.5W from the LED bulbs they could simply be connected in parallel: not series.
 
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