Do CCFL Inverters Prevent Short Circuits and Limit Current Effectively?

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Discussion Overview

The discussion revolves around the functionality of CCFL (Cold Cathode Fluorescent Lamp) inverters, specifically whether they can prevent short circuits and effectively limit current. Participants explore the behavior of CCFL tubes when lit, the design of inverters, and their applicability to non-CCFL loads.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that while CCFL tubes do not become short circuits when lit, their resistance decreases significantly, which can affect current flow.
  • Others argue that the efficiency of CCFL driver circuits varies, with modern circuits designed for higher power applications being more efficient than older designs.
  • A participant notes that CCFL tubes require high voltage to ionize and operate, and that inverters typically use a series impedance to limit current, which may not provide effective short circuit protection.
  • One participant expresses uncertainty about using a CCFL inverter with a non-CCFL load that has a constant resistance of 50 ohms, questioning whether the inverter will function properly under these conditions.
  • Another participant seeks clarification on the specifics of the load and the desired voltage across it, indicating a need for more context regarding the application of the CCFL inverter.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether CCFL inverters can effectively limit current or prevent short circuits, and there are multiple competing views regarding their design and application to different types of loads.

Contextual Notes

Participants mention various factors that influence the performance of CCFL inverters, such as the geometry of the light, gases used, ambient temperature, and drive voltage. There are also unresolved questions about the implications of using a CCFL inverter with a low impedance load.

Who May Find This Useful

Individuals interested in the technical aspects of CCFL inverters, their applications in different load scenarios, and those exploring the behavior of electrical components under varying conditions may find this discussion relevant.

hobbs125
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1. When the CCFL tube lights up does it become a short circuit?

2. Are all CCFL inverters short circuit current limited?


Thanks for the help!
 
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They aren't a short circuit but the resistance certainly goes down when lit (they're practically an open circuit when dark). How much the resistance drops depends on the geometry of the light, gases used, ambient temperature, and drive voltage and duty cycle. Some CCFL driver circuits that drive small (low power) devices are not necessarily designed for efficiency, but modern circuits that drive higher power CCFL lights can be quite efficient, like the circuit that drives the backlight on a modern LCD computer screen. I doubt there are many that have good short circuit protection since many CCFL lights are unlikely to short. I wouldn't rely on it!
 
The ccfl tube typically requires a fairly high voltage, i.e. a thousand volts, to become ionized. Afterwards, it operates at some few hundreds of volts.
To achieve this operation efficiently, the inverters are designed to have an open circuit voltage sufficient to "fire" the tube. Then, a series impedance, typically a small, high voltage capacitor, limits the operating current.
Since the capacitor is a reactive load (not a resistor), it doesn't consume much power in serving it's function, and the circuit remains efficient.

Mike
 
hobbs125 said:
1. When the CCFL tube lights up does it become a short circuit?

2. Are all CCFL inverters short circuit current limited?


Thanks for the help!

Hi hobbs,

What is the context of the question?
 
I am wanting to use a ccfl inverter for something other than a ccfl which has a constant resistance of about 50 ohms. I'm not sure if the ccfl inverter will work with such a low impedance load. I know the inverter puts out a higher voltage at first then it drops. I'm just not sure if the inverter will work when it starts out with a low impedance load?
 
Last edited:
hobbs125 said:
I am wanting to use a ccfl inverter for something other than a ccfl which has a constant resistance of about 50 ohms. I'm not sure if the ccfl inverter will work with such a low impedance load. I know the inverter puts out a higher voltage at first then it drops. I'm just not sure if the inverter will work when it starts out with a low impedance load?

What is the load? What voltage do you want to put across the load? Why do you want to use a CCFL inverter?
 
The load is a resistive load, no reactance, 50 ohms. I want a high voltage across it of at least 500v.
 

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