What is the difference between a transformer and LED Driver / Power Supply.
In the good old days, a transformer was a very heavy mechanical devise which basically had a great big hunk of metal and a whole lot of wires around it. The problem was, as the load (measuered in Amps) was increased, the Voltage dropped. Its all about a principle known as ohms law. – You can google it, but suffice to say that LEDs are very sensitive to changes in voltage.
So, someone came up with the concept of regulating the voltage (or keeping it within a specific band. Most LED Drivers have a + or – next to the output voltage description on the cover. It might say 12VDC +/- 0.5Volts.
The beauty is that its all done electronically, so while the circuitry inside is quite complicated and impressive to the average person, its also very light, and compact.
So what happens if the Current draw exceeds the control limitations of the Driver. Its simple- The Driver switches itself off, rather than damage the LEDs. That is why when the circuit is overloaded- short circuit or or too many LEDs, they flash. The Driver is simply switching off, and as soon as the load drops, it switches back on.
Sound simple? It is, but there are a few other factors that need to be understood. The main one is heat. As a by-product of working, LEDs produce light- Lots of it, but they also produce heat (as a by-product). When you introduce heat to a circuit, the resistance rises (ohms law again) and it takes more Amps to work, so it is possible to cause the Driver to be overloaded, ONLY when hot. This is why we NEVER install a Driver at the same capacity to the load. Here at Sasign- we work to a rule of 80-85% maximum, and will match any LED sale to the correct driver and they do get hot. Very hot. Too hot to hold hot. Some work as high as 60 degrees C.
(Your homes hot water is regulated at 50 degrees)
Features to look for
The first thing to look for is the ERAC compliance tick, or SAA (Standards Australia) compliance logo. ERAC is the new over riding authority and now SAA, does compliance, along with other organisations.
If there is a fire, or electrical fault, and caused by your Driver, the starting point of any investigation will be, who supplied and installed it, and did it comply.
And you will find plenty of non complianced units on the internet. If you import, purchase, supply or install, you will be responsible. My advice- Pay a little more and purchase ONLY from a reputable supplier, who has either done the compliancing themselves, or sited the compliance certificates, like Sasign International
The next most important aspect that needs to be taken in to account when you purchase is its IP Rating- Is it a waterproof LED driver or not? If its going to be located anywhere where it can be exposed to water, it must be. You can find various ratings, but we only stock IP67 rated waterproof units. The unit itself can be emersed in water, and are still safe, so they are Ideal for lighting projects.
- Full protection against dust and other particulates, including a vacuum seal, tested against continuous airflow.
- Protection against full immersion for up to 30 minutes at depths between 15 cm and 1 metre (limited ingress permitted with no harmful effects).
There are various acromyns used to describe specific features, and for our purposed, the two that we tend to want are its efficiency and PWM.
All of our units run at @ 90 percent effciency. Yes, you can get better, but for a small increase you will likely pay a significant increase in price.
Pulse Width Modulation PWM is a process which improves the efficiency, by smoothing the on/off (data signal) back to analoge signal.
When would we notice this in a practical sense. When we use a dimmer. The dimming is much smoother. So, again, Unless this is a specific requirement, you can save some money by despensing with this improvement in operation.
I hope this has been an intersting read and of course, if you want buy at the right price, for a matched driver to your needs, call us at 07 5564 9930, or email us: firstname.lastname@example.org