Led circuit driver

There are also buck-boost drivers that take 5V for example as an input and can drive LED strands up to 20V. They tend to not be as efficient as a drop-down regulator, but it is still an option to consider. We have used an unusual method of driving LEDs with great success. It combines the linear drive and switch-mode drive to offer the benefits of both. It is especially useful when there are a lot of different LED colors. For example, say we have LEDs to drive at 1 amp each, with 5 different colors.

The input power supply is 24VDC, with separately controllable colors. Yes, this is an extreme example — both in the power required, and in the number of LEDs — but we recently designed a board similar to this!

An issue that arises with this approach is that at this high of power, switching drivers will only be able to drive a single strand each. That means we would require a lot of drivers on this board.

The more switching drivers on board, the more switch-mode noise produced. Splitting up the strands gives us:. While it is absolutely possible to drive them like that, it will require extensive filtering, ensuring no coupling of switch-mode noise on the power rails. For this project, a large heatsink would be on the back of the board.

While we wanted to limit the heat generated, we had some flexibility with our design. I would rather deal with the heat, than deal with 15 switchers! Driving all strands linearly from 24V would involve enormous amounts of power dissipation, more than would be possible, especially on the short strands. Good luck finding a standard resistor or linear driver to dissipate 19W of power! What we decided on was to first drive the long strands directly from the 24V rail with a linear drive using resistors.

Strands 1, 2, 4, 5, 7, 9, 10, 12, 13, 14, and 15 are all driven from 24V. Using sized resistors which can dissipate 2W each , CGS series , 3 1. One of these strands is shown below in figure 6. Strands 3, 6, 8, and 11 are left and are too short to drive directly from 24V.

What we did was use two switching buck regulators to drop down the 24V rail to a 6V and a 16V rail. The 16V rail directly drives strands 3 and 11 while the 6V rail drives 6 and 8.

Figure 7: A switching voltage regulator drops the voltage to 6V. Note the CLC filter on the input side, as well as the large amount of output capacitance.

This prevents the switch-mode noise from coupling to any of the other regulators. Figure 7 shows the switching regulator circuit to drop the 24V rail down to 6V. Make sure you know the minimum and maximum input voltages for your LED drivers. In finding what your input voltage should be for an application you can use this simple formula. This determines the minimum input voltage you need to provide. Now this helps us make sure the voltage works, but in order to find the right power supply we also need to find the wattage of the whole LED circuit.

The calculation for LED wattage is:. Overworking the power supply can cause the LEDs to flicker or cause premature failure of the power supply. Just calculate the cushion by multiplying the total wattage by 1. So for our above example we would want at least The closest common power supply size will be 25 watts so it would be within your best interest to get a 25 Watt Power supply with a 24 Volt output.

The FlexBlock LED drivers are boost drivers which means they can output a higher voltage than what is supplied to them. This is extremely helpful in applications where your input voltage is limited and you need to get. As with the BuckPuck driver , the maximum number of LEDs you can power with a single driver in-series is determined by dividing the maximum output voltage of the driver by the forward voltage of your LEDs.

The FlexBlock can be connected in two different configurations and varies when it comes to input voltage. You find the maximum output voltage of the driver in this mode with this formula:. Now with AC input drivers they give off a certain amount of watts to run so you need to find the wattage of your LEDs. You can do this by using this formula:. NOTE: It is important to consider the minimum output voltage of off-line drivers when designing your application.

For instance, the driver above has a minimum output of 15 volts. So now you should have a pretty good idea on what an LED driver is and on what you need to look for in selecting a driver with a power supply that is sufficient enough for your application.

I know there will still be questions and for that you can contact us here at or sales LEDsupply. We also have this Driver Selector tool that helps calculate what driver would be best by inputting your circuit specs. If your application requires custom size and output, please contact LEDdynamics. Thanks for following along and I hope this post helps all those wondering what LED drivers are all about.

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Im looking for 30 meters of led strip with dimmable drivers to 24 volt in warm white can you suggest. So do you need a just one continuous piece that is 30 meters long? They require only about. Thus, I want to drive 50 parallel strings of 10 using a meanwell driver rated at about 40 watts?

I use the figures from this table in several projects, so here i'm just putting them all in one place that i can reference easily.

Why not just connect your battery straight to the LED? It seems so simple! What's the problem? Can I ever do it? So when you just connect your LED to a battery you have little idea how much current is going through it. So maybe you read all that, and you're thinking: "so what!

This is by far the most widely used method to power LED's. Just connect a resistor in series with your LED s. How to do it: There are a lot of great web pages out there already explaining this method. I used one of these in my power-led headlamp project and was quite happy with it. The first set of circuits are all small variations on a super-simple constant-current source. Simplest version first: "Low Cost Constant Current Source 1" This circuit is featured in my simple power-led light project.

How does it work? Q2 starts out turned on by R1. When too much current flows through R3, Q1 will start to turn on, which starts turning off Q2. So we've created a "feedback loop", which continuously monitors the LED current and keeps it exactly at the set point at all times. Any excess power is burned in Q2. Thus for maximum efficiency, we want to configure our LED string so that it is close to the power supply voltage.

It will work fine if we don't do this, we'll just waste power. Calculations: - LED current is approximately equal to: 0. Q2 limits the circuit in two ways: 1 power dissipation. Q2 acts as a variable resistor, stepping down the voltage from the power supply to match the need of the LED's. Now what? This circuit lets you have an adjustable-brightness, but without using a microcontroller. It's fully analog! The main difference is that the NFET is replaced with a voltage regulator. The current-limit circuit works the same way as before, in this case it reduces the resistance across R2, lowering the output of the voltage regulator.

This circuit lets you set the voltage on the LED's to any value using a dial or slider, but it also limits the LED current as before so you can't turn the dial past the safe point. Compared to the previous "simple current source" using two transistors, this circuit has: - even fewer parts.

I'm embarrassed to say i did not think of this method myself, i learned of it when i disassembled a flashlight that had a high brightnesss LED inside it. Although simple, this method has some drawbacks: - Your driving voltage can only be slightly higher than the LED "on" voltage. This is because PTC fuses are not designed for getting rid of a lot of heat so you need to keep the dropped voltage across the PTC fairly low.

PTC fuses do not have a very accurate "trip" current. Typically they vary by a factor of 2 from the rated trip point. The only safe choice of PTC is a bit under-rated.

Connect in series with a PTC rated about mA.