High Power LED driver

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This scheme was manufactured powerful light-emitting diodes, up to 1500mA power supply.
The scheme was taken by the classical buck or step-down DC / DC converter with schematiką gryžtamuoju connection by the current.
The scheme used in the most economical and Lithuania stores (Evita lemon, RCL) received details.
Input voltage 10-30V.
The maximum output current of 1500mA and depends only on the temperature regime trazistoriaus Q1.

The scheme is based on the PWM controller UC3842. Instead of the chip without any changes in the scheme can be used to uc3843,1842,1843,2842,2843.
The minimum voltage at which can still work this chip is about 10V, maximum 30V.
In the light-emitting diodes flowing current is set with a resistor R 4. As this scheme is used gryžtamas connection according to current, the reference voltage is 1V, then R4 denomination is calculated simply: R 4 = 1 / Id where Id - the maximum allowed LED current.
Resistors R4 power of at least 0.5W.
Since the calculated R4 denomination tends to be non-standard, R 4 combined became shallow connecting multiple resistor, or produced from a larger piece of wire resistive available.
Instead of transistor Q1 scheme can be used in any of the series IRLZ24N, IRLZ34N, IRLZ44N.
After collecting scheme, instead of the LED mount Arrow ammeter, test incoming current. If the current is too high or too low, slightly adjusting resistor R4 denomination. After consistently ammeter needs of Architainment mount and re-check the flow, and if necessary, still adjusting to R4.
Came out, that is parallel to the LEDs can be additionally connected 100uFx16V capacitors, it is a little, causing a few mA current. If the current is normal, then it is not required.
LEDs connected in series in this scheme. In LEDs connected in series a voltage amount is less than the minimum 2-3V power supply voltage.
You can connect only one of LEDs, the scheme of work does not change.
The most expensive piece in this scheme is a inductive coil, but it can be the same suvinioti use any form of ferrite cores, winding wire for the thickness and then measuring the resulting inductance. Inductor size is not very critical, it is important to not only lower than 220uH.

Pictures made LED driver. 50x30mm PCB, surface mount.

Another scheme designed užmaitinti series connected LEDs with a total cumulative voltage exceeds the supply voltage. This used classical boost or step-up
DC / DC converter schematika pulsed with gryžtamuoju connection by the current.
Boost, or step-up converter is a little more difficult to produce and match, so the scheme is recommended for more experienced electronics enthusiasts.
A key element here which need to choose the right is the inductive coil, which is regarded as the maximum pulse current and pulse current should not exceed ferrite core saturation mode. Improper selection of the coil, the coil core work greatly to heat up or the scheme's effectiveness will be very small, ie the coil will flow through a large current.

Boost DC / DC converter efficiency, ie the efficiency is lower than the buck-type converters, so this type of converter is not widely used.
The most common type of such Boost converters are used when the LEDs current is up to 100mA and the voltage transformation ratio is 3-4.

This scheme was taken užmaitinti 10pcs series connected LEDs with the following parameters: 8mm, 300mA, 3,4V, 1W, but it can be used for any other parameter and varying the number of LEDs to feed.
As the power source in this case has been used 8 pcs AA 1,2V battery cells connected in series. However, you can use a lower or higher voltage power supply (acute - 8,6V), it is important only to the power supply voltage does not exceed the aggregate of all to gear LEDs tension.
However, it should be borne in mind that the reduction of the supply voltage can be difficult to achieve the desired through the diode current. Orentuotas possible by the fact that at a 10V power source, 300mA, already there is a limit, if it is connected in series 3,4V 10pcs LEDs. Which case a diode to reduce the number or selection of the electric LEDs or to increase the power supply voltage.

In the light-emitting diodes flowing current is determined by the current sensor, resistors R3, R4 aid, which, in order to increase the capacity to connect lygegrečiai. Total R 3, R 4 denomination is equal to 1 / Id where Id - the maximum allowed LED current. For example. in this case the current flows through the LEDs is 300mA required resistor 1 / 0.3 = 3.33 The om. Select two resistors after 6.8om by combining consistently get 3.4om.

Elements C1, R2 is set converter pulse frequency of 18kHz.

It is important to properly choose the inductive coil L2 denomination, which is quite critical and is too high or too low inductance, the scheme will not be able to generate the required power, ie the flowing current will be too low. Debugging time required to achieve a certain "resonance", that momentum could generate the required amount of energy.
Schema is both changing the number of turns L2 (inductance) and C 1 or R 2 denomination. C1 can be adjusted to between 2200pF 3200pF.
During commissioning, if the selection of the current down resistor R3, R4, it is possible immediately to connect the required number of LEDs. Just keep in mind that LEDs total working voltage must be greater than the power supply voltage.
Debugging during the diode is connected to measure the current dial A ammeter.
L2 can make their own, and wrapped the required number of turns on a simple rod or ring-shaped ferrite core, and coordination by increasing or reducing the number of turns. Number of coils and inductors here accurately calculate and disclose is impossible, because in each case may get very different results, and as was mentioned above, the inductive coil is preferably selected experimentally for debugging.
Debugging time needed to achieve that through the diodes passes the required maximum current.
As this diagram for simplicity, there is no protection against over-voltage, because then it would be a need for additional elements of the scheme, it is not recommended to combine thermal insulation without load, because then there will be induced by very high voltage, which may damage some of the elements of the scheme.
PCB_mont.JPG
 

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