Simple LED Driver Design

The Simple LED Driver Design TCA62735AFLG is a charge pump type DC DC Converter specially designed for constant current driving of white LED. IC can outputs LED current 120mA or more to 2.8-4.2V input. IC observes the power-supply voltage and the output voltage, and does an automatic change to the best of step up mode 1, 1.5 or 2 times. It is possible to prolong the battery longevity to its maximum.This IC is especially for driving back light white LEDs in LCD of PDA, Cellular Phone, or Handy Terminal Equipment.

This electronic project t LED driver is very simple and require few external electronic parts. Due of simplicity of this circuit this project not require additional explanations . If you want to change this design , please consult the manufactured datasheet.

Some features of the TCA62735AFLG electronic project are Switching Frequency : 1MHz(Typ.), Output Drive Current Capability : Greater than 120mA , 4 Channels Built in Constant Sink Current Drivers, Sink Current Adjustment by External Resistance, Soft Start Function , Integrated protection circuit TSD (Thermal Shut Down) .

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LED Christmas Star

This circuit can be used to construct an attractive Christmas Star. When we switch on this circuit, the brightness of lamp L1 gradually increases. When it reaches the maximum brightness level, the brightness starts decreasing gradually. And when it reaches the minimum brightness level, it again increases automatically. This cycle repeats. The increase and decrease of brightness of bulb L1 depends on the charging and discharging of capacitor C3. When the output of IC1 is high, capacitor C3 starts discharging and consequently the brightness of lamp L1 decreases. IC2 is an opto-isolator whereas IC1 is configured as an astable multivibrator. The frequency of IC1 can be changed by varying the value of resistor R2 or the value of capacitor C1.

Remember that when you vary the frequency of IC1, you should also vary the values of resistors R3 and R4 correspondingly for better performance. The minimum brightness level of lamp L1 can be changed by adjusting potentiometer VR1. If the brightness of the lamp L1 does not reach a reasonable brightness level, or if the lamp seems to remain in maximum brightness level (watch for a minute), increase the in-circuit resistance of potmeter VR1. If in-circuit resistance of potmeter VR1 is too high, the lamp may flicker in its minimum brightness region, or the lamp may remain in off state for a long time. In such cases, decrease the resistance of potmeter VR1 till the brightness of lamp L1 smoothly increases and decreases. When supply voltage varies, you have to adjust potmeter VR1 as stated above, for proper performance of the circuit. A triac such as BT136 can be used in place of the SCR in this circuit. Caution: While adjusting potmeter VR1, care should be taken to avoid electrical shock.

 

 

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Dimming Controlled LED LM3409

This dimming controlled LED driver circuit is designed using LM3409 P-channel MosFET controller for step-down (buck) current regulators.The LM3409 devices use Constant Off-Time (COFT) control to regulate an accurate constant current without the need for external control loop compensation Dimming controlled LED driver electronic circuit require an input voltage of 36 volts and will provide at output a voltage of 24 volts at a maximum current of 700mA 

Components list

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Build LED Light Pen Schematic

Physicians and repair engineers often use small light pens for visual examination purposes. Rugged and expensive as these pens may be, their weak point is the bulb, which is a ‘serviceable’ part. In practice, that nearly always equates to ‘expensive’ and / or ‘impossible to find’ when you need one.

LEDs have a much longer life than bulbs and the latest ultra bright white ones also offer higher energy-to-light conversion efficiency. On the down side, LEDs require a small electronic helper circuit called ‘constant-current source’ to get the most out of them.
 
LED Light Pen Circuit Diagram


Here, T1 and R1 switch on the LED. R2 acts as a current sensor with T2 shunting off (most of) T1’s base bias current when the voltage developed across R2 exceeds about 0.65 V. The constant current through the white LED is calculated from

R2 = 0.65 / ILED
With some skill the complete circuit can be built such that its size is equal to an AA battery. The four button cells take the place of the other AA battery that used to be inside the light pen. Link

Author: Myo Min – Copyright: Elektor

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LED Driver using LNK454DG

A very simple high efficiency led driver circuit can be designed using LNK454DG controller designed by Power Integrations . This LNK454DG led driver is configured as non-isolated discontinuous flyback converter designed to drive LED strings at voltages of 2.5 V to 3.5 V with an output current of 366 mA The circuit meets both line surge and EMI requirements and the low component count allows board dimensions required for LED candelabra bulb replacement applications. LNK454DG led driver is very easy to be configured and require few external electronic parts.

LED Driver Schematic

Two differential pi (π) filter EMI stages are used with C1, R1, L1 and C2 forming one stage and C2, L2, R2 and C3 the second.The incoming AC is rectified by BR1 and filtered by C1, C2 and C3. The total effective input capacitance, the sum of C1, C2 and C3, was selected to assure correct zero crossing detection of the AC input by the LinkSwitch-PL device and to meet high power factor and low THD. Due to the limited input capacitance (to meet PF) RV1 and VR1 are used to limit component voltage stress during line surges.The LNK454DG device (U1) incorporates the power switching device, oscillator, output constant current control, start-up, and protection functions.

The integrated 725 V MOSFET provides extended voltage margin and ensures high reliability even during line surge events. The device is powered from the BYPASS pin via the decoupling capacitor C5.The rectified and filtered input voltage is applied to one end of the primary winding of T1.The other side of the transformer’s primary winding is driven by the integrated MOSFET in U1. The leakage inductance generated drain voltage spike is limited by an RCD clamp consisting of D1, R3, and C4.Diode D2 is used to protect the IC from negative ringing when the MOSFET is off due to the reflected output voltage exceeding the DC bus voltage, the result of minimal input capacitance to give high power factor.T1 transformer is an SNX R1568 coil from Santronics or some other equivalent .

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SP LED Flashlight Using Supercapacitor

Bored of joking with capacitors? Then its time for you to maneuver on to super-capacitors. These have huge storage capabilities. during this article you may conclude the way to build atiny low LED flashlight using supercapacitors.

The most disadvantage of capacitors is their giant voltage drop. For this project, a minimum voltage of two volts is needed to light-weight the LED. As a result, the “Joule Thief” style would be incorporated here. Using this, a AA battery is used to light-weight an LED until its fully discharged.
 during this case, a supercapacitor would be taking the place of the battery. Here an LED is employed to perform the operate of a diode. This ensures that theres sufficient voltage across the LED.

 the necessities of the project are listed below:
White LED
Super capacitor (10F, 2.7 V)
Transistor
Torus
1 k ohm resistor
Wires
Breadboard
The torus and therefore the transistor used here comes from an energy-saving lamp HS. Care ought to be taken whereas removing this from the lamp as a breakage may lead to the discharge of the mercury vapors. A lamp load along side a USB port is added to the circuit. This makes it compatible with a computer or a automotive radio.

A couple of precautions got to be taken whereas constructing the circuit. The USB port mustnt be supplied with excess power. The capacitor doesnt stand up to a high voltage and hence a zener diode is connected in parallel to handle the high voltage. The diode protects the capacitor when the voltage exceeds an explicit price.

 

 

 

http://streampowers.blogspot.com/2012/07/sp-led-flashlight-using-supercapacitor.html 

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Arrow LED Indicator using 74hc14 IC

This arrow led indicator electronic project can be used in some dark places to show the directions . You can use to indicate direction just an illuminated arrow or a flashing light , but is much nicer if the light moves in the correct direction.

This arrow led indicator is based on 74HC14 circuit and some LEDs which are used to show the way .
For this arrow led indicator we need six series of three LEDs arranged in the shape of arrows and are connected to the outputs . Each time the lit arrows move over by one column so it appears that the arrows run from right to left.

Arrow LED Indicator Circuit Diagram

If we want to change the speed of the moving light it’s need to change the value of C1 to C3 or R1 to R3 ( a lower value for this components decrease the time of moving lights). If we want a longer arrow we can mount in parallel with existing columns another columns .
For power supply we can use batteries or 6V regulated power supply .

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16 Channel LED Driver Using LT3754

The LT3754 16 channel LED driver with a step-up DC DC controller designed by Linear Technology is capable of driving up to 45V of LEDs. Each channel of the LT3754 led driver contains an accurate current sink with ±2.8% current matching.If are used high current Leds channels can be paralleled.

16 Channel LED Driver Circuit Diagram

 

 

The LT3754 16 channel LED driver circuit allows a PWM dimming range up to 3000:1 and an analog dimming range up to 25:1. Operating frequency of the LT3574 16 channel LED driver can be programmed from 100kHz up to 1MHz using just a simple resistor or an external clock .

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Simple Solar LED Lantern

This solar LED lantern can be used as an emergency light. Its 6V battery can be charged either from 230V, 50Hz AC mains or a 12V, 10W solar panel. Two LED indicators have been provided—red LED (LED1) indicates battery charging and green LED (LED2) indicates fully-charged battery.

You can choose to charge the battery either from the mains power or the solar panel by using the single-pole, double-throw (SPDT) switch. Capacitor C1 (1000µF, 35V) removes ripples from the power supply and regulator IC LM7809 (IC1) provides regulated 9V DC to the emitter of pnp transistor T1 (TIP127/BD140) and pin 7 of op-amp IC CA3140 (IC2), which is configured in comparator mode.
The reference voltage of 6.3V at pin 2 of IC2 is obtained through the combination of resistor R7 (1-kilo-ohm) and zener diode ZD1 (6.3V). The comparator controls charging of the battery. Pin 3 of IC2 is connected to the positive terminal of the battery to be charged through resistor R5. When the battery is fully charged, it stops charging and the green LED (LED2) glows to indicate the full-charge status.

When the battery voltage is low, diode D1 (1N4007) forward-biases and the battery connects (through resistor R3) to the collector of T1 for charging (indicated by the glowing of red LED1). Three high-wattage white LEDs (LED3 through LED5), such as KLHP3433 from Kwality Photonics, are used for lighting. These are switched on using switch S3.

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6W Four Channel LED Driver

CAT4106 is an integrated Four channel LED driver (multi-channel LED driver) and high power dc-dc converter suitable for powering backlighting applications up to a total of 6 watts. Up to four matched LED strings can be accurately programmed with uniform drive current set by a single external resistor. The CAT4106 Four channel LED driver automatically adjusts the output voltage to drive the highest forward voltage string with the minimum headroom voltage maximizing the efficiency.

6W Four Channel LED Driver Circuit diagram

High resolution dimming control is achieved by the EN/PWM logic pin which supports multiple frequencies. This ensures precise PWM dimming control while the device remains fully biased. In addition, when held at logic low, the device to enter a full shutdown zero current mode. External programming resistors set the minimum and maximum voltage limits for the acceptable window of operation for LED strings. Any channel which fails to regulate within the window (Open or Short LED) is detected and flagged on the FAULT logic output (active low, open-drain).

Main features of CAT4106 led driver are : four LED channels with tight current matching , integrated dc-dc boost converter , up to 6 W LED total output power , up to 92% efficiency , low dropout LED channels (500 mV at 175 mA) , high frequency PWM interface (up to 2 kHz) ,adjustable short/open LED detection The CAT4106 requires small ceramic capacitors of 1 μF on the VIN pin (C1), 4.7 μF on the inductor input (C2), and 10 μF on the output (C3). Under normal condition, a 4.7 μF input capacitor (C2) is sufficient. A 47 μH inductor is recommended with current rating of 1 A or higher and 1A rated Schottky diode .

A typical value for resistor R7 and R5 is around 20 kΩ. R6 and R4 can be calculated as follows:

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LED Volt Meter Circuit

Here is a Simple LED Volt meter to Monitor the charge level in Lead Acid Battery or Tubular battery. The terminal voltage of the battery is indicated through a four level LED indicators. The nominal terminal voltage of a Lead Acid battery is 13.8 volts and that of a Tubular battery is 14.8 volts when fully charged. The LED voltmeter uses four Zener diodes to light the LEDs at the precise breakdown voltage of the Zener diodes. Usually the Zener diode requires 1.6 volts in excess than its prescribed value to reach the breakdown threshold level. When the battery holds 13.6 volts or more, all the Zener breakdown and all LEDs light up. When the battery is discharged below 10.6 volts, all the LEDs remain dark. So depending on the terminal voltage of the battery, LEDs light up one by one or turns off.
Circuit diagram:

 LED Volt Meter Circuit Diagram

 

 

http://streampowers.blogspot.com/2012/06/led-volt-meter-circuit.html 

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SP LED light weight Box

For beginners, its their 1st project that offers them a lift. And so as to induce that, its continuously necessary to create positive that the project that you just choose is basically helpful. One such project is that the RGB light-weight fader. this is often quite straightforward and may be done simply by a beginner. scan on to understand a lot of concerning this.

 Concerning twenty LEDs are needed here. begin by wiring all the LEDs and connecting it to a breadboard. this is often quite a tedious method and takes quite plenty of your time.

 ensuing step is to create the ability board. Quite plenty needs to be done to drive all the LEDs employing a single PWM channel. therefore to atone for this, a multiplexer IC is employed. a couple of voltage conversions is also needed in such a case.

 As mentioned earlier, one PWM is employed to regulate 3 totally different channels. The MSP430 is employed to modify between the various channels. this offers the impression that there are 3 individual channels. There is also some problems with the glint, however this might not be a show stopper downside.

 The supply code for running the circuit is kind of sophisticated . concerning twelve totally different modes are gift here and switching between the assorted modes is finished employing a single push button.

 

 

http://streampowers.blogspot.com/2012/07/sp-led-light-weight-box.html 

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LED Emergency Light Circuit Using Boost Converter

The following circuit uses a very common voltage boost converter concept for making a group of white LEDs illuminate at relatively lower power supplies. Lets learn how to make this interesting and useful little LED boost emergency light circuit.


Yet again we take the help of the evergreen work horse, the IC555 for implementing the proposed actions. The figure shows a very simple circuit configuration where the IC 555 has been rigged as an astable multivibrator.
In an astable multivibrator design the various components are wired such that the output generates trains of pulses which are self sustaining and keeps coming as long as the circuit remains powered.

In the present configuration the output of the IC which is the pin #3 generates pulses at a frequency determined by the resistors R1 and R2 and also the capacitor C2.
R2 may be typically adjusted or made variable type for enabling dimming control of the LEDs. However here the value of R2 has been fixed for acquiring optimum brightness from the LEDs.

The pulses available at pin#3 of the IC is used for ddriving the transistor T1 which in turn switches in response to the positive pulses.

The switching of the transistor pulls the supply voltage through the inductor in a pulsed mode.
As we know when alternating or pulsed voltage is applied across an inductor it tries to oppose the current and in the process kick an equivalent high voltage for compensating the applied current force.
This action of the inductor is what constitutes the boost action, where the voltage is stepped to higher levels than the actual supply voltage.
The above functioning of the inductor has been exploited in this circuit also. L1 boosts the voltage in an attempt to restrict the applied AC, this high voltage generated across the coil during the non conducting phases of the transistor is fed across a series connected LEDs for illuminating them under lower current levels. This process helps to illuminate the LEDs at relatively lower power consumption.

L1 winding is not so critical, it is a matter of little experimentation, the number of turns, wire guage, the diameter of the core, all are directly involved and affect the boost levels, therefore must be optimized carefully.
In the prototype I had used 50 turns of 22 SWG over an ordinary ferrite rod, which is normally used in small MW radio receivers.

The LEDs used by me were 1 watt, 350 mA types, howver you may use different types if you want.

Parts List

R1 = 100K
R2 = 39K,
R3 = 100 Ohms,
C1 = 680pF,
C2 = 0.01uF
L1 = see text
IC = LM555
LEDs = as per preference.

PLEASE CONNECT A 10 OHM RESISTOR IN SERIES WITH THE LED CHAIN FOR SAFEGUARDING IT FROM HIGH BOOSTED VOLTAGE.

INCREASING THE VALUE OF R2 SHOULD INCREASE THE BRIGHTNESS OF THE LEDs AND VICE VERSA.

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