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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Simple Operational Amplifier DC Motor Driver

Using a simple operational amplifier and some other common electronic components can be designed a very simple DC motor driver that can be used for a 200mA motor application . Rb sets the bias point for transistors Q1 and Q2.

Because Vbe(ON) varies greatly with temperature, a guardband is required to prevent Q1 and Q2 from conducting simultaneously. RB should be selected such that the transistors do not conduct until lM equals the op amp quiescent supply current, Isy . The transistors will begin to conduct at about Vbe (on) = 0.5V. In this project :
RB= [vbe(on)/(lSY+ Im)]= 0.5/(0.0025 + 0.0025)=100 ohms

To maximize voltage swing across the motor, V1 must be minimized. If at full load V1 = 0.2V with V+ = 15V and VBE1 = 0.8V, the voltage across the motor will be:
VM = (V+ - 2) - VBE1 - V1 = (15 - 2) - 0.8 - 0.2 = 12.0V Vin may be scaled with a resistive divider as:
VIN= (R1 + R2)/R2 With R1 = 240k and R2 = 10k, VIN =5 volt lM = 200mA.

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High Power Alarm Driver

In this circuit, a low-powered SCR is used to trigger a higher powered SCR. When a switch is opening (S2, S3, S4) or closing (S5, S6, S7), either SCR1 or SCR2 triggers. This triggers SCR3 via D1, D2, and R5. BZ1 is a high-powered alarm of the noninterrupting type. 

High-Power Alarm Driver Circuit Diagram

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8 Watt Flouroscent Lamp Driver Circuit

This is a design circuit of a simple flouroscent lamp driver circuit based on two transistors. The circuit uses capacitive ballasting for driving the tube. An 8 Watt standard flouroscent tube can be efficiently driven using the circuit.

The two transistors (2SC1983) with associated components form an oscillator around 1KHz. The oscillator is wired so that saturation conditions of the transistors are prohibited. This adds on to the efficiency of the circuit. The circuit produces a clean sine wave with very less noise. The winding details (no of turns) are given in the circuit. Use 0, 8 mm diameter enameled copper wire for primary and 0, 4 mm diameter enameled copper wire for secondary. The core can be a ferrite core. The primary should be wound first and secondary on top of it. The circuit is use a 12 V battery or 12 V DC power supply as the DC voltage source.

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