I was searching for a LED driver that can also act as dimmer for my 10 watts LEDs and found the PT4115 IC which is kind of interesting. It operates from an input supply between 6V and 30V and provides an externally adjustable output current of up to 1.2A, and theoretically can provide up to 30W output power.
The dimming effect is achieved using variable DC voltage by adjusting a variable resistor or PWM signal, for example from a 555 IC. A logic level below 0.3V at DIM forces PT4115 to turn off the LED and the logic level at DIM must be at least 2.5V to turn on the full LED current. The frequency of PWM dimming ranges from 100Hz to more than 20 kHz.
Dimming with the ‘DIM’ pin on the PT4115
The dimming effect is achieved using PWM provided by an Arduino UNO board.
The DIM pin can be driven by an external DC voltage between 0.5V and 2.5V. If the voltage is higher than 2.5V the output current will be constant and won’t increase.
Schematic of the LED Driver with Dimmer Circuit
The circuit is quite simple and uses a 12VAC to 24VAC power supply or you can provide DC voltage that must not exceed 30V but your must remove D1, D2, D3 and D4 diodes. The Rs resistor is calculated using this formula: Rs = 0.1 / Iout (A). For example if we need a 500mA output current to drive the LED then Rs = 0.1 / 0.5A = 0.2Ω (200mΩ)
The value of coil L can be choosed using the table below:
- D1 … D4 = rectifier diodes
- Cin = 100µF/35V
- D5 = 1N5819
- Rs and L = read the article