Here's a very simple dimmable constant current LED driver board design. It's based on the PT4115 chip.
Specifications:
- LED current up to 1.2A (nominally 0.9A with this BOM)
- 12V nominal input voltage
- Duty cycle adjustable
- 150ms power-up blanking delay
- Simple 2-layer PCB construction
| Q | Designator | Part Number | Description |
|---|---|---|---|
| 1 | C1 | EEE-TC1C101P | 100uF 16V aluminum electrolytic, SMD |
| 3 | C2, C5, C7 | 0.1uF 25V ceramic capacitor, 0805 | |
| 1 | C6 | 0.033uF 50V ceramic capacitor, 0805 | |
| 5 | D1, D2, D3, D4, D5 | SS36 | Schottky diode 60V 3A DO214AC |
| 1 | J1 | 0.1" header, 2 pin | |
| 1 | J2 | 0.1" header, 3 pin | |
| 1 | J3 | PJ-002AH | 2.1mm X 5.5mm barrel jack |
| 1 | L1 | SRN8040-470M | 47uH 1.4A 190mOhm SMD inductor |
| 1 | Q1 | 2N7002-7-F | N-channel MOSFET, 60V 115mA SOT23-3 |
| 1 | R1 | KDV12FR120ET | 0.12 ohm 1% resistor, 1/2W 1206 |
| 1 | R2 | 2.2 ohm resistor, 1206 | |
| 1 | R3 | 820K ohm resistor, 0805 | |
| 1 | R4 | (do not install) | |
| 1 | U1 | PT4115 | LED driver, PWM buck |
| 1 | U2 | NE555S-13 | Oscillator timer 8-SOIC |
Not shown on the list is the front panel dimmer potentiometer, which should be a 10K ohm linear taper.
You may want to use hot air to install U1 first, since it is important to make sure the thermal tab has a solid connection to the ground plane.
To adjust the LED current, you can change the values of R1 and R2 such that their parallel value R = 0.1V / Iled.
The turn-on blanking delay can be increased by increasing R3.
The PWM frequency is controlled by C6. For some values, you may get interference with the switching frequency of U1 and that might create audible noise or visual flicker, particularly if you're using this illuminator with a camera.
This hardware project is secured under the CERN Open Hardware Licence Version 2 - Permissive.