Completed simulations of the LED driver circuit and designed the LED PCB assembly.
Simulation
- Solved PSPICE solver convergence issues by setting initial conditions and tuning other simulation parameters.
- The problem is very stiff due to a wide bandwidth of frequencies involved (from 250kHz CC driver switching frequency to >100MHz edge harmonics in the LED-MOSFET current loop. Furthermore, numerous diodes induce non-linearities.
- Verified in simulation that the chosen snubber circuit can successfully dampen the >100MHz ringing on the rising edge of the modulation clock.
- Validated simulation results with multiple sets of values for parasitic inductances and capacitances in the circuit.
PCB Layout
The LEDs need to be mounted on an aluminum-core PCB. However, JLC’s process only supports single-layer aluminum-core boards. It is not feasible to lay out the CC drivers on one-layer board, so the illumination module will consist of a two-board assembly: a standard 4-layer FR-4 board with the CC drivers, as well as an aluminum-based board with just the modulation loop. The modulation board has been laid out, while the driver board is in progress. See pictures of both boards below:
Modulation board (3D, note eight LEDs in the center):
Modulation board (layout, 4 channels each with two LEDs):
CC Driver board:
