@martinisonline Actually the PWM frequency is easy to change, but won't help much. It is based on native 62.5kHz, so in addition to this high frequency the common options are:
1/8 = 7.8kHz (used in v0.9)
1/32 = 1.96kHz
1/64 = 0.98kHz (current default)
I suspect the diode is a standard 6W nubm44, so the recommended CW current is 4A @ 25°C (optical output would be ~6W) but the datasheet does specify a maximum current of 5A at pulse width 0.1us, 50% duty cycle.
15W is totally unreasonable unless you want it to last a few hours, any reputable manufacturer would rate this as a 5.5W.