/diy/ - Do It Yourself

I am still working on my little LED driver circuit.
I plan to power the circuit from a 24 VDC power supply. I did a DC operating point simulation with LTSpice and it shows that the current-limit transistors Q1..4 dissipate about 180 mW of power when operating at 24 V. With an unregulated power supply the voltage may rise above the nominal 24 V, further increasing dissipation.

Do you think the dissipation would be too high for this small signal transistor type (2N3906)? Its datasheet mentions max. dissipation of 250 mW at ambient temp of 60°C.

Are there any ways to improve the efficiency of this kind of constant-current source?