In regular flashlights it is just a contact from the bulb to the bateries. what dose the solid state do to the light to make the bulb brighter?
LEDs are constant current devices which work differently to filament bulbs.To get the advertised life from the LED, the current must be controlled...hence a circuit board is used...note that the circuit is not usually intended to make the LED brighter.
However
there are those who will push the envelope and you will find them on Candlepower Forums.
eng hoe