Patent ID: 8174304

Claim:
A key module comprising: a key operable between on and off states; a light emitting component disposed adjacent to the key, and capable of providing indicating light for the key; and a drive circuit electrically connected to the key and the light emitting component; wherein the drive circuit is triggered upon switching of the key from the off state to the on state to provide a drive signal for driving the light emitting component to provide the indicating light, the drive signal having an intensity that gradually decreases over time once the key switches from the on state to the off state such that the indicating light provided by the light emitting component has a luminance that gradually decreases over time; wherein the drive circuit includes a capacitor, the drive signal provided by the drive circuit being a discharge current of the capacitor, and wherein the drive circuit further includes: a first transistor having a collector coupled to one terminal of the capacitor, the other terminal of the capacitor being grounded; a second transistor having a collector coupled to the light emitting component, and a grounded emitter; a first diode having a cathode terminal coupled to the key; a first resistor adapted to be coupled between a first voltage source and an anode terminal of the first diode; a second diode coupled between a base of the first transistor and the key; a second resistor coupled between the base of the first transistor and an anode terminal of the second diode; a third resistor adapted to be coupled between a second voltage source and an emitter of the first transistor; a fourth resistor coupled between the collector of the first transistor and a base of the second transistor; a fifth resistor coupled between the base of the second transistor and the emitter of the second transistor; and a sixth resistor adapted to be coupled between the second voltage source and the light emitting component.