Key press detecting circuit
AssigneeThomson Licensing
InventorsZhi Jun Liao, Robert Warren Schmidt, Ai Hua Sun
Life of this patent
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Abstract
A key press detecting circuit for detecting the status of the key is provided. The key press detecting circuit comprises a discharging circuit which discharges when the key (K1) is pressed; and a voltage detecting circuit, which comprises a combination of a PNP transistor (T2) and a NPN transistor (T3), wherein when the discharging circuit discharges for a predefined period, the PNP transistor (T2) will be turn on, which causes the NPN transistor (T3) to be turned on and to output a second signal for a second function.
Claims12
A key press detecting circuit for detecting the status of a key (K1), characterized in that it comprising:
- a discharging circuit (1) consisting of a Resistor-Capacitor (R1, C1) circuit, which is connected to the key (K1) and discharges when the key (K1) is pressed, and
- a voltage detecting circuit (2), which is connected to the discharging circuit (1) and comprises a combination of a first transistor (T2) and a second transistor (T3), wherein when the discharging circuit discharges for a predefined period, the first transistor (T2) will be turned on and outputs a voltage to turn on the second transistor (T3) so that the second transistor (T3) outputs a second signal for a second function, and
- wherein both the first transistor (T2) and the second transistor (T3) are PNP transistors and the base of the second transistor is connected to the emitter of the first transistor.
Dependencies are inferred from the claim text.