Reducing power usage in a personal computer

A keyboard for a personal computer, the keyboard having keypresses detected by keyboard control circuitry or, when in an unpowered state, having keypresses not detected by keyboard control circuitry, the keyboard comprising:

• an array of keys;
• a person sensor which detects user interaction with the keyboard when the keyboard is in an unpowered state;
• and
• power control circuitry which is operatively connected to the person sensor and maintains the computer in a first mode only as long as the user is interacting with the keyboard, the first mode including at least the keyboard control circuitry being operated in a more fully powered mode, and thereafter switches the computer to a second mode in which the keyboard control circuitry is switched to a less fully powered mode and in which the amounts of power delivered respectively to the keyboard control circuitry and a portion of the computer are based on the periods required for the keyboard control circuitry and the portion respectively to return to fully operational states from being less fully powered.

A computer system, comprising:

• a keyboard having keypresses detected by keyboard control circuitry or, when in an unpowered state, having keypresses not detected by keyboard control circuitry, the keyboard including an array of keys and a person sensor which detects user interaction with the keyboard when the keyboard is in an unpowered state;
• power control circuitry which is operatively connected to the person sensor and maintains the computer in a first mode only as long as the user is interacting with the keyboard, the first mode including at least a first portion of the computer being operated in a more fully powered mode, and thereafter switches the computer to a second mode in which at least the first portion is switched to a less fully powered mode and in which the amounts of power delivered respectively to the first portion and a second portion of the computer are based on the periods required for the portions respectively to return to fully operational states from being less fully powered;
• and
• a microprocessor configured to receive signals from the power control circuitry.

A keyboard for a personal computer, the keyboard having keycodes detected by keyboard control circuitry or, when in an unpowered state, having keycodes not detected by keyboard control circuitry, comprising:

• an array of keys, each of which has an associated keycode;
• a piezoelectric sensor mounted in a position to detect motion of one of the keys when the keyboard is in the unpowered state and to generate an electric signal in response to the motion;
• and
• power control circuitry connected to receive the electrical signal from the piezoelectric sensor and to switch the keyboard to the powered state quickly enough to allow the keyboard control circuitry to detect the keycode associated with the moving key, the power control circuitry configured to maintain the computer in a first mode only as long as motion of one of the keys is detected, the first mode including at least a first portion of the computer being operated in a more fully powered mode, and thereafter to switch the computer to a second mode in which at least the first portion is switched to a less fully powered mode and in which the amounts of power delivered respectively to the first portion and a second portion of the computer are based on the periods required for the portions respectively to return to fully operational states from being less fully powered.