Input device

1. Field of the Invention

The invention relates to input devices, and more particularly, to an input device that conserves energy when inactive.

2. Description of Related Art

Nowadays, most electronic equipment use keyboards as their input units. The input devices consume power all the time when the electrical equipments are powered on, including the time when not actuated or used. This causes a waste of power.

To accommodate miniaturization of electronic devices, batteries tend to get smaller and so the need for conserving the power of the batteries is largely increased. Thus, if input devices have current flowing inside only when keys are actuated, it would increase the lifetime of the battery.

Therefore, a heretofore need exists in the industry to overcome the aforementioned deficiencies.

An input device includes a power unit, a power switch unit, a processing unit, and an input unit. The power switch unit includes a first switch for supplying power to the processing unit when actuated; the input unit is connected with the processing unit and the power switch unit and is configured for generating input signals that are transmitted to the processing unit and further used for controlling the first switch; and the processing unit is configured for receiving the input signal from the input unit, keeping the first switch switched on during a time period, and performing a task corresponding to the input signal during the time period.

Other systems, methods, features, and advantages will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.

FIG. 1 is a schematic circuit diagram of an input device in accordance with a preferred embodiment of the present invention;

FIG. 1 is a schematic circuit diagram of an input device of the present invention. The input device includes a power unit 1 , a power switch unit 2 , a processing unit 3 , and an input unit 4 . The power unit 1 , the power switch unit 2 and the processing unit 3 are connected as shown. An input terminal E of the power switch unit 2 is connected with the power unit 1 to receive power from the power unit 1 , and an output terminal F of the power switch unit 2 is connected with a positive voltage input pin of the processing unit 3 to supply power to the processing unit 3 . The input unit 4 is connected between the power switch unit 2 and the processing unit 3 , and it serves as an input device of the processing unit 3 .

The power switch unit 2 includes a first switch Q 1 , a second switch Q 2 , and a resistor R 1 . The first switch Q 1 is connected between the input terminal E and the output terminal F of the power switch unit 2 . In the preferred embodiment of the present invention, the first switch Q 1 is a P-channel FET (Field-Effect Transistor) Q 1 having a source, a gate, and a drain. The source of the P-channel FET Q 1 is connected with the input terminal E of the power switch unit 2 , and the drain of the P-channel FET Q 1 is connected with the output terminal F of the power switch unit 2 . In the present invention, the second switch Q 2 is a N-channel FET Q 2 also having a source, a gate, and a drain. The drain of the N-channel FET Q 2 is connected with the gate of the P-channel FET Q 1 through a resistor, the gate of the second FET Q 2 is connected with a latch pin of the processing unit 3 , and the source of the second FET Q 2 is grounded. The resistor RI is connected between the source and the gate of the first FET Q 1 .

The input unit 4 includes one or more keys for generating input signals to the processing unit 3 when they are actuated. The processing unit 3 includes at least one input signal receiving pin for receiving input signals from keys of the input unit 4 respectively. For simplicity and a better understanding of the input unit 4 , only two) keys K 1 and K 2 are shown in the drawing and depicted in the preferred embodiment. The keys K 1 and K 2 correspond to two input signal receiving pins P 1 and P 2 of the processing unit 3 respectively. However the input unit 4 cannot be construed to be limited to any particular number of keys. The input unit 4 further includes at least one pair of diodes. In the preferred embodiment, the number of diode pairs is equal to the number of the keys. The diodes of each diode pair have their cathodes connected together to form a common cathode, and have their anodes respectively connected to the drain of the N-channel FET Q 2 and an input signal receiving pin of the processing unit 3 . In the preferred embodiment, two diode pairs D 1 &D 2 and D 3 &D 4 are shown and depicted. The key K 1 is connected between the common) cathode of the diode pair D 1 &D 2 and ground and transmits input signals to the input signal receiving pin P 1 of the processing unit 3 via the diode pair D 1 &D 2 . The key K 2 is connected between the common cathode of the diode pair D 3 &D 4 and ground and transmits input signals to the input signal receiving pin P 2 of the processing unit 3 via the diode pair D 3 &D 4 .

If no key of the input unit 4 is actuated, no current flows through the resistor RI and no voltage drop between the gate and the source of the P-channel FET Q 1 is produced. The P-channel FET Q 1 is retained in an off state. As a result, no power is outputted to the processing unit 3 and the input unit 4 via the output terminal F of the power switch unit 2 , and accordingly no power is consumed by the input device.

If any key is actuated, for example if key K 1 is actuated, a conduction path from power unit 1 to ground via the resistor R 1 , the diode D 1 and the key K 1 is formed, a current flows through the resistor R 1 and produces a voltage drop between the source and gate of the P-channel FET Q 1 , the P-channel FET Q 1 is accordingly turned on and transports power to the processing unit 3 and the input unit 4 via the output terminal F.

After being powered on, the processing unit 3 sets input signal receiving pins at a high level and receives an input signal from the key K 1 at the pin P 1 . The input signal changes the pin P 1 from the high level to the low level. The processing unit 3 detects the voltage change at the pin P 1 and thereby determines that key K 1 is actuated. The processing unit 3 then sets the latch pin at the high level for a time period during which a task corresponding to the actuation of the key K 1 is performed. The high level latch pin controls the N-channel FET Q 2 to turn on, keeping the P-channel FET Q 1 switching on until the task triggered by the actuation of key K 1 is fully performed.

In the preferred embodiment a LED (light emitting diode) D 5 is also included in the power switch unit 2 . The LED D 5 is positively connected between the output terminal F of the power switch unit 2 and ground. Each time when a key is actuated, power is supplied to the processing unit 3 , and the input unit 4 is resumed, the LED D 5 lights, this confirms the operation of pressing the key to operators.

Although the present invention has been specifically described on the basis of a preferred embodiment and preferred method thereof, the invention is not to be construed as being limited thereto. Various changes or modifications may be made to the embodiment and method without departing from the scope and spirit of the invention.