Protective circuitry for electronic device

• US 7,990,670 B2
• Filed: 08/15/2008
• Issued: 08/02/2011
• Est. Priority Date: 12/27/2007
• Status: Active Grant

• Current Assignee: Chi Mei Communication Systems Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Chi Mei Communication Systems Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Chen, Chien-Chih
• Primary Examiner(s): Fureman; Jared J
• Assistant Examiner(s): BAUER, SCOTT ALLEN
• Application Number:
  US12/192,212
• Publication Number:
  US 20090168272A1
• Time in Patent Office: 1,082 Days
• Field of Search: 361/1, 361/88, 137/78.3, 340/604, 340/620, 340/605
• US Class Current: 361/88
• CPC Class Codes: H02H 5/083 responsive to the entry or leakage of a liquid into an electrical appliance moisture alarm G08B21/20
• CPC Class Codes: Y10T 137/189 Soil moisture sensing

Abstract

A protective circuitry (20) is connected between a power input port (11) and an electronic component (12) of an electronic device. The protective circuitry includes a field effect transistor (21) and a detection unit (25). The field effect transistor has a gate and a drain both electrically connected to an anode of the power input port, and a source electrically connected to a cathode of the power input port via the electronic component. The detection unit has two conductive pads spaced to each other. One pad is electrically connected to the gate and the other pad is electrically connected to the cathode of the power input port.

Claims

1. A protective circuit connected between a power input port and an electronic component of an electronic device, the protective circuit comprising:

a field effect transistor, the field effect transistor having a gate and a drain, the drain electrically connected to an anode of the power input port, and a source electrically connected to a cathode of the power input port via the electronic component; and

a detection unit, the detection unit having two spaced apart conductive pads, and one pad electrically connected to the gate and the other pad electrically connected to the cathode of the power input port, wherein when the conductive pads are connected to each other, the conductive pads having a voltage dividing function to reduce the voltage between the gate and the source to be smaller than a threshold voltage of the field effect transistor to make the field effect transistor switch to a cut-off mode;

an adjustable resistor, and one end of the adjustable resistor electrically connected to the gate, and the other end of the adjustable resistor electrically connected to the drain and the anode of the power input port.

2. The protective circuit as claimed in claim 1, wherein the pads of the detection unit are bar shaped.

3. The protective circuit as claimed in claim 1, wherein a first pad of the detection unit has a circular portion and a plurality of leaves protruding radially outward from the circular portion, and a second pad has a hole defined therein to receive the first pad.

4. The protective circuit as claimed in claim 1, wherein a first pad of the detection unit is a toothed strip having a plurality of leaves protruding outwardly from opposite sides thereof, and a second pad has a hole defined therein to receive the first pad.

5. The protective circuit as claimed in claim 1, wherein the field effect transistor is a metal oxide semiconductor field effect transistor.

6. A circuit comprising:

an electronic component;

a power input port;

a protective circuit comprising;

a field effect transistor, the field effect transistor having a gate, a source and a drain, the drain electrically connected to an anode of the power input port, the electronic component electrically connected in series between the source and the cathode of the power input port;

an adjustable resistor, one end of the adjustable resistor electrically connected to the gate, and the other end of the adjustable resistor electrically connected to the drain and the anode of the power input port;

two spaced apart conductive pads, and one pad electrically connected to the gate and the other pad electrically connected to the cathode of the power input port, wherein when the conductive pads are connected to each other, the conductive pads having a voltage dividing function to reduce the voltage between the gate and the source smaller than a threshold voltage to make the field effect transistor switch to a cut-off mode;

when the conductive pads are not connected, the voltage of between the gate and the source is larger than the threshold voltage to make the field effect transistor work on a turn-on mode for supplying the electronic component.