Humidity detection and power cut-off device

• US 7,557,466 B2
• Filed: 05/10/2007
• Issued: 07/07/2009
• Est. Priority Date: 07/14/2006
• Status: Active Grant

• Current Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Original Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Inventors: Zhang, Jun-Wei, Chuang, Tsung-Jen, Wong, Shih-Fang, Cui, Wen-Jian
• Primary Examiner(s): Paladini; Albert W
• Assistant Examiner(s): RUTLAND WALLIS, MICHAEL
• Application Number:
  US11/746,650
• Publication Number:
  US 20080013241A1
• Time in Patent Office: 789 Days
• Field of Search: 307/118, 307/116
• US Class Current: 307/118
• CPC Class Codes: H02H 5/083 responsive to the entry or leakage of a liquid into an electrical appliance moisture alarm G08B21/20

Abstract

A humidity detection and power cut-off device for electronic equipment is provided. The device is connected between a battery (10) and a motherboard (40) of the electronic equipment and includes an auto protection device (20) and a moisture-triggered device (30). The auto protection device is connected between the battery and the power management module and is used to establish or cut off the connection between the battery and the power management module. The moisture-triggered device is used to detect the immediate ambient humidity and controls the auto protection device. If the moisture-triggered circuit detects that the immediate ambient humidity exceeds a predetermined critical humidity value, the moisture-triggered device outputs a trigger signal to the auto protection device. The trigger signal controls the auto protection circuit to cut off a connection between the battery and the power management module, thus to achieve waterproofing protecting for the electronic equipment.

Claims

1. A humidity detection and power cut-off device connected between a battery and a motherboard of an electronic equipment, the device comprising:

a moisture-triggered device, comprising;

a humidity sensor for sensing an immediate ambient humidity and outputting a voltage value corresponding to the immediate ambient humidity; and

a comparison circuit for comparing the voltage value with a reference voltage corresponding to a predetermined critical humidity value to determine whether the immediate ambient humidity exceeds the predetermined critical humidity value and outputting a trigger signal if the answer is yes; and

an auto protection device, comprising;

a switch circuit for establishing or cutting off a connection between the battery and the motherboard; and

a lock circuit for receiving the trigger signal, controlling the switch circuit to cut off the connection between the battery and the motherboard, and maintaining a disconnection state between the battery and the motherboard until the battery is removed and then re-attached into the electronic equipment.

2. The device according to claim 1, wherein the moisture-triggered device receives power supply from a power management module of the motherboard.

3. The device according to claim 2, wherein the reference voltage is supplied by the power management module.

4. The device according to claim 1, wherein the switch circuit comprises a P-channel enhancement mode MOSFET (EMOSFET) which has a source connected with the battery, a drain connected with the motherboard and a gate is controlled by the lock circuit.

5. The device according to claim 1, wherein the switch circuit comprises a plurality of parallel connected P-channel enhancement mode MOSFETs (EMOSFETs), sources of the P-channel EMOSFETs are connected together to the battery, drains of the P-channel EMOSFETs are connected together to the motherboard and gates of the P-channel EMOSFETs are controlled by the lock circuit.

6. The device according to claim 1, wherein the lock circuit comprises an N-channel enhancement mode MOSFET (EMOSFET), a resistance-capacitance circuit, a discharge resistor and a voltage dividing circuit.

7. The device according to claim 6, wherein the N-channel EMOSFET comprises a source connected with the switch circuit, a drain grounded and a gate controlled by the output of the comparison circuit, the N-channel EMOSFET responds to the trigger signal and controls the switch circuit to cut off the connection between the battery and the motherboard.

8. The device according to claim 6, wherein the resistance-capacitance circuit comprises a resistor and a capacitor which are serially connected between an anode of the battery (node A) and ground, a connection point between the resistor and the capacitor is connected to the source of the N-channel EMOSFET.

9. The device according to claim 6, wherein the discharge resistor is connected between the anode of battery and ground.

10. The device according to claim 6, wherein the voltage dividing circuit is connected between output of the switch circuit and ground and comprises two resistors connected in series, a connection point of the two resistors is connected to the gate of the N-channel EMOSFET.