Protective apparatus

• US 20060126244A1
• Filed: 12/09/2005
• Published: 06/15/2006
• Est. Priority Date: 12/10/2004
• Status: Active Grant

• Current Assignee: Hon Hai Precision Industry Co., Ltd.
• Original Assignee: Hon Hai Precision Industry Co., Ltd.
• Inventors: Kuo, Heng-Chen
• Granted Patent: US 7,414,820 B2
• Time in Patent Office: Days
• US Class Current: 361/77
• CPC Class Codes: H02H 11/002 in case of inverted polarity or connection; with switching for obtaining correct connection

Abstract

A protective apparatus for protecting electric device connected to an AC circuit from being damaged at a time of misconnection between a live line and a neutral line thereof. The protective apparatus includes a detector, a controller, and an alarm. The detector is connected between the neutral line and the earth line. The controller is connected between the live line and the neutral line and includes a DPDT switch. Two blades of the switch switchably connected to the electric device and the alarm. The detector includes a voltage grading circuit, a rectifier-filter, a detect circuit, and an isolating circuit. Once misconnection between the live line and the neutral line occurs, an abnormal voltage is transformed by the detector to a stable DC power output, which drives the controller to disconnect the device from the live line and the neutral line and activate the alarm.

Claims

1. A protective apparatus for preventing an electrical device from being electrically damaged, the device is connected to an AC circuit via the protective apparatus, the circuit comprising a live line, a neutral line, and an earth line, the protective apparatus comprising:

a detector connected between the neutral line and the earth line, the detector comprising a rectifier-filter circuit for processing an abnormal voltage between the neutral line and the earth line; and

a controller connected between the live line and the neutral line, the controller connected to and driven by an output of the detector, the controller allowing power to the device in a normal working state and disconnecting power to the device when a misconnection occurs between the live line and the neutral line.

2. The protective apparatus as claimed in claim 1, wherein the detector further comprises a voltage grading circuit, the voltage grading circuit comprises a first resistor, and a second resistor, connected in series between the neutral line and the earth line.

3. The protective apparatus as claimed in claim 2, wherein the rectifier-filter circuit comprises a diode, a capacitor, and a tantalum capacitor, an anode of the diode is connected to a node between the first and the second resistor, an anode of the diode is connected to an anode of the tantalum capacitor, a cathode of the diode is grounded, the capacitor is connected in parallel to the tantalum capacitor.

4. The protective apparatus as claimed in claim 3, wherein the rectifier-filter circuit further comprises a Zener diode, an anode of the Zener diode is grounded, a cathode of the Zener diode is connected to the anode of the tantalum capacitor.

5. The protective apparatus as claimed in claim 3, wherein the detector further comprises a detection circuit connected in series to the rectifier-filter circuit.

6. The protective apparatus as claimed in claim 5, wherein the detection circuit comprises a third resistor, a forth resistor, a fifth resistor, a first transistor, a second transistor, one end of the third resistor is connected to the cathode of the diode, the forth resistor is connected to the other end of the third resistor and the earth line, a base of the first transistor is connected to a node between the third and the forth resistors, an emitter of the first transistor is grounded, the fifth resistor is connected between a collector of the first transistor and a base of the second transistor, an emitter of second transistor is connected to the cathode of the diode.

7. The protective apparatus as claimed in claim 6, wherein the detector further comprises an isolating circuit connected in series to the detect circuit.

8. The protective apparatus as claimed in claim 7, wherein the isolating circuit comprises a sixth resistor, a seventh resistor, a power supply, and a optical coupler, one end of the sixth resistor is connected to a collector of the second transistor, the other end of the sixth resistor is connected to an anode of the optical coupler, a cathode of the optical coupler is grounded, the seventh resistor is connected between the power source and a collector of the optical coupler, an emitter of the optical coupler is grounded.

9. The protective apparatus as claimed in claim 8, wherein the controller comprises a P-channel field-effect transistor, a switch, a winding with an iron core, a gate of the transistor is connected to a node between the seventh resistor and the collector of the optical coupler, a source of the transistor is connected to the power supply, a drain of the transistor is connected one end of the winding, another end of the winding is grounded.

10. The protective apparatus as claimed in claim 9, wherein the switch is a double-pole double throw switch and located above the winding, the winding comprises a pair of blades connected to the device.

11. The protective apparatus as claimed in claim 9, wherein the controller further comprises a second diode, an anode of the second diode is connected to the drain of the transistor, a cathode of the second diode is connected to the source of the transistor.

12. The protective apparatus as claimed in claim 1, further comprising an alarm connected to the controller.

13. A protective apparatus for disconnecting an electrical device from an AC circuit when misconnection between a live line and a neutral line thereof occurs, the protective apparatus comprising:

a detector connected between the neutral line and the earth line for transforming an abnormal voltage therebetween to a stable DC voltage output; and

a controller connected between the live line and the neutral line, the controller comprising a switch driven by the output from the detector to disconnect power to the device.

14. The protective apparatus as claimed in claim 13, wherein the detector comprises a voltage grading circuit for grading the abnormal voltage, a rectifier-filter circuit for converting the abnormal voltage to a stable DC power, a detection circuit and an isolating circuit to output a start voltage to the controller, connected in series.

15. The protective apparatus as claimed in claim 13, wherein the controller further comprises a P-channel field-effect transistor, and a winding comprising an iron core, the winding is located below the switch, a gate of the transistor is connected to the output of the detector, a source of the transistor is connected to a power supply, a drain of the transistor is connected to one end of the winding, another end of the winding is grounded.

16. The protective apparatus as claimed in claim 15, wherein the switch is a double-pole double throw switch and located above the winding, the winding comprises a pair of blades switchably connected to the device.

17. The protective apparatus as claimed in claim 16, further comprising an alarm switchably connected to the blades of the switch.