Device for identifying AC power supply arrangement

A device for identifying an arrangement of an AC power supply. The device includes first and second voltage detecting circuits and a comparison logic circuit. The first voltage detecting circuit, coupled to ground and hot lines of the AC power supply, receives a first input signal from the hot line and detects the voltage level thereof to generate a first detect signal. The second voltage detecting circuit, coupled to ground and neutral lines of the AC power supply, receives a second input signal from the neutral line and detects the voltage level thereof to generate a second detect signal. The comparison logic circuit, coupled to the first and second voltage detecting circuits, generates first and second identification signals according to the first and second detect signals, indicating the arrangement of the AC power supply.

FIELD OF THE INVENTION

The present invention relates to power arrangement identification, and particularly to a device for identifying an arrangement of an alternating current (AC) power supply.

DESCRIPTION OF RELATED ART

Conventionally, power supplies for electronic equipment employ a three-wire AC configuration. Generally, a “hot line” and a “neutral line” of AC electric wiring are used to provide power, and a “ground line” thereof is connected to ground, protecting users from being electrocuted.

Among AC power supply systems, 110V and 220V power systems are widely used. The 110V AC power system is a single-phase two-wire-plus-ground (1φ2 W+G) system, wherein the voltage carried thereby is 110V with respect to the neutral line. The 220V AC power system includes two different type systems with respect to voltage generation thereof; one is single-phase two-wire-plus-ground (1φ2 W+G) system having a hot line carrying 220V voltage and the other is single-phase three-wire (1φ3 W), having a hot line (first hot line) and a neutral line (second hot line), each carrying 110V voltage. Different voltage, plug, and socket types are used around the world according to the standard defined by International Electrotechnical Commission (IEC) and National Electrical Manufacturers Association (NEMA). However, miswirings may occur when the wiring is installed improperly. One of the miswiring conditions is the swapping of the hot and neutral lines in the wall socket, that is, an inverted single-phase two-wire-plus-ground system. Another type of miswiring is socket misuse between 220V single-phase two-wire-plus-ground and single-phase three-wire systems. The swapping of the hot and neural lines may be an electrocution hazard for individuals with alternating currents flowing on the metal surface of electrical appliances or it may damage internal circuits of precision machines requiring precise power supply. Thus, a fuse is generally connected between the hot and neutral lines, whereby if the power source becomes abnormal, the fuse automatically protects the equipment. The use of fuses has advantages of simplicity and low cost; however, a fuse may mal-function failing to protect equipment. Moreover, replacement of fuses when required is time-consuming.

SUMMARY OF THE INVENTION

A device for identifying an arrangement of an AC power supply is provided. In a preferred embodiment, the device comprises a first voltage detecting circuit, a second voltage detecting circuit, and a comparison logic circuit. The first voltage detecting circuit, coupled to a ground line and a hot line of the AC power supply, receives a first input signal from the hot line of the AC power supply and detects the voltage level thereof to generate a first detect signal. The second voltage detecting circuit, coupled to a ground line and a neutral line of the AC power supply, receives a second input signal from the neutral line of the AC power supply and detects the voltage level thereof to generate a second detect signal. The comparison logic circuit, coupled to the first and second voltage detecting circuits, receives the first and second detect signals to generate first and second identification signals according to the first and second detect signals, indicating the arrangement of the AC power supply.

Another device for identifying an arrangement of an AC power supply is further provided. The device comprises a first detecting circuit, a second detecting circuit, and a comparison logic circuit. The first detecting circuit, coupled between a hot line and a ground line of the AC power supply, detects a voltage level therebetween to generate a first detect signal. The first detecting circuit comprises a first voltage divider, a first resistor-capacitor (RC) filter, and first level determination circuit. The first voltage divider, coupled between the hot and ground lines, receives a first input signal from the hot line and adjusts the voltage level thereof to generate a first divided signal. The first RC filter, coupled to the first voltage divider, receives and rectifies the first divided signal to generate a first rectified signal according to a direct current (DC) component thereof. The first level determination circuit, coupled to the first RC filter, generates the first detect signal in response to the first rectified signal. The second detecting circuit, coupled between a neutral line and the ground line of the AC power supply, detects a voltage level therebetween to generate a second detect signal. The second detecting circuit comprises a second voltage divider, a second RC filter, and a second level determination circuit. The second voltage divider, coupled between the neutral and ground lines, receives a second input signal from the neutral line and adjusts the voltage level thereof to generate a second divided signal. The second RC filter, coupled to the second voltage divider, receives and rectifies the second divided signal to generate a second rectified signal according to a DC component thereof. The second level determination circuit, coupled to the second RC filter, generates the second detect signal in response to the second rectified signal. The comparison logic circuit receives the first and second detect signals to generate first and second identification signals according to the first and second detect signals, indicating the arrangement of the AC power supply.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a device100for identifying an arrangement of an AC power supply according to an embodiment of the invention. The device100comprises voltage detecting circuits10and20, a comparison logic circuit30, and a processor40. The voltage detecting circuit10, coupled to a hot line L and a ground line G of the AC power supply (not shown), detects a voltage level therebetween and transmits a first detect signal18to the comparison logic circuit30. The voltage detecting circuit20, coupled to a neutral line N and the ground line G of the AC power supply (not shown), detects a voltage level therebetween and transmits a second detect signal28to the comparison logic circuit30. The comparison logic circuit30receives the detect signals18and28and generates a first identification signal32and a second identification signal34according to the detect signals18and28to indicate the arrangement of the AC power supply. The processor40receives the identification signals32and34at terminals P1and P2respectively, determining the arrangement of the AC power supply accordingly. It is noted that, the lines L, N, and G of exemplary embodiments represent corresponding lines of 110V or 220V single-phase two-wire AC power supply while in a single-phase three-wire AC power supply, the lines L and N correspond to a first hot line and a second hot line thereof respectively.

FIG. 2shows a detailed circuit diagram of the device100. The voltage detecting circuit10comprises a voltage divider12, a filter14, and a level determination circuit16. The voltage divider12comprises resistors R1and R2coupled in series between the hot line L and the ground line G to adjust the voltage level therebetween. Preferably, the resistance of resistor R1is much greater than that of resistor R2, thus the input voltage level is reduced. The filter14comprises a diode D1and a capacitor C1. An anode of the diode D1is coupled to a junction of the resistors R1and R2. The capacitor C1is coupled between a cathode of the diode D1and the ground line G. The filter14extracts a DC component of an input signal from the junction of the resistors R1and R2and passes it to the level determination circuit16. The level determination circuit16then generates the first detect signal18according to the extracted DC component from the filter14. The level determination circuit16comprises resistors R3˜R6, an NPN transistor Qq, and a PNP transistor Q2. The resistors R3and R4, coupled in series, are disposed between the cathode of the diode D1and the ground line G, forming a voltage divider to adjust the voltage level of the extracted DC component from the filter14. The transistor Q1has a base coupled to a junction between the resistors R3and R4, a collector receiving a supply voltage Vcc1via the resistor R5and an emitter coupled to the ground line G. The transistor Q2has a base coupled to the collector of transistor Q1, an emitter receiving the supply voltage Vcc1via the resistor R6, and a collector coupled to the ground line G, generating the first detect signal18to the comparison logic circuit30.

The voltage detecting circuit20is similar to the voltage detecting circuit10and comprises a voltage divider22, a filter24, and a level determination circuit26. The voltage divider22comprises resistors R7and R8coupled in series between the neutral line N and the ground line G to adjust the voltage level therebetween. Preferably, the resistance of resistor R7is much greater than that of resistor R8; thus the input voltage level is reduced. The filter24comprises a diode D2and a capacitor C2. An anode of the diode D2is coupled to a junction of the resistors R7and R8. The capacitor C2is coupled between a cathode of the diode D2and the ground line L. The filter24extracts a DC component of an input signal from the junction of the resistors R7and R8and passes it to the level determination circuit26. The level determination circuit26then generates the detect signal28according to the extracted DC component from the filter24. The level determination circuit26comprises resistors R9˜R12, an NPN transistor Q3, and a PNP transistor Q4. The resistors R9and R10, coupled in series, are disposed between the cathode of the diode D2and the ground line G, forming a voltage divider to adjust the voltage level of the extracted DC component from the filter24. The transistor Q3has a base coupled to a junction between the resistors R9and R10, a collector receiving a supply voltage Vcc2via the resistor R11and an emitter coupled to the ground line G. The transistor Q4has a base coupled to the collector of transistor Q3, an emitter receiving the supply voltage Vcc2, and a collector via the resistor R12, coupled to the ground line G, transmitting the detect signal28to the comparison logic circuit30.

The comparison logic circuit comprises a NOT gate UC, an AND gate UA and a NOR gate UB. The NOT gate UC receives the detect signal18at a terminal5thereof. The AND gate UA has an input terminal1coupled to an output terminal6of the NOT gate UC, an input terminal2receiving the detect signal28, and an output terminal generating the identification signal32. The NOR gate UB has input terminals3and4receiving the detect signals18and28respectively, and an output terminal generating the identification signal34. The operation of the device100is described as follows.

If the AC power supply is a single-phase two-wire system, the hot line L, ground line G, and neutral line N ofFIGS. 1 and 2are connected to the hot line, ground line, and neutral line of the AC power supply respectively. Receiving the input from the hot line L, the voltage level thereof is reduced by the voltage divider12and a divided signal is provided to the filter14. The filter14then extracts the DC component from the divided signal and outputs the extracted DC component to the level determination circuit16. The voltage divider formed by the resistors R3and R4further adjusts the voltage level of the extracted DC component from the filter14and provides the adjusted DC component to the base of the transistor Q1. The transistor Q1is turned on, turning on the transistor Q2, and the transistor Q2transmits the first detect signal18having a low level to the comparison logic circuit30. With regard to the detecting circuit20, since the voltage divider22receives an input from the neutral line N, the transistor Q3is turned off, and the detect signal28is pulled to high by the pull-up resistor R12. Table 1 shows possible logic combinations of the comparison logic circuit30. It is observed that with the low level detect signal18and high level detect signal28input to the comparison logic circuit30, the arrangment of the AC power supply is identified as single-phase two-wire system.

Similarly, if the AC power supply detected is a single-phase three-wire system, the hot line L, ground line G and neutral line N ofFIGS. 1 and 2are connected to the first hot line, ground line, and second hot line of the AC power supply respectively. In this way, the voltage detecting circuits10and20generate low level detect signals18and28to the comparison logic circuit30. As shown in Table 1, after logic computation in the comparison logic circuit30, the arrangement of the AC power supply is identified as a single-phase three-wire system.

Moreover, in the case of inverted single-phase two-wire AC power supply, that is the hot line and neutral line of a single-phase two-wire system are swapped, the voltage detecting circuits10and20generates high level detect signal18and low level detect signal28to the comparison logic circuit30. After the logic computation of the comparison logic circuit30, the arrangement of the AC power supply is identified as an inverted single-phase two-wire system.

Thus, if miswiring of the AC power supply occurs, it can be identified with exemplary embodiments, avoiding damage to individuals and electronic devices.