Arc fault detector and method

An arc fault detector for a circuit comprising:

• a current shunt resistor coupled in series with said circuit;
• and
• an arc discriminator comprising an amplifier sensing a first voltage on a first side of said current shunt resistor, sensing a second voltage on a second side of said current shunt resistor, and producing a first signal proportional to a current flow through said current shunt resistor, said arc discriminator further comprising a change detector receiving said first signal as input and producing an arc fault detection signal as output when said change detector detects a change in said first signal indicative of a presence of an arc fault in said circuit;
• wherein said change detector comprises a first buffer having an input coupled to said amplifier, said first buffer having a first and second output;
• a delay circuit coupled to said first output of said first buffer, said delay circuit providing a delayed signal as an output;
• a reference circuit coupled to said second output of said first buffer, said reference circuit providing a reference signal as an output;
• a first comparator having a first input coupled to said delay circuit and a second input coupled to said reference circuit, wherein said first comparator is configured to provide a series arc detection signal only when there is a decrease in voltage of said first signal which thereby causes the voltage of said reference signal to be less than said voltage of said delayed signal;
• and a logic gate having a first input coupled to said first comparator, said logic gate being configured to generate said arc fault detection signal as an output when said series arc fault detection signal is detected by said first input.

An arc fault detector for a circuit comprising:

• a current shunt resistor coupled in series with said circuit;
• and
• an arc discriminator comprising an amplifier sensing a first voltage on a first side of said current shunt resistor, sensing a second voltage on a second side of said current shunt resistor, and producing a first signal proportional to a current flow through said current shunt resistor, said arc discriminator further comprising a change detector receiving said first signal as input and producing an arc fault detection signal as output when said change detector detects a change in said first signal indicative of a presence of an arc fault in said circuit;
• wherein said change detector comprises a first buffer having an input coupled with said amplifier, said first buffer having a first and second output;
• a delay circuit coupled to said first output of said second buffer, said delay circuit providing a delayed signal as an output;
• a reference circuit coupled to said second output of said first buffer, said reference circuit providing a reference signal as an output;
• a second comparator having a first input coupled to said delay circuit and a second input coupled to said reference circuit, wherein said second comparator is configured to provide a parallel arc detection signal only when there is a increase in voltage of said first signal which thereby causes the voltage of said reference signal to be greater than said voltage of said delayed signal;
• and a logic gate having a second input coupled to said second comparator, said logic gate being configured to generate said arc fault detection signal as an output when said parallel arc fault detection signal is detected by said second input.

A method of detecting an arc fault in a circuit comprising:

• coupling a current shunt resistor in said circuit;
• monitoring a voltage differential across said current shunt resistor;
• detecting a change in said voltage differential;
• comparing said change to at least one threshold;
• and
• generating a signal when said change exceeds said at least one threshold;
• wherein said step of monitoring comprises sensing a first voltage on a first side of said current shunt resistor and sensing a second voltage on a second side of said current shunt resistor,
• wherein said change is proportional to a current flow through said current shunt resistor;
• and
• wherein said threshold is indicative of a presence of an arc fault in said circuit.