Switch contact arc suppressor

An arc suppression circuit used with a switch carrying a load current, said switch having first and second contacts, said circuit comprising:

• a MOSFET having a drain, and means for coupling the drain to said first contact of the switch,
• said MOSFET having a source, and means for coupling the source to said second contact of the switch,
• said MOSFET also having a gate, and an inherent gate-to-source capacitance,
• a damping resistor, and
• a biasing capacitor coupled at one end to said drain and at the other end through said damping resistor to said gate, such that when the said switch contacts are opened and are at differing potentials, said load current passes through said biasing capacitor and damping resistor to said gate-to-source capacitance to charge said gate-to-source capacitance, turning on the MOSFET whereby the MOSFET shunts the load current around the switch contacts.

An arc suppression circuit used with a switch carrying a load current, said switch having first and second contacts, said current comprising:

• a MOSFET having a drain, and means for coupling the drain to said first contact of the switch, a source, and means for coupling the source to said second contact of the switch,
• said MOSFET also having a gate, and an inherent gate-to-source capacitance,
• a damping resistor,
• a biasing capacitor coupled at one end to said drain and at the other end through said damping resistor to said gate, such that when the said switch contacts are opened and are at differing potentials, load current passes through said biasing capacitor and said damping resistor to charge said gate-to-source capacitance, thereby turning on the MOSFET whereby the MOSFET shunts the load current around the switch contacts,
• a biasing resistor connected between said other end of said biasing capacitor and said MOSFET source for discharging said gate-to-source capacitance such that said MOSFET turns off after it turns on, and
• a zener diode connected in parallel with said biasing resistor for quickly discharging said biasing capacitor when said switch contacts are closed.

An arc suppression circuit used with a switch carrying an AC load current, said switch having first and second contacts, said circuit comprising:

• a first MOSFET having a source, a drain, a gate, an inherent gate-to-source capacitance, and a source-to-drain diode,
• a second MOSFET having a source, a drain, a gate, an inherent gate-to-source capacitance, and a source-to-drain diode,
• means connecting the first and second MOSFETs in series across the switch contacts such that when either of the MOSFETs turns on the AC load current is shunted through the drain-to-source diode of the other MOSFET and through the drain and source of the turned on MOSFET,
• first means to charge said gate-to-source capacitance of said first MOSFET when the switch contacts are opened with the second contact at a higher potential than the first contact so that the first MOSFET turns on and shunts the load current around said switch contacts through said source-to-drain diode of said second MOSFET and through said first MOSFET, and
• second means to charge said gate-to-source capacitance of said second MOSFET when the switch contacts are opened with said first contact at a higher potential than said second contact so that the second MOSFET turns on to shunt the load current around said switch contacts through said source-to-drain diode of said first MOSFET and through said second MOSFET.

An arc suppression circuit used with a switch carrying an AC load current, said switch having first and second contacts, said circuit comprising:

• a first MOSFET having a source, a drain, a gate, an inherent gate-to-source capacitance, and a source-to-drain diode,
• a second MOSFET having a drain, a source, a gate, an inherent gate-to-source capacitance, and a source-to-drain diode,
• means connecting the first and second MOSFETs in series across the switch such that when either one of the MOSFETs turns on, the load current is shunted through the drain-to-source diode of the other MOSFET and through the drain and source of the turned on MOSFET,
• a first biasing resistor, having one end coupled to said gate and another end coupled to said source of said first MOSFET, for discharging said gate-to-source capacitance of said first MOSFET,
• a second biasing resistor, having one end coupled to said gate and another end coupled to said source of said second MOSFET, for discharging said gate-to-source capacitance of said second MOSFET,
• a first biasing capacitor coupled at one end to said first MOSFET drain and at another end to said first MOSFET gate, such that when the said switch contacts are opened with said second switch contact at a higher potential than said first switch contact, said load current passes through said first biasing capacitor and said second MOSFET source-to-drain diode to charge said first MOSFET gate-to-source capacitance,
• a second biasing capacitor coupled at one end to said second MOSFET drain and at another end to said second MOSFET gate, such that when the said switch contacts are opened with said first contact at a higher potential than said second contact, said load current passes through said second biasing capacitor and said first MOSFET source-to-source diode to charge said second MOSFET gate-to-source capacitance,
• a first zener diode, coupled in parallel with said first biasing resistor, for discharging said first MOSFET biasing capacitor when said switch contacts are closed,
• a second zener diode, coupled in parallel with said second biasing resistor, for discharing said second MOSFET biasing capacitor when said switch contacts are closed,
• a first damping resistor, said first biasing capacitor being coupled to said first MOSFET gate through said first damping resistor, and
• a second damping resistor, said second biasing capacitor being coupled to said second MOSFET gate through said second damping resistor.

An arc suppression circuit used with a switch carrying an AC load current, said switch having first and second contacts, said circuit comprising:

• a first MOSFET having a source, a drain, a gate, an inherent gate-to-source capacitance, and a source-to-drain diode,
• a second MOSFET having a source, a drain, a gate, an inherent gate-to-source capacitance, and a source-to-drain diode,
• means connecting the first and second MOSFETs in series across the switch contacts such that when either of the MOSFETs turns on the AC load current is shunted through the source-to-drain diode of the other MOSFET and through the drain and source of the turned on MOSFET,
• first means to charge said gate-to-source capacitance of said first MOSFET when the switch contacts are opened with the second contact at a higher potential than the first contact so that the first MOSFET turns on and shunts the load current around said switch contacts through said source-to-drain diode of said second MOSFET and through said first MOSFET,
• second means to charge said gate-to-source capacitance of said second MOSFET when the switch contacts are opened with said first contact at a higher potential than said second contact so that the second MOSFET turns on to shunt the load current around said switch contacts through said source-to-drain diode of said first MOSFET and through said second MOSFET,
• a first biasing resistor coupled at one end to said gate and at another end to said source of said first MOSFET for discharging said first MOSFET gate-to-source capacitance, and
• a second biasing resistor connected between said gate and said source of said second MOSFET for discharging said second MOSFET gate-to-source capacitance.