Safety switch for photovoltaic systems

An apparatus comprising:

• first and second connectors;
• an auxiliary power supply circuit having an output, and an input coupled between the first connector and the second connector, wherein the auxiliary power supply circuit is configured to convert a first direct current (DC) voltage at a first amplitude received at the input to a second DC voltage at a second amplitude at the output, wherein the second amplitude is greater than the first amplitude;
• a switch comprising a switchable DC serial path connected between the first and the second connectors, and a control terminal connected to the output of the auxiliary power supply circuit;
• and
• a resistor connected between the first connector and the second connector and in parallel with the switch.

A system comprising:

• a photovoltaic string comprising a pair of photovoltaic generators and a safety switch coupled in series;
• wherein the safety switch comprises:
• first and second connectors connecting the safety switch inline between the pair of photovoltaic generators;
• an auxiliary power supply circuit configured to convert a first direct current (DC) voltage at a first amplitude between the first and the second connectors to a second DC voltage at a second amplitude on an output terminal;
• and
• a switch circuit comprising a switchable DC serial path connected between the first and the second connectors, and a control terminal connected to the output terminal of the auxiliary power supply circuit, wherein the second amplitude of the second DC voltage applied to the control terminal is greater than the first amplitude of the first DC voltage while the switchable DC serial path connects the first connector to the second connector;
• and
• a power device comprising:
• a power converter having inputs connected across the photovoltaic string, and
• a control circuit configured to control photovoltaic power generated by the photovoltaic string.

A method comprising:

• receiving, between first and second connectors of a safety switch, power;
• converting, with an auxiliary power supply circuit in the safety switch, a first direct current (DC) voltage at a first amplitude received between the first and the second connectors to a second DC voltage at a second amplitude;
• and
• applying, with the auxiliary power supply circuit, the second DC voltage to a control terminal of a switch comprising a switchable DC serial path connected between the first and the second connectors, wherein the second amplitude of the second DC voltage applied to the control terminal is greater than the first amplitude of the first DC voltage while the switchable DC serial path connects the first connector to the second connector.