Power supply device for protective relay

A power supply device capable of providing a stable power to a control circuit, wherein the control circuit is configured to control a circuit breaker connected to a power system,

• wherein the power supply device comprises a power circuit for supplying a power to the control circuit,
• wherein the power circuit includes:
• a semiconductor switch element having an input terminal connected to a first node for receiving a direct current, and an output terminal connected to a reference node, wherein the reference node has a voltage lower than a voltage of the first node;
• a current-limiting resistor disposed between the first node and a second node;
• a first voltage drop element disposed between the current-limiting resistor and the second node, wherein the second node is connected to a switching terminal of the semiconductor switch element;
• a second voltage drop element disposed between the second node and the reference node, wherein the second voltage drop element is connected in series with the first voltage drop element and the current-limiting resistor between the first node and the reference node;
• and
• a capacitor disposed between the second node and the reference node, wherein the capacitor is connected in parallel with the second voltage drop element,
• wherein the semiconductor switching element is configured to:
• when a gate voltage applied to the switching terminal rises, increase a magnitude of a current flowing from the first node to the reference node, and
• when the gate voltage applied to the switching terminal drops, decrease the magnitude of the current flowing from the first node to the reference node, and
• wherein when a voltage higher than a first breakdown voltage is applied across the first voltage drop element, the first voltage drop element electrically conducts to charge the capacitor, and
• wherein when a charge voltage charged in the capacitor exceeds a second breakdown voltage to protect the semiconductor switch element:
• the second voltage drop element conducts such that a current additionally applied to the capacitor flows to the reference node,
• the capacitor continuously receives a voltage not exceeding the second breakdown voltage, and
• the semiconductor switching element continues to be turned on to operate in a normal range.