Power Supply Device and Luminaire

A power supply device comprising a DC-DC converter including:

• a switching element of a normally on type;
• a current control element of the normally on type connected to the switching element in series and configured to control an electric current flowing to the switching element;
• and
• a rectifying element connected to the current control element in series,
• the DC-DC converter converting, according to ON and OFF of the switching element, an input first direct-current voltage into a second-direct current voltage, which has an absolute value different from an absolute value of the first direct-current voltage, and supplying the second direct-current voltage to a load, wherein
• a saturation current value of the current control element is equal to or larger than a maximum rated current of the switching element.

A luminaire comprising:

• a lighting load;
• and a power supply device configured to supply electric power to the lighting load,
• the power supply device including:
• a DC-DC converter including:
• a switching element of a normally on type;
• a current control element of the normally on type connected to the switching element in series and configured to control an electric current flowing to the switching element;
• and
• a rectifying element connected to the current control element in series.
• the DC-DC converter converting, according to ON and OFF of the switching element, an input first direct-current voltage into a second-direct current voltage, which has an absolute value different from an absolute value of the first direct-current voltage, and supplying the second direct-current voltage to a load;
• and
• a protection circuit configured to cut off, when an electric current equal to or larger than a predetermined value flows to the switching element and the current control element, the electric current flowing to the switching element and the current control element.

A luminaire comprising:

• a lighting load;
• and
• a power supply device configured to supply electric power to the lighting load,
• the power supply device including a DC-DC converter including:
• a switching element of a normally on type;
• a current control element of the normally on type connected to the switching element in series and configured to control an electric current flowing to the switching element;
• and
• a rectifying element connected to the current control element in series,
• the DC-DC converter converting, according to ON and OFF of the switching element, an input first direct-current voltage into a second-direct current voltage, which has an absolute value different from an absolute value of the first direct-current voltage, and supplying the second direct-current voltage to a load, wherein
• a saturation current value of the current control element is equal to or larger than a maximum rated current of the switching element.