Power Supply Circuit and Luminaire

A power supply circuit comprising:

• a bridge circuit including at least one switching element and configured to convert a direct-current voltage into an alternating-current voltage according to ON and OFF of the switching element;
• a transformer including a primary winding wire connected to the bridge circuit and a secondary winding wire magnetically coupled to the primary winding wire;
• a rectifying and smoothing circuit configured to convert the alternating-current voltage output from the secondary winding wire into a direct-current output voltage and supply the direct-current output voltage to a direct-current load;
• a first driver configured to control ON and OFF of the switching element;
• and
• a feedback circuit configured to feedback-control the first driver on the basis of a detection signal of an output current flowing to the direct-current load, wherein
• when an overvoltage is detected by the feedback circuit, the first driver controls the bridge circuit to set the output voltage to be equal to or lower than a predetermined voltage.

A luminaire comprising:

• a lighting load;
• and
• a power supply circuit configured to supply electric power to the lighting load,
• the power supply circuit including:
• a bridge circuit including at least one switching element and configured to convert a direct-current voltage into an alternating-current voltage according to ON and OFF of the switching element;
• a transformer including a primary winding wire connected to the bridge circuit and a secondary winding wire magnetically coupled to the primary winding wire;
• a rectifying and smoothing circuit configured to convert the alternating-current voltage output from the secondary winding wire into a direct-current output voltage and supply the direct-current output voltage to the lighting load;
• a first driver configured to control ON and OFF of the switching element;
• a feedback circuit configured to receive a detection signal of an output current flowing to the lighting load and a differential signal obtained from fluctuation of the output voltage and feedback-control the first driver on the basis of the detection signal and the differential signal;
• and
• a power supply section configured to generate a driving voltage corresponding to the feedback circuit from the output voltage and supply the driving voltage to the feedback circuit.

A luminaire comprising:

• a lighting load;
• and
• a power supply circuit configured to supply electric power to the lighting load,
• the power supply circuit including:
• a bridge circuit including at least one switching element and configured to convert a direct-current voltage into an alternating-current voltage according to ON and OFF of the switching element;
• a transformer including a primary winding wire connected to the bridge circuit and a secondary winding wire magnetically coupled to the primary winding wire;
• a rectifying and smoothing circuit configured to convert the alternating-current voltage output from the secondary winding wire into a direct-current output voltage and supply the direct-current output voltage to the lighting load;
• a first driver configured to control ON and OFF of the switching element;
• and
• a feedback circuit configured to feedback-control the first driver on the basis of a detection signal of an output current flowing to the lighting load, wherein
• when an overvoltage is detected by the feedback circuit, the first driver controls the bridge circuit to set the output voltage to be equal to or lower than a predetermined voltage.