Switching Power-Supply Apparatus

A starting circuit provided in a switching power-supply apparatus and supplying a starting current to a control circuit when a DC power source is turned on, the starting circuit comprising a switching element that is configured to be connected to a DC power source via a primary winding of a transformer;

• a control circuit that controls on-and-off switching of the switching element;
• a first rectifying-and-smoothing circuit that rectifies and smoothes a voltage generated in a secondary winding of the transformer and supply it to a load;
• and a second rectifying-and-smoothing circuit that rectifies and smoothes a voltage generated in a tertiary winding of the transformer and supply it to the control circuit as a power supply voltage,
• wherein the starting circuit supplies:
• a first constant current to the control circuit when the power supply voltage is equal to or lower than a first threshold voltage, which is lower than a starting voltage of the control circuit, and is larger than the starting voltage of the control circuit, as a starting current;
• and
• a second constant current, which is greater than the first constant current, to the control circuit when the power supply voltage is larger than the first threshold voltage and is equal to or lower than the starting voltage, as the starting current.