Switching power supply device, and adjustable power supply system including the same

An adjustable power supply system comprising:

• a phase control circuit configured to phase-control an alternating voltage;
• one of a first switching power supply device and a second switching power supply device, the first switching power supply device and the second switching power supply device being configured to receive an alternating voltage phase-controlled by the phase control circuit to output an output voltage;
• and
• a load configured to be operated by an output voltage of the switching power supply device,
• the first switching power supply device including
• a rectifying circuit configured to receive the alternating voltage phase-controlled to rectify a direct voltage, and
• a switching operation conversion circuit configured to convert the direct voltage to an output voltage different from the direct voltage,
• the switching operation conversion circuit including
• a switching element being of a normally on type and having a main terminal and a first control terminal, the direct voltage being applied to the switching element,
• a current control element having at least a second control terminal, the current control element configured to turn off the switching element by lowering a potential of the first control terminal than a potential of the main terminal when a current passing through the current control element exceeds a prescribed value,
• an inductor passing a current when the switching element is of an on-state, and
• a driving winding configured to control turning on or off the switching element by magnetically coupling with the inductor and supplying an induced voltage to the first control terminal, an end of the driving winding being connected to the inductor, another end of the driving winding being connected to the first control terminal,
• the second switching power supply device including
• a rectifying circuit configured to receive a phase-controlled alternating voltage to rectify to a direct voltage, and
• a switching operation conversion circuit configured to convert the direct voltage to an output voltage different from the direct voltage,
• the switching operation conversion circuit including
• a switching element being of a normally on type and having a main terminal and a first control terminal, the direct voltage being applied to the switching element,
• a current control element having at least a second control terminal, the current control element configured to turn off the switching element by lowering a potential of the first control terminal than a potential of the main terminal when a current passing through the current control element exceeds a prescribed value,
• an inductor passing a current when the switching element is of an on-state,
• a rectifying element connected to an end of the inductor, a current passing through the rectifying element when the switching element is of an off-state, and
• a driving winding configured to control turning on or off the switching element by magnetically coupling with the inductor and supplying an induced voltage to the first control terminal, an end of the driving winding being connected to the rectifying element, another end of the driving winding being connected to the first control terminal.

A switching power supply device comprising:

• a rectifying circuit configured to receive a phase-controlled alternating voltage to rectify to a direct voltage;
• and
• a switching operation conversion circuit configured to convert the direct voltage to an output voltage different from the direct voltage,
• the switching operation conversion circuit including
• a switching element being of a normally on type and having a main terminal and a first control terminal, the direct voltage being applied to the switching element,
• a current control element having at least a second control terminal, the current control element configured to turn off the switching element by lowering a potential of the first control terminal than a potential of the main terminal when a current passing through the current control element exceeds a prescribed value,
• an inductor passing a current when the switching element is of an on-state,
• a rectifying element connected to one end of the inductor, a current passing through the rectifying element when the switching element is of an off-state, and
• a driving winding configured to control turning on or off the switching element by magnetically coupling with the inductor and supplying an induced voltage to the first control terminal, an end of the driving winding being connected to the rectifying element, another end of the driving winding being connected to the first control terminal.