Power supply device and lighting apparatus using the same

摘要

In a power supply device, a primary winding of a transformer is connected in series to a main switching element, and is connected in parallel to a series circuit of a resonance capacitor and a sub switching element. A secondary winding of the transformer is connected in series to a series circuit of a rectifying element and a resonance inductor. The capacitance of the resonance capacitor and the inductance of the resonance inductor are each set such that, when the sub switching element is in an on state, the waveform of the voltage that is generated between the first main terminal and the second main terminal of the main switching element takes a protruding curve shape, the voltage being generated due to a resonance phenomenon of at least the resonance capacitor and the resonance inductor.

主权项

1. A power supply device comprising:
a power supply unit configured to generate a first DC voltage from an input voltage; a conversion unit configured to convert the first DC voltage outputted from the power supply unit to a second DC voltage that is different from the first DC voltage; and a control unit configured to control the conversion unit, the conversion unit being an active clamp type flyback converter, and comprising: a main switching element; a sub switching element; a flyback transformer comprising a primary winding and a secondary winding; and a rectifying element configured to perform half-wave rectification on a first voltage generated in the secondary winding, the main switching element and the sub switching element each comprising a first main terminal, a second main terminal, and a control terminal, the primary winding being connected in series to the main switching element, and being connected in parallel to a series circuit of a resonance capacitor and the sub switching element, the secondary winding being connected in series to a series circuit of the rectifying element and a resonance inductor, the control unit being configured to control the main switching element and the sub switching element, and comprising, as control modes, a first control mode in which the main switching element is put in an on state and the sub switching element is put in an off state, a second control mode in which the main switching element is put in an off state and the sub switching element is put in an on state, and a third control mode in which the main switching element and the sub switching element are both put in off states, the control unit being configured to alternate between the first control mode and the second control mode via the third control mode, and a capacitance of the resonance capacitor and an inductance of the resonance inductor each being set such that, in a period in which the main switching element is in an off state and the sub switching element is in an on state, a waveform, with respect to time in the period, of a second voltage that is generated between the first main terminal and the second main terminal of the main switching element takes a protruding curve shape, the second voltage being generated due to a resonance phenomenon of at least the resonance capacitor, the primary winding, and the resonance inductor.