A power supply device (100A/100B), comprising: a rectifying unit (110A/110B) processing an alternating current, AC, voltage (V AC ) to generate a direct current, DC, voltage; a supplying unit (120A/120B) generating an operation voltage (VCC1) according to an input voltage (Vin); a controlling unit (130A/130B) receiving the operation voltage (VCC1) and generating an enabling signal (S PWM ); a conversion unit (140A/140B) transforming the DC voltage to generate an auxiliary voltage (V AUX ) according to the enabling signal (S PWM ), wherein the auxiliary voltage (V AUX ) is not equal to the operation voltage (VCC1); and a detection unit (150A/150B) for detecting the auxiliary voltage (V AUX ), wherein when the auxiliary voltage (V AUX ) is generated, the detection unit (150A/150B) de-activates the supplying unit (120A/120B) to stop generating the operation voltage (VCC1), wherein the supplying unit (200A/200B) comprises: a start resistor (R START-A /R START-B ); a turn-on module (210/230) connected to the start resistor (R START-A /R START-B ) in series and comprising: a depletion-mode metal oxide semiconductor field effect transistor (MOSFET) (Q1A/Q1B) comprising a control terminal, a first electrode and a second electrode; the supplying unit (200A/200B) further comprising a a storage module (220/240) connected to the turn-on module (210/230) in series and storing energy according to the input voltage (Vin), wherein the energy stored in the storage module (220/240) is transformed as the operation voltage (VCC1). a rectifying unit (110A/110B) processing an alternating current, AC, voltage (V AC ) to generate a direct current, DC, voltage; a supplying unit (120A/120B) generating an operation voltage (VCC1) according to an input voltage (Vin); a controlling unit (130A/130B) receiving the operation voltage (VCC1) and generating an enabling signal (S PWM ); a conversion unit (140A/140B) transforming the DC voltage to generate an auxiliary voltage (V AUX ) according to the enabling signal (S PWM ), wherein the auxiliary voltage (V AUX ) is not equal to the operation voltage (VCC1); and a detection unit (150A/150B) for detecting the auxiliary voltage (V AUX ), wherein when the auxiliary voltage (V AUX ) is generated, the detection unit (150A/150B) de-activates the supplying unit (120A/120B) to stop generating the operation voltage (VCC1), wherein the supplying unit (200A/200B) comprises: a start resistor (R START-A /R START-B ); a turn-on module (210/230) connected to the start resistor (R START-A /R START-B ) in series and comprising: a depletion-mode metal oxide semiconductor field effect transistor (MOSFET) (Q1A/Q1B) comprising a control terminal, a first electrode and a second electrode; the supplying unit (200A/200B) further comprising a a storage module (220/240) connected to the turn-on module (210/230) in series and storing energy according to the input voltage (Vin), wherein the energy stored in the storage module (220/240) is transformed as the operation voltage (VCC1). a start resistor (R START-A /R START-B ); a turn-on module (210/230) connected to the start resistor (R START-A /R START-B ) in series and comprising: a depletion-mode metal oxide semiconductor field effect transistor (MOSFET) (Q1A/Q1B) comprising a control terminal, a first electrode and a second electrode; the supplying unit (200A/200B) further comprising a a storage module (220/240) connected to the turn-on module (210/230) in series and storing energy according to the input voltage (Vin), wherein the energy stored in the storage module (220/240) is transformed as the operation voltage (VCC1). <EOS>