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 according to an input voltage (Vin); a controlling unit (130A/130B) receiving the operation voltage 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; 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, 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. 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 according to an input voltage (Vin); a controlling unit (130A/130B) receiving the operation voltage 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; 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, 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. 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.