Patent ID: 7684215

Claim:
A Switching Mode Power Supply (SMPS), comprising: a power supply unit comprising a switching transistor coupled to a first coil of a primary side of a transformer for transforming an input DC voltage, wherein the power supply unit supplies power to second and third coils of a secondary side of the transformer according to an operation of the switching transistor; and a Pulse Width Modulation (PWM) signal generator configured to receive a feedback voltage corresponding to a first voltage generated from the second coil, a sense signal corresponding to current flowing through the switching transistor, and a third voltage corresponding to a second voltage generated from the third coil, and to control a turn on-off operation of the switching transistor, wherein the PWM signal generator controls an on or off time of the switching transistor so that the SMPS is driven in either a Continuous Conduction Mode (CCM) or Discontinuous Conduction Mode (DCM) in accordance with a determination of a time when a voltage between a drain and a source of the switching transistor is resonated.