Patent ID: 6912141

Claim:
A switching power supply apparatus comprising: a switching control circuit having an input voltage and a hysteresis low-voltage mistaken operation circuit; a rectifying smoothing circuit for producing a driving output for driving said switching control circuit; a capacitor for accumulating energy corresponding to a range of voltages of said hysteresis low-voltage mistaken operation circuit from a protective voltage to a release voltage; a primary side startup circuit for supplying a startup current to said switching control circuit, wherein said hysteresis low-voltage mistaken operation circuit prohibits said primary side startup circuit from starting up said switching control circuit based on energy accumulated in said capacitor; a primary side rectifying circuit having a primary rectified output; a secondary side rectifying circuit having a secondary rectified output; a converter transformer having a primary winding which receives said primary rectified output, a tertiary winding which is wound in a direction opposite to that of the primary winding and has a tertiary output, and a secondary winding wound in a direction opposite to that of the primary winding; a switching element for switching said primary rectified output; and an output detection circuit comprising an error feed back signal to said switching control circuit via a photocoupler to control the switching element by said switching control circuit; wherein after said primary side startup circuit supplies said startup current to said switching control circuit, a tertiary output of said tertiary winding is rectified and smoothed by said rectifying smoothing circuit to produce said driving output; wherein said tertiary output is lower than said protective voltage when a current supplied to said secondary winding is less than a predetermined setting load current, and said tertiary output is higher than said protective voltage when a current into said secondary winding is greater than said predetermined setting load current; and wherein the switching control circuit enters into a standby state when said input voltage is less than or equal to said release voltage.