Switching power supply for speeding up turn-off operation of a switching element

A switching power supply comprising:

• a switching element for controlling the amount of current passing through a main current path on an ON and OFF operation;
• a controlling circuit for detecting an output voltage of said power supply, and outputting pulse signals of on-duty according to said output voltage;
• a driving circuit for driving said switching element according to said pulse signals;
• an inductance part, a first winding thereof being connected to said switching element;
• and
• an auxiliary bias circuit, connected between a second winding of said inductance part and said driving circuit, for supplying a reverse bias voltage to a control terminal of said switching element via said driving circuit when said switching element is turned off.

A switching power supply comprising:

• a switching element for controlling the amount of current passing through a main current path based on an ON and OFF operation;
• a controlling circuit for detecting an output voltage of said power supply, and outputting pulse signals of on-duty according to said output voltage;
• a driving circuit, having a transistor short-circuiting between one end of a main current path and a control terminal of said switching element when said switching element is turned-off, for driving said switching element according to said pulse signals;
• an inductance part, a first winding thereof being connected to said switching element;
• and
• an auxiliary bias circuit, connected between a second winding of said inductance part and a control terminal of said transistor, for supplying a forward bias to said transistor when said transistor is turned on.

A switching power supply comprising:

• a switching element for controlling the amount of current passing through a main current path based on an ON and OFF operation;
• a controlling circuit for detecting an output voltage of said power supply, and outputting pulse signals of on-duty according to said output voltage;
• a driving circuit for driving said switching element according to said pulse signals;
• an auxiliary bias circuit, connected between one end of said main current path of said switching element and said driving circuit, and forming a polarity inversion circuit with said switching element, for supplying a direct-current voltage, which is obtained from said polarity inversion circuit and which has a polarity opposite that of the output voltage of said power supply, to a control terminal of said switching element via said driving circuit as a reverse bias voltage when said switching element is turned off.

A switching power supply comprising:

• a switching element for controlling the amount of current passing through a main current path based on an ON and OFF operation;
• a controller circuit for detecting an output voltage of said power supply, and outputting pulse signals of on-duty according to said output voltage;
• a driving circuit having a transistor short-circuiting between one end of a main current path and a control terminal of said switching element when said switching element is turned off, for driving said switching element according to said pulse signal;
• an auxiliary bias circuit connected between said one end of said main current path of said switching element and a control terminal of said transistor, and forms a polarity inversion circuit with said switching element for supplying a direct-current voltage, which is obtained from said polarity inversion circuit and which has a polarity opposite that of the output voltage of said power supply, to said control terminal of said transistor as a forward bias voltage when said transistor is turned-on.