Quasi-resonant fly-back converter without auxiliary winding
AssigneeLeadtrend Technology Corp.
InventorTsung-Hsiu Wu
Life of this patent
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Abstract
Disclosed is a switching converter without an auxiliary winding. The switching converter has a transformer, a switching transistor, a coupling circuit and a regulating circuit. The transformer has a primary winding and a secondary winding, and is for transforming an input voltage into an output voltage; a first end of the switching transistor is coupled to the primary winding of the transformer, and the switching transistor is for controlling an operation of the transformer according to a control signal; the coupling circuit is for coupling a signal at the first end of the switching transistor to generate a coupled signal; and the regulating circuit is for detecting the coupled signal to generate the control signal according to the detecting result.
Claims9
A switching converter, comprising:
- a transformer, comprising a primary winding and a secondary winding, for transforming an input voltage into an output voltage;
- a switching transistor, a first end of which is directly connected to the primary winding of the transformer and a control end of which is for receiving a control signal, for controlling operation of the transformer according to the control signal;
- a coupling circuit, having a first terminal directly connected to the first end of the switching circuit, for generating a coupled signal at a second terminal of the coupling circuit according to a voltage signal at the first end of the switching transistor;
- and
- a regulating circuit, directly connected to the second terminal of the coupling circuit, for receiving the coupled signal and accordingly generating a detecting result, and generating the control signal according to the detecting result;
- wherein the voltage signal at the first end of the switching transistor is different from the coupled signal at the second terminal of the coupling circuit;
- wherein the regulating circuit comprises:
- a zero-cross detecting circuit, coupled to the coupling circuit, for detecting a zero-crossing point of the coupled signal and generating the detecting result;
- and
- a pulse width modulation (PWM) signal generator, coupled to the switching transistor, for generating the control signal to control the switching transistor according to the detecting result.
A switching converter, comprising:
- a transformer, comprising a primary winding and a secondary winding, for transforming an input voltage into an output voltage;
- a switching transistor, having a drain end connected to the primary winding and a gate end for receiving a control signal, thereby controlling operation of the transformer according to the control signal;
- a capacitor, having a first terminal connected to the drain end of the switching transistor, for generating a coupled signal at a second terminal of the capacitor according to a voltage signal at the drain end of the switching transistor;
- a regulating circuit, for receiving the coupled signal and accordingly outputting the control signal according to the detecting result, wherein the regulating circuit is connected to the capacitor with a current sensing pin, utilized to sense a current flow through the switching transistor when the switching transistor is on, and utilized to detect a demagnetization of the transformer when the switching transistor is off;
- and
- an amplifying circuit, coupled to the capacitor and the regulating circuit, for amplifying and transmitting the coupled signal to the regulating circuit, wherein the amplifying circuit comprises a resistor connected between the current sensing pin and a current sensing resistor, the resistor and the current sensing resistor are jointly connected to a source end of the switch transistor, and the resistance of the resistor is greater than that of the current sensing resistor.
Dependencies are inferred from the claim text.