Adjustable driver voltage source for a switching power supply and method for adjusting driver voltage in a switching power supply

1. An adjustable driver voltage source for a switching power supply including a power switch and a driver for providing a control signal to switch the power switch, the adjustable voltage source comprising:

a linear regulator providing a driver voltage to the driver that determines a voltage level of the control signal, the linear regulator comprising:

a transistor connected to a voltage output terminal of the linear regulator;

an operational amplifier connected to the transistor, controlling a current of the transistor according to a feedback signal to determine the driver voltage; and

a feedback loop connected to the operational amplifier and the voltage output terminal of the linear regulator, generating the feedback signal according to the driver voltage; and

a modulator connected to the linear regulator, responsive to a loading change of the switching power supply to change the feedback signal to adjust the driver voltage;

wherein the feedback loop comprises:

a resistor serially connected to the transistor; and

a feedback terminal between the resistor and the transistor, for providing the feedback signal;

wherein the modulator comprises:

a current sensor sensing a load current of the switching power supply to generate a current sense signal; and

a transconductance amplifier connected to the current sensor and the linear regulator, for sinking a current from the feedback terminal according to a difference value between the current sense signal and a setting value so as to adjust the driver voltage.

2. An adjustable driver voltage source for a switching power supply including a power switch and a driver for providing a control signal to switch the power switch, the adjustable voltage source comprising:

a linear regulator providing a driver voltage to the driver that determines a voltage level of the control signal, the linear regulator comprising:

a transistor connected to a voltage output terminal of the linear regulator;

an operational amplifier connected to the transistor, controlling a current of the transistor according to a feedback signal to determine the driver voltage; and

a feedback loop connected to the operational amplifier and the voltage output terminal of the linear regulator, generating the feedback signal according to the driver voltage; and

a modulator connected to the linear regulator, responsive to a loading change of the switching power supply to change the feedback signal to adjust the driver voltage;

wherein the feedback loop comprises:

a resistor serially connected to the transistor; and

a feedback terminal between the resistor and the transistor, for providing the feedback signal;

wherein the modulator comprises:

a digital-to-analog converter converting a digital signal related to a loading state of the switching power supply to an analog signal; and

a transconductance amplifier connected to the digital-to-analog converter and the linear regulator, for sinking a current from the feedback terminal according to a difference value between the analog signal and a setting value so as to adjust the driver voltage.

3. A method for adjusting driver voltage in a switching power supply including a power switch and a driver for providing a control signal to switch the power switch, the method comprising the steps of:

A.) using a linear regulator to provide the driver voltage to the driver that determines a voltage level of the control signal;

B.) detecting the driver voltage to generate a feedback signal at a feedback terminal to regulate the driver voltage; and

C.) changing the feedback signal in response to a loading change of the switching power supply to adjust the driver voltage;

wherein the step C comprises the steps of:

sensing a load current of the switching power supply to generate a current sense signal; and

sinking a current from the feedback terminal according to a difference value between the current sense signal and a setting value so as to adjust the driver voltage.

4. The method of claim 3 , wherein the step B comprises the step of dividing the driver voltage by a pair of serially connected resistors to generate the feedback signal.

5. A method, for adjusting driver voltage in a switching power supply including a power switch and a driver for providing a control signal to switch the power switch, the method comprising the steps of:

A.) using a linear regulator to provide the driver voltage to the driver that determines a voltage level of the control signal;

B.) detecting the driver voltage to generate a feedback signal at a feedback terminal to regulate the driver voltage; and

C.) changing the feedback signal in response to a loading change of the switching power supply to adjust the driver voltage;

wherein the step C comprises the steps of:

converting a digital signal related to a loading state of the switching power supply to an analog signal; and

sinking a current from the feedback terminal according to a difference value between the analog signal and a setting value so as to adjust the driver voltage.

6. The method of claim 5 , wherein the step B comprises the step of dividing the driver voltage by a pair of serially connected resistors to generate the feedback signal.