Adaptive two-stage voltage regulator and method for two-stage voltage regulation

1. An adaptive two-stage voltage regulator, comprising:

a voltage regulator for converting an input voltage (Vin) to a middle voltage (Vm), wherein the input voltage is smaller than or equal to a maximum value (Vin_max), Vin≦Vin_max;

a linear regulator for converting the middle voltage to an output voltage (Vout); and

a middle voltage controller for adjusting the middle voltage according to

(1) an input voltage indicator and

one of (2a) an output voltage indicator and

(2b) a predetermined first reference signal,

wherein the input voltage indicator and the output voltage indicator or the predetermined first reference signal determines a second reference signal which is supplied to the voltage regulator, such that when Vin≦Vout, Vm=Vout+ΔV and (Vout+ΔV)<Vin_max.

2. The adaptive two-stage voltage regulator of claim 1 , wherein when Vin>Vout, Vm is a one-step or multi-step waveform.

3. The adaptive two-stage voltage regulator of claim 1 , wherein when Vin>Vout, Vm=Vin+ΔV.

4. The adaptive two-stage voltage regulator of claim 1 , wherein the middle voltage controller includes:

a comparator for comparing (1) the input voltage indicator and one of (2a) the output voltage indicator and (2b) the predetermined first reference signal; and

a selection circuit for selecting the second reference signal to be provided to the voltage regulator according to the comparison result.

5. The adaptive two-stage voltage regulator of claim 1 , wherein the middle voltage controller includes:

multiple comparators for comparing the input voltage indicator with multiple predetermined reference signals;

a logic circuit performing a logic operation on the outputs of the multiple comparators; and

a selection circuit for selecting the second reference signal to be provided to the voltage regulator according to an output of the logic circuit.

6. The adaptive two-stage voltage regulator of claim 1 , wherein the middle voltage controller includes:

a subtraction circuit for subtracting the output voltage indicator from the input voltage indictor, and outputting the difference when the difference is positive, but not outputting the difference or outputting zero when the difference is negative;

a conversion circuit for converting the positive difference to a voltage signal; and

an adder circuit for adding the voltage signal converted from the positive difference to a third reference signal to determine the second reference signal which is supplied to the voltage regulator to adjust the middle voltage.

7. The adaptive two-stage voltage regulator of claim 6 , wherein the middle voltage controller further includes:

a first voltage to current converter for converting the input voltage indicator to a first current signal, and a second voltage to current converter for converting the output signal indicator to a second current signal, the first and second current signals being inputted to the subtraction circuit.

8. A method for adaptive two-stage voltage regulation, comprising:

converting an input voltage (Vin) to a middle voltage (Vm), wherein the input voltage is smaller than or equal to a maximum value (Vin_max), Vin≦Vin_max;

converting the middle voltage to an output voltage (Vout);

adjusting the middle voltage according to

(1) an input voltage indicator and

one of (2a) an output voltage indicator and

(2b) a predetermined first reference signal, wherein the input voltage indicator and [the output voltage indicator or the predetermined first reference signal ] determines a second reference signal which is supplied to the voltage regulator, such that when Vin≦Vout, Vm=Vout+ΔV and (Vout+ΔV)<Vin_max.

9. The method of claim 8 , wherein when Vin>Vout, Vm is a one-step or multi-step waveform.

10. The method of claim 9 , wherein the step of adjusting the middle voltage includes:

subtracting the output voltage indicator from the input voltage indictor, and outputting the difference when the difference is positive, but not outputting the difference or outputting zero when the difference is negative;

converting the positive difference to a voltage signal; and

adding the voltage signal converted from the positive difference to a third reference signal to determine the second reference signal which is supplied to the voltage regulator to adjust the middle voltage.

11. The method of claim 10 , wherein the step of adjusting the middle voltage includes:

converting the input voltage indicator and the output voltage indicator to current signals before the subtracting step.

12. The method of claim 8 , wherein when Vin>Vout, Vm=Vin+ΔV.

13. The method of claim 8 , wherein the step of adjusting the middle voltage includes:

comparing (1) the input voltage indicator and one of (2a) the output voltage indicator and (2b) the predetermined first reference signal; and

selecting the second reference signal to be provided to the voltage regulator according to the comparison result.