Method and apparatus for powering electronic circuits

1. A method for powering an electronic circuit, comprising:

(a) providing a plurality of power units, each power unit supplying an output voltage to the electronic circuit, the plurality including:

a power unit having the highest output voltage, comprising:

a power supply; and

a comparator of an output voltage of the power supply; and

voltage step-up and step-down power units, each comprising:

a power supply;

a comparator of an output voltage of the power supply; and

a voltage regulator;

(b) controlling the power supply of the step-up power unit using the comparator of the step-down power unit; and

(c) selectively converting an output voltage of the step-up power unit into an output voltage of the step-down power unit using the regulator of the step-down power unit and providing the converted voltage to an output of the step-down power unit.

2. The method of claim 1 wherein the electronic circuit is a digital, analog, or mixed signal electronic circuit using more than one supply voltage.

3. The method of claim 1 wherein the step (b) further comprises:

applying to a first input of the comparator of the step-down power unit an output voltage of the step-down power unit;

applying to a second input of the comparator of the step-down power unit a first reference voltage that is equal to or greater than a minimal operational output voltage of the step-down power unit;

coupling an output of the comparator of the step-down power unit to an ON/OFF terminal of the power supply of the step-up power unit; and

switching off the power supply of the step-up power unit when the output voltage of the step-down power unit is smaller than the minimal operational output voltage of the step-down power unit.

4. The method of claim 1 wherein the respective voltage regulators of the step-up power unit and the step-down power unit each comprise a network including a voltage comparator and a voltage converter.

5. The method of claim 4 further comprising for at least one of the step-up power unit and the step-down power unit:

applying to a first input of the voltage comparator of the power unit an output voltage of the power unit;

applying to a second input of the voltage comparator of the power unit a second reference voltage that is smaller by a predetermined margin than a minimal operational output voltage of the power unit;

coupling an output of the voltage comparator of the power unit to a control input of the voltage converter of the power unit; and

enabling the voltage converter when the second reference voltage is greater than the output voltage.

6. The method of claim 1 wherein at least one of the power supplies is a DC/DC converter.

7. The method of claim 1 wherein at least one of the power units further comprises at least one capacitor coupled to an output of the power unit.

8. An apparatus for powering an electronic circuit, comprising:

a plurality of power units, each power unit supplying an output voltage to the electronic circuit, the plurality including:

a power unit having the highest output voltage, comprising:

a power supply; and

a comparator of an output voltage of the power supply; and

voltage step-up and step-down power units, each comprising:

a power supply;

a comparator of an output voltage of the power supply; and

a voltage regulator,

wherein the comparator of the step-down power unit controls the power supply of the step-up power unit; and the regulator of the step-down power unit selectively converts an output voltage of the step-up power unit into an output voltage of the step-down power unit and provides the converted voltage to an output of the step-down power unit.

9. The apparatus of claim 8 wherein the electronic circuit is a digital, analog, or mixed signal electronic circuit using more than one supply voltage.

10. The apparatus of claim 9 wherein at least one of the power supplies is a DC/DC converter.

11. The apparatus of claim 8 wherein:

a first input of the comparator of the step-down power unit is coupled to an output of the step-down power unit;

a second input of the comparator of the step-down power unit is coupled to a source of a first reference voltage; and

an output of the comparator of the step-down power unit is coupled to an ON/OFF terminal of the power supply of the step-up power unit.

12. The apparatus of claim 11 wherein the first reference voltage is equal to or greater than a minimal operational output voltage of the step-down power unit.

13. The apparatus of claim 8 wherein the comparator of the step-down power unit switches off the power supply of the step-up power unit when the output voltage of the step-down power unit is smaller than a minimal operational output voltage of the step-down power unit.

14. The apparatus of claim 8 wherein the voltage regulators of the step-up power unit and the step-down power unit each comprise a network including a voltage comparator and a voltage converter.

15. The apparatus of claim 14 wherein for at least one of the step-up power unit and the step-down power unit:

a first input of the voltage comparator of the power unit is coupled to an output of the power unit;

a second input of the voltage comparator of the power unit is coupled to a source of a second reference voltage; and

an output of the voltage comparator is coupled to a control input of the voltage converter of the power unit.

16. The apparatus of claim 15 wherein the second reference voltage is smaller by a predetermined margin than a minimal operational output voltage of the power unit.

17. The apparatus of claim 15 wherein the voltage provided by the regulator of the power unit is equal to or greater than the minimal operational voltage of the step-down power unit.

18. The apparatus of claim 8 wherein at least one of the power units further comprises at least one capacitor coupled to an output of the power unit.