Energy predictive buck converter
A switched-mode buck power converter includes a power source, a first switch, an inductor for storing energy, a diode or second switch, and control circuitry. The inductor has a first end connected to an output node of the power converter, wherein the first switch is connected between the power source and a second end of the inductor. The diode or second switch is connected, at the second end of the inductor, between the first switch and a common node of the power converter. The control circuitry is configured to (i) characterize per cycle energy demand of the power converter, (ii) characterize per cycle inductive energy of the power converter, and (iii) compare the characterized energy demand to the characterized inductive energy to control the first switch.
1. A switched-mode buck power converter comprising:
a power source;
a first switch;
an inductor for storing energy having a first end connected to an output node of the power converter, wherein the first switch is connected between the power source and a second end of the inductor;
a diode or a second switch connected, at the second end of the inductor, between the first switch and a common node of the power converter; and
control circuitry configured to:
(i) characterize per cycle energy demand of the power converter;
(ii) characterize per cycle inductive energy of the power converter; and
(iii) compare the characterized energy demand to the characterized inductive energy to control the first switch.
2. The power converter of claim 1 wherein the control circuitry uses a feedback signal that explicitly incorporates the energy in the inductor from previous cycles.
3. The power converter of claim 2 wherein the feedback signal incorporates a prediction of the energy which will remain in the switched inductor at the end of the present chopping cycle.
4. The power converter of claim 2 wherein the feedback signal incorporates a measured current, a volttime product or estimation based on time alone.
5. The power converter of claim 1 wherein, when the first switch is closed, the control circuitry is configured to open the first switch when the control circuitry determines that the characterized inductive energy reaches the characterized energy demand.
6. The power converter of claim 1 wherein the control circuitry is configured to characterize the energy demand of the power converter based on a determined difference between (i) a square of measured output voltage of the power converter and (ii) a square of a desired output voltage of the power converter.
7. The power converter of claim 1 wherein the control circuitry is configured to characterize the inductive energy of the power converter based on the square of a volttime product.
8. The power converter of claim 1 wherein the control circuitry is configured to characterize the inductive energy of the power converter based on an elapsed charging time.
9. The power converter of claim 8 wherein the control circuitry is configured to characterize the inductive energy of the power converter as a square of the elapsed charging time.
10. The power converter of claim 8 wherein the elapsed charging time is measured from the beginning of a current chopping cycle for the power converter.
11. The power converter of claim 1 wherein the control circuitry is configured to characterize the inductive energy of the power converter based on a ramp signal.
12. The power converter of claim 11 wherein the control circuitry is configured to characterize the inductive energy of the power converter as a square of the ramp signal.
13. The power converter of claim 11 wherein the ramp signal is reset at the beginning of a current chopping cycle for the power converter.
14. The power converter of claim 1 wherein the control circuitry is configured to characterize the inductive energy of the power converter based on a current measurement by a current sensor electrically coupled to the inductor.
15. The power converter of claim 14 wherein the control circuitry is configured to characterize the inductive energy of the power converter as a square of the current measurement.
16. The power converter of claim 1 wherein the control circuitry is configured to characterize the inductive energy of the power converter based on a product of (i) a voltage measurement of voltage across the inductor and (ii) a time measurement of time said voltage was applied.
17. The power converter of claim 1 wherein the characterized energy demand incorporates a square of a desired output voltage less a square of an actual output voltage.
18. The power converter of claim 1 wherein the control circuitry operates the first switch so that, during each chopping cycle of the power converter, the inductor is charged until the characterized inductive energy is greater than the characterized energy demand.
19. The power converter of claim 1 wherein the feedback term is based upon a calculation of a quantity proportional to the square of the ideal inductive charging time less a quantity proportional to the elapsed charging time.
20. The power converter of claim 1 wherein the inductor current at the beginning of a next chopping cycle is predicted and used to adjust energy supply in the power converter.