Methods and systems of operating DC to DC power converters
Operating DC to DC power converters. At least some of the example embodiments are methods including: driving current through an inductance in a first on cycle of the power converter; comparing, by a comparator, a signal indicative of current through the inductance coupled to a first input of the comparator to a threshold applied to a second input of the comparator, and asserting a comparator output responsive to the signal indicative of current meeting the threshold; sampling a differential voltage across the first and second inputs, the sampling responsive to assertion of a comparator output, and the differential voltage indicative of propagation delay through the comparator; and compensating the comparator in a second on cycle for the compensation delay based on the differential voltage, the second on cycle subsequent to the first on cycle.
1. A method of operating a power converter comprising:
driving current through an inductance in a first on cycle of the power converter;
comparing, by a comparator, a signal indicative of current through the inductance coupled to a first input of the comparator to a threshold applied to a second input of the comparator, and asserting a comparator output responsive to the signal indicative of current meeting the threshold;
sampling a differential voltage across the first and second inputs of the comparator, the sampling responsive to assertion of the comparator output, and the differential voltage indicative of propagation delay and/or offset through the comparator; and
compensating the comparator in a second on cycle for the propagation delay and/or offset based on the differential voltage sampled in the first on cycle, the second on cycle subsequent to the first on cycle.
2. The method of claim 1 further comprising, prior to the first on cycle and during a period of time when the power converter is not supplying power to a load:
shorting the first and second inputs of the comparator;
measuring direct current (DC) offset of the comparator output during the shorting; and
compensating the comparator for the DC offset.
3. The method of claim 1 wherein comparing the signal indicative of current to the threshold further comprises comparing the signal indicative of current to the threshold being a peak current threshold at which the first on cycle ends.
4. The method of claim 1 wherein comparing the signal indicative of current to the threshold further comprises comparing the signal indicative of current to the threshold being an average current threshold.
5. The method of claim 1 further comprising:
shorting, during the first on cycle, a first and second inputs of an amplifier of an error controller;
measuring direct current (DC) offset of the amplifier of the error controller during the shorting; and
compensating the amplifier of the error controller for the DC offset.
6. The method of claim 1 wherein compensation the comparator further comprises:
driving, during a first off cycle, a compensation voltage to a capacitor; and
coupling the compensation voltage to compensation inputs of the comparator, the compensation voltage coupled to the compensation inputs of the comparator during the second on cycle.
7. A packaged semiconductor device that implements a driver for a direct current (DC) to DC power converter, the packaged semiconductor device comprising:
a comparator system defining a first input, a second input, and a comparator output, the first input coupled to a voltage indicative of current supplied by the DC to DC converter to a load, and the second input coupled to a reference voltage;
a regulating controller configured to generate a pulse signal that controls supply of current to the load, and with asserted times of the pulse signal based on a value indication of current supplied to the load;
the comparator system further comprises:
a comparator defining the first input, the second input, the comparator output, and a compensation input, the comparator configured to compensate the first and second inputs based on the compensation input;
a sample and hold circuit defining a trigger input, a sample output, a first sample input coupled to the first input, and a second sample input coupled to the second input, the sample and hold circuit configured to sample a differential voltage across the first and second inputs responsive to assertion of the trigger input, and to apply the differential voltage to the sample output responsive to de-assertion of the trigger input;
an error controller defining an error input and a control output, the error input coupled to the sample output, and the control output coupled to the compensation input of the comparator; and
the error controller configured to supply a compensation signal on the control output based on the differential voltage over one or more cycles of the pulse signal, the compensation signal to compensate the comparator for propagation delay through the comparator.
8. The packaged semiconductor device of claim 7 :
wherein the sample and hold circuit is configured to sample the differential voltage on the first and second inputs during a first on cycle of the pulse signal; and
wherein the error controller is further configured to supply the compensation signal during a second on cycle of the pulse signal based on the differential voltage during the first on cycle of the pulse signal.
9. The packaged semiconductor device of claim 7 :
wherein the sample and hold circuit is configured to sample the differential voltage on the first and second inputs at a termination of a first on cycle of the pulse signal; and
wherein the error controller is further configured to supply the compensation signal during a second on cycle of the pulse signal based on the differential voltage during sampled at the termination of the first on cycle of the pulse signal.
10. The packaged semiconductor device of claim 7 wherein the error controller is further configured to create the compensation signal using at least one control methodology from a group comprising: Proportional Integral Differential (PID) control; Proportional Integral (PI) control; integral-only control.
11. The packaged semiconductor device of claim 7 :
wherein the compensation input of the comparator is a differential input comprising a first and second connections; and
wherein the control output is a differential output comprising a first and second connections.
12. The packaged semiconductor device of claim 11 :
wherein the sample output of the sample and hold circuit is a differential output comprising a first and second connections; and
wherein the error input of the error controller is a differential output comprising a first and second connections.
13. The packaged semiconductor device of claim 7 wherein trigger input of the sample and hold circuit is coupled to the comparator output of the comparator.
14. The packaged semiconductor device of claim 7 wherein the error controller further comprises:
an amplifier coupled to the sample output of the sample and hold circuit;
a first capacitor; and
a first switch coupled between the amplifier and the first capacitor;
the error controller configured to make the first switch non-conductive during a first on cycle of the pulse signal, and the error controller configured to make the first switch conductive during a first off cycle of the pulse signal and configured to drive the compensation signal to the first capacitor during the first off cycle.
15. A system for supplying power to a load, comprising:
a power converter;
an inductive load coupled to the power converter;
the power converter comprises:
a comparator system defining a first input, a second input, and a comparator output, and the first input coupled to a voltage indicative of current supplied by the power converter to the inductive load;
a regulating controller configured to generate a pulse signal that controls supply of current to the load, and with asserted times of the pulse signal based on a value indication of current supplied to the inductive load;
wherein the comparator system is configured to:
compare, during a first on cycle of the pulse signal, a signal indicative of current to the inductive load applied to the first input to a threshold applied to the second input, and assert the comparator output when the signal indicative of current meets or exceeds the threshold;
sample a differential voltage across the first and second inputs, the sampling responsive to assertion of a comparator output, and the differential voltage indicative of propagation delay and/or offset through the comparator system; and
compensate the comparator system in a second on cycle, subsequent to the first on cycle, for the propagation delay and/or offset based on the differential voltage.
16. The system of claim 15 wherein when the comparator system compares the signal indicative of current to the threshold, the comparator system is further configured to compare the signal indicative of current to the threshold being a peak current threshold.
17. The system of claim 15 wherein when the comparator system compares the signal indicative of current to the threshold, the comparator system is further configured to compare the signal indicative of current to the threshold being an average current threshold.
18. The system of claim 15 wherein the comparator system is further configured to:
short the first and second inputs of the comparator system;
measure direct current (DC) offset of the comparator output during the shorting; and
compensate the comparator system for the DC offset.
19. The system of claim 15 wherein the comparator system further comprises:
a comparator defining the first input, the second input, the comparator output, and a compensation input, the comparator configured to compensate the first and second inputs based on the compensation input;
a sample and hold circuit defining a trigger input, a first sample input, a second sample input, and a sample output, the sample and hold circuit configured to sample a differential voltage across the first and second inputs responsive to assertion of the trigger input, and to apply the differential voltage to the sample output;
an error controller defining an error input and a control output, the error input coupled to the sample output, and the control output coupled to the compensation input of the comparator;
the error controller configured to supply a compensation signal on the control output based on the differential voltage over one or more cycles of the pulse signal, the compensation signal to compensate the comparator for propagation delay through the comparator.
20. The system of claim 19 wherein the error controller further comprises:
an amplifier coupled to the sample output of the sample and hold circuit;
a first capacitor; and
a first switch coupled between the amplifier and the capacitor;
the error controller configured to make the first switch non-conductive during the first on cycle of the pulse signal, and the error controller configured to make the first switch conductive during the first off cycle of the pulse signal and configured to drive the compensation signal to the first capacitor by the amplifier during the first off cycle.