Systems and methods for DC-to-DC converter control
A regulated, power supply system is described using multiphase DC-DC converters with dynamic fast-turnon, slow-turnoff phase shedding, early phase turn-on, and both load-voltage and drive-transistor feedback to pulsewidth modulators to provide fast response to load transients. In an embodiment, a system master can automatically determine whether all, or only some, slave phase units are fully populated. The programmable system includes fault detection with current and voltage sensing, telemetry capability, and automatic shutdown capability. In an embodiment, these are buck-type converters with or without coupled inductors, however some of the embodiments illustrated include boost configurations.
1. A method for controlling phase current imbalance in a multiphase DC-to-DC converter, comprising:
determining a current magnitude value for each phase of the multiphase DC-to-DC converter, where each current magnitude value corresponds to magnitude of current out of one or more switching devices of the phase;
identifying a smallest current magnitude value;
firing a phase corresponding to the smallest current magnitude value;
generating a desired current signal representing a desired load current of the DC-to-DC converter;
generating a total current signal representing a load current of the DC-to-DC converter, the total current signal derived from the current magnitude value for each phase of the DC-to-DC converter;
generating a current difference signal representing an amount by which the total current signal exceeds the desired current signal;
comparing the current difference signal to a reference signal; and
in response to a magnitude of the current difference signal exceeding a magnitude of the reference signal, turning on a currently turned off freewheeling switching device, before a normal turn-on time of the freewheeling switching device, and turning off a currently turned on control switching device, of one or more phases of the DC-to-DC converter.
2. The method of claim 1 , wherein the step of determining is executed in response to a signal indicating that a phase of the multiphase DC-to-DC converter is to be fired.
3. The method of claim 2 , wherein the signal indicating that the phase of the multiphase DC-to-DC converter is to be fired corresponds to a clock signal edge.
4. A The method of claim 1 , further comprising:
comparing the total current signal to a first threshold value;
decreasing a number of phases that are active if the total current signal falls below the first threshold value; and
temporarily increasing a frequency of a converter cycle of the multiphase DC-to-DC converter for a predetermined duration, whenever the number of phases that are active is altered.
5. The method of claim 4 , the step of comparing the total current signal to the first threshold value comprising comparing a filtered version of the total current signal to the first threshold value.
6. The method of claim 4 , the step of decreasing comprising decreasing a number of phases that are active by two or more phases for at least one number of phases that are active.
7. The method of claim 4 , further comprising:
comparing the total current signal to a second threshold value; and
increasing a number of phases that are active if the total current signal rises above the second threshold value.
8. The method of claim 7 , the step of increasing the number of phases that are active comprising increasing a number of phases that are active by two or more phases for at least one number of phases that are active.
9. The method of claim 7 , wherein:
the step of comparing the total current signal to the first threshold value is performed using an analog comparator; and
the step of comparing the total current signal to the second threshold value is performed using a digital comparator.
10. The method of claim 7 , wherein:
the step of comparing the total current signal to the first threshold value is performed using a digital comparator; and
the step of comparing the total current signal to the second threshold value is performed using an analog comparator.
11. The method of claim 7 , wherein:
the step of comparing the total current signal to the first threshold value is performed using an analog comparator; and
the step of comparing the total current signal to the second threshold value is performed using an analog comparator.
12. The method of claim 7 , wherein:
the step of comparing the total current signal to the first threshold value is performed using a digital comparator; and
the step of comparing the total current signal to the second threshold value is performed using a digital comparator.
13. The method of claim 4 further comprising reallocating phase turn-on times within the converter cycle whenever the number of phases that are active is altered.
14. The method of claim 4 further comprising changing control loop characteristics as the number of active phases changes such that control loop bandwidth and phase margin are sufficient for stability as the number of active phases changes.
15. The method of claim 1 , further comprising:
comparing the total current signal to a second threshold value;
increasing a number of phases that are active if the total current signal rises above the second threshold value; and
temporarily increasing a frequency of a converter cycle of the multiphase DC-to-DC converter for a predetermined duration, whenever the number of phases that are active is altered.
16. The method of claim 15 , the step of increasing the number of phases that are active comprising increasing a number of phases that are active by two or more phases for at least one number of phases that are active.
17. The method of claim 15 further comprising reallocating phase turn-on times within the converter cycle whenever the number of phases that are active is altered.
18. The method of claim 15 further comprising changing control loop characteristics as the number of active phases changes such that control loop bandwidth and phase margin are sufficient for stability as the number of active phases changes.