Multiphase DC-DC Converter Ripple Tracking Control
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Solution Overview
Problem
Multiphase power converters face control issues due to cancellation of current signals when phases are equal and 180° out of phase, leading to limited maximum duty cycle, resulting in unstable operation and erratic behavior, especially in systems with multiple phases.
Innovation Solution
A controller for multiphase power converters that includes a voltage sensing circuit, a pulse generating circuit for pseudo-pulse width modulation, and an ON time signal distribution circuit to drive each DC to DC converter with a constant ON time signal, ensuring stable operation across varying load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current signal combination is used in multiphase power converters, then the control bandwidth is limited, but the system becomes unstable and exhibits erratic behavior at high duty cycles
Solution Approach 1:
The patent changes the control parameter from conventional current signal combination to direct voltage ripple sensing. By sensing the voltage ripple directly at the output node and feeding it back to the control circuit, the system achieves stable operation across a wide duty cycle range (10% to 90%) without the cancellation issues that plague conventional current signal combining methods.
2Speed
If voltage ripple feedback is used for control, then the control bandwidth increases, but the noise immunity decreases
Solution Approach 1:
The patent introduces an intermediary filtering mechanism by sensing the voltage ripple through a voltage divider network and using a capacitor to filter high-frequency noise before the signal reaches the control circuit. This intermediary filtering stage allows the system to maintain high control bandwidth while improving noise immunity, as the filtered ripple signal provides accurate feedback without being corrupted by switching noise.
3Power
If multiphase configuration is used to increase current capacity, then the power delivery capability increases, but the current signals cancel each other out when phases are 180° out of phase
Solution Approach 1:
The patent extracts the control signal from the voltage domain rather than combining current signals from multiple phases. By sensing the voltage ripple at the common output node and using this extracted voltage signal for feedback control, the system eliminates the signal cancellation problem that occurs when current signals from phases 180 degrees out of phase are combined. This extraction approach maintains full control capability while utilizing the multiphase configuration for increased current capacity.
Data Source
AI summary
A controller for a multiphase power converter has a plurality of DC to DC converters coupled in parallel between a voltage source and a single output terminal is provided. The controller includes a voltage sensing circuit coupled to the output terminal. An internal pulse generating circuit is couplable to the voltage sensing circuit for generating an internal pseudo-pulse width modulated signal. An ON time signal distribution circuit is couplable to an output of the internal pulse generating circuit and couplable to driver circuit for driving each of the plurality of DC to DC converters. A multiphase power converter and method also disclosed.