DC-DC Converter Control With Discrete Frequency Hopping
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Solution Overview
Problem
Existing DC-DC converters operating in discontinuous conduction mode face challenges in maintaining efficiency across a wide range of load currents, particularly when used with noise-sensitive loads, as they often generate switching harmonics within the sensitive frequency range of these loads, and their control architectures struggle to ensure harmonics are filtered effectively.
Innovation Solution
A controller that combines continuous on-time control with frequency-hopping control, using an on-time-control-module and a frequency-control-module to regulate the on-time and switching frequency of the DC-DC converter based on compensation signals derived from the output voltage, restricting the on-time and switching frequency to predefined target ranges, thereby maintaining high efficiency and predicting the output voltage spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency is varied continuously to maintain high efficiency across wide load ranges, then efficiency is improved, but the output voltage spectrum becomes unpredictable and may interfere with noise-sensitive loads
Solution Approach 1:
The controller dynamically adjusts the switching frequency between discrete values based on load conditions, maintaining high efficiency while ensuring the frequency remains predictable and filterable. The frequency is varied only among predefined discrete values rather than continuously, resolving the contradiction between efficiency optimization and spectral predictability.
Solution Approach 2:
The patent changes the switching frequency parameter among a set of discrete values rather than allowing continuous variation. This discrete parameter adjustment maintains efficiency across load ranges while keeping the output spectrum predictable and suitable for noise-sensitive applications.
2Object-generated harmful factors
If the switching frequency is fixed to provide a predictable spectrum, then spectral predictability is improved, but efficiency deteriorates across wide load ranges
Solution Approach 1:
The controller dynamically selects from multiple discrete switching frequency values based on operating conditions. This dynamic selection among fixed points provides both spectral predictability (since frequencies are discrete and known) and efficiency (since the optimal frequency can be selected for different load ranges).
Solution Approach 2:
The continuous frequency range is segmented into discrete frequency steps. By operating only at these segmented frequency points rather than any continuous value, the system maintains predictable spectrum characteristics while still adapting to different load conditions for efficiency.
3Loss of energy
If pulse-frequency modulation is used to improve light-load efficiency, then light-load efficiency is improved, but the switching frequency varies widely generating harmonics in noise-sensitive frequency ranges
Solution Approach 1:
The switching frequency is changed among discrete values rather than varying continuously as in traditional PFM. This discrete frequency adjustment improves light-load efficiency while keeping the frequency spectrum predictable and avoidable through filtering, resolving the harm to noise-sensitive loads.
Data Source
AI summary
A controller for controlling a DC-DC converter in a discontinuous conduction mode (DCM) includes an output module configured to provide a switch control signal to the DC-DC converter having an on-time and a switching frequency. The controller includes an on-time-control-module configured to receive a first compensation signal based on the output voltage of the DC-DC converter; and set the on-time of the switch control signal based on the first compensation signal. The controller also includes a frequency-control-module configured to receive a second compensation signal, wherein the second compensation signal is based on the output voltage of the DC-DC converter, and regulate the second compensation signal to a target range by setting the switching frequency of the switch control signal to one of a plurality of pre-defined discrete switching frequencies.