Boost DC-DC Converter Duty Controller Using Delta-Sigma Modulation
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Solution Overview
Problem
Boost DC-DC converters using delta-sigma modulation face issues with duty ratio exceeding maximum limits, leading to unstable output voltage and potential transistor damage due to excessive inductor current, necessitating a method to limit the duty ratio for stable operation.
Innovation Solution
A duty controller for boost DC-DC converters incorporating a delta-sigma modulator, delay module, and shot-signal generator to regulate the duty ratio, ensuring it does not exceed a predetermined maximum, utilizing D flip-flops and logic gates to generate a duty control signal that stabilizes the converter's operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If delta-sigma modulation is used to decrease switching noise and improve conversion efficiency, then electromagnetic interference is reduced and conversion efficiency increases, but the duty ratio may exceed the maximum duty ratio causing output voltage to decrease below target voltage and feedback loop to become unstable
Solution Approach 1:
The duty ratio limiter is configured to limit the duty ratio before it exceeds the maximum duty ratio, preventing the harmful effect of feedback loop instability while maintaining the benefits of delta-sigma modulation. The limiter proactively constrains the duty ratio within a safe range based on the relationship between reference voltage and output voltage.
2Power
If the duty ratio is increased to maintain output voltage when reference voltage is much higher than output voltage, then output voltage can be maintained, but the duty ratio exceeds maximum duty ratio causing excessive inductor current and transistor damage
Solution Approach 1:
The duty ratio limiter acts as an intermediary between the delta-sigma modulator and the boost driving circuit. It mediates the duty ratio signal to prevent excessive inductor current while still allowing the output voltage to be maintained within safe operating limits. The limiter translates the high duty ratio demand into a constrained duty ratio that protects the transistors and inductor.
3Reliability
If a duty ratio limiting method is implemented to ensure steady operation, then feedback loop stability is improved and transistor damage is prevented, but additional circuit components are required
Solution Approach 1:
The duty ratio limiter changes the parameter of duty ratio from unbounded to bounded, constraining it within a specific range to ensure steady operation. By modifying the duty ratio parameter through limiting, the system achieves reliable operation while adding minimal circuit complexity. The limiter uses simple comparison logic to enforce the duty ratio constraint.
Data Source
AI summary
A boost direct current-to-direct current (DC-DC) converter using a delta-sigma modulator (DSM), the boost DC-DC converter may comprise a boost driving circuit outputting an output voltage to output terminals by boosting an input voltage, a resistance distribution circuit outputting a feedback voltage by distributing the output voltage of the boost driving circuit, a compensator outputting a compensated feedback voltage by compensating for the feedback voltage outputted by the resistance distribution circuit based on a reference voltage, a delta-sigma modulator outputting a digital signal by modulating the compensated feedback voltage and a duty controller outputting a duty control signal for controlling a switching duty of the boost driving circuit by receiving the output of the delta-sigma modulator.