DC-DC Converter Mode Transition Control

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Solution Overview

Problem

Conventional current mode DC-DC voltage converters experience undesirable transients in inductor current and deviations in output voltage when transitioning between peak and valley current control modes, due to changes in duty cycle.

Innovation Solution

A PWM signal generator is employed to monitor the duty cycle and generate positive and negative window offset voltages, allowing the PWM controller to switch between peak and valley current control modes smoothly, reducing transients and deviations by transitioning based on inductor current sense signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the PWM controller transitions between peak and valley current control modes based on duty cycle changes, then the DC-DC converter can adapt to different operating conditions, but transients in inductor current and deviations in output voltage occur during transition

Engineering Contradiction:

Improveadaptability to different operating conditionsVSAvoidoutput voltage stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary action by detecting the duty cycle threshold in advance and proactively transitioning between peak and valley current control modes before the transients fully develop. The controller monitors the duty cycle and switches control modes when it exceeds or falls below predetermined thresholds, preventing the harmful transients from occurring in the first place rather than reacting after they appear.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by continuously monitoring the duty cycle of the PWM signal and using this information to determine when to transition between control modes. The controller uses the duty cycle feedback to intelligently switch between peak and valley current control, maintaining output voltage stability while adapting to changing operating conditions. The inductor current sense signal provides additional feedback to confirm proper mode transition.

Inventive Principle:

Principle #23Feedback

2Device complexity

If conventional DC-DC converters use simple duty cycle-based mode switching, then the control logic is simple, but undesirable transients and voltage deviations occur

Engineering Contradiction:

Improvecontrol logic simplicityVSAvoidtransients in inductor current

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces an intermediary mechanism by using the duty cycle as a mediating parameter to intelligently control the transition between peak and valley current control modes. Rather than directly switching modes based on complex conditions, the controller uses duty cycle thresholds as intermediaries to determine when transitions should occur. This intermediary approach maintains relative simplicity while effectively preventing transients in the inductor current.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10768678B2Method and system for reducing transients in DC-DC converters

Publication Date: 2020.09.08 INTERSIL AMERICAS INC

AI summary

One embodiment pertains to a method including determining the duty cycle of a PWM signal, operating in valley current control mode when the duty cycle is greater than fifty percent, operating in peak current control mode when the duty cycle is less than fifty percent, and including, commencing a PWM pulse upon the occurrence of a pulse of a first clock signal pulse, and terminating the PWM pulse upon a level of a signal exceeding a positive window threshold.