Power Converter Skip Mode Control for Low Ripple at Variable Output Voltage

Solution Overview

Problem

Existing power converters enter skip mode at fixed load currents regardless of output voltage, leading to significant voltage ripple and inefficiency, as they transition frequently between skip mode and frequency foldback operation.

Innovation Solution

Implementing a controller that adjusts the skip mode entry based on the output voltage of the power converter, pausing assertions of the control input when the load current falls below a skip threshold specific to the output voltage, thereby optimizing the transition points and reducing voltage ripple.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the power converter enters skip mode at fixed load currents regardless of output voltage, then the control logic is simple, but voltage ripple increases and efficiency deteriorates due to frequent transitions between skip mode and frequency foldback operation

Engineering Contradiction:

Improvecontrol logic complexityVSAvoidefficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent applies dynamics by making the skip mode entry threshold dynamic rather than fixed. The controller adjusts the load current threshold for entering skip mode based on the detected output voltage level. When output voltage is high, the threshold is raised to prevent premature skip mode entry; when output voltage is low, the threshold is lowered to allow skip mode entry at appropriate load levels. This dynamic adaptation eliminates frequent mode transitions and improves efficiency without requiring complex additional hardware.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of skip mode entry threshold from a fixed value to a variable value that depends on output voltage. The controller monitors output voltage and accordingly modifies the load current threshold parameter that triggers skip mode entry. This parameter change ensures optimal operating point selection across different output voltage conditions, reducing energy loss while maintaining simple control logic structure.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If the power converter enters skip mode at fixed load currents regardless of output voltage, then the control logic is simple, but voltage ripple increases due to frequent transitions between skip mode and frequency foldback operation

Engineering Contradiction:

Improvecontrol logic complexityVSAvoidvoltage ripple

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The patent applies dynamics by making the skip mode entry threshold dynamic rather than fixed. The controller adjusts the load current threshold for entering skip mode based on the detected output voltage level. When output voltage is high, the threshold is raised to prevent premature skip mode entry; when output voltage is low, the threshold is lowered to allow skip mode entry at appropriate load levels. This dynamic adaptation eliminates frequent mode transitions and improves efficiency without requiring complex additional hardware.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements feedback by having the controller continuously monitor the output voltage and use this information to adjust the skip mode entry threshold. The output voltage signal feeds back to the control logic, which modifies the threshold parameter accordingly. This closed-loop feedback mechanism ensures stable operation by preventing frequent transitions between operating modes, thereby reducing voltage ripple while maintaining simple overall system architecture.

Inventive Principle:

Principle #23Feedback

3Device complexity

If the power converter operates in frequency foldback operation with a fixed current threshold, then the transition point is simple to implement, but the operating efficiency deteriorates at light loads across varying output voltages

Engineering Contradiction:

Improvetransition point implementationVSAvoidoperating efficiency at light loads

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent applies dynamics by making the frequency foldback current threshold dynamic rather than fixed. The controller adjusts the current threshold based on the detected output voltage level, raising it when output voltage is high and lowering it when output voltage is low. This dynamic adjustment allows the converter to operate efficiently at light loads across varying output voltages by selecting the appropriate transition point, without requiring complex additional hardware or control logic.

Inventive Principle:

Principle #15Dynamics

4Loss of energy

If the power converter operates with voltage-selective skip mode entry, then operating efficiency improves and voltage ripple reduces, but the control logic complexity increases

Engineering Contradiction:

ImproveefficiencyVSAvoidcontrol logic complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent applies dynamics by making the skip mode entry threshold dynamic rather than fixed. The controller adjusts the load current threshold for entering skip mode based on the detected output voltage level. When output voltage is high, the threshold is raised to prevent premature skip mode entry; when output voltage is low, the threshold is lowered to allow skip mode entry at appropriate load levels. This dynamic adaptation eliminates frequent mode transitions and improves efficiency without requiring complex additional hardware.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of skip mode entry threshold from a fixed value to a variable value that depends on output voltage. The controller monitors output voltage and accordingly modifies the load current threshold parameter that triggers skip mode entry. This parameter change ensures optimal operating point selection across different output voltage conditions, reducing energy loss while maintaining simple control logic structure.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach ensures that power converters enter skip mode at consistent load currents across varying output voltages, reducing the frequency of transitions between skip mode and frequency foldback operation, resulting in lower voltage ripple and improved efficiency.

Implementation Method 1

When a primary switch is made conductive, primary current in the transformer stores energy in the field of the transformer. When the primary switch is made non-conductive, a voltage is induced on the secondary winding

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11804779B2Power converter with voltage-selective skip mode entry load compensation

Publication Date: 2023.10.31 SEMICON COMPONENTS IND LLC

AI summary

Power converter with voltage-selective skip mode entry. At least one example is a method of operating a power converter, the method comprising: operating, by a controller, the power converter in discontinuous conduction mode; and then operating, by the controller, the power converter in frequency foldback operation; and entering, by the controller, skip mode when load current falls below a skip threshold implemented based on an output voltage of the converter.