Power Device Controller Current Feed-Forward Loop Gain

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Advanced power device controllers with two-loop control systems still exhibit load dependences, particularly in the low-frequency component of the loop gain, affecting the stability and efficiency of power device control.

Innovation Solution

Incorporating a current feed-forward mechanism within the current mode control loop to modify the slope of the ramp voltage based on sensed inductor current, reducing the load current dependence of the error voltage's gain and enhancing the stability of the control loop.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If two-loop control circuits with current mode control are used, then transient response speed is improved, but load dependence of control characteristics still exists

Engineering Contradiction:

Improvetransient response speedVSAvoidload independence of control characteristics

Core Design Contradiction:

SpeedVSAdaptability or versatility

Solution Approach 1:

The patent applies preliminary action by introducing a feed-forward path that anticipates load current changes and proactively adjusts the control signal before the feedback loop can respond. The feed-forward controller receives the load current signal and generates a compensating voltage that is added to the error signal, pre-correcting for expected variations in loop gain due to load changes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements parameter changes by dynamically adjusting the effective loop gain through the feed-forward path. The feed-forward controller modifies the control characteristics based on the instantaneous load current, changing the system parameters (loop gain) to maintain optimal performance across varying load conditions.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If traditional voltage mode control or standard two-loop control is used, then device complexity is reduced, but load dependence of loop gain affects stability

Engineering Contradiction:

Improvecontrol circuit structureVSAvoidcontrol loop stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent employs feedback by sensing the load current and using this information in the feed-forward path to adjust the control signal. The load current is sensed and fed forward to compensate for its effect on loop gain, creating a closed-loop correction mechanism that improves stability without requiring complex additional hardware.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The feed-forward controller acts as an intermediary element between the load current sensing and the main control loop. It processes the load current signal and generates a compensating voltage that mediates the interaction between load variations and the control loop, isolating the main control architecture from load-dependent instability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If feed-forward current control is added, then load current dependence of loop gain is reduced, but device complexity increases

Engineering Contradiction:

Improveload independence of loop gainVSAvoidcontrol circuit elements

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges the feed-forward control function with the existing two-loop control architecture. The feed-forward path is integrated into the control signal generation process, combining multiple control functions (voltage mode control, current mode control, and load compensation) into a unified control system that shares common hardware resources.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The feed-forward controller is designed with multi-functionality, serving both as a load compensation mechanism and as part of the overall control signal generation. The same feed-forward path that compensates for loop gain variations also contributes to the transient response enhancement, making the additional circuitry serve multiple purposes.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS7615978B2Current mode control with feed-forward for power devices

Publication Date: 2009.11.10 SEMICON COMPONENTS IND LLC

AI summary

A power device controller includes a voltage mode control loop to generate an error voltage and to control a power device and a current mode control loop to generate a current control voltage and to control the power device. The current mode control loop includes a current feed-forward to reduce a load dependence of a loop gain by reducing a load current dependence of a low frequency component of a gain of the error voltage to the output voltage with a current loop closed. A multi-phase power device controller for controlling several power devices includes a shared voltage mode control loop to generate an error voltage and a shared current mode control loop to generate a current control voltage, the shared current mode control loop including a current feed-forward to reduce a load current dependence of a low frequency component of a loop gain.