PWM Controller Two-Level Limiter Power Compensation

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Solution Overview

Problem

Existing power converters face challenges in maintaining consistent maximum output power due to variations in input voltage and delay times, which affect the regulation of output power, especially between high-line and low-line input voltages.

Innovation Solution

A PWM controller with a two-level limiter is introduced, comprising an oscillator, control circuit, and a two-level limiter that generates a two-level limit signal to adjust the on-time of the PWM signal, ensuring identical output power limits for both high-line and low-line input voltages by using distinct limit signals for heavy-load conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a traditional PWM controller with a single threshold is used to limit maximum output power, then the circuit complexity is low, but the output power varies significantly with input voltage variations (90VAC to 264VAC range)

Engineering Contradiction:

Improvecontroller circuit complexityVSAvoidmaximum output power consistency

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The single threshold limiter is segmented into a two-level limiter with distinct first and second thresholds. The first threshold (first threshold signal) limits the on-time of the PWM signal under high-line input voltage conditions, while the second threshold (second threshold signal) limits the on-time under low-line input voltage conditions. This segmentation allows the controller to maintain consistent maximum output power across different input voltage ranges without significantly increasing circuit complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The limiter transitions from a static single threshold to a dynamic two-level threshold system that adapts its limiting behavior based on operating conditions. The controller selectively applies the first threshold signal or second threshold signal based on the detected input voltage level and load conditions, enabling the maximum output power to be dynamically adjusted to maintain consistency despite input voltage variations.

Inventive Principle:

Principle #15Dynamics

2Speed

If the PWM switching frequency is increased to improve regulation response, then the regulation speed is improved, but the delay time impact on maximum output power becomes more significant

Engineering Contradiction:

Improveregulation response speedVSAvoiddelay time impact on output power

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The two-level limiter is configured to account for and compensate the delay time effect in advance. By setting the first and second threshold signals to different levels, the limiter pre-adjusts the on-time of the PWM signal to compensate for the inevitable delay time in the control circuit. This preliminary compensation ensures that the actual output power matches the intended maximum output power despite the delay time, even at higher switching frequencies where the delay time impact is more significant.

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If a single threshold signal is used to limit output power under all conditions, then the control circuit is simple, but the output power cannot be accurately limited under both high-line and low-line input voltage conditions

Engineering Contradiction:

Improvecontrol circuit structureVSAvoidoutput power limitation accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Different threshold levels are applied to different operating conditions: the first threshold signal is optimized for high-line input voltage conditions with heavy load, while the second threshold signal is optimized for low-line input voltage conditions with heavy load. This local quality approach ensures that each threshold is precisely tuned for its specific operating range, achieving accurate output power limitation for both high-line and low-line conditions without requiring an overly complex adaptive control system.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS8031492B2PWM controller for compensating a maximum output power of a power converter

Publication Date: 2011.10.04 SEMICON COMPONENTS IND LLC

AI summary

A PWM controller having an oscillator, a control circuit and a two-level limiter is provided. The oscillator generates a pulse signal. The control circuit couples to the oscillator for generating a PWM signal in response to the pulse signal, wherein the PWM signal controls a power switch. The two-level limiter couples to the control circuit for generating a two-level limit signal in response to an on-time of the PWM signal, wherein the two-level limit signal is formed by a first-level signal and a second-level signal during a switching period of the PWM signal, and the first-level signal is used to limit the maximum output power of the power converter under a high-line input voltage with a heavy-load condition, and the second-level signal is used to limit the maximum output power of the power converter under a low-line input voltage with the heavy-load condition.