Programmable Waveform Control Circuit for Power Converter Output Limiting

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Solution Overview

Problem

Conventional power converters face challenges in maintaining consistent output power limits across varying input voltages, leading to inefficiencies and increased power consumption due to the need for resistors in feed-forward compensation, which complicates component selection and PCB layout.

Innovation Solution

A control circuit with a programmable waveform for output power limit, utilizing an oscillation circuit and a second circuit to generate a waveform signal that programs the output power limit, eliminating the need for resistors to sense line voltage, thereby reducing power consumption and simplifying the design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a resistor is added for feed-forward compensation to achieve identical output power limit for low and high line voltage input, then the output power limit consistency is improved, but the power consumption increases significantly and the component selection and PCB layout become more complex

Engineering Contradiction:

Improveoutput power limit consistencyVSAvoidpower consumption

Core Design Contradiction:

Stability of the object's compositionVSLoss of energy

Solution Approach 1:

The patent extracts and eliminates the feed-forward compensation resistor from the circuit. Instead of using a resistor to sense line voltage and provide compensation, the invention uses a programmable waveform stored in a lookup table that is directly loaded into a waveform generator. This extraction removes the harmful element (resistor) that caused power consumption and complexity while preserving the desired function of consistent output power limiting across different input voltages.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the passive electrical component (resistor-based feed-forward compensation) with an active digital signal processing approach. The analog resistor-based voltage sensing and compensation mechanism is substituted with a digital lookup table containing pre-calculated waveform data and a digital waveform generator. This substitution eliminates the continuous power consumption of the resistor while maintaining accurate power limiting through programmed control signals.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Stability of the object's composition

If a resistor is added for feed-forward compensation to achieve identical output power limit for low and high line voltage input, then the output power limit consistency is improved, but the device complexity increases due to component selection and PCB layout requirements

Engineering Contradiction:

Improveoutput power limit consistencyVSAvoidcomponent selection and PCB layout

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the fundamental parameter of power limiting control from analog voltage sensing through a resistor to digital waveform programming. By storing pre-calculated compensation waveforms in a lookup table and loading them into a waveform generator, the system transforms the continuous analog compensation approach into a discrete digital approach. This parameter change eliminates the need for physical resistor selection and PCB layout considerations while maintaining accurate power limiting across varying input conditions.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the switching frequency is increased to improve productivity, then the power conversion efficiency is improved, but the impact of delay time on output power becomes more significant

Engineering Contradiction:

Improvepower conversion efficiencyVSAvoiddelay time impact

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-calculating and storing compensation waveforms that account for delay time effects at different switching frequencies in a lookup table. Before operation, the system stores corrected waveform data that has already compensated for the delay time tD. During operation, the appropriate pre-compensated waveform is selected and loaded based on the operating conditions, eliminating the need for real-time delay compensation calculations and ensuring accurate power limiting even at high switching frequencies where delay time impact is significant.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7616454B2Control circuit having programmable waveform for limiting output power of power converter

Publication Date: 2009.11.10 SEMICON COMPONENTS IND LLC

AI summary

A control circuit having a programmable waveform for the output power limit comprises an oscillation circuit to generate an oscillation signal. The oscillation signal is used for producing a switching signal to control a switching device in response to a feedback signal of the power converter. A waveform generator generates a waveform signal in accordance with the oscillation signal. The waveform signal controls the control signal and limits the output power of the power converter. A resistor is coupled to the waveform generator to program the waveform of the waveform signal. By properly selecting the resistance of the resistor, which can be used to achieve an identical output power limit of the power converter for the low line and high line voltage input.