DC Power Supply Current Ripple Reduction via Energy Storage

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Solution Overview

Problem

Modern communications systems using complex waveforms cause noise and ripple effects on input power supply lines, leading to stability issues and failure in electromagnetic interference tests, particularly in military and aircraft applications where 28V DC power systems are common.

Innovation Solution

A DC power supply utilizing a switch-mode DC to DC converter with a current limit controller and energy storage device to manage current draw, reducing ripple and noise by charging and discharging during high and low current periods, and employing an active filter to minimize AC input ripple.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a switch-mode DC to DC converter is used to provide power conversion, then power efficiency is improved, but input current ripple and noise increase

Engineering Contradiction:

Improvepower efficiencyVSAvoidinput current ripple and noise

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The energy storage device pre-charges during low current draw periods and immediately discharges during high current draw periods, anticipating and preventing current ripple before it reaches the input power supply line. This preliminary action smooths the current profile seen by the power supply.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The energy storage device acts as an intermediary between the switch-mode converter and the input power supply, absorbing the current ripple generated by the converter and presenting a smoother current profile to the power supply, thereby decoupling the harmful effects from the input side.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If filtering components are added to reduce ripple, then input line stability is improved, but device size and weight increase

Engineering Contradiction:

Improveinput line stabilityVSAvoiddevice weight

Core Design Contradiction:

Stability of the object's compositionVSWeight of stationary object

Solution Approach 1:

The patent changes the operating parameters of the switch-mode converter by implementing current draw limiting, which fundamentally alters the current profile from high-ripple to limited and smoother, achieving stability without relying on traditional passive filtering components that would add weight.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the traditional mechanical/passive filtering approach (using large inductors and capacitors) with an active control approach using the energy storage device and current limiting logic, eliminating the need for heavy filtering components while achieving the same ripple reduction effect.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Stability of the object's composition

If filtering components are added to reduce ripple, then input line stability is improved, but device complexity increases

Engineering Contradiction:

Improveinput line stabilityVSAvoiddevice complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The energy storage device performs multiple functions simultaneously: it stores energy, limits current draw, and reduces input current ripple. This multi-functionality eliminates the need for separate filtering components, reducing overall device complexity while maintaining input line stability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the energy storage function with the current limiting and ripple reduction functions into a single integrated approach, where the energy storage device and current limit controller work together as one system rather than requiring separate filtering stages.

Inventive Principle:

Principle #5Merging (Combining)

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

The solution effectively reduces ripple and noise, improving power supply stability and efficiency, enabling systems to pass stringent EMI tests and maintain functionality under varying current demands with enhanced power delivery and reduced weight and size.

Implementation Method 1

An energy storage device coupled to the switch-mode DC to DC converter is charged from the switch-mode DC to DC converter and discharged while the current limit controller is limiting the current draw of the switch-mode DC to DC converter

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS10361621B2DC power supply with reduced input current ripple

Publication Date: 2019.07.23 ELBIT SYSTEMS OF AMERICA LLC

AI summary

A power supply comprising a DC to DC converter coupled to a current limited controller and an accumulator is disclosed, where the DC to DC converter may be a switch-mode DC to DC converter. The current limit controller may be configured to limit a current draw of the switch-mode DC to DC converter. The accumulator may be configured to discharge to an output terminal of the DC to DC converter while the current limit controller limits the current draw of the DC to DC converter.