Capacitor Charging Circuit with Intermittent Switching for Soft Start

Solution Overview

Problem

Existing power supply circuits face issues with rush currents and potential breakdowns due to abrupt voltage rises during activation, which can be mitigated by reducing the charging current to output capacitors, but this often requires increasing capacitance, which is not always feasible.

Innovation Solution

A circuit design that includes a capacitor, a current source, a comparator, and a switch section that intermittently controls the flow of current to the capacitor, allowing for a gradual voltage change and extended soft start-up time without increasing capacitance or current source value.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the capacitance of the output capacitor is increased to reduce rush current, then the soft start-up time is extended, but the circuit area and device complexity increase

Engineering Contradiction:

Improveprevention of power transistor breakdownVSAvoidcircuit area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent segments the capacitor charging process by introducing a switch section that intermittently connects the current source to the capacitor. This segmentation allows the charging current to be delivered in controlled pulses rather than continuously, extending the soft start-up time without requiring increased capacitance, thereby preventing power transistor breakdown while maintaining compact circuit area.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements periodic action through the switch section that intermittently connects and disconnects the current source from the capacitor at predetermined intervals. This periodic connection extends the charging time constant effectively, providing extended soft start-up protection without increasing the physical capacitance value, thus avoiding increased circuit area while maintaining reliability.

Inventive Principle:

Principle #19Periodic action

2Reliability

If the capacitance is increased to reduce rush current, then the soft start-up time is extended, but the device complexity increases

Engineering Contradiction:

Improveprevention of power transistor breakdownVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the capacitor charging process by introducing a switch section that intermittently connects the current source to the capacitor. This segmentation allows the charging current to be delivered in controlled pulses rather than continuously, extending the soft start-up time without requiring increased capacitance, thereby preventing power transistor breakdown while maintaining compact circuit area.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements periodic action through the switch section that intermittently connects and disconnects the current source from the capacitor at predetermined intervals. This periodic connection extends the charging time constant effectively, providing extended soft start-up protection without increasing the physical capacitance value, thus avoiding increased circuit area while maintaining reliability.

Inventive Principle:

Principle #19Periodic action

3Productivity

If the current source value is increased to charge the capacitor faster, then the productivity is improved, but the rush current increases causing potential breakdown

Engineering Contradiction:

Improvecharging speedVSAvoidrush current

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent implements periodic action through the switch section that intermittently connects and disconnects the current source from the capacitor at predetermined intervals. This periodic connection extends the charging time constant effectively, providing extended soft start-up protection without increasing the physical capacitance value, thus avoiding increased circuit area while maintaining reliability.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent maintains continuous useful action by ensuring the capacitor charging process proceeds without interruption, only modulating the current delivery pattern through intermittent switching. The charging action continues throughout the soft start-up period, maintaining productivity while controlling rush current through the timing and duration of switch connections rather than reducing the current source capability.

Inventive Principle:

Principle #20Continuity of useful action

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 design reduces the capacitance required in the circuit, allows for flexible design and reduced circuit area, and prevents power transistor breakdowns by controlling the charging rate, thereby managing rush currents effectively.

Implementation Method 1

a capacitor (110); a current source (120) to supply a current to the capacitor (110)

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a comparator (130) to output a result of comparison made between a voltage stored in the capacitor (110) and a predetermined voltage

Methodology Applied

Scientific EffectVoltage comparison:

Data Source

PatentUS9559579B2Circuit and power supply circuit with output that transitions between capacitor stored voltage and predetermined voltage

Publication Date: 2017.01.31 SONY GROUP CORP

AI summary

There is provided a circuit including a capacitor, a current source configured to supply a current to the capacitor, a comparator configured to output a result of comparison between a voltage stored in the capacitor and a predetermined voltage, and a switch section configured to intermittently which is caused to flow to the capacitor by the current source.