Power Supply Circuit with Bypass Charging for Ripple Rejection

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Solution Overview

Problem

Conventional power supply circuits face challenges in enhancing ripple rejection characteristics without causing start delay, particularly in applications requiring low current consumption, where increasing drive current is not feasible, and using high resistance RC filters leads to slow output voltage rise and start sequence delays.

Innovation Solution

A power supply circuit design that includes an output transistor, a filter circuit with a resistor and capacitor, and a charging circuit that supplies charging current directly to the capacitor without passing through the resistor, using a comparator and transistors to control the charging process, allowing rapid capacitor charging and maintaining effective filter operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a high resistance RC filter is used to improve ripple rejection characteristic, then ripple rejection characteristic is improved, but start delay of the power supply circuit becomes conspicuous

Engineering Contradiction:

Improveripple rejection characteristicVSAvoidstart delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent segments the capacitor charging function into two distinct paths: a fast charging path through a charging transistor that bypasses the filter resistor, and a normal filtering path through the RC filter. This segmentation allows the system to achieve rapid startup by using the charging transistor to quickly charge the capacitor, while still maintaining good ripple rejection characteristics through the RC filter during normal operation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces dynamic control by using a charging transistor whose on/off state is controlled by a control circuit. During startup, the charging transistor is turned on to provide fast charging current to the capacitor, reducing start delay. After startup, the charging transistor is turned off, allowing the RC filter to perform its ripple rejection function. This dynamic switching resolves the contradiction between fast startup and good ripple rejection.

Inventive Principle:

Principle #15Dynamics

2Reliability

If drive current is increased to enhance power supply circuit characteristics, then characteristics of the power supply circuit are enhanced, but current consumption increases

Engineering Contradiction:

Improvepower supply circuit characteristicsVSAvoidcurrent consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent employs dynamic current control through the charging transistor, which provides high current only during the brief startup period when rapid voltage rise is needed. Once the capacitor is charged and the power supply circuit is operational, the charging transistor is turned off, eliminating additional current consumption. This dynamic approach enhances power supply characteristics during startup without increasing steady-state current consumption.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The charging transistor performs preliminary action by quickly charging the capacitor during startup before the main power supply circuit begins full operation. This preliminary charging action establishes the initial voltage level needed for proper circuit operation, allowing the main circuit to start with optimal characteristics without requiring sustained high current consumption.

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If RC filter is used to smooth output voltage, then output voltage is smoothed, but rising of the output voltage is slow

Engineering Contradiction:

Improveoutput voltage smoothingVSAvoidoutput voltage rise speed

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The charging transistor acts as an intermediary element that temporarily provides a low-impedance charging path during startup. This intermediary component allows fast voltage rise by bypassing the high-resistance filter resistor, while the filter resistor continues to perform its voltage smoothing function during normal operation when the charging transistor is non-conductive.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 enhances ripple rejection characteristics across a low frequency band without start delay, improves tolerance to input variations, and minimizes output voltage variations by enabling rapid output voltage rise and preventing overcharging.

Implementation Method 1

a filter circuit arranged to smooth the stabilized voltage using a resistor and a capacitor so as to generate an output voltage

Methodology Applied

Scientific EffectRC filtering: Filter (electronic)

Implementation Method 2

a charging circuit arranged to supply charging current to the capacitor without the charging current being passed through the resistor

Methodology Applied

Scientific EffectCapacitor charging: Capacitance

Data Source

PatentUS11079783B2Power supply circuit and power supply device

Publication Date: 2021.08.03 ROHM CO LTD

AI summary

A power supply circuit according to the present invention includes, for example, an output circuit arranged to generate a stabilized voltage from an input voltage using an output transistor, a filter circuit arranged to smooth the stabilized voltage using a resistor and a capacitor so as to generate an output voltage, and a charging circuit arranged to supply charging current to the capacitor without the charging current being passed through the resistor.