Power Supply Zero Cross Detection Without Photo Couplers

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Solution Overview

Problem

Existing power supply systems that detect the zero cross point of alternating current voltage using photo couplers consume significant power, necessitating a more power-efficient solution while maintaining detection reliability.

Innovation Solution

A power supply system comprising capacitors, a rectification circuit, a signal generation circuit, an electricity storage unit, a backflow regulation element, and a current limit element, which together allow for the detection of the zero cross point without relying on photo couplers, thereby reducing power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a photo coupler is used to detect the zero cross point, then the zero cross point can be favorably detected, but the power consumption increases

Engineering Contradiction:

Improvezero cross point detection reliabilityVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent extracts the photo coupler from the detection circuit and replaces it with a purely electrical detection method using a capacitor and voltage detection circuit. This removes the light-emitting component that consumes significant power, while maintaining the ability to detect the zero cross point through voltage level changes.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the optical detection system (photo coupler with light emission and detection) with an electrical detection system using a capacitor charged during the AC cycle and detected through voltage levels. This substitution eliminates the need for light-based components and their associated power consumption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Speed

If the electricity storage unit is connected directly to the rectification circuit output, then power is supplied quickly, but current flows excessively to the signal generation circuit

Engineering Contradiction:

Improvepower supply speedVSAvoidexcessive current flow

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent introduces a diode as an intermediary component between the rectification circuit and the electricity storage unit. This diode acts as a one-way valve that allows current to flow from the rectification circuit to charge the capacitor, but prevents backflow, thereby controlling current direction and preventing excessive current consumption by the signal generation circuit.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the power supply path into distinct functional sections: the rectification circuit, the diode-controlled current path, and the capacitor storage unit. This segmentation allows independent optimization of each section, enabling quick power supply to the capacitor while preventing excessive current draw from the rectification circuit through the diode's directional control.

Inventive Principle:

Principle #1Segmentation

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 system effectively detects the zero cross point with reduced power consumption, maintaining reliability and enabling quick detection post-power input, suitable for applications like multifunction apparatuses.

Implementation Method 1

a rectification circuit that is electrically connected between the second electrode of the first capacitor and the second electrode of the second capacitor and is configured to rectify an alternating current voltage applied to the first and second capacitors

Methodology Applied

Scientific EffectRectification:

Implementation Method 2

a backflow regulation element that is provided on the output line of the rectification circuit and is configured to regulate backflow of current from the electricity storage unit towards the signal generation circuit

Methodology Applied

Scientific EffectDiode rectification: Diode

Data Source

PatentUS8965236B2Power supply system and image forming apparatus having the power supply system

Publication Date: 2015.02.24 BROTHER KOGYO KK

AI summary

A power supply system includes: capacitors connected to an alternating current power supply; a rectification circuit connected to the capacitors and rectifying an alternating current voltage applied to the capacitors; a signal generation circuit connected to an output line of the rectification circuit and configured to generate a detection signal corresponding to a zero cross point of an alternating current output; an electricity storage unit connected to the output line of the rectification circuit; a backflow regulation element provided on the output line of the rectification circuit and configured to regulate backflow of current; a current limit element configured to limit current flowing from the output line of the rectification circuit towards the electricity storage unit, and a control unit that is connected to the output line of the rectification circuit, and is configured to detect a zero cross point of the alternating current output.