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Relation of the invention process to TRIZ (Example: High efficiency DC-DC converter for liquid crystal watches)

| On 10, Jan 2001

MITSUO MORIHISA, Systems Planning,
Design Systems Development Center,
Production Technology Dev. Group,
SHARP CORPORATION

Partially presented at Invention Machine Corporation 1999 User Group Conference
Oct. 17-19, 1999, Boston, MA, USA

Abstract

The effectiveness of TechOptimizer is examined through a past invention (USP: 4,279,010) done by the author in 1975 without using TechOptimizer. This invention comprises a DC-DC converter for liquid crystal display watches. It was inevitable to achieve voltage conversion from 1.5V to 15-20V with over 90% conversion efficiency, as the former DSM (Dynamic Scattering Mode) liquid crystal display required 15-20V and the life of the battery had to be longer than 1 year.

After laborious investigations to find voltage transformation principles and examples, the author found a paper written in 1919 by M. Schenkel, a German engineer. He succeeded to generate ultra high voltage of over 100KV by combining capacitors and rectifiers. The author applied his principle and could realize in the 1.5V world a voltage conversion efficiency of over 90% using capacitors and Field Effect Transistors.

The author will explain in this paper how TechOptimizer could have helped a solitary inventor, if it had been available at the time of invention.

1. Introduction

2. Merits of Tracing using TRIZ

3. Structure of TechOptimizer J (Japanese version)

4. Example showing the relation of the invention process to TRIZ

 4-1. Aim of this invention

4-2. Identification of the system problem

4-3. Oscillator-trimmed voltage multiplication circuit

(Expected merits of TechOptimizer modules, if they had been available at the time of invention.)

 4-4. “Product Analysis” module

   4-4-1. Product Analysis

   4-4-2. Trimming results

 4-5. “Principles” module (1)

 4-6. Detailed concrete design

   4-6-1. Engineering investigation

   4-6-2. Findings of the historic paper by Cockcroft-Walton

   4-6-3. Cockcroft-Walton voltage multiplier circuit

   4-6-4. Findings of the historic paper by Schenkel

 4-6-5. Schenkel’s voltage multiplier circuit (1)

   4-6-6. Characteristics and Problems of semiconductor switching elements

   4-6-7. Schenkel’s voltage multiplier circuit (2)

(Expected merits of TechOptimizer modules, if they had been available at the time of invention)

  4-7. “Effects” module

  4-8. “Principles” module (2)

  4-9. “Prediction” module

4-9-1. Trends of Evolution of Technology

4-9-2. Dynamization

4-9-3. Controllability

5. Conclusions

  5-1. Merits of Tracing using TRIZ on the breakthroughs at invention

  5-2. Relation of Characters of Edison to TechOptimizer module functions

6. References

————————————————————————————————————————-

1. Introduction

The author introduced TechOptimizer 3.0 J (Japanese version) in February 1999.

Through the preliminary consultation with engineering users, the author found that they needed educational examples. It is natural that users request to see real world applications using software-assisted TRIZ. But it was difficult to develop and disclose such examples.

So the author analyzed his own technology development works in the early 1970’s (up-to-date technology at that time) and evaluated how TechOptimizer could have been used if it had existed in those days.

This paper opens one of the educational examples which explains how TechOptimizer could help a solitary inventor and be used for promoting TRIZ to engineers.

2. Merits of Tracing using TRIZ

In this paper the author precisely described the process of the contents of invention because it was a past released invention. One of the main merits of invention tracing is that it gives confidence in the effectiveness of TRIZ by ourselves.

Conditions of inventions that fit for the training and verification of TRIZ are….

(1) Effectiveness-proven inventions by applying to actual products
(2) Inventions the situations at which can be interviewed or confirmed
(3) Rights already completed and approved inventions

And by applying to already solved actual engineering problems….

(1) Enables to practically understand the usefulness of TRIZ
(2) Enables to grasp the role of engineers in design and invention
(3) Causes the will to apply TRIZ to new problems

3. Structure of TechOptimizer J (Japanese version)


Fig.1: TechOptimizer Innovation Roadmap

Formerly the process of invention and/or technology development depended on only human brain from the start to the end consistently. TRIZ software supports the engineers by the Problem Statement, Problem Solving, and Patent Retrieval tools. Namely the TRIZ aims the creativity help to the engineers by using scientific methodology and software tools.

The three main aims of TRIZ and corresponding TechOptimizer modules are as follows.

(1) Removes the Psychological Inertia“Product Analysis” module
(2) Avoids the Trade Off’s & CompromisesPrinciples” module, “Prediction” module
(3) Widens the Limited Breadth of KnowledgeEffects” module

But we must recognize that the master should be engineers (humans), not TRIZ, although the TRIZ is effective. We can confirm the dignity of ourselves through the collaborative work with TRIZ. In that sense, TRIZ can be good and clever friend to engineers.

4. Example showing the relation of the invention process to TRIZ

4-1. Aim of this invention

In this paper the effectiveness of TechOptimizer is examined through a past invention (USP: 4,279,010) done by the author in 1975 without using TechOptimizer. The present author will explain how TechOptimizer could help a solitary inventor, if it were available at the time of invention.


Fig.2: High efficiency DC-DC converter for liquid crystal watches

(1) Situations

Early 1970s was a dawn of liquid crystal display age. Main type in those days was DSM (Dynamic Scattering Mode) type developed by Heilmeier of RCA. DSM display required 15-20V drive voltage.

(2) Problems

It was inevitable to achieve voltage conversion from 1.5V to 15-20V with over 90% conversion efficiency as the former DSM liquid crystal display required 15-20V and the life of the 1.5V battery had to be longer than 1 year. The final problem to be solved was to realize a DC-DC converter that has conversion efficiency of over 90% at low voltage, very small current area.

The author made every effort to improve the efficiency within the method of conventional auto-transformer type DC-DC converter, but the efficiency didn’t exceed 50. This meant 3 months battery life. It was “a dream” then to attain over 90% conversion efficiency to secure 1 year battery life needed as a commodity. Obvious breakthrough was inevitable.

(3) Conclusion

First of all, I will show the conclusion. Sharp’s first sample of DSM liquid crystal display watch was equipped with 90% efficiency USP 4,279,010 DC-DC converter. 1), 2), 3) DSM display had old-fashioned, beautiful milky white color letters.


Fig.3: Sharp’s first sample of DSM liquid crystal display watch using new DC-DC converter

4-2. Identification of the system problem

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Fig.4: Auto-transformer type voltage multiplier circuit

There are two oscillators in this watch system. One is the Quartz Xtal Oscillator and another is the one involved in the Auto-transformer. From the watch systems point of view, only the Quartz Xtal Oscillator is essential.

Usually, a voltage conversion process requires 2 functions; the alternating current generation and the voltage transformation. Auto-transformer has also 2 functions and they can’t be divided. The present author challenged to trim the oscillator in the auto-transformer.

4-3. Oscillator-trimmed voltage multiplication circuit


Fig.5: Oscillator-trimmed voltage multiplication circuit

The Oscillator can be trimmed if Voltage Multiplication Function circuit driven by Quartz Xtal Oscillator signal could be found.

(Expected merits of TechOptimizer modules, if they had been available at the time of invention.)

4-4. “Product Analysis” module

This module gives the functional analysis of the system and gives proposals to the trimming of the unnecessary functions and ideas of substitutive function. If TechOptimizer had existed at the time of invention, “Product Analysis” module would have given a proposal of a drive signal use of the Quartz Xtal Oscillator.

4-4-1. Product Analysis


Fig.6: Functional model screen (Before Trimming)

4-4-2. Trimming results


Fig.7: Functional model screen (After Trimming)

4-5. “Principles” module (1) 


Fig.8: “Principles” module (1)Auto-transformer Problems

Principles module’s hint easily seems to lead average electronics engineers to the idea of multiplier circuits which has no oscillator in it. But the idea got from “Principles” module seems to be more abstract than that got from “Product Analysis” module.

4-6. Detailed concrete design

4-6-1. Engineering investigation

I devoted myself to the search of a circuit that had an independent voltage multiplication function. I went to the Osaka University library and found the historic paper of Cockcroft-Walton (1932) 4) and M.Schenkel (1919) 5) on circuits used for ultrahigh voltage generation (100KV).

I was a radio amateur when I was young and I knew voltage doubling circuit composed by diodes and capacitors. But the Cockcroft-Walton and Schenkel circuits had theoretically no limitation in the multiplication stage number. (As explained later in Chapter4-7, “Effects” module had no data on the voltage multiplier circuits.)

4-6-2. Findings of the historic paper by Cockcroft-Walton

Cockcroft and Walton were English and Irish physicists each who succeeded in the experiment to smash the atomic nucleus using their 800KV voltage generation circuit. (Both physicists won the Nobel Prize for physics) As shown in the figure, this circuit was composed of capacitors and switches.


Fig.9: Cockcroft and Walton Proc.Roy.Soc. paper “Experiments with High Velocity Positive Ions ”

Three capacitors, C4, C2, C0, each of capacity C, are connected in series and capacitor C0 is connected to a source of steady potential E. If now two other capacitors, C3, C1, are connected to capacitors C4, C2, C0, first as shown by the dotted lines S5, S3, S1, and then as shown by the full line S6, S4, S2, then in the first cycle when C3 and C1 are connected to C2 and C0, capacitor C1 will be charged to voltage E. When the switches are moved over to the upper position, capacitor C1 will share its charge with capacitor C2 and both will be charged to E/2 if they have equal capacity.

In the next reversal of the switches, capacitors C2 and C3 will be connected and take up potentials E/4 whilst capacitor C1 will be recharged to potential E. It is thus evident that charge will gradually transferred to all the capacitors until, in the absence of loss, a potential 3E will be developed across the capacitors C4, C2, C0 in series. (quoted from the P.620 of Ref.4) )

4-6-3. Cockcroft-Walton voltage multiplier circuit


Fig.10: Cockcroft-Walton voltage multiplier circuit (In case using diodes as switching elements)

This is an actual Cockcroft and Walton type DC-DC converter circuit using PN junction diodes as switching element. This circuit is originally developed in the ultra high voltage area, but in principle there is no limitation to voltage.

4-6-4. Findings of the historic paper by Schenkel


Fig.11: M.Schenkel’s Elektrotechnische Zeitschrift paper “Eine neue Schaltung fuer die Erzeugung hoher Gleichspannungen ”

Cockcroft and Walton cited in their paper, the voltage multiplying circuits invented by M.Schenkel, German engineer in 1919. This circuit differs in the arrangement of capacitors from the Cockcroft and Walton one, but they did not use Schenkel circuit as it required some of the capacitors used to withstand full voltage of output circuit.

4-6-5. Schenkel’s voltage multiplier circuit (1)


Fig.12: Schenkel’s voltage multiplier circuit (In case using diodes as switching elements)

This is an actual Schenkel type DC-DC converter circuit using diodes as switching element. Schenkel type one was superior to Cockcroft and Walton one especially in our applications, so the author adopted Schenkel’s circuit.

4-6-6. Characteristics and Problems of semiconductor switching elements


Fig.13: Semiconductor switching elements

Two kind of semiconductors were shown here as switching elementsone is a diode and the other is a MOS transistor. Diode has forward voltage loss, but MOS Transistor has no such loss. So, the MOS transistor is superior to diode especially in low voltage region. But the MOS transistor operating circuit becomes considerably complex because it needs gate control for ON and OFF.

4-6-7. Schenkel’s voltage multiplier circuit (2)


Fig.14: Schenkel’s Circuit (2) (Using MOS transistors as switching elements)

This is an actual Schenkel type X3 multiplying DC-DC converter circuit invented using MOS transistors as switching elements.

(Expected merits of TechOptimizer modules, if they had been available at the time of invention.)

4-7. “Effects” module

“Effects” module is an Inverted Data Base of science and technology for finding means from goals. As matters now stand, “Effects” module has few effects and examples on electronic circuit. But as most growing part of the TechOptimizer now is “Effects” module, drastic improvement can be expected in future.

Recently, the author went to the library of Osaka University again where the present author first encountered the papers of Cockcroft-Walton (1932) and M.Schenkel (1919) over a quarter century before. There the author again found many papers by European scientists written about a century before. Perhaps few people will read them now. While the author was reading the papers of Cockcroft-Walton and M.Schenkel in the silent space, the author had a momentary illusion that ambitious scientists in those days were giving hot debate.

The author felt by intuition that many epoch making discovery or invention had been stored (or kept idle because it were aged) not only in this libraries or other laboratories.

The present author knows that Henry Altshuller always told people who want advises that “Your engineering problem had been already solved by another person.”

The “Effects” module’s value exists in a tool which makes the best use of predecessors’ wisdom regardless of the restriction of time and space.

4-8. “Principles” module (2)


Fig.15: Problem of voltage multiplier circuits using MOS transistors as switching elements

The derived inventive principle 1. “Segmentation” easily lead electronics engineers to the actual solution “Time segmentation”.

4-9. “Prediction” module

4-9-1. Trends of Evolution of Technology

One of the insights by Altshuller is that all technical systems have a number of trends of evolution which are common across the fields and eras.

Image142.gif (10885 bytes)
Fig.16: Trends of Evolution of Technology (Voltage multiplication from the Switching Means viewpoint)

Trends of Evolution of Technology instruct us:

(1) Eighty years before invented voltage multiplying principle which was then applied in ultra high voltage area now evolves to use in low voltage area.

(2) Owing to the advance of semiconductor technology, the principle of the switching device evolved dramatically especially in low voltage area.

4-9-2. Dynamization

Among the 14 Trends of Technology Evolution view of Prediction module, this case study corresponds to “Dynamization”. This suggests inventors to make the system with more flexibility and higher performance.


Fig.17: Prediction Module (8. Dynamization)

Prediction Module (8. Dynamization) suggests inventors to watch the dynamic trend.

4-9-3. Controllability

Among the 14 Trends of Technology Evolution view of Prediction module, this case study corresponds to “Controllability”. This suggests inventors to make the system with more automated one.


Fig.18: Prediction Module (10. Controllability)

Prediction Module (10. Controllability) suggests inventors that automated trend is a must.

5. Conclusions

5-1. Merits of Tracing using TRIZ on the breakthroughs at invention


Fig.19: Three BREAKTHROUGHS in this invention (Effective TOPE Modules)

Lastly we can conclude as follows

(1) The effectiveness of TechOptimizer has been well verified by applying it to a past invention. TechOptimizer surely will save solitary and serious inventors to make breakthroughs.

(2) The experience of the verification well accelerates the will of inventors (or engineers) to receive benefits of TechOptimizer in solving new problems of theirs.

(3) We regard the advanced Effects Module as a supremely efficient Inverted Knowledge Data Base.

5-2. Relation of Characters of Edison to TechOptimizer module functions

Thomas Alva Edison (1847-1931) is a well-known great inventor.

Here I would like to compare the relation of his seven characteristics 6), 7) to TechOptimizer’s modules functions as follows.

  1. Extensive reader having wide knowledge through rapid reading and outstanding memory.
    àEffects modules

  2. Way of thinking free from usual concept or common sense.
    àProduct Analysis modules
    àPrinciples modules
    àPrediction modules

  3. Thought a great deal of On the Job Training, and despised the usual school education
    àEffects module

  4. Had endeavor, attachment, opponent mind with wide curiosity and pioneer spirit.
    àNo

  5. Heuristics that considered matters in a whole aspect and understood mutual relations under deliberate thinking.
    àProduct Analysis module
    àPrinciples module
    àPrediction module

  6. Had a foresight into the future and prepared for the social system transition
    àPrediction module

  7. Excelled to select the invention themes and proceeded them at the same time
    àNo.

As shown above, TechOptimizer’s five functions seem to correspond to Edison’s seven characteristics. It is said that Edison had many good friends. Among them, Charles Batchelor and John Kruesi 7) were excellent reliable engineers in his laboratory.

The author thinks that Edison would have probably added TechOptimizer as another reliable engineering assistant, if TechOptimizer were available to Edison then.

6. References

  1. M. Morihisa; JPO NO.60-28232, “DC-DC Converter”(J)

  2. M. Morihisa; USP NO.4,279,010, “DC-DC Converter for solid state watches”

  3. M. Morihisa, K. Hachimura, T.Sasaki, T.Nakamura; “CMOS Schenkel type DC-DC converter”Nikkei Electronics Magazine, Dec. 3rd, 1973 (J)

  4. Cockcroft, J.D. and Walton, E.T.S.; “Experiments with High Velocity Positive Ions,” Proc.Roy.Soc, vol.136, pp.619-630, 1932

  5. M. Schenkel; “Eine neue Schaltung fuer die Erzeugung hoher Gleichspannungen”, Elektrotechnische Zeitschrift, vol.40, no.28, pp333-334, 1919

  6. Mitsubishi Research Institute, “Zukai TRIZ (Methodology of Innovative Technology of Design) ”, Nihon Jitsugyo Publishing Co., 1999, pp21. (J)

  7. K. Hamada; “Kaijin Edison”, Nihon Keizai Sinbunsha Co., 1996 (J)

Appendix:

M. Schenkel; “Eine neue Schaltung fuer die Erzeugung hoher Gleichspannungen”, Elektrotechnische Zeitschrift, vol.40, no.28, pp333-334, 1919.

About the Author

Mitsuo Morihisa is a TRIZ practitioner in SHARP Corporation in JAPAN. He was born in 1941 and an eager radio amateur in his youth and since then had been interested in invention. After graduating master’s course on electronic engineering from Tohoku University in 1967, he had been working for SHARP in various fields, from Research Development to Systems Planning. He believes that nations must share a common destiny more and more by sharing wisdom from the different cultures (like TRIZ methodology) towards the coming millennium. He likes music by Moussorgsky and Beethoven very much and he has been one of the chorus member of Beethoven’s 9th Symphony (below is the initiating chorus passage he especially loves) every December.

Email address: mmorihisa@hotmail.co.jp

Acknowledgments

I would like to express sincere thanks to Mr. M. Hotta, Mr. Y. Konishi, Mr. N. Togashi, and Mr. Y. Okubo of Mitsubishi Research Institute for useful discussions.