Page 158 - The Art and Science of Analog Circuit Design

Tripping the Light Fantastic

I've been dating me a long time, so this state of mind doesn't promote
quite the panic and urgency it used to. The treatment is always the same.
Keep busy with mundane chores at work, read, cruise electronic junk
stores, fix things and, in general, look available so that some interesting
problem might ask me to dance. During this time I can do some of the
stuff I completely let go while I was immersed in whatever problem
owned me. The treatment always seems to work, and usually takes a pe-
riod of months. In this case it took exactly three.

What's a Backlight?

Around Christmas my boss, Bob Dobkin, asked me if I ever thought
about the liquid crystal display (LCD) backlights used in portable com-
puters. I had to admit I didn't know what a backlight was. He explained
that LCD displays require an illumination source to make the display
readable, and that this source consumed about half the power in the ma-
chine. Additionally, the light source, a form of fluorescent lamp, requires
high-voltage, high-frequency AC drive. Bob was wondering how this was
done, with what efficiency, and if we couldn't come up with a better way
and peddle it. The thing sounded remotely interesting. I enjoy transducer
work, and that's what a light bulb is. I thought it might be useful to get
my hands on some computers and take a look at the backlights. Then I
went off to return some phone calls, attend to other housekeeping type
items, and, basically, maintain my funk.

Three days later the phone rang. The caller, a guy named Steve Young
from Apple Computer, had seen a cartoon (Figure 11-1)1 stuck on the
back page of an application note in 1989. Since the cartoon invited calls,
he was doing just that. Steve outlined several classes of switching power
supply problems he was interested in. The application was portable com-
puters, and a more efficient backlight circuit was a priority. Dobkin's
interest in backlights suddenly sounded a lot less academic.
This guy seemed like a fairly senior type, and Apple was obviously a
prominent computer company. Also, he was enthusiastic, seemed easy to
work with and quite knowledgeable. This potential customer also knew
what he wanted, and was willing to put a lot of front end thinking and
time in to get it. It was clear he wasn't interested in a quick fix; he wanted
true, "end-to-end" system oriented thinking.
What a customer! He knew what he wanted. He was open and anxious
to work, had time and money, and was willing to sweat to get better solu-
tions. On top of all that, Apple was a large and successful company with
excellent engineering resources. I set up a meeting to introduce him to
Dobkin and, hopefully, get something started.

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