Multiplexing EL Display System

1
Multiplexing EL Display System

• Company Dr. Ringo Lam
• Micro-Glory International Ltd.
• Mentor Ir Dr. C. K. Li
• Dept. of Electronic and Information
  Engineering,
• The Hong Kong Polytechnic University

2
Electroluminescence (EL) display

• An optical phenomenon and electrical phenomenon
• Emits light when an electric current passes
  through it
• Usually driven by an 100 300 VAC source of
  frequency from a few hundreds to a few thousands
  hertz
• Lifetime depends on voltage, frequency,
  temperature and humidity (humidity is the
  strongest contributor to shorten the lifetime)
• Increased voltage and/or frequency, reduce the EL
  lifetime
• EL brightness gradually decreases with time

3
EL Display Structure

• Colors Yellow, Blue Green, Green, Blue, Red,
  Pink White, etc.
• Materials ZnS, Mn/SrS, Ce, etc.

Source Supertex Inc.
4
Our Design

• Analogue and digital circuit design
• Analogue
• Flyback circuit
• Digital
• Switching circuit

5
Existing EL Driver Designs

• Half-wave Inductive Flyback circuit design
• Full-wave Inductive Flyback circuit design
• Oscillator design
• DC-DC converter design
• E.g. Supertex HV809

6
Half-wave Inductor Flyback circuit
7
Full-wave Inductor Flyback Symbolic Circuit
8
Output Waveform
Vpeak 80 150V

• Power (DV)2 / (2fL)
• Where D Duty Cycle
• V Input Voltage
• F converter Frequency
• L Inductor value

9
Full-Wave Output
EL - A point output
EL - B point output
EL output A - B
10
Another Full-wave Flyback Circuit
11
Full-wave Inductor Flyback Circuit
12
Oscillator Type Design
13
Problems

• Low cost
• High luminance
• Low power consumption

14
Advantages

• Full-wave design
• Provide higher luminance than conventional
  half-wave fly-back converter design
• Can multiplex
• Integrate analogue circuit with digital circuit
  to reduce the cost

15
Multiplex EL Circuit
16
Methodology

• Pspice
• Prototyping
• Tanner Pro

17
Pspice

• In the beginning, we test our design in Pspice
• After verified by simulation, we build discrete
  component prototypes

18
Tanner-Pro

• Design Tools
• S-Edit
• LVS
• Netlist Converter
• Simulation Tools
• T-Spice
• GateSim
• W-Edit
• Masking Tools
• L-Edit

19
What we have learnt

• Custom IC layout techniques
• ASIC technologies

20
Our EL Clock Display IC
21
Future Plan

• Employ the IC design techniques learnt in the
  program for another project.
• In our new project, we have to design an
  electronic device to help workers to improve
  their efficiencies. Data can be collected from
  the device to the server through the network.
• Although the device is mainly driven by MCUs, we
  may employ our knowledge learnt in the mentorship
  program to integrate logic control circuitry into
  an ASIC
• Besides, we are writing patent documents and will
  apply for patents to protect our Intellectual
  Property