John Lester S.
Senior Electronic Hardware Design Engineer
More than 10 years of experience in circuit design and product development. Have long time experience in doing electrical and electronic schematics. Experienced in switching converter design such as flayback, boost, buck, forward, ITTF, LLC and others. Have experience in designing low to high power switch mode power supply from proto to mass production. Experienced in LED driver design and LED applications. Capable of doing detailed analysis such as worst case, design failure mode and effects analysis, monte carlo and reliability prediction to come up with a robust and high quality design. Have long experience in implementing customer requirements and designing circuit from scratch that best fit the specifications. Capable of leading people.
Summary of Capabilities:
1. AC-DC power supply design, switching and linear, multiple outputs or single, trimmable or fixed
2. DC-DC power supply design
3. Offline AC-DC adapter design
4. Charger design with constant current and constant voltage, AC-DC
5. Charger design with constant current and constant voltage , DC-DC for Li-Ion, Li-Poly, LiFeP04, Lead acid and so on
6. LED lighting related applications, LED drivers (CC/CV)
7. Solar panel energy harvesting and charging systems
8. Switching converters such as buck, boost, buck-boost, flyback, forward, LLC, half bridge etc
9. Amplifiers, filters, switch
10. MCU, DSP and digital circuits
11. Schematic and PCB using eagle
12. Simulations using LTSpice, Matlab, Simulink, Simetrix and Simplis
13. Design analysis and computations using Mathcad
14. Control system design, type 1,2,3 and PID using spice, SISO tool in Matlab or Simulink control design
1. 750 W AC-DC, efficiency 94%
This is a three stage design consisting of power factor correction circuit (boost topology), buck pre-regualtor and main DC-DC (half bridge resonance). The supply has EMI filter on board and passed CE and FCC or ICES emission limits. This supply is compliant to line surge; can withstand 2.6kV and 1.3kV common mode and differential mode voltage spikes. It complies to ESD, EFT, ringwave, dips and interruptions and harmonics and of course conducted and radiated EMI. The design has an auxilliary circuit which is a flyback topology that provides power to the control and houskeeping circuits. The main controllers are digital signal controllers (DSC). Some features includes but not limited to: a) Current sharing, b) Startup short protection, c) Running Short Protection, d) Over voltage protection, e) Under voltage protection, f) Power limit, g) Higher power factor (close to unity), h) holdup of 20msec, i) over current protection, j) over temperature protection, k) output reporting, l) input reporting, m) higher accuracy
2. 500 W AC-DC, efficiency 92%
Have the same features as above. This PSU is composed of two stage only; PFC and LLC resonant converter.
3. 360 W AC-DC, 90% efficiency, variable output
This power supply has variable output voltage from 14.25V to 16.5V. Two stage design using PFC and LLC resonant converter. All the basic circuits in item number one are in place. All the international standards are also met. This power supply has a convection rating of 220W; meaning it can handle this power without a fan cooling. This is ideal for medical and other fanless applications.
4. 450 W AC-DC, 92% efficiency, multiple outputs
This power supply has multiple outputs. It has 12V/21A, 5V/30A, 3.3V/10A and standby of 5V/4A. All the international standards are in place and has all the protections needed as item number 1 above.
5. 50W buck-boost design
This is used for e-cigarrete. It can handle continuous 50W with variable output voltage of 1V to 10V. It is powered by a 3.7V rechargeable batttery.
6. AC-DC, 5W charger design with constant current and contant voltage
7. Charging circuit for solar panel applications
8. Lithium Ion Charger 32V input to 24V output with variable charge current
9. Energy saving standby circuit
10. Smart Junction boxes for automotive.
This is the one controlling all the body electronics of an automobile. Such as headlights, foglights, wipers, mirrors, heated mirror, fans, etc.