‰  NOW 35 WPM  ‰  TEXT IS FROM JANUARY 2017 QST  PAGE 32‰

HIGH VOLTAGE DESIGN THEORY  THE SIGNIFICANT DESIGN PROBLEMS WERE LIMITED TO
THE HIGH VOLTAGE PART OF THE TOTAL POWER SUPPLY.  THEY WERE, FIRST AND
FOREMOST, LIMITING OUTPUT VOLTAGE VARIATION DUE TO VARYING LOAD SECOND,
VOLTAGE BREAKDOWN OF SEMICONDUCTOR PARTS THIRD, CURRENT HANDLING CAPACITY
OF SEMICONDUCTOR PARTS, AND FOURTH, KEEPING HEAT TO A MINIMUM.  TAMING
OUTPUT VOLTAGE VARIATION LIMITING OUTPUT VOLTAGE VARIATION PROVED TO BE BY
FAR THE MOST DIFFICULT DESIGN CHALLENGE.  MY FIRST APPROACH WAS TO USE A
CLOSED LOOP FEEDBACK CONTROL OF THE OUTPUT BY REGULATING DUTY FACTOR PULSE
WIDTH DRIVE TO THE SWITCHING TRANSISTORS.  A TRANSFORMER IS A FAR MORE
CRITICAL MAGNETIC COMPONENT WHEN COMPARED WITH A SINGLE WINDING INDUCTOR
THAT MIGHT BE USED IN A BUCK OR BOOST TYPE OF SWITCH MODE SUPPLY.  MUCH
EFFORT WAS PUT INTO FEEDBACK CONTROL CIRCUITS AND CONTROLLER CHIPS.  WHAT
THAT WORK REVEALED WAS THAT NO FEEDBACK SYSTEM COULD GET AROUND THE
PROBLEMS OF A LESS THAN PERFECTLY IDEAL TRANSFORMER.  SPICE SIMULATED
PROGRAMMING WITH INTEGRATED CIRCUIT EMPHASIS MODELING SHOWED THAT WITH A
LESS THAN PERFECT TRANSFORMER COEFFICIENT OF COUPLING K LESS THAN 1 AND
WITH THE RESULTANT LEAKAGE REACTANCES IN ALL THE WINDINGS AND PARASITIC
CAPACITANCES BETWEEN WINDINGS, FEEDBACK CONTROL COULD NOT BE ACHIEVED WITH
DUTY FACTOR VARIATION AS THE MEANS OF CONTROL.  THE TRANSFORMER WILL ALWAYS
‰  END OF 35 WPM TEXT  ‰  QST DE W1AW  ƒ