‰ NOW 35 WPM ‰ TEXT IS FROM SEPTEMBER 2018 QST PAGE 56 ‰ TECHNICAL CORRESPONDENCE HIGH EFFICIENCY SWITCHING REGULATOR AND SAFETY PRECAUTIONS FOR MOBILE OPERATIONS A HIGH EFFICIENCY 120 HZ SWITCHING REGULATOR THE DEPARTMENT OF ENERGY REPORTS THAT AN AVERAGE OF SIX WALL WARTS OR SIMILAR DEVICES ARE PRESENT IN EVERY HOUSEHOLD, CONSTANTLY WASTING POWER BECAUSE OF THE INEFFICIENCY OF THE CIRCUITS. THIS TECHNICAL CORRESPONDENCE ITEM PRESENTS AN EFFICIENT AND QUIET LOW FREQUENCY SWITCHING REGULATOR. BECAUSE LOW ON RESISTANCE MOSFETS ARE NOW AVAILABLE, THIS SIMPLE, INEXPENSIVE, AND EASILY CONSTRUCTED REGULATOR CIRCUIT OFFERS A SIGNIFICANT REDUCTION IN THESE POWER LOSSES. BY MY OWN MEASUREMENTS, THIS REGULATOR OPERATES AT OVER 90 EFFICIENCY. TRANSFORMER AND RECTIFIER LOSSES ARE NOT INCLUDED IN THIS, BUT THOSE LOSSES ARE REDUCED WHEN LESS TOTAL POWER IS DEMANDED BY AN EFFICIENT REGULATOR. THE CONCEPT IS SIMPLE PUT A SWITCH BETWEEN THE RECTIFIER AND CAPACITOR, THEN, EACH CYCLE, DISCONNECT THE CAPACITOR FROM THE RECTIFIER WHEN THE CAPACITOR IS CHARGED TO THE VOLTAGE THAT IS REQUIRED BY THE LOAD. THIS MEANS THERES NO EXCESS VOLTAGE TO WASTE IN A REGULATOR. THE CIRCUIT SEE FIGURE 1 HAS TWO FEEDBACK LOOPS. THE NEGATIVE FEEDBACK LOOP LOOKS LIKE A TYPICAL LINEAR REGULATOR AND INCLUDES THE VOLTAGE DIVIDER FORMED BY R1 AND R2, ZENER DIODE D1, NPN TRANSISTOR Q1, AND THE MOSFET Q3 ACTING AS A SWITCH. THE POSITIVE FEEDBACK ‰ END OF 35 WPM TEXT ‰ QST DE W1AW ƒ