‰  NOW 40 WPM  ‰  
VALID.  THE BEST EXAMPLE OF THIS IS THE INCLUSION OF BATTERY MONITORING
SYSTEMS IN ALL LATE MODEL PASSENGER VEHICLES, PARTIALLY SUPPORTING
FEDERALLY MANDATED ENGINE IDLE SHUTDOWN SEE MY ARTICLE, THE MODERN MOBILE,
ON PAGE 35 OF THE MAY 2015 ISSUE OF QST FOR MORE ON THIS.  WHILE THE ENGINE
IS SHUT DOWN, THE ACCESSORIES MUST STILL OPERATE, AND A VARIETY OF
SUBSYSTEMS ARE USED TO SUPPORT THEM.  MAZDAS I ELOOP REGENERATIVE CHARGING
SYSTEM IS ONE OF THE UNIQUE TYPE I MENTI

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

LOOP INCLUDES THE 3R3 K RESISTOR, Q2, Q1, AND THE MOSFET.  THE POSITIVE
LOOP FORCES THE MOSFET SWITCH TO BE EITHER FULL ON OR FULL OFF.  TO
UNDERSTAND THE CIRCUIT OPERATION, START WITH THE CAPACITOR VOLTAGE LESS
THAN IS REQUIRED.  Q1 SENSES THIS AND SATURATES, CLOSING THE MOSFET THE
SWITCH WAVEFORM POINT A BY MAKING THE MOSFET GATE TO SOURCE VOLTAGE 7 V.
WHEN A HALF SINE WAVE PULSE ARRIVES FROM THE RECTIFIER, THE CAPACITOR IS
CHARGED THROUGH THE ALREADY CLOSED MOSFET SWITCH WAVEFORM POINT B.  WHEN
THE CAPACITOR CHARGE REACHES THE DESIRED VOLTAGE, Q1 DETECTS THIS AND OPENS
THE MOSFET SWITCH BY ALLOWING THE MOSFETS GATE TO SOURCE VOLTAGE TO REACH
0.  AS THE MOSFET SWITCH OPENS, LOAD ON THE TRANSFORMER IS REMOVED AND THE
VOLTAGE INCREASES AT THE CONNECTION OF THE RECTIFIER OUTPUT, THE MOSFET
SOURCE, AND THE 3R3 K RESISTOR THE END OF B.  THIS VOLTAGE APPEARS ACROSS
THE 3R3 K RESISTOR AND CAUSES CURRENT TO FLOW INTO THE EMITTER OF Q2.  THAT
CURRENT FLOWS OUT OF THE COLLECTOR OF Q2 AND RAISES THE EMITTER VOLTAGE OF
Q1, CUTTING Q1 OFF.  THIS ENSURES THAT THE MOSFET SWITCH REMAINS IN THE
OPEN CONDITION UNTIL THE RECTIFIER VOLTAGE FALLS BACK BELOW THE OUTPUT
‰  END OF 40 WPM TEXT  ‰  QST DE W1AW  ƒ