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VOLTAGE REGULATOR FOR PHOTOVOLTAIC POWER SYSTEM

IP.com Disclosure Number: IPCOM000005451D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2001-Oct-10
Document File: 2 page(s) / 91K

Publishing Venue

Motorola

Related People

William L. Bailey: AUTHOR [+2]

Abstract

The attached drawing shows the circuit for a simple, reliable voltage regulator for solar photovoltaic applications. This particular circuit Is designed to operate with up to 3A at a nominal 12 volts, and is temperature compensated at - 5 mV/C/cell as recommended by most battery manufaCturerS.

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MOmmOLA Technical Developments Volume 2

January 1982

VOLTAGE REGULATOR FOR PHOTOVOLTAIC POWER SYSTEM

By William L. Bailey and Joseph B. Wise

   The attached drawing shows the circuit for a simple, reliable voltage regulator for solar photovoltaic applications. This particular circuit Is designed to operate with up to 3A at a nominal 12 volts, and is temperature compensated at - 5 mV/C/cell as recommended by most battery manufaCturerS.

   For low voltage systems (12 volts or less) a shunt approach has the advantage of minimum loss dur- ing normal charging; series circuits have loss in the series element continuously during charging Of the battery. For example, at a charging current of say 2.5A the attached circuit has a series voltage drop (across the Schottky blocking diode) of less than 0.5 volts. A corresponding series switching element would drop at least 1.0 volts.

   Shunt regulators to date have been of the linear type, as opposed to the switching type. Photovoltaic modules have the advantage over most dc supplies that they may be shorted without damage. This circuit takes advantage of this fact and shorts out the modules when the battery voltage has reached the re- quired "float" voltage. It removes the short from across the modules when the battery voltage drops ap. proximately 1.0 volt. For example, at room temperature the modules will be shorted at 14.4 volts (the recommended float voltage at that temperature), and when the battery voltage has dropped to 13.5 volts the short will be removed. The amount of hysteresis is adjustable.

   Switching circuits have the advantage over linear circuits of considerably lower dissipation. A linear shunt regulator has to be capable of dissipating the entire output of the modules which it is regulating. A switching shunt regulator, on the other hand, has to dissipate only the module short circuit cur...