STEP_UP_STEP_DOWN_REGULATOR

Published:2009/7/16 23:00:00 Author:Jessie | From:SeekIC

Adding a transformer to a step-up dc-to-dc regulator allows inputs of 20 V and higher to be accepted while operating in a step-down mode. The circuit handles inputs to 30 V, but is easily modifiable for high specific voltages. The transformer's 1:1 turns ratio simplifiers procurement by allowing the use of a standard, product (here, the Coiltronics CTX100-4P). Its 1:1 ratio also enhances stability by producing a duty cycle well below 50 percent. An ideal 1 : 1 transformer would generate Vin + Vout at the bottom of the primary, but real transformers produce somewhat higher voltages. That voltage appears across Q1, so Q1's minimum breakdown voltage should be approximately 2Vin +Vout. R2 limits the peak current (through Q1 and L1) to 0.33 A. The internal shunt regulator is a zener diode that is biased by R1 at approximately 2 mA. To cope with a wide range of input voltages, R1 can be replaced with a constant-current source.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Power_Supply_Circuit/STEP_UP_STEP_DOWN_REGULATOR.html

Print this Page | Comments | Reading(3)