SIMPLE CONSTANT CURRENT LIMIT FOR SEPIC OR BOOST CONVERTER

摘要

A circuit for supplying an error signal to a controller in a boost or SEPIC DC-DC converter is provided, the circuit comprising components including: a first (D301), second (D303) and third (D302) Zener diode; a first (R303), second (R302) and third (R301) resistor; and a MOSFET or BJT switch (Q301). The circuit is formed of at least three branches that are each connected to a common voltage input source (V101); the three branches including: a first branch including: the MOSFET or BJT switch, the first Zener diode and the first resistor; a second branch including: the second Zener diode and the second resistor; wherein the first and second branches are mutually connected to the third resistor, the third resistor being connected to the controller; and a third branch including: the third Zener diode, a connection to the base or gate of the switch and a connection to ground. Each of the first, second and third Zener diodes are reverse- biased; wherein the first Zener diode has a first Zener voltage, the second Zener diode has a second Zener voltage, and the third Zener diode has a third Zener voltage; wherein the second and third Zener voltages are equal, the second and third Zener voltages being higher than the first Zener voltage.