SEPIC or boost DC-DC converter having a current-limiting circuit for supplying an error signal to a controller that comprises: 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. The error signal varies according to a linear relationship of the DC-DC converter to compensate for the non-linear current at the output to provide a pseudo constant current at the power output terminal.
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