Electronics

dave madden · Guest

I have a simple DC-DC step-up circuit using a MAX1771 controller, but
it doesn't actually do any stepping up. It's connected as shown in
Fig. 2c of the datasheet, with different resistors to get the output
voltage I want. (R1=34.2k, R2=330k to get 16v.) Input is 12.85v on
my test bench; will be 12-14.5v or so when connected to a car battery.

I've got a 1.1k load resistor on the output, which is at 12.61v
(essentially the diode drop down from the input). The FET control
signal is putting out a 7v spike at about 130kHz, but the pulse width
is only about 0.04uS.

I think the pulse should be wider to build up more current/field in
the inductor, which would then charge up C4 on the output to the
expected voltage. Anybody have a suggestion for what I should look at
to see why it's not working better?

Thanks,
dhm

neon · Joined: 25 Feb 2006 Posts: 595

i did not look up your device but all conveters use the rise time to transfer power. the width of the pulse is immaterial. as long as it does not run out of time for control

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