TPS61040 boost circuit abnormality

wenuo

TPS61040 boost circuit abnormality [Copy link]

Hey guys, I recently made a boost circuit using tps61040 to boost 5v to around 9v to power an oled display. But now the voltage has risen to 11v, and I measured FB, the fb pin is 1.39v (the manual says 1.233v). I don't know where the problem is, and I hope you can answer it.

chunyang

The manual has a formula for calculating the output voltage. Check to see if the resistor you selected is correct. Pay attention to the measurement, and don't calculate it correctly but use it incorrectly.

chunyang

Also, please note that it must be loaded and no-load measurement is not allowed.

wenuo

chunyang published on 2021-2-4 23:23 Also, please note that it should be loaded with a certain amount of load and cannot be measured without load.

The resistors are the same as in the schematic diagram, and the actual situation is the same. The output voltage is too large because the voltage of fb is too high (1.39V). The formula is 1.39V (1.233V) × 8. But I don't know why fb becomes larger.

wenuo

chunyang published on 2021-2-4 23:23 Also, please note that it should be loaded with a certain amount of load and cannot be measured without load.

The load uses a 4.7k resistor

cruelfox

Wrong selection. You should not use TPS61040 for this application.

dcexpert

Use an oscilloscope to see the waveform

wenuo

dcexpert published on 2021-2-5 08:29 Use an oscilloscope to look at the waveform

No oscilloscope

chunyang

wenuo posted on 2021-2-5 00:00 The load uses a 4.7k resistor

4.7K may be too high a resistance, try lowering it.

qwqwqw2088

Related to R14 and R15

Maybe the resistance value does not match

Or it is related to the control of EN pin

dcexpert

wenuo posted on 2021-2-5 14:11 No oscilloscope

The voltage on FB is not necessarily stable, and the change cannot be seen with a multimeter.