I don't see a schematic.
There is an image showing it powered by 3.3 volt output on an Arduino.

Here it is https://files.waveshare.com/upload/b/b4/1.28inch_LCD_Module_SchDoc.pdf

 

Could try adding a filter capacitor on the output of U6.

 

Could try adding a filter capacitor on the output of U6.

is it because i can give the display's power enough time to raise?

 

Just a filter after D1.
Give it a try, may need to experiment with the value.

 

Hi Guys,

I'd like to start by telling I have gone through a lot of similar threads from allabout circuits but I have concluded my problem is little different from all of those. I have a battery charger circuit that will be powered by USB, which will charge a 3.7V Li-Po battery.

My Requirement:

1. When USB connected -> Charges battery and powers the entire board.
2. When USB removed -> Battery charging stops and battery takes over the powering of board.

What have I implemented:

Attempt 1- I have used a P-Channel MOSFET as below to switch between USB and BAT. However I have made a mistake of not isolating the USB and battery power with a diode there by it's bypassing the charging circuit.

View attachment 341280

Attempt 2 - To correct this I have added a diode at the BATT header as below and made sure the charging circuit will work properly. However it looks like my board is still not working (What I mean by not working is, I have a LCD display connected which is going blank and not recovering as soon as I connect the battery)

View attachment 341281

My Ask - Why is this circuit wrong? If it's wrong what's the correct way to implement such circuit with less components. Any cheaper IC alternatives are also fine as long as they're widely available in hobby market but my preference is analog circuits. I have attached full schematics

Actually we use ETA9742 in power bank. The supplier has similar ICs for lower power application. Check their site: https://www.eta-semi.com/

 

From R8 the 91K resistor. Pulls the gate to ground, remember it's a P channel mosfet.

Right

 

Guys, after lot of thinking and to optimise I have decided to move the input voltage of display to be driven from the LDO, now all my issues with display are gone and the charging circuit is also working fine the moment I isolate the battery input and add a diode at it's input. Really really appreciate the involvement and help offered by everyone. Couldn't ask more from a community.