EG7500 Inverter Drive Board Testing and Query?

Specification EG7500 Inverter Drive Board.
PWM freq 40kHz.
Overvoltage shutdown 15V +-0.5V.
Low voltage buzzer beep 10.5 +-0.5.
Undervoltage shutdown 9.5 +-0.5.
Overcurrent shutdown 48mV.
1A Output current drive.

Carry out a test by varying DC between 9V to 15V. Resulted:
1. At 10V to 10.5V buzzer beep. "OK"
2. At 9V to 9.5V or below 9V the unit shutdown. "OK"
3. At 13V to 13.5V ran into off and trying to restart the unit (Board marked A). "NG"
4. At 14.5V to 15V ran into off and trying to restart the unit (Board marked B). "OK"

Refer to above test how to improve "Board Marked A" overvoltage shutdown? 
Which part of the schematic to begin troubleshoot. What component I needs to change or improve? 

Once power up. This unit draw ~0.5A on standby.
How do I minimize the standby current?

There are no temperature control since P3 "S8550" was not on board.
Can I just put "S8550" on board and use PTC for temperature control?

As proposed by schematic online, pin 4 fan control feet to ad 100uF to ground.
How do I change this part to enable fan control once the temperature rise?

How many FET this unit can drive with 1A at 40kHz?

How to test the overcurrent shutdown?

Thank you

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What IS this thing ? What are you trying to do with it ?

Did you have a load attached, that is usually very important.

tplim (author)  steveastrouk8 days ago

Thank you for your reply

iceng8 days ago

Cannot help modify a board that the small print is unreadable !

tplim (author)  iceng8 days ago

The front driving stage taken here >> https://www.aliexpress.com/item/300W-special-high-frequency-sine-wave-inverter-push-pull-transformer-EE40/32788118159.html?spm=2114.01010208.3.167.igKbGO&ws_ab_test=searchweb0_0,searchweb201602_3_10152_10065_10151_10208_10068_10136_10137_10060_10155_10062_437_10154_10056_10055_10054_10059_303_100031_10099_10103_10102_10096_10052_10053_10142_10107_10050_10051_5300020_10084_10083_10080_10082_10081_10110_519_10175_10111_10112_10113_10114_10182_10078_10079_10076_5030020_10073_10123_10189_142,searchweb201603_2,ppcSwitch_5&btsid=b77a5285-e295-4c7b-9b91-8b55b628f66c&algo_expid=df92082b-4101-4f3e-9ab8-9d2482ae0e27-22&algo_pvid=df92082b-4101-4f3e-9ab8-9d2482ae0e27

tplim (author)  iceng8 days ago

The schematic taken here >> https://www.aliexpress.com/item/5PCS-LOT-EG-TL494-7500-inverter-boost-driver-board-EG7500/32705054577.html?spm=2114.01010208.3.8.SnCIFc&ws_ab_test=searchweb0_0,searchweb201602_3_10152_10065_10151_10208_10068_10136_10137_10060_10155_10062_437_10154_10056_10055_10054_10059_303_100031_10099_10103_10102_10096_10052_10053_10142_10107_10050_10051_5300020_10084_10083_10080_10082_10081_10110_519_10175_10111_10112_10113_10114_10182_10078_10079_10076_5030020_10073_10123_10189_142-10050,searchweb201603_2,ppcSwitch_5&btsid=d71ba70e-6b15-46d2-8810-c93cc1906298&algo_expid=e2d187d7-15ac-4a10-a9ab-e4cea0910143-1&algo_pvid=e2d187d7-15ac-4a10-a9ab-e4cea0910143

iceng8 days ago

A FET (Field Effect Transistor) first pic is turned on by applying voltage to the gate and source pins not current.. It is the bipolar NPN transistor that needs a small current flow from base to emitter...

So in answer to how many the answer is a lot DC On/off but at 40 KHz the input gate capacitance will limit the number of FETs you can drive... Of course different FETs have different gate capacitance.. Read about a FET pdf.

tplim (author)  iceng8 days ago

Thanks for this info. What I have done here is on board and do not have knowhow on calculation.

iceng8 days ago

Over current shut down 48mV = .048 volts !? Only thing is, it might be the trip point on a low ohm power resistor in the current path and when the V=IxR reaches 48mv it turns off the output.

You say EG7500 has one amp output the R=V/I =.048/1=.048 ohm.

tplim (author)  iceng8 days ago

The 1A output current drive specification taken as above link where I buy this board.

iceng8 days ago

Do not think you can minimize standby current without cutting out some of the features.. Adding temperature fan control will undoubtedly increase standby current..

tplim (author)  iceng8 days ago