hi Sir 

jump setup as below

Hi Chen,

1. How much is VIN? Please prove that also. 

2.  Is there external load connected? What is load type?

Regards

Kunal Goel

hi sir

Vin : 48V/320W

Vout: OUTPUT IS THE Led tube 600mA

Thanks. How is the result without LED tube?

hi Sir

load change to DC load is ok,

but change to LED tube, 1~2 tube is ok, but x3 tube, the voltage can output about 7s, let shut down--> OCP?

may i known which condition , the PG pull low, but the SWEN /VOUT IS high?

thanks

Hi Chen,

Due to high load at startup, internal fet is not fully turning on so pg is low and device turns off after startup time out.

Regards 

Kunal Goel

hi  Kunal Goel

We use the TPS1685 as the power switch, 

power->TPS1685-> Led Tube

in this condition, the tps1685 not turn on,  

Load only 600mA

Hi Chen,

Have you added output cap ?

Regards 

Kunal Goel 

hi  Kunal

we use the tps1685  evb, did you mean which need add more cap in the output? when series in more led tube?

thanks

Hi Chen, 

I think fet is not getting fully enhanced because of load and device turns off due to startup time out after 7s because fet did not full turn on within 7s. PG will go high if fet is fully on. Because of load device is entering into current limiting and vgs is reduced to limit current.  Max current device can support during startup is 0.5A. Please share datasheet of led tube.

Regards.

Kunal Goel 

hi Kunal Goel

voltage change to 48v, others same

the parts isn't suit for LED ?

thanks

Hi Chen,

Looks like we will need some workaround.  Can you share more details on led like pin details and circuit ?

We can use PG pin of tps1685 to successfully start. PG will go high when fet is fully on. We can implement small workaround where led will only draw current when PG is high. So device can start without led load and after start PG will go high and led will turn on. 

Regards 

Kunal Goel

HI SIR

We need a e-fuse to protect the LED tube

or did you have others suggestion?

thanks

Hi Chen,

You can try using TPS2663 here. It can support led load at startup. 

Regards

Kunal Goel

hi sir

we need the max current is 600mA*20=12A

Did you have others soultion?

how about the LM5069?

OK. YES LM5069 should be better . 

Regards

Kunal Goel

hi Kunal

could you free the LM5069 evm For us?

thanks

Hi Chen,

I will get back before tomorrow EOD.

Regards

Kunal Goel

hi sir

the LM5069 have the Enable pin to control the output?

Yes. UVLO pin can be used like EN pin.