I designed a PF with PFS7539H , 800W, VOUT 383 V, and PG pin is allways in hight impedance, the threshold resistor set 333K, can help me, to solve?
Thank you for interested in using Power Integrations product.
It looks like you are using the right device for the output power level and the threshold resistor is about the right value. Could you please share the schematic with us in order for us to check if there is any possible fault conditions in the design.
For your quick check, here is a few tips that might cause the PG in high impedance mode. you can check and verify:
The Power Good function is not valid under the following conditions:
A. VCC or VREF are not in a valid range of operation. VCC below
UVLO- or VREF below REFUV- the power good function is not valid
with the POWER GOOD pin in a high-impedance state.
B. Power Good will go to high-impedance state when a soft- shutdown
is initiated by an over-temperature fault to provide early
indication to secondary circuits of an OT fault.
C. PGT is outside the valid programming range of between 225 V and
360 V. PGT voltages above this range, including PGT floating, will
prevent PG from transitioning to active pull-down. PGT voltages
below this range result in PG deassertion at the output undervoltage
D. Once the start-up sequence check has passed and the converter
goes into start-up, if PGT is opened, then the PG signal will
remain latched in the high-impedance state until the controller is
I tested the follow;
A- VCC 12V, VREF5,23V
B- Temperature in start-up 26°C (FPS7539H)
C-the threshold resistor set 333K (pass)
E- VFeedback pin 3,81V
F- Output power 390W lower than minimum of PFS7539H is 690W ,.
G- Voutput 384V
H- PF, 0,99
Well,PG signal remain latched in the high-impedance state
Thank you PI -YY
Can you share the schematic with us? this can help speed up the debug.
You mentioned you have Vpg 3.62V. Do you mean the voltage at PG pin? Did you connect your REF pin to PGT pin on the board?
Sorry the, the correct , voltage PGT pin is 3,62V.
Attach the schematic,
If you have a question, please let me to know.
Can you add another 6.2M resistor in series with your R2 and and R3. In this way you have totally 16Mohms from the bus to Vpin for your input voltage sense. Can you check to see if the PG pin works properly with this configuration.
By the way, when you do the test, how much is your input voltage. did the PG work when the input voltage changes such as change from 115VAC to 230VAC.
Please see that I have 16.14 M, with R1,R2,R3 in series to ADD 6.2M the tottaly will be 22.34M is this ?
Well, this can to decrease power factor, will be necessary to ajdust the FeedBack too, with same total resistence value.
Can you check and reply please.
Thanks so much PI-YY
I checked, your information and, there was not the R1 in the diagram, cause there is label information about D12, is no connected.
Now you can to check, the correct placement, the values of rersistors R1,R2,R3
Another information, about R20 in my design is 30.1K and in PI Expert,xls, the value is 40.2K, please check .
Can you change R21 from 1K to 10K to see if this helps?
By the way, which test you did to tell the PG pin is always in high impedance mode?
I had already changed R21 for to 10K, and PG pin continue in hight impedance.
Well, Im sending attached drawing, for you to understand the tests I did.
For the time beeing I dont got to solve this.
I AM sending 3D pcb for you to check , if there is a something wrong.
Notice to you that I put C16 direct in REFpin, and C17 direct in Vpin, and this way PFS7539H works well, but do not operate the relay.
The components value seems to be alright.
i cannot open the PCB file. Could you please print into PDF for each layer, in this way, i can help check.
By the way, when you put the capacitors close to pins, you say the PFS works well. do you mean the PG pin works but the reply is not wokring?
The PG pin remain in hight impedance yet, and the relay do not operating.
Dear PI-YY if be difficult , to solve this , i will to ADD other circuit of brownout , utilizing a discret circuits , for to operating the relay .
I will inform you that the output voltage is 385 VDC, the power factor is 0.98, the temperature is normal, but the PG pin is still at high impedance, and the relay does not activate, I have already checked the components, such as transistors, resistors, diodes, and the relay itself, and everything is ok, and I have already replaced the PFS7539H, and there was no change, the relay does not activate, and the PG pin continues at high impedance, the test I did was to measure with voltmeter the state of the PG pin with the positive voltmeter test tip on the 12 volt VCC and the negative volt tip on the PG pin and the voltage is zero volts because the PG pin is high impedance.
I believe it is some noise, that is being introduced, in some input of the PFS7539H, and causing this effect. Something happens when I push the voltmeter probe on the V-pin of the PFS7539H, the relay almost triggers, but the PFS7539H stops switching and the boost converter stops working.
Something strange happens, when I remove the capacitor that is close to the REF pin, and put it farther away, the PFS7539H generates a startup delay of about 4 seconds, in which case the relay triggers, but in my project I can not have this delay, from operating the boost converter.
I have already sent you all the information, regarding the measurements I made with voltmeter, on the pins of the PFS7539H, and how I did the tests.
Would I get a demoboard with the PFS7539H for testing?
Thank you for all the detailed information.
Based on all the information we have, i also have a strong suspicious it is noise related. while i cannot open your layout file.I will try to see if i can find some alternative way to open it and then review.
For the demo board, you need to contact our Sales in your district and they will give you the professional support. You can find the contact information in the link below.https://ac-dc.power.com/sales/
Hello, PI-YY reported that I solved the problem, I increased the value of C19 on the PGT pin from 1nF to 10uF, and now the PFS7539H is working satisfactorily, and the relay is operating normally, in the browout function. I hope to consult with PI whenever I need it.
It is good to know that you get your problem solved. It looks like there is noise on the PGT pin which affects the threshold.
You are always welcomed to consult us when you have questions, either from the forum or from our our sales department to get the help of our local field application engineers.