PMP8740

Dear Anjana,

I am doing well, thanks! I hope you are fine too.

Here are the answers to your points:

1) The fan speed is proportional to output current. By the way, at zero current, there is still some internal component to be cooled, therefore I set a minimum RPM of the fan in order to get a bit of ventilation. This minimum RPM corresponds to 415 counts on the compare register.

2) This assignment was intended to drive the load back-to-back switch on DC/DC converter, but after that I didn't use it, so please discard P2.7 management.

3) Also here, at the beginning I wanted to use this power supply only for EU voltage range (184VAC to 274VAC), but then the customer wanted to have universal mains range, so, please, set all parameters in mains.c and flash.c according to universal mains range.

4) Here you are right: probably at the beginning I wanted to set only range of 1A to 11A (per flash.c file) of the trickle charge current, but then I modified it to 2A...20A. I believe that if you set the same range in the flash.c file and in main.c, then you will get always right values when switching on-off or reprogramming the uC. Please let me know if that is correct.

Best regards,

Roberto

Dear Roberto, 

Thanks for your support.

I have tested PFC section it gave expected results. Now I am going to test DC-DC section. till then i need your support :)

Anjana

roberto you mean,

2)I should not care about P2.7_connect load signal.

3) if my required operating range of input AC voltage is 190VAC- 260VAC then I should set parameters in flash.c and main.c as 190 to 260 right?

4) if my maximum output current is 34 A then what will be the trickle charge current range? is it still 2 to 20A or this 2 to 20A range is according to 0-60 A current used in PMP8740 ?

Anjana

Dear Roberto, 

Correct.. I have checked the same by forcing controller into CCM mode. Thanks a lot.

Please tell me, if I want to power up the dc-dc section from PFC output (i.e. 400VDC), is it necessary that microcontroller board is connected on dc-dc board? if not then, how can I test dc-dc section without microcontroller? what temporary changes i need to do? please help.

Anjana 

Dear Anjana,

It is not necessary to have the microcontroller on board. What you need to do is the following:

1) Remove the short circuit on DCM pin 12 of U2.

2) Enable the controller U2 by providing 3.45V to net ENA_FB_P4.7 (R33).

3) Enable the inrush / Precharge back-to-back FETs Q12...Q31 by supplying the net Pre-Charge_P2.2 (R84) with 3.45V.

4) Connect the net PWM_Vref_P2.4 to ground and the net PWM_Iref_P2.3 to ground: this will force the converter to supply 32V (maximum Vout) and to move the current limit to 60A (maximum Iout). If you want to set Vout or Iout to a lower level, just replace R29 and R50 with 100 KOhm trimmer; this way, when setting the trimmer to maximum resistance value, you get the maximum Vout or Iout value. The lower the trimmer value, the lower the output voltage and current limit.

Best regards,

Roberto

Dear Roberto,
I got your answer. The only thing is My output voltage is 54V nominal and 58.5v maximum so I have change resistors as below R12= 49.9Ohm, R14=2.49K, R13=59K, R19=2.37K which give me 2V at pin 2 of U1 at 54V vout

For 20A output current i have change below components as
R92 shunt= 1mOhm, R100 & R101= 178K, R93&R94= 1.8k which give me 1.98V at 20A Iout

Is this OK?

Anjana

Dear Anjana,
The second point is OK, with these values, for 20A out, you get 1.98V.
Regarding the first point, at 2V you get 54V, therefore to get 58.5V you need a reference higher than 2V on pin 3 of U1: please take it into account.
And, of course, the power stage, on secondary side of the full bridge, has to support double voltage compared to my design.
Regards,
Roberto

Dear Roberto,

i have take my design voltage for secondary design and selected components accordingly.

1) My doubt is, my Application is LI-Ion battery charger, and as per system requirements, Constant Voltage value (For Charging profile) start at 54.5V ( configurable) and maximum battery pack voltage is 58.5V, which value should i considered for setting voltage feedback, 54.5V or 58.5V?

2) I have change R42=105K, And R47=4.75K which gives me 2.33V at 54V and 2.51V at 58.5V. Is this ok? Why this Vout_FB P3.6 signal is used?

Anjana

Dear Anjana,
If the maximum output voltage in your case is 58.5V, you should have some margin and set all resistors to get a maximum voltage a bit higher, let's say 60V; that means, if the maximum Vout can be set and read to 60V, set it in the software to 58.5V to charge it to maximum level, but consider 60V as maximum absolute.
If, instead, you want to be sure that, for safety reasons, Vout should never go higher than 58.5V, then select this voltage as maximum.

Answer to question #2: if you want to keep the same voltage level I have on net Vout_FB_P3.6 (input of A/D converter), just use 2.33V on A/D converter when Vout = 58.5V; this means that R47 = 4.75K and R42 = 115K.
Best regards,
Roberto

Dear Roberto,

if I want to test DCDC without microcontroller then, R31 and R51 also should not be there right? otherwise 3.45V witll turn on Q4 and Q2 and reference become 0V?

Anjana

Dear Anjana,

It is not necessary to remove R31 and R51: it is sufficient to short to ground the nets "PWM_Vref P2.4" and "PWM_Iref P2.3".

As alternative, you can remove R31 and R51 , but then you need anyway to short to ground the nets "PWM_Vref P2.4" and "PWM_Iref P2.3", because otherwise the gates of Q2 and Q4 will be floating, and therefore the gate voltages might be undefined.

Best regards,

Roberto