LM5030: WHY IS THE OUTPUTS OF THE CONTROLLER ONE OUT IS NARROW AND OTHER IS WIDE. TOPOLOGY IS PUSH PULL

cs power

Part Number: LM5030

Tool/software:

Hi ,

I AM DEVELOPING A DC DC CONVERTER OF INPUT 16 TO 36V AND OUPUT CONSTANT 24V/7A. WITH FSW 200KHZ USING LM5030 IN PUSH PULL CONFIGURATION

BUT WHEN THE CONTROLLER OUTPUTS IS NOT CONNECTED TO THE GATE OF THE MOSFETS I AM GETTING MAXIMUM AND CLEAN PULSES OF MAX DUTY. BUT WHEN I CONNECT THEM TO THE MOSFET GATES, OUTPUT 2 IS COMING MAX DUTY AND OUTPUT 1 IS COMING MINIMUM DUTY.

I WILL SHARE THE WAVEFORMS OF IT BELOW.

CS AND OUT2

OUT1 AND OUT 2

CAN YOU FIND WHAT MIGHT BE THE ISSUE THATS CAUSING. AND

THE APPLICATION CIRCUIT IS SAME AS FIGURE 8 OF THE DATASHEET WITH SOMKE TUNING FOR MY APPLICATION.

THE TRANSFORMER IS EE25 TDK

AND THE PRIMARY TURNS ARE 4 AND SECONDARY IS 6 AND BIAS WINDING IS 3.

ITS CENTER TAPPED PRIMARY WITH TWO WINDINGS OF 4 TURNS EACH AND CENTER TAPPED SECONDARY WITH TWO WINDS OF 6 TURNS EACH.

CAN YOU SUGGEST WHAT ARE MIGHT BE THE POSSIBLE REASONS THATS CAUSING THIS. SO THAT I WILL CHECK ALL THOSE.

LM5030 100-V Push-Pull Current Mode PWM Controller datasheet (Rev. D)

THANKS.

8 months ago

0 Hong Huang 8 months ago

TI__Guru 74115 points

Hi,

It is likely different current is sensed to cause different duty cycle. Also it is likely due to slope compensation not set up properly. When you did not connect to gate there would be no current so the control was not the same when MOSFETS on and off to cause different current. Please provide your schematics for review.

0 cs power 8 months ago in reply to Hong Huang

Prodigy 145 points

150W_REV2-ACTIVE-PUSH-PULL_2024-11-23.pdf

Hi Kindly find the schematic FOR review

Note the R26 is 0E

and C29 is DNP.

AND ALL THE PROTECTIONS ARE DISABLED BY DNP Q2

THE TRANSFORMER IS

https://www.tdk-electronics.tdk.com/inf/80/db/fer/e_25_13_7.pdf

THE PRIMARY INDUCTANCE IS 42uH

and primary turns is 4 and secondary is 6 and bias is 3.

thanks

0 Hong Huang 8 months ago in reply to cs power

TI__Guru 74115 points

Hi,

Can you please provide CS and OUT1 waveforms?

0 cs power 8 months ago in reply to Hong Huang

Prodigy 145 points

Hi Mr. Hong

Thank You for the patience.

here are the waveforms

Latest Waveforms.zip

Don't know why such simple circuit straight forward but not working as intended.

kindly help with this as soon as possible.

Thanking You

0 Hong Huang 8 months ago in reply to cs power

TI__Guru 74115 points

Hi,

CS spikes causing gate turn off. Also CS shows sort of saturation.

I cannot find your schematics. Please provide that to me for review.

0 cs power 8 months ago in reply to Hong Huang

Prodigy 145 points

150W_REV2-ACTIVE-PUSH-PULL_2024-11-23 (1).pdf

Hi,

I had attached the schematic in this reply and if you want transformer details. its in the older replies of this thread.

Thanks.

0 Hong Huang 8 months ago in reply to cs power

TI__Guru 74115 points

Hi,

Two possible reasons:

1. T2 not reset properly. You need to check SE_S (waveform between SE_S and SE_F) to make sure the T2 reset properly. Also measure CS pin, to make sure its spikes not trigger the threshold to turn off OUT1 or OUT2. Currently your waveforms show CS pin spikes different when OUT1 turns on compared to OUT2 turns on. You need to correct this difference, I suspect T2 is not reset properly to cause the issue.

2. Make sure the transformer not saturation. Your CS waveform indicates the transformer T1 entering saturation.

So it looks T2 is likely the main cause from not reset properly each switching cycle.

0 cs power 8 months ago in reply to Hong Huang

Prodigy 145 points

Hi Hong Sir

Thanks you for the effort.

here as the first cause suggest , T2 is saturating. T2 is a current transformer. does the current transformer saturate normally

because the primary current is like 6 to 7 A peak that's observed at some minimum load.

If Current Transformer is saturating.

What can be the measures to avoid it.

0 Hong Huang 8 months ago in reply to cs power

TI__Guru 74115 points

Hi,

T2 not reset properly, you can try to reduce R40 to see if any help. Or ask the T2 vendor to find how to make T2 reset.

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LM5030: WHY IS THE OUTPUTS OF THE CONTROLLER ONE OUT IS NARROW AND OTHER IS WIDE. TOPOLOGY IS PUSH PULL