AC/DC and Isolated DC/DC Power

Forum Post: RE: Trouble with using UCC38C40 to control boost converter

Flavio Brazzoduro — Wed, 19 Jun 2013 07:06:00 GMT

Hi Siyu,

Your calculations are correct.

Refering to your schematic, R51 = 1K (R4 in paper) and R53 = 2K2 (R2 in paper).

Have a nice day.

Flavio

Forum Post: RE: TPS2811 VCC and Reg IN

Jurjen Huisman — Wed, 19 Jun 2013 06:51:00 GMT

If the supply voltage is 4V to 14V than only use VCC and GND, do not use REG_IN and REG_OUT

If the supply voltage is 14V to 40V than connect the power supply to pin #1 (REG_IN) and connect pin #8 (REG_OUT) to pin #6 (VCC).

So, for 25V supply voltage, connect 25V to pin #1 (REG_IN) and connect pin #8 (REG_OUT) to pin #6 (VCC).

Forum Post: RE: Inquiries regarding PMP2890 (TPS40210) switching frequency and Vdc

Anthony Fagnani — Tue, 18 Jun 2013 20:58:00 GMT

Hi Atsushi,

The G074362LF transformer was specified for 1500 VDC Isolation so it will not meet the 2500Vdc requirement. A new transformer will be needed.

As for 20kHz switching frequency, we only specify it to a minimum frequency of 35kHz. It may support 20kHz with the right RC combination but we cannot guarantee it.

If this is not ok, I can help take a look for an alternative part and let you know.

Best Regards,
Anthony

Forum Post: Inquiry regarding LM5030 push-pull power configuration

Atsushi Okui — Tue, 18 Jun 2013 08:48:00 GMT

Hello, all

Now we are considering to modify the application circuit of LM5030 which is described as Figure 10 on page 10 of this datasheet.

The target specification which is considered on our side is as below;

Vin: DC24V

Vout: AC100V@1~2W (AC power supply)

Output AC frequency: 50 to 60Hz

Here is the main concernings whether this could be achievable on this device.

1. Whether FB pin could be input from 1st order side.(directly connect from GND which is under R4 on this figure)

2. Whether D1 on this figure could be removed to generate full AC waveform.

Please let us clarify whether this modification could be achievable.

If not, please let us know on which point this could not be.

We thank you in advance for your information.

Best regards,

Forum Post: RE: The diode in the circuit LM26480

Kern Wong — Tue, 18 Jun 2013 01:22:00 GMT

Hi DV,

One generally doesn't need the diode, but in some cases (this part is used in industrial as well as in portable handheld gadgets) where noise is a concern locally or on the bus, a low voltage Schottky ( 0.2V or so) can prevent the sw node from diving below ground potential by a -Vpn. This can momentarily forward bias some internal junctions which can cause havoc to the chip (noisy at high peak current operations). The diode also improves the design by a few % point when layout tightly/properly. Most designs don't incorporate the didoe as noise was not an issue and/or when its cost matters. The EVB was designed to address worst case operation where both bucks may be operating at max loading. Hope this helps,

Kern

Forum Post: RE: UCC27531EVM-184 evaluation module

Brandon Vonk — Mon, 17 Jun 2013 14:08:00 GMT

Thilak,

The maximum switching frequency of the EVM will be on the order of signal propagation throughout the EVM. Have a look at the figures on page 10 of the User Guide. The propagation delay from the EVM input, to output is about 45ns. However, the maximum switching frequency for the UCC27531 will be greater than what you will see on the EVM.

Regards,

Brandon Vonk

Forum Post: UCC28950 asymmetric duty cycle operation at light load condition

woosup kim — Mon, 17 Jun 2013 07:32:00 GMT

Dear TI engineer

I've tested my 3kW DC-DC converter with your ucc28950 PWM IC.

However, currently I have unanymous problem.

At light load condition, Output C/D duty was not 50 to 50% but asymmetric ducy cycle.

I found application report ; slua275 ucc3895 OUTC/D asymmetric dyty cycle operation.

Plz check below questions

1. Detail logic block described in in ucc28950 datasheet is the same as which of ucc2895?

2. In slua275, it metioned, " Also, when using synchronous rectifiers in current mode operation this problem does not typically exist due to the additional reflected secondary current added to the primary side current sense.'. I couldn't understand why? Can you explain in datai?

3. Recommand me to escape this problem.. ( ramp pin is already located inside the PWM IC, I couldn't find any external method which you used in slua275.

Forum Post: RE: LM5101A oscillates and burns up

Kening Gao — Sat, 15 Jun 2013 13:03:00 GMT

Related to the size of bootstrap capacitor, the needs for the bypass capacitor should be low ESR and placed as close as possible to the driver.

So a good choice is to place a ceramic capacitor near the driver.

This need also aplys to the decoupling capacitor of VDD.

Of course, you could add a diode from VCC to HB if its conduction voltage is lower than the internal one.

For the damage of driver, the possible cause could be the bootstarp diode damaged inside driver, the negative or positive voltage exceed the spec, the output stage being wrongly shorted.

BTW, why LO(w40,w41) is connected to a floating node? I think it would cause some trouble because LI is low.

Forum Post: RE: LM5106 unstable output

Jean-Philippe Rey — Fri, 14 Jun 2013 15:48:00 GMT

Ok meanwhile I found it. As was driving my H-bridge with continous "1" input instead of PWM, the bootstrap capacitor couldn't stay charged. The workaround is to drive the h-bridge in PWM mode with dutycycle near 99%. This involves sufficient number of transitions to keep the bootstrap capacitor charged.

!?#°@?&% bootstrap capacitors........

Hope this could help someone a day.

J-P

Forum Post: RE: Is there a LM27402 SPICE model that can be imported to TINA9?

SaraR — Fri, 14 Jun 2013 14:32:00 GMT

Hi Anto,

I have requested the translation for you. Once it is scheduled, an update will be posted.

Best regards,

-S

Forum Post: RE: UCC2818 Line to Line PFC

Adria Martinez — Fri, 14 Jun 2013 13:57:00 GMT

That's also what we're doing, we have 3 isolated PFC's, each one connected to a different phase pair.

We're now at the stage of testing one single PFC but we're facing the problems commented before.

Some more information, may be it helps. The input current waveform is senoidal at low output power, but when the power rises, the PF starts to fall and the input current is having some distorsion.

Forum Post: RE: Cheap (non-) isolated solution for off-line 3...5V?

Harmeet Singh — Fri, 14 Jun 2013 10:11:00 GMT

Hi Tobias,

for 5V or 3.3V/30mA requirement in non isolated configuration you can use Capactive drop power supply followed by DC-dc converter like TPS54060.

Please fine the application note link for it. http://www.ti.com/litv/pdf/slva491 and the excel calculator http://www.ti.com/litv/zip/slvc392.

For isolated case you can use UCC28700/UCC28701/UCC28702/UCC28704 PSR controller.PLease find the link http://www.ti.com/product/ucc28700.You can put your values in the web bench and the web bench tool will give the design.

For isolated you can also use a small 50Hz transformer followed by a LDO as your load is very small and the input ac variation is very small.

Regards,

Harmeet

Forum Post: RE: LM5022 - Wide input voltage SMPS

Atul Bhakay — Fri, 14 Jun 2013 02:26:00 GMT

(Please visit the site to view this file)

Hi, kindly refer the attachment for the equations that I used for the wide input design

Regards Atul bhakay

Forum Post: RE: LM5022 Isolated Boost converter solution

Youhao Xi — Thu, 13 Jun 2013 23:37:00 GMT

Do you consider a flyback, or forward for the isolated operation? The LM5022 can easily make a flyback and realize your voltage conversion.

Forum Post: RE: Isolated Power Supply using LM5010 - High Peak to Average Ratio

Vijay Choudhary86929 — Thu, 13 Jun 2013 22:47:00 GMT

You should be able to find the datasheet and user guide for the evaluation board on LM5010 and LM5010A websites. But do you really need 350W!

Forum Post: RE: Large Power Supply

EdWalker — Thu, 13 Jun 2013 22:21:00 GMT

Indeed we don't have any reference designs that match this requirement.
But we can break it into 2 pieces and get a good idea.

1. PFC for the input, 720W output, wide range AC
UCC28070 interleaved design. http://www.ti.com/product/ucc28070
There are some reference designs under TOOLS & SOFTWARE.

Make a 390V DC buss to work from.

2. DCDC for 240V 3A 720W from 390VDC input.
I would do a Phase Shifted Full Bridge UCC3895 style; http://www.ti.com/product/ucc3895
Attached is a preliminary schematic of PMP3525 a 308-572VACin, from a 3 phase bridge, making 320V at 4Amps, isolated.
It is schematic only, no board file, it was not built but was designed by an excellent TI team.
The PFC output of 390Vdc is lower than the 308VAC peak of 431Vdc, however it provides a good idea of how to solve it.
Again the schematics are PRELIMINARY and for reference only.

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Forum Post: RE: Isolated DC/DC power supply

Ramanan Natarajan — Wed, 12 Jun 2013 23:11:00 GMT

Stan,

You can browse through the entire lineup of actively supported products below:

http://www.ti.com/lsds/ti/power-management/isolated-module-products.page

Unfortunately, I dont see one with the 5-10W power capability you are looking for.

thanks,

Ramanan

Forum Post: RE: regulate 12V down to -55V

Jurjen Huisman — Wed, 12 Jun 2013 14:44:00 GMT

I would suggest to just enter these values in the WEBENCH^® Designer (http://www.ti.com/lsds/ti/analog/webench/overview.page)

I entered:

Vin_min = 11V

Vin_max = 13V

Vout= -55V

Iout= 0.03A

which gives several designs.

Forum Post: RE: UCC28950 / TMIN restriction

KENSUKE YAITA — Wed, 12 Jun 2013 04:10:00 GMT

Hi, Mike,

OK, I see.I explain that to my customer.

thank you for the reply.

Regards,

Yaita

Forum Post: ac/dc voltage regulator

or sam — Tue, 11 Jun 2013 14:28:00 GMT

I would like to transfer power using 2 coils.

in the output I get a signal (positive an negative) in freq 100KHz that I can controll on it amplitude.

I want to convert this signal to a 5V or 3.3V signal.

do you have a component that can do it?

if yes how dose it called? I does LDO can do the work? the problem with LDO is that it cannot take negative voltages - and I want component that already has an efficient rectifier embedded.

thanks in advanced.