Isolated Controllers

interfacing the TCL5947

Rene Wassenburg — Fri, 06 Nov 2009 13:35:29 GMT

Hi there,

I'm new on this forum, so i hope i posted this topic in the right forum section.

I'm using a TLC5947, and i want to drive 1W LEDs. For this is I want to use a buck converter from Zetex; the ZXLD1350.

http://www.diodes.com/zetex/_pdfs/3.0/pdf/ZXLD1350.pdf

The outputs of the TLC5947 are constant current and the input of the ZXLD1350 wants to be hooked to an open collector output. The TLC5947 is an open collector, so that should work.

However, my analog skills are not top notch, and the internal schematic of both the TLC5947 and the ZXLD1350 are unclear to me.

Am i right that i CAN hookup the ZXLD1350 straight to the output of the TLC5947?

Or..should I put a pullup resistor to the output of the TLC5947 and the connect the output (via a resistor divider) into the base of an external NPN transistor? The collector of this external transistor can then be hooked to the input of the Zetex.

I'm very confused in this.

Of course I want to minimize the amount of components on my board, but I am really not sure if i can directly drive the Zetex chip with the TLC5947.

Hope somebody can clear this up for me..

Thanx in advance!

I understand that if i do so, i will have inverted PWM, but doesnt matter, my software can correct that.

Can somebody help me out with this?

TPS61140 Vin min Boost regulator

xenpac — Fri, 21 Aug 2009 13:21:22 GMT

We want to use the TPS61140 in a 3V Batt application.

Datasheet says: Vin min = 2.5V.

However we need it to work even at 2.2V minimum.

Low Voltage shutdown is specified at around 1.8V.

anyone has experience in operating it at that low level of 2.2V ?

TPS5430 Question

ler — Mon, 21 Sep 2009 21:40:35 GMT

I am using the TPS5430 to convert 24VDC to 3.6V. I have had two of the convertors fails, where they can

supply a light current load but when loaded up (say 1A) they become quite hot and the thermal protection

circuitry begins to cycle the part off and then back on. What might we be doing to this part that could cause

this? I have seen two of these in the last week.

Thanks.

help finding about SMD Transisters

sajad bilal khan — Fri, 24 Jul 2009 02:46:21 GMT

Hi all , i need help about some SMD or SMT (transistors) used in CDMA WLL sets for charging with ic mc34063 . please i need its equlants or its data sheet for details. transisters are

1A2.........VA ........SOT23 these 2 transistors are used

UCC3895

Paul Decker — Thu, 12 Nov 2009 18:19:41 GMT

Hi,

I'm trying to use the UCC3895 in a fixed frequency pwm controller. In other words, no feedback of any kind, no current sense, no adaptave phase, etc, all I want to do is generate 200 Khz 47% duty cycle square wave on outab and outcd. Can this be done with the ucc3895? I had no problem doing it with the TL494. how should CS, ADS, EAP, EAN, EAOUT, SS, and RAMP, should they all be tied to ground?

Thanks,

Does any have the spice model of ucc38c44 ?

Shanna Zhang — Tue, 17 Nov 2009 18:59:50 GMT

I need to simulate a circuit which has Fuji part FA13844. TI part UCC38C44 is its equivalent. But there is no spice model on TI's website. (There is not spice model for Fuji part either.) So if someone has built a spice model for either part and is willing to share with me, I will greatly appreciate it.

LED-driver solution for bulb replacement

Dmitry Vasilenko - Arrow — Mon, 16 Nov 2009 12:21:12 GMT

Colleagues,

in the recent LED applications cookbook there was presented a solution for bulb replacement on the basis of UCL64010. It's not clear if there is a possibility to dim the LED-lamp by a thyristor dimmer. Can someone specify?

Another problem we see from in this application I can describe as follows. Some of our customers has done tests of the LED-bulb prototypes, and they have detected 100 Hz flickering on LEDs (50 Hz AC signal standard in Russia X 2 rectified). It looks as if the rectified AC mains signal modulates the light from LEDs. This is a very severe problem for the application since this won't allow us using the technology because the lighting sources will not comply regulations. Please, advise if you you are aware this.

Code for generating a sine-triangle pwm for the control of a single phase solar inverter.

Shoaib Hussain — Sun, 15 Nov 2009 17:20:53 GMT

I'm using ti's ezdsp f28335 dsp and have read the epwm manuals (great btw) but still having trouble figuring out how to generate a sine triangle pwm. I've gone through the example code snippets but the epwm manual doesn't any methods of coding for a sine pwm for the single phase inverter.

It would be a great help if any one of you could provide a code snippet for generating a sine triangle pwm signal.

Wide input range power supply

Dmitry Vasilenko - Arrow — Thu, 12 Nov 2009 14:18:26 GMT

Colleagues, what is the best solution for the wide input range power supply with the spec: Vin AC 12-240 V Iout=1 A P=5W

TPS 40210 output cap question

maxthestork — Wed, 11 Nov 2009 05:12:51 GMT

Hi All,

I am using the TPS40210 in a boost app that takes a 12V battery supply and generates 30V at 2.5A to run a motor.

For the output cap, it will have to abosrb some energy dumping from the motor when the motor returns energy to the power supply and the output cap also has to handle the AC component from the boost topology.

Question :

- Is the ESR for the output cap in the example calculation a maximum amount or a target ESR that is required. Can I just use caps in parallel to increase the ripple current rating and also to lower the ESR.

- This is probably a really newbie question but what is the AC current that the caps have to handle. Is it equal to the worst case ripple current in the inductor?

cheers

Peter

DRV8402 - Difference between Half anf Fullbridge Mode

wolfgang weinmann — Sat, 07 Nov 2009 07:28:14 GMT

Hello,

the datasheet-section of the "Differet Mode Operations" contains the confusing statement:

In full bridge and half bridge modes, PWM_A controls half bridge A, PWM_B controls both half bridge B, etc.

Figure 6 shows an application example for full bridge mode operation.

What does this mean?

I interprete this sentence in the way, that at full bridge mode AND half bridge mode each Terminal Out (Out_A, Out_B, Out_C, Out_D) is fully independly controlled by its dedicated input-control-pin (PWM_A ... PWMD) in the manner

PWM_A = L --> Out_A = Gnd

PWM_A = H --> Out_A = Vdd

PWM_B = L --> Out_B = Gnd

and so on

But: If this is true, then where is the difference of half and fullbrigde control. It seems, that the controling logic of both modes is identical?!?!?!?!

Regards Wolf

DRV8402 for stepper motor drive

maxthestork — Wed, 04 Nov 2009 13:22:27 GMT

Hi All,

I hope I am in the right section for this post. I intend to use the DRV8402 in a stepper drive application where the stepper current will be around 3.5A per phase. I was curious about the inclusion of inductors in the datasheet discussion and the EVM. Why are they needed and more specifically would they be needed when driving a stepper that would have 2.65 mH per phase.

I intend to configure the DRV8402 in full bridge mode. Would I be able to place a current sense resistor in the GVDD _B and GVDD_C lines to control the current in the stepper motor.

Apologies if these sound like really dumb questions. Please let me know what further details would clarify the question.

Cheers!

Peter

TPS51222 split rail operation

Keith Keller — Thu, 13 Aug 2009 18:37:42 GMT

Hello,

I'm wondering if the TPS51222 dual controller can be run from split rails. It would be designed into a dual redundant battery pack.

My thought is to have diodes off each battery pack connected to Vin pin. Then connect one battery to top-side of FETs for output1 and the other battery to top-side of FETs for output2.

It's possible that the battery protection FETs could interrupt power to either one these phases.

My question is if this connection scheme will work. If power is lost to one of the phase, will the other phase continue to operate properly for the required redundancy?

Thanks for your help.

TPS40055 not working in a particular Input voltage range.

Gandharva Kumar — Wed, 02 Sep 2009 17:32:12 GMT

One of my customer is facing an issue with the TPS40055 controller. He dosn't see an output in the 18V-29V he doesn't see any output. I am attaching some information, schematics and the scope shots that he took.

Rt / Ct values for frequency calculation in UC3875

Srivatsa Raghunath — Tue, 20 Oct 2009 08:56:53 GMT

Hi,

How do we calculate the switching frequency for UC3875? We do not want to go by the graph given in the datahsheet, do we've some equations to arrive at the switching frequency?

Thanks and regards,

Srivatsa

UCC2891 based 150W board testing

Srivatsa Raghunath — Thu, 22 Oct 2009 16:01:51 GMT

We’ve made a 150W (5V / 30A) design using the UCC2891 active clamp converter

An undervoltage test is to be performed by overloading the UCC2891 to over current limit and let the output voltage droop to 4.8V. Below 4.8V the op-amp – opto-coupler circuit pulls the SD pin of UCC2891 to ground shutting down the device

This protection mechanism works fine till -15 deg C and below this the UCC2891 fails to restart after removing the fault. It seems to be in hic-up mode

I need your advice on whether this type of testing is normal in telecom systems i.e. overloading the output to hit current limit and then droop the output voltage to trigger the protection circuit

The design works fine, if I do the undervoltage testing by just modifying the TL431 reference voltage to set output voltage below 4.8V at -35 deg C

UC28025 Supplies

Kench — Mon, 19 Oct 2009 12:30:50 GMT

Is it possible to run the UC28025 chip with different VC and VCC voltages, providing you keep within the chips limits?

TPS40211

Stephen Taranovich — Mon, 03 Aug 2009 18:54:55 GMT

I am considering using the TPS40211 for a renewable energy application to charge a 48VDC battery from a lower voltage input source (10-40V). In order to limit the charge current, I would probably want to use the TPS40211 in current feedback mode (Fig 29 and 36 of datasheet), but I would also need a way to limit the maximum output voltage. If I run it in voltage feedback mode, then I need a way to regulate the maximum current. Also, I am concerned that if the battery is discharged, the TPS40211 will see this as a short circuit and shut down the gate drive, preventing any current from flowing. Because this is a renewable energy project, I need the maximum efficiency and don't want to add a linear regulator after the TPS40211.

High Power Isolated Converter with PFC

Mike Miles — Mon, 12 Oct 2009 04:17:23 GMT

I need help with selecting a control IC for a new design. This power supply will produce 200V-300V at about 5 or 10 amps max. (two versions, 1.5 kW and 3 kW max. output). Input is 120Vac or preferably 100-240Vac. The 3 kW version only produces full output with 240Vac input. Also we need a PFC circuit at the input, which may be combined or separate from the isolated converter.

I'm considering a resonant/ZVS forward converter and would like a control IC that is well supported with application design info and sample designs. Can someone recommend a suitable device for the application? Or would a traditional PWM forward converter be a better approach?

Options I’ve encountered for a ZVS design include the TI/Unitrode UCC3895 and Intersil ISL6551 or ISL6755. Does anyone have experience with any of these in a high-power application like this?

Thanks!
Mike

TPS28225 Modes of Operation

Jon Koon — Fri, 09 Oct 2009 15:17:11 GMT

In using the TPS28225, we have discovered a couple of behaviors that we were not able to identify in the datasheet.

1. The part outputs do not toggle at low PWM input rates. What is the minimum PWM frequency required to operate this part? We also noticed that it does not operate well at certain duty cycles. What are the minimum and maximum pulse widths required?

2. The part does not work at all if we do not have the PWM running and then pulse the enable signal. Is this expected behavior? Our initial system just had the enable pulled high with a 20K resistor. Then after our microprocessor booted and started running the PWM, we found that we had to transition EN low and then high to get the outputs working. In the example circuits, the enable signal is often just connected to VDD. I'm not sure why we are seeing this behavior. Our controller does not use the 3-state mode and we tried tying a 3.5K ohm resistor between PWM and ground to disable the 3-state mode.

Any light you can shed on these subjects would be appreciated!

Jon

Suitable chip for isolated power supply

Bohdan Jedlicka — Mon, 28 Sep 2009 07:44:25 GMT

Dear Sir

Can somebody give me advice what chip is suitable for power supply

Isolated, max power 21W, flyback, switching frequency among 170 - 200 kHz fixed, input AC 180V - 260V, fast response from 11W load to full load,simple

reference design if available.

I chose UCC3809 but I am not sure if it is good solution.

Thank you

SoftStart Pin 8 on UC28025 - more documentation

Josef Warta — Fri, 25 Sep 2009 09:43:24 GMT

Hello,

is there more information available on SoftStart Pin 8 (SS) of UC28025?
I.e. at which voltage level SoftStart functionality starts, stops?

Thanks, Josef

TI AFA Germany

Line OVP Design Example for UCC2897A, UCC2892 and UCC2894

Hong Huang — Wed, 23 Sep 2009 15:57:09 GMT

UCC2897A - making ZVS or not, and how-to-design an active clamp forward converter

Hong Huang — Mon, 31 Aug 2009 18:56:34 GMT

The paper listed below provides the guidelines on ZVS design of an active clamp forward converter, and explains when ZVS makes efficiency benefit and when not.

Hong Huang, "Design guidelines on the effect of resonant transitions of forward converter on efficiency with active clamp",

Applied Power Electronics Conference and Exposition, 2008. APEC 2008. Twenty-Third Annual IEEE, 24-28 Feb. 2008 Page(s):600 - 606

Although the below is in updating, the existing one is still a good reference for designing an active clamp forword converter.

http://e2e.ti.com/cfs-file.ashx/__key/CommunityServer.Discussions.Components.Files/120/3617.slua303.pdf

More literatures on active clamp forward converters from TI web:

http://focus.ti.com/lit/ml/slup108/slup108.pdf

http://focus.ti.com/lit/ml/slup112/slup112.pdf

http://focus.ti.com/lit/ml/slup175/slup175.pdf

http://focus.ti.com/lit/an/slua322/slua322.pdf