Controller for LLC resonant converter

[Mery96]

Hello everyone, I'm looking for a controller for the LLC resonant converter that I will use in the LED driver application. I have not had experience in this field before so I want to ask you. My LED specs are 2.82-3.15 V forward voltage at 1050 mA current, maximum power 10 watts. My operating frequency will be above 1 MHz. I will use a li-ion battery as a power supply. Waiting for your suggestions for LLC converter controller IC.

 

[ronsimpson]

I need to know what the battery max and min voltage is.

My LED specs are 2.82-3.15 V forward voltage at 1050 mA current, maximum power 10 watts.

So you are using three LEDs in series? About 9 volts?

 

[Mery96]

I will use a single LED, I added it because it says max 10 watts in the datasheet, otherwise my output power is 3.3 watts. The battery voltage is 3.7 - 4.2 V

 

[ronsimpson]

Input voltage is 3.7 to 4.2V and the output voltage is 2.82 to 3.15, so you need a boost-buck supply. A buck might work, 3.7V bucks to 3.15 with little margin.
I will look for a IC after I eat.

 

[ronsimpson]

Here is an example that I have used. Voltage at "FB" is 0.1V. Rs=0.1 ohm for 1A.

 

[Mery96]

I think buck boost makes sense, but this is a school project and I have to use LLC converter because my teacher wants it.

 

[ronsimpson]

Simple low voltage dc to dc, I have not seen one. LLC
If you said 220vac to LED then there are some I think.
Variable frequency resonant .... I will look some more but it will be complex.

 

[ronsimpson]

LLC
Here is an example of LLC. I can not find any that are low voltage.

 

[Mery96]

this project seems to be a bit difficult, thank you so much for your time.

 

[ronsimpson]

The purpose of LLC is to reduce the AC losses in high voltage transistors and HV diodes.
A LED power supply, your project, could use 5V or 10V silicon which is much much faster and will have much less ac losses.

this project seems to be a bit difficult

Here I removed pieces you do not need. Now that I rethink it; the transformer and isolator could be also removed.

 

[Mery96]

Excuse my ignorance, if we remove the transformer, will the load be directly connected to Lr and Cr?

 

[Mery96]

When I researched I saw the ICE2HS01G integration, do you know this IC and do you think this integrated can be used?

 

[ronsimpson]

if we remove the transformer, will the load be directly connected to Lr and Cr?

My thoughts; Pretend the transformer is 1:1. On the secondary there is a full wave rectifier, then off to the load. This works.
A 1:1 transformer really has no function. (isolation) I think if you used a full wave diodes and load, but just moved then to where the primary was it should work.

ICE2HS01G integration

This IC needs 13 volts to run the brains in the IC, and you do not have that. I noticed this problem with all the parts I found.

 

[Mery96]

I understand thank you, I didn't find any other solution either, I will try this example by removing the transformer.

 

[ronsimpson]

Do you need to build it or is this just a paper exercise?

 

[Mery96]

I will simulate first and then build it.

 

[ronsimpson]

I forgot about this part. Simple and used in light bulbs. (high voltage) From Fairchild now by OnSemi. There are several brothers. Needs about 13V on VLcc for it to work but the Vin might work at 4V. I do not know.

How are you at software? There are some micro controllers that have PWM inside. The IC could be a small micro and drives the two MOSFETs.
In software you will need to watch the LED current and adjust the frequency to get the right current. There are many micros what will work at 3 to 5 volts.

 

[Mery96]

I don't have experience except Arduino projects but I know C, I was thinking of using microcontroller for led brightness, you are right, maybe I can drive mosfets with micro controller. it's a good idea

 

[Mery96]

Can I control the frequency, output current and output voltage using only micro controller, without using controller IC?

 

[ronsimpson]

Many new PWM do not allow you to change frequency. Here is a part I know very little about but there is a LT SPICE model for it and the frequency could be programmed from a computer. Computer with a DAC and resistor.

This IC has the two MOSFETs inside and the driver circuits. Frequency is set by a resistor or current source on "RT". I don't have it working right in my head but the idea is close to right.

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Because LLC was never intended to do this job and there is no easy answer I think you need to go back to school and ask more questions. Collect what data you have and make certain this is what you are to make.