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LED Driver ICs Forum Discussions

User22521
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First question asked
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Hi everyone

I am looking at playing around with the TLD5099. I realise its aimed at LED drivers but I would like to make small DC-DC power supplies. A boost converter

There are many appboards to take inspiration from and I would like to discuss the operation of the IC to be sure I understand it

If we consider a boost topology then theres a boost inductor which connects to a switch and the IC measures the output voltage and adjusts the duty cycle in order to maintain the output voltage which you set via a potential divider.

Lets assume we set the voltage to a maximum of 40V, the IC will switch current through the inductor and genreate the boost voltage


My question relates to the dimming, If the enable/pwm pin is pulled high then there is no PWM dimming of the output the current will be limited by a shunt resistor, when the voltage exceeds 300mv the IC will switch off the boost switching

So I could use that as a current limit in a DC boost configuration

Does the PWM dimming affect the boost switching? i.e if I set the output voltage to 40V with a 1ohm feedback resistor then if the load draws less than 300mA I would measure the full 40V across the load?

The IC reached its voltage limit so the amount of current depends on the load impedance, is that correct?

If I increase the load current the the IC will adjust the voltage so that the maximum limit is maintained

But if I add PWM dimming then that seems to chop the current/voltage that comes from the boost output i.e it will be the full 40V but the output is chopped separately is this correct?

Does the PWM dimming affect the switching of the boost switch or are they completely independant

I would like to have a boost circuit to charge a battery and with external measurements I could use the PWM dimming to tail off the charging current and use software to have different charging profiles etc

If theres any detailed explanation of how the IC works it would be appreciated, the data sheet has confused me a little
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1 Solution
fausto_borg
Moderator
Moderator 10 likes received 10 sign-ins 5 solutions authored
Moderator
Hello Jamie,
TLD509xEP are LED DC-DC controller and as you mentioned you can use them as voltage regulator as well.
To use these devices into voltage mode power supply you have to change the connection of the feedback network.
For LED drivers the feedback network is connected in series to the load, while for the constant output power supply the feedback network is in parallel to the load. For this reason you cannot control both voltage and current at output

Does the PWM dimming affect the boost switching?
Yes, PWM dimming affects the boost switching: when it is high the boost switch is enabled, when it is low the boost switch is disabled.

The IC reached its voltage limit so the amount of current depends on the load impedance, is that correct?

When you reach the voltage limit the controlled disable the boost switch. you do not have regulation when you reach the over voltage threshold. (or you have to accept quite high ripple)

I would like to have a boost circuit to charge a battery and with external measurements I could use the PWM dimming to tail off the charging current and use software to have different charging profiles etc


At the moment this application does not fit with TLD509x devices. My suggestion is to use TLD5542-1. We have an Arduino shield that can be used to test this device as battery charger. https://www.infineon.com/cms/en/product/evaluation-boards/tld5542-1chg_shield/

Please keep visiting our LITIX webpage, new devices fitting your requirements are coming....

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1 Reply
fausto_borg
Moderator
Moderator 10 likes received 10 sign-ins 5 solutions authored
Moderator
Hello Jamie,
TLD509xEP are LED DC-DC controller and as you mentioned you can use them as voltage regulator as well.
To use these devices into voltage mode power supply you have to change the connection of the feedback network.
For LED drivers the feedback network is connected in series to the load, while for the constant output power supply the feedback network is in parallel to the load. For this reason you cannot control both voltage and current at output

Does the PWM dimming affect the boost switching?
Yes, PWM dimming affects the boost switching: when it is high the boost switch is enabled, when it is low the boost switch is disabled.

The IC reached its voltage limit so the amount of current depends on the load impedance, is that correct?

When you reach the voltage limit the controlled disable the boost switch. you do not have regulation when you reach the over voltage threshold. (or you have to accept quite high ripple)

I would like to have a boost circuit to charge a battery and with external measurements I could use the PWM dimming to tail off the charging current and use software to have different charging profiles etc


At the moment this application does not fit with TLD509x devices. My suggestion is to use TLD5542-1. We have an Arduino shield that can be used to test this device as battery charger. https://www.infineon.com/cms/en/product/evaluation-boards/tld5542-1chg_shield/

Please keep visiting our LITIX webpage, new devices fitting your requirements are coming....