Add PWM control for a buck converter

Hello Fede,
There are many PWM's that can do what you want for resistive loads.

Please provide:
1. Input voltage range, max min
2. Output voltage
3. Output current, max min
4. Duty cycle range, this relates to minimum ON TIME of the output pulse

This information will allow proper routing to the correct device team.

Thanks for the reply.
This regulator is for a safety critical system.

1) The system is powered by 4 AA batteries, so 6V or a little less in the case of rechargeable batteries.

2,3) My load is 3 emitters with a nominal resistance of 40 ohms, the maximum current is 150 mA each and a voltage of 6V each.
I can connect these 3 emitters in series or in parallel, I have no preferences, I can choose the connection based on the DCDC regulator in order to have the maximum efficiency.

4) The maximum frequency of the PWM is 100 Hz, with duty that can reach 10%. But if it is a problem I can increase the minimum duty to 20%.

Thanks in advance, FM

FM,

Your output voltage is very close to the input voltage.  Can you power your emitters directly form the batteries connected by a load switch?

no, I can't connect the batteries directly because I might need to lightly vary the supply voltage (the emitter must be calibrated by the supply voltage), so I might have situations where I need Vout of 5V and others which I need something like 7V.

Furthermore, for a subsequent development phase we should also make a car version (Vin = 12V) and a truck version (Vin = 24V).

FM,

Sounds like you will need a buck-boost.  Do you want to use a common design for all three applications?  I would need your total input voltage range for each of your three individual apps or combined if you prefer.  Also, are you intending to turn on/off the output completely with your PWM signal, or vary the output voltage?

The perfect solution for me is a converter that can accept the input voltage from 6 to 24 V. But if it's complicated I can also do 3 different design.

to simplify I can give up the output between 5 and 7 V and move it between 4 and 6V so as not to have the buck-boost but only the buck.

and with my PWM signal I have to turn off the emitter completely,
PWM in level 1: Vout = full voltage
PWM in level 0: Vout = 0V

In summary:
Vin: from 6V to 12V
Vout: from 4V to 6V (adjustment with a trimmer or with a resistive divider)
Iout: 450 mA

or I can put the 3 emitters in series and have
Vout: from 12V to 18V
Iout: 150 mA

FM,

Please take a look at

Let me know if this would work for you.

I am going to buy the TPS62170EVM-627 evaluation board.
should I apply my PWM signal to the SLEEP input or to the ENABLE input?

FM,

I will forward this request to the application engineer that directly supports TPS62170.

Hi Fede,

This reference design sounds like exactly what you want to do: http://www.ti.com/tool/PMP9762

Since you have a lower current, and since we have released new devices, I would recommend using the TPS62147/8 in the same way as the reference design.

Also, note that the TPS62170 is a different device to the TPS62175.