EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: SittingBear on August 27, 2014, 02:10:13 pm
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Hello EEVBlog community,
I’ve been attempting to prototype the boost driver with no luck so far. My initial build was on a breadboard, but then after that didn’t work I went over to etching a PCB. I have tested each connection and ensured proper continuity as shown in the schematic. My schematic is a replica of the one found on page 34 of the TPS40210/11 datasheet. I changed a few minor values to fit the closest common commercial value.
The schematic can be found here (https://drive.google.com/file/d/0B0mjxyoOHJurS0FaUTZIb25EN2M/edit?usp=sharing). Page 34 of the TPS40210/11 datasheet is here (http://www.ti.com/lit/ds/symlink/tps40211.pdf#page=34).
The issue I get is that nothing seems to happen at all and the GDRV voltage, when probed with an oscilloscope, remains fixed at VCC. Which is odd, because measuring resistance returns OL or ‘open-circuit’. I believe it’s either an issue with the MOSFETs I chose, or with my handling in the driver (i.e. ESD damage).
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Are you trying to make a constant voltage or a constant current supply? Because the schematic on page 34 of the datasheet is specifically for a constant current supply. Without sufficient load on the output, it will not function and stay off.
What is your input and output voltage?
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Are you trying to make a constant voltage or a constant current supply? Because the schematic on page 34 of the datasheet is specifically for a constant current supply. Without sufficient load on the output, it will not function and stay off.
What is your input and output voltage?
12V in and roughly 23-24 volts out for the LEDs. It's constant current to ensure each LED is at the same brightness.
I believe I found the mistake. I must have done something, because C8 and R5 decide the switching frequency. C8 was supposed to be 100pF, but it is 10uF which is way too large. After de-soldering and reattaching the proper capacitor the circuit seems to work decently! Now to fine tune it.