Building a precision PMT power supply with TMS320F28027

Oleg Kobrin

Other Parts Discussed in Thread: TMS320F28027, INA121, CONTROLSUITE

Hello!

I am designing the PMT power suply with TMS320F28027 MCU. I am using the full-bridge (L6203) loaded with primary coil of transformer, and secondary coil with voltage doubler is generating -1200V level to drive the PMT. The voltage divider (9400kOhms to 15kOms) is used to provide a feedback signal via the INA121 istrumentation amplifier. This signal is connected to ADCINA2/COMP1A port of MCU.

The EPWM2A port is used as PWM source and GPIO0 and GPIO1 is switching the polarity of voltage applyed to primary coli.

I need to understand how to configure the digital comparator as an error amplifier to adjust the duty cicle of the PWM.

Here is the schematic fragment:

Thank you!

over 10 years ago

0 Hrishi Nene over 10 years ago

TI__Genius 10820 points

Hi Oleg,

The on-chip comparator is an analog comparator not a digital comparator. This comparator, in conjunction with its 10-bit DAC, allows fault protection and/or cycle-by-cycle operation of the system. You could use it to implement hysteretic control as well. However, the comparator on this device should not be used as an error amplifier.

These devices allow digital control of power converters by closing the loop in software i.e. the control law is implemented in software. Please refer to some of our example system implementations in the C2000 controlSuite (http://www.ti.com/tool/controlsuite. Some of these examples also use the on-chip comparators for the functions mentioned above.

I hope this helps. Let me know if you have any other questions.

Hrishi

0 Oleg Kobrin over 10 years ago in reply to Hrishi Nene

Expert 1890 points

So, I need to use ADC to adjust the duty cicle, right?

0 Hrishi Nene over 10 years ago in reply to Oleg Kobrin

TI__Genius 10820 points

Yes, that's right.

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Building a precision PMT power supply with TMS320F28027