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PI controller using opamp with -ve output | Cypress Semiconductor

PI controller using opamp with -ve output

Summary: 8 Replies, Latest post by muhammad.yaqoob_1490236 on 20 Oct 2016 08:42 PM PDT
Verified Answers: 1
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muhammad.yaqoob_1490236's picture
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53 posts

Dear All,

I am trying to implement a PI controller for a power converter. Attached is the schematic diagram of the analog part that I want to implement on PSoC-5LP.
The problem is that PI's opamp output is -ve and opamps in PSoC do not support  a -ve voltage. 
Any help in this regard would be appreciated.

 

 

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user_242978793's picture
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1042 posts

You can't use a negative voltage on PsoC parts . You will need an external Opamp.

user_49271930's picture
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421 posts
muhammad.yaqoob_1490236's picture
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53 posts

Thanks for your reply.
But the problem remained intact as I am using PI controller whose output is -ve and input is +ve (in simulation results in PSIM).

 

user_49271930's picture
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421 posts

It is not difficult to create using a converter TIA or OPAMP

muhammad.yaqoob_1490236's picture
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53 posts

Thanks for your reply!

But, TIA also couldn't solve the problem. If you see the attached pic (with my first post), there is -ve signal in between two opamps. So, the problem is that when I feed a +ve signal to the opamp1 the output will be -ve and will go to the input of the opamp2.  With power supply range of 0 to +ve of opamp1 (i.e., opamps in psoc), at output I only get 0 instead of the -ve output.

user_1377889's picture
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9625 posts

When you set Vref to +ve/2 all will be good.

 

Bob

muhammad.yaqoob_1490236's picture
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53 posts

In fact, the range of Vref is relative to the +ve input (from a current sensor) to opamp1. So, if I will keep Vref/2 (0.5) eventually input to opamp1 will also be 0.5 because, Its a PI controller loop. Long story short, the output of opamp1 will remain -ve. 

muhammad.yaqoob_1490236's picture
User
53 posts

Problem solved using external opamps IC with dual power supply.  

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