Completion is tracked in the linked PR.
Design Scope
Design a PWM-dimmable, polarity-switchable driver circuit.
Purpose
The purpose of this driver circuit is to be able to precisely control the heat transfer of a thermoelectric element (Peltier tile).
Function
Inputs:
- DC power
- Control signal (PWM)
Outputs:
It interfaces with/depends on the following systems:
Method
There are a number of ways of going about this.
- All-in-one dimmable current source (aka LED driver) - Pros: Precise power transfer control ($Q$ is proportional to $I$ (source?)); Cons: no models with high enough current output
- Filtered PWM Voltage Source - Pros: Peltiers are fairly resistive/linear in their load under standard operating conditions, so voltage driving should be fine (source?); Cons: Need to build a f*cking filter circuit, need some kind of feedback system to tell how much current we're actually putting through this thing
We're going to go with option 2. There do not exist any LED drivers with sufficient current output.
Features
Each feature should be added to relevant BoMs and CADs where applicable. Design decisions should be well-supported using relevant research and calculations, and should be documented in the Solution Overview. If a feature is complex enough, create a new issue for it using this template, and tag it here.
In order of connection sequence:
- Power MOSFET - Generate 0-16V PWM square wave "signal" voltage
- Low-pass filter - Convert PWM to analog signal (duty cycle -> 0-16V)
- Voltage buffer (Unity-Gain Op Amp) - Use signal without interfering with filter
- Amplifier (Darlington) - No current draw from buffer
- H-bridge - Control polarity
Requirements and Validation
What does this design need to accomplish? How do we know it has accomplished this?
List any applicable metrics with criteria/constraints, applicable to purpose, function, method, and each feature, as well as how to test them.
- Minimize parasitic/"non-load" power consumption
- Load power delivery accuracy ±5%
Verification
Each test should be performed and documented, and the testing documentation attached to the PR. The testing suite should address the full scope of the function (i.e. ensure inputs are met and outputs work), method (all steps execute correctly), and features (each feature performs as expected) with respect to the purpose and requirements.
How does this design achieve its method effectively, safely, and reliably? How do we test this?
Specific testing procedure:
- Test power MOSFET switching and voltage accuracy at load (16±.5V)
- Test low-pass filter attenuation ripple (PWM% x VCC ±5%) and time constant
Completion is tracked in the linked PR.
Design Scope
Design a PWM-dimmable, polarity-switchable driver circuit.
Purpose
The purpose of this driver circuit is to be able to precisely control the heat transfer of a thermoelectric element (Peltier tile).
Function
Inputs:
Outputs:
It interfaces with/depends on the following systems:
Method
There are a number of ways of going about this.
We're going to go with option 2. There do not exist any LED drivers with sufficient current output.
Features
In order of connection sequence:
Requirements and Validation
What does this design need to accomplish? How do we know it has accomplished this?
List any applicable metrics with criteria/constraints, applicable to purpose, function, method, and each feature, as well as how to test them.
Verification
How does this design achieve its method effectively, safely, and reliably? How do we test this?
Specific testing procedure: