Power Supply Controller Feed-Forward Circuit Voltage Accuracy
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Solution Overview
Problem
Existing power supply control systems face accuracy and stability issues due to programmable output impedance, which causes delays in charging output capacitors and reduces the accuracy of output voltage changes.
Innovation Solution
A power supply controller with a differential error amplifier and a feed-forward circuit that maintains constant gain for reference and feedback signals over operating frequencies, and utilizes a feed-forward circuit to rapidly change the output voltage by adjusting the load current in response to changes in the reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If programmable output impedance is used to reduce decouple capacitor requirements, then device size is reduced, but output voltage change accuracy deteriorates due to delay in charging output capacitors
Solution Approach 1:
The feed-forward circuit anticipates the voltage change requirement and begins charging the output capacitors before the main control loop completes its response. When a voltage change is commanded, the feed-forward circuit immediately supplies the necessary current to charge the capacitors, eliminating the delay that would otherwise occur with programmable output impedance alone.
2Adaptability or versatility
If programmable output impedance is used to change output voltage, then adaptability is improved, but response time deteriorates due to delay in charging output capacitors
Solution Approach 1:
The feed-forward circuit performs the capacitor charging action in advance and simultaneously with the voltage change command, rather than waiting for the programmable output impedance to gradually charge the capacitors. This maintains full adaptability while eliminating the time delay.
Solution Approach 2:
The feed-forward circuit acts as an intermediary that supplements the programmable output impedance by providing the additional current needed for rapid capacitor charging. This intermediary path bypasses the limitation of the programmable impedance, allowing both adaptability and fast response.
3Productivity
If extra current is supplied to charge output capacitors during voltage changes, then productivity is improved by faster voltage changes, but manufacturing precision deteriorates due to inaccuracy in control
Solution Approach 1:
The system uses feedback from the output voltage measurement to monitor the charging process. The feed-forward circuit is designed to supply precisely the amount of current needed based on the known capacitor values and desired voltage change, and the feedback loop verifies that the voltage reaches the target accurately, correcting any minor deviations.
Data Source
AI summary
In one embodiment, a power supply controller is configured to form a reference signal that has selectable values. The power supply controller is also configured to form a feed-forward signal in response to change in the value of the reference voltage and to use this feed-forward signal control the value of an output current.