Feed-forward Circuit for Adjustable Output Voltage Controller
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Solution Overview
Problem
Conventional feed-forward control circuits in battery chargers with dynamic AC-DC adapter output voltage adjustments can lead to oscillatory conditions and slow response times, especially under varying system loads, due to the interaction with traditional feed-forward circuits.
Innovation Solution
A variable bandwidth control loop system that adjusts response speed based on error signals and stability measures, using a switch to bypass low-frequency poles and modify the control loop's response characteristics, allowing for faster responses during transients while maintaining stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a traditional feed-forward circuit is used in the end equipment with dynamic AC-DC adapter voltage control, then the loop response can be optimized for input line transients, but oscillatory conditions occur due to conflicting duty cycle adjustments
Solution Approach 1:
The feed-forward control function is extracted from the end equipment control loop and relocated to the AC-DC adapter control loop. This separation eliminates the conflicting control actions that caused oscillations, as the feed-forward duty cycle adjustment now directly responds to input voltage changes at the adapter level without interfering with the end equipment's stability-focused control.
Solution Approach 2:
An intermediary control signal is introduced where the adapter's feed-forward control adjusts its output voltage based on input voltage detection, acting as a mediator between the input voltage variations and the end equipment's control loop. This intermediary action prevents the need for the end equipment to make aggressive duty cycle changes, thereby maintaining system stability while still achieving fast transient response.
2Stability of the object's composition
If the feed-forward function is completely removed from the end equipment, then oscillatory conditions are avoided, but the response to system load transients becomes very slow
Solution Approach 1:
The feed-forward control performs preliminary action by pre-adjusting the adapter's output voltage in response to input voltage changes before the end equipment's control loop needs to react. This proactive voltage adjustment at the adapter level reduces the magnitude and duration of transients that reach the end equipment, thereby maintaining stability while minimizing transient response time loss.
3Loss of energy
If the AC-DC adapter output voltage is dynamically adjusted to deliver power under distinct operating conditions, then power dissipation in end equipment is reduced and system efficiency is improved, but traditional feed-forward control becomes difficult to implement
Solution Approach 1:
The control system is made dynamic by enabling the feed-forward control parameters to adapt based on the adapter's output voltage state and system operating conditions. This dynamic configuration allows the system to maintain optimal performance across varying load conditions and battery states without requiring complex fixed control logic, thereby achieving energy efficiency while managing control complexity through adaptive rather than static control structures.
Data Source
AI summary
A feedback loop in a variable power supply has an adjustable response speed based on operating conditions of the power supply. The response speed can be increased upon encountering a transient to improve response performance to the transient. A response speed control for the control loop modifies or bypasses a major low frequency pole in a compensation network in the control loop to increase response speed. The control limits fast response duration or impact with respect to the low frequency pole to avoid instability issues. The control may include counters or timers to selectively disable or enable the fast response function. The control can operate based on an error feedback signal and a reference to determine when a fast response should be applied. The resulting power supply system provides robust, well-regulated power, with fast responses to system transients.