Buck Converter Cross-Interference Reduction via Feed-Forward Control
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Solution Overview
Problem
Conventional two-step power converters experience cross-interference between output voltages due to load transients, leading to instability and inefficiency, particularly as the output voltage of the first conversion stage is wasted in existing feed-forward methods.
Innovation Solution
A power converter design that includes a first conversion stage and a second conversion stage, where an error signal from the second stage is fed forward to the first stage through an analog summing circuit to stabilize the output voltage, reducing cross-interference by synchronizing current changes between stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a two-step power converter is used to reduce component size and cost, then the switching frequency can be increased and component size reduced, but cross-interference between different voltage outputs occurs due to load transients
Solution Approach 1:
The patent applies preliminary anti-action by injecting a feed-forward signal into the first conversion stage that anticipates and counteracts the cross-interference before it affects the output. When a load transient occurs at the second output, the error signal from the second stage is fed forward to the first stage, pre-compensating for the voltage drop that would otherwise occur at the first output due to increased current demand.
Solution Approach 2:
The patent implements feedback by taking the error signal from the second conversion stage (which reflects load transient conditions at the second output) and using it to adjust the operation of the first conversion stage. This feedback loop allows the system to respond to load changes at one output by adjusting the first stage, thereby preventing cross-interference at the first output.
2Reliability
If conventional PWM control loops are used to regulate output voltages, then voltage regulation is achieved, but load transients at one output cause current changes that affect other outputs
Solution Approach 1:
The patent applies preliminary action by preparing the first conversion stage to counteract expected disturbances before they occur. The feed-forward path takes the error signal from the second stage and immediately adjusts the first stage's operation in anticipation of cross-interference, rather than waiting for the voltage deviation to occur and then correcting it through conventional feedback alone.
Solution Approach 2:
The error signal from the second conversion stage serves as an intermediary that carries information about load transient conditions. This intermediary signal is used to coordinate the operation between the two conversion stages, allowing the first stage to adjust its current output in response to load changes at the second stage, thereby maintaining stability across both outputs.
3Productivity
If the first conversion stage output is used to supply the second stage, then a two-step conversion architecture is achieved with smaller components, but the first output voltage is wasted in existing feed-forward methods
Solution Approach 1:
The patent applies universality by making the first conversion stage serve multiple functions: it continues to provide its designated first output voltage Vout1 to external loads while simultaneously providing its output to the second conversion stage. The feed-forward control mechanism enables the first stage to maintain both functions even during load transients, eliminating the need to waste the first output as some prior solutions required.
Data Source
AI summary
A power converter includes a first conversion stage for converting an input voltage to a first output voltage and a second conversion stage for converting the first output voltage to a second output voltage. An error signal is generated according to a reference voltage and a feedback signal extracted from the second conversion stage, and a feed forward signal is generated from the error signal and injected into the first conversion stage to stabilize the first output voltage. The feedback signal is a function of the second output voltage and thus, the error signal varies with the second output voltage. As a result, the first output voltage will be stabilized when the second output voltage varies, due to the varied feed forward signal.