Buck PFC Power Converter Transient Response Control
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Solution Overview
Problem
Existing power converters with power factor pre-regulation circuits have slow transient response to input line voltage changes and load variations, leading to voltage disturbances and potential output regulation issues.
Innovation Solution
A power converter with a buck PFC circuit and a control unit that measures circuit parameters to provide additional line current to the bulk capacitor, using low side drive and current sensing, and adjusts the loop gain or input resistance to maintain regulation, thereby quickly responding to changes in load and voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power factor pre-regulation circuit is designed to achieve predictable input current performance, then the input current performance is improved, but the transient response becomes slow
Solution Approach 1:
The control unit predicts future bulk capacitor voltage conditions based on current operating parameters and proactively adjusts the buck PFC circuit operation before voltage deviations occur. This predictive control mechanism allows the system to maintain both predictable input current performance and fast transient response by preparing corrective actions in advance.
2Speed
If the power factor pre-regulation circuit responds quickly to load transients, then the transient response is improved, but the circuit complexity increases
Solution Approach 1:
The control unit continuously monitors bulk capacitor voltage and compares it against reference values, using the resulting error signal to dynamically adjust the buck PFC circuit duty cycle. This feedback mechanism enables fast transient response through a relatively simple control structure, avoiding the need for complex circuit modifications.
Solution Approach 2:
The buck PFC circuit automatically adjusts its operation in response to bulk capacitor voltage deviations without requiring external intervention or complex control logic. The control unit implements self-correcting behavior by modulating the PFC duty cycle based on real-time voltage conditions, enabling the system to maintain regulation autonomously.
3Loss of energy
If the bulk capacitor size is reduced to enhance efficiency, then the efficiency is improved, but the voltage regulation becomes more difficult
Solution Approach 1:
The control unit predicts bulk capacitor voltage deviations before they occur and proactively adjusts the buck PFC circuit duty cycle to compensate. This predictive control allows the use of smaller bulk capacitors while maintaining voltage regulation, as the system prepares corrective actions in advance rather than reacting to voltage drops after they occur.
Solution Approach 2:
The control unit dynamically adjusts the buck PFC circuit operation in real-time based on instantaneous bulk capacitor voltage conditions and predicted future states. This dynamic control mechanism compensates for the reduced energy storage capacity of smaller capacitors by continuously optimizing the power transfer from the PFC circuit to the bulk capacitor.
Data Source
AI summary
This invention relates to a power converter (1) comprising a converter input (3), a converter output, a power factor pre-regulation stage (5), an isolation stage (7) and a control unit (9). The power factor pre-regulation stage (5) further comprises a buck power factor correction (PFC) circuit (15) and a bulk capacitor (25) fed by the buck PFC circuit. The amount of line current provided to the bulk capacitor (25) by the buck PFC circuit (15) may be adjusted according to the converter requirements in order to keep the voltage across the bulk capacitor (25) sufficient to ensure uniform operation of the power converter. Monitoring of the voltage across the bulk capacitor (25) and monitoring of the isolation stage (7) output current is provided to determine when additional current is to be applied to the bulk capacitor (25) and to ensure the power converter (1) operates within pre-defined parameters.