PFC Bridge Control Switching Between PLL and AC Feedforward
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Solution Overview
Problem
Existing power factor correction (PFC) systems in switch mode power supplies (SMPS) face challenges in maintaining efficient power conversion under transient conditions, as they often fail to accurately control switch output signals during noise-prone and distorted input voltages, leading to output disturbances and reduced performance.
Innovation Solution
A drive circuit that incorporates a transient detector and controller, utilizing a phased locked loop (PLL) to differentiate between steady-state and transient conditions, adjusts its control output to a bridge circuit by switching between PLL angle and AC input voltage control signals based on detected transients, enhancing noise immunity and PFC performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard PLL control method is used for bridge circuit, then steady-state power factor correction is maintained, but transient response and noise immunity deteriorate under AC input voltage disturbances
Solution Approach 1:
The control method dynamically switches between PLL-based control and feedforward control based on transient detection. During steady-state, PLL maintains accurate phase tracking for power factor correction. During transients, the system detects the disturbance and switches to feedforward control using sensed AC input voltage, enabling adaptive response to changing conditions while maintaining reliability.
2Measurement precision
If PLL angle output signal is used to control switch output signals, then phase-locked control is achieved, but output disturbances occur during transient conditions
Solution Approach 1:
The transient detector acts as an intermediary that monitors the PLL loop error signal and detects transient conditions. When transients are detected, it triggers a switch from PLL-based control to feedforward control, preventing the propagation of PLL-induced output disturbances while maintaining phase tracking accuracy during steady-state operation.
3Productivity
If feedforward control using AC input voltage is applied, then transient response is improved, but steady-state power factor correction performance deteriorates
Solution Approach 1:
The control system periodically evaluates transient conditions by monitoring the PLL loop error signal through the transient detector. This periodic assessment allows the system to switch to fast feedforward control during transients for improved response, then return to precise PLL-based control during steady-state for accurate power factor correction, optimizing both transient response and steady-state performance.
Data Source
AI summary
A drive circuit includes a transient detector that includes a detector input to receive a loop error signal from a phased locked loop (PLL) and generates a transient detected output signal if a transient is detected in an alternating current (AC) input voltage. A controller includes a controller input to receive the transient detected output signal from the transient detector and a feedback input to sense the AC input voltage provided to a bridge circuit. The controller is configured to apply a PLL angle output signal from the PLL to control switch output signals to the bridge circuit if the transient detected output signal is not generated and configured to apply the AC input voltage sensed from the feedback input to control the switch output signals to the bridge circuit if the transient detected output signal is generated.