Boost PFC Circuit Control for Process-Variation Linearity
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Solution Overview
Problem
Power factor correction (PFC) circuits in boost converters face challenges in maintaining efficient power delivery due to switching losses and parasitic capacitances, which affect the implementation of control schemes for discontinuous mode operations.
Innovation Solution
The power factor correction circuit adjusts the turn-on duration (Ton) based on a specific relationship that incorporates process-dependent parameters associated with different circuit components, minimizing the influence of process variations and improving the linear relation between turn-on and turn-off durations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power switch is used to transform distorted input current waveform into a more ideal current waveform, then power factor is improved, but switching losses are created due to parasitic capacitances
Solution Approach 1:
The patent changes the operating parameters of the power switch by controlling its duty cycle to follow a specific relationship (Ton/Toff = k * Vin^2) that optimizes the trade-off between power factor correction and switching loss minimization. This parameter adjustment allows the circuit to operate at optimal efficiency points across varying input voltage conditions.
2Reliability
If discontinuous mode boost operation is used for PFC, then input current can be shaped, but control scheme becomes difficult to implement due to maintaining constant time ratio
Solution Approach 1:
The patent transforms the control difficulty by changing from maintaining a constant time ratio to maintaining a constant duty cycle relationship. The simplified control law Ton/Toff = k * Vin^2 with constant k makes implementation easier while achieving the same power factor correction objective through parameter transformation.
3Ease of manufacture
If process variations in circuit components occur, then manufacturing tolerances are unavoidable, but this affects the linearity and performance of the control scheme
Solution Approach 1:
The patent incorporates feedback mechanisms that continuously monitor the actual operating conditions and adjust the control parameters accordingly. This feedback approach compensates for process variations in circuit components, maintaining control linearity and performance despite manufacturing tolerances in resistors, capacitors, and other elements.
Data Source
AI summary
A power factor correction circuit for a boost converter comprises a voltage converting means and a voltage-to-time converting means. The voltage converting means converts a supply voltage based on a time period of a turn-on duration Ton and a turn-off duration Toff of the boost converter into an output voltage. The voltage-to-time converting means generates the turn-on duration Ton based on the output voltage from the voltage converting means. The power factor correction circuit adjusts the turn-on duration Ton substantially in accordance with the following relationship:Ton =TTon +T offfirst parameter second parameterThe first parameter includes at least one first process-dependent parameter and the second parameter includes at least one second process-dependent parameter. The first process-dependent parameter and the second process-dependent parameter are same electrical characteristic associated with different circuit components in the power factor correction circuit.