Power Converter Controller Circuit for Low THD and High PFC
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Solution Overview
Problem
Existing power converters face challenges in achieving low total harmonic distortion (THD) and high power factor correction (PFC), particularly in critical conducting mode (CrM) operations, which limits their load range and requires additional filtering components.
Innovation Solution
A controller circuit that includes a divider module and an on-time adjuster module, generating a modification factor to modify the waveform for the switch operation, allowing for efficient power factor correction and reduced THD without the need for an input line filter, by adjusting the on-time of the switch based on the ratio of input and output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If Critical Conducting Mode (CrM) is used for full or heavy loads, then a smaller switching transistor and a smaller transformer are used, but the load range for CrM is limited and it cannot effectively handle light loads
Solution Approach 1:
The patent implements dynamic load range extension by dynamically adjusting the on-time of the switch based on the actual load conditions. The controller circuit modifies the CrM waveform timing to enable the converter to operate across both heavy and light load ranges, transforming a static CrM design into a dynamic system that adapts to varying load requirements.
2Reliability
If Power Factor Correction (PFC) circuitry is added to control input current phase, then high power factor correction is achieved, but the circuit complexity increases and requires additional components
Solution Approach 1:
The patent merges the PFC control function with the existing CrM controller circuit by integrating the on-time adjuster module into the primary side control. Instead of adding separate PFC circuitry, the invention combines multiple functions (CrM control, PFC, and load range extension) into a unified controller that generates modified CrM waveforms, thereby achieving high PFC without proportionally increasing circuit complexity.
3Object-generated harmful factors
If Total Harmonic Distortion (THD) is reduced through filtering, then low THD is achieved, but additional input line filter components are required increasing device complexity
Solution Approach 1:
The patent converts the harmful effect of harmonic distortion into a beneficial control parameter by using the modified CrM waveform timing to actively shape the input current waveform. Instead of passively filtering harmonics, the invention actively prevents harmonic generation through precise on-time control, thereby achieving low THD without requiring additional filter components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves low THD and high PFC in power converters, simplifying the circuit design and eliminating the requirement for an input line filter, while effectively controlling the power converter for both heavy and light loads.
Implementation Method 1
a transformer magnetically coupling a primary side and a secondary side of the power converter
Data Source
AI summary
A controller circuit for the control of a power converter is disclosed. An example controller circuit generates a waveform that drives a switch that controls the power converter. The controller circuit includes a divider module that generates a modification factor based on a ratio of the two input signals of the module. The circuit includes a module that generates a first waveform configured for a critical conducting mode of operation of a power converter and an on-time adjuster module that modifies the first waveform based on the modification factor and generates a second waveform. The second waveform is delivered to the switch. An example modification factor is the ratio of the output voltage to the rectified input voltage of the power converter.