Harmonic Modulation Control Circuit for DCM Power Factor Correction
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Solution Overview
Problem
Discontinuous conduction mode power factor correction converters face challenges in achieving high power factor and efficient inductor current management due to increased switching losses and complexity in control circuits, making integration with two-stage converters difficult.
Innovation Solution
A control circuit using harmonic modulation that calculates and outputs a difference between the output voltage and a reference voltage, performs proportional integral control, and multiplies the result with a harmonic modulation factor to generate a PFC control signal for the switch, improving power factor and inductor current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the inductor operates in discontinuous conduction mode (DCM), then the circuit structure is simpler and easier to integrate with two-stage converters, but the peak current increases leading to higher switching losses
Solution Approach 1:
The patent applies harmonic modulation to change the parameter of inductor current by adding a third-harmonic component. This modifies the current waveform shape without changing the fundamental operating mode, reducing peak current while maintaining DCM operation and simplifying circuit structure.
Solution Approach 2:
The patent introduces periodic harmonic modulation at three times the fundamental frequency into the control signal. This periodic action creates a modified current waveform with reduced peaks, addressing the switching loss issue while maintaining the simplicity of DCM operation.
2Loss of energy
If the inductor operates in continuous conduction mode (CCM), then switching losses are reduced, but the control circuit becomes more complex and integration with two-stage converters becomes difficult
Solution Approach 1:
The patent changes the control parameter by implementing harmonic modulation in the duty ratio calculation. This allows the system to operate in DCM with simplified control while achieving low peak currents, avoiding the complexity of CCM control circuits.
3Loss of energy
If harmonic modulation is applied to reduce peak current, then switching losses decrease, but the control algorithm becomes more complex
Solution Approach 1:
The patent implements periodic harmonic modulation by adding a simple sinusoidal term at three times the line frequency to the duty ratio control law. This periodic addition is computationally simple and easily implemented, reducing peak current while maintaining manageable algorithm complexity.
Data Source
AI summary
A control circuit for a discontinuous conduction mode power factor correction converter using harmonic modulation includes: a first difference circuit configured to calculate and output a difference between an output voltage of a discontinuous conduction mode power factor correction converter and a reference voltage; a PI converter configured to perform a proportional integral control on an output signal of the first difference circuit, and output a signal having an arbitrary duty ratio; a second difference circuit configured to output a difference between a rectified input voltage, which is input to the discontinuous conduction mode power factor correction converter, and a harmonic modulation factor DC voltage; and a multiplication circuit configured to multiply an output of the PI controller and an output of the second difference circuit, and output a PFC control signal to a switch of the discontinuous conduction mode power factor correction converter.