Switching Power Supply Third Harmonic Ripple Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing switching power supply devices fail to simultaneously reduce Electromagnetic Interference (EMI) and improve conversion efficiency due to their inability to effectively manage third harmonic components of current ripples, which are not addressed by standard control methods that focus on lowering switching frequencies around peak and bottom phases of input AC power supply voltages.
Innovation Solution
A switching power supply device with a chopper circuit and a switching control circuit that adjusts the switching frequency proportionally to the input voltage-dependent term of the third harmonic component of current ripples flowing through an inductor, ensuring the input voltage and current waveforms have similar shapes and phases, thereby reducing EMI and simplifying the input filter structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency is lowered around the peaks and bottoms of input AC power supply voltage to reduce switching loss and conduction noise, then conversion efficiency is improved, but EMI cannot be effectively reduced due to the third harmonic component of current ripples
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the switching frequency based on the input voltage level. Specifically, the switching frequency is set to be higher around the peaks of the input AC voltage waveform and lower around the bottoms, which is the opposite of conventional approaches. This dynamic parameter adjustment optimizes both conversion efficiency and EMI reduction by addressing the third harmonic component of current ripples effectively.
2Ease of operation
If the switching frequency is set within the ordinary range of 50 kHz to 70 kHz, then the device operates with standard performance, but the third harmonic component of current ripples causes maximum EMI values that cannot be reduced
Solution Approach 1:
The patent implements dynamics by making the switching frequency variable rather than fixed. The switching frequency is dynamically controlled based on the instantaneous input voltage level, being adjusted higher during voltage peaks and lower during voltage bottoms. This dynamic adjustment strategy effectively reduces the third harmonic component of current ripples and consequently reduces normal noise EMI, while maintaining standard operational characteristics.
3Loss of energy
If conventional control methods are used to lower switching frequency around voltage peaks and bottoms, then switching loss is reduced, but the method is not adaptable to third harmonic components and cannot achieve both EMI reduction and efficiency improvement
Solution Approach 1:
The patent applies inversion by reversing the conventional control strategy. Instead of lowering the switching frequency around the peaks of input AC voltage as done in conventional methods, this patent raises the switching frequency around the peaks and lowers it around the bottoms. This inverted approach specifically targets and reduces the third harmonic component of current ripples, thereby achieving both EMI reduction and conversion efficiency improvement simultaneously.
Data Source
AI summary
An object of the present invention is to achieve the reduction of EMI, the improvement of conversion efficiency, and simplification of the input filter. Provided is a switching power supply device that comprises: a chopper circuit that turns on/off the passage of a current to an inductor by means of a switching element; and a switching control circuit that switches the switching element so that an input voltage and an input current have the same phase and a similar shape. The switching control circuit is configured to switch the switching element at a switching frequency that is proportional to an input voltage dependent term of a formula that expresses a third harmonic component of ripples of the current flowing to the inductor.