Power Supply Device Reducing Harmonics via Dynamic Pulse Width Control
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Solution Overview
Problem
Existing methods for reducing harmonic components in AC to DC power supply devices require complex calculations and do not adequately improve power factor, especially under heavy loads.
Innovation Solution
A power supply device with rectification, inductive, switching, and smoothing components, utilizing zero cross detection and control means to generate drive pulse signals with varying pulse widths by comparing AC voltage waveforms with different reference levels, reducing harmonic components and increasing power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If complex calculation methods are used to reduce harmonic components, then harmonic reduction effect is improved, but control circuit load increases and efficiency decreases
Solution Approach 1:
The invention changes the control parameter from complex real-time calculations to a simple counter that counts zero-cross points of the AC voltage waveform. By monitoring the number of zero-cross points within a specific time period and comparing it to a threshold value, the system determines whether to apply harmonic reduction control, thereby reducing computational complexity while maintaining effectiveness in reducing harmonic components.
2Ease of operation
If switching means is controlled with fixed pulse width, then control simplicity is improved, but power factor and harmonic reduction are insufficient
Solution Approach 1:
The invention makes the pulse width dynamic by adjusting it based on the counted number of zero-cross points. When the zero-cross count exceeds a threshold, indicating high harmonic content, the control circuit generates a drive signal with a longer pulse width to increase switching frequency and reduce harmonics. When harmonics are low, the pulse width returns to normal, maintaining simple control while adapting to varying load conditions.
3Object-generated harmful factors
If switching frequency is increased to reduce harmonics, then harmonic components are reduced, but energy loss increases
Solution Approach 1:
The invention implements periodic monitoring of the AC voltage waveform by counting zero-cross points at regular intervals. This periodic measurement allows the system to detect harmonic conditions and apply increased switching frequency only when necessary, rather than continuously operating at high frequency. The control alternates between normal and enhanced switching modes based on detected harmonic levels, reducing overall energy consumption while maintaining harmonic reduction effectiveness.
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 effectively reduces harmonic components in the input current and enhances the power factor by generating drive pulse signals with distinct pulse widths, thereby minimizing the calculation load on the control circuit and improving efficiency.
Implementation Method 1
an inductive element connected in series between an AC power supply input terminal and the rectification means
Implementation Method 2
rectification means that converts AC power input from an AC power supply into DC power and supplies the DC power to a load
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
A power supply device is provided that can further reduce harmonic components contained in an input current. A control circuit of the power supply device generates pulses using a first reference level Vth1 and a second reference level Vth2 different from the first reference level Vth1, and a first pulse P1, a second pulse P2, a third pulse P3, and a fourth pulse P4 are set to have different short-circuit times. For example, the first reference level Vth1 is set lower than the second reference level Vth2 to increase a pulse width of the first pulse P1 and ensure a long short-circuit time, thereby effectively reducing harmonics.