Adaptive DC Power Supply Rectifier Control for Harmonic Reduction
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Solution Overview
Problem
DC power supply units face challenges in achieving high efficiency while reducing harmonic currents and correcting power factor, particularly in zones with large loads or higher power outputs, as increasing the number of short-circuiting operations leads to increased switching losses.
Innovation Solution
A DC power supply unit incorporating a rectifier circuit with diodes and switching elements, a reactor, a smoothing capacitor, and control mechanisms for diode rectification, synchronous rectification, partial switching, and fast switching controls to manage power factor correction and harmonic reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the number of short-circuiting operations is increased to correct power factor in high power zones, then power factor correction is improved, but switching loss increases
Solution Approach 1:
The patent applies dynamics by making the switching control adaptive to load conditions. The control means dynamically selects between diode rectification control, synchronous rectification control, and partial switching control based on the magnitude of the load. This dynamic adaptation allows the system to achieve effective power factor correction in high power zones while minimizing switching losses by choosing the most appropriate control mode for each operating condition.
Solution Approach 2:
The patent changes the control parameter from fixed switching control to variable control based on load magnitude. By monitoring the load magnitude and adjusting the control strategy accordingly, the system optimizes the balance between power factor correction effectiveness and switching loss reduction. The control means transitions between different control modes (diode rectification, synchronous rectification, partial switching) based on predetermined thresholds of load magnitude.
2Loss of energy
If synchronous rectification control is used to improve efficiency, then power conversion efficiency is improved, but power factor correction capability is reduced
Solution Approach 1:
The patent resolves this contradiction through dynamic control mode selection. The control means monitors load magnitude and dynamically switches between synchronous rectification control (for efficiency in low-to-moderate load conditions) and partial switching control (for power factor correction in high load conditions). This dynamic adaptation allows the system to maintain high efficiency when possible while ensuring adequate power factor correction when needed.
Solution Approach 2:
The patent employs periodic evaluation of load conditions to determine the appropriate control mode. The control means continuously monitors load magnitude and periodically transitions between control strategies based on predetermined thresholds. This periodic assessment ensures the system operates in the most efficient mode while maintaining power factor correction capability when required by the operating conditions.
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 enables high efficiency and reduced harmonic currents, effectively addressing the challenges of power factor correction and energy savings in DC power supply units, particularly in air conditioner applications.
Implementation Method 1
a rectifier circuit that is connected to an AC power supply and has first to fourth diodes
Implementation Method 2
a synchronous rectification control that switches between the first and second switching elements in synchronization with a polarity of the voltage of the AC power supply
Implementation Method 3
a reactor that is arranged between the AC power supply and the rectifier circuit
Implementation Method 4
a smoothing capacitor that is connected to an output side of the rectifier circuit and smoothes a voltage applied by the rectifier circuit
Implementation Method 5
a first switching element that is connected in parallel with the third diode, has a withstand voltage characteristic with respect to the direction of the third diode being turned off, and has a saturation voltage lower than forward voltage drops of the first to fourth diodes
Data Source
AI summary
A DC power supply unit is provided that allows for improving efficiency and reducing harmonic currents. A DC power supply unit includes: a bridge rectification circuit having diodes and MOSFETs; a reactor that is arranged between the AC power supply and the bridge rectifier circuit; a smoothing capacitor that is connected to an output side of the bridge rectifier circuit and smoothes a voltage; and a converter control unit that executes, based on predetermined threshold values, a diode rectification control that uses diodes and parasitic diodes of the MOSFETs, a synchronous rectification control that switches the MOSFETs in synchronization with a polarity of the voltage of the AC power supply, a partial switching control that repeats partially short-circuiting the reactor multiple times in a half cycle of the AC power supply, or a fast switching control that short-circuits the reactor at a predetermined frequency over a full AC cycle.