Power Conversion Circuit for Air Conditioners With Low Reactive Power
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional air conditioners face issues with reactive power consumption due to noise filters and lack of inrush-current limiting resistors, leading to increased costs and potential diode failure, while also requiring larger capacitors for stable operation.
Innovation Solution
The air conditioner incorporates a power conversion device with a second noise reduction section having capacitive reactance and an inrush-current inhibition resistor, along with a diode rectifier section to prevent reactive power flow and inrush currents, using wide band-gap semiconductors for efficient power conversion and reduced component size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a noise filter with across-the-line capacitor is mounted on the outdoor unit, then noise removal is achieved, but reactive current flows at all times and reactive power cannot be eliminated
Solution Approach 1:
The patent extracts the across-the-line capacitor from the main power circuit by introducing a relay that disconnects it during standby mode. The capacitor is taken out of the active circuit when not needed, eliminating reactive power consumption while preserving noise filtering capability when the capacitor is connected during operation mode.
Solution Approach 2:
The patent makes the noise filter connection dynamic by using a relay controlled by the control section. The across-the-line capacitor is connected only when needed (during compressor operation) and disconnected during standby mode, transforming a static always-connected filter into a dynamic conditional connection that eliminates unnecessary reactive power consumption.
2Stability of the object's composition
If the smoothing capacitor capacitance is increased for stabilized switching power source operation, then operation stability is improved, but board footprint and cost increase
Solution Approach 1:
The patent applies preliminary action by charging the smoothing capacitor during the startup sequence before the switching power source begins operation. The control section waits for the capacitor voltage to reach a predetermined level before activating the switching power source, ensuring stable operation without requiring excessive capacitance.
Solution Approach 2:
The patent changes the operational parameters of the switching power source by controlling the startup timing based on capacitor charge state. Instead of designing for worst-case stability requirements, the system dynamically adjusts the startup conditions to achieve stable operation with reduced capacitance, thereby reducing board footprint and cost.
3Device complexity
If no inrush-current limiting resistor is provided in the step-up chopper circuit, then device complexity is reduced, but inrush current may cause diode failure
Solution Approach 1:
The patent introduces a relay as an intermediary component between the power source and the step-up chopper circuit. The relay acts as a controlled switch that prevents inrush current from reaching the diode by opening the circuit during standby mode and only closing it when the smoothing capacitor is sufficiently charged, protecting the diode without requiring a current-limiting resistor.
Solution Approach 2:
The patent applies beforehand cushioning by using the smoothing capacitor to absorb and limit inrush current before it can reach the diode. The capacitor is charged in advance during startup, and its voltage builds up to limit the current surge, cushioning the protective effect against the diode without adding complex current-limiting circuitry.
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
This configuration reduces reactive power consumption, prevents diode failure, and minimizes component size and cost, achieving power savings and efficient operation by inhibiting reactive and inrush currents.
Implementation Method 1
a diode rectifier section (21C) that performs rectification on voltage that has undergone AC-DC conversion
Implementation Method 2
a voltage greater than a voltage that has undergone DC conversion by a step-up chopper circuit and a smoothing capacitor
Implementation Method 3
an inrush-current inhibition resistor (21B) that inhibits an inrush current from flowing when power is supplied
Implementation Method 4
a second noise reduction section (12) having capacitive reactance
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A power conversion device according to the present invention includes a first AC-DC conversion section 23 generating DC voltage applied to a compressor drive section 25, a first DC-voltage smoothing section 24 smoothing DC voltage, a first noise reduction section 11 having one end connected to an AC power source 1 and the other end connected to the first AC-DC conversion section 23, a second noise reduction section 12 disposed between the first noise reduction section 11 and the first AC-DC conversion section 23, an inrush-current inhibition circuit (a first inrush-current inhibition resistor 21B and a rectifier diode 21C) connected in parallel with the second noise reduction section 12 and the first AC-DC conversion section 23 for inhibiting inrush current from flowing to the first DC-voltage smoothing section 24, a first AC power-source relay 21 opening/closing a power supply path to the inrush-current inhibition circuit, and a second AC power-source relay 22 opening/closing a power supply path to the second noise reduction section 12.