Power conversion device
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power conversion devices for air conditioner motors face failures in activation due to external noise superimposed on the induced voltage, leading to incorrect determination of activation sequences.
Innovation Solution
A power conversion device with an inverter circuit and a switching controller that performs pulse width modulation and alternately turns ON and OFF a selected lower-arm switching element to reduce impedance, allowing the detection circuit to detect noise-free induced voltage, and determines an activation sequence based on this voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the detection circuit has high impedance to minimize power loss, then power loss is reduced, but external noise is superimposed on the induced voltage detection
Solution Approach 1:
The patent applies dynamics by making the impedance of the detection circuit dynamic rather than static. The switching element alternates between ON and OFF states, changing the impedance level over time. During the OFF period, high impedance minimizes power loss; during the ON period, low impedance reduces noise pickup. This time-varying impedance strategy resolves the contradiction between power loss and detection accuracy.
Solution Approach 2:
The patent employs periodic action through the switching element that alternates between ON and OFF states at specific frequencies. This periodic switching creates time intervals where the detection circuit presents high impedance (reducing power loss) and low impedance (reducing noise). The induced voltage detection is performed during appropriate phases of this periodic cycle, achieving both low power loss and high detection accuracy.
2Measurement precision
If the detection circuit has low impedance to reduce external noise, then detection accuracy is improved, but power loss increases
Solution Approach 1:
The patent resolves this contradiction by dynamically adjusting impedance through the switching element. Instead of maintaining constantly low impedance (which would cause continuous power loss), the system switches between high and low impedance states. The low impedance state is activated only during brief periods necessary for accurate noise-free detection, while the high impedance state dominates to minimize overall power consumption.
Solution Approach 2:
The patent applies partial action by using low impedance only for the minimal necessary duration to perform accurate induced voltage detection. The switching element provides low impedance briefly during detection-critical phases, then returns to high impedance. This partial use of low impedance achieves sufficient detection accuracy without incurring continuous power loss.
3Measurement precision
If the switching element is kept ON to maintain low impedance, then noise rejection is improved, but the motor cannot be properly activated
Solution Approach 1:
The patent uses periodic switching of the element between ON and OFF states. During the OFF period, the detection circuit achieves high impedance for noise-free induced voltage detection. During the ON period, the low impedance state enables proper motor activation. This periodic alternation ensures both reliable detection and reliable motor startup without compromising either function.
Solution Approach 2:
The patent applies preliminary action by performing induced voltage detection during the OFF state before motor activation. The switching element is turned OFF to establish high impedance conditions, allowing noise-free detection of the induced voltage. This preliminary detection informs subsequent motor activation decisions, ensuring reliable startup based on accurate rotational state information.
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 solution reduces the occurrence of motor activation failures by minimizing the impact of external noise on the induced voltage detection, ensuring accurate activation sequences and reliable motor startup.
Implementation Method 1
detecting an induced voltage of a motor before activation
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A failure in the activation, of a motor, caused by external noise superimposed on an induced voltage is reduced. A detection circuit (27) is connected to a connection node (cn3) provided between an upper-arm switching element (25w) and a lower-arm switching element (26w), and detects the induced voltage of a fan motor (77) before activation. The switching controller (28) activates the fan motor (77) in accordance with a result of detection by the detection circuit (27). While the detection circuit (27) detects the induced voltage, the switching controller (28) performs switching control which involves alternately turning ON and OFF of the lower-arm switching element (26w).