Power Conversion Device Discharge Control Logic Circuit
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Solution Overview
Problem
Existing power conversion devices fail to reliably discharge capacitor charges when the controller fails, leading to incomplete discharge of the capacitor.
Innovation Solution
A power conversion device with an inverter circuit, a smoothing capacitor, a discharge resistor, a switching element, a controller circuit, a signal generation circuit, and a logic circuit that outputs rectangular wave signals to control the switching element for discharge, ensuring discharge completion even in controller failure scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a controller is used to control the switching element for discharging capacitor charges, then the discharge control can be implemented, but the system reliability deteriorates when the controller fails
Solution Approach 1:
The control function is segmented into two independent parts: the controller that generates the discharge control signal, and the signal generation circuit that generates the rectangular wave signal. This segmentation ensures that if the controller fails, the signal generation circuit can still independently generate the necessary control signals for discharge, thereby maintaining system reliability.
Solution Approach 2:
A logic circuit is introduced as an intermediary between the controller and the switching element. The logic circuit combines the discharge control signal from the controller with the rectangular wave signal from the signal generation circuit to generate the final control signal. This intermediary structure ensures that even if the controller fails, the rectangular wave signal can still drive the switching element through the logic circuit, maintaining discharge functionality.
2Device complexity
If only a controller is used for discharge control, then the control structure is simple, but the discharge function cannot be ensured when controller failure occurs
Solution Approach 1:
The signal generation circuit is configured to continuously generate the rectangular wave signal in advance, independent of the controller's operational state. This preliminary action ensures that when the controller fails, the rectangular wave signal is already available to drive the switching element through the logic circuit, maintaining the discharge function without requiring complex backup control mechanisms.
Solution Approach 2:
The logic circuit serves multiple functions: it normally combines controller signals with rectangular wave signals for controlled discharge, and it alternatively allows the rectangular wave signal to directly control the switching element when the controller fails. This multi-functionality enables the system to maintain discharge capability across different operational states without significantly increasing overall system complexity.
Data Source
AI summary
An object of the present invention is to provide a power conversion device capable of reliably discharging a voltage smoothing capacitor even when a circuit unit that outputs a discharge control signal fails. The power conversion device includes a voltage smoothing capacitor that is electrically connected in parallel with an inverter circuit unit, a discharge resistor that is electrically connected in parallel with the voltage smoothing capacitor, a switching element that is connected in series with the discharge resistor, a motor controller that selectively outputs a High-level signal and a Low-level signal as a discharge control signal, a switching signal circuit unit that outputs a rectangular wave signal having a predetermined duty, and a logic circuit that outputs any one of a rectangular wave signal having the same duty as the duty of the rectangular wave signal and a rectangular wave signal having a duty to the switching element based on the discharge control signal and the rectangular wave signal.