Boost Circuit Current Equalization for Refrigerator Motor Drive
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Solution Overview
Problem
Conventional motor driving systems for refrigerating apparatuses face inefficiencies and increased costs due to high motor induced voltage at high speeds, leading to insufficient output voltage and increased losses, particularly in the middle to low speed operation range, where the motor cannot be normally driven, and existing boosting methods require numerous semiconductor power devices and complex control circuits.
Innovation Solution
A boost circuit that uses a single current detection device to equalize the current flowing through multiple power devices by adjusting their on-width, connected in series with reactors and diodes, allowing for efficient and cost-effective operation by simplifying the current detection and control circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If motor induced voltage is increased to improve efficiency in middle to low speed operation range, then motor efficiency is improved, but inverter output voltage becomes insufficient at high speed operation
Solution Approach 1:
The patent divides the boosting function into multiple independent boosting choppers (first and second boosting choppers) that operate in parallel. Each chopper handles a portion of the total current, allowing the system to achieve the required voltage boost capacity without overloading individual components. This segmentation enables the system to maintain sufficient inverter output voltage at high speeds while preserving motor efficiency improvements.
2Device complexity
If a single boosting chopper is used to adjust DC voltage, then circuit complexity is reduced, but the capacity and size of power devices and reactors must be significantly increased
Solution Approach 1:
The patent segments the boosting function into multiple smaller boosting choppers operating in parallel. Each chopper uses smaller capacity power devices and reactors compared to a single large chopper, reducing individual component sizes and costs while collectively providing the required total capacity.
Solution Approach 2:
The patent combines multiple boosting choppers in parallel to achieve the required total capacity. By merging the current handling capabilities of multiple smaller choppers, the system attains the necessary power handling capacity without requiring any single chopper to be oversized.
3Quantity of substance
If multiple boosting choppers are arranged in parallel to reduce individual part capacity, then component size is reduced, but the number of current detection devices and control circuits increases
Solution Approach 1:
The patent implements a universal control approach where a single current detection device serves multiple boosting choppers. The control circuit detects the current through the common reactor and uses this information to control the switching of multiple power devices, making one detection device perform the function of what would otherwise require multiple separate detection devices.
Solution Approach 2:
The patent uses the reactor as an intermediary element that provides a common current path for detection. By detecting the current through this shared reactor, the system obtains information about the total current flow that can be used to control multiple parallel boosting choppers without requiring separate detection devices for each chopper.
4Speed
If field-weakening control is used to handle high speed operation, then motor can operate at high speed, but losses of motor and inverter increase
Solution Approach 1:
The patent changes the DC voltage parameter by introducing a boosting function that increases the DC link voltage above the nominal level. This voltage boost enables the inverter to output sufficient voltage at high motor speeds without requiring field-weakening control, thereby avoiding the increased losses associated with field-weakening operation and maintaining higher overall system efficiency.
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 enables a cost-effective and efficient boost circuit, motor driving module, and refrigerating apparatus by equalizing current across power devices, reducing the number of components needed and minimizing losses, thus improving efficiency and reducing product costs.
Implementation Method 1
a rectifying circuit for an AC power source
Implementation Method 2
a plurality of reactors that are connected in parallel to the positive electric potential side of the rectifying circuit
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An object of the present invention is to provide a boost circuit, a motor driving module, and a refrigerating apparatus that detect the current of each power device using one current detection device, and adjust the on width of each power device to substantially equalize the current of each power device. The present invention provides a boost circuit including: a rectifying circuit 2 connected to an AC power source 1; a plurality of reactors that are connected in parallel to the positive electric potential side of the rectifying circuit 2; a plurality of power devices 6a, 6b that are connected in series to the plurality of reactors to turn on or off current; a single resistor that is connected between the plurality of power devices and the negative electric potential side of the rectifying circuit; and a control unit 12 that determines from which of the plurality of power devices 6a, 6b the current flowing to the single current detection resistor 9 has come, and alternately controls the plurality of power devices 6a, 6b so that the current flowing to the plurality of power devices 6a, 6b is substantially equalized.