Motor Drive Circuit Layout Using Lead Frame and PCB Separation
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Solution Overview
Problem
Conventional motor drive circuits for air conditioners are inefficient due to high material costs, large size, noise, and reliability issues, particularly with the use of metal substrates and electrolytic capacitors, which are expensive and wasteful, and require complex manufacturing processes.
Innovation Solution
A motor drive circuit using a lead frame molded board with a printed circuit board, where the power components are mounted on the lead frame molded board and the control components on the printed circuit board, reducing material usage and complexity, and incorporating a shunt resistance for current detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal substrate is used for mounting semiconductor components, then radiation function and power wiring function are integrated, but the cost per unit area becomes 10 to 20 times more expensive than a printed circuit board
Solution Approach 1:
The patent divides the substrate into two separate components: a printed circuit board for wiring and a heat dissipation plate for radiation. This segmentation allows each component to perform its function optimally without the high cost of using a metal substrate for both functions simultaneously. The printed circuit board handles power wiring and control signals, while the heat dissipation plate separately manages thermal radiation from semiconductor components.
2Reliability
If a shell case with insert-molded substrate is used to carry switching elements, then electrical connection is provided, but additional materials and processing equipment (die, molding machine, electrode formation) are required
Solution Approach 1:
The patent extracts the substrate function from the shell case structure. Instead of forming electrodes and performing insert molding within the shell case, the invention uses a separate printed circuit board that provides all necessary electrical connections for switching elements. This eliminates the complex shell case molding process while maintaining reliable electrical connectivity through standard PCB technology.
3Reliability
If a smoothing capacitor large in size is mounted on an insert-molded substrate, then electrical connection is achieved, but mass production is required to cover die and molding machine costs
Solution Approach 1:
The patent replaces the expensive insert-molded substrate with a standard printed circuit board that can be produced more economically. The PCB provides the necessary electrical connections for the smoothing capacitor without requiring costly die and molding machine investments. This approach allows for more flexible production volumes and reduces the minimum economically viable production quantity.
4Reliability
If wiring of copper foil is performed by etching on a metal substrate, then power wiring function is achieved, but etching time becomes long
Solution Approach 1:
The patent uses a printed circuit board that replicates the power wiring function of metal substrates through copper foil etching on a non-metallic base. The PCB manufacturing process uses optimized etching techniques that are faster and more efficient than etching metal substrates, while maintaining the necessary electrical conductivity for power wiring applications.
5Temperature
If radiation of heat is performed through copper foil and insulator to a metal plate, then heat dissipation is achieved, but the configuration is wasteful and uneconomical
Solution Approach 1:
The patent extracts the heat dissipation function from the multi-layer copper foil and insulator structure and implements it through a dedicated heat dissipation plate. This separate heat dissipation plate provides more efficient thermal radiation directly from semiconductor components without the intermediate layers, reducing material usage and manufacturing cost while improving thermal management effectiveness.
Data Source
AI summary
One of the purpose is to obtain a motor drive circuit and an outdoor unit for an air conditioner using the same, which can flexibly support change of a model at a low price and in a small lot without using unnecessary materials, wherein a stress in a soldering part due to self-heating is low, a solder reliability is high, and design constraints are small, while maintaining a low-noise and low-loss power wiring due to lowering inductance. The motor drive circuit according to the present invention, for driving the motor using the converter circuit and the inverter circuit, whereon electronic components making up a converter circuit and an inverter circuit are mounted, which includes a lead frame molded board 100 wherein metal plate leads 37 are molded with a mold resin 36, and a single-sided printed circuit board 31 for a control circuit, and wherein power terminals 30 of the electronic components are connected to the lead frame molded board 100, and control wiring terminals 39 of the electronic components are connected to the single-sided printed circuit board 31.