Description

This is a three phase brushless motor driver board based on the ST L6234PD driver IC. It consists of 3 high power half-bridges that can output up to 5A peak, or 4A continuous (depending on heatsink). It has been designed with a large copper ground plane on the bottom that functions as a heatsink. If the driver IC heatsinking requirements can not be met by the copper layer alone, the bottom of the board could also be fastened to an external heatsink. There is circuitry on board to amplify the winding current, and for sensing the back EMF voltage to assist in commutation.

This driver does not work standalone, and requires a microcontroller to read the 3 back EMF inputs, output 3 PWM signals, and output 3 enable signals, in the proper sequence to make the motor run.

Features

• 3 half bridge drive channels
• 4A continuous, 5A peak output current
• Back EMF sense, and reference resistor dividers
• Very low ESR capacitors are used on the power supply rail to handle the high ripple current that is to be expected when driving a high current motor
• Winding current sense resistor, with amplifier to boost the output signal
• Optional current recirculating diodes to increase efficiency
• ESD protection on all microcontroller I/Os
• Driver die has good thermal coupling to PCB copper layers (this may make hand soldering of the driver IC very difficult)
• 0.200" screw terminal block, or 0.156" Molex headers for high current connections
• Test points for most signals of interest

Project Status

• Circuit boards were ordered from Seeedstudio in China, and they look great.
• A LPC2368 ARM7 microcontroller evaluation board was ordered from micro4you in Thailand. This company is fine to deal with, but shipping took a really long time.
• Assembly of the first board has been completed. The board was soldered in a reflow oven at a customer's site.
• The board has been powered up, and so far, everything works as expected. The real testing can now begin, as the microcontroller evaluation board has arrived.

As the software and testing proceeds, there may be some changes to various component values. This site will be updated when there is something to add.

Documentation

For starters, you might find this datasheet useful to describe the operation of the driver IC used: L6234 Three Phase Motor Driver datasheet

The source archive for the PCB and schematic can be found here: BLDC Motor Driver V1.00.zip

Note that this board was not designed using Eagle, as I have access to professional level tools which are far nicer to use. The schematic was drawn using OrCAD 10.5, and the PCB was done in P-CAD 2006. This may make it difficult for others to edit the files, but gerber files are provided in the source archive so that other individuals can have boards manufactured. Also included in the archive are schematic and PCB plots in PDF format, and a bill of materials file so that there is enough information to allow others to populate a board.

Here are some screen captures of the schematic and PCB layout (with links to PDF files):

Bill Of Materials for BDLC Motor Driver V1.00

Errata

The labels for Ph1, and Ph3 are interchanged on the V1.00 PCB silkscreen layers. The schematic labeling is correct.

Purchase Circuit Boards

This is the company in China that I ordered my prototype circuit boards from, and they stock the extras from the run, and sell them in their webstore. As of this writing, they are priced at $6.50 USD. Shipping charges are very reasonable, and the quality is excellent. Please note that I am not affiliated with them in any way, but I have used their services, and would recommend them.