Selection and basic principles of brushless DC motor driver chips

The brushless DC motor consists of a motor and a driver, and is a typical mechatronics product. The motor rotor winding adopts a three-phase star connection method, which is very similar to a three-phase AC motor. In order to test the rotation of the generator rotor, a phase sensor is installed in the motor. The controller consists of power electronic components and integrated circuit chips, so how is the DC brushless motor driver chip selected?

1. Universal chips are generally used for low-end products of LED displays, such as single-color and two-color screens for indoor use. The most common universal chips have 8-bit latch, serial-parallel shift register and three-state output functions. Each channel can output a maximum current of 35mA of non-constant current.

2. Maximum output current: The maximum output current of the popular constant current source LED driver chip is about 90mA per channel. The maximum value of the stable current output by each channel at the same time is more meaningful for the display, because in the automatic white balance state, it is required that each channel outputs a constant current at the same time.

3. Constant current power supply output channel number: The constant current source output channel has two specifications, 8-bit and 16-bit. Now 16-bit is popular. Its main advantage is that it reduces the chip size, which is beneficial to the LED driver board (PCB) routing, especially for the LED driver board with smaller dot spacing.

4. Accurate current output: one is the current error between channels of the same chip; the other is the output current error between different chips. Accurate current output is a very important parameter, which has a great impact on the display uniformity of the LED display. The greater the deviation, the worse the display uniformity, and it is difficult to make the LED transparent screen achieve automatic white balance. At present, the current deviation between bits of popular constant current source chips (bit to bit) is generally within ±3%, and the current deviation between chips (chip to chip) is within ±6%.

5. Data moving digital clock: It determines the transmission rate of display data and is an important indicator that affects the refresh rate of the display. As a large-capacity display device, the display refresh rate should be above 85Hz to ensure a smooth interface (no scanner flicker). A higher data moving digital clock is the basis for the display to obtain a high refresh rate interface. At present, the popular constant current source drive chip moving clock frequency is generally above 15-25MHz.

Basic Principles of Brushless DC Motor Driver Chip

The brushless DC motor driver chip integrates four DMOS tubes to form a standard H-type driver. The charge pump circuit provides gate voltage control voltage for the two switch tubes on the upper bridge arm. The charge pump circuit has an output frequency of about 300kHz. A capacitor can be connected to pins 1 and 11 to form a second charge pump circuit. The larger the external capacitor, the faster the capacitor charging speed input to the gate voltage of the switch tube, the less time the voltage rises, and the higher the output power can be. Pins 2 and 10 are connected to the brushless DC motor. When rotating forward, the current direction should be from pin 10 to pin 10; when rotating backward, the current direction should be from pin 10 to pin 2. The current detection output pin 8 can be connected to a resistor to ground, and the overcurrent condition can be output through the resistor. The overcurrent threshold set by the internal protection circuit is 10A. When it exceeds this value, the output will be automatically disabled and the output will be automatically restored regularly. If the overcurrent delay is long, the overtemperature protection will shut down all outputs. The over-temperature data signal can also be output through pin 9. When the junction temperature reaches 145 degrees, pin 9 will have an output data signal.