June 15, 2021
In motor-driven building automation and grid infrastructure applications (such as smart meters, smart locks, Internet Protocol (IP) web cameras, and video doorbells), there are multiple ways to design low-voltage systems.
When designing motor drive systems for these applications, common challenges include: meeting the requirements for durable, flexible, and safe motor operation; shrinking printed circuit board (PCB) space; and meeting various system requirements. When considering the current consumption of the motor driver, special attention needs to be paid to: integrated circuit (IC) and necessary component board size; design simplification, flexibility and scalability to meet the needs of multiple platform types.
Reduce power consumption
For battery-powered and motor-driven systems such as smart locks, video doorbells, gas meters, and water meters, one of the key points of the design is to reduce overall power consumption by maintaining low current consumption when the motors are not actively driven, so that consumers do not have to frequently replace batteries . If you are interested in the implementation of these applications, TI provides a reference design suitable for electronic smart locks and IP network camera infrared cut filters.
Below we will use the following devices to compare two ways to reduce the power consumption of the H-bridge when the motor is not driven:
·Discrete load switch between battery and motor drive circuit, used to connect or remove power;
· TI’s DRV8210 and other devices have a dedicated low-power sleep mode with a typical sleep current of 37nA.
Compared with the first device, the second device reduces PCB space by up to 50% and removes power dissipation components when connecting the H-bridge power supply.
(A) Simple implementation of H-bridge with low-power sleep function using external cut-off switch; (b) TI DRV8210 with automatic sleep mode
Reduce PCB and motor drive subsystem size
Modern smart meters and other low-voltage motor drive applications are becoming more and more advanced, integrating sensing, wireless and wired communications, power management, and many other modules.
The large number of these modules means that it is necessary to ensure that subsystems such as motor drives and surrounding components use as little PCB space as possible. Figure 4 shows a commonly used discrete H-bridge implementation for driving low-voltage brushed DC motors. However, the H-bridge does not have some necessary functions, such as over-current protection, under-voltage lockout, thermal shutdown and dead time control, which requires additional firmware and hardware work.
Compared with discrete implementations, motor drivers such as DRV8220 (with a package size of 4mm2 or 1.92mm2) can reduce PCB space by 93% or more, as shown in Figure 5. Check the technical document "Discrete or integrated, the risk is not that big" to learn more about how our motor drives reduce the layout space and the number of components. In addition, all TI brushed DC motor drivers including DRV8220 provide integrated dead-time control and protection functions against overheating, undervoltage lockout and overcurrent events, thereby reducing the need for additional components and further reducing PCB space.
Design flexibility, simplification, reusability and scalability
Many applications in building automation, grid infrastructure, and personal electronics have multiple platforms with different system requirements. Take, for example, a smart sanitary equipment company that designs soap dispensers, automatic toilets, paper towel dispensers, and similar applications, as shown in Figure 6. These applications require different types of automated loads: bidirectional brushed DC motors for dispensing valves, locking solenoids for flushing dosing valves, and unidirectional brushed DC motors for tissue dispensing.
Ideally, you can use flexible solutions for all these scenarios, but this usually requires a lot of time and effort to find discrete components or ICs that support pin compatibility within the voltage and current ranges. To achieve this simplification, scalability and interface flexibility, the same or similar drivers can be used to drive different motors, relays, solenoids and other types of loads. In addition, the reusability of the design is also taken into account, which greatly shortens the time to market. For more details on how the DRV8210 motor driver family can help achieve these advantages, please refer to section 9 of the DRV8210 data sheet.
As described in this article, many low-voltage and battery-powered platforms in building automation and grid infrastructure applications require motor drives to be flexible, scalable, and easy to design. At the same time, these motor drive systems must provide a powerful low-power sleep mode to maximize battery runtime, and only occupy a small area of the PCB in order to leave enough space for other system components. Check out low-voltage H-bridge motor drivers to learn more about how TI achieves the advantages of small size, low power consumption, and design scalability.