In the motor-driven building automation and grid infrastructure applications (such as smart meters, smart locks, Internet Protocol (IP) webcams and visual doorbells, there are a variety of ways to design low-voltage systems, as shown in Figure 1.
Figure 1: Battery power system: visual doorbell, smart meter and electronic smart lock
When designing motor-driven systems for these applications, common challenges include: meeting lasting, elasticity and secure motor operational demand; continuously narrowing printed circuit board (PCB) space; and meets various system requirements. In consideration of motor driver current consumption, special attention is required: integrated circuit (IC) and the necessary component plate size; design simplified, flexibility and scalability to meet multiple platform types.
Reduce power consumption
For smart locks, visual doorbells, gas meters and water meters such as battery powers and motor-driven systems, a focus of design is to reduce overall power consumption by maintaining low current consumption when not active driving motors, so that consumers do not have to change the battery . If you are interested in these applications, TI provides a reference design for electronic intelligent locks and IP network camera infrared cutoffs.
Below we will use the following devices to compare two methods that reduce H bridge power when no drive motor:
Discrete load switches between batteries and motor drive circuits for connecting or removing power supplies;
Ti's DRV8210 and other devices have dedicated low-power sleep modes whose typical sleep current is 37NA.
Compared to the first device, the second device reduces up to 50% PCB space and removes the power component when connecting the H bridge power source. See Figure 2.
(a) (b)
Figure 2: (a) Simple implementation of H bridges with low power sleep function using external truncation switches; (b) TI DRV8210 with automatic sleep mode
Reduce PCB and motor drive subsystem size
Modern smart meters and other low-voltage motor drive applications become more advanced, integrated with sensing, wireless and wired communication, power management, and many other modules, as shown in Figure 3.
Figure 3: Reference design of rotary water meter
The number of these modules is numerous, which means ensuring that subsystems such as motor drivers and surroundings are used to use as little PCB space. Figure 4 shows a commonly used discrete H-bridge implementation for driving a low pressure brush DC motor. However, the H bridge does not have some necessary functions, such as overcurrent protection, undervoltage locking, thermal shutdown and dead time control, require additional firmware and hardware work.
Figure 4: Discrete implementation of the H bridge and the basis circuit; the PCB area is 16mm x 25mm or 400mm2
Motor drivers such as DRV8220 (4 mm 2 or 1.92 mm 2) can be reduced by 93% or more of the PCB space than discrete achievements. As shown in Figure 5. Viewing Technical Documents "Discrete or integration, risk is not so big" to learn how our motor driver reduces the number of box space and components. In addition, all TIs including DRV8220 provide integrated dead time control and protection of overheating, undervoltage locking, and overcurrent events, thereby reducing the need for additional components, further reduction PCB space.
Figure 5: DRV8220DSG integrated motor driver layout; PCB area is 4.5mm x 4.4mm, or 19.8mm2
Design flexibility, simplification, reusability and scalability
Many applications in building automation, grid infrastructure and personal electronic products have multiple platforms with different system requirements. Take the intelligent health equipment company with soap, automatic toilet, paper towel dispenser and similar application as an example, as shown in Figure 6. These applications require different types of automated loads: two-way brush DC motors for allocating valves for flushing the locking solenoid for flushing the fixed valve and a one-way brush DC motor for the paper towel allocation.
Figure 6: Common motor drive intelligent sanitary equipment applications
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 compatible within the voltage and current range. To achieve this simplification, scalability and interface flexibility can drive different motors, relays, solenoids, and other types of loads using the same or similar drive.
Article Source: EdnChina
Edit: YMF, read full text
Our other product:
