SLVAFF1 January   2023 DRV8452 , DRV8462

PRODUCTION DATA  

  1.   Abstract
  2.   Trademarks
  3. 1Power Efficiency of Stepper Motor Drivers
  4. 2Auto-Torque
    1. 2.1 Auto-Torque: Learning Principle
      1. 2.1.1 Configuring Auto-Torque Learning Routine
    2. 2.2 Current Control
      1. 2.2.1 Setting Current Control Parameters
    3. 2.3 PD Control Loop
    4. 2.4 Impact of Auto-Torque Tuning Parameters
      1. 2.4.1 Impact of Learning Parameters on Load Transient Response
      2. 2.4.2 Impact of ATQ_UL, ATQ_LL Hysteresis
      3. 2.4.3 Impact of Load Profile on Power Saving
      4. 2.4.4 Adaptive ATQ_UL, ATQ_LL
      5. 2.4.5 PD Parameter Dependency Curves
        1. 2.4.5.1 Dependency on KP
        2. 2.4.5.2 Dependency on KD and ATQ_D_THR
        3. 2.4.5.3 Dependency on ATQ_FRZ and ATQ_AVG
        4. 2.4.5.4 Dependency on ATQ_ERROR_TRUNCATE
      6. 2.4.6 ATQ_CNT at Different Motor Speeds
      7. 2.4.7 ATQ_CNT at Different Supply Voltages
      8. 2.4.8 Motor Temperature Estimation
    5. 2.5 Efficiency Improvement With Auto-Torque
  5. 3Case Studies
    1. 3.1 Application 1: ATM Machines
      1. 3.1.1 ATM Motor Operating Conditions
      2. 3.1.2 ATM Motor With Auto-Torque
    2. 3.2 Application 2: Textile Machines
      1. 3.2.1 Textile Motor Operating Conditions
      2. 3.2.2 Textile Motor With Auto-Torque
    3. 3.3 Application 3: Printer
      1. 3.3.1 Printer Motor With Auto-Torque
  6. 4Summary
  7. 5References

2 Auto-Torque

The Auto-torque algorithm implemented in the DRV8462, DRV8452 and DRV8461 motor drivers improves system efficiency by dynamically changing the output current according to the load torque. Whenever the load torque is low, the output current is lowered to reduce resistive losses; and when the load torque goes up, the output current increases immediately to prevent motor step loss. This concept is shown in Figure 2-1. As a result of improved efficiency due to auto-torque, the system runs at a lower temperature, which extends the lifetime of the components. Auto-torque can also enable the use of cheaper and smaller sized stepper motors.

Figure 2-1 Power Saving With Auto-Torque

In a stepper motor system, the total power delivered by the power supply goes into providing for the torque requirement of the load and into power losses such as resistive losses caused by motor winding resistance and driver ON resistance. This is represented by Equation 2:

Equation 2. P o w e r   d e l i v e r e d   b y   s u p p l y = C o n s t a n t   l o s s e s +   τ × ω

where τ is load torque and ω is motor speed.

From Equation 2, it is observed that when the load torque increases, the power delivered by the supply increases as well. The auto-torque algorithm obtains information about the load-torque by monitoring the power delivered by the supply. The constant losses are represented by the ATQ_LRN parameter, and the ATQ_CNT parameter represents the power required to support the load torque, as explained in Section 2.1.