DC Motor speed control

This example shows a more detailed circuit- and logic-level implementation of the PID Control Loop shown in the companion example, “PID Speed Control Loop – Continuous”. The ideal motor drive block of the “Continuous” version is expanded here, to include both a H-bridge motor drive, and also the digital logic necessary for converting the continuous PID controller output into the desired PWM signals that are distributed to drive the gates of the power MOSFET switches. The MOSFET model was calibrated to represent an IRF3710, using only information published on the manufacturer’s datasheet.

The rest of the system, including the PID block-diagram controller, the mechanical fan load and the DC Motor characterized to represent an FRC CIM Motor, are the same as in the Continuous version. While the simulation time for this switching version is significantly longer, more detailed information about practical circuit performance and component sizing is available. For example, the fan speed step response is somewhat different from the conceptual design, because of the losses in the MOSFETs under high current conditions, as well as voltage drop in the battery. Also, information regarding component stress levels within the “datasheet specified” MOSFETs and Diodes is provided.

This LED lighting example demonstrates the value of simulating both the electrical and thermal* aspects of power dissipating circuits together, simultaneously.

In this application example, a Vishay NTCS0603 Thermistor provides feedback of the enclosure temperature. This feedback is used to control PWM dimming of the LEDs, thereby limiting the internal temperature when operating at high external ambient temperature conditions.

This is a "Live" design, the user can change key parameter values and then run new simulations to see the results. These parameters include "r_mirror", the resistance of the current mirror that controls the capacitor charging rate of the 555 timer, and thereby set the PWM frequency. The user can also change "r_offset" that controls the temperature level at which the dimming operation begins. Finally, the user can set "r_iLED_set", to control the ON-state operating current of the LEDs.

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* To reduce the time needed to simulate the transition and settling at 6 different temperature levels, all thermal time constants were reduced by approximately 1000x. The actual thermal response time constant of the NTCS0603 is approximately 3 seconds (depends on mounting), not 3 msec! Also, the enclosure thermal capacitance value would more likely be 3 (J/degC) instead of 3 (mJ/degC), giving a thermal time constant for the enclosure of 10 (degC/Watt) * 3 (J/degC) = 30 seconds. This time scaling does not affect the static relationship between the outside temperature and PWM dimming.

Induction Machine (IM) with PWM Drive circuit and mechanical fan load. This design demonstrates use of the Rohm R6076ENZ4 Power MOSFET.

This example shows a more detailed circuit- and logic-level implementation of the PID Control Loop shown in the companion example, “PID Speed Control Loop – Continuous”. The ideal motor drive block of the “Continuous” version is expanded here, to include both a H-bridge motor drive, and also the digital logic necessary for converting the continuous PID controller output into the desired PWM signals that are distributed to drive the gates of the power MOSFET switches. The MOSFET model was calibrated to represent an IRF3710, using only information published on the manufacturer’s datasheet.

The rest of the system, including the PID block-diagram controller, the mechanical fan load and the DC Motor characterized to represent an FRC (First Robotics Competition) CIM Motor, are the same as in the Continuous version. While the simulation time for this switching version is significantly longer, more detailed information about practical circuit performance and component sizing is available. For example, the fan speed step response is somewhat different from the conceptual design, because of the losses in the MOSFETs under high current conditions, as well as voltage drop in the battery. Also, information regarding component stress levels within the “datasheet specified” MOSFETs and Diodes is provided.

This design tests the AS123 for single-string operating conditions.

This LED lighting example demonstrates the value of simulating both the electrical and thermal aspects of power dissipating circuits together, simultaneously.

In this application example, a Vishay NTCS0402 Thermistor provides feedback of the enclosure temperature. This feedback is used to control PWM dimming of the LEDs, thereby limiting the internal temperature when operating at high external ambient temperature conditions.

This is a "Live" design, the user can change key parameter values and then run new simulations to see the results. These parameters include "r_mirror", the resistance of the current mirror that controls the capacitor charging rate of the 555 timer, and thereby sets the PWM frequency*. The user can also change "r_offset" that controls the temperature level at which the dimming operation begins. Finally, the user can set "r_iLED_set", to control the ON-state operating current of the LEDs.

*Note: The PWM switching frequency was intentionally reduced from the practical value of 260 Hz to 2.6 Hz, in order to provide fast simulations and realistic (long) thermal time constants. This was accomplished by increasing the 555 timer capacitor from 100 nF to 10 uF. This should have no significant impact on the thermal feedback or settling behavior that would be observed at the higher PWM frequencies needed to avoid visual "flicker" to the human eye (i.e. > 200 Hz).

This example shows a more detailed circuit- and logic-level implementation of the PID Control Loop shown in the companion example, “PID Speed Control Loop – Continuous”. The ideal motor drive block of the “Continuous” version is expanded here, to include both a H-bridge motor drive, and also the digital logic necessary for converting the continuous PID controller output into the desired PWM signals that are distributed to drive the gates of the power MOSFET switches. The MOSFET model was calibrated to represent an IRF3710, using only information published on the manufacturer’s datasheet.

The rest of the system, including the PID block-diagram controller, the mechanical fan load and the DC Motor characterized to represent an FRC (First Robotics Competition) CIM Motor, are the same as in the Continuous version. While the simulation time for this switching version is significantly longer, more detailed information about practical circuit performance and component sizing is available. For example, the fan speed step response is somewhat different from the conceptual design, because of the losses in the MOSFETs under high current conditions, as well as voltage drop in the battery. Also, information regarding component stress levels within the “datasheet specified” MOSFETs and Diodes is provided.

This LED lighting example demonstrates the value of simulating both the electrical and thermal aspects of power dissipating circuits together, simultaneously.

In this application example, a Vishay NTCS0402 Thermistor provides feedback of the enclosure temperature. This feedback is used to control PWM dimming of the LEDs, thereby limiting the internal temperature when operating at high external ambient temperature conditions.

This is a "Live" design, the user can change key parameter values and then run new simulations to see the results. These parameters include "r_mirror", the resistance of the current mirror that controls the capacitor charging rate of the 555 timer, and thereby sets the PWM frequency*. The user can also change "r_offset" that controls the temperature level at which the dimming operation begins. Finally, the user can set "r_iLED_set", to control the ON-state operating current of the LEDs.

*Note: The PWM switching frequency was intentionally reduced from the practical value of 260 Hz (used in the companion design https://www.systemvision.com/design/led-driver-auto-dimming-thermal-protection), to 2.6 Hz, in order to provide fast simulations and realistic (long) thermal time constants. This was accomplished by increasing the 555 timer capacitor from 100 nF to 10 uF. This should have no significant impact on the thermal feedback or settling behavior that would be observed at the higher PWM frequencies needed to avoid visual "flicker" to the human eye (i.e. > 200 Hz).

Permanent Magnet Synchronous Machine (PMSM) and PWM Drive circuit, with mechanical load. The drive includes a D-Q control algorithm, and uses space-vector modulation (SVM) to generate the digital PWM signals to drive the Power MOSFET switches of the inverter.

There are two other versions of this design. The first, "PMSM Motor And Ideal Drive", uses continuous Clarke and Park Transform models and an ideal voltage drive to represent the main features of the field-oriented control system., Another version, "PMSM Motor and PWM Drive", it similar to this version but uses ideal switches.

This version is the most detailed and therefore simulated the most slowly. It is well suited for understanding the performance of the Power MOSFETs in the context of the system, In the waveform plot on the right, the actual motor shaft angle (orange waveform) and the A-phase current (dark blue waveform) are shown. These are very similar to the results for the other two versions of the design. But the waveform plot on the left provides insight into the performance of the C-phase inverter pull-up switch. The MOSFET current Ids (green waveform), and the average power dissipated in the device (red waveform) are shown. This design can be used to size specific parts in the drive electronics, by comparing the operating conditions to which they are exposed, relative to their rated operational limits.