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Mike copy 1 Cond Losses verify PMSM 7R8 - V2

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Cond Losses verify PMSM 7R8 - V2

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mosfet-switching-compare-BUK7Y7R8E

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Description

This design is similar to the design "Ideal Switching Design for Moog PMSM - BLDC Motor Use-Case", but the ideal switches in the inverter are replaced with "Datasheet" Power MOSFET models. These models are calibrated to match the datasheet specified characteristics of an STW45NM50 device. This replacement required the conversion to the digital signals used to control the switch states, to actual gate voltages. So representative models of the necessary gate drivers were also added.

In addition, a "hot part monitor" model was added to one of the Power MOSFETs. This models the datasheet specified "Rthj_amb" (0.32 degrees C per Watt), in order to predict the internal junction temperature during different phases of inverter operation. A thermal time-constant of 1 ms was assumed, which may be quite unrealistic. It is possible to add much higher fidelity thermal network models of the heat transfer path if valid parameters are given.

Finally, one of the low-pass filters used in the current sense path was changed to reflect a possible circuit implementation using op-amps. This is to show the ability to move seamlessly between ideal signal-flow (or continuous transfer function block) modeling to circuit implementation modeling, anywhere in a system design.

You can also see a version of this design that uses the manufacturer provided SPICE model for the Power MOSFET: "STW45NM50 MOSFET Switching Design for Moog PMSM - BLDC Motor Use-Case"

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Cond Losses verify PMSM 7R8

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tunable example 2

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Description

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.

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