Mechatronics | PartQuest™ Explore

This automotive electrical power distribution system example includes multiple vehicle sub-systems and components. It supports sizing analysis for wires and fuses, under both static and transient loading conditions. This includes multi-discipline (i.e. electro-thermal-mechanical) dynamic operations such as incandescent lamp in-rush current and motor start-up conditions. The example also demonstrates the special characteristics and design considerations needed for constant power loads, such as switching converters used in LED Driver circuits.

This system also uses a special “direction sensitive” current monitor model that can help identify sneak circuits (i.e. unintended current paths), such as the one found in the “door-ajar”, ignition switch, chime and dome lamp interconnect circuit. Challenge: See if you can find it before running the simulation!

After you run the simulation, a "Component Messages" window will pop up and show several problems with the system. These include&nbsp;a "reverse current detected" (i.e. current flow in the opposite&nbsp;direction&nbsp;from the expected)&nbsp;in the wire that carries current to&nbsp;the&nbsp;dome lamp to indicate&nbsp;a&nbsp;door is ajar. Current&nbsp;reversals are often&nbsp;due to a "sneak circuit" in design, which can lead to undesired&nbsp;function or behavior of the system. In this case, the reverse current is showing that if the driver puts the key in the ignition and turns on the dome lamp to read a map, the warning chime will sounds even though there are no doors ajar!

The other message indicates that the fuse supplying the flasher circuit has blown, shortly after the hazard flasher is turned on. Clearly this fuse is undersized to supply all 4 flasher&nbsp;lamps together, but operates fine with when just 2 are operated for normal turn&nbsp;signaling. You can try other operational conditions for this system to test for proper fuse sizing. For example, try changing the LED constant power pulse_value to 50W instead of 20W. You can also&nbsp;change&nbsp;the fan inertia to 200u Kg*meter^2, up from 100u. To fix the problem caused by the increase motor inertia (and correspondingly longer time transitioning for stall to normal operating load current),&nbsp;try increasing the fan fuse I^2*T value from 5 to 36, to represent the performance of a slower-blowing fuse.

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Copy of Loudspeaker with Simple Amplifier - on Thu, 01/30/2025 - 10:26

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Description

This "Live" example design includes a simple analog electronic amplifier, intended only to demonstrates the importance of multi-discipline system modeling.

A swept frequency response test, from 40 Hz to 1000 Hz, shows the effect of the complex amplifier loading by the voice-coil and speaker-cone dynamics*. The electro-mechanical resonances strongly affect the current that must be supplied, in order to maintain a flat (controlled) output voltage over the specified frequency range. For example, the current in the voice-coil reaches a null at time 0.1 seconds, which corresponds to the effective "spring-mass" resonance frequency (60 Hz). The loudspeaker reaches its minimum impedance around 600 Hz, or at 0.6 seconds where the peak load current is observed.

The simulation results also show that the average power (q1/npn/pwr_avg) in the BDP947 BJT exceeds its 5 Watt rating across the entire range, but especially at lower frequencies. The red "hot part monitor", with the junction to ambient thermal resistance set to 10 C/Watt, as given in the datasheet, shows the part temperature rising to over 100 C. These diagnostic indicators make it obvious that we need a bigger transistor!

All of the parameters in blue can be changed by the user and a new simulation run. The updated scope waveform results will show the effect of that change. You can change the electrical resistance and inductance of the voice-coil, as well as the speaker cone mass and linear spring rate that affect the resonance frequency.

* Note: Please refer to this companion example, that shows the input impedance frequency response of the loudspeaker alone:

https://www.systemvision.com/design/loudspeaker-only-frequency-response

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