by Mike Donnelly
7 November 2020
We recently released our first programmable power converter controller model into the PartQuest Explore Partner Library. Working with ON Semiconductor product and application experts, we created a fully-functional model of the NCV78703. It is a single-chip, three-phase high efficiency boost controller that can be used for various automotive LED Front Lighting functions. Thanks to its SPI programmability, a single hardware configuration can support a diverse range of applications just by using different settings.
PartQuest Explore provides an on-line evaluation platform for designers considering use of the NCV78703. A “virtual application circuit”, like the one shown below, can be used to explore all of the programmable and configurable functions of this versatile IC. On top of featuring device programmability, the simulation environment supports sizing of all the major external components. Moreover, the device model is quite accurate and can be used not only during initial evaluation, but also as an aid for system stability and transient behavior studies later in the design process, together with the necessary LAB tests.
As an example of the possibilities offered by the simulation model, the boost output voltage can specified and even changed during a transient simulation run. The initial decimal equivalent values for all of the programmable register settings are specified in the control settings table on the far left side of the schematic. This table includes:
· Boost output voltage
· Power Distribution “per phase” split
· Control gains, including the slope compensation value
· Enable/disable options for many other features
These initial configuration values are passed into the NCV78703 model on the dark-blue SPI interface connection, at the beginning of the simulation run. But any of those values can be overwritten during the time-domain simulation run, using a “SPI Injector” model. The user can then program a time sequence of values on any selected “SPI Address Map register”, to see the effect of that change on the dynamic behavior and performance of the application.
The application schematic shown above is “Live”, meaning you can change any of the parameter values highlighted in blue, then run a new simulation and see the results. You can also push the yellow “Edit in PartQuest Explore” button and create your own copy of this schematic, and begin to modify it any way you want to represent your own design.
Note that for the initial simulation results, the SPI injected “boost_setpoint” value was changed from 96 to 102 at time 0.9msec, and then back to 96 at 1.1msec. The corresponding “bump” on the output voltage can be seen in the lower-right wave-scope (magenta waveform).
Likewise, the phase 3 output is disabled at 1.3msec and re-enable at 1.5msec using the SPI injected “boost3_en” value. Note the corresponding drop-out of the phase3 inductor current, and the increased phase1 inductor current, shown in the lower-left wave-scope, by the green and brown waveforms respectively. Finally, the phase3 disable/enable operation is repeated from 1.6msec to 1.8msec, but this time using the traditional method of applying an external voltage to the enable3 pin on the device.
This simulation runs fairly quickly (~3 minutes), in part due to the ideal switches being used. For more realistic switching behavior, at the cost of somewhat slower simulation speed, see the equivalent example circuit using an NVTFS020N06C MOSFET here.
The NCV78702, a very similar two-phase boost controller, can also be simulated by using the NCV78703 model with only two of the three phases active.
Enjoy learning to use the NCV7870x booster devices in these “virtual” applications, both prior of getting real hardware as well as together with it!
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