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EVM Control Software (GUI)
The GUI is broken up into two tabs:
Standard Drive
and
WaveBuilder
. The
Standard Drive
utilizes
changing the frequency and duty cycle of the PWM signal and is intended for easy prototyping and
evaluating. The
WaveBuilder
tab is for showcasing the DRV2700 as a proportional controller that can
drive a variety of user-created waveforms. On both tabs, the sections are intuitive, however, the following
sections are worth describing:
•
Output Timing:
This button has 3 different modes:
Continuous
,
Pulsed
, and
Single
. These modes help
with a timed EN signal.
•
Boost Voltage Percentage:
This is the duty cycle of the PWM waveform and after filtered will be a
DC value to modulate the output. Note in the scopeshots in
Figure 5
through
Figure 8
, that the PWM
signal's duty cycle is inverse to the output. (As duty cycle increases, the output voltage percentage
decreases.) This has been taken care of through software so that the slider bar will reelect the true
output percentage though. The boost voltage percentage will only have a true "Boost Voltage
Percentage" effect during High Frequency/DC Mode.
•
PWM Input Frequency:
This will change the frequency of the PWM signal coming from the
microcontroller, which is fed into the input filter:
–
Low PWM Frequency (< 1 kHz): When below 1 kHz, the PWM signal will hardly be attenuated such
that the majority of the PWM signal will propagate through. This will cause the output to try and
reflect the PWM signal coming from the microcontroller and the output will try to be a square wave.
The
AC Mode
-
Quick Launch
frequency button will set the frequency to this range.
–
Mid PWM Frequency (1 kHz < freq < 20 kHz): When the frequency is set in this range, the PWM
signal will be somewhat attenuated and the output will still somewhat reflect a PWM signal. This
mode can be used for audio tones, however, the output may not be able to drive to full scale,
depending on the load capacitance.
–
High PWM Frequency (> 20 kHz): As the frequency starts to go higher, the PWM signal will be
greatly attenuated. This will cause the PWM signal to appear DC after this filter. This mode can be
used to drive the output at a DC level which is set by the Boost Voltage Percentage (that is, duty
cycle). The
DC Mode
-
Quick Launch
frequency button will set the frequency to 50 kHz, which is in
this range.
•
Time Between Steps (ms):
The time between steps on the wavebuilder tab is the time step between
points. This is implemented using a series of DC set points occurring at a certain time of the waveform.
The output is limited to 200 sample points.
•
Waveform From Excel/Text:
This text box will build a waveform in the graph based on a comma-
separated string of integers from 0-100%.
It is best practice to have an oscilloscope measure the output to verify how the load is actually being
driven, based on the conditions applied.
11
SLOU407A – April 2015 – Revised May 2015
DRV2700EVM-HV500 High Voltage Piezo Driver Evaluation Kit
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