Microchip Technology AC164133 Data Sheet
BUCK/BOOST CONVERTER
PICtail™ PLUS DAUGHTER
BOARD USER’S GUIDE
© 2008 Microchip Technology Inc.
DS70336A-page 49
Chapter 4. Demonstration Program Operation
The Buck/Boost Converter PICtail Plus Daughter Board CD supplied with the
Buck/Boost Converter PICtail Plus Daughter Board consists of the source code for the
16-bit 28-pin Starter Development Board (Buck 1 stage only) and Explorer 16 Develop-
ment Board (Buck 1, Buck 2 and Boost stages). To demonstrate a program that illus-
trates PID control of the output voltage on the Daughter Board, program the device with
respective source code, available on the Daughter Board’s CD, specified in
Section 3.2 “Creating the Project”. The code can also be downloaded from the
Microchip web site (http://www.microchip.com).
Buck/Boost Converter PICtail Plus Daughter Board consists of the source code for the
16-bit 28-pin Starter Development Board (Buck 1 stage only) and Explorer 16 Develop-
ment Board (Buck 1, Buck 2 and Boost stages). To demonstrate a program that illus-
trates PID control of the output voltage on the Daughter Board, program the device with
respective source code, available on the Daughter Board’s CD, specified in
Section 3.2 “Creating the Project”. The code can also be downloaded from the
Microchip web site (http://www.microchip.com).
The following topics are included in this chapter:
4.1
PROGRAM DEMONSTRATION
The demonstration program provides simultaneous closed-loop control of the output
voltages.
voltages.
The PID control scheme consists of the following parameters:
• Proportional Error Gain (P-Gain) – This parameter produces a correction factor
that is proportional to the magnitude of the output voltage error.
• Integral Error Gain (I-Gain) – This parameter uses the cumulative voltage error
to generate a correction factor that eliminates any residual error due to limitations
in offset voltages and measurement resolution.
in offset voltages and measurement resolution.
• Derivative Error Gain (D-Gain) – This parameter produces a correction factor
that is proportional to the rate of change of the output error voltage, which helps
the system respond quickly to changes in system condition.
the system respond quickly to changes in system condition.
Additional control parameters that the user can add to P, I and D Gain terms are as
follows:
follows:
• Second Derivative, or Jerk Error, Gain (J-Gain) – This parameter produces a
correction factor that is proportional to the change in the differential error (i.e., the
derivative of the derivative). J-Gain is a high frequency term that tends to provide
quick response to an impulse event.
derivative of the derivative). J-Gain is a high frequency term that tends to provide
quick response to an impulse event.
• Feed Forward Gain – This parameter produces a correction factor based on the
desired output voltage that is computed based on the magnitude of the input
voltage, inductor current, and circuit attributes (i.e., inductor and capacitor
values). This term allows the control loop to be proactive rather than reactive. In
other words, when the input voltage changes, feed forward gain responds so that
the control loop does not have to wait until the output voltage changes before
making the appropriate gain correction.
voltage, inductor current, and circuit attributes (i.e., inductor and capacitor
values). This term allows the control loop to be proactive rather than reactive. In
other words, when the input voltage changes, feed forward gain responds so that
the control loop does not have to wait until the output voltage changes before
making the appropriate gain correction.