dsPIC33C Digital Power Starter Kit

Synchronous Buck Converter: Average Current Mode Control

dsPIC33C Digital Power Starter Kit (DPSK3) (Part-No. DM330017-3)

Summary

Dual-Loop Average Current Mode Control (ACMC) example for the buck converter on the Digital Power Starter Kit, version 3 (DPSK3) featuring the dsPIC33CK family of devices.

Description

This code example demonstrates the implementation of a dual-loop average current mode controller for the synchronous buck converter, comprised of an outer voltage loop and an inner current loop. The loop implementation also includes the required state machine managing board status analysis, start-up control, operation monitoring, fault handling and auto-restart capability. The buck converter state machine is based on a generic buck converter library package, which is configured and executed in user code.

This code example also includes the LCD driver allowing users to observe runtime data on the on-board LC display. The on-board user switch USER allows users to change the active display page to observe input voltage, output voltage, output current and board temperature.

Software Used

Hardware Used

dsPIC33C Digital Power Starter Kit, Part-No. DM330017-3

Supported Target Devices

Focus Microchip Technology Devices

48-pin Digital Signal Controller, dsPIC33CK256MP505

Further Microchip Technology Devices used in this Design

a) Power Supply Circuit

b) Protection Circuit

c) Communication, Programming/Debugging and Housekeeping

Security and Safety Requirements

Unattended operating power supplies are always a potential safety risk as short circuits or failures of power components can occur at any time where even seemingly small power converters can cause fire or damage connected equipment.

This development board has not been FCC approved nor certified and must not be used outside a laboratory environment
Never operate the board unattended
Only use power supplies delivered with the board or equal, approved laboratory equipment
Read the user guide for detailed operating instructions to prevent damage to the board or connected equipment

Setup

Connect dsPIC33C Digital Power Starter Kit to the PC using the micro-USB cable
Open and compile the firmware; program the target device
Attach the 9V power supply to the board and observe the run-time values on the LC display

DPSK3 Buck Converter Test Points

Operation

After the device has been programmed and the target device starts up, the LC display will show the startup screen for approx. 3 seconds before switching to the runtime data display, showing the most recent input and output voltages. In case an appropriate power supply has been attached to the DPSK3 power input and the firmware is running correctly, the display should show an output voltage of +3.30 V DC.

When pressing the on-board button USER for one second or longer, the screen can be switched between:

Output Voltage View
Temperature View
Output Current View
Firmware Version

By pressing the Buck Load on-board push button on the right edge of the board for less than a second, changes the static load level in four steps:

no LED: 0% (0 mA)
1 LEDs: 10% (100 mA)
2 LEDs: 50% (500 mA)
3 LEDs: 100% (1000 mA)

(value accuracy +/- 10%)

By pressing the Buck Load on-board push button on the right edge of the board for longer than a second, the load switches into stepping mode.

Flashing LEDs indicate the upper step limit
Static LEDs indicate the lower step limit

Pressing the Buck Load on-board push button again for less than a second, the step load can be adjusted between

10% to 50% Load (100-500 mA)
10% to 100% Load (100-1000 mA)
50% to 100% Load (500-1000 mA)