Microchip Technology MCP6 series Bedienungsanleitung PDF herunterladen (Seite 8)

AN900

DS00900A-page 8  2004 Microchip Technology Inc.

INITIALIZING THE POWER CONTROL PWM

MODULE AND HARDWARE FAULT INPUTS

The Power Control PWM module simplifies the task of

driving a 3-phase inverter bridge by providing three pairs

of complementary PWM outputs, with dead time inserted

between complimentary channels. It also provides hard-

ware-based Fault inputs that are capable of shutting

down the PWM outputs completely in a Fault situation.

To initialize the PCPWM module:

1. Configure the PCPWM time base:

a) Select a PWM time base postscale value of

1:1.

b) Select a PWM time base prescale value

input of 1:1 (F

OSC/4).

c) Configure the PWM time base for

Free-Running mode (for edge-aligned

operation).

2. Load the PTPERH:PTPERL register pair to

obtain a PWM frequency of 20 kHz. The value to

be used depends on the controller’s clock

frequency; refer to the data sheet to determine

the proper value.

3. Configure the PCPWM output:

a) Enable PWM0 through PWM5 as outputs.

b) Set the PWM I/O pairs (PWM0/1, 2/3 and

4/5) as complementary pairs.

4. Configure the special event trigger:

a) Set the special event trigger postscaler to

1:1.

b) Configure the special event trigger to occur

when the time base is counting upwards.

c) Enable updates from duty cycle and period

buffer registers.

d) Configure for asynchronous overrides from

the OVDCON register.

5. Configure the PCPWM dead time:

a) Select F

OSC/2 as the dead-time prescaler.

b) Load DTCON<5:0> with a dead-time value

to achieve a 2 µs dead time. The actual

value depends on the controller’s clock

frequency; refer to the data sheet to

determine the proper value.

6. Disable the output overrides on the PWM pins

by setting bits POVD<5:0>.

7. Clear the special duty cycle register pair

(SEVTCMPH:SEVTCMPL).

8. Clear all of the regular PWM duty cycle register

pairs (PDCxH:PDCxL) to set the duty cycles to 0.

9. Enable the PWM time base.

10. Enable PWM Fault detection:

a) Enable both Fault A and Fault B.

b) Configure both Fault inputs to disable PWM

channels 0 through 5.

c) Configure both Fault inputs to operate in

Cycle-by-Cycle mode.

INITIALIZING THE HIGH-SPEED ADC

MODULE

Three analog values are measured in this application:

• AN0 (DC bus current)

• AN1 (potentiometer input for the speed reference)

• AN8 (IGBT junction temperature in the inverter

module)

The high-speed ADC incorporates several features,

such as Auto-Conversion mode and a FIFO result

buffer, that reduce the firmware overhead associated

with monitoring multiple analog channels and enhance

ADC throughput.

To initialize the HSADC module:

1. Configure ADC operation:

a) Enable Continuous Loop mode.

b) Enable Multi-Channel mode.

c) Configure auto-conversion sequence to

sample sequentially from Group A and

Group B.

d) Assign V

REF+ and VREF- to AVDD and

SS, respectively.

e) Enable the FIFO buffer.

f) Select the left-justified format for the A/D

result.

g) Set the A/D acquisition time to 12 T

(required for sequential conversion).

h) Set the A/D conversion clock to FOSC/32

i) Turn on the ADC.

2. Configure interrupts and event triggers:

a) Set the A/D interrupt to be generated on

every 2nd and 4th write to the FIFO buffer.

b) Disable external ADC triggers.

3. Configure input group assignments:

a) Assign AN0 to Group A. This will alternate

with AN8 on every FIFO interrupt.

b) Assign AN8 to Group B.

4. Configure RA0, RA1 and RE2 as analog inputs:

a) Set the ANSEL0<1:0> and ANSEL<0> bits.

b) Set the TRISA<1:0> and TRISE<2> bits.

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 23 24

Kommentare zu diesen Handbüchern

Keine Kommentare

Microchip Technology MCP6 series Bedienungsanleitung Seite 8

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Motherboards Microchip Technology MCP6 series