PIC16C782 Microchip Technology Inc., PIC16C782 Datasheet - Page 114

• Manufacturer Part Number: PIC16C782
• Description: 8-bit Cmos Microcontrollers With A/d, D/a, Opamp, Comparators And Psmc
• Manufacturer: Microchip Technology Inc.

PIC16C781/782
FIGURE 13-6:
13.3.3
In Figure 13-7, the PSMC acts as a speed control for a
brushless DC motor. The direction of the current in the
motor winding is set by feedback from a Hall effect
position sensor on the motor. The sensor switches the
phase in the motor in response to the rotation of the
rotor so that the magnetic field rotates just ahead of the
rotor, pulling it in the desired direction. The speed at
which the rotor spins is a function of the mechanical
load on the rotor and the current in the field winding.
Speed control is accomplished by monitoring the speed
via the Hall effect sensor and regulating the current in
the winding appropriately. The winding current is regu-
lated by the PSMC to be proportional to the value sup-
plied by the DAC module. The feedback loop is closed
by software making periodic measurement of the rotor
speed using the Hall Effect sensor/Timer1 and adjust-
ing the output value of the DAC appropriately.
DS41171A-page 112
V
REF
EXAMPLE MOTOR SPEED
CONTROL
PIC16C781/782
PSMC
DAC
C1
OPA
EXAMPLE BUCK CONFIGURATION LC POWER SUPPLY
B
A
+
-
+
-
RB6/C1/PSMC1A
RB7/C2/PSMC1B/T1G
RA3/AN3/V
RB2/AN6
RB3/AN7/OPA
RA1/AN1/OPA-
RA0/AN0/OPA+
RB1/AN5/V
REF
DAC
1
Preliminary
MOSFET
DRIVER
MOSFET
DRIVER
The algorithm (used to determine the values output by
the DAC module) depends on:
• mechanical system connected to the motor
• motor characteristics
• characteristics of the high current drive
An analysis of the mechanics of the system and the
design of an appropriate control algorithm is beyond
the scope of this Data Sheet. Therefore, the designer
should consult a text dealing with the design of motor
speed controls and feedback control system, in
general, for the necessary design guidance.
Q2
Q1
+V
IN
CURRENT TRANSFORMER
2001 Microchip Technology Inc.
D1
L1
L2
D2
C
MAIN
D3
D4
R2
R1
LOAD