by Daviid Calldwellll
A dedicated digital controller with intuitive settings makes it quick and easy to
close a loop around a power supply, heater, motor, lamp, or other device.
Closed-loop controllers make automatic adjustments
to maintain constant output despite varying conditions.
Examples include supply voltage, fluid temperature,
motor speed, and light intensity. These parameters
would shift over time and load without consistent
Figure 1. CLOZD loop controller system application.
Microcontrollers executing firmware are replacing
op-amps with feedback networks that used to perform
closed-loop control. These digital implementations are
versatile but time-consuming to program and control
demands often exceed processor resources.
Considerable expertise is required to properly design a
system to avoid oscillations or sluggish responses. We
naturally observe events in the time-domain while control
analysis is typically done in the frequency-domain, which
can be complex and confusing.
One solution to these challenges is an automated
closed-loop controller configured by intuitive
time-domain settings. CLOZD™ is a control chip
developed by Flextek Electronics that is versatile and
easy to use. Just select the desired timing configuration
through pin settings and quickly close a loop around a
power supply, motor drive, lamp, heater, fan, Peltier,
valve, actuator, or amplifier.
Controller drive is automatically adjusted until the
measured sensor signal matches the desired command,
as shown in Figure 1. The Digital-Signal-Processing (DSP)
algorithms within the CLZD010 control chip
compare the feedback sensor signal and the
analog setpoint command to determine
appropriate Pulse-Width-Modulator (PWM)
drive for the plant. Typical plants include
power, thermal, motion, lighting, and flow
Figure 2. A thermal controller (for a 5 W heater).
PWM = 488 Hz (PS=010, BIP=1) CLOZD = 134S (CS=0011, TIM=0).
HI / LO
NUTS & VOLTS
Thermal control systems are challenging
because they have low level signals, long time
constants, and multiple lag elements that can
cause overshoot. However, the one shown in
Figure 2 is quick and easy to configure for
high performance with a few inexpensive
parts. The duty cycle (percentage time