J
John O'Flaherty
- Jan 1, 1970
- 0
I would like to use PWM in a control loop for power-saving purposes.
The controlled device needs to operate over a wide range of powers as
setpoint, so I was thinking of using 16-bit PWM from a microcontroller.
This would potentially have a range from 1/65000 to 1. It occurs to me
that the control will be grainier when operating at narrower duty
cycles. For example, if full power is at 50% duty cycle, and I want to
operate at full power/1000, the duty cycle control number will be
32000/1000 = 32. The minimum adjustment will be +/- 1, or 3% of that
level.
I have two questions about this-
1 Should the gain of the loop be adjusted to different levels depending
on the setpoint, i.e., should correcting signals be adjusted to a
percentage of the current level?
2 Is there a rule of thumb or other way to anticipate what dynamic
range can be had from that kind of control before it becomes too
grainy?
The controlled device needs to operate over a wide range of powers as
setpoint, so I was thinking of using 16-bit PWM from a microcontroller.
This would potentially have a range from 1/65000 to 1. It occurs to me
that the control will be grainier when operating at narrower duty
cycles. For example, if full power is at 50% duty cycle, and I want to
operate at full power/1000, the duty cycle control number will be
32000/1000 = 32. The minimum adjustment will be +/- 1, or 3% of that
level.
I have two questions about this-
1 Should the gain of the loop be adjusted to different levels depending
on the setpoint, i.e., should correcting signals be adjusted to a
percentage of the current level?
2 Is there a rule of thumb or other way to anticipate what dynamic
range can be had from that kind of control before it becomes too
grainy?