Configuring Pulse width modulation (PWM) operating mode

Areas of application

You can use pulse width modulation (PWM) to generate periodic pulses with a constant rated voltage and a variable pulse duration.

Possible applications for pulse width modulation (PWM):

Control of proportional valves and directional valves

- Energy savings as a result of a reduction in holding current or for controlling the valve position

Heating control, for example, via an external additional power unit

Principle of operation

With pulse width modulation, a ** with defined time period and variable pulse duration is output at the digital output. You use pulse width modulation to vary the mean value of the output voltage. This allows you to control the load current or the power in line with the connected load. The pulse duration can be between 0 (no pulse, always off) and full-scale deflection (no pulse, always on).

Pulse width modulation (PWM) is based on the specification of a base frequency of 1, 2, 4, 8 or 16 kHz. You can alter the base frequency in terms of period and pulse-pause ratio over the control interface (32-bit value). The bit pattern is shown in each base period. The base period is defined on the basis of the base frequency. A "0" is LOW and a "1" is HIGH.

Examples

Base frequency: 1 kHz → Base period: 1 ms

1111 0000 0000 0000 1111 0000 0000 0000

Time period: 500 µs; 375 µs LOW; 125 µs HIGH

图片: Pulse width modulation

Base frequency: 1 kHz

1111 1111 1111 1111 0000 0000 0000 0000

Time period: 1 ms; 500 µs LOW; 500 µs HIGH

1111 1111 0000 0000 0000 0000 0000 0000

Time period: 1 ms; 750 µs LOW; 250 µs HIGH

1111 0000 1111 0000 1111 0000 1111 0000

Time period: 250 µs; 125 µs LOW; 125 µs HIGH

Base frequency: 2 kHz

1010 1010 1010 1010 1010 1010 1010 1010

Time period: 31.25 µs; 15.625 µs LOW; 15.625 µs HIGH

Configuring Pulse width modulation (PWM) operating mode

To configure PWM operating mode, first define the required base frequency of pulse width modulation. You can configure the base frequency as 1, 2, 4, 8 or 16 kHz. The selected base frequency then applies to all channels of interface X142.

图片: Base frequency of pulse width modulation

Now select the channels for PWM operating mode. If you want to configure very short pulses, enable the high-speed output function.

图片: Pulse width modulation channel

The selected digital output is switched with the selected base frequency and the switching pattern from the control interface.

Inversion

You can invert the 24 V ** to adjust it to your process. By default, the ** is not inverted.

High-speed output

If you select the high-speed output option, the digital output is switched alternately to 24 V DC and ground. Allows for extremely steep edges (output delay in the 1 μs range).

To allow **s pending very briefly to be output with pulse width modulation (for example, level duration of 0.1 ms), you must operate the output as a high-speed output.

Further information