What Is the Duty Cycle?

The duty cycle refers to the proportion of the power-on time to the total time in a pulse cycle. Duty ratio has the following meanings in the field of telecommunications: for example: a pulse sequence with a pulse width of 1 s and a signal period of 4 s has a duty cycle of 0.25. ^[1]

The ratio of the time occupied by the pulse to the total time during a continuous working period.

Extended meaning:

In a periodic phenomenon, the ratio of the duration of a phenomenon to the total time.

For example, there is a saying in the saying: "Three days fishing, two days of drying the net" means that there are three days in total, one day is fishing, and two days are fishing nets. Fishing has a duty cycle of 1/3.

The duty cycle is the percentage of time that the circuit is switched on in the entire circuit duty cycle. For example, if a circuit is turned on half the time during a working cycle, its duty cycle is 50%. If the signal voltage applied to the working element is 5V, the actual average working voltage or effective voltage value is 2.5V. Assume that this component is an electronic valve. When the circuit is fully closed, the valve is fully open; when the duty cycle is 50%, the valve state is half open. Similarly, when the duty cycle is set to 20%, the valve opening degree should obviously be 20%. In this way, the valve can be arbitrarily adjusted in the range of 0% (fully closed) to 100% (fully open).

In some technical materials, the duty cycle control is also called electrical control pulse width modulation technology. It uses the electronic control unit to modulate the pulse width of a certain frequency voltage signal applied to the work execution element, that is, the duty cycle control, in order to achieve accurate and continuous control of the working condition of the element. Ohm's law of classical electrician theory tells us that voltage = current x resistance. Most of the electronically controlled actuators are coils or conductors with a certain constant resistance value. In many cases, the electromotive force of the power supply is also basically constant and unchanged. Therefore, simple control circuits can only realize the connection of the working element circuit or the cutting of the working element circuit These two operating conditions, that is, on or off, cannot achieve a certain range of stepless linear regulation from gradually opening to gradually closing.

However, the duty cycle control technology takes a different approach. By performing duty cycle control on the voltage signal applied to the working element at a certain frequency, the ratio of the on and off of the simple switching circuit is controlled to achieve the voltage on the working element The voltage average value of the signal is controlled, so that the current control through the working element is finally realized.

Several factors of duty cycle

1. Circuit operating frequency. The computer works with a fixed frequency. Similarly, to achieve accurate duty cycle control, the circuit must have a constant operating frequency to ensure. In fact, the frequency is fixed, that is, the period of the working circuit is fixed. Because the circuit on-duty ratio of the duty cycle control is based on a constant duty cycle, if the cycle of the electronic control module control circuit cannot guarantee a constant, then the so-called duty cycle control is meaningless.

2. Working voltage. The working voltage is a constant voltage applied by the computer to the actuator. There are 5V or 8V, etc., depending on the impedance of the working element. With an oscilloscope, you can clearly see the constant operating voltage.

3. Average working voltage. Refers to the average value of the voltage added to the working circuit in one cycle after the computer's duty cycle modulation. This is the voltage that is really used to drive the working executive element. Just use a simple multimeter to detect the average operating voltage.

4. Pulse width. Refers to the real time that a circuit is switched on or operated during a working cycle.

Duty cycle classification

The duty cycle control system can be divided into positive duty cycle control and negative duty cycle control according to the position of the actuator. Generally, the control of the power supply end of the actuator is called positive duty cycle control, and the control of the ground end is called negative duty cycle control.