PWM Signal Controls in DC Motors

Pelonis Technologies, Inc. (PTI) is a leading global manufacturer of brushless DC fans, axial AC fans, and motors serving a wide array of industries including the aerospace, defense, medical, heating and air conditions, appliances, and automotive sectors.

With more than 25 years of experience in developing and manufacturing new and custom products, PTI has built a strong specialization in highly technical fan solutions for the original equipment manufacturing (OEM) field and developed state-of-the-art, fully ISO certified production facilities.

As is often required in highly specialized applications, our expertise includes complex electronics required to make fans run in specific ways. One such method is pulse width modulation (PWM) signal controls for fan speed. 

What are PWM Signal Controls?

Our Pulse Width Modulation Signal (PPWM) Controls control the speed of a fan by applying dc-fan.jpga PWM signal, which has a frequency ranging from 30 Hz to 30 KHz.

PPWM Controls take incoming electricity and convert it into what is called a “Duty Cycle” by creating square waves. Square waves occur when the voltage of electricity instantaneously spikes from a prescribed minimum level to a prescribed maximum level and remains there for a predetermined amount of time. Together, the peak (maximum voltage) and trough (minimum voltage) of a PWM signal comprise the Duty Cycle.

The percentage of a Duty Cycle during which maximum voltage is important and ultimately determines the fan speed. If the square wave is at its maximum voltage for 10% of the Duty Cycle, it is a 10% Duty Cycle; if it is at its maximum voltage for 50%, it is a 50% Duty Cycle, and so on. According to prewritten equations, our PPWM controls adjust a fan’s speed based on the Duty Cycle percentage — the higher the percentage, the faster the fan speed.

Types of Pulse Width Modulation (PWM) Techniques

Pulse width modulation sign control units typically employ one of three methods: lead edge modulation, trail edge modulation, and pulse center two-edge modulation. Each technique modulates or stabilizes the lead edge and/or the trail edge of the PWM signal to achieve and maintain control of the duty cycle. Below we outline their key characteristics.

Lead Edge Modulation

In the lead edge modulation technique, the lead edge of the signal (i.e., the beginning of the PWM signal) is fixed, while the trail edge (i.e., the end of the PWM signal) is modulated. 

Trail Edge Modulation

In the trail edge modulation technique, the reverse is true. The trail edge of the signal is fixed, while the lead edge is modulated.

Pulse Center Two Edge Modulation (Phase Correct Pulse Width Modulation)

In pulse center two edge modulation—also known as phase correct pulse width modulation—the center of the PWM pulse is fixed while both the lead edge and trail edge are modulated to control the cycle. This technique allows the width of the signal wavelength to be compressed or expanded as necessary.

Why PWM Controls?

PWM control remains a popular method of fan speed control for a number of reasons.

One reason is that motors, DC motors in particular, are very responsive to PWM. They adjust their speed with little lag time after receiving a PWM signal. Another factor is that PWM signals themselves are very fast, especially when few or no computations are required.

Finally, motor responsiveness and innate PWM speed combine to make PWM Controllers extremely efficient, especially in applications that are highly temperature sensitive and require temperature changes to be made quickly.

In addition to the superior compatibility with motor components, responsiveness, and efficiency offered by PWM control units, other advantages include:

  • Greater accuracy. PWM allows for quick and reliable control over motors, ensuring they provide consistent performance in different situations.
  • Smaller risk of overheating. The PWM technique prevents LED components from overheating without sacrificing their brightness levels.
  • Higher input power factor. PWM allows connected systems to achieve a higher input power factor (i.e., the ratio of real power taken in by the load to the apparent power running through the circuit). This quality results in less energy loss.
  • Lower initial costs. Compared to other motor control components, PWM components come with a lower initial investment cost.
  • Better torque generation. When used alongside motors, PWM facilitates the generation of high torque even at lower speeds.

Controls at PTI

PTI has worked diligently over the years to master all aspects of fan and motor design and production. This includes a deep knowledge of fan speed signal controls, PWM and others. 

To learn more about pulse width modulation signal controls, as well as other types of signal controls, download our eBook, “How to Select a Cooling Fan,” for free today.

How to select a cooling fan eBook