The advantages of having a power factor corrector in MEAN WELL products


One of the essential factors when choosing a power source is the presence of a power factor corrector (KCM), or power factor correction (PFC) in English notation. The power factor characterizes the quality of energy consumption from the AC power supply network, and the lower the value of the power factor, the worse the quality of consumption.

As is known from the course of electrical engineering, the total power in an alternating current circuit is defined as a vector between active power and reactive power:

Соотношение мощности в цепи переменного токаThe power ratio in the AC circuit

The power factor is the cosine of the angle between the active power (lower catheter) and the full power (hypotenuse) – the sharper this angle, the higher the cosine value and the lower the reactive power. There are several different ways to reduce reactive power, for example, using special filters that balance different loads in order to minimize or eliminate phase shift between voltage and flowing current. This approach is a passive way to correct the power factor.

For switching power supplies, the method of using active power factor correction has become reliable and well–proven - through the use of power semiconductors that ensure the flow of current synchronously (in one phase) with a change in the voltage of the power supply network. In this case, the load behaves almost like a resistive load and losses on reactive power are minimal.

Влияние корректора коэффициента мощности на форму токаThe effect of the power factor corrector on the shape of the current

Depending on the power supply capacity, its purpose and efficiency, various power factor correction methods are used in a number of series of MEAN WELL power supplies. Active power factor correctors of one or two stages have become the most widespread. The comparative features are presented in the table:

KKM topology AdvantagesDisadvantagesLimitations
One stage
  • Low manufacturing cost
  • Low design complexity
  • High efficiency
  • Large ripples make it difficult to optimize the feedback loop
  • The power factor is average (higher than for passive KKM)
  • Without delay, the output (noise and ripple) will depend directly on the AC network
  • Higher output current ripples
  • Slow feedback that is affected by a change in load
Two stages
  • Applicable for high-power power supplies
  • The highest value of the power factor
  • Easily configurable to compensate for feedback
  • Good performance when changing the load
  • The cost of manufacturing is higher
  • Increased design complexity
  • It can be used in various environments, just like a conventional power supply. There are no special restrictions.

How the two-stage power factor corrector works is best illustrated by the example of a block diagram of a switching power supply on a DIN rail of the SDR-960 series:

Корректор коэффициента мощности две стадии на примере SDR-960Two-stage power factor corrector using the example of SDR-960

The two stages are characterized by the connection of the power factor corrector (PFC) with the PWM control driver of the power semiconductor controller (highlighted in red), which allows you to optimize current consumption from the power supply network with the load consumption current at the output of the power source. A two-stage power factor corrector is most often found in medium and high-power high-efficiency power supplies.

Thus, the following advantages of having a power factor corrector in switching power supplies can be distinguished:

  1. The load in the power supply circuit is as close as possible to the resistive one, that is, the most complete consumption of electricity occurs with minimal power losses. In other words, more electricity consumers can be "suspended" on the allocated connection power and get its more efficient use (increase energy efficiency).
  2. In a three-phase power supply network, with an active load, the currents flowing in the lines coincide in phase with the phase voltage, therefore there is no skew in the sum of the reverse currents in the neutral, respectively, overheating does not occur in it, and the danger of "zero burnout" is minimized.
  3. The electromagnetic compatibility of various devices connected to the power supply network is improved. At active load, the harmonic components of the flowing current are significantly smaller than in circuits with a phase shift between voltage and current, plus the shape of the flowing current is as close as possible to harmonic, therefore there is less interference in the power supply network, and fewer additional measures are required to filter the input voltage.

The disadvantage of having a KKM is only one – since this is an additional node in the power supply circuit, then, accordingly, the cost of the power supply unit (in general) is slightly higher than without a KKM, all other things being equal. But this difference does not outweigh the benefits that are provided by having a power factor corrector in the power supply.

Taking into account these advantages, the MEAN WELL company includes a power factor corrector in most switching power supplies of its production – the RSP, HRP, UHP, MSP series. A complete selection of switching power supplies with a case-type power factor corrector is presented on our website.

For advice or clarification of information on MEAN WELL power supplies, please contact us by e-mail .