Deployment of smart meters is in full swing worldwide. Traditionally, consumers like me and you pay only for the kWh (kilowatt-hour) we consumed to power all the electrical equipment in our homes – from air conditioners to internet-enabled, big-screen HDTVs, etc. However, for all equipment without Power Factor Correction (PFC), the energy draw from the electrical outlet is, in fact, much higher and represented by the kVAh (kiloVoltAmp-hour). The cost of the difference is graciously borne by our friendly, neighborhood utility company.
Smart meters can measure both the kWh we consume and kVAh that the utility company generates and delivers in the first place. Beware - these smart devices are in a position to expose our bad consuming habits. We’d better get that Power Factor corrected quick, lest the utility companies get smart and decide to come at us with vengeance for their pound of flesh.
One way to protect ourselves form this vengeance is using TI’s brand new power factor correction controller, UCC28180. It operates in Continuous conduction mode which lends itself to a wide range of power levels, from a few-100Ws to several-kWs, and can thus be applied to a broad variety of equipment in home and office such as TVs, air-conditioners, wide-area lighting, projectors, workstations and in industrial/IT infrastructure environments such as power supplies for process automation, programmable logic controllers, datacenter servers in networking/telecommunication, cellular base-stations and many more.
Achieving power factor correction using the UCC28180 falls into the category of “Active” PFC control versus “Passive” PFC control.
“Active” PFC control uses a switch mode power converter. “Passive” PFC control involves simply inserting passive electrical components, our good old inductors and capacitors, at the front end of electrical equipment.
Although component count may be higher, there is huge savings in overall equipment cost, size and weight by moving from passive PFC control to active PFC control. A classic example is in a commercial multi-kW air-conditioner (A/C). In this instance, the size and weight of the passive PFC inductor is so huge, the manufacturers had to bolt it to the chassis and add a wire harness to connect it to rest of the electronics driving the main compressors and motors. Adopting an active PFC approach utilizing high-frequency switching, the size and weight of the inductor shrink manifold resulting in reduced magnetics cost. Furthermore, from a mechanical design perspective, the inductor could be mounted directly onto the main electronics board, thus reducing special assembly costs.
The UCC28180 can operate down at a conveniently low switching frequency of 18kHz which facilitates using efficient, high-current IGBT power switches delivering superior performance compared to power MOSFETs in the multi-kW range.
At the same time, with novel power devices such as SiC MOSFETs and GaN HEMTs on the horizon, the UCC28180 supports switching frequencies as high as 250kHz allowing you to harness the promise of these wide band-gap power semiconductors to achieve the 50+W/in3, 98+% peak efficiency holy grail of power supplies.
Total Harmonic Distortion (THD) is a much desired performance metric these days, in the context of power factor correction controllers. Simply put, this parameter represents what fraction of the fundamental AC input line current harmonic (47-63Hz) is represented by all the rest of the harmonics combined. Measured as a % of the fundamental harmonic, the goal is to keep this metric as low as 5-10%, especially when the equipment is consuming significant power, understood as 50% to 100% of nameplate power rating.
Related post on THD in LED lighting: How to reduce total harmonic distortion to below 10%
In equipment powered by uninterruptable power supplies (UPS), the need for low THD may extend down to even 10-20% of nameplate power rating if the equipment tends to dwell at these load conditions for a prolonged period. This is due to the fact that UPS face a difficult task of delivering a well regulated AC output under a high THD load. A classic example of this situation is a datacenter server power supply running off a UPS, where the server would be idling at these ‘light’ load conditions for several hours during night time, when businesses and offices are closed.
With the analog PFC controllers available in the industry today, low THD is achievable when a strong current sensing signal is supplied to the device. However, a strong current sense signal, especially at light loads, implies designing with big shunt resistors to measure the input AC current, which penalizes by dissipating more power (IRMS2R). By using the UCC28180 with internally trimmed precision current loop circuits, you can achieve THD as low as 5% with shunt resistance that is 50% smaller than what is employed by devices in the industry today, enabling truly high-performance power factor correction converters. So, better get that Power factor corrected with UCC28180!
For more on the UCC28180 - download datasheet, order samples, order EVM
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