UC3854DWG4

Technology Brief
           Technology Brief 1 SLUA263 AC Requirements for Power Factor Correction Circuits John Bottrill Systems Power ABSTRACT This technical brief identifies the recommended range of IAC for each of the devices within the UCC3854 family of PFC controllers. The family of UC3854, UC3854A/B, and UC3855A/B power factor correction controllers use three parameters to control the power drawn from the AC power lines; the output voltage of the converter, the input RMS voltage, and the instantaneous input voltage as represented by the instantaneous current into the control chip (IAC). These inputs generate a current at the output of the arithmetic (multiplier) unit that represents the desired input current. There are many documents describing these devices written by several different authors but because the designers/authors do not use the same criteria for selecting the IAC levels, there is some level of confusion. For example, the design of the UC3854A multiplier is optimized for a peak IAC of 250 µA, but in order to get a better signal to noise ratio, it is sometimes desireable to increase the current as high as 500 µA. The values listed in Table 1 are intended to clear up any confusion and has been expanded to included other PFC controllers including some soon-to-be-released devices. Table 1. Recommended Device Family Current Settings MINIMUM IAC (µA) AT MAXIMUM VIN MAXIMUM IAC (µA) AT MAXIMUM VIN “NOT TO EXCEED” LEVEL (µA) UC3854 250 500 750 UC3854A/B 250 500 750 UC3855A/B 250 500 700 UCC3817/18/19 250 500 700 UCC38500/1/2/3 250 500 700 UC3853 250 500 750 UCC38510–517 250 500 750 DEVICE FAMILY 2 AC Requirements for Power Factor Correction Circuits IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third–party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright  2002, Texas Instruments Incorporated