AN349: Migrating from the L6562 to the CS1601 Power Factor Correction IC

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1 Smaller Boost Inductor The CS1601 has a digitally implemented variable-frequency, discontinuous conduction mode (VF-DCM) -based algorithm that permits delivering the same power and the same peak current ratings with a significantly smaller inductance. In traditional analog solutions, placing capacitors at the output of the bridge rectifiers increases THD, especially at light-load conditions and high line voltage. IF THE CUSTOMER OR CUSTOMER'S CUSTOMER USES OR PERMITS THE USE OF CIRRUS PRODUCTS IN CRITICAL APPLICATIONS, CUSTOMER AGREES, BY SUCH USE, TO FULLY INDEMNIFY CIRRUS, ITS OFFICERS, DIRECTORS, EMPLOYEES, DISTRIBUTORS AND OTHER AGENTS FROM ANY AND ALL LIABILITY, INCLUDING ATTORNEYS' FEES AND COSTS, THAT MAY RESULT FROM OR ARISE IN CONNECTION WITH THESE USES. Placing capacitors at the input side of the bridge reduces PF since the EMI capacitor swings to twice the input voltage. The advantages were demonstrated in an equivalent comparison by retrofitting an existing ballast product designed with the L6562 with the CS1601. 1 Ballast Specifications & Requirements - Input Voltage Range: 108V to 305V 50/60Hz - Output Load: 2x T5HO lamps amounting to ~108W nominal - Link capacitor: 2x 47uF, 250V caps in series - Low THD (<10%) - High Power Factor (>0. This eliminates the need for expensive AC capacitors and reduces overall bill of material (BOM) cost. In the CS1601-based ballast, the link voltage does not go above 492 V, which is the voltage threshold for the over voltage protection (OVP). The selection of inductor shifts the frequency profile across load conditions and line voltages. 4 1% Over Current Protection Over Voltage Protection Over Temperature Protection Open /Short Circuit Protection Brownout Protection Vcc Under Voltage Lockout Over Power Protection 9 9 9 8 8 9 8 9 9 9 9 9 9 9 5. - The EXL Core™ signal processing core computes the correct Ton, Toff, and switching frequency for the measured line and link voltages and programmed PID coefficients. The CS1601 offers optimal performance with minimal design constraints. Cirrus Logic, Cirrus, and the Cirrus Logic logo designs are trademarks of Cirrus Logic, Inc. It is important that the capacitor be at close to the pins as possible. The frequency of operation across the line voltage is shown in Figure 8. 1 Footprint Compatibility The CS1601 is packaged in the industry-standard 8-pin SOIC and is footprint-compatible with the L6562. CS1601 Block Diagram The basic principle of operation of the L6562 can be summarized as follows: - The L6562 is a CRM controller which sets a peak current reference which is a function of the line voltage multiplied with the output of the error amplifier. - The EXL Core turns off the gate once Ton is reached. Because the voltage swing on capacitors on the AC line side of the bridge rectifier is twice that of the capacitors placed on the DC side of the bridge, power factor is reduced. 5 Auxiliary Supply Design There are many ways to design the auxiliary supply