Part # AN667 datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics


Part Details:

® APPLICATION NOTE DESIGNING A HIGH POWER FACTOR SWITCHING PREREGULATOR WITH THE L6560/A TRANSITION MODE I.C. by G. Comandatore and U. Moriconi Active power factor correction techniques are going to grow in conversion applications. Market inter-est (legislation to be considered) is also moving towards fairly low (36-150W) conversion powerranges (lighting, monitor).This paper describes an "easy to use" 8 Pin Controller that allows the realization of very low cost off-line Power Factor Correction. Introduction Switching at a frequency much higher than theline, the preregulator draws a half-sinusoidal input Conventional AC to DC converters employ a full current, in phase with the line voltage. BOOST wave rectifier bridge with a simple capacitor filter TOPOLOGY with its inductor at the input is well to draw DC power from the mains AC. This filter suited for PFC application. The input di/dt is low capacitor must be large enough to supply the total because the inductor is located between the power during most of each half-cycle while instan- bridge and the switch. This minimizes line noise taneous line voltage is below the DC output volt- and, in addition, the line spikes can be absorbed age. With this bulk capacitor filter, the line current by the Boost Inductor. waveform is a narrow pulse. Consequently thepower factor is poor (0.5-0.6) due to high har-monic distortion of the current waveform. L6560/A PFC controller Integrated Circuit With a high power factor switching preregulator, The L6560/A is an integrated circuit in Minidip interposed between the input rectifier bridge and and SO8 packages designed to perform the con- the bulk filter capacitor, the power factor will be trol of active power factor correction circuits. The improved (up to 0.99). The current capability in- I.C. is optimized for electronic ballast, but it can creased, the bulk capacitor peak current and the be easily used in switched mode AC-DC conver- harmonic disturbances are reduced. sion. It can directly drive Mosfet or Igbt (see blockdiagram fig.1). Figure 1: Block Diagram Obsolete Product(s) - Obsolete Product(s) AN667/1003 1/11 APPLICATION NOTE The on chip features are: lows the feedback for the boosted output DC volt- · age regulation. The E/A output will be connected Undervoltage lockout with hysteresis and to the compensation capacitor (see biasing of micropower start-up. I.C.) to filter the twice rectified mains frequency · Stable error amplifier. (2f) so that the circuit doesn t attempt to regulate · Output overvoltage protection. the output ripple. · Transition Mode Operating

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