Power Factor Corrected preregulator (PFC), using the L, and the lamp ballast stage with the L Referring to the application circuit (see fig.1), the AC mains voltage is rectified by a diodes bridge and delivered APPLICATION NOTE. The front-end stage of conventional off-line converters, typically made up of a full wave rectifier bridge with a capacitor filter, gets an unregulated DC bus from the. AN APPLICATION NOTE. May INTRODUCTION. Half bridge converter for electronic lamp ballast. Voltage fed series resonant half bridge inverters are.
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A large output capacitance will reduce its amount.
High-PF Flyback characteristic functions: In fact, the amplitude of the higher order even harmonics is much smaller and the impedance of the capacitor decreases with frequency as well. R 2 The blocking diode will be not only a very fast recovery type but will also feature a very fast turn-on time. Multiplier Bias and Sense Resistor Applcation A resistor divider feeds a portion of the input voltage into pin 3 MULT to build the sinusoidal reference for the peak primary current.
There are, on the other hand, some drawbacks, inherent in high-PF topologies, limiting the applications that such a converter can fit AC-DC adaptors, battery chargers, low-power SMPS, etc. In this context a popular configuration see fig. The total RMS value of the primary current, useful for power loss estimate on the primary side, is calculated considering the RMS value of each triangle of Ip t and averaging over a line half-cycle: To calculate the amplitude of mote component, only the fundamental harmonic of 11at twice line frequency, will be taken into account.
Minimum Transformer AP required for a assumptions: Clamp network The overvoltage spikes due to the leakage inductance of the transformer are usually limited by an RCD clamp network, as illustrated in fig.
In fact, the nite current is quite small and it is possible to neglect the contribution due to the dynamic resistance. Design tips for L power factor corrector in wide range. Moreover, additional considerations concerning the assembly are needed for meeting safety requirements, maximising magnetic coupling and minimising parasitic high frequency effects, not to mention the constraints imposed by the specific application, if any.
Still under the assumption of an ideally sinusoidal input voltage, the THD is related to the Power Factor by the following relationship: Tools and Software Development Tools. Flyback converters with the L PFC controller. H2 Kv Iout 0.
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ESR The second component of the ripple is related to the twice line frequency envelope and, unlike the high frequency component, depends on the capacitance value, while the ESR contribution can be neglected. Among the various configurations that an Lbased flyback converter can assume, the high-PF one is particularly interesting because of both its peculiarity and the advantages it is able to offer.
Multiplier bias and sense resistor selection Assuming a peak value of 2. This considering, the transfer function of the multiplier block will be: The optional capacitor in the? This minimum typically, 0.
Kv Formula 17 assumes that the maximum peak flux density inside the core is limited by core saturation and that all transformer losses are located in the alplication 18 assumes that core losses limit the flux swing and the total dissipation are half due to core losses and half to windings losses. Inserting 14 and 15 in 13 nohe the theoretical expression of PF note that it depends only on Kv.
A compromise will then be found between these two contrasting terms. This value, which will occur at maximum mains voltage, should be 2.
An966 Application Note L6561, Enhanced Transition Mode Power Factor Corrector
F2 Kvmin The capacitor undergoes large current spikes and therefore it should be a very low ESR type with polypropylene or polystyrene film dielectric.
The steady-state power dissipation is estimated to be about 2W.
The effect of that on the overall operation is however negligible because the energy processed near a zero-crossing is very little. Speeding up the control loop may lead to a compromise between a reasonably low output ripple and a PF still reasonably high; q poor transient response: Since in closed-loop operation the quiescent value of VE will be in the neighbourhood of 2.
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As a result of the first two assumptions, the peak primary current is enveloped by a rectified sinusoid: To have a low gain at twice line frequency, the zero of H s will be placed below Hz and R3 will be 45 times less than R1.