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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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F2 Kv which will assume its maximum value at minimum mains voltage. However, this is true also for a standard flyback; q the system is unable to app,ication with line missing cycles at heavy load unless an exceedingly high output capacitance is used.

From energetic balance, it is possible to write: Timing relationships The ON-time of the power switch is expressed by: Internal Block Diagram of the L Not Recommended for New Design.

An966 Application Note L6561, Enhanced Transition Mode Power Factor Corrector

One is related to the high frequency triangles and depends almost entirely on the ESR of the output capacitor, being the capacitive contribution practically negligible.

These advantages can be summarised as follows: This ripple has two components. Finally, R8 and C2 will be adjusted so that the crossover frequency of the open-loop gain is a good compromise between a high enough PF and an acceptable transient response, ensuring also sufficient phase margin.


IRMS1 can be simply calculated from the numerator of Analysis and design of Minimum Transformer AP required for a assumptions: Besides, to achieve a reasonably high PF, the voltage control loop is slow typically, its bandwidth is below Nlte.

L, enhanced transition mode power factor corrector. It can be advantageous the use of a zener or transil clamp see fig. Primary Current fL time scale 1 0.


In the real-world operation, it must be considered that TON cannot go below a minimum amount applicatipn so will do the switching period as well. 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.

It is advantageous to selects a low IC value e. The steady-state power dissipation capability must be at least: Since the linearity appliction 1. Its maximum amplitude, occurring on the peak of the sinusoid, will be: F2 Kvmin The capacitor undergoes large current spikes and therefore it should be a very low ESR type with polypropylene or polystyrene film dielectric.

An Lbased high-PF flyback converter can easily meet Blue Angel regulations; q additional functions available: The application was actually realised and some experimental results are here presented. Furthermore the start up current has been reduced at few tens of mA and applicafion disable function has been implemented on the ZCD pin, guaranteeing lower current consumption in stand by mode.


The two diodes decouple the capacitor during steady-state operation so that it does not interfere with the loop gain and provide a discharge path when the converter is turned off. C Configurations a and b are basically conventional flyback converters.

STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.

The value of R6 will be such that the twice mains frequency ripple notr on the static VE cannot trip the dynamic overvoltage protection of the L 40? 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: Mains current Right, lower trace: This minimum typically, 0. This would degrade the transient response to line and load changes without any benefit.

Inserting 14 and 15 in 13 yields the theoretical expression of PF note l661 it depends only on Kv. When this minimum is reached, the energy drawn each cycle exceeds the short-term demand from the load, thus the control loop causes some cycles to be skipped so as to maintain the long-term energy balance.