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Power Supply Designed for Power Factor Correction And Availability

IP.com Disclosure Number: IPCOM000099673D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 115K

Publishing Venue

IBM

Related People

Kress, JE: AUTHOR [+2]

Abstract

This article describes a power supply design which has a power factor greater than ninety percent while yielding greater operating availability.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Power Supply Designed for Power Factor Correction And Availability

       This article describes a power supply design which has a
power factor greater than ninety percent while yielding greater
operating availability.

      The power supply design of this disclosure is shown in Fig. 1.
Bridge B1 supplies energy to capacitors C1 and C2. Capacitor C1
supplies high frequency (100 to 200 kHz) switching current and
reduces bridge current harmonics, as Fig. 2 illustrates.  Capacitor
C2 charges on V1 peaks because diode D1 isolates capacitor C2 from
bridge B1. Transistors Q1 and Q2 transfer energy from bridge
capacitors C1 and C2 to the output bridge circuits which apply the
energy to load L1.

      Transistors Q1 and Q2 share responsibilities. Referring to Fig.
 3, transistors Q1 operates from time T0 to T1 and T2 to T3.
Likewise, transistor Q2 functions from T1 until T2.  Both operate
alternately throughout all 60 cycle periods and switch between 100
and 200 kHz.  This division of labor allows transistor Q1 to draw
energy from bulk capacitor C2 rather than from the bridge of
capacitor C1.

      This action reduces the current required from bridge B1 when
the bridge voltage V1 dips.  Further, transistor Q2 operates when V1
is high and produces the current waveform given in Fig. 4.  Combining
Fig.  4 with the charging current for capacitor C2 yields a rough
approximation of the bridge current.  This current waveform
calculates to a .85 power factor.  Capacitor C1 and the manner in
which transistors Q1 and Q2 switch, further improves the power factor
above the .9 requirement.

      Capacitor C1 removes the edges from the current waveform in
Fig.  4.  In addition, a rotation between using transistors Q1 and Q2
occurs during these peak current periods so as to reduce the peak
current drawn from the bridge B1 by stealing the needed current from
capacitor C2. This makes the total current from the bridge B1 more
sinusoidal and gives a power factor above .9.

      Additional power factor correction can be achieved by placing
an inductor in series with diode D1.

      A side effect resulting from switching between transistors Q1
and Q2 allows balancing the power load felt by each device.  Should
one device get hotter than the other, the poin...