ADP1048 Analog Devices, ADP1048 Datasheet - Page 17

• Manufacturer Part Number: ADP1048
• Description: Digital Power Factor Correction Controller with accurate AC Power Metering
• Manufacturer: Analog Devices

Data Sheet
POWER FACTOR CORRECTION CONTROL LOOP
The
power factor correction control loop using a traditional multi-
plier approach. The implementation of the loop is digital, and
all the signals are converted from analog to digital before they
are processed by the control loop. Σ-Δ ADCs are used to achieve
high performance, cost-effective implementation. Each ADC
has its own dedicated voltage reference.
DIGITAL COMPENSATION FILTERS
The
monitoring. They are implemented in the digital domain using
a dedicated state machine, which allows the user to program the
loop response specifically, with no need for external loop
compensation.
The detailed control loop configuration is illustrated in Figure 14.
V
back voltage of the output. The difference between V
is processed first by the voltage loop filter (H
is then multiplied by the instantaneous rectified input voltage,
V
I
the current loop filter (H
mathematical expression is
Both the voltage loop and current loop digital compensating
filters, H
function in the digital domain is
where:
a is the filter zero.
b is the filter gain.
k is related to the switching frequency.
Table 8. Summary of the PFC Digital Compensation Filters for Soft Start
Line Filter
High Line
Low Line
REF
REF
AC
, is used as the reference signal for the current. The output of
, and divided by the square of the rms value of V
ADP1047/ADP1048
ADP1047/ADP1048
is the digital reference voltage setting; V
I
H(z)
REF
V
(z) and H
=
=
V
k
V
EA
×
AC
2
×
b
_ RMS
×
V
AC
I
(z), are programmable. The filter transfer
⎛ −
⎜
⎝
z
(
z
are digital PFC controllers with ac power
−
I
256
implement the average current mode
) is the duty cycle command. The
1
a
)
Normal Compensation Filter
Low line current filter, normal voltage filter
High line current filter, normal voltage filter
⎞
⎟
⎠
V
REF
V
+
FB
FB
–
V
is the sensed feed-
). Its output, V
AC
H
. The result,
REF
V
Figure 14. Control Loop Digital Filters
(z)
and V
V
2
AC_RMS
V
V
EA
Rev. 0 | Page 17 of 84
AC
EA
FB
,
I
REF
+
I
L
The frequency gains and zero locations can all be programmed
individually to tailor the loop response to the application. It is
recommended that the Analog Devices, Inc., GUI software be
used to program the filter (see the Software GUI section). The
GUI displays the filter response in Bode plot format and can be
used to calculate all stability criteria for the power supply.
Optimized Compensation Filters
Instead of a single programmable compensation filter, the
ADP1047/ADP1048
the dynamic response of the control loop can be tailored to
optimize different operating conditions.
•
•
•
The
matically between the high and low line filters when the rms
value of the ac line crosses the programmed threshold between
the high and low lines. (The high line threshold is programmed
in Register 0xFE35; the low line threshold is programmed in
Register 0xFE36.)
The
voltage at each half line cycle. When a transition between the
high and low line threshold is detected, the part waits for four
full line cycles before switching to the correct filter at the zero
crossing of the input line cycle. This is done to avoid spurious
transitions due to a missing or distorted voltage line cycle.
During soft start, one of four combinations of filters can be
used, depending on whether the fast loop mode is enabled
and whether the high line or low line is detected for soft start
(see Table 8).
–
ADP1047/ADP1048
ADP1047/ADP1048
Low line current filter
High line current filter
Fast voltage compensation filter
H
I
(z)
Fast Voltage Compensation Filter
High line current filter, fast voltage filter
Low line current filter, fast voltage filter
DUTY CYCLE
offer the following filter presets so that
can be configured to switch auto-
check for the value of the rms input
ADP1047/ADP1048