ADP1048 Analog Devices, ADP1048 Datasheet - Page 22

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

ADP1047/ADP1048
SOFT START PROCEDURE
The PSON signal is used to enable or disable the PFC stage.
After PSON is asserted, the
ing VAC and, if the ac line conditions are met, they initiate the
soft start procedure, as shown in Figure 21.
Startup is gated by the rms value of the ac line voltage measured
on one half period of the ac line frequency. When VAC is above
the VIN_ON value, the BROWN_OUT flag is reset and the soft
start sequence is initiated. At the same time, the inrush delay
time and soft start delay time timers begin. Both of these timers
can be programmed to count 0 to 7 line cycles (or 0 to 14 half
line cycles in steps of 2).
After the inrush delay time programmed in Register 0xFE2E,
Bits[2:0], the INRUSH flag is reset and the inrush signal (Pin 17)
is asserted, closing the inrush current relay. (Note that the INRUSH
flag is active low.) The inrush signal is set at the zero crossing of
the ac voltage, if this crossing is detected. This setting allows
zero voltage turn-on if a solid-state switch is used (zero voltage
turn-on is not relevant with mechanical relays).
After the soft start delay time (programmed in Register 0xFE2D,
Bits[5:3]), the output voltage is ramped up according to the soft
start time programmed in Register 0xFE2D, Bits[2:0].
Some of the flags can be blanked during soft start so that the
programmed action of the flag does not take place if the flag
is set during the soft start period (see Register 0xFE08 and
Register 0xFE09).
BROWN_OUT FLAG
(REG 0xFE80[2])
VIN_LOW FLAG
(REG 0x7C[3])
INRUSH PIN
ADP1047/ADP1048
VOUT
VAC
VIN_OFF (REG 0x36)
VIN_ON (REG 0x35)
Figure 21. Soft Start and Inrush Current Control Timing
start monitor-
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(REG 0xFE2E[2:0])
DELAY TIME = 2
INRUSH
(REG 0xFE2D[5:3])
DELAY TIME = 3
SOFT START
When output voltage regulation is reached and all flags are OK, the
POWER_GOOD# flag is reset and the PGOOD signal (Pin 16)
is set to Logic Level 1. (Note that the POWER_GOOD# flag is
active low.)
The soft start time can be programmed to one of eight values:
112 ms, 168 ms, 224 ms, 280 ms, 392 ms, 504 ms, 616 ms, or
728 ms (set in Register 0xFE2D, Bits[2:0]).
The soft start delay time (Register 0xFE2D, Bits[5:3]) can be
programmed from 0 to 7 full line cycles in increments of 1
(that is, two of the rectified half line cycles).
The inrush delay time (Register 0xFE2E, Bits[2:0]) can be pro-
grammed from 0 to 7 full line cycles in increments of 1 (that is,
two of the rectified half line cycles).
If no zero crossings are detected, the programmed maximum ac
line period, MAX_AC_PERIOD_SET (Register 0xFE28), is used.
LINE FAULT PROTECTIONS
Line faults occur when the ac line is not behaving correctly
and include anomalies such as a missing ac line cycle (can be
partial), brownout, or high distortion levels. When a line fault
occurs, the
according to the situation.
ADP1047/ADP1048
SOFT START TIME
(REG 0xFE2D[2:0])
can be programmed to react
Data Sheet