ADP1048 Analog Devices, ADP1048 Datasheet - Page 14

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

ADP1047/ADP1048
CURRENT BALANCING (IBAL PIN,
The
in each interleaved phase when operating in interleaved PFC
topology. This ensures that each interleaved phase provides equal
power regardless of the tolerance of the inductor and the boost
switch driving circuitry.
The input is through the IBAL pin specifically provided for the
ADP1048. The current balancing circuit monitors the current
flowing in both switches of the interleaved PFC topology and
stores this information. It compensates the PWM signals,
ensuring equal current flow to balance the current between
interleaved phases. Several switching cycles are required for
the circuit to operate effectively. The current balance settings
are programmed in Register 0xFE43 and Register 0xFE95.
VOLTAGE SENSE
Voltage sensing is used for the control, protection, and monitor-
ing of the PFC stage. Input and output voltages are sensed using
dedicated ADCs and references (see Figure 11).
ADP1048
IBAL
ADP1048
VAC
Figure 10. Current Balancing (IBAL) for the
V
11-BIT
REC
ADC
Figure 11. Typical Voltage Sense Configuration
+ –
has a dedicated circuit to maintain current balance
PGND
PGND
PWM
11-BIT
180° TO 360°
+ –
ADC
0° TO 180°
VFB
ADC
ADC
PWM2
+
–
OLP
ADP1047/ADP1048
V
OUT
PWM
OVP
+ –
OVP
ADP1048
OUTPUT OF PFC
CURRENT LOOP
K
ADP1048
7-BIT
DAC
ONLY)
Rev. 0 | Page 14 of 84
The voltage sense can be calibrated digitally to remove any
errors due to external components (see the Output Voltage
(VFB) Calibration and Trim section). This calibration can
be performed in the production environment; the settings
are saved in the EEPROM of the ADP1047/ADP1048.
Input Voltage Sensing (VAC Pin)
The VAC pin is used for the monitoring and protection of the
rectified power supply input voltage. The sense point on the
power rail requires an external resistor divider to bring the signal
within the operating input range of the ADC (0 V to 1.6 V).
This scaled-down signal is fed into a high speed Σ-Δ ADC.
The output of the Σ-Δ ADC goes to the digital filter and is used
for the following purposes:
•
•
Output Voltage Sensing (VFB Pin)
The VFB pin is used for the control, monitoring, and protection
of the output voltage. This voltage is the main feedback loop for
the power supply control loop. The sense point on the power rail
requires an external resistor divider to bring the signal within the
operating input range of the ADC (0 V to 1.6 V). This scaled-
down signal is fed into a high speed Σ-Δ ADC.
The output of the Σ-Δ ADC goes to the digital filter and is used
for the following purposes:
•
•
To reduce the current distortion from the output voltage feed-
back, a prefilter is implemented before the voltage loop filter.
The prefilter detects the zero-crossing point of the input voltage
to identify the half input line cycle. The prefilter then performs
an averaging function for the sampled VFB signal during this
half line cycle. In this way, the fundamental frequency of the
output bulk voltage ripple and its harmonics are significantly
attenuated.
The output is decimated at the switching frequency for the
control loop. The effective number of bits (ENOB) is >7
when the current loop bandwidth is 10 kHz; the ENOB
is >10 when the current loop bandwidth is 1 kHz.
The 11-bit result is calculated and updated at each half line
cycle for high accuracy input voltage and power monitoring.
The 11-bit result is used at each half line cycle for the
normal control loop to control the value of the output
voltage.
The 10-bit, 1.5 kHz update rate is used for the fast voltage
control loop to control the value of the output voltage
during large transients.
Data Sheet