PFS704 POWERINT [Power Integrations, Inc.], PFS704 Datasheet - Page 8

• Manufacturer Part Number: PFS704
• Description: High Power PFC Controller with Integrated High-Voltage MOSFET
• Manufacturer: POWERINT [Power Integrations, Inc.]

to decay the power MOSFET on-time to zero. At peak power
(V
internal error-voltage is held at 0 V for as long as the input peak
voltage is below the brown-in (I
error-voltage controlled slew to 0 V gradually reduces the switch
on-time to zero to deplete energy stored in the boost choke as
well as input EMI filter for power-down. Once the error-voltage
reaches zero volts the controller is effectively in an off-state
(gated by 5 ms timer) and will restart once all the conditions of
soft-start are satisfied.
The brown-out threshold is reduced to I
the FEEDBACK pin exceeds approximately 5.8 V. Temporarily
reducing the brown-out threshold prevents false turn-off at high
power start-up when the voltage drop across the input bridge
rectifier and filter stage may cause the rectified input to sag
below the brown-out threshold.
Fast Output Voltage Overvoltage Protection (FB
The FEEDBACK pin features a means to detect an output
overvoltage condition through the FEEDBACK pin and disables
the power MOSFET until the sensed output voltage falls below
the FB
the controller from falsely triggering this mode. An FB
excess of the 2 ms delay will terminate the switch cycle immediately.
This detection circuit also includes some hysteresis.
Output Voltage Undervoltage Protection (FB
The FEEDBACK pin features an undervoltage detection to
detect an output overload or a broken feedback loop. If the IC
detects the falling edge on the FEEDBACK pin that has fallen
below FB
and reinitiate the start-up sequence. Similar to the FB
detection, this mode has a deglitch filter of approximately 100 ms.
VCC Undervoltage Protection (UVLO)
The BIAS POWER (VCC) pin has an undervoltage lock-out
protection which inhibits the IC from starting unless the applied
V
soft-start once the VCC pin voltage exceeds the V
After start-up the IC will continue to operate until the VCC pin
voltage has fallen below V
voltage of the VCC pin is 13.4 V which must be externally limited
to prevent damage to the IC.
Over-Current Protection
The device includes a cycle-by-cycle over-current-protection
(OCP) mode which protects the device in the event of a
catastrophic fault. The OCP mode in the PFS704-716 is input
line dependent as shown in Figure 10. The intention of OCP in
this device is strictly protection of the internal power MOSFET
and is not intended to protect the converter from output
short-circuit or overload fault conditions.
The PFS704-716 controller latches the high line OCP for a 1/2
line cycle and updates the OCP status after the expiration of a
5 ms block-out timer. This feature has particular benefit for
hard-start after an AC line cycle drop where the peak detector
may falsely detect a low input line condition even though the
input is at high input line.
Rev. D 12/11
CC
E
~5 V) the shutdown time will be approximately 5 ms. The
8
voltage is above the V
OV
threshold. A deglitch filter (~2 ms) is used to prevent
UV
PFS704-729EG
threshold, it will turn-off the internal power MOSFET
CC+
CC-
level. The absolute maximum
threshold. The IC initiates a
UV+
) threshold. The internal
UV-SS
during start-up until
UV
)
CC+
OV
OV
)
threshold.
OV
event in
Figure 10. Line Dependant OCP.
The leading edge blanking circuit inhibits the current limit
comparator for a short time (t
turned on. This leading edge blanking time must be set so that
current spikes caused by capacitance and rectifier reverse
recovery time will not cause premature termination of the
MOSFET conduction.
Safe Operating Range (SOA) Mode
Since the cycle-by-cycle OCP mechanism described above
does not prevent the possibility of inductor current “stair-
casing”, an SOA mode is required. Rapid build up of the device
current can occur in event of inductor saturation or when the
input and output voltages are equal (non or very short
inductor reset time).
The SOA mode is triggered whenever the device reaches
current limit (I
The SOA mode forces an off-time equal to t
internal error-voltage (V
value.
Open FEEDBACK Pin Protection
The FEEDBACK pin also features a static current of I
continuously sourced out of the pin to protect against a fault
related to an open FEEDBACK pin. The internal current source
introduces a static offset to the output regulation which must be
accounted for in selecting the output feedback regulation
components.
Hysteretic Thermal Shutdown
The thermal shutdown circuitry senses the controller die
temperature. The threshold is set at 118 °C typical with a 50 °C
hysteresis. When the die temperature rises above this threshold
(118 °C +8/-7 °C), the power MOSFET switching is disabled and
remains disabled until the die temperature falls by ~50 °C, at
which point the device will reinitiate a soft-start and start-up
sequence.
I
I
V
V
< 48 µA
> 59 µA
OCP
) and the on-time is less than t
~140 VAC
E
) down to approximately 1/2 of its set
LEB
) after the power MOSFET is
PFS704-716
~170 VAC
PI-5470-110810
OCP
www.powerint.com
SOA
and pulls the
.
FB
that is
V
IN