SEN012 Datasheet, PDF (4/8 Pages) Power Integrations, Inc. – Zero Loss High Voltage Sense Signal Disconnect IC

SEN012-013
Application Example
SENZero in PFC Bus Voltage Feedback Network
VCC
Commercial PFC IC’s typically has a pin dedicated for sensing
the output voltage of the PFC Stage. The information on this
pin is typically used by the PFC IC for various major functions.
SENZero
ON
1. Output regulation – input to the non-inverting input of the
OFF
OFF
error amplifier
ON
2. OVP detection - input to the OVP comparator
PFC
3. Open loop protection – used to detect open loop conditions
OFF
OFF
The last 2 functions were used for protecting the bus from
overvoltage condition.
PI-6205-102510
Figure 11. Timing between PFC IC and SENZzero during Power-up and
Power-Down.
PFC V_OUT
In case of shared VCC Connection, it must be ensure that
SENZero have a lower turn-on and turn-off threshold voltage
compared to the PFC IC.
C_BULK
R1
R2
R3
SENZero
Switch
FB
R_FB
Figure 10. PFC Bus Voltage Sense Network.
PFC IC
OLP
OVP
Error Amplifier
PI-6203-102510
PS_(ON)
ON
OFF
ON
SENZero
OFF
ON
PFC
OFF
OFF
OFF
OFF
PI-6206-102510
Figure 12. Timing between PFC IC and SENZero with PS_(ON) Signal.
From off-state to on-state, SENZero must turn-on ahead of the
PFC. From on-state to off-state, PFC must shutdown ahead of
the SENZero. This is to ensure that whenever PFC is operating
(switching), SENZero is invincible to the PFC. SENZero only
disconnects the sense resistors when PFC is in off-condition
and thus eliminates its associated losses during standby
condition.
The SENZero objective is to eliminate the losses associated
with the sense resistors without affecting the functionality of the
circuit. To keep the operation of the PFC IC unaffected,
SENZero and PFC on and off event must follow the required
timing sequence during power-up, power-down, remote-on,
and remote-off event.
4
Rev. B 11/05/10
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