UCC28630 Datasheet, PDF (35/68 Pages) Texas Instruments – High-Power Flyback Controller with Primary-Side Regulation and Peak-Power Mode

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UCC28630
SLUSBW3A – MARCH 2014 – REVISED MARCH 2014
8.3.15 Terminal-Fault Detection and Protection
The controller includes protection against most practical terminal faults. These faults include open terminals,
terminals shorted to adjacent terminals, terminals shorted to GND and terminals shorted to VDD. The device
performs terminal fault checking at start-up, before the PWM is enabled. Table 3 summarizes the response to
terminal faults. Most faults cause either a latched shut-down, or failure to start-up.
A short-circuit from the HV terminal (terminal 8) to the VDD terminal (terminal 6) is unlikely to occur, because
terminal 7 is not included in the package. The HV terminal and tracking requires additional PCB spacing in any
event to meet creepage requirements. However, if such a fault does occur, the device continues to charge the
VDD capacitor through the HV terminal external series resistor, and the power supply starts up and appears to
operate normally. But because the HV and VDD terminals are shorted, the internal HV current source cannot
switch-out the external HV resistor, so it always dissipates power. This condition results in a large increase in no-
load standby power. A 200-kΩ external HV resistor, dissipates 66 mW at 115 V_AC, and 265 mW at 230 V_AC. At
load levels where the X-capacitor discharge function is operational, the short to VDD appears to be an AC-
disconnect event, and causes the device to cycle on and off.
TERMINAL
NAME
NO.
VSENSE
1
SD
2
CS
3
GND
4
DRV
5
VDD
6
no terminal
7
HV
8
Table 3. Terminal Faults and Associated Responses
OPEN
ADJACENT SHORT
GND SHORT
Latched fault
Normal operation
Latched fault
Device fails, power supply
damaged
Hiccup fault
No start-up
N/A
No start-up
Latched fault
Latched fault
Latched fault
Latched fault
No start-up
No start-up
N/A
N/A
Latched fault
Latched fault
Latched fault
N/A
Latched fault
No start-up
N/A
No start-up
VDD SHORT
No start-up
Latched fault
No start-up
No start-up
No start-up
N/A
N/A
Fault not detected/Hiccup
fault
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