First time startup sequence
- When AC is plugged in, voltage is
applied on HV pin. If VCCP voltage is below VCCShort, VCCP pin
is charged with IHVLow. If VCCP voltage is higher than
VCCShort, VCCP pin is charged with
IHVHigh.
- When VCCP voltage is higher than
VCCUVLOr, an internal LDO regulates the VCCP voltage
untill the device initialization is complete.
- V5P is established. LL pin &
TSET pin are used for burst mode and internal VCR Synthesizer programming.
- If the HV startup option is
enabled, the TSET pin outputs high (means PFC OFF) to prevent PFC from turning
on before VCCP is full established.
- When VCCP is higher than
VCCStartSelf, HV charge current stops. LLC startup
process begins. TSET voltage is kept lower than 1V, allowing PFC to
startup.
- If during stages 3 and 4, VCCP
voltage drops below VCCReStart, HV charge current enables
again and VCCP gets charged with IHVHigh
- Once LLC finishes startup, HV
charge current is disabled until VCCP drops below
VCCReStartJfet.
- During normal operation if the
VCCP voltage falls below VCCStopSwitching, a fault occurs and
UCC25660 shuts down. Normal restart sequence
is then followed.
Restart sequence
- After a fault is detected, UCC25660 shuts down. For fault retry mode, after
1s idle time, UCC25660retries (TSET outputs high
when VCCP is still higher than VCCUVLOf).
- if VCCP voltage is below
VCCShort, VCCP pin is charged with
IHVLow. If VCCP voltage is higher than
VCCShort, VCCP pin is charged with
IHVHigh. If VCCP pin voltage is higher than
VCCStartSelf, HV startup is not enabled (Phase I is
skipped). V5P is established and LL pin is released for burst mode
programming.