TEA1716T
NXP Semiconductors
Resonant power supply control IC with PFC
The low charge/discharge speed is used for the lower frequency range where
SSHBC/EN exceeds Vss(hf-lf)(SSHBC) (5.6 V typical). In the lower frequency range, the
V
currents in the converter react strongly to frequency variations.
Section 7.8.10.2 describes how the two-speed soft start function is used for overcurrent
regulation.
The soft start capacitor is not charged or discharged during non-operation time in Burst
mode. The soft start voltage does not change during this time.
7.8.8.3 Soft start reset
Some protection functions, such as overcurrent protection, require fast correction of the
operating frequency set point, but do not require switching to stop. See the protection
overview in Section 7.9 for details on which protection functions use this step to the
maximum frequency. The TEA1716 has a special fast soft start reset feature for the HBC
controller that forces Vfmax(ss)(RFMAX) on pin RFMAX. Soft start reset is also used when the
HBC controller is enabled via the SSHBC/EN pin or after a restart to ensure a safe start at
maximum frequency. Soft start reset is not used when the operation was stopped in Burst
mode.
When a protection function is activated, the oscillator control input is disconnected from
the soft start capacitor, Css(HBC), which is connected between pin SSHBC/EN and ground.
The switching frequency is immediately set to a maximum. Setting the switching
frequency to a maximum restores safe switching operation in most cases. At the same
time, the capacitor is discharged to the maximum frequency level, Vfmax(SSHBC). Once
V
SSHBC/EN has reached this level, the oscillator control input is connected to the pin again
and the normal soft start sweep follows. Figure 14 shows the soft start reset and the
two-speed frequency sweep downwards.
on
Protection
off
V
fmin(SSHBC)
V
ss(hf-lf)(SSHBC)
V
SSHBC/EN
V
fmax(SSHBC)
0
f
max
f
HB
f
min
0
t
f
max
regulation
fast
sweep
slow sweep
regulation
forced
014aaa864
Fig 14. Soft start reset and two-speed soft start
TEA1716T
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© NXP B.V. 2012. All rights reserved.
Objective data sheet
Rev. 1 — 27 January 2012
27 of 46
ETC [ ETC ]
