ld7522 Leadtrend Technology, ld7522 Datasheet - Page 12

• Manufacturer Part Number: ld7522
• Description: Smart Green-mode Pwm Controller With Multiple Protections
• Manufacturer: Leadtrend Technology

On the other hand, LD7522 detects the voltage on the BNO
pin to feed the line compensation signal on the current
sense circuit. Figure 23 shows the circuit. Thanks to this
implementation, the OCP level of high-line and low-line can
be achieve to very closed point.
The voltage gain from the BNO voltage to line compensation
is 0.04 (V/V). The relationship between BNO pin voltage
and the line compensation is illustrated in figure 24.
Leadtrend Technology Corporation
LD7522-DS-03 January 2008
UVLO(on)
UVLO(off)
1.25V
1.10V
Line Voltage
Vcc
OUT
V
BNO
Non-Switching
2
V ⋅
ac
Fig. 22
Fig. 23
AC OK area
Switching
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∑
Non-
Switching
t
t
t
t
12
Over Load Protection (OLP)
To protect the circuit from the damage during over load
condition or short condition, a smart OLP function is
implemented in the LD7522. Figure 25 shows the
waveforms of the OLP operation.
condition, the feedback system will force the voltage loop
toward the saturation and thus pull the voltage on COMP pin
(VCOMP) to high. Whenever the VCOMP trips the OLP
threshold 5.0V and keeps longer than 30mS, the protection
is activated and then turns off the gate output to stop the
switching of power circuit.
prevent the false trigger from the power-on and turn-off
transient.
Fig. 24
Fig. 25
The 30mS delay time is to
LD7522
Under such fault