L6599A STMicroelectronics, L6599A Datasheet - Page 29

• Manufacturer Part Number: L6599A
• Description: IMPROVED HIGH-VOLTAGE RESONANT CONTROLLER
• Manufacturer: STMicroelectronics

Specifications of L6599A

• Two-level Ocp: frequency-shift and latched shutdown

L6599A
Figure 30. Line sensing function: internal block diagram and timing diagram
With reference to
(Vin
Equation 11
which, solved for R
Equation 12
While the line undervoltage is active the start-up generator keeps on working but there is no
PWM activity, thus the Vcc voltage (if not supplied by another source) continuously
oscillates between the start-up and the UVLO thresholds, as shown in the timing diagram of
Figure 30
As an additional measure of safety (e.g. in case the low-side resistor is open or missing, or
in non-power factor corrected systems in case of abnormally high input voltage) if the
voltage on the pin exceeds 7 V the L6599A is shutdown. If its supply voltage is always above
the UVLO threshold, the IC will restart as the voltage falls below 7 V.
The LINE pin, while the device is operating, is a high impedance input connected to high
value resistors, thus it is prone to pick up noise, which might alter the OFF threshold or give
origin to undesired switch-off of the IC during ESD tests. It is possible to bypass the pin to
ground with a small film capacitor (e.g. 1-10 nF) to prevent any malfunctioning of this kind. If
ON
) and OFF (Vin
.
Vin
Figure 28
H
ON
and R
R
R
OFF
H
−
H
. 1
=
) thresholds of the input voltage:
24
L
Vin
, the following relationships can be established for the ON
, yield:
=
13
Doc ID 15308 Rev 5
ON
13
⋅
−
10
⋅
10
Vin
−
6
−
6
OFF
+
. 1
;
R
24
L
R
L
=
R
Vin
H
Vin
OFF
R
OFF
. 1
H
−
24
. 1
−
24
. 1
Application information
24
=
. 1
R
24
L
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