EVAL6599-90W STMicroelectronics, EVAL6599-90W Datasheet - Page 12

• Manufacturer Part Number: EVAL6599-90W
• Description: EVAL BOARD FOR L6599
• Manufacturer: STMicroelectronics
• Type: Power Factor Correctionr

Specifications of EVAL6599-90W

• Main Purpose: AC/DC, Primary Side and PFC
• Outputs And Type: 1, Isolated
• Power - Output: 90W
• Voltage - Output: 19V
• Current - Output: 4.7A
• Voltage - Input: 90 ~ 264VAC
• Regulator Topology: Resonant
• Frequency - Switching: 90kHz
• Board Type: Fully Populated
• Utilized Ic / Part: L6563, L6599
• Input Voltage: 90 V to 264 V
• Output Voltage: 19 V
• Dimensions: 78 mm x 174 mm
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: L6599
• Other names: 497-5497

Test results
2.4
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Figure 10. O/P short circuit waveforms
CH1: L6599 - V
CH2: L6599 - V
CH3: L6599 - V
CH4: Output current
Short circuit protection
The L6599 is equipped with a current sensing input (pin #6, ISEN) and a dedicated over
current management system. The current flowing in the circuit is detected and the signal is
fed into the ISEN pin. It is internally connected to the input of a first comparator, referenced
to 0.8 V, and to that of a second comparator referenced to 1.5 V. If the voltage externally
applied to the pin by either circuit in
causing an internal switch to be turned on and discharging the soft-start capacitor CSS.
Under output short circuit, this operation results in a nearly constant peak primary current.
With the L6599 the designer can program externally the maximum time (TSH) that the
converter is allowed to run overloaded or under short circuit conditions. Overloads or short
circuits lasting less than TSH will not cause any other action, hence providing the system
with immunity to short duration phenomena. If, instead, TSH is exceeded, an overload
protection (OLP) procedure is activated that shuts down the L6599 and, in case of
continuous overload/short circuit, results in continuous intermittent operation with a user-
defined duty cycle. This function is realized with the pin DELAY (#2), by means of a
capacitor C45 and the parallel resistor R24 connected to ground. As the voltage on the
ISEN pin exceeds 0.8V the first OCP comparator, in addition to discharging CSS, turns on
an internal current generator that via the DELAY pin charges C45. As the voltage on C45 is
3.5 V, the L6599 stops switching and the PFC_STOP pin is pulled low. Also the internal
generator is turned off, so that C45 will now be slowly discharged by R24. The IC will restart
when the voltage on C45 will be less than 0.3 V. Additionally, if the voltage on the ISEN pin
reaches 1.5 V for any reason (e.g. transformer saturation), the second comparator will be
triggered, the L6599 will shutdown and the operation will be resumed after an on-off cycle.
The L6599 short circuit protection sequence described above is visible in the
on/off operation is controlled by the voltage on pin #2 (DELAY), providing for the hiccup
mode of the circuit.
Thanks to this control pin, the designer can select the hiccup mode timing and thus keep the
average output current at a safe level. Please note on the picture left side the very low mean
current flowing in the shorted output, less than 0.3 A. A better detail of the waveforms can
PIN
PIN
PIN
#14 (HB voltage)
#2 (DELAY)
#6 (ISEN)
Figure 8
Figure 11. O/P short circuit waveforms
CH2: L6599 - V
CH3: L6599 - V
CH4: Output current
exceeds 0.8 V, the first comparator is tripped
(zoomed)
PIN
PIN
#2 (DELAY)
#6 (ISEN)
Figure
AN2321
10. The