EVL170W-FTV STMicroelectronics, EVL170W-FTV Datasheet - Page 24

• Manufacturer Part Number: EVL170W-FTV
• Description: DEMO BOARD VIPER27 L6599A L6564
• Manufacturer: STMicroelectronics
• Series: VIPER™r

Specifications of EVL170W-FTV

• Main Purpose: Power Supply with PFC
• Outputs And Type: 2, Isolated
• Power - Output: 170W
• Voltage - Output: 24V, 12V, 5V
• Current - Output: 6A, 2A, 2A
• Voltage - Input: 90 ~ 264VAC
• Regulator Topology: Flyback
• Frequency - Switching: 130kHz
• Board Type: Fully Populated
• Utilized Ic / Part: Viper27LN, L6564, L6599A
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-11254

Functional check
AN3329
Figure 44. 12 V - 2 A; 24 V 0 ÷ 6 A - 300 Hz
Figure 45. 24 V - 6 A; 12 V 1 ÷ 2 A - 300 Hz
transition at 115 Vac - 60 Hz
transition at 115 Vac - 60 Hz
CH2: +12 V O/P voltage CH3: +24 V O/P voltage
CH2: +12 V O/P voltage CH3: +24 V O/P voltage
CH4: +24 V O/P current
CH4: +12 V O/P current
Overcurrent and short-circuit protection
The L6599A is provided with a current sensing input (pin #6, ISEN) and a dedicated
overcurrent management system. Current flowing in the resonant tank is detected and the
signal is fed into the ISEN pin, which is internally connected to a first comparator, referenced
to 0.8 V, and to a second comparator referenced to 1.5 V. If the voltage externally applied to
the pin exceeds 0.8 V, the first comparator is tripped causing an internal switch to be turned
on and discharge the soft-start capacitor CSS, increasing the switching frequency and so
limiting the output power, while the second, referenced to 1.5 V, latches the L6599A,
protecting the circuit against dead short-circuit. These two comparators, together with the
DELAY pin (#2) are dedicated to offering the possibility of implementing the overload
protection in either auto-restart or latch mode, according to the whole equipment needs. In
this case, being a flat TV, the final application to which this demonstration board is
dedicated, the desired overload and short protection is latched.
If the 12 V output is failing short-circuit as in
Figure
46, the ISEN pin (#6) voltage rapidly
rises over 1.5 V, triggering the second comparator of the overcurrent protection. In this case,
as shown, the protection intervention is very quick, protecting properly the circuit. Then, the
L6599A shuts down and operation can be resumed after an off-on signal or a mains voltage
recycling. In
Figure 47
details of half bridge voltage and current during the higher current
peaks have been captured, showing the correct ZVS operation by the circuit.
If the 24 V output is failing shorts
(Figure
48), the L6599A ISEN pin reaches 0.8 V, triggers
the first comparator, and the capacitor C10 connected to the DELAY and DIS pins, starts
being charged by an internal 150 µA current generator while the soft-start capacitor C21 is
discharged, increasing the switching frequency to limit the output power. When the voltage
on the DELAY and DIS pins reaches 1.85 V, an internal comparator is triggered, then the
L6599A is shut down and its consumption is reduced. The PFC_STOP pin is pulled down.
The capacitor C10 is discharged by the external resistor R12. The latch condition is kept
until the L6599A Vcc drops below the UVLO. Therefore, to resume the operation an off-on
signal or a mains voltage recycling is necessary.
Figure 48
details HB switching transitions
as soon as the short is detected, where the borderline between inductive and capacitive
mode could be critical. As can be seen, the resonant current has the correct polarity during
both HB transitions and the converter is properly working in the inductive region even in this
case.
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Doc ID 18376 Rev 1