L6599D STMicroelectronics, L6599D Datasheet - Page 21

• Manufacturer Part Number: L6599D
• Description: IC RESONANT CONVRTR CTRLR 16SOIC
• Manufacturer: STMicroelectronics
• Type: Phase Shift Resonant Controllersr

Specifications of L6599D

• Applications: Resonant Converter Controller
• Voltage - Supply: 8.85 V ~ 16 V
• Current - Supply: 3.5mA
• Operating Temperature: 0°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Number Of Outputs: Single
• Output Current: 800 mA (Max)
• Switching Frequency: 500 KHz
• Operating Supply Voltage: 8.85 V to 16 V
• Maximum Operating Temperature: + 150 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Supply Voltage Range: 8.85V To 16V
• Digital Ic Case Style: SOIC
• No. Of Pins: 16
• Operating Temperature Range: -40°C To +150°C
• Svhc: No SVHC (15-Dec-2010)
• Base Number: 6599
• Device Type: Power
• Rohs Compliant: Yes
• For Use With: 497-10542 - BOARD EVAL BASED ON L6599497-8429 - BOARD ADAPTER L6599/STP12NM50N497-8265 - BOARD EVAL BASED ON L6599497-5857 - DEMO BOARD FOR L6599497-5856 - DEMO BOARD FOR L6599497-5497 - EVAL BOARD FOR L6599497-5496 - EVAL BOARD FOR L6599
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Input: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

L6599
7.3
Soft-start
Generally speaking, purpose of soft-start is to progressively increase converter's power
capability when it is started up, so as to avoid excessive inrush current. In resonant
converters the deliverable power depends inversely on frequency, then soft- start is done by
sweeping the operating frequency from an initial high value until the control loop takes over.
With the L6599 converter's soft start-up is simply realized with the addition of an R-C series
circuit from pin 4 (RF
Initially, the capacitor C
in parallel to RF
since the optocoupler's phototransistor is cut off (as long as the output voltage is not too far
away from the regulated value):
The C
(2V) and, consequently, the current through R
time constants R
regulated value and the feedback loop taken over, so that it will be the optocoupler's
phototransistor to determine the operating frequency from that moment onwards.
During this frequency sweep phase the operating frequency will decay following the
exponential charge of C
change will get slower and slower. This counteracts the non-linear frequency dependence
of the tank circuit that makes converter's power capability change little as frequency is away
from resonance and change very quickly as frequency approaches resonance frequency
(see
Figure 28. Soft-start circuit
Figure
SS
capacitor is progressively charged until its voltage reaches the reference voltage
29).
min
R
SS
Fmin
·C
and the resulting initial frequency is determined by R
min
SS
SS
SS
) to ground (see
but, before that time, the output voltage will have got close to the
is totally discharged, so that the series resistor R
, that is, initially it will change relatively quickly but the rate of
R
C
SS
SS
f
RFmin
start
Css
=
---------------------------------------------------------------
3 CF
⋅
4
1
Figure
⋅
(
L6599
SS
R F
28).
(
1
goes to zero. This conventionally takes 5
min
||
R
SS
)
)
Application information
SS
SS
and RF
| Z ( f ) |
is effectively
min
only,
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