L6699D STMicroelectronics, L6699D Datasheet - Page 12

• Manufacturer Part Number: L6699D
• Description: AC/DC Switching Converters Enhanced High Volt Res CTRL 600V
• Manufacturer: STMicroelectronics
• Type: High Voltage Controllersr

Specifications of L6699D

• Product Category: AC/DC Switching Converters
• Output Voltage: 13.3 V
• Input / Supply Voltage (max): 8.85 V
• Input / Supply Voltage (min): 16 V
• Switching Frequency: 235 kHz
• Supply Current: 3 mA
• Operating Temperature Range: - 25 C to + 125 C
• Mounting Style: SMD/SMT
• Package / Case: SO-16
• Number Of Outputs: 1
• Output Current: 800 mA

Application information
6
12/38
Application information
The L6699 is an advanced double-ended controller specific to resonant half bridge topology.
In these converters the MOSFETs of the half bridge leg are alternately switched on and off
(180° out-of-phase) for exactly the same time. This is commonly referred to as symmetrical
operation at “50% duty cycle”, although the real duty cycle, i.e. the ratio of the ON-time of
either switch to the switching period, is actually less than 50%. The reason is that there is a
deadtime T
one, where both MOSFETs are off. This deadtime is essential in order for the converter to
work correctly: it enables soft-switching and, then, high-frequency operation with high
efficiency and low EMI emissions.
A special feature of this IC is that it is able to automatically adjust T
best fits the transition times of the half bridge midpoint (adaptive deadtime). This allows the
user to optimize the design of the resonant tank so that soft-switching can be achieved with
a lower level of reactive energy (i.e. magnetizing current), therefore optimizing efficiency
under a broader load range, from full to light load.
To perform converter output voltage regulation the device is able to operate in different
modes (
1.
2.
Figure 4.
Variable frequency at heavy and medium/light load. A relaxation oscillator (see
Section 6.1: Oscillator
which MOSFET switching is locked to. The frequency of this waveform is related to a
current that is modulated by the feedback circuitry. As a result, the tank circuit driven by
the half bridge is stimulated at a frequency dictated by the feedback loop to keep the
output voltage regulated, therefore exploiting its frequency-dependent transfer
characteristics.
Burst-mode control with no or very light load. When the load falls below a value, the
converter enters a controlled intermittent operation, where a series of a few switching
cycles at a nearly fixed frequency are spaced out by long idle periods where both
MOSFETs are in the OFF-state. A further load decrease is translated into longer idle
periods and then in a reduction of the average switching frequency. When the converter
is completely unloaded, the average switching frequency can go down even to few
hundred hertz, therefore minimizing magnetizing current losses as well as all
frequency-related losses and making it easier to comply with energy saving
specifications.
Figure 1
D
Multimode operation of the L6699
inserted between the turn-off of either MOSFET and the turn-on of the other
), depending on the load conditions:
for more details) generates a symmetrical triangular waveform,
Doc ID 022835 Rev 2
D
within a range so that it
L6699