L6599DTR STMicroelectronics, L6599DTR Datasheet - Page 23

• Manufacturer Part Number: L6599DTR
• Description: IC RESONANT CONVRTR CTRLR 16SOIC
• Manufacturer: STMicroelectronics
• Type: Phase Shift Resonant Controllerr

Specifications of L6599DTR

• 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
• Output Current: 800 mA
• 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
• 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
• Other names: 497-6156-2

L6599
7.4
Current sense, OCP and OLP
The resonant half-bridge is essentially voltage-mode controlled; hence a current sense input
will only serve as an overcurrent protection (OCP).
Unlike PWM-controlled converters, where energy flow is controlled by the duty cycle of the
primary switch (or switches), in a resonant half-bridge the duty cycle is fixed and energy flow
is controlled by its switching frequency. This impacts on the way current limitation can be
realized. While in PWM-controlled converters energy flow can be limited simply by
terminating switch conduction beforehand when the sensed current exceeds a preset
threshold (this is commonly now as cycle-by-cycle limitation), in a resonant half-bridge the
switching frequency, that is, its oscillator's frequency must be increased and this cannot be
done as quickly as turning off a switch: it takes at least the next oscillator cycle to see the
frequency change. This implies that to have an effective increase, able to change the energy
flow significantly, the rate of change of the frequency must be slower than the frequency
itself. This, in turn, implies that cycle-by-cycle limitation is not feasible and that, therefore,
the information on the primary current fed to the current sensing input must be somehow
averaged. Of course, the averaging time must not be too long to prevent the primary current
from reaching too high values.
In
described in the following. The circuit of
resistor Rs might not be negligible, hurting efficiency; the circuit of
complex but virtually lossless and recommended when the efficiency target is very high.
Figure 30. Current sensing technique with sense resistor
Figure 30 and Figure 31
L6599
6
a couple of current sensing methods are illustrated that will be
ISEN
τ
≈
f
10
min
Figure 30
Rs
Cr
is simpler but the dissipation on the sense
I
Cr
Vspk
0
Application information
Figure 31
is more
L6599
23/36
6