ICE2HS01G Datasheet, PDF (14/29 Pages) Infineon Technologies AG – High Performance Resonant Mode Controller

High Performance Resonant Mode Controller
ICE2HS01G
Functional description
3.6 Light load operation
The switching frequency of a half-bridge LLC resonant converter can be very high at no load or light load
operations. High switching frequency results in higher switching loss and magnetized core loss. In most cases,
reduction of the switching frequency will result in efficiency increase, which highly depends on the balance
between switching losses and conduction losses in the converter.
ICE2HS01G offers various options of light load operation to meet the different requirements in applications. These
including Missing Cycle mode in light load and Burst Mode in no load. In addition, both modes can be enabled/
disabled with parameter selctions. For detailed operation of light load, the block diagram is shown in Figure 10.
Figure 10 Light load control module
If the current sense voltage is lower than the preset reference level on Vmc pin for 20ms, IC enters into a Missing
Cylce (MC) mode, where every two out of five switches are removed to reduce the average switching frequency.
Vref pin is the output of internal reference voltage, which is an accurate 5V voltage source, with up to 2 mA. A
typical output gate drive waveforms in MC mode is shown in Figure 11.
Figure 11 ICE2HS01G gate outpus during Missing Cycle
The entering and leaving missing cycle level can be adjusted through connecting different resistors to V_mc pin. The
actual values can be calculated from equations [2] and [3]. The current source I_mc is 50µΑ built inside with high
accuracy. For example, with R_mc1=33kΩ and R_mc2=1.3kΩ, the current sense voltage for entering and leaving
missing cylce mode can be calculated to be 0.19V and 0.252V.
V_LMC
=
V_ref
⋅
----------R----^m---^c--²----------
R_mc1 + R_mc2
[2]
V_EMC
=
V_ref
⋅
----------R----^m---^c--²----------
R_mc1 + R_mc2
+
I_mc
⋅
-R-----^m---^c--¹----^â‹---R----^m---^c--²--
R_mc1 + R_mc2
[3]
Version 2.0
14
11 May 2010