AN3014
Application note
19 V, 90 W resonant converter with synchronous rectification
using the L6563H, L6599A and SRK2000
Introduction
This application note describes the characteristics and the features of a 90 W demonstration
board (EVL90WADP-LLCSR), tailored to specifications for a typical high-end portable
computer power supply. A peculiarity of this SMPS design is the very high efficiency
compliant with ENERGY STAR
®
eligibility criteria (EPA rev. 2.0 EPS). One of the key factors
in achieving this result is the SRK2000. This synchronous rectification driver for LLC
resonant converters allows significantly reduced secondary-side losses. Thanks to this
improvement, secondary-side heatsinks, which are typically needed for this power range,
can be dramatically reduced or even removed.
Figure 1.
EVL90WADP-LLCSR: 90 W adapter demonstration board
December 2010
Doc ID 16064 Rev 2
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www.st.com
Contents
AN3014
Contents
1
2
3
4
5
6
7
8
9
10
Main characteristics and circuit description . . . . . . . . . . . . . . . . . . . . . 5
Efficiency measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Harmonic content measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Functional check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Thermal map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Conducted emission pre-compliance test . . . . . . . . . . . . . . . . . . . . . . 18
Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
PFC coil specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Transformer specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
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AN3014
List of tables
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Overall efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Efficiency comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Light load efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Thermal map reference points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
EVL90WADP-LLCSR demonstration board bill of material . . . . . . . . . . . . . . . . . . . . . . . . 19
PFC coil winding data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Transformer winding data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
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List of figures
AN3014
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
EVL90WADP-LLCSR: 90 W adapter demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . 1
Electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Light load efficiency diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Compliance to EN61000-3-2 at 230 Vac - 50 Hz, full load . . . . . . . . . . . . . . . . . . . . . . . . . 12
Compliance to JEITA-MITI at 100 Vac - 50 Hz, full load. . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Resonant stage oscillator at 230 V - 50 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Resonant stage waveforms at 230 V - 50 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Secondary waveforms at 230 V - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Startup sequencing at 230 V - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
No load operation at 230 V - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
No load operation - detail at 230 V - 50 Hz. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Transition full load to no load at 265 Vac - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Transition no load to full load at 265 Vac - 50 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Short-circuit at full load and 115 Vac - 60 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Short-circuit detail at full load and 115 Vac - 60 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Thermal map at 115 Vac - 60 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Thermal map at 230 Vac - 50 Hz - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
CE average measurement at 115 Vac and full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
CE average measurement at 230 Vac and full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
PFC coil electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
PFC coil mechanical aspect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Transformer electrical diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Transformer overall drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
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AN3014
Main characteristics and circuit description
1
Main characteristics and circuit description
The main features of the SMPS are:
●
●
●
●
●
●
●
●
●
Universal input mains range: 90
−
264 Vac, frequency 45
−
65 Hz
Output voltage: 19 V at 4.75 A continuous operation
Mains harmonics: according to EN61000-3-2 class-D or JEITA-MITI class-D
Standby mains consumption: < 0.26 W at 230 Vac
Efficiency at nominal load: > 92% at 115 Vac
EMI: according to EN55022-class-B
Safety: according to EN60950
Dimensions: 65 x 155 mm, 25 mm maximum component height
PCB: double-sided, 70 µm, FR-4, mixed PTH/SMT
The circuit is composed of two stages: a front-end PFC using the L6563H, and a LLC
resonant converter based on the L6599A. The SRK2000 controls the synchronous
rectification on the secondary side. The PFC stage works as a preregulator and powers the
resonant stage with a constant voltage of 400 V. The downstream converter operates only if
the PFC is on and regulating. In this way, the resonant stage can be optimized for a narrow
input voltage range.
Startup sequence
As indicated previously, the PFC acts as master and the resonant stage can operate only if
the PFC output is delivering the nominal output voltage. Therefore the circuit is designed so
that at startup the PFC starts first, then the downstream converter turns on. Initially, the
L6563H is supplied by the integrated high voltage startup circuit, but as soon as the PFC
starts switching, a charge pump connected to the PFC inductor supplies both the PFC and
resonant controllers. Once both stages have been activated, the controllers are supplied
also by the auxiliary winding of the resonant transformer, assuring correct supply voltage
even during standby operation.
Because the L6563H integrated HV startup circuit is turned off and therefore is not
dissipative during normal operation, it significantly contributes to the reduction of power
consumption when the power supply operates at light load, in accordance with current
world-wide standby consumption standards.
Brownout protection
Brownout protection prevents the circuit from working with abnormal mains levels. It is easily
achieved using the RUN pin (pin12) of the L6563H. This pin is connected through a resistor
divider to the VFF pin (pin 5), which provides the mains voltage peak value information. An
internal comparator enables the IC operations if the mains level is correct, within the
nominal limits. At startup, if the input voltage is below 90 Vac (typ), circuit operations are
inhibited.
The L6599A has similar protection on the LINE pin (pin 7). It is used to prevent the resonant
converter from working with too low an input voltage, which can cause incorrect capacitive
mode operation. If the bulk voltage (PFC output) is below 380 V, the resonant startup is not
allowed. The L6599A internal comparator has a hysteresis which allows the turn-on and
turn-off voltage to be set independently. The turn-off threshold has been set to 300 V in
Doc ID 16064 Rev 2
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