Texas Instruments UCC28610EVM-474 User manual

Using the UCC28610EVM-474
User's Guide
Literature Number: SLUU383B
November 2009–Revised May 2011

User's Guide
SLUU383B–November 2009–Revised May 2011
UCC28610EVM-474 25-W Universal Off-Line Flyback
Converter
1 Introduction
The UCC28610EVM-474 evaluation module is a 25-W off-line Discontinuous Mode (DCM) flyback
converter providing 12 V at 2.1-A maximum load current, operating from a universal AC input. The module
is controlled with the UCC28610 Green-Mode Flyback Controller which uses a cascoded architecture that
allows fully integrated current control without an external sense resistor. The converter maintains
discontinuous mode operation over the entire operating range. This innovative approach results in
efficiency, reliability, and system cost improvements over a conventional flyback.
2 Description
This evaluation module uses the UCC28610 Green-Mode Flyback Controller (TI Literature Number
SLUS888) in a 25-W DCM flyback converter that exceeds Energy Star™EPS version 2.0 for efficiency
during active load and no-load power consumption. The input accepts a voltage range of 85 VAC to 265
VAC. The output provides a regulated output voltage of 12 VDC at a load current of up to 2.1 A. The
converter will transition through three operating modes: green mode (GM), amplitude modulation (AM),
and frequency modulation (FM), depending upon the power level and FB current. In FM mode, the on-time
is fixed, resulting in a fixed peak primary current at each cycle, and the switching frequency is increased
with increasing load. In AM mode, the switching frequency is fixed at 30 kHz and the peak primary current
is modulated with the on-time as with any typical PWM controller. Green mode operation at light load
consists of burst packets of 30-kHz pulses with a fixed on-time and peak primary currents of 33% of the
maximum programmed level. Low system parts count and built in advanced protection features result in a
cost-effective solution that meets stringent world-wide energy efficiency requirements.
This user’s guide provides the schematic, component list, assembly drawing, art work, and test set up
necessary to evaluate the UCC28610 in a typical off-line converter application.
2UCC28610EVM-474 25-W Universal Off-Line Flyback Converter SLUU383B–November 2009–Revised May 2011
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www.ti.com Description
2.1 Applications
The UCC28610 is suited for use in isolated off-line systems requiring high efficiency and advanced fault
protection features including:
•AC/DC Adaptors that have a Peak Power Output of 12 W to 65 W
•Housekeeping and Auxiliary Power Supplies
•Off-line Battery Chargers
•Consumer Electronics (DVD players, set-top boxes, gaming, printers, etc.)
2.2 Features
The UCC28610EVM-474 features include:
•Isolated 25 W, 12-V output
•Universal Off-Line Input Voltage Range
•Exceeds Energy Star™EPS Version 2.0 Requirements for Active Load Efficiency and No-Load Power
Consumption
•Cascoded Configuration Allows Fully Integrated Current Control Without an External Sense Resistor
•Multiple Operating Modes for Optimum Efficiency Over entire Operating Range
•Over Current Protection to Limit RMS Input and Output Current
•Timed overload with Shutdown/Retry Response
•Opto-Less Output Overload Protection
CAUTION
High voltage levels are present on the evaluation module whenever it is
energized. Proper precautions must be taken when working with the EVM. The
large bulk capacitor, C9, and the output capacitors, C15 and C16, must be
completely discharged before the EVM can be handled. Serious injury can
occur if proper safety precautions are not followed.
3
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Electrical Performance Specifications www.ti.com
3 Electrical Performance Specifications
Table 1. UCC28610EVM-474 Electrical Performance Specifications
PARAMETER CONDITIONS MIN NOM MAX UNITS
INPUT CHARACTERISTICS
VIN Input voltage 85 265 VRMS
IIN Input current VIN = 115 VRMS, IOUT = max 0.3 A
VIN = 115 VRMS, IOUT = 0 A 0.03 A
VUVLO Brown out IOUT = max 72 V
OUTPUT CHARACTERISTICS
VOUT Output voltage VIN = min to max, IOUT = min to max 10.8 12 13.2 V
Vripple Output voltage ripple VIN = 115 VRMS, IOUT = max 80 120 mVpp
IOUT Output current VIN = min to max 0 2.1 A
IOCP Output over current VIN = max 3 A
inception point
VOVP Output OVP IOUT = min to max 16 V
Transient response voltage IOUT = min to max 500 mV
over shoot
SYSTEM CHARACTERISTICS
fSW Switching frequency 26.3 140.4 kHz
hPEAK Peak efficiency VIN = 115 VRMS, IOUT = 1.05 A 85.7 %
No load power consumption VIN = 115 VRMS 67 mW
VIN = 230 VRMS 107
Operating temperature VIN = min to max, IOUT = min to max 25 °C
range
MECHANICAL CHARACTERISTICS
Width Dimensions 2.3
Length 3.5 inches
Height Component height 1
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INSTRUMENTS
EXAS
www.ti.com Schematic/Revision Code Placement
4 Schematic/Revision Code Placement
NOTE: For revision A versions of the evaluation module, please refer to Appendix A of this user's
guide for the schematic, list of materials and board layout. The EVM revision code can be
found on the lower right corner of the top side of the board, as shown in Figure 1.
Figure 1. Placement of Revision Code for the Evaluation Module.
5
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+
+
++
Schematic/Revision Code Placement www.ti.com
Figure 2. UCC28610EVM-474 Schematic
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www.ti.com Schematic/Revision Code Placement
4.1 Circuit Description
A brief description of the circuit elements follows:
•Diode bridge D1, input capacitor C9, transformer (a.k.a. flyback inductor) T1, HV MOSFET Q1,
UCC28610 controller U1, Schottky rectifier D6, Output capacitors C15 and C16 form the power stage
of the converter. Note that the UCC28610 U1 is part of the power stage. This is because the DRV and
GND pins carry the full peak primary side current of the converter.
•Capacitors C12, C14, and C17 filter the high frequency noise directly across the electrolytic input and
output capacitors.
•The input EMI filter is made up of X2 capacitors, C1 and C6, and common mode inductor L1 and Y2
capacitors, C4 and C5. Excessive surge current protection is provided by a slow blow fuse, F1.
•Resistor R11, capacitor C11, and diode D5 make up the primary side voltage clamp for the HV
MOSFET. The clamp prevents the drain voltage on Q1 from exceeding its maximum rating. The
integrated snubber, composed of R12 and C11, reduces the ringing on the primary side windings that
might inadvertently trigger the zero current detection circuit in the device.
•Resistors R7, R8, and R9 supply start up bias current to the VGG shunt regulator. Schottky diode D3
is required to provide initial start up to VDD from VGG at start up.
•Operating bias to the controller is provided by the auxiliary winding on T1, diode D2, and bulk capacitor
C7. The zener diode, D4, maintains the bias voltage on VDD below the absolute maximum rating at full
load.
•Gate drive circuitry is composed of gate drive resistor R10, used for damping oscillations during turn
on. Resistor R16 and diode D8 are required to provide a current path at turn off because the gate is
shorted to the source of the HV MOSFET during each switching cycle. For circuits that experience high
ringing on VGG at turn off, R16 can be replaced with a ferrite bead.
•Capacitors C8 and C10 are decoupling capacitors which should always be good quality low ESR/ESL
type capacitors placed as close to the device pins as possible and returned directly to the device
ground reference.
•C13 filters the common mode noise between the primary and secondary sides.
•Inductor L2, with capacitor C16, reduces the output voltage ripple.
•Resistors R5 and R3 program the over voltage threshold. Capacitor C3 can be used to add a small
delay to ZCD, to align the turn on time of the primary switch with the resonant valley of the primary
winding.
•Resistor R6 programs the maximum on time of the HV MOSFET.
•Resistor R4 sets the maximum value for the peak primary current.
•Resistor R2 and capacitor C2 provide a filter for the FB signal while resistor R1 ensures that the
optocoupler emitter current can go to 0A. Resistor R19 provides a non-intrusive point to monitor the FB
by measuring the voltage drop across R19.
•The simple output voltage feedback loop is composed of zener diode D7, resistors R14 and R15, and
the optocoupler U2. Using an opto with a low CTR provides better noise immunity. Resistor R13 is
used as an injection point for small signal frequency response testing.
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EVM Test Set Up www.ti.com
5 EVM Test Set Up
Figure 2 shows the equipment set up when measuring the input power consumption during no load. Note
the addition of the 10-Ωshunt resistor in Figure 3. During the no-load test, the power analyzer should be
set for long averaging in order to include several cycles of operation and an appropriate current scale
factor for using the external shunt must be used. Figure 3 shows the basic test set up recommended to
evaluate the UCC28610EVM-474 with a load.
WARNING
High voltages that may cause injury exist on this evaluation
module (EVM). Please ensure all safety procedures are followed
when working on this EVM. Never leave a powered EVM
unattended.
5.1 Test Equipment
See Figure 3 and Figure 4 for recommended test set ups.
•AC Input Source: The input source shall be an isolated variable AC source capable of supplying
between 85 VRMS and 265 VRMS at no less than 30 W and connected as shown in Figure 3 and
Figure 4. For accurate efficiency calculations, a power meter should be inserted between the neutral
line of the AC source and the Neutral terminal of the EVM. For highest accuracy, connect the voltage
terminals of the power meter directly across the Line and Neutral terminals of the EVM.
•Load: For the output load, a programmable electronic load set to constant current mode and capable
of sinking 0 to 3 ADC at 12 VDC shall be used. For highest accuracy, VOUT can be monitored by
connecting a DC voltmeter, DMM V1, directly across the +Vout and –Vout terminals as shown in
Figure 3 and Figure 4. A DC current meter, DMM A1, should be placed in series with the electronic
load for accurate output current measurements.
•Power Meter: The power analyzer shall be capable of measuring low input current, typically less than
10 mA, and a long averaging mode if low power standby mode input power measurements are to be
taken. An example of such an analyzer is the Voltech PM100 Single Phase Power Analyzer. To
measure the intermittent bursts of current and power drawn from the line during no-load operation, an
external 10-Ωshunt, with a current scale factor of 10 A/V, was used at a high sample rate over an
extended period of time in order to display the averaged results (refer to Figure 3).
•Multimeters: Two digital multimeters are used to measure the regulated output voltage (DMM V1) and
load current (DMM A1).
•Oscilloscope: A digital or analog oscilloscope with a 500-MHz scope probe is recommended.
•Fan: Forced air cooling is not required.
•Recommended Wire Gauge: a minimum of AWG18 wire is recommended. The wire connections
between the AC source and the EVM , and the wire connections between the EVM and the load
should be less than two feet long.
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INSTRUMENTS
EXAS
AC SOURCE
Line
Neutral
DMM V1
+ -
Oscilloscope
POWER METER
VHI VLO AHI ALO AEXT
+ + -
-
10
AC SOURCE
LineNeutral
DMM A 1
+ -
DMM V1
+ -
Oscilloscope
ELECTRONIC
LOAD
+-
POWER METER
VHI VLO AHI ALO AEXT
+ + --
T
INSTRUMENTS
EXAS
www.ti.com EVM Test Set Up
5.2 Recommended Test Set Up for Operation Without a Load
Figure 3. UCC28610EVM-474 Recommended Test Set Up Without a Load
5.3 Recommended Test Set Up for Operation With a Load
Figure 4. UCC28610EVM-474 Recommended Test Set Up With a Load
9
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5.4 List of Test Points
Table 2. Test Point Functional Description
TEST POINT NAME DESCRIPTION
Output voltage of EVM; this designator is not populated with a pin in order to
TP1 +Vout facilitate tip and barrel output ripple voltage measurements.
TP2 -Vout Return of the output of the EVM, secondary side GND reference.
TP3 Pwr RTN Primary side power ground
TP4 QGND Primary side signal ground
TP5 +LOOP Loop injection point, EVM output
TP6 -LOOP Loop injection point
J1-1 Neutral Neutral input from the AC source
J1-2 Earth Earth reference from the AC source
J1-3 AC Line Line input from AC source
J2-1 +Vout Positive output terminal of the EVM to the load
J2-2 -Vout Return connection of the EVM output to the load
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