Texas Instruments UCC2977EVM User Manual Download Page 22 | Manualshive

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Test Setup

3-4

3.1.3

Burst Dimming Test

Connect pin 2 to pin 3 of JP1 to disable the open-lamp detection circuit during
burst dimming. A low frequency ( >100 Hz) 0~4 V square wave applied to BD
modulates the lamp current.

Figure 3–3. Test Setup for Burst Dimming

Power Supply

Function

Generator

+

–

CCFL

Lamp

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20
21
22
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Summary of Contents for UCC2977EVM

Page 1: ... July 2002 PMP Systems Power User s Guide SLLU049 ...

Page 2: ...nt that any license either express or implied is granted under any TI patent right copyright mask work right or other TI intellectual property right relating to any combination machine or process in which TI products or services are used Information published by TI regarding third party products or services does not constitute a license from TI to use such products or services or a warranty or end...

Page 3: ... handling or use of the goods Please be aware that the products received may not be regulatory compliant or agency certified FCC UL CE etc Due to the open construction of the product it is the user s responsibility to take any and all appropriate precautions with regard to electrostatic discharge EXCEPT TO THE EXTENT OF THE INDEMNITY SET FORTH ABOVE NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR A...

Page 4: ...re is uncertainty as to the load specification please contact a TI field representative During normal operation some circuit components may have case temperatures greater than 60 C The EVM is designed to operate properly with certain components above 60 C as long as the input and output ranges are maintained These components include but are not limited to linear regulators switching transistors pa...

Page 5: ...anual UCC3976 7 Users Manual TI Literature Number SLUU108 Texas Instruments Data Sheet UCC2977 TI Literature Number SLUS499A FCC Warning This equipment is intended for use in a laboratory test environment only It gen erates uses and can radiate radio frequency energy and has not been tested for compliance with the limits of computing devices pursuant to subpart J of part 15 of FCC rules which are ...

Page 6: ...iv ...

Page 7: ... 2 1 2 1 Push Pull Inductor Selection 2 2 2 2 Frequency Range Setting 2 2 2 3 Analog Dimming of the Lamp 2 2 2 4 Open Lamp Voltage Programming 2 3 2 5 Shutdown 2 3 2 6 No Lock 2 3 2 7 Burst Dimming 2 4 2 8 Clamp Circuit Optional 2 4 3 Test Results 3 1 3 1 Test Setup 3 2 3 1 1 Lighting CCFL 3 2 3 1 2 Analog Dimming Test 3 3 3 1 3 Burst Dimming Test 3 4 3 2 Test Results 3 5 ...

Page 8: ...imming 3 4 3 4 Efficiency With a Low Profile Sumida Inductor 3 5 3 5 Efficiency With a High Profile Toko Inductor 3 5 3 6 Transformer Input Output Voltages at VI 3 V 3 6 3 7 Transformer Input Output Voltages at VI 6 V 3 6 3 8 Burst Dimming With 50 Duty Cycle 3 6 3 9 Burst Dimming With 80 Duty Cycle 3 7 3 10 Open Lamp Protection 3 7 Tables 1 1 Operating Specifications 1 2 1 2 Bill of Materials Requ...

Page 9: ...acklight controller The device contains all of the circuitry necessary to control a backlight converter This chapter contains the schematic board layout and the bill of materials The evaluation module EVM performance specifications are also given Topic Page 1 1 Introduction 1 2 1 2 Operating Specifications 1 2 1 3 Schematic 1 3 1 4 Bill of Materials 1 4 1 5 Board Layout 1 5 Chapter 1 ...

Page 10: ...ation section of the UCC2977 data sheet 1 2 Operating Specifications This section summarizes the performance specifications of the SLUP178 converter Table 1 1 lists the operating specifications for the SLUP178 Table 1 1 Operating Specifications Input voltage VIN 3 6 Vdc Output voltage Lamp_HV Lamp LV 300 Vac rms Output current lamp current 4 7 mA rms Operating frequency kHz 100 kHz Burst dimming B...

Page 11: ...Schematic 1 3 Hardware 1 3 Schematic Figure 1 1 UCC2977EVM Schematic ...

Page 12: ...3 mm Sumida CDRH6D28 220NC or Toko inductor 22 µH 115 mΩ 7 6 7 6 5 1 mm Toko 646CY 220M 1 Q1 Transistor NPN high perfor mance 500 mA SOT23 ZeTek FMMT491A 1 Q2 XSTR MOSFET N channel 30 V 4 6 A Rds 35 mΩ TSSOP8 IR IRF7752 1 R1 Resistor chip 22 kΩ 1 16 W 1 603 Std Std 1 R10 Resistor chip 50 kΩ 1 16 W 1 603 Std Std 2 R12 R13 Resistor chip 10 Ω 1 16 W 1 603 Std Std 1 R15 Resistor chip 909 Ω 1 16 W 1 60...

Page 13: ...Board Layout 1 5 Hardware 1 5 Board Layout Figure 1 2 Top Silk Screen With Top Copper Layer Figure 1 3 Top Layer Copper Figure 1 4 Bottom Layer Copper ...

Page 14: ...1 6 ...

Page 15: ...design the UCC2977EVM Topic Page 2 1 Push Pull Inductor Selection 2 2 2 2 Frequency Range Setting 2 2 2 3 Analog Dimming of the Lamp 2 2 2 4 Open Lamp Voltage Programming 2 3 2 5 Shutdown 2 3 2 6 No Lock 2 3 2 7 Burst Dimming 2 4 2 8 Clamp Circuit Optional 2 4 Chapter 2 ...

Page 16: ...H inductors are used A suitable capacitor must be chosen so that the peak to peak output ripple is within the limits allowable for the application 2 2 Frequency Range Setting The VCO frequency range is programmed with external components R1 R3 and C2 The frequency is determined by the voltage decay from 1 7 V to 0 6 V at the OSC pin When the voltage reaches 0 6 V an internal current source charges...

Page 17: ...tage at the secondary is 1220 VRMS The value of capacitor C1 should be large enough to filter the sinusoid waveform into dc For this board 2200 pF was chosen If C5 is too large it takes extra time for OPEN SD to climb to 1 5 V when the output voltage hits the open lamp threshold resulting in a higher output voltage than the set value The open lamp level should be set high enough to avoid tripping ...

Page 18: ...ent The duty cycle of the square wave determines the lamp brightness as a percent of rated lamp current 2 8 Clamp Circuit Optional There is also a clamp circuit to limit the maximum secondary voltage This circuit is typically not needed since the CCFL strikes or the open lamp circuit triggers before destructive levels are reached If R5 and Q1 are added to the board the peak clamp voltage for the E...

Page 19: ...s This chapter describes how to properly connect and setup the UCC2977EVM It also presents the test results which cover efficiency burst dimming and open lamp protection Topic Page 3 1 Test Setup 3 2 3 2 Test Results 3 5 Chapter 3 ...

Page 20: ...A power supply with a power capability of 6 V 0 5 A is required for this test Figure 3 1 shows the input output connections to the SLUP178 Connect a 270 V lamp BF3100 20B Connect pin 1 to pin 2 of jumper JP1 Figure 3 1 Test Setup Power Supply CCFL Lamp ...

Page 21: ... 5 A is required for this test Figure 3 2 shows the input output connections to the SLUP178 The lamp intensity is controlled by VAD 0 3 Vdc Make sure the wire of the lamp is as short as possible and the lamp reflector if there is one is grounded to board ground Do not let the high voltage wire cross any part of the board Figure 3 2 Test Setup for Analog Dimming Power Supply Power Supply CCFL Lamp ...

Page 22: ...pin 2 to pin 3 of JP1 to disable the open lamp detection circuit during burst dimming A low frequency 100 Hz 0 4 V square wave applied to BD modulates the lamp current Figure 3 3 Test Setup for Burst Dimming Power Supply Function Generator CCFL Lamp ...

Page 23: ...or CDRH6D28 22 µH 128 mΩ 6 7 6 7 3 mm 50 55 60 65 70 75 80 85 90 3 4 5 6 VI Input Voltage V Efficiency EFFICIENCY vs INPUT VOLTAGE 4 7 mA 4 mA 3 mA 2 mA Figure 3 5 Efficiency With a High Profile Toko Inductor 646CY 220M 22 µH 115 mΩ 7 6 7 6 5 1 mm 50 55 60 65 70 75 80 85 90 3 4 5 6 VI Input Voltage V Efficiency EFFICIENCY vs INPUT VOLTAGE 4 8 mA 4 mA 3 mA 2 mA ...

Page 24: ... CH4 Primary 2 M1 Transformer Primary Voltage CH3 Lamp Voltage Figure 3 7 Transformer Input Output Voltages at VI 6 V CH1 Primary 1 CH4 Primary 2 M1 Transformer Primary Voltage CH3 Lamp Voltage Figure 3 8 Burst Dimming With 50 Duty Cycle CH1 Burst Dimming Control Signal CH3 Lamp Voltage ...

Page 25: ...Test Results 3 7 Test Results Figure 3 9 Burst Dimming With 80 Duty Cycle CH1 Burst Dimming Control Signal CH3 Lamp Voltage Figure 3 10 Open Lamp Protection CH1 Comp C2 Open SD ...

Page 26: ...3 8 ...

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