Related Manuals for Texas Instruments UCC2977EVM
Summary of Contents for Texas Instruments UCC2977EVM
- Page 1 UCC2977EVM High Efficiency CCFL Backlight Push Pull Converter (1.8 W) User’s Guide July 2002 PMP Systems Power SLLU049...
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Page 2: Important Notice
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. -
Page 3: Evm Important Notice
EVM IMPORTANT NOTICE Texas Instruments (TI) provides the enclosed product(s) under the following conditions: This evaluation kit being sold by TI is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not considered by TI to be fit for commercial use. As such, the goods being provided may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including product safety measures typically found in the end product incorporating the goods. - Page 4 EVM schematic located in the EVM User’s Guide. When placing measurement probes near these devices during operation, please be aware that these devices may be very warm to the touch. Copyright 2002, Texas Instruments Incorporated Mailing Address: Texas Instruments Post Office Box 655303...
- Page 5 This document contains the following chapters: Chapter 1—Hardware Chapter 2—Design Procedure Chapter 3—Test Results Related Documentation From Texas Instruments Texas Instruments Users Manual, 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.
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Page 7: Table Of Contents
Hardware ............... Introduction . - Page 8 1–1 UCC2977EVM Schematic ............
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Page 9: Hardware
The UCC2977 evaluation module (SLUP178) provides a reference design for evaluating the performance of a high efficiency CCFL backlight converter using the UCC2977 (push-pull backlight 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. -
Page 10: Introduction
Introduction 1.1 Introduction The UCC2977 EVM (SLUP178) is a 1.8-W dc/ac inverter module used to drive a cold cathode fluorescent lamp (CCFL) with a piezoelectric transformer (PZT). This EVM consists of a push-pull circuit using the UCC2977 controller. The principle of operation for the inverter is explained in the application section of the UCC2977 data sheet. -
Page 11: Schematic
Schematic 1.3 Schematic Figure 1–1. UCC2977EVM Schematic Hardware... -
Page 12: Bill Of Materials
Bill of Materials 1.4 Bill of Materials Table 1–2. Bill of Materials Required for the UCC2977 (SLUP178) Count Ref Des Description Capacitor, ceramic, 2200 pF, 50 V, X7R, 20% Capacitor, ceramic, 220 pF, 50 V, X7R, 20% C3, C7 Capacitor, ceramic, 0.1 F, 25 V, X7R, 20% Capacitor, ceramic, 0.022 F, 25 V, X7R, 20%... -
Page 13: Board Layout
Board Layout 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 Hardware... -
Page 15: Design Procedure
This chapter describes how to design the UCC2977EVM. Topic Push-Pull Inductor Selection ........ -
Page 16: Push-Pull Inductor Selection
Push-Pull Inductor Selection 2.1 Push-Pull Inductor Selection The push-pull topology requires a different approach for calculating the external inductor values. Referring to Figure 1–1, Q2A and Q2B are driven out of phase at 50% duty cycle. When Q2A is on, current is ramped up in L1. During the next switch cycle Q2B is turned on, Q2A is turned off, and the energy stored in L1 is transferred through the piezoelectric transformer. -
Page 17: Open-Lamp Voltage Programming
Zero volts on V current. For the initially configured EVM, maximum current is 4.8 mA. R15 is selected to be 909 set to 150 K, R10 is calculated to be 50 K. The control-voltage to lamp-current equation for the EVM is: (mA) + 4.89 * 1.22 LAMP 2.4 Open-Lamp Voltage Programming... -
Page 18: Clamp Circuit (Optional)
Burst Dimming 2.7 Burst Dimming Burst dimming can be implemented at the OPEN/SD pin at the cost of open-lamp detection. Connect pin 2 to pin 3 of JP1 to disable the open-lamp detection circuit during burst dimming mode. Since the feedback loop does not need to operate with minimum lamp current (as with analog dimming), the feedback capacitor, C4, can be reduced to 22 nF to improve the response time when the lamp restrikes. -
Page 19: Test Results
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 Test Setup ........... . -
Page 20: Lighting Ccfl
Test Setup 3.1 Test Setup 3.1.1 Lighting CCFL 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. -
Page 21: Analog Dimming Test
3.1.2 Analog Dimming Test For analog dimming, enable the open-lamp detection by connecting pin 1 to pin 2 of jumper JP1. A power supply that has a power capability of 6 V/0.5 A is required for this test. Figure 3–2 shows the input/output connections to the SLUP178. -
Page 22: Burst Dimming Test
Test Setup 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. -
Page 23: Efficiency With A Low Profile Sumida Inductor
3.2 Test Results The test results for the SLUP178 are shown in this section. Figure 3–4. Efficiency With a Low Profile Sumida Inductor (CDRH6D28; 22 H, 128 m , 3 mm) Figure 3–5. Efficiency With a High Profile Toko Inductor (646CY–220M; 22 H, 115 m , 7.6 5.1 mm) EFFICIENCY... -
Page 24: Transformer Input/Output Voltages At V I = 3 V
Test Results Figure 3–6. Transformer Input/Output Voltages at V CH4=Primary 2, M1=Transformer Primary Voltage, CH3=Lamp Voltage) Figure 3–7. Transformer Input/Output Voltages at V 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) = 3 V (CH1=Primary 1, = 6 V (CH1=Primary 1,... -
Page 25: Burst Dimming With 80% Duty Cycle
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) Test Results...
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