工业控制 | 能源技术 | 汽车电子 | 通信网络 | 安防监控 | 智能电网 | 移动手持 | 无线技术 | 家用电器 | 数字广播 | 消费电子 | 应用软件 | 其他方案

电路设计->机动车 电动车电路图->汽车电子电路图->真空荧光显示器件参考设计为汽车应用-Vacuum Fl

真空荧光显示器件参考设计为汽车应用-Vacuum Fl

作者:dolphin时间:2011-07-20

Abstract: This article describes a vacuum fluorescent display (VFD) and some ideal applications for the technology. The reference design then shows how to use a MAX15005 power-supply controller in a flyback topology to obtain multiple output voltages for a vacuum fluorescent display.

Introduction

This reference design shows a solution for obtaining the drive voltage required for a vacuum fluorescent display (VFD) power supply in automotive applications. The design includes the complete schematic, and presents the bill of materials (BOM), load/line regulation measurements, and test results.

VFD Basics

The VFD is composed of three basic electrodes—the cathode filaments, anodes (phosphor), and grids—under a high-vacuum condition in a glass envelope. The cathode consists of fine tungsten wires, coated by alkaline earth metal oxides which emit electrons. The grids are a thin metal mesh, which controls and diffuses electrons emitted from the cathode. The anodes are conductive electrodes on which the phosphor is printed to indicate characters, icons, or symbols. Electrons emitted from the cathode are accelerated with positive potential applied to both grid and anode; upon collision with the anode the electrons excite the phosphor to emit light. The desired illuminated patterns can be achieved by controlling the positive or negative potentials on each grid and anode. The anode and grid require a DC-regulated voltage to avoid flickering of the display. For driving large VFDs, the cathode requires AC drive to prevent luminance slant, i.e., the difference in brightness from one side of the display to the other. A frequency range of 20kHz to 200kHz is recommended to avoid audible noise and flicker.

Design Specifications and Setup

This reference design features the MAX15005 power-supply controller optimized for automotive and VFD applications. The application circuit is designed to meet the following specifications:

  • VIN: 9V to 16V continuous, 5.5V to 40V transient
  • VANODE: 77VDC ±10% at 18mA (typ), 58mA (max)
  • VGRID: 55VDC ±10% at 14mA (typ), 41mA (max)
  • VFILAMENT: 3.1VAC ±10% at 350mA (typ), 385mA (max)
  • Output ripple: 77V: 1VP-P; 55V: 0.5VP-P
  • Line regulation, VIN = 9V to 16V:
    VANODE = ±3%
    VGRID = ±3%
    VFILAMENT = ±5%
  • Load regulation: (see Line/Load Regulation Data section below)
  • Switching frequency: 22kHz
  • Temperature: -40°C to 125°C
The schematic for the above specifications is shown in Figure 1. In this design MAX15005A is used in the flyback configuration for obtaining three output voltages.

 Figure 1: Schematic of the MAX15005B Fly back converter for FSW = 22kHz.
Figure 1. Schematic of the MAX15005B flyback converter for FSW = 22kHz.

The bill of materials (BOM) for this reference design is given in Table 1.

Table 1. Bill of Materials for VFD Reference Design
DesignatorValueDescriptionPart NumberFootprintManufacturerQuantity
C1, C11, C1210nF, 100VCapacitorC2012X7R2A103K0805TDK®3
C2, C7270pF, 100VCapacitorGRM188R72A271KA01D0805Murata®2
C3, C5100nF, 100VCapacitorC2012X7R2A104K0805TDK2
C43.3nF, 25VCapacitor08053A332FAT2A0805AVX® Corporation1
C6, C81µF, 50VCapacitorC3216X7R1H105K1206TDK2
C9100pF, 100VCapacitorGRM2165C2A101JA01D0805Murata1
C10330µF, 35VCapacitorSMDTDK1
C13, C14, C15, C16, C17, C182.2µF, 100VCapacitorGRM32ER72A225KA35L1210Murata6
D13A, 400VDiodeS3GSMCVishay®1
D2, D3, D41A, 200VDiodeES1DSMAVishay3
Q111A, 55Vn-FETBUK92150-55ANXP®1
R132.4kΩResistorSMD, 5%, 0.125W0805KOA1
R2, R9, R17100kΩResistorSMD, 5%, 0.125W0805KOA3
R321kΩResistorSMD, 1%, 0.125W0805KOA1
R4, R6100kΩResistorSMD, 1%, 0.250W1206KOA2
R51.62kΩResistorSMD, 1%, 0.125W0805KOA1
R71.43kΩResistorSMD, 1%, 0.125W0805KOA1
R810kΩResistorSMD, 5%, 0.125W0805KOA1
R10499ΩResistorSMD, 1%, 0.125W0805KOA1
R11100ΩResistorSMD, 5%, 0.125W0805KOA1
R121kΩResistorSMD, 1%, 0.333W1210KOA1
R130.06ΩResistorSMD, 1%, SL1SL1KOA1
R1433kΩResistorSMD, 5%, 0.125W0805KOA1
R15, R161.0ΩResistorSMD, 1%, 0.250W1206KOA2
T154µHTransformerDCT20EFD-UxxSOA5SMDTDK1
Z19.1VZener diode1SMB5924BTSMBVishay1
IC1MAX15005BBoost controllerMAX15005BAUE+16TSSOPMAXIM®1

Waveform Measurements

The following test results were generated from the board built for evaluating the circuit.

Test conditions: VIN = 14V; RANODE = 3.3kΩ; RGRID = 3.3kΩ; RFILAMENT = 8Ω.
Figure 02.
Ch1: MOSFET Q1 drain voltage (VDRAIN); Ch2: current-sense voltage across R13 (VISENSE).


Test conditions: VIN = 14V; RANODE = 3.3kΩ; RGRID = 3.3kΩ; RFILAMENT = 8Ω.
Figure 03.
Ch1: anode output voltage ripple; Ch2: grid output voltage ripple.


Test conditions: VIN = 14V; RANODE = 3.3kΩ; RGRID = 3.3kΩ; RFILAMENT = 8Ω.
Figure 04.
Ch1: filament positive node voltage (VF1); Ch2: filament negative node voltage (VF2).


Test conditions: VIN = 14V; RANODE = 3.3kΩ; RGRID = 3.3kΩ; RFILAMENT = 8Ω.
Figure 05.
M: effective filament voltage (VF1 - VF2)

Line/Load Regulation Data

The following line/load regulation data was taken from the test board over the input voltage range and load.

VINI77 (mA)I55 (mA)V77 (VDC)V55 (VDC)VF (VRMS)
9.07.75.577.055.22.41
7.716.777.055.02.64
7.744.077.054.83.03
23.05.577.055.42.82
23.016.777.055.22.97
23.044.077.055.03.24
61.65.577.055.83.35
61.616.777.055.63.43
61.644.077.055.43.62
14.07.75.577.055.22.52
7.716.777.055.02.75
7.744.077.054.83.14
23.05.577.055.42.80
23.016.777.055.23.08
23.044.077.055.03.36
61.65.577.055.83.50
61.616.777.055.73.59
61.644.077.055.43.79
16.07.75.577.055.22.63
7.716.777.055.02.86
7.744.077.054.83.25
23.05.577.055.43.04
23.016.777.055.23.20
23.044.077.055.03.49
61.65.577.054.83.25
61.616.777.055.03.49
61.644.077.055.43.92

Conclusion

This application note presents a power-supply reference design for driving a typical vacuum fluorescent display in an automotive application. The design was built to the specifications presented here. The design was then tested. The circuit schematic, BOM, and typical waveforms have been presented.

AVX is a registered trademark of AVX Corporation.
Maxim is a registered trademark of Maxim Integrated Products, Inc.
Murata is a registered trademark of Murata Manufacturing Co., Ltd.
NXP is a registered trademark of NXP Semiconductors.
TDK is a registered trademark of TDK Corporation.
Vishay is a registered trademark of Vishay Intertechnology, Inc.



评论

技术专区