原标题：Supertex HV816高压可调光场致发光(EL)屏驱动方案

　　Supertex 公司的HV816是高压可调光场致发光(EL)屏驱动器,可驱动电容达150nF的灯或大约42平方吋的面积.输入电压为2.7V-5.5V,和单个锂离子电池兼容,输出电压为360VPP,输出电压可调整,以便进行调光,输出放电速率可控制,音频噪音低,可用于平板电脑键盘,笔记本电脑键盘,显示器,手提仪表和电子记事簿.本文介绍了HV816主要特性, 方框图和典型应用电路图.

　　HV816:High Voltage, Dimmable EL(Electro Luminescence) Lamp Driver

　　(EL) lamp driver designed for driving a lamp capacitance of up to 150nF, or an area of approximately 42 square inches.

　　It is comprised of a boost converter followed by an H-bridge. The boost converter produces a regulated output voltage, which is set at a nominal value of 180V using an internal reference voltage. The H-bridge is used to produce a differential output drive and the EL lamp will therefore see ±180V (360V peak-to-peak). The HV816 has two internal oscillators, one for controlling the boost converter switching frequency and the other for controlling the H-bridge switching frequency.

　　Having separate control of each switching frequency allows flexibility in the circuit design.

　　The operating input supply voltage is 2.7 to 5.5V, but the Enable (EN) and Select (SEL) interface to the device will accept The Supertex HV816 is a high voltage Electroluminescent logic high levels down to 1.5V. The EN input is for turning the device ON and OFF. The SEL input is for external logic control of the H-bridge switching frequency, if required.

　　The HV816 boost converter stage uses a single inductor and a minimum number of external components. The input voltage to the inductor can be different from the input voltage to the HV816 (split supply). The external inductor is connected either between the LX and VDD pins or, for split supply applications, between the LX pin and a higher voltage supply (shown as VIN in the Block Diagram). An external MOSFET has to be driven by the switch oscillator to generate a high voltage. The switching frequency for this MOSFET is set by an external resistor connected between the RSW-Osc pin and the supply pin VDD. During operation, the external switching MOSFET turns on and allows energy to be stored in the inductor; this energy is transferred into the capacitor CS when the MOSFET turns off. The voltage at CS will increase with every switching cycle. Once the voltage at CS reaches the desired regulation limit, nominally 180V, the external switching MOSFET is turned OFF to conserve power.

　　The CS capacitor is connected between the CS pin and ground; the CS pin is internally connected to the H-bridge. Energy from the boost converter stage is stored in the capacitor before being transferred to the EL lamp. Depending on the EL lamp sizes, a 1.0nF to 15nF capacitor should be used for CS.

　　The EL lamp switching frequency can be in the range 100Hz to 1.0kHz. This frequency can be set by either an external logic signal at the SEL pin, with a frequency that is 4 times the desired EL lamp switching frequency, or by an external resistor connected between the REL-Osc and VDD pins. If external frequency is input to the device at the SEL pin, the REL-Osc pin should be connected to ground.

　　The HV816 has the provision to control the discharge rate of the output to minimize audible noise emitted by the EL lamp, which is connected between the pins VA and VB. An external resistor from the RSLEW-OUT pin to ground controls the VA, VB output discharge rate.

　　EL lamp dimming can be accomplished by changing the input voltage to the VREG pin. The VREG pin allows an external voltage source to control the VCS amplitude. The VCS voltage is approximately 135 times the voltage at the VREG pin.

　　HV816主要特性:

　　360VPP output voltage for high brightness

　　Large output load capability of up to 150nF

　　2.7 to 5.5V operating supply voltage

　　Single lithium ion cell compatible

　　Adjustable output regulation for dimming

　　External switching MOSFET

　　Low audible noise

　　Output discharge slew rate control

　　1.5V logic

　　Dedicated Enable pin

　　Two EL frequency controls

　　Independent lamp and converter frequency setting

　　Split supply capability

　　Available in 4x4 QFN and 16-Lead SOW packages

　　HV816应用:

　　Laptop keyboards

　　Netbook keyboards

　　Display signs

　　Portable instrumentation equipment

　　Electronic organizers

　　图1.HV816方框图

　　图2.HV816典型应用电路图