HV8051 Ver la hoja de datos (PDF) - Supertex Inc

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componentes Descripción

Fabricante

HV8051

High-Voltage EL Lamp Driver

Supertex Inc 

HV8051/HV8053

External Component Description

External Component

Selection Guide Line

Diode

Fast reverse recovery diode, 1N4148 or equivalent.

Cs Capacitor

REL-osc

0.01µF to 0.1µF, 100V capacitor to GND is used to store the energy transferred from the inductor.

The EL lamp frequency is controlled via an external REL resistor connected between REL-osc and VDD of the

device. The lamp frequency increases as REL decreases. As the EL lamp frequency increases, the amount

of current drawn from the battery will increase and the output voltage VCS will decrease. The color of the

EL lamp is dependent upon its frequency.

RSW-osc

CSW Capacitor

CLx Capacitor

The switching frequency of the converter is controlled via an external resistor, RSW between RSW-osc and

VDD of the device. The switching frequency increases as RSW decreases. With a given inductor, as the

switching frequency increases, the amount of current drawn from the battery will decrease and the output

voltage, VCS, will also decrease.

A 1nF capacitor is typically recommended on RSW-osc to GND for HV8053. As the input voltage of the device

increases, a faster switching converter frequency is required to avoid saturating the inductor. With the

higher switching frequency, more noise will be introduced. This capacitor is used to shunt any switching

noise that may couple into the RSW-osc pin.

In order to drive the HV8053 more efficiently when high brightness is required, a 47pF, 100V CLx capacitor

needs to be used at the Lx pin to GND. This capacitor reduces the total amount of current drawn by the

circuit by reducing the dv/dt voltage on the internal switch.

Lx Inductor

The inductor Lx is used to boost the low input voltage by inductive flyback. When the internal switch is on,

the inductor is being charged. When the internal switch is off, the charge stored in the inductor will be

transferred to the high voltage capacitor CS. The energy stored in the capacitor is then available to the

internal H-bridge and therefore to the EL lamp. In general, smaller value inductors, which can handle

more current, are more suitable to drive larger size lamps. As the inductor size decreases, the switching

frequency of the inductor (controlled by RSW) should be increased to avoid saturation.

560µH Murata inductors with 14.5Ω series DC resistance is typically recommended. For inductors with the

same inductance value but with lower series DC resistance, lower RSW value is needed to prevent high

current draw and inductor saturation.

Lamp Size

As the EL lamp size increases, more current will be drawn from the battery to maintain high voltage across

the EL lamp. The input power, (VIN x IIN), will also increase. If the input power is greater than the power

dissipation of the package (350mW), an external resistor in series with one side of the lamp is recom-

– OBSOLETE – mended to help reduce the package power dissipation.

Application Hints

should be bypassed with a capacitor located close to the lamp

driver. Values can range from 0.1µF to 1µF depending on supply

Start with a high conversion frequency to avoid inductor satura-

impedance. A supply bypass capacitor elsewhere in the host

tion. Adjust converter frequency (via RSW-osc) and inductor value

circuit is sufficient if located close to the driver.

to obtain desired lamp drive voltage and supply current. Make

sure that inductor current does not approach saturation as

For lower power consumption, set a low lamp drive frequency,

specified on the inductor data sheet. Higher VIN’s and smaller

inductors require a higher conversion frequency to avoid satura-

use a 1mH inductor, and adjust power conversion frequency for

minimum current draw.

tion.

For high brightness, set lamp drive frequency for desired hue,

Adjust the lamp drive frequency via REL-osc to obtain desired

lamp brightness and hue.

use a 330µH inductor and adjust power conversion frequency

until desired brightness is obtained.

If the desired VCS cannot be obtained, try decreasing lamp drive

frequency slightly.

If VCS is above 80 volts, insert a 2kΩ resistor in series with the

lamp.

Monitor overall power consumption. If above 350mW, insert a

resistor in series with the lamp to decrease device power

dissipation.

For longer lamp life, use as low a lamp drive frequency as is

acceptable. Adjust converter frequency and inductor value to

obtain acceptable brightness.

For high lamp drive frequencies, employ a FET follower on the

output. See application note AN-H33.

In keeping with good circuit design practice, the supply voltage

15-12

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