D365A Datasheet, PDF (4/12 Pages) List of Unclassifed Manufacturers – Electroluminescent Lamp Driver IC

Block Diagram of the Inverter Circuitry
Theory of Operation
Electroluminescent (EL) lamps are essentially capacitors with one transparent electrode and a special phosphor material
in the dielectric. When a strong AC voltage is applied across the EL lamp electrodes, the phosphor glows. The
required AC voltage is typically not present in most systems and must be generated from a low voltage DC source.
Durel developed its patented 3-Port (3P) switch-mode inverter circuit to convert the available DC supply to an optimal
drive signal for high brightness and low-noise EL lamp applications. The Durel 3P topology offers the simplicity of a
single DC input, single AC output, and a shared common ground that provides an integrated EMI shielding.
The D365 drives the EL lamp by repeatedly pumping charge through an external inductor with current from a DC
source and discharging into the capacitance of the EL lamp load. With each high frequency (HF) charging cycle the
voltage on the lamp is increased. After 32 HF charging cycles, the lamp voltage is discharged to ground in the period
of 4 HF cycles. Then, the polarity of the inductive charging is reversed, and the charging and discharging cycles are
repeated. By this means, a low frequency alternating positive and negative voltage is developed at the single output
lead of the device to one of the electrodes of the EL lamp. Commonly connected to ground, the other lamp electrode
can then be considered as electrical shielding for any underlying circuitry in the application.
The EL driving system is divided into several parts: on-chip logic and control, on-chip high voltage output circuitry,
discharge logic circuitry, and off-chip components. The on-chip logic controls the lamp operating frequency (LF), as
well as the inductor switching frequency (HF), and the HF and LF duty cycles. These signals are combined and
buffered to drive the high voltage output circuitry. The output circuitry handles the power through the inductor and
delivers the high voltage to the lamp. The integrated discharge logic circuit enables the low-noise functionality of this
EL driver. The selection of off-chip components provides a degree of flexibility to accommodate various lamp sizes,
system voltages, and brightness levels. Since a key objective of EL driver systems is to save space and cost, required
off-chip components were kept to a minimum.
Durel provides a D365 Designer’s Kit, which includes a PC board intended to aid you in developing an EL lamp driver
configuration using the D365 that meets your requirements. A section on designing with the D365 is included in this
datasheet to serve as a guide to help you select the appropriate external components to complete your D365 EL driver
system.
Typical D365 configurations for driving EL lamps in various applications are shown on the following page. The
expected system outputs, such as lamp luminance, lamp output frequency and voltage, and average supply current
draw, for the various circuit configurations are also shown with each respective figure.
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