May 2000 TOKO, Inc.
Page 15
TK6591x
APPLICATION INFORMATION (CONT.)
PART NO.
f lamp
f converter
min.Vp L type
TK65910
175 Hz
22.4 kHz
TK65911
200 Hz
25.6 kHz
TK65912
225 Hz
28.8 kHz
TK65913
250 Hz
32.0 kHz
TK65914
275 Hz
35.2 kHz
TK65915
300 Hz
38.4 kHz
TK65916
325 Hz
41.6 kHz
TK65917
350 Hz
44.8 kHz
TK65918
375 Hz
48.0 kHz
TK65919
400 Hz
51.2 kHz
D31FU
0.9V D32FU
D52FU
330 μH
390 μH
560 μH
270 μH
390 μH
470 μH
270 μH
390 μH
470 μH
270 μH
330 μH
390 μH
270 μH
330 μH
390 μH
220 μH
330 μH
390 μH
220 μH
330 μH
330 μH
220 μH
---
330 μH
220 μH
---
330 μH
220 μH
---
330 μH
D31FU
1.8V D32FU
D52FU
680 μH
1000 μH
1200 μH
680 μH
820 μH
1200 μH
680 μH
820 μH
1000 μH
680 μH
820 μH
1000 μH
680 μH
680 μH
820 μH
560 μH
680 μH
820 μH
560 μH
680 μH
820 μH
560 μH
680 μH
820 μH
560 μH
680 μH
680 μH
470 μH
560 μH
680 μH
After selecting the inductor type and value, Table 4 of the TK6591X data sheet can be used to determine the typical output
voltage for a given loading of EL lamp capacitance. If you wish to reduce this output voltage, just reduce the inductor
’
s
inductance value.
The TK6591X is the recommended part type to use in the low voltage single cell (0.9 V input) split supply application
because it has the lowest peak current set point of the TK659XX family of EL drivers. This, therefore, restricts the size
of EL panels that can be driven to those with smaller capacitance values.
TABLE 5: INDUCTANCE SELECTION TABLE FOR SINGLE AND DUAL CELL ALKALINE SYSTEMS
NOISE CONSIDERATIONS
There are two specific noise types relevant to the user when it comes to choosing EL Drivers: the Audio Noise and the
Electromagnetic Interference(EMI) Noise.
The EMI Noise would most likely come from the boost converter/coil section. The Toko EL Driver has specifically been
designed to address this issue.
The device runs at a fixed frequency and the frequency is controlled tightly in order to avoid interference.
Furthermore, the panel frequency is forced to be a 128 submultiple of the boost frequency avoiding any type of beating
frequencies.
By choosing shielded coils, the EMI noise problem can further be reduced.
The Audio Noise can come from several components which make up the system.
The coil, if operated in the audio range would be a source of noise. The Toko EL Driver was carefully designed to give
the user the choice of 10 frequencies such that the coil frequency will always be above audio range. Since the device
operates at a fixed frequency in discontinuous conduction mode, there are no possible submultiples which would cause
audible noise.
The filter capacitor can be a source of audio noise. Furthermore, depending on how this cap is mounted, the mounting
can act as an amplifier (as a speaker box). Certain ceramic caps driven from a high voltage source as in the EL Driver
case, demonstrate a PIEZOELECTRIC effect which is distinguishable in the Audio Range.
Other types of caps, such as film type do not denote an audio noise.
The panel itself, being operated well into the Audio Range (175 Hz to 400 Hz) and of a capacitive nature driven from high
voltage may also display Audible Noise. Mounting of this panel can enhance or diminish this natural effect of the panel.