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Inverters
Most Kyocera transmissive and transflective LCDs have cold fluorescent light (CFL or CCFL) tubes which
provide bright white light at the back of the LCD. Inverters are required to provide high voltage
alternating-current power to the CFL tubes. The inverter circuit takes an continuous DC voltage and
inverts it to AC and transforms it to a higher voltage. Most Kyocera LCDs require the AC frequency to
be in the 50-100 kHz range.
An inverter will have a high no load voltage. The CFL will pull that down to a less high
Starting Discharge Voltage. As the gas in the CFL is ionized, the Discharging Tube Current
begins to flow and the voltage drops further to a steady Discharging Tube Voltage. The starting
discharge voltage is a strong function of temperature, requiring perhaps 30% more voltage to start
at 0°C compared to room temperature. It is also a function of tube length, with longer tubes requiring
more voltage. These CFL ratings are given in section 13 of each full LCD specification. An important function
of the inverter is to limit the discharging tube current. If the current is increased, the CFL life will be
reduced, although the brightness will increase. See ERG's paper on
Selection of Backlight Inverters.
Dimming
Some LCD applications require that the operator be able to control the brightness of the LCD backlight, for
example when operating a vehicle or boat at night. There are two common ways for an inverter to reduce
the brightness of a CFL. The amplitude of the alternating current can be reduced. However at about 40%
of the typical full current, the CFL suddenly ceases to carry any current and the CFL goes dark. This is
called Amplitude Dimming. The amount of analog dimming is indicated by a variable voltage or a variable
resistance. Analog dimming can be used on both CSTN and TFT LCDs.
The other common way to reduce the brightness of a CFL tube is to rapidly start and stop the current.
This is done with pulse width modulation and is called PWM
dimming. As the amount of OFF time in a
PWM cycle is increased, the brightness decreases. PWM dimming can easily reduce the brightness to 2% of
full brightness. However when used with a CSTN LCD there is very often an interaction between the PWM
frequency and the LCD frame frequency which results in an undesirable pulsing of the LCD brightness. The
pulsing gets better as the brightness approaches maximum. It is not a problem if the CSTN LCD is always
operated at full brightness and it is not a problem with TFT LCDs. Some inverters have on-board PWM,
which is controlled by a variable voltage. Some inverters have an input for customer-provided PWM. A PWM
output is often available at no extra cost as a software-controlled feature of a microprocessor. This
reduces the cost of the inverter and eliminates the cost of a mechanically-controlled or digitally-controlled
potentiometer to provide a control input to the inverter.
Disclaimer
The customer, not Kyocera, is responsible for choosing an inverter which performs properly in the customer's
system and environment. The Kyocera factory recommends an inverter in section 1 of the full specification
for each LCD. This inverter will have been tested with the LCD across the LCD's temperature range, but not
across all electromagnetic environments. Additional inverters are suggested below based only
on data sheet data, without test.
Primary Kyocera Inverters
In order to give customers the assurance of single vendor responsibility, Kyocera sells open-component
inverter boards for many Kyocera LCDs. These are analog dimming inverters, meaning that if the customer installs
a variable resistor, then the user can adjust the brightness down to 40% of its maximum value. They
are also switchable on-off by logic, for easy implementation of power saving features. The recommended
Kyocera inverter is given in section 2 of each full LCD specification.
The Kyocera inverters described below all require 12VDC input. They all have the same JST S5B-ZR-SM3
(JST) input connector and they all ship with an input cable, having the matching ZHR-5 (JST) connector
and 5 unterminated wires. To quickly set-up the cable for maximum brightness, the customer should:
- Twist wire 2 (black) and wire 3 (yellow) together and attach to customer's GND. For on-off control,
the customer may switch the yellow wire to GND with mechanical switch or digital logic.
- Twist wire 4 (black) and wire 5 (blue) together, but do not attach to anything else. To dim the LCD,
the customer may connect a 5K Ohm variable resistor between them, which will reduce discharge current down
to 40% of design point.
- Attach wire 1 (red) to 12Vdc
These Kyocera inverters are all rated for 0 to 50°C
operating temperature. Many Kyocera LCDs are rated for -20
to 70°C operating range. Consequently Kyocera cannot
recommend a Kyocera inverter for them. For demonstration of wide temperature LCDs at room temperatures, customers can use the same inverter as
recommended for similarly named LCDs with 0 to 50°C range.
K1 Inverter, part number PH-BLC08-K1, single QZ-19-A3MYL (Honda) output connector. The K1 inverter
is specified for most single tube models of the 6.0", 7.7", 8.4" and 10.4" legacy LCD
families.
K2 Inverter, part number PH-BLC08-K2, single SM02(8.)B-BHS-1 (JST) output connector. The K2 inverter
is specified for most single tube models of the 6.2", 6.5" and 7.2" LCD families. K1 and K2
are exactly the same, except for the output connector.
K3 Inverter, part number PH-BLC08-K3, single SM02(8.)B-BHS-1 (JST) output connector. The K3 inverter
is specified for most models of the 3.8", 4.3", 4.7" and legacy 5.7" LCD families. K3
differs from K2 in that it's no-load voltage is lower and the range of its AC frequency is wider. K2 can
always be substituted for K3, but not the reverse.
KCI-15 Inverter, part number KCI-15, dual QZ-19-A3MYL (Honda) output connectors.
Other Inverter Vendors
ERG, the Endicott Research Group, phone +1-607-754-9187,
www.ergpower.com.
ERG offers both open board and encapsulated inverters for both 5 and 12 Vdc inputs. Most ERG inverters
are rated for -20 to +70°C, which matches the Kyocera wide temperature range. They have a convenient
cross reference list on their home page which crosses many Kyocera LCDs to ERG standard parts. They offer
a very useful Design Guide.
TDK, TDK Corporation of America, phone +1-214-239-3100,
power.tdk.com/dcac/cxa_function/dcac_cxa_function.htm.
TDK offers both open board and encapsulated inverters, for 5, 12 & 24 Vdc inputs. They have a downloadable
cross reference list which crosses many older Kyocera LCDs to TDK standard parts. Their CXA-L0612A-VJL is the
recommended inverter for Kyocera LCDs with U-shaped CFL tubes (TCG057 and KCG057) because it provides the
high start voltage required at 0°C. Their CXA-P1212-VJL and CXA-0217 are recommended inverters for the
TCG075VG2 and KCG075VG2 LCDs. TDK inverters typically provide much more current than is recommended for
Kyocera LCDs, therefore a dimming voltage must be provided.
Zippy, Zippy Technology Corporation, phone +1-973-463-9499,
Zippy Inverters.
Zippy inverters are unique in that they use Piezo-ceramic to provide mechanical resonant energy conversion.
There is no magnetic flux and therefore no EMI noise. They claim that their true sine wave output makes
the CFL run cooler, resulting in longer lamp life. They feature wide operating temperature ranges and a
high starting voltage, which makes them a good choice at low temperatures.
Taiyo Yuden, North America, phone 800-348-2496, CCFL inverters page.
Taiyo Yuden previously used the name Xentek and offers two inverters for Kyocera LCDs.
Inverters for Kyocera KCG057 & TCG057 series LCDs
The Kyocera KCG057QV1, TCG057QV1 and TCG057VG1 LCDs achieve their high brightness from a "U"
shaped CFL. The longer length of the CFL requires an inverter that produces a
rather high starting discharge
voltage. Their worst case starting voltage requirement is 1550 Vrms at 0°C when new. As the CFL tube
ages, this requirement will increase. The length of the CFL wires results in some leakage. For both these
reasons, Kyocera believes that a 30% margin is prudent, which accounts for the recommendation in these
specifications for a minimum 2015 Vrms inverter no-load voltage. Kyocera does not offer an inverter like
this and existing low cost inverters do not produce this much voltage.
The Kyocera factory recommends the TDK model CXA-L0612A-VJL inverter although its minimum no-load voltage
specification is only 1500 Vrms, well below the recommended 2015 Vrms.
However it has performed fine in tests across the -10°C to
+70°C temperature range when powered by full 12.0 Vdc. The CFL
tube start voltage is greatly affected by temperature.
The long life of the CFL tube and the cool operation of the LCD depend on the CFL tube current being around
4.0 mA rms. It must never exceed 6.0 mA rms. There is a natural tendency for inverter manufacturers to design
for higher current as they design for higher voltage. So customers should expect to bias the dimming input
of the inverter to limit the CFL tube current.
Inverters for KCG057 & TCG057 series Hi-Brite LCDs
Manufacturer
Inverter |
Notes |
ERG
+1-607-754-9187
10m123411
|
12Vdc. 2200Vrms min. 4 mArms typ. -20 to +80°C.
No onboard dimming, input for external PWM. |
ERG
+1-607-754-9187
10mD3412
|
12Vdc. 2200Vrms min. 4 mArms typ. -20 to +80°C.
PWM dimming. |
TDK
+1-214-239-3100
CXA-L0612A-VJL |
12Vdc. 1500 Vrms min so avoid near freezing. 6.7 mArms max so needs dimming voltage.
Amplitude dimming. |
TDK
+1-214-239-3100
CXA-L0605A-VJL |
5Vdc. 1600 Vrms min so avoid near freezing. 6.7 mArms max so needs dimming voltage.
Amplitude dimming. |
Zippy
+1-973-463-9499
D00-8888-048 |
12Vdc. 2500 Vrms min at 0°C. -40 to +85°C
operating. Install both jumpers for 5.0mArms typ.
PWM dimming. |
Zippy
+1-973-463-9499
D00-0084-003 |
12Vdc. 2500 Vrms min at 0°C. -40 to +85°C
operating. Install both jumpers for 4.0mArms typ
or one jumper for 5.0mArms typ. PWM dimming. |
Zippy
+1-973-463-9499
D00-0084-004 |
12Vdc. 2500 Vrms min at 0°C. -40 to +85°C
operating. Install both jumpers for 4.0mArms typ
or one jumper for 5.0mArms typ. Amplitude dimming. |
Inverters for Kyocera KCG075 & TCG075 series LCDs
The new Kyocera KCG075VG2BE-G00 and TCG075VG2AC-G00 LCDs achieve their high brightness
from dual CFL tubes. Their worst case starting voltage requirement is 1235 Vrms at -10°C when
new. As the CFL tube ages, this requirement will increase. The length of the CFL wires results in
some leakage. For both these reasons, Kyocera believes that a 30% margin is prudent, which
accounts for the recommendation in these specifications for a minimum 1600 Vrms inverter no-load
voltage. Kyocera does not offer an inverter like this.
The Kyocera factory recommends the TDK model
CXA-P1212-VJL
inverter although its no-load voltage specification is only 1400 Vrms minimum and 1500 Vrms typical,
below the recommended 1600 Vrms. It has performed fine in tests. This recommendation is conditional on 12V
being present to power the inverter, even though a wider voltage range is allowed in the TDK specification.
Size may be an issue because this inverter is longer than the height of these LCDs.
In North America, the ERG inverters listed below are better choices
because of their higher starting voltages and easily limited current.
Dual-tube Inverters for KCG075/TCG075-series Hi-Brite LCDs
Manufacturer
Inverter |
Notes |
ERG
+1-607-754-9187
E3255
|
5 Vdc. 1500Vrms min. 5 mArms typ. 0 to +70°C.
No onboard dimming. Encapsulated package. |
ERG
+1-607-754-9187
K3573
|
12 Vdc. 1500Vrms min. 5 mArms typ. -20 to
+80°C. No onboard dimming, input for external
PWM. |
TDK
+1-214-239-3100
CXA-P1212-VJL |
12Vdc. 1400Vrms min / 1500Vrms typ so avoid near freezing. 6.7 mArms max so needs dimming voltage.
Amplitude dimming. |
Zippy
+1-973-463-9499
D00-8888-136 |
12Vdc. 2500 Vrms min at 0°C. -40 to +85°C
operating. Install both jumpers for 5.0mArms typ.
PWM dimming. |
Zippy
+1-973-463-9499
D00-0084-101 |
12Vdc. 2500 Vrms min at 0°C. -40 to +85°C
operating. Install both jumpers for 4.0mArms typ
or one jumper for 5.0mArms typ. PWM dimming. |
Inverters for Kyocera TCG104VG2AA-G00
The new Kyocera TCG104VG2AA-G00 LCD achieves its high brightness from dual CFL tubes, but they are
both powered from the same connector, requiring inverters with different connectors. The worst case
starting voltage requirement is 1325 Vrms at -10°C when new. As the CFL tube ages, this requirement
will increase. The length of the CFL wires results in some leakage. For both these reasons, Kyocera believes
that a 30% margin is prudent, which accounts for the recommendation in these specifications for a minimum
1720 Vrms inverter open circuit voltage. Kyocera does not offer an inverter like this.
The Kyocera factory recommends the TDK model
CXA-0308
inverter although its no-load voltage specification is only 1200 Vrms minimum and 1250 Vrms typical,
below the recommended 1720 Vrms. It has performed fine in
tests. This recommendation is conditional on 12V being
present to power the inverter, even though a wider voltage
range is allowed in the TDK specification.
Dual-tube Inverters for TCG104VG2AA-G00 Hi-Brite LCD
Manufacturer and
Inverter |
Notes |
TDK
+1-214-239-3100
CXA-0308
|
12Vdc. 1200Vrms min / 1200Vrms typ so avoid
near freezing. Current limitation already matches LCD. |
NEC
104PW161
|
12Vdc. 1200Vrms min / 1200Vrms typ so avoid near freezing. Its limitation of current already
matches the LCD. Same as TDK CXA-0308. |
ERG
+1-607-754-9187
8mAD2910
|
12 Vdc. 1300Vrms min so avoid near freezing. Its limitation of current already matches the LCD. |
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