307C Lighting Thermistors
Vishay Cera-Mite
PTC Thermistors For Electronic Fluorescent Ballasts
FEATURES
• Electrode preheat thermistors for use in compact
fluorescent lamps (CFL) and electronic ballasts.
• Current limiting, time-delayed start-up extends lamp life.
• Quiet, flicker-free operation.
• Developed in cooperation with leading ballast designers.
• Both standard and custom parts are available.
• Economical, reliable and proven in millions of lamps
throughout the world.
APPLICATION CONSIDERATIONS
• Ignition time can be optimized to increase life of lamp.
• PTC resistance (R
25
) is chosen, along with filament
resistance and application voltage, to control desired
electrode preheat current.
• Lamp preheat time is determined by time required for
thermistor to switch from low to high resistance state.
Preheat currents shown result in switch times of
approximately 1 second at 25°C. Lower currents result in
longer switch times.
PTC THERMISTORS FOR ELECTRONIC FLUORESCENT BALLASTS
FLUORESCENT LAMP
C
PTC
Tinned Copper Clad Steel Wire
24 AWG when D
≤
8.5mm
22 AWG when D
≥
10mm
5mm
max
32mm min
4.5mm
max.
D
LS = 5mm
Options:
• High Temperature Coating
• Short Clipped Leads
• Other Wire Forms and Lead
Spacings
RESISTANCE INSTANTANEOUS CONTINUOUS PREHEAT
R
25
VOLTAGE
VOLTAGE
CURRENT
(OHMS)
(V
RMS
)
(V
RMS
)
(mA)
4
1
2
3
150
265
80
215
150
280
200
200
50
175
50
430
70
265
150
350
100
260
95
370
125
230
80
280
150
235
90
260
200
320
145
300
240
350
150
260
300
400
165
225
380
410
170
205
600
420
120
185
600
460
200
170
850
450
340
140
100
340
265
390
150
340
150
400
180
350
165
380
200
355
265
300
300
370
75
270
300
420
320
230
500
480
400
190
800
530
450
155
850
520
175
190
70
210
50
750
70
300
140
725
85
210
50
670
150
400
100
550
85
280
60
820
100
310
90
750
400
430
120
420
D
MAX.
(mm)
4.5
4.5
5.5
5.5
5.5
5.5
5.5
5.5
5.5
5.5
5.5
5.5
5.5
5.5
7
7
7
7
7
7
7
7
7
8.5
8.5
8.5
8.5
10
10
10
5
PART
NUMBER
307C1407
307C1414
307C1230
307C1654
307C1364
307C1259
307C1253
307C1223
307C1171
307C1225
307C1390
307C1252
307C1224
307C1622
307C1403
307C1306
307C1569
307C1375
307C1242
307C1360
307C1361
307C1362
307C1260
307C1367
307C1366
307C1363
307C1287
307C1258
307C1365
307C1422
6
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
R
25
- Nominal zero power resistance
±
25% at 25°C. For given diameter, higher resistance thermistors offer higher maximum voltages.
Instantaneous Voltage - Maximum rms voltage permitted across thermistor during fluorescent lamp start-up cycle.
Continuous Voltage - Maximum rms voltage continuously applied across thermistor during normal lamp operation.
Preheat Current - rms current (60Hz) which switches thermistor to high resistance in approximately 1 second at 25°C ambient.
Size (mass) of PTC influences rate of I
2
R temperature increase. For given resistance, larger thermistors have longer switch times.
Optional coating slightly increases switch time.
Note 6:
P/N suffix (not shown) describes wire lead forms and other options.
www.vishay.com
10
ceramite.support@vishay.com
Document Number: 23088
Revision 14-May-02
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