AC16DGM Teccor Electronics, AC16DGM Datasheet - Page 177

• Manufacturer Part Number: AC16DGM
• Manufacturer: Teccor Electronics

Application Notes
tally that general purpose AC circuits will generate minimum
electromagnetic interference (EMI) if energized at zero voltage.
The ideal AC circuit switch, therefore, consists of a contact which
closes at the instant when voltage across it is zero and opens at
the instant when current through it is zero. This has become
known as “zero-voltage switching.”
For applications that require synchronized zero-crossing turn-on,
the illustration in Figure AN1007.11 shows a circuit which incor-
porates an optocoupler with a built-in zero-crossing detector
Figure AN1007.11
Also, this circuit includes a dv/dt snubber network connected
across the power triac. This typical circuit illustrates switching the
hot line; however, the load may be connected to either the hot or
neutral line. Also, note that the series gate resistor is low in value
(22
crossing turn-on is ensured in any initial half cycle.
Summary of Zero Crossing Turn-on Circuits
Zero voltage crossing turn-on opto-drivers are designed to limit
turn-on voltage to less than 20 V. This reduces the amount of RFI
and EMI generated when the thyristor switches on. Because of
this zero turn-on, these devices cannot be used to phase control
loads. Therefore, speed control of a motor and dimming of a
lamp cannot be accomplished with zero turn-on opto-couplers.
Since the voltage is limited to 20 V or less, the series gate resis-
tor that limits the gate drive current has to be much lower with a
zero crossing opto-driver. With typical inhibit voltage of 5 V, an
alternistor triac gate could require a 160 mA at -30 °C (5 V/
0.16 A = 31
then drive the gate of the triac with as much current as reliably
possible but stay under the I
22
with only 5 V, but limited to 909 mA if the voltage goes to 20 V. As
shown in Figure AN1007.12, Figure AN1007.13, and Figure
AN1007.14, a 22
zero crossing controllers.
©2002 Teccor Electronics
Thyristor Product Catalog
V cc
for the gate resistor, a current of at least 227 mA is supplied
, which is possible on a 120 V line and above, since zero-
R in
1
2
3
gate resistor). If the load has a high inrush current,
Crossing
Optocoupled Circuit with Zero-crossing Turn-on
(Triac or Alternistor)
Circuit
gate resistor is a good choice for various
Zero
TSM
6
5
4
rating of the opto-driver. By using
22
G
MT2
MT1
100
0.1 µF
Load
120 V ac
Hot
Neutral
AN1007 - 5
Figure AN1007.12
Figure AN1007.13
Figure AN1007.14
Input
Input
Input
R in 1
R in 1
R in
Non-sensitive Gate SCRs
Sensitive Gate SCRs
*
2
3
2
3
Gate Diodes to Have
Same PIV as SCRs
1
2
3
Crossing
Crossing
Circuit
Circuit
Zero
Zero
Crossing
Circuit
Zero
Zero Crossing Turn-on Opto Triac Driver
Zero Crossing Turn-on Non-sensitive SCR Driver
Zero Crossing Turn-on Opto-sensitive Gate SCR
Driver
6
5
4
6
5
4
6
5
4
22
22
G
1 K
1 K
22
Alternistor
Triac or
instead of lower location
instead of lower location
K
A
G
*
*
G
Load could be here
Load could be here
G
K
A
MT2
MT1
G
A
K
100
A
K
Load could be here
instead of lower location
http://www.teccor.com
100
0.1µf
Load
100
0.1 F
0.1 F
Load
Load
[phone]
120/240 V ac
120/240 V ac
120/240 V ac
Neutral
Hot
AN1007