NOTICE
The OM5428 is now superseded
by the IES5528.
The information below is provided
for your convenience only.
Please refer to IES5528 for more details.
Nov 20 2009
OM5428
Phase Controller and Triac Triggering IC
1
FEATURES
It is mains powered, not requiring an expensive DC supply,
while also providing an external DC supply rail for
powering sensors or low power ICs.
The OM5428 allows the engineer design flexibility when
implementing a triac driven phase control or switching
application. It provides a complete triac control solution.
3
APPLICATIONS
•
Design flexibility for phase control applications
•
Adjustable proportional range
•
Adjustable hysteresis
•
Adjustable firing burst repetition time
•
Adjustable pulse width
•
Supplied from the mains
•
Provides supply for external temperature bridge
•
Low supply current, low dissipation
2
GENERAL DESCRIPTION
The flexibility of the OM5428 makes it suitable for a variety
of applications, such as:
•
Light Dimming
•
Motor Control
•
Zero Crossing on/off switching
•
Temperature Control
•
Time-proportional Control
•
Home Heating and Cooling
•
Ventilation Systems
•
Soft Start Motor Control
The OM5428 Phase Control and General Purpose Triac
Triggering IC is a bipolar integrated circuit that delivers
negative gate pulses for triggering a triac.
The OM5428 has numerous control options which,
coupled with the external IC configurability makes the
device suitable for a wide variety of applications in mains
power control.
4
BLOCK DIAGRAM
Active
LOAD
Rs
150 kΩ
VR37
Rz
1MΩ
VR25
T1
BTA208X
-600E
230
Vac
0V
R1
150kΩ
R4
120KΩ
Neutral
R2
300KΩ
Rg
910Ω
RMNS
VCC
OM5428
ZERO-
CROSSING
DETECTOR
13
12
PW
1
DC
SUPPLY
11
VEE
POT1
100KΩ
2
XOUT
5
IC+
6
IC−
QC+
4
DIFFERENCE
AMPLIFIER
SAWTOOTH
GENERATOR
SAW
14
OUTPUT
AMPIN AMPLIFIER
10
TRIG
9
15
FLY
16
XDIS
3
7
QC−
8
SDIS
DIFFEN
C2
100nF
−14V
OM5428cct1
C1
100µF
16V
R5
4k7
R3
1MΩ
C3
4.7nF
Fig.1 Block diagram of the OM5428
© 2006 Integrated Electronic Solutions Pty Ltd. trading as
Hendon Semiconductors, all rights reserved.
Contents are subject to the Disclaimer
2008 Jul 29, Revision 6.0
1
Product Specification
OM5428
Phase Controller and Triac Triggering IC
5
PINNING INFORMATION
5.1
Pinning Layout
5.2
Pin Description
PIN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
DESCRIPTION
pulse width control input
zero-crossing detector output
difference amplifier enable output
comparator non-inverting output
comparator non-inverting input
comparator inverting input
comparator inverting output
triac gate sense disable input
output stage input
output stage output
negative supply
positive supply
external power resistor
sawtooth generator trigger input
sawtooth generator output
zero crossing detector disable input
SYMBOL
PW
PW
XOUT
1
16
XDIS
XOUT
DIFFEN
QC+
IC+
IC−
QC−
SDIS
AMPIN
TRIG
V
EE
V
CC
RMNS
SAW
FLY
XDIS
2
15
FLY
DIFFEN
3
14 SAW
QC+
IC+
4
13
RMNS
OM5428
5
12
VCC
IC−
6
11
VEE
TRIG
AMPIN
QC−
7
10
SDIS
8
9
5428-pin
Fig.2 Pin configuration
6 QUICK REFERENCE DATA
T
amb
= 25°C
SYMBOL
−V
EE
−I
EE
I
TRIG
t
w
P
tot
T
amb
PARAMETER
DC supply voltage
supply current
output current
zero crossing pulse width
sawtooth pulse width
total power dissipation
operating ambient
temperature range
CONDITIONS
derived from mains voltage
quiescent current
set via gate resistor (Rg)
Rz = 500KΩ
RC (R = 300KΩ; C = 4.7nF)
maximum
−
−
−
−
−
−
−40
MIN
TYP
14.7
180
−
100
100
−
−
−
−
80
−
−
300
+85
MAX
V
µA
mA
µs
µs
mW
°C
UNIT
2008 Jul 29, Revision 6.0
2
Product Specification
OM5428
Phase Controller and Triac Triggering IC
7
FUNCTIONAL DESCRIPTION
The OM5428 comprises the following sections:
•
supply derived from mains via dropping resistor (Rs);
•
reset to ensure correct start-up;
•
gate sense for reduction in the number of pulses
produced when firing the triac;
•
zero-crossing detector synchronizes triac gate pulses;
•
difference amplifier passing a signal from a sensor, or
indication of a potentiometer setting or switch position.
•
ramp function generator operating as the saw-tooth
oscillator in time proportional or phase control;
•
output amplifier driving the triac gate.
7.1
Supply
input SAW (pin14) to the saw-tooth generator is also held
at a low state until the reset threshold has been reached.
During start-up the reset is also responsible for holding the
input pins to the difference amplifier, IC+ (pin 5) at a high
state and IC- (pin 6) at a low state. As a result, functions
such as soft and hard start while phase firing can be
realised.
7.3
Zero Crossing Detector
The OM5428 contains a zero- crossing detector to
produce pulses that coincide with the zero crossings of the
mains voltage to minimise RF interference and transients
on the mains supply.
In a static switch application (see figure 5) where the load
to be driven is purely resistive, the synchronization voltage
is obtained direct from the mains via a resistor. As a result
trigger pulses start shortly before, and end shortly after,
each zero-crossing of the mains voltage. In this manner
triac conduction is maintained through the mains voltage
zero-crossing, reducing radio interference to a minimum.
If the load contains an inductive component, the
synchronization will be produced by the internal gate
sense circuit rather than the zero-crossing detector. The
trigger pulse is then produced at the earliest possible
moment, i.e. immediately following zero-crossing of the
phase-shifted load current.
During phase control the zero- crossing detector is used to
generate a saw-tooth voltage synchronous with the mains.
As soon as the d.c. control voltage corresponding to a
preset trigger angle is exceeded the output is pulsed.
7.3.1
PW
The OM5428 has been designed so that it is supplied
directly from mains voltage via a dropping resistor. For this
purpose a regulator circuit is included to limit the DC
supply voltage. The external supply dropping resistor Rs
(mains voltage rated) is connected between the mains
active and pin RMNS; V
CC
is connected to the neutral or
common line. A smoothing capacitor C1 is connected
between V
CC
and V
EE
. The circuit produces a negative
supply voltage at V
EE
, which may be used to supply an
external circuit such as a temperature sensing bridge.
During the negative half of mains, current through the
external voltage dropping resistor Rs charges the external
smoothing capacitor C1 to the shunt voltage of the
regulator. The value of Rs should be chosen such that it
can supply the current for the OM5428, plus the charge
required to drive the triac gate and any external
(peripheral) circuits connected to V
EE
by recharging the
smoothing capacitor C1 on the mains negative half cycles.
Any excess current is bypassed through the shunt
transistor of the regulator. The maximum rated current
must not be exceeded.
During the positive half of the mains cycle the external
smoothing capacitor C1 supplies the circuit. Its
capacitance must be large enough to maintain the supply
voltage above the minimum specified limit.
A suitable VDR may be connected across the mains to
provide protection for the OM5428 and the triac against
mains-born transients.
7.2
Reset
The pulse width control input PW (pin 1) allows adjustment
of the pulse width at output XOUT (pin 2), to the value
required for the triac. This is done by choosing the value of
external synchronization resistor Rz between PW and the
AC mains. The pulse width is determined by the amount of
current flowing to or from pin PW. Any current exceeding
9µA will result in the output of the zero-crossing detector
being disabled. The zero-crossing detector output is also
inhibited when the XDIS input (pin 16) is HIGH, and
enabled when LOW, e.g. connected to V
EE
.
The pulse width can be determined using the following
formula:
⎛
asin
⎛
(
9
×10 ⋅
Rz
)
rad
⎞ ⎞
⎜
⎝
-----------------------------------
⎠⎟
Vmains
(
pk
)
-
P W
=
2
⎜
--------------------------------------------------------------
⎟
s
100π
⎜
⎟
⎝
⎠
–
6
A reset circuit providing four reset functions throughout the
OM5428 has been included. Initially the reset signal
ensures that trigger pulses are not produced until V
EE
has
reached its minimum value and C1 is fully charged. The
2008 Jul 29, Revision 6.0
3
Product Specification
OM5428
Phase Controller and Triac Triggering IC
7.3.2
XOUT
repetition frequency of load switching that can be adjusted
with the control voltage.
In phase control, the flyback of the saw-tooth is used as
the drive signal for generating the trigger pulse.
7.5.1
SAW
Output XOUT, which produces negative-going output
pulses, is an n-p-n open-collector output that for some
applications may require an external pull-up resistor
connected to V
CC
.
7.3.3
XDIS
Input XDIS can be used to disable the zero-crossing
detector, to inhibit the synchronised pulses provided by
XOUT. This is done by injecting a current into XDIS,
typically by connecting it via a 1MΩ resistor to V
CC
. Input
XDIS is connected directly to the base on an n-p-n
transistor referenced to V
EE
, and when not used it should
be connected directly to V
EE
.
XDIS must never be left floating.
7.4
7.4.1
Difference Amplifier
IC+, IC-, QC+, QC-
The firing burst repetition time is usually determined by an
external resistor and capacitor connected to the saw-tooth
generator trigger input SAW (pin 14). The capacitor
connected to SAW is charged via R2 connected to Vcc,
and discharged via an internal 10k resistor. Provided the
value of resistor R2 is much greater than the internal 10k
resistor, the repetition time is approximately 0.43 x RC.
R2 should not be less than 300kΩ. Repetition rate and
gate pulse width can be set by selecting a suitable value
for C3.
Typical gate pulse width is approximately.
t
g
= R.C.(0.102) s
When not used, SAW can be left unconnected.
7.5.2
FLY
IC+ and IC− (pins 5 and 6) are differential inputs of the
comparator or differential amplifier, with QC+ and QC−
(pins 4 and 7) as complementary outputs. QC+ and QC−
are n-p-n open collector outputs requiring external
collector resistors to V
CC
. QC+ will be HIGH and QC− will
be LOW when IC+ is higher than IC−.
IC+ and IC- are both the base drive of separate p-n-p
transistors. In order for correct operation of the
comparator, the input voltage on these pins should be set
up such that current is able to be drawn from them. Such
arrangements may involve a pot controlled voltage divider.
Complementary outputs QC+ and QC− are open collector
n-p-n outputs, and therefore require external pull-ups to
realise a “high” on the output. When not used these
outputs can be left open circuit.
7.4.2
DIFFEN
The output FLY (pin 15) is an n-p-n open-collector output.
During the flyback period of the saw-tooth pulse the
transistor is ON and is capable of sinking current.
7.6
Output Amplifier
The output stage is used to provide gate pulses of
sufficient current to drive a triac.
The output has been designed to produce negative going
pulses with respect to mains neutral. This allows a triac to
be fired in its more sensitive regions, reducing the amount
of gate current needed to latch the triac and hence
reducing the overall current consumption.
Depending on the configuration of the drive circuit, the
output can be used to provide single gate pulses, or a burst
of pulses. This operating mode needs to be taken into
account when calculating power supply requirements.
7.6.1
AMPIN
The comparator contains a p-n-p current mirror source
(referenced to V
CC
) that is activated by a current out of
DIFFEN (pin 3). The current drawn from pin 3 determines
the drive for the comparator outputs. Typically this current
is provided by a resistor connected between DIFFEN and
the negative supply rail V
EE
7.5
Saw-tooth Generator
The output stage is driven via an internal pull-up and
therefore may be inhibited by drawing current from input
AMPIN (pin 9). In typical applications this can be driven by
simple connection to the open collector FLY pin.
7.6.2
TRG
The saw-tooth generator may be used to produce bursts of
trigger pulses, with the net effect that the load is
periodically switched on and off.
With a time-proportional switch, the ramp voltage
produced by the saw-tooth generator serves to provide the
2008 Jul 29, Revision 6.0
4
The output TRIG (pin 10) is an n-p-n open-collector output
capable of sinking current i.e. conventional current flow
into the circuit.
Product Specification
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