Zero Voltage Switch
Power Controller
The UAA2016 is designed to drive triacs with the Zero Voltage
technique which allows RFIfree power regulation of resistive loads.
Operating directly on the AC power line, its main application is the
precision regulation of electrical heating systems such as panel heaters
or irons.
A builtin digital sawtooth waveform permits proportional
temperature regulation action over a
1
C band around the set point.
For energy savings there is a programmable temperature reduction
function, and for security a sensor failsafe inhibits output pulses when
the sensor connection is broken. Preset temperature (i.e. defrost)
application is also possible. In applications where high hysteresis is
needed, its value can be adjusted up to 5
C around the set point. All
these features are implemented with a very low external component
count.
Zero Voltage Switch for Triacs, up to 2.0 kW (MAC212A8)
Direct AC Line Operation
Proportional Regulation of Temperature over a 1
C Band
Programmable Temperature Reduction
Preset Temperature (i.e. Defrost)
Sensor Failsafe
Adjustable Hysteresis
Low External Component Count
Representative Block Diagram
Sense Input
Sampling
Full Wave
Logic
+
-
1/2
Failsafe
Hysteresis
Adjust
4
3
4-Bit DAC
Temperature
Reduction
Voltage
Reference
Internal
Reference
+
1
+
V
EE
5
Pulse
Amplifier
Supply
Voltage
+
Output
6
7
2
11-Bit Counter
+V
CC
Sync
UAA2016
8
Synchronization
ON Semiconductort
Semiconductor Components Industries, LLC, 2001
August, 2001 Rev. 7
1
Publication Order Number:
UAA2016/D
Device
Operating
Temperature Range
Package
UAA2016
SEMICONDUCTOR
TECHNICAL DATA
ZERO VOLTAGE SWITCH
POWER CONTROLLER
ORDERING INFORMATION
UAA2016D
UAA2016P
T
A
= 20
to +85
C
SO8
Plastic DIP
3
V
ref
1
PIN CONNECTIONS
4
8
7
6
5
2
Hys. Adj.
Sensor
Temp. Reduc.
Sync
V
CC
Output
V
EE
(Top View)
P SUFFIX
PLASTIC PACKAGE
CASE 626
D SUFFIX
PLASTIC PACKAGE
CASE 751
(SO8)
1
8
1
8
UAA2016
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2
MAXIMUM RATINGS
(Voltages referenced to Pin 7)
Rating
Symbol
Value
Unit
Supply Current (I
Pin 5
)
I
CC
15
mA
NonRepetitive Supply Current
(Pulse Width = 1.0
s)
I
CCP
200
mA
AC Synchronization Current
I
sync
3.0
mA
Pin Voltages
V
Pin 2
V
Pin 3
V
Pin 4
V
Pin 6
0; V
ref
0; V
ref
0; V
ref
0; V
EE
V
V
ref
Current Sink
I
Pin 1
1.0
mA
Output Current (Pin 6)
(Pulse Width < 400
s)
I
O
150
mA
Power Dissipation
P
D
625
mW
Thermal Resistance, JunctiontoAir
R
JA
100
C/W
Operating Temperature Range
T
A
20 to + 85
C
ELECTRICAL CHARACTERISTICS
(T
A
= 25
C, V
EE
= 7.0 V, voltages referred to Pin 7, unless otherwise noted.)
Characteristic
Symbol
Min
Typ
Max
Unit
Supply Current (Pins 6, 8 not connected)
(T
A
= 20
to + 85
C)
I
CC
--
0.9
1.5
mA
Stabilized Supply Voltage (Pin 5) (I
CC
= 2.0 mA)
V
EE
10
9.0
8.0
V
Reference Voltage (Pin 1)
V
ref
6.5
5.5
4.5
V
Output Pulse Current (T
A
= 20
to + 85
C)
(R
out
= 60 W, V
EE
= 8.0 V)
I
O
90
100
130
mA
Output Leakage Current (V
out
= 0 V)
I
OL
--
--
10
A
Output Pulse Width (T
A
= 20
to + 85
C) (Note 1)
(Mains = 220 Vrms, R
sync
= 220 k
)
T
P
50
--
100
s
Comparator Offset (Note 5)
V
off
10
--
+10
mV
Sensor Input Bias Current
I
IB
--
--
0.1
A
Sawtooth Period (Note 2)
T
S
--
40.96
--
sec
Sawtooth Amplitude (Note 6)
A
S
50
70
90
mV
Temperature Reduction Voltage (Note 3)
(Pin 4 Connected to V
CC
)
V
TR
280
350
420
mV
Internal Hysteresis Voltage
(Pin 2 Not Connected)
V
IH
--
10
--
mV
Additional Hysteresis (Note 4)
(Pin 2 Connected to V
CC
)
V
H
280
350
420
mV
Failsafe Threshold (T
A
= 20
to + 85
C) (Note 7)
V
FSth
180
--
300
mV
NOTES: 1. Output pulses are centered with respect to zero crossing point. Pulse width is adjusted by the value of R
sync
. Refer to application curves.
2. The actual sawtooth period depends on the AC power line frequency. It is exactly 2048 times the corresponding period. For the 50 Hz case it is 40.96
sec. For the 60 Hz case it is 34.13 sec. This is to comply with the European standard, namely that 2.0 kW loads cannot be connected or removed from
the line more than once every 30 sec.
3. 350 mV corresponds to 5
C temperature reduction. This is tested at probe using internal test pad. Smaller temperature reduction can be obtained by
adding an external resistor between Pin 4 and V
CC
. Refer to application curves.
4. 350 mV corresponds to a hysteresis of 5
C. This is tested at probe using internal test pad. Smaller additional hysteresis can be obtained by adding an
external resistor between Pin 2 and V
CC
. Refer to application curves.
5. Parameter guaranteed but not tested. Worst case 10 mV corresponds to 0.15
C shift on set point.
6. Measured at probe by internal test pad. 70 mV corresponds to 1
C. Note that the proportional band is independent of the NTC value.
7. At very low temperature the NTC resistor increases quickly. This can cause the sensor input voltage to reach the failsafe threshold, thus inhibiting output
pulses; refer to application schematics. The corresponding temperature is the limit at which the circuit works in the typical application. By setting this
threshold at 0.05 V
ref
, the NTC value can increase up to 20 times its nominal value, thus the application works below 20
C.
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Load
C
F
MAC212A8
R
out
8
5
R
sync
V
EE
V
ref
Temp. Red.
R
def
Hys
Adj
S2
R
S
Figure 1. Application Schematic
R
1
Synchronization
+
1
S1
R
2
4
R
3
-
11-Bit Counter
4-Bit DAC
3
UAA2016
1/2
Failsafe
Pulse
Amplifier
Sampling
Full Wave
Logic
Internal
Reference
Supply
Voltage
2
+V
CC
7
Output
6
R
S
Sync
+
+
+
Sense Input
NTC
220 V
a
c
APPLICATION INFORMATION
(For simplicity, the LED in series with R
out
is omitted in
the following calculations.)
Triac Choice and R
out
Determination
Depending on the power in the load, choose the triac that
has the lowest peak gate trigger current. This will limit the
output current of the UAA2016 and thus its power
consumption. Use Figure 4 to determine R
out
according to
the triac maximum gate current (I
GT
) and the application
low temperature limit. For a 2.0 kW load at 220 Vrms, a good
triac choice is the ON Semiconductor MAC212A8. Its
maximum peak gate trigger current at 25
C is 50 mA.
For an application to work down to 20
C, R
out
should be
60
. It is assumed that: I
GT
(T) = I
GT
(25
C)
exp (T/125)
with T in
C, which applies to the MAC212A8.
Output Pulse Width, R
sync
The pulse with T
P
is determined by the triac's I
Hold
, I
Latch
together with the load value and working conditions
(frequency and voltage):
Given the RMS AC voltage and the load power, the load
value is:
R
L
= V
2
rms/POWER
The load current is then:
I
Load
+
(Vrms
2
sin(2
p
ft)V
TM
) R
L
where V
TM
is the maximum on state voltage of the triac, f is
the line frequency.
Set I
Load
= I
Latch
for t = T
P
/2 to calculate T
P
.
Figures 6 and 7 give the value of T
P
which corresponds to
the higher of the values of I
Hold
and I
Latch
, assuming that
V
TM
= 1.6 V. Figure 8 gives the R
sync
that produces the
corresponding T
P
.
R
Supply
and Filter Capacitor
With the output current and the pulse width determined as
above, use Figures 9 and 10 to determine R
Supply
, assuming
that the sinking current at V
ref
pin (including NTC bridge
current) is less than 0.5 mA. Then use Figure 11 and 12 to
determine the filter capacitor (C
F
) according to the ripple
desired on supply voltage. The maximum ripple allowed is
1.0 V.
Temperature Reduction Determined by R
1
(Refer to Figures 13 and 14.)
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Figure 2. Comparison Between Proportional Control and ON/OFF Control
Overshoot
Time (minutes, Typ.)
Time (minutes, Typ.)
Time (minutes, Typ.)
Heating
Power
P(W)
Room
Temperature
T (
C)
Time (minutes, Typ.)
Proportional Band
Proportional Temperature Control
D Reduced Overshoot
D Good Stability
ON/OFF Temperature Control
D Large Overshoot
D Marginal Stability
T
P
is centered on the zero-crossing.
AC Line
Waveform
I
Latch
T
P
I
Hold
Figure 3. Zero Voltage Technique
Gate Current
Pulse
f = AC Line Frequency (Hz)
Vrms = AC Line RMS Voltage (V)
R
sync
= Synchronization Resistor (
)
TP +
14 x Rsync ) 7
105
Vrms
2 x
p
f
(
s)
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CIRCUIT FUNCTIONAL DESCRIPTION
Power Supply (Pin 5 and Pin 7)
The application uses a current source supplied by a single
high voltage rectifier in series with a power dropping
resistor. An integrated shunt regulator delivers a V
EE
voltage of 8.6 V with respect to Pin 7. The current used by
the total regulating system can be shared in four functional
blocks: IC supply, sensing bridge, triac gate firing pulses and
zener current. The integrated zener, as in any shunt
regulator, absorbs the excess supply current. The 50 Hz
pulsed supply current is smoothed by the large value
capacitor connected between Pins 5 and 7.
Temperature Sensing (Pin 3)
The actual temperature is sensed by a negative
temperature coefficient element connected in a resistor
divider fashion. This two element network is connected
between the ground terminal Pin 5 and the reference voltage
5.5 V available on Pin 1. The resulting voltage, a function
of the measured temperature, is applied to Pin 3 and
internally compared to a control voltage whose value
depends on several elements: Sawtooth, Temperature
Reduction and Hysteresis Adjust. (Refer to Application
Information.)
Temperature Reduction
For energy saving, a remotely programmable temperature
reduction is available on Pin 4. The choice of resistor R
1
connected between Pin 4 and V
CC
sets the temperature
reduction level.
Comparator
When the positive input (Pin 3) receives a voltage greater
than the internal reference value, the comparator allows the
triggering logic to deliver pulses to the triac gate. To
improve the noise immunity, the comparator has an
adjustable hysteresis. The external resistor R
3
connected to
Pin 2 sets the hysteresis level. Setting Pin 2 open makes a 10
mV hysteresis level, corresponding to 0.15
C. Maximum
hysteresis is obtained by connecting Pin 2 to V
CC
. In that
case the level is set at 5
C. This configuration can be useful
for low temperature inertia systems.
Sawtooth Generator
In order to comply with European norms, the ON/OFF
period on the load must exceed 30 seconds. This is achieved
by an internal digital sawtooth which performs the
proportional regulation without any additional component.
The sawtooth signal is added to the reference applied to the
comparator negative input. Figure 2 shows the regulation
improvement using the proportional band action.
Noise Immunity
The noisy environment requires good immunity. Both the
voltage reference and the comparator hysteresis minimize
the noise effect on the comparator input. In addition the
effective triac triggering is enabled every 1/3 sec.
Failsafe
Output pulses are inhibited by the "failsafe" circuit if the
comparator input voltage exceeds the specified threshold
voltage. This would occur if the temperature sensor circuit
is open.
Sampling Full Wave Logic
Two consecutive zerocrossing trigger pulses are
generated at every positive mains halfcycle. This ensures
that the number of delivered pulses is even in every case. The
pulse length is selectable by R
sync
connected on Pin 8. The
pulse is centered on the zerocrossing mains waveform.
Pulse Amplifier
The pulse amplifier circuit sinks current pulses from Pin
6 to V
EE
. The minimum amplitude is 70 mA. The triac is
then triggered in quadrants II and III. The effective output
current amplitude is given by the external resistor R
out
.
Eventually, an LED can be inserted in series with the Triac
gate (see Figure 1).
T
A
= - 20
C
T
A
= 0
C
140
80
200
Figure 4. Output Resistor versus
Triac Gate Current
I
GT
, TRIAC GATE CURRENT SPECIFIED AT 25
C (mA)
20
60
160
180
40
50
40
30
60
120
100
R , OUTPUT
RESIST
OR ( )
out
Figure 5. Minimum Output Current
versus Output Resistor
T
A
= - 20
C
T
A
= + 85
C
200
180
160
140
120
100
80
60
40
100
R
out
, OUTPUT RESISTOR (
)
0
20
40
60
80
I , MINIMUM OUTPUT
CURRENT
(mA)
Out(min)
T
A
= +10
C
T
A
= -10
C
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