ST UM0575 User manual

February 2009 Rev 1 1/20
UM0575
User manual
STEVAL- IHT003V1, e-STARTER demonstration board
based on the ACST6 and X02
Introduction
The e-STARTER demonstration board (Figure 1) presents an innovative solution, patented
by STMicroelectronics, to reduce the power losses due to the positive thermal coefficient
(PTC) resistors in compressor starter circuits.
This solution features an ACST6 device which is used to turn off the PTC current after the
motor startup. It should be noted that the traditional PTC is still used in the electronic starter
circuit because it increases safety in case of ACST short-circuit or diode-mode failure (ref.
EN60335-1). This solution allows the starter standby losses to be decreased from typically
2.5 W to 380 mW or 40 mW, respectively for 230 V and 100 V applications.
The e-STARTER operation principle along with detailed schematics are given as well as
demonstration board performances and the method to adapt the circuit to a dedicated
compressor.
It should be noted that this board is not a "plug and play" solution. First, the PTC behavior
has to be checked (especially VPTC1 & VPTC2 levels as explained in Section 3.1) and then
the R4 resistor value has to be chosen before using the board with a compressor.
Figure 1. STEVAL- IHT003V1, e-STARTER demonstration board
AM01038v1
www.st.com

Contents UM0575
2/20
Contents
1 Operation principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Compressor starter application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Standard PTC behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 e-STARTER operation mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.1 Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.2 ON state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 Board performances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 Maximum current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Standby power losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 Fast transient voltages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4 Surge voltages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.5 Reliability and safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3 Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1 Voltage level setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2 Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Appendix A Component layout and printed circuit board . . . . . . . . . . . . . . . . . 15
Appendix B Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

UM0575 List of figures
3/20
List of figures
Figure 1. STEVAL- IHT003V1, e-STARTER demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Figure 2. Compressor starter application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Figure 3. PTC operation, no RUN cap. (compressor OFF time > 10' mains: 198 V RMS) . . . . . . . . . 5
Figure 4. PTC operation with RUN cap.(compressor OFF time < 1' mains: 264 V RMS) . . . . . . . . . . 5
Figure 5. e-STARTER schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 6. Voltage spikes at zero current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 7. PTC turnoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 8. e-STARTER maximum current versus conduction time . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 9. Spurious e-STARTER triggering with a 2 kV surge (230 V compressor) . . . . . . . . . . . . . . 10
Figure 10. e-STARTER voltage limited to 648 V thanks to the RUN capacitor
(2 kV IEC61000-4-5 surge). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 11. VPTC1 and VPTC2 definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 12. e-STARTER connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 13. e-STARTER topside silk screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 14. e-STARTER SMD components layout (bottom view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 15. e-STARTER copper side (bottom view, dimensions in cm) . . . . . . . . . . . . . . . . . . . . . . . . 16

Operation principle UM0575
4/20
1 Operation principle
1.1 Compressor starter application
Single-phase induction motors, used for compressor control, use an auxiliary winding. This
winding permits a higher torque to be applied at startup. The most popular method to control
the start winding is to add a positive temperature coefficient (PTC) resistor in series with this
winding and the thermostat (Figure 2). Then, each time the thermostat is closed, the current
flows through the start winding and begins to heat the PTC. After a few hundreds of
milliseconds, the PTC value rapidly increases from a few W to several tens of kW. This
results in reducing the start winding current to a few tens of mA. This winding can then be
considered as open. The PTC then behaves like a switch in OFF state, but with a high
leakage current, resulting in high power losses (approx. 2.5 W).
Figure 2 gives the typical schematics of this application where a run or a start capacitor can
be connected in parallel (point 1) or in series (point 2) respectively with the PTC.
1.2 Standard PTC behavior
The transition between PTC ON and OFF states brings a voltage increase across this
variable resistor. Figure 3 and Figure 4 show two oscillograms of the same PTC in two
different operating conditions, for a 230 V compressor which can use both a start and run
capacitor. We see that, at the end of the PTC conduction, the voltage across it reaches
approximately 250 V (refer to "VPTC_OFF" indication). This voltage level is similar whatever
the operating conditions are (min or max RMS line voltage, run capacitor or not, etc.). The
PTC could be turned off as soon as this level has been reached. Section 1.3 explains how to
implement an electronic solution to achieve this function.
Figure 2. Compressor starter application
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UM0575 Operation principle
5/20
1.3 e-STARTER operation mode
1.3.1 Schematics
Figure 5 gives the typical schematics of an "e-STARTER" for a 230 V application. The
demonstration board presented here also features some optional pads to add a snubber
(components R6 and C4) as shown in Appendix A and B. The figure also gives the names of
the main electrical parameters which will be detailed in the following sections.
The traditional PTC resistor has to be connected between the "START" and the "PTC"
solder pads (refer also to Section 3.2).
Note: The C3 capacitor is not soldered on the breadboards. It can be added if one wants to
evaluate its impact on board immunity.
Figure 3. PTC operation, no RUN cap.
(compressor OFF time > 10' mains:
198 V RMS)
Figure 4. PTC operation with RUN
cap.(compressor OFF time < 1'
mains: 264 V RMS)
VPTC(100V/div)
IPTC(10A/div) VPTC_OFF
VPTC(100V/div)
IPTC(10A/div)
VPTC (100 V/div)
IPTC(10 A/div) VPTC_OFF
AM00899v1
V PTC (100V/div)
V PTC_OFF
I PTC (10A/div)
AM00900v1

Operation principle UM0575
6/20
1.3.2 ON state
As soon as the mains voltage is applied:
●M1 is OFF because the voltage drop across the PTC is not high enough to reach the
DZ1 clamping level
●T2 is then turned on, thanks to the gate current provided by R2
●T1 is turned on thanks to the gate current provided by T2
Both T1 and the PTC are then ON.
At each zero-current crossing point, the ACST6 turns off. The reapplied voltage across
T1/T2 triggers back T1 which results in some voltage spikes at each zero-current crossing
point (typically around 40 V as shown in Figure 6 for a 230 V compressor).
Applying the click test of norm EN55014, the noise duration could last more than 200 ms
(depending on the type of compressor and PTC). The individual spikes last a few hundreds
of microseconds and are spaced at intervals of 10 ms, so the limits of continuous
disturbance are applicable. Since the spike peaks are less than 100 V, the e-STARTER
solution should fulfill the requirements of EN55014. It should be noted that tests results
greatly depend on the compressor used during the tests.
Figure 5. e-STARTER schematics
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UM0575 Operation principle
7/20
When the PTC conduction time has been sufficient to start the compressor, its voltage
suddenly rises. This voltage rise is sensed by the R3/R4 divisor bridge.
If the level is higher than the DZ1 clamping level, the thyristor, consisting of Q1 and Q2, is
latched. M1 is then turned on.
As M1 is ON, there is no more gate current to trigger T2, so T1 also stays OFF. The PTC is
then turned off.
No more current circulates through the PTC, thus no power is dissipated in it.
Figure 7 shows the typical behavior of this circuit. The C1 capacitor voltage gives an image
of the PTC voltage. When its value reaches the DZ1 clamping level (15 V), the MOS gate is
latched to 15 V. The PTC is then turned off (refer to the IA ACST6 current waveform).
Figure 6. Voltage spikes at zero current
Figure 7. PTC turnoff
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Board performances UM0575
8/20
2 Board performances
2.1 Maximum current
During e-STARTER conduction, the power losses are similar to those of the standard PTC
solution as the same current circulates through this resistor. The only difference is that a
small part of the voltage is also held by T1.
In the case of an ACST6, its forward voltage drop can be considered to be a constant
forward voltage, Vt0, of at worst 0.8 V and a dynamic resistance, Rd, of at worst 80 m. So
even with a 10 A peak current, the voltage drop is less than 1 V.
This forward voltage drop should be taken into account mainly to evaluate the junction
temperature elevation of the semiconductor switch.
For an ACST6 in the TO220AB package, without any heatsink, this junction temperature
elevation is equal to:
●30° C after a 5 A RMS current during 3 s (worst case of typical 100 V/60 Hz
compressors)
●50° C after an 11 A RMS current during 0.5 s (worst case of typical 230 V/50 Hz
compressors)
This ensures that TJremains below its maximum allowed temperature (125° C), even with a
75° C initial temperature. Figure 8 gives the maximum repetitive RMS current that the
ACST6-7ST can withstand without any heatsink. This curve is given for 40° C and 75° C
ambient temperatures. As with the e-STARTER solution, the heating time of the PTC is not
long enough to warm the electronic devices, so the 40° C curve is closer to the real
e-STARTER operating conditions.
2.2 Standby power losses
During e-STARTER standby, the losses are caused only by the resistors, which are still
connected to the mains voltage. Indeed, the ACST leakage current is in practice very much
lower than 20 µA so that the resulting losses can be neglected.
Figure 8. e-STARTER maximum current versus conduction time
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UM0575 Board performances
9/20
The two resistors which are mainly dissipating power at standby are:
●R2 - used to provide T2 with gate current during the e-STARTER on state
●R3 - used to sense the voltage level across the PTC
As R2 is connected just behind the diodes’ bridges, the VAK voltage is applied across it, in
full-wave mode. R3 senses only half the voltage across the PTC and T1. This voltage is also
equal to VAK as T1 is OFF, and so no current is circulating through the PTC.
We can neglect the voltage drops of M1 and of C1, which are lower than 0.6 V and 16 V
respectively. The power losses, dissipated by the two resistors, are given by the following
equations:
Equation 1
An example with R2 = 470 kΩand R3 = 510 kΩgives:
●For a 230 V / 50 Hz application using a run capacitor, VAK can reach up to 350 V RMS.
The overall power losses then equal 380 mW.
●For a 100 V / 60 Hz application using or not a run capacitor, VAK stays around the line
voltage, i.e at worst 115 V RMS. The overall power losses then equal 41 mW.
2.3 Fast transient voltages
Immunity tests, as described by the IEC 61000-4-4 standard, have been performed with the
schematics of Figure 5, connected in series with a compressor without a RUN or START
capacitor. e-STARTER spurious triggerings have not been detected with spikes up to 2 kV.
This high immunity level has been reached thanks to:
●the high dV/dt capability of the ACST6
●the improved dV/dt capability of the very sensitive SCR X0202M (20 µA < Igt < 50 µA)
thanks to the fact that its gate is short-circuited to the cathode via M1 in OFF state, and
also thanks to the R6-C4 snubber circuit
●the RGK (R7) resistor which is added on the ACST6 device to derivate the current
provided by R2 when M1 is ON
●the immunity provided by the layout of the printed circuit board (refer to Figure 15)
It should be noted that spurious triggering of the e-STARTER is not a problem as such
behavior is not seen by the end user, and as these turn-ons do not lead to any component
failure.
2.4 Surge voltages
The ACST6 device is an overvoltage protected device which means that it can be used
without any varistor in parallel with its terminals. If a high energy surge is applied to the
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Board performances UM0575
10/20
mains, as described in the IEC 61000-4-5 standard, when the e-STARTER is off, two cases
can occur:
●A no-run capacitor is connected across the e-STARTER: the surge voltage is then
entirely held by the ACST6. If the energy is high enough, the leakage current of the
device can exceed its break-over level, leading to a turn-on of the e-STARTER lasting
at worst 10 ms (refer to Figure 9).
●A run capacitor is used: the surge energy is absorbed by this capacitor. The voltage
level is then limited below 1 kV, which is the typical clamping level of the ACST6. No
spurious turn-on occurs in this case (refer to Figure 10).
It should be noted that in case of a spurious triggering in break-over mode, the ACST6
current is limited by the START winding inductance. The current value is then typically in the
range of 2 A. This is far below the level guaranteed with ACST6, where a 47 Ωload can be
used in such operation mode (refer to the ACST6 datasheet). With a 2 kV surge, the peak
current then equals 40 A in this case.
2.5 Reliability and safety
Reliability tests have been performed with ACST6-7ST samples submitted to a current
shape equivalent to an inrush current of 11 A RMS during 0.5 s. No parameter evolution of
these samples has been detected after 450,000 cycles, which is representative of the
lifetime of a refrigerator. This result demonstrates the excellent capability of these 6 A
products even for applications with high inrush currents.
Concerning safety, the EN6033561 standard imposes the consideration of short-circuit or
diode-mode failures of all silicon power switches involved in safety features. The failure of an
entire e-STARTER cannot lead to safety issues (electrical or mechanical shock, fire). If the
e-STARTER power switch dies in short-circuit or diode-mode, the start winding current is still
limited by the PTC. The start winding is then protected and the compressor still works.
Indeed, the starter function is still ensured by the PTC. The only drawback is that the
standby losses increase back to 2.5 W.
Figure 9. Spurious e-STARTER triggering
with a 2 kV surge (230 V
compressor)
Figure 10. e-STARTER voltage limited to 648 V
thanks to the RUN capacitor (2 kV
IEC61000-4-5 surge)
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AM00905v1
+ 648V
VAK
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