ST UM0575, STEVAL-IHT003V1 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 V
PTC1
& V
PTC2
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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THERMOSTAT
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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)
V
PTC
(100V/div)
I
PTC
(10A/div)
V
PTC_OFF
V
PTC
(100V/div)
I
PTC
(10A/div)
V
PTC
(100 V/div)
I
PTC
(10 A/div)
V
PTC_OFF
AM00899v1
V
PTC
(100V/div)
V
PTC_OFF
I
PTC
(10A/div)
AM00900v1
Operation principle UM0575
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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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