UM0575 datasheet(12/20 Pages) STMICROELECTRONICS

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Getting started

UM0575

12/20

Getting started

3.1

Voltage level setting

To make the demonstration board operate with a given compressor-PTC couple, the only

thing to do is to check the divisor ratio of the R3/R4 resistors bridge.

First, the PTC voltage level, which is representative of a long enough START winding

activation, has to be defined. This level is called "VPTC-OFF".

To proceed, we propose to measure the PTC peak voltages in ON and in OFF state for the

whole range of operation, that is:

●

min and max values of the line voltage

●

at least one sample of all different compressors that could be used with the

e-STARTER

●

min and max values of the ambient temperature.

The PTC peak voltages in ON and in OFF state are called VPTC1 and VPTC2 respectively

(refer to the dashed lines in Figure 11).

Then, the "VPTC-OFF" level has to be chosen higher than the maximum value of VPTC1 in

order to ensure that the ACST6 has indeed been turned on at the beginning. The "VPTC-

OFF" level also has to be lower than the minimum value of VPTC2 in order to turn off the

ACST6 at the end of the required PTC conduction time.

In order to ensure a safe margin between these two levels, VPTC-OFF should be calculated

using the following equation:

Equation 2

According to Figure 4, the maximum VPTC1 level is 220 V. According to Figure 3, the

minimum VPTC2 level (198 V RMS line, no RUN cap, test conditions) equals 320 V (from the

Figure 11.

VPTC1 and VPTC2 definitions

V PTC1

V PTC2

V PTC

IPTC

V PTC1

V PTC2

V PTC

IPTC

AM00907v1

MIN

PTC

MAX

PTC

OFF

PTC

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