AN2383 datasheet(11/39 Pages) STMICROELECTRONICS

11 / 39 page

AN2383

Schematic

Doc ID 12433 Rev 3

11/39

3.4

Feedbacks

Figure 5.

Current peak, current phase and alarm

Feedback signals are output by the current transformer placed in series with the plate, and

temperature sensors.

The most important feedback is the current signal (label I-CTRL), which sends the MCU an

image of the current flowing through the plate. This signal is used to monitor the current and

set it in accordance with the selected working level.

In addition, the signal coming from the current transformer is sent to an operational

amplifier. If for any reason the current increases too much, exceeding the alarm threshold

set by the potentiometer, the MCU immediately takes action to prevent damage to the power

stage.

A NTC has been glued to the heatsink between the IGBTs. The signal is sent to the MCU to

monitor the heatsink temperature and drive the fan accordingly. In the same way, a PT1000

is placed in the middle of the plate to monitor the plate temperature. The signal is amplified

and sent to the MCU for processing.

Waveforms and a description of how these signals interact with the MCU are given in

Section 5: Measurements at 50 Hz.

AI12610

R41

100K

+15V

C19

22nF

R36

4K7

R34

1K8

Alarm management

R44

C18

22nF

R33

n.c.

TMP2

R40

62K

+15V

I-CTRL

C21

100nF

NTC2

PT1000

R18

100R

+15V

STTH102

–

U3A

LM 258

R35

2K2

+15V

–

U3B LM 258

with

PT1000 sensors

R45

12K

TP18

ALARM

C31

100nF

R32

2K7

Temperature control

for plate

TP19

C20

22nF

1:200

TH1

110

PT1

50K

R31

33R

R37

10K

C44

10nF

NTC4

47K

+5V

TMP1

R68

R69

100K

STTH102

TP20

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