Operations of Shortcircuit Protector Circuit

Anode

TTL, microcomputer, etc.

Photodiode

Amp.

Constant voltage circuit

Interface

IGBT protector circuit

GND

C

FS

GND

Cathode

IGBT

8

9

10

11

12

13

14

Light emitting diode

PC929

2. Reduction of the IGBT gate voltage, and suppression of the collector current.

3. Simultaneous output of signals to indicate the shortcircuit condition (FS signal) from FS terminal to the microcomputer

4. Judgement and processing by the microcomputer

PC929

3

1

Feedback to primary side

Precautions for Operation

1. It is recommended that a capacitor of about 1000pF is added between C-terminal and GND in order to prevent

malfunction of C-terminal due to noise. In the case of capacitor added, rise of the detecting voltage is delayed.

Thus, use together a resistance of about 1k

Ω set between Vcc and C-terminal.

The C-terminal rise time varies with the time constant of CR added. Check sufficiently before use.

2. The light-detecting element used for this product is provided with a parasitic diode between each terminal and GND.

When a terminal happens to reach electric potential lower than GND potential even in a moment, malfunction

or rupture may result. Design the circuit so that each terminal will be kept at electric potential lower than the

GND potential at all times.

In the case of instantaneous shortcircuit, run continues.

At fault, input to the photocoupler is cut off, and IGBT is turned OFF.

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