R3612 데이터 시트보기 (PDF) - Power Innovations

부품명

상세내역

제조사

R3612

PROGRAMMABLE OVERVOLTAGE PROTECTOR FOR ERICSSON COMPONENTS 3357/3 DCLIC

Power Innovations 

R3612

PROGRAMMABLE OVERVOLTAGE PROTECTOR

FOR ERICSSON COMPONENTS 3357/3 DCLIC

DECEMBER 1995 - REVISED SEPTEMBER 1997

R1

WIRE A

R2

WIRE B

SLIC

~1

~2

D3 - D5 D4 VGG

NEGATIVE

SLIC

SUPPLY

D1

TH

D2 C1 D6

+

Figure 4. DISCRETE GATED THYRISTOR PROTECTION CIRCUIT

VFD3/4 is the forward voltage of diode D3 or D4

VFD5 is the forward voltage of diode D5

VGG is the gate reference voltage provided from the negative SLIC supply voltage VBAT.

VGK is the gate-cathode voltage of the thyristor.

The basic protection voltage is equal to the SLIC supply voltage plus a few volts. If the over voltage produced

sufficient cathode current, the thyristor would regenerate and crowbar into a low voltage on-state condition.

This action removes the voltage stress from the SLIC. The series gate diode, D5, is needed to prevent

shorting the SLIC supply rail when the thyristor crowbars. When the thyristor comes to delatch it will be

conducting the combined current of both SLIC outputs, via diodes D3 and D4, and so its holding current

needs to be above this current level.

This protection arrangement minimises the voltage stress on the SLIC, no matter what value of supply

voltage. In some SLIC designs, to minimise power consumption, the supply voltage is automatically adjusted

to a value that is just sufficient to drive the required line current. For short lines the supply voltage would be

low, but for long lines a higher supply voltage would be generated to drive sufficient line current. Thus a

protection scheme which tracks the battery voltage is ideal for this type of application. The normal protection

implementation used a small diode bridge (D1 to D4), an RCA SGT10S10 high holding current thyristor (TH)

and a fast diode (D5).

One or possibly two extra components are needed to ensure the correct functioning of the protection. Figure

5 shows how the finite thyristor regeneration time allows a small fraction of the fast impulse (12 A/µs) to

appear as gate current. The following negative gate current is the series gate diode recovery as the thyristor

switches. A gate decoupling capacitor, C1, is needed to maintain a reasonably constant gate supply voltage

during the clamping period.

In Figure 5, the positive gate charge (QGS) is about 0.1 µC which, with the 1 µF gate decoupling capacitor

used, increased the gate supply by about 0.1 V (= QGS/C5). This change is not visible on the -72 V gate

PRODUCT INFORMATION

9

Share Link: