Application Note

High Power Semiconductor Crowbar

Protector for AC Power Line Applications

Power Input Line Risks and Protection

AC power line disturbances are the cause of many equipment failures. The damage can be as elusive as occasional data loss or as

dramatic as the destruction of a power supply, LED Lighting, Industrial system and consumer equipment such as ovens or refrigerators

and television sets.

Power line disturbances go by many names---transients, surges, spikes, glitches, etc. But regardless of the speciﬁc name, an

understanding of their characteristics and the operation of the various protection components available is necessary to design an

effective protection circuit.

There are some popular protection components for these power input lines. The most common over voltage protection components

are MOVs (Metal Oxide Varistor), high power TVS (Transient Voltage Suppression) Diodes and GDTs (Gas Discharge Tube). In this article,

we are going to discuss a new and innovative method of using a silicon crowbar component known as, the SIDACtor

Protection

Thyristor, for the main over voltage protection solution for AC power lines.

Surge Protection

Surge protection components can be divided into two basic types: Crowbar type devices such as GDTs and protection thyristor type

SIDACtor

components and clamp type components such as TVS diodes, MOVs etc.

The clamp type components have faster response time but are limited in their current handling ability because the transient energy

must be dissipated by the clamping component. Also, the voltage drop across a clamp type component increases as a function of the

conducted current passing through it. Thus a higher clamping voltage threshold component will have a lower peak current capability.

(The power rating remains the same for all components in a particular series but since power is the product of the voltage and current,

an increasing voltage demands a decrease of current).

A crowbar type component can handle much higher surge current because during their on-state condition, the voltage across the

component is extremely low. These crowbarring components act as a “near short circuit value” path shunting the transient energy

away from the protected equipment. And this, low on-state voltage will further reduce any electrical over stress to the protected circuit.

SIDACtor

Component in AC Power Line Protection

Questions may arise due to the nature of the SIDACtor

component being a crowbar protection and its compatibility with an AC power

source. This article will review the design parameters for selecting a SIDACtor

component for AC power line protection. Please note

that this discussion of the SIDACtor

component use is conﬁned to AC power line only; it is not compatible for high current DC supply

ports. The SIDACtor

component will reset on an AC port at the zero-crossing every half-cycle for an AC signal. However, for high

current DC power lines, the SIDACtor

component will not reset if the short circuit current available is higher than its holding current

parameter. Of course if you connect the SIDACtor

component with TVS or MOV in series, it can be used on DC power line too. TVS or

MOV Vbr should be equal or higher than DC max voltage

Application Note

Littelfuse Pxxx0FNL, Pxxx0ME and Pxxx0S3N Series SIDACtor

Component

The Littelfuse Pxxx0FNL, Pxxx0ME and Pxxx0S3N Series high energy SIDACtor

component has a crowbarring characteristic, which

offers low on-state voltage values that are much lower than the arc voltage of the traditional GDT and it offers a much lower voltage

threshold than the clamping voltage of an MOV. Compared to clamping silicon TVS diodes, the Pxxx0FNL, Pxxx0ME and Pxxx0S3N

SIDACtor

component can handle a much higher surge current since its on-state-voltage is so low. It also provides a much lower over-

shoot characteristic for high dv/dt or high di/dt events as compared to the GDT, MOVs or TVS components.

The Pxxx0FNL, Pxxx0ME and Pxxx0S3N series have component working voltage (V

DRM

) (also known as off-state voltage) ranging from

58 V to 350 V. Referring to the I

surge current and I

TSM

table, the Pxxx0ME provides 5000 A 8/20 I

(peak pulse current rating) and a

minimum 400 A I

TSM

for 50/60 Hz AC single cycle sinusoidal wave surge event while Pxxx0FNL and Pxxx0S3N both can provides 3000

A 8/20 I

, a minimum 300 A and 250 A I

TSM

respectively for 50/60 Hz AC single cycle sinusoidal wave surge event.

Product Series of Pxxx0ME Series in TO-218

Surge I

and I

TSM

Part Number Marking

DRM

@ I

DRM

= 5 µA V

@ 100 V/µs

min

max

P1500MEL P1500ME 140 180

P1900MEL P1900ME 155 220

P2300MEL P2300ME 180 260

P3800MEL P3800ME 350 430

P4800MEL P4800ME 450 600

TSM

50/60 Hz

8/20

1.2x50

min

5000

400

Pxxx0ME Series in TO-218

Product Series of Pxxx0FNL Series in TO-262M

Surge I

and I

TSM

Part Number Marking

DRM

@ I

DRM

= 5 µA V

@ 100 V/µs

min

max

P0640FNL P0640FN 58 77

P0720FNL P0720FN 65 88

P0900FNL P0900FN 75 98

P1100FNL P1100FN 90 130

P1300FNL P1300FN 120 160

P1500FNL P1500FN 140 180

P1900FNL P1900FN 155 220

P2300FNL P2300FN 180 260

P2600FNL P2600FN 220 300

P3100FNL P3100FN 275 350

P3500FNL P3500FN 320 400

P3800FNL P3800FN 350 430

TSM

50/60 Hz

8/20

1.2x50

min

3000 300

Pxxx0FNL Series in TO-262M

Notes:

1. Current waveform is µs

2. Voltage waveform is µs

3. P1500MEL to P2300MEL have surge rating of 5 kA @ 8/20. For surge rating of P3800MEL, it is a minimum 4 kA and

typical 5kA @ 8/20 μs.

Notes:

1. Current waveform is µs

2. Voltage waveform is µs