PDP Power Devices characteristics

AN2503

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4.1.1

Measurement set-up

Power losses and thermal analysis measurements were performed based on an average

switching frequency. In fact, switching performances have to be related to the maximum

frequency in the system, usually 250 kHz, whereas power losses and thermal management

have to be related to an average frequency. The Average Switching frequency takes into

account the fact that during a picture time, the power devices do not switch at the maximum

frequency for the whole time, but only during the sustain phases. The sustain duration, and

consequently the number of sustain pulses, increases starting from subfield 1 to subfield 10.

Average frequency can be calculated starting from sustain duty ratio.

Note:

Picture time = 16.67 ms

SF = number of sustain pulses

N = number of lines

The sustain duty ratio is carried out for a 10 subfield case in both single scan and dual scan

operations, varying the scan speed duration (time needed to scan a single line in the

display), for VGA (480 lines), XGA (768 lines) and HD (1080 lines).

According to the following formula,

For a VGA display

This means that power devices in ERC and discharge circuit need to be designed for an

average frequency of 140 kHz (maximum) in terms of power losses and thermal

management. Clearly peak current and peak voltage rating do not change when we perform

this averaged analysis.

Table 1.

10 subfield / single scan

Scan speed

VGA 480

XGA 768

HD 1080

3 µsec

-

-

-

2.5 µsec

0.130

-

-

2 µsec

0.274

-

-

1.5 µsec

0.418

0.159

-

1 µsec

0.562

0.389

0.202

Table 2.

10 subfield / dual scan

Scan speed

VGA 480

XGA 768

HD 1080

3 µsec

0.418

0.158

-

2.5 µsec

0.490

0.274

0.040

2 µsec

0.562

0.389

0.202

1.5 µsec

0.634

0.504

0.364

1 µsec

0.706

0.620

0.526