SIP11203DB Просмотр технического описания (PDF) - Vishay Semiconductors

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SIP11203DB

SiP11203 Demonstration Board

Vishay Semiconductors 

SiP11203DB

Vishay Siliconix

90

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35 Vin

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48 Vin

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75 Vin

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2 A 4 A 6 A 8 A 10 A 12 A 14 A 15 A

Io (A)

Figure 5. Converter efficiency over line voltage and load range

Primary VCC

Start Up Waveform

(2 V/DIV)

Output Voltage

Start Up Waveform

(1 V/DIV)

The secondary bias supply (VIN on the SiP11203) is

provided from VCC via the timing signals SRH and SRL

generated by the Si9122. These timing signals drive

the positive and negative terminals of the primary

winding of pulse transformer T1. This transformer has

a step-down ratio of 4:3 for each secondary winding.

The secondary windings are center tapped, with a

capacitive filter placed at the center tap point, and rec-

tifier diodes anode-connected to ground, connected to

each end of the secondary windings. This arrange-

ment means that the timing information is coupled to

the SiP11203, while a bias voltage is also available at

the center-tap to power the SiP11203. This bias volt-

age VIN is used to power the output drivers OUTA and

OUTB. It is also internally regulated to a 5 V bias, VL,

which powers the other internal circuitry on the

SiP11203. The voltage on one of the pulse transformer

secondary windings wrt ground is shown in Figure 6

(b). It can be seen from this that the center-tap voltage,

which provides the VIN supply to the SiP11203, is

equal to the average value of the secondary voltage.

Output of pulse

tansformer (2 V/DIV)

VIN for SiP11203

(2 V/DIV)

1.00 mS/DIV

(a)

1.00 µS/DIV

(b)

Figure 6. (a)VCC, VO, during startup (b)Pulse Transformer Secondary Voltage, Pulse Transformer Center-Tap Voltage, VIN.

Magnetic Component

The main power transformer structure is illustrated in

Figure 7. The multilayer PCB layout is described in

Table 1. The primary magnetizing inductance is

between 11 µH and 15 µH, and the turns ratio is 4:1:1.

The core is a combination of an E14/3.5/5 core and its

associated I-plate in 3F3 material. The output filter

inductor structure is illustrated in Figure 8 and the mul-

tilayer PCB layout is described in Table 2. The inductor

has 2 sections of 3 turns connected in parallel, with a

custom ground center gap to yield an inductance value

between 850 nH and 900 nH. The auxiliary winding is

constructed of 10 turns, divided between 2 layers,

resulting in a 10:3 turns ratio between the auxiliary and

main windings. The core is a combination of an E14/

3.5/5 core and its associated I-plate in 3F3 material.

www.vishay.com

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P1

P2

Primary

P3

S1 S2 Secondary

S3 S4 Secondary

P4

Figure 7. Power Transformer Structure

Document Number: 74254

S-60997–Rev. A, 12-Jun-06

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