AN701 データシートの表示（PDF） - Vishay Semiconductors

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AN701

Designing High-Frequency DC-to-DC Converters With the Si9114A Switchmode Controller

Vishay Semiconductors 

➀

➁

➂

➀ VDS of MOSFET 50 V/div

➁ Voltage across sense resistor 1 V/div

➂ Voltage across gate 5 V/div

Figure 23 Time Base 500 ns/div.

AN701

Vishay Siliconix

➀

➁

➀ VDS of MOSFET 50 V/div

➁ Output ripple 10 mV/div

Figure 24 Time Base 500 ns/div.

➀

➀ Output transient response for 1.5 to 3 A.

Figure 25 Time Base 200 ms/div.

100

90

80

70

60

0 2 4 6 8 10 12 14 16 18

Output Power (W)

Figure 27 Si9114A 15-W, 500-kHz Converter Efficiency

Document Number: 70575

16-Jan-01

➀

➀ Output transient response for 1.5 to 3 A.

Figure 26 Time Base 5 ms/div.

In Figure 24, the low output ripple (<20 mV) is obtained with two

10-mF capacitors.1 In Figure 26, note the excellent recovery

time of <25 ms to within 1% of output for a 50% load step with

total excursion of <300 mV. The efficiency of the converter is

measured in Figure 27.

BENEFITS OF USING SI9114A

Low power consumption

at 500 kHz, the Si9114A consumes only 8 mA from the 12-V

supply. This amounts to a total of 96 mW or 5.6% of the losses.

It is important to remember that this figure represents both the

power MOSFET losses as well as the control circuit. The

control circuit was measured to consume only 3.2 mA or 2% of

the total losses. In comparison, typical bipolar circuits would

consume 35 mA, or 21% of the losses.

Short delay times:

with typical delay time approaching 65 ns, short circuit current

can be lowered, and operation at higher frequencies is

possible.

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