FA6A11N データシートの表示（PDF） - Fuji Electric

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FA6A11N

2nd Generation LLC Current Resonant Control IC, “FA6A00N Series”

Fuji Electric 

Output voltage Vo

Peak value of VW voltage: 2.8 V

Resonant current

IS voltage

MODE voltage

VW voltage

Reference value of VW voltage: 0 V

Fig.7 Operation waveform during overload protection

400

300

FA5760N

200

FA6A00N Series

100

0

50

100

150

200

250

300

Input voltage (V)

Fig.8 Input voltage and overload protection operating power

protection level is highly dependent on the input volt-

age when the input voltage range is wide, and this has

necessitated the addition of a dedicated overload pro-

tection circuit. With the FA6A00N Series, variation of

the overload protection level is small even if the input

voltage varies, allowing for a high-accuracy overload

protection function without a dedicated overload pro-

tection circuit. As a result, the number of power sup-

ply system components can be reduced, allowing for a

cost reduction of a power supply system.

3.3 Over-current protection function with variable delay

time

When a load short circuit occurs and an over-

current state has continued for the specified time Tocp,

switching stops. This is called the over-current protec-

tion function. The power device has a possibility of

being damaged if the Tocp setting is too long. If the

Tocp setting is too short, it causes an over-current state

at start-up, and this may be detected as a load short

circuit state and might hinder the start-up. The opti-

mum Tocp depends on a power supply and capability to

adjust Tocp with an external component offers a higher

VS voltage

Fig.9 Waveform during over-current protection operation

degree of flexibility in power supply design.

With the FA6A00N Series, adjustment of Tocp is

shared by the MODE terminal for state setting, which

has led to the realization of the over-current protection

function with a variable delay time without increasing

the number of terminals. Figure 9 shows a measured

waveform. When a resonant current rapidly increases,

an over-current state is detected on the IS terminal.

The MODE terminal voltage is clamped to 0.5 V after

state setting and, when an overload state is detected,

oscillates between 0.6 and 0.8 V. When the number of

oscillations reaches 36, switching stops and provides

over-current protection. The duration of one oscilla-

tion can be adjusted by the capacitor connected to the

MODE terminal.

4. Effect on Application to Power Circuit

4.1 Standby power reduction effect

Figure 10 shows a sample application circuit and

Tables 4 and 5 the specification of the sample appli-

cation circuit and major semiconductor components

in the circuit. Figure 11 shows the measured standby

power with a 35 mW load. The FA6A00N Series can

reduce the standby power by approximately 20% from

FA5760N, which allows elimination of the standby

converter even if requirements for standby power are

severe.

4.2 Number of circuit components reduction effect

Figure 12 shows the configuration of a general LLC

current resonant power supply. A general LLC cur-

rent resonant power supply is composed of a filter for

EMI (electromagnetic interference) noise elimination,

PFC converter for power factor correction, standby con-

verter and LLC converter. Use of the FA6A00N Series

allows significant reduction in the number of compo-

nents, making it possible to build a low-cost LLC cur-

rent resonant power supply (see Table 6).

248

FUJI ELECTRIC REVIEW vol.59 no.4 2013

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