FSFR1800HSL データシートの表示（PDF） - Unspecified

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FSFR1800HSL

FSFR-HS Series — Advanced Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converters

Unspecified 

The initial maximum frequency can be set up to 600 kHz,

which is given by:

f ss

=

1

792 p × Rmin || RSS + 0.54μ

[ Hz ]

(3)

The soft-start time, tSS, can be calculated by:

tSS = 3 × RSS ⋅ CSS [ s ]

(4)

4. Self Auto-Restart: The FSFR-HS series can restart

automatically even though any built-in protections are

triggered in case external supply voltage is applied. As

shown in Figure 22 and Figure 23; once a protection is

triggered, the power MOSFET immediately stops. The

counter starts to operate and 1008-clocks are counted,

then the V-I converter is disabled. CSS starts to be naturally

discharged with the series impedance of RSS and Rmin until

VRT drops to VRT,RESET, typically 0.1 V. Then, all protections

are reset and the V-I converter resumes. The FSFR-HS

starts switching again with soft-start.

The counter operating time for 1008-clocks after

protection activation is set by the current out of the RT

pin until VRT drops to VRT,RESET. Finally, the stop time of

FSFR-HS can be estimated, without considering the

counter operation time, as:

tSTOP = 3 CSS ⋅ (RSS + Rmin ) [ s ]

(5)

Figure 22. Internal Block for Auto-Restart

Figure 23. Self Auto-Restart Operation

5. Protection Circuits: The FSFR-HS series has several

self-protective functions; such as Over-Current Protection

(OCP), Abnormal Over-Current Protection (AOCP), Over-

Voltage Protection (OVP), Thermal Shutdown (TSD), and

Line Under-Voltage Lockout (LUVLO or Brownout).

These protections are Auto-Restart Mode protections, as

shown in Figure 24.

Once a fault condition is detected, switching is instantly

terminated and the MOSFETs remain off. When LVCC falls

to the LVCC stop voltage of 10 V and VRT is lower than

VRT,RESET of 0.1 V, the protection is reset. The FSFR-HS

resumes normal operation when LVCC reaches the start

voltage of 12.5 V.

Figure 24. Protection Blocks

5.1 Over-Current Protection (OCP): When the

sensing pin voltage drops below -0.58 V and its

duration becomes more than OCP blanking time of

1.5 µs, OCP is triggered and the MOSFETs remain off.

5.2 Abnormal Over-Current Protection (AOCP):

If the secondary rectifier diodes are shorted, large

current with extremely high di/dt can flow through the

MOSFET before OCP is triggered. AOCP is triggered

without shutdown delay if the sensing pin voltage drops

below -0.9 V.

5.3 Over-Voltage Protection (OVP): When the LVCC

reaches 23 V, OVP is triggered. This protection is used

when auxiliary winding of the transformer supplies VCC

to the FPS™.

5.4 Thermal Shutdown (TSD): The MOSFETs and

the control IC in one package make it easier for the

control IC to detect the abnormal over-temperature of

the MOSFETs. If the temperature exceeds

approximately 130°C, thermal shutdown triggers.

6. Line Under-Voltage Lockout (UVLO): FSFR-HS

includes precise line UVLO (or brownout) with

programmable hysteresis voltage. This function can start

or restart the IC when VLS for the scale-down voltage of

the DC-link by the sensing resistors, R1 and R2, is higher

than VLINE of 2.5 V as the DC-link voltage increases and

vice versa. A hysteresis voltage between the start and

stop voltage of the IC is programmable by ILINE. In normal

operation, the comparator’s output is HIGH and ILINE is

deactivated so that a voltage on LS pin, VLS, can be

obtained as a divided voltage by R1 and R2. On the

contrary, ILINE is activated when the comparator’s output

is LOW. VLS is generated by the difference between the

current through R1 and ILINE.

© 2011 Fairchild Semiconductor Corporation

FSFR1800 / FSFR1700-HS • Rev.1.0.1

11

www.fairchildsemi.com

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