The highly integrated SG5842A/JA series of PWM controllers provides several
features to enhance the performance of flyback converters. To minimize standby
power consumption, a proprietary green-mode function provides off-time
modulation to continuously decrease the switching frequency at light-load
conditions. To avoid acoustic-noise problem, the minimum PWM frequency set above
22KHz. This green-mode function enables the power supply to meet international
power conservation requirements. To further reduce power consumption, SG5842A/JA
is manufactured using the BiCMOS process. This allows a low start-up current,
around 14ľA, and an operating current of only 4mA. As a result, a large start-up
resistance can be used.
The SG5842A/JA built-in synchronized slope compensation achieves stable
peak-current-mode control.
SG5842JA integrates a frequency hopping function that helps reduce EMI
emission of a power supply with minimum line filters.
SG5842A/JA provides many protection functions. In addition to cycle-by-cycle
current limiting, the internal open-loop protection circuit ensures safety
should an open loop or output short-circuit failure occur. PWM output is
disabled until VDD drops below the UVLO lower limit, then the
controller starts again. As long as VDD exceeds about 24V, the
internal OVP circuit is triggered. An external NTC thermistor can be applied for
over-temperature protection.
SG5842A/JA is available in an 8-pin DIP or SOP package.
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