L6599

Device description

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Device description

The L6599 is a double-ended controller specific for the resonant half-bridge topology. It

provides 50% complementary duty cycle: the high-side switch and the low-side switch are

driven ON 180° out-of-phase for exactly the same time.

Output voltage regulation is obtained by modulating the operating frequency. A fixed dead-

time inserted between the turn-OFF of one switch and the turn-ON of the other one

guarantees soft-switching and enables high-frequency operation.

To drive the high-side switch with the bootstrap approach, the IC incorporates a high-voltage

floating structure able to withstand more than 600V with a synchronous-driven high-voltage

DMOS that replaces the external fast-recovery bootstrap diode.

The IC enables the designer to set the operating frequency range of the converter by means

of an externally programmable oscillator.

At start-up, to prevent uncontrolled inrush current, the switching frequency starts from a

programmable maximum value and progressively decays until it reaches the steady-state

value determined by the control loop. This frequency shift is non linear to minimize output

voltage overshoots; its duration is programmable as well.

The IC can be forced to enter a controlled burst-mode operation at light load, so as to keep

converter's input consumption to a minimum.

IC's functions include a not-latched active-low disable input with current hysteresis useful for

power sequencing or for brownout protection, a current sense input for OCP with frequency

shift and delayed shutdown with automatic restart.

A higher level OCP latches off the IC if the first-level protection is not sufficient to control the

primary current. Their combination offers complete protection against overload and short

circuits. An additional latched disable input (DIS) allows easy implementation of OTP and/or

OVP.

An interface with the PFC controller is provided that enables to switch off the pre-regulator

during fault conditions, such as OCP shutdown and DIS high, or during burst-mode

operation.