L6591 데이터 시트보기 (PDF) - STMicroelectronics

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L6591

PWM controller for ZVS half bridge

STMicroelectronics 

L6591

1

Description

Description

The L6591 is a double-ended PWM controller specific to the soft-switched half bridge

topology. It provides complementary PWM control, where the high-side switch is driven ON

for a duty cycle D and the low-side switch for a duty cycle 1-D, with D < 50%. An externally

programmable deadtime 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 600 V with a synchronous-driven high-voltage

DMOS that replaces the external fast-recovery bootstrap diode.

The IC enables the user to set the operating frequency of the converter by means of an

externally programmable oscillator: the maximum duty cycle is digitally clipped at 50% by a

T-flip-flop, so that the operating frequency is half that of the oscillator.

At very light load the IC enters a controlled burst mode operation that, along with the built-in

non-dissipative high-voltage startup circuit and the low quiescent current, helps keep the

consumption from the mains low and is compliant with energy saving recommendations.

To allow compliance with these standards also in two-stage power-factor-corrected systems,

an interface with the PFC controller is provided that enables the pre-regulator to be switched

off between one burst and the following one.

An innovative adaptive UVLO helps minimize the issues related to fluctuations of the self-

supply voltage with the output load, due to the transformer's parasitic.

IC protection functions include: not-latched input undervoltage (brownout), a first-level OCP

with delayed shutdown able to protect the system during overload and short-circuit

conditions (either auto-restart or latch mode can be selected) and a second-level OCP that

latches off the IC when the transformer saturates or one of the secondary diodes fails short.

Finally, a latched disable function allows easy implementation of OTP or OVP.

Programmable soft-start and digital leading-edge blanking on the current sense input pin

complete the equipment of the IC.

Figure 2. Typical system block diagram

PFC PRE-REGULATOR

ZVS HALF-BRIDGE

Vinac

Voutd c

PW M is turned off in case of PFC's

anomalous operation, for safety

L6561/2

or

L6563

L6591

PFC can be turn ed off at light

load to ease compliance with

energy saving r egulatio ns.

AM13253v1

Doc ID 14821 Rev 6

3/41

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