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ST unrolls controller for resonant half-bridge topology

Posted: 29 Jun 2006 ?? ?Print Version ?Bookmark and Share

Keywords:STMicroelectronics? ST? double-ended controller? L6599?

STMicroelectronics (ST) introduced an advanced double-ended controller specifically designed for the series-resonant half-bridge topology. Rich in functions and robust in design, the new-generation high-voltage IC guarantees excellent performance, allowing the design of fully protected and highly reliable power supplies suited for use in applications such as LCD and PDP TVs, high-end AC/DC adapters for laptops and game consoles, 80+ initiative-compliant ATX silver boxes, servers and telecom SMPS.

The new L6599 features a dedicated output for direct Power Factor Corrector (PFC) connection, two-level Over-Current Protection (OCP), latched Disable input, burst-mode operation at light-load, and an input for power-on/off sequencing or brownout protection. It operates at 50 percent complementary duty-cycle with a fixed dead-time inserted to ensure soft-switching and enables high-frequency (up to 500kHz) operation with high efficiency and low EMI emissions.

To drive the high-side switch with the bootstrap approach, the new device combines a high-voltage floating structure, able to withstand more than 600V, with a synchronous-driven high-voltage LDMOS that eliminates the need for an external fast-recovery bootstrap diode, ST said. L6599 also provides a typical peak current capability for both gate drivers of 0.6A source and 1.2A sink and enables designers to set the operating frequency range by using an externally programmable oscillator.

Additionally, a non linear soft-start prevents inrush current and minimizes output-voltage overshoot. The device also features a controlled burst-mode operation, thus considerably reducing the average switching frequency and the associated losses under lightly loaded or unloaded conditions. With the new resonant controller, designers can meet energy-saving requirements even in power-factor-corrected systems. A dedicated output enables the IC to switch off the PFC pre-regulator during burst-mode operation, hence eliminating the no-load consumption of this stage.

Other key features of the L6599 include low power consumption (<30mW), guaranteed latch-up free operation with slew rates up to 50V/ns, a not-latched disable input, and a high-performance OCP providing complete protection against both overload and short circuits. An additional latched disable input allows easy implementation of over-temperature and/or over-voltage protection.

The L6599 is offered in three versions: type L6599N is assembled in a PDIP16 package; L6599D and L6599DTR in a SO16N package. Already in production, the chips is priced at $1.20 each in 25,000-unit quantities.

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