The L6599D is a high-voltage resonant controller IC manufactured by STMicroelectronics, designed specifically for resonant half-bridge topologies used in soft-switching power supplies. Below is a detailed overview based on its key features, functionality, and applications:

Key Features of L6599D

1. Resonant Half-Bridge Control:
   • Provides 50% complementary duty cycle, driving high-side and low-side switches 180° out-of-phase for equal ON/OFF times.
   • Regulates output voltage by modulating the operating frequency rather than duty cycle, typical for resonant converters.
2. Soft-Switching Support:
   • Inserts a fixed deadtime between the turn-off of one switch and the turn-on of the other to ensure zero-voltage switching (ZVS), reducing switching losses and enabling high-frequency operation (up to 500 kHz).
3. High-Voltage Capability:
   • Incorporates a high-voltage floating structure that can withstand over 600 V, suitable for driving the high-side switch using a bootstrap approach.
   • Features a synchronous-driven high-voltage DMOS transistor, eliminating the need for an external fast-recovery bootstrap diode.
4. Programmable Oscillator:
   • Allows designers to set the operating frequency range using an external programmable oscillator, typically from 30 kHz to 500 kHz.
5. Protection Features:
   • Overcurrent protection (OCP) with frequency shift and delayed shutdown, plus a higher-level OCP that latches off the IC for robust fault handling.
   • Brownout protection via a non-latched disable input with current hysteresis.
   • Additional latched disable input for over-temperature protection (OTP) or over-voltage protection (OVP).
6. Burst-Mode Operation:
   • Supports controlled burst-mode at light loads to minimize power consumption, activated via the STBY pin (enters idle state below 1.25 V).
7. Soft-Start:
   • Implements a non-linear soft-start to prevent inrush currents, starting from a programmable maximum frequency and gradually reducing to the steady-state value to avoid output voltage overshoots.
8. PFC Interface:
   • Includes an interface to switch off a power factor correction (PFC) pre-regulator during fault conditions or burst-mode operation, enhancing system efficiency.
9. Electrical Specifications:
   • Operating voltage range: 8.85 V to 16 V.
   • Maximum output current: 800 mA.
   • Power consumption: Approximately 0.83 W.
   • Operating temperature range: -40°C to 150°C.
   • Package: SOIC-16 or DIP-16.

Working Principle

The L6599D controls a resonant half-bridge circuit, typically used in LLC resonant converters. It modulates the switching frequency to regulate the output voltage, leveraging the resonant characteristics of an LC tank (inductance and capacitance). The soft-switching mechanism (ZVS) minimizes switching losses by ensuring switches turn on when their voltage is near zero, improving efficiency and reducing EMI.

• Resonant Waveform Control: The IC generates control signals to modulate the resonant waveform, precisely timing the switching to stabilize the output voltage.
• Deadtime Control: Prevents cross-conduction by ensuring a brief delay between switching transitions, avoiding short-circuit conditions.
• Feedback Mechanism: Adjusts the PWM frequency based on output voltage feedback to maintain regulation.

Applications

The L6599D is widely used in high-efficiency power supply designs, particularly where compact size, high efficiency, and low EMI are critical. Common applications include:

• Computer power supplies (ATX, server PSUs).
• LCD/LED monitors and TVs.
• AC-DC adapters and open-frame SMPS.
• Industrial power supplies (e.g., LLC resonant converters for 400 V - 24 V / 10.5 A DC-DC conversion).
• Telecom power systems.
• Power management for devices like the Antminer APW12 power supply (fan driver chip).

Troubleshooting Common Issues

1. No Output Voltage:
   • Check the LINE pin voltage (pin 7) against the 1.25 V reference to ensure the IC is not disabled due to brownout.
   • Verify the bootstrap capacitor and high-side gate drive functionality.
2. Overheating:
   • Ensure proper deadtime configuration to maintain ZVS, as hard-switching increases losses.
   • Confirm the operating frequency is within the resonant circuit’s design range.
3. Unstable Output:
   • Inspect the feedback loop and compensation network for proper tuning.
   • Verify the resonant tank components (inductor, capacitor) match the design specifications.
4. Burst-Mode Failure:
   • Check the STBY pin voltage (pin 5); if below 1.25 V, the IC enters idle mode, which may be unintended.

Comparison with Variants

• L6599AD: An improved version with enhanced features like better noise immunity and refined soft-start control.
• L6599DTR: Same functionality as L6599D but in a tape-and-reel package for automated assembly.

Availability and Packaging

• Package: Available in SOIC-16 (surface-mount) and DIP-16 (through-hole).
• Lifecycle: Not recommended for new designs (NRND) by STMicroelectronics, but still widely available through distributors like Future Electronics, Mouser, Arrow, and Jotrin Electronics.
• Note: Always verify stock and pricing, as inventory fluctuates.