Overview
The L6591 is a double-ended PWM controller designed specifically for soft-switched half bridge topology by STMicroelectronics. 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%. This controller incorporates a high-voltage floating structure to drive the high-side switch using the bootstrap approach, capable of withstanding more than 600 V. The L6591 features an externally programmable oscillator to set the operating frequency, with a maximum duty cycle digitally clipped at 50%. It also includes advanced light load management, adaptive undervoltage lockout (UVLO), and various protection mechanisms such as pulse-by-pulse overcurrent protection (OCP) and transformer saturation detection.
Key Specifications
| Parameter | Value | Unit |
|---|---|---|
| Operating Frequency | Up to 500 kHz | |
| Supply Voltage Range | 11.3 to 22 V | V |
| Turn-on Threshold | 13 to 15 V | V |
| Turn-off Threshold | 9.2 to 11.3 V | V |
| High-Voltage Startup | Up to 700 V | V |
| Gate Drive Peak Current | Self-limited | A |
| Junction Temperature Range | -40 to 150 °C | °C |
| Package Type | SO16N |
Key Features
- Complementary PWM control for soft-switched half bridge with programmable deadtime
- Up to 500 kHz operating frequency
- Onboard high-voltage startup
- Advanced light load management
- Adaptive UVLO
- Pulse-by-pulse OCP
- OLP (latched or autorestart)
- Transformer saturation detection
- Interface with PFC controller
- Latched disable input
- Input for power-on sequencing or brownout protection
- Programmable soft-start
- 4% precision external reference
- 600 V-rail compatible high-side gate driver with integrated bootstrap diode and high dV/dt immunity
Applications
- High power AC-DC adapters and chargers
- Desktop PCs and entry-level servers
- Telecom SMPS
- Two-stage power-factor-corrected systems
Q & A
- What is the primary function of the L6591?
The L6591 is a double-ended PWM controller designed for soft-switched half bridge topology, providing complementary PWM control.
- What is the maximum operating frequency of the L6591?
The L6591 can operate up to 500 kHz.
- How does the L6591 manage light load conditions?
The L6591 enters a controlled burst mode operation at very light loads, which helps keep the consumption from the mains low and is compliant with energy saving recommendations.
- What protection mechanisms are included in the L6591?
The L6591 includes pulse-by-pulse OCP, OLP (latched or autorestart), transformer saturation detection, and a latched disable function for easy implementation of OTP or OVP.
- How does the adaptive UVLO function in the L6591 work?
The adaptive UVLO helps minimize issues related to fluctuations of the self-supply voltage with the output load, due to the transformer's parasitic effects.
- What is the package type of the L6591?
The L6591 is available in an SO16N package.
- Can the L6591 be used in power-factor-corrected systems?
Yes, the L6591 has an interface with the PFC controller that enables the pre-regulator to be switched off between bursts, aiding in compliance with energy saving regulations.
- What is the purpose of the high-voltage startup circuit in the L6591?
The high-voltage startup circuit allows the IC to start up with a high voltage, ensuring proper operation even at high voltage levels.
- How does the programmable soft-start feature work in the L6591?
The programmable soft-start feature allows an external capacitor to be charged by an internal 20 µA generator, generating a voltage ramp during startup.
- What is the significance of the 600 V-rail compatible high-side gate driver in the L6591?
The 600 V-rail compatible high-side gate driver, with an integrated bootstrap diode and high dV/dt immunity, ensures reliable operation at high voltage levels.
