CoolSET™ PWM FF G5 Pro

CoolSET™ PWM FF G5 Pro is a fixed-frequency PWM controller family designed for off-line flyback switch-mode power supplies operating across wide AC and DC input ranges. The device supports both isolated and non-isolated flyback topologies and is intended for cascode configurations driving external silicon or silicon carbide MOSFETs. It operates at fixed switching frequencies of 65 kHz or 100 kHz with integrated frequency jittering to reduce conducted EMI. The controller incorporates peak current-mode control with slope compensation, enabling stable operation in both discontinuous and continuous conduction modes. Selectable gate-drive voltage of 10 V, 15 V, or 18 V allows compatibility with different MOSFET technologies. The comprehensive protection functions include line overvoltage, VCC over- and undervoltage, overload, and thermal protection with auto-restart mechanisms. 

CoolSET™ PWM FF G5 Pro Features  

CoolSET™ PWM FF G5 Pro integrates fixed-frequency control, adaptive efficiency modes, and protection logic for off-line flyback power converters requiring stable, high-voltage operation. Let’s go through its features in detail:

External MOSFET Drive and Gate-Level Selection

CoolSET™ PWM FF G5 Pro is designed to drive external Si MOSFETs and high-voltage SiC MOSFETs (e.g., 1200 V/1700 V) in cascode flyback applications. The gate high-level clamp is externally programmable through an RSEL resistor sensed on the FB pin, with selectable gate-drive levels (10 V, 15 V, or 18 V) to match different MOSFET technologies and gate-charge targets.

Fixed-Frequency Operation with EMI-Oriented Modulation

The controller operates at fixed switching frequencies of 65 kHz or 100 kHz and includes frequency jittering to reduce EMI. The documented jitter behavior includes ±4% frequency deviation with a 4 ms modulation period.

Light-Load Efficiency Modes

The device transitions into Eco Mode at a decreasing load, using frequency reduction to improve efficiency from light load up to mid-load conditions. For very low load and standby, it supports an enhanced active burst mode to reduce standby power. 

Current-Mode Control and CCM Support

The PWM section uses peak current-mode control and supports both DCM and CCM operation. CCM stability is supported through internal slope compensation, intended to prevent sub-harmonic oscillation at higher duty cycles.

Startup Method and Soft-Start Stress Control

Startup is implemented through VCC pre-charging using the rectified bus and a VING-based pull-up path that biases the external MOSFET gate until VCC charging begins. The VCC capacitor is charged in two steps using controlled current sources, with an initial low-current phase to protect against VCC short-to-GND conditions, followed by higher current until VVCC-ON is reached. The controller further begins switching with a soft-start sequence; the described approach can keep the external MOSFET in linear mode for ~300 ms with a recommended 22 µF VCC capacitor.

Integrated Feedback Options and Protection/Restart Behavior

For non-isolated flyback designs, an integrated error amplifier enables direct-sense control without an optocoupler. Protection coverage includes line overvoltage detection via the VING pin, VCC over/undervoltage monitoring, overload/open-loop detection via the FB pin, and overtemperature protection. Fault handling uses defined auto-restart behaviors, including non-switch auto-restart and extended cycle-skip auto-restart modes depending on the fault type.

Applications

CoolSET™ PWM FF G5 Pro is used in off-line flyback power supply designs that require fixed-frequency operation, wide input voltage handling, and high-voltage capability. The typical applications include auxiliary power supplies for industrial drives, telecom and networking equipment, server standby power, and power supplies for renewable energy systems. It is suitable for AC/DC adapters, battery chargers, and bias supplies operating from universal AC mains or high-voltage DC buses. The controller supports isolated and non-isolated flyback topologies, including cascode configurations with external silicon or silicon carbide MOSFETs. Its control and protection features enable use in industrial power modules, instrumentation, and embedded power systems requiring stable regulation and reliable fault handling.