I. UCC25710: LLC Half-Bridge Controller Quick Start Guide for LED Lighting
The TI UCC25710 is an LLC half-bridge controller for accurate control of multi-string LED backlight applications. It is optimized for multi-transformer, multi-string LED architectures. The controller and architecture enable excellent LED current matching across multiple LED strings. This multi-transformer architecture relies on AC inputs to provide the highest total efficiency to LED loads compared to existing LED backlight solutions. The LLC controller features a voltage-controlled oscillator (VCO) minimum and F-maximum with programmable F, a half-bridge gate driver with 500ns fixed dead time, and a GM current amplifier. The LLC power delivery is adjusted by the controller's VCO frequency. The VCO has an accurate and programmable frequency range. At ultra-low power levels, the VCO frequency changes from F to zero to maximize efficiency at low LED currents.
characteristic:
Adjustable F minimum (3% accuracy), and F maximum (7.5% accuracy)
LLC and series LED switch control for dimming
Programmable dimming LLC ON/OFF ramp for audible noise cancellation
Closed loop current control programmable soft start with low dimming duty cycle
Accurate VREF for tight output regulation
Overvoltage, undervoltage, and input overcurrent protection with automatic restart response
Second overcurrent threshold with lock-off response
400mA/-800mA gate drive current
Low starting current and operating current
Lead-free 20-lead SOIC package
application:
LED backlight for LCDTVs and monitors
LED general illumination
Second, UCC25710: LED lighting for the application of LLC half-bridge controller
The design adopts TIUCC25710 multi-string transformer LLC control patent technology to realize a new off-line LED lighting drive solution. Compared to traditional high power (>100W) AC/DC plus multiple constant current DC/DC converter LED lighting drivers, the new two-stage topology provides higher efficiency and lower system cost. Based on this multi-string transformer LLC control technology, a 100W LED lighting driver reference design PMP4302A has been developed, and its load can be directly connected to 4 strings of LED loads (each string can be connected with 10~15 LEDs, each string output current is 500mA). Experimental results show that the new topology is ideal for general-purpose LED lighting applications using PWM or analog circuit dimming in outdoor and commercial applications. At the same time, the circuit system architecture can also be used as a power source for high efficiency, ultra-light LED backlighting TVs.
The UCC25710 is an LLC half-bridge controller for accurate control of multi-string LED backlight applications. It is optimized for multi-transformer, multi-string LED architectures. The controller and architecture enable excellent LED current matching across multiple LED strings. This multi-transformer architecture relies on AC inputs to provide the highest total efficiency to LED loads compared to existing LED backlight solutions. The LLC controller features a voltage-controlled oscillator (VCO) minimum and F-maximum with programmable F, a half-bridge gate driver with 500ns fixed dead time, and a GM current amplifier. The LLC power delivery is adjusted by the controller's VCO frequency. The VCO has an accurate and programmable frequency range. At ultra-low power levels, the VCO frequency changes from F to zero to maximize efficiency at low LED currents.
New high power offline LED lighting drive topology
Based on the problems in the traditional topology, this paper uses a Texas Instruments (TI) multi-string transformer LLC resonant controller UCC25710 to achieve a new topology design. Figure 2 is a block diagram of the new topology, which consists of a two-stage circuit structure of a PFC and a multi-string isolation transformer LLC converter, eliminating the DC/DC multi-string constant current portion of the conventional structure. There is a half-bridge isolated multi-string LLC resonant converter behind the PFC circuit, which allows the transformer primary windings to be connected in series. Based on the magnetic balance theory, because the primary winding current and the series current are the same, each isolated transformer will have the same output current for driving each string of LED loads, and each transformer can drive two strings of independent LED loads with electrical appliances. isolation.
The multi-string transformer LLC resonant controller (used in this design is UCC25710) is placed on the secondary side, which monitors the total current of the LED load and uses a current feedback loop to adjust the sinusoidal AC current flowing through the primary winding of the transformer while passing Magnetic balance theory guarantees a constant current output per string of LED loads.
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