LLC topology is currently a high-power switching power supply used more schemes, with high working frequency, high conversion efficiency, large output power advantages, suitable for notebook power, USB PD fast charging, high-power charger and other applications, to meet people's pursuit of power efficiency, small volume.
Now that USB PD3.1 has been introduced, Wenxian Micro has launched three LLC controller chips, and based on the WS2699 LLC controller, it has launched a 12V240W switching power supply reference scheme that supports 90-264V wide voltage input. With the PFC controller WS2862A and LLC synchronous rectifier controller WS2994 to achieve a fully localized high-performance LLC power supply design, Wenxian Micro can provide USB PD3.1 140W fast charging one-stop solution.
The reference design of the 240W LLC power supply is 12V and the maximum output current is 20A, which can be used for DC output applications such as PC power supplies. The LLC topology has high conversion efficiency, low output ripple, and very low standby power consumption.
Wenxian Micro has launched a total of three LLC controllers, of which WS2695 and WS2696 internal undesigned drivers, suitable for driving the current gradually popular ganium nitride half-bridge chip, or using gallium nitride special driver with E-mode gallium nitride switch tube, the chip supports switching frequency up to 1MHz, can achieve high frequency and high power density gaN switching power supply design.
The WS2699 is a full-featured LLC controller with a built-in 700V withstand voltage driver that can directly drive MOS tubes or E-mode Gallium nitride switch tubes for simple and efficient applications.
The 240W LLC power supply reference design uses the WS2862A PFC controller for power factor correction and input voltage regulation to provide a stable voltage input for the WS2699 LLC controller, and the output is synchronously rectified using the WS2994 synchronous rectifier controller to achieve efficient power conversion.
The Wenxian Micro WS2699 LLC controller adopts digital-analog hybrid current multi-mode control, advanced multi-mode control, and adaptive dead-time adjustment to achieve efficiency optimization in the full load range. Protection and control parameters can be configured by registers, simplifying circuit design. The WS2699 uses a current mode control architecture with excellent loop stability and an energy-saving design for light load and standby, optimizing light load efficiency and standby power consumption.
WS2699 internally integrated 700V withstand voltage half-bridge driver, with 2A sinking capacity and 750mA current pulling capability, short rise and fall time, can fully drive the external power tube, reduce switching losses. The integrated half-bridge driver can drive the MOS tube directly or the GaN switch tube without the driver, supporting a 500KHz switching frequency.
The WS2699 also integrates high voltage start-up and X capacitor discharge functions, and integrates rich protection functions, such as input overvoltage, undervoltage protection, overpower protection, cycle-by-cycle overcurrent protection, capacitive mode adjustment, output short-circuit protection, output overvoltage protection, and device overtemperature protection for external thermistors. The WS2699 is available in sop16 package and can be used for USB PD fast charging, computer power supplies, TV and display power supplies, LED lighting, medical and industrial power supplies and other applications.
PFC is a power factor correction circuit used to increase the input power factor of a high-power switching power supply. PFC usually adopts a boost method, which boosts the rectified voltage and outputs a stable DC current to power the switching power supply. Boost PFC can reduce the capacity of primary filter electrolysis and reduce the volume of the power supply.
The WS2862A is a PFC boost controller that operates in critical continuous mode for high PF values and optimized THD. The WS2862A has very low start-up and operating currents, and larger start-up resistors can be used at the power supply to reduce losses. The built-in gate driver has a 600mA sink capability and 800mA pull capability. The current sampling circuitry has built-in filtering circuitry and leading-edge blanking to simplify external anti-interference devices.
At the same time, the WS2862A also has comprehensive protection functions such as cycle-by-cycle overcurrent protection, dynamic and static output overvoltage protection, feedback open-loop protection, VCC overvoltage clamping, power supply undervoltage protection, gate drive output voltage clamping and so on.
The WS2862A performs zero current sensing through auxiliary windings, and the system operates in inductor current critical continuous mode, which reduces the conduction loss of the switch tube.
In the past, the power output rectification was to use Schottky diode rectification, but the forward voltage drop of the diode will cause considerable power loss when the current flows through, and a larger heat sink is required to dissipate heat for the diode, and the loss of the diode also reduces the power conversion efficiency.
Synchronous rectification uses a VERY low conductivity MOS tube instead of a Schottky diode, and the synchronous rectifier controller controls the MOS tube opening and shutting down instead of diode rectification, which greatly reduces the loss compared to diode rectification, improves the conversion efficiency of the power supply, and is the rectification mode of the mainstream high-power power supply.
The WS2994 is a dual synchronous rectifier controller for LLC power supplies for secondary synchronous rectification of LLC topologies. The WS2994 controls the synchronous rectifier to achieve reliable turn-on and shutdown by sensing the Vds voltage of the rectifier, replacing the Schottky diode and eliminating the loss on the Schottky diode voltage drop, thereby improving the efficiency of the LLC converter.
The WS2994 supports CCM, CrM and DCM operating modes and supports automatic optimization control. Supports a 4-36V output voltage range for most adapter applications, gate drive voltage up to 10.5V, and very good compatibility with synchronous rectifiers. At the same time, the dual driver has an interlock function to prevent two synchronous rectifiers from passing on at the same time.
The WS2994 supports 1MHz switching frequency, effectively supporting future high frequency power supply applications. The WS2994 supports a light-load energy-saving function that stops the drive signal output when the output current is reduced to a certain extent, reducing losses.
Charging head net summary
With the intensification of the shortage of semiconductor chip products, the shortage of products from foreign manufacturers has brought major development opportunities for domestic chip manufacturers. Wenxian Micro has seized the rare opportunity to launch a series of LLC controllers, as well as PFC controllers and synchronous rectifier controllers corresponding to LLC applications, to achieve localization substitution.
THE LLC controller has previously been controlled by Infineon, NXP, ON Semiconductors and other first-line manufacturers, and no domestic manufacturers have launched similar products for a long time. The digital core LLC controller launched by Wenxian Micro can configure control and protection parameters through registers, which is at the same level as international manufacturers, demonstrating the technical strength of domestic manufacturers.