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In the design of high voltage power conversion circuit , such as power supply noise , the switching frequency, the switching loss, the volume of supply and reliability has been the key. Compared with other high-voltage topology , LLC converter design due to the high efficiency and power , small size, high-voltage power supply in the field of application has been the designer of all ages, but it is also very difficult to design large . Power Integrations, Inc. (PI) will soon launch HiperLCS series LCS700-708 high-voltage LLC power supply IC, the inverter controller, high-side and low -side MOSFET driver and two simultaneously integrated into a low-cost package, with excellent design flexibility its maximum load efficiency of over 97% , and to reduce the use of high-frequency switching transformer size and output capacitor footprint , thereby achieving the purpose of narrowing the size of the power supply . Figure 1 is a schematic circuit HiperLCS power level , wherein the LLC resonant inductor is integrated in the transformer. Zero voltage variable frequency controller (ZVS) switching power MOSFET, eliminating switching losses , so as to achieve high efficiency.

Design structure and key features

LLC converter design is more complex, the biggest challenge is the need to configure all reasonable circuitry to eliminate cross conduction, and various parasitic elements for precise control . According to Andrew Smith PI product marketing manager , HiperLCS integration of key components, including multifunction controllers, high-side and low -side power MOSFET gate drivers and two of LLC half-bridge power stage (which can be up to 30 external components omitted ) and in the manufacturing process to optimize the fine-tuning of the drive MOSFET pair . The frequency controller of the device to provide zero voltage switching , eliminating switching losses.

The maximum operating frequency HiperLCS device is 1MHz, the nominal steady-state operating frequency of up to 500kHz, and allows the use of low-cost SMD ceramic output capacitor loop , thereby replacing the bulky , unreliable electrolytic capacitors , but can also reduce the required core size. It can also achieve excellent transformer utilization peak at 750kHz switching frequency . In addition , HiperLCS device has a precise duty cycle symmetry to balance the output rectifier current, thereby enhancing efficiency. Under the 300kHz typical 50% ± 0.3%.

Taking into account the different design requirements , HiperLCS devices used in two ways . For high efficiency design , its resonant control circuitry provides very low power consumption , enabling the design of more than 97% efficiency at 66kHz nominal switching frequency. If the cost and size determines the design criteria , priority use of high switching frequency. In the latter case , can still achieve high efficiency , for example, 250kHz ( maximum power frequency ) at 96% efficiency . In addition , HiperLCS devices allow users to get the best solution by setting the dead time and soft-start circuitry and other key parameters to achieve the purpose of improving the design . During the design process , design engineers can apply real-time PI PI Xls design and modeling tools to simplify the power supply design.

Protection and packaging

Like other power IC with PI , HiperLCS has a comprehensive fault handling and current limiting, including programmable voltage ramp / drop threshold and hysteresis , undervoltage (UV) and overvoltage (OV) protection, programmable over-current protection ( OCP), Short Circuit Protection (SCP) and over temperature protection (OTP). On the package , HiperLCS series uses for high power and high frequency thin eSIP-16C package, which can reduce assembly costs and reduce the loop area PCB layout can be quickly installed by a clip to the heat sink, eliminating the need for multiple external MOSFET TO220 package ( Figure 2 ) . Cooling exposed metal part which is connected to the ground potential , so that thermal insulation without Silpad spacer between the package and the heat sink .

package pin staggered eSIP-16C , and simplifies PCB traces the path and meet the high voltage creepage requirements , HiperLCS introduction of improved end- PI complete power products, including EMI filter circuit , PFC stage and the main power supply and standby level power . "With HiperLCS device design easily exceeds ENERGY STAR4.0 and 5.0 , as well as 80PLUS Gold and Silver PC energy efficiency standards set performance benchmarks ." Andrew said , "HiperLCS with HiperPFS PFC design with full-featured products , high efficiency, low component count power , can be applied to servers, industrial control , LCD TV , LED street lamps and outdoor lighting, printers and audio amplifier 75W ~ 440W high voltage power supply . "