Use eSIP power package to reduce power supply size

Switching power supplies are used worldwide in wall adapters and internal power supplies for a wide variety of devices. Power supply design engineers have long sought to reduce the design cost of switching power supplies, improve power efficiency, and make the design meet the requirements of the smallest space. Achieving such a switching power supply requires the use of breakthrough new technologies. POWER Integrations has successfully developed a new power package called eSIP. This package is much smaller than the traditional TO-220 package and is an alternative to the latter. In addition, the eSIP package is particularly suitable for high-noise power supply environments. For example, when POWER Integrations' latest offline switcher IC with integrated TOPSwitch-HX adopts the new eSIP package, a 132kHz flyback converter power supply with great cost and performance advantages can be designed.

Circuit boards designed with eSIP packages are completely comparable to those designed with traditional TO-220 packages. They have the same low thermal impedance, but the assembly height of the eSIP package on the PCB is less than 10MM, which is only half the height of the 45-year-old TO-220 package. In addition, the eSIP package has a smaller footprint and uses a smaller circuit board area. Such a small package can meet the market requirements for electronic products such as ultra-thin LCD monitors, flat-panel TVs and set-top boxes.

Figure 1: The eSIP package offers comparable performance to the TO-220 package in a smaller footprint.

The pinout of the eSIP allows for self-marking, which allows for correct component height when the component is inserted into the PCB without the need for a spacer. A simple clip provides a low-cost method of securing the device to the heat sink. The clip holds the eSIP and heat sink firmly in place, meeting the shock and vibration test requirements of the IEC 60068 standard. The heat sink attached to the eSIP package is located at the source of the device, eliminating the need for an insulating spacer and therefore does not interfere with the signal.

TOPSwitch-HX is an offline switch that integrates a 700V high-power MOSFET, a multimode controller, integrated current limiting, undervoltage and overvoltage fault protection, thermal shutdown protection, and other control circuitry into a single-chip device (Figure 2).

Figure 2: Typical flyback application of TOPSwitch-HX.

The TOPSwitch-HX product family covers a power range of 6.5W to 333W. It requires only a small number of external components (Figure 3), which can greatly reduce the cost of power systems operating at a 132kHz switching frequency. The TOPSwitch-HX power supply uses a multi-mode control mechanism that can smoothly switch between different switching modes and achieve optimal efficiency in any load mode. This multi-mode control feature enables the TOPSwitch-HX-based power supply design to meet all implemented and proposed energy efficiency standards such as Energy Star 2.0 and EU COC.

Figure 3: 40W low-cost LCD display power supply circuit using TOPSwitch operating at 132kHz switching frequency.

The eSIP package and TOPSwitch-HX are breakthrough technologies that allow power supply manufacturers to fully meet increasingly stringent EMI requirements and energy efficiency standards at a lower cost.

Frequency jittering and optimized switching techniques are used to reduce radiated EMI and conducted EMI. The combination of these two technologies and POWER Integrations' unique low-cost transformer EMI shielding technology greatly reduces the number and size of EMI filter components. MOSFETs are built using lateral diffusion technology and have very low parasitic capacitance, which allows MOSFETs to operate at a 132kHz switching frequency without high switching losses. Another important feature of this technology is the high breakdown voltage, up to 700V. This allows a higher turns ratio to be used in the transformer, so that for a given DC output, the secondary voltage can be reduced, thereby reducing the power consumption and cost of the rectifier diode.

Significant cost reductions are achieved thanks to TOPSwitch-HX, the eSIP package, and the 132kHz operating frequency. Compared to designs operating at 65kHz, the choke (L1 in Figure 3) and transformer (T1) used in a 132kHz system can be smaller, saving 30% of the transformer cost. High-frequency designs also reduce output ripple, thereby reducing the size and number of required output capacitors, further reducing output stage costs. The tight tolerances and built-in input overvoltage protection features of TOPSwitch-HX, combined with the 700V breakdown voltage of the switching MOSFET, allow the input surge protection circuit (usually an MOV) to be eliminated without compromising the reliability of the circuit design.