How to realize miniaturization of charger based on powigan

On April 9, 2021, PI successfully held an online sharing meeting with the theme of "how to use powigan to design a compact, efficient and high-density charger".

In this live broadcast, Jason, senior technical training manager of PI, explained in detail Pi's innoswitch3 IC product series and the newly launched mine cap IC, and also introduced the current sharing characteristics of its innoswitch3 Pro Flyback Switch IC.

The following is the whole video interpretation of PI technical solution by Yan Jinguang, senior technical training manager of PI in this live broadcast:

In addition, Jason also answered the questions from netizens during the live broadcast

  1. How does mine-cap reduce the size of the adapter?

A: mine-cap is mainly suitable for applications with wide input voltage range. By reducing the volume of large capacitance, the volume of power supply can be reduced without changing the working state of the later stage circuit.

  1. Is the current sharing accuracy of innoswitch3 Pro greatly affected by the sampling resistance?

A: the current detection of innoswitch3 Pro is realized by detecting the voltage drop between the is and GND pins. The voltage drop is only about 35mV, which is realized by the bonding line impedance inside the IC. The accuracy can be guaranteed. In addition, the adjustment accuracy of 10mV / gear can ensure a very accurate power sharing between the two channels.

  1. How high power density can be achieved by using the wide voltage adapter of innoswitch3 pro and mine cap?

A: our der822 reference design can achieve 2.1w/cm3. Thanks to our high integration and smaller input capacitance.

  1. In general, how much power of PD fast charging can fully show the advantages of mine-cap?

A: according to the relationship curve between large capacitance withstand voltage and volume, the volume difference between high and low voltage capacitors between 40-100uf is relatively large. The larger the capacity is, the more significant the volume saving is. For wide voltage input, the design principle is 2-3uf / W, so the output power above 30W will save more space. The higher the power, the more obvious the effect. Of course, if there are PFC lines in the front stage, the advantages of mine-cap will not be reflected.

 

  1. Is mine-cap suitable for high power PD fast charging above 100W?

A: under normal circumstances, mine-cap can be used without the requirements of PFC.

  1. Does mine-cap have to match PI Gan master chip to work normally?

A: This IC can work alone with other main control chips. It needs to supply power to mine-cap, and the main control chip is required to be able to start and shut down according to the input voltage information provided by mine-cap.

  1. What is the power consumption of mine cap? Will it affect the efficiency of the whole machine?

A: mine-cap only consumes 500uA of current from BPP pin, so its power consumption is only a few milliwatts, which has little impact on the no-load power consumption and efficiency of the whole power supply.

  1. What strategies or design tips does PI have for the development trend of power miniaturization?

A: the traditional method is to use higher switching frequency to reduce the size of power supply, mainly to reduce the volume of transformer and electrolytic capacitor. PI is highly integrated, which is reflected in the integration of no optocoupler, switch tube, synchronous rectifier drive and output pass switch drive.

 

With the miniaturization of the input filter capacitor, we can achieve the design of small volume power supply with as few components and PCB as possible. It is not only beneficial to production, but also to improve the reliability of the whole power supply. In the future, the development trend of small volume power supply must be to see more IC use on PCB board.

  1. What is the switching frequency of powigan?

A: at present, the maximum switching frequency of innoswitch3 is 132KHZ.

  1. Will the 160V capacitor withstand voltage be lower?

A: actually, when the voltage exceeds 148v, mine-cap will turn off the internal switch, so there is no need to worry about the margin.

  1. Can't innoswitch3 and mine cap be integrated into one package?

A: power devices are bridged between primary stages, and mine cap is only tested in primary stage. In addition, different requirements do not necessarily need to be used at the same time.

  1. Compared with the two-stage transformation, is it difficult for the two-way AC-DC of pi to take into account the volume? After all, there are two transformers in the charger.

 

A: in the two-level scheme, the two dc-dcs in the latter level also occupy a large space. The latter stage uses two high frequency DC-DC, EMI design is facing challenges, and more EMI filter elements may be needed to reduce the internal space utilization. Using two AC-DC transformers can better help to evenly distribute the internal heat on the surface of the power supply, which is conducive to heat dissipation.