Digital power supply and analog power supply-EEWORLD

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Digital power supply is different from common analog power supply. The former uses digital PWM, a smaller chip integrating digital MOSFET and DRIVER, and a smaller digital row inductor, with multiple MLCCs; while analog power supply is different, using traditional PWM chips, with 2-4 relatively large MOSFETs per phase, an independent inductor per phase, and a relatively large capacitor. So from the appearance, it is easy for us to distinguish between digital power supply and analog power supply.

It can be seen that this graphics card of GALAX uses digital PWM VT1165MF, a very small CSP package of VOLTERRA's VT1195SF MULTIPHASE power chip that integrates MOSFET and DRIVER, as well as CPL-4-50 digital row inductor and MLCC. Obviously, this is a typical digital power supply. However, the significance of digital power supply is not only in "volume", but also in performance. The PWM

IC used in digital power supply

The PWM chip used in the graphics card is VT1165MF, which is very common on NVIDIA flagship graphics cards and can easily handle top graphics cards with hundreds of watts of power consumption. The conversion efficiency of the digital power supply composed of VT1165MF is much higher than the 70-80% generally maintained by analog power supply, and reaches 90%. Not only that, the digital power supply composed of it is also more accurate. The peak amplitude of GPU voltage is only 140mV, while the peak amplitude of analog power supply GPU voltage is 300mV. More accurate power supply is conducive to ensuring the stable operation of GPU, and it is easier to reach the limit of overclocking, and the life is longer.

MOSFET used

in digital power supply We have already talked about one of the most obvious characteristics of digital power supply and analog power supply, that is, MOSFET and DRIVER. This digital power supply graphics card uses VT1195SF, which integrates MOSFET and DRIVER internally. Compared with the MOSFET with an operating frequency of 300KHz commonly used in analog power supply, the operating frequency of digital power supply MOSFET is very high, reaching 800KHz. The higher switching frequency makes the digital power supply better in transient performance, lower power consumption and higher conversion efficiency. At the same time, the current that the digital power supply can drive can reach 40A per phase, far exceeding the 30A limit of analog power supply. Combined with the 4-phase digital power supply design of this graphics card, it can provide a current of up to 160A, and such a large current is more suitable for overclocking.

Not only that, the MOSFET of digital power supply can withstand higher temperatures and can adapt to more severe working environments. Although the MOSFET used in ordinary analog power supply is independently designed and has better heat dissipation, the maximum temperature they can withstand is only about 100 degrees. The digital MOSFET above can withstand a maximum temperature of 200 degrees. In this way, the application range of digital power supply is also wider. Putting aside the cost, the prospect of digital MOSFET is brighter. The array inductor

used in digital power supply

is also a very obvious feature of digital power supply. Common analog power supply uses a single package inductor, which is relatively large in size and occupies a large PCB area. However, the digital power supply inductor CPL-4-50 used in this graphics card is a bit like multiple inductors "integrated" together, and the volume is smaller. Not only that, the array inductor used in digital power supply is also better in performance. Taking the working frequency as an example, the working frequency of the inductor used in ordinary analog power supply is generally 300KHz, while the working frequency of the digital array inductor can reach 1MHz. In addition, the internal resistance of the digital array inductor is lower, so the heat loss caused by the inductor is also smaller, and the digital power supply conversion efficiency is also higher.

Finally, let's summarize the characteristics of digital power supply:

1. Small size, digital MOSFET, DRIVER CSP package, small size, small digital inductor, small PCB area can also be smaller.

2. More accurate power supply, digital power supply GPU peak voltage is only 140mV, analog power supply GPU peak voltage reaches 300 mV.

3. Digital power supply conversion efficiency is higher, analog power supply usually has a conversion efficiency of 70-80%, and digital power supply conversion efficiency is about 90%.

4. Digital power supply current is larger, analog power supply is usually limited to 30A per phase, and digital power supply can reach 40A per phase.

5. Digital power supply is more resistant to high temperature, the upper limit of the operating temperature of CSP package MOSFET is 200 degrees, while the upper limit of the operating temperature of MOSFET used in analog power supply is about 100 degrees.

6. The operating frequency of digital power supply is higher. The operating frequency of digital power supply MOSFET reaches 800KHz, while the operating frequency of MOSFET commonly used in analog power supply is only 300KHz; the operating frequency of digital power supply inductor array reaches 1MHz, while the operating frequency of inductor commonly used in analog power supply is only 300KHz.

7. The internal resistance of digital power supply is smaller. The internal resistance of the inductor array used in digital power supply is smaller than that of the inductor commonly used in analog power supply.

Reference address：Digital power supply and analog power supply

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