[FrontPage] [TitleIndex] [WordIndex

USB Power Supplies


General Background

LinearPowerSupplyDesign

MultiRailPSU

Test Kit/Method

DSCN0599s.jpg

As can be seen above, testing was performed with a breadboard configured to allow a number of resistors to be switched in parallel across the supply under test via a DIL switch package. Four (56Ω) resistors were mounted on the top-side of the board and the other four (47Ω) were mounted underneath. Virtually all of the components were items purchased, maybe, 20-30 years ago - the exception being the USB socket. Ideally I would have liked to use eight resistors of the same value but I didn't have such "in stock". The calculated and measured parallel resistances are shown in the table below - for a (constant) 5V supply this leads to expected nominal load currents of 100-800mA in 100mA steps.

Switches "On"

Calculated Ω

Measured Ω

1xxxxxxx

47.0

45.9

12xxxxxx

25.6

25.4

123xxxxx

16.6

16.4

1234xxxx

12.8

12.7

12345xxx

10.0

10.0

123456xx

8.5

8.6

1234567x

7.2

7.3

12345678

6.4

6.4

Tested Devices

DSCN0518sac.jpg

Test Results

(See also OEM Hub PSU, DVE Hub PSU, iLuv i108 5V 2A PSU, Powered USB Hubs and Other Tested PSU's.)

FX1000mA.jpg

TCB2x500mA.jpg

Mean slope resistance: 0.27 Ω1, Mean Vmax: 4.93 V2

Slope resistance: 0.25 Ω1, Vmax: 4.97 V2

SonyEricsson850mA.jpg

Generic1000mA.jpg

Mean slope resistance: 0.11 Ω1, Mean Vmax: 4.84 V3

Mean slope resistance: 16.1 Ω4, Mean Vmax: 1.35 V3

Sony Ericsson 850ma "Re-visited" (2018)5

SonyEricsson850mSE3Revisited.jpg

Good Enough for the Pi (Models A|B1|B2)?

The power budget of the original model B Pi is associated with a nominal "self-current" of 700mA plus 200-300mA for attached USB devices. Hence a 5 Watt (5V at 1000mA) PSU should be fine. The "FX" and "TCB" devices both meet that specification and the samples measured confirm their suitability. Whilst the Sony Ericsson chargers have a "below spec." maximum current, they are the most stable of the devices tested and one has been used to power a first generation model B Pi running "headless" ie. without monitor, keyboard or mouse but with one or two USB flash drives plugged in. This is the Pi shown on the front page and on which this wiki ran for nearly three years. Whilst the "Generic" devices were specified as "5V 1000mA" they do not strictly meet this, or rather the "1000mA" appears to be their short-circuit current limit, and hence these are not recommended. Since the above measurements were performed (2012) a number of other PSU's have become available (see here for more info.), of these two are noteworthy: the Pluscom Hub PSU and the FX Factory TR9202 Dual Charger. The first is the best PSU supplied with a hub tested so far, and the second can power both a Pi and an isolated (non-back-powering) hub.

The "Official Raspberry Pi PSU" (All Pi Models)

Original, White, 5V 2A Version

P1020256rcs.JPG

P1020258rcs.JPG

OfficialRasPiPSU.jpg

Compact Test Board Extrapolation: Slope resistance: ~0.2 Ω6, Vmax: 4.8 V7, Ibrownout: ~2.8 A8

Post Pi3B+, Black, 5V 2.5A Version (Dec.2018)

P1070016rcs.JPG

P1070017rcs.JPG

P1070013rcs.JPG

P1070015rcs.JPG
P1070014rccfs.JPG

OfficialRasPiPSU_2018.jpg

P4B, USB 'C' connected, 5.1V 3A (June 2019)

(See also this Tronsmart 18W Charger)

Raspberry_Pi_official_USB-C_PSU_5V_3As.jpg

OfficialRasPiP4BPSU.jpg

Ref: "Testing official USB-C Power Supply rpi4"

P4B, USB 'C' connected, 5.1V 3A (October 2019)

P1090087rrcs.JPG

P1090088s.JPG

OfficialRasPiP4BPSU_201910.jpg

P4B, USB 'C' connected, 5.1V 3A (Spring 2020)

P1090935rcs.JPG

P1090936rcs.JPG

P1090937rcs.JPG

P1100215rcs.JPG

P1100216rcs.JPG

P4B, USB 'C' connected, 5.1V 3A (4th. Sample, August 2020)

P1100931brcs.JPG

P1100932brcs.JPG

OfficialRasPiPSU_20200810.jpg

Post Pi Zero2W, White, uUSB connected, 5.1V 2.5A (Autumn 2021)

P1130394rcs.JPG

P1130395rcs.JPG

P1130396rcs.JPG

P1130397rcs.JPG

OfficialRasPi_uUSB_PSU2021.jpg

Ref: "Testing 2021 new Official Micro USB Power Supply."

Pi5, 27W USB 'C' connected, PD 5.1V 5A

P1000052rcs.JPG

P1000056rrcs.JPG


  1. Between 2nd. & 7th. data points (1 2 3)

  2. Imax 1000mA (4 5)

  3. Imax 850mA (6 7)

  4. Between 7th. & 8th. data points (8)

  5. Using the Electronic "Load Resistor" & the "Charger Detector" Multimeter (9)

  6. Between 5th. & 8th. data points (10)

  7. Imax 2.0A (11)

  8. Vbrownout 4.6 V (12)


2024-02-11 21:50