Power supply unit
Power supply unit receives filtered output voltage from batteries and transforms it into required set of stable DC voltages. Its main purpose is to provide a wide spectrum of different voltages, transformed efficiently, and also provide enough power rails and current for any actual or future device. In this sense it is very similar to a power supply of a personal computer. However, this power supply unit is not designed to run robot's embedded computer, but only electronic schemes. Embedded computer is powered up from the one or several widely spread DC-DC ATX converters.
The input voltage range is 17V-28VDC.
There is a range of required output voltages:
- 5.0 VDC (standby) - to power up Primary Power Controller and Side Panel Interface while in standby or in active mode;
- 1.8 VDC - to power up all LED's, some sensors, and low-voltage logic (e.g. ARM7 uC kernel);
- 3.3 VDC - to power up low-voltage logic (e.g. ARM7 uC peripherals), stepper motors;
- 5.0 VDC - to power up almost all ICs (CMOS and TTL);
- 12.0 VDC - to power up some stepper motors, operational amplifiers (high voltage), power transistors drivers, solenoids, fans;
- -5.0 VDC - to power up operational amplifiers, some ADC and DAC ICs;
Optional rails:
- 2.5 VDC - (optional) to power up some stepper motors;
- -12.0 VDC - (optional) to power up some operational amplifiers;
All of 1.8 VDC, 3.3 VDC, 5.0 VDC and 12.0 VDC - are high current rails, short circuit protected; Negative voltage lines -5.0 VDC and -12.0 VDC - are low current rails (up to 0.3A total per rail);
Contents |
Version 2
Version 2 is planned and must come as close to the initial requirements as possible. Also there must be an option to manually disable each of the conversion rails, to reduce power consumption.
Schematic capture
PCB Layout
Two-sided PCB is shown below:
Device photo
Specifications
Preliminary ratings
| Output rail voltage, VDC | Max current, Amps | Device name | Description |
|---|---|---|---|
| 12 | 10 | Vicor V24C12T100BG (24V->12V) | Total power: 100W. Vicor Brick DC-DC converter. Can be switched on with the jumper or by the external logic (CMOS-compatible). |
| 5 | 10 | Vicor VI-JW0-EY (24V->5V) | Total power: 50W. Vicor Mini DC-DC converter. Can be switched on with the jumper or by the external logic (CMOS-compatible). |
| 5 (external standby) | 30 mA @ 24V input; 18 mA @ 40V input |
LM2936 | Total power: 600 mW. Linear regulation from input voltage 22.2V (18-27V) with LM2936 (linear regulator with low quiescent current). External standby can be switched ON with the jumper (default - jumper closed). Internal standby is always ON. |
| 3.3 | 18 | ACON DH50S24033 (24V->3.3V) | Total power: 50W. Efficiently converted with integrated switched mode DC-DC from input voltage (range 18-36V). ACON DC-DC switched mode, single output 3.3V with trim. Can be switched on with the jumper or by the signal of external logic (CMOS-compatible). |
| 1.8 | 8 | PT6526L | Total power: 14W. Converted with switched mode DC-DC converter. input voltage range 3.1-5.5V. Fed by the 3.3V power supply output rail. Can be switched on with the jumper or by the signal of the external logic (CMOS-compatible). |
| -5 | 0.1A | LMC7660 (IC 5V->(-5V)) | Total power: 1.2W. Efficiently converted from standby voltage source. Can be turned on by the jumper, but not externally controllable. |
Tested ratings
- 3.3V DC-DC failed to start. It will be changed to sink from linear low drop voltage regulator, dependent on 5V rail;
- 1.8V rail is now dependent on 5V rail (circuit redesigned). 1V8 output is Ok;
- -5V rail is Ok;
- 12V rail is Ok;
- 5V rail is Ok, but emits low volume high-frequency sound noise;
- 5Vsb rail is Ok but gives too little output current to source SPInt.
Standby current
| Output rail voltage, VDC | Standby current, mA | No load current, mA | Device name | Description |
|---|---|---|---|---|
| 12 | 4mA | 4.4-6.1 Watts | Vicor V24C12T100BG (24V->12V) | |
| 5 | 6mA | 1.35-2.0 Watts | Vicor VI-JW0-EY (24V->5V) | |
| 5 (external standby) | 15uA @ no load (100uA) | 0.5mA @ 10mA + Iload | LM2936 (IC 24V->5V) | |
| 3.3 | 30-50mA | PT6601 (5V->3.3V) | ||
| 1.8 | 15-25mA | PT6526L (5V->1.8V) | ||
| -5 | N/A | 400uA | LMC7660 (IC 5V->(-5V)) |
Recommendations
- Increase +5Vsb (external) and internal radiator size
- Increase +5Vsb output power
- Ensure -5V sinks power from +5V power rail (Ensure there's enough jumpers to choice from where to sink power)
- Ensure low-drop diodes are used for control inputs
- Ensure there is a high-side switching transistor to control power flow to non-standby PSU rails.
Parts list
- Power input socket 4-pin: MF-4MA (p/n Molex 50-30-4461)
- Type1 power connector (output): PWL-2 (3.96mm pitch)
- Type2 power connector (output): WF-2 (2.54mm pitch)
- Diodes: VD1-VD4 - low drop schottky (SMA DO-214AC or SMB DO-214AA package models: SS24, 10MQ060N, 10BQ40, FR1A) (preferred), or 1N4007 surface-mounted
- LEDs: HV1 [1.8V] (FYLS-1206UYC yellow,2.0V, 20mA) or (KP-3216SEC orange, 2.0V, 20mA), HV2 [3.3V] (KP-3216QBC blue, 3.3V, 20mA), HV3 [5.0V] (FYLS-1206UGC, 2.1V, 20mA), HV4 [12V] (FYLS-1206URC, 2.0V, 20mA)
Version 1
There is a first, preliminary, version of a Power Supply Unit.
Schematic capture
PCB Layout
Device photo
It is capable to provide the following outputs:
- 12V rail - up to 30A (max) from car DC-DC (10A recommended);
- 5V rail - up to 3A output (inefficiently linear regulated from 12VDC) - with turn-off option;
- 3.3V rail - up to 18A, efficiently converted with integrated switched mode DC-DC from input voltage (range 18-36V). ACON DC-DC switched mode, single output 3.3V with trim, 50W, 18A, model = DH50S24033;
- 1.8V rail - up to 1.5A (inefficiently linear regulated from 3.3VDC) - with turn-off option;
However, since 24/3.3VDC converter lacks a ballast load, and because of its switching nature, there is some extra heating of converter's surface and increased energy consumption, even when it is not loaded.
Also, as appeared, this version is not mountable into the back capsule of the robot because of not properly placed mounting holes.
