Help with power supply design for portable device

In summary, the power supply for this device must provide multiple voltages with pcb size and power efficiency in mind. The analog components will use dual power supplies (+/-), while the digital components will use a single power supply. The battery will be used with a 3.6 V LiPo battery.
  • #1
jibjab123
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I need help designing a power supply for a portable medical research device for animals. My problem is designing a configuration for multiple voltages with pcb size and power efficiency in mind. I need 3.3 V, +/- 1.5 V, and +/- 20 V.

Below I’ve listed device info and estimated current consumption of both the analog and digital components.

Device Info: My device will be worn by small rodents and used to (1) amplify low-voltage and low frequency (< 15 kHz) analog signals, (2) output 100uA@20V constant current pulses, and (3) communicate with PC via BT. This device will be small (2’x2’ double sided pcb) and light weight. Thus, efficiency and pcb footprint are extremely important. Component cost isn’t much of a concern.

Digital Components:
1. MCU: 10 mA @ 3.3 V (Supply Range: 1.7 - 5.0 V )
2. Bluetooth Module: 15 mA @ 3.3V (Supply Range: 3.0 - 3.6 V, peak current 50mA)

Analog Components: All analog components use dual power supplies (+/-).
1. Section A: 1mA @ +/- 1.5 V (<1% duty cycle, Supply Range: 1.0 - 3.3 V)
2. Section B: 2mA @ +/- 20.0 V (1% duty cycle)

Battery: I was hoping to use a 3.6 V LiPo battery unless there is a more appropriate battery or source voltage.

Questions: Where and how should I use LDO, switching, or linear regulators together for this application? What’s the best way to get the +/- 20 V? Should I adjust any component supply voltages for higher efficiency? ... etc...? Any help would be tremendously appreciated.
 
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  • #2
There are several free on-line or downloadable design/simulators specifically for power supplies. I'm sure you will need to balance overall weight/size/power consumption, and simulations can be helpful in quickly running numerous design iterations to compare results.

A few to get you started:
http://www.ti.com/ww/en/analog/webench/power.shtml
http://www.poweresim.com/
http://www.fairchildsemi.com/design_tools/

Don't forget that switching supplies may introduce noise in your data sampling circuits.
 
  • #3
jibjab123 said:
My device will be worn by small rodents ... This device will be small (2’x2’ double sided pcb) ...

Big rodents. :devil:
 

1. What are the key factors to consider when designing a power supply for a portable device?

The key factors to consider are size, weight, efficiency, and reliability. Portable devices typically have limited space and need to be lightweight, so the power supply must be compact. It should also be highly efficient to prolong battery life and reliable to ensure the device functions properly.

2. How can I determine the power requirements for my portable device?

The power requirements can be determined by calculating the maximum current and voltage needed for the device to function. This can be done by considering the power consumption of each component and factoring in any necessary safety margins. It is also important to consider any power spikes or surges that may occur during operation.

3. Is it better to use a battery or a power adapter for a portable device?

This ultimately depends on the specific needs and use case of the device. Batteries offer portability and convenience, but may need to be replaced or recharged frequently. Power adapters provide a constant power source but may limit mobility. In some cases, a combination of both may be the best solution.

4. How can I ensure the power supply design is safe for the user?

Safety should be a top priority when designing a power supply for a portable device. This can be achieved by following safety standards and guidelines, such as those set by regulatory agencies like UL or IEC. It is also important to incorporate protection circuitry, such as overcurrent and overvoltage protection, to prevent any potential hazards.

5. What are some common challenges when designing a power supply for a portable device?

Some common challenges include meeting size and weight constraints, achieving high efficiency, minimizing heat dissipation, and ensuring compatibility with different power sources. Cost and reliability may also be challenges, as well as navigating regulatory and safety requirements. Thorough testing and prototyping can help address these challenges and ensure a successful power supply design.

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