7.4V 10Ah Backup Power Design Scheme of Medical Infusion Pump

Foreword: (keyword: lithium ion battery of medical infusion pump) as the development of living standard, medical service and products has kept improving. Traditional stationary medical devices are replaced by new medical products with flexibility, high precision and intelligence. New intelligent infusion pump replaces the traditional infusion method. It can work out intelligent and reasonable infusion speed and method according to different patients. What’s more, it is also convenient for different people to use in different places and under different environment. Large Electronics lithium ion battery of medical infusion pump can provide continuously stable power for fixing or moving the devices and work under stable, efficient, continuous and stable circumstance.

1) Lithium ion battery design requirements of medical infusion pump

Medical infusion pump is a new intelligent infusion product. Due to the particularity of people and environmental application, it has very strict requirements on battery. For example, the battery needs to input and output on the same port, so that relevant personnel can use safely and conveniently. It must have charging and discharging capacity display. Keep the capacity indicator on for patients and relevant personnel to check at any time. Battery safety performance and fire rating have to meet the special requirements of medical products.

1. The design requirements of lithium ion battery pack: 18650-2S4P/10Ah/7.4V

2. Input and output characteristics: input and output on the same port. Apply automatic switching function according to the medical special requirements.

• Output characteristics: the output port of battery DC circuit outputs 5V/2A automatically when the battery doesn’t charge.

• Input characteristics: insert a 9V/2A adapter on DC output line, and then the battery will charge automatically.

• Status characteristics: no output status when charge at 9V/2A. Change to 5V/2.5A automatically when take away 9V/2A charging.

3. Indicator of charging and discharging: assemble a monochromatic lamp and a bi-color light to indicate for battery capacity of high, medium and low signal.

• 6.4V±0.1V red light on

• 7.3V±0.1V blue light on

• 7.9V±0.1V blue light on (two green lights on)

4. Discharge condition: it can discharge for about 10-20 minutes after the red light is off.

5. The fundamental characteristics of guard plate

• Over-charged protection voltage of single battery: 4.28±0.25V

• Over-charged recovery voltage of single battery: 4.10±0.10V

• Over-discharged protection voltage of single battery: 2.80±0.08V

• Over-discharged recovery voltage of single battery: 3.00±0.10V

• Over-discharge cut-off current of battery pack (10ms): 8~12A

• Over temperature protection value of battery pack (restorable): 70±5℃

• The finished product has protective function of short circuit and reverse-charging.

6. The design requirements of battery cycle life: 300~500 times (national charging and discharging standard)

7. Design requirements of battery dimension

2) Lithium ion battery design scheme of medical infusion pump

1. Intelligent buck-boost modular circuit: input 9V/2A to adapter for transition from DC/DC to CC/CV, which is the charging mode that is suitable for two lithium ion batteries in series, and then decrease the voltage of two batteries in series into 5V/2A constant voltage output status. At that moment, open automatic shift mode of input and output status.

2. Guard plate (PCM): it is protective circuit of rechargeable lithium ion battery pack. Because of the chemical characteristics of lithium ion battery, it needs protective function of intelligent capacity calculation, overcharging, over-discharging, short circuit, overcurrent, etc. so as to avoid combustion, explosion, etc.
   

3. Protection IC: it is the chip has main protective function in the design scheme. The chip monitors the cell on the functions of overcharging, over-discharging, overcurrent, short circuit, etc. at any time, which helps the battery works under safe, stable and efficient circumstance.
   

4. Temperature switch: it is designed for temperature protection. When the battery is heated up to 70±5℃ due to any issues, the temperature switch begins to protect the battery.
   

5. 18650 lithium ion battery/18650/2500mAh/3.7V Li-ion cell（SANYO）
   

6. MOSFET: it works as the switch in protective circuit to make sure that the voltages of two ends won’t be up and down, so that the voltage will be stable.
   

7. DC output line: lithium ion battery inputs and outputs electricity to the infusion bump.
   

8. Battery case: it meets the medical product fire rating and is part of the battery module.

Schematic diagram of design solution