ALLPCB
1. Introduction
In the past, medical institutions at all levels in China still used paper-based medical management models. The cumbersome visit procedures greatly reduced the efficiency of medical resource utilization and no longer met patients' needs for more convenient care. In recent years, with China’s socioeconomic development and especially advances in electronic information, conditions for digitizing medical resources have improved. Mobile medical devices are central to this trend and support industry transformation and upgrading.
Currently the healthcare sector faces two major problems: first, complex paper-based data management; second, tangible and intangible barriers between hospitals. The main issues with traditional paper-based medical data storage and processing include the following.
Paper stores important patient information and requires long-term retention. Management difficulty increases with the quantity of paper and films, consuming significant financial, material, and storage resources. Manual archive management is inefficient, searches are slow, and transferring medical images requires a great deal of time. Paper loss and damage are difficult to resolve.
Barriers when patients visit different hospitals appear as follows: when a patient has undergone a series of examinations at one hospital but must visit another hospital for various reasons, previous tests are often invalidated. The patient then incurs additional costs and must undergo repeated examinations and laboratory tests. This imposes substantial economic, physical, and psychological burdens.
Electronic medical devices are varied but often single-function and lack integration. Building a complete mobile medical system with these devices typically requires purchasing multiple units, which increases cost and reduces mobility as device count grows. For cost and mobility reasons, a digital data management solution for hospitals is needed to enable paperless workflows and accelerate information sharing. The designed health companion device provides a more integrated set of functions, including ECG, body temperature, blood glucose, and blood pressure measurement. Auxiliary features for mobile medical service include remote control, user-friendly operation, emergency call, and real-time data backup.
2. Hardware Design
2.1 Hardware Overview and System Block Diagram
The system hardware integrates lithium battery charging management and DC-DC regulation, providing a stable supply voltage while improving portability. Functionally, the device implements accurate ECG, temperature, blood pressure, and blood glucose measurement, and integrates a GSM module to enable one-button emergency calls. The system features a 3.2-inch resistive touchscreen for human-machine interaction and a button for one-key standby/screen-off to reduce power consumption. Common data such as phone number and resistive touchscreen calibration values are stored in a low-cost EEPROM. Acquired physiological data can be sent to a PC via Bluetooth or saved to the system SD card.
2.2 Power Circuit Design
The system integrates multiple functions, so a reliable power supply is necessary for stable operation. To improve portability and user convenience, the system uses a dual power supply: an AC adapter and a lithium battery. When mains power is unavailable the device runs from the lithium battery; when mains power is present the adapter supplies the system and charges the battery.
The battery is a 1380 mAh dual-cell lithium pack, offering high output current, no memory effect, low self-discharge for long storage, and long service life. To protect the lithium battery, the system includes a protection board. The battery's fully charged voltage is 8.4 V and the discharge cutoff voltage is 6.0 V.
The system also includes a lithium battery charge management circuit. The management chip is Maxim's low-cost multi-cell charger controller MAX846A. This chip supports single/double-cell lithium batteries, nickel-metal hydride, and nickel-cadmium batteries.
In the charging circuit, C6 and R9 are selected by experience as a 0.01 uF capacitor and a 660 ohm resistor. C7, C8, and R12 are chosen according to the chip datasheet. R11 (in K) = 1.65 V / I; taking 165 mV. When set to 0.4, the charging current is 400 mA. The diode is a Schottky diode 1N5817, chosen for its low forward drop. The PMOS is an AO3415, which has low Rds(on) (around 40 mΩ) to reduce switch losses and improve efficiency. Its 1450 pF input capacitance allows direct drive by the MAX846A's internal transistor, saving cost.
