Power supplies for medical devices are available in many styles, including enclosed, open frame, table top, or wall mounted. Whichever one you choose, safety must be a priority.

 

Patients in hospitals are often in a weakened state and small leakage currents can worsen their condition even further. Small leakage currents are defined as the unintended electric currents that may pass through the human body. To a healthy person, the leakage has little to no effect but to ill patients there is much more cause for concern.

 

For this reason, medical devices that have direct physical contact with patients must have limited leakage current and must be regulated to be at the lowest prescribed levels.

 

Because medical devices are designed to the highest standards, medical power supplies must meet the same standards to protect patients and operators from electrocution.

 

Medical standards for electrical equipment and power supplies

Power supplies used in medical devices must meet IEC 60601 “Medical Electrical Equipment, Part 1: General Requirements for Safety” for global compliance. They must also meet regional and national variations, depending on where the medical devices are used. Europe, for example, follows the European EN 60601-1, the United States follows the U.S. ANSI/AAMI ES 60601-1, and Japan follows the Japanese JIS T 0601-1 standards.

 

These different standards make designing power supplies for medical applications uniquely challenging for many engineers.

 

The latest changes in Medical Power Supply Safety Standards is specified in the IEC60601-1 third edition. Some of the new requirements added are the isolation between the AC input to the power supply, the DC output, and the internal high voltage stages.

 

To assure isolation a double layer of insulation or reinforced insulation is designed to prevent electric shock to patients. Furthermore, testing requires medical supplies to be subjected to a much higher voltage than it normally faces.

 

Classification of applied parts

There are three types of applied parts used in Medical power supplies—body type (B), body floating type (BF), and cardiac floating type (CF). The regulating standards required for the several attributes, such as leakage current, creepage requirement, and isolation voltage, are determined by the applied parts.

 

Type B refers to devices used within the patient vicinity or 6 feet around the patient’s chair or bed. These devices, such as hospital beds, operating room lights, and x-ray machines, are grounded and do not touch the patient electronically.

  • Creepage Requirement: 2.5 mm
  • Isolation Requirement: 1500 Vac
  • Insulation Requirement: Double

 

Type BF refers to devices that deliver electrical energy signals to or from the patient, such as electrical thermometers, endoscopes, and electrosurgical devices.

  • Creepage Requirement: 5 mm
  • Isolation Requirement: 3000 Vac
  • Insulation Requirement: Basic

 

Types CF refers to devices that operate within the patient vicinity, like a BF type, but supply power to devices connected to the heart. These include a defibrillator, intracardiac ECG electrodes, and an external pacemaker. For this reason, such devices must have a higher degree of protection against electrical shock.

  • Creepage Requirement: 8 mm
  • Isolation Requirement: 4000 Vac
  • Insulation Requirement: Double

 

The leakage current for all medical devices must not exceed 500uA or 300uA for UL approved devices.

 

Means of production (MOP) classification

To prevent patients and operators from electrocution, all medical power supplies must include at least one MOP, such as protective insulation, safety insulation, and protective earth and creepage insulation.

 

MOP differs in requirements based on whether it is for Means of Patient Protection (MOPP) and Means of Operator Protection (MOOP).

 

Jasper Electronics has been working closely with medical device manufacturers over the last 20 years to provide reliable & cost-effective solutions. JE operates under ISO 9001 to ensure that process controls are always in place. For Further information about Jasper Electronics Power Supplies for the Medical market as well as other power supplies contact Peninsula Technical Sales at 650-965-3636 or write us at  sales@pentech.com

 


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