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Mastering the intricate and complex endoscopic technology faces enormous challenges. As an invasive instrument, endoscopes must meet strict leakage current requirements while meeting various power demands from lighting to powering motors and cameras. To address these complexities, P-DUKE offers a range of fully customized DC/DC power converters specifically designed to meet Type CF requirements, ensuring leakage current remains below 10 μ A.

The electrical safety of medical equipment is essentially ensured through two protective measures:

1. Isolation barrier between high-risk AC or DC voltage and low power supply voltage of electronic devices connected to patients. Our patient monitoring instrument case study covers this topic.
2. The leakage current that may flow through the patient’s body is limited. Although leakage currents of up to 30mA are allowed in industrial and household applications, the limitations in medical applications are much lower. The medical standards define three categories:

Type B (body) – Application part without patient connection
Type BF (body floating) – Application part connected to patients
Type CF (cardiac floating) – Application part connected to patients, suitable for cardiac use

Under normal working conditions, the leakage current shall not exceed the following limits:

Leakage Current	Type B	Type BF	Type CF
Earth leakage current	500µA	500µA	500µA
Enclosure Leakage Current	100µA	100µA	100µA
Patient Leakage Current	100µA	100µA	10µA

The main source of leakage current is the EMI filter used on the primary side of the AC/DC power supply. P-DUKE has many AC/DC power supplies with built-in EMI Class B filters, meeting the 100 μ A leakage current requirement for BF type applications (patient contact) (see Figure 1). However, using only an AC/DC power supply to meet the 10 μ A limit for Type CF applications will require a very large EMI filter.

Figure 1: potential applications for AC/DC and DC/DC converters.

Therefore, a combination of AC/DC power supply and downstream CF compatible DC/DC power converter was used. Let’s take a look at a practical example.

Nowadays, medical endoscopes are not only used for diagnosis, but also for minimally invasive surgery, combining modern optical, motor, and software technologies with high-precision machinery. These devices are used in the human body and can be placed close to the heart and come into contact with blood. Therefore, they must meet the 10 μ A leakage current limit for CF type applications.

This client wants to design a smaller video endoscope equipped with LED light sources, a camera built into the internal view lens, and a small motor to control the movement of the head.

How does P-DUKE’s comprehensive power solution promote the creation of efficient power solutions for medical endoscopes?

The system consists of a central processing unit with a microprocessor, an interface with an external video processing unit, a hospital information system, and optional external storage devices. The total power consumption is about 26W.

The endoscope requires a 5V/20W power supply for the LED and camera, as well as a 12V/5W power supply for a small motor that moves the head through a Bowden cable.

The total power consumption of the system is within the range of 44W. Through P-DUKE’s complete range of power converters, it is easy to establish highly flexible solutions (see Figure 2).

Figure 2: Block diagram endoscope power solution

The 65W MAD65 medical AC/DC power supply generates a 12V bus voltage from the AC power source. It is a plug and play solution as it has a built-in EMI Class B filter and meets the medical field requirements of 4000Vac enhanced isolation and 2xMOPP.

P-DUKE has a very comprehensive set of AC/DC power supplies with a power range from 15W to 450W. All products comply with the 2xMOPP standard and have been updated to the latest medical safety certification EN60601-1 ED3.2.

The various power voltages of electronic devices are generated by the downstream medical DC/DC power converter of P-DUKE. Due to the leakage current being much lower than the limit of 10 μ A, they all comply with the CF type standard.

For microprocessors, use a 5V/20W module and an additional 5/10W power converter to isolate all interfaces from the internal system.

The 5V/20W module, which is the same as the microprocessor, is used to power the LED and camera of the endoscope, and the 12V/5W converter drives the motor. If a 3.3V power supply is required, it can be easily generated using a small additional converter.