Switching power supply is a kind of power supply that utilizes modern power electronics technology to control the time ratio of switching on and off, and maintain a stable output voltage. Switching power supply is generally composed of pulse width modulation (PWM) control ICs and MOSFETs. With the development and innovation of power electronics technology, switching power supply technology is also constantly innovating. At present, switching power supply is widely used in almost all electronic devices due to its small size, light weight, and high efficiency. It is an indispensable power supply mode for the rapid development of the electronic information industry today。

In our company, switching power supply brands include Phoenix Contact, DEUTRONIC D/C power supply, etc. Switching power supply products are widely used in industrial automation control, military equipment, scientific research equipment, LED lighting, industrial control equipment, communication equipment, electrical equipment, instrumentation, medical equipment, semiconductor refrigeration and heating, air purifiers, electronic refrigerators, liquid crystal displays, LED lighting, communication equipment, audio-visual products, security monitoring, LED light bags, computer chassis, digital products and instruments.

Let's witness the application of power switches in medical sensors. The following is a partial circuit diagram of a switching power supply in a medical device. (For reference only)

With the continuous development of modern medical devices, especially electronic instruments that are directly connected to the human body, in addition to the requirements for their own performance, the consideration of human safety has also received increasing attention, such as life monitors, maternal and infant monitors, infant thermal insulation devices, and other instruments that are in close contact with the human body, That is to say, patients should not cause electric shock or other hazards to the human body due to the equipment they are using. Currently, there are many DC/DC module power supplies on the market, but due to the special industry of medical electronics, the requirements for its power supply are very high. To ensure the safety performance of human body and equipment, the selection of DC/DC module power supplies is particularly important.

The application of DC/DC module power supplies in the medical electronics industry, especially in sensor detection circuits, should pay attention to the following:

1. The external capacitance of the DC/DC power supply module adopts a low internal resistance capacitance, and excessive capacitance should be avoided to prevent damage to the module due to excessive capacitance causing transient overcurrent during startup

2. In order to ensure the reliability of the long-term operation of the module, it is necessary to ensure that the module operates above 10% of the rated power to prevent the output voltage instability caused by the module due to no-load or light load from affecting the circuit operation. If the load power consumption is indeed small, a dummy load (resistance) of - 10% of the rated power can be applied to the output terminal in the form of an external dummy load to improve the reliability of the product

3、Since the DC/DC power supply module is implemented using a switching oscillation circuit, it can also generate common mode and differential mode noise interference. For situations where there is a high demand for ripple noise, a passive filter network can be connected to the output of the DC/DC power supply module to further reduce the ripple noise of the power supply. However, it is important to note that the resonant frequency of the module should be much higher than the switching frequency of the module, and the allowable current value should preferably be more than twice the input current of the module, Internal resistance should be small to reduce DC loss。