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Suppress Interference Technology (1)

Suppress Interference Technology


1#  Professional lines

In order to suppress mutual interference between instruments and equipments, the simplest method is to adopt the split-phase power supply system. That is to say, in a three-wire power supply line, one phase is regarded as a power supply for sensitive devices; one phase is used as a power supply for external devices; and the other phase is used as a power supply for commonly used test instruments or other auxiliary devices. This solution is often used in large medical equipment power supply systems.
In modern medical electronic equipment and equipment systems, due to the use of non-linear loads in the distribution line, harmonic currents exist in the line, and the zero-sequence component harmonics cannot cancel each other out in the middle line, oppositely, they are superimposed. Hence, too thin midwire will cause the impedance of the circuit to increase, and the interference will increase.

2#  Transient interference suppressor

Gas Discharge Tube

Commonly known as lightning strikes. The advantages are high insulation resistance, small parasitic capacitance, and strong surge absorption capability. The disadvantage is the low response to surge voltage.
Metal Oxide Varistors

The main parameters of the varistor are the nominal voltage and the through-flow capacity. The voltage of the varistor need to considerate the fluctuating voltage that may be present on the protected circuit, typically 1.2 to 1.4 times. If it is an AC circuit, have to pay attention to the relationship between the effective value and the peak value. For example, when the voltage is 220V, the nominal voltage of the varistor should be 220 x 1.4 x 1.4 = 430V. The former is due to the high-speed performance level of the varistor when it absorbs transients. The longer the lead, the greater the induced voltage. The latter is due to the inherent capacitance of the varistor.

3#  Silicon Transient Voltage Absorbing Diodes

TVS tube is also called transient voltage suppression circuit. When the transient voltage protection diode is subjected to reverse transient high-energy shocks, the high impedance between its two poles is changed into a low impedance at a speed of 1×10-12 s, absorbing up to several kilowatts of surge power, making the bipolar between The voltage clamp is located at a predetermined value, effectively protecting the sensitive elements of the electronic circuit. Specifically divided into one-way and two-way two. The main parameters are breakdown voltage, leakage current and capacitance.

Features are fast response time, high surge absorption capability, high transient power, low leakage current, easy control of clamp voltage, no damage limit, and small size. It is widely used in the static electricity of medical equipment, transient voltage generated when inductive load is switched, and overvoltage protection caused by lightning.