Safety X2 Capacitors are mainly designed for differential-mode EMI suppression and capacitive dropper applications. They are not specifically designed as snubber capacitors for absorbing high-frequency switching spikes.

Although X2 capacitors have high voltage ratings, their internal structure is not optimized for high-frequency switching transients. When directly used for absorbing high-power switching spikes, issues such as rapid capacitance degradation, increased temperature rise, or premature failure may occur.

For switching spike suppression applications, it is recommended to use capacitors specifically designed for high dv/dt environments, such as the MPB-22 (MKP82) series film capacitors, which provide better pulse current capability and transient performance.

The key difference between X2 and Y capacitors lies in their interference suppression type and connection location.

X2 Capacitors:
X2 capacitors are connected between the Live (L) and Neutral (N) lines to suppress differential-mode interference. Their capacitance values are typically in the microfarad (μF) range, such as 0.1μF.

Y Capacitors:
Y capacitors are connected between the Live/Neutral (L/N) lines and Earth (PE/GND) to suppress common-mode interference. Their capacitance values are usually in the nanofarad (nF) range, such as 2200pF, with higher insulation and safety requirements.

Both X2 and Y capacitors are safety-certified capacitors. They are designed with controlled failure modes to prevent electric shock hazards and are manufactured using flame-retardant materials, providing much higher safety performance than standard capacitors.

The selection of a varistor for surge protection should consider three key parameters:

1. Varistor Voltage (V1mA)
The varistor voltage should generally be selected at 1.5 to 2.2 times the normal operating voltage of the circuit to ensure proper protection without affecting normal operation.

2. Maximum Clamping Voltage (Vc)
The maximum clamping voltage should be lower than the withstand voltage of the protected device to effectively limit surge voltage and protect the circuit.

3. Surge Current Capability
The surge current rating should be selected according to the expected surge current level and application requirements, such as the IEC 61000-4-5 surge immunity standard.

Hawtry varistors are available in multiple sizes from 5D to 20D, covering a wide voltage range from 14V to 1800V, and are widely used for surge protection in home appliances, communication equipment, and industrial applications.

Standard and high-energy varistors differ mainly in energy absorption capability and surge performance.

• Standard Varistors: Designed for general surge protection, featuring lower clamping voltage and suitable for normal power grid environments with short-duration surge pulses.

• High-Energy Varistors: Designed for higher surge energy absorption and longer-duration impact conditions, suitable for unstable power grids, frequent lightning environments, and high-reliability applications.

The two types are optimized for different applications and should be selected according to the actual surge environment.

For equipment requiring a 3750VAC withstand voltage test, a Y1 Safety Capacitor is recommended due to its higher insulation strength and larger safety margin.

Y1 capacitors are designed for higher impulse withstand capability (typically ≥8kV), while Y2 capacitors may not provide sufficient margin for such high-voltage stress conditions.

The final selection should also consider leakage current, rated voltage, certification requirements, and EMC performance to ensure safe and reliable operation.

An NTC thermistor is connected in series with the power input to limit the inrush current when the equipment is switched on.

At room temperature, the NTC thermistor has a relatively high resistance (for example, 5Ω–20Ω), which effectively limits the initial surge current to a safe level. After power is applied, the current flowing through the NTC causes it to heat up, reducing its resistance to a very low level (milliohm range), thereby minimizing power loss during normal operation.

Hawtry NTC thermistors feature fast response, high steady-state current capability, and reliable performance, making them widely used in applications such as power adapters, inverters, and power supply systems.

CBB21 and CBB22 are both metallized polypropylene film capacitors. Historically, CBB21 was commonly used in coupling and filtering applications, while CBB22 was preferred for high-frequency, high-current, and pulse applications.

With improvements in film materials and manufacturing processes, the performance difference between CBB21 and CBB22 has become minimal. Both are suitable for DC, pulse, and high-frequency circuits. Today, CBB22 is more widely used in the market, while CBB21 is mainly provided according to specific customer requirements.