Cbb22 capacitor action step-down principle _cbb22 capacitor advantages

Introduction to CBB22:

The CBB in the CBB22 capacitor is a metallized polypropylene film capacitor, 22 is the model, the nominal capacity of the CBB capacitor less than 1μF is specified by E6, and the first two digits are 6 kinds, 10, 15, 22, 33, 47, 68. The latter 2 is the CBB film capacitor serial number code rule: (0: axial lead; 1: radial lead; 2: DC voltage; 6: AC voltage; 8: DC high voltage)

Internal structure of CBB22:

The metallized polypropylene film is used as a medium and an electrode, which is wound up, encapsulated with flame-retardant insulating material, non-inductive structure, unidirectional copper wire lead-out, with outsourcing, epoxy resin sealing, special spray gold and encapsulation Process.

CBB22 technical requirements:

Reference standard: GB10190 (IEC60384-14)

Climate type: 40/85/21

Rated voltage: 250V, 400V, 630V

Capacitance range: 0.0047-3.3Uf

Dielectric deviation: ± 5% (J), ± 10% (K), ± 20% (M)

Withstand voltage: 1.5UR (5S)

Loss angle: ≤0.1% (20°C, 1KHZ)

Insulation resistance:

≥25000MΩCR≤0.33Uf (20°C, 1min)

≥7500sCR>0.33Uf (20°C, 1min)

CBB22 Capacitance / Use:

The cbb capacitor is a type of film winding type capacitor. The cbb capacitor has a high withstand voltage, a small loss angle, and a stability number. It is generally used in applications where the performance of the capacitor is relatively high.

It is widely used in DC pulse, pulse, high frequency and AC step-down in instruments, meters, TV sets and household appliances. It is especially suitable for various types of energy-saving lamps and electronic rectifiers and welding machine inverter circuits.

CBB22 advantages:

It has the advantages of excellent electrical performance, good reliability, low loss and good self-healing properties.

CBB22 capacitor step-down principle:

1, the principle of resistance and pressure reduction

The working principle of capacitor buck is not complicated. His working principle is to limit the maximum operating current by using the capacitive reactance generated by a capacitor at a certain AC signal frequency. For example, at a power frequency of 50 Hz, a 1 uF capacitor produces a capacitive reactance of approximately 3180 ohms. When an AC voltage of 220V is applied across the capacitor, the maximum current flowing through the capacitor is approximately 70 mA. Although the current flowing through the capacitor is 70 mA, there is no power consumption on the capacitor. If the capacitor is an ideal capacitor, the current flowing through the capacitor is the imaginary current, and the work done is reactive power. According to this feature, if we connect a resistive component in series with a 1uF capacitor, the voltage obtained across the resistive component and the power dissipation it generates depends entirely on the characteristics of the resistive component. For example, we connect a 110V/8W bulb in series with a 1uF capacitor. When connected to an AC voltage of 220V/50Hz, the bulb is illuminated and emits normal brightness without being burned. Because the 110V/8W bulb requires 8W/110V=72mA, it matches the current limiting characteristics of the 1uF capacitor. Similarly, we can also connect a 5W/65V bulb and a 1uF capacitor in series to 220V/50Hz AC. The bulb will also be lit without being burned. Because the 5W/65V bulb also has an operating current of about 70mA. Therefore, the capacitor buck is actually using the capacitive reactance current limit. The capacitor actually acts as a limiting current and dynamically distributing the voltage across the capacitor and the load.

2, device selection

1) When designing the circuit, first determine the exact value of the load current, then refer to the example to select the capacity of the step-down capacitor. Since the current Io supplied to the load through the step-down capacitor C1 is actually the charge and discharge current Ic flowing through C1. The larger the capacity of C1 is, the smaller the capacitive reactance Xc is, and the larger the charging and discharging current flowing through C1 is. When the load current Io is less than the charge and discharge current of C1, the excess current will flow through the Zener diode. If the maximum allowable current Idmax of the Zener diode is less than Ic-Io, the regulator tube will burn out.

2) In order to ensure reliable operation of C1, the withstand voltage selection should be greater than twice the power supply voltage. 3. The selection of the bleeder resistor R1 must ensure that the charge on C1 is released during the required time.

3, design examples

It is known that C1 is 0.33μF and the AC input is 220V/50Hz. The maximum current that the circuit can supply to the load is obtained. The capacitive reactance Xc of C1 in the circuit is:

Xc=1/(2πfC)=1/(2*3.14*50*0.33*10-6)=9.65K The charging current (Ic) flowing through capacitor C1 is:

Ic = U / Xc = 220 / 9.65 = 22 mA.

Generally, the relationship between the capacity C of the step-down capacitor C1 and the load current Io can be approximated as: C=14.5I, where the capacity unit of C is μF, and the unit of Io is A.

Capacitor buck power supply is a non-isolated power supply. In application, special attention should be paid to isolation to prevent electric shock.