Capacitive dimmer switch circuit (2)

The dimmer switch introduced in this example is made by using the principle of capacitor charging and
discharging. It is suitable for dimming incandescent lamps, and will not cause radio frequency interference to household appliances such as radios and televisions when used.
Its circuit is shown in Figure 10.
    Close the power switch Sl, and the 220V alternating current becomes pulsating direct current through VD half-transition rectification. If the switches S2-
S4 are all open, the output voltage, that is, the voltage across the bulb E is the lowest, only 0 45 × 220V = 99V; when
the switch S2 is closed, This pulsating voltage has been filtered and turned into direct current. If the output is no-load, the output voltage
Y)-l20/2V-SI.V. After connecting r to the load bulb,
the output voltage is the voltage across the bulb Vr. Will F drop,
the greater the power of the light bulb, the mine. The more the value drops. If the power of the bulb
remains unchanged, changing the size of the filter capacitor will also affect
the value of the voltage VF across the bulb. The larger the filter capacitance
. The higher the VL value, the dimmer is
made using this principle. By closing or opening F s2 - S4, and
realizing different combinations, different voltages can be obtained to achieve the purpose of changing light. Obviously, when S2~
S- are all open, the brightness of spider F is the dimmest, and when S2-S4 are all closed, the brightness of F is the brightest. The circuit can
obtain 8 different brightnesses. When E uses a 60W incandescent lamp, at 8 different brightnesses,
the actual measured values ​​of the voltage at both ends of the lamp F are shown in Table 1. (1.~(j should use electrolytic capacitors with a withstand voltage of 4joV.