Double button field effect tube dimmer circuit

The double-button field effect tube dimming lamp circuit is shown in the figure
. It uses two touch button switches for dimming, one for brightening and the other for clearing. It has
the advantages of easy use and beautiful appearance.
    G.C. , VD and VS2
, etc. form a simple capacitor step-down
half-wave rectified voltage-stabilized power supply to
supply power to the entire control circuit.
This power supply is controlled on and off by switch S.
It can be...an
ordinary small toggle switch,
or It can be a
touch button switch hidden on the desk lamp panel
. Normally, when switch S is turned on,
the desk lamp does not light up. When you need to turn on the light, you only need to place a small doll on it, the switch is pressed, the contacts are closed, and the circuit
is energized. SB1 and SB2 are touch button switches used for brightening and dimming respectively. The luminous tubes I and ED serve as indicator lights
for the circuit T.
    The M()S field effect transistor VF and the resistor-capacitor components T, R, C, etc. constitute the trigger circuit of the bidirectional thyristor VTH
, and the VS1 star is used to protect the VF-. When SB1 is pressed, the power supply turns R. , SB1 charges G, causing
the gate voltage of VF to rise, its source current to increase, the thyristor VTH trigger current to increase, the conduction angle to increase, and
the brightness of bulb E to increase; when SJB2 is pressed. The charge stored in G passes through SB2 and R. Discharge causes the VF gate
voltage to drop, the drain-source current to decrease, the VTH trigger current to decrease, the conduction angle to decrease, and
the brightness of the bulb E to weaken. When S1 and SB2 are both open, since the gate-source resistance of the MOS field effect transistor
is extremely large, c, the voltage at both ends can remain basically unchanged, so the conduction angle of the thyristor VTH also remains basically unchanged, so the lamp F, the
brightness The atr can be kept unchanged. In order to make the brightness of the bulb more stable, the capacity of the capacitor C should be appropriately increased, and
the leakage current of c_ should be as small as possible.