| 摘要 |
The proposed circuit is for supplying power to an electroluminescent or light-emitting diode from a.c. power grid, and comprises a rectifier circuit (D2) in series with a resistor (R2), an inductor (L1) connected in series with the light-emitting diode (D1), a diode (D3), a transistor (T1), a resistor (R1), and a control circuit (26) connected to the gate of transistor. The control circuit (26) comprises a bistable circuit (28) with analog inputs (THR,TRG), direct digital output (q) and analog output (DIS), a Zener diode (Z1) in parallel with a capacitor (C2), a diode (D4) in series with a resistor (R4) connected to node A, a capacitor (C1), and a resistor (R3) between node A and analog output (DIS). The bistable circuit (28), commercially available as TS555, contains a chain of resistors for voltage division to two operational amplifiers with outputs connected to inputs of a balanced circuit, and a bipolar transistor in the line of inverted output. The transistor (T1) is of MOS (metal-oxide-semiconductor) type and acts as a commutator at given frequency and in cyclic mode, as controlled by the bistable circuit (28). The bistable circuit (28) is in active state in connection with first reference voltage, and the voltage on capacitor (C1) via the resistor (R3); it is in passive state in connection with second reference voltage, and the voltage on capacitor via the resistor (R4). The circuit comprises additional components to ensure that a current flows through the resistor (R4) only when the bistable circuit (28) is in active state. The direct output (q) of the bistable circuit (28) is connected to a blocking diode (D4) in series with the resistor (R4) to force a current to the capacitor (C1).
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