| 摘要 |
The invention relates to a lighting apparatus with LEDs, which is supplied directly from the main AC network. According to the invention, the apparatus comprises a source of constant current, trapezoidal in amplitude, in phase with the network voltage (U), comprising a rectifying diode (D36) connected in series with resistive dividers consisting of resistors (R34, R39, R32), two voltage-limiter stages consisting of Zener diodes (D38, D3, D2, D1), two bipolar transistors (Q33, Q52), a polarization resistor (R50) and a resistor (R42) setting the plateau of the current absorbed by the source, a rectifying bridge (GR2) having the "plus" outlet connected in series with the constant current source and the "minus"outlet connected to the ground, a string of LEDs connected in series and partitioned into several segments (D79.1...D79.9), some comparator circuits (U1.1...U1.4, U2.1...U2.4), some MOSFET transistors (Q59, Q67, Q3, Q4, Q5, Q6, Q25, Q26) the switching of which is controlled by the comparator circuits, some resistors (R10...R16, R19, R24) setting the voltage thresholds at which the comparator circuits perform the switching, a filtering capacitor (C73) mounted in parallel on the series group formed of the rectifying diode (D36) and a resistor (R32), a resistor (R51) mounted between a resistor (R34) and a point (J5) in the drain of the transistor (Q5), a limiting resistor (R27) mounted between the cathode of the segment (D79.1) and the drain of the transistor (Q59) and a capacitor (C60) connected between the anode of the LED string and the ground. |
