LED LAMP DRIVER WITH RESISTIVE VOLT-AMP CHARACTERISTIC

摘要

The device relates to LED lamp drivers working directly from an AC voltage rectified by a diode bridge without an AC-DC converter. For its operation, it is not necessary to smooth out the rectified voltage with high-voltage electrolytic capacitors, which reduce the operating time of LED lamps. The device contains a rectifying diode bridge, high-voltage transistor switches, a resistive shunt for measuring current in a load, and a key management circuit that, to increase the efficiency of the device, as the rectified mains voltage increases, it switches LED sections in a series LED loading circuit, including another section in the current path when it reaches a sufficient voltage level. With a decrease in the mains voltage rectified by the diode bridge and the impossibility of the flow of the set current, the control circuit switches the high-voltage transistor switches and sequentially excludes the next section of the LEDs from the current path. With the help of an operational amplifier and a circuit for shifting the levels of control voltage with transistor switches, a feedback circuit is organized that provides automatic, smooth, without current surges turning on (off) the next section of LEDs. At the same time, regulation of the load current in proportion to the effective value of the rectified input voltage gives a resistive characteristic, like incandescent lamps, of the current consumed from the mains and, accordingly, a power factor close to unity. The driver circuit is simple and does not contain specialized