Circuit capable of adjusting output current according to load change

Abstract

The invention relates to a circuit capable of adjusting output current according to load change. The circuit comprises a power supply end (1) and a load end (2), and is characterized by further comprising a controllable constant current source (3) which is arranged between the power supply end (1) and the load end (2) and can adjust a bus output current (I) according to the voltage change of the load end (2), so as to control power of the controllable constant current source and a voltage of the load end (2) formed by parasitic resistance (R'). The circuit can effectively solve the problems that a constant current source device is burnt down and the signal transmission quality is poor.

Description

technical field [0001] The invention relates to the field of electronic technology, in particular to a circuit capable of adjusting output current according to load changes. Background technique [0002] DALI dimming system plays an important role in the field of lighting control in the market, and DALI Power Supply (hereinafter referred to as DALI PS) is an indispensable special equipment in the DALI dimming system and the guarantee basis for DALI bus signal transmission. According to the IEC82386 standard, the voltage output range of DALI PS should be between 9.5-22.5V, and the maximum output current should not exceed 250mA. [0003] In the existing DALI PS design, the conventional design of the circuit is that the load end is connected to the power end through a single constant current source, such as figure 1 shown. This kind of circuit design is simple, but there are many problems. One of the problems is that the DALI system uses Manchester encoding to transmit data. ...

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Problems solved by technology

This kind of circuit design is simple, but there are many problems. One of the problems is that the DALI system uses Manchester encoding to transmit data. When sending data, the DALI bus will be short-circuited. At this time, the bus current I may reach 250mA, while a single constant current The characteristics of the source determine that in this case, the two ends of the MOS device Q1 in the constant current source will carry an excessive voltage, which may reach 15.3V in this circuit, and the maximum power can be as high as 3.8W, which may cause the device to be damaged due to power Excessively large and rapid heating will cause damage, or increase the difficulty and cost of product design

[0004] At the same time, the DALI signal will be carried on the load voltage by the carrier after a certain calculation during transmission, and the current single constant current source circuit design, when the load line is very long, the wire will generate parasitic resistance, and the parasitic resistance will consume part of the voltage , so that the signal transmitted by the DALI device receiving the load end is incomplete. In order to ensure the quality of the signal reception, the laying area of ​​the DALI system has to be sacrificed, which greatly limits the application of the DALI system; The effect of high pressure is not ideal

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