Current source circuit of multiplex parallel LED driven by one reference current

A reference current, multi-channel driving technology, applied in the direction of electric light source, light source, electrical components, etc., can solve problems such as influence and failure to work normally, and achieve the effect of avoiding damage, improving system fault tolerance, and improving system reliability.

Inactive Publication Date: 2007-02-14
CHIPHOMER TECH SHANGHAI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0030] When LED1 is disconnected or open circuit is damaged, other LEDs will be affected and cannot work normally

Method used

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  • Current source circuit of multiplex parallel LED driven by one reference current
  • Current source circuit of multiplex parallel LED driven by one reference current
  • Current source circuit of multiplex parallel LED driven by one reference current

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Embodiment Construction

[0052] VDS clamping circuit (206) is actually a gate circuit for selecting one of two, as Figure 4 As shown, it includes a hysteresis comparator (301), an inverter (302), two transmission gates (303) and (304). The two input signals are VSAFE and VDS respectively, VSAFE is a protection voltage, for example, 200mV, and VDS is the source-drain voltage difference of MN1. When LED1 works normally, VDS is greater than VSAFE, the comparator (301) output is high, the transmission gate (303) is turned on, the transmission gate (304) is disconnected, and VOUT is VDS. When LED1 is floating or open due to failure, the source-drain voltage difference of MN1 is lower than VSAFE, the comparator (301) output is low, the transmission gate (304) is turned on, the transmission gate (303) is disconnected, and VOUT is VSAFE.

[0053] extreme cases

[0054] If VDS is small, the drive tube enters the linear region.

[0055] According to formula (8), assuming VDS2=VDS1+200mV, when VDS1=VSAFE=200...

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PUM

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Abstract

A current source circuit for the multi-parallel circuited LED driven by a single reference current including: a current mirror, a error amplifier, a regulator tube, a reference current, other multi-driving tubes and VDS clamp circuit. The characteristic is that: the VDS clamp circuit respectively connects with the drain-leakage end of the MN1 and the input of the error amplifier. The current mirror and the grid terminals of other multi-driving tubes are driven by a common Vdrive signal. During the normal working hours, the MN0 and MN1 drain-leakage end voltages of the MOS tube keep consistent under the effects of the error amplifier and the regulator tubes, the other driving tubes and MN1 can obtain a good current-matching even there is a small difference between the drain-leakage end voltages. During the abnormal working hours, the VDS clamp circuit can provide an appropriate bias voltage to make sure that the other driving tubes do not guide a high current and keep the LED in a normal state regardless of the leakage of MN1.

Description

technical field [0001] The invention relates to a current source circuit for driving multiple parallel LEDs (Light-Emitting Diodes) by one reference current. Background technique [0002] White light LED has low calorific value, low power consumption (one-eighth of incandescent bulbs, one-half of fluorescent bulbs), long life (more than tens of thousands of hours, 10 times that of fluorescent lamps), fast response, small size With the advantages of planar packaging, it is easy to develop into thin, light and short products, and it is a potential commodity to replace traditional lighting fixtures. In the context of rising concerns about global energy shortages, the prospect of white LEDs in the lighting market has attracted worldwide attention. Advanced countries such as Europe, the United States, and Japan have invested a lot of manpower and established special institutions to promote the research and development of white LEDs. It will become a new generation of light sourc...

Claims

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Application Information

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IPC IPC(8): H05B41/14
Inventor 孙洪军吴珂
Owner CHIPHOMER TECH SHANGHAI
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