GB2514929A

GB2514929A - Active self-regulating circuit

Info

Publication number: GB2514929A
Application number: GB1409892.5A
Authority: GB
Inventors: Jin-Fa Li
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-06-04
Filing date: 2014-06-04
Publication date: 2014-12-10
Also published as: GB201409892D0; CN104219827A; TWI508615B; TW201448659A

Abstract

An LED driver circuit includes an AC source 1, a bridge rectifier 2 connected to the AC source, an LED driving unit 14 connected to the AC source via the bridge rectifier, a plurality of LEDs 3 connected to the LED driving unit, and an active discharge regulation circuit connected between the rectifier and the LED driving unit, wherein the active discharge regulation circuit comprise a diode 4, a resistor 5, a Zener diode 9, a BJT 11, and a MOSFET 10 connected to each other and wherein the MOSFET is connected in parallel with the resistor and the Zener diode. The discharge circuit provides a bleed current via the MOSFET and resistor 6 when the current drawn by the LED driving unit is too low to maintain a holding current through a triac dimmer and is able to detect an open-circuit condition of the driving unit and disable the bleed current accordingly.

Description

ACTIVE SELF-REGULATING CIRCUIT

TECHNICAL FIELD

[001] The present invention relates to a light dimming circuit, more especially an active self-regulating circuit,

BACKGROUND

[002] Currently, TRIAC (Triode for Alternating Current) dimmer is implemented in the traditional lighting apparatus or LED lighting apparatus. In operation, the TRIAC dimmer needs a minimum holding current to keep the TRTAC dimmer operating in a normal conduction. In order to generate the minimum holding current, the RC phase shifting circuit is employed in the TR.IAC to generate the holding current based on the charge/discharge characteristics of the phase shifting circuit. Thus, the operating current can be generated during the whole duty cycle of the AC input in the TRT.AC dimmer. However, it causes the low efficiency of the lighting apparatus and the problem of the current of the minimum conduction angle cannot be consecutive and the insufficient of the operating current so as to bring the phenomenon of the twinkling and impact the life time of the lighting apparatus.

SUMMARY

[003] One of the purposes of the invention is to provide an active self-regulating circuit to fix the aforementioned drawbacks.

[004] The present invention provides an active self-regulating circuit, which includes an AC source, a bridge rectifier is connected to the AC source, an LED driving unit is connected to the AC source via the bridge rectifier, a plurality of LEDs are connected in parallel to the LED driving unit, and an active discharge regulation circuit is connected in series between the rectifier and the LED driving unit, wherein, the active discharge regulation circuit comprises a diode, a resistor, a Zener diode, a BJT (bipolar junction transistor), a mosfet which connected to each other and where the mosfet is connected in parallel connected with the resistor and the Zener diode.

[005] The beneficial effects of present invention are: the active self-regulating circuit with the active discharge regulation circuit can adjust the kinetic energy regulator and the conduction time of the switch according to the holding current of the TRIAC and a total system current. When the total system current is less than the minimum holding current, the self-regulating circuit increases the conduction time of the driving signal, to drive the current which flows through the TRIAC increases to the level of the minimum holding current, so as to keep the normal conduction of the TRIAC, improve the efficient of the lighting power driver and increase the match ability of the TRIAC.

BRIEF DESCRIPTION OF THE DRAWINGS

[006] Features and advantages of embodiments of the subject matter will become apparent as the following detailed description proceeds, and upon reference to the drawings, wherein like numerals depict like parts, and in which: [007] FIG. I illustrates a schematic of active self-regulating circuit in accordance with one embodiment of the present invention.

[008] FIG. 2 illustrates a detail schematic of the active self-regulating circuit shown in FIG. 1 in accordance with one embodiment of the present invention.

[009] FIG. 3 illustrates a flow structure of the active self-regulating circuit accordance with one embodiment of the present invention.

[0101 FIG. 4 illustrates a system block diagram of the active self-regulating circuit accordance with one embodiment of the present invention.

[011] FIG. 5 illustrates waveforms of the system current, the voltage of the rectifier, and the current of the active discharge regulation circuit with one embodiment of the present invention.

[012] FIG. 6 illustrates the waveforms of the voltage and the current of AC source.

DETATLED DESCRIPTION

[013] Reference will now be made in detail to the embodiments of the present invention. While the invention will be described in conjunction with these embodiments, it l1 be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit arid scope of the invention.

[014] Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details, In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention.

[015] The description of the "arid/or" in this specification includes one of the listed objects or any combination of the multiple objects. In addition, unless specifically stated by this specification, otherwise, the usage of any singular terms in this specification includes the meaning of plural also.

[016] Please refer to FIG. 1 to FIG. 6, the present invention includes an AC source 1, a bridge rectifier 2, an LED driving unit 14, a plurality of light-emitting diodes (LED5) 3, and an active discharge regulation circuit. The AC source I is connected to the LED driving unit 14 via the bridge rectifier 2, and the LED driving unit 14 is connected in parallel with the LEDs 3. The active discharge regulation circuit is connected in series between the bridge rectifier 2 and the LED driving unit 14. Wherein, the active discharge regulation circuit includes a diode 4, resistors 5-7, Zener diodes 8 and 9, arid mosfet iO and BJT 11 which connected with each other, The mosfet 10 is connected in parallel with the resistor S and the Zener diode 9, and the BJT 11 is connected in parallel with the resistor 6 and the Zener diode 8. The resistor 7 and the diode 4 are connected in series at the output terminal of the bridge rectifier 2. Wherein, the mosfet 10 and BJT 11 are connected in parallel in the output line of the bridge rectifier 2. In addition, a resistor 12 is configured between the Zener diode 9 and the LED driving circuit 14 and a capacitor i3 is configured in parallel with the resistor 7.

In one embodiment, the resistors 5, 6, 7, and 12 can be variable resistors, [017] Tn operation, when a system current decreased, the current flow through the resistor 7 decreases and the voltage crossing the resistor 7 drops. When the voltage crossing the resistor 7 drops to a level which is lower than the voltage VUE of the BJT II, then the mosfet 10 becomes turned on, At this time, the active self-regulating circuit increases the AC current from the AC source I to flow through the resistor 6 via the mosfet 10 so as to pull up the AC current higher than a minimum operating current of the TRIAC and further drives the lighting apparatus operates in normal without twinkling.

[018] Otherwise, when the system current increased, the current flows through the resistor 7 also increased and the voltage crossing the resistor 7 is increased. When the voltage crossing the resistor 7 is increased to a level which is higher than the voltage Vflf of the BJT II, then the mosfet 0 becomes turned off [019] When the LED driving circuit 14 becomes an open circuit and the load side open-loaded, the voltage VI is divided by the resistor 5 and the resistor 12. The BJT 11 will be activated and the mosfet 10 will be turned off when the divided voltage is lower than the break-down voltage of the Zener diode 9. This can increase the current of the active discharge regulation circuit to reduce the power consumption of the system.

[020] Regardless the type of the LED drivers, the AC current will only be generated to flow through the TRLALC when the power is consumed. So when the system current decreases, the AC current will lower than the minimum holding current of the TRIAC. Once the total system current detection unit L/ (shown in FIG. 4) detects the system current becomes lower than the minimum holding current of the TRIAC, the active discharge regulation circuit will be enabled, The active self-regulating circuit increases the minimum holding current by streaming the current from the AC source 1 via the path of the mosfet 10, so as to operate the TRAIC dimmer work in normal, In one embodiment, when the system open-circuit, a LED open-circuit detection unit 15 (shown in FIG. 4) drives a control unit 16 (shown in FIG. 4) for controlling the active discharge regulation circuit to disabled the mosfet 10 so as to reduce the power consumption.

[0211 The active self-regulating circuit with an active discharge regulation circuit can adjust the kinetic energy regulator and the conduction time of the switch according to the ho'ding current of the TRIAC and a total system current. When the total system current is less than the minimum holding current, the self-regulating circuit increases the conduction time of the driving signal, to drive the current which flows through the TRIAC increases to the level of the minimum holding current, so as to keep the normal conduction of the TRIAC, improve the efficient of the lighting power driver and increase the match ability of the TRIAC, [022] While the foregoing description and drawings represent embodiments of the present invention, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope of the principles of the present invention. One skilled in the art will appreciate that the invention may be used with many modifications of fonn, structure, arangement, proportions, materials, elements, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, and not limited to the foregoing description.

Claims

CLAIMSWhat is claimed is: 1. An active self-regulating circuit, comprising: an AC source; a bridge rectifier connected to said AC source; an LED driving unit connected to said AC source via said bridge rectifier; a plurality of LEDs parallel connected to said LED driving unit; and an active discharge regulation circuit connected in series between said rectifier and said LED driving unit, wherein, said active discharge regulation circuit comprise a diode, a resistor, a Zener diode, a BJT, a mosfet which connected to each other and where said mosfet is connected in parallel with said resistor and said Zener diode.
2. The circuit as claimed in claim t, wherein said resistor and said diode are configured in series at the output terminal of said bridge rectifier.
3. The circuit as claimed in claim 1 or claim 2, wherein at least one of said TRI.AC is connected in parallel in the output line of said bridge rectifier.
4. The circuit as claimed in any preceding claim, further comprising a resistor configured between said Zener diode and said LED driving unit.
5. The circuit as claimed in any preceding claim, further comprising a capacitor configured in parallel with said resistor.
6. The circuit as claimed in any preceding claim, wherein said resistor is a variable resistor.