CN108235492B

CN108235492B - LED zero-current ripple drive circuit compatible with dimming

Info

Publication number: CN108235492B
Application number: CN201611159563.0A
Authority: CN
Inventors: 庄华龙; 曹磊; 王磊
Original assignee: DIAO MICROELECTRONICS CO LTD
Current assignee: Jiangsu Dior Microelectronics Co., Ltd
Priority date: 2016-12-15
Filing date: 2016-12-15
Publication date: 2020-11-10
Anticipated expiration: 2036-12-15
Also published as: CN108235492A

Abstract

A light-dimming compatible LED zero-current ripple driving circuit is applied to a light-emitting diode driving circuit and comprises a voltage follower module and an internal current source module. The voltage follower module is used for sampling a voltage signal from the light-emitting diode driving circuit; the internal current source module is connected with the voltage follower module and is used for outputting a current signal to the light-emitting diode driving circuit; wherein the current signal is directly proportional to the voltage signal.

Description

LED zero-current ripple drive circuit compatible with dimming

Technical Field

The present invention relates to a light-dimming compatible LED zero-current ripple driving circuit, and more particularly, to a light-dimming compatible LED zero-current ripple driving circuit applied to a light-emitting diode driving circuit.

Background

In the existing Light Emitting Diode (LED) dimming system, in order to control compatible with high Power Factor and cost, a single-stage PFC (Power Factor Correction) circuit is usually adopted, and the output current of this control method contains a Power frequency ripple component, the frequency of which is about 2 times of the Power grid frequency, i.e. 100Hz/120Hz, and the light emitting diode driving circuit is operated under such low frequency stroboflash for a long time, which is easy to cause visual fatigue of people and may affect the service life of the lamp, so the light emitting diode driving circuit needs a method for removing the current ripple.

Referring to fig. 1, fig. 1 is a circuit diagram of a light emitting diode driving circuit in the prior art. The LED drive circuit comprises an LED, a current source I with ripple_ACComparator CMP, switch S_U、S_DNMOSFET M1, error amplifier EA, and internal current reference source I_U、I_D. Wherein, when the voltage of the output terminal CMPOUT of the comparator is high, the switch S_UIs turned on, and when the output terminal CMPOUT of the comparator is low, the switch S_DAnd conducting.

The basic principle of the ripple removing method of the light emitting diode driving circuit in the prior art is that the voltage ripple of the non-inverting input terminal VC of the error amplifier EA is controlled, and then the voltage ripple of the inverting input terminal CS of the error amplifier EA is controlled, so that the current ripple flowing through the light emitting diode LED is positively correlated with the voltage ripple of the non-inverting input terminal VC. Therefore, the existing ripple removing methods are all internal current reference sources I for charging and discharging the non-inverting input end VC_U、I_DAnd controlling the current value to be smaller so as to realize smaller current ripple. The problem caused by the control method is that the ripple ratio of the current of the single-stage PFC dimming system can be reducedThe output current of the Light Emitting Diode (LED) is increased along with the reduction of the output current of the LED, so that the requirement of zero current ripple cannot be met under the condition of dimming low current, and the stroboscopic phenomenon of the LED is caused.

Therefore, it is an urgent issue to be solved by various industries to provide a compatible dimming LED zero-current ripple driving circuit that is compatible with a PFC dimming system and can effectively remove current ripples.

Disclosure of Invention

In view of the shortcomings of the prior art, the main object of the present invention is to provide a dimming-compatible LED zero-current-ripple driving circuit that is compatible with the PFC dimming system and can effectively remove the current ripple.

In order to achieve the above and other objects, the present invention provides a light-dimming compatible LED zero-current ripple driving circuit, which is applied to a light emitting diode driving circuit and includes a voltage follower module and an internal current source module. The voltage follower module is used for sampling a voltage signal from the light-emitting diode driving circuit; the internal current source module is connected with the voltage follower module and is used for outputting a current signal to the light-emitting diode driving circuit; wherein the current signal is directly proportional to the voltage signal.

Further, the voltage follower module includes an operational amplifier.

Furthermore, the non-inverting input terminal of the operational amplifier is connected to the led driving circuit, and the inverting input terminal of the operational amplifier is connected to the output terminal and the internal current source module.

Further, the internal current source module includes a variable current source and a switch connected in series with the variable current source.

Compared with the prior art, the LED zero-current ripple driving circuit compatible with dimming adopts an optimized dimming self-adaptive technology, the voltage follower module samples a voltage signal from the LED driving circuit, and the internal current source module outputs a current signal to the LED driving circuit, wherein the current signal is maintained at a higher level under the condition of higher voltage signal; when the output current of the LED driving circuit is gradually reduced, the voltage signal is gradually reduced, and the current signal is also adaptively reduced. That is, the current signal is directly proportional to the voltage signal, achieving optimal ripple current matching. Finally, zero ripple current in the full output current range can be achieved, the ripple current deterioration phenomenon caused by the fact that the current ripple of the single-stage PFC dimming system is reduced along with the output current is eliminated, and the defects in the prior art are fully overcome.

Drawings

FIG. 1 is a circuit diagram of a prior art LED driving circuit;

fig. 2 is a circuit schematic diagram of a dimming-compatible LED zero-current ripple driving circuit according to the present invention;

fig. 3 is a schematic diagram of a waveform timing diagram of a key node of the dimming-compatible LED zero-current ripple driving circuit according to the present invention.

Description of the symbols:

1 compatible dimming LED zero current ripple drive circuit

10 voltage follower module

11 internal current source module

C_CCapacitor with a capacitor element

CMP comparator

Output terminal of CMPOUT comparator

CS inverting input terminal

EA error amplifier

I_ACCurrent source

I_U、I_DInternal current reference source

I_UAInternal current source

I_LEDOutput current

I_UA1Current signal

LED light emitting diode

M1 transistor

OP operational amplifier

S_U、S_DSwitch with a switch body

S_UASwitch with a switch body

t₀、t₁、t₂Point in time

VC non-inverting input terminal

VC₁Voltage signal

V_INVoltage signal

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways.

Please refer to fig. 2, which is a schematic circuit diagram of the dimming compatible LED zero current ripple driving circuit according to the present invention. As shown in the figure, the dimming compatible LED zero-current ripple driving circuit 1 of the present invention is applied to a light emitting diode driving circuit, and the dimming compatible LED zero-current ripple driving circuit 1 includes a voltage follower module 10 and an internal current source module 11. The voltage follower module 10 is used for sampling a voltage signal from the led driving circuit, that is, a voltage signal at the non-inverting input terminal VC of the error amplifier EA; the internal current source module 11 is connected to the voltage follower module 10 and is configured to output a current signal to the led driving circuit, where the current signal is output to the non-inverting input terminal VC of the error amplifier EA; wherein the current signal is directly proportional to the voltage signal.

Further, under the condition that the voltage signal is higher, the current signal also maintains a higher level; when the output current I of the light emitting diode LED_LEDAnd when the voltage signal is gradually reduced, and the current signal is also adaptively reduced. Wherein the output current I_LEDThe peak-to-peak value of the current ripple is in direct proportion to the peak-to-peak value of the voltage signal, and the current signal is in direct proportion to the voltage signal, so that self-adaptive loop feedback is formed, and the current ripple of the single-stage PFC dimming system can be eliminated along with the output current I_LEDThe ripple current deterioration phenomenon brought by the reduction.

In one embodiment, the voltage follower module 10 may include an operational amplifier OP.

In one embodiment, the non-inverting input terminal of the operational amplifier OP may be connected to the led driving circuit, and the inverting input terminal of the operational amplifier OP is connected to the output terminal of the operational amplifier OP and the internal current source module 11.

In one embodiment, the internal current source module 11 may include a variable current source I_UAAnd with a variable current source I_UASeries-connected switch S_UA。

Further, the voltage follower module 10 employs a negative feedback operational amplifier OP, and can output real signals of the voltage signal of the non-inverting input terminal VC sampled by the led driving circuit in real time. Under the condition that the voltage signal is higher, the internal current source I_UAThe output current signal also maintains a higher level; when the output current I of the light emitting diode LED_LEDGradually decreasing, the voltage signal gradually decreases, the internal current source I_UAThe output current signal will also adaptively decrease, i.e. the current signal and the voltage signal are proportional.

Is expressed by formula

Wherein, I_{LED_PP}To output a current I_LEDCurrent ripple peak-to-peak value of, VC_PPK is constant and C is the peak-to-peak value of the voltage signal_C1Is a capacitor C_CCapacitance value of (t)_SATTime for transistor M1 to operate in saturation region, and I_U1And I_UA1Are respectively an internal current source I_UAnd I_UAThe output current.

From the above formula, the peak-to-peak value of the current ripple I_{LED_PP}And the peak-to-peak value VC of the voltage signal_PPProportional to the current (I)_U1+I_UA1) Is in direct proportion. Thus forming an adaptive loop feedbackThe optimal ripple current matching is realized, the zero ripple current in the full output current range can be finally achieved, and the current ripple of the single-stage PFC dimming system is eliminated along with the output current I_LEDThe ripple current deterioration phenomenon brought by the reduction.

Referring to fig. 2 and fig. 3, fig. 3 is a schematic diagram of a waveform timing diagram of a key node of the dimming-compatible LED zero-current ripple driving circuit according to the present invention. As shown, at a time point t₀To a point of time t₁In the interval (c), the LED operates stably, and the voltage signal VC at the non-inverting input terminal VC of the error amplifier EA₁And a current signal I_UA1And the stability is maintained.

At a point in time t₁To a point of time t₂With the output current I_LEDGradually decreasing, voltage signal V_INGradually decreasing, voltage signal VC₁The synchronization is reduced, at which time the internal adaptation module starts to operate, the internal current source I_UAOutput current signal I_UA1With the gradual decrease, the time for operating the transistor M1 in the saturation region is fixed, and the voltage signal VC is then obtained₁The voltage ripple of the capacitor is reduced. Due to voltage signal VC₁And an output current I_LEDThe feedback is closed loop, so the ripple peak value of the output current is reduced, and the ripple proportion is stable under the condition of small current.

The features and spirit of the present invention will become more apparent to those skilled in the art from the description of the preferred embodiments given above, which are given by way of illustration only, and not by way of limitation, of the principles of the present invention and its functions. Thus, any modifications and variations may be made to the above-described embodiments without departing from the spirit of the invention, and the scope of the invention is to be determined by the appended claims.

Claims

1. The utility model provides a compatible LED zero current ripple drive circuit who adjusts luminance, is applied to emitting diode drive circuit in, its characterized in that includes:

the voltage follower module is used for sampling a voltage signal from the light-emitting diode driving circuit; and

an internal current source module connected with the voltage follower module and used for outputting a current signal to the LED drive circuit, wherein the internal current source module comprises a variable current source I_UAAnd the variable current source I_UAA switch in series;

wherein the current signal is directly proportional to the voltage signal;

wherein, the formula is shown as follows:

wherein, I_{LED_PP}Is a current signal I_LEDCurrent ripple peak-to-peak value of, VC_PPK is a constant value, C, for the peak-to-peak value of the voltage signal_C1Is a capacitor C_CA capacitance value of, the capacitor C_CConnected between the internal current source module and the voltage follower module and ground, t_SATFor the time that the transistor M1 works in the saturation region, the transistor M1 connects the internal current source module and the voltage follower module through an amplifier, I_U1And I_UA1Are respectively an internal current source I_UAnd a variable current source I_UACurrent of output, the insidePartial current source I_UAnd the variable current source I_UAAre connected in parallel.

2. The dimming-compatible LED zero-current ripple drive circuit according to claim 1, wherein the voltage follower module comprises an operational amplifier.

3. The dimming-compatible LED zero-current ripple driver circuit according to claim 2, wherein the non-inverting input terminal of the operational amplifier is connected to the LED driver circuit, and the inverting input terminal of the operational amplifier is connected to the output terminal and the internal current source module.