CN102469668B - LED power supply circuit capable of being matched with electronic transformer - Google Patents

LED power supply circuit capable of being matched with electronic transformer Download PDF

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Publication number
CN102469668B
CN102469668B CN 201110114111 CN201110114111A CN102469668B CN 102469668 B CN102469668 B CN 102469668B CN 201110114111 CN201110114111 CN 201110114111 CN 201110114111 A CN201110114111 A CN 201110114111A CN 102469668 B CN102469668 B CN 102469668B
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circuit
control circuit
led
resistor
voltage
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CN102469668A (en
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刘单
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SHENZHEN CITY KINGLUMI PHOTOELECTRIC TECHNOLOGY Co Ltd
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SHENZHEN CITY KINGLUMI PHOTOELECTRIC TECHNOLOGY Co Ltd
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Abstract

The invention provides an LED power supply circuit capable of being matched with an electronic transformer, comprising a power supply and an LED, wherein the LED power supply circuit further comprises a rectifying and filtering circuit, a boosting circuit and a voltage-reducing constant-current circuit which are connected in turn. The rectifying and filtering circuit is connected with a power supply and used for rectifying and filtering the input signals of the power supply. The boosting circuit comprises a first inductor, a first diode and a second capacitor which are connected in turn; and the boosting circuit further comprises a boost control circuit. One end of the boost control circuit is connected between the first inductor and the first diode, and the other end is grounded. The voltage-reducing constant-current circuit is connected between the anode of the second capacitor and the LED. The LED power supply circuit capable of being matched with the electronic transformer in the invention can be matched with various electronic transformers, and has wide range of the work circuit and high power factor.

Description

LED power supply circuit matched with electronic transformer
Technical Field
The invention belongs to the field of novel electric light source application, and particularly relates to a pulse-driven LED lighting circuit.
Background
The LED lamp is used as a substitute light source of the traditional halogen lamp, and in order to simplify installation and save cost, the original lighting circuit and the electronic transformer cannot be replaced when the LED lamp is replaced. The original electronic transformer is specially designed for halogen lamps, and the electronic transformer is designed with under-power protection and over-power protection, namely when the load power is too low, the electronic transformer can turn off the output, when the load power is too high, the electronic transformer can also turn off the output, and only when the load power is kept within a certain range, the electronic transformer can normally work and output.
Fig. 1 shows a most-used LED constant current driving circuit. When the input is connected with an AC (DC) power supply, the input is rectified through D1, filtered through C1, and then a constant working current is provided for the LED by the voltage-reducing constant-current IC. The biggest disadvantage of fig. 1 is that after the input voltage is rectified and filtered, if the voltage at C1 is lower than Vled + Vmos + Vic + VRs, the LED brightness is lower than normal, or even completely not bright. Wherein Vled is the forward voltage drop of the LED lamp string; vmos is the conduction voltage drop of the MOS tube; vic is IC constant current critical voltage; VRs is the sense resistor drop.
When the input voltage is low when the circuit inputs DC or AC (50Hz), the brightness of the LED lamp is only reduced, and the circuit is barely acceptable for users. However, when the input is an electronic transformer, since the electronic transformer charges C1 every time it oscillates, in one case, when the voltage Va is low, the charging current is large, and the electronic transformer may detect an overcurrent, thereby protecting and stopping the output voltage; one is that when the Va voltage is high and the load is light (the load power is small), the charging current will be small, the electronic transformer will detect that the power is too small, and will also protect, stop outputting the voltage; another situation is that when the electronic transformer charges the C1 to the output voltage of the electronic transformer, the output current of the electronic transformer is very small, so that under-power protection is performed, the output voltage is stopped, but after the load works for a certain time, Va starts to drop, the electronic transformer can be charged again, and after the C1 is full, the electronic transformer stops working again, so that a low-frequency ripple is superimposed on the C1 in addition to a 100Hz power frequency ripple, a single 100Hz ripple is difficult to recognize by human eyes, but when another low-frequency ripple is superimposed, a new very low-frequency ripple is generated, so that human eyes can feel that the LED lamp flickers.
Certainly, because the under-power protection point, the over-power protection point and the detection delay time of each electronic transformer are different as much as possible, when the LED lamps of the circuit are matched with electronic transformers of different models, some LED lamps can flicker and some LED lamps cannot flicker; some of them are harmful and some of them are not obvious. Because of the scattered errors of the components, even the same batch of electronic transformers and the same batch of LED lamps have different results.
Fig. 2 shows a constant current circuit of an LED lamp with better performance. In contrast to fig. 1, there is also a failure to light the LED lamp due to under-power or over-power. However, because the circuit uses a step-up/step-down structure, when the voltage (Va) of C1 is higher than Vled + Vmos + VRs, the circuit operates in the step-down mode to ensure a constant current to the LED, and when the voltage (Va) of C1 is lower than Vled + Vmos + VRs, the circuit operates in the step-up mode to ensure a constant current to the LED. However, when the ripple on C1 is too large, i.e. the minimum voltage is not enough for the circuit to supply the constant current to the LED, the brightness of the LED will also decrease or even become unlit, so that the LED lamp will flash, but this phenomenon will occur much less frequently than the circuit of fig. 1.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides an LED power circuit matched with an electronic transformer.
The invention provides an LED power circuit matched with an electronic transformer, which comprises a power supply, an LED, a rectifying and filtering circuit, a boosting circuit and a voltage-reducing constant-current circuit which are sequentially connected, wherein,
the rectification filter circuit is connected with the power supply and is used for rectifying and filtering an input signal of the power supply;
the boost circuit comprises a first inductor, a first diode and a second capacitor which are sequentially connected, and also comprises a boost control circuit, wherein one end of the boost control circuit is connected between the first inductor and the first diode, and the other end of the boost control circuit is grounded;
and the voltage reduction constant current circuit is connected between the anode of the second capacitor and the LED.
As a further improvement of the invention, the LEDs are a plurality of groups of LEDs which are connected in parallel or connected in series and then connected in parallel and have consistent or inconsistent forward conduction voltage drops.
As a further improvement of the present invention, the boost control circuit includes a first MOS transistor, a first pulse width control circuit, a first resistor, and a second resistor, the first MOS transistor is connected in series with the first inductor, a gate of the first MOS transistor is connected to an output terminal of the first pulse width control circuit, the first diode, the first resistor, and the second resistor are connected in series in sequence, an input terminal of the first pulse width control circuit is connected between the first resistor and the second resistor, and a source of the first MOS transistor, the second capacitor, and the second resistor are grounded.
As a further improvement of the present invention, the voltage-reducing constant current circuit includes a second diode, a third resistor, a second pulse width control circuit, a second inductor, a second MOS transistor, a third resistor, an LED, and a second inductor, which are connected in series and then connected in parallel with the second diode, and then connected with the second MOS transistor and then grounded, wherein an input end of the second pulse width control circuit is connected in parallel with the third resistor, and an output end of the second pulse width control circuit is connected with a gate of the second MOS transistor.
As a further improvement of the invention, the rectification filter circuit comprises a rectifier bridge and a filter capacitor.
The LED power supply circuit matched with the electronic transformer can be matched with various electronic transformers, and is wide in working voltage range and high in power factor.
Because the booster circuit is added as a buffer, the voltage on the first capacitor C1 can be boosted to a certain range by the booster circuit no matter whether the electronic transformer works continuously or not, so that even if the ripple on the C1 is large, the voltage on the second capacitor C2 always fluctuates in a certain range, and the minimum voltage is higher than Vled + Vmos + Vic + VRs, so that the LED current is always kept in the designed range and does not flicker with the voltage fluctuation of the C1. The matching problem of the LED constant current driving circuit and the electronic transformer is well solved.
The boost control circuit boosts the voltage at C1, and as long as the power of the boost circuit is enough, the difference between the voltage of Vc and Vd in fig. 3 is large enough, and the range of the input power source can be very low. Tests show that under the drive of some electronic transformers, when the 230V electronic transformer inputs AC150V, the LED current is still constant in a normal range.
At each half sine wave cycle, when Va in fig. 3 is less than the electronic transformer output voltage, the electronic transformer charges C1, when Va is equal to or greater than the electronic transformer output voltage, the electronic transformer stops charging C1, the Va voltage waveform is always close to the electronic transformer input voltage waveform, and the power factor is high. Tests prove that the power factor of most electronic transformers is more than 0.8 when supplying power, a few electronic transformers can achieve more than 0.86, and the power factor of the conventional common LED drive circuit is less than 0.6, and some electronic transformers even only have 0.45.
When the input is a 12VDC or 12V/AC50Hz power supply of +/-10%, the voltage boosting circuit can always boost the voltage Va to a voltage higher than Vled + Vmos + Vic + VRs because the power supply is continuous, so the novel circuit can work well. .
[ description of the drawings ]
FIG. 1 is a prior art common buck constant current circuit;
FIG. 2 is a prior art common buck-boost constant current circuit;
FIG. 3 is an LED constant current drive circuit of the present invention;
FIG. 4 is a LED constant current drive embodiment of the present invention;
FIG. 5 is the Va waveform of FIG. 3;
FIG. 6 is waveform 1 of Vb in FIG. 3;
FIG. 7 is waveform 2 Vb of FIG. 3;
FIG. 8 is the Vc waveform of FIG. 3;
FIG. 9 is the Vd waveform of FIG. 3;
FIG. 10 is the ILED waveform of FIG. 3;
FIG. 11 is a comparison waveform of Va and Iled of FIG. 3;
fig. 12 is a circuit diagram of a common buck-boost constant current circuit in the prior art of fig. 2.
[ detailed description ] embodiments
The invention is further described with reference to the following description and embodiments in conjunction with the accompanying drawings.
As shown in fig. 3, the constant current driving circuit is composed of three parts, the first part is a rectifying and filtering circuit, the second part is a voltage boosting circuit, and the third part is a voltage reducing constant current circuit.
Wherein,
a rectifying and filtering circuit 3 connected to the power supply 1 for rectifying and filtering an input signal of the power supply;
the boost circuit 4 comprises a first inductor 6, a first diode 7 and a second capacitor 9 which are connected in sequence, and further comprises a boost control circuit 10, wherein one end of the boost control circuit 10 is connected between the first inductor 6 and the first diode 7, and the other end of the boost control circuit is grounded;
and a step-down constant current circuit 5 connected between the anode of the second capacitor 9 and the LED 2.
The LEDs are a plurality of groups of LEDs which are connected in parallel or connected in series and then connected in parallel, and the forward conduction voltage drops of the LEDs are consistent or inconsistent.
The first part of the rectifying and filtering circuit consists of a rectifying bridge D1 and a filtering capacitor C1, an input alternating current signal is converted into a direct current pulse signal through D1, and C1 mainly plays a role in filtering high-frequency ripples and has a poor filtering effect on 100Hz direct current pulses. The second part of the circuit is to boost the voltage at C1 (hereafter denoted as Va) well above Vled + Vmos + Vic + VRs. The third part of the circuit changes the boosted voltage Vc into the constant current required by the LED. The specific working principle is as follows (taking an electronic transformer with a 5WLED lamp as an example):
the electronic transformer starts oscillation work when being electrified, the output end of the electronic transformer is rectified by D1, a direct current pulse level is output, filtering is carried out after the C1, the capacity of the C1 is only 150uF, and the capacity is very small compared with the capacity of a rear-stage load, so that the charging current is not enough to enable the electronic transformer to carry out over-power protection, and the voltage waveform on the C1 is close to the voltage waveform of a power grid, as shown in figure 5. The Va voltage is about 11V pulse voltage when normal, and after the boost circuit, the original pulse voltage close to the power frequency is boosted to pulse voltage of more than 20V, because the Vled value of the 5W3LED is only about 9.6V, and when the Va wave valley, the electric quantity stored on the C2 is enough to maintain the operation of the rear-stage circuit more than 5mS, so that the Vc voltage after boosting can still effectively ensure that the rear-stage voltage reduction constant current circuit outputs constant current despite large Va wave form ripple. As shown in FIGS. 6 to 11, the circuit works normally, and the LED circuit is always kept at 430 mA. The boost control circuit adopts an IC with lower working voltage, so that when the voltage Va is very low, the boost circuit can still work normally, and the power factor of the circuit can be increased to a great extent.
As shown in fig. 4, the boost control circuit 10 includes a first MOS 101, a first pulse width control circuit 102, a first resistor 103, and a second resistor 104, where the first MOS 101 is connected in series with the first inductor 6, a gate of the first MOS 101 is connected to an output terminal of the first pulse width control circuit 102, the first diode 7, the first resistor 103, and the second resistor 104 are connected in series in sequence, an input terminal of the first pulse width control circuit 102 is connected between the first resistor 103 and the second resistor 104, and a source of the first MOS 101, the second capacitor 9, and the second resistor 104 are grounded;
the voltage-reducing constant current circuit 5 comprises a second diode 105, a third resistor 106, a second pulse width control circuit 107, a second inductor 108, a second MOS tube 109, a third resistor 106, an LED2 and a second inductor 108 which are connected in series and then connected in parallel with the second diode 105, and then connected with the second MOS tube 109 and then grounded, wherein the input end of the second pulse width control circuit 107 is connected in parallel with the third resistor 106, and the output end of the second pulse width control circuit is connected with the gate of the second MOS tube 109;
the rectifying and filtering circuit 3 comprises a rectifying bridge and a filtering capacitor.
The circuit of fig. 4 operates as follows:
the input power is rectified by D1 and filtered by C1 to become DC power.
The working principle of the booster circuit is as follows: as shown in the middle dotted frame, the pulse width control circuit outputs a square wave with variable heights, when the output high level is high, the first MOS transistor 101 is turned on, current flows through L1 and Q2, the current flows through L1, and simultaneously L1 converts electric energy into magnetism and stores the magnetism on L1, when the control circuit outputs low level, Q2 is turned off, the magnetic energy stored on L1 is converted into electric energy, and the capacitor C2 is charged through D2. When the voltage of C2 is higher, the control circuit reduces the width of pulse width, and when the voltage of C2 is lower, the control circuit increases the width of pulse width, thus the voltage value of C2 is always controlled in a certain range.
The working principle of the voltage-reducing constant-current circuit is as follows: when the motor is started, the current flowing through the R4 is 0, a pulse width control circuit (hereinafter referred to as a "control circuit") outputs a high level, the Q3 is switched on, the current flows through the R4, the D7, the L3 and the Q3, the current cannot change suddenly due to the connection of the inductor L3, the current gradually increases from zero, when the current increases to an upper limit value detected by the control circuit, the control circuit outputs a low level, the Q3 is switched off, the L3 is discharged by the D3, the R4 and the D7, the control circuit simultaneously detects the current flowing through the R4, when the current decreases to a lower limit value detected by the control circuit, the control circuit outputs a high level, the Q3 is switched on … … again, and the current of the R4 is ensured to be always maintained at a fixed value through the continuous switching of the Q3. Since R4 and D7 are connected in series, the current of D7 is also always maintained at one value.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims (3)

1. An LED power supply circuit matched with an electronic transformer comprises a power supply (1) and an LED (2), and is characterized in that: also comprises a rectifying and filtering circuit (3), a boosting circuit (4) and a voltage-reducing constant current circuit (5) which are connected in sequence, wherein,
the rectification filter circuit (3) is connected with the power supply (1) and is used for rectifying and filtering an input signal of the power supply; the rectifying and filtering circuit (3) comprises a rectifying bridge and a filtering capacitor;
the boost circuit (4) comprises a first inductor (6), a first diode (7) and a second capacitor (9) which are sequentially connected, and further comprises a boost control circuit (10), one end of the boost control circuit (10) is connected between the first inductor (6) and the first diode (7), and the other end of the boost control circuit is grounded;
a voltage-reducing constant current circuit (5) connected between the anode of the second capacitor (9) and the LED (2);
the voltage-reducing constant current circuit (5) comprises a second diode (105), a third resistor (106), a second pulse width control circuit (107), a second inductor (108), a second MOS (metal oxide semiconductor) tube (109), the third resistor (106), the LED (2) and the second inductor (108) which are connected in series and then connected with the second diode (105) in parallel, the third diode, the LED (2) and the second inductor (108) are connected with the second MOS tube (109) in series and then connected with the second MOS tube and then grounded, the input end of the second pulse width control circuit (107) is connected on the third resistor (106) in parallel, and the output end of the second pulse width control circuit is connected with the grid electrode of.
2. The matched electronic transformer LED power circuit as defined in claim 1, wherein: the LEDs are a plurality of groups of LEDs which are connected in parallel or connected in series and then connected in parallel, and the forward conduction voltage drops of the LEDs are consistent or inconsistent.
3. The matched electronic transformer LED power circuit as defined in claim 1, wherein: the boost control circuit (10) comprises a first MOS (metal oxide semiconductor) tube (101), a first pulse width control circuit (102), a first resistor (103) and a second resistor (104), wherein the first MOS tube (101) is connected with a first inductor (6) in series, the grid of the first MOS tube (101) is connected with the output end of the first pulse width control circuit (102), a first diode (7), the first resistor (103) and the second resistor (104) are connected in series in sequence, the input end of the first pulse width control circuit (102) is connected between the first resistor (103) and the second resistor (104), and the source electrode of the first MOS tube (101), a second capacitor (9) and the second resistor (104) are grounded.
CN 201110114111 2011-05-04 2011-05-04 LED power supply circuit capable of being matched with electronic transformer Expired - Fee Related CN102469668B (en)

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CN102469668B true CN102469668B (en) 2013-12-18

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Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN202759632U (en) * 2012-06-20 2013-02-27 伟思科技控股有限公司 Drive circuit and lighting device of light emitting diode
CN103269537B (en) * 2013-05-28 2015-04-01 上海路千电子科技有限公司 Multi-circuit current-limiting power supplying circuit, controlling method thereof and current-limiting power supplying method thereof
WO2015024224A1 (en) * 2013-08-22 2015-02-26 Liu Xiaofeng Led constant-current circuit and led lamp
CN103945616B (en) * 2014-04-30 2016-03-30 深圳市晟碟半导体有限公司 A kind of light fixture and LED drive device thereof
CN105263235B (en) * 2015-11-16 2016-08-17 江苏力行电力电子科技有限公司 Various dimensions for LED drive power compare type current control method and LED drive circuit

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CN2927593Y (en) * 2006-04-30 2007-07-25 上海复展照明科技有限公司 Digital driving control circuit of red, green and blue triple color luminescent diode
CN201185198Y (en) * 2008-02-22 2009-01-21 吴世武 Power supply capable of matching multi-model number battery
CN201210761Y (en) * 2008-05-29 2009-03-18 上海恒烁光电科技有限公司 Road lamp controller
CN101778507A (en) * 2009-12-10 2010-07-14 海洋王照明科技股份有限公司 LED control circuit
CN101925232A (en) * 2010-08-12 2010-12-22 无锡科尔华电子有限公司 LED street lamp constant current control power supply
CN202077230U (en) * 2011-05-04 2011-12-14 深圳市金流明光电技术有限公司 LED power circuit matched with electronic transformer

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN2927593Y (en) * 2006-04-30 2007-07-25 上海复展照明科技有限公司 Digital driving control circuit of red, green and blue triple color luminescent diode
CN201185198Y (en) * 2008-02-22 2009-01-21 吴世武 Power supply capable of matching multi-model number battery
CN201210761Y (en) * 2008-05-29 2009-03-18 上海恒烁光电科技有限公司 Road lamp controller
CN101778507A (en) * 2009-12-10 2010-07-14 海洋王照明科技股份有限公司 LED control circuit
CN101925232A (en) * 2010-08-12 2010-12-22 无锡科尔华电子有限公司 LED street lamp constant current control power supply
CN202077230U (en) * 2011-05-04 2011-12-14 深圳市金流明光电技术有限公司 LED power circuit matched with electronic transformer

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