CN108463022B

CN108463022B - Multilayer ceramic capacitor LED constant current driving circuit

Info

Publication number: CN108463022B
Application number: CN201710086365.4A
Authority: CN
Inventors: 周徐达
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-02-17
Filing date: 2017-02-17
Publication date: 2024-05-07
Anticipated expiration: 2037-02-17
Also published as: CN108463022A

Abstract

The invention relates to an LED driving circuit, in particular to a multilayer ceramic capacitor LED constant current driving circuit, which comprises: the LED lamp set comprises a multilayer ceramic capacitor and an iron core inductor, wherein the multilayer ceramic capacitor and the iron core inductor are connected in series between a driven LED lamp set and an input end of a power frequency alternating current power supply; the multilayer ceramic capacitor has a DC bias effect, the capacity of the multilayer ceramic capacitor under the maximum allowable DC bias condition is not more than 70% of the nominal capacity of the multilayer ceramic capacitor, and the effective value of the voltage at two ends of the multilayer ceramic capacitor under the rated maximum flowing current is not less than 50% of the effective value of the rated power supply voltage; the withstand voltage value of the multilayer ceramic capacitor is not lower than 0.8 times of the peak value of rated power supply voltage; the effective value of the voltage at two ends of the iron core inductor at the rated maximum flowing current is not lower than 20% of the effective value of the rated power supply voltage. The scheme has the advantages of strong lightning resistance, self-healing capability, available scrapped element resources, available scrapped lamp ballasts, power grid loss reduction, no electromagnetic interference, strong power supply voltage wave resistance capability, convenience in flickering or dimming operation and the like.

Description

Multilayer ceramic capacitor LED constant current driving circuit

Technical Field

The invention relates to an LED driving circuit, in particular to a multilayer ceramic capacitor LED constant current driving circuit.

Background

The LED light source has long service life and high light efficiency, can adjust light in a large range, and is expected to replace the traditional gas discharge lamp and incandescent lamp as a green lighting technology, thereby saving a large amount of energy for society. The LED is a device with constant voltage characteristic, and a driving circuit is needed to pass through when mains supply is adopted for supplying power, however, the driving circuits in the prior art have some defects, so that the popularization of an LED light source in the lighting field is influenced, especially in the high-power outdoor or industrial and mining lighting field, the market share of LED lighting is less than 20%, and various researches show that the service life reliability bottleneck of the driving power supply is the most fundamental reason for restricting the development of the driving power supply.

The most commonly used LED commercial power driving circuits in the prior art mainly comprise 3 types: the first is a resistance-capacitance driving circuit, which uses the capacitance reactance of the capacitor to reduce the voltage and limit the current of the commercial power alternating voltage, and provides a relatively stable current for the connected LED lamp string. The second is a linear constant current driving circuit, which limits the LED current by using a constant current diode device, and has the advantages of low cost and small volume, but the efficiency is low, the heat generation is large, the energy-saving advantage of the LED light source can not be exerted, and the large power is difficult to realize because a resistive element is used as a current limiting device. The third class is a high-frequency switch power supply circuit, the control method and the topology structure of the circuit are various, the circuit has the advantages of high efficiency and good constant current characteristic, however, the circuit has complex structure, the number of elements is as high as 30-60, the lightning protection capability is poor, the reliability and the service life are poor, the actual service life is only 2-4 years, the circuit is used for indoor illumination without problems, but the circuit is used for high-power outdoor or industrial and mining illumination, and the circuit has short service life and high early failure rate due to the severe working environment which are generally reflected by users.

With the rapid development of the LED technology, the market permeability of the current LED illumination is nearly 50%, a large number of traditional incandescent lamps and energy-saving lamps are replaced by LED light sources, however, in the field of high-power outdoor illumination, the market acceptance of the LEDs is generally low, the traditional gas discharge light sources still occupy the main stream, so that the energy conservation in the field of high-power outdoor illumination is slow to progress, the root cause is that the only switching power supply circuit suitable for high-power LED driving is generally low in reliability, short in service life and high in later repair rate, even if the prior art has made a large number of improvements on the switching power supply circuit, the durability and the reliability of the switching power supply circuit are not fundamentally improved until now due to the unchangeable circuit complexity of the prior art.

The Chinese patent CN102088811A discloses an LED constant current driving circuit based on an LCL resonant network, the circuit adopts a simple passive reactor and a capacitor element, realizes constant current driving of an LED light source by utilizing the resonance effect of a capacitor inductor, has a simple structure and no active switching device, overcomes the defects of short service life and low reliability of the traditional switching power supply driving circuit, has very large capacity of the reactor required by the technology, has 5-8 times of the product volume and weight of the switching power supply product in the prior art, has very high component precision requirement due to the requirement of resonance, has very high cost and does not have practicability, and therefore, develops a novel constant current driving power supply circuit with long service life, high reliability, low failure rate and lower cost weight volume, and is particularly necessary.

The invention skillfully utilizes the bias characteristic of the multilayer ceramic capacitor, realizes the performances of constant current, wide input voltage, high power factor, low harmonic, small volume and light weight which can be realized by a switch power supply circuit by using a simple passive circuit scheme, simultaneously also realizes the characteristics of high reliability and long service life of the LCL resonance scheme disclosed in the Chinese patent CN102088811A, and also has other beneficial effects which are not possessed by the scheme, thereby being expected to greatly improve the performance and cost index of the high-power LED lighting technology and the popularization speed of the LED in the field of high-power outdoor lighting.

Disclosure of Invention

In view of the technical problems, the invention provides a multilayer ceramic capacitor LED constant current driving circuit which can effectively overcome the short board in the prior art and has the outstanding advantages of good constant current effect, high reliability, long service life, low cost, small impact current and high power factor.

The technical scheme adopted for solving the technical problems is as follows:

A multi-layer ceramic capacitor LED constant current driving circuit comprises:

the LED lamp comprises a multilayer ceramic capacitor C1 and an iron core inductor L1, wherein the multilayer ceramic capacitor C1 and the iron core inductor L1 are connected in series between a driven LED lamp group and an input end of a power frequency alternating current power supply;

The multilayer ceramic capacitor (C1) has a DC bias effect, the capacity of which under the maximum allowable DC bias condition is not more than 70% of the nominal capacity thereof; the voltage effective value of the two ends of the multilayer ceramic capacitor (C1) at the rated maximum flowing current is not lower than 25% of the rated power supply voltage effective value; the withstand voltage value of the multilayer ceramic capacitor (C1) is not lower than 20% of the rated power supply voltage peak value; the effective value of the voltage at two ends of the iron core inductor (L1) at the rated maximum flowing current is not lower than 20% of the effective value of the rated power supply voltage.

Preferably, the multi-layer ceramic capacitor LED constant current driving circuit is characterized in that the multi-layer ceramic capacitor C1 is formed by connecting a plurality of multi-layer ceramic capacitors in series, in parallel or in series-parallel.

Preferably, in the above multilayer ceramic capacitor LED constant current driving circuit, the multilayer ceramic capacitor C1 is formed by connecting a plurality of multilayer ceramic capacitors in series into a plurality of groups, and after each group is connected with the fuse F1 in series, the plurality of groups are connected in parallel, and the rated fusing current of the fuse F1 is smaller than the rated current effective value of the whole group of multilayer ceramic capacitors C1.

Preferably, in the multilayer ceramic capacitor LED constant current driving circuit, the core of the core inductor L1 is provided with an unequally-spaced air gap, and the impedance value of the unequally-spaced air gap at the rated maximum current is 40-100% of the initial impedance value.

Preferably, the multilayer ceramic capacitor LED constant current driving circuit comprises a multilayer ceramic capacitor LED constant current driving circuit, wherein the core inductor L1 comprises a gas discharge lamp impedance type inductance ballast.

Preferably, in the above multilayer ceramic capacitor LED constant current driving circuit, a rectifier bridge D1 is connected between the driven LED lamp set and the input end of the power frequency ac power supply, the ac side of the rectifier bridge D1 is connected with the input end of the power frequency ac power supply after being connected in series with the multilayer ceramic capacitor C1, the dc side of the rectifier bridge D1 is connected with the driven LED lamp set, and the core inductor L1 is connected in series with the ac side or the dc side of the rectifier bridge D1.

Preferably, in the multilayer ceramic capacitor LED constant current driving circuit, the filter capacitor C2 and the discharge resistor R2 are connected in parallel to the dc side of the rectifier bridge D1.

Preferably, in the multilayer ceramic capacitor LED constant current driving circuit, a power frequency transformer T is connected between the driven LED lamp set and the power frequency ac power input end.

Preferably, in the multilayer ceramic capacitor LED constant current driving circuit, a step-down capacitor C3 is connected in series between the driven LED lamp set and the input end of the power frequency ac power supply.

Preferably, the multi-layer ceramic capacitor LED constant current driving circuit further comprises an overvoltage protector R1, wherein the overvoltage protector R1 is connected with the multi-layer ceramic capacitor C1 in parallel; and the temperature switch or the thermosensitive protector S is in contact with the outer surface of the overvoltage protector R1 and is connected with the input end of the power frequency alternating current power supply in series.

Preferably, the multilayer ceramic capacitor LED constant current driving circuit further comprises an overcurrent protector F, wherein the overcurrent protector F is connected with the input end of the power frequency alternating current power supply in series.

Preferably, the multilayer ceramic capacitor LED constant current driving circuit further comprises an overvoltage protector (R3), wherein the overvoltage protector (R3) and a fuse (F2) are connected in series and then connected in parallel with the power frequency alternating current power supply input end or connected between the power frequency alternating current power supply input end and the shell grounding end.

The technical scheme has the following advantages or beneficial effects:

1. The cost is low: the invention skillfully utilizes the defect of the multilayer ceramic capacitor bias characteristic, changes the defect into an automatic control circuit capable of automatically constant current through a simple scheme, realizes the current accurate control function of the LED through an extremely simple passive circuit, avoids the use of active devices such as chips and transistors, and the number of the whole device can be reduced to about 10, and the volume of an inductance element is small, so the cost is only a fraction of the constant current scheme of the switch power supply in the prior art.

2. The reliability is extremely high: the whole circuit is completely composed of passive devices such as inductors and capacitors, the core passive devices are only provided with serial circuits, active control devices such as chips and transistors are avoided, overresonance overstress of the T-shaped resonant circuit of the LCL resonant scheme due to element parameter changes is avoided, product stability can be effectively improved, severe environment adaptability such as high temperature, humidity, overvoltage and grid resonance is also greatly improved, extremely high reliability and long-life durability are brought by the inherent sturdiness and durability of the LCL resonant scheme under the severe environment such as outdoor sun, rain and lightning impulse, and early failure rate of the LCL resonant scheme can reach less than 0.5 thousandth, which is less than one tenth of the prior art switching power supply and is further improved than the reliability of the LCL resonant scheme.

3. The volume is small, the weight is light: the ceramic capacitor adopted by the invention has very high power density, and the power density is 20-300 times that of a common film capacitor; the invention has the advantages that the rated current of the iron core inductor with the largest volume is equivalent to the input or output current, and the voltage is only slightly larger than 20% of the power supply voltage, so the volume is very small, the whole volume weight of the invention is slightly smaller than that of a fluorescent lamp ballast with the same power, the invention is equivalent to the LED driving power supply of the prior main flow technology, the LCL resonance scheme needs two inductors, the capacity of one inductor exceeds 2 times of the capacity of the iron core inductor of the invention, the whole volume weight of the invention is 5-8 times of the invention, the precision requirement on the element is very high, the cost is more than 6 times of the invention, and the invention has little practical value in view of the development direction of miniaturization and low cost of LED illumination.

4. The lightning resistance is strong: as the lightning invasion wave and high-current stress tolerance capability of the passive device are far higher than those of the active semiconductor device, the lightning resistance of the invention is far higher than that of the switch power supply in the prior art, and the experiment proves that the invention can achieve the comprehensive lightning protection performance of tens of times in the prior art by matching with the special connection method of the iron core inductor, and the annual cumulative fault rate used in the multi-lightning area can be lower than one thousandth.

5. The self-healing capacity of the fault is provided: the invention has the essence that a simple series circuit of a capacitor and an inductor with automatically changed impedance is adopted to directly control alternating current to constant LED current, under the most adverse condition, if the problems of ceramic capacitor breakdown, internal short circuit of a reactor, dry filter capacitor and the like are met, only the resistance capacitance element parameter selection is reasonable, the LED lamp group is only the series impedance element parameter change for controlling the current, the current control capability is reduced, the luminous illumination can still be maintained, only the brightness or stroboscopic index is reduced, the lamp group can still emit light for illumination, and the whole lamp is usually extinguished and loses efficacy immediately as long as one of dozens of elements is damaged in the switch power supply in the prior art; for the LCL resonance scheme, due to the complexity of a T-shaped resonance network, once elements are short-circuited and broken down or parameters are slightly changed, the resonance condition is broken down to burn out the LED lamp set in an overcurrent way, so that the invention has the capability of 'self-healing' the core element fault which is not possessed by the prior art, thereby bringing extremely low failure rate, and the invention can greatly reduce maintenance cost when being adopted in high-tower illumination occasions with difficult maintenance such as expressways, airport wharfs, mine railways and the like. If the ceramic capacitor C1 adopts a plurality of groups of ceramic capacitors in series-parallel connection or through fuses in series-parallel connection, a certain ceramic capacitor breaks down or opens a circuit, only causes the trace change of the output current of the whole power supply, almost has no change in performance index, realizes more outstanding self-healing capacity, and can ensure that the complete failure rate in practical application is less than ten thousandth and less than one tenth of the prior art.

6. Has a spontaneous temperature compensation function: the two types of ceramic capacitors adopted by the invention have obvious temperature coefficients, namely the capacity is reduced after the temperature is increased, so that when the temperature of the lamp is higher, the heated capacity of the ceramic capacitor is reduced, the capacitance resistance is increased, the output current is reduced, the spontaneous temperature compensation function is realized, and for the two types of ceramic capacitors with most specifications, the capacity of the two types of ceramic capacitors at the limit temperature is about 90 percent when the temperature is about 20 degrees, so that when the temperature of the lamp is higher, the output current of a power supply can be automatically reduced by several percent, the service life of an LED element is prolonged, the illumination is not influenced, and because the temperature compensation effect is spontaneously generated by the physical property of the ceramic capacitor, the cost is increased to zero without an additional control element, and the product with the temperature compensation function in the prior art is generally higher in price.

7. The scrapped component resources can be utilized: the ceramic capacitor is scrapped because the bias characteristic test is not up to standard, but the invention uses the disadvantage of the ceramic capacitor and becomes waste, for the invention, the bad ceramic capacitor with the capacity reduced by more than 70% of the initial value under the maximum voltage is the key for achieving the technical purpose of the invention, and the invention not only further reduces the production cost of the ceramic capacitor by reusing a large number of waste ceramic capacitors which cannot be sold by leaving a factory originally because of the unqualified bias index, but also uses a large number of waste component resources, in particular to avoid wasting and recycling rare metal resources in the waste ceramic capacitors.

8. Recyclable scrapped light source electric appliance: in recent years, along with the energy-saving reformation of LEDs of a large number of fluorescent lamps, a large number of inductive ballasts are abandoned, the inductive ballasts have stable performance and extremely long service life, the iron core inductor of the invention is close to the inductive ballasts, and the inductive ballasts of the gas discharge lamps can be directly utilized, so that a large number of originally abandoned inductive ballasts can be recycled, a large number of nonferrous metal resources such as iron and copper are saved, the energy-saving reformation of LEDs can also be formed, the environment-friendly benefit of the invention is further developed, and in addition, the iron core inductor is the part with the largest proportion in the cost, and the cost is hopefully reduced to a very considerable extent because the recycled regeneration components can be used, so that the inductive element of the prior art scheme has large frequency and inductance resistance parameters different from those of the inductive ballasts and cannot be utilized at all.

9. Ultra-long life: the passive device adopted by the invention has extremely low self aging speed, unobvious performance decline, simple structure and extremely long service life, and even if the electrolytic capacitor is adopted for filtering, the electrolytic capacitor is only used for improving stroboscopic effect, even if a dead circuit is used, the LED can continue to emit light and illuminate, the obvious ultra-long service life of hundreds of thousands of hours is 5-10 times that of the switch power supply in the prior art, and the long service life is completely realized by the intuitive, simple and firm circuit structure of the switch power supply, thus having higher customer acceptance.

10. And the power grid loss is reduced: the ceramic capacitor element of the invention can generate a certain proportion of inductive reactive power by deducting the compensation offset part of the iron core inductance from the terminal voltage which is more than 25% of the power supply voltage when controlling the current, and can automatically provide inductive reactive power for the power grid, which is about 5-20% of the power of the lamp, and realize a certain reactive power compensation for the power grid, thereby reducing the line loss of the power grid and stabilizing the power grid voltage, generating indirect energy-saving benefit, and the prior art is a resistive load no matter a switching power supply or a linear power supply or an LCL resonance scheme, and can not provide reactive power compensation.

11. Low harmonic wave and no electromagnetic interference: the switch power supply type driving power supply in the prior art has serious electromagnetic interference, even if a good EMI filter circuit is adopted, a small amount of electromagnetic interference leakage still exists, and the electromagnetic interference is easy to generate larger influence on special lighting occasions such as military, scientific research, medical treatment and the like.

12. The production process is simple and environment-friendly: the invention has no active control circuit, and the normal parameter error of the components does not cause great deviation of the output current, so the design is simple, the production is simple, the test is simple, the design flow of the switching power supply is much more complex, the uncertain factors are also much, as for the LCL resonance scheme, the requirement on the component precision is very high, the component parameter error is slightly large, the resonance condition is greatly changed, the output current is greatly changed, and the design and the production are extremely troublesome. Because of the firmness of the passive device, the circuit does not need to be filled with glue and the shell does not need to consider sealing and heat dissipation, the production process is simplified, and the chemical solvent emission pollution caused by the glue filling and moisture proofing necessary in the prior art is reduced.

13. The power supply voltage fluctuation tolerance capability is strong: the insulation performance of the ceramic capacitor can bear twice rated voltage in a short time, so that breakdown is avoided, (certainly, the invention can emit light and illuminate even if a lamp breaks down), the ceramic capacitor can bear abnormal power supply voltage above 300V to avoid damage as long as the withstand voltage of the ceramic capacitor is slightly improved, the power supply voltage of the switch power supply in the prior art exceeds 265V to cause damage, the quality of the power supply voltage of the street lamp in China is generally low, the voltage at late night exceeds 270V to cause frequent damage of the LED street lamp, and the ceramic capacitor can bear the power supply voltage exceeding 300V to avoid damage by virtue of the excellent withstand voltage performance of the ceramic capacitor. For the LCL resonant constant current scheme, if the LCL resonant constant current scheme needs to bear high voltage of 300V, the volume of the two resonant inductors is increased by about 20%, and the volume weight cost is almost inconceivable.

14. No impact current, and can flash operation: the extremely simple impedance current limiting principle and the current limiting function of the iron core reactor enable the starting impact current to be less than 2 times of rated current, which is ten times of that of a switch power supply in the prior art, so that the switch power supply is not easy to damage when being started in a concentrated mode, a power grid voltage is not sunken, and the switch power supply can directly flash and intermittently operate, and can be used for replacing incandescent lamps in occasions such as signal lamps and barrier lamps to obtain obvious energy-saving effects.

15. Providing an extremely inexpensive dimmable drive power supply: the LED is suitable for dimming, however, the switching power supply based on the prior art has the advantages of high price, complex circuit, higher fault rate and frequent flickering in a large dimming range, and the impedance constant current principle of the invention ensures that the LED has natural external dimming capability, so that the brightness can be conveniently changed only by serially connecting impedance, capacitance or changing input voltage, and the LED does not contain a semiconductor control circuit which makes the work unstable, so that flickering is impossible in principle.

16. The recovery value of the scrapped products is high, and the environmental burden is small: as can be seen from the circuit structure, the invention has the advantages that more than 70% of the weight is concentrated on the iron core inductor, the ceramic capacitor is taken as the main total amount, more than 90% of the iron core inductor and the ceramic capacitor are recyclable and nontoxic metal simple substances such as iron, copper, aluminum, nickel and the like, and the number of other electronic elements is small, so that the recycling value after scrapping is high, and even if the electronic elements are not properly recycled, the electronic elements cannot cause great harm to the environment.

17. The novel technical scheme is provided for the technical field of LED constant current control: in the field of LED driving power sources, the constant current control techniques accepted so far are only two: the invention is a new scheme for realizing automatic current control by utilizing the physical property of special functional materials, which is not chopper control of the power electronic technology or linear control of the analog electronic technology, and is not dependent on the resonance process of a conventional passive element, thus being a novel control scheme completely different from the prior art and providing a different brand new technical scheme for the technical field of LED control.

Drawings

The invention and its features, aspects and advantages will become more apparent from the detailed description of non-limiting embodiments with reference to the following drawings. Like numbers refer to like parts throughout. The drawings may not be to scale, emphasis instead being placed upon illustrating the principles of the invention.

FIG. 1 is a circuit diagram of a multilayer ceramic capacitor LED constant current drive circuit in accordance with a first embodiment of the present invention;

FIG. 2 is a schematic diagram of the current-voltage characteristics of the multilayer ceramic capacitor LED constant current driving circuit;

FIG. 3 is a schematic diagram of the bias characteristics of the multilayer ceramic capacitor LED constant current driving circuit of the invention;

FIG. 4 is a circuit diagram of a multilayer ceramic capacitor LED constant current drive circuit in a second embodiment of the invention;

fig. 5 is a circuit diagram of a multilayer ceramic capacitor LED constant current drive circuit in a third embodiment of the present invention;

Fig. 6 is a circuit diagram of a multilayer ceramic capacitor LED constant current drive circuit in a fourth embodiment of the present invention;

Fig. 7 is a circuit diagram of a multilayer ceramic capacitor LED constant current drive circuit in accordance with a fifth embodiment of the present invention.

Fig. 8 is a circuit diagram of a multilayer ceramic capacitor LED constant current drive circuit in a sixth embodiment of the present invention.

Detailed Description

The invention will now be further described with reference to the accompanying drawings and specific examples, which are not intended to limit the invention.

Referring to fig. 1, which is a circuit diagram of a first embodiment of the present invention, the circuit structure is quite simple, namely, a multilayer ceramic capacitor and an iron core inductor are connected in series between an ac power supply and an LED lamp set, however, in fact, the simple circuit creatively obtains a series of beneficial effects which are difficult to reach by skillfully combining and selecting components.

The working principle of the circuit is similar to that of the prior art LED resistance-capacitance driving circuit, alternating current is blocked by the capacitance reactance of the capacitor in an alternating current loop, so that current applied to the LED element is basically stable when the power supply voltage changes, however, the capacitance reactance of the conventional resistance-capacitance driving technology is fixed and unchanged by adopting a common film capacitor, so that the change amplitude of the current flowing through the LED can only be controlled when the alternating current power supply voltage changes, and the current cannot be completely constant, for example, when the power supply voltage is 10% higher, the output current of the prior art resistance-capacitance power supply is 12-25% higher, the service life of the LED element is influenced, and the end voltage of the LED lamp set can only be reduced for preventing the current fluctuation from being overlarge due to the fact that the voltage-current distribution relation of each element of the resistance-capacitance power supply is subjected to the impedance triangle relation. Therefore, the resistor-capacitor driving circuit in the prior art is difficult to realize high power, and the high-power driving power supply has high requirements on power factor and constant current performance. The invention is characterized in that, the multilayer ceramic capacitor (MLCC capacitor) has the advantages of small volume and reliable operation, however, the disadvantage is obvious for the two types of ceramic capacitors adopting ferroelectric piezoelectric medium, namely, the capacity is unstable, the capacity of the multilayer ceramic capacitor can be greatly changed due to the change of temperature, direct current bias and frequency, and troubles are brought to the application design of a plurality of electric devices, for example, the capacity of the multilayer ceramic capacitor is rapidly reduced along with the increase of the applied direct current voltage, as shown in figure 2, while the invention utilizes the disadvantage of the multilayer ceramic capacitor, a large number of experiments show that the multilayer ceramic capacitor also has obvious bias effect under the power frequency, namely, the capacity is rapidly reduced along with the increase of the working voltage, and the volt-ampere characteristic of the typical multilayer ceramic capacitor tested shows that the capacity resistance is rapidly increased along with the increase of the applied voltage, so that the current is not significantly increased after the voltage is greatly increased after the applied voltage exceeds a certain amplitude, and the spontaneous constant current effect is generated.

In the invention, the selection requirement of the DC bias effect of the multilayer ceramic capacitor C1 is that the capacity of the multilayer ceramic capacitor C1 is not more than 70% of the rated capacity of the multilayer ceramic capacitor C1 at the nominal DC working voltage, and experiments prove that the multilayer ceramic capacitor C1 has obvious constant current effect, and if the bias effect is weaker, the constant current effect is poorer; because the bias effect is obvious under the power frequency of the multilayer ceramic capacitor and the nonlinear characteristic is strong, it is difficult to directly determine the current parameter of the whole machine through the nominal capacity, generally, a safety margin can be reserved according to the maximum allowable ripple current and the temperature rise condition of the whole machine, the maximum allowable ripple current is used as the rated maximum flowing current value, then the voltage range of the two ends of the multilayer ceramic capacitor under the maximum current is determined, at least not lower than 25% of the effective value of the rated power voltage can generate a certain constant current effect, if the capacity is further reduced to improve the end voltage, the constant current effect is better, and if the voltage is divided by connecting a step-down capacitor C3 in series on the circuit like the third embodiment, the end voltage with the 25% ratio can also have an obvious constant current effect; if the bias effect of the selected ceramic capacitor is not obvious and the voltage-reducing capacitor is not provided, the terminal voltage under the maximum current is also increased; if the constant current precision requirement is high or the power supply voltage fluctuation is large, the terminal voltage under the maximum current is also regulated to be large, and experiments show that after the terminal voltage is regulated to be more than 80%, the output current increase when the power supply voltage is increased by 20% can be controlled to be less than 10%. The specification type of the capacitor can be determined through simple experiments and voltage distribution calculation of the impedance triangle, and in addition, the withstand voltage of the ceramic capacitor C1 cannot be lower than 20% of the rated power supply voltage peak value, because of the reverse voltage compensation function of the iron core inductor, even if the capacitor is serially connected with the capacitor, the terminal voltage of the ceramic capacitor C1 can exceed the level of half the power supply voltage, and considering that the insulation allowance of the ceramic capacitor is larger, the withstand voltage cannot be lower than 0.2 times the rated power supply voltage peak value, so that breakdown is prevented. The ceramic capacitor C1 of this embodiment is formed by connecting a plurality of multilayer ceramic capacitors in series and parallel, and each capacitor is connected with a discharge resistor in parallel, and the specification parameters of each capacitor only need to meet the requirements of the total withstand voltage, capacity and other parameters after series-parallel connection. Because ceramic capacitors are small in common capacity and low in voltage resistance, a plurality of ceramic capacitors are required to be connected in series and parallel to reach the required capacity and voltage resistance, and the embodiment adopts the plurality of ceramic capacitors which are connected in series and then in parallel, any capacitor breaks down, the capacity change of the whole group of capacitors is small, the continuous operation of the whole power supply device can be ensured, the performance index is not changed much, and a good fault self-healing effect is achieved.

It should be noted that, compared with the thin film capacitor, the multilayer ceramic capacitor has larger equivalent series resistance, especially in the power frequency ac application, a certain amount of heat generation is generated, so in the aspect of circuit board design, the heat dissipation problem needs to be properly considered, for example, the thickness and the area of the copper foil at the position where the ceramic capacitor is welded on the circuit board, the back surface of the circuit board is attached to the radiating fin or the inner wall of the metal shell, etc., so that the working temperature of the ceramic capacitor is lower than the allowable maximum temperature, and the adhesive for connecting the circuit board and the shell needs to be a glue with better heat conductivity and certain elasticity, thereby avoiding damaging the ceramic capacitor due to external force impact, and avoiding uncomfortable feeling caused by noise amplification of the ceramic capacitor. Other embodiments of the invention are also the same.

However, the use of the multilayer ceramic capacitor for constant current is far insufficient (the prior art also has the adoption of the capacitor for current limiting), because the constant current performance of the ceramic capacitor is not good enough, the constant current precision performance requirement of an LED power supply can not be met, the higher harmonic wave and the power factor problem of a circuit can not meet the requirement of high-power illumination, and finally, the multilayer ceramic capacitor has obvious audible noise, so that people can not normally tolerate the illumination lamp which emits the squeak noise; in addition, the saturation effect of the iron core inductor can be used for further improving the constant current performance, when the ceramic capacitor is in a constant current interval, the capacitance resistance of the ceramic capacitor is increased along with the current increase, and if the inductance resistance of the inductor L1 is reduced along with the current increase at the moment, the change rate of the impedance of the whole loop under the unit current increment can be increased, so that the constant current precision is improved. The iron core inductor of the embodiment adopts uneven iron core air gaps, a part of iron cores have no air gaps or are inserted in a crossing way, so that the iron core inductor can be saturated relatively quickly, assist constant current, maintain a linear state under the rated maximum current, play the roles of smoothing current and improving power factor, and certainly, the inductor can be completely linear, but can also improve the constant current effect, and the voltage of the two ends of the ceramic capacitor is increased due to the compensated voltage, so that the ceramic capacitor works in a more vertical volt-ampere characteristic curve section. Experiments show that the inductor has better constant current effect when the impedance value of the inductor is 40-100% of the initial impedance value when the inductor is rated with maximum current; the terminal voltage of the iron core inductor L1 is not lower than 20% of the effective value of the rated power supply voltage when the rated maximum current is reached, and is preferably more than 40% of the power supply voltage, and if the terminal voltage is too small, the filtering effect is poor, and the harmonic index cannot reach the standard. The iron core inductance also enables the waveform of the current flowing through the ceramic capacitor C1 to be smooth, so that audible noise and generated low-frequency vibration of the ceramic capacitor can be reduced, and negative influence of the noise is prevented. In the prior art, a small amount of LED resistance-capacitance driving power supply also adopts a ceramic capacitor, but the ceramic capacitor has no special physical property, and the unreasonable matching and circuit structure make the ceramic capacitor have almost no constant current effect, and indexes such as harmonic wave, power factor, noise, cost and the like are also bad, so the ceramic capacitor is only applied to the field of low-power and low-cost LED bulbs, and is difficult to realize large power.

When the voltage of the LED lamp set reaches 220V, the current fluctuation within the range of +/-20% of the power voltage fluctuation of the drive power supply designed by the embodiment can be not more than 6%, and the power factor can reach more than 0.9, and meanwhile, the drive power supply has good constant current characteristic and higher power factor.

The beneficial effects of this embodiment lie in:

1. The cost is low: the method has the advantages that the defects of the multilayer ceramic capacitor bias characteristic are skillfully utilized, the harm is reduced, the defects are changed into an automatic control circuit capable of automatically constant current through a simple scheme, the accurate control function of the current of the LED is realized through an extremely simple passive circuit, the use of active devices such as chips and transistors is avoided, the number of the whole device is very small, and the cost is only a fraction of the constant current scheme of the switch power supply in the prior art.

2. The reliability is high: the whole circuit is formed by serially connecting passive devices such as an inductor, a capacitor and the like, a complex T-shaped resonant network is not needed, the stability of a product can be effectively improved, the adaptability to severe environments such as high temperature, humidity and the like is also greatly improved, and the inherent sturdiness and durability of the circuit can bring extremely high reliability and long service life and durability under the severe environments such as outdoor sun, rain and lightning impulse.

3. The lightning resistance is strong: because the lightning invasion wave and high-current stress tolerance capability of the passive device are far higher than those of the active semiconductor device, the lightning tolerance performance of the invention is far higher than that of the switching power supply in the prior art, and the annual cumulative fault rate used in the lightning region can be lower than one thousandth.

4. The self-healing capacity is provided: under the most unfavorable condition, if the problems of ceramic capacitor breakdown, internal short circuit of a reactor, dry filter capacitor and the like are encountered, the luminous illumination can still be maintained as long as the resistance-capacitance element parameter selection is reasonable, and the brightness or stroboscopic index is only reduced, so that the complete failure rate in the practical application can be ensured to reach the level of tens of thousands.

5. Has a spontaneous temperature compensation function: the second-class ceramic capacitors have obvious temperature coefficients, when the temperature of the lamp is higher, the output current of the power supply can be automatically reduced by several percent, the service life of the LED element is prolonged, the illumination is not influenced, an additional control element is not needed, and the cost is increased to zero.

6. The scrapped component resources can be utilized: the production cost of the capacitor is further reduced by reusing a large amount of waste ceramic capacitors which cannot be sold by leaving factories originally due to unqualified bias indexes, and a large amount of waste component resources are utilized, so that the rare metal resources in the waste ceramic capacitors are not wasted and reused.

7. Ultra-long life: the passive device adopted by the embodiment has extremely low self aging speed, insignificant performance decay, simple structure and extremely long service life, and has obvious extremely long service life of hundreds of thousands of hours.

8. And the power grid loss is reduced: the ceramic capacitor element of the embodiment can generate a certain proportion of inductive reactive power while controlling current, automatically provide the inductive reactive power for a power grid, and account for about 5-20% of the active power of a lamp, and realize a certain reactive power compensation for the power grid, thereby reducing the line loss of the power grid, stabilizing the voltage of the power grid and generating indirect energy-saving benefit.

9. Low harmonic wave and no electromagnetic interference: the embodiment is a simple impedance circuit, can enable the alternating-current side current of the whole power supply to be a stable power frequency sine wave, does not need an EMI filter circuit and can not generate any interference on sensitive equipment, and the content of higher harmonic waves is extremely low, so that the power factor of the power supply is higher than 0.9.

10. The production process is simple and environment-friendly: the embodiment has no active control circuit, normal parameter deviation of elements can not amplify current errors, the production and assembly technology is simple, the test is simple, the production process is simplified, and the chemical solvent emission pollution caused by glue filling and moisture proofing which are indispensable in the prior art is also reduced.

11. The power supply voltage fluctuation resistance capability is extremely strong: the insulating property of the ceramic capacitor can withstand twice the rated voltage for a short time without breakdown, while the embodiment can withstand power supply voltage exceeding 300V without damage by virtue of the excellent withstand voltage property of the ceramic capacitor.

12. No impact current, and can flash operation: the extremely simple impedance current limiting principle and the current limiting function of the iron core reactor lead the starting impact current to be less than 2 times of rated current, which is more than ten times of the switching power supply in the prior art, and the switching power supply can directly flash and intermittently operate.

13. Providing an extremely inexpensive dimmable drive power supply: the impedance constant current principle of the embodiment enables the LED to have natural external light adjusting capability, and brightness can be conveniently changed only by serially connecting impedance, capacitance or changing input voltage, and flicker is unlikely to occur.

14. The novel technical scheme is provided for the technical field of LED constant current control: the LED control system is a novel control scheme which is completely different from the existing semiconductor electronic technology, and provides a distinctive novel technical scheme for the technical field of LED control.

15. The volume is small, the weight is light: the whole machine volume weight of the invention is smaller than that of the fluorescent lamp ballast with the same power, and is equivalent to or slightly smaller than that of the existing mainstream LED driving power supply.

16. The recovery value of the scrapped products is high, and the environmental burden is small: it is apparent from the circuit structure that most of the weight of the embodiment is concentrated on the iron core inductor and the ceramic capacitor, wherein most of the materials are recyclable and nontoxic metal simple substances such as iron, copper, aluminum and nickel, and the recycling value is high after scrapping, and even if the materials are not properly recycled, the materials cannot cause great harm to the environment.

FIG. 4 is a circuit diagram of a second embodiment of the present invention, which is also composed of a multilayer ceramic capacitor C1 and an iron core inductor L1, wherein the multilayer ceramic capacitor C1 and the iron core inductor L1 are connected in series between a driven LED lamp group and a power frequency AC power supply input end, a rectifier bridge D1 is connected between the LED lamp group and the power frequency AC power supply, an AC side of the rectifier bridge D1 is connected in series with the multilayer ceramic capacitor C1 and then connected with the power frequency AC power supply input end, a DC side of the rectifier bridge D1 is connected with the driven LED lamp group, and the iron core inductor L1 is connected in series with the AC side of the rectifier bridge D1 and is composed of a gas discharge lamp impedance type induction ballast; the DC side is connected in parallel with a filter capacitor C2. In addition, an overvoltage protector R1 is connected in parallel with the multilayer ceramic capacitor C1; the temperature switch or the thermosensitive protector S is contacted with the outer surface of the overvoltage protector R1 and is connected with the input end of the power frequency alternating current power supply in series; in addition, an overcurrent protector F is connected in series with the input end of the industrial frequency alternating current power supply.

The principle of the embodiment is the same as that of the first embodiment, the capacitive reactance change generated by the multilayer ceramic capacitor bias effect is matched with the iron core inductance, the output current is automatically controlled, the effect of providing constant current for the LEDs is achieved, the design method of selecting elements is the same as that of the first embodiment, and the embodiment is mainly characterized in that a rectifier bridge D1 is further arranged, alternating current is converted into direct current through the rectifier bridge D1, a group of unidirectional LED lamp groups can be directly driven, the embodiment does not need to adopt two groups of anti-parallel LED lamp groups, and the parallel filter capacitor C2 is used for smoothing, so that quite stable direct current can be provided for the LEDs, and stroboscopic is eliminated. In this embodiment, the electrolytic capacitor is also flat, but because the invention works at power frequency, unlike the prior art switching power supply, a large amount of high-frequency ripple is generated, so the filter electrolytic capacitor of the invention hardly generates heat, and therefore, the service life is extremely long, and the service life bottleneck of the electrolytic capacitor in the switching power supply is avoided. The discharging resistor R2 is used for discharging residual voltage of the capacitor after shutdown, the current limiting resistor R5 is used for limiting short circuit or impact current and protecting the LED lamp group, and the discharging resistor R5 is the same as the prior art.

The iron core inductor of the embodiment consists of an impedance type induction ballast of the gas discharge lamp, the impedance type induction ballast of the gas discharge lamp is known to be an iron core inductor, for 220V grid voltage, the rated end voltage is 140-205V, the rated current is 0.15-10A, the impedance parameter can basically and effectively inhibit harmonic waves generated by a circuit, and can enable a ceramic capacitor to work in a constant current curve section close to the rated voltage, therefore, the induction ballast with a certain current specification is adopted to replace the inductor of the invention to be fully feasible, in recent years, along with the energy-saving transformation of a large number of LEDs of fluorescent lamps, a large number of induction ballasts are abandoned, the performance of the induction ballast is stable, the service life is extremely long, the iron core inductor of the invention can directly utilize the induction ballast of the gas discharge lamp, so that a large number of originally abandoned induction ballasts can be recycled, not only a large number of nonferrous metal resources such as iron copper and the like are saved, but also can form green cycle ecology for energy-saving transformation of LEDs and recycling waste light source appliances, the invention is further developed, the environmental protection benefit is further reduced, and the manufacturing cost is further greatly lowered, and the iron core inductor L1 is a highest element device in the invention.

The embodiment is provided with an overvoltage protector R1 connected with the multilayer ceramic capacitor C1 in parallel for absorbing overvoltage and protecting the ceramic capacitor; when the output end of the embodiment is short-circuited, the two ends of the ceramic capacitor C1 can generate higher overvoltage, and the overvoltage protector can generate a large amount of heat after absorbing the overvoltage, so that the temperature switch S contacted with the overvoltage protector reaches an action temperature threshold value to cut off the input of the alternating current power supply to play a role of short-circuit protection, and in addition, when the temperature of the whole driving power supply is too high, the temperature switch can act to cut off the power supply to play a role of overheat protection, and the temperature switch can be replaced by the thermosensitive protector or the PPTC self-recovery protector and the like. As both the short circuit and overheat protection of the invention are realized spontaneously by the hard junction temperature switch or the PTC thermosensitive element, compared with the prior art realized by adopting control chip software, the invention has the advantages of simple structure, high reliability and difficult misoperation. The overcurrent protector F is connected in series with the input end of the power frequency alternating current power supply and is used for total overcurrent or short-circuit protection of the whole driving circuit, so that the safety of the power supply is further improved.

The ceramic capacitor C1 of this embodiment is formed by connecting a plurality of multi-layer ceramic capacitors in series into a plurality of groups, and after each group is connected with the fuse F1 in series, the plurality of groups are connected in parallel, and the rated fusing current of the fuse F1 is smaller than the rated current effective value of the whole group of multi-layer ceramic capacitors C1. The purpose is that once one ceramic capacitor element breaks down, the other ceramic capacitor element connected in series with the ceramic capacitor element can break down due to overvoltage, although the LED lamp group still can be lightened through the current limiting function of the iron core inductor, the power supply loses the constant current capacity, the ceramic capacitor of the fault group is cut off and isolated due to the connection of the fuse F1, and the residual ceramic capacitors play a role in constant current, so that the fuse F1 is reliably fused, the fusing current is smaller than the rated current of the whole ceramic capacitor group C1, the output current is slightly reduced, the whole power supply still has the constant current effect, and other performance indexes are not reduced, so that the self-healing function is realized.

In order to further consolidate the lightning protection performance, the embodiment is further provided with the fuse F2 and the overvoltage protector R3 at the input end of the alternating current power supply, and the fuse F2 and the overvoltage protector R3 are connected between the phase line and the zero line of the input end of the alternating current power supply for the advanced protection of overvoltage invasion waves, and the whole power supply short circuit failure caused by the aging breakdown of the overvoltage protector can be avoided due to the connection of the fuse F2, the fuse F2 is fused and cut off after the breakdown of the overvoltage protector, the normal operation of the power supply can not be influenced, the cost is reduced, the F2 can be omitted, or the overcurrent protector F is shared as in the prior art, the overvoltage protector R3 can be replaced by a TVS diode, a gas discharge tube and the like, and the parameter selection method is the same as in the prior art.

Obviously, the embodiment also has the advantages of low cost, high reliability, long service life, strong lightning resistance, temperature compensation, self-healing capability, capability of utilizing scrapped element resources, power grid loss reduction, no electromagnetic interference, simple and environment-friendly production process, strong power supply voltage wave resistance capability, convenience in flashing or dimming operation, high recovery value after scrapping and the like.

Fig. 5 is a circuit diagram of a third embodiment of the present invention, which is also composed of a multilayer ceramic capacitor C1 and an iron core inductor L1, wherein the multilayer ceramic capacitor C1 is connected between the LED lamp set driven and the input end of the power frequency ac power supply, a rectifier bridge D1 is connected between the LED lamp set and the power frequency ac power supply, the ac side of the rectifier bridge D1 is connected with the multilayer ceramic capacitor C1 and the buck capacitor C3 in series and then connected with the input end of the power frequency ac power supply, the dc side of the rectifier bridge D1 is connected with the LED lamp set driven, and the iron core inductor L1 is connected in series with the dc side of the rectifier bridge D1. The overcurrent protector F is connected in series with the input end of the power frequency alternating current power supply, and the multilayer ceramic capacitor C1 is also formed by connecting a plurality of groups of multilayer ceramic capacitors in series and then connecting the multilayer ceramic capacitors with the fuse F1 in series.

The principle of the embodiment is the same as that of the first and second embodiments, the capacitance resistance change generated by the multilayer ceramic capacitor bias effect is matched with the iron core inductor to automatically control the output current, the effect of providing constant current for the LED is achieved, the iron core inductor of the embodiment is arranged on the direct current side of the rectifier bridge, the iron core inductor of the embodiment can be composed of a gas discharge lamp impedance type inductance ballast, the iron core inductor is connected on the direct current side, the effect of inhibiting harmonic waves and impulse current can be achieved, but the inductor on the direct current side forms smaller reactive power on the alternating current side, the end voltage of the ceramic capacitor cannot be increased obviously, so that the constant current performance of the ceramic capacitor is reduced, but the advantages are that the end voltage of the ceramic capacitor C1 is smaller, the ceramic capacitor with lower withstand voltage value is adopted, so that the cost is reduced, in addition, the ceramic capacitor C3 connected in series is added, the end voltage of the ceramic capacitor C1 is further reduced, even if the output end is short-circuited, the voltage at two ends of the ceramic capacitor is not increased greatly, the ceramic capacitor with low withstand voltage is also protected by a special overvoltage protector, the discharge resistor R4 is used for releasing the residual charge of the ceramic capacitor C3, and the current of the ceramic capacitor is stable, and the LED is prevented from flowing through the direct current side. In addition, the embodiment also provides an overcurrent protector F which is connected in series with the input end of the power frequency alternating current power supply and used for total overcurrent or short-circuit protection of the whole driving circuit, and an overvoltage protector R3 which is used for overvoltage intrusion wave protection of the input end of the power supply, so that the safety and the reliability of the power supply are further improved. In addition to the TVS diode, the overvoltage protector R3 may be replaced by a composite varistor having a breakdown protection function, and a special fuse may be omitted.

Obviously, the embodiment also has the advantages of low cost, high reliability, long service life, strong lightning resistance, self-healing capacity, temperature compensation capacity, capability of utilizing scrapped element resources, power grid loss reduction, no electromagnetic interference, simple and environment-friendly production process, strong power supply voltage wave resistance capacity, convenience in flickering or dimming operation, high recovery value after scrapping and the like.

Fig. 6 is a circuit diagram of a fourth embodiment of the present invention, which is also composed of a multilayer ceramic capacitor C1 and an iron core inductor L1, wherein a power frequency transformer T is connected between the LED lamp set and the input end of the power frequency ac power supply, the secondary winding of the power frequency transformer T is connected to the ac side of the rectifier bridge D1, the multilayer ceramic capacitor C1 is connected in series between the secondary winding of the power frequency transformer T and the ac side of the rectifier bridge, the dc side of the rectifier bridge D1 is connected with the LED lamp set driven, and the iron core inductor L1 is connected in series between the primary winding of the power frequency transformer T and the input end of the ac power supply. An overcurrent protector F is connected in series with the input end of the power frequency alternating current power supply. The multilayer ceramic capacitor C1 can also be formed by connecting a plurality of groups of multilayer ceramic capacitors in series and parallel or connecting a plurality of groups of multilayer ceramic capacitors in series and parallel with a fuse.

The principle of this embodiment is the same as that of the other embodiments described above, and the capacitance resistance change generated by using the bias effect of the multilayer ceramic capacitor is matched with the iron core inductance to automatically control the output current, so as to provide a constant current for the LED. The short-circuit impedance of the transformer provides a part of inductance, so that the volume and inductance value of the iron core inductor can be reduced by about 15-30% compared with those without the transformer, and the iron core inductor can be arranged on the direct current side of the rectifier bridge by utilizing a gas discharge lamp inductance ballast. The embodiment also sets up overcurrent protector F and power frequency alternating current power supply input series connection equally, is used for total overcurrent or short-circuit protection of whole drive circuit, further promotes the security of power. Because the transformer has strong overvoltage tolerance and lightning invasion waves are difficult to transmit to the low-voltage side through the transformer, the overvoltage protection of the embodiment is simpler and basically no overvoltage protection element is needed.

It should be noted that, in this embodiment, because the inductance provided by the short-circuit impedance of the transformer is not high in requirement on the harmonic index, the iron core inductance L1 can be omitted, but basically the same is achieved by only using the short-circuit impedance of the transformer itself, if the harmonic index is to be improved, the volume is to be reduced, the transformer T can be designed as a leakage transformer, the filtering effect of the iron core inductance L1 is achieved by using the larger leakage reactance of the leakage transformer, and the harmonic forced authentication standard can be achieved on the basis of omitting the iron core inductance L1. In addition, the rectifier bridge can be changed according to the characteristics of the secondary winding of the transformer, such as adopting a voltage doubling rectifier bridge and a double-diode full-wave rectifier circuit to replace a common rectifier bridge, or adopting a common cathode common Yang Xiaote base diode to form a low-loss rectifier bridge, and the like, and the conventional variation means are completely equivalent to the technical scheme of the invention.

Obviously, the embodiment also has the advantages of low cost, high reliability, long service life, strong lightning resistance, self-healing capability, capability of utilizing scrapped element resources, power grid loss reduction, no electromagnetic interference, simple and environment-friendly production process, strong power supply voltage wave resistance capability, convenience in flickering or dimming operation and the like of other embodiments of the invention, and further has better primary and secondary electric isolation performance than the isolation type driving power supply in the prior art.

FIG. 7 is a circuit diagram of a fifth embodiment of the present invention, which also comprises a multilayer ceramic capacitor C1 and an iron core inductor L1, wherein the multilayer ceramic capacitor C1 and the iron core inductor L1 are connected in series between the driven LED lamp group and the input end of the power frequency alternating current power supply, the multilayer ceramic capacitor C1 is formed by connecting several multilayer ceramic capacitors in series, once one of the multilayer ceramic capacitors breaks down due to the bias constant current effect, the remaining multilayer ceramic capacitors can still maintain the output current without increasing much, and the constant current performance of the circuit can still be ensured; a rectifier bridge D1 is connected between the LED lamp group and the power frequency alternating current power supply, the alternating current side of the rectifier bridge D1 is connected with the input end of the power frequency alternating current power supply after being connected with the multilayer ceramic capacitor C1 in series, the direct current side of the rectifier bridge D1 is connected with the driven LED lamp group, the iron core inductor L1 is provided with two groups of windings, and one ends of the two windings are connected with the input end of the power frequency alternating current power supply and are connected with the alternating current side of the rectifier bridge D1 in series; the DC side is connected in parallel with a filter capacitor C2 and a discharge resistor R2, the filter capacitor C2 adopts a nonpolar film capacitor to realize longer service life than an electrolytic capacitor, in addition, an overvoltage protector R1, an overcurrent protector F and a power frequency alternating current power supply input end are connected in series, and finally, a follow current resistor R6 is connected in parallel with the alternating current power supply input end, and is used for providing trigger circuit charging current in a non-conduction time period for a thyristor trigger circuit when the thyristor is used for dimming, and the trigger circuit charging current is the same as the follow current resistor of a phase control dimming power supply in the prior art.

The principle of the embodiment is the same as that of other embodiments, the capacitance resistance change generated by the multilayer ceramic capacitor bias effect is matched with the iron core inductor, the output current is automatically controlled, the effect of providing constant current for the LED is achieved, the iron core inductor of the embodiment is composed of two groups of windings, the two groups of windings are connected to the input end of an alternating current power supply, the purpose of the embodiment is to achieve a lightning protection effect better, the frequency of the wave head of lightning invasion waves is very high, the huge inductance of the iron core inductor can play a very large role in weakening the lightning invasion waves, the windings of the iron core inductor are divided into two parts, and the windings are respectively connected with the input end of the alternating current power supply in series, so that overvoltage invasion waves of the ground and zero line to the ground can be effectively absorbed, and if the lightning protection device is matched, a very excellent lightning protection effect can be achieved. Although the simple and firm structure of the invention has the innate lightning protection capability, the lightning protection device can play a more prominent role in special areas such as mountain areas, thunder areas and the like, and the device can continuously bear 15KV and 1ms surge impact voltage between the ground and the zero ground for tens of times without damage through test, the comprehensive lightning protection effect is higher than tens of times of that of the switch power supply product in the prior art, the annual lightning strike damage rate in the multi-thunder area in practical application is only one thousandth, and the damage probability is only about one percent of that of the switch power supply in the prior art. In order to further improve lightning protection performance, in this embodiment, the input end of the ac power supply and the dc output end are both connected with a fuse F2 and an overvoltage protector R3, and the two elements are divided into three groups, one group is connected between the phase line and the zero line of the input end of the ac power supply, the other group is connected between the phase line or the zero line and the grounding end of the shell, and the last group is connected between the positive electrode and the negative electrode of the dc output end for comprehensive protection of overvoltage intrusion waves, and the function of the fuse F2 is the same as that of the embodiment. Of course, the overvoltage protector R3 may be replaced by a TVS diode, a gas discharge tube, or the like. In this embodiment, an overvoltage protector R1 is also provided in parallel with the multilayer ceramic capacitor C1, and a temperature switch S in contact with the overvoltage protector is used for short-circuit protection, so as to play a role in short-circuit protection, and the temperature switch S may also be composed of similar elements such as a thermosensitive protector, etc., and the overcurrent protector F is connected in series with the input end of the power frequency ac power supply, so as to be used for overcurrent or short-circuit protection of the whole driving circuit.

Obviously, the embodiment also has the advantages of low cost, high reliability, long service life, outstanding lightning resistance, self-healing capacity and temperature compensation capacity, capability of utilizing scrapped element resources, power grid loss reduction, no electromagnetic interference, simple and environment-friendly production process, strong power supply voltage wave resistance capacity, high recovery value after scrapping, convenience in flickering or dimming operation and the like.

Fig. 8 is a circuit diagram of a sixth embodiment of the present invention, which is also composed of a multilayer ceramic capacitor C1 and an iron core inductance L1, and adds a step-down capacitor C3 to divide the voltage to reduce the withstand voltage of the ceramic capacitor C1 as in the third embodiment, so as to further reduce the cost, the multilayer ceramic capacitor C1 of the present embodiment is divided into three groups, and the three groups are respectively connected in series with the contacts of the switching controller S1 and then are connected in series with the iron core inductance L1 between the LED lamp group driven and the power frequency ac power input terminal, so that the contacts of the switching controller S1 can be switched to select different ceramic capacitor groups, thereby realizing the step-down dimming or switching. The principle of other parts of the circuit is exactly the same as in other embodiments. Of course, the principle of the present embodiment is the same as that of the present embodiment, in which the step-down capacitor C3 or the core inductor L1 is connected in series and in parallel in groups, and the switching device contact or the tap is provided, so that dimming or switching control can be realized.

Obviously, the embodiment also has the advantages of low cost, high reliability, long service life, outstanding lightning resistance, self-healing capacity and temperature compensation capacity, capability of utilizing scrapped element resources, power grid loss reduction, no electromagnetic interference, high recovery value after scrapping, simple and environment-friendly production process, strong power supply voltage wave resistance capacity, convenience in flickering or dimming operation and the like.

Those skilled in the art will understand that the variations may be implemented in combination with the prior art and the above embodiments, and are not described herein. Such modifications do not affect the essence of the present invention, and are not described herein.

The preferred embodiments of the present invention have been described above. It is to be understood that the invention is not limited to the specific embodiments described above, wherein devices and structures not described in detail are to be understood as being implemented in a manner common in the art; any person skilled in the art may make many possible variations and modifications to the technical solution of the present invention, or modify the technical solution of the present invention into equivalent embodiments with equivalent variations, such as adding reactive compensation elements, adding redundancy with multiple elements connected in series-parallel, connecting some conventional control devices, etc., without affecting the essence of the present invention, and "a" or "an" preceding an element of the present invention does not exclude the presence of multiple such elements, so that any simple modification, equivalent variation and modification made to the above embodiments according to the technical solution of the present invention still falls within the scope of the technical solution of the present invention, without departing from the scope of the technical solution of the present invention.

Claims

1. A multilayer ceramic capacitor LED constant current drive circuit, comprising:

A multilayer ceramic capacitor C1, an iron core inductance L1, an overvoltage protector R1, a temperature switch or heat sensitive protector S, an overcurrent protector F and an overvoltage protector R3;

The multilayer ceramic capacitor C1 and the iron core inductor L1 are connected in series between the driven LED lamp group and the input end of the power frequency alternating current power supply;

the multilayer ceramic capacitor C1 is formed by connecting a plurality of multilayer ceramic capacitors in series into a plurality of groups, and after each group is connected with the fuse F1 in series, the plurality of groups are connected in parallel, and the rated fusing current of the fuse F1 is smaller than the rated current effective value of the whole group of multilayer ceramic capacitors;

A rectifier bridge D1 is connected between the driven LED lamp set and the power frequency alternating current power supply input end, the alternating current side of the rectifier bridge D1 is connected with the multilayer ceramic capacitor C1 in series and then is connected with the power frequency alternating current power supply input end, the direct current side of the rectifier bridge D1 is connected with the driven LED lamp set, and the iron core inductor L1 is connected with the alternating current side of the rectifier bridge D1 in series;

the direct current side of the rectifier bridge D1 is connected with a filter capacitor C2 and a discharge resistor R2 in parallel;

the overvoltage protector R1 is connected with the multilayer ceramic capacitor C1 in parallel; the temperature switch or the thermosensitive protector S is contacted with the outer surface of the overvoltage protector R1 and is connected in series with the input end of the power frequency alternating current power supply;

The overcurrent protector F is connected with the input end of the power frequency alternating current power supply in series;

The overvoltage protector R3 is connected with a fuse F2 in series and then connected with the input end of the power frequency alternating current power supply in parallel;

The multilayer ceramic capacitor C1 has a DC bias effect, and the capacity of the multilayer ceramic capacitor C1 under the maximum allowable DC bias condition is not more than 70% of the nominal capacity; the voltage effective value of the two ends of the multilayer ceramic capacitor C1 at the rated maximum flowing current is not lower than 25% of the rated power supply voltage effective value; the withstand voltage value of the multilayer ceramic capacitor C1 is not lower than 20% of the rated power supply voltage peak value; the effective value of the voltage at two ends of the iron core inductor L1 at the rated maximum flowing current is not lower than 20% of the effective value of the rated power supply voltage.

2. The multi-layer ceramic capacitor LED constant current driving circuit according to claim 1, wherein the core of the core inductor L1 is provided with non-equidistant air gaps, the impedance value of which at the rated maximum current is 40-100% of the initial impedance value thereof.

3. The multilayer ceramic capacitor LED constant current drive circuit of claim 1, wherein the core inductance L1 is comprised of a gas discharge lamp impedance type inductive ballast.