CN202206604U

CN202206604U - Led driving power supply control circuit

Info

Publication number: CN202206604U
Application number: CN201120276250XU
Authority: CN
Inventors: 蔡轶群
Original assignee: Shenzhen Alpha Electronic Tech Co ltd
Current assignee: Shenzhen Alpha Electronic Tech Co ltd
Priority date: 2011-08-01
Filing date: 2011-08-01
Publication date: 2012-04-25
Anticipated expiration: 2021-08-01

Abstract

The utility model provides an LED (Light Emitting Diode) driving power supply control circuit comprising: a power supply converter; a rectification filter circuit which is connected out with a secondary coil of the power supply converter; a constant-current circuit which is connected in series with an output circuit of the rectification filter circuit and provided with a constant-current feedback end; a voltage-limiting circuit which is connected in series between an output end of the constant-current circuit and the ground and provided with a voltage-limiting feedback end; and a current-limiting protection circuit which is connected in series with the output circuit of the rectification filter circuit and at least comprises one triode and one current-limiting resistor. According to the LED driving power supply control circuit of the utility model, one current-limiting circuit taking the master control triode and the current-limiting resistor as a core is connected in series in back of an output high-frequency filter capacitor of the LED driving power supply, when an output current of the driving power supply is greater than a preset current-limiting value, the current-limiting circuit can consume superfluous energy of the current on a collector junction of the master control triode, thus a transient overcurrent which may occur when a load assembly and the high-frequency filter capacitor are switched on can be effectively protected.

Description

LED driving power control circuit

Technical field

The utility model relates to the LED field, relates in particular to a kind of LED driving power control circuit with current-limiting protection function.

Background technology

LED is a kind of energy-saving and environmental protection, small size and long-life novel solid light source, is constantly promoted and be applied to the normal lighting field in recent years.But because the forward volt-ampere characteristic of LED is very steep, dynamic electric resistor is less, make it not steep the direct voltage fed of using as ordinary incandescent lamp, otherwise voltage has increase slightly, and the electric current that flows through LED will sharply increase, to such an extent as to can burn the LED load.

Therefore, can work on normal reliable ground in order to guarantee LED, a lot of manufacturers both at home and abroad all are devoted to develop various led drive circuits, and improve constantly the constant current voltage regulation performance of led drive circuit.Existing LED constant-current driving power supply belongs to free-standing constant-current driving power supply mostly, and the connection switch is placed on input power supply one side and the LED load connects.Before connecting switch and closing, there is not initial energy storage in the output high-frequency filter capacitor, and closes the back circuit working at the state of a constant current connecting switch, to guarantee the operate as normal of LED load.

The control circuit principle of existing incorporate LED Switching Power Supply is shown in figure l; The DC power supply of input power supply after the secondary coil L of power supply changeover device will change outputs to current rectifying and wave filtering circuit; Through behind the rectifying and wave-filtering once more, obtain stable low-voltage direct out-put supply.Wherein, Optocoupler IC is mainly constant-current circuit and pressure limiting circuit provides feedback control loop; The constant current feedback end FB1 of constant-current circuit, the pressure limiting feedback end FB2 of pressure limiting circuit be all through the input circuit ground connection of optocoupler IC, the FEEDBACK CONTROL end FB3 that the output loop of optocoupler lC is then gone here and there at power supply changeover device and and the ground of power supply changeover device between.

But,, require the connection switch of driver to be connected on dc output end along with incorporate led driver occurs.Because LED belongs to the constant current device work; So LED is connected in the circuit with series connection or series-parallel mode generally speaking, it is the several times of single the desired forward voltage of LED that the desired ceiling voltage of its circuit tends to, if on existing LED constant current pressure limiting switching power circuit topology, do not add any current limiting measures; So when the operating load of LED electronic transformer during less than nominal load; As following problem will occur when only connecting the LED load of one or two 1W: owing on the output high-frequency filter capacitor initial energy storage is arranged, led driver is in electriferous state all the time, and before connecting switch and closing; The pressure drop at output high-frequency filter capacitor two ends is a load voltage value; Therefore, when connecting switch and close moment constant-current circuit also do not come reach operate as normal, be stored in most of energy of exporting on the high-frequency filter capacitor and all can be added in the LED load; At this moment will produce the immediate current overshoot phenomenon, and nearly tens milliseconds of holding time of this overshoot current.At this moment, if output current is not limited, can badly influence the useful life of LED, even possibly burn LED.

Summary of the invention

The purpose of the utility model is to provide a kind of LED driving power control circuit that can effectively prevent to connect the overshoot of switch closure immediate current.

The purpose of the utility model realizes through following technical scheme.

A kind of LED driving power control circuit comprises: power supply changeover device; Current rectifying and wave filtering circuit, this current rectifying and wave filtering circuit is picked out by the secondary coil of said power supply changeover device; Constant-current circuit, this constant-current circuit are serially connected on the output loop of current rectifying and wave filtering circuit and have a constant current feedback end; Pressure limiting circuit; This pressure limiting circuit is serially connected between the output and ground of said constant-current circuit; And has a pressure limiting feedback end; On the output loop of current rectifying and wave filtering circuit, also be serially connected with the current-limiting protection circuit that comprises a triode and a current-limiting resistance at least, this current-limiting protection circuit can make the electric current that flows through LED within the trouble free service current range in the output current size of connection switch closure moment of out-put supply restriction current rectifying and wave filtering circuit.

Preferably, also include an optocoupler, described constant current feedback end, pressure limiting feedback end be all through the input circuit ground connection of optocoupler, the output loop of optocoupler then go here and there the FEEDBACK CONTROL end of power supply changeover device and and the ground of power supply changeover device between.

Preferably; Described current-limiting protection circuit is to be made up of first triode and first resistance; The grounded collector of first triode; The emitter of first triode connects the output of current rectifying and wave filtering circuit, and behind first resistance one the tunnel connect first triode base stage, the input of constant-current circuit is received on another road.

The utility model compared with prior art; Its advantage is; Because the utility model has been connected in series current-limiting circuit behind the output high-frequency filter capacitor of original LED driving power; This current-limiting circuit is a core with a master control triode and a current-limiting resistance, and this master control triode is connected in the current-limiting circuit with the mode of parallel connection or series connection.Through utilizing the switching characteristic of triode, when the current rectifying and wave filtering circuit output current when driving power was lower than predefined cut-off current, the master control triode was in saturation conduction or cut-off state, the circuit operate as normal; When the current rectifying and wave filtering circuit output current of driving power during greater than predefined cut-off current; Current-limiting circuit will electric current is unnecessary energy consumption on the collector junction of this master control triode; Thereby can be good at the electric current in the output loading is realized control comparatively accurately that the of short duration overcurrent that occurs during promptly to load component and high-frequency filter capacitor connection is realized effective must the protection.And this current-limiting circuit only only plays the effect of protection load to the almost not influence of service behaviour of primary circuit in the moment that pulse current occurs.

Description of drawings

Figure l is the circuit theory sketch map of existing integral LED driver;

Fig. 2 is the circuit theory sketch map of the utility model;

Fig. 3 is the electrical block diagram of the utility model embodiment one.

Embodiment

For the purpose, technical scheme and the advantage that make the utility model is clearer,, the utility model is further elaborated below in conjunction with accompanying drawing and embodiment.Should be appreciated that specific embodiment described herein only in order to explanation the utility model, and be not used in qualification the utility model.

See also shown in Figure 2, to having problems among Fig. 1, current-limiting protection circuit I who comprises a triode and a current-limiting resistance at least of serial connection on the output loop of the current rectifying and wave filtering circuit that constitutes by diode D and filter capacitor C.

Described current-limiting protection circuit I can have various ways; But all accomplish same～individual function; Promptly can be in the output current size of the closed moment restriction of the connection switch S of out-put supply current rectifying and wave filtering circuit; Make the electric current that flows through LED within the trouble free service current range, concrete circuit form is described below.

As shown in Figure 3; Embodiment one for this practical property; Wherein current-limiting circuit is formed by the positive-negative-positive first triode Q1 with as the first resistance R l of current-limiting resistance, the grounded collector of the first triode Ql, and the emitter of the first triode Ql connects the output of current rectifying and wave filtering circuit; And behind the first resistance R l one the tunnel meet the first triode Ql base stage, the input of constant-current circuit is received on another road.

When output current value during less than the pre-set threshold electric current, the pressure drop at the first resistance R l two ends is less than the 0.7V operating voltage, and the positive-negative-positive first triode Ql is in cut-off state, the circuit operate as normal; When output current value during greater than the pre-set threshold electric current, the pressure drop at the first resistance R l two ends is greater than 0.7V, the collector electrode of the first triode Ql.The emitter passage becomes low resistance, makes most electric current flow through the collector electrode of the first triode Ql, on the emitter passage, and with the form consumption of heat energy on the collector junction of the first triode Ql, thereby protected over-current phenomenon avoidance of short duration in the load effectively.

The above is merely the preferred embodiment of the utility model; Not in order to restriction the utility model; Any modification of being done within all spirit and principles at the utility model, be equal to replacement and improvement etc., all should be included within the protection range of the utility model.

Claims

1. a LED driving power control circuit comprises: power supply changeover device; Current rectifying and wave filtering circuit, this current rectifying and wave filtering circuit is picked out by the secondary coil of said power supply changeover device; Constant-current circuit, this constant-current circuit are serially connected on the output loop of current rectifying and wave filtering circuit and have a constant current feedback end; Pressure limiting circuit; This pressure limiting circuit is serially connected between the output and ground of said constant-current circuit; And have a pressure limiting feedback end, it is characterized in that: on the output loop of current rectifying and wave filtering circuit, also be serially connected with the current-limiting protection circuit that comprises a triode and a current-limiting resistance at least.

2. LED driving power control circuit as claimed in claim 1; It is characterized in that; Also include an optocoupler; Described constant current feedback end, pressure limiting feedback end be all through the input circuit ground connection of optocoupler, the output loop of optocoupler then go here and there the FEEDBACK CONTROL end of power supply changeover device and and the ground of power supply changeover device between.

3. LED driving power control circuit as claimed in claim 1; It is characterized in that; Described current-limiting protection circuit is to be made up of first triode and first resistance, the grounded collector of first triode, and the emitter of first triode connects the output of current rectifying and wave filtering circuit; And behind first resistance one the tunnel connect first triode base stage, the input of constant-current circuit is received on another road.