CN102447392A

CN102447392A - Current control circuit

Info

Publication number: CN102447392A
Application number: CN2010102999869A
Authority: CN
Inventors: 曾创炜
Original assignee: Hongfujin Precision Industry Shenzhen Co Ltd; Hon Hai Precision Industry Co Ltd
Current assignee: Hongfujin Precision Industry Shenzhen Co Ltd; Hon Hai Precision Industry Co Ltd
Priority date: 2010-10-08
Filing date: 2010-10-08
Publication date: 2012-05-09

Abstract

The invention provides a current control circuit. The current control circuit comprises a full-wave rectification unit, a control unit and a plurality of transformers, wherein, the full-wave rectification unit comprises four field-effect transistors (FETs); and the control unit controls connection or disconnection of the four FETs in a pairwise alternation manner so as to provide an alternating current (AC) for the plurality of transformers, each transformer comprises a primary coil and a secondary coil, the primary coils of the plurality of transformers are sequentially connected in series, and each secondary coil is electrically connected with a group of loads. The current control circuit provided by the invention can keep the load current consistent and has the advantage of low design cost.

Description

Current control circuit

Technical field

The present invention relates to a kind of control circuit, relate in particular to a kind of current control circuit.

Background technology

(the many also phenomenons of the many strings of LED also get more and more for Low Emitting Diode, widely-used (like large-scale LCD TV) LED) along with light-emitting diode.It is consistent through the electric current of each group LED that existing current control circuit mostly adopts many group integrated chips (Integrated Circuit) and FET (MO SFET) to cooperate with control flows.Yet this type of current control circuit needs more IC on the one hand, and design cost is high; On the other hand, after LED used often, because the variation of LED internal resistance, a plurality of LED connect, and (Forward Voltage's forward voltage drop that causes LED easily VF) added up, and then the MOSFET temperature is risen, and influences the MOSFET operate as normal; A plurality of LED parallel connections are then easily because the difference of the electric current of each LED that flows through causes the LED luminosity to differ.

Summary of the invention

In view of above situation, but be necessary to provide the current control circuit of the low and balanced balanced current of a kind of cost.

A kind of current control circuit; It comprises full-wave rectification unit, control unit and plural transformer, and this full-wave rectification unit comprises four FETs, and the on-off of leading that four FETs of this control unit control replace in twos each other closes; Think that plural transformer provides alternating current; Each transformer includes primary coil and secondary coil, and the primary coil of this plural number transformer is connected successively, and each secondary coil and one group of load electrically connect.

Above-mentioned current control circuit makes the secondary current of transformer consistent, and then keeps the load current unanimity through the primary coil series connection of just plural transformer.Simultaneously, the on-off of leading that the present invention only needs four FETs of a control unit control to replace closes, and can keep plural transformer and plural loaded work piece simultaneously, the design cost that fallen ground effectively.

Description of drawings

Fig. 1 is the circuit diagram of the current control circuit of the present invention's first preferred embodiments;

Fig. 2 is the circuit diagram of the current control circuit of the present invention's second preferred embodiments.

The main element symbol description

Current control circuit 100

Power supply 10

Control unit 20

Full-wave rectification unit 30

The first FET A

The second FET B

The 3rd FET C

The 4th FET D

Transformer 40-43

Primary coil TP

Elementary end H of the same name

Elementary different name end S

Secondary coil TS

Secondary end F of the same name

Secondary different name end K

Rectifier diode 50

Light-emitting diode group 200

Embodiment

See also Fig. 1, first preferred embodiment of the present invention provides a kind of current control circuit 100, with thinking that the light-emitting diode group 200 of a plurality of parallel/series provides stable electric current.This current control circuit 100 comprises power supply 10, control unit 20, full-wave rectification unit 30, plural transformer 40-43 and plural rectifier diode 50.

This power supply 10 is that civil power is through bridge rectifier and Active PFC (Power FactorCorrection, PFC) the high voltage pulse direct current of back formation.These power supply 10 usefulness think that full-wave rectification unit 30 provides direct current.

This control unit 20 electrically connects with full-wave rectification unit 30, and this control unit 20 is through producing the driving pulse of two groups of phase phasic difference 180 degree, constant amplitude, equifrequency, with control full-wave rectification unit 30.

This full-wave rectification unit 30 electrically connects with power supply 10, converts alternating current to the direct current that power supply is transmitted.This full-wave rectification unit 30 comprises four the first FET A, the second FET B, the 3rd FET C and the 4th FET D that model is identical.Wherein, The first FET A, the second FET B, the 3rd FET C and the 4th FET D grid separately all are electrically connected at control unit 20; To receive two groups of driving pulses that control unit 20 sends, the on-off of leading that so this first FET A and the 4th FET D, the second FET B and the 3rd FET C replace closes.The drain electrode of this first FET A and the second FET B all electrically connects with the positive pole of power supply 10; The source electrode of the first FET A and the second FET B electrically connects with the drain electrode of the 3rd FET C and the 4th FET D respectively, the source electrode of the 3rd FET C and the 4th FET D all with the negative pole electric connection of power supply 10.So, form a full-wave rectifying circuit, convert the direct current that power supply 10 transmits to alternating current with HF switch effect through FET.

Transformer 40-43 includes primary coil TP and secondary coil TS; The primary coil TP of this transformer 40-43 is consistent with the turn ratio of secondary coil TS; Alternating current in order to 30 outputs of full-wave rectification unit carries out lifting/voltage reducing, and then 200 work of driven for emitting lights diode group.In the present embodiment, the polarity of the primary coil TP of this transformer 40-43 is identical, and the polarity of secondary coil TS is identical.Primary coil TP comprises elementary end H of the same name and elementary different name end S; Wherein the end H elementary of the same name of the primary coil TP of transformer 40 is electrically connected between the drain electrode of source electrode and the 3rd FET C of the first FET A; The end H elementary of the same name of the primary coil TP of elementary different name end S and transformer 41 electrically connects; This plural number primary coil TP is arranged by polarity; Series connection successively is electrically connected at until the elementary different name end S of the primary coil TP of transformer 43 between the drain electrode of source electrode and the 4th FET D of the second FET B.The light-emitting diode group 200 that the secondary coil TS of transformer 40-43 is provided with in order to one group of series/parallel of separate connection respectively.Secondary coil TS comprises secondary end F of the same name and secondary different name end K, this secondary different name end K ground connection, and the positive pole of secondary end F of the same name and rectifier diode 50 electrically connects.The negative pole of this rectifier diode 50 and light-emitting diode group 200 anodal ends electrically connect; Alternating current in order to transformer 40-43 secondary coil TS is transmitted converts DC pulse into; With 200 work of driven for emitting lights diode group, the equal ground connection of negative pole one end of this plural number light-emitting diode group 200.

When these current control circuit 100 work, form power supply 10 after civil power process bridge rectifier and the Active PFC.At this moment, control unit 20 is controlled the on-off of leading that the first FET A and the 4th FET D, the second FET B and the 3rd FET C replace respectively and is closed, to produce high-frequency alternating current.This moment is because the primary coil TP series connection of transformer 40-43; The electric current I tp of each primary coil TP all equates so flow through; And because the primary coil TP of transformer 40-43 is consistent with the turn ratio of secondary coil TS; So the electric current I ts of each secondary coil TS is also consistent, this moment, the electric current of light-emitting diode group 200 was also consistent, i.e. the brightness of each light-emitting diode is all consistent.

Shown in Figure 2 is second preferred embodiment of the present invention; Different with first preferred embodiment is: the polarity of the secondary coil TS of transformer 40 and transformer 41 is inequality; The polarity of the secondary coil TS of transformer 42 and transformer 43 is inequality, and the secondary coil TS of opposed polarity is staggered to drive the different light-emitting diode group 200 of positive-negative polarity.In like manner, the present invention also can change transformer 40-43 primary coil TP polarity, and the positive-negative polarity that only need change light-emitting diode group 200 this moment accordingly gets final product.

The quantity that is appreciated that transformer of the present invention is not limited to 4 described in the embodiment, also can do corresponding increase and decrease according to the quantity of light-emitting diode group 200.

Be appreciated that because light-emitting diode group 200 itself has rectified action, so rectifier diode of the present invention 50 also can omit.

Be appreciated that current control circuit 100 of the present invention is not limited to control light-emitting diode group 200, also can be other load, like the LCD backlight lighting tube.

Current control circuit 100 of the present invention makes secondary coil TS electric current consistent all the time through the primary coil TP series connection with plural transformer, makes the brightness of light-emitting diode group 200 all consistent by this.Simultaneously, current control circuit 100 of the present invention is on the one hand because light-emitting diode group 200 forms electrical isolation, not fragile FET with FET; The on-off of leading that replaces through four FETs of individual control unit 20 controls on the other hand closes, and can keep plural transformer and light-emitting diode group 200 work simultaneously, fallen effectively design cost.

Claims

1. current control circuit; It is characterized in that: this current control circuit comprises full-wave rectification unit, control unit and plural transformer, and this full-wave rectification unit comprises four FETs, and the on-off of leading that four FETs of this control unit control replace in twos each other closes; Think that plural transformer provides alternating current; Each transformer includes primary coil and secondary coil, and the primary coil of this plural number transformer is connected successively, and each secondary coil and one group of load electrically connect.

2. current control circuit as claimed in claim 1 is characterized in that: the primary coil of said plural transformer is consistent with the turn ratio of secondary coil.

3. current control circuit as claimed in claim 1 is characterized in that: the polarity of the primary coil of said plural transformer is identical, and the polarity of secondary coil is identical.

4. current control circuit as claimed in claim 1 is characterized in that: the polarity of the primary coil of said plural transformer is identical, and the polarity of secondary coil is inequality.

5. current control circuit as claimed in claim 1 is characterized in that: the primary coil polarity of said plural transformer connects.

6. current control circuit as claimed in claim 1 is characterized in that: said current control circuit also comprises power supply, and the drain electrode of said positive source and two FETs electrically connects, and the source electrode of negative pole and two FETs electrically connects.

7. current control circuit as claimed in claim 1; It is characterized in that: said current control circuit also comprises plural rectifier diode; This rectifier diode is electrically connected between secondary coil and the load, converts DC pulse in order to the alternating current that secondary coil is transmitted.

8. current control circuit as claimed in claim 1; It is characterized in that: said primary coil comprises elementary end of the same name and elementary different name end; The electrical connecting wires of the end elementary of the same name of the primary coil of a said transformer and the source electrode of two FETs and drain electrode electrically connects, and the electrical connecting wires of the elementary different name end of the primary coil of another transformer and the source electrode of other two FETs and drain electrode electrically connects.