CN102724799A - Light emitting diode (LED) drive circuit and method without auxiliary winding - Google Patents
Light emitting diode (LED) drive circuit and method without auxiliary winding Download PDFInfo
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Abstract
The invention relates to the field of light emitting diodes, and discloses a light emitting diode (LED) drive circuit without an auxiliary winding and an LED drive method without the auxiliary winding. Grid voltage and source voltage of a power switch metal oxide semiconductor (MOS) transistor, which are detected by a voltage sampling network, are compared, and a current zero moment of a freewheel diode D1 is obtained according to a comparison result, so that the switch-off time of the freewheel diode D1 can be determined; average current of an LED load is detected, so constant current drive of an LED is realized; moreover, auxiliary winding is eliminated, so the design of an LED drive power supply is simplified, the size of the LED drive power supply is reduced, and the cost of LED drive power supply is reduced.
Description
Technical field
The present invention relates to the LED field, particularly need not the led drive circuit of auxiliary winding.
Background technology
Fig. 1 is traditional anti-rough schematic view that swashs led drive circuit.As shown in Figure 1, after capacitor C1 filtering produces a direct current power supply, resistance R 1 produces a low-voltage DC with capacitor C2 starts control chip to alternating current through the rectifier bridge rectification.Transformer has three windings, comprises a former limit winding, is connected between the drain electrode of DC power supply and power switch MOS transistor M1; A secondary winding; Be connected between sustained diode 1 and the secondary output capacitor C3, an auxiliary winding is connected between diode D2 and the circuit ground.Behind circuit start, auxiliary winding is the control chip power supply, and auxiliary simultaneously winding also provides output diode current over-zero and the information that detects the output voltage overvoltage of detecting.
In above-mentioned traditional anti-sharp led drive circuit, there are following two shortcomings:
The first, auxiliary winding, rectifier diode D2 and divider resistance increase system cost and volume.
The second, power supply and drive circuit loss are high, cause system effectiveness low.Power switch MOS transistor M1 drives through grid; When M1 closes; Gate charge is released to ground, and these gate charges all will lose in each cycle, makes chip for driving need bigger electric current to accomplish the driving of power switch MOS transistor M1; These electric current major parts are provided by auxiliary winding, cause certain loss.
Summary of the invention
The object of the present invention is to provide a kind of led drive circuit and method that need not auxiliary winding, make led drive circuit need not auxiliary winding, can simplify the design of LED driving power, dwindle LED driving power volume, reduce LED driving power cost.
For solving the problems of the technologies described above; Execution mode of the present invention provides a kind of led drive circuit that need not auxiliary winding; Comprise the first capacitor C1 that is connected between input direct voltage and the circuit ground; First resistance R 1 that is connected in series and the second capacitor C2, the voltage-stabiliser tube ZD1 that is connected in parallel with the second capacitor C2
Said led drive circuit also comprises: the first voltage sample network 202, the second voltage sample network 203, voltage sample network comparator 201;
The input of the said first voltage sample network 202 is connected in the grid of power switch MOS transistor M1, and output connects the first input end of said voltage sample network comparator 201, is used to detect the grid voltage of said power switch MOS transistor M1;
The input of the said second voltage sample network 203 is connected in the source electrode of power switch MOS transistor M1, and output connects second input of said voltage sample network comparator 201, is used to detect the source voltage of said power switch MOS transistor M1;
Said voltage sample network comparator 201 is used for the output valve of the comparison first voltage sample network and the second voltage sample network, and when the output generation saltus step as a result of said voltage sample network comparator, the current over-zero that obtains sustained diode 1 constantly.
Execution mode of the present invention also provides a kind of LED driving method that need not auxiliary winding, comprises following steps:
The grid voltage of detection power switch mos transistor;
Detect the source voltage of said power switch MOS transistor;
Detected said grid voltage and said source voltage are compared, obtain the current over-zero moment of sustained diode 1 according to comparative result.
Embodiment of the present invention in terms of existing technologies; The grid voltage and the source voltage of the power switch MOS transistor that network measuring obtains to voltage sample compare; Obtain the current over-zero moment of sustained diode 1 according to comparative result; Thereby confirm the turn-off time of sustained diode 1, detect the average current of LED load, realize the LED constant-current driving; Save auxiliary Winding Design, can simplify the design of LED driving power, dwindle LED driving power volume, reduce LED driving power cost.
In addition, said led drive circuit also comprises: the overvoltage protection logical circuit 206 that is used for said led drive circuit is carried out overvoltage protection;
An input of said overvoltage protection logical circuit 206 connects the output of said voltage sample network comparator; Another input connects minimum time of afterflow timing circuit 205; The ON time that detects sustained diode 1 when said overvoltage protection logical circuit 206 is during less than a preset minimum time of afterflow; The overvoltage protection logical circuit is triggered, and wherein, the ON time of said sustained diode 1 obtains according to the output result of said voltage sample network comparator.
Through above-mentioned simple overvoltage protection design, can when the led drive circuit output open circuit, prevent that output voltage is too high.
In addition; The grid of said power switch MOS transistor M1 is connected to the positive pole of the said first capacitor C1; Drain electrode is connected to the magnetic couplings device that is connected with the LED load; Source electrode is connected to the positive pole of feedback stream diode D2, and the negative pole of this feedback stream diode D2 is connected to the positive pole of the said first capacitor C1;
Said led drive circuit also comprises: source drive control circuit and switch control logic circuit 204;
Said source drive control circuit comprises low tension switch MOS transistor M2 and sampling resistor R2; The drain electrode of said low tension switch MOS transistor M2 is connected to the source electrode of power switch MOS transistor M1; The source electrode of said low tension switch MOS transistor M2 is connected to the end of said sampling resistor R2; The other end connection circuit ground of said sampling resistor R2, the grid of said low tension switch MOS transistor M2 is controlled by said switch control logic circuit 204;
An input of said switch control logic circuit 204 connects the output of said voltage sample network comparator 201; An input connects the source electrode of said sampling resistor R2 and said low tension switch MOS transistor M2, and output connects the grid of said low tension switch MOS transistor M2;
When the voltage on the said sampling resistor R2 reached pre-set threshold value, said switch control logic circuit 204 output signals were closed said low tension switch MOS transistor M2; Output generation saltus step as a result when said voltage sample network comparator; The current over-zero that obtains sustained diode 1 is during the moment; According to the average current of LED load, the said low tension switch MOS transistor of said switch control logic circuit 204 output signal controlling M2 opens constantly.
Source electrode through adopting the power switch MOS transistor drives; And supply power to control circuit through feedback stream diode from the source electrode of power switch MOS transistor; Can reduce the voltage on the supply access greatly, make the power consumption of drive circuit reduce, efficient is improved.
In addition, the said led drive circuit that need not auxiliary winding also comprises the source electrode that is connected in said power switch MOS transistor M1 and the 4th capacitor C4 between the drain electrode; Said the 4th capacitor is an external capacitive, and perhaps the 4th capacitor is the parasitic capacitance between power switch MOS transistor M1 source electrode and the drain electrode.This capacitor is behind sustained diode 1 current over-zero, and the voltage oscillation that M1 is drained is coupled to source electrode, to strengthen the input voltage amplitude of the second voltage sample network.
In addition, the said led drive circuit that need not auxiliary winding further comprises the 3rd resistance R 3 that is series at said feedback stream diode D2, with the restriction current spike.
In addition, the said magnetic couplings device that is connected with the LED load is transformer T1, and the secondary of said transformer T1 is formed the loop through sustained diode 1 and LED load, for led drive circuit provides the isolated form connected mode.
In addition, the said magnetic couplings device that is connected with the LED load is an inductance L 1, and said inductance L 1 is connected in parallel or is connected in series with said LED load.Multiple connected modes such as non-isolation type step-down or buck are provided for led drive circuit, are widely used.
Description of drawings
Fig. 1 is traditional anti-sharp LED constant-current drive circuit sketch map;
Fig. 2 is the sketch map according to the led drive circuit that need not auxiliary winding of first embodiment of the invention;
Fig. 3 is the voltage sample network diagram that constitutes according to resistance and resistance in the led drive circuit that need not auxiliary winding of first embodiment of the invention;
Fig. 4 is the voltage sample network diagram that constitutes according to resistance and electric capacity in the led drive circuit that need not auxiliary winding of first embodiment of the invention;
Fig. 5 is according to the voltage of each signaling point in the led drive circuit that need not auxiliary winding of first embodiment of the invention or electric current output sketch map;
Fig. 6 is the sketch map that is connected in parallel of the non-isolation type according to the led drive circuit that need not auxiliary winding of second embodiment of the invention and LED load;
Fig. 7 is the sketch map that is connected in series of the non-isolation type according to the led drive circuit that need not auxiliary winding of second embodiment of the invention and LED load.
Embodiment
For making the object of the invention, technical scheme and advantage clearer, will combine accompanying drawing that each execution mode of the present invention is carried out detailed elaboration below.Yet, persons of ordinary skill in the art may appreciate that in each execution mode of the present invention, in order to make the reader understand the application better many ins and outs have been proposed.But,, also can realize each claim of the application technical scheme required for protection even without these ins and outs with based on the many variations and the modification of following each execution mode.
First execution mode of the present invention relates to a kind of led drive circuit that need not auxiliary winding; The constant current LED drive circuit that need not auxiliary winding according to this execution mode has been made improvement to the type of drive and the control mode of existing drive circuit as shown in Figure 1, is illustrated in figure 2 as the sketch map of isolated form led drive circuit.With prior art similar be: at the parallelly connected first capacitor C1 between input power supply DC side and the circuit ground; First resistance R 1 that is connected in series and the second capacitor C2; With the voltage-stabiliser tube ZD1 that the second capacitor C2 is connected in parallel, the former limit winding of transformer T1 is connected between the drain electrode of input power supply DC side and power switch MOS transistor M1, and the secondary winding of transformer T1 is connected between LED load and the sustained diode 1; The 3rd capacitor C3 is a filter capacitor, is parallel to LED load two ends.
And different with prior art be: this execution mode adopts source drive and has cancelled auxiliary winding power supply.Specifically, led drive circuit of the present invention also comprises two voltage sample networks and voltage sample network comparator, and the current over-zero that is used for fly-wheel diode detects.
Wherein, The input of the first voltage sample network (being 202 voltage sample networks 1 among Fig. 2) is connected in the grid of power switch MOS transistor M1; Output connects the first input end of voltage sample network comparator 201, is used for the grid voltage of detection power switch mos transistor M1;
The input of the second voltage sample network (being 203 voltage sample networks 2 among Fig. 2) is connected in the source electrode of power switch MOS transistor M1; Output connects second input of voltage sample network comparator 201, is used for the source voltage of detection power switch mos transistor M1;
Voltage sample network comparator 201 is used for the output valve of the comparison first voltage sample network and the second voltage sample network, and when the output generation saltus step as a result of said voltage sample network comparator, the current over-zero that obtains sustained diode 1 constantly.
In addition, it will be understood by those skilled in the art that the voltage sample network can be by resistance and resistance; Perhaps electric capacity and electric capacity; Perhaps constituting of resistance and electric capacity, the sampling network for being made up of resistance and resistance as shown in Figure 3 is illustrated in figure 4 as the sampling network of resistance and electric capacity formation.
Because this execution mode adopts source drive; Therefore; The grid of power switch MOS transistor M1 is connected to the positive pole of the first capacitor C1; Drain electrode is connected to the magnetic couplings device (being the transformer T1 in this execution mode) that is connected with the LED load, and source electrode is connected to the positive pole of feedback stream diode D2, and the negative pole of this feedback stream diode D2 is connected to the positive pole of the first capacitor C1.
In addition, the led drive circuit of this execution mode also comprises source drive control circuit and switch control logic circuit.Wherein, The source drive control circuit comprises low tension switch MOS transistor M2 and sampling resistor R2; The drain electrode of this low tension switch MOS transistor M2 is connected to the source electrode of power switch MOS transistor M1; Source electrode is connected to the end of sampling resistor R2, the other end connection circuit ground of sampling resistor R2, and the grid of low tension switch MOS transistor M2 is controlled by switch control logic circuit 204; And an input of switch control logic circuit 204 connects the output of voltage sample network comparator 201, and an input connects the source electrode of sampling resistor R2 and low tension switch MOS transistor M2, and output connects the grid of low tension switch MOS transistor M2.
Specifically describe the course of work below in conjunction with Fig. 2 and Fig. 5 according to the led drive circuit of this execution mode:
When low tension switch MOS transistor M2 opens; Also conducting of power switch MOS transistor M1, the primary current of transformer T1 rises, the voltage on the sampling resistor R2 also rise (be among Fig. 5 CS of living in 501 constantly); When the voltage on the sampling resistor R2 reaches pre-set threshold value (CS of living in 502 constantly among Fig. 5); Switch control logic circuit 204 output signals are closed low tension switch MOS transistor M2, and power switch MOS transistor M1 also closes simultaneously, feedback stream diode D2 conducting; The source voltage that makes power switch MOS transistor M1 by clamp to VCC; The secondary sustained diode 1 beginning conducting of transformer T1 simultaneously, the secondary current of transformer T1 rise to peak value and begin to descend (being I_sec 502 moment of living among Fig. 5) very soon, when the electric current of sustained diode 1 drops to zero (I_sec of living in 503 constantly among Fig. 5); The drain voltage of power switch MOS transistor M1 also begins to descend; Because the drain electrode of M1 and the capacitive coupling effect of source electrode, the source voltage of power switch MOS transistor M1 also begin to descend simultaneously, this moment, the output valve of the first voltage sample network 202 and the second voltage sample network 203 compared in voltage sample network comparator 201; Obtain the turn-off time of sustained diode 1; Thereby system can detect the average current of LED load, controls opening constantly of low tension switch MOS transistor M2 through switch control logic circuit 204 again, thereby realizes the purpose of LED constant-current driving.
Can find out in conjunction with Fig. 2 and Fig. 5; The output voltage values of the first voltage sample network 202 is VCC; The output voltage values of the second voltage sample network 203 is OUT; When the OUT value by become greater than VCC less than the moment 503 of VCC be transformer T1 secondary current (I_sec among Fig. 5) zero passage constantly, just, the electric current of sustained diode 1 drops to zero; Therefore can adopt two the voltage sample networks and the voltage sample network comparator of this execution mode to detect this moment, thereby obtain the turn-off time of sustained diode 1.
In addition; What deserves to be mentioned is; The led drive circuit of this execution mode also comprises the overvoltage protection logical circuit 206 that is used for led drive circuit is carried out overvoltage protection, and an input of this overvoltage protection logical circuit 206 connects the output of voltage sample network comparator 201, and another input connects minimum time of afterflow timing circuit 205; The ON time that detects sustained diode 1 when overvoltage protection logical circuit 206 is during less than a preset minimum time of afterflow; The overvoltage protection logical circuit is triggered, and wherein, the ON time of sustained diode 1 obtains according to the output result of voltage sample network comparator.Through above-mentioned simple overvoltage protection design, can when the led drive circuit output open circuit, prevent that output voltage is too high.
It is pointed out that between the source electrode of power switch MOS transistor M1 and drain electrode can parallel connection the 4th capacitor C4, and the 4th capacitor can be external capacitive, the parasitic capacitance between also can using power switch MOS transistor source electrode and draining; This capacitor is behind sustained diode 1 current over-zero, and the voltage oscillation that M1 is drained is coupled to source electrode, to strengthen the input voltage amplitude of the second voltage sample network.But series resistance R3 on feedback stream diode D2 is with the restriction current spike.And the position of this feedback stream diode D2 and resistance R 3 can exchange.
In this execution mode, the secondary of transformer T1 is formed the loop through sustained diode 1 and LED load, and at LED load two ends parallel connection the 3rd capacitor C3, be used for filtering.Also can connect buffering at two ends, the former limit of transformer T1 and absorb circuit, this buffering absorbs circuit can be by diode, resistance, and electric capacity or voltage-stabiliser tube are formed.
Compared with prior art; The grid voltage and the source voltage of this execution mode power switch MOS transistor that network measuring obtains to voltage sample compare; Obtain the current over-zero moment of sustained diode 1 according to comparative result; Thereby confirm the turn-off time of sustained diode 1, detect the average current of LED load, realize the LED constant-current driving; Save auxiliary Winding Design, can simplify the design of LED driving power, dwindle LED driving power volume, reduce LED driving power cost.
Second execution mode of the present invention relates to a kind of led drive circuit that need not auxiliary winding.Second execution mode and first execution mode are roughly the same, and main distinction part is: in the first embodiment, the connected mode of led drive circuit and LED load is an isolated form.And in second embodiment of the invention, the connected mode of led drive circuit and LED load is a non-isolation type.
Specifically, the design of the source drive of the power switch MOS transistor of this execution mode, voltage sample network, Drive and Control Circuit and overvoltage crowbar is all identical with first execution mode, and its course of work is also identical, repeats no more at this.Different is: the magnetic couplings device that is connected with the LED load in the first embodiment is transformer T1; And the magnetic couplings device that is connected with the LED load in this execution mode is an inductance L 1; Wherein, Inductance L 1 can be connected in parallel (as shown in Figure 6) with the LED load, and (as shown in Figure 7) also can be connected in series.
Third embodiment of the invention relates to a kind of LED driving method that need not auxiliary winding, comprises following steps:
The grid voltage of detection power switch mos transistor;
The source voltage of detection power switch mos transistor;
Detected grid voltage and source voltage are compared, obtain current over-zero constantly according to comparative result.
In addition, the LED driving method of this execution mode also adopts source drive, and concrete grammar is:
The grid of power switch MOS transistor M1 is connected to the positive pole of the first capacitor C1, and drain electrode is connected to the magnetic couplings device that is connected with the LED load, and source electrode is connected to the positive pole that diode D2 is flowed in feedback;
The negative pole of feedback stream diode D2 is connected to the positive pole of the said first capacitor C1;
The drain electrode of low tension switch MOS transistor M2 is connected to the source electrode of said power switch MOS transistor M1;
The source electrode of low tension switch MOS transistor M2 is connected to the end of sampling resistor R2;
Other end connection circuit ground with sampling resistor R2;
The grid of low tension switch MOS transistor M2 is connected to the output of switch control logic circuit 204;
An input of switch control logic circuit 204 is connected to the output of voltage sample network comparator 201; An input is connected to the source electrode of sampling resistor R2 and low tension switch MOS transistor M2, and output connects the grid of low tension switch MOS transistor M2;
When the voltage on the sampling resistor R2 reached pre-set threshold value, switch control logic circuit 204 output signals were closed low tension switch MOS transistor M2; When the output generation saltus step as a result of voltage sample network comparator, the current over-zero that obtains sustained diode 1 is during the moment, and according to the average current of LED load, switch control logic circuit 204 output signal controlling low tension switch MOS transistor M2 open constantly.
In addition, after detected grid voltage and source voltage are compared, obtain the ON time of fly-wheel diode according to comparative result; If the ON time that obtains then can carry out overvoltage protection to led drive circuit less than a preset minimum time of afterflow.
Be not difficult to find that this execution mode is and the corresponding method embodiment of first execution mode, this execution mode can with the enforcement of working in coordination of first execution mode.The correlation technique details of mentioning in first execution mode is still effective in this execution mode, in order to reduce repetition, repeats no more here.Correspondingly, the correlation technique details of mentioning in this execution mode also can be applicable in first execution mode.
Persons of ordinary skill in the art may appreciate that above-mentioned each execution mode is to realize specific embodiment of the present invention, and in practical application, can be in form with on the details it is done various changes, and without departing from the spirit and scope of the present invention.
Claims (14)
1. led drive circuit that need not auxiliary winding; Comprise first capacitor (C1) that is connected between input direct voltage and the circuit ground; First resistance (R1) that is connected in series and second capacitor (C2), the voltage-stabiliser tube (ZD1) that is connected in parallel with second capacitor (C2); It is characterized in that said led drive circuit also comprises: the first voltage sample network (202), the second voltage sample network (203), voltage sample network comparator (201);
The input of the said first voltage sample network (202) is connected in the grid of power switch MOS transistor (M1); Output connects the first input end of said voltage sample network comparator (201), is used to detect the grid voltage of said power switch MOS transistor (M1);
The input of the said second voltage sample network (203) is connected in the source electrode of power switch MOS transistor (M1); Output connects second input of said voltage sample network comparator (201), is used to detect the source voltage of said power switch MOS transistor (M1);
Said voltage sample network comparator (201); The output valve that is used for the comparison first voltage sample network and the second voltage sample network; When the output generation saltus step as a result of said voltage sample network comparator, the current over-zero that obtains fly-wheel diode (D1) constantly.
2. the led drive circuit that need not auxiliary winding according to claim 1 is characterized in that, said voltage sample network is by resistance and resistance, perhaps electric capacity and electric capacity, and perhaps resistance and electric capacity constitutes.
3. the led drive circuit that need not auxiliary winding according to claim 1 is characterized in that said led drive circuit also comprises: the overvoltage protection logical circuit (206) that is used for said led drive circuit is carried out overvoltage protection;
An input of said overvoltage protection logical circuit (206) connects the output of said voltage sample network comparator; Another input connects minimum time of afterflow timing circuit (205); The ON time that detects fly-wheel diode (D1) when said overvoltage protection logical circuit (206) is during less than a preset minimum time of afterflow; The overvoltage protection logical circuit is triggered; Wherein, the ON time of said fly-wheel diode (D 1) obtains according to the output result of said voltage sample network comparator.
4. the led drive circuit that need not auxiliary winding according to claim 1; It is characterized in that; The grid of said power switch MOS transistor (M1) is connected to the positive pole of said first capacitor (C 1); Drain electrode is connected to the magnetic couplings device that is connected with the LED load, and source electrode is connected to the positive pole of feedback stream diode (D2), and the negative pole of this feedback stream diode (D2) is connected to the positive pole of said first capacitor (C 1);
Said led drive circuit also comprises: source drive control circuit and switch control logic circuit (204);
Said source drive control circuit comprises low tension switch MOS transistor (M2) and sampling resistor (R2); The drain electrode of said low tension switch MOS transistor (M2) is connected to the source electrode of power switch MOS transistor (M1); The source electrode of said low tension switch MOS transistor (M2) is connected to an end of said sampling resistor (R2); The other end connection circuit ground of said sampling resistor (R2), the grid of said low tension switch MOS transistor (M2) is controlled by said switch control logic circuit (204);
An input of said switch control logic circuit (204) connects the output of said voltage sample network comparator (201); An input connects the source electrode of said sampling resistor (R2) and said low tension switch MOS transistor (M2), and output connects the grid of said low tension switch MOS transistor (M2);
When the voltage on the said sampling resistor (R2) reached pre-set threshold value, said switch control logic circuit (204) output signal was closed said low tension switch MOS transistor (M2); Output generation saltus step as a result when said voltage sample network comparator; The current over-zero that obtains fly-wheel diode (D1) is during the moment; According to the average current of LED load, said switch control logic circuit (204) the output said low tension switch MOS transistor of signal controlling (M2) is opened constantly.
5. the led drive circuit that need not auxiliary winding according to claim 4 is characterized in that, the said led drive circuit that need not auxiliary winding also comprises the source electrode that is connected in said power switch MOS transistor M 1 and the 4th capacitor (C4) between the drain electrode; Said the 4th capacitor is an external capacitive, and perhaps the 4th capacitor is the parasitic capacitance between power switch MOS transistor (M1) source electrode and the drain electrode.
6. the led drive circuit that need not auxiliary winding according to claim 5 is characterized in that, further comprises the 3rd resistance (R3) that is series at said feedback stream diode (D2).
7. the led drive circuit that need not auxiliary winding according to claim 6 is characterized in that, further comprises the 3rd capacitor (C3) that is connected in parallel with the LED load.
8. the led drive circuit that need not auxiliary winding according to claim 7; It is characterized in that; The said magnetic couplings device that is connected with the LED load is transformer (T1), and the secondary of said transformer (T1) is formed the loop through fly-wheel diode (D1) and LED load.
9. the led drive circuit that need not auxiliary winding according to claim 8 is characterized in that, comprises that further the buffering that is connected in transformer (T1) two ends absorbs circuit, and this buffering absorbs circuit and is made up of diode, resistance, electric capacity or voltage-stabiliser tube.
10. the led drive circuit that need not auxiliary winding according to claim 7 is characterized in that the said magnetic couplings device that is connected with the LED load is inductance (L1), and said inductance (L1) is connected in parallel or is connected in series with said LED load.
11. the led drive circuit that need not auxiliary winding according to claim 1 is characterized in that, further comprises the rectifier bridge or the diode that are connected between alternating current input power supplying and the said filtering capacitor (C1).
12. a LED driving method that need not auxiliary winding is characterized in that, comprises following steps:
The grid voltage of detection power switch mos transistor;
Detect the source voltage of said power switch MOS transistor;
Detected said grid voltage and said source voltage are compared, obtain current over-zero constantly according to comparative result.
13. the LED driving method that need not auxiliary winding according to claim 12 is characterized in that, also comprises following steps:
After detected said grid voltage and said source voltage are compared, obtain the ON time of fly-wheel diode according to comparative result;
If the said ON time that obtains then carries out overvoltage protection to led drive circuit less than a preset minimum time of afterflow.
14. the LED driving method that need not auxiliary winding according to claim 12 is characterized in that, also comprises following steps:
The grid of said power switch MOS transistor (M1) is connected to the positive pole of first capacitor (C1), and drain electrode is connected to the magnetic couplings device that is connected with the LED load, and source electrode is connected to the positive pole that diode (D2) is flowed in feedback;
The negative pole of said feedback stream diode (D2) is connected to the positive pole of said first capacitor (C1);
The drain electrode of low tension switch MOS transistor (M2) is connected to the source electrode of said power switch MOS transistor (M1);
The source electrode of said low tension switch MOS transistor (M2) is connected to an end of sampling resistor (R2);
Other end connection circuit ground with said sampling resistor (R2);
The grid of said low tension switch MOS transistor (M2) is connected to the output of said switch control logic circuit (204);
An input of said switch control logic circuit (204) is connected to the output of said voltage sample network comparator (201); An input is connected to the source electrode of said sampling resistor (R2) and said low tension switch MOS transistor M2, and output connects the grid of said low tension switch MOS transistor (M2);
When the voltage on the said sampling resistor (R2) reached pre-set threshold value, said switch control logic circuit (204) output signal was closed said low tension switch MOS transistor (M2); Output generation saltus step as a result when said voltage sample network comparator; The current over-zero that obtains fly-wheel diode (D1) is during the moment; According to the average current of LED load, said switch control logic circuit (204) the output said low tension switch MOS transistor of signal controlling (M2) is open-minded.
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| CN2012102192524A CN102724799A (en) | 2012-06-28 | 2012-06-28 | Light emitting diode (LED) drive circuit and method without auxiliary winding |
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| CN103887770A (en) * | 2013-12-13 | 2014-06-25 | 上海新进半导体制造有限公司 | Overvoltage protective circuit in LED driving power supply without auxiliary winding |
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| CN103619095A (en) * | 2013-11-08 | 2014-03-05 | 苏州聚元微电子有限公司 | LED driving circuit |
| CN103887770B (en) * | 2013-12-13 | 2017-10-24 | 上海新进半导体制造有限公司 | A kind of overvoltage crowbar in LED drive power without assists winding |
| CN103731049B (en) * | 2013-12-13 | 2017-05-31 | 上海新进半导体制造有限公司 | Current zero-crossing point detects circuit and method, drive circuit and method, Switching Power Supply |
| CN103887770A (en) * | 2013-12-13 | 2014-06-25 | 上海新进半导体制造有限公司 | Overvoltage protective circuit in LED driving power supply without auxiliary winding |
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| CN103746543A (en) * | 2013-12-31 | 2014-04-23 | 广东威灵电机制造有限公司 | Current detection device of bridge-type driving circuit |
| CN103746543B (en) * | 2013-12-31 | 2016-07-06 | 广东威灵电机制造有限公司 | A kind of current sensing means of bridge drive circuit |
| CN103715918A (en) * | 2014-01-09 | 2014-04-09 | 惠州天能源科技有限公司 | Digitally-controlled power converter |
| CN104602390A (en) * | 2014-01-14 | 2015-05-06 | 深圳市稳先微电子有限公司 | Dual-winding single-stage primary feedback LED (Light Emitting Diode) lamp drive circuit |
| CN104602390B (en) * | 2014-01-14 | 2018-10-19 | 深圳市稳先微电子有限公司 | The LED lamp drive circuit of double winding single-stage primary side feedback |
| CN103986335A (en) * | 2014-05-23 | 2014-08-13 | 浙江大学 | Flyback type LED constant-current driver based on structure without auxiliary winding |
| CN103986335B (en) * | 2014-05-23 | 2016-03-02 | 浙江大学 | A kind of based on the inverse-excitation type LED constant-current driver without auxiliary winding construction |
| CN104093254A (en) * | 2014-07-22 | 2014-10-08 | 矽力杰半导体技术(杭州)有限公司 | LED overvoltage detection circuit, drive circuit and LED illuminating system |
| CN104411035A (en) * | 2014-10-16 | 2015-03-11 | 宁波芯辰微电子有限公司 | LED drive circuit without auxiliary winding for power supply |
| CN104360143B (en) * | 2014-12-04 | 2017-08-08 | 杰华特微电子（杭州）有限公司 | Current zero-crossing point detects circuit and method, load voltage detection circuit and method |
| CN104360143A (en) * | 2014-12-04 | 2015-02-18 | 杰华特微电子（杭州）有限公司 | Load zero crossing point detection circuit and method and load voltage detection circuit and method |
| CN104410252A (en) * | 2014-12-11 | 2015-03-11 | 矽力杰半导体技术(杭州)有限公司 | Source electrode drive circuit and controlling method thereof |
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| CN107612107A (en) * | 2017-08-23 | 2018-01-19 | 成都芯源系统有限公司 | Power supply voltage generating circuit and integrated circuit thereof |
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