CN106602905B - LED driving circuit - Google Patents

LED driving circuit Download PDF

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Publication number
CN106602905B
CN106602905B CN201710117591.4A CN201710117591A CN106602905B CN 106602905 B CN106602905 B CN 106602905B CN 201710117591 A CN201710117591 A CN 201710117591A CN 106602905 B CN106602905 B CN 106602905B
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synchronous rectifier
synchronous
circuit
control circuit
power supply
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CN106602905A (en
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姜德来
梅进光
王元
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Inventronics Hangzhou Co Ltd
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Inventronics Hangzhou Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0006—Arrangements for supplying an adequate voltage to the control circuit of converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0038—Circuits or arrangements for suppressing, e.g. by masking incorrect turn-on or turn-off signals, e.g. due to current spikes in current mode control

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)
  • Rectifiers (AREA)

Abstract

The invention provides an LED driving circuit, which comprises: a high-frequency pulse current source, an isolation transformer and a secondary side rectifying circuit; the secondary rectifying circuit comprises a first synchronous rectifying tube, a second synchronous rectifying tube, a first driving control circuit, a second driving control circuit and a capacitor; the capacitor is used for inhibiting reverse voltage spikes of the first synchronous rectifying tube and the second synchronous rectifying tube and supplying power to the first driving control circuit; the second drive control circuit is powered by a direct current power supply. The LED driving circuit can solve the problems of large on-state loss and power supply of the driving control circuit of the synchronous rectifying tube.

Description

LED driving circuit
Technical Field
The invention relates to the technical field of LED driving circuits, in particular to an LED driving circuit.
Background
A common switching power supply driven by a dc load includes: the high-frequency pulse current source, the isolation transformer and the rectifying circuit are arranged on the secondary side of the isolation transformer. Wherein the high-frequency pulse current source is controlled by a high-frequency switch; the secondary side rectifying circuit is in the form of a full-bridge rectifying circuit or a half-bridge rectifying circuit and the like.
In the prior art, the secondary rectifying circuit adopts diodes as rectifying devices, but the on-state loss of the diodes is large under the condition of large output current due to high conduction voltage drop of the diodes, so that the efficiency of the circuit in the switching power supply is low.
The problem of large on-state loss is solved by introducing the synchronous rectifying tube as the rectifying device, but the synchronous rectifying tube needs a drive control circuit for working, and the drive control circuit cannot be powered by using the same direct current power supply source due to the difference of reference ends.
Therefore, how to provide a driving circuit capable of solving the problem of large on-state loss and the problem of power supply of all driving control circuits is a problem to be solved by those skilled in the art.
Disclosure of Invention
In order to solve the technical problems, the invention provides an LED driving circuit, which solves the problem of large on-state loss caused by a diode serving as a rectifying device and solves the power supply problem of different driving control circuits.
In order to achieve the above purpose, the present invention provides the following technical solutions:
an LED driving circuit comprising: a high-frequency pulse current source, an isolation transformer and a secondary side rectifying circuit;
wherein, the isolation transformer includes: a first winding, a second winding and a third winding; the high-frequency pulse current source is connected with the first winding;
the secondary side rectifying circuit includes: the first synchronous rectifying tube, the second synchronous rectifying tube, the first driving control circuit, the second driving control circuit and the capacitor; the capacitor is used for inhibiting the reverse voltage spike of the first synchronous rectifying tube and the second synchronous rectifying tube;
the homonymous end of the second winding, the source electrode of the first synchronous rectifying tube and the reference end of the first drive control circuit are respectively connected with the first end of the capacitor; the same-name end of the third winding, the drain electrode of the second synchronous rectifying tube and the power supply end of the first drive control circuit are respectively connected with the second end of the capacitor, and the capacitor is used for supplying power to the first drive control circuit;
the drain electrode of the first synchronous rectifying tube is connected with the synonym end of the third winding and is used as the output positive end of the LED driving circuit; the synonym end of the second winding and the reference end of the second drive control circuit are connected with the source electrode of the second synchronous rectifying tube and serve as the output ground end of the LED drive circuit;
the driving end of the first driving control circuit is connected with the grid electrode of the first synchronous rectifying tube; the driving end of the second driving control circuit is connected with the grid electrode of the second synchronous rectifying tube;
the power supply end of the second drive control circuit is connected with a direct current power supply, and the grounding end of the direct current power supply is a reference end of the second drive control circuit and is used for supplying power to the second drive control circuit.
Preferably, the first end of the capacitor is a low potential end, and the second end of the capacitor is a high potential end.
Preferably, the first driving control circuit includes: the first processing unit and the first detection unit;
the first detection unit is connected with the first synchronous rectifying tube in parallel and is used for detecting the source-drain voltage of the first synchronous rectifying tube and sending a detection result to the first processing unit;
the first processing unit is used for generating a driving signal according to the detection result; and transmitting the driving signal to the gate of the first synchronous rectifier tube;
the second drive control circuit includes: the second processing unit and the second detection unit;
the second detection unit is connected with the second synchronous rectifying tube in parallel and is used for detecting the source-drain voltage of the second synchronous rectifying tube and sending a detection result to the second processing unit;
the second processing unit is used for generating a driving signal according to the detection result; and transmitting the driving signal to the grid electrode of the second synchronous rectifying tube.
Preferably, when the first detection unit detects that the source-drain voltage of the first synchronous rectifier tube is a forward conduction voltage, the first processing unit generates a first conduction driving signal; when the first detection unit detects that the source-drain voltage forward voltage drop of the first synchronous rectifying tube is zero or is reverse voltage drop, the first processing unit generates a first turn-off driving signal;
when the second detection unit detects that the source-drain voltage of the second synchronous rectifier tube is forward conduction voltage, the second processing unit generates a second conduction driving signal; and when the second detection unit detects that the source-drain voltage forward voltage drop of the second synchronous rectifying tube is zero or the reverse voltage drop, the second processing unit generates a second turn-off driving signal.
Preferably, the first synchronous rectifier tube and the first drive control circuit are integrated in a first synchronous rectifier;
the first synchronous rectifier includes: a source electrode, a drain electrode and a power supply end; the source electrode of the first synchronous rectifier is the source electrode of the first synchronous rectifier; the drain electrode of the first synchronous rectifier is the drain electrode of the first synchronous rectifier, and the power supply end of the first synchronous rectifier is the power supply end of the first drive control circuit;
or the second synchronous rectifier tube and the second driving control circuit are integrated in a second synchronous rectifier;
the second synchronous rectifier includes: a source electrode, a drain electrode and a power supply end; the source electrode of the second synchronous rectifier is the source electrode of the second synchronous rectifier; the drain electrode of the second synchronous rectifier is the drain electrode of the second synchronous rectifier, and the power supply end of the second synchronous rectifier is the power supply end of the second drive control circuit.
Preferably, the capacitor supplies power to the first synchronous rectifier through a power supply end of the first synchronous rectifier;
the direct current power supply supplies power to the second synchronous rectifier through a power supply end of the second synchronous rectifier.
Preferably, the power supply end of the first synchronous rectifier is connected with the second end of the capacitor through a voltage matching circuit.
Preferably, the voltage matching circuit is a voltage stabilizing circuit.
Preferably, the direct current power supply is an auxiliary source circuit.
Preferably, the high-frequency pulse current source is an LLC circuit topology or an LCC circuit topology.
According to the technical scheme, the LED driving circuit provided by the invention replaces the diode of the rectifying component in the prior art by arranging the first synchronous rectifying tube and the second synchronous rectifying tube, so that the problem of high on-state loss caused by the diode serving as the rectifying component is solved, and the first driving control circuit and the second driving control circuit are used for conducting the first synchronous rectifying tube and the second synchronous rectifying tube to enable current to flow from the source electrode to the drain electrode, and the body diode in the first synchronous rectifying tube and the body diode in the second synchronous rectifying tube is not used, so that loss is not generated on the body diode.
And because the turn-off process of the first synchronous rectifier tube or the second synchronous rectifier tube can generate larger reverse voltage peak, the capacitor is arranged to restrain the reverse voltage peak of the first synchronous rectifier tube and the second synchronous rectifier tube.
Meanwhile, the capacitor supplies power for the first drive control circuit, the direct current power supply supplies power for the second drive control circuit, and the power supply problem of different drive control circuits is solved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a structure of an LED driving circuit in the prior art;
fig. 2 is a schematic structural diagram of an LED driving circuit according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a driving control circuit according to an embodiment of the present invention;
fig. 4 is a schematic waveform diagram of source-drain voltages of a synchronous rectifier according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a synchronous rectifier according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of another synchronous rectifier according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of another LED driving circuit according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, fig. 1 is a schematic diagram of an LED driving circuit according to the prior art. In the prior art, the secondary rectifying circuit adopts diodes as rectifying devices, but the on-state loss of the diodes is large under the condition of large output current due to high conduction voltage drop of the diodes, so that the efficiency of the circuit in the switching power supply is low.
The problem of large on-state loss is solved by introducing the synchronous rectifying tube as the rectifying device, but the synchronous rectifying tube needs a drive control circuit for working, and the drive control circuit cannot be powered by using the same direct current power supply source due to the difference of reference ends.
Therefore, how to provide a driving circuit capable of solving the problem of large on-state loss and the problem of power supply of all driving control circuits is a problem to be solved by those skilled in the art.
In order to solve the above-described problems, the present invention provides an LED driving circuit including: a high-frequency pulse current source, an isolation transformer and a secondary side rectifying circuit;
wherein, the isolation transformer includes: a first winding, a second winding and a third winding; the high-frequency pulse current source is connected with the first winding;
the secondary side rectifying circuit includes: the first synchronous rectifying tube, the second synchronous rectifying tube, the first driving control circuit, the second driving control circuit and the capacitor; the capacitor is used for inhibiting the reverse voltage spike of the first synchronous rectifying tube and the second synchronous rectifying tube;
the homonymous end of the second winding, the source electrode of the first synchronous rectifying tube and the reference end of the first drive control circuit are respectively connected with the first end of the capacitor; the same-name end of the third winding, the drain electrode of the second synchronous rectifying tube and the power supply end of the first drive control circuit are respectively connected with the second end of the capacitor, and the capacitor is used for supplying power to the first drive control circuit;
the drain electrode of the first synchronous rectifying tube is connected with the synonym end of the third winding and is used as the output positive end of the LED driving circuit; the synonym end of the second winding and the reference end of the second drive control circuit are connected with the source electrode of the second synchronous rectifying tube and serve as the output ground end of the LED drive circuit;
the driving end of the first driving control circuit is connected with the grid electrode of the first synchronous rectifying tube; the driving end of the second driving control circuit is connected with the grid electrode of the second synchronous rectifying tube;
the power supply end of the second drive control circuit is connected with a direct current power supply, and the grounding end of the direct current power supply is a reference end of the second drive control circuit and is used for supplying power to the second drive control circuit.
It should be noted that the homonymous terminal and the heteronymous terminal are only for convenience of description, but not limited to, the homonymous terminal and the heteronymous terminal of the second winding and the third winding can be interchanged at the same time, that is, the heteronymous terminal of the second winding becomes the homonymous terminal; the homonym terminal becomes a heteronym terminal. Meanwhile, the different-name end of the third winding also becomes the same-name end; the homonym terminal becomes a heteronym terminal.
It should be noted that, the dc power supply in the present application may be a dc power supply generated in the LED driving circuit, or may be a dc power supply externally input to the LED driving circuit, and the dc power supply is not limited in the present application.
It should be noted that, in this application, the term "power … …" refers to that the capacitor "powers" the first driving control circuit, or that the capacitor powers the first synchronous rectifier, or that the dc power supply powers the second driving control circuit, or the like: to which a direct current power supply is provided to assist in its operation.
The first synchronous rectifying tube and the second synchronous rectifying tube are arranged to replace a free wheeling diode in the prior art, so that the problem of high on-state loss caused by the fact that the diode is used as a rectifying component is solved, and the first driving control circuit and the second driving control circuit are used for conducting the first synchronous rectifying tube and the second synchronous rectifying tube, so that current flows from a source electrode to a drain electrode, does not pass through a body diode in the first synchronous rectifying tube and the second synchronous rectifying tube, and further cannot generate loss on the body diode.
And because the turn-off process of the first synchronous rectifier tube or the second synchronous rectifier tube can generate larger reverse voltage peak, the capacitor is arranged to restrain the reverse voltage peak of the first synchronous rectifier tube and the second synchronous rectifier tube.
Meanwhile, the capacitor supplies power for the first drive control circuit, the direct current power supply supplies power for the second drive control circuit, and the power supply sources of all the drive control circuits are solved.
In order to better explain the embodiments of the present invention, the embodiments provided by the present invention are specifically explained below with reference to the figures.
Referring to fig. 2, fig. 2 is a schematic structural diagram of an LED driving circuit according to an embodiment of the present invention.
The LED driving circuit includes: a high-frequency pulse current source 23, an isolation transformer T and a secondary side rectifying circuit;
the isolation transformer T includes: a first winding S1, a second winding S2, and a third winding S3; and the high-frequency pulse current source 23 is connected with the first winding S1;
the high frequency pulse current source 23 is implemented by various switching topologies such as LLC or LCC, and is an ac source, but is not limited in the present invention.
The secondary side rectifying circuit includes: a first synchronous rectifier Q1, a second synchronous rectifier Q2, a first drive control circuit 21, a second drive control circuit 22, and a capacitor C1; the capacitor C1 is configured to suppress reverse voltage spikes of the first synchronous rectifier Q1 and the second synchronous rectifier Q2;
wherein, the homonymous terminal a of the second winding S2, the source VS of the first synchronous rectifier Q1, and the reference terminal GND1 of the first drive control circuit 21 are respectively connected with the first terminal of the capacitor C1;
the homonymous terminal C of the third winding S3, the drain VD of the second synchronous rectifier Q2, and the power supply terminal VCC1 of the first drive control circuit 21 are respectively connected with the second terminal of the capacitor C1, and the capacitor C1 is used for supplying power to the first drive control circuit 21;
the drain VD of the first synchronous rectifier Q1 is connected with the synonym end D of the third winding S3 and is used as an output positive end Vo of the LED driving circuit;
the synonym terminal B of the second winding S2 and the reference terminal GND2 of the second drive control circuit 22 are connected to the source VS of the second synchronous rectifier Q2 and serve as the output ground GND of the LED drive circuit;
the driving end of the first driving control circuit 21 is connected with the grid VG of the first synchronous rectifying tube; the driving end of the second driving control circuit 22 is connected with the grid VG of the second synchronous rectifying tube; that is, the first synchronous rectifier Q1 and the second synchronous rectifier Q2 both need corresponding driving control circuits to drive;
the power supply end VCC2 of the second drive control circuit 22 is connected to a dc power supply, and the ground end of the dc power supply is a reference end of the second drive control circuit 22, i.e. is connected to the output ground end GND, for supplying power to the second drive control circuit 22. Note that, the dc power supply is not shown in fig. 2; and the homonymous end and the heteronymous end of the two windings S2 and the third winding S3 can be changed at the same time, namely A, C is the heteronymous end and B, D is the homonymous end.
As shown in fig. 2, since the source VS of the first synchronous rectifier Q1 is not the output ground GND of the LED driving circuit, the reference point of the driving signal of the first synchronous rectifier Q1 is not the output ground GND of the LED driving circuit, but the source VS of the first synchronous rectifier Q1, and the dc power supply source with the ground connected to the output ground cannot supply the power to the first driving control circuit 21. Therefore, the present invention supplies power to the first drive control circuit 21 through the capacitor C1; the specific working principle is as follows:
when the homonymous end A of the second winding S2 and the homonymous end C of the third winding are positive, the second winding S2, the first synchronous rectifier Q1 and the load Cout form a loop, and the second winding S2 supplies power to the load Cout; the third winding S3, the capacitor C1 and the first synchronous rectifying tube Q1 form a loop, and the third winding S3 charges the capacitor C1.
When the synonym end B of the second winding S2 and the synonym end D of the third winding are positive, the second winding S2, the second synchronous rectifying tube Q2 and the capacitor C1 form a loop, and the second winding S2 charges the capacitor C1; the third winding S3, the load Cout and the second synchronous rectifying tube Q2 form a loop, and the third winding S3 supplies power to the load Cout.
Therefore, the first end of the capacitor C1 is a low potential end, and the second end of the capacitor C1 is a high potential end, so that the power supply end VCC1 of the first drive control circuit 21 is connected to the second end of the capacitor C1, and the reference end GND1 of the first drive control circuit 21 is connected to the first end of the capacitor C1, thereby achieving the purpose of supplying power to the first drive control circuit 21 by the capacitor C1.
As described above, the capacitor C1 is also used to suppress reverse voltage spikes of the first synchronous rectifier Q1 and the second synchronous rectifier Q2.
The specific principle of suppressing reverse voltage spike is as follows: since the parasitic capacitance of the first rectifying tube Q1 and the leakage inductance of the second winding S2 will resonate after the first rectifying tube Q1 is turned on to off when the capacitor C1 is not connected in the LED driving circuit, and the resonant energy will cause the first rectifying tube Q1 to generate a very high reverse voltage spike if all the resonant energy acts on the first rectifying tube Q1.
Similarly, after the second synchronous rectifying tube Q2 is turned on to off, the parasitic capacitance of the second synchronous rectifying tube Q2 and the leakage inductance of the third winding S3 will resonate, and if all the resonance energy acts on the second synchronous rectifying tube Q2, the second synchronous rectifying tube Q2 will generate a very high reverse voltage spike.
When the capacitor C1 is connected to the LED driving circuit, the capacitor C1 absorbs part of the resonance energy, so as to inhibit the reverse voltage spikes of the first synchronous rectifier Q1 and the second synchronous rectifier Q2.
Further, the direct current power supply is an auxiliary source circuit of the LED driving circuit, and the grounding end of the auxiliary source circuit is connected with the output ground end GND. As shown in fig. 2, with respect to the second synchronous rectifier Q2, the output ground GND of the LED driving circuit is the source VS of the second synchronous rectifier Q2, the source VS of the second synchronous rectifier Q2 is connected to the output ground GND of the LED driving circuit, and the reference terminal GND2 of the second driving control circuit 22 is connected to the output ground GND of the LED driving control circuit, so that the power supply source of the second driving control circuit 22 may be an auxiliary source circuit of the LED driving circuit, so that the power supply terminal VCC2 of the second driving control circuit 22 is connected to an auxiliary source circuit in the LED driving circuit for obtaining a power supply.
As is apparent from the above description, the LED driving circuit solves the problem of large on-state loss caused by the use of the diode as the rectifying part, and solves the power supply problem of all driving control circuits by using the synchronous rectifying tube as the rectifying part instead of the diode.
Based on the above embodiments, referring to fig. 3, fig. 3 is a schematic structural diagram of a driving control circuit according to an embodiment of the present invention. Wherein the first driving control circuit 21 includes: a first processing unit 32 and a first detecting unit 31; the first detection circuit 31 is connected in parallel with the first synchronous rectifier Q1, and is configured to detect a source-drain voltage of the first synchronous rectifier Q1, and send the detection result to the first processing unit 32; the first processing unit 32 is configured to generate a driving signal according to a detection result of the first detecting unit 31, and send the driving signal to the first synchronous rectifying tube Q1, specifically, to the gate VG of the first synchronous rectifying tube Q1;
the second drive control circuit 22 includes: the second processing unit and the second detection unit; the second detection circuit is connected with the second synchronous rectifying tube in parallel and is used for detecting the source-drain voltage of the second synchronous rectifying tube and sending the detection result to the second processing unit; the second processing unit is configured to generate a driving signal according to a detection result of the second detection unit, and send the driving signal to the second synchronous rectifying tube, specifically, to a gate of the second synchronous rectifying tube.
Taking the first synchronous rectifier Q1 as an example, as shown in fig. 3, when the first detecting unit 31 detects that the source-drain voltage of the first synchronous rectifier Q1 is a forward conduction voltage (i.e., the body diode D1 of the first synchronous rectifier Q1 is forward conducting), the first processing unit 32 generates a first on driving signal to turn on the first synchronous rectifier Q1, and when the first detecting unit 31 detects that the source-drain voltage of the first synchronous rectifier Q1 is zero in forward voltage drop (i.e., no current flows through the first synchronous rectifier Q1) or that the source-drain voltage is a reverse voltage drop (i.e., the drain voltage of the first synchronous rectifier Q1 is higher than the source), the first processing unit 32 generates a first off driving signal.
Since the current I in the circuit flows from the source VS to the drain VD through the on-resistance of the first synchronous rectifier Q1 and does not pass through the body diode D1 after the first synchronous rectifier Q1 is turned on, no loss occurs in the body diode D1. This on-resistance is not shown in fig. 3.
Since the current I will pass through the on-resistance Rdson, the loss qr=i due to the on-resistance 2 * Rdson, if current I passes through body diode D1, loss qd=i×vd generated by body diode D1. However, since the on-resistance Rdson of the first synchronous rectifier Q1 has a very small resistance value, vd of the body diode is generally fixed at 0.7V. Therefore, qr is much smaller than Qd, so to speakIt is clear that using the first synchronous rectifier Q1 as a rectifier device can improve circuit efficiency.
Referring to fig. 4, fig. 4 is a schematic waveform diagram of source-drain voltages of a synchronous rectifier according to an embodiment of the present invention. As shown in the figure, in the period of 0-t1, the synonym end B of the second winding S2 and the synonym end D of the third winding S3 are positive, and the second synchronous rectifying tube Q2 is turned on, so that the second winding S2, the second synchronous rectifying tube Q2 and the capacitor C1 form a path; the third winding S3, the load Cout and the second synchronous rectifying tube Q2 form a passage; the source-drain voltage vsd= -2 x Vo of the first synchronous rectifier Q1, where Vo is the voltage across the capacitor C1.
In the time period of t1-t2, the synonym end B of the second winding S2 and the synonym end D of the third winding S3 are negative, and the synonym end is positive; at time t1, the source-drain voltage Vsd of the first synchronous rectifier Q1 is changed from-2×vo to the on-voltage drop Vd1 of the body diode D1, that is, when the first detection unit 31 detects that the source-drain voltage Vsd of the first synchronous rectifier Q1 is changed from negative voltage (-2×vo) to the forward on-voltage (Vd 1), a conduction control signal is sent to the first processing unit 32, and the first processing unit 32 generates a first conduction driving signal according to the conduction control signal, so that the first synchronous rectifier Q1 is turned on, and after the first synchronous rectifier Q1 is turned on, the source-drain voltage Vsd of the first synchronous rectifier Q1 is changed to the voltage drop Von of the on-resistance after the current flows through the first synchronous rectifier Q1. At time t2, the positive and negative directions of the second winding S2 and the third winding S3 are changed again, the source-drain voltage Vsd of the first synchronous rectifier Q1 is changed to-2 x vo again, at this time, the first detecting unit 31 sends a turn-off control signal, and the first processing unit 32 generates a first turn-off driving signal according to the turn-off control signal, so that the first synchronous rectifier Q1 is turned off.
For the second synchronous rectifying tube Q2, when the second detection unit detects that the source-drain voltage of the second synchronous rectifying tube Q2 is a forward conduction voltage, the second processing unit generates a second conduction driving signal; when the second detection unit detects that the forward voltage drop of the source-drain voltage of the second synchronous rectifier Q2 is zero (i.e. no current flows through the second synchronous rectifier Q1) or the source-drain voltage is a reverse voltage drop (i.e. the drain voltage of the second synchronous rectifier Q1 is higher than the source), the second processing unit generates a second turn-off driving signal.
Note that, the states of the first synchronous rectifier Q1 and the second synchronous rectifier Q2 are opposite, when the first synchronous rectifier Q1 is turned on, the second synchronous rectifier Q2 is turned off, and when the first synchronous rectifier Q1 is turned off, the second synchronous rectifier Q2 is turned on.
Optionally, in an embodiment of the present invention, referring to fig. 5, fig. 5 is a schematic structural diagram of a synchronous rectifier according to an embodiment of the present invention. The first synchronous rectifier Q1 and the first driving control circuit 21 are integrated in a first synchronous rectifier TQ1, that is, the first synchronous rectifier Q1, the first processing unit 32 and the first detecting unit 31 are integrated in the first synchronous rectifier TQ 1; the source VS of the first synchronous rectifier Q1 is connected to the reference terminal GND1 of the first driving control circuit 21.
The source S of the first synchronous rectifier is the source VS of the first synchronous rectifier; the drain D of the first synchronous rectifier is the drain VD of the first synchronous rectifier, and the power supply terminal VCC of the first synchronous rectifier is the power supply terminal VCC1 of the first driving control circuit.
That is, the first synchronous rectifier Q1 and the first driving control circuit 21 are used as an integrated circuit, which is defined as the first synchronous rectifier TQ1, and the first synchronous rectifier TQ1 includes: the source S, drain D and supply terminal VCC are referred to as a three terminal synchronous rectifier.
Referring to fig. 6, fig. 6 is a schematic structural diagram of another synchronous rectifier according to an embodiment of the present invention. The second synchronous rectifying tube Q2 and the second driving control circuit 22 are integrated in a second synchronous rectifier TQ2, that is, the second synchronous rectifying tube Q2, the second processing unit and the second detecting unit are integrated in the second synchronous rectifier TQ 2; the source VS of the second synchronous rectifier Q2 is connected to the reference terminal GND2 of the second driving control circuit 22.
The source S of the second synchronous rectifier is the source VS of the second synchronous rectifier; the drain D of the second synchronous rectifier is the drain VD of the second synchronous rectifier, and the power supply terminal VCC of the second synchronous rectifier is the power supply terminal VCC2 of the second driving control circuit.
That is, the second synchronous rectifier Q2 and the second driving control circuit 22 are used as an integrated circuit, which is defined as the second synchronous rectifier TQ2, and the second synchronous rectifier TQ2 includes: the source S, drain D and supply terminal VCC are referred to as a three terminal synchronous rectifier.
Referring to fig. 7, fig. 7 is a schematic structural diagram of another LED driving circuit according to an embodiment of the present invention. The source S of the first synchronous rectifier TQ1 is connected with the first end of the capacitor C1; the power supply end VCC of the first synchronous rectifier TQ1 is connected to the second end of the capacitor C1, and is used for obtaining a power supply.
It should be noted that, because the voltage vc1=vo at two ends of the capacitor C1, if the magnitude of Vo matches with the supply voltage of the first synchronous rectifier TQ1, the supply end VCC of the first synchronous rectifier TQ1 is directly connected with the second end, i.e. the high-potential end, of the capacitor C1; if the Vo is not matched with the power supply voltage of the first synchronous rectifier TQ1, the first synchronous rectifier TQ1 is connected with the second end, namely the high potential end, of the capacitor C1 through a voltage matching circuit; when Vo is greater than the power supply voltage of the first synchronous rectifier TQ1, the voltage matching circuit is a voltage stabilizing circuit, and the common voltage stabilizing circuit is a three-terminal voltage stabilizing circuit.
As shown in fig. 7, the source S of the second synchronous rectifier TQ2 is connected to the output ground GND of the LED driving circuit, and the power supply end VCC of the second synchronous rectifier TQ2 is connected to a dc power supply in the LED driving circuit, where the dc power supply is an auxiliary source circuit. The dc power supply is not shown in fig. 7.
As can be seen from the above description, the LED driving circuit provided by the present invention replaces the diode of the rectifying component in the prior art by providing the first synchronous rectifying tube and the second synchronous rectifying tube, so that the problem of large on-state loss caused by the diode as the rectifying component is solved, and the first driving control circuit and the second driving control circuit are used for controlling the first synchronous rectifying tube and the second synchronous rectifying tube, when the first synchronous rectifying tube or the second synchronous rectifying tube is turned on, the current flowing from the source to the drain does not pass through the body diode in the first synchronous rectifying tube or the second synchronous rectifying tube, and further, loss is not generated on the body diode.
And because the turn-off process of the first synchronous rectifier tube or the second synchronous rectifier tube can generate larger reverse voltage peak, the capacitor is arranged to restrain the reverse voltage peak of the first synchronous rectifier tube and the second synchronous rectifier tube.
Meanwhile, the capacitor supplies power for the first drive control circuit, the direct current power supply supplies power for the second drive control circuit, and the power supply sources of all the drive control circuits are solved.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. An LED driving circuit, comprising: a high-frequency pulse current source, an isolation transformer and a secondary side rectifying circuit;
wherein, the isolation transformer includes: a first winding, a second winding and a third winding; the high-frequency pulse current source is connected with the first winding;
the secondary side rectifying circuit includes: the first synchronous rectifying tube, the second synchronous rectifying tube, the first driving control circuit, the second driving control circuit and the capacitor; the capacitor is used for inhibiting the reverse voltage spike of the first synchronous rectifying tube and the second synchronous rectifying tube;
the homonymous end of the second winding, the source electrode of the first synchronous rectifying tube and the reference end of the first drive control circuit are respectively connected with the first end of the capacitor; the same-name end of the third winding, the drain electrode of the second synchronous rectifying tube and the power supply end of the first drive control circuit are respectively connected with the second end of the capacitor, and the capacitor is used for supplying power to the first drive control circuit;
the drain electrode of the first synchronous rectifying tube is connected with the synonym end of the third winding and is used as the output positive end of the LED driving circuit; the synonym end of the second winding and the reference end of the second drive control circuit are connected with the source electrode of the second synchronous rectifying tube and serve as the output ground end of the LED drive circuit;
the driving end of the first driving control circuit is connected with the grid electrode of the first synchronous rectifying tube; the driving end of the second driving control circuit is connected with the grid electrode of the second synchronous rectifying tube;
the power supply end of the second drive control circuit is connected with a direct current power supply, and the grounding end of the direct current power supply is a reference end of the second drive control circuit and is used for supplying power to the second drive control circuit.
2. The LED driving circuit of claim 1, wherein the first terminal of the capacitor is a low potential terminal and the second terminal of the capacitor is a high potential terminal.
3. The LED driving circuit according to claim 2, wherein the first driving control circuit includes: the first processing unit and the first detection unit;
the first detection unit is connected with the first synchronous rectifying tube in parallel and is used for detecting the source-drain voltage of the first synchronous rectifying tube and sending a detection result to the first processing unit;
the first processing unit is used for generating a driving signal according to the detection result; and transmitting the driving signal to the gate of the first synchronous rectifier tube;
the second drive control circuit includes: the second processing unit and the second detection unit;
the second detection unit is connected with the second synchronous rectifying tube in parallel and is used for detecting the source-drain voltage of the second synchronous rectifying tube and sending a detection result to the second processing unit;
the second processing unit is used for generating a driving signal according to the detection result; and transmitting the driving signal to the grid electrode of the second synchronous rectifying tube.
4. The LED driving circuit according to claim 3, wherein the first processing unit generates a first on driving signal when the first detecting unit detects that the source-drain voltage of the first synchronous rectifier tube is a forward on voltage; when the first detection unit detects that the source-drain voltage forward voltage drop of the first synchronous rectifying tube is zero or is reverse voltage drop, the first processing unit generates a first turn-off driving signal;
when the second detection unit detects that the source-drain voltage of the second synchronous rectifier tube is forward conduction voltage, the second processing unit generates a second conduction driving signal; and when the second detection unit detects that the source-drain voltage forward voltage drop of the second synchronous rectifying tube is zero or the reverse voltage drop, the second processing unit generates a second turn-off driving signal.
5. The LED driving circuit of claim 1, wherein the first synchronous rectifier tube is integrated with the first drive control circuit in a first synchronous rectifier;
the first synchronous rectifier includes: a source electrode, a drain electrode and a power supply end; the source electrode of the first synchronous rectifier is the source electrode of the first synchronous rectifier; the drain electrode of the first synchronous rectifier is the drain electrode of the first synchronous rectifier, and the power supply end of the first synchronous rectifier is the power supply end of the first drive control circuit;
or the second synchronous rectifier tube and the second driving control circuit are integrated in a second synchronous rectifier;
the second synchronous rectifier includes: a source electrode, a drain electrode and a power supply end; the source electrode of the second synchronous rectifier is the source electrode of the second synchronous rectifier; the drain electrode of the second synchronous rectifier is the drain electrode of the second synchronous rectifier, and the power supply end of the second synchronous rectifier is the power supply end of the second drive control circuit.
6. The LED driver circuit of claim 5, wherein the capacitor powers the first synchronous rectifier through a power terminal of the first synchronous rectifier;
the direct current power supply supplies power to the second synchronous rectifier through a power supply end of the second synchronous rectifier.
7. The LED driving circuit of claim 6, wherein the power supply terminal of the first synchronous rectifier is connected to the second terminal of the capacitor through a voltage matching circuit.
8. The LED driving circuit of claim 7, wherein the voltage matching circuit is a voltage stabilizing circuit.
9. The LED driving circuit of claim 8, wherein the dc power supply is an auxiliary source circuit.
10. An LED driving circuit according to any of claims 1-9, wherein the high frequency pulsed current source is an LLC circuit topology or an LCC circuit topology.
CN201710117591.4A 2017-03-01 2017-03-01 LED driving circuit Active CN106602905B (en)

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CN206759767U (en) * 2017-03-01 2017-12-15 浙江英飞特光电有限公司 A kind of LED drive circuit

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WO2009072058A2 (en) * 2007-12-07 2009-06-11 Koninklijke Philips Electronics N.V. Led lamp power management system and method

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Publication number Priority date Publication date Assignee Title
JP2004208407A (en) * 2002-12-25 2004-07-22 Fuji Electric Device Technology Co Ltd Control circuit of mosfet for synchronous rectification
CN1985427A (en) * 2004-09-30 2007-06-20 三垦电气株式会社 DC power supply apparatus
CN102412709A (en) * 2010-09-17 2012-04-11 东芝照明技术株式会社 Switching power supply device and adjustable power supply system including the same
CN206759767U (en) * 2017-03-01 2017-12-15 浙江英飞特光电有限公司 A kind of LED drive circuit

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