CN103152951B - LED (light emitting diode) driving control circuit and driving circuit structure of LED driving control circuit - Google Patents

Abstract

The invention relates to an LED drive control circuit, wherein a peak current detection circuit detects the source voltage of a built-in power tube, and outputs a signal to a logic control circuit when a fixed threshold voltage is reached, and the secondary conduction time detection circuit detects the second resistor and the second resistor. The voltage inflection point between the three resistors, and output the signal to the logic control circuit, the logic control circuit receives the output signals of the secondary conduction time detection circuit and the peak current detection circuit, calculates and sends the output signal to the drive circuit, and controls the built-in power tube The turn-on and turn-off of the circuit ensures a constant output current. The invention also relates to an LED driving circuit structure with the control circuit. The LED drive control circuit and drive circuit structure with this structure can directly sample the voltage change signal of the primary winding of the transformer through the voltage divider circuit without the need for an auxiliary winding, which simplifies the circuit structure of the LED drive power supply and reduces the drive power supply. Low cost, stable and reliable working performance, and a wide range of applications.

Description

LED drive control circuit and its drive circuit structure

technical field

The invention relates to the field of switching power supplies, in particular to the technical field of light-emitting diode (LED) drive power supplies, and specifically refers to an LED drive control circuit and its drive circuit structure.

Background technique

Compared with the traditional switching power supply controller controlled by the secondary side, the switching power supply controller controlled by the primary side has the characteristics of small size, simple circuit, good stability and low cost. Therefore, more and more switching power supply controllers controlled by the primary side have been widely used in LED drive power supplies, mobile phone chargers, and power adapters.

FIG. 1 is a schematic diagram of a low-power LED driving power supply system in the prior art. The switching power supply consists of a bridge rectifier circuit 100, a high-voltage filter capacitor 101, a transformer primary winding 104, a transformer auxiliary winding 105 and a transformer secondary winding 106. It is mainly used for electrical isolation and energy transmission of input and output. The gate of the power switch tube 112 is connected to the primary side control circuit 121 , the drain is connected to the same terminal of the transformer primary winding 104 , and the source series resistor 115 is grounded. The same end of transformer auxiliary winding 105 is connected to two resistors 113 and 114 connected in series to ground, the same end of transformer auxiliary winding 105 is connected to the anode of diode 110, the cathode of the diode is connected to the common end of resistor 102 and capacitor 111, and the opposite end is grounded. The same-name end of the secondary winding 106 of the transformer is connected to the anode of the diode 107, the capacitor 108 and the LED load 109 are connected in parallel between the cathode of the diode 107 and the ground, and the opposite-end of the secondary winding 106 of the transformer is grounded.

In the switching power supply, the drive circuit 116 of the primary side control circuit 121 controls the turn-on and turn-off of the power switch tube 112 , thereby realizing the process of transferring energy from the transformer primary winding 104 to the output end of the transformer secondary winding 106 . The FB pin of the primary side control circuit 121 controls the turn-on and turn-off of the power switch tube 112 by sampling the high-level time of the common terminal voltage on the resistor 113 and the resistor 114 connected in series to the ground by the auxiliary winding 105 of the transformer, so as to realize the LED drive power supply constant current output.

Although the above-mentioned LED drive power supply has been reduced in cost and volume compared with the switching power supply controlled by the secondary side, the auxiliary winding is still required for sampling, which makes the solution still larger in size and slightly higher in cost, which brings difficulties to the popularization and application of LEDs. Certain obstacles.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned shortcomings in the prior art, and to provide a power supply system that can significantly optimize the power supply system, ensure the constant current output of the LED drive power supply, reduce the cost of the overall solution, have small volume, simple and practical structure, and excellent working performance. The LED drive control circuit and its drive circuit structure are stable, reliable and widely applicable.

In order to achieve the above-mentioned purpose, the LED drive control circuit and its drive circuit structure of the present invention have the following composition:

The main feature of the LED drive control circuit is that the control circuit includes a built-in power tube, the drain of the built-in power tube is coupled and connected to an external power supply load circuit, and the drain of the built-in power tube passes through the first The second resistor and the third resistor are grounded, and the drain of the built-in power tube is also grounded through the high-voltage current source and the second capacitor in turn; the source of the built-in power tube is grounded through the first resistor, and the source of the built-in power tube is sequentially grounded The peak current detection circuit, the logic control circuit, and the drive circuit are connected to the gate of the built-in power transistor, and the input terminal of the logic control circuit is connected to the second resistor and the second resistor through the secondary conduction time detection circuit. Between the three resistors, the peak current detection circuit detects the source voltage of the built-in power transistor, and outputs a signal to the logic control circuit when it reaches the preset fixed threshold voltage of the control circuit, and the secondary side The conduction time detection circuit detects the voltage inflection point between the second resistor and the third resistance, and outputs a signal to the logic control circuit, and the logic control circuit receives the secondary conduction time detection circuit and the output signal of the peak current detection circuit are calculated and processed and the output signal is sent to the drive circuit to control the on and off of the built-in power tube to ensure a constant output current.

The peak current detection circuit in the LED driving control circuit is a first comparator, the positive terminal of the first comparator is connected with the source of the built-in power tube, and the negative terminal of the first comparator is connected with the The preset fixed threshold voltage terminal Vlimit of the control circuit is connected, and the output terminal of the first comparator is connected with the input terminal of the logic control circuit.

The secondary turn-on time detection circuit in the LED drive control circuit includes an RS flip-flop, the S input of the RS flip-flop is connected to the output of the first comparator, and the Q output of the RS flip-flop The terminal is connected between the second resistor and the third resistor through an internal switch, and the Q output terminal of the RS flip-flop is connected to the negative terminal of the second comparator through the first delay circuit and the voltage divider circuit in turn, The first delay circuit is connected to the positive terminal of the second comparator through the second delay circuit, and the output terminal of the second comparator is connected to the input terminal of the logic control circuit, The output terminal of the second comparator is also connected with the R input terminal of the RS flip-flop through an inverter.

The built-in power tube in the LED drive control circuit is a field effect tube.

The main feature of the LED drive circuit structure with the above-mentioned control circuit is that the circuit structure may also include a bridge rectifier circuit, a first high-voltage filter capacitor, a primary winding of a transformer, and a secondary winding of a transformer. The primary winding of the transformer is coupled to the secondary winding of the transformer, the bridge rectifier circuit is grounded through the first high-voltage filter capacitor, and the bridge rectifier circuit is connected to the opposite end of the primary winding of the transformer, so The drain of the built-in power tube is connected to the terminal with the same name of the primary winding of the transformer, and the secondary winding of the transformer is connected to the LED load circuit.

The LED load circuit in the LED drive circuit structure includes a diode, and the same terminal of the secondary winding of the transformer is connected to the positive pole of the diode, and the negative pole of the diode is grounded through the third capacitor connected in parallel with the LED load. The opposite end of the side winding is grounded.

The main feature of the LED driving circuit structure with the above-mentioned control circuit is that the circuit structure may also include a bridge rectifier circuit, a first high-voltage filter capacitor and a transformer coil, and the bridge rectifier circuit passes through the The first high-voltage filter capacitor is grounded, and the bridge rectifier circuit is connected to the drain of the built-in power tube through the transformer coil, and the transformer coil is connected to the LED load circuit.

The LED load circuit in the LED driving circuit structure includes a diode, and the diode is connected in series with the third capacitor connected in parallel with the LED load, and connected across the two ends of the transformer coil.

The main feature of the LED drive circuit structure with the above-mentioned control circuit is that the circuit structure may also include a bridge rectifier circuit, a first high-voltage filter capacitor, an LED load circuit and a transformer coil. The rectifier circuit is grounded through the first high-voltage filter capacitor, and the bridge rectifier circuit is connected to the drain of the built-in power tube through the LED load circuit and the transformer coil in sequence.

The LED load circuit in the LED driving circuit structure includes a diode, a third capacitor and an LED load connected in parallel with each other, and the third capacitor and the LED load connected in parallel are connected between the bridge rectifier circuit and the transformer coil, And the positive end of the diode is connected to the drain of the built-in power transistor, and the negative end of the diode is connected to the bridge rectifier circuit.

The LED drive control circuit and its drive circuit structure of the invention are adopted. Since the auxiliary winding and its sampling circuit are omitted, the voltage inflection point signal of the primary winding is mainly sampled and detected through the voltage divider circuit, and the current zero crossing of the freewheeling diode is obtained. Time, so as to determine the freewheeling time of the freewheeling diode, calculate the average current of the LED load, and realize the LED constant current drive, so that the signal of the voltage change of the primary winding of the transformer can be sampled directly through the voltage divider circuit without the auxiliary winding. Realize the control of the output current, thereby simplifying the circuit structure of the LED driving power supply, reducing the size of the LED driving power supply, reducing the cost of the LED driving power supply, stable and reliable working performance, and a wide range of applications. It can not only be used for isolated power converters, It can also be applied to non-isolated power converters or other types of converters.

Description of drawings

FIG. 1 is a schematic diagram of a flyback LED constant current drive circuit in the prior art.

Fig. 2 is a schematic block diagram of the flyback LED drive circuit of the present invention.

FIG. 3 is a schematic diagram of the circuit structure of the flyback LED driving circuit of the present invention.

Fig. 4 is a logic signal diagram of various points in the actual working process of the LED drive control circuit and its drive circuit structure of the present invention.

Fig. 5 is a schematic diagram of the non-isolated parallel connection between the LED driving circuit and the LED load of the present invention.

FIG. 6 is a schematic diagram of the non-isolated series connection between the LED driving circuit and the LED load of the present invention.

Detailed ways

In order to understand the technical content of the present invention more clearly, the following examples are given in detail.

Please refer to Figures 2 to 4, the LED drive control circuit, wherein, the control circuit includes a built-in power tube 213, the drain of the built-in power tube 213 is coupled with the external power supply load circuit, the built-in power tube The drain of 213 is grounded successively through the second resistor 216 and the third resistor 217 connected in series, and the drain of the built-in power transistor 213 is also grounded sequentially through the high-voltage current source 208 and the second capacitor 214; the source of the built-in power transistor 213 The pole is grounded through the first resistor 207, and the source of the built-in power transistor 213 is connected to the grid of the built-in power transistor 213 through the peak current detection circuit 210, the logic control circuit 211, and the drive circuit 209 in sequence, and the logic control The input terminal of the circuit 211 is connected between the second resistor 216 and the third resistor 217 through the secondary conduction time detection circuit 212, and the peak current detection circuit 210 is responsible for detecting the source of the built-in power transistor 213 voltage, when it reaches the preset fixed threshold voltage of the control circuit, it outputs a signal to the logic control circuit 211, and the secondary conduction time detection circuit 212 detects the difference between the second resistor 216 and the third resistor 217. The voltage inflection point between them, and output the signal to the logic control circuit 211, the logic control circuit 211 receives the output signals of the secondary conduction time detection circuit 212 and the peak current detection circuit 210, performs calculation processing and The output signal is sent to the driving circuit 209 to control the turn-on and turn-off of the built-in power transistor 213 to ensure a constant output current.

Wherein, the peak current detection circuit 210 is a first comparator 315, the positive end of the first comparator 315 is connected to the source of the built-in power transistor 213, and the negative end of the first comparator 315 is terminal is connected to the preset fixed threshold voltage terminal Vlimit of the control circuit, and the output terminal of the first comparator 315 is connected to the input terminal of the logic control circuit 211; the secondary conduction time detection circuit 212 includes an RS flip-flop 316, the S input of the RS flip-flop 316 is connected to the output of the first comparator 315, and the Q output of the RS flip-flop 316 is connected to the between the second resistor 216 and the third resistor 217, and the Q output terminal of the RS flip-flop 316 is connected to the negative terminal of the second comparator 318 through the first delay circuit 320 and the voltage divider circuit 319 in turn, the The first delay circuit 320 is connected to the positive terminal of the second comparator 318 through the second delay circuit 321, and the output terminal of the second comparator 318 is connected to the input terminal of the logic control circuit 211 The output terminal of the second comparator 318 is also connected to the R input terminal of the RS flip-flop 316 through the inverter 317 .

Meanwhile, the built-in power transistor 213 in the LED driving control circuit is a field effect transistor.

Please refer to FIG. 3 again, the structure of the LED driving circuit with the above-mentioned control circuit may further include a bridge rectifier circuit 200, a first high-voltage filter capacitor 201, a transformer primary winding 202 and a transformer secondary winding 203, so The transformer primary winding 202 is coupled with the transformer secondary winding 203, the bridge rectifier circuit 200 is grounded through the first high-voltage filter capacitor 201, and the bridge rectifier circuit 200 is connected to the transformer primary winding 202 The drain of the built-in power tube 213 is connected to the same-named end of the primary winding 202 of the transformer, and the secondary winding 203 of the transformer is connected to the LED load circuit.

Wherein, the LED load circuit includes a diode 205, the same terminal of the transformer secondary winding 203 is connected to the anode of the diode 205, and the cathode of the diode 205 is connected to the ground through the third capacitor 206 and the LED load 204 connected in parallel. , the opposite end of the secondary winding 203 of the transformer is grounded.

Please refer to Fig. 5 again, which is the non-isolated parallel connection mode of the LED drive circuit and the LED load of the present invention, which includes a bridge rectifier circuit 200, a first high-voltage filter capacitor 201 and a transformer coil. The rectifier circuit 200 is grounded through the first high-voltage filter capacitor 201, and the bridge rectifier circuit 200 is connected to the drain of the built-in power tube 213 through the transformer coil, and the transformer coil is connected to the LED load circuit connected.

Wherein, the LED load circuit includes a diode 205, the diode 205 is connected in series with the third capacitor 206 and the LED load 204 connected in parallel, and is connected across the two ends of the transformer coil.

Please refer to FIG. 6 again, which is a non-isolated series connection mode of the LED drive circuit and LED load of the present invention, which includes a bridge rectifier circuit 200, a first high-voltage filter capacitor 201, an LED load circuit and a transformer coil. The bridge rectifier circuit 200 is grounded through the first high-voltage filter capacitor 201 , and the bridge rectifier circuit 200 is connected to the drain of the built-in power transistor 213 through the LED load circuit and the transformer coil in sequence.

Wherein, the LED load circuit includes a diode 205, a third capacitor 206 and an LED load 204 connected in parallel, and the third capacitor 206 and the LED load 204 connected in parallel are connected to the bridge rectifier circuit 200 and the transformer between the coils, and the positive end of the diode 205 is connected to the drain of the built-in power transistor 213 , and the negative end of the diode 205 is connected to the bridge rectifier circuit 200 .

In actual use, please refer to FIG. 2, the structure of the LED drive circuit includes a bridge rectifier circuit 200, a first high-voltage filter capacitor 201, a transformer primary winding 202, a transformer secondary winding 203, and a transformer coupled to the primary LED drive circuit 215 of side winding 202 . The drain of the built-in power tube 213 of the LED drive circuit 215 is connected to the terminal of the same name of the transformer primary winding 202, the source of the built-in power tube 213 is grounded through the first resistor 207, and the source of the built-in power tube 213 It is connected with the sampling pin CS of the LED driving circuit 215. The terminal with the same name of the transformer primary winding 202 is also connected to the ground through the second resistor 216 and the third resistor 217 connected in series, and the common terminal of the second resistor 216 and the third resistor 217 is connected to the FB pin of the LED driving circuit 215 . The second capacitor 214 is respectively connected to the VCC pin and the GND pin of the LED driving circuit 215; the transformer secondary winding 203 with the same name is connected to the anode of the diode 205, and the third capacitor 206 and the LED load 204 are connected in parallel between the cathode of the diode 205 and the ground. The opposite end of the winding 203 is grounded.

The LED drive circuit 215 also includes a high-voltage current source 208, a drive circuit 209, a peak current detection circuit 210, a logic control circuit 211, a secondary conduction time detection circuit 212, and a built-in power tube 213; the high voltage of the LED drive circuit 215 One end of the current source 208 is connected to the drain of the built-in power transistor 213 , the other end is connected to the VCC pin of the LED driving power supply 215 and grounded through the second capacitor 214 . The high-voltage current source 208 is responsible for charging the capacitor 214 to ensure the normal operation of the chip.

The output end of the drive circuit 209 of the LED drive circuit 215 is connected to the gate of the internal power transistor 213, and the input end is connected to the logic control circuit 211. After receiving the signal from the logic control circuit 211, the drive circuit 209 is responsible for controlling the internal power transistor 213. On and off; the peak current detection circuit 210 is responsible for detecting the voltage on the sampling pin CS of the LED drive circuit 215, and outputs a signal to the logic control circuit 211 when it reaches a fixed threshold.

The secondary conduction time detection circuit 212 is responsible for detecting the voltage inflection point of the common terminal of the second resistor 216 and the third resistor 217, obtains the zero-crossing moment of the current of the freewheeling diode 205, and outputs a signal to the logic control circuit 211 to facilitate logic control The circuit calculates the conduction time of the freewheeling diode 205 and outputs a corresponding control signal to the built-in power transistor 213 .

The logic control circuit 211 is responsible for receiving the output signals of the secondary turn-on time detection circuit 212 and the peak current detection circuit 210, and outputs the signal to the drive circuit 209 after calculation, so as to control the on and off of the internal power tube 213, ensuring The output current is constant at the set value.

Please refer to Fig. 3 again, wherein the isolated LED drive power supply includes a bridge rectifier circuit 300, a high voltage filter capacitor 301 connected in parallel with the bridge rectifier circuit, a transformer primary winding 302, a transformer secondary winding 303, coupled to the The LED driving circuit 323 of the primary winding 302 of the transformer. The sampling pin CS of the LED driving circuit 323 is connected to the ground through the first resistor 307 connected in series. The sampling pin FB of the LED driving circuit 323 is connected to the common end of the second resistor and the third resistor, the pin VCC of the LED driving circuit 323 is connected to one end of the second capacitor 310 , and the other end is connected to GND. The terminal with the same name of the transformer primary winding 302 is connected to the ground through the second resistor 308 and the third resistor 309 connected in series. The same terminal of the secondary winding 303 of the transformer is connected to the anode of the diode 305, the third capacitor 306 and the LED load 304 are connected in parallel between the cathode of the diode 305 and the ground, and the negative terminal of the auxiliary winding 303 of the transformer is grounded. The above-mentioned LED drive circuit includes a high-voltage current source HV Current Source 311, an internal switch 312, an internal drive circuit Driver 313, a built-in power tube 314, an internal first comparator 315, an internal RS flip-flop 316, an internal inverter 317, and an internal second comparator 318 , an internal voltage divider circuit 319 , an internal first delay circuit 320 , an internal second delay circuit 321 , and a logic control circuit 322 .

The working mode and principle of the LED driving power supply composed of the LED driving circuit 323 of the present invention will be introduced in detail below.

One end of the high-voltage current source HV Current Source 311 of the LED drive circuit 323 is connected to the drain of the built-in power transistor 314. When the LED drive power supply is normally output, the high-voltage current source (HV Current Source) 311 is connected in parallel when the built-in power transistor 314 is turned off. The second capacitor 310 between VCC and GND is charged. In order to ensure that VCC is within the normal operating voltage range, the chip can work normally.

The internal drive circuit Driver 313 of the LED drive circuit 323 stores AC energy in the primary winding 302 of the transformer when the built-in power tube 314 is turned on through control. When the internal drive circuit Driver 313 controls the built-in power tube 314 to turn off, the transformer secondary winding 303 coupled with the transformer primary winding 302 transmits energy to the LED lamp load 304 .

One end of the internal comparator 315 is connected to the first resistor 307, and the other end is connected to the fixed threshold Vlimit. When the voltage on the first resistor is higher than the fixed threshold Vlimit, the output signal is sent to the logic control circuit Logic322 to turn off the built-in power transistor 314 to achieve The purpose of the primary winding 302 of the transformer is to store energy to ensure normal operation in each cycle. When the voltage on the first resistor is higher than the fixed threshold Vlimit, the output signal of the first internal comparator 315 will set the output of the internal RS flip-flop 316 high, so that the internal switch 312 is turned on, and the sampling signal on FB reaches the first delay circuit 320, and output to the negative terminal of the internal second comparator 318 after being latched and held by the voltage divider circuit 319. At this time, the signal passed by the first delay circuit 320 is output to the positive terminal of the internal second comparator 318 through the second delay circuit 321 at the same time. When the FB sampling signal is lower than the previous latch hold signal, it outputs a low level to the inverter 317 and the logic circuit Logic322, and the inverter 317 makes the internal RS flip-flop output low, so that the internal switch 312 is turned off, no longer sample signal.

The internal logic circuit Logic322 receives the output signals of the first comparator 315 and the second comparator 318, calculates the conduction time of the freewheeling diode 305 on the secondary side, and controls the precise time conduction of the built-in power transistor 314 to achieve a constant output current At the set value, if the resulting conduction time is less than the preset minimum freewheeling time, the LED drive circuit can be protected against overvoltage. In order to ensure the stable and safe work of the LED drive power supply.

As shown in FIG. 4 is the working waveform of the present invention, specifically the logic signal diagram of each point in the actual working process of the LED drive control circuit and its drive circuit structure. The Logic signal is the output signal of the logic control circuit, and the switching of the power tube 314 is realized through the driving circuit 313. The waveform of Vds is the waveform of the same name terminal of the primary winding 302 to ground, and Ipk is the peak current waveform of the primary side. The waveform of VFB is the waveform of the notification end of the second resistor 308 and the third resistor 309. The VFB of the LED drive control circuit of the present invention samples the waveform to realize the detection of the conduction time of the secondary freewheeling diode. The waveform of the Detector is The output waveform of the internal detector, Ispk shows the waveform of the peak current of the secondary side.

The basic idea of the LED drive circuit of the present invention is that the auxiliary winding and its sampling circuit are omitted, and the constant current output of the LED drive power supply is realized, the volume of the power supply is reduced, and the cost of the overall solution is reduced. The serial resistance between the end of the same name of the winding, the drain of the power tube or the corresponding equivalent potential and the ground, the LED drive circuit detects the change of the voltage of the end of the same name of the primary winding, the drain of the power tube or the corresponding equivalent potential, thereby Realize the detection of the conduction time of the freewheeling diode on the secondary side. At the same time, it can be seen that the power tube can be a power MOS tube, a power triode or other power switches. The power tube can be built-in or external. The corresponding equivalent potential of the drain and so on. For the application of the LED power supply of the present invention, it can include an isolation change circuit or a non-isolated conversion circuit, wherein the isolation circuit can be an AC-DC Flyback converter, a DC-DC Flyback converter or other types of converters, and the non-isolation conversion circuit can be a Buck conversion converter or Buck-Boost converter or other types of converters. It should be noted that the above terms are only used to refer to one of the names they mean, so any names that mean the same or similar names should be regarded as their equivalents.

The above-mentioned LED driving control circuit and its driving circuit structure are adopted. Since the auxiliary winding and its sampling circuit are omitted, the voltage inflection point signal of the primary winding 202 is mainly sampled and detected through the voltage divider circuit, and the current overcurrent of the freewheeling diode 205 is obtained. Zero moment, so as to determine the freewheeling time of the freewheeling diode 205, calculate the average current of the LED load, and realize the LED constant current drive, so that the voltage change of the primary winding of the transformer can be sampled directly through the voltage divider circuit without the auxiliary winding signal to realize the control of the output current, thereby simplifying the circuit structure of the LED drive power supply, reducing the size of the LED drive power supply, reducing the cost of the LED drive power supply, stable and reliable performance, and a wide range of applications, not only for isolated power conversion converter, and can also be applied to non-isolated power converters or other types of converters.

In this specification, the invention has been described with reference to specific embodiments thereof. However, it is obvious that various modifications and changes can be made without departing from the spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive.

Claims (9)

1. a LED Drive and Control Circuit, it is characterized in that, described control circuit comprises built-in power pipe (213), the drain electrode of this built-in power pipe (213) is coupled with externally fed load circuit and is connected, the drain electrode of this built-in power pipe (213) is successively by the second resistance (216) and the 3rd resistance (217) ground connection of series connection mutually, and the drain electrode of this built-in power pipe (213) is also successively by high-voltage current source (208) and the second electric capacity (214) ground connection; the source electrode of this built-in power pipe (213) is by the first resistance (207) ground connection, and the source electrode of this built-in power pipe (213) is successively by peak current detection circuit (210), logic control circuit (211), drive circuit (209) is connected with the grid of this built-in power pipe (213), the input of described logic control circuit (211) is connected between described the second resistance (216) and the 3rd resistance (217) by secondary ON time testing circuit (212), described peak current detection circuit (210) detects the voltage of the source electrode of this built-in power pipe (213), described logic control circuit (211) is outputed signal to when reaching the fixed threshold voltage that this control circuit is preset, the second resistance (216) described in described secondary ON time testing circuit (212) detects and the voltage knee between the 3rd resistance (217), and output signal to described logic control circuit (211), secondary ON time testing circuit (212) described in described logic control circuit (211) receives and the output signal of peak current detection circuit (210), carry out computing and output signal is delivered to described drive circuit (209), the turn-on and turn-off of the built-in power pipe (213) described in control, ensure constant output current, described secondary ON time testing circuit (212) comprises rest-set flip-flop (316), the S input of described rest-set flip-flop (316) is connected with the output of described peak current detection circuit (210), the Q output of this rest-set flip-flop (316) is connected between described the second resistance (216) and the 3rd resistance (217) by internal switch (312), and the Q output of this rest-set flip-flop (316) is connected with the negative terminal of bleeder circuit (319) with the second comparator (318) by the first delay circuit (320) successively, described the first delay circuit (320) is connected by the anode of the second delay circuit (321) with described the second comparator (318), and the output of this second comparator (318) is connected with the input of described logic control circuit (211), the output of this second comparator (318) is also connected by the R input of inverter (317) with described rest-set flip-flop (316).

2. LED Drive and Control Circuit according to claim 1, it is characterized in that, described peak current detection circuit (210) is the first comparator (315), the anode of described the first comparator (315) is connected with the source electrode of described built-in power pipe (213), the fixed threshold voltage end (Vlimit) that negative terminal and this control circuit of this first comparator (315) are preset is connected, and the output of this first comparator (315) is connected with the input of described logic control circuit (211).

3. LED Drive and Control Circuit according to any one of claim 1 to 2, is characterized in that, described built-in power pipe (213) is field effect transistor.

4. one kind has the LED drive circuit structure of control circuit according to claim 1, it is characterized in that, bridge rectifier (200) is also comprised in described circuit structure, first high-voltage filtering capacitor (201), transformer primary side winding (202) and transformer secondary winding (203), described transformer primary side winding (202) and transformer secondary winding (203) are coupled, described bridge rectifier (200) is by this first high-voltage filtering capacitor (201) ground connection, and this bridge rectifier (200) is connected with the different name end of described transformer primary side winding (202), the drain electrode of described built-in power pipe (213) is connected with the Same Name of Ends of described transformer primary side winding (202), described transformer secondary winding (203) is connected with LED load circuit.

5. LED drive circuit structure according to claim 4, it is characterized in that, described LED load circuit comprises diode (205), described transformer secondary winding (203) Same Name of Ends is connected with the positive pole of this diode (205), and the negative pole of this diode (205) is by the 3rd electric capacity (206) parallel with one another and LED load (204) ground connection, the different name end ground connection of this transformer secondary winding (203).

6. one kind has the LED drive circuit structure of control circuit according to claim 1, it is characterized in that, bridge rectifier (200), the first high-voltage filtering capacitor (201) and transformer coil is also comprised in described circuit structure, described bridge rectifier (200) is by this first high-voltage filtering capacitor (201) ground connection, and this bridge rectifier (200) is connected by the drain electrode of described transformer coil with described built-in power pipe (213), and described transformer coil is connected with LED load circuit.

7. LED drive circuit structure according to claim 6, it is characterized in that, described LED load circuit comprises diode (205), described diode (205) is in series with the 3rd electric capacity (206) parallel with one another and LED load (204), and is connected across described transformer coil two ends.

8. one kind has the LED drive circuit structure of control circuit according to claim 1, it is characterized in that, bridge rectifier (200), the first high-voltage filtering capacitor (201), LED load circuit and transformer coil is also comprised in described circuit structure, described bridge rectifier (200) is by this first high-voltage filtering capacitor (201) ground connection, and this bridge rectifier (200) is connected with the drain electrode of described built-in power pipe (213) by described LED load circuit, transformer coil successively.

9. LED drive circuit structure according to claim 8, it is characterized in that, described LED load circuit comprises diode (205) and the 3rd electric capacity (206) parallel with one another and LED load (204), described the 3rd electric capacity (206) parallel with one another and LED load (204) are connected between described bridge rectifier (200) and transformer coil, and the anode of described diode (205) is connected to the drain electrode of described built-in power pipe (213), the negative terminal of this diode (205) is connected to described bridge rectifier (200).