CN103108459A - Primary side feedback constant current control circuit - Google Patents
Primary side feedback constant current control circuit Download PDFInfo
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- CN103108459A CN103108459A CN2013100276642A CN201310027664A CN103108459A CN 103108459 A CN103108459 A CN 103108459A CN 2013100276642 A CN2013100276642 A CN 2013100276642A CN 201310027664 A CN201310027664 A CN 201310027664A CN 103108459 A CN103108459 A CN 103108459A
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Abstract
The invention discloses a primary side feedback constant current control circuit which comprises a transformer, a power switch field-effect transistor (FET), a constant current controller and a sampling resistor. The transformer comprises a primary side winding and a secondary side winding, and one end of the primary side winding is connected with a drain electrode of the power switch FET. One end of the sampling resistor is grounded, and the other end of the sampling resistor is connected with a source electrode of the power switch FET. A primary side current detection end of the constant current controller is connected with the source electrode of the power switch FET, and the constant current controller shuts off the power switch FET according to a result of the comparison between acquired sampling voltage across the sampling resistor and preset reference voltage so as to control the peak current of the primary side winding. A secondary side current detection and output multiplex end of the constant current controller is connected with a grid electrode of the power switch FET, and the constant current controller controls the conducting time or the non-conducting time of the secondary side current by detecting the grid electrode current of the power switch FET. Through the detection of the grid electrode current (Ig), the time point when the secondary side current (Is) is zero is obtained, an auxiliary winding and a feed back (FB) pin of the transformer are omitted, and therefore the cost and the area of a chip are reduced.
Description
Technical field
The present invention relates to integrated circuit fields, relate in particular to a kind of former limit feedback constant flow control circuit.
Background technology
In integrated circuit fields, need to realize constant current in a lot of the application.For example, throw light on for light-emitting diode (LED:Light Emitting Diode), because the voltage-current characteristic of LED and diode-like are seemingly, the LED electric current is responsive especially to the added voltage in two ends, and very small change in voltage all can cause very large curent change.In the excessive life-span that not only can affect LED of curent change, even can cause LED to burn.In order to control well the electric current of the LED that flows through, it is inappropriate obviously coming driving LED with a constant pressure source, and constant-current source is only suitable selection.
In order to realize constant current, need to detect output current, and information is fed back to control chip, chip is controlled power output according to this information, thereby realizes constant current.The simplest method is exactly current sampling resistor of series connection in output loop, and pressure reduction and the reference voltage at resistance two ends compared, and produces an error signal, and this error signal feeds back to chip by optocoupler.The advantage of this control model is, the precision of output current is higher, but shortcoming is due to series resistance in output loop, can cause loss to increase, and has reduced the efficient of whole system, in addition, need more peripheral cell, for example optocoupler and secondary constant-current control circuit, not only cost is high, and need the area of larger printed circuit board (PCB), this will cause can't with the size compatibility of existing light fixture.
In order to reduce costs and save the area of printed circuit board (PCB), need to save secondary current sampling resistor, optocoupler and secondary constant-current control circuit.Thus, secondary current information arrives the control chip on former limit by transformer feedback, and Fig. 1 shows the schematic diagram of limit, prior art Central Plains feedback constant flow control circuit.As shown in Figure 1, transformer 100 also comprises feedback winding 101 except comprising former limit winding and secondary winding, and the major function of feedback winding 101 has two: the one, and to the control chip power supply, the 2nd, feedback secondary current information.The FB pin 102 of chip is the reception pin that secondary current information feeds back.
In order to realize output constant current, the information that control chip 103 need to obtain is the peak current Ipk of former limit power switch pipe 106, the peak current of secondary current Is and the ON time Tons of secondary current.Fig. 2 a shows electric current I s and the output current Iout of secondary diode 107, and Iout is the average current of Is, can calculate by following formula (1) to obtain:
Can find out from formula (1), as long as guarantee the peak value of Ispk(secondary current) and Tons/ (Tons+Toff) be steady state value, that just can realize that output current Iout is constant.And the relation of the peak I pk of the peak I spk of secondary current Is and primary current Is is as shown in Equation (2):
Therefore the function of control chip 103 is exactly in order to guarantee that Ipk and Tons/ (Tons+Toff) are steady state value.
Fig. 2 b shows the waveform 203 of the dividing potential drop FB of the waveform 202 of drain terminal voltage Vds of waveform 201, power switch pipe of waveform 200, the secondary current Is of the driving signal OUT of power switch pipe and auxiliary winding 101.
In conjunction with shown in Figure 1, control chip 103 detects by 104 couples of primary current Ip of CS pin, control chip 103 compares Ip and a fixing reference voltage, as Ip greater than reference voltage, control chip 103 turn-offs former limit power switch pipe 106, is therefore fixed value with regard to the peak value that has guaranteed primary current Ip.
Be fixed value in order to control Tons/ (Tons+Toff), control chip 103 must be known two information, namely drives the time point of signal shutoff and the time point that secondary current Is equals 0, and the time difference between these two time points is secondary ON time Tons.Due to the waveform 200 that drives in signal OUT(Fig. 2 a) be the signal that control chip 103 produces, so the time point that this signal turn-offs is easy to obtain.Equal the detection of 0 time point for secondary current Is, control chip 103 must just can obtain according to the relation of the waveform 201 of the waveform 202 of the drain voltage Vds of the waveform 203 of feedback pin FB, power switch pipe and secondary current Is.When Is equals 0, the waveform that occurs resonance in the waveform 202 of the drain voltage Vds of power switch pipe, control chip 103 detects by auxiliary 101 pairs of these harmonic waves of winding, be FB signal 203 and inner default threshold voltage signal (for example control chip 103,0.1V signal) compare, the waveform of FB signal 203 is the time point that Is equals 0 during less than 0.1V.Strictly speaking, also can find out from Fig. 2 a, have a time difference Td204 although the waveform of FB signal 203 equals 0 time point less than the time point of 0.1V and Is,, as long as 103 pairs of these time differences of control chip compensate, just can not affect the precision of electric current.
Summary of the invention
The technical problem to be solved in the present invention is for the defective that needs to obtain with the auxiliary feedback winding of transformer secondary current in prior art, and a kind of former limit feedback constant flow control circuit is provided.
The technical solution adopted for the present invention to solve the technical problems is: a kind of former limit feedback constant flow control circuit is provided, has comprised transformer, power switch pipe, constant-current controller and sampling resistor; Wherein,
Described transformer comprises former limit winding and secondary winding, and an end of described former limit winding is connected with the drain electrode of described power switch pipe, and the two ends of described secondary winding connect load circuit;
One end ground connection of described sampling resistor, the other end is connected with the source electrode of described power switch pipe;
The primary current test side of described constant-current controller is connected with the source electrode of described power switch pipe, and the voltage by obtaining described sampling resistor two ends turn-offs described power switch pipe with the comparative result of default reference voltage, to control the peak value of primary current; The secondary current of described constant-current controller detects and is connected multiplexing end and is connected with the grid of described power switch pipe, controls conducting or the shutoff duration of described secondary current by the grid current that detects described power switch pipe.
In the feedback constant flow control circuit of the former limit of the foundation embodiment of the present invention, described constant-current controller comprises:
The current limliting comparison module, the positive input terminal of described current limliting comparison module is connected with described primary current end, and the negative input end of described current limliting comparison module receives described reference voltage;
Current detection module, the input of described current detection module and described secondary current detect and are connected multiplexing end and are connected, with reception with detect the grid current of described power switch pipe;
Constant-current control module, the input of described constant-current control module is connected with the output of described current detection module, generates conducting or the shutoff duration of secondary current by the testing result of described grid current;
The switching signal generation module, the first input end of described switching signal generation module is connected with the output of described current limliting comparison module, and the second input is connected with the output of described constant-current control module; With comparative result and the conducting of described secondary current or conducting or the cut-off signals that the shutoff duration generates described power switch pipe by obtaining described sampled voltage and described reference voltage;
The output driver module, the input of described output driver module is connected with the output of described switching signal generation module; The output of described output driver module and described secondary current detect and are connected multiplexing end and are connected; To come conducting or to turn-off described power switch pipe based on the described conducting or the cut-off signals that receive from described switching signal generation module.
In the feedback constant flow control circuit of the former limit of the foundation embodiment of the present invention, described current detection module comprises:
The electric current comparing unit, the first end of described electric current comparing unit receives default reference current, the second end and described secondary current and the grid current of being connected multiplexing end and being connected to receive described power switch pipe are to produce voltage drop at described the second end place at described grid current during greater than described reference current;
The semaphore lock unit, the input of described semaphore lock unit is connected with described the second end, to detect the change in voltage at described the second end place.
In the feedback constant flow control circuit of the former limit of the foundation embodiment of the present invention, described electric current comparing unit comprises the first identical field-effect transistor and the second field-effect transistor;
Wherein, two source shorted and two grid short circuits of described the first and second field-effect transistors, the drain electrode of described the first field-effect transistor and described secondary current be connected multiplexing end and be connected, the drain electrode of described the second field-effect transistor receives reference current;
The input of described semaphore lock unit is connected with the drain electrode of described the first field-effect transistor, and output is connected with the input of described constant-current control module.
In the feedback constant flow control circuit of the former limit of the foundation embodiment of the present invention, described current detection module comprises:
Detection capacitance, the first end of described Detection capacitance connect described secondary current and the multiplexing end of output, the second end ground connection;
The semaphore lock unit, the input of described semaphore lock unit is connected with the first end of described Detection capacitance, and output is connected with the input of described constant-current control module, detects described grid current with the variation of the voltage that receives by detection.
In the feedback constant flow control circuit of the former limit of the foundation embodiment of the present invention, described current detection module further comprises the pressure limiting diode, the plus earth of described pressure limiting diode, negative pole and described secondary current be connected multiplexing end and be connected.
In the feedback constant flow control circuit of the former limit of the foundation embodiment of the present invention, described current detection module further comprises the reset switch that resets for to described Detection capacitance, the drain electrode of described reset switch is connected with the first end of described Detection capacitance, and its source electrode and grid are unsettled.
The beneficial effect that the present invention produces is: the information that no longer obtains secondary current Is by the extra auxiliary winding feedback of transformer, but according to the grid current Ig of power switch pipe and the corresponding relation of secondary current Is, obtaining secondary current Is by detection grid current Ig is zero time point, thereby controlling Tons/ (Tons+Toff) is fixed value, to obtain constant current.In this process, on the one hand, transformer only has former limit winding and secondary winding, and auxiliary winding is removed.Because transformer only has two windings, simplified the production process of transformer, reduced the cost of transformer.On the other hand, the input of grid current and the output of drive control signal utilize the pin bit multiplex, have saved FB pin of the prior art, have then saved the divider resistance that is connected with this FB pin, reduced peripheral component, thereby reduced cost and reduced chip area.
Description of drawings
The invention will be further described below in conjunction with drawings and Examples, in accompanying drawing:
Fig. 1 shows the schematic diagram of limit, prior art Central Plains feedback constant flow control circuit;
Fig. 2 a shows the oscillogram of secondary current Is and output current Iout;
Fig. 2 b shows the oscillogram of the dividing potential drop FB of the drain terminal voltage Vds of driving signal OUT, secondary current Is, power switch pipe of power switch pipe and auxiliary winding 101;
Fig. 3 shows the schematic diagram according to the former limit feedback constant flow control circuit of the embodiment of the present invention;
Fig. 4 shows the schematic diagram of the power switch pipe with parasitic capacitance;
Fig. 5 shows driving signal OUT, the secondary current Is of power switch pipe 320 in Fig. 3, the drain terminal voltage Vds of power switch pipe 320 and the oscillogram of grid current Ig;
Fig. 6 shows the logic diagram of constant-current controller 330 in Fig. 3;
Fig. 7 shows the exemplary circuit figure of the former limit feedback constant flow control circuit that adopts the constant-current controller 330 in Fig. 6;
Fig. 8 shows the circuit diagram according to the current detection module 332 of first embodiment of the invention;
Fig. 9 a shows the circuit diagram according to the current detection module 332 of second embodiment of the invention;
Fig. 9 b shows the waveform of driving signal of the power switch pipe 320 in Fig. 9 a and the voltage waveform at node 905 places.
Embodiment
In order to make purpose of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, is not intended to limit the present invention.
Fig. 3 shows the schematic diagram according to the former limit feedback constant flow control circuit of the embodiment of the present invention, and as shown in Figure 3, this former limit feedback constant flow control circuit comprises transformer 310, power switch pipe 320, constant-current controller 330 and sampling resistor 340.Wherein, transformer 310 comprises former limit winding and secondary winding, and an end of former limit winding is connected with the drain electrode of power switch pipe 320, another termination power Vin; The two ends of secondary winding connect load circuit.One end ground connection of sampling resistor 340, the other end is connected with the source electrode of power switch pipe 320.Constant-current controller 330 comprises four pins: primary current test side CS, secondary current detect and export multiplexing end OUT, earth terminal Gnd and power end Vcc.Wherein, primary current test side CS is connected with the source electrode of power switch pipe 320, and secondary current detects and is connected multiplexing end OUT and is connected with the grid of power switch pipe 320, earth terminal Gnd ground connection, and power end Vcc meets power supply Vin.
For power switch pipe 320, there is a parasitic capacitance 401 between its grid (Gate) G and drain electrode (Drain) D, as shown in Figure 4.When the secondary current Is that flows through the secondary winding equals 0, the waveform of resonance appears in the voltage Vds of the drain electrode of power switch pipe 320, the variation of this Vds voltage will cause the flow through parasitic capacitance 401 of power switch pipe 320 of grid current Ig, as shown in Figure 5, Fig. 5 shows the waveform 502 of drain terminal voltage Vds of waveform 501, power switch pipe 320 of waveform 500, the secondary current Is of the driving signal OUT of power switch pipe 320 in Fig. 3 and the waveform 503 of grid current Ig.In prior art, the voltage signal (the FB signal in Fig. 2 b) of the auxiliary winding feedback by transformer 310 detects the null time point of secondary current Is.But can find out from the oscillogram of Fig. 5, the grid current Ig of secondary current Is and power switch pipe 320 has corresponding relation equally, if the time point that grid current Ig produces detected at work, can obtain equally the null time point of secondary current Is.
In concrete operations, the constant-current controller 330 of the former limit feedback constant flow control circuit in Fig. 3 can record the voltage (can be referred to as sampled voltage) that is carried in sampling resistor 340 two ends by primary current test side CS, the size of this sampled voltage flows through the source-drain current of power switch pipe 320 when being 320 conducting of primary current Ip(power switch pipe) with the product of the resistance of sampling resistor 340, it has directly reflected the size of primary current Ip.Can come switch-off power switching tube 320 according to the comparative result of sampled voltage and the reference voltage of presetting subsequently, to control the peak value of primary current Ip.For example, with this sampled voltage and default reference voltage relatively, when sampled voltage during greater than reference voltage, constant-current controller 330 switch-off power switching tubes 320, thus the peak value that guarantees primary current Ip is fixed value.
Be fixed value in order to control Tons/ (Tons+Toff), constant-current controller 330 can detect and export the grid current Ig that multiplexing end OUT records power switch pipe 320 by secondary current, for example obtain the time point that grid current Ig produces, be zero time point thereby obtain secondary current Is, driving signal in conjunction with power switch pipe 320, obtain secondary conducting duration Tons or turn-off duration Toff, conducting or shutoff duration by regulating secondary (or secondary current), make Tons/ (Tons+Toff) be fixed value thus.In case the peak value of primary current Ip and Tons/ (Tons+Toff) are fixed value, can obtain desirable constant current.
Fig. 6 shows the logic diagram of constant-current controller 330 in Fig. 3, Fig. 7 shows the exemplary circuit figure of the former limit feedback constant flow control circuit that adopts the constant-current controller 330 in Fig. 6, wherein, the load circuit in Fig. 7 is LED, and the secondary winding is connected with LED by current rectifying and wave filtering circuit.
As shown in Figure 6 and Figure 7, constant-current controller 330 comprises: current limliting comparison module 331, current detection module 332, constant-current control module 333, switching signal generation module 334, output driver module 335.Wherein, the positive input terminal of current limliting comparison module 331 is connected with primary current test side CS, and the negative input end of current limliting comparison module 331 receives reference voltage, for example Vcs in Fig. 7.The input of current detection module 332 and secondary current detect and are connected multiplexing end OUT and are connected, with the grid current of reception and detection power switching tube 320.The input of constant-current control module 333 is connected with the output of current detection module 332, generates conducting or the shutoff duration of secondary current by the testing result of grid current.The first input end of switching signal generation module 334 is connected with the output of current limliting comparison module 331, the second input is connected with the output of constant-current control module 333, thus comparative result and the conducting of secondary current or conducting or the cut-off signals that the shutoff duration comes generating power switching tube 320 by obtaining sampled voltage and reference voltage.The control input end of output driver module 335 is connected with the output of switching signal generation module 334, and voltage input end is connected with power end, the detection of its output and secondary current be connected multiplexing end OUT and be connected; Thereby come conducting or switch-off power switching tube 320 based on the conducting or the cut-off signals that receive from switching signal generation module 334.
Particularly, current limliting comparison module 331 compares the voltage (can be referred to as sampled voltage) at sampling resistor 340 two ends with reference voltage, for example compare with reference voltage Vcs, and this sampled voltage has reflected the size of primary current Ip.During greater than reference voltage, switching signal generation module 334 generates the control signal of switch-off power switching tubes 320 when sampled voltage, and by output driver module 335 switch-off power switching tubes 320, thereby the peak I pk that guarantees primary current Ip is fixed value.
As can be seen from the above, adopt the constant-current controller 330 according to the embodiment of the present invention, can be simultaneously peak value and the Tons/ (Tons+Toff) of secondary current Is be controlled to be fixed value, thereby obtains comparatively desirable constant current.In concrete enforcement, no longer obtain the information of secondary current by the extra auxiliary winding feedback of transformer 310, but according to the grid current Ig of power switch pipe 320 and the corresponding relation of secondary current Is, obtaining secondary current Is by detection grid current Ig is zero time point, thereby controlling Tons/ (Tons+Toff) is fixed value, to obtain constant current.
In this process, on the one hand, transformer 310 only has former limit winding and secondary winding, and auxiliary winding is removed.Because transformer 310 only has two windings, simplified the production process of transformer 310, reduced the cost of transformer 310, play a positive role to reducing costs.On the other hand, the input of grid current and the output of drive control signal utilize the pin bit multiplex, have saved FB pin of the prior art.Owing to having saved the FB pin, the divider resistance 108 and 109 that is attached thereto in Fig. 1 also is removed.Simultaneously, owing to having saved the FB pin, control chip can be used less encapsulation format, and this is also helpful to reducing system dimension.For example, under the restriction of the size that has light fixture now, the size of LED driving power is extremely important.The size of existing light fixture that this is not only can be better compatible, and reduced the cost of driving power, to universal the playing a positive role of LED illumination.Meanwhile, saved the auxiliary winding of feedback resistance 108 and 109, FB pin and transformer 310, the components and parts on printed circuit board (PCB) reduce, and can reserve enough safe distances, and this is very useful to the reliability that improves the LED driving power.
Fig. 8 shows the circuit diagram according to the current detection module 332 of first embodiment of the invention, and as shown in Figure 8, this current detection module 332 comprises electric current comparing unit 801 and semaphore lock unit 802.Wherein, the first end of electric current comparing unit 801 receives default reference current 803, the second end and secondary current detect and are connected multiplexing end OUT and are connected grid current Ig with received power switching tube 320, with grid current Ig during greater than reference current in second end place's generation voltage drop.The input of semaphore lock unit is connected with the second end, to detect the change in voltage at the second end place.
For example, in a preferred embodiment of the invention, this electric current comparing unit comprises the first identical field-effect transistor and the second field-effect transistor.Wherein, two source shorted and two grid short circuits of the first and second field-effect transistors, the drain electrode of the first field-effect transistor and secondary current detect and are connected multiplexing end OUT and are connected, the drain electrode reception reference current of the second field-effect transistor.The input of semaphore lock unit is connected with the drain electrode of the first field-effect transistor, and output is connected with the input of constant-current control module 333.In work, when grid current produces and during greater than reference current, voltage drop will appear in node 804 places.After semaphore lock unit 802 detects this voltage drop, this information is sent to constant-current control module 333.Constant-current control module 333 calculates secondary ON time Tons according to the trailing edge of the driving signal of this this information and power switch pipe 320, and calculates Toffs and generating power switching tube 320 control driving signals according to Tons.
Fig. 9 a shows the circuit diagram according to the current detection module 332 of second embodiment of the invention, and Fig. 9 b shows the waveform 907 of driving signal of the power switch pipe 320 in Fig. 9 a and the voltage waveform 908 at node 905 places.As shown in Fig. 9 a, this current detection module 332 comprises Detection capacitance 901 and semaphore lock unit 902.Wherein, the first end of Detection capacitance 901 connects the secondary current detection and exports multiplexing end OUT, the second end ground connection; The input of semaphore lock unit 902 is connected with the first end of Detection capacitance 901, and output is connected with the input of constant-current control module 333, detects grid current with the variation of the voltage that receives by detection.
Preferably, current detection module 332 further comprises pressure limiting diode 904, the plus earth of pressure limiting diode 904, and negative pole and secondary current detect and are connected multiplexing end OUT and are connected.It is too low that its main function is that voltage that the restriction secondary current detected and exported multiplexing end OUT can not occur, in order to avoid cause latch-up.
Preferably, current detection module 332 further comprises reset switch 903, and the drain electrode of reset switch 903 is connected with the first end of Detection capacitance 901, and its source electrode and grid are unsettled.As shown in Fig. 9 b, the control signal of reset switch is waveform 906, and this control signal is triggered and a burst pulse of generation by the trailing edge of the driving signal (waveform 907) of power switch pipe 320.After this burst pulse appears at the trailing edge of driving signal (waveform 907) of power switch pipe 320.The effect of reset switch pipe is, before new one-period begins, Detection capacitance resetted, and prepares electric current I g is detected.
In work, when resonance appearred in Vds, namely Is equaled at 0 o'clock, detected and export at secondary current the electric current I g that the parasitic capacitance 401 of the power switch pipe 320 of flowing through appears in multiplexing end OUT, this electric current I g Detection capacitance of flowing through simultaneously.Be far longer than the area of Detection capacitance due to the area of former limit power switch pipe 320, therefore the parasitic capacitance 401 of former limit power switch pipe 320 is far longer than Detection capacitance, and Detection capacitance is very little, so according to the characteristic of capacitances in series, the appearance of grid current lg can cause the decline of node 905 place's voltages.Signal lock circuit detects the voltage at node 905 places, and output signal is input to constant-current control module 333 for calculating Toffs and generating power switching tube 320 control driving signals.
Should be understood that, for those of ordinary skills, can be improved according to the above description or conversion, and all these improve and conversion all should belong to the protection range of claims of the present invention.
Claims (7)
1. a former limit feedback constant flow control circuit, is characterized in that, comprises transformer, power switch pipe, constant-current controller and sampling resistor; Wherein,
Described transformer comprises former limit winding and secondary winding, and an end of described former limit winding is connected with the drain electrode of described power switch pipe, and the two ends of described secondary winding connect load circuit;
One end ground connection of described sampling resistor, the other end is connected with the source electrode of described power switch pipe;
The primary current test side of described constant-current controller is connected with the source electrode of described power switch pipe, and the voltage by obtaining described sampling resistor two ends turn-offs described power switch pipe with the comparative result of default reference voltage, to control the peak value of primary current; The secondary current of described constant-current controller detects and is connected multiplexing end and is connected with the grid of described power switch pipe, controls conducting or the shutoff duration of described secondary current by the grid current that detects described power switch pipe.
2. former limit according to claim 1 feedback constant flow control circuit, is characterized in that, described constant-current controller comprises:
The current limliting comparison module, the positive input terminal of described current limliting comparison module is connected with described primary current end, and the negative input end of described current limliting comparison module receives described reference voltage;
Current detection module, the input of described current detection module and described secondary current detect and are connected multiplexing end and are connected, with reception with detect the grid current of described power switch pipe;
Constant-current control module, the input of described constant-current control module is connected with the output of described current detection module, generates conducting or the shutoff duration of secondary current by the testing result of described grid current;
The switching signal generation module, the first input end of described switching signal generation module is connected with the output of described current limliting comparison module, and the second input is connected with the output of described constant-current control module; With comparative result and the conducting of described secondary current or conducting or the cut-off signals that the shutoff duration generates described power switch pipe by obtaining described sampled voltage and described reference voltage;
The output driver module, the input of described output driver module is connected with the output of described switching signal generation module; The output of described output driver module and described secondary current detect and are connected multiplexing end and are connected; To come conducting or to turn-off described power switch pipe based on the described conducting or the cut-off signals that receive from described switching signal generation module.
3. former limit according to claim 2 feedback constant flow control circuit, is characterized in that, described current detection module comprises:
The electric current comparing unit, the first end of described electric current comparing unit receives default reference current, the second end and described secondary current and the grid current of being connected multiplexing end and being connected to receive described power switch pipe are to produce voltage drop at described the second end place at described grid current during greater than described reference current;
The semaphore lock unit, the input of described semaphore lock unit is connected with described the second end, to detect the change in voltage at described the second end place.
4. former limit according to claim 3 feedback constant flow control circuit, is characterized in that, described electric current comparing unit comprises the first identical field-effect transistor and the second field-effect transistor;
Wherein, two source shorted and two grid short circuits of described the first and second field-effect transistors, the drain electrode of described the first field-effect transistor and described secondary current be connected multiplexing end and be connected, the drain electrode of described the second field-effect transistor receives reference current;
The input of described semaphore lock unit is connected with the drain electrode of described the first field-effect transistor, and output is connected with the input of described constant-current control module.
5. former limit according to claim 2 feedback constant flow control circuit, is characterized in that, described current detection module comprises:
Detection capacitance, the first end of described Detection capacitance connect described secondary current and the multiplexing end of output, the second end ground connection;
The semaphore lock unit, the input of described semaphore lock unit is connected with the first end of described Detection capacitance, and output is connected with the input of described constant-current control module, detects described grid current with the variation of the voltage that receives by detection.
6. former limit according to claim 5 feedback constant flow control circuit, is characterized in that, described current detection module further comprises the pressure limiting diode, the plus earth of described pressure limiting diode, negative pole and described secondary current be connected multiplexing end and be connected.
7. former limit according to claim 5 feedback constant flow control circuit, it is characterized in that, described current detection module further comprises the reset switch that resets for to described Detection capacitance, and the drain electrode of described reset switch is connected with the first end of described Detection capacitance, and its source electrode and grid are unsettled.
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| CN104703357A (en) * | 2015-03-23 | 2015-06-10 | 深圳市稳先微电子有限公司 | Primary-side feedback LED (Light Emitting Diode) driving circuit |
| CN106604478A (en) * | 2017-01-22 | 2017-04-26 | 上海新进半导体制造有限公司 | High-power LED backlight driving system |
| CN107765067A (en) * | 2017-10-17 | 2018-03-06 | 深圳南云微电子有限公司 | Current detection circuit and electric current detecting method |
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| JP2001157454A (en) * | 1999-11-25 | 2001-06-08 | Toshiba Lighting & Technology Corp | Constant-current power supply |
| CN102055357A (en) * | 2009-10-27 | 2011-05-11 | 聚辰半导体(上海)有限公司 | Switch power supply controller circuit and switch power supply system |
| CN101867295A (en) * | 2010-03-16 | 2010-10-20 | 成都芯源系统有限公司 | Circuit and control method |
| CN102437740A (en) * | 2011-12-22 | 2012-05-02 | 成都成电硅海科技股份有限公司 | Primary-side feedback flyback constant-current power supply with input voltage compensation function |
| CN102724799A (en) * | 2012-06-28 | 2012-10-10 | 上海晶丰明源半导体有限公司 | Light emitting diode (LED) drive circuit and method without auxiliary winding |
| CN203072221U (en) * | 2013-01-24 | 2013-07-17 | 深圳市芯飞凌半导体有限公司 | Primary side feedback constant current control circuit |
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Application publication date: 20130515 |