CN206948673U - A kind of BUCK type LED drive circuits for preventing lower electric backflash - Google Patents
A kind of BUCK type LED drive circuits for preventing lower electric backflash Download PDFInfo
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- CN206948673U CN206948673U CN201720914396.XU CN201720914396U CN206948673U CN 206948673 U CN206948673 U CN 206948673U CN 201720914396 U CN201720914396 U CN 201720914396U CN 206948673 U CN206948673 U CN 206948673U
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
Abstract
It the utility model is related to LED drive circuit technical field, a kind of more particularly to BUCK type LED drive circuits for preventing lower electric backflash, including power supply, switch, first diode, second diode, 3rd diode, 4th diode, 5th diode, inductance, LED, technotron, first electric capacity, second electric capacity, first NOT gate, resistance, metal-oxide-semiconductor, power tube, VCC under-voltage protection units, counter resets unit, counter unit and constant-current control circuit, the utility model solves the problems, such as LED backflash after electricity under BUCK type LED drive circuits, and the VCC signal input of constant-current control circuit is not discharged in system start-up phase, system starting current will not be increased, the system electrification time will not increase, system start-up time is short；The electric capacity charging and discharging number of VCC signal input is many simultaneously, increased periods so that constant-current control circuit discharge current can be set smaller, so as to avoid the high current because of instantaneous discharge from causing chip to damage, improve system reliability.
Description
Technical field
LED drive circuit technical field is the utility model is related to, more particularly to a kind of BUCK types LED for preventing lower electric backflash
Drive circuit.
Background technology
Existing driving power circuit is broadly divided into BUCK types, BOOST types, wherein three kinds of BUCK/BOOST types, BUCK types
Driving power is widely used and LED drive circuit field because its circuit structure is simple, cost is cheap.Existing BUCK types LED
In drive circuit, constant-current control circuit is generally powered by the JFET that circuit is internally integrated to constant-current control circuit, JFET drain electrode
Drain electrode with power tube is shorted together, so as to save externally fed resistance.But this LED drive circuit is in power switch
After disconnection, usually occur that LED can also flash several lower phenomenons (i.e. backflash phenomenon) that could extinguish completely after extinguishing, it is produced
The reason for be：BUCK types LED drive circuit power switch disconnection after, line voltage VIN is gradually reduced, JFET drain voltages with
With decline, so as to cause the decline of JFET electric currents, when JFET electric currents drop below constant-current control circuit operating current, constant current control
Circuit power VCC voltages processed, which decline, can trigger VCC under-voltage protections, and power tube is stopped, and LED is extinguished, and now line voltage is simultaneously
Non- power-off, still store on the storage capacitor at line voltage end compared with multi-charge, after power tube is stopped, current constant control electricity
The electric current of road consumption reduces, and the electric current of now constant-current control circuit consumption is much smaller than JFET electric currents, constant-current control circuit VCC voltages
It can rise to start and voltage and be again started up, power tube task again, cause LED to be lighted again.With power tube work again
Make, constant-current control circuit operating current increase, constant-current control circuit power supply VCC voltages decline triggering VCC under-voltage protections, work(again
Rate pipe is stopped again, and LED is extinguished again, and this lights-and extinguishing process is repeated several times, until line voltage power-off, LED
Could thoroughly it extinguish.This backflash phenomenon can cause bad sensory experience to user.
In order to solve the problems, such as this backflash, the Technological improvement plan of generally use is as shown in figure 1, its work in the prior art
Principle is：VCC under-voltage protections unit detection VCC voltages and output control signal UVLO, after power switch disconnects, current constant control
Circuit power VCC voltages decline triggering VCC under-voltage protection units, and VCC under-voltage protections unit output control signal UVLO is by high electricity
Flat to be changed into low level, metal-oxide-semiconductor N1 grid voltages discharge is changed into high level from low level, and metal-oxide-semiconductor N1 is turned on, and to VCC ends
The electric capacity C2 electric discharges of connection, resistance R1 are used to set metal-oxide-semiconductor N1 discharge current values, and the metal-oxide-semiconductor N1 discharge currents of setting must be big
In JFET electric currents, because if metal-oxide-semiconductor N1 discharge currents are more than JFET electric currents, under constant-current control circuit power supply VCC voltages continue
Drop, constant-current control circuit would not restart work again, and LED keeps OFF state, is not in backflash phenomenon.Such as Fig. 2 institutes
Show, for waveform diagram of the circuit after power switch shut-off.
Although foregoing circuit design solves the problems, such as LED backflash after power switch shut-off, but reduce simultaneously
To the electric current of constant-current control circuit power supply VCC ends electric capacity charging in system starting process, that is, system starting current is reduced, this
Allow in constant-current control circuit start-up course, the output of VCC under-voltage protecting circuits keeps high level, and metal-oxide-semiconductor N1 turns on simultaneously right
VCC discharges, many so as to cause the charging current of VCC ends electric capacity to reduce, and electric capacity charging in constant-current control circuit power supply VCC ends becomes
It is very slow, ultimately result in startup overlong time when system normally goes up electric.System electrification start overlong time not only can give user with
Carry out poor usage experience, also limit the selectivity of constant-current control circuit power supply VCC ends electric capacity (can only select the electricity of smaller value
Hold), made troubles to system debug；At the same time, because JFET electric currents are generally bigger, in order to avoid current constant control electric completely
Work is restarted on road, and power supply VCC discharge current is needed to set very big, causes instantaneous large-current to pass through JFET and current constant control
Circuit, damage risk be present to JFET and constant-current control circuit.
Utility model content
For the problems of the prior art, a kind of the utility model offer system electrification startup time is short, effectively avoids wink
Between high current to control circuit cause damage preventing under electric backflash BUCK type LED drive circuits.
To realize above technical purpose, the technical solution of the utility model is：A kind of BUCK types LED for preventing lower electric backflash
Drive circuit, including power supply, switch, the first diode, the second diode, the 3rd diode, the 4th diode, the five or two pole
Pipe, inductance, LED, technotron, the first electric capacity, the second electric capacity, the first NOT gate, resistance, metal-oxide-semiconductor, power tube, VCC is under-voltage
Protection location, counter resets unit, counter unit and constant-current control circuit；
The anode of first diode is connected with the negative electrode of the 3rd diode；
The negative electrode of first diode, the negative electrode of the second diode, one end of the first electric capacity, the negative electrode of the 5th diode
It is connected with LED anode；
The anode of second diode is connected with the negative electrode of the 4th diode；
The anode of 3rd diode and the anode of the 4th diode are connected and are grounded；
One end of the power supply is connected by switching with the anode of the first diode, the negative electrode of the other end and the 4th diode
It is connected；
The other end ground connection of first electric capacity；
The grounded-grid of the technotron, drain the anode with the 5th diode, one end of inductance and work(respectively
The drain electrode of rate pipe is connected, the VCC signal end phase of source electrode one end with resistance, one end of the second electric capacity and constant-current control circuit respectively
Even；
The other end of the inductance is connected with LED negative electrode；
The grid of the power tube is connected with the signal output part of constant-current control circuit, source ground；
The other end ground connection of second electric capacity；
The input with the discharge signal output parts and the first NOT gate of counter unit respectively of the grid of the metal-oxide-semiconductor
End is connected, source ground, and drain electrode is connected with the other end of resistance；
The output end of first NOT gate is connected with the Enable signal input parts of constant-current control circuit；
The input of the VCC under-voltage protections unit is connected with the VCC signal input of constant-current control circuit, output end point
It is not connected with the UVLO signal input parts of counter unit and the UVLO signal input parts of constant-current control circuit；
The input of the counter resets unit is connected with the VCC signal input of constant-current control circuit, output end with
The Reset signal input parts of counter unit are connected；
The VCC under-voltage protections unit is hysteresis comparator, for detecting the electricity of constant-current control circuit VCC signal input
Press signal and by it compared with the threshold voltage of itself, producing square wave control signal UVLO, UVLO signal according to comparative result uses
In control constant-current control circuit and be used as the input signal of counter unit, the threshold voltage include high threshold voltage VON with
Low threshold voltage VOFF；
The counter resets unit is comparator, and the voltage for detecting constant-current control circuit VCC signal input is believed
Number and by it compared with the threshold voltage of itself, the threshold voltage is VReset, according to comparative result produce counter unit
Reset signals needed for resetting；
The relation of the threshold voltage of the VCC under-voltage protections unit and the threshold voltage of counter resets unit is：
VReset<VOFF<VON；
The counter unit is used to count the cycle of UVLO signals, according to the difference of counting stage, counter
Unit discharge signal output parts export different signals, before starting counting up, counter unit discharge signal outputs
The signal of end output is low level, and before counter starts counting up rear and counter counts completely, counter unit discharge signals are defeated
The signal for going out end output is high level, and after counter counts are full, the signal of counter unit discharge signal output parts output is
Low level；
The constant-current control circuit is high level in the signal of its UVLO signal input part and Enable signal input parts
When work, otherwise do not work.
From the above, it can be seen that the utility model possesses advantages below：
1. circuit described in the utility model solves the problems, such as LED backflash after electricity under BUCK type LED drive circuits；
2. circuit described in the utility model is not put in system start-up phase to the VCC signal input of constant-current control circuit
Electricity, system starting current will not be increased, the system electrification time will not increase, so as to realize that it is shorter that system starts power-on time；
3. circuit described in the utility model is after power supply disconnection, the electric capacity C2 of the VCC signal input of constant-current control circuit
Carry out 2N-1It is secondary to be charged and discharged repeatedly, the storage capacitor C1 at line voltage end can be substantially discharged so that line voltage is complete
Complete lower electricity, the electric capacity C2 charging and discharging numbers of VCC signal input are a lot, increased periods so that constant-current control circuit is put
Electric current can be set smaller, so as to avoid the high current because of instantaneous discharge from causing technotron and current constant control electricity
Path loss is hindered, and improves system reliability.
Preferably, the counter unit include delay unit, the second NOT gate, the 3rd NOT gate, with door, N number of D to connect
Trigger and rest-set flip-flop, the rest-set flip-flop include the first nor gate and the second nor gate, the input of the delay unit,
The input end of clock Clk of the input of second NOT gate and the 1st d type flip flop is connected and defeated as the UVLO signals of counter unit
Enter end, the first output end Q of each d type flip flop is connected with the input end of clock Clk of the d type flip flop of its rear stage, described
First output end Q of n-th d type flip flop is connected with the second input of the second nor gate, the input of each d type flip flop
The the second output end Q of D with itself are connected, the Reset ends of N number of d type flip flop be connected with the input of the 3rd NOT gate and
As the Reset signal input parts of counter, the first input end of first nor gate is connected with the output end with door, and second
Input is connected with the output end of the second nor gate, and output end is connected with the first input end of the second nor gate, described second or
3rd input of NOT gate is connected with the output end of the 3rd NOT gate, and output end is defeated as the discharge signals of counter unit
Go out end.
Brief description of the drawings
Fig. 1 is the structural representation of the existing LED drive circuit for preventing lower electric backflash；
Fig. 2 is waveform diagram of the circuit structure after power remove shown in Fig. 1；
Fig. 3 is electrical block diagram of the present utility model；
Fig. 4 is the structural representation of counter unit of the present utility model；
Fig. 5 is waveform diagram of the circuit structure of the present utility model after power remove.
Embodiment
With reference to Fig. 3 to Fig. 5, a specific embodiment of the present utility model is described in detail, but not to power of the present utility model
Profit requires to do any restriction.
As shown in figure 3, a kind of BUCK type LED drive circuits for preventing lower electric backflash, including power supply Vac, switch S1, first
Diode D1, the second diode D2, the 3rd diode D3, the 4th diode D4, the 5th diode D5, inductance L1, LED, junction type
FET JFET1, the first electric capacity C1, the second electric capacity C2, the first NOT gate NOT1, resistance R, metal-oxide-semiconductor N1, power tube Q1, VCC are owed
Press protection location, counter resets unit, counter unit and constant-current control circuit；
First diode D1 anode is connected with the 3rd diode D3 negative electrode；
First diode D1 negative electrode, the second diode D2 negative electrode, the first electric capacity C1 one end, the 5th diode D5
Negative electrode is connected with LED anode；
Second diode D2 anode is connected with the 4th diode D4 negative electrode；
3rd diode D3 anode and the 4th diode D4 anode are connected and are grounded；
Power supply Vac one end is connected by switching S1 with the first diode D1 anode, the other end and the 4th diode D4
Negative electrode be connected；
First electric capacity C1 other end ground connection；
Technotron JFET1 grounded-grid, the drain electrode anode with the 5th diode D5, inductance L1 respectively one end
Drain electrode with power tube Q1 is connected, source electrode one end with resistance R1, the second electric capacity C2 one end and constant-current control circuit respectively
VCC signal end is connected；
The inductance L1 other end is connected with LED negative electrode；
Power tube Q1 grid is connected with the signal output part of constant-current control circuit, source ground；
Second electric capacity C2 other end ground connection；
Metal-oxide-semiconductor N1 grid is defeated with the discharge signal output parts of counter unit and the first NOT gate NOT1 respectively
Enter end to be connected, source ground, drain electrode is connected with the resistance R1 other end；
First NOT gate NOT1 output end is connected with the Enable signal input parts of constant-current control circuit；
The input of VCC under-voltage protection units is connected with the VCC signal input of constant-current control circuit, output end respectively with
The UVLO signal input parts of counter unit are connected with the UVLO signal input parts of constant-current control circuit；
The input of counter resets unit is connected with the VCC signal input of constant-current control circuit, and output end is with counting
The Reset signal input parts of device unit are connected.
VCC under-voltage protections unit is hysteresis comparator, and the voltage for detecting constant-current control circuit VCC signal input is believed
Number and by it compared with the threshold voltage of itself, square wave control signal UVLO, UVLO signal is produced according to comparative result and is used to control
Constant-current control circuit processed and include high threshold voltage VON and low threshold as the input signal of counter unit, the threshold voltage
Threshold voltage VOFF；
Counter resets unit is comparator, for detecting the voltage signal of constant-current control circuit VCC signal input simultaneously
By it compared with the threshold voltage of itself, the threshold voltage is VReset, and producing counter unit according to comparative result resets
Required Reset signals；
The relation of the threshold voltage of VCC under-voltage protection units and the threshold voltage of counter resets unit is：VReset<
VOFF<VON
Counter unit is used to count the cycle of UVLO signals, according to the difference of counting stage, counter unit
Discharge signal output parts export different signals, and before starting counting up, counter unit discharge signal output parts are defeated
The signal gone out is low level, before counter starts counting up rear and counter counts completely, counter unit discharge signal output parts
The signal of output is high level, and after counter counts are full, the signal of counter unit discharge signal output parts output is low electricity
It is flat；
Constant-current control circuit work when the signal of its UVLO signal input part and Enable signal input parts is high level
Make, otherwise do not work.
Operation principle of the present utility model is：
The signal that power tube Q1 only inputs in the UVLO signal input parts and Enable signal input parts of constant-current control circuit
It can just be worked when being simultaneously high level.Counter resets unit is a comparator, and input signal is the electricity of constant-current control circuit
Source VCC voltages, threshold voltage VReset.VCC under-voltage protections unit is a hysteresis comparator, and input signal is current constant control
The power supply VCC voltages of circuit, low threshold voltage VOFF, high threshold voltage VON.Wherein, counter resets unit and VCC are owed
The magnitude relationship of each threshold voltage of protection location is pressed to be arranged to：VReset<VOFF<VON.
When system starts, the voltage signal of the VCC signal input of constant-current control circuit is risen by 0V, when VCC signal is defeated
Enter end voltage signal values be less than counter resets unit threshold voltage VReset when, counter resets unit output end is defeated
The Reset signals gone out are low level, and counter unit is resetted.The signal of counter unit output end output is low level
When, electric discharge metal-oxide-semiconductor N1 is closed, and the signal of constant-current control circuit Enable signal input parts is high level.
The voltage signal of VCC signal input is continuously risen to higher than VReset but less than the height of VCC under-voltage protection units
Threshold voltage VON (i.e. VReset<VCC<When VON), the UVLO signals of VCC under-voltage protection unit output ends are low level always,
The Reset signals of counter resets unit output end output are high level always, and the signal of counter unit output end is always
Low level, electric discharge metal-oxide-semiconductor N1 are closed always, and the signal of constant-current control circuit Enable signal input parts is high level always.
When the high threshold electricity that the voltage of VCC signal input is continuously risen to be higher than VCC under-voltage protection units by VReset
After pressing VON (the startup voltage that i.e. constant-current control circuit is started working), the UVLO signals of VCC under-voltage protection units output end output
High level is changed into from low level, constant-current control circuit is started working, and driving power pipe Q1 starts working, and LED is lighted.
In said process, when starting due to system, electric discharge metal-oxide-semiconductor N1 is remained turned-off, and the VCC of constant-current control circuit is not believed
The electric discharge of number input, technotron JFET1 electric current are equal to the electric capacity C2 of VCC signal input charging current, VCC letters
The electric capacity C2 of number input charging current is very big, so system start-up time can very little.
After power switch S1 disconnects, the voltage of constant-current control circuit VCC signal input declines, when VCC signal input
Voltage when dropping below the low threshold voltage VOFF of VCC under-voltage protection units, the output of VCC under-voltage protection units output end
UVLO signals are changed into low level from high level, and counter unit starts that the square-wave signal of its UVLO signal input part is started to count
Number, the signal of the discharge signal output parts of metal-oxide-semiconductor N1 grids connection are changed into high level from low level, and metal-oxide-semiconductor N1 is turned on,
And the electric capacity C2 of constant-current control circuit VCC signal input connection is discharged；Meanwhile constant-current control circuit Enable signals input
The signal at end is changed into low level, and power tube Q1 is stopped.Resistance R1 is used for the discharge current value for setting metal-oxide-semiconductor N1, the electric current
Value can be set smaller than technotron JFET1 electric current.Because metal-oxide-semiconductor N1 discharge currents are less than technotron
JFET1 electric current, and the voltage of VCC signal input drops below the low threshold voltage VOFF of VCC under-voltage protection units
When, the electric current of constant-current control circuit consumption reduces, so the voltage of VCC signal input can rise.When VCC signal input
After voltage rises above the high threshold voltage VON of VCC under-voltage protection units, the UVLO signals of VCC under-voltage protection member output ends
High level, the electric current increase of constant-current control circuit consumption are changed into from low level, the voltage of VCC signal input declines again.Such as
This repeatedly, the electric capacity C2 of VCC signal input can repeatedly discharge and and charge.
In C2 discharges simultaneously charging process again repeatedly, the signal lock of counter unit discharge signal output parts output
It is set to high level, metal-oxide-semiconductor N1 is held on, and keeps the VCC signal input electric discharge to constant-current control circuit；Constant-current control circuit
Enable signal input parts be locked as low level, power tube Q1 does not work；Counter unit inputs to UVL0 signal input parts
Square wave counted, the square-wave signal of the corresponding UVLO signal input part of each electric capacity C2 charge and discharge process.Only when
Electric capacity C2 passes through 2N-1After secondary electric discharge and again charging process, the signal just meeting of counter unit discharge signal output parts output
Low level is changed into from high level and turns off metal-oxide-semiconductor N1, the signal of constant-current control circuit Enable signal input parts is become by low level
For high level and power tube Q1 is allowed to work.Because the resetting voltage VReset of counter unit is less than VCC under-voltage protection units
Low threshold voltage VOFF, so the voltage of VCC signal input drops to VCC under-voltage protection unit low threshold voltages VOFF
When, the change of Reset signal levels will not be triggered, thus discharged repeatedly in C2 and charging process Counter unit does not reset again.
Because simultaneously charging process (at most repeats 2 to the electric discharge of VCC electric capacity againN-1Secondary, N is determined by the counts of counter in itself, Ke Yigen
According to demand sets itself), the storage capacitor C1 connected on line voltage VIN can be substantially discharged, make line voltage power-off, keep away
Exempt from LED to light again.Because simultaneously charging times are many again for the electric capacity C2 electric discharges of VCC signal input, increased periods, pass through electricity
Resistance R1 set discharge current can set it is smaller, so as to avoid the high current because of instantaneous discharge from causing constant-current control circuit
With technotron JFET1 damage, so as to improve the reliability of system.
It is illustrated in figure 4 circuit waveform schematic diagram of the circuit described in the utility model after power remove.
Counter unit described in the utility model can use structure as described in Figure 4, and counter unit includes delay
Unit, the second NOT gate NOT2, the 3rd NOT gate NOT3, with door AND1, N number of d type flip flop and rest-set flip-flop connected, rest-set flip-flop bag
Include the first nor gate NOR1 and the second nor gate NOR2, the input of delay unit, the second NOT gate NOT2 input and the 1st
The input end of clock Clk of d type flip flop is connected and as the UVLO signal input part of counter unit, and the first of each d type flip flop
Output end Q is connected with the input end of clock Clk of the d type flip flop of its rear stage, the first output end Q of n-th d type flip flop and second
Nor gate NOR2 the second input is connected, and the second output end Q of the input D of each d type flip flop with itself is connected, described
The Reset ends of N number of d type flip flop are connected with the 3rd NOT gate NOT3 input and as the Reset signal input parts of counter,
First nor gate NOR1 first input end is connected with door AND1 output end, the second input and the second nor gate NOR2's
Output end is connected, and output end is connected with the second nor gate NOR2 first input end, the second nor gate NOR2 the 3rd input
It is connected with the 3rd NOT gate NOT3 output end, discharge signal output part of the output end as counter unit.
Its operation principle is：The voltage of the VCC signal input of constant-current control circuit rises to resetting voltage by 0V
VReset stages, the signals of Reset signal input parts are low level, and the signals of UVLO signal input parts is low level, d type flip flop
It is cleared with rest-set flip-flop, the signals of discharge signal output parts is set to low level, thus constant-current control circuit
The signal of Enable signal input parts is set to high level.When the voltage of the VCC signal input of constant-current control circuit is more than
During VReset, the signal of Reset signal input parts remains high level.When C2 discharges repeatedly and charges again, each UVLO letters
The signal of number input is changed into low level from high level, and the first nor gate of rest-set flip-flop NOR1 first input end occurs once high
Level pulse, a set is carried out to rest-set flip-flop, the signal for resetting discharge signal output parts is high level.Work as constant current
When control circuit is restarted repeatedly, the signal of each UVLO signal input parts is changed into high level from low level, and d type flip flop is carried out once
Count, until the signal that the output end Q of last d type flip flop is exported is changed into high level (D triggerings in such a structure from low level
The number N of device is to be equal to the repetition 2 being noted aboveN-1N in secondary), the signal of discharge signal output parts is just by high electricity
Flat to be changed into low level, the signal of constant-current control circuit Enable signal input parts is changed into high level from low level, and power tube Q1 can
To start working.
In summary, the utility model has advantages below：
1. the utility model solves the problems, such as LED backflash after electricity under BUCK type LED drive circuits；
2. circuit described in the utility model is not put in system start-up phase to the VCC signal input of constant-current control circuit
Electricity, system starting current will not be increased, the system electrification time will not increase, so as to realize that it is shorter that system starts power-on time；
3. circuit described in the utility model is after power supply disconnection, the electric capacity C2 of the VCC signal input of constant-current control circuit
Carry out 2N-1It is secondary to be charged and discharged repeatedly, the storage capacitor C1 at line voltage end can be substantially discharged so that line voltage is complete
Complete lower electricity, the electric capacity C2 charging and discharging numbers of VCC signal input are a lot, increased periods so that constant-current control circuit is put
Electric current can be set smaller, so as to avoid the high current because of instantaneous discharge from causing technotron and current constant control electricity
Path loss is hindered, and improves system reliability.
It is understood that above with respect to specific descriptions of the present utility model, it is merely to illustrate the utility model and is not
It is limited to the technical scheme described by the utility model embodiment.It will be understood by those within the art that still can be with
The utility model is modified or equivalent substitution, to reach identical technique effect；As long as satisfaction uses needs, all in this reality
Within new protection domain.
Claims (2)
- A kind of 1. BUCK type LED drive circuits for preventing lower electric backflash, it is characterised in that：Including power supply, switch, the one or two pole Pipe, the second diode, the 3rd diode, the 4th diode, the 5th diode, inductance, LED, technotron, the first electricity Appearance, the second electric capacity, the first NOT gate, resistance, metal-oxide-semiconductor, power tube, VCC under-voltage protections unit, counter resets unit, counter Unit and constant-current control circuit；The anode of first diode is connected with the negative electrode of the 3rd diode；The negative electrode of first diode, the negative electrode of the second diode, one end of the first electric capacity, the 5th diode negative electrode and LED anode is connected；The anode of second diode is connected with the negative electrode of the 4th diode；The anode of 3rd diode and the anode of the 4th diode are connected and are grounded；One end of the power supply is connected by switching with the anode of the first diode, the negative electrode phase of the other end and the 4th diode Even；The other end ground connection of first electric capacity；The grounded-grid of the technotron, drain the anode with the 5th diode, one end of inductance and power tube respectively Drain electrode be connected, the VCC signal end of source electrode one end with resistance, one end of the second electric capacity and constant-current control circuit respectively is connected；The other end of the inductance is connected with LED negative electrode；The grid of the power tube is connected with the signal output part of constant-current control circuit, source ground；The other end ground connection of second electric capacity；The grid of the metal-oxide-semiconductor respectively with the discharge signal output parts of counter unit and the input phase of the first NOT gate Even, source ground, drain electrode are connected with the other end of resistance；The output end of first NOT gate is connected with the Enable signal input parts of constant-current control circuit；The input of the VCC under-voltage protections unit is connected with the VCC signal input of constant-current control circuit, output end respectively with The UVLO signal input parts of counter unit are connected with the UVLO signal input parts of constant-current control circuit；The input of the counter resets unit is connected with the VCC signal input of constant-current control circuit, and output end is with counting The Reset signal input parts of device unit are connected；The VCC under-voltage protections unit is hysteresis comparator, and the voltage for detecting constant-current control circuit VCC signal input is believed Number and by it compared with the threshold voltage of itself, square wave control signal UVLO, UVLO signal is produced according to comparative result and is used to control Constant-current control circuit processed and include high threshold voltage VON and low threshold as the input signal of counter unit, the threshold voltage Threshold voltage VOFF；The counter resets unit is comparator, for detecting the voltage signal of constant-current control circuit VCC signal input simultaneously By it compared with the threshold voltage of itself, the threshold voltage is VReset, and producing counter unit according to comparative result resets Required Reset signals；The relation of the threshold voltage of the VCC under-voltage protections unit and the threshold voltage of counter resets unit is：VReset< VOFF<VON；The counter unit is used to count the cycle of UVLO signals, according to the difference of counting stage, counter unit Discharge signal output parts export different signals, and before starting counting up, counter unit discharge signal output parts are defeated The signal gone out is low level, before counter starts counting up rear and counter counts completely, counter unit discharge signal output parts The signal of output is high level, and after counter counts are full, the signal of counter unit discharge signal output parts output is low electricity It is flat；Constant-current control circuit work when the signal of its UVLO signal input part and Enable signal input parts is high level Make, otherwise do not work.
- 2. the BUCK type LED drive circuits according to claim 1 for preventing lower electric backflash, it is characterised in that：The counting Device unit includes delay unit, the second NOT gate, the 3rd NOT gate, touched with door, N number of d type flip flop and rest-set flip-flop connected, the RS Hair device includes the first nor gate and the second nor gate, the input of the delay unit, the input of the second NOT gate and the 1st D The input end of clock Clk of trigger is connected and is used as the UVLO signal input parts of counter unit, each the of the d type flip flop One output end Q is connected with the input end of clock Clk of the d type flip flop of its rear stage, the first output end Q of the n-th d type flip flop It is connected with the second input of the second nor gate, each the second output end Q phases of the input D of the d type flip flop with itself Even, the Reset ends of N number of d type flip flop are connected with the input of the 3rd NOT gate and inputted as the Reset signals of counter End, the first input end of first nor gate are connected with the output end with door, the output of the second input and the second nor gate End is connected, and output end is connected with the first input end of the second nor gate, the 3rd input of second nor gate and the 3rd non- The output end of door is connected, discharge signal output part of the output end as counter unit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201720914396.XU CN206948673U (en) | 2017-07-26 | 2017-07-26 | A kind of BUCK type LED drive circuits for preventing lower electric backflash |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201720914396.XU CN206948673U (en) | 2017-07-26 | 2017-07-26 | A kind of BUCK type LED drive circuits for preventing lower electric backflash |
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| CN206948673U true CN206948673U (en) | 2018-01-30 |
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|---|---|---|---|
| CN201720914396.XU Withdrawn - After Issue CN206948673U (en) | 2017-07-26 | 2017-07-26 | A kind of BUCK type LED drive circuits for preventing lower electric backflash |
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| CN (1) | CN206948673U (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107197571A (en) * | 2017-07-26 | 2017-09-22 | 无锡麟力科技有限公司 | It is a kind of to prevent the BUCK type LED drive circuits of lower electric backflash |
| CN111182677A (en) * | 2019-12-24 | 2020-05-19 | 普联国际有限公司 | LED control circuit |
| CN113484589A (en) * | 2021-06-30 | 2021-10-08 | 杭州加速科技有限公司 | Power-off detection circuit with hysteresis function and control system |
-
2017
- 2017-07-26 CN CN201720914396.XU patent/CN206948673U/en not_active Withdrawn - After Issue
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107197571A (en) * | 2017-07-26 | 2017-09-22 | 无锡麟力科技有限公司 | It is a kind of to prevent the BUCK type LED drive circuits of lower electric backflash |
| CN107197571B (en) * | 2017-07-26 | 2023-10-24 | 无锡麟力科技有限公司 | BUCK type LED driving circuit capable of preventing power-down back flash |
| CN111182677A (en) * | 2019-12-24 | 2020-05-19 | 普联国际有限公司 | LED control circuit |
| CN111182677B (en) * | 2019-12-24 | 2022-03-01 | 普联国际有限公司 | LED control circuit |
| CN113484589A (en) * | 2021-06-30 | 2021-10-08 | 杭州加速科技有限公司 | Power-off detection circuit with hysteresis function and control system |
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