CN205541824U

CN205541824U - LED drive arrangement and liquid crystal disply device

Info

Publication number: CN205541824U
Application number: CN201620013429.9U
Authority: CN
Inventors: 山野敦浩; 温水真; 温水真一
Original assignee: Japan Display Central Inc
Current assignee: Japan Display Central Inc
Priority date: 2015-01-09
Filing date: 2016-01-07
Publication date: 2016-08-31
Anticipated expiration: 2026-01-07
Also published as: JP2016129098A

Abstract

The utility model provides a LED drive arrangement and liquid crystal disply device, has: boost circuit enlargies input voltage to predetermined voltage, ON -OFF control circuit makes boost circuit carry out work or stop work according to the signal of adjusting luminance, the overvoltage protection circuit when the voltage after stepping up is the overvoltage, makes the boost circuit stop work, cable fetch is carried to the supervisory signal, connects in anode line from the voltage after stepping up to LED and the reference voltage supply line of supplying with, the circuit is cut apart to resistance, locates the supervisory signal and carries cable fetch, and the partial pressure of the voltage after will stepping up is drawed to the control voltage to the input of overvoltage protection circuit, the sound prevents the switch, locates the supervisory signal and carries cable fetch, and according to adjusting luminance signal interruption or continue the supervisory signal and carry being connected between cable fetch and the anode line, the sound prevents that the switch according to adjusting luminance the signal, is in the during operation at boost circuit, continues the supervisory signal and carries being connected between cable fetch and the anode line, is in the during operation at boost circuit, suspends the supervisory signal and carries being connected between cable fetch and the anode line.

Description

LED drive device and liquid crystal indicator

Technical field

This utility model relates to a kind of LED drive device and liquid crystal indicator.

Background technology

In recent years, LED (Light Emitting Diode: light emitting diode) due to have low power consumption, The features such as life-span length, are not only used as the succedaneum of existing bulb, are also widely used in such as liquid crystal display Device, vehicle-mounted equipment, ligthing paraphernalia etc..

LED drive device is the circuit for controlling the lighting of LED, light-off.Drive as LED Flowing mode, discloses to control the lighting of multiple LED, the light-off that are connected in series, utilizes boosting Chopper circuit carries out the side that PWM (Pulse Width Modulation: pulse width modulation) dims Formula.

But, when utilizing above-mentioned LED drive device to carry out PWM light modulation, sometimes send sound Sound.

Utility model content

The purpose of this utility model is to provide a kind of sound being prevented from when PWM dims LED drive device and liquid crystal indicator.

One mode provides a kind of LED drive device, and input voltage is amplified backward LED supply, It is characterized in that, described LED drive device has: booster circuit, by flowing to described LED Dynamic electric current controls, in predetermined value, described input voltage to be amplified to predetermined voltage；On-off control Circuit, makes described booster circuit be operated or quit work according to dim signal, this dim signal It it is the square-wave signal of two values；Excess voltage protection, when the voltage after boosting is overvoltage, Described booster circuit is made to quit work；Monitoring signal extraction line, is connected to rise to described LED supply The anode line of the voltage after pressure and reference voltage supply line；Resistance partitioning circuitry, is located at described monitoring letter Number extract line, the dividing potential drop of voltage after boosting is extracted as the prison inputted to described excess voltage protection Control voltage；And sound prevents switch, it is located at described monitoring signal extraction line, according to described light modulation letter Number interrupt or continue the connection between described monitoring signal extraction line and described anode line, described sound Prevent switch according to described dim signal, when described booster circuit is in work, continue described monitoring Connection between signal extraction line and described anode line, when described booster circuit is not in work, in Disconnected connection between described monitoring signal extraction line and described anode line.

Can also be that described sound prevents from switching electricity described in the ratio being located on described monitoring signal extraction line Resistance partitioning circuitry is close at described anode line side.

Can also be that described sound prevents switch to have: level displacement shifter, to described dim signal Level is amplified；And the second switch of P-channel FET, receive described level at gate terminal The output signal of shifter, thus interrupt or continue described monitoring signal extraction line.

Can also be that described level displacement shifter has: resistance, one end be connected to described anode line, separately One end is connected to the gate terminal of described second switch；And the 3rd switch of N-channel FET, leakage Extreme son is connected to the described other end of described resistance, and source terminal is connected to reference voltage supply line, Described dim signal inputs to gate terminal.

Can also be that described level displacement shifter has: the 3rd switch and the P ditch of P-channel FET 5th switch of road FET, gate terminal and drain terminal connection intersected with each other；N-channel FET's 4th switch, source terminal is connected to reference voltage supply line, and drain terminal is connected to the described 3rd and opens The drain terminal closed；And the 6th switch of N-channel FET, source terminal is connected to reference voltage Supply line, drain terminal is connected to the drain terminal of described 5th switch, to the grid of described 4th switch Extreme son input inverts the signal of described dim signal, defeated to the gate terminal of described 6th switch Entering described dim signal, the source terminal of described 3rd switch and described 5th switch is connected to described Anode line, the drain terminal of described 6th switch is connected to the gate terminal of described second switch.

Can also be that described sound prevents from switching being applied in and institute of being located in described resistance partitioning circuitry State the voltage signal of monitoring signal same level and be close to institute than the position extracting described monitoring signal State the position of anode line side.

Can also be that described sound prevents switch to have N-channel FET switch, described N-channel FET Switch and interrupt or continue described monitoring signal extraction by receiving described dim signal at gate terminal Line.

Can also be that described LED drive device also has is located at LED driving IC and this LED Driving the circuit of the outside of IC, described LED drives IC to be built-in with described ON-OFF control circuit, structure Become the first of described booster circuit to switch, described excess voltage protection and described sound prevent out Close.

Can also be that described LED drives IC to be also built-in with described resistance partitioning circuitry.

Can also be that the described sound that described LED drives IC to be comprised prevents from switching by high pressure Operation makes.

Another way provides a kind of LED drive device, input voltage is amplified backward LED and supplies Giving, described LED drive device has: capacitor, and one end is connected to the first reference potential, another End is connected to the positive pole of described LED；Coil, one end is supplied to input voltage；Diode, anode Being connected to the other end of described coil, negative electrode is connected to the other end of described capacitor；N-channel FET First switch, source terminal is connected to the first reference potential, and drain terminal is connected to described coil The other end；The second switch of P-channel FET, the first resistance and the second resistance, be connected in series in institute State between the other end of capacitor and described first reference potential；3rd resistance, is connected to described second The source terminal of switch and gate terminal；3rd switch of N-channel FET, drain terminal is connected to institute Stating the gate terminal of second switch, source terminal is connected to the first reference potential, and gate terminal is connected to The holding wire of supply dim signal, described dim signal is to turn on level and disconnects two value weights of level Multiple square-wave signal；Comparator block, first input end is electrically connected to described first resistance and described the The junction point of two resistance and be transfused to monitoring voltage, the second input terminal is connected to pay standard threshold voltage Power line；Excess voltage protection, input terminal is connected to the lead-out terminal of described comparator block, and Possesses the outfan of output silence signal when described monitoring voltage is more than described standard value voltage Son；LED current control circuit, possess the electric current flowed to described LED for input terminal, It is connected to the outfan of input terminal and the output signal supplying the holding wire of described dim signal Son, and to described lead-out terminal output control signal so that the electric current flowed to described LED reaches Predetermined current value, and make institute when described dim signal is for disconnecting level to the output of described lead-out terminal State the signal that LED turns off the light；And ON-OFF control circuit, possess and be connected to supply described dim signal First input end of holding wire and the described lead-out terminal electricity of described LED current control circuit The second input terminal connected electrically connect with the described lead-out terminal of described excess voltage protection the The lead-out terminal that three input terminals and the gate terminal with described first switch electrically connect, this switch Control circuit exports to the gate terminal of described first switch when described dim signal is turn-on level The driving signal of switching frequency, and according to from described excess voltage protection and described LED electricity The signal of flow control circuit, controls the electric current flowed to described LED.

Another way provides a kind of LED drive device, input voltage is amplified backward LED and supplies Giving, it is characterised in that described LED drive device has: capacitor, one end is connected to the first base Quasi-current potential, the other end is connected to the positive pole of described LED；Coil, one end is supplied to input voltage； Diode, anode is connected to the other end of described coil, and negative electrode is connected to the other end of described capacitor； First switch of N-channel FET, source terminal is connected to the first reference potential, and drain terminal is connected to The other end of described coil；The second switch of P-channel FET, the first resistance and the second resistance, string Connection is connected between the other end of described capacitor and described first reference potential；Level displacement shifter, electricity It is connected to source terminal and the gate terminal of described second switch, and is connected to for supplying dim signal Holding wire, this level displacement shifter makes described second switch when described dim signal is turn-on level Turn between source electrode and drain electrode, cut off described second switch when described dim signal is and disconnects level Between source electrode and drain electrode, described dim signal is to turn on level and disconnects the square that two values of level repeat Shape ripple signal；Comparator block, first input end is electrically connected to described first resistance and described second resistance Junction point and be transfused to monitoring voltage, the second input terminal is connected to the power supply of pay standard threshold voltage Line；Excess voltage protection, input terminal is connected to the lead-out terminal of described comparator block, and possesses Described monitoring voltage is more than the lead-out terminal of output silence signal during described standard value voltage；LED Current control circuit, possesses the terminal of the electric current flowed to described LED for input, is connected to supply To input terminal and the lead-out terminal of output signal of the holding wire of described dim signal, and to Described lead-out terminal output control signal is so that the electric current that flows to described LED reaches predetermined electric current Value, and make described LED put out when described dim signal is for disconnecting level to the output of described lead-out terminal The signal of lamp；And ON-OFF control circuit, possess the holding wire that is connected to supply described dim signal First input end electrically connect with the described lead-out terminal of described LED current control circuit second The 3rd input that input terminal electrically connects with the described lead-out terminal of described excess voltage protection The lead-out terminal that son and the gate terminal with described first switch electrically connect, this ON-OFF control circuit When described dim signal is turn-on level to the gate terminal output switching frequency of described first switch Driving signal, and control electricity according to from described excess voltage protection and described LED current The signal on road, controls the electric current flowed to described LED.

Another way provides a kind of liquid crystal indicator, possess input voltage is amplified backward The supply unit of LED supply, it is characterised in that described supply unit has: power circuit, to defeated Go out the booster voltage of terminal output-input voltage；First switch element, is connected to described power circuit Between described lead-out terminal and primary nodal point；First resistance, is connected to described primary nodal point and second section Between point；Second resistance, is connected between described secondary nodal point and the first reference voltage；At least one LED element, forward is connected between the described lead-out terminal of described power circuit and negative feedback terminal； And comparator, non-inverting input terminal is connected to described secondary nodal point, and inversing input terminal is connected to Second reference voltage, described power circuit has: FET, source electrode or drain electrode are connected to described first base Quasi-current potential, drain electrode or source electrode are connected to the 3rd node；Diode, anode terminal is connected to the described 3rd Node, cathode terminal is connected to the described lead-out terminal of described power circuit；And coil, an end Son is supplied to input voltage, and another terminal is connected to described 3rd node, the output of described comparator Terminal is electrically connected to the grid of described FET, and described negative feedback terminal is electrically connected to the grid of described FET Pole.

According to LED drive device of the present utility model and liquid crystal indicator, it is possible to prevent PWM Sound during light modulation.

Accompanying drawing explanation

Fig. 1 is the figure of the composition of the LED drive device together illustrating the first embodiment with LED.

Fig. 2 is the reason being prevented from sound for explanation in the LED drive device of present embodiment By figure.

Fig. 3 is to be not provided with sound in the LED drive device illustrating present embodiment to prevent when switching The figure of the voltage waveform of anode line.

Fig. 4 is for illustrating that in the LED drive device of the first embodiment, dim signal is for connecting electricity Sound at ordinary times prevents the figure of the work of switch.

Fig. 5 is for illustrating that in the LED drive device of the first embodiment, dim signal is for disconnecting electricity Sound at ordinary times prevents the figure of the work of switch.

Fig. 6 is the variation pattern of the LED drive device together illustrating the first embodiment with LED Figure.

Fig. 7 is another the change side of the LED drive device together illustrating the first embodiment with LED The figure of formula.

Fig. 8 is the figure of the composition of the LED drive device together illustrating the second embodiment with LED.

Fig. 9 is for illustrating that in the LED drive device of the second embodiment, dim signal is for connecting electricity Sound at ordinary times prevents the figure of the work of switch.

Figure 10 is for illustrating that in the LED drive device of the second embodiment, dim signal is for disconnecting electricity Sound at ordinary times prevents the figure of the work of switch.

Figure 11 is the variation pattern of the LED drive device together illustrating the second embodiment with LED Figure.

Figure 12 is another change of the LED drive device together illustrating the second embodiment with LED The figure of mode.

Figure 13 is the figure of the composition of the LED drive device together illustrating the 3rd embodiment with LED.

Figure 14 A is on the monitoring signal extraction line of the LED drive device illustrating the 3rd embodiment The figure of voltage's distribiuting example.

Figure 14 B is on the monitoring signal extraction line of the LED drive device illustrating the 3rd embodiment The figure of the load curve characteristic example of load resistance and Nch-FET.

Figure 15 is the variation pattern of the LED drive device together illustrating the 3rd embodiment with LED Figure.

Figure 16 is another change of the LED drive device together illustrating the 3rd embodiment with LED The figure of mode.

Detailed description of the invention

Below, referring to the drawings the general framework realizing various feature of the present utility model is illustrated. Thering is provided accompanying drawing and related description thereof to illustrate embodiment of the present utility model, it does not limit this practicality Novel scope.

In the ordinary course of things, according to an embodiment, input voltage is put by LED drive device 1 Big backward LED supplies, and it has:

Booster circuit L1, Q1, D1, C2, by controlling the electric current flowed to described LED Predetermined value, is amplified to predetermined voltage by described input voltage；

ON-OFF control circuit 11, makes described booster circuit L1, Q1, D1, C2 according to dim signal Being operated or quit work, this dim signal is the square-wave signal of two values；

Excess voltage protection 13, when the voltage after boosting is overvoltage, makes described booster circuit L1, Q1, D1, C2 quit work；

Monitoring signal extraction line 5, is connected to the anode line of the voltage after described LED supply boosting With reference voltage supply line；

Resistance partitioning circuitry R1, R2, be located at described monitoring signal extraction line 5, by the electricity after boosting The dividing potential drop of pressure is extracted as the monitoring voltage to the input of described excess voltage protection 13；And

Sound prevents from switching 2, is located at described monitoring signal extraction line 5, comes according to described dim signal Interrupt or continue the connection between described monitoring signal extraction line 5 and described anode line,

Described sound prevents from switching 2 according to described dim signal, described booster circuit L1, Q1, When D1, C2 are in work, continue the company between described monitoring signal extraction line 5 and described anode line Connect, when described booster circuit L1, Q1, D1, C2 are not in work, interrupt described monitoring signal Extract the connection between line 5 and described anode line.

Below, it is described with reference to each embodiment of the present utility model.

It should be noted that a kind of example of following public content, those skilled in the art are not Depart from the suitably change being readily apparent that in the range of this utility model objective and be included in this utility model In the range of.It addition, in the accompanying drawings, in order to clearly state further, compared with practical ways, have Time schematically show the width of each several part, thickness, shape etc., but this is an example, is not to use In limiting explanation of the present utility model.It addition, in each figure of this specification, for have shown that The key element that the key element that illustrated in figure is identical, marks identical reference, and suitably omits specifically Bright.

[the first embodiment]

Fig. 1 is the figure of the composition of the LED drive device together illustrating the first embodiment with LED. LED drive device 1 shown in Fig. 1 is carried out IC by by the part being used for driving the circuit of LED The LED driver IC10 changed is constituted.However, it is also possible to constituted this not carry out the state of ICization The LED drive device of utility model.

Input voltage VIN is via fuse F1, smoothing capacity device C1 input to coil L1.Coil The outfan of L1 is connected to diode D1, and the outfan of coil L1 is by LED driver IC10 Terminal LX be connected to boosted switch Q1.It addition, the output of diode D1 is via output capacitor C2 inputs to anode line.Wherein, if vehicle-mounted purposes, then input voltage VIN is about 12V, If mobile device, then it is 5～6V.

It is provided with for jointed anode line and the monitoring signal extraction line of earth lead (reference voltage supply line) 5.On monitoring signal extraction line 5, be sequentially connected in series from anode line side be provided with sound prevent from switching 2, electricity Resistance R1, resistance R2, and it is connected to earth lead.Resistance R1 and resistance R2 constitutes resistance partitioning circuitry, Medium voltage between resistance R1 and resistance R2 passes through LED driver IC10 as monitoring voltage Terminal OVP be connected to comparator block 14.

Sound prevent from switching 2 possess the switch Q2 of P-channel FET, the switch Q3 of N-channel FET, And resistance R3.The source terminal of switch Q2 is connected to anode line, and drain terminal is connected to resistance One end of R1.One end of resistance R3 is connected to switch the source terminal of Q2, and the other end is connected to out Close the gate terminal of Q2.The drain terminal of switch Q3 is connected to switch the gate terminal of Q2, switch The source terminal of Q3 is connected to ground wire.It addition, the dim signal being discussed below is input to switch Q3 Gate terminal.Wherein, switch Q3 and resistance R3 constitutes level displacement shifter 3.

Anode line is provided with multiple LED that multiple row (being here two row) is connected in series.Series connection is even The positive pole of the multiple LED connect is connected to anode line, and the negative pole of the multiple LED being connected in series passes through Terminal LED1, LED2 of LED driver IC10 are connected to LED current control circuit 12.

LED driver IC10 possesses ON-OFF control circuit 11, LED current control circuit 12, mistake Voltage protection circuit 13, comparator block 14 and boosted switch Q1.ON-OFF control circuit 11 is based on logical Cross dim signal that terminals P WM receives to control disconnection or the connection of boosted switch Q1.LED Current control circuit 12 exports control signal to ON-OFF control circuit 11 so that by terminal LED1, The LED current that LED2 receives reaches predetermined current value, thus controls anode line and reach pre- Fixed booster voltage.Comparator block 14 compares the monitoring voltage and standard value inputted by terminal OVP Vovp.Excess voltage protection 13 when monitoring voltage is above standard value Vovp to ON-OFF control circuit 11 output silence signals.

It should be noted that the coil L1 shown in Fig. 1, boosted switch Q1, diode D1 and Output capacitor C2 constitutes boost chopper.

Then, the work of the LED drive device of the first embodiment is described.

Dim signal be repeatedly switched on level (being here 3.3V) and disconnect level (be here 0V) the square-wave signal of the signal of person two value.The repetition rate of dim signal is generally About 100Hz～2kHz.When dim signal is to turn on level (3.3V), ON-OFF control circuit 11 to The driving signal of the gate terminal output switching frequency of boosted switch Q1.Switching frequency is generally About 500kHz～2MHz.

When dim signal is to turn on level (3.3V), boosted switch Q1 repeats to connect according to switching frequency On/off is opened.When boosted switch Q1 is to turn on, coil L1 flows through electric current, put aside energy.When When boosted switch Q1 is disconnected, savings energy in coil L1 is electric to output by diode D1 Container C2 is charged.So, when boosted switch Q1 is repeatedly switched on/disconnects, savings is online Output capacitor C2 is charged by the energy in circle L1 by diode D1, output capacitor C2 is charged the voltage higher than input voltage VIN.

Output capacitor C2 connects the anode of LED, if the voltage of therefore output capacitor C2 (voltage of anode line) exceedes the threshold voltage of the LED being connected in series, then electric current flows through LED, Thus LED is luminous.Generally, the threshold value of LED is about 3V, so such as 10 series connection When LED (10 LED being connected in series) is connected to LED drive device 1, work as output capacitor When the voltage of the anode line of C2 reaches about 30V, the LED of 10 series connection i.e. luminescence.Even if at string When the LED group that connection connects is connected in parallel to multiple row, if the voltage of anode line is about 30V, institute Some LED are the most luminous.

The electric current flowing through LED is input to the LED current control circuit 12 of LED driver IC10. LED current control circuit 12 controls the output driving signal and the stopping of ON-OFF control circuit 11, with The electric current flowing through LED is made to reach current value set in advance.Thus, control boosted switch Q1, LED In flow through constant electric current all the time, LED is with constant Intensity LEDs.

But, as it has been described above, LED driver IC10 generates due to switch operating higher than input electricity The voltage of pressure VIN, occurs to send out accordingly, it would be desirable to prevent misoperation from causing in LED drive device 1 Heat, smolder, the accident such as on fire.To this end, LED driver IC10 possesses excess voltage protection 13.

When dim signal is turn-on level (3.3V), sound prevents from switching the level displacement shifter 3 of 2 The gate terminal of switch Q3 be applied in the current potential of turn-on level, therefore switch Q3 becomes connection shape State (is to turn on state) between source terminal and drain terminal.Thus, the gate terminal quilt of switch Q2 Apply GND (earth lead) current potential, so switch Q2 becomes on-state.Its result, anode line Voltage carried out dividing potential drop by the resistance partitioning circuitry of R1 and R2, the medium voltage extracting R1, R2 is made For monitoring voltage.

Monitoring voltage is inputted to comparator block 14 by the terminal OVP of LED driver IC10.Relatively Monitoring voltage is compared by instrument 14 with standard value Vovp.The value if monitoring voltage is above standard Vovp, then excess voltage protection 13 controls ON-OFF control circuit 11, stops boosted switch Q1's Switch operating.

The voltage Va of the anode line that excess voltage protection is operated passes through Va=(1+R1/R2) * Vovp calculates.Such as, when R1=900k Ω, R2=30k Ω, Vovp=1.2V, overvoltage protection The voltage Va of the anode line that circuit is operated is Va=37.2V.The maximum of the threshold value of LED is Therefore about 3.5V, even if the most just reaching 35V the voltage of 10 series LED middle-jiao yang, function of the spleen and stomach polar curves is the highest Left and right, if so excess voltage protection is operated at 37.2V, it is simply that feasible voltage.Need It is noted that standard value Vovp is preferably set to 1～about 2V.This is because, drive at LED In device IC10, available band gap voltage easily generates standard value Vovp.

On the other hand, when dim signal is off (0V), LED current control circuit 12 is forced Property ground cut off LED current.Thus LED turns off the light.So, by with dim signal connect on and off Open lighting matchingly and light-off LED, change the luminous intensity of LED, adjust the brightness of LED.

When dim signal is off (0V), mandatory cut-out LED current, and on-off control Circuit 11 makes the mandatory off-state that becomes of boosted switch Q1 (between source terminal and drain terminal be Non-conducting state), stop boosting work.

When dim signal is off (0V), sound prevents from switching opening of the level displacement shifter 3 of 2 The gate terminal closing Q3 is applied in the current potential disconnecting level, so switch Q3 becomes off-state (source It is non-conducting state between extreme son and drain terminal).Therefore, the gate terminal of switch Q2 is applied in The current potential of anode line, switch Q2 becomes off-state.Even if switch Q2 becomes off-state, logical Cross terminal OVP and apply GND current potential to comparator block 14, so excess voltage protection 13 will not be given Work bring harmful effect.

Secondly, illustrate to prevent from switching 2 reasons being capable of preventing sound by sound.

Fig. 2 is to be capable of sound in the LED drive device for illustrate present embodiment to prevent The figure of reason.Fig. 2 is not provided with the sound shown in Fig. 1 prevent from switching 2, other positions and Fig. 1 Identical.

Connect on anode line and have for generating the monitoring voltage for protecting overvoltage as described above Resistance R1, R2, if so dim signal is disconnected, stop boosting work, then pass through resistance R1, R2 release leakage current to GND, thus the voltage of anode line declines.Dim signal once becomes Turn-on level, then start again at boosting work, so the voltage of anode line recovers again to LED electricity Stream.The on/off of dim signal is coordinated to repeat above work.

, it is also possible to as far as possible big by resistance R1, R2 being set to, anode line is reduced as far as possible Voltage declines.But, if resistance R1, R2 are excessive, then by for LED driver IC10 Comparator block 14 in the impact of input impedance of operational amplifier (Operational Amplifier), The amplification disconnecting setting voltage of comparator block 14 or the lower degradation of traceability are likely to result in mistake occur Work.In order to prevent excess voltage protection 13 from carrying out misoperation, it is preferable that resistance R1, R2 It is set to below 1M Ω, but, only leaning on this setting is cannot fully to suppress leakage current, sometimes occurs The problem producing sound owing to voltage declines.

It is connected to the current potential of output capacitor C2 of anode line with dim signal synchronously, according to Fig. 3 The jagged waveform that is similar to illustrated fluctuates.That is, (connect when dim signal is 3.3V Time), LED drive device 1 carries out work of boosting, and when 0V (during disconnection), stops boosting work. When stopping boosting work, by savings electric charge in output capacitor C2, keep the liter of anode line Piezoelectricity pressure, but, savings electric charge in output capacitor C2 is leaked by resistance R1, R2, Thus the voltage of anode line declines.Therefore, carry propagation on the substrate of LED drive device and have above-mentioned The output capacitor C2 that causes of voltage pulsation flexible.The vibration of this substrate or output capacitor The flexible of C2 itself becomes the reason producing sound.In figure 3, the threshold voltage of 10 series LEDs It is 3V, it is shown that have dropped the state of 0.5V voltage, according to condition (resistance R1, R2, light modulation The frequency of signal, dimming ratio), voltage drop-out value or change greatly or diminish.Especially, if dimming ratio (on/off ratio) becomes about 1%, then voltage declines relatively big, and anode voltage declines 0.5V～1V Left and right.Certainly, voltage drop-out value is the biggest, and the sound of output capacitor C2 is the biggest.

Then, describe sound in the LED drive device of the first embodiment in detail to prevent from switching 2 Constitute and work.

In order to suppress the voltage pulsation of anode line that the on/off of above-mentioned dim signal brings to prevent The output capacitor C2 being only connected to anode line sends sound, is provided with sound and prevents from switching 2.If Prevent the switch Q2 switching on 2 from being to be located at anode line and resistance R1, R2 at the sound shown in Fig. 1 Between Pch-FET.When LED is multiple, the voltage of anode line typically 10～about 40V, Therefore cannot realize switching the connection of Q2 when low-voltage (generally about the 3.3V) of dim signal / disconnect.To this end, by the level displacement shifter circuit being made up of switch Q3 and resistance R3 and light modulation letter Number on/off synchronously realize switch Q2 on/off.Preferably, resistance R3 is 1M About Ω.

As shown in Figure 4, when dim signal is to turn on (3.3V), switch Q3 (Nch-FET) Gate terminal be applied in high level (3.3V), switch Q3 becomes on-state.Its result, switch The gate terminal of Q2 (Pch-FET) is applied in low level, and switch Q2 becomes on-state.Therefore, The voltage of anode line puts on resistance R1, R2, from the intermediate point output monitoring electricity of resistance R1, R2 Pressure.Monitoring voltage is via the terminal OPV of LED driver IC10, and passes through comparator block 14 and mark Quasi-value Vovp compares.Value Vovp if monitoring voltage is above standard, then excess voltage protection 13 are stopped work of boosting by the control of ON-OFF control circuit 11.If monitoring voltage is less than standard Value Vovp, then boosted switch Q1 continues to turn on/disconnects work as usual, continues boosting work.

Fig. 5 is for illustrating that in the LED drive device of the first embodiment, dim signal is off electricity Sound at ordinary times prevents the figure of the work of switch.

As it is shown in figure 5, when dim signal is off (0V), switch Q3 (Nch-FET) Grid is applied in low level, and switch Q3 becomes off-state.Its result, switch Q2 (Pch-FET) Gate terminal be applied in high level (with anode line same potential), switch Q2 becomes off-state. Therefore, the voltage of anode line divides out with resistance R1, R2, even if dim signal is disconnected, stops rising Volt circuit, also will not make the leakage current stream from output capacitor C2 leakage that resistance R1, R2 cause Cross, decline almost without voltage.Even if from anode line separation resistance R1, R2, due to resistance R2 It is connected to GND, so the terminal OVP of LED driver IC10 is transfused to GND level, because of This comparator block 14 will not error detection overvoltage.

As described above, even if dim signal is repeatedly switched on/disconnects, the voltage of anode line is the most hardly Change, it is possible to prevent the output capacitor C2 from being connected to anode line from sending sound.Separately Outward, employing Pch-FET as switch Q2, therefore when switching Q2 and connecting, (dim signal is During connection), it is applied in the high voltage (10～40V) of anode line, institute between gate terminal and source terminal So that the connection resistance (voltage substantially 0 between Drain-Source) of switch Q2 almost can be ignored.Cause This, when designing resistance R1 and R2, it is not necessary to considers the characteristic of switch Q2.It should be noted that Pressure between the Drain-Source of Pch-FET must be the high pressure-resistive products of more than the voltage of anode line. It addition, pressure between the Source-Gate of Pch-FET also must to be the height of more than the voltage of anode line resistance to Die pressing product, however, it is also possible to by arranging the voltage limiting circuits such as diode between Source-Gate, Use the pressure relatively low Pch-FET between Source-Gate.

(change 1 of the first embodiment)

In variation pattern, in the LED drive device of the first above-mentioned embodiment, it is located at LED Sound outside driver IC 10 prevents from switching 2, i.e. switchs Q2 and constitute level displacement shifter 3 Switch Q3 and resistance R3 be built in LED driver IC10.Prevent from switching 2 by sound It is built in LED driver IC10, thus LED driver IC10 is provided with the input of anode line Terminal AIN and the lead-out terminal AOUT of switch Q2.

When the quantity being connected in series of LED is many, the voltage of anode line becomes high voltage (about 40V Left and right), so needing to be manufactured by high pressure flow process to be built in opening in LED driver IC10 Close Q2 and switch Q3.It addition, resistance R3 is preferably 1M about Ω, but, for precision Requirement is not the highest, so from the standpoint of area, it is preferable that utilize diffusion resistance manufacture, Rather than utilize polycrystalline resistor.

The basic operation principle of the LED drive device of this variation pattern and the first embodiment phase With.It is built in LED driver IC10 by preventing from sound switching 2, simplifies LED and drive The composition of device, it is possible to prevent output capacitor from producing sound.

(change 2 of the first embodiment)

In another variation pattern, it is located in the LED drive device of the first above-mentioned embodiment Sound outside LED driver IC10 prevent from switching 2 and resistance R1, R2 be built in LED and drive In dynamic device IC10.Thus, there is the composition of simplification LED drive device, it is possible to prevent output capacitance The advantage that device produces sound.

[the second embodiment]

In this second embodiment, the composition of level displacement shifter is different from the first embodiment.For with The position identical reference of mark that first embodiment is identical and same, and omit it specifically Bright.

The level displacement shifter 3 being made up of switch Q3 and resistance R3 used in the first embodiment In, when dim signal is to turn on (3.3V), switch Q3 connects, thus leakage current is from anode line Flow to resistance R3 (about 1M Ω), therefore affect the efficiency of LED.

In the LED drive device of the second embodiment, utilize the electricity of (Crossed) mode of intersection Flat shifter 31, thus prevent level displacement shifter 31 from leakage current occurring, it is possible to do not affecting efficiency In the case of, prevent output capacitor C2 from producing sound.

Sound shown in Fig. 8 prevents from switching the 2 switch Q2 possessing P-channel FET and intersection sides The level displacement shifter 31 of formula.The level displacement shifter 31 of interleaved mode includes the switch of P-channel FET Q3, the switch Q4 of N-channel FET, the switch Q5 of P-channel FET, the switch of N-channel FET Q6 and phase inverter INV.

Illustrate that the circuit of level displacement shifter 31 is constituted.The switch Q3 of interconnection P-channel FET and The gate terminal of the switch Q5 of P-channel FET and drain terminal.It addition, the leakage of connecting valve Q3 Extreme son with by the drain terminal of the switch Q4 of source ground, the drain terminal of connecting valve Q5 and By the drain terminal of the switch Q6 of source ground, as the output unit of level displacement shifter 31.

Dim signal as the input signal towards level displacement shifter 31 is divided into two, is branched An input signal by phase inverter INV invert after be connected to switch Q4 gate terminal.Divided Another input signal propped up is connected to switch the gate terminal of Q6.It addition, from the leakage of switch Q6 Extreme son extracts output signal.

It addition, the source terminal of switch Q3, Q5 of level displacement shifter 31 is connected to anode line, electricity The output unit of flat shifter 31 is connected to switch the gate terminal of Q2.

Fig. 9 is for illustrating that in the LED drive device of the second embodiment, dim signal is to turn on electricity Sound at ordinary times prevents the figure of the work of switch.

As it is shown in figure 9, when dim signal is to turn on (3.3V), switch Q4 (Nch-FET) Gate terminal be applied in low level (0V), so switch Q4 go off state.Switch Q6 (Nch-FET) gate terminal is applied in high level (3.3V), so switch Q6 becomes connection shape State.Owing to switch Q6 is to turn on state, so the gate terminal of switch Q3 (Pch-FET) is executed Adding low level (0V), switch Q3 becomes on-state.Owing to switch Q3 is to turn on state, so The gate terminal of switch Q5 (Pch-FET) is applied in high level (voltage of anode line), switchs Q5 Become off-state.Therefore, switch Q5 becomes off-state, and switch Q6 becomes on-state, The gate terminal of switch Q2 (Pch-FET) is applied in low level (0V), and switch Q2 becomes connection State.

Above result, owing to switch Q2 is to turn on state, so the voltage of anode line is applied to electricity Resistance R1, R2, from the intermediate point output monitoring voltage of resistance R1, R2.Monitoring voltage is via LED The terminal OPV of driver IC 10, and compared with standard value Vovp by comparator block 14.If Monitoring voltage is above standard value Vovp, then controlled ON-OFF control circuit 11 by excess voltage protection 13, Stop boosting work.If monitoring voltage is less than standard value Vovp, then boosted switch Q1 as generally that Sample continues to turn on/disconnects work, continues boosting work.

In the level displacement shifter circuit of interleaved mode, when dim signal is to turn on, switch Q3 becomes Becoming on-state, switch Q4 to become off-state, switch Q5 becomes off-state, and switch Q6 becomes Become on-state, the most there is not the path of electric current flowing.That is, when dim signal is to turn on, can With will not be in the case of anode alignment level displacement shifter 31 flows into leakage current, ON switch Q2.

Figure 10 is for illustrating that in the LED drive device of the second embodiment, dim signal is off electricity Sound at ordinary times prevents the figure of the work of switch.

As shown in Figure 10, when dim signal is off (0V), switch Q4 (Nch-FET) Gate terminal is applied in high level (3.3V), so switch Q4 becomes on-state.Switch Q6 (Nch-FET) gate terminal is applied in low level (0V), so switch Q6 becomes off-state. Owing to switch Q4 is to turn on state, so the gate terminal of switch Q5 (Pch-FET) is applied in low Level (0V), switch Q5 becomes on-state.Owing to switch Q5 is to turn on state, so switch The gate terminal of Q3 (Pch-FET) is applied in high level (voltage of anode line), and switch Q3 becomes Off-state.Thus, owing to switch Q5 is to turn on state, switch Q6 is off state, so The gate terminal of switch Q2 (Pch-FET) is applied in high level (voltage of anode line), switchs Q2 Become off-state.

Above result, owing to switch Q2 is off state, so the voltage of anode line and resistance R1, R2 divide out, even if dim signal is disconnected and stopped boosting work, also do not have leakage current, Decline almost without voltage.Even if resistance R1, R2 separate with anode line, owing to resistance R2 connects In GND, so the terminal OVP of LED driver IC10 is transfused to GND level, thus compare Relatively instrument 14 will not error detection overvoltage.

In the level displacement shifter 31 of interleaved mode, when dim signal is off, due to switch Q3 Being off state, switch Q4 is to turn on state, and switch Q5 is to turn on state, and switch Q6 is off , so there is not the path of electric current flowing in state.That is, when dim signal is off, it is possible to not In the case of flowing into leakage current in anode alignment level displacement shifter 31, switch Q2 is made to become disconnection State.

By above-mentioned work, even if dim signal is repeatedly switched on/disconnects, the level shift of interleaved mode Will not be flowed in device 31 leakage current, and the voltage of anode line changes hardly, therefore, it is possible to In the case of not reducing the efficiency of LED, prevent the output capacitor C2 from being connected to anode line from producing Sound.

(change 1 of the second embodiment)

In variation pattern, in the LED drive device of the second above-mentioned embodiment, it is located at LED Sound outside driver IC 10 prevents from switching 2, i.e. switch Q2 and level displacement shifter 31 is built-in In LED driver IC10.It is built in LED drives it should be noted that sound prevents from switching 2 In dynamic device IC10, thus LED driver IC10 is provided with the input terminal AIN of anode line and opens Close the lead-out terminal AOUT of Q2.

When the quantity being connected in series of LED is many, the voltage of anode line becomes high voltage (about 40V Left and right), so needing to be manufactured by high pressure flow process to be built in opening in LED driver IC10 Close Q2, switch Q3, switch Q4, switch Q5, switch Q6.But, phase inverter INV is simply Reversion dim signal (about 3.3V), it is possible to manufactured by low pressure flow process.

The basic functional principle of the LED drive device of this variation pattern is identical with the second embodiment. It is built in LED driver IC10 by preventing from sound switching 2, it is possible to simplify LED and drive The composition of device, prevents output capacitor from producing sound.

(change 2 of the second embodiment)

In another variation pattern, it is located in the LED drive device of the second above-mentioned embodiment Sound outside LED driver IC10 prevent from switching 2 and resistance R1, R2 be built in LED In driver IC 10.Therefore, there is the composition that can simplify LED drive device, prevent output electricity The advantage that container produces sound.

[the 3rd embodiment]

In the third embodiment, sound prevents the composition switched different from the first embodiment.For Identical with the first embodiment and as the position identical reference of mark, and it is detailed to omit it Explanation.

In the LED drive device of the 3rd embodiment, sound is prevented switchs 2 and is located at resistance R1 Centre with resistance R2.As it has been described above, in order to extract monitoring voltage to LED driver IC10, The current potential of the intermediate point of resistance R1 and resistance R2 is set to the current potential of such as 1～2V.Sound prevents switch The grid of 2 is supplied to dim signal.The threshold voltage that use can be connected when dim signal is 3.3V The Nch-FET of Vth, thus without being configured to as the first embodiment and the second embodiment use , can be the structure of high potential by level conversion.Therefore, the sound at the 3rd embodiment prevents In switch 2, it is provided only with the switch QN2 of Nch-FET, and is not provided with level displacement shifter.

In Figure 14 A, if forming standard value Vovp, then standard value Vovp by band-gap circuit Voltage be about 1.2V.At this moment, the monitoring voltage after the output reversion of comparator block 14 is such as 1.2V, Dim signal is 3.3V.At this moment, constitute sound prevent from switching the switch QN2 of 2 Source-Gate it Between potential difference Δ be 2.1 (=3.3-1.2) V.As this switch QN2, use threshold voltage vt h Switch QN2 at below 2.1V.By use threshold voltage vt h at the switch QN2 of below 2.1V, Even if near the switching of comparator block 14 (monitoring voltage is the vicinity of 1.2V), switch QN2 also may be used To connect.That is, the voltage at anode line is the relatively low electricity that excess voltage protection 13 is not operated Pressure, when the voltage of dim signal is 3.3V, the voltage between the Source-Gate of switch QN2 is at 2.1V Above, switch QN2 becomes on-state.

Connect that resistance is low can ignore to the value relative to resistance R1, resistance R2 as switch QN2 Degree time, monitoring voltage becomes by resistance R1, R2, the voltage of anode line is carried out resistance segmentation Value.When the voltage of anode line rises due to misoperation etc., if monitoring voltage 1.2V with On, boosted switch Q1 is disconnected by excess voltage protection 13, and anode line cannot rise to more than it again Voltage, monitoring voltage will not become more than 1.2V.Its result, switch QN2 Source-Gate it Between voltage keep about more than 2.1V, switch QN2 maintains on-state.

When dim signal is 0V, switch QN2 disconnects, and does not haves from anode line via resistance The electric current of R1, R2 flowing, maintains the voltage kept by output capacitor C2.

It should be noted that the pressure needs of drain electrode of switch QN2 are more than the maximum voltage of anode line, But, the voltage between Source-Gate is not up to the connection voltage of dim signal, i.e. more than 3.3V, Therefore, if the pressure maximum voltage value that disclosure satisfy that dim signal between Source-Gate, the most permissible Use the Nch-MOS transistor of the low pressurized system of a few about V.Electricity is connected therefore, it is possible to use The resistance little Nch-MOS transistor to negligible value of value relative to resistance R1, R2.

It should be noted that in the above description, illustrate that monitoring voltage is the example of 1.2V, When monitoring voltage is 2V, by threshold voltage=below 3.3V-2V=1.3V be used as switch QN2.

It addition, when using, as switch QN2, Nch-FET that its connection resistance can be ignored, profit With characteristic curve as shown in Figure 14B, set the value of resistance R1 and R2.Such as, monitoring is worked as When voltage is 1.2V, the Vgs of switch QN2 becomes curve as shown in Figure 14B.Wherein, flow through Resistance R1, R2, switch QN2 electric current Id1 equal, therefore, Id1=1.2V/R2.At this moment, will The value of resistance R1 and R2 is set to switch the point that the load curve of the curve of QN2 and resistance R1 intersects On the value that electric current is Id1=1.2V/R2.

As described above, by inserting the switch of Nch-FET between resistance R1 and resistance R2 QN2 prevents from switching 2 as sound, it is thus possible to be not provided with level displacement shifter.But, there is also The Nch-MOS transistor connecting resistance of Nch-FET cannot be ignored, accordingly, it would be desirable to take into full account Characteristic curve and the deviation of transistor design circuit, to prevent excess voltage protection 13 from carrying out Misoperation.

(change 1 of the 3rd embodiment)

In variation pattern, in the LED drive device of the 3rd above-mentioned embodiment, it is located at LED Sound outside driver IC 10 prevents from switching 2, i.e. switch QN2 is built in LED driver IC10 In.Sound prevents switching 2 and is built in LED driver IC10, thus LED driver IC10 It is provided with the input terminal MIN and the lead-out terminal MOUT of switch QN2 of monitoring signal extraction line.

When being difficult to the Nch-MOS transistor obtaining small area analysis formula, can be by Nch-MOS crystal Pipe is built in inside IC, thus makes the Nch-MOS transistor of small area analysis formula in IC.

The basic functional principle of the LED drive device of this variation pattern is identical with the 3rd embodiment. It is built in LED driver IC10 by preventing from sound switching 2, it is possible to simplify LED and drive The composition of device, prevents output capacitor from producing sound.

(change 2 of the 3rd embodiment)

In another variation pattern, it is located in the LED drive device of the 3rd above-mentioned embodiment Sound outside LED driver IC10 prevent from switching 2 and resistance R1, R2 be built in LED In driver IC 10.Thus, there is the composition that can simplify LED drive device further, prevent The advantage that output capacitor produces sound.

Above, prevent from switching 2 by arranging sound at monitoring voltage extraction line 5, utilize dim signal Control this sound and prevent from switching 2, suppress OVP (the overvoltage guarantor extracting in line from monitoring voltage Protect) leakage current of setting resistance R1, R2, it is possible to the voltage pulsation of suppression output capacitor C2, It is prevented from producing sound.Sound prevents switching 2 can be located at anode line and OVP setting resistance Between R1, R2 or in the middle of two OVP setting use resistance R1, R2.When sound being prevented switch 2 when being located between anode line and OVP setting resistance R1, R2, uses Pch-FET switch, also Need level displacement shifter.Sound is prevented switch be located at two OVP setting resistance R1, R2 it Between time, use Nch-FET switch, it is not necessary to level displacement shifter.

No matter in the case of which kind of, it is built in LED driver IC10 by preventing from sound switching 2 In, unnecessary adjunct circuit can be eliminated, prevent output capacitor C2 from producing sound, its practical effect Fruit is the biggest.Further, by built-in level displacement shifter is set to interleaved mode, can suppress Flow through the leakage current in level displacement shifter, therefore, it is possible in the case of will not reducing LED efficiency, Preventing output capacitor C2 from producing sound, its practical function is the biggest.It addition, at this utility model In, in addition to level displacement shifter, it is also possible to OVP setting resistance R1, R2 are built in LED In driver IC 10.

It should be noted that the LED of the first above-mentioned embodiment can be embodied in the following manner Driving means 1.

[LED drive device of first method]

A kind of LED drive device, is amplified backward LED supply by input voltage, and its feature exists In, described LED drive device has:

Capacitor C2, one end is connected to the first reference potential, and the other end is just being connected to described LED Pole；

Coil L1, one end is supplied to input voltage；

Diode D1, anode is connected to the other end of described coil L1, and negative electrode is connected to described electricity The other end of container C2；

The first switch Q1 of N-channel FET, source terminal is connected to the first reference potential, drain electrode end Son is connected to the other end of described coil L1；

The second switch Q2 of P-channel FET, the first resistance R1 and the second resistance R2, series connection is even It is connected between the other end of described capacitor C2 and described first reference potential；

3rd resistance R3, is connected to source terminal and the gate terminal of described second switch Q2；

The 3rd switch Q3 of N-channel FET, drain terminal is connected to the grid of described second switch Q2 Extreme son, source terminal is connected to the first reference potential, and gate terminal is connected to supply dim signal Holding wire, described dim signal is to turn on level and disconnects the square wave letter that two values of level repeat Number；

Comparator block 14, first input end is electrically connected to described first resistance R1 and described second resistance The junction point of R2 and be transfused to monitoring voltage, the second input terminal is connected to supply predetermined benchmark electricity The pressure i.e. power line of standard value voltage；

Excess voltage protection 13, input terminal is connected to the lead-out terminal of described comparator block 14, and Possesses the outfan of output silence signal when described monitoring voltage is more than described standard value voltage Son；

LED current control circuit 12, possess the electric current flowed to described LED for input terminal, It is connected to the outfan of input terminal and the output signal supplying the holding wire of described dim signal Son, and to described lead-out terminal output control signal so that the electric current flowed to described LED reaches Predetermined current value, and make institute when described dim signal is for disconnecting level to the output of described lead-out terminal State the signal that LED turns off the light；And

ON-OFF control circuit 11, possesses and is connected to supply the first defeated of the holding wire of described dim signal Enter the second input that terminal electrically connects with the described lead-out terminal of described LED current control circuit 12 The 3rd input terminal that terminal electrically connects with the described lead-out terminal of described excess voltage protection 13, And with the lead-out terminal that electrically connects of gate terminal of described first switch Q1, this ON-OFF control circuit 11 when described dim signal is turn-on level to described first switch Q1 gate terminal output switching The driving signal of frequency, and according to from described excess voltage protection 13 and described LED current The signal of control circuit 12, controls the electric current flowed to described LED.

It addition, can by limiting according to first part of LED drive device expressed with function, It is expressed as the LED drive device 1 of the first above-mentioned embodiment.

[LED drive device of second method]

Coil L1, one end is supplied to input voltage；

Level displacement shifter 3, is electrically connected to source terminal and the gate terminal of described second switch Q2, And it being connected to the holding wire for supplying dim signal, this level displacement shifter 3 at described dim signal is Make during turn-on level to turn on, at described dim signal between the source electrode of described second switch Q2 and drain electrode Cutting off during for disconnecting level between the source electrode of described second switch Q2 and drain electrode, described dim signal is The square-wave signals that two values of turn-on level and disconnection level repeat；

Comparator block 14, first input end is electrically connected to described first resistance R1 and described second resistance The junction point of R2 and be transfused to monitoring voltage, the second input terminal is connected to pay standard threshold voltage Power line；

[liquid crystal indicator possessing LED drive device (supply unit) of Third Way]

A kind of liquid crystal indicator, possesses the power supply that input voltage is amplified backward LED supply Device 1, it is characterised in that

Described supply unit 1 has:

Power circuit L1, D1, Q1,11,12, to the liter piezoelectricity of lead-out terminal output-input voltage Pressure；

First switch element Q2, Q3, R3, be connected to described power circuit L1, D1, Q1,11, Between described lead-out terminal and the primary nodal point of 12；

First resistance R1, is connected between described primary nodal point and secondary nodal point；

Second resistance R2, is connected between described secondary nodal point and the first reference voltage；

At least one LED element, forward be connected to described power circuit L1, D1, Q1,11, Between described lead-out terminal and negative feedback terminal LED1, LED2 of 12；And

Comparator 14, non-inverting input terminal is connected to described secondary nodal point, and inversing input terminal is even It is connected to the second reference voltage,

Described power circuit L1, D1, Q1,11,12 have:

FETQ1, source electrode or drain electrode are connected to described first reference potential, and drain electrode or source electrode are connected to the Three nodes；

Diode D1, anode terminal is connected to described 3rd node, and cathode terminal is connected to described electricity Source circuit L1, D1, the described lead-out terminal of Q1,11,12；And

Coil L1, a terminal is supplied to input voltage, and another terminal is connected to described Section three Point,

The lead-out terminal of described comparator 14 is electrically connected to the grid of described FETQ1,

Described negative feedback terminal LED1, LED2 are electrically connected to the grid of described FETQ1.

Wherein,

(1) power circuit includes that L1, D1, Q1, ON-OFF control circuit 11, LED current control Circuit 12.

(2) first switch elements include Q2, Q3, R3.

(3) primary nodal point is the junction point of Q2 Yu R1.Secondary nodal point is the connection of R1 Yu R2 Point.3rd node is the junction point of L1 Yu D1.

(4) negative feedback terminal is terminal LED1, LED2.

(5) first reference potentials correspond to earth lead current potential, and the second reference potential corresponds to standard value.

(6) grid of described FET " lead-out terminal of described comparator be electrically connected to " refers to compare The output of instrument 14 via excess voltage protection 13 and ON-OFF control circuit 11 to boosted switch 11 Grid transmission signal.

(7) grid of described FET " the described negative feedback terminal be electrically connected to " refers to negative feedback terminal LED1, LED2 via LED current control circuit 12 and ON-OFF control circuit 11 to boosted switch The grid transmission signal of 11.

As embodiment of the present utility model, those skilled in the art are based on above-mentioned display device energy As long as enough suitable design for change and all of display device implemented its comprise objective of the present utility model Just belong in the range of this utility model.

In design category of the present utility model, it may occur to persons skilled in the art that various modification with And modification, it should be appreciated that these modifications and modification belong to scope of the present utility model.Example As, for above-mentioned each embodiment, constitute even if those skilled in the art suitably add or delete Key element or design for change or add or omit operation or change condition, as long as it possesses this practicality Novel objective, is just included in the range of this utility model.

It will additionally be understood that be according to this specification record can be clear and definite, according in present embodiment Record mode be capable of other effect or those skilled in the art can suitably expect its He acts on, and is all the effect realized by this utility model.

Various practicality can be formed with the multiple elements disclosed in appropriately combined above-mentioned embodiment Novel.Such as, several element can be deleted from all elements shown in embodiment. Moreover, it is also possible to the appropriately combined element relating to different embodiments.

Some embodiments are illustrated, but these embodiments are intended only as example and present, It is not used to limit the scope of utility model.It practice, new method and system described herein can be used Other various modes are implemented, without departing from can carry out in the range of the objective of utility model various omission, Replace and change.These modes and deformation thereof are included in the scope and spirit of utility model, equally, It is included in the range of claims and equivalent thereof.

The application based on and require on January 9th, 2015 submit to Japanese patent application The benefit of priority of No. 2015-003102, and entire contents is hereby expressly incorporated by reference.

Claims

1. a LED drive device, is amplified backward LED supply, its feature by input voltage Being, described LED drive device has:

Booster circuit (L1, Q1, D1, C2), by the electricity that will flow to described LED Described input voltage, in predetermined value, is amplified to predetermined voltage by flow control；

ON-OFF control circuit (11), according to dim signal make described booster circuit (L1, Q1, D1, C2) it is operated or quits work, this dim signal is the square wave letter of two values Number；

Excess voltage protection (13), when the voltage after boosting is overvoltage, makes described Booster circuit (L1, Q1, D1, C2) quits work；

Monitoring signal extraction line (5), is connected to the voltage after described LED supply boosting Anode line and reference voltage supply line；

Resistance partitioning circuitry (R1, R2), is located at described monitoring signal extraction line (5), will The dividing potential drop of the voltage after boosting is extracted as the prison inputted to described excess voltage protection (13) Control voltage；And

Sound prevents from switching (2), is located at described monitoring signal extraction line (5), according to described Dim signal interrupts or continues between described monitoring signal extraction line (5) and described anode line Connection,

Described sound prevent switch (2) according to described dim signal, at described booster circuit When (L1, Q1, D1, C2) is in work, continue described monitoring signal extraction line (5) And the connection between described anode line, at described booster circuit (L1, Q1, D1, C2) When being not in work, interrupt between described monitoring signal extraction line (5) and described anode line Connect.

LED drive device the most according to claim 1, it is characterised in that

Described sound prevents switching (2) and is located at the ratio on described monitoring signal extraction line (5) Described resistance partitioning circuitry (R1, R2) is close at described anode line side.

LED drive device the most according to claim 2, it is characterised in that

Described sound prevents switching (2) to be had:

Level displacement shifter (3), is amplified the level of described dim signal；And

The second switch (Q2) of P-channel FET, receives described level shift at gate terminal The output signal of device (3), thus interrupt or continue described monitoring signal extraction line (5).

LED drive device the most according to claim 3, it is characterised in that

Described level displacement shifter (3) has:

Resistance (R3), one end is connected to described anode line, and the other end is connected to described second The gate terminal of switch (Q2)；And

3rd switch (Q3) of N-channel FET, drain terminal is connected to described resistance (R3) The described other end, source terminal is connected to reference voltage supply line, and described dim signal is defeated Enter to gate terminal.

LED drive device the most according to claim 3, it is characterised in that

Described level displacement shifter (31) has:

3rd switch (Q3) of P-channel FET and the 5th switch (Q5) of P-channel FET, Gate terminal and drain terminal connection intersected with each other；

4th switch (Q4) of N-channel FET, source terminal is connected to reference voltage supply Line, drain terminal is connected to the drain terminal of described 3rd switch (Q3)；And

6th switch (Q6) of N-channel FET, source terminal is connected to reference voltage supply Line, drain terminal is connected to the drain terminal of described 5th switch (Q5),

Gate terminal input to described 4th switch (Q4) inverts described dim signal and forms Signal,

Gate terminal to described 6th switch (Q6) inputs described dim signal,

The source terminal of described 3rd switch (Q3) and described 5th switch (Q5) is even It is connected to described anode line,

The drain terminal of described 6th switch (Q6) is connected to described second switch (Q2) Gate terminal.

LED drive device the most according to claim 1, it is characterised in that

Described sound prevents switching (2) and is located in described resistance partitioning circuitry (R1, R2) Be applied in the voltage signal with described monitoring signal same level and than extract described monitoring The position of signal is close to the position of described anode line side.

LED drive device the most according to claim 6, it is characterised in that

Described sound prevents switching (2) and has N-channel FET switch (QN2), described N Channel FET switch (QN2) by gate terminal receive described dim signal and interrupt or Continue described monitoring signal extraction line (5).

8. according to the LED drive device described in claim 2 or 6, it is characterised in that

Described LED drive device also has is located at LED driving IC (10) and this LED Drive the circuit of the outside of IC (10),

Described LED drives IC (10) to be built-in with described ON-OFF control circuit (11), constitute First switch (Q1), described overvoltage of described booster circuit (L1, Q1, D1, C2) Protection circuit (13) and described sound prevent from switching (2).

LED drive device the most according to claim 8, it is characterised in that

Described LED drives IC (10) to be also built-in with described resistance partitioning circuitry (R1, R2).

LED drive device the most according to claim 8, it is characterised in that

The described sound that described LED drives IC (10) to be comprised prevents switching (2) to be passed through High pressure operation makes.

11. 1 kinds of LED drive device, are amplified backward LED supply, its feature by input voltage Being, described LED drive device has:

Capacitor (C2), one end is connected to the first reference potential, and the other end is connected to described The positive pole of LED；

Coil (L1), one end is supplied to input voltage；

Diode (D1), anode is connected to the other end of described coil (L1), and negative electrode is even It is connected to the other end of described capacitor (C2)；

First switch (Q1) of N-channel FET, source terminal is connected to the first reference potential, Drain terminal is connected to the other end of described coil (L1)；

The second switch (Q2) of P-channel FET, the first resistance (R1) and the second resistance (R2) other end of described capacitor (C2) and described first benchmark electricity, it are connected in series in Between Wei；

3rd resistance (R3), is connected to source terminal and the grid of described second switch (Q2) Extreme son；

3rd switch (Q3) of N-channel FET, drain terminal is connected to described second switch (Q2) gate terminal, source terminal is connected to the first reference potential, and gate terminal connects In the holding wire of supply dim signal, described dim signal is to turn on level and disconnects level The square-wave signal that two values repeat；

Comparator block (14), first input end be electrically connected to described first resistance (R1) with The junction point of described second resistance (R2) and be transfused to monitoring voltage, the second input terminal is even It is connected to the power line of pay standard threshold voltage；

Excess voltage protection (13), input terminal is connected to described comparator block (14) Lead-out terminal, and possess the output stopping when described monitoring voltage is more than described standard value voltage The lead-out terminal of working signal；

LED current control circuit (12), possesses the electricity flowed for input to described LED The terminal of stream, it is connected to supply the input terminal of the holding wire of described dim signal and defeated Go out the lead-out terminal of signal, and to described lead-out terminal output control signal to described The electric current of LED flowing reaches predetermined current value, and at described dim signal for disconnecting level Time make, to the output of described lead-out terminal, the signal that described LED turns off the light；And

ON-OFF control circuit (11), possesses the holding wire being connected to supply described dim signal First input end and the described lead-out terminal of described LED current control circuit (12) Second input terminal of electrical connection and the described output of described excess voltage protection (13) Terminal electrical connection the 3rd input terminal and with described first switch (Q1) gate terminal Son electrical connection lead-out terminal, this ON-OFF control circuit (11) at described dim signal for connecing Energising is at ordinary times to the driving letter of the gate terminal output switching frequency of described first switch (Q1) Number, and control according to from described excess voltage protection (13) and described LED current The signal of circuit (12), controls the electric current flowed to described LED.

12. 1 kinds of LED drive device, are amplified backward LED supply, its feature by input voltage Being, described LED drive device has:

Coil (L1), one end is supplied to input voltage；

Level displacement shifter (3), be electrically connected to described second switch (Q2) source terminal and Gate terminal, and it is connected to the holding wire for supplying dim signal, this level displacement shifter (3) Source electrode and the drain electrode of described second switch (Q2) is made when described dim signal is turn-on level Between turn on, described dim signal for disconnect level time cut off described second switch (Q2) Source electrode and drain electrode between, described dim signal be to turn on level and disconnect level two values The square-wave signal repeated；

13. 1 kinds of liquid crystal indicators, possess the power supply that input voltage is amplified backward LED supply Device (1), it is characterised in that

Described supply unit (1) has:

Power circuit (L1, D1, Q1,11,12), to lead-out terminal output-input voltage Booster voltage；

First switch element (Q2, Q3, R3), be connected to described power circuit (L1, D1, Q1,11,12) described lead-out terminal and primary nodal point between；

First resistance (R1), is connected between described primary nodal point and secondary nodal point；

Second resistance (R2), is connected between described secondary nodal point and the first reference voltage；

At least one LED element, forward be connected to described power circuit (L1, D1, Q1, 11,12) between described lead-out terminal and negative feedback terminal (LED1, LED2)；With And

Comparator (14), non-inverting input terminal is connected to described secondary nodal point, inverts defeated Enter terminal and be connected to the second reference voltage,

Described power circuit (L1, D1, Q1,11,12) has:

FET (Q1), source electrode or drain electrode are connected to described first reference potential, drain electrode or source Pole is connected to the 3rd node；

Diode (D1), anode terminal is connected to described 3rd node, and cathode terminal connects Described lead-out terminal in described power circuit (L1, D1, Q1,11,12)；And

Coil (L1), a terminal is supplied to input voltage, and another terminal is connected to institute State the 3rd node,

The lead-out terminal of described comparator (14) is electrically connected to the grid of described FET (Q1),

Described negative feedback terminal (LED1, LED2) is electrically connected to described FET's (Q1) Grid.