CN104427721A - Led drive circuit - Google Patents
Led drive circuit Download PDFInfo
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- CN104427721A CN104427721A CN201410411953.7A CN201410411953A CN104427721A CN 104427721 A CN104427721 A CN 104427721A CN 201410411953 A CN201410411953 A CN 201410411953A CN 104427721 A CN104427721 A CN 104427721A
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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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- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
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Abstract
The invention provides an LED drive circuit which can provide a power supply for a microcomputer when LED is at standby and not lit up. The LED drive circuit comprises a constant current control signal output circuit (a current detection resistor Rs), which outputs a constant current control signal corresponding to a reactor current flowing through a reactor (L); a voltage control signal output circuit (CV), which outputs a constant voltage control signal corresponding to output voltage (Vout); and a control circuit (Ta), which conducts constant current control for the LED current through the constant current control signal in the normal operation with no input of a standby signal and conducts constant voltage control of the output voltage (Vout) lower than the lighting voltage of an LED array (LD) through the constant voltage control signal is the standby operation with an input of a standby signal.
Description
Technical field
The present invention relates to the LED drive circuit using the switch element of normal open type to light LED with constant current.
Background technology
In recent years, following technology is proposed: the switch element (such as with reference to patent documentation 1) the low-loss wide bandgap semiconductor element employing GaAs (GaAs), GaN (gallium nitride), SiC (carborundum) etc. in semiconductor substrate being used as switching power circuit.By using wide bandgap semiconductor element as switch element, operating frequency can be improved when not reducing power-efficient, can the miniaturization of implement device, subminiature nonisulated copped wave modular power source switch element and inductor being sealing into same encapsulation can be formed.
No. 2011-199024, [patent documentation 1] Japanese Unexamined Patent Publication
But, in the lighting apparatus such as pendent lamp, employ microcomputer for light modulation and these actions of toning, therefore except being used as the subminiature nonisulated copped wave modular power source of LED drive circuit, also need the power source special (about 5V10mA) of microcomputer.Particularly, high order harmonic component is tackled at needs more than the lighting apparatus of 25W, and when also using power factor correction circuit, be made up of the power source special of power factor correction circuit, LED drive circuit, microcomputer and 3 converters, become complicated circuit structure, thus cause cost increase.
Summary of the invention
The object of the invention is in view of the above problems, solve the problem of prior art, provide a kind of can when not lighting LED standby the LED drive circuit of the power supply of supply microcomputer.
LED drive circuit of the present invention, it is exported by direct current and lights LED with constant current, wherein, this direct current exports and utilizes the discharge and recharge of reactor to generate, the discharge and recharge of this reactor performs based on the on-off action of the switch element of normal open type, the feature of described LED drive circuit is to have: constant-current control signal output circuit, and it exports the constant-current control signal corresponding with the reactor current flowing through described reactor; Isobarically Control signal output apparatus, it exports the Isobarically Control signal corresponding with output voltage; And control circuit, its in the usual action not being transfused to standby signal time, this control circuit carries out current constant control by described constant-current control signal to the LED current flowing through described LED, when the standby action being transfused to standby signal, this control circuit makes the output voltage lower than the ignition voltage of described LED by described Isobarically Control signal constant is voltage-controlled.
According to the present invention, can when not lighting LED standby the power supply of supply microcomputer.
Accompanying drawing explanation
Fig. 1 is the circuit structure diagram of the 1st execution mode structure that LED drive circuit of the present invention is shown.
Fig. 2 is the circuit structure diagram of the structure example that the Isobarically Control signal output apparatus CV shown in Fig. 1 is shown.
Fig. 3 is the oscillogram of the 1st execution mode action for illustration of LED drive circuit of the present invention.
Fig. 4 is the circuit structure diagram of the 2nd execution mode structure that LED drive circuit of the present invention is shown.
Fig. 5 is the circuit structure diagram of the 3rd execution mode structure that LED drive circuit of the present invention is shown.
Label declaration
10a:LED drive circuit (the 1st execution mode); 10b:LED drive circuit (the 2nd execution mode); 10c:LED drive circuit (the 3rd execution mode); BF: buffer circuit; C1: by-pass capacitor; C2: output capacitor; C3, C4: coupling capacitor; Ccomp, C5: capacitor; MCU: microcomputer; CV: Isobarically Control signal output apparatus; D1: regeneration diode; D2, D3, D4: diode; L: reactor; LD:LED array; OTA: trsanscondutance amplifier; OSC: triangular wave oscillator; Q1: switch element (the 1st switch element); Q2: switch element (the 2nd switch element); Q3: bipolar transistor; Q4: switch element; R1, R2, R3, R10, R11, R12: resistance; Reg: constant voltage regulator circuit; Rs: current sense resistor; Ta: control circuit (the 1st execution mode); Tb: control circuit (the 2nd, the 3rd execution mode); Ton: comparator; Vref1: reference voltage; ZD1, ZD2: Zener diode.
Embodiment
Then, embodiments of the present invention are specifically described with reference to accompanying drawing.In addition, in the various figures, identical label is marked and clipped explanation to same structure.
(the 1st execution mode)
The auto-excitation type buck circuit of the wide bandgap semiconductor element of normal open type is the use of with reference to Fig. 1, the LED drive circuit 10a of the 1st execution mode.LED drive circuit 10a has rectification circuit DB, switch element Q1, Q2 as the wide bandgap semiconductor element of normal open type, control circuit Ta switch element Q2 being carried out to current constant control, by-pass capacitor C1, reactor L, winding AW, regeneration diode D1, output capacitor C2, Zener diode ZD1, resistance R1, R2, R3, diode D2, current sense resistor Rs, capacitor Ccomp, Isobarically Control signal output apparatus CV and constant voltage regulator circuit Reg.Further, LED drive circuit 10a drives the LED array LD as load circuit using constant current, and powers to the microcomputer MCU carrying out brightness adjustment control and toning control.Below, in order to distinguish switch element Q1 and switch element Q2, switch element Q1 is called the 1st switch element Q1, switch element Q2 is called the 2nd switch element Q2.
The input terminal V+ and input terminal V0 of LED drive circuit 10a are connected to the rectification output cathode terminal of the rectification circuit DB be made up of diode bridge, the rectification output negative pole terminal of ground connection.AC input terminal ACin1, ACin2 of rectification circuit DB are connected with commercial ac power source AC1, and the ac input voltage from commercial ac power source AC1 exports from rectification circuit DB after full-wave rectification.
Between the rectification output cathode terminal and the rectification output negative pole terminal of input terminal V0, i.e. rectification circuit DB of input terminal V+, i.e. rectification circuit DB, be connected in parallel to following series circuit and by-pass capacitor C1, this series circuit is made up of the 1st switch element Q1, the 2nd switch element Q2, reactor L, output capacitor C2, current sense resistor Rs.Input terminal V+ is connected with the drain terminal of the 1st switch element Q1, the source terminal of the 1st switch element Q1 is connected with the drain terminal of the 2nd switch element Q2, and on the source terminal of the 2nd switch element Q2, be connected with a terminal of reactor L.Another terminal of reactor L is connected with the positive electrode of output capacitor C2, and the negative electrode of output capacitor C2 is connected with a terminal of current sense resistor Rs.
The two ends of output capacitor C2 are the output of LED drive circuit 10a, the positive electricity very output terminal Vout of output capacitor C2+, the negative electricity very output terminal Vout of output capacitor C2-.This output terminal Vout+, on Vout-, the mode being in output terminal Vout+side using anode is connected with the LED array LD as load.In addition, between output terminal Vout+and input terminal V0, be connected with Isobarically Control signal output apparatus CV, and be connected with microcomputer MCU via constant voltage regulator circuit Reg.In addition, constant voltage regulator circuit Reg be by output terminal Vout+voltage transitions be the operating voltage of microcomputer MCU and be supplied to the circuit of microcomputer MCU.
Between the tie point and input terminal V0 of the source terminal of the 2nd switch element Q2 and a terminal of reactor L, be connected with regeneration diode D1.The tie point of the source terminal of the 2nd switch element Q2 and a terminal of reactor L is connected with the negative electrode regenerating diode D1, input terminal V0 is connected with the anode of regeneration diode D1.Thus, when the 1st switch element Q1 and the 2nd switch element Q2 two side connect, apply voltage to reactor L and LED array LD, thus accumulate electric power in reactor L.Further, even if when any one party in the 1st switch element Q1 and the 2nd switch element Q2 disconnects, become the state that reactor L and output capacitor C2 is connected in parallel, the electric power that reactor L accumulates is supplied to LED array LD.
1st switch element Q1 of high side is used in the negative voltage induced in magnetic-coupled winding AW with reactor L to carry out disconnection and controls.Be connected with the tie point of the source terminal of reactor L and the 2nd switch element Q2 with one end of the magnetic-coupled winding AW of reactor L, the other end is connected with the gate terminal of the 1st switch element Q1 via coupling capacitor C3.Thus, when the polarity of voltage reversion of reactor L, in winding AW, induce the voltage making the gate terminal of the 1st switch element Q1 become negative potential, thus the 1st switch element Q1 is maintained to off-state.In addition, between the gate terminal and input terminal V0 of the 1st switch element Q1, diode D2 is connected with.The gate terminal of the 1st switch element Q1 is connected with the negative electrode of diode D2, input terminal V0 is connected with the anode of diode D2.Thus, voltage clamping is carried out by the gate terminal of forward voltage VF to the 1st switch element Q1 of diode D2.
Between the gate terminal and source terminal of the 2nd switch element Q2 of downside, be connected in parallel to Zener diode ZD1 and resistance R1.The anode of Zener diode ZD1 is connected with the gate terminal of the 2nd switch element Q2, and negative electrode is connected with the source terminal of the 2nd switch element Q2.
Control circuit Ta is the IC circuit for carrying out current constant control to the 2nd switch element Q2, has trsanscondutance amplifier (Voltage-current conversion amplifier) OTA, buffer BF, reference voltage V ref1, bipolar transistor Q3, diode D3, public terminal COM, current feedback terminal Isense, external phase compensation terminal COMP, drive singal lead-out terminal OUT, starting current input terminal ST and standby terminal Stby.
The public terminal COM of control circuit Ta is connected with the input terminal V0 of ground connection, current feedback terminal Isense and output terminal Vout-, namely the tie point of LED array LD and current sense resistor Rs be connected, external phase compensates terminal COMP and is connected with earth terminal via capacitor Ccomp, drive singal lead-out terminal OUT is connected with the gate terminal of the 2nd switch element Q2 of downside via resistance R2, and starting current input terminal ST is connected with input terminal V+ via resistance R3.
In control circuit Ta, the 1st non-inverting input sub-connection of current feedback terminal Isense and trsanscondutance amplifier OTA, the 2nd non-inverting input sub-connection of standby terminal Stby and trsanscondutance amplifier OTA, the non-inverting input terminal of trsanscondutance amplifier OTA is connected with the positive terminal of reference voltage V ref1, and the negative terminal of reference voltage V ref1 is connected with public terminal COM.In addition, the lead-out terminal of trsanscondutance amplifier OTA compensates terminal COMP with external phase and is connected.Trsanscondutance amplifier OTA is by the voltage of the higher side be input to respectively in the voltage of the 1st inversing input terminal and the 2nd inversing input terminal, be converted to electric current with the potential difference of the reference voltage V ref1 that is input to non-inverting input terminal and export.Therefore, using voltage (voltage of the 1st inversing input terminal) between the two ends as the reactor current and detected detection resistance Rs that flow through reactor L be input to the voltage of the higher side in the voltage (voltage of the 2nd inversing input terminal) of standby terminal Stby and reference voltage V ref1 compares, its potential difference is converted to electric current and exports from trsanscondutance amplifier OTA.
And, the lead-out terminal of trsanscondutance amplifier OTA is connected with the base stage of bipolar transistor Q3 via buffer BF, the collector electrode of bipolar transistor Q3 is connected with drive singal lead-out terminal OUT via diode D3, and the emitter of bipolar transistor Q3 is connected with public terminal COM.In addition, the negative electrode of diode D3 is connected with the collector electrode of bipolar transistor Q3, and anode is connected with drive singal lead-out terminal OUT.
Thus, when between the two ends as the reactor current and detected detection resistance Rs that flow through reactor L, voltage (voltage of the 1st inversing input terminal) is higher than the voltage (voltage of the 2nd inversing input terminal) being input to standby terminal Stby, the collector current of bipolar transistor Q3 becomes value corresponding to the mean value of charge volume, the i.e. reactor current compensating the capacitor Ccomp that terminal COMP connects with external phase.Therefore, when switch element Q1, the Q2 of the wide bandgap semiconductor element as normal open type are on-state, by the voltage drop of the resistance R1 be connected between gate terminal and source terminal with the 2nd switch element Q2, determine the Vgs of voltage between the gate/source as the 2nd switch element Q2, therefore, it is possible to Vgs to be controlled to negative potential corresponding to the charge volume that compensates the capacitor Ccomp that terminal COMP connects with external phase.Make wide bandgap semiconductor element carry out in the scope of action as constant flow element by being set to by the Vgs controlled like this, the 2nd switch element Q2 plays a role as the constant flow element of the constant current value corresponding with the mean value of reactor current.
With reference to Fig. 2, Isobarically Control signal output apparatus CV is connected in series with resistance R10, resistance R11, resistance R12 between output terminal Vout+and input terminal V0 (earth terminal), and resistance R10 is connected with the tie point A of resistance R11 and the standby terminal Stby of control circuit Ta.In addition, have switch element Q4 in parallel with resistance R12, it carries out on-off by the standby signal from outside.
Then, the action of the LED drive circuit 10a of the 1st execution mode is described in detail with reference to Fig. 3.Below, as shown in bracket, by the setting of the resistance value of each resistance R10, R11, the R12 in Isobarically Control signal output apparatus CV in order to 239r:1r:5r, and by when usually exporting (NOM) be set to roughly 60V from the voltage Vout of output terminal Vout+output, be set to reference voltage V ref1=0.3V.
When connecting DC power supply, switch element Q1, Q2 connect, and therefore reactor current flows out and linearly increases.Thus, in reactor L, accumulate electric power, and charge to compensating with external phase the capacitor Ccomp that terminal COMP is connected.When the usual output not being transfused to standby signal (NOM), switch element Q4 is on-state, when being set to output voltage Vout=60V, correspond to the voltage of the standby terminal Stby being input to control circuit Ta from Isobarically Control signal output apparatus CV, input the 0.25V lower than reference voltage V ref1=0.3V.Thus, voltage (voltage of the 1st inversing input terminal) between the two ends as the reactor current and detected detection resistance Rs that flow through reactor L is compared with reference voltage V ref1=0.3V, its potential difference is converted to electric current and exports from trsanscondutance amplifier OTA, the collector current of bipolar transistor Q3 becomes value corresponding to the mean value of charge volume, the i.e. reactor current compensating the capacitor Ccomp that terminal COMP connects with external phase.And, even if when the reactor current increased reaches the constant current value of the 2nd switch element Q2 corresponding to the mean value of charge volume, the i.e. reactor current compensating the capacitor Ccomp that terminal COMP connects with external phase, because reactor current will increase further, therefore drain terminal, the i.e. voltage of the source terminal of switch element Q1 of switch element Q1 sharply rise.Thus, the Vgs of switch element Q1 becomes the negative potential lower than threshold value Vth (negative voltage), and switch element Q1 disconnects.
When switch element Q1 disconnects, the polarity of voltage reversion of reactor L, in winding AW, induce the voltage making the gate terminal of the 1st switch element Q1 become negative potential, thus the 1st switch element Q1 is maintained to off-state, become the regeneration period that electric power that reactor L accumulates is released.And, when not having reactor current to flow through reactor L by releasing electric power in regeneration period, the voltage becoming negative potential is not induced in the gate terminal of switch element Q1, turn on-switch element Q1, Q2 again, action repeatedly identical with above-mentioned action afterwards, thus as shown in Figure 3, become during LED current being carried out to the current constant control of current constant control with such as 100mA.
When being transfused to standby signal standby (Stby), switch element Q4 becomes off-state.In this situation, output voltage Vout=12.25V, and the voltage being input to the standby terminal Stby of control circuit Ta from Isobarically Control signal output apparatus CV becomes reference voltage V ref1=0.3V.Output voltage Vout=12.25V is enough low value compared with the lighting start voltage of LED array LD, based on the voltage (voltage of the 2nd inversing input terminal) being input to standby terminal Stby, as shown in Figure 3, during becoming and output voltage being carried out to the Isobarically Control of Isobarically Control with 12.25V.In addition, output voltage Vout=12.25V is set as the voltage higher than the operating voltage of microcomputer MCU, is converted to operating voltage by constant voltage regulator circuit Reg and is supplied to microcomputer MCU.
In addition, Isobarically Control signal output apparatus CV plays a role as secondary side excess voltage protection.That is, when becoming output voltage Vout=72V, the voltage rise of the standby terminal Stby of control circuit Ta is input to from Isobarically Control signal output apparatus CV to the voltage consistent with reference voltage V ref1=0.3V.Thereby, it is possible to prevent output voltage Vout from rising to more than 72V.
As described above, according to the 1st execution mode, have: constant-current control signal output circuit (current sense resistor Rs), it exports the constant-current control signal corresponding with the reactor current flowing through reactor L; Isobarically Control signal output apparatus CV, it exports the Isobarically Control signal corresponding with output voltage Vout; And control circuit Ta, it is when the usual action not being transfused to standby signal (NOM), by constant-current control signal, current constant control is carried out to LED current, when the standby action being transfused to standby signal (Stby), make the output voltage Vout lower than the ignition voltage of LED array LD by Isobarically Control signal constant is voltage-controlled.
Utilize this structure, can when not lighting LED array LD standby by the power supply of Isobarically Control supply microcomputer, therefore play following effect: the power source special not needing to arrange microcomputer, can circuit structure be simplified, cost can be realized and reduce.In addition, when employing multiple modular power source in pendent lamp etc., multiple modular power source can also be made to carry out redundancy running side by side by the output voltage Vout of (Stby) during standby action.
And, according to the 1st execution mode, control circuit Ta is configured to have the average detection circuit (trsanscondutance amplifier OTA and the capacitor Ccomp be connected with the lead-out terminal of trsanscondutance amplifier OTA) utilizing constant-current control signal (between the two ends of current sense resistor Rs voltage: the voltage of the 1st inversing input terminal) and the mean value of the potential difference between reference voltage V ref1 to reactor current to detect, and carries out current constant control according to the mean value of the reactor current detected by average detection circuit to LED current.
Utilize this structure, when usual action (NOM), use wide bandgap semiconductor as switch element and carried out in the buck circuit of high frequency, the mean value that can carry out LED current equivalently controls, even if there is input voltage variation also constant-current characteristics can be maintained, therefore, it is possible to provide the microminiature LED drive device of corresponding whole world input.
And, according to the 1st execution mode, Isobarically Control signal output apparatus CV is configured to when the standby action being transfused to standby signal (Stby), to have carried out the output voltage lower than the ignition voltage of LED array LD of Isobarically Control, export the Isobarically Control signal consistent with the reference voltage V ref1 of average detection circuit, control circuit Ta carries out Isobarically Control in the mode that Isobarically Control signal is consistent with reference voltage to output voltage Vout by average detection circuit.
Utilizing this structure, when not arranging complicated commutation circuit, Isobarically Control can be carried out with the output voltage lower than the ignition voltage of LED array LD.
And, according to the 1st execution mode, Isobarically Control signal output apparatus CV is configured to when output voltage Vout reaches the overvoltage preset, export the voltage consistent with the reference voltage V ref1 of average detection circuit as Isobarically Control signal, control circuit Ta carries out Isobarically Control in the mode that Isobarically Control signal is consistent with reference voltage V ref1 to output voltage Vout by average detection circuit.
Utilize this structure, Isobarically Control signal output apparatus CV can be used as secondary side excess voltage protection.
(the 2nd execution mode)
The separated exciting buck circuit of the wide bandgap semiconductor element of normal open type is the use of with reference to Fig. 4, the LED drive circuit 10b of the 2nd execution mode.In the LED drive circuit 10 of the 1st execution mode, the 2nd switch element Q2 of downside is used as constant flow element, and in the LED drive circuit 10b of the 2nd execution mode, carries out on-off control by the 2nd switch element Q2 of control circuit Tb to downside.
Between the gate terminal and source terminal of the 2nd switch element Q2 of downside, be connected with Zener diode ZD2.The anode of Zener diode ZD2 is connected with the gate terminal of the 2nd switch element Q2, and negative electrode is connected with the source terminal of the 2nd switch element Q2.In addition, between the gate terminal and input terminal V0 of the 2nd switch element Q2, enough high-resistance resistance R2 is connected with.Zener diode ZD2 and resistance R2 before control circuit Tb carries out action during in, as the current potential of the source terminal according to the 2nd switch element Q2, the autobias circuit making the 2nd switch element Q2 carry out disconnection action plays a role.Namely, the 1st switch element Q1 be connected in series and the 2nd switch element Q2 disconnects the normal open type of this characteristic when being and having connection, Vgs=negative potential when Vgs=0V, therefore when connecting to power supply etc. control circuit Tb carry out action before during in, when 1st switch element Q1 becomes the current potential identical with source potential with the grid voltage of the 2nd switch element Q2, become on-state, flow through big current.Therefore, high-resistance resistance R2 is connected between gate terminal and input terminal V0 (earth terminal), make the grid voltage of the 2nd switch element Q2 by negative voltage by abundant automatic bias to the Zener voltage Vz of the Zener diode ZD2 be connected between gate terminal and source terminal, thus the 2nd switch element Q2 is disconnected.Thus, even if control circuit Tb does not carry out action, also the 2nd switch element Q2 can be made when power supply is connected to carry out disconnection action, therefore before control circuit Tb carries out action, the 2nd switch element Q2 stably can be processed as the semiconductor element of nomal closed type.
Control circuit Tb is the IC circuit for carrying out on-off control to the 2nd switch element Q2, has trsanscondutance amplifier (Voltage-current conversion amplifier) OTA, reference voltage V ref1, triangular wave oscillator OSC, comparator Ton, buffer BF, public terminal COM, current feedback terminal Isense, external phase compensation terminal COMP, drive singal lead-out terminal OUT, starting current input terminal ST, control part power supply terminal Vcc and standby terminal Stby.
In the LED drive circuit 10b of the 2nd execution mode, be connected between the source terminal of current sense resistor Rs and the 2nd switch element Q2 and the tie point of reactor L, the public terminal COM of control circuit Tb is connected with the tie point of current sense resistor Rs and reactor L, and current feedback terminal Isense is connected with the source terminal of the 2nd switch element Q2 and the tie point of current sense resistor Rs.And, external phase compensates terminal COMP and is connected with the tie point of current sense resistor Rs and reactor L via capacitor Ccomp, drive singal lead-out terminal OUT is connected with the gate terminal of the 2nd switch element Q2 of downside via coupling capacitor C4, and starting current input terminal ST is connected with input terminal V+ via resistance R3.
In control circuit Tb, the 1st non-inverting input sub-connection of current feedback terminal Isense and trsanscondutance amplifier OTA, the 2nd non-inverting input sub-connection of standby terminal Stby and trsanscondutance amplifier OTA, the non-inverting input terminal of trsanscondutance amplifier OTA is connected with the positive terminal of reference voltage V ref1, and the negative terminal of reference voltage V ref1 is connected with public terminal COM.In addition, the lead-out terminal of trsanscondutance amplifier OTA compensates terminal COMP with external phase and is connected.Potential difference between the voltage of the higher side be input to respectively in the voltage of the 1st inversing input terminal and the 2nd inversing input terminal and the reference voltage V ref1 being input to non-inverting input terminal is converted to electric current and exports by trsanscondutance amplifier OTA.Therefore, using voltage (voltage of the 1st inversing input terminal) between the two ends as the reactor current and detected detection resistance Rs that flow through reactor L be input to the voltage of the higher side in the voltage (voltage of the 2nd inversing input terminal) of standby terminal Stby and reference voltage V ref1 compares, its potential difference is converted to electric current and exports from trsanscondutance amplifier OTA.
In addition, the lead-out terminal of trsanscondutance amplifier OTA is connected with the non-inverting input terminal of comparator Ton, and the inversing input terminal of comparator Ton is connected with the lead-out terminal of triangular wave oscillator OSC.Further, the lead-out terminal of comparator Ton is connected with drive singal lead-out terminal OUT via buffer BF.In addition, triangular wave oscillator OSC becomes the structure being transfused to critical actuating signal from the anode-side of LED array LD via the diode D5 that adverse current prevents, and after in regeneration period, reactor current L has become 0, triangular wave rises.
Thus, when between the two ends as the reactor current and detected detection resistance Rs that flow through reactor L, voltage (voltage of the 1st inversing input terminal) is higher than the voltage (voltage of the 2nd inversing input terminal) being input to standby terminal Stby, when the triangular wave exported from triangular wave oscillator OSC exceedes voltage corresponding to the mean value of charge volume, the i.e. reactor current compensating the capacitor Ccomp that terminal COMP connects with external phase, the output of comparator Ton is reversed to low level.Thus, being output into rectangular wave from buffer circuit BF, when carrying out capacitor-coupled by coupling capacitor C4 to the output from buffer circuit BF, being converted into the positive voltage after the area of original waveform is split up and down and negative voltage.Therefore, when turning off to the gate terminal applying negative voltage sharply of the 2nd switch element Q2, therefore, it is possible to make the 2nd switch element Q2 disconnect rapidly, and off-state is maintained to.That is, coupling capacitor C4 plays a role as pulse signal change-over circuit, and the pulse signal exported from buffer circuit BF is converted to negative waveform from common potential by it, and by the gate terminal of the output of pulse signal after conversion to the 2nd switch element Q2.In addition, positive voltage more than the gate withstand voltage of the 2nd switch element Q2, but carries out voltage clamping by the forward voltage VF of Zener diode ZD2, therefore, it is possible to make the 2nd switch element Q2 connect when not causing the damage of the 2nd switch element Q2.
In addition, in LED drive circuit 10b, 1st switch element Q1 and the 2nd switch element Q2 has carried out cascade connection, therefore by the 1st switch element Q1 is set to high withstand voltage element, the 2nd switch element Q2 is set to low withstand voltage element, controlled by the on-off of the 2nd switch element Q2 and utilize the 1st switch element Q1 to have withstand voltage.Therefore, in action, the 1st switch element Q1 can also be replaced into low withstand voltage SiMOSFET etc.
In addition, between control part power supply terminal Vcc and public terminal COM, be connected with capacitor C5, and be connected with diode D2 between output terminal Vout+and the control part power supply terminal Vcc of control circuit Tb.The anode of diode D2 and output terminal Vout+be connected, negative electrode is connected with control part power supply terminal Vcc.Utilize this structure, after the starting of control circuit Tb, utilize bootstrap configuration to supply electric power to capacitor C5 from the LED array LD as load circuit, capacitor C5 supplies power for operation to control circuit Tb.
Further, be connected between the control part power supply terminal Vcc of Isobarically Control signal output apparatus CV and control circuit Tb and public terminal COM, the detection of output voltage Vout is undertaken by boostrap circuit.Thereby, it is possible to carry out Isobarically Control at high side configuration Isobarically Control signal output apparatus CV, do not need the level shift etc. of high pressure.
As described above, according to the 2nd execution mode, be configured to have the power supply circuit (diode D4) utilizing the power supply of bootstrap configuration supply control circuit Tb from the anode-side of LED array LD, Isobarically Control signal output apparatus CV exports the Isobarically Control signal corresponding with the supply voltage of control circuit Tb.
Utilize this structure, Isobarically Control can be carried out at high side configuration Isobarically Control signal output apparatus CV, not need the level shift etc. of high pressure.
(the 3rd execution mode)
With reference to Fig. 5, the LED drive circuit 10c of the 3rd execution mode eliminates the 1st switch element Q1, winding AW and the capacitor C3 of high side from the LED drive circuit 10b of the 2nd execution mode, only carry out on-off to the 2nd switch element Q2 by control circuit Tb to control, generate direct current thus and export.Like this, control the 2nd switch element Q2 by separated exciting, do not need other switch element and constant-current circuit and the 2nd switch element Q2 are connected in series, therefore, it is possible to simplify circuit structure.
In addition, the present invention is not limited to the respective embodiments described above, known in the scope of technological thought of the present invention, suitably can change each execution mode.In addition, the quantity, position, shape etc. of said structure parts are not limited to above-mentioned execution mode, can become and be applicable to implementing quantity of the present invention, position, shape etc.In addition, in the various figures, to the identical label of same structure element annotation.
Claims (5)
1. a LED drive circuit, it is exported by direct current and lights LED with constant current, wherein, this direct current exports and utilizes the discharge and recharge of reactor to generate, the discharge and recharge of this reactor performs based on the on-off action of the switch element of normal open type, the feature of described LED drive circuit is to have:
Constant-current control signal output circuit, it exports the constant-current control signal corresponding with the reactor current flowing through described reactor;
Isobarically Control signal output apparatus, it exports the Isobarically Control signal corresponding with output voltage; And
Control circuit, when the usual action not being transfused to standby signal, this control circuit carries out current constant control by described constant-current control signal to the LED current flowing through described LED, when the standby action being transfused to standby signal, this control circuit makes the output voltage lower than the ignition voltage of described LED by described Isobarically Control signal constant is voltage-controlled.
2. LED drive circuit according to claim 1, is characterized in that,
Described control circuit has average detection circuit, this average detection circuit is detected by the mean value of the potential difference between described constant-current control signal and reference voltage to described reactor current, and described control circuit carries out current constant control according to the mean value of the described reactor current detected by described average detection circuit to described LED current.
3. LED drive circuit according to claim 2, is characterized in that,
Described Isobarically Control signal output apparatus
When the standby action being transfused to described standby signal, with the output voltage that the ignition voltage of LED described in the ratio having carried out Isobarically Control is low, export the described Isobarically Control signal consistent with the described reference voltage of described average detection circuit,
Described control circuit carries out Isobarically Control to make the described Isobarically Control signal mode consistent with described reference voltage to output voltage by described average detection circuit.
4. the LED drive circuit according to Claims 2 or 3, is characterized in that,
When output voltage reaches the overvoltage preset, described Isobarically Control signal output apparatus exports the voltage consistent with the described reference voltage of described average detection circuit, as described Isobarically Control signal,
Described control circuit carries out Isobarically Control to make the described Isobarically Control signal mode consistent with described reference voltage to output voltage by described average detection circuit.
5. the LED drive circuit according to any one in Claims 1 to 4, is characterized in that,
Described LED drive circuit has power supply circuit, and this power supply circuit utilizes bootstrap configuration to supply the power supply of described control circuit from the anode-side of described LED,
Isobarically Control signal output apparatus exports the described Isobarically Control signal corresponding with the supply voltage of described control circuit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2013-186383 | 2013-09-09 | ||
| JP2013186383A JP2015053225A (en) | 2013-09-09 | 2013-09-09 | Led drive circuit |
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| Publication Number | Publication Date |
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| CN104427721A true CN104427721A (en) | 2015-03-18 |
| CN104427721B CN104427721B (en) | 2016-08-24 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201410411953.7A Active CN104427721B (en) | 2013-09-09 | 2014-08-20 | Led drive circuit |
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| JP (1) | JP2015053225A (en) |
| CN (1) | CN104427721B (en) |
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| JP6771870B2 (en) * | 2015-08-31 | 2020-10-21 | 三菱電機株式会社 | Lighting device and lighting device |
| JP6593694B2 (en) * | 2015-09-10 | 2019-10-23 | パナソニックＩｐマネジメント株式会社 | Visible light communication device and method for manufacturing visible light communication device |
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Also Published As
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| CN104427721B (en) | 2016-08-24 |
| JP2015053225A (en) | 2015-03-19 |
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