WO2019011193A1 - Current selection circuit and drive circuit - Google Patents

Current selection circuit and drive circuit Download PDF

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Publication number
WO2019011193A1
WO2019011193A1 PCT/CN2018/094839 CN2018094839W WO2019011193A1 WO 2019011193 A1 WO2019011193 A1 WO 2019011193A1 CN 2018094839 W CN2018094839 W CN 2018094839W WO 2019011193 A1 WO2019011193 A1 WO 2019011193A1
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WO
WIPO (PCT)
Prior art keywords
current
current selection
resistor
selection circuit
circuit
Prior art date
Application number
PCT/CN2018/094839
Other languages
French (fr)
Inventor
Huiping FENG
Original Assignee
Tridonic Gmbh & Co Kg
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Publication date
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Publication of WO2019011193A1 publication Critical patent/WO2019011193A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/10—Regulating voltage or current
    • G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
    • G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0012—Control circuits using digital or numerical techniques
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/375—Switched mode power supply [SMPS] using buck topology
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/38—Switched mode power supply [SMPS] using boost topology
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/385—Switched mode power supply [SMPS] using flyback topology

Definitions

  • the present invention relates to the technical field of power supplies, in particular to a current selection circuit and a drive circuit having same.
  • a drive circuit When a drive circuit is used to drive an electronic device, a user will sometimes need to adjust the size of a drive current outputted by the drive circuit, so the drive circuit is required to have a current selection function.
  • a digital integrated circuit may be provided to realize the current selection function; the digital IC may output different current selection signals through 2 ports.
  • an analogue circuit could also be provided to realize the current selection function; the analogue circuit may have multiple output ports to output different current selection signals, thereby causing the drive circuit to output currents of different sizes.
  • the input voltage may be AC (Alternative Current) voltage
  • the output voltage may be DC voltage, which can be applied to a lighting device, such as LED (Light Emission Diode) etc.
  • the drive circuit may comprise a power converter for a light source as a lighting device, such as a LED.
  • the inventors of the present application have discovered that in an existing technical solution in which a current selection function is realized by providing a digital IC, the digital IC outputs a current selection signal in DC (direct current) form, and the cost of realizing current selection is high; in an existing technology in which a current selection function is realized by providing an analogue circuit, if the number of current selection settings to be outputted increases, then the number of output ports of the analogue circuit must also increase.
  • Embodiments of the present application provide a current selection circuit and a drive circuit, wherein by changing a resistance value of a current selection resistor connected to an input end of the current selection circuit, a resistance value of a resistor connected to a power converter is adjusted, so as to adjust a current value of a current outputted by the power converter; thus, current selection can be carried out flexibly, and the number of output ports of the current selection circuit will not increase.
  • a current selection circuit selects an output current setting according to a resistance value of a preset current selection resistor, the current selection circuit has an input end and an output end, the input end is connected to the current selection resistor, the output end is connected to a power converter, the current selection circuit causes a resistor corresponding to the output current setting and having a predetermined resistance value to be connected to the power converter via the output end, according to the resistance value of the current selection resistor, and the power converter outputs a current corresponding to the setting according to the resistor selected by the current selection circuit.
  • Embodiments of the present application have the following beneficial effects: by changing the resistance value of the current selection resistor connected to the input end of the current selection circuit, the resistance value of the resistor connected to the power converter is adjusted, so as to adjust the current value of the current outputted by the power converter, so that current selection can be carried out flexibly; moreover, there will be no increase in the number of output ports of the current selection circuit.
  • a drive circuit for a light source comprising a power converter according to the invention.
  • the power converter of the drive circuit may form a driver for a light source, such as LED.
  • the power converter may be formed by a flyback converter comprising a switch element and a transformer.
  • the power converter may be formed by resonant halfbridge converter, a buck converter, a boost converter or by another switch mode power supply topology.
  • Fig. 1 is a schematic diagram of a current selection circuit in embodiment 1 of the present application.
  • Fig. 2 is a schematic diagram of a power converter paired with a current selection circuit in embodiment 2 of the present application.
  • Embodiment 1 of the present application provides a current selection apparatus.
  • Fig. 1 is a schematic diagram of the current selection circuit.
  • the current selection apparatus 100 may have a preset current selection resistor 101 and a current selection circuit 102; the current selection circuit 102 can select an output current setting according to a resistance value of the current selection resistor 101.
  • the current selection circuit 102 may have an input end and an output end, with the input end being connected to the current selection resistor 101, and the output end being connected to a power converter.
  • the current selection circuit 102 can, on the basis of a resistance value of the current selection resistor 101, cause a resistor corresponding to the output current setting and having a predetermined resistance value to be connected to the power converter 200 via the output end; the power converter 200 can output a corresponding current according to the resistor selected by the current selection circuit 102.
  • the power converter 200 may have a current control end 201; a resistance value between the current control end 201 and an earth terminal may control a drive current value outputted by the power converter 200.
  • a current sense resistor 2011 may be connected between the current control end 201 and the earth terminal, and the resistor selected by the current selection circuit 102 may be connected in parallel with the current sense resistor 2011; thus, the resistance value of the resistor selected by the current selection circuit 102 can be adjusted by adjusting the resistance value of the current selection resistor 101 at the input end of the current selection circuit 102, so as to adjust the resistance value between the earth terminal and the current control end 201 of the power converter 200, so as to adjust the output current value of the power converter 200.
  • the resistance value of the current selection resistor connected to the input end of the current selection circuit is adjusted, so as to adjust the current value of the current outputted by the power converter; thus, current selection can be carried out flexibly, e.g. the resistance value of the current selection resistor can vary sinusoidally with time, so that the drive current outputted by the power converter 200 can also vary sinusoidally with time, thereby increasing the flexibility of current selection; furthermore, the number of output ports of the current selection circuit will not increase.
  • the power converter 200 can convert an input voltage to a drive current output, and the value of the drive current outputted can be controlled by the resistance value between the current control end 201 and the earth terminal.
  • Prior art may be referred to for information relating to the structure and operating principle of the power converter 200.
  • the power converter 200 may have a rectification circuit, a smoothing circuit, a switch element, a transformer, an output-side rectification circuit and a central control apparatus, etc., wherein the rectification circuit and the smoothing circuit can rectify and smooth inputted AC (alternating current) electricity; the central control apparatus can have an ON/OFF control port, which can output a control signal to control the ON/OFF switching of the switch element, and thereby cause a smoothed electrical signal to resonate; the transformer causes the resonant electrical signal to be delivered to an output side of a switching power supply; the output-side rectification circuit rectifies the electrical signal delivered to the output side of the switching power supply, to form and output a drive current.
  • the central control apparatus may also have a control port, i.e. the current control end 201 of the power converter 200; the resistance value between the control port and the earth terminal can control the outputted drive current value of the power transformer 200.
  • the current selection circuit 102 may have two terminals X1 and X2, and the output end of the current selection circuit 102 may have two terminals X3 and X4, wherein terminal X2 and terminal X4 may be connected to an earth terminal of the current selection apparatus 100.
  • the current selection resistor 101 may be connected between terminals X1 and X2; terminal X3 may be connected to the current control end 201 of the power converter 200.
  • the current selection circuit 102 may have a voltage dividing resistor R1; the current selection resistor 101 and the voltage dividing resistor R1 are connected in series between a power supply end Vcc of the current selection circuit and the earth terminal, and by adjusting the resistance value of the current selection resistor 101, the value of a voltage across the current selection resistor 101 can be adjusted.
  • the current selection circuit 102 may also have at least one current sense resistor string; fig. 1 shows 4 current sense resistor strings 1021, 1022, 1023 and 1024.
  • each current sense resistor string is connected to the output end, e.g. the current sense resistor strings 1021, 1022, 1023 and 1024 are connected in parallel between terminals X3 and X4 of the output end of the current selection circuit 102.
  • each current sense resistor string may have a first switch element and a first resistor connected in series; the current selection resistor 101 controls whether the first switch element in each current sense resistor string is switched on.
  • the current sense resistor string 1021 has a first switch element Q1 and a first resistor R2
  • the current sense resistor string 1022 has a first switch element Q2 and a first resistor R3
  • the current sense resistor string 1023 has a first switch element Q3 and a first resistor R4
  • the current sense resistor string 1024 has a first switch element Q4 and a first resistor R5.
  • the first switch element may be a metal oxide semiconductor field effect transistor (MOSFET) , e.g. an N-type MOSFET, or may be a switch element of another type.
  • MOSFET metal oxide semiconductor field effect transistor
  • the first resistor of the current sense resistor string is connected to the power converter 200 via the output end, e.g. the first resistor is connected between the earth terminal and the current control end 201 of the power converter 200, in parallel with the current sense resistor 2011.
  • the resistance values of the first resistors of the current sense resistor strings may be different from one another; thus, when different first switch elements are switched on, first resistors with different resistance values can be connected in parallel with the current sense resistor, so as to have different resistance values between the earth terminal and the current control end 201 of the power converter 200.
  • this embodiment need not be limited to this; the resistance values of the first resistors of the current sense resistor strings could also be set to other values, e.g. the resistance values of certain first resistors could be the same.
  • the current selection circuit 102 may also have at least one switch control circuit; fig. 1 shows 4 switch control circuits 1025, 1026, 1027 and 1028, wherein the voltage across each switch control circuit can control whether the switch control circuit is switched on.
  • the switch control circuits 1025, 1026, 1027 and 1028 are connected in parallel with the current selection resistor 101, therefore the voltage across the current selection resistor 101 is the same as the voltage across each switch control circuit; thus, by adjusting the resistance value of the current selection resistor 101, the value of the voltage across the current selection resistor 101 can be adjusted, so as to control whether each switch control circuit is switched on.
  • each switch control circuit may require a different switch-on threshold voltage in order to be switched on; thus, as the voltage across the current selection resistor 101 gradually rises, a switch control circuit with a lower switch-on threshold voltage may be switched on earlier, and a switch control circuit with a higher switch-on threshold voltage may be switched on later.
  • the switch control circuits 1025, 1026, 1027 and 1028 may respectively control whether the first switch elements Q1, Q2, Q3 and Q4 in the current sense resistor strings 1021, 1022, 1023 and 1024 connected thereto are switched on; thus, the current selection resistor 101, by controlling whether the switch control circuits 1025, 1026, 1027 and 1028 are switched on, controls whether the first switch elements Q1, Q2, Q3 and Q4 in the corresponding current sense resistor strings 1021, 1022, 1023 and 1024 are switched on.
  • each switch control circuit may have a second switch element (Q5, Q6, Q7 and Q8) , a voltage regulating element (D1, D2, D3 and D4) and a second resistor (R6, R7, R8 and R9) , wherein a current inflow end and a current outflow end of the second switch element, the second resistor and the voltage regulating element are connected in series between terminal X1 and the earth terminal, and furthermore, a connection point between the second resistor and the voltage regulating element is connected to a control end, e.g. a gate, of the first switch element.
  • a control end e.g. a gate
  • switch control circuit 1025 when the voltage across the switch control circuit 1025 causes the voltage regulating element D1 to experience breakdown, the second switch element Q5 is switched on, causing the voltage across the second resistor R6 to rise, and thereby causing the first switch element Q1 to be switched on; when the voltage across the switch control circuit 1025 is not enough to cause the voltage regulating element D1 to experience breakdown, the second switch element Q5 is switched off, and the voltage across the second resistor R6 is the same as the earth terminal, hence the first switch element Q1 is switched off.
  • the second switch elements Q5, Q6, Q7 and Q8 may be npn bipolar transistors, but this embodiment is not limited to this; the second switch elements could also be switch elements of another type.
  • the switch-on threshold voltage needed to switch on each switch control circuit may be related to a breakdown voltage of each voltage regulating element; the higher the breakdown voltage of the voltage regulating element, the higher the switch-on threshold voltage needed to switch on the switch control circuit. In one embodiment, the breakdown voltages of the voltage regulating elements may be different.
  • the voltage regulating element may be a Zener diode, e.g. voltage regulating element D1 may have a breakdown voltage of 6.2 V and a model number of BZX79-6V2; voltage regulating element D2 may have a breakdown voltage of 5.1 V and a model number of BZX79-5V1; voltage regulating element D3 may have a breakdown voltage of 3.9 V and a model number of BZX79-3V9; voltage regulating element D4 may have a breakdown voltage of 2.4 V and a model number of BZX79-2V4.
  • each voltage regulating element could also be of another type and model number.
  • the switch control circuits 1025, 1026, 1027 and 1028 may also have third resistors R10, R11, R12 and R13; each third resistor may be connected between terminal X1 and a base of each second switch element.
  • two or more switch control circuits may be switched on, e.g. when the voltage across the current selection resistor 101 is higher than the switch-on threshold voltages of the switch control circuits 1027 and 1028, the switch control circuits 1027 and 1028 may both be switched on, thereby causing the first resistors R4 and R5 to both be connected in parallel between the earth terminal and the current control end 201 of the power converter 200.
  • This embodiment need not be limited to this, e.g. when one switch control circuit is switched on, the other switch control circuits may be switched off, thereby avoiding a situation where two or more switch control circuits are switched on at the same time.
  • the current selection circuit 102 may also have at least one additional control unit; fig. 1 shows 3 additional control units 1031, 1032 and 1033.
  • the additional control unit may implement control so that when the first switch element of one current sense resistor string is switched on, the first switch element of another current sense resistor string is switched off, e.g. the additional control unit causes a switch control circuit having a lower switch-on threshold voltage to be switched off when a switch control circuit having a higher switch-on threshold voltage is switched on.
  • the additional control units may be respectively connected to the switch control circuits other than the switch control circuit having the highest switch-on threshold voltage, e.g. in fig. 1, the switch control circuit with the highest switch-on threshold voltage is 1025, and the other switch control circuits are 1026, 1027 and 1028, therefore the additional control units 1031, 1032 and 1033 are respectively connected to the other switch control circuits 1026, 1027 and 1028.
  • the additional control units 1031, 1032 and 1033 are not provided, then when the switch control circuit 1025 with the highest switch-on threshold voltage is switched on, the other switch control circuits 1026, 1027 and 1028 will also be switched on; therefore, by connecting the additional control units 1031, 1032 and 1033 respectively to the switch control circuits 1026, 1027 and 1028 with the lower switch-on thresholds, the present application can avoid a situation where two or more switch control circuits are switched on at the same time.
  • the additional control units may have third switch elements Q9, Q10 and Q11; the third switch element may be an npn bipolar transistor or a switch element of another type.
  • each third switch element may be connected to the base of the corresponding second switch element (Q6, Q7 and Q8) , and a base of each third switch element (Q9, Q10 and Q11) may be connected via a fourth resistor (R20, R21 and R22) to the gate of the first switch element corresponding to a switch control circuit having a higher switch-on threshold voltage than the switch control circuit controlled by the third switch element.
  • the switch control circuit controlled by the third switch element Q9 is 1026, and the switch control circuit having a higher switch-on threshold voltage than switch control circuit 1026 is 1025, therefore the base of Q9 is connected via the fourth resistor R20 to the gate of the first switch element Q1 corresponding to the switch control circuit 1025; thus, when Q1 is switched on, Q9 is also switched on, the potential at the base of Q6 falls, causing Q6 to be switched off, and so Q2 is switched off.
  • the switch control circuit controlled by the third switch element Q10 is 1027, and the switch control circuits having higher switch-on threshold voltages than switch control circuit 1027 are 1025 and 1026, therefore the base of Q10 is connected via the fourth resistor R20 to the gate of the first switch element Q1 corresponding to the switch control circuit 1025, and the base of Q10 is also connected via the fourth resistor R21 to the gate of the first switch element Q2 corresponding to the switch control circuit 1026; thus, when Q1 or Q2 is switched on, Q10 is switched on, so that Q7 is switched off, causing Q3 to be switched off.
  • the switch control circuit controlled by the third switch element Q11 is 1028, and the switch control circuits having higher switch-on threshold voltages than switch control circuit 1028 are 1025, 1026 and 1027, therefore the base of Q11 is connected via the fourth resistor R20 to the gate of the first switch element Q1 corresponding to the switch control circuit 1025, the base of Q11 is also connected via the fourth resistor R21 to the gate of the first switch element Q2 corresponding to the switch control circuit 1026, and the base of Q11 is also connected via the fourth resistor R22 to the gate of the first switch element Q3 corresponding to the switch control circuit 1027; thus, when Q1, Q2 or Q3 is switched on, Q11 is switched on, so that Q8 is switched off, causing Q4 to be switched off.
  • a diode may also be provided on a connection path connected to the gate of each first switch element, to prevent signals on different connection paths from interfering with each other.
  • diodes D6 and D7 are respectively provided on the connection paths from the base of the third switch element Q10 to the gate of Q1 and the gate of Q2; diodes D9, D10 and D11 are respectively provided on the connection paths from the base of the third switch element Q11 to the gate of Q1, the gate of Q2 and the gate of Q3.
  • the power converter 200 may be formed by resonant halfbridge converter, a buck converter, a boost converter or by another switch mode power supply topology.
  • the resistance value of the resistor connected to the power converter is adjusted, so as to adjust the current value of the current outputted by the power converter, so that current selection can be carried out flexibly; moreover, there will be no increase in the number of output ports of the current selection circuit.
  • Embodiment 2 of the present application provides a drive circuit, which may have the current selection apparatus 100 shown in embodiment 1, and the power converter 200 shown in fig. 1.
  • the power converter 200 may output a current according to a resistance selected by the current selection circuit 102 of the current selection apparatus 100.
  • Fig. 2 is a schematic diagram of this embodiment, in which the power converter is paired with the current selection circuit to form the drive circuit; as shown in fig. 2, a drive circuit 300a has the current selection apparatus 100 and a power converter 200a, wherein the current selection apparatus 100 in fig. 2 has the same structure as in fig. 1, so embodiment 1 may be referred to for an explanation of the current selection apparatus 100, and the power converter 200a in fig. 2 is a particular circuit structure of the power converter 200 in fig. 1.
  • the drive circuit 300a in fig. 2 is explained below.
  • the power converter 200a may have a rectification circuit BD1 and a smoothing capacitor C22, wherein the rectification circuit BD1 for example may be a diode bridge circuit, and can rectify an AC voltage inputted by an AC power supply AC; the smoothing capacitor C22 can smooth a voltage resulting from rectification by the rectification circuit BD1 to form a DC power supply.
  • the rectification circuit BD1 for example may be a diode bridge circuit, and can rectify an AC voltage inputted by an AC power supply AC
  • the smoothing capacitor C22 can smooth a voltage resulting from rectification by the rectification circuit BD1 to form a DC power supply.
  • the power converter 200a may also have a switch element Q21; a central control unit U1 outputs a control signal from a port 4 to control the ON/OFF switching of the switch element Q21.
  • the power converter 200a may also have a transformer T1; the transformer T1 has a primary winding P1, a secondary winding S1 and an auxiliary winding Aux, wherein the auxiliary winding Aux supplies an operating voltage to a port 1 of the central control unit U1, and port 1 of the central control unit U1 is connected to the power supply end Vcc of the current selection apparatus 100.
  • the power converter 200a may also have a rectification diode D52 and smoothing capacitors C28 and C29, wherein the rectification diode D52 is connected to the secondary winding S1, for the purpose of rectifying a sensing voltage of the secondary winding S1; the smoothing capacitors C28 and C29 are used for smoothing a rectified voltage to form a drive current for output.
  • the output voltage provided on the first output port + and the second output port - may be supplied to a light source (not shown) such as a LED.
  • the power converter 200a may provide a supply current to the light source connected to the first output port +and the second output port -.
  • the voltage at the output ports + and – may be stabilized by the smoothing capacitors C28 and C29.
  • the power converter 200a may form a driver for a light source, such as LED.
  • the power converter 200a is formed by a flyback converter comprising the switch element Q21 and the transformer T1.
  • resistors R29, R211 and R212 are connected in series between an earth terminal and port 5 of the central control unit U1 of the power converter 200a, ports X3 and X4 of the current selection apparatus 100 are connected across the resistors R211 and R212, and by adjusting the resistance value of the current selection resistor between ports X1 and X2 of the current selection apparatus 100, the resistance value of the resistor connected in parallel with the resistors R211 and R212 via ports X3 and X4 can be adjusted, so as to adjust the current value of the outputted drive current of the power converter 200a.
  • the power converter 200a in fig. 2 may also have a varistor RV1, a fuse F1, an inductor L1, an inductor L2, a resistor R21, a resistor R22, capacitors CX1 and CY1, a resistor R23, an inductor L3, resistors R24, R25, R26, R28, R210, R214 and R215, capacitors C23, C24, C25, C26 and C41, diodes D32, D22 and D42; prior art may be referred to for an explanation of the abovementioned elements, which are not described superfluously in this embodiment.
  • Prior art may also be referred to for an explanation of a port 2, a port 3 and a port 4 of the central control unit U1 in fig. 2.
  • the power converter 200a in fig. 2 is merely one embodiment of the power converter 200, and this embodiment is not limited to this; the power converter could also have another structure.
  • the resistance value of the resistor connected to the power converter is adjusted, so as to adjust the current value of the current outputted by the power converter, so that current selection can be carried out flexibly; moreover, there will be no increase in the number of output ports of the current selection apparatus.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Dc-Dc Converters (AREA)
  • Power Conversion In General (AREA)

Abstract

A current selection circuit (102) and a drive circuit (300); the current selection circuit (102) selects an output current setting according to a resistance value of a preset current selection resistor (101), the current selection circuit (102) has an input end and an output end, the input end is connected to the current selection resistor (101), the output end is connected to a power converter (200), the current selection circuit (102) causes a resistor corresponding to the output current setting and having a predetermined resistance value to be connected to the power converter (200) via the output end, according to the resistance value of the current selection resistor (101), and the power converter (200) outputs a current according to the resistor selected by the current selection circuit (102). Current selection can be carried out flexibly, and the number of input ports of a current selection apparatus will not increase as the number of output current settings increases.

Description

Current selection circuit and drive circuit Technical field
The present invention relates to the technical field of power supplies, in particular to a current selection circuit and a drive circuit having same.
Background art
When a drive circuit is used to drive an electronic device, a user will sometimes need to adjust the size of a drive current outputted by the drive circuit, so the drive circuit is required to have a current selection function.
In an existing drive circuit, a digital integrated circuit (digital IC) may be provided to realize the current selection function; the digital IC may output different current selection signals through 2 ports.
In an existing drive circuit, an analogue circuit could also be provided to realize the current selection function; the analogue circuit may have multiple output ports to output different current selection signals, thereby causing the drive circuit to output currents of different sizes.
In the field of lighting technology, a drive circuit is needed to convert input voltage to output voltage. The input voltage may be AC (Alternative Current) voltage, and the output voltage may be DC voltage, which can be applied to a lighting device, such as LED (Light Emission Diode) etc. The drive circuit may comprise a power converter for a light source as a lighting device, such as a LED. It should be noted that the introduction to the technical background above is related purely for the purpose of facilitating clear and complete explanation of the technical solution of the present application, and facilitating understanding by those skilled in the art. It cannot be assumed, simply because these solutions have been expounded in the background art section of the present application, that the abovementioned technical solutions are known to those skilled in the art.
Content of the invention
The inventors of the present application have discovered that in an existing technical solution in which a current selection function is realized by providing a digital IC, the digital IC outputs a current selection signal in DC (direct current) form, and the cost of realizing current selection is high; in an existing technology in which a current selection function is realized by providing an analogue circuit, if the number of current selection settings to be outputted increases, then the number of output ports of the analogue circuit must also increase.
Embodiments of the present application provide a current selection circuit and a drive circuit, wherein by changing a resistance value of a current selection resistor connected to an input end of the current selection circuit, a resistance value of a resistor connected to a power converter is adjusted, so as to adjust a current value of a current outputted by the power converter; thus, current selection can be carried out flexibly, and the number of output ports of the current selection circuit will not increase.
According to an embodiment of the present application, a current selection circuit is provided; the current selection circuit selects an output current setting according to a resistance value of a preset current selection resistor, the current selection circuit has an input end and an output end, the input end is connected to the current selection resistor, the output end is connected to a power converter, the current selection circuit causes a resistor corresponding to the output current setting and having a predetermined resistance value to be connected to the power converter via the output end, according to the resistance value of the current selection resistor, and the power converter outputs a current corresponding to the setting according to the resistor selected by the current selection circuit.
Embodiments of the present application have the following beneficial effects: by changing the resistance value of the current selection resistor connected to the input end of the current selection circuit, the resistance value of the resistor connected to the power converter is adjusted, so as to adjust the current value of the current outputted by the power converter, so that current selection can be carried out flexibly; moreover, there will be no increase in the number of output ports of the current selection circuit.
According to one aspect of the invention, there is provided a drive circuit for a light source comprising a power converter according to the invention.
The power converter of the drive circuit may form a driver for a light source, such as LED.
The power converter may be formed by a flyback converter comprising a switch  element and a transformer.
The power converter may be formed by resonant halfbridge converter, a buck converter, a boost converter or by another switch mode power supply topology.
Referring to the following explanation and the accompanying drawings, specific embodiments of the present invention are disclosed in detail, and ways in which the principles of the present invention can be adopted are demonstrated. It should be understood that the embodiments of the present invention are not restricted in scope as a result. The embodiments of the present invention include many changes, amendments and equivalents within the scope of the spirit and provisions of the attached claims.
Features described and/or shown in relation to one embodiment could be used in one or more other embodiments in an identical or similar manner, combined with features in other embodiments, or be used to replace features in other embodiments.
It should be emphasized that the terms “comprise/contain” as used herein denote the existence of a feature, entire piece, step or assembly, but do not exclude the existence or addition of one or more other features, entire pieces, steps or assemblies.
Description of the accompanying drawings
The accompanying drawings included are used to provide further understanding of embodiments of the present invention, and form part of this Description, for the purpose of demonstrating embodiments of the present invention, and expounding the principles of the present invention together with textual description. Obviously, the drawings in the following description are merely some embodiments of the present invention; other drawings could be obtained by those skilled in the art on the basis of these drawings without expending any inventive effort. In the drawings:
Fig. 1 is a schematic diagram of a current selection circuit in embodiment 1 of the present application.
Fig. 2 is a schematic diagram of a power converter paired with a current selection circuit in embodiment 2 of the present application.
Particular embodiments
Referring to the accompanying drawings, the abovementioned and other features of the present invention will become obvious herein below. In this Description and the drawings, specific embodiments of the present invention are specifically disclosed; these  demonstrate a portion of embodiments in which the principles of the present invention may be adopted. It should be understood that the present invention is not limited to the embodiments described; on the contrary, the present invention comprises all amendments, changes in form and equivalents which fall within the scope of the attached claims.
Embodiment 1
Embodiment 1 of the present application provides a current selection apparatus. Fig. 1 is a schematic diagram of the current selection circuit.
As shown in fig. 1, the current selection apparatus 100 may have a preset current selection resistor 101 and a current selection circuit 102; the current selection circuit 102 can select an output current setting according to a resistance value of the current selection resistor 101.
In this embodiment, the current selection circuit 102 may have an input end and an output end, with the input end being connected to the current selection resistor 101, and the output end being connected to a power converter.
In this embodiment, the current selection circuit 102 can, on the basis of a resistance value of the current selection resistor 101, cause a resistor corresponding to the output current setting and having a predetermined resistance value to be connected to the power converter 200 via the output end; the power converter 200 can output a corresponding current according to the resistor selected by the current selection circuit 102.
In this embodiment, the power converter 200 may have a current control end 201; a resistance value between the current control end 201 and an earth terminal may control a drive current value outputted by the power converter 200. In one embodiment, a current sense resistor 2011 may be connected between the current control end 201 and the earth terminal, and the resistor selected by the current selection circuit 102 may be connected in parallel with the current sense resistor 2011; thus, the resistance value of the resistor selected by the current selection circuit 102 can be adjusted by adjusting the resistance value of the current selection resistor 101 at the input end of the current selection circuit 102, so as to adjust the resistance value between the earth terminal and the current control end 201 of the power converter 200, so as to adjust the output current value of the power converter 200.
According to this embodiment, by changing the resistance value of the current selection resistor connected to the input end of the current selection circuit, the resistance  value of the resistor connected to the power converter is adjusted, so as to adjust the current value of the current outputted by the power converter; thus, current selection can be carried out flexibly, e.g. the resistance value of the current selection resistor can vary sinusoidally with time, so that the drive current outputted by the power converter 200 can also vary sinusoidally with time, thereby increasing the flexibility of current selection; furthermore, the number of output ports of the current selection circuit will not increase.
In this embodiment, the power converter 200 can convert an input voltage to a drive current output, and the value of the drive current outputted can be controlled by the resistance value between the current control end 201 and the earth terminal. Prior art may be referred to for information relating to the structure and operating principle of the power converter 200.
For example, the power converter 200 may have a rectification circuit, a smoothing circuit, a switch element, a transformer, an output-side rectification circuit and a central control apparatus, etc., wherein the rectification circuit and the smoothing circuit can rectify and smooth inputted AC (alternating current) electricity; the central control apparatus can have an ON/OFF control port, which can output a control signal to control the ON/OFF switching of the switch element, and thereby cause a smoothed electrical signal to resonate; the transformer causes the resonant electrical signal to be delivered to an output side of a switching power supply; the output-side rectification circuit rectifies the electrical signal delivered to the output side of the switching power supply, to form and output a drive current. The central control apparatus may also have a control port, i.e. the current control end 201 of the power converter 200; the resistance value between the control port and the earth terminal can control the outputted drive current value of the power transformer 200.
The structure and operating principles of the current selection apparatus 100 are explained in detail below with reference to the accompanying drawings.
As shown in fig. 1, the current selection circuit 102 may have two terminals X1 and X2, and the output end of the current selection circuit 102 may have two terminals X3 and X4, wherein terminal X2 and terminal X4 may be connected to an earth terminal of the current selection apparatus 100. The current selection resistor 101 may be connected between terminals X1 and X2; terminal X3 may be connected to the current control end 201 of the power converter 200.
In this embodiment, as shown in fig. 1, the current selection circuit 102 may have a  voltage dividing resistor R1; the current selection resistor 101 and the voltage dividing resistor R1 are connected in series between a power supply end Vcc of the current selection circuit and the earth terminal, and by adjusting the resistance value of the current selection resistor 101, the value of a voltage across the current selection resistor 101 can be adjusted.
In this embodiment, the current selection circuit 102 may also have at least one current sense resistor string; fig. 1 shows 4 current  sense resistor strings  1021, 1022, 1023 and 1024.
In this embodiment, each current sense resistor string is connected to the output end, e.g. the current  sense resistor strings  1021, 1022, 1023 and 1024 are connected in parallel between terminals X3 and X4 of the output end of the current selection circuit 102.
In this embodiment, each current sense resistor string may have a first switch element and a first resistor connected in series; the current selection resistor 101 controls whether the first switch element in each current sense resistor string is switched on. For example, the current sense resistor string 1021 has a first switch element Q1 and a first resistor R2, the current sense resistor string 1022 has a first switch element Q2 and a first resistor R3, the current sense resistor string 1023 has a first switch element Q3 and a first resistor R4, and the current sense resistor string 1024 has a first switch element Q4 and a first resistor R5.In this embodiment, the first switch element may be a metal oxide semiconductor field effect transistor (MOSFET) , e.g. an N-type MOSFET, or may be a switch element of another type.
In this embodiment, when the first switch element of a particular current sense resistor string is switched on, the first resistor of the current sense resistor string is connected to the power converter 200 via the output end, e.g. the first resistor is connected between the earth terminal and the current control end 201 of the power converter 200, in parallel with the current sense resistor 2011.
In this embodiment, the resistance values of the first resistors of the current sense resistor strings may be different from one another; thus, when different first switch elements are switched on, first resistors with different resistance values can be connected in parallel with the current sense resistor, so as to have different resistance values between the earth terminal and the current control end 201 of the power converter 200.
Furthermore, this embodiment need not be limited to this; the resistance values of the first resistors of the current sense resistor strings could also be set to other values, e.g. the resistance values of certain first resistors could be the same.
In this embodiment, the current selection circuit 102 may also have at least one switch control circuit; fig. 1 shows 4  switch control circuits  1025, 1026, 1027 and 1028, wherein the voltage across each switch control circuit can control whether the switch control circuit is switched on.
In this embodiment, the  switch control circuits  1025, 1026, 1027 and 1028 are connected in parallel with the current selection resistor 101, therefore the voltage across the current selection resistor 101 is the same as the voltage across each switch control circuit; thus, by adjusting the resistance value of the current selection resistor 101, the value of the voltage across the current selection resistor 101 can be adjusted, so as to control whether each switch control circuit is switched on.
In this embodiment, each switch control circuit may require a different switch-on threshold voltage in order to be switched on; thus, as the voltage across the current selection resistor 101 gradually rises, a switch control circuit with a lower switch-on threshold voltage may be switched on earlier, and a switch control circuit with a higher switch-on threshold voltage may be switched on later.
In this embodiment, the  switch control circuits  1025, 1026, 1027 and 1028 may respectively control whether the first switch elements Q1, Q2, Q3 and Q4 in the current  sense resistor strings  1021, 1022, 1023 and 1024 connected thereto are switched on; thus, the current selection resistor 101, by controlling whether the  switch control circuits  1025, 1026, 1027 and 1028 are switched on, controls whether the first switch elements Q1, Q2, Q3 and Q4 in the corresponding current  sense resistor strings  1021, 1022, 1023 and 1024 are switched on.
In this embodiment, each switch control circuit may have a second switch element (Q5, Q6, Q7 and Q8) , a voltage regulating element (D1, D2, D3 and D4) and a second resistor (R6, R7, R8 and R9) , wherein a current inflow end and a current outflow end of the second switch element, the second resistor and the voltage regulating element are connected in series between terminal X1 and the earth terminal, and furthermore, a connection point between the second resistor and the voltage regulating element is connected to a control end, e.g. a gate, of the first switch element.
In this embodiment, taking switch control circuit 1025 as an example, when the voltage across the switch control circuit 1025 causes the voltage regulating element D1 to experience breakdown, the second switch element Q5 is switched on, causing the voltage across the second resistor R6 to rise, and thereby causing the first switch element Q1 to be  switched on; when the voltage across the switch control circuit 1025 is not enough to cause the voltage regulating element D1 to experience breakdown, the second switch element Q5 is switched off, and the voltage across the second resistor R6 is the same as the earth terminal, hence the first switch element Q1 is switched off.
In this embodiment, the second switch elements Q5, Q6, Q7 and Q8 may be npn bipolar transistors, but this embodiment is not limited to this; the second switch elements could also be switch elements of another type.
In this embodiment, the switch-on threshold voltage needed to switch on each switch control circuit may be related to a breakdown voltage of each voltage regulating element; the higher the breakdown voltage of the voltage regulating element, the higher the switch-on threshold voltage needed to switch on the switch control circuit. In one embodiment, the breakdown voltages of the voltage regulating elements may be different.
In this embodiment, the voltage regulating element may be a Zener diode, e.g. voltage regulating element D1 may have a breakdown voltage of 6.2 V and a model number of BZX79-6V2; voltage regulating element D2 may have a breakdown voltage of 5.1 V and a model number of BZX79-5V1; voltage regulating element D3 may have a breakdown voltage of 3.9 V and a model number of BZX79-3V9; voltage regulating element D4 may have a breakdown voltage of 2.4 V and a model number of BZX79-2V4. Furthermore, each voltage regulating element could also be of another type and model number.
Furthermore, as shown in fig. 1, the  switch control circuits  1025, 1026, 1027 and 1028 may also have third resistors R10, R11, R12 and R13; each third resistor may be connected between terminal X1 and a base of each second switch element.
In this embodiment, at a specific voltage, two or more switch control circuits may be switched on, e.g. when the voltage across the current selection resistor 101 is higher than the switch-on threshold voltages of the  switch control circuits  1027 and 1028, the  switch control circuits  1027 and 1028 may both be switched on, thereby causing the first resistors R4 and R5 to both be connected in parallel between the earth terminal and the current control end 201 of the power converter 200.
This embodiment need not be limited to this, e.g. when one switch control circuit is switched on, the other switch control circuits may be switched off, thereby avoiding a situation where two or more switch control circuits are switched on at the same time.
As shown in fig. 1, the current selection circuit 102 may also have at least one additional control unit; fig. 1 shows 3  additional control units  1031, 1032 and 1033.
In this embodiment, the additional control unit may implement control so that when the first switch element of one current sense resistor string is switched on, the first switch element of another current sense resistor string is switched off, e.g. the additional control unit causes a switch control circuit having a lower switch-on threshold voltage to be switched off when a switch control circuit having a higher switch-on threshold voltage is switched on.
In this embodiment, the additional control units may be respectively connected to the switch control circuits other than the switch control circuit having the highest switch-on threshold voltage, e.g. in fig. 1, the switch control circuit with the highest switch-on threshold voltage is 1025, and the other switch control circuits are 1026, 1027 and 1028, therefore the  additional control units  1031, 1032 and 1033 are respectively connected to the other  switch control circuits  1026, 1027 and 1028. If the  additional control units  1031, 1032 and 1033 are not provided, then when the switch control circuit 1025 with the highest switch-on threshold voltage is switched on, the other  switch control circuits  1026, 1027 and 1028 will also be switched on; therefore, by connecting the  additional control units  1031, 1032 and 1033 respectively to the  switch control circuits  1026, 1027 and 1028 with the lower switch-on thresholds, the present application can avoid a situation where two or more switch control circuits are switched on at the same time.
In this embodiment, as shown in fig. 1, the additional control units may have third switch elements Q9, Q10 and Q11; the third switch element may be an npn bipolar transistor or a switch element of another type.
In this embodiment, a collector of each third switch element (Q9, Q10 and Q11) may be connected to the base of the corresponding second switch element (Q6, Q7 and Q8) , and a base of each third switch element (Q9, Q10 and Q11) may be connected via a fourth resistor (R20, R21 and R22) to the gate of the first switch element corresponding to a switch control circuit having a higher switch-on threshold voltage than the switch control circuit controlled by the third switch element.
For example, as shown in fig. 1, the switch control circuit controlled by the third switch element Q9 is 1026, and the switch control circuit having a higher switch-on threshold voltage than switch control circuit 1026 is 1025, therefore the base of Q9 is connected via the fourth resistor R20 to the gate of the first switch element Q1 corresponding to the switch control circuit 1025; thus, when Q1 is switched on, Q9 is also switched on, the potential at the base of Q6 falls, causing Q6 to be switched off, and so Q2  is switched off. Similarly, the switch control circuit controlled by the third switch element Q10 is 1027, and the switch control circuits having higher switch-on threshold voltages than switch control circuit 1027 are 1025 and 1026, therefore the base of Q10 is connected via the fourth resistor R20 to the gate of the first switch element Q1 corresponding to the switch control circuit 1025, and the base of Q10 is also connected via the fourth resistor R21 to the gate of the first switch element Q2 corresponding to the switch control circuit 1026; thus, when Q1 or Q2 is switched on, Q10 is switched on, so that Q7 is switched off, causing Q3 to be switched off. Similarly, the switch control circuit controlled by the third switch element Q11 is 1028, and the switch control circuits having higher switch-on threshold voltages than switch control circuit 1028 are 1025, 1026 and 1027, therefore the base of Q11 is connected via the fourth resistor R20 to the gate of the first switch element Q1 corresponding to the switch control circuit 1025, the base of Q11 is also connected via the fourth resistor R21 to the gate of the first switch element Q2 corresponding to the switch control circuit 1026, and the base of Q11 is also connected via the fourth resistor R22 to the gate of the first switch element Q3 corresponding to the switch control circuit 1027; thus, when Q1, Q2 or Q3 is switched on, Q11 is switched on, so that Q8 is switched off, causing Q4 to be switched off.
In this embodiment, when the base of the third switch element is connected to the gates of two or more first switch elements, a diode may also be provided on a connection path connected to the gate of each first switch element, to prevent signals on different connection paths from interfering with each other. For example, diodes D6 and D7 are respectively provided on the connection paths from the base of the third switch element Q10 to the gate of Q1 and the gate of Q2; diodes D9, D10 and D11 are respectively provided on the connection paths from the base of the third switch element Q11 to the gate of Q1, the gate of Q2 and the gate of Q3.
In this embodiment, by providing the additional control units (1031, 1032 and 1033) , a situation where two or more switch control circuits are switched on at the same time can be avoided, so that the current selection circuit 102 only selects one first resistor at a time for connection to the power converter 200.
The power converter 200 may be formed by resonant halfbridge converter, a buck converter, a boost converter or by another switch mode power supply topology.
According to an embodiment of the present application, by changing the resistance value of the current selection resistor connected to the input end of the current selection  circuit, the resistance value of the resistor connected to the power converter is adjusted, so as to adjust the current value of the current outputted by the power converter, so that current selection can be carried out flexibly; moreover, there will be no increase in the number of output ports of the current selection circuit.
Embodiment 2
Embodiment 2 of the present application provides a drive circuit, which may have the current selection apparatus 100 shown in embodiment 1, and the power converter 200 shown in fig. 1.
As shown in fig. 1, in the drive circuit 300, the power converter 200 may output a current according to a resistance selected by the current selection circuit 102 of the current selection apparatus 100.
Fig. 2 is a schematic diagram of this embodiment, in which the power converter is paired with the current selection circuit to form the drive circuit; as shown in fig. 2, a drive circuit 300a has the current selection apparatus 100 and a power converter 200a, wherein the current selection apparatus 100 in fig. 2 has the same structure as in fig. 1, so embodiment 1 may be referred to for an explanation of the current selection apparatus 100, and the power converter 200a in fig. 2 is a particular circuit structure of the power converter 200 in fig. 1.
The drive circuit 300a in fig. 2 is explained below.
As shown in fig. 2, the power converter 200a may have a rectification circuit BD1 and a smoothing capacitor C22, wherein the rectification circuit BD1 for example may be a diode bridge circuit, and can rectify an AC voltage inputted by an AC power supply AC; the smoothing capacitor C22 can smooth a voltage resulting from rectification by the rectification circuit BD1 to form a DC power supply.
The power converter 200a may also have a switch element Q21; a central control unit U1 outputs a control signal from a port 4 to control the ON/OFF switching of the switch element Q21.
The power converter 200a may also have a transformer T1; the transformer T1 has a primary winding P1, a secondary winding S1 and an auxiliary winding Aux, wherein the auxiliary winding Aux supplies an operating voltage to a port 1 of the central control unit U1, and port 1 of the central control unit U1 is connected to the power supply end Vcc of the current selection apparatus 100.
The power converter 200a may also have a rectification diode D52 and smoothing capacitors C28 and C29, wherein the rectification diode D52 is connected to the secondary winding S1, for the purpose of rectifying a sensing voltage of the secondary winding S1; the smoothing capacitors C28 and C29 are used for smoothing a rectified voltage to form a drive current for output.
The output voltage provided on the first output port + and the second output port -may be supplied to a light source (not shown) such as a LED. Thereby the power converter 200a may provide a supply current to the light source connected to the first output port +and the second output port -. The voltage at the output ports + and –may be stabilized by the smoothing capacitors C28 and C29.
The power converter 200a may form a driver for a light source, such as LED.
The power converter 200a is formed by a flyback converter comprising the switch element Q21 and the transformer T1.
As shown in fig. 2, resistors R29, R211 and R212 are connected in series between an earth terminal and port 5 of the central control unit U1 of the power converter 200a, ports X3 and X4 of the current selection apparatus 100 are connected across the resistors R211 and R212, and by adjusting the resistance value of the current selection resistor between ports X1 and X2 of the current selection apparatus 100, the resistance value of the resistor connected in parallel with the resistors R211 and R212 via ports X3 and X4 can be adjusted, so as to adjust the current value of the outputted drive current of the power converter 200a.
Furthermore, as shown in fig. 2, the power converter 200a in fig. 2 may also have a varistor RV1, a fuse F1, an inductor L1, an inductor L2, a resistor R21, a resistor R22, capacitors CX1 and CY1, a resistor R23, an inductor L3, resistors R24, R25, R26, R28, R210, R214 and R215, capacitors C23, C24, C25, C26 and C41, diodes D32, D22 and D42; prior art may be referred to for an explanation of the abovementioned elements, which are not described superfluously in this embodiment.
Prior art may also be referred to for an explanation of a port 2, a port 3 and a port 4 of the central control unit U1 in fig. 2.
It must be explained that the power converter 200a in fig. 2 is merely one embodiment of the power converter 200, and this embodiment is not limited to this; the power converter could also have another structure.
In the drive circuit of this embodiment, by changing the resistance value of the current selection resistor connected to the input end of the current selection apparatus, the  resistance value of the resistor connected to the power converter is adjusted, so as to adjust the current value of the current outputted by the power converter, so that current selection can be carried out flexibly; moreover, there will be no increase in the number of output ports of the current selection apparatus.
The present application has been described above with reference to particular embodiments, but those skilled in the art should understand that these descriptions are demonstrative, and are not a restriction on the scope of protection of the present application. Those skilled in the art could make various changes in form and amendments to the present application on the basis of the spirit and principles thereof; all such changes in form and amendments are also included in the scope of the present application.

Claims (10)

  1. Current selection circuit, characterized in that the current selection circuit selects an output current setting according to a resistance value of a preset current selection resistor,
    the current selection circuit has an input end and an output end,
    the input end is connected to the current selection resistor,
    the output end is connected to a power converter,
    the current selection circuit causes a resistor corresponding to the output current setting and having a predetermined resistance value to be connected to the power converter via the output end, according to the resistance value of the current selection resistor, and
    the power converter outputs a current according to the resistor selected by the current selection circuit.
  2. Current selection circuit according to Claim 1, wherein
    the power converter has a current control end connected to a current sense resistor, and
    the resistor selected by the current selection circuit is connected in parallel with the current sense resistor.
  3. Current selection circuit according to Claim 1, wherein
    the current selection circuit has at least one current sense resistor string,
    each said current sense resistor string is connected to the output end,
    each said current sense resistor string has a first switch element and a first resistor connected in series, and
    the current selection resistor controls whether the first switch element in the current sense resistor string is switched on.
  4. Current selection circuit according to Claim 3, wherein
    resistance values of the first resistors of the current sense resistor strings are different from one another.
  5. Current selection circuit according to Claim 3, wherein
    the current selection circuit also has at least one switch control circuit,
    each said switch control circuit is connected in parallel with the current selection  resistor,
    the current selection resistor controls whether the switch control circuit is switched on, and
    each said switch control circuit controls whether the first switch element of the current sense resistor string connected thereto is switched on.
  6. Current selection circuit according to Claim 5, wherein
    the current selection circuit also has a voltage dividing resistor, and
    the current selection resistor and the voltage dividing resistor are connected in series between an earth terminal and a power supply end of the current selection circuit.
  7. Current selection circuit according to Claim 5, wherein
    the current selection circuit also has at least one additional control unit, and
    the additional control unit is used for implementing control, such that when the first switch element of one current sense resistor string is switched on, the first switch element of another current sense resistor string is switched off.
  8. Current selection circuit according to Claim 7, wherein
    the additional control unit causes a switch control circuit having a lower switch-on threshold voltage to be switched off when a switch control circuit having a higher switch-on threshold voltage is switched on.
  9. Drive circuit, having a power converter, a preset current selection resistor and the current selection circuit according to any one of Claims 1 -8, wherein the power converter outputs a current according to the resistor selected by the current selection circuit.
  10. Drive circuit according to claim 9 wherein the power converter of the drive circuit forms a driver for a light source, preferably a LED.
PCT/CN2018/094839 2017-07-12 2018-07-06 Current selection circuit and drive circuit WO2019011193A1 (en)

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CN104333933A (en) * 2013-07-22 2015-02-04 全汉企业股份有限公司 Light emitting diode driving device and light emitting diode illumination system applying same
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CN103547009A (en) * 2012-07-09 2014-01-29 晶洋微电子股份有限公司 Linear current regulator
CN104238609A (en) * 2013-06-14 2014-12-24 鸿富锦精密工业（深圳）有限公司 Voltage regulation circuit
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CN105700606A (en) * 2016-01-22 2016-06-22 深圳微步信息股份有限公司 Power module and output voltage regulating method thereof

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