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CN102752898B - Load drive circuit - Google Patents

Load drive circuit Download PDF

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Publication number
CN102752898B
CN102752898B CN201110083372.1A CN201110083372A CN102752898B CN 102752898 B CN102752898 B CN 102752898B CN 201110083372 A CN201110083372 A CN 201110083372A CN 102752898 B CN102752898 B CN 102752898B
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China
Prior art keywords
current
resistor
load
voltage
circuit
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CN201110083372.1A
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Chinese (zh)
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CN102752898A (en
Inventor
葛良安
姚晓莉
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Led One Hangzhou Co Ltd
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Led One Hangzhou Co Ltd
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Priority to CN201110083372.1A priority Critical patent/CN102752898B/en
Priority to PCT/CN2011/074884 priority patent/WO2012129836A1/en
Publication of CN102752898A publication Critical patent/CN102752898A/en
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    • 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
    • H05B45/395—Linear regulators
    • 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
    • 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]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • H05B45/48—Details of LED load circuits with an active control inside an LED matrix having LEDs organised in strings and incorporating parallel shunting devices
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

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  • Continuous-Control Power Sources That Use Transistors (AREA)

Abstract

The invention discloses a load drive circuit. The circuit comprises: a current-limiting circuit, a regulating transistor, a current sampler, and a current feedback controller. The current-limiting circuit and a driven load set are connected between two output ends of a direct voltage source in series, and the current-limiting circuit is used for controlling a load current value of the load set not larger than a preset current-limiting point. The regulating transistor is connected in parallel with a subset of load set and the series connected current-limiting circuit. A sampled signal output end of the current sampler is connected with an input end of the current feedback controller, and the current sampler is used for sampling load current of the load set and transmitting a current signal obtained by sampling to the current feedback controller. An output end of the current feedback controller is connected with an on-off control end of the regulating transistor, and the current feedback controller is used for receiving the current signal. If the current value of the current signal is not less than a preset stable current point, the current feedback controller controls the regulating transistor to shut off, and if the current value of the current signal is less than the preset stable current point, the current feedback controller controls breakover of the regulating transistor. In addition, the current feedback controller controls a breakover impedance value of the regulating transistor according to the current value of the current signal. The load drive circuit can reduce electric energy loss and improve load drive efficiency.

Description

Load driving circuit
Technical Field
The present invention relates to load driving technologies, and in particular, to a load driving circuit.
Background
For alternating current input Light Emitting Diode (LED) light sources, the most common driving scheme is to implement constant current driving of the LEDs with an AC/DC switching power supply. However, the switching power supply contains a magnetic element, so that the problem of high-frequency electromagnetic interference needs to be solved, and a relatively complex control chip is needed, so that for some low-power LED light sources, the switching power supply is adopted for constant-current driving, the size of a driving circuit is relatively large, and the cost is relatively high. In this case, the LED light source is generally driven by a simple LED constant current drive circuit.
Fig. 1 shows a conventional simple LED constant current driving circuit, in which a linear current limiting circuit, which may be a constant current diode or the like, and an LED set are connected in series and then connected in parallel to a dc side of a rectifying circuit, and a grid voltage is rectified by the rectifying circuit to supply power to the LED set.
When the voltage loaded at the two ends of the LED set and the linear current limiting circuit exceeds the total rated voltage of the LED set connected in series, the part exceeding the total rated voltage of the LED set is borne by the linear current limiting circuit; when the voltage loaded at the two ends of the LED set and the linear current limiting circuit is lower than the total rated voltage of the LED set, the linear current limiting circuit is in saturated conduction, and at the moment, the current flowing through the LED is lower than the current limiting point of the current limiting circuit.
The driving circuit shown in fig. 1 is simple in structure and low in cost, however, when the power grid voltage fluctuation is large, if the constant current driving of the LEDs is to be realized in the whole power grid voltage fluctuation range, the total rated voltage of the LED set is required to be approximately equal to the rectified voltage of the power grid voltage fluctuation lower limit value, at this time, in the whole driving process, when the voltage value of the rectified power grid voltage is higher than the total rated voltage of the LED set, the current is required to be limited through the linear current limiting circuit, the power consumption is large, the driving efficiency of the LEDs is low, especially when the power grid voltage is close to the voltage upper limit value, the power consumption of the linear current limiting circuit is larger, the power consumption is larger, and the driving efficiency of the LEDs is also lower.
Disclosure of Invention
In view of the above, the present invention provides a load driving circuit, which can reduce power consumption and improve driving efficiency of a load.
Therefore, the embodiment of the invention adopts the following technical scheme:
an embodiment of the present invention provides a load driving circuit, including:
the current limiting circuit and the driven load set are connected in series between two output ends of the direct-current voltage; the current limiting circuit is used for controlling the load current value of the load set not to be larger than a preset current limiting point;
the adjusting tube is connected in parallel with the subset of the load set and the current limiting circuit which are connected in series; the number k of the loads in the subset of the load set is greater than or equal to 1 and is less than the total number of the loads in the load set;
the current sampler is used for sampling the load current of the load set and transmitting the sampled current signal to the current feedback controller;
the output end of the current feedback controller is connected with the switch control end of the adjusting tube and used for receiving the current signal and controlling the adjusting tube to be switched off when the current value of the current signal is judged to be not less than the preset current stabilization point; and when the current value of the current signal is judged to be smaller than the preset current stabilization point, controlling the adjusting tube to be in a linear conduction state, and controlling the conduction impedance of the adjusting tube according to the current value of the current signal.
The flow limiting point is larger than the flow stabilizing point.
The sum of the rated voltages of all loads in the set of loads, except the subset, is equal to the lower limit value of the direct current voltage.
The current sampler, the current limiting circuit and the driven load set are connected in series between two output ends of the direct-current voltage.
The current feedback controller includes:
the output end of the second operational amplifier is connected with the switch control end of the adjusting tube, the positive phase input end of the second operational amplifier is connected with a second reference voltage through a third resistor, and the positive phase input end of the second operational amplifier is also connected with the sampling signal output end of the current sampler through a fourth resistor; the inverting input end of the second operational amplifier is grounded and is connected with the output end of the second operational amplifier through a second capacitor and a fifth resistor which are connected in series.
The current limiting circuit is realized by a constant current diode or a linear adjusting circuit.
When the current limiting circuit is realized through a linear adjusting circuit, the current limiting circuit comprises:
the grid electrode of the field effect transistor is connected with the output end of the first operational amplifier, the drain electrode of the field effect transistor is connected with the load set, and the source electrode of the field effect transistor is connected with the current sampler through the second sampling resistor; the positive phase input end of the first operational amplifier is connected with a first reference voltage, and the negative phase input end of the first operational amplifier is connected with the output end of the first operational amplifier through a first capacitor and a first resistor which are connected in series and is also connected with the source electrode of the field effect transistor through a second resistor.
Further comprising: the series-connected current sampler and the adjusting tube are connected in parallel with the subset of the series-connected load set and the current limiting circuit.
The current limiting circuit includes: the grid electrode of the field effect transistor is connected with the output end of the first operational amplifier, the drain electrode of the field effect transistor is connected with the load set, and the source electrode of the field effect transistor is connected with the output end of the direct-current voltage through the second sampling resistor; the positive phase input end of the first operational amplifier is connected with a first reference voltage, and the negative phase input end of the first operational amplifier is connected with the output end of the first operational amplifier through a first capacitor and a first resistor which are connected in series and is also connected with the source electrode of the field effect transistor through a second resistor;
the current feedback controller includes: the output end of the third operational amplifier is connected with the switch control end of the adjusting tube; the positive phase input end is connected with a second reference voltage; the inverting input end is connected with the sampling signal output end of the current sampler through a sixth resistor, is also connected with the source electrode of the field effect transistor through a seventh resistor, and is also connected with the output end of a third operational amplifier through a third capacitor and an eighth resistor which are connected in series.
Further comprising: and the reference voltage control unit is used for controlling the second reference voltage to be increased by a preset voltage value when the current in the first load subset is smaller than the current in the second load subset.
The reference voltage control unit includes: and the sampling signal output end of the current sampler is connected with a second reference voltage through a fourteenth resistor.
The current sampler is realized by a sampling resistor.
The adjusting tube is realized through an MOS tube or a triode.
The direct current voltage is obtained through the following circuit:
the second diode and the third diode which are connected in series are connected with the fourth diode and the fifth diode which are connected in series in parallel; the anode of the second diode is connected with the cathode of the third diode, and the anode of the fourth diode is connected with the cathode of the fifth diode; the anode of the second diode is also connected with the first output end of the alternating current voltage source through a fourth capacitor; and the anode of the fourth diode is connected with the second output end of the alternating current voltage source.
Further comprising: an auxiliary source; wherein,
the input end of the auxiliary source is connected with the high potential end of the third load subset, and the input end is connected with the collector electrode of the third triode and is also connected with the base electrode of the third triode through a ninth resistor; the base electrode of the third triode is connected with the cathode of the first voltage-stabilizing tube, and the anode of the first voltage-stabilizing tube is grounded; the emitter of the third triode is grounded through a fifth capacitor, the emitter of the third triode is used as the output end of the auxiliary source, and the output end is used for supplying power to the operational amplifier in the load driving circuit;
the emitter of the third triode is grounded through a tenth resistor and a first three-terminal adjustable reference source which are connected in series, and the cathode of the first three-terminal adjustable reference source is grounded through an eleventh resistor, a twelfth resistor and a thirteenth resistor which are connected in series after being connected with the reference terminal; the voltage of a connection point of the eleventh resistor and the twelfth resistor is used as a first reference voltage, and the voltage of a connection point of the twelfth resistor and the thirteenth resistor is used as a second reference voltage;
the number of the loads in the third load subset is greater than that in the first load subset and is less than or equal to that of the loads in the load set.
Further comprising: an auxiliary source; wherein,
the input end of the auxiliary source is connected with the high potential end of the first load subset, and the input end is connected with the collector electrode of the third triode and is also connected with the base electrode of the third triode through a ninth resistor; the base electrode of the third triode is connected with the cathode of the first voltage-stabilizing tube, and the anode of the first voltage-stabilizing tube is grounded; the emitter of the third triode is grounded through a fifth capacitor, the emitter of the third triode is used as the output end of the auxiliary source, and the output end is used for supplying power to the operational amplifier in the load driving circuit;
the emitter of the third triode is grounded through a tenth resistor and a first three-terminal adjustable reference source which are connected in series, and the cathode of the first three-terminal adjustable reference source is grounded through an eleventh resistor, a twelfth resistor and a thirteenth resistor which are connected in series after being connected with the reference terminal; the voltage of a connection point of the eleventh resistor and the twelfth resistor is used as a first reference voltage, and the voltage of a connection point of the twelfth resistor and the thirteenth resistor is used as a second reference voltage;
and a third voltage-stabilizing tube is connected between one end of the first load subset and the adjusting tube in series.
The technical effect analysis of the technical scheme is as follows:
the total rated voltage of the load set can be larger than the lower limit value of the direct current voltage for supplying power to the load, at the moment, in the whole driving process, only when the direct current voltage for supplying power to the load is larger than the total rated voltage, the current is limited through the linear current limiting circuit, the power consumption is reduced, the load driving efficiency is high, and particularly when the power grid voltage is close to the upper limit value of the voltage, the power consumption of the linear current limiting circuit is relatively lower, the power consumption is small, and the load driving efficiency is high.
Drawings
FIG. 1 is a schematic diagram of a driving circuit of an LED in the prior art;
FIG. 2 is a schematic diagram of a load driving circuit according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a first load driving circuit according to an embodiment of the invention;
fig. 4 is a schematic structural diagram of a second load driving circuit according to the embodiment of the invention;
FIG. 5 is a schematic diagram of a third load driving circuit according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a fourth load driving circuit according to an embodiment of the present invention;
FIG. 7a is a schematic diagram of a circuit implementation structure of a first auxiliary source according to an embodiment of the present invention;
FIG. 7b is a schematic diagram of a circuit implementation structure of a second auxiliary source according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of a fifth load driving circuit according to an embodiment of the invention;
fig. 9 is a schematic structural diagram of a sixth load driving circuit according to an embodiment of the invention.
Detailed Description
Hereinafter, the implementation of the load driving circuit according to the embodiment of the present invention will be described in detail with reference to the drawings.
Fig. 2 is a schematic structural diagram of a load driving circuit according to an embodiment of the present invention, and as shown in fig. 2, the load driving circuit includes: current limiting circuit 201, regulating tube Q1, current sampler 202, and current feedback controller 203, wherein,
the current limiting circuit 201, the current sampler 202 and the load set A are connected in series between a first output end and a second output end of the power supply 204; the current limiting circuit 201 is configured to control a load current value of the load set not to be greater than a preset current limiting point; wherein the current limit point is greater than a current stabilization point of the current feedback controller, preferably the current stabilization point is close to the current limit point.
The adjusting tube Q1 is connected in parallel with the first load subset A1 and the current limiting circuit 201 in series;
a current sampler 202, the sampling signal output end of which is connected to the input end of the current feedback controller 203, for sampling the load current of the load set and transmitting the sampled current signal to the current feedback controller 203;
and the output end of the current feedback controller 203 is connected with the control end of the regulating tube Q1 and is used for receiving a current signal, comparing the current value of the current signal with a preset current stabilization point, controlling the regulating tube Q1 to be switched off when the current value is greater than or equal to the current stabilization point, and controlling the on-resistance of the regulating tube according to the current value of the current signal when the current value is less than the current stabilization point.
Therefore, the current feedback controller controls the regulating tube Q1 to be in a linear conducting state, and finally the load current value of the load set is stabilized at a steady-current point.
Wherein the load set A comprises a first load subset A1 and a second load subset A2; the number k of the loads in the first load subset a1 is greater than or equal to 1 and less than m, where m is the total number of the loads in the load set a. Preferably, the rated voltage of all the loads in the second load subset a2 is equal to the lower limit value of the input voltage of the power supply, so that the first load subset a1 and the second load subset a2 in the load set a can be divided by this principle in practical applications.
As shown in FIG. 2, the first load subset A1 corresponds to LEDn +1 to LEDm; the second load subset A2 corresponds to LEDs 1-LEDn.
The operating principle of the circuit shown in fig. 2 is:
when the direct-current voltage for supplying power to the load is exactly equal to the total rated voltage of the load set, the current limiting circuit is just saturated and conducted, and the adjusting tube Q1 is open-circuited; when the direct current voltage is higher than the total rated voltage of the load set, the current limiting circuit bears the difference value between the direct current voltage and the total rated voltage of the load set, the load current of the load set is maintained at a current limiting point, and at the moment, the adjusting tube Q1 is still in a high-impedance open circuit state; when the direct current voltage is lower than the total rated voltage of the load set and higher than the rated voltage of all the loads in the second load subset A2, the current limiting circuit is in a low-impedance saturated conduction state, the current feedback controller controls the adjusting tube Q1 to be in a linear adjusting state, the adjusting tube Q1 and the first load subset A1 are shunted, the smaller the direct current voltage is, the smaller the current Io flowing through the first load subset A1 is, the larger the current flowing through the adjusting tube Q1 is, the smaller the Q1 conduction impedance is, until the direct current voltage is equal to the rated voltage of the second load subset A2, the adjusting tube Q1 is in saturated conduction, the first load subset is completely bypassed, and the current value flowing through each load in the second load subset A2 is always equal to the stable current point; the dc voltage is further reduced and the current through each load of the second subset of loads is further reduced.
In the circuit shown in fig. 2, the total rated voltage of the load set may be greater than the lower limit of the dc voltage for supplying power to the load, and at this time, in the whole driving process, only when the dc voltage for supplying power to the load is greater than the total rated voltage, the current needs to be limited by the linear current limiting circuit, so that the power loss is reduced, the load driving efficiency is high, and especially when the grid voltage approaches the upper voltage limit, the power consumption of the linear current limiting circuit is lower than that of the circuit shown in fig. 1, the power loss is small, and the load driving efficiency is high.
And when the direct-current voltage is less than the total rated voltage, the adjusting tube Q1 is controlled to be conducted by the current feedback controller, so that the current flowing in the second load subset is maintained to be stable at a stable point, and the current ripple of the current in the load is small.
And compared with the constant current driving of a load by using a switching power supply, the constant current driving device has no electromagnetic interference (EMI) problem and is low in cost.
Preferably, the dc voltage may be a dc voltage source, as shown in fig. 2; the dc voltage may also be a dc voltage obtained by rectifying or rectifying and filtering the grid voltage, as shown in fig. 3 and 4, which is not limited herein.
Preferably, as shown in fig. 3 and 4, the current sampler 202 may be implemented by a first sampling resistor Rs 1.
Preferably, as shown in fig. 3, the current limiting circuit 201 may be implemented by a constant current diode D1; alternatively, as shown in fig. 4, the current limiting circuit 201 may be implemented by a linear adjusting circuit, specifically, as shown in fig. 4, the current limiting circuit may include:
the gate of the field effect transistor Q2 is connected with the output end of the first operational amplifier U1, the drain is connected with the load set A, and the source is connected with the current sampler 202 through a second sampling resistor Rs 2; the non-inverting input terminal of the first operational amplifier U1 is connected to a first reference voltage Vref1, and the inverting input terminal is connected to the output terminal of the first operational amplifier U1 through a first capacitor C1 and a first resistor R1 connected in series, and is also connected to the source of the field effect transistor Q2 through a second resistor R2.
In the current limiting circuit structure, a sampling signal on the second sampling resistor Rs2 is input to an inverting input terminal of the first operational amplifier U1 through the second resistor R2, a first reference voltage Vref1 is input to a non-inverting input terminal of the first operational amplifier U1, an output terminal of the first operational amplifier U1 controls a gate of the field effect transistor to be conductive, and the field effect transistor operates in a linear state, and a current limiting point I1 of the current limiting circuit is equal to Vref1/Rs 2.
In addition, the current feedback controller 203 may be implemented by software, or may be implemented by a specific circuit structure, as shown in fig. 4, where the current feedback controller 203 may include: the output end of the second operational amplifier U2 is connected to the control end of the regulating tube Q1, the non-inverting input end is connected to the second reference voltage Vref2 through the third resistor R3, and is also connected to the sampling signal output end of the current sampler 202 through the fourth resistor R4; the inverting input terminal of the second operational amplifier U2 is grounded and is connected to the output terminal of the second operational amplifier U2 through the second capacitor C2 and the fifth resistor R5 connected in series.
Under the circuit structure, a current signal sampled by the first sampling resistor Rs1 is input to a non-inverting input end of the second operational amplifier U2 through the fourth resistor R4, the non-inverting input end of the second operational amplifier U2 is connected to the second reference voltage Vref2 through the pull-up resistor R3, the inverting input end of the second operational amplifier U2 is grounded, and the output end of the second operational amplifier U2 controls the operation of the adjusting tube Q1 in a linear state, so that a steady current point I2 of the current feedback controller meets the requirements of Vref 2/R3-I2 × Rs 1/R4.
The adjusting tube Q1 can be realized by an MOS tube or a triode, wherein when the adjusting tube Q1 is realized by the MOS tube, the switch control end is the grid electrode of the MOS tube; when the regulating tube Q1 is implemented by a triode, its switch control terminal is the base of the triode.
Referring to fig. 5, a current limiting circuit according to another embodiment of the present invention is the same as the embodiment shown in fig. 4, except that: the current sampler is connected in series with the adjusting tube Q1, and then is connected in parallel with the subset of the load set and the current limiting circuit which are connected in series; as shown in fig. 5, the current sampler is implemented by the first sampling resistor Rs1, and then the adjusting tube Q1 is connected in series with the first sampling resistor Rs1 and then connected in parallel with the first load subset a1 and the current limiting circuit 201.
In addition, the current feedback controller has a different structure. The current feedback controller in fig. 5 may include: the output end of the third operational amplifier U3 is connected with the switch control end of the regulating tube Q1; the non-inverting input end is connected with a second reference voltage Vref 2; the inverting input end is connected with the sampling signal output end of the current sampler through a sixth resistor, is also connected with the source electrode of a field-effect tube Q2 through a seventh resistor R7, and is also connected with the output end of a third operational amplifier U3 through a third capacitor C3 and an eighth resistor R8 which are connected in series; the current sampler Is realized by a first sampling resistor Rs1, and the inverting input end of the third operational amplifier U3 Is connected with high potential ends Vs1 and Vs2 of sampling resistors Rs1 and Rs2 through resistors R6 and R7 respectively to sample branch currents Is1 and Is 2.
Under the circuit structure, when the output end of the third operational amplifier U3 works in a linear state through the control regulating tube Q1, the current stabilization point I2 of the current feedback controller meets the following conditions: vs1 × R7+ Vs2 × R6 ═ Is1 × Rs1 × R7+ Is2 × Rs2 × R6 ═ Vref2(R6+ R7), where I2 ═ Is1+ Is 2.
Preferably, when R2 is R6 and Rs1 is Rs2, the steady flow point I2 is 2Vref2/Rs1 is 2Vref2/Rs 2.
As shown in fig. 3 to 5, the dc voltage is obtained by the following circuit: the second diode D2 and the third diode D3 connected in series are connected in parallel with the fourth diode D4 and the fifth diode D5 connected in series; the anode of the second diode D2 is connected to the cathode of the third diode D3, and the anode of the fourth diode D4 is connected to the cathode of the fifth diode D5; the anode of the second diode D2 is connected to a first output terminal L of an alternating voltage source (not shown); the anode of the fourth diode D4 is connected to the second output terminal N of the ac voltage source. Preferably, a fourth capacitor C4 may be added to the input terminal of the ac voltage source, and the configuration of the number of series-connected LED lamps may be more flexible by the voltage division of the capacitor C2 and the impedance on the dc side of the rectifier bridge. For example, in the embodiment shown in fig. 6, based on the embodiment shown in fig. 3, a fourth capacitor C4 is added between the first output terminal L of the ac voltage source and the anode of the second diode D2, and the configuration of the number of series-connected LED lamps can be made more flexible by the fourth capacitor C4 and the impedance voltage division on the dc side of the rectifier bridge. This improvement is equally applicable to the embodiments shown in fig. 4 and 5.
The implementation of the auxiliary source of the op-amp and the non-inverting terminal reference of the op-amp in the above embodiments may be implemented using the circuits shown in fig. 7a and 7 b.
The input end Vi of the auxiliary source is connected to the high potential end of the third load subset a3, and the output end Vcc of the auxiliary source is the supply voltage of each operational amplifier.
The third load subset A3 is a part of the load set a, and the number of loads in the third load subset A3 should be equal to or greater than the number of loads in the first load subset a1 and equal to or less than the number of loads in the load set a.
To prevent the loads in the first load subset a1 from extinguishing and the regulating tube Q1 from being saturated and conducting when the grid fluctuates to the low voltage end so that the input Vi of the auxiliary source is too small, the number of loads in the third load subset A3 to which the input Vi of the auxiliary source is connected should be larger than that in the first load subset a1 (as shown in fig. 7 a); after a regulator tube is connected in series to the branch of the regulator tube Q1 (as shown in fig. 7 b), the number of loads in the third load subset A3 to which the input terminal Vi of the auxiliary source is connected may be equal to the number of loads in the first load subset a 1.
The reference voltages at the non-inverting terminal of the operational amplifier in the embodiments of fig. 4 and 5, such as the first reference voltage Vref1 and the second reference voltage Vref2, can be obtained from the output terminal Vcc of the auxiliary source through voltage regulation by a voltage regulator and resistance division.
Specifically, as shown in fig. 7a, an implementation of an auxiliary source and a reference voltage (e.g., Vref1 and Vref2) based on fig. 2 is provided, where the circuit includes: the input end Vi is connected with the collector of the third triode Q3 and is also connected with the base of the third triode Q3 through a ninth resistor R9; the base electrode of the third triode Q3 is grounded through a first voltage regulator tube TV 1; the emitter of the third triode Q3 is grounded through a fifth capacitor C5, and the emitter of the third triode Q3 is also used as the output terminal Vcc;
the emitter of the third triode Q3 is grounded through a tenth resistor R10 and a first three-terminal adjustable reference source TV2 which are connected in series, and the cathode of the first three-terminal adjustable reference source TV2 is grounded through an eleventh resistor R11, a twelfth resistor R12 and a thirteenth resistor R13 which are connected in series; a voltage at a connection point of the eleventh resistor R11 and the twelfth resistor R12 is set as a first reference voltage Vref1, and a voltage at a connection point of the twelfth resistor R12 and the thirteenth resistor R13 is set as a second reference voltage Vref 2.
Fig. 7b is a diagram based on another implementation of the auxiliary source and the reference voltage (e.g., Vref1 and Vref2) in fig. 2, and fig. 7b differs from fig. 7a in that fig. 7b has a third regulator tube TV3 connected in series in the branch of the regulator tube Q1, and the input Vi of the auxiliary source is connected to the connection point of the first load subset a1 and the second load subset a 2. Due to the voltage stabilizing effect of the third voltage-regulator tube TV3, when the power grid fluctuates to the low-voltage end, the load in the first load subset A1 is extinguished, and the adjusting tube Q1 is in saturated conduction, the input end Vi of the auxiliary power supply can be ensured to be larger than the voltage stabilizing value of the third voltage-regulator tube TV3, so that the auxiliary power supply can normally work.
It should be noted that the third transistor Q3 in the auxiliary source shown in fig. 7a and 7b can be replaced by a MOS transistor.
In the invention, when the power grid fluctuates to the low-voltage end, the loads in the first load subset A1 become dark or even go out, the overall brightness of the load set can be kept unchanged by increasing the brightness of the second load subset A2. For example, in the embodiments of fig. 4 and 5, when the grid fluctuates to the low voltage end, the brightness of the second load subset a2 is increased by raising the non-inverting terminal reference of the operational amplifier. That is, in practical applications, the load driving circuit according to the embodiment of the present invention may further include:
and a reference voltage control unit for controlling the second reference voltage Vref to be increased by a preset voltage value when the current in the first load subset a1 is less than the current in the second load subset a 2.
In practical applications, the preset voltage value may be set autonomously, and the specific value is not limited herein.
Fig. 8 is a diagram of an implementation of the non-inverting terminal reference of the elevated op-amp according to the embodiment of fig. 5, wherein one terminal of a fourteenth resistor R14 is connected to the high potential terminal Vs1 of the first sampling resistor Rs1, and the other terminal is connected to the second reference voltage Vref 2. When the voltage of the power grid is reduced and the loads in the first load subset A1 become dark or even go out, the current of the branch where the adjusting tube Q1 is located is increased, the Vs1 potential is raised, and therefore the reference Vref2 is raised through the fourteenth resistor R14, and the brightness of the second load subset A2 is adjusted to be increased through the closed loop of the operational amplifier. In practical applications, the value of the Vs1 potential and the value of the fourteenth resistor R14 jointly determine the rising degree of the second reference voltage Vref2, that is, the preset voltage value.
It should be noted that, since the sampling resistor is generally small, it may cause the high potential end Vs1 of the first sampling resistor Rs1 to be too small to raise the reference, and at this time, a resistor with a resistance larger than that of Rs1 may be connected in series in the branch of the first sampling resistor Rs1, so that the high potential end of the added resistor is connected to the fourteenth resistor R14 instead of the original Vs 1.
Fig. 9 is an implementation of raising the non-inverting terminal reference of the operational amplifier based on the embodiment of fig. 4, as long as the loads in the first load subset a1 become dark or even go out when the power grid fluctuates to the low voltage terminal, the resistance of the resistor R13 is manually adjusted to raise the second reference voltage Vref2, and the brightness of the second load subset a2 is increased through the closed-loop regulation of the operational amplifier, so as to ensure that the overall brightness of the load set can be kept unchanged even under the condition of the power grid fluctuation.
In the drawings of the embodiments of the present invention, the LED is taken as an example for explanation, and in practical application, the load driving circuit according to the present invention may be used for driving a load, which is not limited herein.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (16)

1. A load driving circuit, comprising:
the current limiting circuit and the driven load set are connected in series between two output ends of the direct-current voltage; the current limiting circuit is used for controlling the load current value of the load set not to be larger than a preset current limiting point;
the adjusting tube is connected in parallel with the subset of the load set and the current limiting circuit which are connected in series; the number k of the loads in the subset of the load set is greater than or equal to 1 and is less than the total number of the loads in the load set;
the current sampler is used for sampling the load current of the load set and transmitting the sampled current signal to the current feedback controller;
the output end of the current feedback controller is connected with the switch control end of the adjusting tube and used for receiving the current signal and controlling the adjusting tube to be switched off when the current value of the current signal is judged to be not less than the preset current stabilization point; and when the current value of the current signal is judged to be smaller than the preset current stabilization point, controlling the adjusting tube to be in a linear conduction state, and controlling the conduction impedance of the adjusting tube according to the current value of the current signal so as to stabilize the load current value of the load set at the current stabilization point.
2. The circuit of claim 1, wherein the current limit point is greater than the current regulation point.
3. The circuit of claim 1, wherein the sum of the voltage ratings of all loads in the set of loads except the subset is equal to the lower limit of the dc voltage.
4. The circuit of claim 1, wherein the current sampler is connected in series with the current limiting circuit and the driven load set between two output terminals of the dc voltage.
5. The circuit of claim 4, wherein the current feedback controller comprises:
the output end of the second operational amplifier is connected with the switch control end of the adjusting tube, the positive phase input end of the second operational amplifier is connected with a second reference voltage through a third resistor, and the positive phase input end of the second operational amplifier is also connected with the sampling signal output end of the current sampler through a fourth resistor; the inverting input end of the second operational amplifier is grounded and is connected with the output end of the second operational amplifier through a second capacitor and a fifth resistor which are connected in series.
6. The circuit of claim 4, wherein the current limiting circuit is implemented by a constant current diode, or a linear regulator circuit.
7. The circuit of claim 6, wherein the current limiting circuit, when implemented by a linear regulator circuit, comprises:
the grid electrode of the field effect transistor is connected with the output end of the first operational amplifier, the drain electrode of the field effect transistor is connected with the load set, and the source electrode of the field effect transistor is connected with the current sampler through the second sampling resistor; the positive phase input end of the first operational amplifier is connected with a first reference voltage, and the negative phase input end of the first operational amplifier is connected with the output end of the first operational amplifier through a first capacitor and a first resistor which are connected in series and is also connected with the source electrode of the field effect transistor through a second resistor.
8. The circuit of claim 1, further comprising:
the series-connected current sampler and the adjusting tube are connected in parallel with the subset of the series-connected load set and the current limiting circuit.
9. The circuit of claim 8, wherein the current limiting circuit comprises: the grid electrode of the field effect transistor is connected with the output end of the first operational amplifier, the drain electrode of the field effect transistor is connected with the load set, and the source electrode of the field effect transistor is connected with the output end of the direct-current voltage through the second sampling resistor; the positive phase input end of the first operational amplifier is connected with a first reference voltage, and the negative phase input end of the first operational amplifier is connected with the output end of the first operational amplifier through a first capacitor and a first resistor which are connected in series and is also connected with the source electrode of the field effect transistor through a second resistor;
the current feedback controller includes: the output end of the third operational amplifier is connected with the switch control end of the adjusting tube; the positive phase input end is connected with a second reference voltage; the inverting input end is connected with the sampling signal output end of the current sampler through a sixth resistor, is also connected with the source electrode of the field effect transistor through a seventh resistor, and is also connected with the output end of a third operational amplifier through a third capacitor and an eighth resistor which are connected in series.
10. The circuit according to any one of claims 5 and 9, further comprising:
and the reference voltage control unit is used for controlling the second reference voltage to be increased by a preset voltage value when the current in the first load subset is smaller than the current in the second load subset.
11. The circuit according to claim 10, wherein the reference voltage control unit comprises: and the sampling signal output end of the current sampler is connected with a second reference voltage through a fourteenth resistor.
12. The circuit according to any one of claims 1 to 9 and 11, wherein the current sampler is implemented by a sampling resistor.
13. The circuit according to any one of claims 1 to 9 and 11, wherein the adjusting tube is implemented by a MOS tube or a triode.
14. The circuit according to any one of claims 1 to 9 and 11, wherein the dc voltage is obtained by:
the second diode and the third diode which are connected in series are connected with the fourth diode and the fifth diode which are connected in series in parallel; the anode of the second diode is connected with the cathode of the third diode, and the anode of the fourth diode is connected with the cathode of the fifth diode; the anode of the second diode is also connected with the first output end of the alternating current voltage source through a fourth capacitor; and the anode of the fourth diode is connected with the second output end of the alternating current voltage source.
15. The circuit of any one of claims 5, 7, and 9, further comprising: an auxiliary source; wherein,
the input end of the auxiliary source is connected with the high potential end of the third load subset, and the input end is connected with the collector electrode of the third triode and is also connected with the base electrode of the third triode through a ninth resistor; the base electrode of the third triode is connected with the cathode of the first voltage-stabilizing tube, and the anode of the first voltage-stabilizing tube is grounded; the emitter of the third triode is grounded through a fifth capacitor, the emitter of the third triode is used as the output end of the auxiliary source, and the output end is used for supplying power to the operational amplifier in the load driving circuit;
the emitter of the third triode is grounded through a tenth resistor and a first three-terminal adjustable reference source which are connected in series, and the cathode of the first three-terminal adjustable reference source is grounded through an eleventh resistor, a twelfth resistor and a thirteenth resistor which are connected in series after being connected with the reference terminal; the voltage of a connection point of the eleventh resistor and the twelfth resistor is used as a first reference voltage, and the voltage of a connection point of the twelfth resistor and the thirteenth resistor is used as a second reference voltage;
the number of the loads in the third load subset is greater than that in the first load subset and is less than or equal to that of the loads in the load set.
16. The circuit of any one of claims 5, 7, and 9, further comprising: an auxiliary source; wherein,
the input end of the auxiliary source is connected with the high potential end of the first load subset, and the input end is connected with the collector electrode of the third triode and is also connected with the base electrode of the third triode through a ninth resistor; the base electrode of the third triode is connected with the cathode of the first voltage-stabilizing tube, and the anode of the first voltage-stabilizing tube is grounded; the emitter of the third triode is grounded through a fifth capacitor, the emitter of the third triode is used as the output end of the auxiliary source, and the output end is used for supplying power to the operational amplifier in the load driving circuit;
the emitter of the third triode is grounded through a tenth resistor and a first three-terminal adjustable reference source which are connected in series, and the cathode of the first three-terminal adjustable reference source is grounded through an eleventh resistor, a twelfth resistor and a thirteenth resistor which are connected in series after being connected with the reference terminal; the voltage of a connection point of the eleventh resistor and the twelfth resistor is used as a first reference voltage, and the voltage of a connection point of the twelfth resistor and the thirteenth resistor is used as a second reference voltage;
and a third voltage-stabilizing tube is connected between one end of the first load subset and the adjusting tube in series.
CN201110083372.1A 2011-04-01 2011-04-01 Load drive circuit Active CN102752898B (en)

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