WO2012129836A1

WO2012129836A1 - Load driving circuit

Info

Publication number: WO2012129836A1
Application number: PCT/CN2011/074884
Authority: WO
Inventors: 葛良安; 姚晓莉
Original assignee: 英飞特电子（杭州）有限公司
Priority date: 2011-04-01
Filing date: 2011-05-30
Publication date: 2012-10-04
Also published as: CN102752898B; CN102752898A

Abstract

A load driving circuit includes: a limited current circuit and a set of loads being driven are connected in series between the two outputs of direct voltage; the limited current circuit is used to control the current value of the loads within the set of loads not larger than a preset limited current point; a first adjusting transistor is connected in parallel with the subset of the set of loads and the limited current circuit which are connected in series; a sampling signal output of a current sampler is connected with an input of a current feedback controller, and is used to sample the load current of the set of loads to transmit the current signal obtained by sampling to the current feedback controller; the current feedback controller, an output of which is connected with the switching controller of the first adjusting transistor, is used to receive the current signal, to control the first adjusting transistor to turn off when it is determined that the current value of the current signal is not smaller than a preset stabilized current point, to control the first adjusting transistor to turn on when it is determined that the current value of the current signal is smaller than a preset stabilized current point, and to control the conducting impendence of the first adjusting transistor according to the current value of the current signal. The load driving circuit can reduce the power loss and improve the driving efficiency of load.

Description

A load drive circuit is claimed in the Chinese Patent Application No. 201110083372.1, entitled "A Load Drive Circuit", which is filed on April 1, 2011, the entire contents of which are incorporated by reference. In this application. Technical field

The present invention relates to load drive technology, and more particularly to a load drive circuit.

Background technique

For the light-emitting diode (LED) source of the AC input, the most common drive scheme is to achieve constant current drive of the LED with an AC/DC switching power supply. However, because the switching power supply contains magnetic components, it needs to solve the problem of high-frequency electromagnetic interference, and requires a relatively complicated control chip. Therefore, for some low-power LED light sources, the switching power supply is used for constant current driving, and the driving circuit is relatively large. The cost is also relatively high. At this time, the LED light source is generally driven by the LED constant current driving circuit of the cartridge.

1 is a conventional LED constant current driving circuit of a single tube. In this circuit, a linear current limiting circuit and an LED assembly are connected in series and then connected in parallel to the DC side of the rectifier circuit, and the grid voltage is rectified by the rectifier circuit to be an LED assembly. For power supply, the linear current limiting circuit may be a constant current diode or the like.

When the voltage across the LED set and the linear current limiting circuit exceeds the total rated voltage of the series of LEDs in series, the portion of the total rated voltage that exceeds the LED set is assumed by the linear current limiting circuit; when loaded in the LED set and the linear current limiting circuit When the voltage at both ends is lower than the total rated voltage of the LED assembly, the linear current limiting circuit is saturated and turned on. At this time, the current flowing through the LED is lower than the current limiting point of the current limiting circuit.

The drive circuit structure shown in Figure 1 has a low cost. However, when the grid voltage fluctuates greatly, to achieve constant current driving of the LED within the entire grid voltage fluctuation range, the total rated voltage of the LED set is required to be approximately equal to The rectified voltage of the lower limit of the grid voltage fluctuation. At this time, during the whole driving process, when the voltage value after the rectification of the grid voltage is higher than the total rated voltage of the LED assembly, the current limiting circuit needs to be used for current limiting, power loss. Large, LED driving efficiency is low, especially when the grid voltage is close to the upper voltage limit, the linear current limiting circuit consumes more power, the power loss is greater, and the LED driving efficiency is lower.

Summary of the invention In view of this, the technical problem to be solved by the present invention is to provide a load driving circuit capable of reducing power loss and improving driving efficiency of a load. To this end, the embodiment of the present invention adopts the following technical solutions:

An embodiment of the present invention provides a load driving circuit, including: a current limiting circuit, a first adjusting tube, a current sampler, and a current feedback controller, where

The current limiting circuit and the load set driven by the load driving circuit are serially connected between the two output ends of the DC voltage; the current limiting circuit is configured to control the load current value of the load set to be no greater than the preset current limiting point;

The first adjustment tube is connected in parallel with the series of the load sets of the series and the current limiting circuit; the number k of the loads in the subset of the load collection is greater than or equal to 1 and less than the total number of loads in the load set;

The current sampler is connected to the input end of the current feedback controller for sampling the load current of the load set, and transmitting the sampled current signal to the current feedback controller; the current feedback controller, and the output end is connected The switch control end of the first adjusting tube is configured to receive the current signal, and determine that the current value of the current signal is not less than the preset steady flow point, and the first adjusting tube is controlled to be turned off; determining that the current value of the current signal is less than the preset steady current point The first adjustment tube is controlled to be in a linear conduction state, and the conduction resistance of the first adjustment tube is controlled according to the current value of the current signal.

The current limit point is greater than the steady flow point.

The sum of the rated voltages of all loads except the subset in the load set is equal to the lower limit of the DC voltage.

The current sampler is coupled in series with the current limiting circuit and the driven load set between the two outputs of the DC voltage.

The current feedback controller includes:

The output end of the second operational amplifier is connected to the switch control end of the first adjustment tube, the non-inverting input terminal is connected to the second reference voltage through the third resistor, and the sampling signal output end of the current sampler is connected through the fourth resistor; the second operational amplifier The inverting input is grounded, and the output of the second operational amplifier is connected through a second capacitor connected in series and a fifth resistor.

The current limiting circuit is implemented by a constant current diode or a linear adjustment circuit.

When the current limiting circuit is implemented by a linear adjustment circuit, the method includes: The gate of the FET is connected to the output of the first operational amplifier, the drain is connected to the load set, and the source is connected to the current sampler through the second sampling resistor; the non-inverting input of the first operational amplifier is connected to the first reference voltage, inverting The input terminal is connected to the output end of the first operational amplifier through the first capacitor connected in series and the first resistor, and is also connected to the source of the FET through the second resistor.

The method further includes: a series connected current sampler and a first adjustment tube, in parallel with the subset of the series of connected loads and the current limiting circuit.

The current limiting circuit comprises: a gate of the FET connected to the output of the first operational amplifier, a drain connected to the load set, and a source connected to the output of the DC voltage through the second sampling resistor; a positive input of the first operational amplifier The first reference voltage is connected to the first reference voltage, and the inverting input terminal is connected to the output end of the first operational amplifier through the first capacitor connected in series and the first resistor, and is also connected to the source of the FET through the second resistor; the current feedback controller The output terminal of the third operational amplifier is connected to the switch control end of the first adjustment tube; the positive phase input terminal is connected to the second reference voltage; the inverting input terminal is connected to the sampling signal output end of the current sampler through the sixth resistor, and The seven resistors are connected to the source of the FET, and are also connected to the output of the third operational amplifier through a third capacitor connected in series and an eighth resistor.

The method further includes: a reference voltage control unit, configured to control the second reference voltage to increase the preset voltage value when the current in the first load subset is less than the current in the second load subset.

The reference voltage control unit includes: the sampling signal output end of the current sampler is connected to the second reference voltage through a fourteenth resistor.

The current sampler is implemented by a sampling resistor.

The first adjustment tube is realized by a MOS tube or a triode.

The DC voltage is obtained by the following circuit:

a second diode connected in series and a third diode connected in parallel with the fourth diode and the fifth diode connected in series; the anode of the second diode is connected to the cathode of the third diode, fourth The anode of the diode is connected to the cathode of the fifth diode; the anode of the second diode is also connected to the first output of the AC voltage source through the fourth capacitor; the anode of the fourth diode is connected to the second source of the AC voltage source Output.

Also included: auxiliary source;

The input end of the auxiliary source is connected to the high potential end of the third load subset, and the input end is connected to the collector of the third triode, and is also connected to the base of the third triode through the ninth resistor; The base of the triode is connected to the cathode of the first Zener tube, the anode of the first Zener tube is grounded; the emitter of the third transistor is connected Passing through the fifth capacitor to ground, the emitter of the third transistor serving as an output of the auxiliary source, and the output terminal is for supplying power to the operational amplifier in the load driving circuit;

The emitter of the third triode is grounded through the series connected tenth resistor and the first three-terminal adjustable reference source, and the cathode of the first three-terminal adjustable reference source is connected to the reference end and then passed through the eleventh resistor connected in series, The twelfth resistor and the thirteenth resistor are grounded; wherein a voltage of a connection point of the eleventh resistor and the twelfth resistor is used as a first reference voltage, and a voltage of a connection point of the twelfth resistor and the thirteenth resistor is used as a second The reference voltage;

The number of loads in the third subset of loads is greater than the number of loads in the first subset of loads, less than the number of loads equal to the set of loads.

Also included: auxiliary source;

The input end of the auxiliary source is connected to the high potential end of the first load subset, and the input end is connected to the collector of the third connected third triode, and is also connected to the base of the third triode through the ninth resistor; The base of the third triode is connected to the cathode of the first Zener tube, the anode of the first Zener tube is grounded; the emitter of the third triode is grounded through the fifth capacitor, and the emitter of the third triode is used as an auxiliary An output of the source, the output being used to power an operational amplifier in the load drive circuit;

A third Zener tube is connected in series between one end of the first load subset and the first adjustment tube.

The embodiment of the invention further provides a load driving circuit, comprising: a current limiting circuit and a bypass circuit; wherein

The current limiting circuit and the load set driven by the load driving circuit are serially connected between the two output ends of the DC voltage; all loads in the load set are connected in series, and are divided into two load sub-sets, and current limiting The load sub-set of the circuit connection is a first load sub-set, and the other load sub-set is a second load sub-set; the quantity k of the load in the first load sub-set is greater than or equal to 1 and less than the total number of loads in the load set; The current limiting circuit is configured to control a current of the first load subset or a total current of the load set is not greater than a preset current limit point;

The bypass circuit is configured to detect a total current of the load set, and determine that the total current of the load set is less than a preset steady flow point, and reduce impedances of the two ends of the series branch formed by the first load subset and the current limiting circuit, So that the current of the first subset of loads becomes smaller or becomes zero.

The current limit point is greater than the steady flow point.

The bypass circuit includes:

a first adjustment tube connected in parallel with the first load subset and the current limiting circuit connected in series;

a current sampler, the sampling signal output end is connected to the input end of the current feedback controller, is used for sampling the total current of the load set, and transmitting the sampled current signal to the current feedback controller; the current feedback controller, and the output end is connected The switch control end of the first adjusting tube is configured to receive the current signal, and determine that the current value of the current signal is not less than the preset steady flow point, and the first adjusting tube is controlled to be turned off; determining that the current value of the current signal is less than the preset steady current point When the first adjustment tube is controlled to be turned on.

The current sampler includes: a third sampling resistor, the third sampling resistor being connected in series with the current limiting circuit and the driven load set in series between the two output terminals of the DC voltage.

The first end of the third sampling resistor is connected to the negative output end of the DC voltage, the second end is connected to the common end of the current limiting circuit and the first adjusting tube, and the common end is the ground end;

The current feedback controller includes:

The output end of the second operational amplifier is used as an output end of the current feedback controller, and is connected to the switch control end of the first adjustment tube; the non-inverting input end of the second operational amplifier is connected to the second reference voltage through the third resistor, and is also passed through the fourth resistor Connecting a first end of the third sampling resistor; the inverting input of the second operational amplifier is grounded;

Alternatively, the current feedback controller includes: an output end of the second operational amplifier as an output end of the current feedback controller, connected to the switch control end of the first adjustment tube; and a non-inverting input end of the second operational amplifier connected to the second through the third resistor The reference voltage is further connected to the first end of the third sampling resistor through the fourth resistor; the inverting input terminal of the second operational amplifier is grounded, and the output of the second operational amplifier is also connected through the second capacitor connected in series and the fifth resistor.

The first end of the third sampling resistor is connected to the negative output end of the DC voltage, and serves as a ground end, and the second end is connected to the common end of the current limiting circuit and the first adjusting tube; The current feedback controller includes: an output end of the fourth operational amplifier as an output end of the current feedback controller, and a switch control end connected to the first adjustment tube; a positive input terminal of the fourth operational amplifier is connected to the second reference voltage; The inverting input terminal of the fourth operational amplifier is connected to the second end of the third sampling resistor through the eighteenth resistor, and is further connected to the output end of the fourth operational amplifier through the sixth capacitor and the nineteenth resistor connected in series;

Alternatively, the current feedback controller includes: an output end of the fifth operational amplifier as an output end of the current feedback controller, and a switch control end connected to the first adjustment tube; and a non-inverting input terminal of the fifth operational amplifier connected to the second reference voltage The inverting input is connected to the second end of the third sampling resistor.

The current limiting circuit includes a first constant current diode, a cathode of the first constant current diode is connected to a second end of the third sampling resistor, and an anode is connected to the first end of the first load subset; or

The current limiting circuit includes: a sampling subunit and a first adjusting subcircuit; wherein

a sampling subunit, configured to sample a current of the first subset of loads, and input the sampled current signal to an input end of the adjustment subcircuit;

a first adjusting sub-circuit, configured to control, according to the current signal input by the sampling subunit, a current of the first load sub-collection not greater than a preset current limiting point; or

The current limiting circuit includes: a second adjusting sub-circuit, configured to control, according to the current signal sampled by the current sampler, that the current of the first load subset is not greater than a preset current limit.

The sampling subunit includes: a second sampling resistor; a first end of the second sampling resistor is connected to the second end of the third sampling resistor;

The first adjustment sub-circuit includes: a switch control end of the second adjustment tube is connected to an output end of the first operational amplifier, the first end is connected to the first end of the first load subset, and the second end is connected to the second sampling resistor The second end of the first operational amplifier is connected to the first reference voltage, and the inverting input end of the first operational amplifier is connected to the output of the first operational amplifier through the first capacitor connected in series and the first resistor, Connecting the second end of the second adjusting tube through the second resistor;

Alternatively, the first adjusting sub-circuit includes: a switch control end of the second adjusting tube is connected to an output end of the sixth operational amplifier, the first end is connected to the first end of the first load subset, and the second end is connected to the second sampling resistor The second end of the sixth operational amplifier is connected to the second end of the second adjusting tube; the non-inverting input is connected to the first reference voltage. The second adjusting sub-circuit includes: a switch control end of the second adjusting tube is connected to an output end of the first operational amplifier, the first end is connected to the first end of the first load subset, and the second end is connected to the third sampling resistor The second end of the first operational amplifier is connected to the first reference voltage, and the inverting input end of the first operational amplifier is connected to the output of the first operational amplifier through the first capacitor connected in series and the first resistor, Connecting the second end of the second adjusting tube through the second resistor;

Alternatively, the second adjustment sub-circuit includes: a switch control end of the second adjustment tube is connected to an output end of the sixth operational amplifier, the first end is connected to the first end of the first load subset, and the second end is connected to the third sampling resistor The second end of the sixth operational amplifier is connected to the second end of the second adjusting tube; the non-inverting input is connected to the first reference voltage.

The first adjusting sub-circuit is configured to control, according to the current signal input by the sampling subunit, that the current of the first load sub-collection is not greater than a preset current limiting point.

The sampling subunit includes: a second sampling resistor; a first end of the second sampling resistor is connected to a negative output terminal of the DC voltage;

Alternatively, the first adjusting sub-circuit includes: a switch control end of the second adjusting tube is connected to an output end of the sixth operational amplifier, the first end is connected to the first end of the first load subset, and the second end is connected to the second sampling resistor The second end of the sixth operational amplifier is connected to the second end of the second adjusting tube; the non-inverting input is connected to the first reference voltage.

The current limiting circuit includes:

The third adjustment sub-circuit is configured to control the current of the first subset of loads not to be greater than a preset current limit point. The third adjustment sub-circuit includes: a second constant current diode connected in series between the first end of the first load subset and the negative output of the DC voltage. The current sampler includes: a first sampling resistor and a second sampling resistor; a first sampling resistor connected in series with the first adjusting tube, in parallel with the serial branch of the first load subset and the current limiting circuit; The first end of the resistor is connected to the negative output end of the DC voltage, the second end is connected to the first input end of the current feedback controller; the first end of the second sampling resistor is connected to the negative output end of the DC voltage, and the second end is connected to the current feedback control The second input of the device.

The current feedback controller includes:

The output end of the third operational amplifier is connected to the switch control end of the first adjustment tube; the non-inverting input terminal of the third operational amplifier is connected to the second reference voltage; the inverting input terminal is connected to the first end of the sixth resistor, and is also connected to the seventh a first end of the resistor is connected, a second end of the sixth resistor serves as a first input of the current feedback controller, and a second end of the seventh resistor serves as a second input of the current feedback controller;

Or the output end of the third operational amplifier is connected to the switch control end of the first adjustment tube; the non-inverting input end of the third operational amplifier is connected to the second reference voltage; the inverting input end is connected to the first end of the sixth resistor, and a first end of the seventh resistor is connected, a second end of the sixth resistor serves as a first input of the current feedback controller, and a second end of the seventh resistor serves as a second input of the current feedback controller, the third operational amplifier The inverting input terminal is also coupled to the output of the third operational amplifier through a third capacitor connected in series and an eighth resistor.

The first adjustment tube, the current sampler, the current feedback controller, and the current limiting circuit are integrated as an integrated circuit.

The first adjustment tube, the current sampler, the current feedback controller, the current limiting circuit, and the first load subset are integrated together as an integrated circuit.

The bypass circuit further includes:

The reference voltage control unit is configured to: when the total current of the load set is less than the preset steady flow point, increase the steady flow point according to a preset rule.

The reference voltage control unit is specifically configured to: when the current of the branch where the first adjustment tube is located is not zero, superimpose the sampling signal of the branch current of the first adjustment tube to the second reference voltage.

The current feedback controller is implemented by a corresponding circuit of the third operational amplifier:

The reference voltage control unit includes: a fourteenth resistor, a first end of the fourteenth resistor is connected to a non-inverting input end of the third operational amplifier, and a second end is connected to the second end of the first sampling resistor; Correspondingly, the non-inverting input terminal of the third operational amplifier in the current feedback controller is connected to the second reference voltage through the fifteenth resistor.

When the current sampler is implemented by the third sampling resistor:

The current feedback controller includes: an output end of the seventh operational amplifier is connected to the switch control end of the first adjustment tube; and an inverting input end of the seventh operational amplifier is connected to the seventh operation through the seventh capacitance and the twentieth resistance connected in series The output end of the amplifier is further connected to the second end of the third sampling resistor; the non-inverting input terminal of the seventh operational amplifier is connected to the second reference voltage through the sixteenth resistor;

The reference voltage control unit includes: a seventeenth resistor, the first end of the seventeenth resistor is grounded, and the second end is connected to the inverting input terminal of the seventh operational amplifier; the seventeenth resistor and/or the sixteenth resistor It is an adjustable resistor.

The first adjustment tube, the current sampler, the current feedback controller, the reference voltage control unit, and the current limiting circuit are integrated into one integrated circuit.

The first adjustment tube, the current sampler, the current feedback controller, the current limiting circuit, the reference voltage control unit, and the first subset of loads are integrated into one integrated circuit.

The adjusting tube is realized by a MOS tube or a triode having a base series resistor.

The DC voltage is obtained by the following circuit:

The method further includes: an auxiliary source, configured to convert a voltage of the input auxiliary source into a constant amplitude DC voltage; wherein

The input end of the auxiliary source is connected to the high potential end and the ground end of the third load subset.

The input end of the auxiliary source is connected to the high potential end and the ground end of the first load subset;

A third Zener tube is connected in series between the second end of the first subset of loads and the first adjustment tube. The current limiting circuit, the bypass circuit, and the auxiliary source are integrated into one integrated circuit.

The current limiting circuit, the bypass circuit, the first subset of loads, and the auxiliary source are integrated into one integrated circuit.

The technical effects of the above technical solutions are analyzed as follows:

The total rated voltage of the load set may be greater than the lower limit of the DC voltage supplied to the load. At this time, during the entire driving process, only when the DC voltage for supplying the load is greater than the total rated voltage, the linear limit is required. The current circuit performs current limiting, the power loss is reduced, and the load driving efficiency is high. Especially when the grid voltage is close to the upper voltage limit, the linear current limiting circuit has relatively lower power consumption, less power loss, and high load driving efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic structural view of a driving circuit of an LED in the prior art;

2 is a schematic structural diagram of a load driving circuit according to an embodiment of the present invention;

3 is a schematic structural diagram of a first load driving circuit according to an embodiment of the present invention;

4 is a schematic structural diagram of a second load driving circuit according to an embodiment of the present invention;

4a is a schematic structural diagram of a third load driving circuit according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a fourth load driving circuit according to an embodiment of the present invention; FIG.

5a is a schematic structural diagram of a fifth load driving circuit according to an embodiment of the present invention;

5b is a schematic structural diagram of a sixth load driving circuit according to an embodiment of the present invention;

6 is a schematic structural diagram of a seventh load driving circuit according to an embodiment of the present invention;

7a is a schematic structural diagram of a circuit of a first auxiliary source according to an embodiment of the present invention;

7b is a schematic structural diagram of circuit implementation of a second auxiliary source according to an embodiment of the present invention;

8 is a schematic structural diagram of an eighth load driving circuit according to an embodiment of the present invention;

8a is a schematic structural diagram of a load driving circuit according to a ninth embodiment of the present invention;

8b is a schematic structural diagram of a tenth load driving circuit according to an embodiment of the present invention;

9 is a schematic structural diagram of a load driving circuit according to an eleventh embodiment of the present invention;

10 is a schematic structural diagram of a twelfth load driving circuit according to an embodiment of the present invention;

FIG. 10a is a schematic structural diagram of a thirteenth load driving circuit according to an embodiment of the present invention. detailed description Hereinafter, the implementation of the load driving circuit of the embodiment of the present invention will be described in detail with reference to the accompanying drawings. 2 is a schematic structural diagram of a load driving circuit according to an embodiment of the present invention. As shown in FIG. 2, the load driving circuit includes: a current limiting circuit 201, a first adjusting transistor Q1, a current sampler 202, and a current feedback controller 203, where

The current limiting circuit 201 and the current sampler 202 are connected in series with the load set A between the first output end and the second output end of the power source 204; the current limiting circuit 201 is configured to control the load current value of the load set is not greater than Presetting a current limit point; wherein the current limit point is greater than a steady flow point of the current feedback controller, and preferably, the steady flow point is close to the current limit point.

The first adjusting tube Q1 is connected in parallel with the serially connected first load subset A1 and the current limiting circuit 201. The current sampler 202 is connected to the input end of the current feedback controller 203 for the load set. The load current is sampled, and the sampled current signal is transmitted to the current feedback controller 203;

The current feedback controller 203 is connected to the control end of the first adjusting tube Q1 for receiving the current signal, and comparing the current value of the current signal with the preset steady current point. When the current value is greater than or equal to the steady current point, the control unit An adjustment tube Q1 is turned off, when the current value is less than the steady current point, and the on-resistance of the first adjustment tube is controlled according to the magnitude of the current value of the current signal.

Therefore, the first adjustment tube Q1 is controlled to be in a linear conduction state by the current feedback controller, and finally the load current value of the load set is stabilized at the steady current point.

The load may be an LED, and the series connection means that the LED lamps are connected in series with the positive and negative electrodes.

The load set A includes a first load subset A1 and a second load subset A2. The number k of loads in the first load subset A1 is greater than or equal to 1, less than m, and m is in the load set A. The total number of loads. 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 source. Therefore, in the practical application, the first load subset A1 and the second load in the load set A can be performed by the principle. The division of sub-set A2.

As shown in FIG. 2, taking the load as an LED lamp, the first load subset A1 corresponds to LEDn+1-LEDm; and the second load subset A2 corresponds to LED1~LEDn.

The circuit shown in Figure 2 works as follows:

When the DC voltage supplied to the load is exactly equal to the total rated voltage of the load set, the current limiting circuit The first adjusting tube is just saturated and the first adjusting tube Q1 is open; when the DC voltage is higher than the total rated voltage of the load set, the current limiting circuit will bear the difference between the DC voltage and the total rated voltage of the load set, maintaining the load The collected load current is at the current limit point. At this time, the first adjustment tube Q1 is still in the high impedance open state; when the DC 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 When the current limiting circuit is in a low impedance saturated conduction state, the current feedback controller controls the first adjustment tube Q1 to be in a linear adjustment state, and the first adjustment tube Q1 and the first load subset A1 are shunted, and the DC voltage is smaller, flowing through The smaller the current Io of the first load subset A1 is, the larger the current flowing through the first adjustment tube Q1 is, the smaller the Q1 conduction impedance is, until the DC voltage is equal to the rated voltage of the second load subset A2, the first adjustment tube Q1 is saturated, 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 steady current point; DC voltage further Low, will further reduce the current subset of the respective second load flowing through the load.

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 supplied to the load. At this time, only the DC voltage for supplying the load is greater than the total during the entire driving process. At the rated voltage, the current limiting circuit is required for current limiting, the power loss is reduced, and the load driving efficiency is high. Especially when the grid voltage is close to the upper voltage limit, the power consumption of the linear current limiting circuit is relative to the circuit shown in FIG. Lower, low power loss, and high load drive efficiency.

Moreover, when the DC voltage is less than the total rated voltage, the first adjusting tube Q1 is controlled to be turned on by the current feedback controller, and the current flowing in the second load subset is stabilized at the steady current point, and the current pattern of the current in the load is maintained. The waves are small. Thus, the current in the load set does not exceed the current limit due to the action of the current limiting circuit, and the minimum value is set at the steady current point due to the action of the bypass circuit. Therefore, the current of the load set follows The input DC voltage changes little and the constant current characteristics are good.

Moreover, there is no electromagnetic interference (EMI) problem and low cost compared to constant current driving using a switching power supply for load.

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 after the grid voltage is rectified or rectified and filtered, as shown in FIGS. 3 and 4, limit. That is, the DC voltage may be a pulsating DC voltage or may be a non-pulsating direct voltage.

When the input DC voltage is a pulsating DC voltage, the pulsating DC voltage has a voltage less than or equal to the rated voltage of the second load subset in each pulsation period, in each pulsation period, The first adjustment tube in the flow circuit switches between a linear adjustment state and a saturation state, and the first adjustment tube in the bypass circuit switches between a shutdown and a linear adjustment state or a saturation state.

Since the circuit of the present invention can input a pulsating DC voltage, the circuit can be connected to the power grid through a rectifier bridge, and the rectifier bridge rectifies the AC sinusoidal voltage of the power grid into a DC ripple voltage, which is input to the circuit of the present invention, and is limited by current. The function of the circuit and the bypass circuit is that the input current waveform is trapezoidal, that is, the power factor of the circuit is high, the electromagnetic interference is low, and the influence on the power grid is small.

When the input DC voltage is a non-pulsating DC voltage, that is, a constant amplitude DC voltage, the first adjustment tube in the current limiting circuit is in a linear adjustment state, or is in a saturated state, the first in the bypass circuit. The adjustment tube will be in the off state, or in a linear adjustment state, or saturation state, that is, if the amplitude of the input constant DC voltage is constant, the state of the first adjustment tube will not change, when the input is constant The amplitude of the DC voltage changes, and each of the first adjustment tubes changes accordingly.

Preferably, as shown in Figures 3 and 4, the current sampler 202 can be implemented by a third sampling resistor Rs3.

Preferably, as shown in FIG. 3, the current limiting circuit 201 can be implemented by a constant current diode D1; or, as shown in FIG. 4, can be implemented by a linear adjustment circuit. Specifically, as shown in FIG. The stream circuit 201 can include:

The gate of the FET Q2 is connected to the output terminal of the first operational amplifier U1, the drain is connected to the load set A, and the source is connected to the current sampler 202 through the second sampling resistor Rs2; the positive input terminal of the first operational amplifier U1 is connected A reference voltage Vref1 is connected to the output terminal of the first operational amplifier U1 through the first capacitor C1 and the first resistor R1 connected in series, and is also connected to the source of the FET Q2 through the second resistor R2.

In the current limiting circuit structure, the sampling signal on the second sampling resistor Rs2 is input to the inverting input terminal of the first operational amplifier U1 via the second resistor R2, and the first reference voltage is input to the non-inverting input terminal of the first operational amplifier U1. Vrefl, the output of the first operational amplifier U1 controls the gate of the FET, turns it on, and operates in a linear state, and the current limiting point of the current limiting circuit is Il=Vrefl/Rs2.

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, the current feedback controller 203 may include: an output end of the second operational amplifier U2. Connected to the control end of the first adjustment tube Q1, the non-inverting input terminal is connected to the second reference voltage Vref2 through the third resistor R3, and the sampling of the current sampler 202 is also connected through the fourth resistor R4. a signal output terminal; 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.

In the circuit structure, the current signal sampled by the third sampling resistor Rs3 is input to the non-inverting input terminal of the second operational amplifier U2 via the fourth resistor R4, and the non-inverting input terminal of the second operational amplifier U2 is pulled through the pull-up resistor R3. The second reference voltage Vref2, the inverting input terminal of the second operational amplifier U2 is grounded, and the output end of the second operational amplifier U2 controls the first regulating tube Q1 to operate in a linear state, so that the steady current point 12 of the current feedback controller satisfies Vref2/R3 =I2*Rsl/R4.

The first adjustment tube Q1 can be realized by a MOS tube or a triode, wherein when the first adjustment tube Q1 is realized by the MOS tube, the switch control end thereof is the gate of the MOS tube; when the first adjustment tube Q1 is realized by the triode, The switch control terminal is the base of the triode. Generally, in the specific implementation, when the first adjustment tube is realized by the triode, it is required to be connected to the base of the triode as a resistor and then as the switch control end.

Referring to FIG. 5, in another embodiment of the present invention, the current limiting circuit is the same as the embodiment shown in FIG. 4, and the difference is: the current sampler is connected in series with the first adjusting tube Q1, and then connected in series with The subset of the load set is connected in parallel with the current limiting circuit. As shown in FIG. 5, the current sampler is implemented by the first sampling resistor Rs1, and then the first adjusting tube Q1 and the first sampling resistor Rs1 are connected in series and then connected in series. The first load subset A1 and the current limiting circuit 201 are connected in parallel.

In addition, the structure of the current feedback controller is also different. The current feedback controller in FIG. 5 may include: an output terminal of the third operational amplifier U3 is connected to the switch control end of the first adjustment tube Q1; a positive phase input terminal is connected to the second reference voltage Vref2; and an inverting input terminal is connected through the sixth resistor. The sampling signal output end of the current sampler is also connected to the source of the FET Q2 through the seventh resistor R7, and is also connected to the output end of the third operational amplifier U3 through the third capacitor C3 and the eighth resistor R8 connected in series; The current sampler is implemented by a first sampling resistor Rs1, and the inverting input terminal of the third operational amplifier U3 is connected to the high-potential terminals Vsl and Vs2 of the sampling resistors Rs1 and Rs2 through resistors R6 and R7, respectively, to sample the branch current Is. 1 and Is2.

Under the circuit structure, when the output of the third operational amplifier U3 is operated in a linear state by controlling the first regulating tube Q1, the steady current point 12 of the current feedback controller is satisfied: Vsl* R7+ Vs2* R6= Is 1* Rsl * R7+ Is2* Rs2* R6=Vref2 ( R6+R7 ), where 12= Isl+ Is2„

Preferably, taking R2=R6 and taking Rs 1 =Rs2, the steady flow point 12=2 Vref2/ Rs 1 =2 Vref2/ Rs2. As shown in FIGS. 3 to 5, the DC voltage is obtained by the following circuit: a second diode D2 and a third diode D3 connected in series, and a fourth diode D4 and a fifth diode connected in series D5 is connected in parallel; the anode of the second diode D2 is connected to the cathode of the third diode D3, the anode of the fourth diode D4 is connected to the cathode of the fifth diode D5; and the anode of the second diode D2 is connected to the alternating voltage The first output terminal L of the source (not shown); the anode of the fourth diode D4 is connected to the second output terminal N of the alternating voltage source. Preferably, a fourth capacitor C4 can be added at the input end of the AC voltage source, and the number of LED lamps in series can be more flexible through the capacitor C2 and the impedance division of the DC side of the rectifier bridge. For example, the embodiment shown in FIG. 6 is based on the embodiment of FIG. 3, adding a fourth capacitor C4 between the first output terminal L of the alternating voltage source and the anode of the second diode D2, through the fourth capacitor. The impedance division of the C4 and the DC side of the rectifier bridge makes the number of LED lamps connected in series more flexible. This improvement also applies to the embodiment shown in Figures 4 and 5. The circuit implementation shown in Figures 7a and 7b.

The input terminal Vi of the auxiliary source is connected to the high potential end of the third load subset A3, and the output terminal Vcc of the auxiliary source is the supply voltage of each operational amplifier.

The third load subset A3 is part of the load set A, and the number of loads of the third load subset A3 should be greater than or equal to the number of loads in the first load subset A1, less than or equal to the number of loads in the load set A.

In order to prevent the load in the first load subset A1 from being extinguished when the power grid fluctuates to the low voltage end and the first adjustment tube Q1 is saturated and the input terminal Vi of the auxiliary source is too small, the third load subset of the auxiliary source input Vi is connected. The number of loads in A3 should be greater than the number of loads in the first subset of loads A1 (as shown in Figure 7a); when a voltage regulator is connected in series on the branch of the first adjustment tube Q1 (as shown in Figure 7b) The number of loads in the third subset of loads A3 connected to the input Vi of the auxiliary source may be equal to the number of loads in the first subset of loads A1.

In the embodiment of Figures 4 and 5, the reference voltage of the non-inverting terminal of the operational amplifier, such as the first reference voltage Vref 1 and the second reference voltage Vref2, can be obtained from the output terminal Vcc of the auxiliary source via the Zener voltage regulator and the resistor divider.

Specifically, as shown in FIG. 7a, based on an implementation of an auxiliary source and a reference voltage (such as Vref1 and Vref2) of FIG. 2, the circuit includes: an input terminal Vi connected to a collector of the third transistor Q3, The base of the third transistor Q3 is also connected through the ninth resistor R9; the base of the third transistor Q3 is grounded through the first Zener diode TV1; the emitter of the third transistor Q3 is grounded through the fifth capacitor C5 The emitter of the third transistor Q3 also serves as the output terminal Vcc;

The emitter of the third transistor Q3 is grounded through the series connected tenth resistor R10 and the first three-terminal adjustable reference source TV2, and the cathode of the first three-terminal adjustable reference source TV2 passes through the eleventh resistor R11 connected in series, The twelfth resistor R12 and the thirteenth resistor R13 are grounded; wherein the voltage of the connection point of the eleventh resistor R11 and the twelfth resistor R12 is used as the first reference voltage Vref1, the twelfth resistor R12 and the thirteenth resistor R13 The voltage of the connection point is taken as the second reference voltage Vref2.

Figure 7b is an implementation of another auxiliary source and reference voltage (e.g., Vrefl and Vref2) based on Fig. 2. The difference between Fig. 7b and Fig. 7a is that Fig. 7b is connected in series with the branch of the first adjusting tube Q1. The Zener diode TV3, and the input terminal Vi of the auxiliary source is connected to the connection point of the first load subset A1 and the second load subset A2. Due to the voltage regulation of the third Zener diode TV3, when the load in the first load subset A1 is extinguished and the first adjustment tube Q1 is saturated and turned on when the power grid fluctuates to the low voltage end, the input terminal Vi of the auxiliary power supply can be ensured to be larger than The voltage regulation value of the third voltage regulator TV3 makes the auxiliary source work normally.

It should be noted that the third transistor Q3 in the auxiliary source shown in Figures 7a and 7b can be replaced by

MOS tube.

In the present invention, when the power grid fluctuates to the low voltage end, the load in the first load subset A1 becomes dark or even extinguished, and the overall brightness of the load set can be kept constant by increasing the brightness of the second load subset A2. For example, in the embodiment of Figures 4 and 5, when the grid fluctuates to the low voltage side, the brightness of the second load subset A2 is increased by raising the in-phase reference of the op amp. That is to say, as shown in FIG. 9, in a practical application, the load driving circuit of the embodiment of the present invention may further include:

The reference voltage control unit is configured to control the second reference voltage Vref to increase the preset voltage value when the current in the first load subset A1 is less than the current in the second load subset A2. Specifically, the reference voltage control unit may be configured to: when the current of the branch where the first adjustment tube is located is not zero, superimpose the sampling signal of the branch current of the first adjustment tube to the second reference voltage.

At this time, its output signal is sent to the current feedback controller 203 to increase the preset steady flow point. Based on the working principle of the current feedback controller, if the preset steady flow point is increased, the current flowing through the second load subset A2 is adjusted to stabilize the increased steady current after controlling the impedance of the first adjustment tube. point.

If the load is a luminaire, when the current flowing through the first load subset A1 is less than the second load subset When the current of A2 is decreased, the brightness of A1 is decreased, and the overall brightness of the load set A is decreased. Due to the action of the reference voltage control unit, the preset steady flow point is increased, and then the regulation of the current feedback controller 203 is performed. , increase the brightness of A2, and finally make the overall brightness of the load set A remain basically unchanged.

The reference voltage control unit directly samples the current signal of the branch where the first adjustment tube is located, and controls the current flowing through the second load subset A2 to increase when a current flows through the branch of the first adjustment tube.

In practical applications, the preset voltage value can be set autonomously, and the specific value is not limited herein. 8 is an implementation of an in-phase reference of an elevated operational amplifier based on the embodiment of FIG. 5, the reference voltage control unit includes: one end of the fourteenth resistor R14 is connected to the high potential end Vsl of the first sampling resistor Rsl, and One end is connected to the second reference voltage Vref2. Correspondingly, a fifteenth resistor R15 is connected in series between the second reference voltage Vref2 and the non-inverting input terminal of the third operational amplifier U3, so that the reference voltage input to the non-inverting terminal of the operational amplifier is the second reference voltage Vref2 and the first sampling The sum of the resistors Rsl. Therefore, when the load in the first load subset A1 becomes dark or even extinguished when the grid voltage becomes small, the current of the branch of the first adjustment tube Q1 increases, and the potential of Vsl rises, so the reference Vref2 is raised by the fourteenth resistor R14. The brightness of the second load subset A2 is increased by the closed loop adjustment of the operational amplifier. In practical applications, the Vsl potential and the value of the fourteenth resistor R14 together determine the degree to which the second reference voltage Vref2 rises, that is, the predetermined steady flow point.

It should be noted that, since the sampling resistance is generally small, the high potential terminal Vsl of the first sampling resistor Rs1 may be too small to raise the reference, and in this case, may be in the branch of the first sampling resistor Rs1. A resistor is connected in series, and its resistance value is greater than the resistance value of Rsl, so that the high potential end of the added resistor is connected to the fourteenth resistor R14 instead of the original Vsl.

The implementation of the in-phase reference of an elevated operational amplifier of the embodiment of FIG. 5b is also implemented by the fourteenth resistor R14, which is not described herein.

8b is an implementation manner of the in-phase end reference of the elevated operational amplifier based on the embodiment of FIG. 4, as long as the load in the first load subset A1 becomes dark or even extinguished when the power grid fluctuates to the low voltage end, manually adjusting the resistor R13 The resistance increases the second reference voltage Vref2. After the closed-loop adjustment of the operational amplifier, the brightness of the second load subset A2 increases, thereby ensuring that the load set maintains the overall brightness even under the fluctuation of the power grid. At this time, as shown in FIG. 8b, the current feedback controller includes: an output end of the seventh operational amplifier U7 is connected to the switch control end of the first adjustment tube Q1; and an inverting input end of the seventh operational amplifier U7 is connected in series The seventh capacitor C7 and the twentieth resistor R20 are connected to the seventh operational amplifier The output of U7 is also connected to the second end of the third sampling resistor Rs3; the non-inverting input of the seventh operational amplifier U7 is connected to the second reference voltage Vref2 through the sixteenth resistor R16.

The reference voltage control unit includes: a seventeenth resistor R17, the first end of the seventeenth resistor R17 is grounded, and the second end is connected to the non-inverting input terminal of the seventh operational amplifier U7; the seventeenth resistor R17 and/or The sixteenth resistor R16 can be an adjustable resistor.

As shown in FIG. 4a, a schematic diagram of a structure of a load driving circuit according to an embodiment of the present invention is shown. Compared with FIG. 4, the difference is only: The implementation structure of the current limiting circuit is different. As shown in FIG. 4a, the current limiting circuit includes: The gate of the FET Q2 is connected to the output end of the sixth operational amplifier U6, the drain is connected to the first end of the first load subset A1, the source is connected to the second end of the second sampling resistor Rs2, and the sixth operational amplifier U6 is The inverting input terminal is connected to the source of the FET Q2; the non-inverting input terminal is connected to the first reference voltage Vref1.

5a is similar to the load driving circuit structure of the embodiment of the present invention shown in FIG. 5, the only difference is that the implementation structure of the current limiting circuit is different, and the implementation structure of the current limiting circuit is the same as that of the current limiting circuit in FIG. 4a. I won't go into details here.

The difference between the load driving circuit and the second embodiment of the present invention is as follows: The anode of the diode D2 is connected to the first end of the first load subset A1, the cathode is connected to the second end of the second sampling resistor Rs2, and the first end of the second sampling resistor Rs2 is connected to the negative output of the DC voltage, and the first Grounded at the end.

The load driving circuit of the embodiment of the present invention shown in FIG. 10 has an implementation structure similar to that of the load driving circuit shown in FIG. 4, and the only difference is that: the current limiting circuit does not include the second sampling resistor Rs2, and the third sampling resistor Rs3 The first end is grounded, and the implementation of the current feedback controller is different;

As shown in FIG. 10, the current feedback controller may include: an output end of the fourth operational amplifier U4 as an output end of the current feedback controller, connected to the switch control end of the first adjustment tube Q1; and a positive operation of the fourth operational amplifier U4 The phase input terminal is connected to the second reference voltage Vref2; the inverting input terminal of the fourth operational amplifier U4 is connected to the second end of the third sampling resistor Rs3 through the eighteenth resistor R18, and also through the sixth capacitor C6 and the nineteenth connected in series A resistor R19 is coupled to the output of the fourth operational amplifier U4.

The load driving circuit of the embodiment of the present invention shown in FIG. 10a has an implementation structure similar to that of the load driving circuit shown in FIG. 4a. The only difference is that: the current limiting circuit does not include the second sampling resistor Rs2, The first end of the three-sampling resistor Rs3 is grounded, and the implementation of the current feedback controller is different; as shown in FIG. 10a, the current feedback controller may include: an output of the fifth operational amplifier U5 as an output of the current feedback controller The first operational terminal of the fifth operational amplifier U5 is connected to the second reference voltage Vref2, and the inverting input terminal is connected to the second terminal of the third sampling resistor Rs3. Based on the above embodiments, the embodiment of the present invention further provides a load driving circuit, including: a current limiting circuit, a bypass circuit;

The current limiting circuit and the load set driven by the load driving circuit are serially connected between the two output ends of the DC voltage; all loads in the load set are connected in series, and are divided into two load sub-sets, and current limiting The load sub-set of the circuit connection is a first load sub-set, and the other load sub-set is a second load sub-set; the quantity k of the load in the first load sub-set is greater than or equal to 1 and less than the total number of loads in the load set;

The current limiting circuit is configured to control a current of the first load subset or a total current of the load set is not greater than a preset current limit point;

The current limit point is greater than the steady flow point.

Additionally, the bypass circuit can include:

After the first adjustment tube is turned on, when the first adjustment tube is in the linear conduction state, the conduction resistance of the first adjustment tube becomes correspondingly larger or smaller according to the current value of the current signal, and finally the first adjustment tube is at Saturated state. As shown in the load driving circuit of FIG. 2, the first adjusting transistor Q1, the current sampler 202, and the current feedback controller 203 constitute the bypass circuit.

As shown in FIG. 3, 4, 4a, 8b, 10 and 10a, the current sampler according to the embodiment of the present invention can be implemented by a third sampling resistor Rs3, the third sampling resistor Rs3 and the current limiting circuit and the driven The load set is commonly connected in series between the two outputs of the DC voltage.

Specifically, as shown in FIG. 4 and FIG. 4a, the first end of the third sampling resistor Rs3 is connected to the negative output end of the DC voltage, and the second end is connected to the common end of the current limiting circuit and the first adjusting tube, and the common End is the ground;

At this time, the current feedback controller may include the following structure:

The output end of the second operational amplifier U2 is used as an output end of the current feedback controller, and is connected to the switch control end of the first adjustment tube Q1; the non-inverting input end of the second operational amplifier U2 is connected to the second reference voltage Vref2 through the third resistor R3, The first terminal of the third sampling resistor Rs3 is also connected through the fourth resistor R4; the inverting input terminal of the second operational amplifier U2 is grounded, and is connected to the second operational amplifier U2 through the second capacitor C2 and the fifth resistor R5 connected in series Output.

It should be noted that the second capacitor C2 and the fifth resistor R5 in FIG. 4 and FIG. 4a can be deleted, so that the response of the current feedback controller is faster.

Or, as shown in FIG. 10 and FIG. 10a, the first end of the third sampling resistor Rs3 is connected to the negative output end of the DC voltage, and serves as a ground end, and the second end is connected to the common of the current limiting circuit and the first adjusting tube. end. at this time,

Alternatively, as shown in FIG. 10a, the current feedback controller can also be implemented by: the output end of the fifth operational amplifier U5 is used as an output end of the current feedback controller, and is connected to the switch control end of the first adjustment tube Q1; The non-inverting input terminal of the fifth operational amplifier U5 is connected to the second reference voltage Vref2, and the inverting input terminal is connected to the second end of the third sampling resistor Rs3. As shown in FIG. 3, the current limiting circuit in the embodiment of the present invention may include: a first constant current diode D1, a cathode of the first constant current diode D1 is connected to a second end of the third sampling resistor Rs3, and the anode is connected first. The first end of the load sub-set A1; or

The current limiting circuit may further include: a sampling subunit and a first adjusting subcircuit, wherein

a first adjusting sub-circuit, configured to control, according to the current signal input by the sampling subunit, a current of the first load subset to be no greater than a preset current limiting point; or directly controlling a current of the first load subset to be greater than a preset current limiting Point (for example, when the first adjustment sub-circuit is implemented by a constant current diode, it is not necessary to perform current control of the first load subset according to the current signal input by the sampling subunit);

Or, according to 10 and FIG. 10a, the current limiting circuit may further include: a second adjusting sub-circuit, wherein the second adjusting sub-circuit is configured to control the first load according to the current signal sampled by the third sampling resistor The current of the subset is not greater than the preset current limit.

Specifically, as shown in FIG. 4, the sampling subunit may include: a second sampling resistor Rs2; a first end of the second sampling resistor Rs2 is connected to a second end of the third sampling resistor Rs3;

The first adjustment sub-circuit includes: a gate of the FET Q2 is connected to an output end of the first operational amplifier U1, a drain is connected to a first end of the first load subset A1, and a source is connected to the second sampling resistor Rs2 The second terminal of the first operational amplifier U1 is connected to the first reference voltage Vrefl, and the inverting input terminal of the first operational amplifier U1 is connected to the first operational amplifier through the first capacitor C1 connected in series and the first resistor R1 The output terminal of the U1 is further connected to the source of the FET through the second resistor R2; or, as shown in FIG. 4a, the sampling subunit may include: a second sampling resistor Rs2; a first end of the second sampling resistor Rs2 Connecting the second end of the third sampling resistor Rs3; the first adjusting sub-circuit comprises: the gate of the FET Q2 is connected to the output end of the sixth operational amplifier U6, and the drain is connected to the first end of the first load sub-set A1 The source is connected to the second end of the second sampling resistor Rs2; the inverting input of the sixth operational amplifier U6 is connected to the source of the FET; the non-inverting input is connected to the first reference voltage Vrefl o

10 and FIG. 4, the current limiting circuit of FIG. 10a and FIG. 4a are different only in that: FIG. 10 and FIG. 10a do not include the sampling subunit formed by the second sampling resistor Rs2, and no longer 赘 Said.

As shown in FIG. 5 to FIG. 5a, when the current limiting circuit includes the sampling sub-circuit formed by the second sampling resistor Rs2, the current sampler can be implemented by the first sampling resistor Rs1 and the second sampling resistor Rs2, as shown in FIG. 5. As shown in FIG. 5a, at this time, the second sampling resistor Rs2 serves as both a sampling sub-circuit in the current limiting circuit and a part of the current sampler, that is, the second sampling resistor Rs2 is a current limiting circuit and a current sampler. Share.

Alternatively, as shown in FIG. 5b, the current limiting circuit may further include: a third adjusting sub-circuit, configured to control a current of the first subset of loads not greater than a preset current limiting point. As shown in FIG. 5b, the third adjusting sub-circuit is realized by the second constant current diode D2, and the second constant current diode D2 is connected in series between the first end of the first load subset A1 and the negative output end of the DC voltage, specifically The anode of the second constant current diode D2 is connected to the first end of the first load subset A1, and the cathode is connected to the second end of the second sampling resistor Rs2. At this time, the second sampling resistor R _S 2 is only used as a part of the current sampler, and samples the current of the branch in which the first load subset A1 is located, and the second constant current diode D2 controls the current of the first load subset independently. Greater than the preset current limit.

At this time, as shown in FIG. 5 to 5b, the current sampler includes: a first sampling resistor Rs1 and the second sampling resistor Rs2; a first sampling resistor Rs1 connected in series with the first adjusting tube Q1, and the first The load sub-set A1 and the series connection circuit of the current limiting circuit are connected in parallel; the first end of the first sampling resistor Rs1 is connected to the negative output end of the DC voltage, wherein the negative output end of the DC voltage is the ground end, and the first sampling resistor Rsl is The second end is connected to the first input end of the current feedback controller; the first end of the second sampling resistor Rs2 is connected to the ground end, and the second end of the second sampling resistor Rs2 is connected to the second input end of the current feedback controller.

At this time, as shown in FIG. 5 to FIG. 51), the current feedback controller includes: an output end of the third operational amplifier U3 is connected to the switch control end of the first adjustment tube Q1; and a positive input terminal of the third operational amplifier U3 is connected. The second reference voltage Vref2; the inverting input terminal is connected to the first end of the sixth resistor R6, and is further connected to the first end of the seventh resistor R7, and the second end of the sixth resistor R6 is used as the first input end of the current feedback controller The second end of the seventh resistor R7 serves as a second input terminal of the current feedback controller. The inverting input terminal is further connected to the output end of the third operational amplifier U3 through the third capacitor C3 and the eighth resistor R8 connected in series.

It should be noted that the third capacitor C3 and the eighth resistor R8 in FIG. 5, FIG. 5a and FIG. 5b can be deleted, so that the response of the current feedback controller is faster. In addition, as shown in FIG. 9, the bypass circuit may further include:

The reference voltage control unit is configured to: when the total current of the load set is less than the preset steady flow point, increase the steady flow point according to a preset rule. Preferably, the reference voltage control unit is specifically configured to: when the current of the branch where the first adjustment tube is located is not zero, superimpose the sampling signal of the branch current of the first adjustment tube to the second reference voltage. The specific implementation structure of the reference voltage control unit is shown in Figure 8~8b. Please refer to the implementation structure description of the reference voltage control unit in the previous section, which will not be described here.

It should be noted that, in all embodiments of the present invention, in addition to the DC voltage or its implementation circuit, any part of the circuit or any part of the circuit can be integrated into an integrated chip: for example, except for the load set A and the DC voltage. The components and their connection relationships can be integrated; components other than the second load subset A2 and the DC voltage and their connection relationships can also be integrated. For example, the first adjustment tube, the current sampler, the current feedback controller, and the current limiting circuit are integrated as an integrated circuit; or, the first adjustment tube, the current sampler, the current feedback controller, and the current limiting The circuit is integrated with the first subset of loads as an integrated circuit; or the first adjustment tube, the current sampler, the current feedback controller, the reference voltage control unit, and the current limiting circuit are integrated as one An integrated circuit of the terminal; or, the first adjustment tube, the current sampler, the current feedback controller, the current limiting circuit, the reference voltage control unit, and the first load subset are integrated as a two-terminal integrated circuit Or, the current limiting circuit, the bypass circuit, and the auxiliary source are integrated into one integrated circuit; or the current limiting circuit, the bypass circuit, the first load subset, and the auxiliary source are integrated into one integrated circuit.

In the drawing of the embodiment of the present invention, the second adjusting tube is implemented by the FET Q2, wherein the gate of the FET corresponds to the switching control end of the second adjusting tube, and the drain corresponds to the second adjustment The first end of the tube, the source corresponds to the second end of the second adjusting tube; in practical applications, the second adjusting tube can also be realized by a series of resistors in series with a base transistor. At this time, the base connecting resistor in the triode The first end of the resistor corresponds to the switch control end of the second adjustment tube, and the emitter of the triode corresponds to the second end of the second adjustment tube, and the collector corresponds to the first end of the second adjustment tube. The structure of the load driving circuit of the embodiment of the present invention is not described herein.

In the drawings of the embodiments of the present invention, the LED is used as a load as an example for description. In practical applications, other loads may be used, so that the load driving circuit is driven by the load driving circuit of the present invention, which is not limited herein. . The above is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. It should be considered as the scope of protection of the present invention.

Claims

Rights request

A load driving circuit, comprising: a current limiting circuit, a first adjusting tube, a current sampler, and a current feedback controller, wherein

2. The circuit of claim 1 wherein said current limit point is greater than said steady current point.

3. The circuit of claim 1 wherein the sum of the rated voltages of all of the loads outside said subset of the set of loads is equal to the lower limit of the DC voltage.

4. The circuit according to claim 1, wherein the current sampler is connected in series with the current limiting circuit and the driven load set in series between the two output terminals of the direct current voltage.

The circuit of claim 4, wherein the current feedback controller comprises: the output of the second operational amplifier is connected to the switch control end of the first adjustment tube, and the non-inverting input is connected to the second reference via the third resistor The voltage is also connected to the sampling signal output terminal of the current sampler through a fourth resistor; the inverting input terminal of the second operational amplifier is grounded, and the output of the second operational amplifier is connected through the second capacitor connected in series and the fifth resistor.

6. The circuit according to claim 4, wherein the current limiting circuit is implemented by a constant current diode or a linear adjustment circuit.

The circuit according to claim 6, wherein when the current limiting circuit is implemented by a linear adjustment circuit, the method includes: The gate of the FET is connected to the output of the first operational amplifier, the drain is connected to the load set, and the source is connected to the current sampler through the second sampling resistor; the non-inverting input of the first operational amplifier is connected to the first reference voltage, inverting The input terminal is connected to the output end of the first operational amplifier through the first capacitor connected in series and the first resistor, and is also connected to the source of the FET through the second resistor.

8. The circuit of claim 1, further comprising:

The serial current sampler and the first adjustment tube are connected in parallel with the subset of the series of connected loads and the current limiting circuit.

The circuit of claim 8, wherein the current limiting circuit comprises: a gate of the FET connected to an output of the first operational amplifier, a drain connected to the load set, and a source passing through the second sampling resistor An output terminal connected to the DC voltage; a non-inverting input terminal of the first operational amplifier is connected to the first reference voltage, and the inverting input terminal is connected to the output end of the first operational amplifier through the first capacitor connected in series and the first resistor, and is also passed through the second a resistor connected to the source of the FET;

The current feedback controller includes: an output end of the third operational amplifier connected to the switch control end of the first adjustment tube; a positive phase input terminal connected to the second reference voltage; and an inverting input terminal connected to the sampling signal of the current sampler through the sixth resistor The output terminal is further connected to the source of the FET through a seventh resistor, and is also connected to the output terminal of the third operational amplifier through a third capacitor connected in series and an eighth resistor.

10. The circuit according to claim 5, wherein the method further comprises: a reference voltage control unit configured to control when the current in the first subset of loads is less than the current in the second subset of loads The second reference voltage rises by a preset voltage value.

The circuit according to claim 10, wherein the reference voltage control unit comprises: the sampling signal output end of the current sampler is connected to the second reference voltage through the fourteenth resistor.

The circuit according to any one of claims 1 to 9, wherein the current sampler is implemented by a sampling resistor.

The circuit according to any one of claims 1 to 9, wherein the first adjustment tube is realized by a MOS tube or a triode.

The circuit according to any one of claims 1 to 9, wherein the DC voltage is obtained by the following circuit:

a second diode connected in series and a third diode connected in parallel with the fourth diode and the fifth diode connected in series; the anode of the second diode is connected to the cathode of the third diode, fourth Diode anode connection fifth The cathode of the diode; the anode of the second diode is also connected to the first output of the AC voltage source via a fourth capacitor; the anode of the fourth diode is connected to the second output of the AC voltage source.

The circuit according to any one of claims 5 to 7, 9 to 11, further comprising: an auxiliary source;

The input end of the auxiliary source is connected to the high potential end of the third load subset, and the input end is connected to the collector of the third triode, and is also connected to the base of the third triode through the ninth resistor; The base of the triode is connected to the cathode of the first Zener tube, the anode of the first Zener tube is grounded; the emitter of the third transistor is grounded through the fifth capacitor, and the emitter of the third transistor is used as an auxiliary source Output, the output is used to supply an operational amplifier in a load driving circuit;

The circuit according to any one of claims 5 to 7, 9 to 11, further comprising: an auxiliary source; wherein

The input end of the auxiliary source is connected to the high potential end of the first load subset, and the input end is connected to the collector of the third triode, and is also connected to the base of the third triode through the ninth resistor; The base of the pole tube is connected to the cathode of the first Zener tube, the anode of the first Zener tube is grounded; the emitter of the third transistor is grounded through the fifth capacitor, and the emitter of the third transistor is used as an auxiliary source. The output is used to supply an operational amplifier in the load driving circuit;

A load driving circuit, comprising: a current limiting circuit, a bypass circuit; wherein the current limiting circuit and the load set driven by the load driving circuit are serially connected between the two output ends of the DC voltage All the loads in the load set are connected in series, and are divided into two load sub-sets, the load sub-set connected to the current limiting circuit is the first load sub-set, and the other load sub-set is the second load sub-set; The number k of loads in the first load subset is greater than or equal to 1, which is less than the total number of loads in the load set;

18. The circuit of claim 17, wherein the current limit point is greater than the current stabilizing point.

The circuit according to claim 17, wherein the bypass circuit comprises: a first adjustment tube connected in parallel with the first load subset and the current limiting circuit connected in series;

The circuit of claim 19, wherein the current sampler comprises: a third sampling resistor, the third sampling resistor and the current limiting circuit and the driven load set are serially connected to the DC voltage Between the two outputs.

The circuit according to claim 20, wherein the first end of the third sampling resistor is connected to the negative output end of the DC voltage, and the second end is connected to the common end of the current limiting circuit and the first adjusting tube, and The public end is the ground end;

The current feedback controller includes:

The output end of the second operational amplifier is used as the output end of the current feedback controller, and is connected to the switch control end of the first adjustment tube; the non-inverting input end of the second operational amplifier is connected to the second reference current through the third resistor Pressing, further connecting the first end of the third sampling resistor through the fourth resistor; the inverting input terminal of the second operational amplifier is grounded;

The circuit according to claim 20, wherein the first end of the third sampling resistor is connected to the negative output end of the DC voltage, and serves as a ground end, and the second end is connected to the current limiting circuit and the first adjustment Common end of the pipe;

The current feedback controller includes: an output end of the fourth operational amplifier as an output end of the current feedback controller, and a switch control end connected to the first adjustment tube; a positive input terminal of the fourth operational amplifier is connected to the second reference voltage; The inverting input terminal of the fourth operational amplifier is connected to the second end of the third sampling resistor through the eighteenth resistor, and is further connected to the output end of the fourth operational amplifier through the sixth capacitor and the nineteenth resistor connected in series;

The circuit according to any one of claims 20 to 22, wherein the current limiting circuit comprises a first constant current diode, and the cathode of the first constant current diode is connected to the second end of the third sampling resistor, the anode Connecting the first end of the first subset of load; or

The current limiting circuit includes: a second adjusting sub-circuit, configured to control, according to the current signal sampled by the current sampler, that the current of the first load subset is not greater than a preset current limit point.

The circuit of claim 23, wherein the sampling subunit comprises: a second sampling resistor; a first end of the second sampling resistor is coupled to the second end of the third sampling resistor;

The circuit according to claim 23, wherein the second adjustment sub-circuit comprises: a switch control end of the second adjustment tube is connected to an output end of the first operational amplifier, and the first end is connected to the first load subset a first end, the second end is connected to the second end of the third sampling resistor; the non-inverting input of the first operational amplifier is connected to the first reference voltage, and the inverting input end of the first operational amplifier is connected through the first The capacitor and the first resistor are connected to the output end of the first operational amplifier, and are further connected to the second end of the second adjusting tube through the second resistor;

The circuit of claim 19, wherein the current limiting circuit comprises: a sampling subunit and a first adjusting subcircuit; wherein

The circuit according to claim 26, wherein the sampling subunit comprises: a second sampling resistor; a first end of the second sampling resistor is connected to a negative output terminal of the DC voltage; The first adjustment sub-circuit includes: a switch control end of the second adjustment tube is connected to an output end of the first operational amplifier, the first end is connected to the first end of the first load subset, and the second end is connected to the second sampling resistor The second end of the first operational amplifier is connected to the first reference voltage, and the inverting input end of the first operational amplifier is connected to the output of the first operational amplifier through the first capacitor connected in series and the first resistor, Connecting the second end of the second adjusting tube through the second resistor;

The circuit according to claim 19, wherein the current limiting circuit comprises: a third adjusting sub-circuit, configured to control a current of the first subset of loads to be no greater than a preset current limiting point.

The circuit according to claim 28, wherein the third adjustment sub-circuit comprises: a second constant current diode, wherein the second constant current diode is serially connected to the first end of the first load subset and the DC voltage Between the negative outputs.

The circuit according to claim 27 or 29, wherein the current sampler comprises: a first sampling resistor and a second sampling resistor; a first sampling resistor connected in series with the first adjusting tube, and the first The load sub-collection and the series connection circuit of the current limiting circuit are connected in parallel; the first end of the first sampling resistor is connected to the negative output end of the DC voltage, the second end is connected to the first input end of the current feedback controller; One end is connected to the negative output of the DC voltage, and the second end is connected to the second input of the current feedback controller.

31. The circuit according to claim 30, wherein the current feedback controller comprises: an output end of the third operational amplifier connected to the switch control end of the first adjustment tube; and a positive phase input end of the third operational amplifier connected to the second a reference voltage; the inverting input terminal is connected to the first end of the sixth resistor, and is further connected to the first end of the seventh resistor, and the second end of the sixth resistor is used as the first input end of the current feedback controller, and the seventh resistor The second end serves as a second input of the current feedback controller;

Or the output end of the third operational amplifier is connected to the switch control end of the first adjustment tube; the non-inverting input end of the third operational amplifier is connected to the second reference voltage; the inverting input end is connected to the first end of the sixth resistor, and The first end of the seventh resistor is connected, the second end of the sixth resistor serves as a first input end of the current feedback controller, and the second end of the seventh resistor serves as a second input end of the current feedback controller, and the third operational amplifier The inverting input of the amplifier is also connected to the output of the third operational amplifier through a third capacitor connected in series and an eighth resistor.

The circuit according to any one of claims 19 to 31, characterized in that the first adjustment tube, the current sampler, the current feedback controller and the current limiting circuit are integrated as an integrated circuit.

The circuit according to any one of claims 19 to 31, wherein the first adjustment tube, the current sampler, the current feedback controller, the current limiting circuit and the first load subset are integrated An integrated circuit.

The circuit according to any one of claims 17 to 31, wherein the bypass circuit further comprises:

The circuit according to claim 34, wherein the reference voltage control unit is specifically configured to: when the current of the branch where the first adjustment tube is located is not zero, the branch of the first adjustment tube is located The sampled signal of the current is superimposed on the second reference voltage.

36. The circuit of claim 35, wherein the current feedback controller is implemented by a corresponding circuit of the third operational amplifier:

The reference voltage control unit includes: a fourteenth resistor, a first end of the fourteenth resistor is connected to a non-inverting input end of the third operational amplifier, and a second end is connected to the second end of the first sampling resistor;

Correspondingly, the non-inverting input of the third operational amplifier in the current feedback controller is connected to the second reference voltage through the fifteenth resistor.

37. The circuit of claim 35, wherein the current sampler is implemented by a third sampling resistor:

The current feedback controller includes: an output end of the seventh operational amplifier is connected to the switch control end of the first adjustment tube; and an inverting input end of the seventh operational amplifier is connected to the seventh operation through the seventh capacitance and the twentieth resistance connected in series The output end of the amplifier is further connected to the second end of the third sampling resistor; the non-inverting input terminal of the seventh operational amplifier is connected to the second reference voltage through the sixteenth resistor; The reference voltage control unit includes: a seventeenth resistor, the first end of the seventeenth resistor is grounded, and the second end is connected to the inverting input terminal of the seventh operational amplifier; the seventeenth resistor and/or the sixteenth resistor It is an adjustable resistor.

The circuit according to any one of claims 34 to 37, wherein said first adjustment tube, current sampler, current feedback controller, reference voltage control unit and current limiting circuit are integrated as an integrated circuit.

The circuit according to any one of claims 34 to 37, wherein the first adjustment tube, the current sampler, the current feedback controller, the current limiting circuit, the reference voltage control unit, and the first loader The collection is integrated into an integrated circuit.

40. Circuit according to any one of claims 18 to 39, characterized in that the first adjustment tube and/or the second adjustment tube can be realized by a MOS tube or a triode with a base series resistor.

The circuit according to any one of claims 17 to 40, characterized in that the DC voltage is obtained by the following circuit:

The circuit according to any one of claims 17 to 40, further comprising: an auxiliary source for converting a voltage of the input auxiliary source into a constant amplitude DC voltage;

A third Zener tube is connected in series between the second end of the first subset of loads and the first adjustment tube.

44. The circuit of claim 42 or 43, wherein the current limiting circuit, the bypass circuit, and the auxiliary source are integrated into one integrated circuit.

45. The circuit of claim 42 or 43, wherein the current limiting circuit, the bypass circuit, the first subset of loads, and the auxiliary source are integrated into one integrated circuit.