CN117406822A

CN117406822A - High-conversion-efficiency linear current source circuit and operation control method thereof

Info

Publication number: CN117406822A
Application number: CN202311639105.7A
Authority: CN
Inventors: 赵翔; 郭晓东; 郭磊; 葛浩山; 黄雄; 白云昌; 林兴泰
Original assignee: Hubei Jiuzhiyang Information Technology Co ltd
Current assignee: Hubei Jiuzhiyang Information Technology Co ltd
Priority date: 2023-11-30
Filing date: 2023-11-30
Publication date: 2024-01-16

Abstract

The utility model discloses a high conversion efficiency linear current source circuit and an operation control method thereof, wherein the circuit comprises a programmable linear current source circuit, an output direct-current voltage programmable power module and a control circuit thereof, a current adjusting tube N-MOSFET drain voltage acquisition circuit, a digital programmable chip DPD and a peripheral interface circuit thereof; maintaining the drain voltage of the N-MOSFET higher than the N-MOSFET load current I _SET Corresponding to the sum of the minimum tube voltage drop required by the constant current area and the voltage drop on the current sampling resistor. According to the utility model, through the N-MOSFET drain voltage acquisition circuit and the related control method, the drain voltage can be compressed as much as possible under the premise of ensuring the required current of an electric load, and different currents required by the electric load can be ensured under various temperature conditions, so that the electric energy conversion rate and the environmental adaptability of the circuit are greatly improved, and the working reliability of the N-MOSFET is further improved.

Description

High-conversion-efficiency linear current source circuit and operation control method thereof

Technical Field

The utility model belongs to the technical field of electronic circuits, and particularly relates to a high-conversion-efficiency linear current source circuit and an operation control method thereof.

Background

In the fields of semiconductor lighting, semiconductor laser, and the like, since an electric load such as an LED, an LD, and the like is used as a light source or a pumping source, and in order to have a relatively stable output wavelength and generate different energy or power, a programmable constant current source is required to be used as a driving circuit of the LED and the LD.

The linear current source has the prominent advantage of small electromagnetic interference as a driving circuit of an LED, an LD and the like. Based on the utility model patent of a programmable current source circuit (grant bulletin No. CN 216210707U), an LED (LD) driving device with simple topology, testability and good safety can be manufactured. In the linear current source, a transistor (such as an N-MOSFET) working in a constant current area is required to be used as a current adjusting tube, and the transistor can bear a certain tube voltage drop under a certain driving current value condition; a low-resistance resistor is arranged between the transistor and the power ground to be used as a current sampling element; an electrical load (i.e., an LED or LD) is connected between the transistor and the dc voltage source.

Similar to the linear voltage source input voltage which must be greater than the output voltage, the dc voltage source voltage used by the linear current source must also be greater than the sum of the voltage drop of the electrical load under a certain operating current condition, the minimum tube voltage drop of the current regulator tube operating under the current value condition, and the voltage drop of the current sampling resistor. If the tube voltage drop of the current adjusting tube increases, the electric energy conversion efficiency of the device decreases. As an electrical load, considering that the output characteristic curve of the LED (LD) is closely related to temperature, i.e. the higher the ambient temperature (or junction temperature) is, the lower the forward voltage drop of the PN junction of the LED (LD) is, so that under the premise that the direct-current power supply voltage and the working current of the LED (LD) are unchanged, the voltage drop of the LED (LD) is reduced under the high-temperature environment, the voltage drop of the N-MOSFET serving as a current adjusting tube is increased compared with that under the normal-temperature condition, thereby increasing the heat power consumption of the transistor, and then overlapping the higher ambient temperature factors, the transistor is possibly damaged due to thermal breakdown caused by the fact that the transistor is separated from a safe working area, which is unfavorable for the reliable operation of the device. In contrast, if the normal temperature environment can normally operate the LED (LD) with constant current under the condition that the direct current voltage source voltage is unchanged, the voltage drop of the field effect transistor is reduced due to the increase of the forward voltage drop of the PN junction of the LED (LD) under the low temperature environment, which may cause the transistor to deviate from the constant current operation area and enter the pinch-off area, thereby losing the current regulation function, and causing the current source to fail to normally drive the LED (LD).

On the other hand, in order to realize a power adjustable (or pump energy adjustable) function required for an illumination system (or an optoelectronic system), it is necessary to change a driving current of an LED (LD). Although this function can be achieved by using the utility model patent "a programmable current source circuit" (grant publication No. CN 216210707U), if the input voltage of the current source is unchanged, the current adjusting tube also suffers from the above-mentioned problem of being out of the constant current operating region (when the operating current increases) or out of the safe operating region (when the operating current decreases) even under normal temperature environment (constant temperature).

In order to solve the above problems, the present utility model provides a programmable linear current source circuit and an operation control method thereof, which can drive loads such as LEDs (LD) to operate at different constant currents and different ambient temperatures, and can make transistors safely and reliably operate in constant current regions thereof, and reduce voltage drop of the transistors as much as possible, thereby improving the power conversion efficiency of the current source.

Disclosure of Invention

The present utility model aims to provide a linear current source circuit with high conversion efficiency and an operation control method thereof, which solve the two problems as set forth above: 1. when the ambient temperature (junction temperature) rises or falls, the linear current source can be ensured to drive the electric load with the same working current, and the current adjusting tube can reliably work in the constant current area; 2. when the current required by the electric load needs to be regulated, the linear current source can still provide the current which is newly set, and the current regulating tube can reliably work in the constant current area.

The technical scheme of the utility model is as follows:

in a first aspect, the present utility model provides a high conversion efficiency linear current source circuit, the circuit includes a programmable linear current source circuit, a programmable power module for outputting a direct voltage and a control circuit thereof, a current adjusting tube N-MOSFET drain voltage acquisition circuit, and a digital programmable chip DPD and a peripheral interface circuit thereof;

the output direct-current voltage programmable power supply module and the control circuit thereof comprise a direct-current output voltage programmable power supply module and a second digital-to-analog converter DAC2; the second DAC2 is connected with a voltage adjustment pin of the direct-current output voltage programmable power module and is used for adjusting the output voltage;

the programmable linear current source circuit comprises an N-MOSFET as a current adjusting tube, an electric load, a current sampling resistor, a current series negative feedback control circuit, a first digital-to-analog converter DAC1 and an analog switch; the power load is connected in series between the positive electrode of the direct-current output voltage programmable power module and the drain electrode of the N-MOSFET, and the current sampling resistor is connected in series between the source electrode of the N-MOSFET and the analog ground AGND; the current series negative feedback control circuit is connected with the grid electrode and the source electrode of the N-MOSFET and is used for stably controlling the current I required by the electric load _SET The method comprises the steps of carrying out a first treatment on the surface of the The first DAC1 is connected with a current series negative feedback control circuit and is used for setting current I required by an electric load _SET The method comprises the steps of carrying out a first treatment on the surface of the The analog switch is connected with the current series negative feedback control circuit and is used for starting and closing the programmable linear current source circuit;

the current adjusting tube N-MOSFET drain voltage acquisition circuit is connected with the drain electrode of the N-MOSFET and is used for acquiring the drain voltage of the N-MOSFET;

the digital programmable chip DPD and the peripheral interface circuit thereof comprise the digital programmable chip DPD; the digital programmable chip DPD is connected with the first digital-to-analog converter DA through a bus isolatorC1 is connected to set the current I required by the electric load by setting the output voltage of the first DAC1 _SET The method comprises the steps of carrying out a first treatment on the surface of the The digital programmable chip DPD is also connected with a drain voltage acquisition circuit of the current adjusting tube N-MOSFET through a bus isolator and is used for acquiring the current I _SET The drain voltage VD of the N-MOSFET is connected to the second DAC2 via another bus isolator to adjust the output voltage of the dc output voltage programmable power module to the voltage required by the power load, so that the obtained voltage VD is slightly higher than the N-MOSFET holding current I _SET Corresponding to the sum of the minimum tube voltage drop required by the constant current area and the voltage drop on the current sampling resistor.

Optionally, the current adjusting tube N-MOSFET drain voltage acquisition circuit comprises a first operational amplifier OPA1, a second operational amplifier OPA2, a voltage stabilizing tube V2 and a current limiting resistor R _Z And an analog-to-digital converter ADC; the non-inverting input end of the first operational amplifier OPA1 is connected with the drain electrode of the N-MOSFET, the inverting input end of the first operational amplifier OPA1 is connected with the output end of the first operational amplifier OPA1, and the output end of the first operational amplifier OPA1 is connected with the output end of the first operational amplifier OPA1 through a current-limiting resistor R _Z The non-inverting input end of the second operational amplifier OPA2 is connected with the output end of the second operational amplifier OPA2, the output end of the second operational amplifier OPA2 is connected with the digital programmable chip DPD through the analog-digital converter ADC and the digital isolator, and the negative electrode of the voltage stabilizing tube V2 is connected with the non-inverting input end of the second operational amplifier OPA2 and the positive electrode is grounded.

Alternatively, the regulated voltage of the regulator V2 is higher than the maximum value of the drain voltage of the programmable linear current source circuit when the load current passes through the N-MOSFET, and lower than the highest input analog voltage value allowed by the analog-to-digital converter ADC.

Alternatively, the first operational amplifier OPA1 and the second operational amplifier OPA2 may operate normally under a supply voltage condition higher than the maximum value of the drain voltage of the N-MOSFET.

Optionally, the digital programmable chip DPD is further connected to an analog switch through a digital level isolator, through which the programmable linear current source circuit is turned on and off.

Optionally, the digital programmable chip DPD and the peripheral interface circuit thereof further include an upper computer UC; the upper computer UC communicates with the digital programmable chip DPD through a serial communication interface to set key parameters including current I _SET Meanwhile, the digital programmable chip DPD uploads relevant information to the upper computer UC to realize monitoring, and the relevant information comprises voltage VD.

Optionally, the N-MOSFET is selected according to the following principle and characteristics:

(1) The withstand voltage value is larger than the output voltage of the direct-current output voltage programmable power module;

(2) The bearable current value is larger than the maximum current value required by the electric load;

(3) Current I required by an electrical load _SET The lowest voltage drop of the corresponding constant current region on the output characteristic curve of the transistor is small.

Optionally, the second DAC2 is replaced by a digital varistor, so that the function of adjusting the output voltage of the dc output voltage programmable power module can be implemented as well.

In a second aspect, the present utility model provides a method for controlling operation of the high conversion efficiency linear current source circuit according to any one of the above, comprising the steps of:

initializing and setting current I required by an electric load _SET ；

Adjusting the output voltage of the direct-current output voltage programmable power supply module to the maximum value through a second digital-to-analog converter DAC2;

starting the programmable linear current source circuit through an analog switch;

delaying for a period of time after starting, and collecting the drain voltage of the N-MOSFET through a current adjusting tube N-MOSFET drain voltage collecting circuit;

judging whether the drain voltage of the collected N-MOSFET is within a preset range; if the drain voltage of the collected N-MOSFET is lower than the preset range, the output voltage of the direct-current output voltage programmable power supply module is increased through the second DAC2, and the N-MOSFET is collected againThe drain voltage continues to be judged; if the collected drain voltage of the N-MOSFET is higher than the preset range, reducing the output voltage of the direct-current output voltage programmable power module through a second digital-to-analog converter DAC2, and collecting the drain voltage of the N-MOSFET again for continuous judgment; if the collected drain voltage of the N-MOSFET is within the preset range, judging whether the current I required for updating the power load is received _SET Instructions of (2); the preset range is based on the N-MOSFET maintaining current I _SET Determining the sum of the minimum voltage drop required by the constant current area and the voltage drop on the current sampling resistor;

if receiving the current I required by updating the electric load _SET Instructions of (2); when a new current I _SET If the output voltage is larger than the original value, the output voltage of the direct-current output voltage programmable power supply module is adjusted to the maximum value through the second digital-to-analog converter DAC2; when a new current I _SET And if the voltage is smaller than the original value, the drain voltage of the N-MOSFET is collected again and the judgment is continued.

Compared with the prior art, the utility model has the following advantages:

1. by means of the N-MOSFET drain voltage acquisition circuit and related control algorithm, the power consumption load can be ensured to be controlled under the required current (I _SET ) On the premise of compressing the drain voltage as much as possible, different currents required by an electric load can be ensured under various temperature conditions, so that the electric energy conversion rate and the environmental adaptability of the circuit are greatly improved, and the working reliability of the N-MOSFET is further improved.

2. The element-level bus isolator is used for electrically isolating power supply ground (analog ground) from digital ground and serial port ground from digital ground, and has good electromagnetic compatibility and man-machine safety.

3. The digital programmable device is adopted, so that the testability, the function expandability and the information interaction capability of the whole circuit are greatly improved.

Drawings

FIG. 1 is a schematic block diagram of a high conversion efficiency linear current source circuit of the present utility model;

FIG. 2 is a circuit diagram of a preferred embodiment of the present utility model;

FIG. 3 is a graph of the output characteristics of an N-MOSFET as a current regulator tube in an embodiment;

fig. 4 is a flowchart of a key control procedure adopted by the MCU in the embodiment.

Detailed Description

The present utility model will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present utility model more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the utility model. In addition, the technical features of the embodiments of the present utility model described below may be combined with each other as long as they do not collide with each other.

The utility model relates to a programmable linear current source circuit with a high conversion efficiency control algorithm and an operation control method thereof, belonging to the technical field of electronics. The utility model only shows a linear current source circuit with high conversion efficiency and a control method thereof by way of illustration and example, and can be applied to various occasions such as laser diodes, light emitting diodes and the like which need programmable constant current driving electric loads. It will be appreciated that the use of the present utility model can meet the power requirements of a current driven load, so the present utility model has a wider range of applications.

The utility model discloses a circuit capable of improving the electric energy conversion efficiency of a linear current source and provides a corresponding operation control method. The circuit comprises: using N-MOSFET, low-side current sampling resistor R _SEN Components such as a digital-to-analog converter DAC1 and a linear current source constructed based on a current series negative feedback framework described in an utility model patent (a programmable current source circuit) (grant publication number CN 216210707U); the digital programmable device DPD uses the on-chip bus interface CBI1 and sets the output voltage of DAC1 via the associated element-level bus to set the current I required by the power load _SET The method comprises the steps of carrying out a first treatment on the surface of the DPD obtains the ADC at the set I through the chip-level bus interface CBI0 and the related element-level bus thereof _SET The voltage VD value of the drain electrode of the N-MOSFET is collected under the condition; the primary power source PW is connected with the DC output power source module (or conversion circuit) with the output voltage being adjusted in a programmable mannerRi is converted into a direct-current voltage source V required by an electric load _out The method comprises the steps of carrying out a first treatment on the surface of the On the premise of knowing the output characteristic curve of the N-MOSFET, the output voltage (or resistance) of the digital-to-analog converter DAC2 (or the digital rheostat RDAC) is set through the on-chip bus interface CBI2 of the DPD and the related bus thereof, and is connected to the pin of the adjusting end of the direct-current output power supply module (or the conversion circuit) in a butt joint way, so that the output voltage V of the module (or the conversion circuit) is changed _out The value of VD voltage collected by the ADC is slightly higher than the value of the N-MOSFET maintenance I _SET Corresponding to the minimum tube pressure drop and R required by the constant flow area _SEN The sum of the voltage drops on; the key parameters such as I can be communicated with the upper computer UC by using the DPD on-chip serial communication interface SCI and the related external bus _SET Etc. to facilitate remote control and upload relevant information, such as VD voltage values, to the UC to enable real-time monitoring and comprehensive power management.

Example 1

The embodiment provides a programmable linear current source circuit with high conversion efficiency. The circuit comprises:

the programmable linear current source circuit comprises an N-MOSFET as a current adjusting tube, a current sampling resistor, an electric load, an analog switch and a digital-to-analog converter, and an N-MOSFET grid control circuit (an input end of the analog switch is provided with an output pin connected with the DAC 1) which is formed by a voltage feedback type operational amplifier and is in accordance with the utility model patent of a programmable current source circuit (grant publication No. CN 216210707U). The power utilization load is connected in series with the positive end of the power supply and the drain electrode of the N-MOSFET; the current sampling resistor is positioned between the source electrode of the N-MOSFET and the negative electrode of the power supply. The analog switch is used to turn on and off the linear current source, i.e., when the high-low signal from the general input output pin of the digital programmable device is high (or low), the current source is turned on, and vice versa. The digital-to-analog converter (or the digital rheostat) is used for setting the working current of the electric load, and the output voltage (or the resistance value) of the digital-to-analog converter (or the digital rheostat) can be in one-to-one correspondence with the current value to be set. Wherein, the selection principle and characteristic of the N-MOSFET-1, the withstand voltage value of which must be larger than the DC output voltageAn output voltage Vout of the programming power supply module (or circuit); 2. the current value that it can withstand must be greater than the maximum current value required by the electrical load; 3. operating current I required by an electrical load _SET The lowest voltage drop in the constant current region corresponding to the transistor output characteristic curve is as small as possible.

The direct-current output voltage programmable circuit comprises a direct-current output voltage programmable power module (or a conversion circuit) and a digital-to-analog converter DAC (or a digital rheostat RDAC). The dc output voltage programmable power module (or circuit) refers to a device (or electrical unit) that can adjust the output voltage by changing the voltage value (or resistance value) of its voltage adjustment pin (or the unit group has at least one electrical network node, and the output voltage can be adjusted by changing the voltage of the node) regardless of whether the primary power source input by the device is dc voltage or ac voltage. The analog voltage output end (or equivalent resistance end) of the digital-analog converter (or digital rheostat) can be directly connected with the voltage adjustment pin of the direct-current output voltage programmable power supply module (or circuit), or can be connected with the pin after buffer or amplification by an operational amplifier. The unit circuit is characterized in that the analog voltage value (or equivalent resistance value) output by the digital-to-analog converter (or digital rheostat) corresponds to the direct-current output voltage of the programmable power supply module (or conversion circuit) one by one.

The N-MOSFET drain voltage acquisition circuit comprises a drain voltage buffer output circuit at the front end, a related voltage limiting circuit and an analog-to-digital converter. The drain voltage buffer output circuit outputs drain voltage in real time no matter whether the linear current source circuit is enabled to work or not; when the linear current source has no working current, the drain voltage may exceed the highest input voltage that the analog-to-digital converter can withstand. Therefore, on one hand, the voltage output by the voltage limiting circuit is not higher than the highest input voltage which can be tolerated by the analog-to-digital converter, and on the other hand, when the working current controlled by the adjusting tube exists in the linear current source, the drain voltage is not influenced by the voltage limiting circuit and can be accurately fed into an analog input channel of the analog-to-digital converter (ADC) so as to be converted into digital quantity.

The digital programmable chip DPD and its peripheral interface circuits include a DPD chip and a bus isolator in communication with the ADC, DAC (or RDAC) described above. The DPD chip is provided with an on-chip hardware interface or a functionally equivalent interface by writing a firmware program, so that the DPD chip can send instructions for setting current and output voltage of a programmable power module (or a conversion circuit) to each DAC through an element-level bus and a related isolator, and acquire N-MOSFET drain voltage data acquired by the ADC through the element-level bus and the related isolator; in addition, DPD can exchange data with an upper computer through a serial communication interface to obtain the drain voltage of the N-MOSFET after the linear current source is enabled to work, and the current of the linear current source or the duty ratio of a PWM dimming signal is set.

Wherein the linear current source circuit is configured as a circuit constructed according to the framework of the utility model patent of a programmable current source circuit (grant publication number CN 216210707U), and its main components include an N-channel enhancement type field effect transistor (N-mosfet) for current adjustment, a low-side current sampling resistor, a digital-to-analog converter DAC1 for setting a current value, and an analog switch for enabling/disabling the operation of the current source circuit;

the N-MOSEFT drain voltage acquisition circuit is configured to send an instruction to the analog-to-digital converter ADC through the on-chip bus interface CBI0 and the related bus isolator BISO0 of the digital programmable device DPD, so that the ADC acquires the drain voltage VD of the N-MOSEFT under the condition that working current flows through an electric load;

a power module (or conversion circuit) with a programmable output voltage, configured to send an instruction for changing its output analog quantity (or changing the output resistance value of a digital rheostat) to the digital-to-analog converter DAC2 through the on-chip bus interface CBI2 and the related bus isolator BISO2 of the DPD, so as to change the voltage value of the adjustment terminal pin (or the electrical node of the output voltage adjustment function) of the power module (or the conversion circuit) relative to the output ground pin thereof, and finally achieve the goal of changing the output direct current voltage of the power module (or the conversion circuit);

the integrated power management and control circuit is configured to receive an instruction of the upper computer UC through the serial communication interface SCI and the related external bus on the DPD chip, so as to start or disable the linear current source circuit, set the current value of the current source circuit and the like, and upload key information such as the drain voltage of the N-MOSEFT, whether an open circuit fault occurs in an electricity load during the working period of the current source circuit and the like to the UC.

In some embodiments, the DPD has on-chip hardware units to support on-chip bus interfaces CBI0, CBI1, CBI2 to communicate with the on-board chip and SCI to send and receive asynchronous data to and from the UC through the external bus, or by programming firmware programs to have various interface functions to communicate with the corresponding ADC, DAC1, DAC2, and UC, respectively.

In some embodiments, the power module (or the conversion circuit) with the output direct-current voltage being adjusted in a programmable manner is provided with a voltage adjustment pin (or an electrical external node), when the voltage value (or the resistance value) of the pin (or the node) relative to the output voltage negative end of the power module (or the conversion circuit) changes, the output voltage value of the power module (or the conversion circuit) changes, and the pin (or the node) has a one-to-one correspondence with the output voltage value.

In some embodiments, DPD changes the corresponding analog output voltage value (or resistance value) through DAC2 (or RDAC), and the maximum voltage value output by the programmable dc output power module (or conversion circuit) is greater than the sum of the voltage required by the electrical load to operate under its rated current condition, the minimum voltage drop of the N-MOSFET regulator operating in the corresponding constant current region, and the voltage drop of the low-side current sampling resistor.

On the premise of knowing an N-MOSFET output characteristic curve and learning a linear current source enabling/disabling control time sequence, reading a drain voltage value of an N-MOSFET of the current source by an ADC (analog-digital converter) through a CBI0 and a related bus, and sending an instruction for changing an output voltage of a programmable regulated DC output power supply module (or a conversion circuit) to a DAC (digital-to-analog converter) 2 through a CBI2 according to the drain voltage value of the current source, wherein the voltage drop of the N-MOSFET is ensured to be slightly larger than a minimum voltage drop required by a transistor constant current region corresponding to the working current; when DPD sends a command for changing the current of the current source to DAC1 through CBI1, it may be necessary to change the output voltage of the dc output power module (or the conversion circuit) first, and after the standby electric load stably works under the new current value condition, the output voltage of the dc output power module (or the conversion circuit) is adjusted according to the same control method until the voltage drop of the N-MOSFET is slightly greater than the minimum voltage drop required by the current source corresponding to the transistor constant current region.

The linear current source circuit has the following technical advantages: 1. by means of the N-MOSFET drain voltage acquisition circuit and related control algorithm, the power consumption load can be ensured to be controlled under the required current (I _SET ) On the premise of compressing the drain voltage as much as possible, different currents required by an electric load can be ensured under various temperature conditions, so that the electric energy conversion rate and the environmental adaptability of the circuit are greatly improved, and the working reliability of the N-MOSFET is further improved. 2. The element-level bus isolator is used for electrically isolating power supply ground (analog ground) from digital ground and serial port ground from digital ground, and has good electromagnetic compatibility and man-machine safety. 3. The digital programmable device is adopted, so that the testability, the function expandability and the information interaction capability of the whole circuit are greatly improved.

Example 2

Fig. 1 is a schematic block diagram of the present utility model, which can be functionally divided into four components, including a programmable linear current source circuit 100, an output dc voltage programmable power module and its control circuit 200, a current regulator N-MOSFET drain voltage acquisition circuit 300, a digital programmable chip DPD and its peripheral interface circuit 400. Further details of these circuits may be illustrated and described in connection with the embodiments herein.

The programmable linear current source circuit 100 comprises an N-MOSFET (corresponding to NCE6080K type FET V1 of FIG. 2), a sampling resistor R connected in series between the source of the transistor and analog ground AGND _SEN (corresponding to the resistor R5 of 0.5 ohm in FIG. 2), an electrical load (corresponding to the string of six LEDs in FIG. 2) connected in series between the positive pole of the DC output voltage source (corresponding to the electrical network PWR+ in FIG. 2) and the drain of the transistor, aCurrent I required for stable control of electric load _SET A digital-to-analog converter DAC1 for setting the current and an analog switch for turning on and off the current source circuit (the structure, the operation principle, etc. of the unit circuit are identical to those of the utility model patent of a programmable current source circuit). From the output characteristic curve of NCE6080K type N-MOSFET shown in FIG. 3, the lowest tube voltage drop corresponding to the 10A constant current curve is only about 0.5V, so that it can be deduced that: when the LED string is operated at the maximum current of 3A, the transistor can be completely operated in a constant current region when the transistor has a voltage drop of 0.5V.

The dc output voltage programmable circuit 200 includes a dc output voltage programmable power module (corresponding to the V24C24T100BL power module N1 in fig. 2) and a digital-to-analog converter DAC2 (corresponding to the model number MS5221M in fig. 2). The DAC2 receives an instruction from the DPD (corresponding to the model STM32F103CBT6 in fig. 2) through the element-level bus 2 (SPI is used in fig. 2) to change the analog voltage value output by the DAC (in fig. 2, the voltage adjustment pin of the power module N1 is directly connected to the analog output terminal of the MS 5221M). In addition, if the electromagnetic interference of the power module to the 100 circuit units needs to be reduced, a 0 ohm resistor (or magnetic beads), a common mode inductor, a pi type filter network and the like can be used for isolating and filtering the Power Ground (PGND) of the power module and the Analog Ground (AGND) of the 100 circuit units; if the EMC performance of the power supply module is good, the PGND and the AGND can be directly connected.

The N-MOSFET drain voltage acquisition circuit 300 includes two operational amplifiers OPA1 and OPA2 (corresponding to model LTA8092 in FIG. 2), a regulator V2 (corresponding to model 1N4681 in FIG. 2), and a current limiting resistor R _Z (corresponding to the resistor R8 in fig. 2, the resistance value is 1kΩ) and an analog-to-digital converter ADC (corresponding to the model AD7980BRMZ in fig. 2). Wherein OPA1 voltage-buffers the drain voltage of N-MOSFET, and outputs to voltage stabilizing tube V2 and a current limiting resistor R _Z The cathode voltage of V2 is buffered by OPA2 and then connected to the analog input end of ADC, so that the analog voltage value collected by ADC will not be higher than the highest allowable analog voltage value (in terms of V _SAmax Marking). Here, since the 100-cell circuit has a high N-MOSFET drain voltage (e.g., near V) _out ) And N-MOSFET drain voltage (in V) when 100 cell circuit is loaded with current _Dnom Marker) is low, so the type selection of the V2 tube must ensure that its regulated voltage is higher than V _Dnom And is lower than the maximum analog voltage value V allowed by ADC _SAmax The method comprises the steps of carrying out a first treatment on the surface of the When the model of OPA1 and OPA2 is selected, the model can be ensured to work normally under the condition of the supply voltage higher than the maximum value of the drain voltage of the N-MOSFET; in addition, the model of ADC, OPA1 and OPA2 is chosen to ensure that it has a reasonable signal processing speed, i.e. V can be set in a sufficiently short time after the 100 unit circuit has started and stably controlled the current required by the load _Dnom Converted into digital signals (information).

The digital programmable chip DPD and its peripheral interface circuit 400 includes an MCU (corresponding to the MCU in fig. 2), a bus isolator 0 (corresponding to the model CA-IS3641HW in fig. 2) capable of communicating with the component level bus (shown as SPI bus in fig. 2) of the ADC in the 300 unit circuit, a bus isolator 2 (corresponding to the model CA-IS3640HW in fig. 2) capable of communicating with the component level bus of the DAC2 in the 200 unit circuit, a bus isolator 1 capable of communicating with the component level bus of the DAC1 in the 100 unit circuit, and a serial data transceiver (corresponding to the model CA-IS2092W in fig. 2) capable of communicating with the host computer UC. The buses and the related isolators function to realize data communication under the condition of electric isolation between the digital DGND corresponding to DPD and the analog AGND (or the power source PGND) corresponding to the 100, 200 and 300 unit circuits respectively, so that the DPD can send instructions for setting corresponding analog voltages to DAC1, DAC2 (or RDAC) and acquire N-MOSFET drain voltage V through the ADC _Dnom A value of the parameter. It should be noted that these buses may be either physically separate buses (i.e., three groups of buses each lead from the MCU pins) or a group of buses that can be addressed independently (as shown in fig. 2, only one group of SPI's is used, but each has a corresponding chip select signal pin). As for the communication between the upper computer and the MCU, the MCU can be used for the key parameters of the circuit related to the utility model, such as V _Dnom Value etcUploading the current to UC, and can also carry out the current (I) required by the power load on a 100-unit circuit _SET ) Is set to perform integrated power management for the circuit.

Example 3

As shown in fig. 4, the present utility model provides a method for controlling the operation of the high conversion efficiency linear current source circuit according to any one of the above, comprising the steps of:

initializing and setting current I required by an electric load _SET ；

judging whether the drain voltage of the collected N-MOSFET is within a preset range; if the collected drain voltage of the N-MOSFET is lower than the preset range, the output voltage of the direct-current output voltage programmable power module is increased through the second digital-to-analog converter DAC2, and the drain voltage of the N-MOSFET is collected again to continue judging; if the collected drain voltage of the N-MOSFET is higher than the preset range, reducing the output voltage of the direct-current output voltage programmable power module through a second digital-to-analog converter DAC2, and collecting the drain voltage of the N-MOSFET again for continuous judgment; if the collected drain voltage of the N-MOSFET is within the preset range, judging whether the current I required for updating the power load is received _SET Instructions of (2); the preset range is based on the N-MOSFET maintaining current I _SET Determining the sum of the minimum voltage drop required by the constant current area and the voltage drop on the current sampling resistor;

if receiving the current I required by updating the electric load _SET Instructions of (2); when a new current I _SET If the output voltage is larger than the original value, the output voltage of the direct-current output voltage programmable power supply module is adjusted to the maximum value through the second digital-to-analog converter DAC2; when a new current I _SET Less than the original value, the drain voltage of the N-MOSFET is collected again and continuesAnd (5) judging.

As shown in fig. 3, when the output characteristic curve of the NCE6080K type N-MOSFET shown in fig. 3 is examined, if the transistor voltage drop reaches 0.5V, the transistor has a necessary condition to operate at a constant current of 10A. Therefore, for the embodiment shown in FIG. 2, it is ensured that the drain voltage VD of the current source circuit is slightly greater than (0.5+I) during operation _SET ·R _SEN ) V is sufficient, i.e., (0.5+3 x 0.5) V. Therefore, if the LED string is operated at the rated current of 3A, the optimum operation state can be realized by controlling the VD voltage value to about 2.05V.

It should be noted that, the voltage value slightly larger than the above value can be set according to the actual requirement, and in this embodiment is 0.05V.

In summary, the present utility model provides these physical and implementation advantages when used to configure specific circuits: the linear current source circuit is easy to develop and debug; the output direct-current voltage programmable module (or conversion circuit) adopted in the circuit is easy to obtain and purchase, such as 'Micro' series isolated DC-DC module products such as Vicor company; one ADC, two DACs and related bus isolators and N-MOSFETs are used, a large number of models are available for selection, and the supply chain is stable; the performance index requirement on the digital programmable device is not high, and if the MCU is adopted as the digital programmable device, the digital programmable device has the advantages of low power consumption, low cost and high product development speed.

It should be noted that each step/component described in the present application may be split into more steps/components, or two or more steps/components or part of the operations of the steps/components may be combined into new steps/components, as needed for implementation, to achieve the object of the present utility model.

While a particular embodiment of the utility model has been described, those skilled in the art will appreciate that there are other embodiments equivalent to the described embodiments. Thus, the present utility model should not be construed as being limited to the embodiments shown. The utility model is defined by the scope of the claims.

Claims

1. The circuit is characterized by comprising a programmable linear current source circuit, an output direct-current voltage programmable power module and a control circuit thereof, a current adjusting tube N-MOSFET drain voltage acquisition circuit, a digital programmable chip DPD and a peripheral interface circuit thereof;

the digital programmable chip DPD and the peripheral interface circuit thereof comprise the digital programmable chip DPD; the digital programmable chip DPD is connected with the first digital-to-analog converter DAC1 through a bus isolator, and the current I required by the electric load is set by setting the output voltage of the first digital-to-analog converter DAC1 _SET The method comprises the steps of carrying out a first treatment on the surface of the The digital programmable chip DPD is also connected with a drain voltage acquisition circuit of the current adjusting tube N-MOSFET through a bus isolator and is used for acquiring the current I _SET The drain voltage VD of the N-MOSFET under conditions; the digital programmable chip DPD is also connected with the second digital-to-analog converter DAC2 through another bus isolator to regulate the output voltage of the DC output voltage programmable power supply moduleThe voltage is regulated to the voltage required by the electric load, and finally the obtained voltage VD is slightly higher than the N-MOSFET maintaining current I _SET Corresponding to the sum of the minimum tube voltage drop required by the constant current area and the voltage drop on the current sampling resistor.

2. The high conversion efficiency linear current source circuit according to claim 1, wherein the current adjusting tube N-MOSFET drain voltage acquisition circuit comprises a first operational amplifier OPA1, a second operational amplifier OPA2, a voltage stabilizing tube V2, and a current limiting resistor R _Z And an analog-to-digital converter ADC; the non-inverting input end of the first operational amplifier OPA1 is connected with the drain electrode of the N-MOSFET, the inverting input end of the first operational amplifier OPA1 is connected with the output end of the first operational amplifier OPA1, and the output end of the first operational amplifier OPA1 is connected with the output end of the first operational amplifier OPA1 through a current-limiting resistor R _Z The digital port of the analog-to-digital converter ADC is connected with the digital programmable chip DPD through a bus isolator, and the negative electrode of the voltage stabilizing tube V2 is connected with the non-inverting input end of the second operational amplifier OPA2 and the positive electrode is grounded.

3. The high conversion efficiency linear current source circuit of claim 2, wherein the regulated value of the regulated voltage tube V2 is higher than the maximum value of the drain voltage of the programmable linear current source circuit when the load current passes through the N-MOSFET tube and lower than the highest input analog voltage value allowed by the analog-to-digital converter ADC.

4. The high conversion efficiency linear current source circuit according to claim 2, wherein the first operational amplifier OPA1 and the second operational amplifier OPA2 are operable normally under a supply voltage condition higher than a drain voltage maximum of the N-MOSFET transistor.

5. The high conversion efficiency linear current source circuit of claim 1, wherein the digital programmable chip DPD is further connected to an analog switch through a digital level isolator, the programmable linear current source circuit being turned on and off by the analog switch.

6. The high conversion efficiency linear current source circuit according to claim 1, wherein the digital programmable chip DPD and its peripheral interface circuit further comprises a host computer UC; the upper computer UC communicates with the digital programmable chip DPD through a serial communication interface to set key parameters including current I _SET Meanwhile, the digital programmable chip DPD uploads relevant information to the upper computer UC to realize monitoring, and the relevant information comprises voltage VD.

7. The high conversion efficiency linear current source circuit of claim 1, wherein the N-MOSFET transistor is selected based on the following criteria and characteristics:

8. The high conversion efficiency linear current source circuit according to claim 1, wherein the second digital-to-analog converter DAC2 is replaced by a digital varistor, thereby realizing the output voltage adjusting function of the dc output voltage programmable power supply module as well.

9. An operation control method of the high conversion efficiency linear current source circuit according to any one of claims 1 to 8, comprising the steps of:

initializing and setting current I required by an electric load _SET ；

judging whether the collected drain voltage of the N-MOSFET is within a preset range; if the collected drain voltage of the N-MOSFET is lower than the preset range, the output voltage of the direct-current output voltage programmable power module is increased through the second digital-to-analog converter DAC2, and the drain voltage of the N-MOSFET is collected again to continue judging; if the collected drain voltage of the N-MOSFET is higher than the preset range, reducing the output voltage of the direct-current output voltage programmable power module through a second digital-to-analog converter DAC2, and collecting the drain voltage of the N-MOSFET again for continuous judgment; if the collected drain voltage of the N-MOSFET is within the preset range, judging whether the current I required for updating the power load is received or not _SET Instructions of (2);

10. The operation control method of a high conversion efficiency linear current source circuit according to claim 9, wherein the preset range is based on an N-MOSFET holding current I _SET The sum of the minimum tube voltage drop required by the constant current area and the voltage drop on the current sampling resistor is determined.