CN1848577A - overcurrent protection circuit - Google Patents

Abstract

A over current protective circuit consists of current sampling circuit connected to power supply and load for outputting the sampling voltage value of sampling current, control unit for confirming reference voltage value according to over current valve value, voltage output circuit connected to control unit for outputting reference voltage value confirmed by control unit and voltage comparator for comparing the sampling voltage value with reference voltage value and for being used to output over current signal to indicate power supply switch to switch power off when sampling voltage value is greater then reference voltage value.

Description

Current foldback circuit

Technical field

The present invention relates to the circuit design technique field, relate in particular to a kind of current foldback circuit.

Background technology

In the traditional circuit technical field, current foldback circuit is a kind of a kind of circuit that can protect entire circuit under the excessive situation of the electric current of flowing through.

Please refer to Fig. 1, this figure is the application principle block diagram of existing current foldback circuit; The main effect of current foldback circuit 10 is the output currents that detect power supply among the figure, when detecting the electric current of flowing through above the predetermined electric current threshold values, closes automatically or deenergization.

Come in and with reference to Fig. 2, and this figure is the circuit theory composition frame chart of existing current foldback circuit; Traditional current foldback circuit is mainly finished overcurrent protection work jointly by following three functional units:

Current sampling circuit 101, one end is connected with power supply, the other end is connected with load, be used for being responsible for current value is sampled, usual way is at resistance of power output end series connection, because the voltage (being sampled voltage) and the electric current of this series resistance of flowing through at these series resistance two ends are directly proportional: (I is the current value of this series resistance of flowing through to U=IR, R is the resistance value of this series connection, U is the magnitude of voltage at this series resistance R two ends, be sampled voltage), therefore this magnitude of voltage that obtains just can be used as the sampled value of electric current;

Voltage comparator 102, the sample voltage value and the reference voltage level that are used forcurrent sampling circuit 101 is obtained compare, the output termination mains switch ofvoltage comparator 102 wherein, the signal of its output output is the overcurrent index signal, this signal flows to mains switch with as power switch signal.When the electric current of thecurrent sampling circuit 101 of flowing through increases; its sampled voltage that obtains increases; when sample voltage value during greater than reference voltage level, the overcurrent index signal ofvoltage comparator 102 outputs effectively and trigger the mains switch power cutoff, to reach the effect of entire circuit being carried out overcurrent protection.

Wherein, make the minimum sample rate current value ofvoltage comparator 102 output overcurrent index signals be referred to as the overcurrent threshold values.

Reference voltage source 103 can produce or employing dedicated reference voltage source (voltage source that promptly has fixed voltage value) by electric resistance partial pressure, provides reference voltage level to be used tovoltage comparator 102.

Above-mentioned current foldback circuit of the prior art can only could realize setting different overcurrent threshold values by the reference voltage level that adjustingreference voltage source 103 provides, promptly when needs are adjusted the overcurrent threshold values, can only could realize by the reference voltage level that modificationreference voltage source 103 provides, therefore be not suitable for being applied in the application scenario that needs often to revise the overcurrent threshold values, the application scenario that wherein needs often to revise the overcurrent threshold values refers to the occasion that load often changes, so that different overcurrent threshold values need be set according to different loads; As the lowest high-current value that can allow to pass through when load is 1 ampere-hour, and overcurrent threshold values that can current foldback circuit is set to 1 ampere; When changing a bigger load, its lowest high-current value that can allow to pass through is 2 ampere-hours, just the overcurrent threshold values of current foldback circuit need be revised as 2 amperes.

Summary of the invention

The technical problem to be solved in the present invention is to provide a kind of can be applied in the current foldback circuit that needs often to revise overcurrent threshold values application scenario.

For addressing the above problem, the technical scheme that the present invention proposes is as follows:

A kind of current foldback circuit comprises:

The current sampling circuit that connects power supply and load respectively is used for the electric current of the load of flowing through is sampled, and the sample voltage value of output sample rate current;

Control unit is used for determining reference voltage level according to the overcurrent threshold values that the load that current sampling circuit connects can bear;

The voltage follower circuit that is connected with control unit is used for the reference voltage level output that control unit is determined; With

Voltage comparator is used for the sample voltage value of current sampling circuit output and the reference voltage level of voltage follower circuit output are compared, and when sample voltage value is higher than reference voltage level, output overcurrent index signal indication mains switch power cutoff.

Wherein said current sampling circuit is the resistance that is connected on power output end.

Wherein said control unit specifically comprises:

The reference voltage level computation subunit is used for overcurrent threshold values that the load that current sampling circuit connects be can bear and the resistance value that is connected on power output end and multiplies each other, and obtains described reference voltage level;

The indication subelement is used to the reference voltage level output of indicating voltage follower circuit that the reference voltage level computation subunit is calculated.

Wherein said voltage follower circuit is a digital to analog converter; The control port of described digital to analog converter is connected with control unit, and output port is used for the output reference voltage value.

The beneficial effect that the present invention can reach is as follows:

The overcurrent threshold values that current foldback circuit of the present invention can bear by the load that will adopt electric resistance partial pressure or dedicated reference voltage source to provide the mode of reference voltage level to change in traditional current foldback circuit to be connected according to current sampling circuit by control unit is dynamically adjusted and is determined reference voltage level; and export to voltage comparator by the reference voltage level that voltage follower circuit is determined control unit; compare the sample voltage value of current sampling circuit output and the reference voltage level of voltage follower circuit output by voltage comparator; determining whether sending the overcurrent index signal, thereby reach the purpose of entire circuit being carried out overcurrent protection to mains switch.Because current foldback circuit of the present invention can connect the adjustment reference voltage level of the overcurrent threshold values dynamic flexible that load can bear according to current sampling circuit by control unit, therefore is applicable to because the frequent conversion of load needs causes taking the application scenario of normal modification overcurrent threshold values.

Description of drawings

Fig. 1 is the application principle block diagram of existing current foldback circuit;

Fig. 2 is the circuit theory composition frame chart of existing current foldback circuit;

Fig. 3 is the main composition structured flowchart of current foldback circuit of the present invention;

Fig. 4 forms structured flowchart for a kind of embodiment of current foldback circuit of the present invention;

Fig. 5 is the application principle block diagram of current foldback circuit of the present invention.

Embodiment

Design aim of the present invention provides a kind of different overcurrent threshold values that can bear according to different loads; by software flexible control adjust in requisition for the current foldback circuit of reference voltage level, to be applicable to because the frequent transformation load of needs causes taking the application scenario of normal modification overcurrent threshold values.

Be explained in detail below in conjunction with the specific implementation process of each accompanying drawing current foldback circuit of the present invention; please refer to Fig. 3; this figure is the main composition structured flowchart of current foldback circuit of the present invention; its chief component comprisescurrent sampling circuit 101,voltage comparator 102,control unit 1031 and 1,032 four parts of voltage follower circuit, the concrete function of each part and act on as follows:

Current sampling circuit 101 is connected with load with power supply respectively, and the electric current that is mainly used in the load of flowing through carries out sampling processing, and according to the linear relationship of electric current and voltage, the sample voltage value of output sample rate current; Wherein thiscurrent sampling circuit 101 can be by realizing at resistance of power output end series connection.

Control unit 1031 is mainly used in the overcurrent threshold values that the load that connects according tocurrent sampling circuit 101 can bear and determines reference voltage level flexibly; Whereincontrol unit 1031 can be realized by the software in the system control cpu, promptly the resistance value of the control unit of being realized bysoftware 1031 overcurrent threshold values that can bear according to the load thatcurrent sampling circuit 101 connects and power output end series connection is determined the reference voltage level of the overcurrent threshold values that can bear corresponding to load, and the reference voltage level of determining exported tovoltage comparator 102, whether surpass the comparison judgement basis of the overcurrent threshold values that load can bear with the electric current of the load of determining asvoltage comparator 102 to flow through.

Voltage follower circuit 1032 is connected withcontrol unit 1031, is mainly used in the reference voltage level thatcontrol unit 1031 is determined and exports tovoltage comparator 102; Whereinvoltage follower circuit 1032 can adopt digital to analog converter (DAC, Digital-Analog Converter) to realize.

Voltage comparator 102; being used for the sample voltage value (sample voltage value is from "+" utmost point input of voltage comparator 102) tocurrent sampling circuit 101 output and the reference voltage level (reference voltage level is imported from "-" utmost point of voltage comparator 102) ofvoltage follower circuit 1032 outputs compares; and relatively drawing when being higher than reference voltage level from the input of "-" utmost point from the sample voltage value of "+" utmost point input; the output overcurrent index signal is given mains switch; with indication mains switch power cutoff, reach the purpose of entire circuit being carried out overcurrent protection.

Please refer to Fig. 4, this figure is that a kind of embodiment of current foldback circuit of the present invention is formed structured flowchart, and wherein the concrete composition structure of this execution mode is as follows:

Current sampling circuit 101 is responsible for the current value of the load of flowing through is sampled, and method commonly used is exactly that wherein the voltage with these series resistance two ends outputs tovoltage comparator 102 at the power output end resistance of connecting, with as sample voltage value.

Voltage comparator 102, wherein thisvoltage comparator 102+/-input in, the output of a terminationcurrent sampling circuit 101 is with the sample voltage value of receivedcurrent sample circuit 101 output; The output of one termination digital to analog converter (DAC, Digital-Analog Converter) 1033 is to receive the reference voltage level ofDAC 1033 outputs; The output of thisvoltage comparator 102 connects the power switch circuit of power supply; Relatively draw from the sample voltage value of "+" utmost point input greater than the time whenvoltage comparator 102 like this from the reference voltage level of "-" utmost point input;voltage comparator 102 is given power switch circuit with the output overcurrent index signal; indication power switch circuit power cutoff; so that entire circuit is carried out overcurrent protection, prevent load owing to flow through electric current when being higher than the overcurrent threshold values that self can bear and the phenomenon of being burnt occurs.Here requirevoltage comparator 102 will have higher response speed.

Digital toanalog converter DAC 1033, its control portaccess control unit 1031, output port connects "-" utmost point ofvoltage comparator 102, and thisDAC 1033 is controlled by the reference voltage level ofoutput control unit 1031 indicated outputs.

Control unit 1031 can be realized by software is set in system control cpu, specifically comprises reference voltagelevel computation subunit 1035 andindication subelement 1034, wherein:

Reference voltagelevel computation subunit 1035, be mainly used in overcurrent threshold values I that load thatcurrent sampling circuit 101 is connected can bear and the resistance value R that is connected on power output end and multiply each other, to obtain reference voltage level U the overcurrent threshold values I that should load can bear;

Indication subelement 1034, the reference voltage level U that is used for reference voltagelevel computation subunit 1035 is calculated sends toDAC 1033, andDAC 1033 exports tovoltage comparator 102 with reference voltage level from output port with indication.

To sum up, just can realize exporting the corresponding reference magnitudes of voltage according to the different DAC of control flexibly 1033 thatcurrent sampling circuit 101 connects load, to realize being provided with flexibly the purpose of different reference voltage levels according to the unequally loaded situation by the software in the system control cpu.Wherein the degree of regulation of reference voltage level and DAC choose relevant.

See also Fig. 5; this figure is the application principle block diagram of current foldback circuit of the present invention; current foldback circuit of the present invention as shown in the figure can be according to connecting different loading conditions; realize being provided with flexibly the reference voltage level of the overcurrent threshold values that corresponding different loads can bear by the software that is provided with in the system control cpu; can play overcurrent protection preferably to the circuit that often needs transformation load, when guaranteeing that different loads can not be higher than the overcurrent threshold values that load can bear because of the electric current of flowing through and be damaged.Current foldback circuit wherein of the present invention can be applied on the equipment such as various power supplys, instrument; and the overcurrent threshold values that can bear according to different loads is provided with different reference voltage levels; and need not revise any circuit hardware, only need can realize by software setting.

Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.

Claims (4)

Translated fromChinese

1、一种过流保护电路，其特征在于，包括：1. An overcurrent protection circuit, characterized in that, comprising:分别连接电源和负载的电流采样电路，用于对流经负载的电流进行采样，并输出采样电流的采样电压值；The current sampling circuit connected to the power supply and the load respectively is used to sample the current flowing through the load and output the sampling voltage value of the sampling current;控制单元，用于根据电流采样电路连接的负载所能承受的过流阀值确定参考电压值；The control unit is used to determine the reference voltage value according to the overcurrent threshold that the load connected to the current sampling circuit can withstand;与控制单元连接的电压输出电路，用于将控制单元确定的参考电压值输出；和a voltage output circuit connected to the control unit, for outputting the reference voltage value determined by the control unit; and电压比较器，用于对电流采样电路输出的采样电压值和电压输出电路输出的参考电压值进行比较，并在采样电压值高于参考电压值时，输出过流指示信号指示电源开关关断电源。The voltage comparator is used to compare the sampling voltage value output by the current sampling circuit with the reference voltage value output by the voltage output circuit, and when the sampling voltage value is higher than the reference voltage value, output an overcurrent indication signal to instruct the power switch to shut down the power supply .2、如权利要求1所述的过流保护电路，其特征在于，所述电流采样电路为串联在电源输出端的电阻。2. The overcurrent protection circuit according to claim 1, wherein the current sampling circuit is a resistor connected in series at the output terminal of the power supply.3、如权利要求2所述的过流保护电路，其特征在于，所述控制单元具体包括：3. The overcurrent protection circuit according to claim 2, wherein the control unit specifically comprises:参考电压值计算子单元，用于将电流采样电路连接的负载所能承受的过流阀值和串联在电源输出端的电阻值相乘，得到所述参考电压值；The reference voltage value calculation subunit is used to multiply the overcurrent threshold value that the load connected to the current sampling circuit can withstand by the resistance value connected in series at the output terminal of the power supply to obtain the reference voltage value;指示子单元，用于指示电压输出电路将参考电压值计算子单元计算得到的参考电压值输出。The indication subunit is used to instruct the voltage output circuit to output the reference voltage value calculated by the reference voltage value calculation subunit.4、如权利要求1、2或3所述的过流保护电路，其特征在于，所述电压输出电路为数模转换器；所述数模转换器的控制端口与控制单元连接，并输出端口用于输出参考电压值。4. The overcurrent protection circuit according to claim 1, 2 or 3, wherein the voltage output circuit is a digital-to-analog converter; the control port of the digital-to-analog converter is connected to the control unit, and the output port Used to output the reference voltage value.

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