CN205176715U - Adopt CT to replace voltage control current source circuit of electric current sensing resistance - Google Patents

Abstract

The utility model discloses an adopt CT to replace voltage control current source circuit of electric current sensing resistance, combine large current output's characteristics to improve float load type and ground connection load type voltage control current source circuit topological structure, substitute traditional electric current sensing resistance through introducing the accurate CT of sampling, CT once inclines and directly concatenates in power op amp output return circuit, the secondary side is through switching through the feedback of trading resistance and carrying out voltage signal, unsteady load type and ground connection load type voltage control current source circuit have been eliminated because of the restriction of electric current sensing resistance to circuit current output ability to this kind of mode, avoided producing the consumption because of the electric current flows through electric current sensing resistance, thereby make voltage control electric current source efficiency improve greatly.

Description

A voltage-controlled current source circuit using CT instead of current sensing resistor

technical field

The utility model belongs to the design field of high-power power electronic circuits, and more specifically relates to a novel voltage-controlled current source (VCCS) circuit, which mainly completes the conversion from voltage to current and realizes the function of the voltage-controlled current source circuit.

Background technique

Voltage-controlled current source (VCCS for short) is widely used in the fields of high-power semiconductor component testing, motor torque control and power measurement. VCCS is used for characteristic testing of high-power semiconductor components, and mainly plays the role of excitation source; VCCS is used for motor torque control because the torque and motor current present a functional relationship, so it is relatively simple, and the use of current drive in the servo loop can reduce the The phase lag caused by the inductance of the motor improves the stability of the loop; while VCCS is used for power measurement and is mainly used in comparative current measurement systems, VCCS provides a reference or standard quantity for comparison with the measured current.

In the application of low-power VCCS, it is usually implemented by using operational amplifiers and voltage stabilizing circuit devices. The circuit is connected in a closed-loop control mode, and the test accuracy is high.

In the occasions that require a large power current source, power devices such as field effect transistors and Darlington transistors are generally used to realize the conversion of voltage to current, and open-loop control methods are mostly used, and the test accuracy is low.

The traditional VCCS circuit for floating load is shown in Figure 1. The feedback branch introduces negative feedback from the output terminal of the amplifier to the input terminal, where VIN is the input voltage, RS is the current sensing resistor, RF, Rd and Cf are two negative The resistance and capacitance on the feedback branch, the resistance RB is to prevent the non-inverting input signal from floating when the input voltage source is disconnected or turned into a high-impedance state during the power-on cycle. The amplifier loop gain will force the voltage across RS to a value equal to the voltage applied to the non-inverting input, resulting in the following transfer function of output current versus input voltage:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; V</span>}\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; S</span>}}$

A voltage-controlled current source implemented by an operational amplifier for a grounded load is shown in Figure 2, and it is actually a different type of amplifier that senses the input signal and the feedback signal differentially, where VIN is the input voltage, R1 is the input resistor, and the two RF resistors respectively complete the positive feedback and negative feedback of the input signal from both ends of the sensing resistor. When RS<<RF or R1, the following transfer function can be generated:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; V</span>}\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; N</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 1</span>}\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; S</span>}}$

Since the above-mentioned floating load and ground load type voltage control current source circuit topologies both use _RS as the current sensing resistor and perform feedback control of the current output, the output current flows directly through the current sensing resistor RS. When the output current is large, The loss and heat generated on RS reduce the conversion efficiency of the VCCS circuit and directly affect the safe and reliable operation of the VCCS. If you choose a current sensing resistor with a very low resistance value, you can theoretically reduce the loss on the resistor, but from the current resistor manufacturing process, the accuracy of the low resistance value (less than 0.1 ohm) resistor is difficult to guarantee, so VCCS The accuracy of the voltage conversion current is difficult to be guaranteed.

Utility model content

In order to solve the technical problems of the above-mentioned voltage-controlled current source, reduce the power loss of the current sensing resistor, and improve the voltage-current conversion accuracy of high-power VCCS, the utility model proposes a new type of voltage-controlled current source circuit, the specific scheme as described below.

A voltage-controlled current source circuit using CT instead of a current sensing resistor, characterized in that it includes a power operational amplifier, a sampling CT and a conversion resistor, the primary side of the sampling CT is directly connected in series with the output circuit of the power operational amplifier, and the secondary side of the sampling CT The secondary side is connected to a switching resistor, one end of the switching resistor is grounded, and the other end of the switching resistor is connected to a power operational amplifier through a feedback resistor for voltage signal feedback.

The aforementioned voltage-controlled current source circuit that uses CT to replace the current sensing resistor is characterized in that: the floating load type voltage-controlled current source circuit includes a power operational amplifier A1, an input voltage VIN, a feedback resistor RF, and a conversion resistor RS , the grounding resistor RB and the sampling CT, the input voltage VIN is connected to the positive input terminal of the power operational amplifier A1, the positive input terminal of the power operational amplifier A1 is grounded through the grounding resistor RB, and the primary side of the sampling CT passes through the load directly Connected in series to the output end of the power operational amplifier A1, the other end of the primary side of the sampling CT is grounded, the secondary side of the sampling CT is connected to the switching resistor RS, one end of the switching resistor RS is grounded, and the other end of the switching resistor RS is fed back The resistor RF is connected to the inverting input terminal of the power operational amplifier A1.

The aforementioned voltage-controlled current source circuit that uses CT to replace the current sensing resistor is characterized in that: the grounded load type voltage-controlled current source circuit includes a power operational amplifier A2, an input voltage VIN, a feedback resistor RF, and a conversion resistor RS, Input resistance RI, sampling CT, the input voltage VIN is connected to the reverse input terminal of the power operational amplifier A2 through the input resistance RI, the positive input terminal of the power operational amplifier A2 is grounded through the input resistance RI, and one end of the primary side of the sampling CT Connected in series to the output end of the power operational amplifier A2, the other end of the primary side of the sampling CT is grounded through the load, the secondary side of the sampling CT is connected to the switching resistor RS, one end of the switching resistor RS is grounded, and the other end of the switching resistor RS It is connected to the inverting input terminal of the power operational amplifier A2 through the feedback resistor RF.

The aforementioned voltage-controlled current source circuit using CT instead of a current sensing resistor is characterized in that the power operational amplifier is a PA50 power operational amplifier.

The aforementioned voltage-controlled current source circuit that uses CT to replace the current sensing resistor is characterized in that: the sampling CT ratio is 1:n, and the power loss of the improved voltage-controlled current source circuit is equal to that of the traditional voltage-controlled current source circuit 1/n, where n is 100 or 1000.

The beneficial effects achieved by the utility model:

First, instead of the current sensing resistor, the sampling precision CT plus conversion resistor is directly connected in series to the output circuit of the power operational amplifier. The primary side of the sampling CT is directly connected in series to the output circuit of the amplifier, and the secondary side is connected to the conversion resistor. The feedback of the voltage signal is carried out at both ends of the conversion resistor, which avoids the contradiction in the selection of the current sensing resistor in the traditional voltage control current source circuit. At the same time, because the output circuit does not directly connect the resistor in series, when a large current flows, there will be no loss, which solves the problem. The traditional voltage-controlled current source circuit has a problem that the efficiency of the entire voltage-controlled current source is reduced due to the large power loss generated by the current sensing resistor.

Second, the introduction of sampling precision CT plus conversion resistance, one end of the sampling precision CT secondary side is grounded, and the other end is used for voltage signal feedback. Compared with the traditional floating load type voltage control current source circuit, the voltage control current source current is improved. The output capability improves the working efficiency of the voltage-controlled current source.

Third, the introduction of sampling precision CT plus conversion resistance, one end of the secondary side of the precision CT is grounded, and the other end is used for voltage signal feedback. Compared with the traditional grounded load-type voltage-controlled current source circuit, one feedback branch is reduced, simplifying the The circuit improves the current output capability of the voltage-controlled current source and improves the working efficiency of the voltage-controlled current source.

Description of drawings

Figure 1 is a floating load-type basic voltage-controlled current source circuit.

Figure 2 is a grounded load-type basic voltage-controlled current source circuit.

Figure 3 is a floating load-type voltage-controlled current source circuit that uses a precision CT instead of a current-sensing resistor.

Figure 4 is a voltage-controlled current source circuit that uses a precision CT instead of a current-sensing resistor grounded load.

detailed description

Below in conjunction with accompanying drawing, the utility model is further described. The following examples are only used to illustrate the technical solution of the utility model more clearly, but not to limit the protection scope of the utility model.

Refer to Figure 3, the precision CT is used to replace the current sensing resistor floating load type voltage control current source circuit, which is applied to the power system current test and the large current output is 10V/36A. A1 is the PA50 power operational amplifier, VIN is the input voltage, and RF is the feedback resistor , RS conversion resistance, the sampling CT in the dotted line box, the input voltage VIN is connected to the reverse input terminal of the power operational amplifier A2 through the input resistance RI, the positive input terminal of the power operational amplifier A2 is grounded through the input resistance RI, the One end of the primary side of the sampling CT is connected in series with the output end of the power operational amplifier A2, the other end of the primary side of the sampling CT is grounded through the load, the secondary side of the sampling CT is connected to a switching resistor RS, and one end of the switching resistor RS is grounded, and the The other end of the conversion resistor RS is connected to the inverting input end of the power operational amplifier A2 through the feedback resistor RF.

In the utility model, the primary side of the sampling CT is directly connected in series to the output circuit of the power operational amplifier, and the secondary side is connected to the switching resistor, and the voltage signal is fed back from both ends of the switching resistor. This voltage-controlled current source circuit adopts sampling CT+ conversion resistor instead of the current sensing resistor to be directly connected in series in the output circuit of the amplifier, which solves the problem of reducing the current due to the loss of the traditional floating load voltage-controlled current source circuit due to the large current flowing through the current sensing resistor. Compared with the technical problem of the working efficiency of the source, compared with the input-output relationship of the traditional floating load voltage-controlled current source circuit, it can be obtained: $I_o=\frac{\mathrm{no}VIN}{RS}.$

As long as the switching resistance RS in the improved circuit is n times the switching resistance of the traditional circuit, the current obtained from the output terminal of the circuit, that is, I ₀ , can be guaranteed to be equal, thereby improving the efficiency of the voltage control current source and ensuring The linear relationship between the input voltage and output current of the new voltage control current source improves the accuracy of the test.

Refer to Figure 4, the CT is used to replace the current sensing resistor grounded load-type voltage control current source circuit for component testing with a large current output of 10V/36A, A2 is the PA50 power operational amplifier, VIN is the input voltage, RF is the feedback resistor, RS Conversion resistance, RI is the input resistance, the sampling CT is inside the dotted line box, the input voltage VIN is connected to the reverse input terminal of the power operational amplifier A2 through the input resistance RI, and the positive input terminal of the power operational amplifier A2 is grounded through the input resistance RI , one end of the primary side of the sampling CT is connected in series with the output end of the power operational amplifier A2, the other end of the primary side of the sampling CT is grounded through the load, the secondary side of the sampling CT is connected to a switching resistor RS, and one end of the switching resistor RS is grounded , the other end of the switching resistor RS is connected to the inverting input end of the power operational amplifier A2 through the feedback resistor RF.

The primary side of the sampling CT is directly connected to the output circuit of the power operational amplifier, and the secondary side is connected to the conversion resistor. One end of the secondary side of the CT is grounded, and the other end is used for voltage signal feedback. This voltage-controlled current source circuit uses a sampling CT plus a conversion resistor instead of a current-sensing resistor to be directly connected in series in the output circuit of the amplifier, which simplifies the traditional grounded load-type voltage-controlled current source circuit and improves the work of the grounded-loaded voltage-controlled current source circuit. Efficiency is the same as the input-output relationship of the traditional floating load voltage-controlled current source circuit. As long as the switching resistance RS in the improved circuit is n times the switching resistance of the traditional circuit, the current obtained from the output terminal of the circuit, that is, I ₀ , can be guaranteed to be equal, thereby improving the efficiency of the voltage control current source and simplifying The traditional grounded load type voltage-controlled current source circuit is improved, and the current output capability of the voltage-controlled current source is improved.

The utility model adopts the precision CT to replace the voltage control current source circuit of the current sensing resistor. Since the sampling CT and the conversion resistor are directly connected in series in the output circuit of the power amplifier, there is no resistance in the output circuit to be directly connected in series, but indirectly sensed by the CT. A small current is used to realize the voltage feedback, which avoids the loss in the resistance caused by the large current flowing through the current sensing resistor in the classical voltage-controlled current source circuit. Due to the introduction of sampling CT, the utility model has the characteristics of simple circuit topology, low cost of voltage control current source, high working efficiency, high safety margin, good voltage input range and current output range, and good linearity. At the same time, the utility model provides a new design idea for the design of a high-current, high-power voltage-controlled current source.

The basic principles, main features and advantages of the present utility model have been shown and described above. Those skilled in the art should understand that the utility model is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions only illustrate the principle of the utility model. Without departing from the spirit and scope of the utility model, the utility model The new model also has various changes and improvements, and these changes and improvements all fall within the scope of the claimed utility model. The scope of protection required by the utility model is defined by the appended claims and their equivalents.

Claims (5)

1. A voltage-controlled current source circuit that adopts a CT to replace a current sensing resistor, is characterized in that: it comprises a power operational amplifier, a sampling CT and a conversion resistor, and the primary side of the sampling CT is directly connected in series in the output circuit of the power operational amplifier, and the sampling The secondary side of the CT is connected to a switching resistor, one end of the switching resistor is grounded, and the other end of the switching resistor is connected to a power operational amplifier through a feedback resistor for voltage signal feedback. 2. A voltage-controlled current source circuit that uses a CT instead of a current sensing resistor according to claim 1, wherein the floating-load voltage-controlled current source circuit includes a power operational amplifier A1, an input voltage VIN, and a feedback resistor RF, switching resistor RS, grounding resistor RB and sampling CT, the input voltage VIN is connected to the positive input terminal of the power operational amplifier A1, the positive input terminal of the power operational amplifier A1 is grounded through the grounding resistor RB, and the sampling CT is once One end of the side is directly connected in series with the output end of the power operational amplifier A1 through the load, the other end of the primary side of the sampling CT is grounded, the secondary side of the sampling CT is connected to the switching resistor RS, one end of the switching resistor RS is grounded, and the switching resistor The other end of RS is connected to the inverting input end of the power operational amplifier A1 through the feedback resistor RF. 3. A voltage-controlled current source circuit that uses a CT to replace a current sensing resistor according to claim 1, wherein the grounded load-type voltage-controlled current source circuit includes a power operational amplifier A2, an input voltage VIN, and a feedback resistor RF , conversion resistance RS, input resistance RI, sampling CT, the input voltage VIN is connected to the inverting input terminal of the power operational amplifier A2 through the input resistance RI, the positive input terminal of the power operational amplifier A2 is grounded through the input resistance RI, and the One end of the primary side of the sampling CT is connected in series with the output end of the power operational amplifier A2, the other end of the primary side of the sampling CT is grounded through the load, the secondary side of the sampling CT is connected to a switching resistor RS, and one end of the switching resistor RS is grounded, and the The other end of the conversion resistor RS is connected to the inverting input end of the power operational amplifier A2 through the feedback resistor RF. 4. A voltage-controlled current source circuit using a CT instead of a current sensing resistor according to claim 2 or 3, wherein the power operational amplifier is a PA50 power operational amplifier. 5. A voltage-controlled current source circuit using CT instead of a current sensing resistor according to claim 4, characterized in that: the sampling CT transformation ratio is 1:n, and the power loss of the improved voltage-controlled current source circuit is 1/n of the traditional voltage-controlled current source circuit loss, where n is 100 or 1000.