Adjustable constant current source power control circuit

Abstract

The embodiment of the invention discloses an adjustable constant current source power control circuit, which is used for controlling the power of an adjustable constant current power supply and comprises a voltage sampling circuit, a divider circuit and a voltage selection circuit, the voltage sampling circuit is connected with the adjustable constant current source and is used for acquiring a first voltage from the adjustable constant current source according to a preset proportionality coefficient; the divider circuit is connected with the voltage sampling circuit and is used for calculating and dividing according to a preset reference voltage and the first voltage to obtain a second voltage; the voltage selection circuit is formed by connecting a first voltage follower and a second voltage follower in parallel, the first voltage follower is connected with the divider circuit and used for following a second voltage, the second voltage follower is used for following a third voltage, and the third voltage is determined according to a preset value; a selective switch is formed between the first voltage follower and the second voltage follower, and the selective switch is used for selecting the output of the first voltage follower or the output of the second voltage follower to be connected to the adjustable constant current source. According to the technical scheme provided by the invention, tedious designs of other circuits such as a PWM pulse width detection circuit and a maximum pulse limiting circuit are omitted, and the circuit has the characteristics of simplicity and high efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of analog electronic technology, in particular to a power control circuit of an adjustable constant current source. BACKGROUND

[0002] Power control is one of the important functions of power supply products. For a power supply with fixed voltage output, power control can be achieved by limiting the maximum output current. For a power supply with fixed output current, power control can be achieved by limiting the maximum output voltage. However, for an adjustable constant current source with adjustable reference voltage and output current, power control cannot be achieved by limiting the maximum current or voltage.

[0003] In the prior art, an adjustable constant current source is usually combined with PWM control. Based on the reference voltage of the adjustable constant current source, the output current is adjusted by adjusting the duty cycle of the PWM. However, the PWM circuit structure is complex and is not conducive to engineering application. SUMMARY

[0004] In view of this, the purpose of the embodiments of the present application is to provide a power control circuit of an adjustable constant current source with a simple circuit structure to alleviate the existing technical problems.

[0005] According to some embodiments, the present application provides a power control circuit of an adjustable constant current source for controlling the power of an adjustable constant current power supply, comprising a voltage sampling circuit, a divider circuit and a voltage selection circuit. The voltage sampling circuit is connected to the adjustable constant current source and is used to collect a first voltage from the adjustable constant current source according to a preset proportion coefficient. The divider circuit is connected to the voltage sampling circuit and is used to calculate a second voltage by dividing the preset reference voltage and the first voltage. The voltage selection circuit is formed by connecting a first voltage follower and a second voltage follower in parallel. The first voltage follower is connected to the divider circuit and is used to follow the second voltage. The second voltage follower is used to follow a third voltage, and the third voltage is determined according to a preset value. A selection switch is formed between the first voltage follower and the second voltage follower, and the selection switch is used to select the output of the first voltage follower or the output of the second voltage follower to access the adjustable constant current source.

[0006] In one embodiment, the voltage sampling circuit comprises a first resistor, a second resistor and a first operational amplifier. The preset proportion coefficient is determined according to the size of the first resistor and the second resistor. One end of the first resistor and one end of the second resistor are connected to the non-inverting input terminal of the first operational amplifier, respectively. The other end of the first resistor is connected to the adjustable constant current source.

[0007] In one embodiment, the divider circuit comprises a multiplier and a second operational amplifier. The input terminal of the multiplier is connected to the output terminal of the second operational amplifier. The output terminal of the multiplier is connected to the inverting input terminal of the second operational amplifier.

[0008] In one embodiment, between the first voltage follower and the divider circuit, there is also a voltage dividing circuit for obtaining a fourth voltage from the second voltage in a preset ratio.

[0009] In one embodiment, the selection switch is one of a diode, a triode or a thyristor.

[0010] The embodiments of the present disclosure can have / at least have the following advantages. Through the voltage sampling circuit, the divider circuit and the voltage selection circuit, the voltage sampling circuit obtains the first voltage based on the reference voltage of the adjustable constant current source, the divider circuit converts the power control into voltage control through the division operation, and the voltage selection circuit selects the rated value and the set value of the adjustable constant current source power; the technical solution proposed in the present application realizes the method of directly using the adjustable constant current source output signal for power control, and eliminates the cumbersome design of other circuits such as the PWM pulse width detection circuit and the maximum pulse limiting circuit, and has the characteristics of simplification and efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a schematic diagram of the overall structure of an adjustable constant current source power control circuit according to an embodiment of the present application;

[0012] Figure 2 is a schematic diagram of a voltage sampling circuit in an adjustable constant current source power control circuit according to an embodiment of the present application;

[0013] Figure 3 is a schematic diagram of a divider circuit in an adjustable constant current source power control circuit according to an embodiment of the present application;

[0014] Figure 4 is a schematic diagram of a voltage selection circuit in an adjustable constant current source power control circuit according to an embodiment of the present application;

[0015] Figure 5 is a schematic diagram of the reference voltage and the first voltage curve of an adjustable constant current source power control circuit according to an embodiment of the present application;

[0016] Figure 6 is a schematic diagram of the second voltage curve of an adjustable constant current source power control circuit according to an embodiment of the present application. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the present application clearer and more comprehensible, the present application will be further described in detail below with reference to the specific embodiments and the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present application. In addition, in the following description, the description of the known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present application.

[0018] The layer structure diagrams according to the embodiments of the present application are shown in the drawings. The drawings are not necessarily drawn to scale, in which some details are exaggerated for clarity and some details are omitted. The shapes of various regions, layers shown in the drawings and their relative sizes and positional relationships are merely exemplary, and in actuality, they can be deviated due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes, relative positions can be additionally designed by those skilled in the art according to actual needs.

[0019] It is obvious that the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application. The present application will be described in more detail below with reference to the drawings. In each drawing, the same elements are denoted by similar reference numerals. Each part in the drawings is not drawn to scale for clarity.

[0020] Figure 1 is a schematic diagram of an overall structure of a power control circuit of a tunable constant current source according to an embodiment of the present application; Figure 2 is a schematic diagram of a voltage sampling circuit in a power control circuit of a tunable constant current source according to an embodiment of the present application;

[0021] Figure 3 is a schematic diagram of a divider circuit in a power control circuit of a tunable constant current source according to an embodiment of the present application;

[0022] Figure 4 is a schematic diagram of a voltage selection circuit in a power control circuit of a tunable constant current source according to an embodiment of the present application.

[0023] Reference is made to Figure 1 — Figure 4 , a power control circuit of a tunable constant current source is provided according to an embodiment of the present application, for controlling the power of a tunable constant current source, comprising a voltage sampling circuit, a divider circuit and a voltage selection circuit; the voltage sampling circuit is connected to the tunable constant current source, for collecting a first voltage from the tunable constant current source according to a preset proportionality coefficient; the divider circuit is connected to the voltage sampling circuit, for calculating a second voltage by dividing according to a preset reference voltage and the first voltage; the voltage selection circuit is formed by a first voltage follower and a second voltage follower in parallel, the first voltage follower is connected to the divider circuit, for following the second voltage, the second voltage follower is for following a third voltage, the third voltage is determined according to a preset value; a selection switch is formed between the first voltage follower and the second voltage follower, the selection switch is for selecting the output of the first voltage follower or the output of the second voltage follower to access the tunable constant current source.

[0024] Exemplarily, reference is made to Figure 1The adjustable constant current source can be a voltage-controlled constant current source, the output end of which is connected to a voltage sampling circuit, the voltage sampling circuit is connected to a divider circuit, the divider circuit is connected to a voltage selection circuit, the voltage selection circuit is connected to the control end of the adjustable constant current source, forming a power control loop of the adjustable constant current source; when the reference voltage output by the adjustable constant current source changes, it will also be transmitted to the control end of the adjustable constant current source through the above-mentioned loop, thereby forming a feedback control.

[0025] It should be noted that the voltage sampling circuit can isolate the adjustable constant current source and the divider circuit on the one hand, avoiding mutual interference; on the other hand, it can convert the high voltage of the adjustable constant current source into the input voltage allowed by the divider circuit. According to the calculation formula of power, voltage and current, under the condition of constant voltage, power and current are inversely proportional. Based on the reference voltage of the adjustable constant current source, the power regulation of the adjustable constant current source is realized by adjusting the current of the adjustable constant current source. Therefore, the role of the divider circuit is to convert the first voltage obtained by the voltage sampling circuit into the current control amount under the preset power.

[0026] In one embodiment, the voltage sampling circuit comprises a first resistor, a second resistor and a first operational amplifier, and the preset proportion coefficient is determined according to the size of the first resistor and the second resistor; one end of the first resistor and one end of the second resistor are respectively connected to the non-inverting input end of the first operational amplifier, and the other end of the first resistor is connected to the adjustable constant current source. Figure 2 The first resistor is an equivalent resistor formed by R1 and R2 in series, and the second resistor is R4; according to the virtual short-circuit principle of the operational amplifier, Vf = R4 / (R1+R2+R4) x Vout, wherein the preset proportion coefficient is R4 / (R1+R2+R4), Vout is the reference voltage output by the adjustable constant current source, and Vf is the voltage at the output end of the first operational amplifier, i.e. the first voltage output by the voltage sampling circuit. Exemplarily, as shown in Figure 2 R1 = 220KΩ, R2 = 220KΩ, R4 = 20.95KΩ, and if Vout is 220V, then Vf = 9.998V ≈ 10V.

[0027] Referring to Figure 3 In one embodiment, the divider circuit comprises a multiplier and a second operational amplifier, the input end of the multiplier is connected to the output end of the second operational amplifier, and the output end of the multiplier is connected to the inverting input end of the second operational amplifier. The multiplier and the second operational amplifier form a closed-loop feedback loop, and the reciprocal of the multiplication operation is used to form the division operation output. Exemplarily, as shown in Figure 3As shown, the multiplier chip is AD633J, with ports 1-4 used for input signals and port 7 used for output signals. According to the definition of a multiplier chip, V7 = -V12 × V34 / 10, where V7 is the output voltage at port 7, V12 is the voltage between ports 1 and 2, and V34 is the voltage between ports 3 and 4. Based on the principle of virtual short circuit in operational amplifiers, the current at the non-inverting and inverting input terminals of the second operational amplifier is 0, therefore V7 = VREF; Figure 3 It can be seen that V12 = Vf, V34 = VM3, therefore the second voltage

[0028] refer to Figure 1 In one embodiment, a voltage divider circuit is also present between the first voltage follower and the divider circuit to obtain a fourth voltage from the second voltage according to a preset ratio. For example, if R10 = R11 = 4.7KΩ, then V3 = R11 / (R10 + R11) × VM3, and the fourth voltage V3 = 0.5 × VM3.

[0029] In one embodiment, the selection switch is one of a diode, a transistor, or a thyristor. When the selection switch is on or off, the output of the first voltage follower or the output of the second voltage follower is respectively connected to an adjustable constant current source. For example, refer to... Figure 4 The third voltage, VG1, is adjustable based on the specific value of the sliding rheostat RS. When VG1 is less than V3, diode D1 is forward biased and in a conducting state, at which point the output of the voltage selection circuit VM2 = V3. When VG1 is greater than V3, diode D1 is reverse biased and in an open-circuit state, at which point the output of the voltage selection circuit VM2 = VG1. It should be noted that, in addition to diodes, transistors and thyristors also have similar conduction and open-circuit properties; therefore, diodes can be replaced with transistors or thyristors.

[0030] In one embodiment, the adjustable constant current source has a voltage protection value of 220V, an adjustable current output range of 0-8A, and a rated power of 880W. (Divider circuit calculation formula) VREF can be a fixed 5V voltage, and the value range of the third voltage VG1 is (0 to -5V), corresponding to an output current of 0-8A. For example, in the circuit, R11 = 4.7kΩ, R10 = 4.7kΩ, and the VM3 output should be (0 to -10V). When the adjustable constant current source Vout takes its maximum output of 220V, to achieve the rated power output of the power supply, the current should be I = 880W / 220V = 4A. At this time, the actual current given voltage value VM2 should be half of the full-scale range (-5V), which should be -2.5V. Correspondingly, V3 should be limited to -2.5V, and VM3 should be limited to -5V, according to... The calculated value is Vf = 10V. Therefore, the first resistor can be 440KΩ, and the corresponding values ​​are R1 = 220KΩ, R2 = 220KΩ, and the second resistor is R4 = 20.95KΩ.

[0031] Figure 5 This is a schematic diagram of the reference voltage and first voltage curve of an adjustable constant current source power control circuit according to an embodiment of this application.

[0032] When Vout is the maximum output of 220V, R1 = 220KΩ, R2 = 220KΩ, and the second resistor R4 = 20.95KΩ, as follows: Figure 5 As shown, Vout = 219.96V, Vf ≈ 10V.

[0033] Figure 6 This is a schematic diagram of the second voltage curve of an adjustable constant current source power control circuit according to an embodiment of this application.

[0034] refer to Figure 6 Based on the above embodiment, Vf≈10V, VREF=5V, according to the calculation formula Therefore, VM3≈-5V.

[0035] It should also be noted that, according to Vf = R4 / (R1 + R2 + R4) × Vout, It can be obtained That is, the second voltage VM3 is inversely proportional to the reference voltage output by the adjustable constant current source. When the reference voltage output by the adjustable constant current source decreases, the second voltage VM3 increases, thereby ensuring that the output power remains constant, and vice versa. Therefore, this embodiment achieves power stability through the automatic adjustment of VM3. In addition, the introduction of the third voltage VG1 enables the adjustable constant current source to perform manual power adjustment; furthermore, through the selection switch, the adjustable constant current source can have the function of selecting automatic or manual power control.

[0036] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of this application and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of this application should be included within the protection scope of this application. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. An adjustable constant current source power control circuit for controlling the power of an adjustable constant current source, characterized by, The voltage sampling circuit, the divider circuit and the voltage selection circuit are included. The voltage sampling circuit is connected to the adjustable constant current source and is used to collect a first voltage from the adjustable constant current source according to a preset proportion coefficient. The divider circuit is connected to the voltage sampling circuit and is used to calculate a second voltage by dividing according to a preset reference voltage and the first voltage. The voltage selection circuit is formed by a first voltage follower and a second voltage follower in parallel, the first voltage follower is connected to the divider circuit and is used to follow the second voltage, the second voltage follower is used to follow a third voltage, and the third voltage is determined according to a preset value. A selection switch is formed between the first voltage follower and the second voltage follower, and the selection switch is used to select an output of the first voltage follower or an output of the second voltage follower to access the adjustable constant current source.

2. The circuit of claim 1, wherein, The voltage sampling circuit includes a first resistor, a second resistor and a first operational amplifier, the preset proportion coefficient is determined according to sizes of the first resistor and the second resistor, one end of the first resistor and one end of the second resistor are respectively connected to non-inverting input terminals of the first operational amplifier, and the other end of the first resistor is connected to the adjustable constant current source.

3. The circuit of claim 1, wherein, The divider circuit includes a multiplier and a second operational amplifier, an input terminal of the multiplier is connected to an output terminal of the second operational amplifier, and an output terminal of the multiplier is connected to an inverting input terminal of the second operational amplifier.

4. The circuit of claim 1, wherein, There is also a voltage dividing circuit between the first voltage follower and the divider circuit, and the voltage dividing circuit is used to obtain a fourth voltage from the second voltage according to a preset proportion.

5. The circuit of claim 1, wherein, The selection switch is one of a diode, a triode and a thyristor.

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