Constant-current and constant-voltage control circuit

Abstract

The utility model discloses a constant-current constant-voltage control circuit, which comprises a control circuit, a constant-voltage ring and a constant-current ring, wherein the constant-voltage ring and the constant-current ring are electrically connected with the control circuit; the control circuit collects numerical values of an operational amplifier U2 and an operational amplifier U3 which are respectively included in the constant voltage ring and the constant current ring and amplifies the differential pressure of the operational amplifier U2 and the operational amplifier U3, and the constant voltage ring and the constant current ring are respectively connected with the switching diode D4 through a switching diode D2 and a switching diode D3. The power supply constant-voltage loop is only slightly higher than a constant-current loop in open loop, and enters a closed loop in advance in operation, so that the operational amplifier saturation of the constant-voltage loop is prevented, and the problem of power supply output overshoot is effectively suppressed.

Description

Technical Field

[0001] The utility model belongs to the technical field of power supply circuit control, and in particular relates to a constant current and constant voltage control circuit. Background Art

[0002] In most current constant current and constant voltage power supply devices, when the power supply output changes from constant current to constant voltage, the output voltage has a certain overshoot, and then is controlled by the loop closed loop to return to the predetermined output voltage.

[0003] Since the constant voltage loop is in an open-loop state in the constant current state, the constant voltage loop will only start when the output voltage reaches the set voltage. When the output voltage of the constant voltage loop reaches a certain value, the output voltage can be adjusted. The response speed of this process is limited by the negative feedback of the loop, and the speed is usually very slow, causing overshoot of the power supply output. Utility Model Content

[0004] The utility model improves the switching of constant voltage and constant current, adjusts the constant voltage loop in real time according to the constant current state, keeps the constant voltage loop in a closed loop state at all times, and minimizes the pressure difference adjusted when the constant voltage loop is closed, thereby improving the response speed and reducing the overshoot of the power supply output.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A constant current and constant voltage control circuit, comprising:

[0007] A control circuit and a constant voltage ring and a constant current ring electrically connected to the control circuit;

[0008] The control circuit collects the values ​​of the operational amplifier U2 and the operational amplifier U3 respectively included in the constant voltage loop and the constant current loop, and amplifies the voltage difference between the operational amplifier U2 and the operational amplifier U3;

[0009] It also includes a switching diode D4, and the constant voltage loop and the constant current loop are connected to the switching diode D4 through the switching diode D2 and the switching diode D3 respectively.

[0010] Furthermore, the control circuit includes a differential amplifier circuit composed of an operational amplifier U1 , and resistors R1 , R2 , R3 , R4 , R5 , and a switching diode D1 electrically connected to the operational amplifier U1 .

[0011] Furthermore, the resistor R1 = resistor R3 , and the resistor R2 = resistor R4 .

[0012] Furthermore, the constant voltage loop has a negative feedback composed of a resistor R8 and a capacitor C1.

[0013] Furthermore, the bandwidth of the operational amplifier U1 is larger than that of the operational amplifier U2.

[0014] Furthermore, in steady state, the output voltage of the constant voltage loop is 1.1-1.5 times higher than the output voltage of the constant current loop.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The utility model adds a control circuit so that the voltage of the constant voltage loop of the power supply is only slightly higher than that of the constant current loop when the loop is open. It enters the closed loop in advance during operation, prevents the saturation of the constant voltage loop operational amplifier, and effectively suppresses the problem of power supply output overshoot. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of a constant current and constant voltage control circuit embodying an embodiment of the present utility model. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the present invention, the technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0019] The accompanying drawings are for illustrative purposes only and are schematic rather than physical representations, and should not be construed as limiting this patent. To better illustrate the embodiments of the present invention, certain components of the accompanying drawings may be omitted, enlarged, or reduced in size, and do not represent the dimensions of actual products. It is understandable to those skilled in the art that certain well-known structures and their descriptions may be omitted from the accompanying drawings. Identical or similar reference numerals in the accompanying drawings of the embodiments of the present invention correspond to identical or similar components. In the description of the present invention, it should be understood that the terms "upper," "lower," "left," "right," "inner," "outer," and the like, indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific direction, be constructed, or operate in a specific direction. Therefore, the terms describing positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent. Those skilled in the art will understand the specific meanings of the above terms based on specific circumstances.

[0020] like Figure 1 As shown, a constant current and constant voltage control circuit of the utility model includes:

[0021] A control circuit and a constant voltage loop and a constant current loop electrically connected to the control circuit;

[0022] The control circuit collects the values ​​of the operational amplifier U2 and the operational amplifier U3 respectively contained in the constant voltage loop and the constant current loop, and amplifies the voltage difference between the operational amplifier U2 and the operational amplifier U3;

[0023] Also includes switch diode D4, constant voltage ring, constant current ring is connected with switch diode D4 through switch diode D2, switch diode D3 respectively.

[0024] In the conventional power supply loop, in constant current state, constant voltage ring input open loop. When cutting from constant current to constant voltage state, constant voltage loop starts from open loop to closed loop, in this control logic, the power supply generally exists output overshoot problem.

[0025] The size of overshoot is mainly determined by the time of open loop op amp output voltage changing to a certain closed loop voltage, which is actually affected by negative feedback, the longer the output voltage overshoot is.

[0026] Specifically, in Figure 1 The control circuit shown in the figure is composed of differential amplifier circuit of op amp U1 and surrounding components, wherein R1=R3, R2=R4, D1 is a switch diode, and R5 is a limiting resistor.

[0027] In the constant voltage loop, resistors R6 and R7 are divided to output to the negative input of op amp U2, resistors R8 and capacitor C1 are feedback components of the constant voltage loop, and the positive input Vref of op amp U2 is a reference voltage source for control input.

[0028] In the constant current loop, CS is the voltage on the overcurrent resistor input to the negative input of op amp U3, R9 is a current limiting resistor, R10 and C2 are feedback components of the constant current loop, and the positive input Vref of op amp U3 is a reference voltage source for control input.

[0029] Among them, the constant voltage loop and the constant current loop are in the whole circuit, and only one of them is working. The current flowing through D4 through R11 will flow to the loop with lower output voltage.

[0030] When the constant current loop is working, the VOUT output voltage is divided by resistors R6 and R7, and the reference voltage at the positive input of the constant voltage loop is lower. At this time, the output of op amp U2 in the constant voltage loop is high.

[0031] When the constant current is cut to constant voltage state, the constant current loop output is high, and as the output voltage begins to rise, the output voltage of the constant voltage loop begins to drop only when the divided voltage is greater than the reference voltage. When it drops to a certain voltage, it enters the closed loop state. The drop time is mainly limited by the negative feedback parameters of resistors R8 and capacitor C1.

[0032] The principle of the control circuit is to collect the voltages of the constant voltage loop and the constant current loop op amp, and amplify the voltage difference between them.

[0033] For example, the constant current loop outputs 1V, and the constant voltage loop open-loop output voltage VCC is 5V. After the voltage difference of 4V between them is amplified, the output reaches the maximum output voltage of the op amp 5V, which increases the negative input voltage of the constant voltage loop op amp U2 and reduces the output voltage of the op amp. As the output voltage of the constant voltage loop op amp decreases, the voltage amplified by the control circuit will also decrease, and the voltage given to the constant voltage loop negative feedback will also decrease.

[0034] After a steady-state closed loop is finally formed, in the constant current mode, the output voltage of the constant voltage loop is slightly higher than the output voltage of the constant current. Adding this circuit avoids the occurrence of constant voltage op amp saturation.

[0035] When switching from constant current mode to constant pressure mode, the constant pressure loop can enter the closed loop state more quickly.

[0036] The utility model adds a control circuit so that the voltage of the constant voltage loop of the power supply is only slightly higher than that of the constant current loop when the loop is open. It enters the closed loop in advance during operation, prevents the saturation of the constant voltage loop operational amplifier, and effectively suppresses the problem of power supply output overshoot.

[0037] It should be noted that in order to ensure the effective operation of the circuit, the bandwidth of op amp U1 should be much larger than the bandwidth of op amp U2 to avoid self-oscillation of the entire constant current and constant voltage control circuit due to insufficient bandwidth of op amp U1.

[0038] In addition, the differential gain in the constant current and constant voltage control circuit should be selected appropriately. In steady state, the output voltage of the constant voltage loop is 1.1-1.5 times higher than the output voltage of the constant current loop. Excessive gain can easily cause the entire circuit to self-oscillate.

[0039] The above connection method can use existing technology and is easy to implement. It does not fall within the scope of protection of this application. Therefore, it at least has the beneficial effects brought by the technical solutions of the above embodiments and will not be repeated here.

[0040] The above are only embodiments of the present invention. Common knowledge such as the known specific structures and characteristics in the scheme is not described in detail here. Ordinary technicians in the relevant field are aware of all common technical knowledge in the technical field of the utility model before the application date or priority date, can obtain all existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the relevant field can improve and implement this scheme based on their own abilities under the guidance of this application. Some typical known structures or methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the utility model, they can also make several variations and improvements, which should also be regarded as the scope of protection of the utility model. These will not affect the effect of the implementation of the utility model and the practicality of the patent.

Claims

1. A constant current and constant voltage control circuit, characterized in that: include: A control circuit and a constant voltage ring and a constant current ring electrically connected to the control circuit; The control circuit collects the values ​​of the operational amplifier U2 and the operational amplifier U3 respectively included in the constant voltage loop and the constant current loop, and amplifies the voltage difference between the operational amplifier U2 and the operational amplifier U3; It also includes a switching diode D4, and the constant voltage loop and the constant current loop are connected to the switching diode D4 through the switching diode D2 and the switching diode D3 respectively.

2. The constant current and constant voltage control circuit according to claim 1, wherein: The control circuit includes a differential amplifier circuit composed of an operational amplifier U1 , and resistors R1 , R2 , R3 , R4 , R5 , and a switching diode D1 electrically connected to the operational amplifier U1 .

3. A constant current and constant voltage control circuit according to claim 2, characterized in that: The resistor R1 = resistor R3 , and the resistor R2 = resistor R4 .

4. A constant current and constant voltage control circuit according to claim 1 or 2, characterized in that: The constant voltage loop has a negative feedback composed of a resistor R8 and a capacitor C1.

5. The constant current and constant voltage control circuit according to claim 2, wherein: The bandwidth of the operational amplifier U1 is greater than that of the operational amplifier U2.

6. The constant current and constant voltage control circuit according to claim 1, wherein: In steady state, the output voltage of the constant voltage loop is 1.1-1.5 times higher than the output voltage of the constant current loop.

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