CN216490213U - Constant current output control circuit - Google Patents
Constant current output control circuit Download PDFInfo
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- CN216490213U CN216490213U CN202122914108.XU CN202122914108U CN216490213U CN 216490213 U CN216490213 U CN 216490213U CN 202122914108 U CN202122914108 U CN 202122914108U CN 216490213 U CN216490213 U CN 216490213U
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Abstract
The utility model belongs to the technical field of integrated circuits, and particularly relates to a constant current output control circuit. A constant current output control circuit comprising: the output end of the operational amplifier is connected with the signal input end of a main control chip of the switching power supply; the current sampling end is connected with the reverse input end of the operational amplifier; the reference voltage end is connected with the non-inverting input end of the operational amplifier; further comprising: one end of the first resistor is connected with the non-inverting input end of the operational amplifier; one end of the second resistor is connected with the other end of the first resistor, and the other end of the second resistor is a reference voltage end; and the anode of the first diode is connected with the common end of the first resistor and the second resistor, and the cathode of the first diode is connected with the output voltage end of the switching power supply. The circuit is simple and easy to implement, and solves the problems that the traditional constant current circuit is large in short-circuit power consumption and easy to cause serious damage to a load circuit at the later stage.
Description
Technical Field
The utility model belongs to the technical field of integrated circuits, and particularly relates to a constant current output control circuit.
Background
The current output types of the switching power supply include two types, one is constant voltage output, and the other is constant current output. Common constant-voltage output type switching power supplies in life mainly comprise a mobile phone charger, a notebook computer adapter and the like; constant current output type switching power supplies are commonly used for LED driving, battery chargers, and the like. The output form of the switching power supply is determined by a control circuit, taking constant current control as an example, the conventional constant current control circuit generally comprises a current sampling end for outputting current, a reference voltage end, an operational amplifier and other devices, an output control signal of the constant current control circuit is connected with a main control chip of the switching power supply, and the duty ratio (PWM control) of a driving signal or the frequency (PFM control) of the driving signal is adjusted through the main control chip to achieve the purpose of constant current output.
However, when the output of the switching power supply is short-circuited, the conventional constant current control circuit still works, so that the switching power supply still outputs the current set during normal operation when the output is short-circuited, the short-circuit power consumption is large, and meanwhile, the load circuit at the rear stage is extremely easy to be seriously damaged, and even the rear-stage circuit is burnt.
SUMMERY OF THE UTILITY MODEL
The utility model aims to solve the technical problem that when the output of a switching power supply is short-circuited, the conventional constant current control circuit still enables the switching power supply to work normally, and a load circuit at the rear stage is easy to damage seriously, and provides a constant current output control circuit.
A constant current output control circuit comprising:
the output end of the operational amplifier is connected with the signal input end of a main control chip of the switching power supply;
the current sampling end is connected with the reverse input end of the operational amplifier;
the reference voltage end is used for providing reference voltage and is connected with the non-inverting input end of the operational amplifier;
further comprising:
one end of the first resistor is connected with the non-inverting input end of the operational amplifier;
one end of the second resistor is connected with the other end of the first resistor, and the other end of the second resistor is the reference voltage end;
and the anode of the first diode is connected with the common end of the first resistor and the second resistor, and the cathode of the first diode is connected with the output voltage end of the switching power supply.
When the switching power supply normally works, the output voltage of the output voltage end of the switching power supply is higher, the first diode is in a reverse bias state, no influence is caused on the constant current output control circuit, and the circuit still works in a constant current mode according to the existing control circuit. When the rear stage of the switching power supply is short-circuited, namely the output voltage end of the switching power supply is short-circuited to the ground, the first diode is conducted, and the first resistor and the second resistor are clamped to the conduction voltage drop of the diode, so that the value of constant current output is reduced, and the switching power supply and the rear stage circuit are protected.
The first diode is preferably a schottky diode.
Further comprising:
and the cathode of the second diode is connected with the common end of the first resistor and the second resistor, and the anode of the second diode is grounded.
After the first diode is connected, the utility model can effectively protect the rear-stage circuit when the output of the switching power supply is short-circuited. However, because the first diode belongs to a semiconductor device, the reverse leakage current is greatly influenced by temperature, and the difference of high and low temperature constant current points is large, the temperature compensation is performed by connecting the second diode, and therefore the problem that the difference of the high and low temperature constant current points is large is solved.
Further comprising:
one end of the first capacitor is connected with the inverting input end of the operational amplifier;
one end of the third resistor is connected with the other end of the first capacitor, and the other end of the third resistor is connected with the output end of the operational amplifier;
one end of the second capacitor is connected with the non-inverting input end of the operational amplifier, and the other end of the second capacitor is grounded;
and one end of the fourth resistor is connected with the non-inverting input end of the operational amplifier, and the other end of the fourth resistor is grounded.
The current sampling end is connected with the reverse input end of the operational amplifier through a filter circuit, and the filter circuit comprises:
one end of the fifth resistor is connected with the current sampling end, and the other end of the fifth resistor is connected with the reverse input end of the operational amplifier;
and one end of the third capacitor is connected with the reverse input end of the operational amplifier, and the other end of the third capacitor is grounded.
The output end of the operational amplifier is connected with the signal input end of the main control chip through a feedback circuit, and the feedback circuit comprises:
the cathode of the third diode is connected with the output end of the operational amplifier;
the negative electrode of the internal light-emitting diode is connected with the positive electrode of the third diode, the collector electrode of the internal phototriode is used as a feedback end to be connected with the signal input end of the main control chip, and the emission set of the phototriode is grounded;
and one end of the sixth resistor is connected with the anode of the light-emitting diode, and the other end of the sixth resistor is connected with a power supply.
The reference voltage end is connected with a reference chip, and the reference chip provides reference voltage for the reference voltage end.
The positive progress effects of the utility model are as follows: the utility model adopts the constant current output control circuit, the circuit is simple and easy to realize, and the problems that the traditional constant current circuit has large short-circuit power consumption during short circuit and is easy to cause serious damage to a load circuit at the later stage are solved.
Drawings
FIG. 1 is a schematic circuit diagram of the present invention.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the utility model easy to understand, the utility model is further described with the specific drawings.
Referring to fig. 1, a constant current output control circuit includes a current sampling terminal Iout, a reference voltage terminal Vref, an operational amplifier U1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a first diode D1, a second diode D2, a third diode D3, a first capacitor C1, a second capacitor C2, a third capacitor C3, an optical couple OC1, a power supply Vcc, and a feedback terminal FB.
The current sampling end Iout collects sampling signals of output current of the switching power supply, a sampling resistor is usually connected to the output end of the switching power supply and is used for sampling the output current, and the larger the output current of the switching power supply is, the larger the current sampling end Iout is. The current sampling terminal Iout is connected to the inverting input terminal of the operational amplifier U1 through a filter circuit, i.e., the current sampling terminal Iout is sent to the inverting input terminal of the operational amplifier U1 after being low-pass filtered by the filter circuit. The filter circuit comprises a fifth resistor R5 and a third capacitor C3. Specifically, the current sampling end Iout is connected to one end of the fifth resistor R5, and the other end of the fifth resistor R5 is connected to the inverting input end of the operational amplifier U1. One end of the third capacitor C3 is connected to the inverting input terminal of the operational amplifier U1, and the other end of the third capacitor C3 is grounded.
The reference voltage terminal Vref provides a reference voltage, and the magnitude of the constant current can be adjusted by adjusting the reference voltage of the reference voltage terminal Vref. The reference voltage terminal Vref supplies a reference voltage which can be obtained by connecting a reference chip to which the reference voltage terminal Vref is supplied.
The reference voltage terminal Vref is connected to the non-inverting input terminal of the operational amplifier U1 through the second resistor R2 and the first resistor R1 which are connected in series. The common terminal of the first resistor R1 and the second resistor R2 is connected to the anode of the first diode D1, and the cathode of the first diode D1 is connected to the output voltage terminal Vo of the switching power supply. The first diode D1 is preferably a schottky diode. The common terminal of the first resistor R1 and the second resistor R2 is also connected with the cathode of the second diode D2, and the anode of the second diode D2 is grounded.
The operational amplifier U1 is used for comparing the voltage of the current sampling end Iout after low-pass filtering with a reference voltage and outputting the voltage to the signal input end of the main control chip. One end of a first capacitor C1 is connected with the inverting input end of the operational amplifier U1, the other end of the first capacitor C1 is connected with one end of a third resistor R3, the other end of the third resistor R3 is connected with the output end of the operational amplifier U1, one end of a second capacitor C2 is connected with the non-inverting input end of the operational amplifier U1, the other end of the second capacitor C2 is grounded, one end of a fourth resistor R4 is connected with the non-inverting input end of the operational amplifier U1, and the other end of the fourth resistor R4 is grounded.
The output end of the operational amplifier U1 is connected with the signal input end of the main control chip through a feedback circuit, and the feedback circuit comprises a third diode D3, an optical couple OC1 and a sixth resistor R6. Specifically, the cathode of the third diode D3 is connected to the output end of the operational amplifier U1, the anode of the third diode D3 is connected to the cathode of the light emitting diode inside the optical couple OC1, and the anode of the light emitting diode is connected to the power supply Vcc through the sixth resistor R6. The power supply Vcc is an auxiliary voltage for supplying power to the constant current output control circuit of the present invention. The collector electrode of the phototriode in the optical couple OC1 is used as a feedback end FB to be connected with the signal input end of the main control chip, and the emission set of the phototriode is grounded.
The working principle of the utility model is as follows:
the current sampling end Iout collects the current of the output voltage end of the switch power supply, when the output current of the switch power supply is increased, the numerical value of the current sampling end Iout is increased, the current is transmitted to the reverse input end of the operational amplifier U1 after being subjected to low-pass filtering by the fifth resistor R5 and the third capacitor C3, the net input voltage of the operational amplifier U1 is reduced, and therefore the output voltage of the operational amplifier U1 is also reduced, the current flowing through the light emitting diode inside the optical coupler OC1 is increased, the impedance of the phototriode inside the optical coupler OC1 is reduced, the FB voltage of the feedback end is reduced, the duty ratio of a driving signal of the main control chip is reduced, the output voltage is reduced, the output current is also reduced, and therefore the output automatic constant current is achieved. When the output current of the switching power supply is reduced, the regulation process is opposite to the above, and finally, the output constant current can be realized.
When the switching power supply normally operates, the first diode D1 and the second diode D2 are in a reverse bias state due to a high output voltage, and thus, the circuit is not affected and still operates in a constant current mode.
When the output of the switching power supply is short-circuited, which is equivalent to the short-circuit of the output voltage Vo to the ground, the first diode D1 is conducted, the common end of the first resistor R1 and the second resistor R2 is clamped to the conduction voltage drop of the first diode D1, if the first diode D1 selects a schottky diode, the common end of the first resistor R1 and the second resistor R2 is clamped to about 0.2V-0.3V, so that the value of the constant current output is reduced, and the switching power supply and a rear-stage circuit are protected. However, after the first diode D1 is connected, since the first diode D1 belongs to a semiconductor device, the reverse leakage current is greatly affected by temperature, which causes a large difference between the high and low temperature constant current points, and therefore the second diode D2 is connected for temperature compensation, thereby solving the problem of a large difference between the high and low temperature constant current points.
The foregoing shows and describes the general principles, essential features, and advantages of the utility model. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the utility model as claimed. The scope of the utility model is defined by the appended claims and equivalents thereof.
Claims (7)
1. A constant current output control circuit comprising:
the output end of the operational amplifier is connected with the signal input end of a main control chip of the switching power supply;
the current sampling end is connected with the reverse input end of the operational amplifier;
the reference voltage end is used for providing reference voltage and is connected with the non-inverting input end of the operational amplifier;
it is characterized by also comprising:
one end of the first resistor is connected with the non-inverting input end of the operational amplifier;
one end of the second resistor is connected with the other end of the first resistor, and the other end of the second resistor is the reference voltage end;
and the anode of the first diode is connected with the common end of the first resistor and the second resistor, and the cathode of the first diode is connected with the output voltage end of the switching power supply.
2. The constant current output control circuit according to claim 1, wherein the first diode is a schottky diode.
3. The constant current output control circuit according to claim 1, further comprising:
and the cathode of the second diode is connected with the common end of the first resistor and the second resistor, and the anode of the second diode is grounded.
4. The constant current output control circuit according to claim 1, 2 or 3, further comprising:
one end of the first capacitor is connected with the inverting input end of the operational amplifier;
one end of the third resistor is connected with the other end of the first capacitor, and the other end of the third resistor is connected with the output end of the operational amplifier;
one end of the second capacitor is connected with the non-inverting input end of the operational amplifier, and the other end of the second capacitor is grounded;
and one end of the fourth resistor is connected with the non-inverting input end of the operational amplifier, and the other end of the fourth resistor is grounded.
5. A constant current output control circuit as claimed in claim 1, 2 or 3, wherein the current sampling terminal is connected to the inverting input terminal of the operational amplifier via a filter circuit, the filter circuit comprising:
one end of the fifth resistor is connected with the current sampling end, and the other end of the fifth resistor is connected with the reverse input end of the operational amplifier;
and one end of the third capacitor is connected with the reverse input end of the operational amplifier, and the other end of the third capacitor is grounded.
6. The constant current output control circuit according to claim 1, 2 or 3, wherein the output terminal of the operational amplifier is connected to the signal input terminal of the main control chip via a feedback circuit, the feedback circuit comprising:
the cathode of the third diode is connected with the output end of the operational amplifier;
the negative electrode of the internal light-emitting diode is connected with the positive electrode of the third diode, the collector electrode of the internal phototriode is used as a feedback end to be connected with the signal input end of the main control chip, and the emission set of the phototriode is grounded;
and one end of the sixth resistor is connected with the anode of the light-emitting diode, and the other end of the sixth resistor is connected with a power supply.
7. The constant current output control circuit according to claim 1, 2 or 3, wherein the reference voltage terminal is connected to a reference chip.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202122914108.XU CN216490213U (en) | 2021-11-25 | 2021-11-25 | Constant current output control circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202122914108.XU CN216490213U (en) | 2021-11-25 | 2021-11-25 | Constant current output control circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN216490213U true CN216490213U (en) | 2022-05-10 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202122914108.XU Active CN216490213U (en) | 2021-11-25 | 2021-11-25 | Constant current output control circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN216490213U (en) |
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2021
- 2021-11-25 CN CN202122914108.XU patent/CN216490213U/en active Active
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