Constant current output circuit

Abstract

The application discloses a constant current output circuit, and belongs to the technical field of control circuits. The circuit comprises a first comparison module, a second comparison module, a level conversion module and a signal output module. The first comparison module is used for collecting a negative output voltage of a secondary side of a transformer and comparing the negative output voltage with a set first reference voltage to output a first comparison signal. The second comparison module is used for collecting a positive output voltage of the secondary side of the transformer and comparing the positive output voltage with a set second reference voltage to output a second comparison signal. The level conversion module is used for converting and adjusting the first comparison signal and the second comparison signal to output an adjusting signal. The signal output module is used for outputting a control signal in response to the adjusting signal, so that a control chip of a primary side of the transformer controls an output of the primary side of the transformer in response to the control signal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of control circuit, more particularly, to a constant current output circuit. BACKGROUND

[0002] With the rapid development of switching power supply, the requirement for controlling the voltage or current of switching power supply output is also increasing. At present, the output voltage of switching power supply to the secondary side of transformer can be controlled by the control chip on the primary side of transformer. However, it is difficult for the control chip to continuously output constant current when the output voltage continuously changes. SUMMARY

[0003] An object of the present application is to provide a new technical solution of constant current output circuit.

[0004] According to a first aspect of the present application, there is provided a constant current output circuit, comprising:

[0005] a first comparison module configured to collect the negative output voltage of the secondary side of transformer and compare it with a set first reference voltage, and output a first comparison signal;

[0006] a second comparison module configured to collect the positive output voltage of the secondary side of transformer and compare it with a set second reference voltage, and output a second comparison signal;

[0007] a level conversion module configured to convert and adjust the first comparison signal and the second comparison signal, and output an adjusted signal; and

[0008] a signal output module configured to output a control signal in response to the adjusted signal, so that the control chip on the primary side of transformer controls the output of the primary side of transformer in response to the control signal.

[0009] Optionally, the first comparison module comprises:

[0010] a reference voltage output sub-module configured to output the set first reference voltage;

[0011] a first comparison sub-module configured to compare the collected negative output voltage of the secondary side of transformer with the first reference voltage, and output the first comparison signal; and

[0012] a constant current adjustment sub-module configured to adjust the output first comparison signal to a constant value.

[0013] Optionally, the first comparison sub-module comprises an operational amplifier U1, and the constant current adjustment sub-module comprises a resistor R1 and a capacitor C1.

[0014] The inverting terminal of the operational amplifier U1 is used to collect the negative output voltage of the secondary side of the transformer, the non-inverting terminal of the operational amplifier U1 is used to respond to the first reference voltage; the resistance R1 and the capacitor C1 connected in series, the other end of the capacitor C1 is connected with the inverting terminal of the operational amplifier U1, the other end of the resistance R1 is connected with the output terminal of the operational amplifier U1 for outputting the first comparison signal.

[0015] Optionally, the reference voltage output sub-module comprises a capacitor C2, a voltage stabilizing tube IC1, resistances R2, R3, R4 and R5 connected in series;

[0016] The other end of the resistance R2 is used to respond to the first input voltage; the other end of the resistance R5 is grounded, the connection point of the resistance R2 and the resistance R3 is connected with the cathode of the voltage stabilizing tube IC1, the anode of the voltage stabilizing tube IC2 is grounded, the connection point of the capacitor C2 and the resistance R3 is connected with the reference end of the voltage stabilizing tube IC2, the other end of the capacitor C2 is grounded, and the connection point of the resistance R3 and the resistance R4 is used to output the first reference voltage.

[0017] Optionally, the first comparison sub-module further comprises a filtering sub-module, the filtering sub-module comprises a resistance R6 and a capacitor C3 connected in series, the other end of the resistance R6 is used to collect the negative output voltage of the secondary side of the transformer, and the connection point of the resistance R6 and the capacitor C3 is used to output the filtered negative output voltage.

[0018] Optionally, the second comparison module comprises:

[0019] A voltage sampling sub-module, configured to collect a positive output voltage of the secondary side of the transformer and output a sampling voltage;

[0020] A second comparison sub-module, configured to compare the sampling voltage with a set second reference voltage and output a second comparison signal; and

[0021] A constant voltage adjusting sub-module, configured to adjust the output second comparison signal to a constant value.

[0022] Optionally, the voltage sampling sub-module comprises a voltage stabilizing tube IC2, resistances R7, R8, R9 and R10;

[0023] The resistance R9 and the resistance R10 are connected in parallel, one end of the resistance R9 is connected with the connection point of the resistance R7 and the resistance R8, the other end of the resistance R9 is grounded, the resistance R7 and the resistance R8 are connected in series, the other end of the resistance R7 is used for collecting the forward output voltage of the secondary side of the transformer, the other end of the resistance R8 is used for outputting the sampling voltage, the connection point of the resistance R9 and the resistance R10 is connected with the reference end of the voltage stabilizing tube IC2, the cathode of the voltage stabilizing tube IC2 is used for receiving the output adjustment signal, and the anode of the voltage stabilizing tube IC2 is grounded.

[0024] Optionally, the second comparison submodule comprises an operational amplifier U2, and the constant voltage adjustment submodule comprises a resistance R11 and a capacitor C4 connected in series.

[0025] The first power supply end of the operational amplifier U2 is used for responding to the first input voltage, the second power supply end of the operational amplifier U2 is grounded, the inverting end of the operational amplifier U2 is used for responding to the sampling voltage, the non-inverting end of the operational amplifier U2 is used for responding to the second reference voltage, the output end of the operational amplifier U2 is used for outputting the second comparison signal, the other end of the resistance R11 is connected with the inverting end of the operational amplifier U2, and the other end of the capacitor C4 is connected with the output end of the operational amplifier U2.

[0026] Optionally, the level conversion module comprises diodes D1 and D2.

[0027] The cathode of the diode D1 is used for responding to the first comparison signal, the cathode of the diode D2 is used for responding to the second comparison signal, and the connection point of the anode of the diode D1 and the anode of the diode D2 is used for outputting the adjustment signal.

[0028] Optionally, the signal output module comprises an optical coupler PH1, a capacitor C5, resistances R12 and R13 connected in series.

[0029] The other end of the resistance R13 is used for responding to the first input voltage, the other end of the resistance R12 is connected with the connection point of the cathode of the light-emitting diode of the optical coupler PH1 and is used for responding to the adjustment signal, the connection point of the resistance R12 and the resistance R13 is connected with the anode of the light-emitting diode of the optical coupler PH1, the emitter of the light-receiving triode of the optical coupler PH1 is grounded, the collector of the light-receiving triode of the optical coupler PH1 is used for outputting the control signal, and the capacitor C5 is connected between the emitter and the collector of the light-receiving triode of the optical coupler PH1.

[0030] According to one embodiment of the present disclosure, by collecting the positive output voltage and the negative output voltage, the first comparison signal and the second comparison signal can be output, and the current output circuit determines the adjustment signal required for the current output circuit to reach the set constant current through the level conversion module, and the signal output module outputs the control signal to the control chip in response to the adjustment signal, so that the control chip controls the output of the primary side of the transformer to make the output current constant, thereby improving the service life of the load connected to the switching power supply.

[0031] Other features of the present application, and their advantages, will become apparent from the following detailed description of illustrative embodiments of the present application, when considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0032] The accompanying drawings incorporated in and forming a part of the specification, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the application.

[0033] Figure 1 is a structural block diagram of the constant current output circuit in the embodiment of the present application;

[0034] Figure 2 is a circuit diagram of the constant current output circuit in the embodiment of the present application;

[0035] Figure 3 is a circuit diagram of the signal output module in the embodiment of the present application.

[0036] Reference Signs:

[0037] Circuit 100;

[0038] First comparison module 10; first comparison submodule 11; reference voltage output submodule 12; constant current adjustment submodule 13; filter submodule 14;

[0039] Second comparison module 20; output voltage sampling module 21; second comparison submodule 22; constant voltage adjustment submodule 23;

[0040] Level conversion module 30;

[0041] Signal output module 40;

[0042] Control chip 200. DETAILED DESCRIPTION

[0043] Various illustrative embodiments of the present application will now be described in detail with reference to the accompanying figures. It should be noted that the relative arrangements of the components and steps set forth in these embodiments, as well as the numerical expressions and numerical values, are not limiting to the scope of the present application, unless otherwise specifically stated.

[0044] The following description of at least one illustrative embodiment is merely exemplary in nature and is in no way intended to limit the present application or its application or uses.

[0045] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0046] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0047] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0048] The following section will first combine the appendix. Figures 1-3 A detailed description of the constant current output circuit according to an embodiment of this application.

[0049] According to an embodiment of this application, a constant current output circuit 100 includes a first comparison module 10 for acquiring the negative output voltage of the secondary side of a transformer and comparing it with a set first reference voltage to output a first comparison signal; a second comparison module 20 for acquiring the positive output voltage of the secondary side of the transformer and comparing it with a set second reference voltage to output a second comparison signal; a level conversion module 30 for converting and adjusting the first comparison signal and the second comparison signal to output an adjustment signal; and a signal output module 40 for outputting a control signal in response to the adjustment signal, so that the control chip 200 on the primary side of the transformer controls the output of the primary side of the transformer in response to the control signal.

[0050] Specifically, such as Figure 1 As shown, the input terminal of the first comparison module 10 can be directly connected to the negative terminal of the output terminal of the transformer secondary side, and the input terminal of the second comparison module 20 can be directly connected to the positive terminal of the output terminal of the transformer secondary side. This allows the first comparison module 10 to acquire the negative output voltage of the transformer secondary side, and the second comparison module 20 to acquire the positive output voltage of the transformer secondary side. The difference between the positive and negative output voltages can be any voltage value between 0 and 5V. In other words, by acquiring the positive and negative output voltages, a first comparison signal and a second comparison signal can be output. The level conversion module 30 determines the adjustment signal required for the current output voltage to reach the set constant current. The signal output module 40 responds to the adjustment signal and outputs a control signal to the control chip 200, so that the control chip 200 controls the output of the transformer primary side to keep the output current constant, thereby improving the output of constant current to the load connected to the switching power supply and improving the service life of the load.

[0051] In one embodiment, the first comparison module 10 includes: a reference voltage output submodule 12 for outputting a set first reference voltage; a first comparison submodule 11 for comparing the collected negative output voltage of the transformer secondary side with the first reference voltage and outputting a first comparison signal; and a constant current adjustment submodule 13 for adjusting the output first comparison signal to a constant value.

[0052] By setting the first reference voltage, a reference value can be provided for the subsequent level conversion module 30 to adjust the conversion, thereby enabling the subsequent control chip 200 to control the output constant current.

[0053] In one embodiment, the first comparison submodule 11 includes an operational amplifier U1, and the constant current regulation submodule 13 includes a resistor R1 and a capacitor C1; the inverting input of the operational amplifier U1 is used to acquire the negative output voltage of the secondary side of the transformer, and the non-inverting input of the operational amplifier U1 is used to respond to the first reference voltage; the resistor R1 and the capacitor C1 are connected in series, the other end of the capacitor C1 is connected to the inverting input of the operational amplifier U1, and the other end of the resistor R1 is connected to the output terminal of the operational amplifier U1 to output the first comparison signal.

[0054] Among them, such as Figure 2 As shown, operational amplifier U1 is a dual operational amplifier. Resistor R1 and capacitor C1 act as PI regulators, keeping the first comparison signal at a constant value to enable the subsequent level conversion module 30 to adjust the signal.

[0055] In one embodiment, the reference voltage output submodule 12 includes a capacitor C2, a Zener diode IC1, and resistors R2, R3, R4, and R5 connected in series; the other end of resistor R2 is used to respond to a first input voltage; the other end of resistor R5 is grounded; the connection point of resistors R2 and R3 is connected to the cathode of Zener diode IC1; the anode of Zener diode IC2 is grounded; the connection point of capacitor C2 and resistor R3 is connected to the reference terminal of Zener diode IC2; the other end of capacitor C2 is grounded; and the connection point of resistors R3 and R4 is used to output the first reference voltage.

[0056] Among them, such as Figure 2 As shown, the first input voltage can be provided by an auxiliary power supply. The value of the first input voltage can be 6V, 12V, or 15V; no specific limitation is made here. The connection point of resistors R3 and R4 is connected to the non-inverting input of the operational amplifier U1. In other words, by setting an auxiliary power supply, a constant first reference voltage can be provided to the non-inverting input of the operational amplifier U1, thereby enabling the output of a corresponding first comparison signal through the first reference voltage.

[0057] In one embodiment, the first comparison module 10 further comprises a filtering sub-module 14, which comprises a resistor R6 and a capacitor C3 connected in series, the other end of the resistor R6 is used to collect the negative output voltage of the secondary side of the transformer, and the connection point of the resistor R6 and the capacitor C3 is used to output the filtered negative output voltage.

[0058] Specifically, as shown in Figure 2 the connection point of the resistor R6 and the capacitor C3 is connected with the inverting terminal of the operational amplifier U1 described above. By setting the resistor R6 and the capacitor C3, the negative output voltage input to the operational amplifier U1 is filtered, thereby improving the stability of the input negative output voltage.

[0059] In one embodiment, the second comparison module 20 comprises: a voltage sampling sub-module 21, which is used to collect the positive output voltage of the secondary side of the transformer and output a sampling voltage; a second comparison sub-module 22, which is used to compare the sampling voltage with a set second reference voltage and output a second comparison signal; and a constant voltage adjustment sub-module 23, which is used to adjust the output second comparison signal to a constant value.

[0060] Among them, as shown in Figure 2 the operational amplifier U2 is a double operational amplifier, and the resistor R6 and the capacitor C3 play a PI adjustment role, so that the output second comparison signal is at a constant value, so as to realize the conversion adjustment of the subsequent level conversion module 30.

[0061] In one embodiment, the voltage sampling sub-module 21 comprises a voltage stabilizing tube IC2, resistors R7, R8, R9 and R10; the resistor R9 and the resistor R10 are connected in parallel, the connection point of the resistor R7 and the resistor R8 is connected with one end of the resistor R9, the other end of the resistor R9 is grounded, the resistor R7 and the resistor R8 are connected in series, the other end of the resistor R7 is used to collect the positive output voltage of the secondary side of the transformer, the other end of the resistor R8 is used to output the sampling voltage, the connection point of the resistor R9 and the resistor R10 is connected with the reference end of the voltage stabilizing tube IC2, the cathode of the voltage stabilizing tube IC2 is used to receive the output adjustment signal, and the anode of the voltage stabilizing tube IC2 is grounded.

[0062] Specifically, as shown in Figure 2 the voltage stabilizing tube IC2 can be turned on in the case of excessive output voltage, thereby reducing the case that the overvoltage in the circuit 100 causes the damage of the components in the circuit 100.

[0063] In one embodiment, the second comparison sub-module 22 comprises an operational amplifier U2, and the constant voltage adjustment sub-module 23 comprises a resistor R11 and a capacitor C4 connected in series; a first power supply end of the operational amplifier U2 is responsive to the first input voltage, a second power supply end of the operational amplifier U2 is grounded, an inverting end of the operational amplifier U2 is responsive to the sampling voltage, a non-inverting end of the operational amplifier U2 is responsive to the second reference voltage, an output end of the operational amplifier U2 is used to output the second comparison signal, the other end of the resistor R11 is connected to the inverting end of the operational amplifier U2, and the other end of the capacitor C4 is connected to the output end of the operational amplifier U2.

[0064] The operational amplifier U2 can also be powered by an auxiliary power supply. The sampling voltage can be provided by different auxiliary power supplies, and the sampling voltage can be 2.5V. The resistor R1 and the capacitor C1 function as PI adjustment, so that the output first comparison signal is at a constant value, to achieve the conversion adjustment of the subsequent level conversion module 30.

[0065] In one embodiment, the level conversion module 30 comprises diodes D1 and D2; a cathode of the diode D1 is responsive to the first comparison signal, a cathode of the diode D2 is responsive to the second comparison signal, and a connection point of an anode of the diode D1 and an anode of the diode D2 is used to output the adjustment signal.

[0066] Specifically, as shown in Figure 2 , the diode D1 is connected to the output end of the above-mentioned operational amplifier U1, and the diode D2 is connected to the output end of the above-mentioned operational amplifier U2. The diode D1 and the diode D2 can function as clamping to achieve the level conversion between the first comparison signal and the second comparison signal, thereby obtaining the adjustment signal.

[0067] In one embodiment, the signal output module 40 comprises an optical coupler PH1, a capacitor C5, and resistors R12 and R13 connected in series; the other end of the resistor R13 is responsive to the first input voltage; the other end of the resistor R12 and the cathode of the light-emitting diode of the optical coupler PH1 are connected to be responsive to the adjustment signal, the connection point of the resistor R12 and the resistor R13 is connected to the anode of the light-emitting diode of the optical coupler PH1, the emitter of the phototriode of the optical coupler PH1 is grounded, the collector of the phototriode of the optical coupler PH1 is used to output the control signal, and the capacitor C5 is connected across the emitter and the collector of the phototriode of the optical coupler PH1.

[0068] Specifically, as shown in Figure 2 and Figure 3As shown, the connection point of the anode of the diode D1 and the anode of the diode D2 is connected to the connection point of the resistor R12 and the cathode of the light emitting diode of the photo-coupler PH1, so that the connection point of the resistor R12 and the cathode of the light emitting diode of the photo-coupler PH1 can respond to the adjusting signal. The collector of the light receiving triode of the photo-coupler PH1 is used to output a control signal to the FB end of the control chip 200, so as to realize that the control chip 200 controls the current to be constant after obtaining the control signal. Wherein, by setting the capacitor C5, the filtering effect can be achieved, so as to improve the stability of the control signal input into the control chip 200.

[0069] Although some specific embodiments of the present application have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, but not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A constant current output circuit, characterized by comprising: The circuit comprises: A first comparison module is used for collecting the negative output voltage of the secondary side of the transformer and comparing with the set first reference voltage to output a first comparison signal; A second comparison module is used for collecting the positive output voltage of the secondary side of the transformer and comparing with the set second reference voltage to output a second comparison signal; A level conversion module is used for converting and adjusting the first comparison signal and the second comparison signal to output an adjusted signal; and A signal output module is used for outputting a control signal in response to the adjusted signal so that the control chip of the primary side of the transformer controls the output of the primary side of the transformer in response to the control signal; A reference voltage output submodule is used for outputting the set first reference voltage; A first comparison submodule is used for comparing the collected negative output voltage of the secondary side of the transformer with the first reference voltage to output the first comparison signal; and A constant current adjustment submodule is used for adjusting the output first comparison signal to a constant value; The first comparison submodule comprises an operational amplifier U1, and the constant current adjustment submodule comprises a resistor R1 and a capacitor C1; The inverting terminal of the operational amplifier U1 is used for collecting the negative output voltage of the secondary side of the transformer, the non-inverting terminal of the operational amplifier U1 is used for responding to the first reference voltage; the resistor R1 and the capacitor C1 are connected in series, the other end of the capacitor C1 is connected with the inverting terminal of the operational amplifier U1, and the other end of the resistor R1 is connected with the output terminal of the operational amplifier U1 and is used for outputting the first comparison signal; The second comparison module comprises: A voltage sampling submodule is used for collecting the positive output voltage of the secondary side of the transformer to output a sampling voltage; A second comparison submodule is used for comparing the sampling voltage with the set second reference voltage to output the second comparison signal; and A constant voltage adjustment submodule is used for adjusting the output second comparison signal to a constant value; The voltage sampling submodule comprises a voltage stabilizing tube IC2, resistors R7, R8, R9 and R10; The resistor R9 and the resistor R10 are connected in parallel, one end of the resistor R9 is connected with the connection point of the resistor R7 and the resistor R8, the other end of the resistor R9 is grounded, the resistor R7 and the resistor R8 are connected in series, the other end of the resistor R7 is used for collecting the positive output voltage of the secondary side of the transformer, the other end of the resistor R8 is used for outputting the sampling voltage, the connection point of the resistor R9 and the resistor R10 is connected with the reference terminal of the voltage stabilizing tube IC2, the cathode of the voltage stabilizing tube IC2 is used for receiving the output adjusted signal, and the anode of the voltage stabilizing tube IC2 is grounded; The reference voltage output submodule comprises a capacitor C2, a voltage stabilizing tube IC1, resistors R2, R3, R4 and R5 connected in series; The other end of the resistor R2 is used for responding to the first input voltage, the other end of the resistor R5 is grounded, the connection point of the resistor R2 and the resistor R3 is connected with the cathode of the voltage stabilizing tube IC1, the anode of the voltage stabilizing tube IC2 is grounded, the connection point of the capacitor C2 and the resistor R3 is connected with the reference terminal of the voltage stabilizing tube IC1, the other end of the capacitor C2 is grounded, and the connection point of the resistor R3 and the resistor R4 is used for outputting the first reference voltage.

2. The constant current output circuit according to claim 1, characterized by, The first comparison submodule further comprises a filtering submodule, the filtering submodule comprises a resistor R6 and a capacitor C3 connected in series, the other end of the resistor R6 is used for collecting the negative output voltage of the secondary side of the transformer, and the connection point of the resistor R6 and the capacitor C3 is used for outputting the filtered negative output voltage.

3. The constant current output circuit according to claim 1, wherein The second comparison submodule comprises an operational amplifier U2, and the constant voltage adjustment submodule comprises a resistor R11 and a capacitor C4 connected in series. The first power supply end of the operational amplifier U2 is used for responding to the first input voltage, the second power supply end of the operational amplifier U2 is grounded, the inverting end of the operational amplifier U2 is used for responding to the sampling voltage, the non-inverting end of the operational amplifier U2 is used for responding to the second reference voltage, the output end of the operational amplifier U2 is used for outputting the second comparison signal, the other end of the resistor R11 is connected with the inverting end of the operational amplifier U2, and the other end of the capacitor C4 is connected with the output end of the operational amplifier U2.

4. The constant current output circuit according to claim 1, wherein The level conversion module comprises diodes D1 and D2. The cathode of the diode D1 is used for responding to the first comparison signal, the cathode of the diode D2 is used for responding to the second comparison signal, and the connection point of the anode of the diode D1 and the anode of the diode D2 is used for outputting an adjustment signal.

5. The constant current output circuit according to claim 1, wherein The signal output module comprises an optical coupler PH1, a capacitor C5, resistors R12 and R13 connected in series, and the other end of the resistor R13 is used for responding to the first input voltage; the other end of the resistor R12 is connected with the connection point of the cathode of the light-emitting diode of the optical coupler PH1 and is used for responding to the adjustment signal, the connection point of the resistor R12 and the resistor R13 is connected with the anode of the light-emitting diode of the optical coupler PH1, the emitter of the photosensitive triode of the optical coupler PH1 is grounded, the collector of the photosensitive triode of the optical coupler PH1 is used for outputting a control signal, and the capacitor C5 is connected between the emitter and the collector of the photosensitive triode of the optical coupler PH1. ​

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