Power output control circuit and image signal generator

Abstract

The utility model provides a power supply output control circuit and an image signal generator. The power supply output control circuit comprises a constant current source module, a level output module and a switch control module, one end of the constant current source module is connected with the output end of the power supply; one end of the switch control module is connected with the level output module and the other end is connected with the constant-current source module; when the power supply is turned on, the level output module outputs a first level to the switch control module, and when the switch control module is connected with the first level, the constant current source module is conducted with the output end of the power supply; when the power supply is turned off, the level output module outputs a second level to the switch control module, and the switch control module disconnects the constant current source module from the output end of the power supply when the second level is connected. By adopting the scheme, the situation that extra voltage is generated to the output end of the power supply when the power supply does not output can be avoided, and the overall output stability is improved.

Description

Technical Field

[0001] The present application relates to the technical field of electronic circuits, and in particular to a power output control circuit and an image signal generator. Background Art

[0002] When switching power supplies are used to power loads, circuit stability must be considered. For example, a DC-DC power supply used to power a display screen typically regulates the output voltage by controlling the voltage at the DC-DC power supply's feedback point (FB). However, once the hardware circuit is fixed, the loop stability coefficient is determined, making it difficult to maintain stability over a wide output voltage range.

[0003] By increasing the load current at the output of the DCDC power supply, the loop of the DCDC power supply can be guaranteed to be stable within a relatively large output voltage range. Among existing designs, one is to directly add a pure resistor to the output of the DCDC power supply. However, as the output voltage changes, the power on the pure resistor will gradually increase, and the power and volume requirements of the resistor are relatively high. Another way is to add a constant current source to the output of the DCDC power supply. Compared with adding a pure resistor, it is more ideal. However, when the DCDC power supply is turned off, since the constant current source is connected to a voltage source, the constant current source will generate a voltage to the output end, causing the overall output of the power supply to be unstable. Utility Model Content

[0004] The present application provides a power output control circuit and an image signal generator to solve the above-mentioned technical problems in the prior art.

[0005] According to a first aspect of the present application, there is provided a power output control circuit, comprising: a constant current source module, a level output module and a switch control module;

[0006] One end of the constant current source module is connected to the output end of the power supply, and the other end is connected to the voltage input end;

[0007] One end of the switch control module is connected to the level output module, and the other end is connected to the constant current source module;

[0008] When the power supply is turned on, the level output module outputs a first level to the switch control module, and the switch control module connects the constant current source module to the output end of the power supply when the first level is connected;

[0009] When the power supply is turned off, the level output module outputs a second level to the switch control module. When the switch control module receives the second level, the constant current source module is disconnected from the output end of the power supply.

[0010] In some embodiments, the constant current source module includes a first switch tube and a resistor, wherein a first end of the first switch tube is connected to the output end of the power supply, a control end of the first switch tube is grounded, and a second end of the first switch tube is connected to the voltage access end through the resistor;

[0011] The other end of the switch control module is connected to the constant current source module and further includes:

[0012] The other end of the switch control module is connected between the resistor and the voltage input terminal; or

[0013] The other end of the switch control module is connected between the second end of the first switch tube and the resistor; or

[0014] The other end of the switch control module is connected to the first end of the first switch tube.

[0015] In some embodiments, the switch control module includes a second switch tube and a control circuit for controlling the second switch tube, one end of the control circuit is connected to the level output module, and the other end of the control circuit is connected to the control end of the second switch tube;

[0016] The first end of the second switch tube is connected to the constant current source module, and the second end of the second switch tube is connected to the voltage access terminal, so that the constant current source module is connected to the voltage access terminal through the second switch tube.

[0017] In some embodiments, the control circuit includes a third switch tube, a pull-up resistor, and a current-limiting resistor;

[0018] One end of the current-limiting resistor is connected to the level output module, and the other end is connected to the control end of the third switch tube. The first end of the third switch tube is connected to a level equal to the second level, and the second end of the third switch tube is connected to the control end of the second switch tube.

[0019] One end of the pull-up resistor is connected to the connection node between the current limiting resistor and the level output module, and the other end is connected to the first end of the third switch tube.

[0020] In some embodiments, the control circuit further includes a first voltage-dividing resistor and a second voltage-dividing resistor;

[0021] One end of the first voltage-dividing resistor is connected to the second end of the third switching tube, and the other end is connected to the control end of the second switching tube;

[0022] One end of the second voltage-dividing resistor is connected to the control end of the second switching tube, and the other end is connected to the second end of the second switching tube.

[0023] In some embodiments, the voltage input terminal is connected to a -5V voltage, and the first terminal of the third switch tube is connected to a 3.3V level.

[0024] In some embodiments, the first switch tube is an NPN transistor, the second switch tube is an N-type field effect transistor, and the third switch tube is a PNP transistor.

[0025] In some embodiments, the power output control circuit further includes: an output voltage control circuit, wherein the input end of the output voltage control circuit is connected to the output end of the power supply, and the output end of the output voltage control circuit is connected to the feedback end of the power supply.

[0026] According to a second aspect of the present application, an image signal generator is provided, comprising a power supply and the above-mentioned power output control circuit, wherein the power output control circuit is connected to an output end of the power supply.

[0027] In some embodiments, there are multiple power supplies and power output control circuits in a one-to-one correspondence.

[0028] In summary, the power output control circuit and image signal generator provided by this application have at least the following beneficial effects:

[0029] The output end of the power supply is connected to the constant current source module. The level output module and the constant current source module are connected by adopting a switch control module. The level output module outputs a first level when the power supply is turned on to control the switch control module to connect the constant current source module with the output end of the power supply, so that when the power supply has output, the constant current source module works normally; the level output module outputs a second level when the power supply is turned off to control the switch control module to disconnect the constant current source module from the output end of the power supply, so that when the power supply has no output, the voltage of the voltage access end at the other end of the constant current source module will not act on the output end of the power supply, thereby avoiding the situation where additional voltage is generated to the output end of the power supply when the power supply has no output, thereby improving the stability of the overall output. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the specific implementation methods of this application, the following will briefly introduce the drawings required for the specific implementation methods in conjunction with the accompanying drawings. Obviously, the drawings described below are some implementation methods of this application. For those skilled in the art, other drawings or solutions can be obtained based on these drawings without any creative work.

[0031] Figure 1 This is a structural diagram of a power output control circuit in one embodiment of the present application;

[0032] Figure 2 This is a circuit schematic diagram of a power output control circuit in another embodiment of the present application. DETAILED DESCRIPTION

[0033] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like appear to indicate the orientation or position relationship, unless otherwise specified, they are understood to be based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting this application.

[0034] Furthermore, the use of "first" or "second" in describing features is for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features identified. Features identified as "first" or "second" may explicitly or implicitly include at least one of the identified features. The use of the word "plurality" generally implies at least two, such as two or three, unless otherwise specifically defined.

[0035] In this application, unless otherwise specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be interpreted broadly. For example, they can refer to fixed connections, removable connections, or integration; mechanical connections, electrical connections, direct connections, or indirect connections through an intermediary; and internal connections between two components or interactions between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0036] In the description of this specification, if the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" appear, it means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0037] In one embodiment of the present application, a power output control circuit is provided, and its structure diagram is shown in FIG. Figure 1The power output control circuit comprises a constant current source module 110, a switch control module 120 and a level output module 130. The constant current source module 110 is connected to the output end PPS of the power supply at one end, specifically, the constant current source module 110 is connected to the output end PPS of the power supply and the connection node of the load connected to the power supply at one end, for stabilizing the current output from the output end PPS of the power supply to the load; the constant current source module 110 is connected to the voltage input end ISource at the other end. Specifically, the power supply can be a DCDC power supply or other types of power supply, which is not limited in the present application.

[0038] The switch control module 120 is connected to the level output module 130 at one end and to the constant current source module 110 at the other end. The level output module 130 is used to output a level to the switch control module 120 to drive the switch control module 120 to be in different states, and the switch control module 120 controls the connection state of the constant current source module 110.

[0039] Specifically, when the power supply is turned on, i.e. the output end PPS of the power supply has voltage output, the level output module 130 outputs a first level to the switch control module 120, and the switch control module 120 makes the constant current source module 110 conduct with the output end PPS of the power supply when the first level is input, so that the constant current source module 110 works normally and the current output from the output end PPS of the power supply to the load is stabilized. When the power supply is turned off, i.e. the output end PPS of the power supply has no voltage output, the level output module 130 outputs a second level to the switch control module 120, and the switch control module 120 makes the constant current source module 110 disconnected with the output end PPS of the power supply when the second level is input, so that the output end PPS of the power supply is disconnected with the voltage input end ISource at the other end of the constant current source module 110, and the voltage of the voltage input end ISource will not act on the output end PPS of the power supply, avoiding abnormal output voltage when the power supply is turned off.

[0040] For example, the level output module 130 can be a controller with logic level selection output function, such as PLC (programmable logic controller), which selects to output the first level when the input signal is a signal indicating that the power supply is turned on, and selects to output the second level when the input signal is a signal indicating that the power supply is turned off. The switch control module 120 is controlled by using simple logic level, and then the constant current source module 110 and the output end PPS of the power supply are controlled to be conducted or turned off, which has low design cost.

[0041] The above-mentioned power output control circuit connects the constant current source module 110 to the output terminal PPS of the power supply, and uses the switch control module 120 to connect the level output module 130 and the constant current source module 110. When the power supply is turned on, the level output module 130 outputs a first level to control the switch control module 120 to connect the constant current source module 110 to the output terminal PPS of the power supply, so that when the power supply has output, the constant current source module 110 works normally; when the power supply is turned off, the level output module 130 outputs a second level to control the switch control module 120 to disconnect the constant current source module 110 from the output terminal PPS of the power supply. Then, the voltage access terminal ISource at the other end of the constant current source module 110 is disconnected from the output terminal PPS of the power supply. Therefore, when the power supply has no output, the voltage of the voltage access terminal ISource will not act on the output terminal PPS of the power supply, thereby avoiding the situation where additional voltage is generated at the output terminal of the power supply when the power supply has no output, thereby improving the stability of the overall output.

[0042] In one embodiment, reference Figure 2 The constant current source module 110 includes a first switch tube Q1 and a resistor R19. Figure 2 Pin 3 of the first switch Q1 is the first terminal, pin 1 of the first switch Q1 is the control terminal, and pin 2 of the first switch Q1 is the second terminal. The first terminal of the first switch Q1 is connected to the power supply output terminal PPS, the control terminal of the first switch Q1 is grounded, and the second terminal of the first switch Q1 is connected to one end of resistor R19. The other end of resistor R19 is connected to the voltage input terminal ISource. In this way, a simple constant current source circuit is constructed using the first switch Q1 and resistor R19.

[0043] Specifically, the other end of the switch control module 120 is connected to the constant current source module 110, which further includes: the other end of the switch control module 120 is connected between the resistor R10 and the voltage input terminal ISource, that is, Figure 2 As shown, the resistor R19 is connected to -5V_ISoutce (the voltage input terminal ISource with a voltage of -5V) through the switch control module 120 .

[0044] In existing designs, only the constant current source module 110 is used, and resistor R19 of constant current source module 110 is directly connected to -5V_ISoutce. When the power is off, due to the presence of constant current source module 110, -5V_ISoutce acts as a -5V power supply. Pin 1 of the first switch Q1 is 0V, and a 0.7V constant voltage source is located between pins 1 and 2 of the first switch Q1. Pin 2 of the first switch Q1 is -0.7V, and the VCEsat (saturation voltage drop) of the first switch Q1 is 0.2V. Therefore, pin 3 is approximately -0.5V. This results in an output voltage of approximately -0.5V when the power is off. Therefore, voltage is still supplied to the load when the power is off, which is abnormal.

[0045] In the present application, by adopting the switch control module 120, when the switch control module 120 receives a first electrical level, the resistor R19 is electrically connected to the voltage access terminal ISource, and the constant current source module 110 can operate normally; when the switch control module 120 receives a second electrical level, the resistor R19 is disconnected from the voltage access terminal ISource, and the connection between the constant current source module 110 and the output terminal PPS of the power supply is disconnected. In this way, the constant current source module 110 can be disconnected from the output terminal PPS of the power supply through the switch control module 120 when the power supply is turned off, thereby avoiding abnormal voltage output at the output terminal of the power supply.

[0046] It is understood that in other embodiments, the other end of the switch control module 120 can also be connected to other locations of the constant current source module 110, as long as the connection and disconnection between the output terminal PPS of the power supply and the constant current source module 110 can be controlled. For example, in another embodiment, the other end of the switch control module 120 is connected between the second end (pin 2) of the first switch tube Q1 and the resistor R19. In yet another embodiment, the other end of the switch control module 120 is connected to the first end (pin 3) of the first switch tube Q1.

[0047] Specifically, the first switch tube Q1 may be an NPN transistor. It is understood that in other embodiments, the first switch tube Q1 may also be other types of switching devices, such as a field effect transistor.

[0048] In one embodiment, reference Figure 2 The switch control module 120 includes a second switch Q33 and a control circuit that controls the second switch Q33. One end of the control circuit is connected to the level output module 130, and the other end of the control circuit is connected to the control end of the second switch Q33. A first end of the second switch Q33 is connected to the constant current source module 110, specifically to the resistor R19 of the constant current source module 110. A second end of the second switch Q33 is connected to the voltage access terminal ISource, so that the constant current source module 110 is connected to the voltage access terminal ISource through the second switch Q33.

[0049] Specifically, when the control circuit receives the first level output by the level output module 130, it drives the second switch Q33 to conduct, thereby connecting the constant current source module 110 to -5V_ISoutce to start normal operation. When the control circuit receives the second level output by the level output module 130, it turns off the second switch Q33, thereby disabling the constant current source module 110. In this way, the operation of the constant current source module 110 can be easily controlled.

[0050] Specifically, the second switch Q33 is an N-type field effect transistor. It is understood that in other embodiments, the second switch Q33 may also be other types of switching devices, such as a P-type field effect transistor, an IGBT (insulated gate bipolar transistor), etc.

[0051] It will be appreciated that in embodiments where the switch control module 120 is connected to other locations of the constant current source module 110, the connection locations of the first end of the second switch tube Q33 and the second end of the second switch tube Q33 are different. For example, in another embodiment, the first end of the second switch tube Q33 is connected to the second end of the first switch tube Q1 (pin 2 of the first switch tube Q1), and the second end of the second switch tube Q33 is connected to one end of the resistor R19, the other end of the resistor R19 being connected to -5V_ISoutce. In yet another embodiment, the first end of the second switch tube Q33 is connected to the output terminal PPS of the power supply, and the second end of the second switch tube Q33 is connected to the first end of the first switch tube Q1 (pin 3 of the first switch tube Q1).

[0052] In one of the embodiments, please refer to Figure 2 The control circuit includes a third switch tube Q45, a pull-up resistor R332 and a current-limiting resistor R322.

[0053] One end of the current-limiting resistor R322 is connected to the level output module 130, and the other end is connected to the control terminal of the third switch Q45. The first end of the third switch Q45 is connected to a voltage level equal to the second voltage level, and the second end of the third switch Q45 is connected to the control terminal of the second switch Q33. One end of the pull-up resistor R332 is connected to the connection node between the current-limiting resistor R322 and the level output module 130, and the other end is connected to the first end of the third switch Q45. The first and second voltage levels are used to control the on / off state of the third switch Q45, thereby controlling the on / off state of the second switch Q33. This structure is simple and easy to implement.

[0054] Specifically, the third switch tube Q45 is a PNP transistor. It is understood that in other embodiments, the third switch tube Q45 can also be other types of switching devices, such as an NPN transistor, a field effect transistor, an IGBT, etc.

[0055] In one implementation, Figure 2 As shown, the control circuit also includes a first voltage-dividing resistor R280 and a second voltage-dividing resistor R314. One end of the first voltage-dividing resistor R314 is connected to the second end of the third switching transistor Q45, and the other end is connected to the control end of the second switching transistor Q3. One end of the second voltage-dividing resistor R280 is connected to the control end of the second switching transistor Q33, and the other end is connected to the second end of the second switching transistor Q33. The first voltage-dividing resistor R314 and the second voltage-dividing resistor R280 are used to ensure that the voltage input to the control end of the second switching transistor Q33 meets the requirements.

[0056] In one embodiment, the voltage input terminal is connected to a -5V voltage, and the first terminal of the third switch tube is connected to a 3.3V level. Then, the second level output by the level output module 130 is 3.3V, and the first level can be 0V or other levels lower than 3.3V. Figure 2 As shown, when the level output module 130 outputs the second level of 3.3V, the third switch Q45 is turned off, the voltage between pins 1 and 2 of the second switch Q33 is equal, and the second switch Q33 is turned off. As a result, the voltage at pin 2 of the first switch Q1 is 0V, the first switch Q1 is turned off, and the constant current source module 110 is turned off. When the level output module 130 outputs the first level of 0V, the third switch Q45 is turned on, and the voltage between pins 1 and 2 of the second switch Q33 is 5.7V. If the voltage is greater than 5V, the second switch Q33 is ensured to be turned on. As a result, the voltage at pin 2 of the first switch Q1 is -0.7V, the first switch Q1 is turned on, and the constant current source module 110 is operational.

[0057] In one embodiment, the power supply output control circuit further includes an output voltage control circuit, wherein the input of the output voltage control circuit is connected to the output terminal PPS of the power supply, and the output of the output voltage control circuit is connected to the feedback terminal of the power supply. By using the output voltage control circuit, the output voltage of the power supply can be precisely regulated.

[0058] In addition, the present application provides an image signal generator, including a power supply and the power output control circuit in the above embodiments, wherein the power output control circuit is connected to the output terminal PPS of the power supply.

[0059] Specifically, there may be multiple power supplies and power output control circuits in a one-to-one correspondence, that is, one power supply is connected to one power output control circuit.

[0060] The above-mentioned image signal generator adopts the above-mentioned power output control circuit. The power output control circuit stabilizes the voltage output by the power supply and avoids abnormal voltage. Therefore, the working stability of the image signal generator can be improved.

[0061] The various technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification as long as such combination does not conflict.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A power output control circuit, characterized in that: include: Constant current source module, level output module and switch control module; One end of the constant current source module is connected to the output end of the power supply, and the other end is connected to the voltage input end; One end of the switch control module is connected to the level output module, and the other end is connected to the constant current source module; When the power supply is turned on, the level output module outputs a first level to the switch control module, and the switch control module connects the constant current source module to the output end of the power supply when the first level is connected; When the power supply is turned off, the level output module outputs a second level to the switch control module. When the switch control module receives the second level, the constant current source module is disconnected from the output end of the power supply.

2. The power output control circuit according to claim 1, wherein: The constant current source module includes a first switch tube and a resistor, wherein a first end of the first switch tube is connected to the output end of the power supply, a control end of the first switch tube is grounded, and a second end of the first switch tube is connected to the voltage input end through the resistor; The other end of the switch control module is connected to the constant current source module and further includes: The other end of the switch control module is connected between the resistor and the voltage input terminal; or The other end of the switch control module is connected between the second end of the first switch tube and the resistor; or The other end of the switch control module is connected to the first end of the first switch tube.

3. The power output control circuit according to claim 2, wherein: The switch control module includes a second switch tube and a control circuit for controlling the second switch tube, one end of the control circuit is connected to the level output module, and the other end of the control circuit is connected to the control end of the second switch tube; The first end of the second switch tube is connected to the constant current source module, and the second end of the second switch tube is connected to the voltage access terminal, so that the constant current source module is connected to the voltage access terminal through the second switch tube.

4. The power output control circuit according to claim 3, wherein: The control circuit includes a third switch tube, a pull-up resistor and a current-limiting resistor; One end of the current-limiting resistor is connected to the level output module, and the other end is connected to the control end of the third switch tube. The first end of the third switch tube is connected to a level equal to the second level, and the second end of the third switch tube is connected to the control end of the second switch tube. One end of the pull-up resistor is connected to the connection node between the current limiting resistor and the level output module, and the other end is connected to the first end of the third switch tube.

5. The power output control circuit according to claim 4, characterized in that: The control circuit further includes a first voltage-dividing resistor and a second voltage-dividing resistor; One end of the first voltage-dividing resistor is connected to the second end of the third switching tube, and the other end is connected to the control end of the second switching tube; One end of the second voltage-dividing resistor is connected to the control end of the second switching tube, and the other end is connected to the second end of the second switching tube.

6. The power output control circuit according to claim 4, characterized in that: The first switch tube is an NPN transistor, the second switch tube is an N-type field effect transistor, and the third switch tube is a PNP transistor.

7. The power output control circuit according to claim 4, wherein: The voltage input terminal is connected to a -5V voltage, and the first terminal of the third switch tube is connected to a 3.3V level.

8. The power output control circuit according to claim 1, wherein: It also includes: an output voltage control circuit, wherein the input end of the output voltage control circuit is connected to the output end of the power supply, and the output end of the output voltage control circuit is connected to the feedback end of the power supply.

9. An image signal generator, characterized in that: The invention comprises a power supply and a power output control circuit according to any one of claims 1 to 8, wherein the power output control circuit is connected to the output end of the power supply.

10. The image signal generator according to claim 9, characterized in that: There are multiple power supplies and power output control circuits in a one-to-one correspondence.

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