Patent Application
20190339309
The present disclosure relates to the technical field of switch power supplies, and particularly relates to a voltage sampling circuit and a switch power supply with the voltage sampling circuit.
Due to the advantages of small volume, high efficiency, heavy current and the like, switch power supplies are widely applied to power solutions such as mobile phone chargers and adapters. In the related technologies, a voltage sampling circuit of a switch power supply usually samples the change of the voltage of a feedback coil by means of a voltage feedback pin, and the working frequency and switching-on duty ratio of a power switch tube are controlled according to the sampled voltage value so as to adjust the output voltage of a secondary coil.
However, the related technologies have the defects that the voltage of the voltage feedback pin is influenced by the load magnitude, then sampled voltage value is changed accordingly, and the magnitude of the output voltage cannot be accurately expressed, so that the output voltage of the secondary coil is difficult to keep stable, and the constant voltage precision of the switch power supply is reduced.
Therefore, the related technologies need to be improved.
An objective of the present disclosure is to at least resolve one of the technical problems in the related art to some extent. Therefore, the present disclosure is directed to a voltage sampling circuit. The circuit can increase the constant voltage precision of the switch power supply.
Another objective of the present disclosure is to provide a switch power supply.
In order to achieve the above objectives, the voltage sampling circuit provided by embodiments of one aspect of the present disclosure comprises: a sampling and holding circuit, wherein the sampling and holding circuit includes a sampling input end, a sampling output end, and a sampling control end, the sampling input end is connected with a voltage sampling point, and the sampling and holding circuit is configured to sample a voltage of the voltage sampling point in a sampling stage so as to enable a sampling voltage of the sampling output end to follow the voltage of the voltage sampling point, and holding the sampling voltage of the sampling output end after the sampling stage is ended; and a controller, wherein the controller is respectively connected with the voltage sampling point and the control end and the sampling output end of the sampling and holding circuit, and the controller is configured to control the sampling and holding circuit to enter the sampling stage when determining that the voltage of the voltage sampling point is in a sampling voltage segment according to the voltage of the voltage sampling point, and controlling the sampling stage of the sampling and holding circuit to be ended when determining that the voltage of the voltage sampling point is in a voltage inflection point according to the voltage of the voltage sampling point and the sampling voltage of the sampling output end, so as to enable the sampling voltage of the sampling output end to be held at the voltage corresponding to the voltage inflection point.
According to the voltage sampling circuit provided by the embodiment of the present disclosure, the controller controls the sampling and holding circuit to enter the sampling stage when the voltage of the voltage sampling point is in a sampling voltage segment so as to enable the sampling voltage of the sampling output end to follow the voltage of the voltage sampling point, and controls the sampling stage of the sampling and holding circuit to be ended when the voltage of the voltage sampling point is in the voltage inflection point so as to enable the sampling voltage of the sampling output end to be held at the voltage corresponding to the voltage inflection point. Therefore, by sampling the voltage of the voltage inflection point, the magnitude of the output voltage can be accurately reflected, the influence on the sampling voltage caused by the load change of the switch power supply can be avoided, the stability and accuracy of a control system are improved, the constant voltage precision of the output voltage of the switch power supply is increased, and the user experience is promoted.
In order to achieve the above objectives, the switch power supply provided by embodiments of another aspect of the present disclosure includes the voltage sampling circuit.
According to the switch power supply provided by the embodiment of the present disclosure, by sampling the voltage of the voltage inflection point by means of the voltage sampling circuit, the magnitude of the output voltage can be accurately reflected, the influence on the sampling voltage caused by the load change of the switch power supply can be avoided, the stability and accuracy of the control system are improved, the constant voltage precision of the output voltage of the switch power supply is increased, and the user experience is promoted.
The following describes in detail embodiments of the present disclosure. Examples of the embodiments are shown in the accompanying drawings, where reference signs that are the same or similar from beginning to end represent same or similar components or components that have same or similar functions. The following embodiments described with reference to the accompanying drawings are exemplary, and are intended to describe the present disclosure and cannot be construed as a limitation to the present disclosure.
For convenience of understanding, the working principle of the voltage sampling circuit in the related technologies is briefly introduced firstly.
In the related technologies, the voltage sampling circuit performs filtering processing by means of RC to filter out the high-frequency interference in the waveform of the voltage V1′ of the voltage sampling point. When the voltage V1′ of the voltage sampling point rises and exceeds a preset threshold value (such as 0.1V), an output signal of a comparator of the voltage sampling circuit jumps from a low level to a high level. Because the waveform of the voltage V1′ of the voltage sampling point has resonance fluctuation at the initial stage, the output signal of the comparator is delayed for a preset delay time T′ by means of a delay circuit so as to prevent the voltage of a resonance fluctuation region from being sampled. After the output signal of the comparator is delayed for the preset delay time T′, the voltage of the middle segment of a voltage platform of the voltage V1′ of the voltage sampling point can be sampled, and the sampled voltage is closer to the average value of the voltage V1′ of the voltage sampling point. Further, a leading edge blanking (LEB) module generates a PWM signal SH′ with a tiny pulse according to the delayed output signal, and the PWM signal SH′ controls a transmission gate TR; when the PWM signal SH′ is a high level, the transmission gate TR is switched on, and the voltage sampling circuit enters a sampling stage so as to acquire the current voltage value; and when the PWM signal SH′ is a low level, the transmission gate TR is switched off, the sampling stage of the voltage sampling circuit is ended, and the voltage sampling circuit enters a holding stage. The sequential logic of the whole sampling process is as shown in
As shown in
Based on the above, the embodiments of the present disclosure provide a switch power supply and a voltage sampling circuit thereof.
The switch power supply and the voltage sampling circuit thereof provided by the embodiments of the present disclosure are described below with reference to the accompanying drawings.
The sampling and holding circuit 10 includes a sampling input end IN, a sampling output end OUT, and a sampling control end P, the sampling input end IN is connected with a voltage sampling point M, and the sampling and holding circuit 10 is used for sampling the voltage V1 of the voltage sampling point M in a sampling stage so as to enable the sampling voltage V2 of the sampling output end to follow the voltage V1 of the voltage sampling point M, and holding the sampling voltage V2 of the sampling output end after the sampling stage is ended. The controller 20 is respectively connected with the voltage sampling point M and the sampling control end P and the sampling output end OUT of the sampling and holding circuit 10, and the controller 20 is used for controlling the sampling and holding circuit 10 to enter the sampling stage when judging that the voltage V1 of the voltage sampling point M is in a sampling voltage segment according to the voltage V1 of the voltage sampling point M, and controlling the sampling stage of the sampling and holding circuit 10 to be ended when judging that the voltage V1 of the voltage sampling point M is in a voltage inflection point according to the voltage V1 of the voltage sampling point M and the sampling voltage V2 of the sampling output end, so as to enable the sampling voltage V2 of the sampling output end to be held at the voltage corresponding to the voltage inflection point.
In other words, the controller 20 receives the voltage V1 of the voltage sampling point M and judges whether the voltage V1 of the voltage sampling point M is in a sampling voltage segment or not. When the voltage V1 of the voltage sampling point M is in the sampling voltage segment, the controller 20 outputs a switching-on control signal SH (such as a high level) to the sampling control end P of the sampling and holding circuit 10, the sampling and holding circuit 10 enters the sampling stage when receiving the switching-on control signal SH, and at this time, the sampling and holding circuit 10 samples the voltage V1 of the voltage sampling point M so as to enable the sampling voltage V2 of the sampling output end to follow the voltage V1 of the voltage sampling point M. When the voltage V1 of the voltage sampling point M is changed to a voltage inflection point, the controller 20 outputs a switching-off control signal SH (such as a low level) to the sampling control end P of the sampling and holding circuit 10, the sampling and holding circuit 10 ends the sampling stage and enters the holding stage when receiving the switching-off control signal SH, and at this time, the sampling voltage V2 of the sampling output end is held at the voltage corresponding to the voltage inflection point.
It should be noted that in conjunction with the embodiment as shown in
Therefore, the sampling and holding circuit 10 can sample the voltage corresponding to the voltage inflection point, takes the voltage corresponding to the voltage inflection point as the final sampling voltage to be output to the error amplifier, and adjusts the control signal output by the power control chip according to the sampling voltage so as to adjust the working frequency and switching-on duty ratio of the power switch tube to keep the output voltage of the secondary coil stable, so that the influence on the sampling voltage caused by the load change of the switch power supply can be avoided, the stability and accuracy of the control system are improved, the constant voltage precision of the output voltage of the switch power supply is increased, and the user experience is promoted.
The circuit structure and the working principle of the voltage sampling circuit according to the embodiments of the present disclosure are specifically described below with reference to
According to an embodiment of the present disclosure, as shown in
The trigger 201 includes a setting end S, a resetting end R, and an output end O, and the output end O of the trigger 201 is connected with the sampling control end P of the sampling and holding circuit 10; the input end IN1 of the first control unit 202 is connected with the voltage sampling point M, the output end OUT1 of the first control unit 202 is connected with the setting end S of the trigger 201, and the first control unit 202 is used for controlling the setting of the trigger 201 to control the sampling and holding circuit 10 to enter the sampling stage when judging that the voltage V1 of the voltage sampling point M is in a sampling voltage segment; and the input end IN2 of the second control unit 203 is respectively connected with the voltage sampling point M and the sampling output end, the output end OUT2 of the second control unit 203 is connected with the resetting end R of the trigger 201, and the second control unit 203 is used for controlling the resetting of the trigger 201 to control the sampling stage of the sampling and holding circuit 10 to be ended when judging that the voltage of the voltage sampling point M is in a voltage inflection point.
Specifically, when the voltage V1 of the voltage sampling point M is in the sampling voltage segment, the output end OUT1 of the first control unit 202 outputs a sampling signal (such as a high level) to the setting end S of the trigger 201 so as to control the setting of the trigger 201, and the trigger 201 outputs a switching-on control signal SH to the sampling control end P of the sampling and holding circuit 10 so as to control the sampling and holding circuit 10 to enter the sampling stage; and when the voltage of the voltage sampling point M is in the voltage inflection point, the output end OUT2 of the second control unit 203 outputs a sampling end signal (such as a high level) to the resetting end R of the trigger 201 so as to control the resetting of the trigger 201, and the trigger 201 outputs a switching-off control signal SH to the sampling control end P of the sampling and holding circuit 10 so as to control the sampling stage of the sampling and holding circuit 10 to be ended to enter a holding stage.
It should be noted that the sampling voltage segment can refer to the middle segment of a voltage platform of the voltage V1 of the voltage sampling point M. In the embodiment of the present disclosure, the voltage V1 of the voltage sampling point M is compared with a preset voltage V0, and after the voltage V1 of the voltage sampling point M is greater than the preset voltage V0, the preset delay time is delayed to judge that the voltage V1 of the voltage sampling point M is in the sampling voltage segment, namely the middle segment of the voltage platform.
According to an embodiment of the present disclosure, as shown in
Specifically, the preset voltage V0 supplied by the preset voltage supply end Vref can be 0.1V; when the voltage V1 of the voltage sampling point M is less than or equal to 0.1V, the first comparator CMP1 outputs a first sampling signal (such as a low level); and when the voltage V1 of the voltage sampling point M is greater than 0.1V, the output of the first comparator CMP1 is inverted to output a second sampling signal (such as a high level). The delay circuit 210 delays the sampling signal output by the first comparator CMP1 for the preset delay time T and then outputs the sampling signal to the setting end S of the trigger 201, so that after the first comparator CMP1 outputs a high level, the preset delay time T is delayed to control the setting of the trigger 201, and the sampling and holding circuit 10 enters the sampling stage.
It should be noted that as shown in
According to an embodiment of the present disclosure, as shown in
According to a specific embodiment of the present disclosure, the second comparator CMP2 can be a comparator with a tiny mismatch at the input end. In other words, when the difference value between the first input end and the second input end of the second comparator CMP2 is smaller, the level output by the second comparator CMP2 is not inverted.
Specifically, in the voltage sampling stage, the change of the sampling voltage V2 output by the sampling output end is later than the change of the voltage V1 of the voltage sampling point M. As shown in
According to an embodiment of the present disclosure, as shown in
The sampling and holding unit 101 is respectively connected with the voltage sampling point M and the controller 20, the sampling and holding unit 101 comprises a transmission gate TR, and the controller 20 controls the sampling and holding circuit 10 to enter the sampling stage by controlling the transmission gate TR to be switched on, and controls the sampling stage to be ended by controlling the transmission gate TR to be switched off; the switch unit 102 is connected with the sampling and holding unit 101 in parallel; and the trigger unit 103 is respectively connected with the controller 20 and the switch unit 102, and the trigger unit 103 is used for generating a trigger signal when the sampling and holding circuit 10 enters the sampling stage to trigger the switch unit 102 to be switched on for a preset time, so as to enable the output end of the sampling and holding circuit 10 to firstly follow the voltage of the voltage sampling point M by means of the switch unit 102 and then follow the voltage of the voltage sampling point M by means of the sampling and holding unit 101 after the preset time.
The situation that the voltage platform of the voltage sampling point M has already been ended but the sampling voltage V2 output by the sampling output end OUT has not kept up with the voltage V1 of the voltage sampling point M can be avoided, thereby ensuring that the voltage sampling circuit can sample the voltage of the voltage inflection point.
According to an embodiment of the present disclosure, as shown in
Specifically, the first resistor R1 and the first capacitor C1 can constitute a first-order RC filter circuit, and the second resistor R2 and the second capacitor C2 can constitute a second-order RC filter circuit. The first end of the first resistor R1 can serve as the sampling input end IN of the sampling and holding circuit 10, the control end of the transmission gate TR can serve as the sampling control end P of the sampling and holding circuit 10, the first node can serve as a first sampling output end OUT′ of the sampling and holding circuit 10, and the second node can serve as a second sampling output end OUT″ of the sampling and holding circuit 10. The sampling voltage can be output to an error amplifier of a switch power supply by means of the first sampling output end OUT′, and the sampling voltage can be output to the controller 20 by means of the second sampling output end OUT″.
It should be understood that the sampling voltage can also be output to the error amplifier of the switch power supply by means of the second sampling output end OUT″.
According to an embodiment of the present disclosure, as shown in
According to an embodiment of the present disclosure, as shown in
According to a specific embodiment of the present disclosure, as shown in
Specifically, at the time t1, the voltage V1 of the voltage sampling point M is greater than 0.1V, the first comparator CMP1 outputs a sampling signal (such as a high level), the delay unit 210 outputs the sampling signal to the setting end S of the trigger 201 at the time t2 as shown in
When the PWM signal SHFA is changed into a low level, the first MOS transistor MOS1 and the second MOS transistor MOS2 are switched off, and the sampling voltage V2 output by the sampling output end OUT follows the voltage V1 of the voltage sampling point M by means of the sampling and holding unit 101. Specifically, the transmission gate TR is switched on under the control of the switching-on control signal SH, the transmission gate TR and the first-order RC filter circuit process the voltage V1 of the voltage sampling point M and then output the sampling voltage V2 to the error amplifier of the switch power supply, and the transmission gate TR, the first-order RC filter circuit and the second-order RC filter circuit process the voltage V1 of the voltage sampling point M and then output the sampling voltage V2 to the first input end of the second comparator CMP2. Because the time constant of the RC filter circuit is larger, the change of the sampling voltage V2 output by the sampling output end OUT is later than the change of the voltage V1 of the voltage sampling point M.
During the time period from t2 to t3, the change of the voltage V1 of the voltage sampling point M is slower, the difference value between the sampling voltage V2 and the voltage V1 of the voltage sampling point M is less than the preset threshold value, the second comparator CMP2 outputs a first sampling end signal (such as a low level) to the resetting end R of the trigger 201, the trigger 201 holds the setting to continue to output a high level, the transmission gate TR is controlled to be switched on to perform continuous sampling, and the sampling voltage V2 follows the voltage V1 of the voltage sampling point M. If the change of the voltage V1 of the voltage sampling point M is larger, a difference value is generated between the sampling voltage V2 and the voltage V1 of the voltage sampling point M. At the time t3, the voltage V1 of the voltage sampling point M has a fast drop trend, i.e., the voltage V1 of the voltage sampling point M is in the voltage inflection point. At this time, the difference value between the sampling voltage V2 output by the sampling output end and the voltage V1 of the voltage sampling point M is greater than the preset threshold value, the second comparator CMP2 outputs a second sampling end signal (such as a high level) to the resetting end R of the trigger 201, the trigger 201 resets to output a low level, the transmission gate TR is controlled to be switched off so as to control the sampling stage to be ended to enter a holding stage, and the sampling voltage V2 is held at the voltage corresponding to the voltage inflection point.
In conclusion, according to the voltage sampling circuit provided by the embodiment of the present disclosure, the controller controls the sampling and holding circuit to enter the sampling stage when the voltage of the voltage sampling point is in the sampling voltage segment so as to enable the sampling voltage of the sampling output end to follow the voltage of the voltage sampling point, and controls the sampling stage of the sampling and holding circuit to be ended when the voltage of the voltage sampling point is in the voltage inflection point so as to enable the sampling voltage of the sampling output end to be held at the voltage corresponding to the voltage inflection point. Therefore, by sampling the voltage of the voltage inflection point, the magnitude of the output voltage can be accurately reflected, the influence on the sampling voltage caused by the load change of the switch power supply can be avoided, the stability and accuracy of the control system are improved, the constant voltage precision of the output voltage of the switch power supply is increased, and the user experience is promoted.
According to an embodiment of the present disclosure, as shown in
Specifically, the power control chip 40 is used for outputting a control signal to control the power switch tube Q1 (such as an MOS transistor) to be switched on or switched off so as to realize primary and secondary energy transfer of the transformer component 50, and the output voltage and output current of the secondary coil 502 are controlled by controlling the working frequency and switching-on duty ratio of the power switch tube Q 1 . The power control chip 40 is further used for sampling the output voltage of the secondary coil 502 by means of the feedback coil 503 so as to adjust the output frequency and duty ratio of the control signal, so as to enable the output voltage of the secondary coil 502 to be kept stable.
According to a specific embodiment of the present disclosure, as shown in
In the embodiment of the present disclosure, as shown in
The input end of the voltage sampling circuit 100 is connected with the voltage feedback pin VFB, and the output end (such as OUT' in the embodiment as shown in
Specifically, the reference offset module 401 is used for supplying the voltage reference and current offset required in the power control chip 40; the starting module 402 is used for controlling the power control chip 40 to be started or stopped; the voltage sampling circuit 100 is used for sampling the voltage V1 of a feedback winding and outputting the sampling voltage V2; the time sampling circuit 403 is used for sampling the voltage platform time of the voltage sampling point so as to perform constant current control on the switch power supply; the error amplifier 404 is used for comparing the sampling voltage V2 with the reference voltage and performing error amplification; the pulse modulation module 405 is used for performing pulse width modulation and pulse frequency modulation, so as to output and convert an analog signal output by the error amplifier 404 into a PWM signal, and output the PWM signal to the logical processing module 406; the logical processing module 406 is used for logically processing the PWM signal so as to generate a corresponding control signal; the driving module 407 is used for generating a driving control signal so as to drive the power switch tube Q1; and the overcurrent protection module 408 is used for detecting the peak current of the primary current, and generating a power switch tube switching-off signal when the peak current of the primary current exceeds the preset current threshold so as to perform overcurrent protection on the switch power supply.
Thus, the switch power supply can sample the output voltage of the secondary coil by means of the feedback coil. The voltage sampling circuit generates the corresponding sampling voltage V2 according to the voltage V1 of the voltage sampling point M and outputs the sampling voltage V2 to the error amplifier, and the error amplifier 404 processes the sampling voltage V2, adjusts the whole system loop according to the sampling voltage V2, and adjusts the control signal output by the power control chip 40 according to the sampling voltage V2 so as to adjust the working frequency and switching-on duty ratio of the power switch tube Q1, so that the output voltage of the secondary coil is kept stable.
In conclusion, according to the switch power supply provided by the embodiment of the present disclosure, by sampling the voltage of the voltage inflection point by means of the voltage sampling circuit, the magnitude of the output voltage can be accurately reflected, the influence on the sampling voltage caused by the load change of the switch power supply can be avoided, the stability and accuracy of the control system are improved, the constant voltage precision of the output voltage of the switch power supply is increased, and the user experience is promoted.
In the description of the present disclosure, it should be understood that, orientations or position relationships indicated by terms such as “center”, “longitudinal”, “transverse”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer”, “clockwise”, “counterclockwise”, “axial”, “radial”, and “circumferential” are orientations or position relationship shown based on the accompanying drawings, and are merely used for describing the present disclosure and simplifying the description, rather than indicating or implying that the apparatus or element should have a particular orientation or be constructed and operated in a particular orientation, and therefore, should not be construed as a limitation on the present disclosure.
In addition, terms “first” and “second” are used only for description purposes, and shall not be understood as indicating or suggesting relative importance or implicitly indicating a quantity of indicated technical features. Therefore, features defined by “first” and “second” may explicitly or implicitly include at least one feature. In the description of the present disclosure, unless otherwise specifically limited, “multiple” means at least two, for example, two or three.
In the present disclosure, it should be noted that unless otherwise clearly specified and limited, the terms “mounted”, “connected”, “connection”, and “fixed” should be understood in a broad sense. For example, a connection may be a fixed connection, a detachable connection, or an integral connection; may be a mechanical connection or an electrical connection; may be a direct connection or an indirect connection by means of an intermediate medium; or may be internal communication between two elements or interaction relationship between two elements, unless otherwise clearly limited. A person of ordinary skill in the art may understand specific meanings of the terms in the present disclosure according to specific situations.
In the present disclosure, unless explicitly specified or limited otherwise, a first characteristic “on” or “under” a second characteristic may be the first characteristic in direct contact with the second characteristic, or the first characteristic in indirect contact with the second characteristic by using an intermediate medium. Moreover, that the first feature is “above”, “over”, and “on” the second feature may be that the first feature is right above the second feature or at an inclined top of the second feature, or may merely indicate that the horizontal height of the first feature is higher than that of the second feature. That the first feature is “below”, “under”, and “beneath” the second feature may be that the first feature is right below the second feature or at an inclined bottom of the second feature, or may merely indicate that the horizontal height of the first feature is lower than that of the second feature.
In the descriptions of this specification, a description of a reference term such as “an embodiment”, “some embodiments”, “an example”, “a specific example”, or “some examples” means that a specific feature, structure, material, or characteristic that is described with reference to the embodiment or the example is included in at least one embodiment or example of the present disclosure. In this specification, exemplary descriptions of the foregoing terms do not necessarily refer to a same embodiment or example. In addition, the described specific features, structures, materials, or characteristics may be combined in a proper manner in any one or more of the embodiments or examples. In addition, a person skilled in the art may integrate or combine different embodiments or examples and characteristics of different embodiments or examples described in the specification, as long as they do not conflict each other.
Although the embodiments of the present disclosure are shown and described above, it can be understood that, the foregoing embodiments are exemplary, and cannot be construed as a limitation to the present disclosure. Within the scope of the present disclosure, a person of ordinary skill in the art may make changes, modifications, replacement, and variations to the foregoing embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201611247084.4 | Dec 2016 | CN | national |
This application is the U.S. national phase entry of PCT Application No. PCT/CN2017/117396, filed Dec. 20, 2017, which claims priority to and benefits of Chinese Patent Application No. 201611247084.4, filed with the State Intellectual Property Office of P. R. China on Dec. 29, 2016. The entire contents of the above-referenced applications are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2017/117396 | 12/20/2017 | WO | 00 |
