CN112532032B

CN112532032B - Overshoot prevention circuit for constant voltage control power supply

Info

Publication number: CN112532032B
Application number: CN202011354930.9A
Authority: CN
Inventors: 吴强; 李勋; 唐波; 许刚颖
Original assignee: Chengdu Chip Rail Microelectronics Co ltd
Current assignee: Chengdu Chip Rail Microelectronics Co ltd
Priority date: 2020-11-27
Filing date: 2020-11-27
Publication date: 2021-10-22
Anticipated expiration: 2040-11-27
Also published as: CN112532032A

Abstract

The invention discloses an overshoot prevention circuit for a constant voltage control power supply, which belongs to the technical field of integrated circuits, wherein a power supply control circuit in the circuit comprises an operational amplifier, wherein the positive input end of the operational amplifier is connected with a feedback voltage VFB, and the negative input end of the operational amplifier is connected with a reference voltage VREF; the overshoot prevention circuit is connected with the reverse input end of the operational amplifier and obtains a comparison voltage and a set voltage through the overshoot prevention circuit; the output end of the switched capacitor is connected with the input end of the compensation controller, the output end of the compensation controller is connected with the operational amplifier OVCT, and the compensation controller generates compensation control voltage for controlling the operational amplifier; by comparing the feedback voltage with the comparison voltage, the set voltage is switched to be connected or not connected to the input end of the compensation controller, so that the problems of long starting time and high overshoot voltage are solved.

Description

Overshoot prevention circuit for constant voltage control power supply

Technical Field

The invention belongs to the technical field of integrated circuits, and particularly relates to an overshoot prevention circuit for a constant voltage control power supply.

Background

The IC manufactured by adopting a more advanced integrated circuit process can effectively improve the integration level of the transistor and reduce the working voltage of the IC, which brings wide development space for portable and multifunctional equipment, so that more and more equipment adopt more advanced IC manufacturing processes. The advanced manufacturing process brings many benefits, increases the equipment cost, and sharply reduces the tolerable voltage fluctuation, and has higher design requirements on the power supply compared with the prior art. Overshoot is one of the inevitable problems in power supply design, and most likely causes equipment damage at the initial stage of startup, reducing equipment safety and service life.

The current mainstream switching power supply usually bears larger overshoot voltage when the system is powered on for the first time, which is particularly obvious when the system is started under light load and no load, and thus the system is more easily damaged due to the voltage overshoot. The method adopted at present is mainly a compromise consideration between the power supply starting time and the overshoot voltage according to the bearable voltage range of equipment, the overshoot voltage is lower in exchange for longer starting time, the bearable overshoot voltage is smaller, and correspondingly, the power supply starting time is longer. The longer power supply starting time influences the response speed of the equipment when the equipment is powered on and after the sleep mode, and the applicable range is limited. At present, the starting stage control schemes with fast starting and low overshoot voltage are fewer in the market.

Disclosure of Invention

In view of the above, the present invention provides an overshoot protection circuit for a constant voltage control power supply to solve the problems of long start-up time and high overshoot voltage.

The technical scheme adopted by the invention is as follows: an overshoot prevention circuit for a constant voltage control power supply, the overshoot prevention circuit comprising:

the power supply control circuit comprises an operational amplifier with compensation, wherein the positive input end of the operational amplifier is connected with an output feedback voltage, and the negative input end of the operational amplifier is connected with a reference voltage VREF;

an anti-overshoot control circuit, comprising: the overshoot protection circuit comprises an overshoot protection sub-circuit, an output power conversion circuit and a compensation controller CCV, wherein the overshoot protection control circuit is connected with the reverse input end of a VEA (operational amplifier with compensation) and obtains compensation control voltage through the overshoot protection control circuit; the switch capacitor is connected with the input end of the compensation controller, the output end of the compensation controller is connected with the OVCT with the compensation operational amplifier, and the compensation controller generates a compensation control voltage and inputs the compensation control voltage to the VEA;

and switching whether the set voltage is connected to the input end of the compensation controller or not by comparing the feedback voltage with the comparison voltage.

Furthermore, the operational amplifier VEA is an operational amplifier with compensation control, and the output terminal of the compensation controller is connected to the compensation control terminal of the operational amplifier.

Further, the overshoot prevention control circuit includes: the resistor R3, the resistor R2, the resistor R1, the switch tube N1 and the switch tube N2 are sequentially connected in series, one end of the resistor R3 is connected with the reverse input end of the operational amplifier, and the source electrode of the switch tube N1 is grounded;

a sampling point of comparison voltage is arranged between the resistor R2 and the resistor R3, the resistor R2 and the resistor R1 are connected to the input end of the compensation controller through a switch tube N2, and the source electrode of the switch tube N2 is a sampling point of set voltage;

the set voltage is switched to be connected or not connected to the input end of the compensation controller through the on-off switching of the switching tube N1 and the switching tube N2.

Further, when the setting voltage is connected to the compensation controller, the compensation control voltage converted by the compensation controller is the maximum value of the compensation control voltage of the operational amplifier, specifically, the internal compensation of the control circuit is to the maximum value or the minimum value, and the working state is set to be no-load.

Further, the overshoot protection control circuit further comprises a comparator, a positive input end and a negative input end of the comparator are respectively connected with the comparison voltage a103 and the feedback voltage VFB, and an output end of the comparator is connected to the gates of the switch tube N1 and the switch tube N2.

Further, the output power conversion circuit comprises a switched capacitor, wherein the input end of the switched capacitor is respectively connected to the power output power control signal OUTP and the reference voltage REF1, and the output end of the switched capacitor is connected to the compensation controller. The main function of the power conversion circuit is to convert a reference voltage into a voltage value corresponding to the output power through a switched capacitor.

The invention has the beneficial effects that:

the invention provides an overshoot prevention circuit for a constant voltage control power supply, which consists of a power supply control circuit and an overshoot prevention control circuit. The overshoot-proof control circuit controls the internal compensation of the power supply control circuit at the initial starting stage, has wide applicable range and can be used for the control circuit with compensation. The overshoot-proof control circuit is used for regulating and controlling the compensation control voltage of the power supply control circuit, the load condition is forcedly determined to be no-load at the initial charging stage, the output voltage is rapidly increased, after the output voltage is close to a stable value, the control right of the compensation control voltage is rapidly switched and handed over to the output power conversion circuit for control, the charging start is divided into two stages, and the charging start time and the overshoot voltage are greatly reduced.

Drawings

Fig. 1 is a schematic diagram of an overall circuit structure of an overshoot protection circuit for a constant voltage control power supply according to the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar modules or modules having the same or similar functionality throughout. The embodiments described below with reference to the drawings are exemplary only for the purpose of explaining the present application and are not to be construed as limiting the present application. On the contrary, the embodiments of the application include all changes, modifications and equivalents coming within the spirit and terms of the claims appended hereto.

Name interpretation

Switching on and off the tube: the NMOS tube is used as a switching tube, works in a saturation region and a cut-off region, is equivalent to the connection and the cut-off of a circuit, and is controlled to be connected and disconnected by the voltage of an output end AOC of a comparator COMP.

Overshoot: the first peak or valley exceeds the set voltage, primarily as a spike, and can lead to failure of circuit components.

Example 1

As shown in fig. 1, the present embodiment provides an overshoot protection circuit for a constant voltage control power supply, which is intended to solve the problems of long start-up time and high overshoot voltage, and the core of the overshoot protection circuit is to perform forced control on the compensation control voltage during the start-up phase. The anti-overshoot circuit comprises: a power supply control circuit and an overshoot prevention control circuit.

Power supply control circuit part

The power supply control circuit is an output power control part of the constant voltage control power supply, obtains an output power control result according to the comparison between the current feedback voltage VFB and the internal reference voltage VREF, and improves (reduces) the output power of the power supply through the control result.

The power supply control circuit comprises an operational amplifier VEA, wherein a forward input end IP of the operational amplifier VEA is connected with a feedback voltage VFB through a line A101, and a reverse input end IN of the operational amplifier VEA is connected with a reference voltage VREF through a line A102; the operational amplifier VEA is set as an operational amplifier with compensation control, the output end of the compensation voltage controller CCV is connected with the compensation control input end OVCT of the operational amplifier VEA, and the output Vea voltage is output to regulate and control the output power by the compensation regulation and control in the operational amplifier VEA and the current load feedback.

② overshoot-proof control circuit part

The overshoot-proof control circuit is mainly used for compensating (compensating control voltage) the regulation and control circuit at the initial starting stage, reducing the time required by starting, preventing the overshoot voltage from being overlarge and avoiding equipment damage. The overshoot-prevention control circuit includes: the anti-overshoot control circuit comprises an anti-overshoot sub-circuit, a comparator, an output power conversion circuit and a compensation voltage controller, and the compensation control voltage of the operational amplifier is regulated and controlled through the anti-overshoot control circuit.

(a) Anti-overshoot sub-circuit

The overshoot prevention sub-circuit is connected with the reverse input end of the operational amplifier, the comparison voltage and the set voltage are obtained through sampling of the overshoot prevention sub-circuit, and the overshoot prevention sub-circuit is specifically designed as follows: the resistor R3, the resistor R2, the resistor R1 and the switch tube N1 are sequentially connected in series, one end of the resistor R3 is connected with the reverse input end of the operational amplifier, the resistor R1 is connected with the drain electrode of the switch tube N1 through a line A106, and the source electrode of the switch tube N1 is grounded;

a wire A103 is connected between the resistor R2 and the resistor R3, the wire A103 is used as a sampling point of comparison voltage, a wire A104 is connected between the resistor R2 and the resistor R1, the other end of the wire A104 is connected to the drain electrode of the switch tube N2, the source electrode of the switch tube N2 is connected to the input end of the compensation controller through a wire A105, and the source electrode of the switch tube N2 is a sampling point of set voltage, namely a voltage value on the wire A105;

the gates of the switch tube N1 and the switch tube N2 are connected to the output end of the comparator COMP through the AOC, and the on-off of the switch tube N1 and the switch tube N2 is switched by the high and low levels output by the output end of the comparator COMP, so that the set voltage is connected or not connected to the input end of the compensation controller, that is: when the switch tube N1 and the switch tube N2 are both in an on state, the voltage of the line a105 is set, and the voltage value of the set voltage is determined by the resistance values of the resistor R3, the resistor R2 and the resistor R1 and the drain-source voltage value of the switch tube N1; on the contrary, when the switch tube N1 and the switch tube N2 are both in the off state, since the switch tube N2 is turned off, the voltage on the line a105 is regulated by the output power converting circuit, and the control right of the compensation control voltage is transferred to the output power converting circuit.

The parameter design for the anti-overshoot sub-circuit mainly comprises the following aspects:

on one hand, the resistance value matching of the resistor R3, the resistor R2 and the resistor R1 needs to meet the requirement that the magnitude of the set voltage on the line a105 is converted into the compensation control voltage of the operational amplifier VEA through the compensation controller CCV to be the maximum when the switch tube N1 and the switch tube N2 are turned on at the initial stage of charging start;

on the other hand, the pre-design of the voltage on line A103 should be designed according to the voltage ratio that needs to be handed over to the voltage control authority of line A105.

(b) Comparator with a comparator circuit

A forward input end IP (internet protocol) of the comparator COMP is connected to a comparison voltage through a line A103, a reverse input end IN of the comparator COMP is connected to a feedback voltage VFB through a line A101, an output end of the comparator COMP is connected to a grid electrode of the switch tube N1 and a grid electrode of the switch tube N2 through an AOC, and when the output end of the comparator COMP is at a high level, the switch tube N1 and the switch tube N2 are connected; on the contrary, when the output terminal of the comparator COMP is at a low level, the switch tube N1 and the switch tube N2 are turned off.

(c) Output power conversion circuit

The output power conversion circuit comprises a switched capacitor Sc1, an input end A1 of the switched capacitor Sc1 is connected with a reference voltage REF1 through a line A107, an input end A2 of the switched capacitor Sc1 is connected with a power supply output power OUTP through a line A108, an output end B1 of the switched capacitor Sc1 is connected with an input end of a compensation controller CCV, and the design of the switched capacitor Sc1 and the compensation controller CCV mainly aims at: the switched capacitor Sc1 should be sized so that the line a105 voltage does not saturate, thereby affecting the compensation; the compensation controller CCV should be designed such that the voltage on line a105 is converted to a suitable voltage for controlling the compensation control inside the operational amplifier VEA.

(d) Compensation controller

An output end B1 of a switch capacitor Sc1 in the output power conversion circuit is connected with an input end of a compensation controller CCV, an output end of the compensation controller CCV is connected with an operational amplifier VEA through a line A111, compensation control voltage for controlling the operational amplifier VEA is generated by the compensation controller CCV, compensation Vos inside the operational amplifier VEA is regulated and controlled through the compensation control voltage to affect output voltage Vea, and the output voltage Vea is used for reflecting the load condition. In one case, when the switch N1 and the switch N2 are turned on, the set voltage on the line a105 is connected to the input terminal of the compensation controller CCV, and the compensation controller CCV generates a proper voltage for controlling the internal compensation of the operational amplifier VEA; alternatively, when the switch N1 and the switch N2 are turned off, the control right of the compensation control voltage is handed over to the output power conversion circuit, and the compensation controller CCV also generates a suitable voltage for controlling the compensation control inside the operational amplifier VEA.

The overshoot prevention circuit for the constant voltage control power supply has the following working principle:

after the charging is normally started in the internal reference of the constant voltage control power supply, in the initial stage of the charging, the output voltage Vea is zero, the feedback voltage VFB is zero, the voltage difference between the feedback voltage VFB and the line a103 is overlarge, the output comparison result of the comparator COMP is positive, the switch tube N1 and the switch tube N2 are both turned on, the overshoot-prevention sub-circuit is turned on, the voltage on the line a105 is set, the set voltage on the line a105 is converted into the current compensation control voltage through the compensation controller CCV, the compensation Vos (compensation voltage) inside the operational amplifier VEA is set to the maximum value (in particular, the control circuit is internally compensated to the maximum or minimum value, the operating state is set to no load) by the compensation control voltage, and when the compensation voltage inside the operational amplifier VEA is the highest, it is equivalent to forcibly set the load to be no-load, and when the system is no-load, the output voltage Vea rises quickly, so that the start-up time can be greatly reduced.

As the feedback voltage VFB continuously increases until the voltage value (comparison voltage) on the line a103 is exceeded, the output voltage of the comparator COMP changes from high to low, the switch transistor N1 and the switch transistor N2 are turned off, the voltage on the line a105 is set, in other words, the control right of the voltage on the line a105 is handed over to be controlled by the output power conversion circuit (at this time, the circuit may not timely sense that the control right of the compensation control voltage has been handed over due to slow reaction inside the circuit, and the output voltage Vea may still be rapidly increased in a no-load state, but at this time, the output voltage Vea has a certain difference from the output stable voltage value, the start-up time may be further decreased, and at the same time, the switch capacitor Sc1 controls the charge-discharge time of the capacitor using the PWM wave of the power output according to the current magnitude of the output load, so as to convert the power of the power output into a voltage changing with the output power, and then the voltage is output to a compensation controller CCV, the voltage is converted into compensation control voltage through the compensation controller CCV, and the compensation control voltage regulates and controls the internal compensation of the operational amplifier VEA.

In the above working principle, the charging start phase is divided into two phases, as follows:

first phase-fast rise phase of output voltage: the high level output by the comparator COMP controls the switch tube N1 and the switch tube N2 to be turned on, and sets the voltage on the line a105, so as to set the compensation Vos (compensation voltage) inside the operational amplifier VEA to be the highest, when the compensation voltage inside the operational amplifier VEA is the maximum value (specifically, the compensation voltage inside the control circuit is the maximum value or the minimum value, and the working state is set to be no-load), the load is regarded as no-load forcibly, when the system is no-load, the output voltage VEA rises quickly, the start-up time can be greatly reduced, and when the feedback voltage VFB reaches the set voltage comparison point of the a103, the control right of the compensation control voltage is transferred to the output power conversion circuit, and the second stage is entered;

second stage-slow change stage: after the feedback voltage VFB is greater than the voltage comparison point a103, the comparator COMP outputs a comparison voltage at a low level, the path where the switch tube N1 and the switch tube N2 are located is closed, at this time, the feedback voltage VFB is compared with the reference voltage VREF conversion voltage, whether the current power output power matches the load power is determined (here, the comparison of the feedback voltage VFB and the reference voltage VREF is used as the main judgment of power control, the reference voltage VREF is compensated and adjusted to match the feedback voltage VFB fed back when the load is different), the current output voltage Vea is slowly increased, the response time is increased by a small margin, and the overshoot voltage is greatly reduced.

It should be noted that, in the description of the present application, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Further, in the description of the present application, the meaning of "a plurality" means at least two unless otherwise specified.

Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps of the process, and the scope of the preferred embodiments of the present application includes other implementations in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present application.

It should be understood that portions of the present application may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.

It will be understood by those skilled in the art that all or part of the steps carried by the method for implementing the above embodiments may be implemented by hardware related to instructions of a program, which may be stored in a computer readable storage medium, and when the program is executed, the program includes one or a combination of the steps of the method embodiments.

In addition, functional units in the embodiments of the present application may be integrated into one processing module, or each unit may exist alone physically, or two or more units are integrated into one module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. The integrated module, if implemented in the form of a software functional module and sold or used as a stand-alone product, may also be stored in a computer readable storage medium.

The storage medium mentioned above may be a read-only memory, a magnetic or optical disk, etc.

In the description herein, reference to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and that variations, modifications, substitutions and alterations may be made to the above embodiments by those of ordinary skill in the art within the scope of the present application.

Claims

1. An overshoot prevention circuit for a constant voltage control power supply, comprising:

the power supply control circuit comprises an operational amplifier, wherein the positive input end of the operational amplifier is connected with a feedback voltage, and the negative input end of the operational amplifier is connected with a reference voltage VREF;

the overshoot protection circuit comprises a resistance voltage division circuit, an output power conversion circuit, a comparator COMP and a compensation controller CCV, and is connected with the reverse input end of an operational amplifier VEA and obtains comparison voltage and set voltage through the overshoot protection circuit; the output power conversion circuit is connected with the input end of the compensation controller, the output end of the compensation controller is connected with the operational amplifier, and the compensation controller generates compensation control voltage for controlling the operational amplifier;

and the feedback voltage is compared with the comparison voltage, and the set voltage is switched to be connected or not connected to the input end of the compensation controller.

2. The overshoot-prevention circuit for a constant voltage controlled power supply according to claim 1, wherein the operational amplifier is configured as an operational amplifier with compensation control, and an output terminal of the compensation controller is connected to a compensation control terminal of the operational amplifier.

3. The overshoot protection circuit for a constant voltage control power supply according to claim 1, wherein the overshoot protection control circuit comprises: the resistor R3, the resistor R2, the resistor R1, the switch tube N1 and the switch tube N2 are connected in series, the resistor R3, the resistor R2, the resistor R1 and the switch tube N1 are connected in series, one end of the resistor R3 is connected with the reverse input end of the operational amplifier, and the source electrode of the switch tube N1 is grounded;

4. The overshoot-prevention circuit for a constant voltage controlled power supply according to claim 1, wherein when the set voltage is connected to the compensation controller, the compensation control voltage converted by the compensation controller is the maximum value of the compensation control voltage of the operational amplifier.

5. The overshoot protection circuit for the constant voltage controlled power supply as claimed in claim 1, further comprising a comparator having a positive input terminal and a negative input terminal connected to the comparison voltage a103 and the feedback voltage VFB, respectively, and an output terminal connected to the gates of the switching transistor N1 and the switching transistor N2.

6. The overshoot protection circuit of claim 1, wherein the output power converting circuit comprises a switched capacitor, the input terminals of the switched capacitor are respectively connected to the power output power control signal and the reference voltage REF1, and the output terminal of the switched capacitor is connected to the compensation controller.