CN113885635A - Quick reference voltage discharge circuit - Google Patents
Quick reference voltage discharge circuit Download PDFInfo
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- CN113885635A CN113885635A CN202111305938.0A CN202111305938A CN113885635A CN 113885635 A CN113885635 A CN 113885635A CN 202111305938 A CN202111305938 A CN 202111305938A CN 113885635 A CN113885635 A CN 113885635A
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
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Abstract
The invention discloses a rapid reference voltage discharge circuit, which is a variable current source for charging a capacitor; a current amount adjusting circuit having a 1 st resistor for applying a 1 st voltage and a 2 nd resistor for applying a 2 nd voltage, the current amount adjusting circuit adjusting the current amount of the variable current source to a current amount corresponding to a difference voltage of the 1 st voltage and the 2 nd voltage; a comparator circuit for comparing a magnitude of a charging voltage generated at one end of the capacitor with a magnitude of a reference voltage; and a discharge circuit for discharging the capacitor based on a comparison result of the comparison circuit when the charging voltage exceeds the reference voltage; the comparison circuit generates a frequency signal corresponding to the difference voltage of the 1 st voltage and the 2 nd voltage, and is characterized by comprising a reference voltage discharge circuit, wherein when the power supply restarts, the reference voltage discharge circuit ensures the stability of voltage output.
Description
Technical Field
The invention belongs to the technical field of control circuits, and particularly relates to a rapid reference voltage discharge circuit.
Background
The switching power supply has the advantages of small volume, light weight, high efficiency and the like, and is widely applied to various industries. The switching power supply utilizes the control chip to control the on-off time of the switching tube to maintain the stability of the output voltage, and compared with a linear power supply, the switching power supply needs a feedback loop to stabilize the voltage, and the difference is that the adjusting tube of the switching power supply works in a switching state and the adjusting tube of the linear power supply works in a linear amplification state.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a quick reference voltage discharge circuit.
The purpose of the invention is realized by the following technical scheme:
a fast reference voltage discharge circuit, characterized by: comprises that
A variable current source for charging;
a current amount adjusting circuit having a 1 st resistor for applying a 1 st voltage and a 2 nd resistor for applying a 2 nd voltage, the current amount adjusting circuit adjusting the current amount of the variable current source to a current amount corresponding to a difference voltage of the 1 st voltage and the 2 nd voltage;
a comparison circuit that compares the magnitude of a charging voltage generated at one end of the capacitor with a reference voltage;
a discharge circuit that discharges the capacitor based on a comparison result of the comparison circuit when the charge voltage exceeds the reference voltage;
and a reference voltage circuit that changes the reference voltage to a value corresponding to a change in the resistance value of the 1 st resistor or the 2 nd resistor so that the frequency signal from the comparator circuit is constant when the resistance value of the 1 st resistor or the 2 nd resistor changes depending on the temperature characteristic.
Further, the current amount adjusting circuit includes a current amount adjusting error amplifier for supplying a current corresponding to a difference voltage between the 1 st voltage and the 2 nd voltage to either the 1 st resistor or the 2 nd resistor and the capacitor.
Further, the reference voltage discharge circuit includes:
an inversely proportional variable current source which supplies a current corresponding to a difference voltage between the 1 st voltage and the 2 nd voltage and generates a current inversely proportional to a resistance value of either the 1 st resistor or the 2 nd resistor;
a capacitor for charging and discharging;
a switching circuit that charges the charge/discharge capacitor only during a 1 st period by using a current from the inverse-proportional variable current source, then holds a charge voltage of the charge/discharge capacitor only during a 2 nd period, and then discharges the charge voltage of the charge/discharge capacitor only during a 3 rd period;
a switch control circuit for controlling the opening and closing operations of the switch circuit;
and an output circuit for outputting the reference voltage by using the holding voltage of the charge/discharge capacitor.
Further, the inversely proportional variable current source has:
a 3 rd resistor which supplies a current corresponding to a difference voltage between the 1 st voltage and the 2 nd voltage and has the same temperature characteristic as either the 1 st resistor or the 2 nd resistor;
an error amplifier which operates according to a difference voltage between the voltage generated in the 3 rd resistor and the constant voltage;
a transistor for adjusting the amount of current supplied to the 3 rd resistor by using the output of the error amplifier;
the current flowing through the 3 rd resistor is set to be inversely proportional to the current.
The invention has the beneficial effects that:
1) the invention ensures that the output voltage is in monotonous rise when the switch power supply is started by adding the reference discharge circuit to the power supply, so that the voltage output is stable.
Drawings
FIG. 1 is a schematic block diagram of a flyback topology with a reference voltage fast discharge circuit;
FIG. 2 is a schematic block diagram of a flyback topology;
FIG. 3 is a schematic diagram of the operation of the reference voltage fast discharge circuit;
FIG. 4 is a diagram of a power-on waveform;
FIG. 5 is a diagram of a fast reboot waveform;
FIG. 6 is a diagram of a power-on waveform when the reference voltage fast discharging circuit is in operation.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.
Referring to fig. 1-6, the present invention provides a technical solution:
a fast reference voltage discharge circuit, characterized by: comprises that
A variable current source for charging;
a current amount adjusting circuit having a 1 st resistor for applying a 1 st voltage and a 2 nd resistor for applying a 2 nd voltage, the current amount adjusting circuit adjusting the current amount of the variable current source to a current amount corresponding to a difference voltage of the 1 st voltage and the 2 nd voltage;
a comparison circuit that compares the magnitude of a charging voltage generated at one end of the capacitor with a reference voltage;
a discharge circuit that discharges the capacitor based on a comparison result of the comparison circuit when the charge voltage exceeds the reference voltage;
and a reference voltage circuit that changes the reference voltage to a value corresponding to a change in the resistance value of the 1 st resistor or the 2 nd resistor so that the frequency signal from the comparator circuit is constant when the resistance value of the 1 st resistor or the 2 nd resistor changes depending on the temperature characteristic.
Further, the current amount adjusting circuit includes a current amount adjusting error amplifier for supplying a current corresponding to a difference voltage between the 1 st voltage and the 2 nd voltage to either the 1 st resistor or the 2 nd resistor and the capacitor.
Further, the reference voltage discharge circuit includes:
an inversely proportional variable current source which supplies a current corresponding to a difference voltage between the 1 st voltage and the 2 nd voltage and generates a current inversely proportional to a resistance value of either the 1 st resistor or the 2 nd resistor;
a capacitor for charging and discharging;
a switching circuit that charges the charge/discharge capacitor only during a 1 st period by using a current from the inverse-proportional variable current source, then holds a charge voltage of the charge/discharge capacitor only during a 2 nd period, and then discharges the charge voltage of the charge/discharge capacitor only during a 3 rd period;
a switch control circuit for controlling the opening and closing operations of the switch circuit;
and an output circuit for outputting the reference voltage by using the holding voltage of the charge/discharge capacitor.
Further, the inversely proportional variable current source has:
a 3 rd resistor which supplies a current corresponding to a difference voltage between the 1 st voltage and the 2 nd voltage and has the same temperature characteristic as either the 1 st resistor or the 2 nd resistor;
an error amplifier which operates according to a difference voltage between the voltage generated in the 3 rd resistor and the constant voltage;
a transistor for adjusting the amount of current supplied to the 3 rd resistor by using the output of the error amplifier;
the current flowing through the 3 rd resistor is set to be inversely proportional to the current.
This example provides the following embodiments:
the switching power supply has quick loop response, so that the switching power supply can be quickly adjusted when the input voltage changes and the load changes to keep the output voltage stable, otherwise, the output voltage waveform of the switching power supply monotonically rises to the rated output voltage when the switching power supply is started, and the overshoot condition cannot occur. The starting waveform of the switching power supply has a great relationship with the working condition of a reference source inside the switching power supply, a flyback topology is taken as an example to explain the situation, the schematic block diagram of the flyback topology is shown in fig. 2, C1-C3 are capacitors, R1-R3 are resistors, Q1 and Q2 are MOS tubes, U1 is an isolator used for realizing electrical isolation of a primary side and a secondary side and transmitting a primary side PWM signal to the secondary side, U2 is a PWM controller, U3 is an optocoupler, U4 is a reference source, U5 is an operational amplifier, U6 is a driver used for driving a secondary side rectifying MOS tube, TC1 is a current transformer used for collecting a primary side input current signal, and T1 is a transformer. The flyback topology operating principle is briefly described that output voltage is divided by resistors R2 and R3 and then sent to a U5 to be compared with reference voltage Vref generated by a U4, an error signal is output by the U5, the error signal is transmitted to a primary side U2 through an optical coupler U3, a driving signal of a MOS tube Q1 is generated together with a signal collected by a current transformer TC1, meanwhile, a driving signal generated by a U2 and used for driving a secondary side rectifying MOS tube is transmitted to a driver U6 through a channel 1 of an isolator U1, the U6 obtains a signal and then drives a rectifying tube Q2, when the output voltage is increased, the duty ratio of a Q1 driving signal output by a PWM controller is reduced, when the output voltage is reduced, the duty ratio of a Q1 driving signal output by the PWM controller is increased, and therefore output voltage stabilization is achieved. When the power supply is turned on, the reference voltage Vref starts to rise from the low potential to the designed value, and the output voltage also monotonically rises to the rated output voltage, as shown in fig. 2. When the switching power supply is debugged, the capacitor C2 is often connected in parallel at the reference voltage Vref end, the parallel capacitors have a relatively obvious effect on optimizing a startup waveform, when the power supply is started up again quickly after being shut down, the capacitor C2 may not discharge to a low potential in time, the reference voltage Vref starts to rise from a relatively high voltage level, the + potential of the U5 equidirectional input end and the-potential of the reverse input end have a relatively large difference, the output end of the U5 outputs a large error signal, so that the PWM controller rapidly increases the duty ratio of the driving signal, the output voltage rapidly rises, the output voltage is easily increased at the moment, when the U5 detects that the output voltage is increased, the error signal is rapidly output, so that the PWM controller reduces the duty ratio of the driving signal, and after such an adjustment process, the output voltage is easily overshot, as shown in 53. The output voltage has an overshoot phenomenon in the starting process, sometimes harms the rear-stage electric equipment or system, the overvoltage damage of the rear-stage equipment can be caused when the voltage is too high, sometimes, the overshoot peak can trigger the opening threshold of the rear-stage system, the rear-stage system is closed and then opened after being opened for a short time, and the closing process in the period can cause the rear-stage system to detect the closing action by mistake and take protective measures, so that the rear-stage system cannot work normally;
after the discharge with the added reference voltage, the circuit diagram is shown in the dashed box of fig. 1, where D1 is a diode, C4 is a capacitor, R4, R5 are resistors, and Q3 is a PNP transistor. When the switching power supply normally works, a square wave signal generated by the PWM controller is transmitted to the secondary side through a channel 2 of the isolator U1, and the base electrode of the PNP type triode Q3 is enabled to be at a high potential after passing through the diode D1, the capacitor C4 and the resistor R4, the Q3 is in a closed state, and at the moment, the Q3 has no influence on the reference voltage Vref; when the switching power supply is turned off, the square wave signal output by the PWM controller is immediately turned off, at this time, the capacitor C4 discharges through the R4, the base potential of the Q3 rapidly decreases, the Q3 immediately turns on to form a discharge path to the reference voltage Vref together with the resistor R5, the reference voltage Vref rapidly decreases, the reference voltage rises from a very low position when the switching power supply is turned on again, so that the turn-on waveform when the switching power supply is turned on again rapidly rises smoothly, the turn-on waveform is as shown in fig. 5, the working process is as shown in fig. 3, the discharge time can be adjusted by changing the values of the capacitor C4 and the resistors R4 and R5, and the output voltage of the switching power supply is ensured to rise monotonically when the switching power supply is turned on. The foregoing is illustrative of the preferred embodiments of this invention, and it is to be understood that the invention is not limited to the precise form disclosed herein and that various other combinations, modifications, and environments may be resorted to, falling within the scope of the concept as disclosed herein, as can be modified by the teachings or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (4)
1. A fast reference voltage discharge circuit, characterized by: comprises that
A variable current source for charging;
a current amount adjusting circuit having a 1 st resistor for applying a 1 st voltage and a 2 nd resistor for applying a 2 nd voltage, the current amount adjusting circuit adjusting the current amount of the variable current source to a current amount corresponding to a difference voltage of the 1 st voltage and the 2 nd voltage;
a comparison circuit that compares the magnitude of a charging voltage generated at one end of the capacitor with a reference voltage;
a discharge circuit that discharges the capacitor based on a comparison result of the comparison circuit when the charge voltage exceeds the reference voltage;
and a reference voltage circuit that changes the reference voltage to a value corresponding to a change in the resistance value of the 1 st resistor or the 2 nd resistor so that the frequency signal from the comparator circuit is constant when the resistance value of the 1 st resistor or the 2 nd resistor changes depending on the temperature characteristic.
2. The fast reference voltage discharge circuit of claim 1, wherein: the current amount adjusting circuit includes a current amount adjusting error amplifier for supplying a current corresponding to a difference voltage between the 1 st voltage and the 2 nd voltage to either the 1 st resistor or the 2 nd resistor and the capacitor.
3. The fast reference voltage discharge circuit of claim 1, wherein: the reference voltage discharge circuit includes:
an inversely proportional variable current source which supplies a current corresponding to a difference voltage between the 1 st voltage and the 2 nd voltage and generates a current inversely proportional to a resistance value of either the 1 st resistor or the 2 nd resistor;
a capacitor for charging and discharging;
a switching circuit that charges the charge/discharge capacitor only during a 1 st period by using a current from the inverse-proportional variable current source, then holds a charge voltage of the charge/discharge capacitor only during a 2 nd period, and then discharges the charge voltage of the charge/discharge capacitor only during a 3 rd period;
a switch control circuit for controlling the opening and closing operations of the switch circuit;
and an output circuit for outputting the reference voltage by using the holding voltage of the charge/discharge capacitor.
4. The fast reference voltage discharge circuit of claim 1, wherein: the inversely proportional variable current source has:
a 3 rd resistor which supplies a current corresponding to a difference voltage between the 1 st voltage and the 2 nd voltage and has the same temperature characteristic as either the 1 st resistor or the 2 nd resistor;
an error amplifier which operates according to a difference voltage between the voltage generated in the 3 rd resistor and the constant voltage;
a transistor for adjusting the amount of current supplied to the 3 rd resistor by using the output of the error amplifier;
the current flowing through the 3 rd resistor is set to be inversely proportional to the current.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111305938.0A CN113885635A (en) | 2021-11-05 | 2021-11-05 | Quick reference voltage discharge circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111305938.0A CN113885635A (en) | 2021-11-05 | 2021-11-05 | Quick reference voltage discharge circuit |
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| Publication Number | Publication Date |
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| CN113885635A true CN113885635A (en) | 2022-01-04 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202111305938.0A Pending CN113885635A (en) | 2021-11-05 | 2021-11-05 | Quick reference voltage discharge circuit |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1818705A (en) * | 2005-01-18 | 2006-08-16 | 三洋电机株式会社 | Voltage-frequency conversion apparatus and method of generating reference voltage therefor |
| CN1818681A (en) * | 2005-01-21 | 2006-08-16 | 三洋电机株式会社 | Voltage-frequency conversion apparatus and method of changing reference voltage thereof |
| TW200632331A (en) * | 2005-01-21 | 2006-09-16 | Sanyo Electric Co | Voltage-frequency conversion device and reference voltage changing method of the same |
-
2021
- 2021-11-05 CN CN202111305938.0A patent/CN113885635A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1818705A (en) * | 2005-01-18 | 2006-08-16 | 三洋电机株式会社 | Voltage-frequency conversion apparatus and method of generating reference voltage therefor |
| CN1818681A (en) * | 2005-01-21 | 2006-08-16 | 三洋电机株式会社 | Voltage-frequency conversion apparatus and method of changing reference voltage thereof |
| TW200632331A (en) * | 2005-01-21 | 2006-09-16 | Sanyo Electric Co | Voltage-frequency conversion device and reference voltage changing method of the same |
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Application publication date: 20220104 |
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