CN114759768A - Switch control circuit, switch control method and switch power supply - Google Patents

Switch control circuit, switch control method and switch power supply Download PDF

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Publication number
CN114759768A
CN114759768A CN202210404447.XA CN202210404447A CN114759768A CN 114759768 A CN114759768 A CN 114759768A CN 202210404447 A CN202210404447 A CN 202210404447A CN 114759768 A CN114759768 A CN 114759768A
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China
Prior art keywords
resistor
coupled
pin
circuit
current
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CN202210404447.XA
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Chinese (zh)
Inventor
俞秀峰
赵卫
张波
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Shenzhen Biyi Microelectronics Co ltd
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Shenzhen Biyi Microelectronics Co ltd
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Priority to CN202210404447.XA priority Critical patent/CN114759768A/en
Publication of CN114759768A publication Critical patent/CN114759768A/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
    • G01K7/22—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1582—Buck-boost converters

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention provides a switch control circuit, a switch control method and a switch power supply, wherein the switch control circuit is used for controlling a main switch tube in the switch power supply and comprises a control chip, a first resistor, a thermosensitive element and a filter circuit; the control chip is provided with a first pin, a first resistor is connected with the filter circuit in series and coupled between the first pin and a sampling resistor, the sampling resistor is used for sampling current flowing through the main switching tube, and the thermosensitive element is connected with the first resistor in parallel; when the main switching tube is in an open state, the control chip samples through the first pin to obtain a current sampling signal, and the current sampling signal represents current flowing through the main switching tube. When the main switching tube is in a turn-off state, the control chip outputs preset current or preset voltage through the first pin so as to obtain a detection signal to realize temperature detection. The switch control circuit, the switch control method and the switch power supply effectively simplify the circuit structure and obtain higher control precision.

Description

Switch control circuit, switch control method and switch power supply
Technical Field
The invention belongs to the field of power electronics, relates to a switch control technology, and particularly relates to a switch control circuit, a switch control method and a switch power supply.
Background
The switching power supply is one of the major products in the field of power electronics, and is widely applied to most electronic devices such as consumer electronics and communication equipment due to its advantages of light weight, miniaturization, wide input voltage range, high power density and conversion efficiency, low standby power consumption, and the like.
In order to enable the switching power supply to be suitable for different load conditions and complex working conditions and ensure that the switching power supply works normally and is not easy to damage, a corresponding protection circuit is arranged during the design of the switching control circuit. As shown in fig. 1, the switching power supply includes a control chip, a main switch Q1, a sampling resistor Rcs, a resistor R2, a capacitor C1, and the like. The control chip is provided with a CS pin, a first end of the resistor R2 is coupled with the CS pin, a first end of the sampling resistor Rcs is respectively coupled with a second end of the resistor R2 and the drain electrode of the main switching tube Q1, and a second end of the sampling resistor Rcs is coupled with the ground. A first terminal of the capacitor C1 is coupled to a first terminal of the resistor R2, and a second terminal of the capacitor C1 is coupled to ground. In addition, the switching power supply further includes a resistor R1, a thermistor NTC, a diode D2, and the like. The anode of the diode D2 is coupled to one end of the auxiliary winding, the cathode of the diode D2 is coupled to a first end of the thermistor NTC, a second end of the thermistor NTC is coupled to a first end of the resistor R1, and a second end of the resistor R1 is coupled to the CS pin. When the main switch tube Q1 is in the on state, the control chip can obtain a current sampling signal representing the current flowing through the main switch tube Q1. When the main switching tube Q1 is in an off state, current is generated at the auxiliary winding, the diode D2 is conducted, so that the control chip can obtain detection voltage, the resistance value of the thermistor NTC can change along with the change of the detection temperature, the detection voltage can represent the detection temperature, and the over-temperature protection of the switching power supply is realized. According to the technical scheme, the current detection and the over-temperature detection are realized through the CS pin, and the pin requirements of the control chip during setting are reduced. However, this solution also has some problems: on one hand, the voltage stress of the diode D1 is high, so that the selection of the diode is limited, and the corresponding cost is increased; on the other hand, the diode D1 has reverse recovery current due to fast switching along with the main switching tube Q1, so that interference is caused to the current sampling signal; in addition, the detection voltage obtained at the CS pin is related to not only the resistance value of the NTC thermistor but also the terminal voltage of the auxiliary winding, and therefore, the wide output voltage application has certain limitations.
In view of the above, there is a need to provide a new structure or control method for solving at least some of the problems described above.
Disclosure of Invention
The invention provides a switch control circuit, a switch control method and a switch power supply, aiming at one or more problems in the prior art.
According to one aspect of the invention, a switch control circuit is disclosed, the switch control circuit is used for controlling a main switching tube in a switch power supply and comprises a control chip, a first resistor, a thermosensitive element and a filter circuit; the control chip is provided with a first pin, a first resistor is connected with the filter circuit in series, the first resistor and the filter circuit are coupled between the first pin and a sampling resistor, the sampling resistor is used for sampling current flowing through the main switching tube, and the thermosensitive element is connected with the first resistor in parallel; wherein the content of the first and second substances,
the control chip samples and obtains a current sampling signal through the first pin when the main switching tube is in a switched-on state, and the current sampling signal represents current flowing through the main switching tube; and
when the main switching tube is in a turn-off state, the control chip outputs preset current or preset voltage through the first pin so as to obtain a detection signal to realize temperature detection.
In an embodiment of the present invention, the switch control circuit further includes:
a first diode, the anode of which is coupled with the auxiliary winding; and
and a first end of the second capacitor is respectively coupled with the cathode of the first diode and the second pin of the control chip, and a second end of the second capacitor is coupled with the ground.
In an embodiment of the present invention, the switch control circuit further includes: the first end of the third capacitor is coupled to the first pin, and the second end of the third capacitor is coupled to the ground.
In an embodiment of the present invention, the switch control circuit further includes: the first end of the third capacitor is coupled to the first end of the first resistor, and the second end of the third capacitor is coupled to the second end of the first resistor.
In an embodiment of the present invention, the filter circuit includes:
a first end of the second resistor is coupled to the second end of the first resistor, and a second end of the second resistor is coupled to the first end of the sampling resistor; and
the first end of the first capacitor is coupled to the second end of the first resistor, and the second end of the first capacitor is coupled to ground.
In an embodiment of the present invention, the control chip includes:
the first input end of the current control circuit is coupled with the first pin to obtain a current sampling signal, and the second input end of the current control circuit is coupled with the first threshold and used for outputting a current control signal according to the current sampling signal and the first threshold so as to control the switching state of the main switching tube; and
the input end of the driving circuit is coupled with the current control circuit, and the output end of the driving circuit is coupled with the main switching tube.
In an embodiment of the present invention, the control chip includes a temperature control circuit, and the temperature control circuit includes:
the output end of the power supply circuit is coupled with the first pin and used for outputting preset current or preset voltage through the first pin when the main switching tube is in a turn-off state; and
and a first input end of the detection circuit is coupled with the first pin to obtain a detection signal, a second input end of the detection circuit is coupled with the second threshold value, and an output end of the detection circuit is coupled with the driving circuit and used for outputting a temperature control signal according to the detection signal and the second threshold value so as to control the on-off state of the main switching tube.
In an embodiment of the invention, the power supply circuit includes a current source or a voltage source, the current source is configured to provide the predetermined current, and the voltage source is configured to provide the predetermined voltage.
According to another aspect of the invention, a switching power supply is disclosed, comprising a switching control circuit as described in any of the above.
According to another aspect of the invention, a switch control method is disclosed, the switch control method is used for controlling a switch control circuit, and the switch control circuit comprises a control chip, a first resistor, a thermosensitive element and a filter circuit; the control chip is provided with a first pin, a first resistor is connected with the filter circuit in series, the first resistor and the filter circuit are coupled between the first pin and a sampling resistor, the sampling resistor is used for sampling current flowing through the main switching tube, and the thermosensitive element is connected with the first resistor in parallel; the switch control method comprises the following steps:
when the main switching tube is in a switching-on state, a current sampling signal is obtained through sampling of a first pin, and the current sampling signal represents current flowing through the main switching tube; and
when the main switching tube is in a turn-off state, a preset current or a preset voltage is output through the first pin, so that a detection signal is obtained to realize temperature detection.
The invention provides a switch control circuit, a switch control method and a switch power supply, wherein the switch control circuit is used for controlling a main switch tube in the switch power supply and comprises a control chip, a first resistor, a thermosensitive element and a filter circuit; the control chip is provided with a first pin, a first resistor is connected with the filter circuit in series, the first resistor and the filter circuit are coupled between the first pin and the sampling resistor, the sampling resistor is used for sampling current flowing through the main switching tube, and the thermosensitive element is connected with the first resistor in parallel. When the main switching tube is in an on state, the control chip obtains a current sampling signal through the first pin, and the current sampling signal represents current flowing through the main switching tube. When the main switching tube is in a turn-off state, the control chip outputs preset current or preset voltage through the first pin so as to obtain a detection signal to realize temperature detection. The switch control circuit, the switch control method and the switch power supply provided by the invention have the advantages that the circuit structure is effectively simplified, and higher control precision is obtained.
Drawings
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention. In the drawings:
fig. 1 shows a schematic circuit diagram of a prior art switching power supply;
fig. 2 is a schematic diagram showing a circuit configuration of a switching power supply according to an embodiment of the present invention;
fig. 3 shows a schematic circuit configuration diagram of a switching power supply according to another embodiment of the present invention;
fig. 4 is a schematic circuit diagram of a switching power supply according to another embodiment of the present invention.
Detailed Description
For a further understanding of the present invention, reference will now be made to the following preferred embodiments of the invention in conjunction with the examples, but it is to be understood that the description is intended to further illustrate the features and advantages of the invention and is not intended to limit the scope of the claims which follow.
The description in this section is for several exemplary embodiments only and the invention is not to be limited in scope by the embodiments described. Combinations of different embodiments, and substitutions of features from different embodiments, or similar prior art means may be substituted for or substituted for features of the embodiments shown and described.
The term "coupled" or "connected" in this specification includes both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a conductor, wherein the electrically conductive medium may contain parasitic inductance or parasitic capacitance, or through an intermediate circuit or component as described in the embodiments in the specification; indirect connections may also include connections through other active or passive devices that perform the same or similar function, such as connections through switches, signal amplification circuits, follower circuits, and so on. "plurality" or "plurality" means two or more. In addition, in the present invention, terms such as first and second are mainly used for distinguishing one technical feature from another technical feature, and do not necessarily require or imply any actual relationship or order between the technical features.
The embodiment of the invention discloses a switch control circuit, which is used for controlling a main switch tube in a switch power supply. As shown in fig. 2, the switch control circuit includes a control chip, a first resistor R1, a thermistor, and a filter circuit. The control chip is provided with a first pin which is a CS pin. The first end of the first resistor R1 is coupled to the first pin, the first end of the filter circuit is coupled to the second end of the first resistor R1, the second end of the filter circuit is coupled to the sampling resistor Rcs, and the thermistor is connected in parallel with the first resistor R1. When the main switch tube Q1 is in the on state, the control chip obtains a current sampling signal through the first pin sampling, and the current sampling signal represents the current flowing through the main switch tube Q1. In addition, when the main switching tube Q1 is in an off state, the control chip outputs a preset current or a preset voltage to the first resistor through the first pin, so that a detection signal is obtained through the first pin to realize temperature detection. The detection signal can represent the temperature of the chip, the temperature can be controlled according to the detection signal, and when the chip is overheated, the over-temperature protection can be triggered. In order to reduce power consumption, the control chip stops outputting the preset current or the preset voltage through the first pin after obtaining the detection signal. In one embodiment as shown in fig. 2, when the main switch Q1 is in the on state, the current flows through the main switch Q1, and the control chip can obtain a current sampling signal through the CS pin, where the current sampling signal represents the current flowing through the main switch Q1. Specifically, the voltage signal of the first end of the sampling resistor Rcs is filtered and outputs a signal to the second end of the first resistor R1. In addition, when the main switching tube Q1 is in an off state, the control chip outputs a preset current from the CS pin to the first resistor R1, so that the control chip can obtain a detection signal through the CS pin, and perform temperature detection to realize over-temperature protection control.
In an embodiment of the invention, the main switch Q1 is disposed outside the control chip, and the control chip is provided with a driving pin Gate, and the driving pin Gate is coupled to the control end of the main switch Q1. Preferably, a third resistor R3 is further coupled between the driving pin Gate and the main switch tube Q1. In another embodiment, the main switch Q1 is disposed in a control chip, the control chip has a Drain pin Drain, and the Drain of the main switch Q1 is coupled to the Drain pin Drain of the control chip. In an embodiment of the present invention, the main switch Q1 is a transistor, and the main switch Q1 may be one of a metal oxide semiconductor field effect transistor (MOSFET for short), a junction field effect transistor (JFET for short), an insulated gate bipolar transistor (IGBT for short), and the like.
In an embodiment of the invention, the filter circuit includes a second resistor and a first capacitor. The first end of the second resistor is coupled to the second end of the first resistor, and the second end of the second resistor is coupled to the first end of the sampling resistor. The first end of the first capacitor is coupled to the second end of the first resistor, and the second end of the first capacitor is coupled to ground.
In one embodiment of the present invention, the thermosensitive element includes a thermistor. At normal temperature (which can be defined as 25 ℃ in general), the ratio of the resistance value of the thermosensitive element to the resistance value of the first resistor is less than 5. In another embodiment of the present invention, the thermistor includes at least one of a positive temperature coefficient thermistor, a negative temperature coefficient thermistor, a temperature controlled switch, and the like.
In an embodiment of the invention, as shown in fig. 2, the switch control circuit further includes a first diode D1 and a second capacitor C2. An anode of the first diode D1 is coupled to an auxiliary winding in the switching power supply, a first end of the second capacitor C2 is coupled to a cathode of the first diode D2 and a second pin of the control chip, respectively, the second pin is a VDD pin, and a second end of the second capacitor C2 is coupled to ground. When the main switch tube Q1 is in an off state, the second capacitor C2 coupled to the VDD pin of the control chip may be charged through the auxiliary winding.
In another embodiment of the present invention, as shown in fig. 3, the switch control circuit includes a control chip, a first resistor R1, a thermal sensor NTC, a second resistor R2, a first capacitor C1, and a third capacitor C3. The control chip is provided with a CS pin, a first end of the third capacitor C3 is coupled with the CS pin, and a second end of the third capacitor C3 is coupled with the ground. The first end of the first resistor R1 is coupled to the CS pin, the first end of the second resistor R2 is coupled to the second end of the first resistor R1, the first end of the sampling resistor Rcs is coupled to the second end of the second resistor R2, and the second end of the sampling resistor Rcs is coupled to ground. The first terminal of the thermistor NTC is coupled to the first terminal of the first resistor R1, and the second terminal of the thermistor NTC is coupled to the second terminal of the first resistor R1. The first end of the first capacitor C1 is coupled to the second end of the first resistor R1, and the second end of the first capacitor C1 is coupled to ground. The CS pin is coupled with the ground capacitor, so that an external interference signal to the CS pin can be filtered, and the control precision of the switch control circuit is effectively improved.
In another embodiment of the present invention, as shown in fig. 4, the switch control circuit includes a control chip, a first resistor R1, a thermal sensor NTC, a third capacitor C3, a second resistor R2, a sampling resistor Rcs, and a first capacitor C1. The control chip is provided with a first pin, the first pin is a CS pin, a first end of the first resistor R1 is coupled to the CS pin, a first end of the second resistor R2 is coupled to a second end of the first resistor R1, a first end of the sampling resistor Rcs is coupled to a second end of the second resistor R2, and a second end of the sampling resistor Rcs is coupled to ground. The thermistor NTC and the third capacitor C3 are respectively connected in parallel with the first resistor R1. The first terminal of the first capacitor C1 is coupled to the first terminal of the second resistor R2, and the second terminal of the first capacitor C1 is coupled to the second terminal of the sampling resistor Rcs. The third capacitor is connected in parallel to the thermosensitive element, so that interference signals of the outside to the CS pin can be filtered, and the control precision of the switch control circuit is effectively improved.
In an embodiment of the invention, the control chip comprises a current control circuit and a drive circuit. The first input end of the current control circuit is coupled with the first pin to obtain a current sampling signal, the second input end of the current control circuit is coupled with the first threshold, and the current control circuit is used for outputting a current control signal according to the current sampling signal and the first threshold and outputting the current control signal to the driving circuit so as to control the switching state of the main switching tube. Specifically, the current control circuit obtains the current control signal by comparing the current sampling signal with a first threshold value. The input end of the driving circuit is coupled with the output end of the current control circuit, the output end of the driving circuit is coupled with the control end of the main switching tube, and the driving circuit outputs a driving signal to control the switching state of the main switching tube.
In another embodiment of the present invention, the control chip includes a temperature control circuit and a driving circuit. The temperature control circuit includes a current source and a detection circuit. The output end of the current source is coupled with the first pin, the first pin is a CS pin, and the current source is used for outputting preset current to obtain a detection signal when the main switching tube is in a turn-off state. After the detection signal is obtained, the control chip can control to stop outputting the preset current, so that the loss is reduced. In a specific embodiment, the control chip outputs a preset current from the CS pin, and obtains a detection signal by detecting the CS pin, where the detection signal is a detection voltage, and the detection voltage can represent a detection temperature, so as to implement over-temperature protection control. A first input terminal of the detection circuit is coupled to the first pin to obtain a detection signal, specifically, the detection signal is a detection voltage. The second input end of the detection circuit is coupled with the second threshold, the output end of the detection circuit is coupled with the input end of the driving circuit, the detection circuit is used for comparing the detection signal with the second threshold to obtain a temperature control signal, and the detection circuit outputs the temperature control signal to the driving circuit. The driving circuit controls the on-off state of the main switching tube according to the temperature control signal. When the control chip triggers the over-temperature protection (for example, when the detection signal is greater than a second threshold), the control chip controls to stop outputting the switch control signal PWM or reduce the energy output to the load, wherein the switch control signal PWM is a driving signal of the main switching tube.
In yet another embodiment of the present invention, the control chip includes a temperature control circuit and a driving circuit. The temperature control circuit includes a voltage source and a detection circuit. The output end of the voltage source is coupled with a first pin, the first pin is a CS pin, and the voltage source is used for outputting a preset voltage when the main switching tube is in a turn-off state. After the detection signal is obtained, the control chip can control to stop outputting the preset voltage, so that the loss is reduced. In a specific embodiment, the control chip provides a preset voltage to the CS pin, and obtains a detection signal by detecting the CS pin, where the detection signal is an electrical signal representing a detection current, the detection current is a current flowing through the CS pin, and the detection current can represent a detection temperature, thereby implementing over-temperature protection control. In an embodiment of the invention, the first input terminal of the detection circuit is coupled to the first pin to obtain the detection signal, and specifically, the detection signal may be a voltage signal or a current signal. The second input end of the detection circuit is coupled with the second threshold, the output end of the detection circuit is coupled with the input end of the driving circuit, the detection circuit is used for comparing the detection signal with the second threshold to obtain a temperature control signal, and the detection circuit outputs the temperature control signal to the driving circuit. The driving circuit controls the on-off state of the main switching tube according to the temperature control signal.
In an embodiment of the present invention, the control chip includes a temperature control circuit, and the temperature control circuit includes a power supply circuit and a detection circuit. The output end of the power supply circuit is coupled with the first pin, and the power supply circuit is used for outputting preset current or preset voltage to the first pin through the first pin when the main switching tube is in a turn-off state. The first input end of the detection circuit is coupled with the first pin to obtain a detection signal, the second input end of the detection circuit is coupled with the second threshold, the output end of the detection circuit is coupled with the driving circuit, and the detection circuit is used for outputting a temperature control signal according to the detection signal and the second threshold so as to control the on-off state of the main switching tube.
According to the switch control circuit provided by the invention, current detection and temperature detection can be realized through a single pin, and the requirements on chip pins are reduced. In addition, the diode in the prior art is omitted and the technical problems in the prior art are solved. The invention couples the heat sensitive element between the first pin and the chip ground. When the main switching tube is in a switching-on state, a current sampling signal is obtained through sampling of the first pin, and the control chip controls current flowing through the main switching tube according to the current sampling signal. When the main switching tube is in a turn-off state, the temperature change can be represented according to the change of the resistance value externally connected with the first pin, and the control chip outputs preset current or preset voltage to the first resistor through the first pin so as to obtain a detection signal and realize over-temperature protection control. In the invention, the thermosensitive element is connected with the first resistor in parallel, and the circuit structure that the thermosensitive element is connected with the filter circuit in series is combined, so that the resistance value of the thermosensitive element is prevented from influencing the filter constant of the filter circuit. If the thermosensitive element is arranged in the filter circuit, the thermosensitive element will influence the RC filter constant, which will cause the sampling RC delay time to change along with the change of temperature, thereby influencing the sampling precision of the current sampling signal. In the invention, the thermosensitive element is connected with the filter circuit in series, and when the current sampling signal is acquired, the thermosensitive element is behind the filter circuit, and no sampling delay is introduced, so that no additional gain compensation is needed when the current sampling signal is acquired, and the current detection is not influenced when the main switch tube is in the on period. In addition, if the thermistor is connected in parallel with the resistor in the filter circuit, since the resistance of the resistor in the filter circuit is relatively small (the resistance is generally about 1k-2k ohm), while the resistance of the thermistor connected in parallel with the resistor in the filter circuit is in the order of 10k ohm, the resistance change of the thermistor connected in parallel has little influence on the resistance after parallel connection, and thus the temperature detection precision is low. In the invention, the first resistor connected in parallel with the thermosensitive element can select a resistor with a larger resistance value, so that the temperature detection precision is improved. In conclusion, the invention effectively simplifies the circuit structure and obtains higher control precision while considering the function realization.
The invention further discloses a switching power supply, which comprises the switching control circuit, wherein the switching control circuit is used for controlling the switching state of the main switching tube, and the output of the switching power supply can be accurately controlled by controlling the switching state of the main switching tube. In an embodiment of the invention, the switching power supply is one of a Buck type switching power supply, a Boost type switching power supply, a Buck-Boost type switching power supply, a flyback type switching power supply, a full-bridge type switching power supply, a half-bridge type switching power supply, an LLC type switching power supply, and the like.
The invention also discloses a switch control method, which is used for controlling the switch control circuit, wherein the switch control circuit comprises a control chip, a first resistor, a thermosensitive element and a filter circuit; the control chip is provided with a first pin, the first end of the first resistor is coupled with the first pin, the first end of the filter circuit is coupled with the second end of the first resistor, the second end of the filter circuit is coupled with the sampling resistor, and the thermosensitive element is connected with the first resistor in parallel; the switch control method comprises the following steps: when the main switching tube is in a switching-on state, a current sampling signal is obtained through sampling of a first pin, and the current sampling signal represents current flowing through the main switching tube; and when the main switching tube is in a turn-off state, outputting a preset current or a preset voltage through the first pin so as to obtain a detection signal to realize temperature detection.
In another embodiment of the present invention, the switching control method further includes controlling the switching state of the main switching tube according to the current sampling signal and the detection signal. Specifically, the control chip generates a current control signal according to the current sampling signal and a first threshold, the control chip generates a temperature control signal according to the detection signal and a second threshold, and the control chip generates a driving signal according to the current control signal and the temperature control signal to control the on-off state of the main switching tube.
Those skilled in the art should understand that the logic controls such as "high level" and "low level", "set" and "reset", "and gate" and "or gate", "non-inverting input" and "inverting input" in the logic controls referred to in the specification or the drawings can be interchanged or changed, and the subsequent logic controls can be adjusted to achieve the same functions or purposes as the above-described embodiments.
The description and applications of the invention herein are illustrative and are not intended to limit the scope of the invention to the embodiments described above. The description related to the effect or advantage mentioned in the specification may not be embodied in the actual experimental examples due to the uncertainty of specific condition parameters or other factors, and the description related to the effect or advantage is not intended to limit the scope of the invention. Variations and modifications of the embodiments disclosed herein are possible, and alternative and equivalent various components of the embodiments will be apparent to those skilled in the art. It will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, and with other components, materials, and parts, without departing from the spirit or essential characteristics thereof. Other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention.

Claims (10)

1. A switch control circuit is used for controlling a main switch tube in a switch power supply and is characterized by comprising a control chip, a first resistor, a thermosensitive element and a filter circuit; the control chip is provided with a first pin, a first resistor is connected with the filter circuit in series, the first resistor and the filter circuit are coupled between the first pin and the sampling resistor, the sampling resistor is used for sampling current flowing through the main switching tube, and the thermosensitive element is connected with the first resistor in parallel; wherein the content of the first and second substances,
the control chip samples and obtains a current sampling signal through the first pin when the main switching tube is in a switched-on state, and the current sampling signal represents current flowing through the main switching tube; and
when the main switching tube is in a turn-off state, the control chip outputs preset current or preset voltage through the first pin so as to obtain a detection signal to realize temperature detection.
2. The switch control circuit of claim 1, further comprising:
a first diode, the anode of which is coupled with the auxiliary winding; and
and a first end of the second capacitor is respectively coupled with the cathode of the first diode and the second pin of the control chip, and a second end of the second capacitor is coupled with the ground.
3. The switch control circuit of claim 1, further comprising:
the first end of the third capacitor is coupled to the first pin, and the second end of the third capacitor is coupled to ground.
4. The switch control circuit of claim 1, further comprising:
the first end of the third capacitor is coupled to the first end of the first resistor, and the second end of the third capacitor is coupled to the second end of the first resistor.
5. The switch control circuit of claim 1, wherein the filter circuit comprises:
a first end of the second resistor is coupled to the second end of the first resistor, and a second end of the second resistor is coupled to the first end of the sampling resistor; and
the first end of the first capacitor is coupled to the second end of the first resistor, and the second end of the first capacitor is coupled to ground.
6. The switch control circuit of claim 1, wherein the control chip comprises:
the first input end of the current control circuit is coupled with the first pin to obtain a current sampling signal, and the second input end of the current control circuit is coupled with the first threshold and used for outputting a current control signal according to the current sampling signal and the first threshold so as to control the switching state of the main switching tube; and
the input end of the driving circuit is coupled with the current control circuit, and the output end of the driving circuit is coupled with the main switching tube.
7. The switch control circuit of claim 6, wherein the control chip comprises a temperature control circuit, the temperature control circuit comprising:
the output end of the power supply circuit is coupled with the first pin and used for outputting preset current or preset voltage through the first pin when the main switching tube is in a turn-off state; and
the first input end of the detection circuit is coupled with the first pin to obtain a detection signal, the second input end of the detection circuit is coupled with the second threshold value, and the output end of the detection circuit is coupled with the driving circuit and used for outputting a temperature control signal according to the detection signal and the second threshold value so as to control the switching state of the main switching tube.
8. The switch control circuit of claim 7, wherein the power supply circuit comprises a current source to provide the predetermined current or a voltage source to provide the predetermined voltage.
9. A switching power supply, characterized in that it comprises a switch control circuit according to any one of claims 1-8.
10. A switch control method is used for controlling a switch control circuit and is characterized in that the switch control circuit comprises a control chip, a first resistor, a thermosensitive element and a filter circuit; the control chip is provided with a first pin, a first resistor is connected with the filter circuit in series, the first resistor and the filter circuit are coupled between the first pin and a sampling resistor, the sampling resistor is used for sampling current flowing through the main switching tube, and the thermosensitive element is connected with the first resistor in parallel; the switch control method comprises the following steps:
when the main switching tube is in a switching-on state, a current sampling signal is obtained through sampling of a first pin, and the current sampling signal represents current flowing through the main switching tube; and
when the main switching tube is in a turn-off state, a preset current or a preset voltage is output through the first pin, so that a detection signal is obtained to realize temperature detection.
CN202210404447.XA 2022-04-18 2022-04-18 Switch control circuit, switch control method and switch power supply Pending CN114759768A (en)

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CN202210404447.XA CN114759768A (en) 2022-04-18 2022-04-18 Switch control circuit, switch control method and switch power supply

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210404447.XA CN114759768A (en) 2022-04-18 2022-04-18 Switch control circuit, switch control method and switch power supply

Publications (1)

Publication Number Publication Date
CN114759768A true CN114759768A (en) 2022-07-15

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