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CN115118150B - Method and circuit for automatically identifying and adapting X capacitor discharging function in switch circuit - Google Patents

Method and circuit for automatically identifying and adapting X capacitor discharging function in switch circuit Download PDF

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Publication number
CN115118150B
CN115118150B CN202210783618.4A CN202210783618A CN115118150B CN 115118150 B CN115118150 B CN 115118150B CN 202210783618 A CN202210783618 A CN 202210783618A CN 115118150 B CN115118150 B CN 115118150B
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circuit
voltage
identification
nmos transistor
starting
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CN115118150A (en
Inventor
程兆辉
于玮
蒋金星
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Dongke Semiconductor Anhui Co ltd
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Dongke Semiconductor Anhui Co ltd
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS 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
    • H02M1/00Details of apparatus for conversion
    • H02M1/36Means for starting or stopping converters
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS 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
    • H02M1/00Details of apparatus for conversion
    • H02M1/08Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS 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
    • H02M1/00Details of apparatus for conversion
    • H02M1/32Means for protecting converters other than automatic disconnection
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS 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
    • H02M7/00Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
    • H02M7/02Conversion of AC power input into DC power output without possibility of reversal
    • H02M7/04Conversion of AC power input into DC power output without possibility of reversal by static converters
    • H02M7/06Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
    • H02M7/08Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode arranged for operation in parallel
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The embodiment of the invention relates to a method and a circuit for automatically identifying and adapting an X capacitor discharging function in a switch circuit, wherein the method comprises the following steps: when the voltage of the starting capacitor is larger than the reset voltage set in the starting circuit, the starting circuit outputs a power-on reset signal POR to start the identification circuit; the identification circuit starts a first timing, in a first timing period, the identification circuit detects a voltage Vhv from an input end HV of the high-voltage starting circuit connected with the switching power supply circuit and provides a pull-down current to the ground, the voltage Vhv is compared with a reference voltage Vref arranged in the identification circuit, when the voltage Vhv is more than Vref, a voltage state indication signal GHV=1 output by the identification circuit is generated, and otherwise, GHV=0; the identification circuit counts whether the duration of the voltage state indication signal ghv=0 in the first timing period is greater than a set time threshold, if so, the identification result is that the switching power supply circuit needs the X capacitor discharging function, otherwise, the identification result is that the switching power supply circuit does not need the X capacitor discharging function.

Description

Method and circuit for automatically identifying and adapting X capacitor discharging function in switch circuit
Technical Field
The invention relates to the technical field of switching power supply circuits, in particular to a method and a circuit for automatically identifying and adapting an X capacitor discharging function in a switching circuit.
Background
The safety X capacitor is a capacitor connected between the live wire and the zero wire in a bridging way, is generally used for filtering in an anti-interference circuit and mainly plays a role in filtering differential mode interference. When the X capacitor is used, the power line plug is electrified for a long time when the power line is required to be prevented from being pulled out, so that the power line plug is required to be reduced to a specified voltage within a specified time after being pulled out according to the relevant safety certification standard.
Taking flyback switching power supplies as an example, the existing control chips are divided into two types:
One type of capacitor discharge without X, as shown in figure 1, needs to discharge in parallel with the discharge resistor Rx at the X capacitance Cx. The chip is simple in design and application, but the light load efficiency and standby power consumption of the switching power supply are affected because the bleeder resistor always consumes energy, and the chip is suitable for application with low requirements on efficiency and standby power consumption.
In another type of capacitor discharging function with X, as shown in FIG. 2, there is no need of connecting Rx in parallel, two rectifying diodes D1 and D2 are required to be connected to HV pins, when the chip detects that the power line is pulled out, the chip performs the discharging work of the X capacitor, and the chip can avoid reactive power consumption of the switching power supply during working, thereby being suitable for application with high requirements on the switching power supply.
For different application environments, the two types of chips with and without the X capacitor discharging function are selected to be different. From the perspective of a chip application user, the chip needs to be selected according to the application when the product is developed, but when the application environment or the application scene changes, for example, when the product is required to be upgraded, the previously selected chip is possibly not suitable for a new application environment any more, and the chip needs to be replaced at the moment, so that the product is difficult to update, and the time and the technical difficulty brought by re-debugging the product after the chip is replaced are not negligible. For chip designers and manufacturers, two kinds of chips are researched and manufactured simultaneously, and the problems of long design period, long production period, high research and development cost and the like are also existed.
Disclosure of Invention
The invention aims to provide a method and a circuit for automatically identifying and adapting an X capacitor discharging function in a switch circuit, which can enable the switch circuit to be simultaneously suitable for application occasions needing X capacitor discharging, can also be applied to application occasions needing X capacitor discharging, can realize automatic identification and adaptation of X capacitor discharging, not only simplifies the complexity of chip design and production, but also enables products to obtain better applicability and compatibility, and simultaneously reduces the cost. The identification circuit can be automatically turned off under the application environment without discharging the X capacitor, so that the power consumption is reduced.
To this end, in a first aspect, an embodiment of the present invention provides a method for automatically identifying and adapting an X capacitor discharging function in a switching circuit, where the method includes:
After the switch power supply circuit is powered on, charging a starting capacitor, and when the voltage of the starting capacitor is larger than the reset voltage set in the starting circuit, outputting a power-on reset signal POR by the starting circuit to start the identification circuit;
The identification circuit starts a first timing, in a first timing period, the identification circuit detects a voltage Vhv from an input end HV of the high-voltage starting circuit connected with the switching power supply circuit and provides a pull-down current to the ground, the voltage Vhv is compared with a reference voltage Vref arranged in the identification circuit, when the Vhv is more than Vref, the voltage state output by the identification circuit indicates a signal GHV=1, otherwise, GHV=0;
The identification circuit counts whether the duration of the voltage state indication signal ghv=0 in the first timing period is greater than a set time threshold, if so, the identification result is that the switching power supply circuit needs the X capacitor discharging function, otherwise, the identification result is that the switching power supply circuit does not need the X capacitor discharging function.
Preferably, the identification circuit is connected to the input end HV of the high-voltage starting circuit through an NMOS transistor;
the input end HV of the high-voltage starting circuit is connected to the front or rear of the rectifier bridge of the switching power supply circuit.
Preferably, the method further comprises an automatic adaptation process;
The automatic adaptation process specifically comprises the following steps: and when the duration of the voltage state indicating signal GHV=0 in the timing period is larger than a set time threshold, the identification circuit generates an identification result signal of a first level to enable an X capacitance discharging function of the switching power supply circuit, and otherwise, generates an identification result signal of a second level to disconnect the identification circuit from the switching power supply circuit.
Further preferably, after the identification circuit generates the identification result signal of the first level to enable the X capacitance discharging function of the switching power supply circuit, the method further includes:
And discharging X capacitance to the switching power supply circuit through the identification circuit.
Preferably, after the starting circuit outputs a power-on reset signal to start the identification circuit, the identification circuit outputs a starting circuit control signal PS to control the starting circuit to be turned off.
In a second aspect, an embodiment of the present invention provides a circuit for automatically identifying and adapting an X capacitor discharging function in a switching circuit, including: a start-up capacitor, a start-up circuit, an identification circuit and an NMOS transistor M2;
The starting capacitor is connected with the comparison signal input end of the starting circuit;
The drain electrode of the NMOS transistor M2 is connected with the input end HV of a high-voltage starting circuit connected with the switching power supply circuit, and the input end HV of the high-voltage starting circuit is connected in front of or behind a rectifier bridge of the switching power supply circuit; the grid electrode and the source electrode of the NMOS transistor M2 are respectively connected with the starting circuit and the identification circuit;
after the switch power supply circuit is powered on, the NMOS transistor M2 is conducted, a starting capacitor is charged through the input end HV of the high-voltage starting circuit, the NMOS transistor M2 and the starting circuit, and when the voltage of the starting capacitor is larger than the reset voltage set in the starting circuit, the starting circuit outputs a power-on reset signal POR to the identification circuit;
the identification circuit starts first timing according to the power-on reset signal, and provides a source-to-ground pull-down current of the NMOS transistor M2 for the input end HV of the high-voltage starting circuit through the NMOS transistor M2 and the identification circuit;
The identification circuit detects the voltage Vhv of the input end HV of the high-voltage starting circuit in a first timing period, compares the voltage Vhv with a reference voltage Vref arranged in the identification circuit, and outputs a voltage state indication signal GHV=1 when the voltage Vhv is more than Vref, otherwise, GHV=0;
And the identification circuit counts whether the duration of the voltage state indication signal GHV=0 in the timing period is larger than a set time threshold, if so, a first-level identification result signal is generated to enable an X capacitor discharging function of the switching power supply circuit, otherwise, a second-level identification result signal is generated to control the NMOS transistor M2 to disconnect the identification circuit from the switching power supply circuit.
Preferably, the starting circuit specifically includes: the device comprises an NMOS transistor N1, a first resistor R1, a voltage stabilizing tube VR1 and a starting module;
the drain electrode of the NMOS transistor M2 is connected with the input end HV of the high-voltage starting circuit;
The voltage stabilizing tube VR1 is reversely connected between the grid electrode of the NMOS transistor M2 and the ground;
The first resistor R1 is connected between the grid electrode of the NMOS transistor M2 and the input end HV of the high-voltage starting circuit;
The drain of the NMOS transistor N1 is connected with the gate of the NMOS transistor M2, and the source of the NMOS transistor N1 is grounded.
The identification circuit specifically comprises: the device comprises a control module, an analog-to-digital conversion module, a bleeding module and an identification output module;
the control module is connected with the starting circuit, receives the power-on reset signal and a clock signal of the switching power supply circuit, starts first timing, and outputs a preset digital voltage parameter for controlling the magnitude of the release current in the release module and a release control signal of a first level;
The analog-to-digital conversion module is connected with the control module and converts the analog voltage into an analog voltage value according to the preset digital voltage parameter;
The bleeder module is respectively connected with the source electrode of the NMOS transistor M2, the analog-to-digital conversion module and the control module, is controlled to start according to the bleeder control signal of the first level, and is converted into a current value on the bleeder resistor according to the analog voltage value, so that the earth bleeder of the input end HV of the high-voltage starting circuit is formed;
The identification output module is connected with the source electrode of the NMOS transistor M2, compares the Vhv with the Vref, and outputs a voltage state indication signal GHV=1 when the Vhv is more than the Vref, otherwise, the GHV=0;
The control module is further connected with the identification output module, receives the voltage state indication signal GHV output by the identification output module, counts whether the duration of the voltage state indication signal ghv=0 is greater than a set time threshold value in a first timing period, generates the identification result signal of the first level if the duration is greater than the set time threshold value, and generates the identification result signal of the second level if the duration is not greater than the set time threshold value.
Preferably, the control module is further connected to the gate of the NMOS transistor N1, and controls the NMOS transistor N1 to be turned on according to the second level identification result signal, so that the gate potential of the NMOS transistor M2 is pulled down, so that the NMOS transistor M2 is turned off, and the identification circuit is disconnected from the switching power supply circuit.
In a third aspect, an embodiment of the present invention provides a switching circuit, including a circuit for automatically identifying and adapting an X capacitor discharging function in the switching circuit according to the second aspect.
The method for automatically identifying and adapting the X capacitor discharging function in the switch circuit provided by the embodiment of the invention can ensure that the switch circuit is simultaneously applicable to the application occasions needing X capacitor discharging, and can also be applied to the application occasions needing X capacitor discharging. The identification circuit can be automatically turned off under the application environment without discharging the X capacitor, so that the power consumption is reduced.
Drawings
FIG. 1 is a schematic diagram of a prior art discharge-flyback switching power supply without an X capacitor;
FIG. 2 is a schematic diagram of a discharging-flyback switching power supply circuit with X capacitor according to the prior art;
Fig. 3 is a schematic diagram of a switching power supply circuit according to an embodiment of the present invention;
FIG. 4 is a flowchart of a method for automatically identifying and adapting an X capacitor discharging function in a switching circuit according to an embodiment of the present invention;
FIG. 5 is a circuit diagram of an automatic identification and adaptation switch circuit for X capacitor discharge function according to an embodiment of the present invention;
Fig. 6 is a schematic circuit waveform diagram of a switching power supply circuit according to an embodiment of the present invention, in which an input end HV of a high-voltage starting circuit is connected to a front of a rectifier bridge;
Fig. 7 is a schematic circuit waveform diagram of a switching power supply circuit according to an embodiment of the present invention, in which an input end HV of a high-voltage starting circuit is connected to a rectifier bridge;
fig. 8 is a flyback control chip integrated with a circuit for automatically identifying and adapting the X-capacitor discharging function in a switching circuit according to an embodiment of the present invention.
Detailed Description
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
The embodiment of the invention provides a method for automatically identifying and adapting an X capacitor discharging function in a switch circuit, which is applied to the switch circuit shown in fig. 3.
The circuit shown in fig. 3 is a switching power supply circuit provided in an embodiment of the present invention, and a circuit provided in a dashed box is a circuit for implementing a method for automatically identifying and adapting an X capacitor discharging function in a switching circuit according to the present invention, including: a start-up capacitor Cvcc, a start-up circuit 1, a recognition circuit 2 and an NMOS transistor M2. Since the start-up capacitance Cvcc is also the peripheral circuit of the control chip, it is not drawn into the dashed box. The circuit may be integrated in the control chip shown in fig. 1 and 2, or may be a separate chip externally connected to the control chip shown in fig. 1 and 2. Fig. 3 mainly illustrates the switching-in position of the circuit for automatically detecting and adapting the X-capacitor discharging function in the switching power supply circuit, so that the control chip is not shown here.
Fig. 4 is a main step flow of a method for automatically identifying and adapting an X capacitor discharging function in a switch circuit according to an embodiment of the present invention. The description is given with reference to fig. 3 and 4.
Step 110, after the switch power circuit is powered on, charging the starting capacitor, and when the voltage of the starting capacitor is greater than the reset voltage set in the starting circuit, outputting a power-on reset signal POR by the starting circuit to start the identification circuit;
The starting circuit and the identification circuit are connected to the input end HV of the high-voltage starting circuit through an NMOS crystal M2; the input HV of the high voltage start circuit may be connected to one of the ends vac_abs (before the rectifier bridge), vsw (after the rectifier bridge) or Vdc (after the rectifier bridge) before the rectifier bridge or after the rectifier bridge of the switching power supply circuit as shown in fig. 3.
Further, after the identification circuit is started by outputting the power-on reset signal, the identification circuit outputs a start circuit control signal PS to control the start circuit to be turned off.
Step 120, the identification circuit starts a first timing, in a first timing period, the identification circuit detects a voltage Vhv from an input end HV of the high-voltage starting circuit connected with the switching power supply circuit, and provides a pull-down current to ground, the voltage Vhv is compared with a reference voltage Vref set in the identification circuit, when Vhv is greater than Vref, the voltage state outputted by the identification circuit indicates a signal ghv=1, otherwise ghv=0;
In the above step 120, the first timer T1 is started in the identification circuit, and because the HV pin is not close to the ground voltage even if the HV pin is connected to the ac input terminal before the rectifier bridge if the pull-down current is not applied to the ground due to the leakage of the rectifier diodes D1 and D2, in order to accurately measure whether the ac signal is connected, the pull-down current from the source of M2 to the ground needs to be generated in the identification circuit, so that the voltage Vhv of the HV can be pulled down to the ground when the input ac voltage Vac crosses zero when the HV is connected to the front of the rectifier bridge.
The identification circuit detects Vhv and compares it with an internally set reference voltage Vref. During the first timing T1, if ghv=0 is detected, that is, vhv+.vref is present, it is indicated that the switching power supply circuit may have a need for X-capacitor discharge.
In step 130, the identification circuit counts whether the duration of the voltage status indication signal ghv=0 in the first timing period is greater than the set time threshold, if so, the identification result indicates that the switching power supply circuit needs the X capacitor discharging function, otherwise, the identification result indicates that the switching power supply circuit does not need the X capacitor discharging function.
The judgment is carried out by the set time threshold, so that misjudgment caused by signal interference or accidental abnormal jump can be avoided.
When the duration of the voltage state indication signal ghv=0 in the timing period is greater than the set time threshold after the end of the timing period of the first timing T1, it can be determined that HV is connected to the vac_abs terminal of the switching power supply circuit, and the identification circuit generates an identification result signal of the first level to enable the X capacitor discharging function of the switching power supply circuit. In this case, the switching power supply circuit may be further X-capacitively discharged by the identification circuit when the switching power supply circuit is powered off.
If GHV is always equal to 1 or the GHV is equal to 0 and the time is smaller than or equal to a time threshold Tref in the timing period, namely, HV is judged to be connected to the Vdc or the Vsw end, and a second-level identification result signal is generated and used for disconnecting the identification circuit from the switching power supply circuit.
Therefore, whether the switching circuit needs X capacitor discharging or not can be realized, and under the condition that the X capacitor discharging function is needed, the X capacitor discharging function is automatically adapted to be performed on the switching power supply circuit when the switching power supply circuit is powered off.
The principle realized by the method of the present invention is described above, and the method and circuit for automatically identifying and adapting the X capacitor discharging function in the switch circuit of the present invention are described in detail below with reference to the circuit diagrams and waveform diagrams of FIGS. 5-7. FIG. 5 is a circuit diagram of an automatic identification and adaptation switch circuit for X capacitor discharge function according to an embodiment of the present invention; fig. 6 is a schematic circuit waveform diagram of a switching power supply circuit according to an embodiment of the present invention, in which an input end HV of a high-voltage starting circuit is connected to a front of a rectifier bridge; fig. 7 is a schematic circuit waveform diagram of a switching power supply circuit according to an embodiment of the present invention, in which an input end HV of a high voltage start circuit is connected to a rectifier bridge.
One specific circuit form of the present invention for implementing the above method may be as shown in fig. 5, including: a start-up capacitor Cvcc, a start-up circuit 1, an identification circuit 2 and an NMOS transistor M2;
The starting capacitor Cvcc is connected with the comparison signal input end of the starting circuit 1; the drain electrode of the NMOS transistor M2 is connected with the input end HV of a high-voltage starting circuit of the switching power supply circuit, and the input end HV of the high-voltage starting circuit is connected in front of or behind a rectifier bridge of the switching power supply circuit; the grid electrode and the source electrode of the NMOS transistor M2 are respectively connected with the starting circuit 1 and the identification circuit 2;
The starting circuit 1 specifically includes: an NMOS transistor N1, a first resistor R1, a voltage regulator VR1 and a starting module 10; the drain electrode of the NMOS transistor M2 is connected with the input end HV of the high-voltage starting circuit; the voltage stabilizing tube VR1 is reversely connected between the grid electrode of the NMOS transistor M2 and the ground; the first resistor R1 is connected between the grid electrode of the NMOS transistor M2 and the input end HV of the high-voltage starting circuit; the drain of the NMOS transistor N1 is connected with the gate of the NMOS transistor M2, and the source of the NMOS transistor N1 is grounded. .
The identification circuit 2 specifically includes: a control module 21, an analog-to-digital conversion module (D/a) 22, a bleeder module 23, and an identification output module 24;
The control module 21 is connected with the output end of a power-on reset signal POR of the starting module 10, and the analog-to-digital conversion module 22 is connected with the digital voltage parameter signal output end of the control module 21; the bleeder module 23 is composed of an operational amplifier OP, an NMOS transistor N2 and a resistor R2 in FIG. 4, and the bleeder module 23 is respectively connected with a source electrode of the NMOS transistor M2, the analog-to-digital conversion module 22 and the control module 21; the identification output module 24 Is composed of the PMOS transistor P3, the NMOS transistor N3, the current source Is and the schmitt trigger 20 in fig. 4, and the identification output module 24 Is connected to the source of the NMOS transistor M2 and connected to the power-on reset signal POR output by the start-up module 10. Meanwhile, the voltage state indication signal GHV output by the output end of the identification output module 24 is fed back to the control module 21, the control module 21 is further connected with the gate of the NMOS transistor N1, and outputs a circuit access control signal GN1 for controlling the gate voltage of the NMOS transistor N1 according to the received voltage state indication signal GHV, and thereby controls the on or off of the NMOS transistor N1, and further controls the on or off of the NMOS transistor M2, and thereby starts the holding access or disconnection of the unit 1 and the control unit 2.
Based on the circuit structure, after the switching power supply circuit is powered on, the control module 21 outputs a preset digital voltage parameter DIS [1:0] =00, enop is set to 0, the operational amplifier OP and the N2 discharging path are turned off, the circuit access control signal gn1=0, and the control module 21 outputs a high-level start circuit control signal PS to control the start module 10 to be started.
At this time, the NMOS transistor N1 is turned off, and as the HV voltage at the input end of the high voltage start circuit increases, vgs of the NMOS transistor M2 is greater than V TH, the NMOS transistor M2 is turned on, and charge Cvcc through the NMOS transistor M2 and the start module 10; when VCC is charged to above the reset voltage set in the start-up module 10, the start-up module 10 outputs a low-level power-on reset signal POR to the identification circuit 2;
After the control module 21 receives the low-level power-on reset signal POR, the control module 21 outputs a low-level start circuit control signal PS to control the shutdown start module 10, the cvcc charge stops, and the control module 21 starts timing, and the circuit enters the recognition phase.
The control module 21 receives the low power-on reset signal POR and the clock signal CLK of the switching power supply circuit, starts the first timing, and the timing time T1 may be 16ms to 32ms. The control module 21 outputs a preset digital voltage parameter DIS [1:0] =01 and a high-level bleed control signal ENOP that control the magnitude of the bleed current in the bleed module 23.
The bleeder module 23 controls the start operational amplifier OP to work according to the high-level bleeder control signal ENOP, the digital voltage parameter DIS [1:0] =01 is sent to the operational amplifier OP after being converted by the analog-to-digital conversion module (D/a) 22, the NMOS transistor N2 is controlled to be started through the output of the operational amplifier OP, and the voltage at the input end HV of the high-voltage start circuit is bleeder to the ground through the NMOS transistor M2, the NMOS transistor N2 and the resistor R2.
It should be noted that if the input terminal HV of the high voltage start circuit is connected to the front vac_abs of the rectifier bridge, the waveform is shown in fig. 6, so that Vhv can be pulled to 0V at the time of Vac zero crossing, and thus the current IR2 of R2 needs to be sufficiently large. In the implementation of the present invention, the corresponding relationship and the value between the digital voltage parameter and the corresponding analog-to-digital converted voltage Vrds and IR2 current are used as shown in table 1 below. The corresponding IR2 of the digital voltage parameter DIS [1:0] =01 takes 1.6mA to ensure that the current IR2 of R2 needs to be large enough to pull Vhv of the input end HV of the high voltage start circuit to 0V at the moment of Vac zero crossing.
The identification output module 24 Is composed of a PMOS transistor P3, an NMOS transistor N3, and a current source Is (with a value of 2 to 4 uA), and gates of the PMOS transistor P3 and the NMOS transistor N3 are controlled by an internal reference voltage Vref1 (with a value of about 5V).
Thus, the sum of Vref1 and the on threshold Vt of the PMOS transistor P3 becomes the reference voltage for the PMOS transistor to be turned on, that is, the reference voltage Vref set inside the identification circuit in the foregoing method.
In the case of a high-voltage starting circuit input HV connected upstream of the rectifier bridge, the following conditions exist: when Vhv > Vref, the PMOS transistor P3 is turned on, the input terminal of the schmitt trigger 20 is a high level signal, and the voltage state indication signal ghv=1 outputted by the identification circuit; when Vhv Is equal to or less than Vref, the PMOS transistor P3 Is turned off, the input level of the schmitt trigger 20 Is pulled to a low level signal by the current source Is, and ghv=0 Is output.
In the case of a rectifier bridge connected to the high-voltage starting circuit input HV, only the following are present: vhv > Vref, the PMOS transistor P3 is turned on, the input of the schmitt trigger 20 is a high level signal, and the voltage state indication signal ghv=1 outputted by the identification circuit.
The control module 21 receives the voltage status indication signal GHV output by the identification output module 24, and counts whether the duration of the voltage status indication signal ghv=0 is greater than the set time threshold Tref in the first timing period T1, if so, generates the identification result signal ENCHG =1 of the first level in the first timing period T1, otherwise, generates the identification result signal ENCHG =0 of the second level. The identification result signal ENCHG is an internal signal of the control module.
If the identification result signal of the first level is generated, it is determined that the input end HV of the high-voltage starting circuit is connected to the front of the rectifier bridge, the waveform in the circuit is as shown in fig. 6, the internal signal ENCHG is set to 1, at this time, the control module 21 continues to set the circuit access control signal GN1 to 0, so that the NMOS transistor N1 is kept turned off, and thus the gate voltage of the NMOS transistor M2 is kept at the high level, and the NMOS transistor M2 is kept turned on;
If the second level identification result signal is generated, it is determined that the input end HV of the high-voltage starting circuit is connected to the rectifier bridge, the waveform in the circuit is as shown in fig. 7, the internal signal ENCHG is set to 0, at this time, the control module 21 continues to set the circuit access control signal GN1 to 1, so that the NMOS transistor N1 becomes on, thereby pulling down the gate voltage of the NMOS transistor M2, and the NMOS transistor M2 is turned off, thereby disconnecting the circuit for automatically identifying and adapting the X capacitor discharging function in the switching power supply circuit according to the present invention, achieving the function of automatic adaptation according to the application requirements, and reducing the power consumption.
In case of generating the identification result signal ENCHG =1 of the first level, the identification circuit 2 can also be automatically adapted to perform an X-capacitor discharge of the switching power supply circuit when the switching power supply circuit is powered off.
The identification result signal ENCHG =1, and at the same time, the third timing is started, the timing time T3 takes 700ms in this embodiment, that is, the plug is monitored after 700ms intervals, and the second timing stage is entered when the timing time T3 arrives. The third timing stage ENOP is set to 0, which turns off the discharge paths of the operational amplifier OP and the NMOS transistor N2, reducing the dc loss.
The second timer is started, ENOP is set to 1, that is, the bleeding control signal is set to high level, so as to eliminate the influence of the leakage of the rectifier diode in the switching power supply circuit, and therefore, when detecting whether the switching power supply circuit is powered off (the power plug is pulled out), the ground current IR2 of the input end HV of the high-voltage starting circuit is also required to be started.
DIS [1:0] value Corresponding to Vrds voltage Corresponding to IR2 current
00 / /
01 800mV 1.6mA
10 2000mV 4mA
TABLE 1
In the implementation of the present invention, the second timing time T2 takes 72ms, and within the timing time T2, DIS [1:0] =01 is output; if ghv=0 is detected at any time between 0 and 72ms, the timer time T2 is cleared, and the plug is considered not to be pulled out.
At this time, ENOP is set to 0 again, the third timing is started again, the above process is repeated, and when the timing time T3 arrives, the second timing phase is entered again. Therefore, the plug pulling-out can be continuously monitored on line, and the power consumption can be reduced to a certain extent. Of course, it is also possible to dispense with the third timing phase and to continuously carry out the monitoring of the second timing phase.
If the second timing phase is executed, and GHV=0 is not detected yet until the timing of T2 reaches 72ms, the plug is considered to be pulled out, and DIS [1:0] =10 is output, and the X capacitor discharging action is executed through the large current on R2.
The method and the circuit for automatically identifying and adapting the X capacitor discharging function in the switch circuit provided by the embodiment of the invention enable the switch circuit to be simultaneously applicable to the application occasions needing X capacitor discharging and also applicable to the application occasions needing X capacitor discharging, and simplify the complexity of chip design and production, obtain better applicability and compatibility of products and reduce the cost through automatically identifying and adapting the application requirements of X capacitor discharging. The identification circuit can be automatically turned off under the application environment without discharging the X capacitor, so that the power consumption is reduced.
Fig. 8 is a flyback control chip integrated with a circuit for automatically identifying and adapting the X-capacitor discharging function in a switching circuit according to an embodiment of the present invention. It can be seen from fig. 8 that the circuit for automatically identifying and adapting the X-capacitor discharging function in a switching circuit provided by the present invention is integrated in one specific application in a switching circuit.
The chip is composed of a starting circuit, an identification circuit, a high-voltage MOS device M2, a PWM generating circuit and a driving circuit. The start-up circuit is used to provide power to the VCC pin when power is on and supplemental power is needed. The identification circuit is used for identifying whether an X capacitor discharging function is needed according to the external connection method of the HV pin, and detecting whether the power plug is pulled out or not in a normal working stage when the X capacitor discharging function is enabled, and making corresponding actions; when the X capacitor discharging function is not enabled, the circuit does not work and does not consume current; the PWM generating circuit generates a control signal PWM of the main power device according to the feedback signal FB; the driving circuit generates a driving signal GT that can directly drive the main power device according to PWM.
The application of the invention in the switching power supply is not limited to the flyback architecture in the switching power supply, and is applicable to any application occasion needing X discharge function; in fig. 8, only necessary pins are marked on the chip pins, and pins can be increased or decreased according to specific switch power supply architecture and functions, which belong to the protection scope of the present patent.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative elements and steps are described above generally in terms of function in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may be disposed in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the scope of the invention, but to limit the invention to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (7)

1. A circuit for automatically identifying and adapting an X-capacitor discharge function in a switching circuit, said circuit comprising: a start-up capacitor, a start-up circuit, an identification circuit and an NMOS transistor M2;
The starting capacitor is connected with the comparison signal input end of the starting circuit;
The drain electrode of the NMOS transistor M2 is connected with the input end HV of a high-voltage starting circuit connected with the switching power supply circuit, and the input end HV of the high-voltage starting circuit is connected in front of or behind a rectifier bridge of the switching power supply circuit; the grid electrode and the source electrode of the NMOS transistor M2 are respectively connected with the starting circuit and the identification circuit;
after the switch power supply circuit is powered on, the NMOS transistor M2 is conducted, a starting capacitor is charged through the input end HV of the high-voltage starting circuit, the NMOS transistor M2 and the starting circuit, and when the voltage of the starting capacitor is larger than the reset voltage set in the starting circuit, the starting circuit outputs a power-on reset signal POR to the identification circuit;
the identification circuit starts first timing according to the power-on reset signal, and provides a source-to-ground pull-down current of the NMOS transistor M2 for the input end HV of the high-voltage starting circuit through the NMOS transistor M2 and the identification circuit;
the identification circuit detects the voltage Vhv of the input end HV of the high-voltage starting circuit in a first timing period, compares the voltage Vhv with a reference voltage Vref arranged in the identification circuit, and outputs a voltage state indication signal GHV=1 when the voltage Vhv is more than Vref, otherwise, GHV=0;
The identification circuit counts whether the duration of the voltage state indication signal ghv=0 in the first timing period is larger than a set time threshold, if so, a first-level identification result signal is generated to enable an X capacitor discharging function of the switching power supply circuit, otherwise, a second-level identification result signal is generated to control the NMOS transistor M2 to disconnect the identification circuit from the switching power supply circuit;
the starting circuit specifically comprises: the device comprises an NMOS transistor N1, a first resistor R1, a voltage stabilizing tube VR1 and a starting module;
the drain electrode of the NMOS transistor M2 is connected with the input end HV of the high-voltage starting circuit;
The voltage stabilizing tube VR1 is reversely connected between the grid electrode of the NMOS transistor M2 and the ground;
The first resistor R1 is connected between the grid electrode of the NMOS transistor M2 and the input end HV of the high-voltage starting circuit;
The drain electrode of the NMOS transistor N1 is connected with the grid electrode of the NMOS transistor M2, and the source electrode of the NMOS transistor N1 is grounded;
The identification circuit specifically comprises: the device comprises a control module, an analog-to-digital conversion module, a bleeding module and an identification output module;
the control module is connected with the starting circuit, receives the power-on reset signal and a clock signal of the switching power supply circuit, starts first timing, and outputs a preset digital voltage parameter for controlling the magnitude of the release current in the release module and a release control signal of a first level;
The analog-to-digital conversion module is connected with the control module and converts the analog voltage into an analog voltage value according to the preset digital voltage parameter;
The bleeder module is respectively connected with the source electrode of the NMOS transistor M2, the analog-to-digital conversion module and the control module, is controlled to start according to the bleeder control signal of the first level, and is converted into a current value on the bleeder resistor according to the analog voltage value, so that the earth bleeder of the input end HV of the high-voltage starting circuit is formed;
The identification output module is connected with the source electrode of the NMOS transistor M2, compares the Vhv with the Vref, and outputs a voltage state indication signal GHV=1 when the Vhv is more than the Vref, otherwise, the GHV=0;
The control module is further connected with the identification output module, receives the voltage state indication signal GHV output by the identification output module, counts whether the duration of the voltage state indication signal GHV=0 is larger than a set time threshold value in a first timing period, generates an identification result signal of the first level if the duration is larger than the set time threshold value, and generates an identification result signal of the second level if the duration is not larger than the set time threshold value;
The control module is further connected with the grid electrode of the NMOS transistor N1, and controls the NMOS transistor N1 to be conducted according to the identification result signal of the second level, so that the grid potential of the NMOS transistor M2 is pulled down, the NMOS transistor M2 is turned off, and the identification circuit is disconnected from the switching power supply circuit.
2. A method for automatically identifying and adapting an X-capacitor discharge function in a switching circuit, implemented using the circuit of claim 1, the method comprising:
After the switch power supply circuit is powered on, charging a starting capacitor, and when the voltage of the starting capacitor is larger than the reset voltage set in the starting circuit, outputting a power-on reset signal POR by the starting circuit to start the identification circuit;
The identification circuit starts a first timing, in a first timing period, the identification circuit detects a voltage Vhv from an input end HV of the high-voltage starting circuit connected with the switching power supply circuit and provides a pull-down current to the ground, the voltage Vhv is compared with a reference voltage Vref arranged in the identification circuit, when the Vhv is more than Vref, the voltage state output by the identification circuit indicates a signal GHV=1, otherwise, GHV=0;
The identification circuit counts whether the duration of the voltage state indication signal ghv=0 in the first timing period is greater than a set time threshold, if so, the identification result is that the switching power supply circuit needs the X capacitor discharging function, otherwise, the identification result is that the switching power supply circuit does not need the X capacitor discharging function.
3. The method according to claim 2, characterized in that the identification circuit is connected to the high voltage start-up circuit input HV via an NMOS transistor;
the input end HV of the high-voltage starting circuit is connected to the front or rear of the rectifier bridge of the switching power supply circuit.
4. The method of claim 2, further comprising an automatic adaptation process;
The automatic adaptation process specifically comprises the following steps: and when the duration of the voltage state indicating signal GHV=0 in the timing period is larger than a set time threshold, the identification circuit generates an identification result signal of a first level to enable an X capacitance discharging function of the switching power supply circuit, and otherwise, generates an identification result signal of a second level to disconnect the identification circuit from the switching power supply circuit.
5. The method of claim 4, wherein after the identification circuit generates an identification result signal of a first level to enable an X-capacitance discharging function for the switching power supply circuit, the method further comprises:
And discharging X capacitance to the switching power supply circuit through the identification circuit.
6. The method of claim 2, wherein the identification circuit outputs a start-up circuit control signal PS to control the start-up circuit to be turned off after the start-up circuit outputs a power-on reset signal to start up the identification circuit.
7. A switching circuit, characterized in that it comprises a circuit for automatically identifying and adapting the X-capacitance discharging function in a switching circuit according to claim 1.
CN202210783618.4A 2022-07-05 2022-07-05 Method and circuit for automatically identifying and adapting X capacitor discharging function in switch circuit Active CN115118150B (en)

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CN103199690A (en) * 2012-01-06 2013-07-10 西安展芯微电子技术有限公司 X capacitor discharge control device applied to flyback power source
CN111277130A (en) * 2020-03-20 2020-06-12 苏州力生美半导体有限公司 High-voltage starting circuit and method integrating zero-crossing detection and X capacitor discharge

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CN104038082B (en) * 2013-03-04 2017-12-12 比亚迪股份有限公司 Switching Power Supply, the control method of Switching Power Supply and control chip
CN211321213U (en) * 2020-03-20 2020-08-21 苏州力生美半导体有限公司 High-voltage starting circuit integrating zero-crossing detection and X capacitor discharge

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CN103199690A (en) * 2012-01-06 2013-07-10 西安展芯微电子技术有限公司 X capacitor discharge control device applied to flyback power source
CN111277130A (en) * 2020-03-20 2020-06-12 苏州力生美半导体有限公司 High-voltage starting circuit and method integrating zero-crossing detection and X capacitor discharge

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