CN116995941A - Power supply circuit of switching power supply, power supply method of power supply circuit and switching power supply system - Google Patents

Power supply circuit of switching power supply, power supply method of power supply circuit and switching power supply system Download PDF

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Publication number
CN116995941A
CN116995941A CN202211024981.4A CN202211024981A CN116995941A CN 116995941 A CN116995941 A CN 116995941A CN 202211024981 A CN202211024981 A CN 202211024981A CN 116995941 A CN116995941 A CN 116995941A
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CN
China
Prior art keywords
power supply
tube
switching
switching tube
circuit
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Pending
Application number
CN202211024981.4A
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Chinese (zh)
Inventor
杨晨涛
陈伟
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Shenzhen Injoinic Technology Co Ltd
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Shenzhen Injoinic Technology Co Ltd
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Priority to CN202211024981.4A priority Critical patent/CN116995941A/en
Publication of CN116995941A publication Critical patent/CN116995941A/en
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Classifications

    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/06—Conversion 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
    • H02M7/068—Conversion 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 mounted on a transformer
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
    • G05F3/02—Regulating voltage or current
    • G05F3/08—Regulating voltage or current wherein the variable is dc
    • G05F3/10—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics
    • G05F3/16—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices
    • G05F3/20—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations
    • G05F3/26—Current mirrors
    • G05F3/262—Current mirrors using field-effect transistors only
    • Y—GENERAL 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies 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

Abstract

The application provides a power supply circuit of a switching power supply, a power supply method thereof and a switching power supply system, wherein the power supply circuit of the switching power supply comprises: the main power tube and the auxiliary power tube are integrated in the chip, the drain electrode of the main power tube is connected with the pin DN, the grid electrode is connected with the starting resistor, the source electrode is connected with the drain electrode of the auxiliary power tube, and the rear HV is externally connected with the starting resistor R start1 And the starting circuit is connected with an AC input, the connection point of the two power tubes is connected with a diode D3, and then the two power tubes are connected to a pin VDD to form a unidirectional charging circuit, a module Delay 4 and a module Select 5 are respectively connected with the grid electrodes of the main power tube 1 and the auxiliary power tube 2, the other ends of the two power tubes are connected to a control module PWM controller3 together to generate PWM control signals, and the PWM control module can adopt a general PWM control module. The technical scheme provided by the application has the advantage of high safety.

Description

Power supply circuit of switching power supply, power supply method of power supply circuit and switching power supply system
Technical Field
The application relates to the field of electronic equipment, in particular to a power supply circuit of a switching power supply, a power supply method thereof and a switching power supply system.
Background
The switching power supply is widely applied to power supply systems of loads such as computers, electric appliances, portable electronic equipment and the like based on the advantages of high efficiency, small volume and the like. Which is capable of converting general power to a power supply more suitable for load applications. In a common application, the power input is mainly from the mains (50 Hz, 220V ac), and the switching power supply is then able to convert this power to the low voltage dc power supply required by the load. As a key to the normal operation of the switching power supply, the controller itself also requires a certain operating voltage to maintain its basic function.
The existing switching power supply is generally based on auxiliary winding power supply, and the power supply mode based on the auxiliary winding brings about the risk of chip pin overvoltage caused by rising of output voltage, namely, the rising of the output voltage, the voltage on the auxiliary winding is also increased, and then the voltage withstand requirement of the pins is exceeded, so that potential safety hazards are generated.
Disclosure of Invention
The embodiment of the application provides a power supply circuit of a switching power supply, a power supply method thereof and a switching power supply system, which can supply power to the switching power supply without an auxiliary winding, thereby avoiding overhigh withstand voltage of pins and improving the safety performance of the power supply circuit.
In a first aspect, an embodiment of the present application provides a power supply circuit of a switching power supply, including: a control chip, a transformer, a bridge rectifier circuit, a switch tube, a capacitor and a resistor,
the control chip includes: main power tube, auxiliary power tube and second starting resistor R start2 The system comprises a delay module and a selection module; wherein, the liquid crystal display device comprises a liquid crystal display device,
outside the control chip, DN pin of the control chip is connected with primary winding L of the transformer p The HV pin is connected with the first starting resistor R start1 The other end of the first starting resistor R start1 One end of the second switch tube D2 is connected with the cathode of the second switch tube D2, and the anode of the second switch tube D2 is connected with the mains supply output end; the control coreVDD pin connection capacitor C of chip VDD Capacitance C VDD The other end of the first electrode is connected with an equipotential point; inside the control chip, HV pin is connected with a second starting resistor R start2 A second start resistor R start2 The other end of the main power tube is connected with the grid electrode of the main power tube, the grid electrode of the main power tube is also connected with the output end of the delay module, the drain electrode of the main power tube is connected with the DN pin, the source electrode of the main power tube is connected with one end of the first switch tube and is connected with the drain electrode of the auxiliary power tube, the other end of the first switch tube is connected with the VDD pin of the control chip, and the grid electrode of the auxiliary power tube is connected with the output end of the selection module; the input end of the delay module is connected with a PWM signal, one input end of the selection module is connected with the PWM signal, and the other input end of the selection module is connected with a VDD signal; also included within the control chip is: the mirror current sampling circuit comprises a third switching tube, a fourth switching tube, a comparator, a fifth switching tube and a current mirror circuit; wherein, the liquid crystal display device comprises a liquid crystal display device,
the grid electrodes of the third switching tube and the fourth switching tube are both connected with the grid electrode of the auxiliary power tube, the drain electrode of the fourth switching tube is connected with the drain electrode of the auxiliary power tube, the source electrode of the fourth switching tube is connected with the forward input end of the comparator, the source electrode of the third switching tube is connected with the source electrode of the auxiliary power tube, the drain electrode of the third switching tube is connected with the reverse input end of the comparator, the output end of the comparator is connected with the grid electrode of the fifth switching tube, the source electrode of the fifth switching tube is connected with one end of a resistor, the other end of the resistor is connected with the drain electrode of the third switching tube, the drain electrode of the fifth switching tube is connected with the input end of the current mirror circuit, and the output end of the current mirror circuit is connected with the CS pin of the control chip;
the delay module is used for delaying the PWM signal for a set time length; the selection module is a module for selecting whether to supply power.
In a second aspect, there is provided an image current sampling circuit applied to the switching power supply circuit provided in the first aspect; the mirror current sampling circuit comprises a third switching tube, a fourth switching tube, a comparator, a fifth switching tube and a current mirror circuit; the mirror current sampling circuit comprises a third switching tube, a fourth switching tube, a comparator, a fifth switching tube and a current mirror circuit; wherein, the liquid crystal display device comprises a liquid crystal display device,
the grid electrodes of the third switching tube and the fourth switching tube are both connected with the grid electrode of the auxiliary power tube, the drain electrode of the fourth switching tube is connected with the drain electrode of the auxiliary power tube, the source electrode of the fourth switching tube is connected with the forward input end of the comparator, the source electrode of the third switching tube is connected with the source electrode of the auxiliary power tube, the drain electrode of the third switching tube is connected with the reverse input end of the comparator, the output end of the comparator is connected with the grid electrode of the fifth switching tube, the source electrode of the fifth switching tube is connected with one end of the resistor, the other end of the resistor is connected with the drain electrode of the third switching tube, the drain electrode of the fifth switching tube is connected with the input end of the current mirror circuit, and the output end of the current mirror circuit is connected with the CS pin of the control chip.
In a third aspect, there is provided a power supply method of a power supply circuit of a switching power supply, the method being applied to the power supply circuit of the switching power supply provided in the first aspect, the method comprising the steps of:
if the control chip works normally and V DD Less than the voltage threshold V m And the power supply is enabled, a control PWM signal is input to the delay module and the selection module, and the main power tube is turned on or off in a hysteresis way relative to the auxiliary power tube.
In a fourth aspect, a switching power supply system is provided, the power supply system comprising the circuit and method of the first two aspects.
The embodiment of the application has the following beneficial effects:
it can be seen that the circuit provided by the application does not need an auxiliary winding to supply power, and the voltage on the auxiliary winding can be increased along with the increase of the output voltage, so that the voltage withstand requirement of the pin is exceeded, and the safety of the circuit is improved. In addition, on the one hand, the charging process takes place at a current I p When the Peak value (Peak 1) is reached, the charging efficiency is high, and the voltage V can be effectively increased in a shorter time DD The method comprises the steps of carrying out a first treatment on the surface of the On the other hand, due to the clamping effect of the diode D3, the voltage and V received by the auxiliary power tube at the time of turn-off DD And the high voltage resistance is not needed, so that the design cost is effectively reduced. In addition, the starting circuit (second switch tubeD2 and series start-up resistor) from the AC input, the losses generated by the branch during start-up and normal operation can be reduced. The mirror current sampling circuit enables current flowing through the sampling resistor to be obviously reduced, and loss generated by the sampling resistor is effectively reduced.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic circuit diagram of a switching power supply circuit;
FIG. 2 is a schematic circuit diagram of another switching power supply circuit;
FIG. 3 is a schematic circuit diagram of a switching power supply circuit according to the present application;
FIG. 4 is a schematic diagram of a selection module according to the present application;
FIG. 5 is a schematic circuit diagram of a mirror current sampling module according to the present application;
FIG. 6 is a schematic diagram of another switching power supply circuit according to the present application;
fig. 7 is a schematic waveform diagram of a switching power supply circuit provided by the application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The terms "first," "second," "third," and "fourth" and the like in the description and in the claims and drawings are used for distinguishing between different objects and not necessarily for describing a particular sequential or chronological order. Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed steps or elements but may include other steps or elements not listed or inherent to such process, method, article, or apparatus.
Reference herein to "an embodiment" means that a particular feature, result, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.
Referring to fig. 1, a switching power supply circuit is shown in fig. 1, and mainly includes a resistor R HV1 、R HV2 And a high-voltage power supply line composed of a high-voltage switching tube 1 and an auxiliary winding power supply line composed of an auxiliary winding AUX and a second switching tube D2. In the high-voltage supply line, the current flows from V in Starting to flow through the resistor, the pin HV, the high-voltage-resistant switch tube 1 and the pin VDD in sequence until the capacitor C VDD . This approach is mainly used for capacitor C during start-up VDD And charging until the chip is started. The auxiliary winding circuit is C in normal operation VDD Supplying power when the voltage on the auxiliary winding is insufficient to be C VDD During charging, the high-voltage-resistant switch tube 1 can be turned on, and high-voltage power supply is started.
Because of certain requirement on the power-on speed of the chip, the resistor R HV1 And R is HV2 Cannot be too large, primary side voltage V in The high-voltage power supply is always maintained at a high level, so that the high-voltage power supply mode has large loss, and the circuit efficiency is reduced. Meanwhile, the high-voltage-resistant switch tube also promotes the design cost of the chip. For the power supply line of the auxiliary winding, the voltage on the auxiliary winding is generated when the power tube is turned offV AUX In a multiple relationship with the output voltage such that at high output voltages, voltage V DD The upper limit of the withstand voltage is easily exceeded, resulting in chip damage.
Referring to fig. 2, fig. 2 provides another switching power supply circuit, which includes a rectifying tube 1, a series resistor, a high voltage switching tube 2, a diode D3, and a high voltage power supply line from HV to VDD and an auxiliary winding power supply line, wherein the former is a main power supply mode. The high voltage power supply circuit is controlled to be connected and disconnected by the high voltage withstand switch tube 2. The high voltage-resistant switch tube 2 is long-connected in the power-on process until V DD Reaching a preset value. During normal operation, voltage V on HV pin is monitored HV (which is related to the rectified voltage V rec Near) when the voltage is smaller than a boundary value, judging that the voltage is in a valley interval, and opening the high-voltage-resistant switching tube 2 to carry out high-voltage charging; when V is HV When the voltage is larger than the boundary value again, the high-voltage-resistant switching tube 2 is closed to stop power supply. In addition, when V AUX Greater than V DD When the high-voltage power supply line is closed, only the auxiliary winding supplies power.
When charging in valley region, V DD Is in wave type rising (V) rec Greater than V DD Charging at a time less than V DD And does not charge), and the loss during high-voltage power supply is reduced. But need to set V DD Upper and lower boundary (V) top And V bottom ) According to V DD Dynamically adjusting boundary values to avoid V DD The voltage exceeds the normal working voltage range, and a high-voltage-resistant switching tube is still required to control the on and off of a high-voltage power supply line.
Referring to fig. 3, fig. 3 shows a switching power supply circuit provided by the present application, as shown in fig. 3, a main power tube 1 and an auxiliary power tube 2 are integrated in a chip, wherein the drain electrode of the main power tube is connected to a pin DN, and the gate electrode is connected to a starting resistor R start2 The source is connected to the drain of the latter. R is R start2 The other end is connected to the pin HV, and then HV is externally connected to the starting resistor R start1 And a starting circuit formed by the second switching tube D2, wherein the starting circuit is connected with the AC input. The connection point of the two power tubes is connected with a diode D3 and then connected to a pin VDD to form a unidirectional charging circuit. Module DelayAnd the module Select 5 are respectively connected with the grid electrodes of the main power tube 1 and the auxiliary power tube 2, and the other ends of the main power tube 1 and the auxiliary power tube are jointly connected to the control module PWM controller 3. The module PWM controller3 generates corresponding PWM control signals by acquiring information of VS, VIN and FB, and the PWM control module may be a general PWM control module.
The power supply method mainly comprises two processes:
1. at power-on, the AC input first passes through the second switch tube D2 and the starting resistor R start1 、R start2 The gate of the main power tube 1 is charged to raise the gate-source voltage. When the gate-source voltage is greater than the critical value V th When the main power tube is turned on, the voltage V is measured at one time in Will pass through the primary side of the transformer, the main power tube 1 and the diode D3 to the capacitor C VDD And (5) charging. Voltage V DD Will start to rise until reaching the preset value V PG . And then the chip and the whole switching power supply start to work normally.
2. Normally work and V DD Less than threshold V m When the power supply is enabled. The PWM controller3 outputs a PWM signal to Delay 4 and Select 5. The module Delay 4 generates a fixed Delay, delays the PWM signal, and the module Select 5 selects the input to be consistent with the output, namely the PWM signal has no Delay. So the on and off of the main power tube will lag the auxiliary power tube for a fixed time. In the turn-off stage, the primary current reaches the peak value, the secondary power tube 2 is turned off first to form the same charging loop as that in the power-on process, namely V in The primary side of the transformer, the main power tube 1 and the diode D3 are used for leading the capacitor C VDD And (5) charging. And then the main power tube is turned off, charging is stopped, and the charging time is the fixed Delay time of the module Delay 4. When V is DD Greater than threshold V m When the power supply is not enabled. The module Select 5 will Select to output high level, the auxiliary power tube 2 will keep on state, at this time, the charging loop cannot be formed, C VDD Is not charged.
At the beginning of each cycle, V is set by module Select 5 DD And V m Make a size determination to determine whether the power supply is enabled (i.e. auxiliary switch tubeWith PWM action or kept on), the schematic of the circuit of module Select 5 is shown in FIG. 4. When the rising edge of Select-in (PWM signal) arrives, if V m Greater than V DD Then Charge-en sets 1 (high level), and the module output Select-out is the same as the input Select-in; if at this time V m Greater than V DD The module output Select-out is always high.
In normal operation, the relevant signal waveforms are shown in fig. 7. Wherein PWM is the output of a module PWM controller3, PWM1 and PWM2 respectively represent the gate-source control signals of the main power tube 1 and the auxiliary power tube 2, I p Is the primary current. When the Charge is enabled (i.e., charge-en is high) and the current reaches Peak value Peak1, the PWM signal is reduced to low level, the auxiliary power tube 2 is turned off, and the power supply starts to supply power to C VDD After charging, the main power tube 1 is turned off. During charging, primary current I p Will continue to rise until Peak2 (end of charge). When the Charge is not enabled (i.e. Charge-en is low), since the hysteresis of the control signal PWM1 of the main power tube 1 relative to PWM is always present, I p The PWM continues to rise after it falls to a low level until the main power tube 1 is turned off. It can be seen that the actual Peak current (Peak 2) is always greater than the desired Peak current (Peak 1), but because the lag (delay) time is fixed, the larger amplitude is substantially uniform. The compensation can thus be performed directly by adjusting the peak current dependent threshold value without additional measures.
On the one hand, the charging process of the circuit provided by the application occurs in the current I p When the Peak value (Peak 1) is reached, the charging efficiency is high, and the voltage V can be effectively increased in a shorter time DD The method comprises the steps of carrying out a first treatment on the surface of the On the other hand, due to the clamping effect of the diode D3, the voltage and V received by the sub-power tube 2 at the time of turn-off are DD And the high voltage resistance is not needed, so that the design cost is effectively reduced. In addition, the input of the starting circuit (the second switching tube D2 and the series starting resistor) is from the AC input, so that the loss generated by the branch circuit during starting and normal operation can be reduced.
Referring to the power supply circuit of the switching power supply shown in fig. 3, the circuit comprises: a control chip, a transformer, a bridge rectifier circuit, a switch tube, a capacitor and a resistor,
the control chip includes: main power tube, auxiliary power tube and second starting resistor R start2 The system comprises a delay module and a selection module; wherein, the liquid crystal display device comprises a liquid crystal display device,
outside the control chip, DN pin of the control chip is connected with primary winding L of the transformer p The HV pin is connected with the first starting resistor R start1 The other end of the first starting resistor R start1 One end of the second switch tube D2 is connected with the cathode of the second switch tube D2, and the anode of the second switch tube D2 is connected with the mains supply output end; the VDD pin of the control chip is connected with the capacitor C VDD Capacitance C VDD The other end of the first electrode is connected with an equipotential point;
inside the control chip, HV pin is connected with a second starting resistor R start2 A second start resistor R start2 The other end of the main power tube is connected with the grid electrode of the main power tube, the grid electrode of the main power tube is also connected with the output end of the delay module, the drain electrode of the main power tube is connected with the DN pin, the source electrode of the main power tube is connected with one end of the first switch tube and is connected with the drain electrode of the auxiliary power tube, the other end of the first switch tube is connected with the VDD pin of the control chip, the grid electrode of the auxiliary power tube is connected with the output end of the selection module, and the source electrode of the auxiliary power tube is connected with the CS pin; the input end of the delay module is connected with a PWM signal, one input end of the selection module is connected with the PWM signal, and the other input end of the selection module is connected with a VDD signal;
the delay module is used for delaying the PWM signal for a set time length; the selection module is a module for selecting whether to supply power.
In an alternative scheme, outside the control chip, the CS pin of the control chip passes through a resistor R cs The equipotential points are connected.
In an alternative arrangement, the first and second modules,
the first switching tube is a diode or a field effect tube.
In an alternative, the selecting module includes: comparator, D flip-flop, and gate, not gate and or gate, wherein,
the comparatorVoltage threshold V is connected to the positive pin of (2) m The negative pin is connected with VDD; the output end of the comparator is connected with a D pin of a D trigger, a CP pin of the D trigger is connected with a PWM signal, the PWM signal is also connected with one input end of the AND gate, and the other input end of the AND gate is connected with a Q output end Charge-en of the D trigger; the Q output end of the D trigger is also connected with the input end of the NOT gate, the output end of the NOT gate is connected with the other input end of the OR gate, one input end of the OR gate is connected with the output end of the AND gate, and the output end of the OR gate is the output end of the selection module.
The present application also provides an image current sampling circuit, which may be disposed inside the control chip, and may also be referred to as: the image current sampling module SNS6, referring to fig. 5, fig. 5 provides a circuit schematic diagram of an image current sampling circuit, referring to fig. 6, and fig. 6 is a circuit schematic diagram with SNS6 added. As shown in fig. 5, the mirror current sampling circuit includes a third switching tube 7, a fourth switching tube 8, a comparator, a fifth switching tube and a current mirror circuit; wherein, the liquid crystal display device comprises a liquid crystal display device,
the grid of the third switch tube 7, the grid of the fourth switch tube 8 connects the grid of the auxiliary power tube after connecting, the drain electrode of the fourth switch tube 8 connects the drain electrode of the auxiliary power tube, the source electrode of the fourth switch tube connects the positive input end of the comparator, the source electrode of the third switch tube 7 connects the source electrode of the auxiliary power tube, the drain electrode of the third switch tube connects the reverse input end of the comparator, the output end of the comparator connects the grid of the fifth switch tube, the source electrode of the fifth switch tube connects one end of the resistance, the other end of the resistance connects the drain electrode of the third switch tube, the drain electrode of the fifth switch tube connects the input end of the current mirror circuit 9, the output end of the current mirror circuit 9 connects CS pin of the said control chip.
The on-resistance of the third switching tube 7 and the auxiliary power tube 2 are in a multiple relation. When the drive gate is set high, the switching tubes 2, 7 and 8 are conducted, and the positive and negative input voltages of the operational amplifier are equal based on the 'virtual short and virtual break' characteristic of the operational amplifier, namely the drain voltages of the third switching tube 7 and the auxiliary power tube 2 are equal. Because the on-resistance of the third switch tube 7 is amplified in a certain proportion compared with the on-resistance of the auxiliary power tube 2Then the mirror current I flowing through the third switching tube 7 psns Compared with the power current I flowing through the auxiliary power tube 2 p The equal proportion is reduced. Further, the current mirror circuit 9 is based on the mirror current I psns Generating a further (scaled up, scaled down or equal) mirror current I SNS And output to pin CS. Compared with the traditional sampling mode, the current flows through the external sampling resistor R CS Current (I) SNS ) Will be significantly reduced so that the losses generated thereon are significantly reduced. In an alternative scheme, when the auxiliary power tube is turned on, the third switching tube and the fourth switching tube are turned on, current sampling is enabled, and mirror current is output to a CS pin of the control chip.
In an alternative, the magnitude of the mirrored current is related to the magnitude of the current flowing through the secondary power tube. Specifically, the first ratio between the mirror current and the current flowing through the auxiliary power tube is in proportional relation with the second ratio between the on-resistances of the auxiliary power tube and the third switching tube.
The application also provides a power supply method of the power supply circuit of the switching power supply, which is applied to the power supply circuit of the switching power supply shown in fig. 3, and comprises the following steps:
if the control chip works normally and V DD Less than the voltage threshold V m And the power supply is enabled, a control PWM signal is input to the delay module and the selection module, and the main power tube is in hysteresis action (on or off) relative to the auxiliary power tube.
For example, the method may further include:
if V DD Greater than or equal to voltage threshold V m The power supply is not enabled, and the selection module outputs a high level.
For example, the method may further include: in the starting stage of the power supply circuit of the switching power supply, alternating current input passes through a second switching tube and a starting resistor R start1 And R is start2 Driving the main power tube to be conducted so as to lead V DD And after the starting threshold value is increased, the chip is controlled to work.
The embodiment of the application also provides a switching power supply system, which may include the power supply circuit of the switching power supply of the embodiment shown in fig. 3 or fig. 6, and may also include the mirror current sampling circuit shown in fig. 5. The embodiment of the application also provides a switching power supply system, which can supply power by applying the power supply method of the power supply circuit of the switching power supply.
It should be noted that, for simplicity of description, the foregoing method embodiments are all described as a series of acts, but it should be understood by those skilled in the art that the present application is not limited by the order of acts, as some steps may be performed in other orders or concurrently in accordance with the present application. Further, those skilled in the art will also appreciate that the embodiments described in the specification are alternative embodiments, and that the acts and modules referred to are not necessarily required for the present application.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and for parts of one embodiment that are not described in detail, reference may be made to related descriptions of other embodiments.
In the several embodiments provided by the present application, it should be understood that the disclosed apparatus may be implemented in other manners. For example, the apparatus embodiments described above are merely illustrative, such as the division of the units, merely a logical function division, and there may be additional manners of dividing the actual implementation, such as multiple units or components may be combined or integrated into another system, or some features may be omitted, or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, or may be in electrical or other forms.
Those of ordinary skill in the art will appreciate that all or a portion of the steps in the various methods of the above embodiments may be implemented by a program that instructs associated hardware, and the program may be stored in a computer readable memory, which may include: flash disk, read-Only Memory (ROM), random access Memory (Random Access Memory, RAM), magnetic disk or optical disk.
The foregoing has outlined rather broadly the more detailed description of embodiments of the application, wherein the principles and embodiments of the application are explained in detail using specific examples, the above examples being provided solely to facilitate the understanding of the method and core concepts of the application; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present application, the present description should not be construed as limiting the present application in view of the above.

Claims (10)

1. A power supply circuit for a switching power supply, the circuit comprising: the control chip, the transformer, the bridge rectifier circuit, the switch tube, the capacitor and the resistor are characterized in that,
the control chip includes: the power supply comprises a main power tube, an auxiliary power tube, a second starting resistor Rstart2, a delay module and a selection module; wherein, the liquid crystal display device comprises a liquid crystal display device,
outside the control chip, a DN pin of the control chip is connected with an output end of a primary winding Lp of the transformer, an HV pin is connected with the other end of a first starting resistor Rstart1, one end of the first starting resistor Rstart1 is connected with a cathode of a second switching tube D2, and an anode of the second switching tube D2 is connected with a mains supply output end; the VDD pin of the control chip is connected with one end of a capacitor CVDD, and the other end of the capacitor CVDD is connected with an equipotential point; inside the control chip, an HV pin is connected with one end of a second starting resistor Rstart2, the other end of the second starting resistor Rstart2 is connected with a grid electrode of a main power tube, the grid electrode of the main power tube is also connected with an output end of a delay module, a drain electrode of the main power tube is connected with the DN pin, a source electrode of the main power tube is connected with one end of a first switch tube and is connected with a drain electrode of a secondary power tube, the other end of the first switch tube is connected with a VDD pin of the control chip, an input end of the delay module is connected with a PWM signal, one input end of the selection module is connected with the PWM signal, and the other input end of the selection module is connected with a VDD signal; also included within the control chip is: the mirror current sampling circuit comprises a third switching tube, a fourth switching tube, a comparator, a fifth switching tube and a current mirror circuit; wherein, the liquid crystal display device comprises a liquid crystal display device,
the grid electrodes of the third switching tube and the fourth switching tube are both connected with the grid electrode of the auxiliary power tube, the drain electrode of the fourth switching tube is connected with the drain electrode of the auxiliary power tube, the source electrode of the fourth switching tube is connected with the forward input end of the comparator, the source electrode of the third switching tube is connected with the source electrode of the auxiliary power tube, the drain electrode of the third switching tube is connected with the reverse input end of the comparator, the output end of the comparator is connected with the grid electrode of the fifth switching tube, the source electrode of the fifth switching tube is connected with one end of a resistor, the other end of the resistor is connected with the drain electrode of the third switching tube, the drain electrode of the fifth switching tube is connected with the input end of the current mirror circuit, and the output end of the current mirror circuit is connected with the CS pin of the control chip;
the delay module is used for delaying the PWM signal for a set time length; the selection module is a module for selecting whether to supply power.
2. The power supply circuit of claim 1, wherein the power supply circuit comprises a power supply circuit,
and a CS pin of the control chip is connected with an equipotential point through a resistor Rcs outside the control chip.
3. The power supply circuit of claim 1, wherein the power supply circuit comprises a power supply circuit,
the first switching tube is a diode or a field effect tube.
4. A power supply circuit according to any one of claims 1 to 3, wherein the selection module comprises: comparator, D flip-flop, and gate, not gate and or gate, wherein,
the positive pin of the comparator is connected with a voltage threshold Vm, and the negative pin of the comparator is connected with VDD; the output end of the comparator is connected with a D pin of a D trigger, a CP pin of the D trigger is connected with a PWM signal, the PWM signal is also connected with one input end of the AND gate, and the other input end of the AND gate is connected with a Q output end Charge-en of the D trigger; the Q output end of the D trigger is also connected with the input end of the NOT gate, the output end of the NOT gate is connected with the other input end of the OR gate, one input end of the OR gate is connected with the output end of the AND gate, and the output end of the OR gate is the output end of the selection module.
5. The mirror current sampling circuit is characterized by comprising a third switching tube, a fourth switching tube, a comparator, a fifth switching tube and a current mirror circuit; wherein, the liquid crystal display device comprises a liquid crystal display device,
the grid electrodes of the third switching tube and the fourth switching tube are both connected with the grid electrode of the auxiliary power tube, the drain electrode of the fourth switching tube is connected with the drain electrode of the auxiliary power tube, the source electrode of the fourth switching tube is connected with the forward input end of the comparator, the source electrode of the third switching tube is connected with the source electrode of the auxiliary power tube, the drain electrode of the third switching tube is connected with the reverse input end of the comparator, the output end of the comparator is connected with the grid electrode of the fifth switching tube, the source electrode of the fifth switching tube is connected with one end of the resistor, the other end of the resistor is connected with the drain electrode of the third switching tube, the drain electrode of the fifth switching tube is connected with the input end of the current mirror circuit, and the output end of the current mirror circuit is connected with the CS pin of the control chip.
6. A method of supplying a supply circuit of a switching power supply, characterized in that the method is applied to a supply circuit of a switching power supply as claimed in any one of claims 1-4, the method comprising the steps of:
if the control chip works normally and VDD is smaller than the voltage threshold Vm, power supply is enabled, PWM signals are controlled to be input into the delay module and the selection module, and the main power tube is turned on or turned off in a hysteresis way relative to the auxiliary power tube.
7. The method of claim 6, wherein the method further comprises: if VDD is greater than or equal to the voltage threshold Vm, the power supply is disabled and the selection module outputs a high level.
8. The method of claim 7, wherein the ac input drives the main power transistor through the second switching transistor and the start resistors Rstart1 and Rstart2 during a start-up phase of the power supply circuit of the switching power supply, so that the control chip operates after VDD rises to a start-up threshold.
9. A switching power supply system comprising a power supply circuit of a switching power supply according to any one of claims 1 to 4 or an image current sampling circuit according to any one of claims 5.
10. A switching power supply system, characterized in that the switching power supply system is supplied with power by a method according to any of claims 6-8.
CN202211024981.4A 2022-04-26 2022-04-26 Power supply circuit of switching power supply, power supply method of power supply circuit and switching power supply system Pending CN116995941A (en)

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