CN114336532A - Short-circuit protection method for sampling resistor - Google Patents

Short-circuit protection method for sampling resistor Download PDF

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Publication number
CN114336532A
CN114336532A CN202110248483.7A CN202110248483A CN114336532A CN 114336532 A CN114336532 A CN 114336532A CN 202110248483 A CN202110248483 A CN 202110248483A CN 114336532 A CN114336532 A CN 114336532A
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circuit
sampling
sampling resistor
signal
short
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CN114336532B (en
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陈伟
张洞田
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Shenzhen Injoinic Technology Co Ltd
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Shenzhen Injoinic Technology Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • H02J7/00304—Overcurrent protection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • 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

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

Abstract

The invention provides a short-circuit protection method for a sampling resistor.A switch control circuit is used for periodically sending out a first on signal and a first off signal; the method comprises the steps of detecting a first sampling electric signal of a detection sampling circuit, acquiring a first on signal and a first off signal of a switch control circuit, obtaining a switching period and an on time of the switch control circuit according to the first on signal and the first off signal, judging whether the circuit enters a sampling resistor short-circuit protection state or not according to the switching period, the on time and the first sampling electric signal, and outputting a first switch control signal aiming at a transmission path switch according to a judgment result. The invention can conveniently and effectively provide short-circuit protection control of the circuit.

Description

Short-circuit protection method for sampling resistor
Technical Field
The invention relates to the technical field of charging protection, in particular to a sampling resistor short-circuit protection method.
Background
With the wide application of the fast charging technology, the market has higher and higher safety requirements for electronic products with the fast charging function, and stricter requirements for the protection function of charging equipment such as mobile phones, the specification of protocols, and the like, for example, the LPS (power limited power supply) requirement is specified in the IEC60950-1 standard, the LPS requirement can be used to define a power supply with relatively low maximum voltage, current, and capacitance, and the LPS power supply brings about an advantage for customers that a system installer only needs to comply with relatively loose requirements when wiring and installing loads for supplying power by the LPS authentication power supply on the spot.
For meeting the requirement of the LPS, the LPS power supply is required to be limited when delivering output current and voltage to a load, and the delivered output current and voltage are required to be relatively stable and cannot generate abnormity such as overhigh or overlow. In the current control technology for the output current, the output current is directly detected by detecting the voltage difference value at two ends of a sampling resistor Rs through an AC-DC control chip, and the output power is controlled through a primary PWM duty ratio; if the sampling resistor Rs is short-circuited, the AC-DC control chip enters a protection state when the primary PWM changes beyond a certain ratio, and the maximum output current is limited by controlling the working state of the main power switch circuit; if the sampling resistor Rs is operating normally, the maximum output current will be limited by controlling the current through the sampling resistor Rs. The method has the advantages of difficult technical means, complex control method, inconvenient treatment and high cost.
Disclosure of Invention
The invention aims to provide a sampling resistor short-circuit protection circuit and method and a quick-charging charger, which can conveniently and effectively provide short-circuit protection control of the circuit.
In a first aspect, a sampling resistor short-circuit protection circuit is provided for a fast charger, the sampling resistor short-circuit protection circuit includes a switch control circuit, a logic control circuit, a detection sampling circuit, and a transmission path switch, the logic control circuit respectively with the switch control circuit, the detection sampling circuit, the transmission path switch is electrically connected, wherein:
the switch control circuit comprises a switch module and a switch control module, the switch control module is used for controlling the on-off of the switch module, the logic control circuit is arranged in the quick charge chip, the detection sampling circuit comprises a sampling resistor, the switch module is electrically connected with the switch control module, the switch module is electrically connected with the sampling resistor, the switch control module is electrically connected with the logic control circuit, and the logic control circuit is connected with two ends of the sampling resistor in parallel;
the switch control circuit: the first switch is used for periodically sending out a first on signal and a first off signal;
the logic control circuit: the first sampling electric signal used for detecting the detection sampling circuit, the first conducting signal and the first turn-off signal used for collecting the switch control circuit, and the switching period T and the conducting time T of the switch control circuit obtained according to the first conducting signal and the first turn-off signalonAnd for switching on and off in dependence on said switching period T, said on-time TonAnd the first sampling electric signal judging circuit judges whether the circuit enters a sampling resistor short-circuit protection state or not, and is used for outputting a first switch control signal aiming at the transmission path switch corresponding to the sampling resistor according to the judgment result.
In one implementation manner, the switch module is a synchronous rectification switch, the switch control module is a synchronous rectification controller, and the synchronous rectification controller is configured to periodically send a first on signal and a first off signal to the synchronous rectification switch, where a time difference between the first off signal and the first on signal in the same period is the on time tonAnd the time difference between the first conducting signals of two adjacent periods is the switching period T.
In one implementation manner, the synchronous rectification switch is a first NMOS transistor, a gate of the first NMOS transistor is electrically connected to the synchronous rectification controller, the first turn-on signal is a rising edge signal, and the first turn-off signal is a falling edge signal.
In one implementation, the sampling resistor short-circuit protection circuit further includes a secondary power module, a charging capacitor, and an output load of a fast charging port, where the secondary power module, the charging capacitor, and the synchronous rectification switch form a first power transmission loop, and the transmission path switch, the output load, the sampling resistor, and the charging capacitor form a second power transmission loop.
In one implementation, the first sampling electrical signal is an output sampling current Io, the transmission path switch is a second NMOS transistor, the logic control circuit includes a sampling detection module, a time detection module and a judgment module, the sampling detection module includes an amplifier and an analog-to-digital converter, the amplifier is connected in parallel to two ends of the sampling resistor, the analog-to-digital converter is electrically connected to the amplifier, the judgment module is electrically connected to the analog-to-digital converter, the time detection module is respectively electrically connected to the switching control circuit and the judgment module, the judgment module is electrically connected to a gate of the second NMOS transistor, wherein:
the sampling detection module is used for detecting the output sampling current Io by detecting a voltage difference value at two ends of the sampling resistor and outputting the output sampling current Io to the judgment module;
the time detection module is configured to acquire the first on signal and the first off signal of the switch control circuit, and obtain a switching period T and an on time T of the switch control circuit according to the first on signal and the first off signalonAnd for sending said switching period T and said on-time T to said judging moduleon；
The judging module is used for receiving the switching period T and the conduction time TonAnd the output sampling current Io according to the switching period T and the conduction time TonAnd the output sampling current Io judges whether the circuit enters a sampling resistor short-circuit protection state or not, and outputs a first switch control signal for the transmission path switch according to the judgment result.
In one implementation, the on-time T is determined according to the switching period TonAnd the output sampling current Io is judged whether the circuit is switched on or offEntering a sampling resistor short-circuit protection state, and outputting a first switch control signal for the transmission path switch according to the judgment result, wherein the judgment module is specifically configured to: when it is judged that
Figure BDA0002964359120000031
When the counter is increased by one; when the value of the counter is greater than or equal to a first preset number of times N1, the determination circuit enters a sampling resistor short-circuit protection state and outputs a first switch control signal, wherein the first switch control signal is used for controlling the transmission path switch to be switched to an off state.
In one implementation, the
Figure BDA0002964359120000044
Based on the following steps:
executing an energy conservation law and an inductive current piecewise equation to the first power transmission loop and the second power transmission loop to obtain a first equation group;
obtaining a first discriminant by analyzing the first equation group, wherein the first discriminant is used for keeping the sampling resistor in a normal state when the first discriminant is established;
obtaining the first discriminant
Figure BDA0002964359120000041
Wherein the first system of equations is:
Figure BDA0002964359120000042
the first discriminant is as follows:
Figure BDA0002964359120000043
wherein, IAIs the dc component of the inductor current.
In one implementation, the switching period T is determined based on the currentOn time tonAnd the output sampling current Io judges whether the circuit enters a sampling resistor short-circuit protection state, and outputs a first switch control signal for the transmission path switch according to the judgment result, wherein the judgment module is specifically configured to: when it is judged that
Figure BDA0002964359120000045
When the counter is increased by one; when the value of the counter is greater than or equal to a first preset number of times N1, the determination circuit enters a sampling resistor short-circuit protection state and outputs a first switch control signal, wherein the first switch control signal is used for controlling the transmission path switch to be switched to an off state.
Wherein A is an error coefficient, and the value range of the error coefficient is 5-95%; v0Is the voltage across the output load, LsAnd the inductance is corresponding to the secondary power supply module.
In one implementation manner, the sampling resistor short-circuit protection circuit further includes a primary power module, a primary path switch, and a primary inductor of a flyback converter, where the primary power module, the primary path switch, and the primary inductor of the flyback converter form a third power transmission loop, the secondary power module is a secondary inductor of the flyback converter, and the primary inductor of the flyback converter is used to supply power to the protection circuit through the secondary inductor of the flyback converter.
In a second aspect, a fast charger is provided, the fast charger includes a sampling resistor short-circuit protection circuit, the sampling resistor short-circuit protection circuit includes a switch control circuit, a logic control circuit, a detection sampling circuit, and a transmission path switch, the logic control circuit respectively with the switch control circuit, the detection sampling circuit, the transmission path switch is electrically connected, wherein: the switch control circuit comprises a switch module and a switch control module, the switch control module is used for controlling the on-off of the switch module, the logic control circuit is internally provided with a quick charging chip, the detection sampling circuit comprises a sampling resistor, the switch module is electrically connected with the switch control module, and the switch control module is connected with the sampling resistorThe switch control module is electrically connected with the logic control circuit, and the logic control circuit is connected in parallel with two ends of the sampling resistor; the switch control circuit: the first switch is used for periodically sending out a first on signal and a first off signal; the logic control circuit: the first sampling electric signal used for detecting the detection sampling circuit, the first conducting signal and the first turn-off signal used for collecting the switch control circuit, and the switching period T and the conducting time T of the switch control circuit obtained according to the first conducting signal and the first turn-off signalonAnd for switching on and off in dependence on said switching period T, said on-time TonAnd the first sampling electric signal judging circuit judges whether the circuit enters a sampling resistor short-circuit protection state or not, and is used for outputting a first switch control signal aiming at the transmission path switch corresponding to the sampling resistor according to the judgment result.
In one implementation, the fast charger includes a fast charging chip, a micro control unit MCU is built in the fast charging chip, the MCU includes the sampling resistor short-circuit protection circuit according to the first aspect, and the fast charging chip is a charging chip supporting fast charging.
In a third aspect, a sampling resistor short-circuit protection method is provided, which is applied to the sampling resistor short-circuit protection circuit according to the first aspect, and includes: collecting a first on signal and a first off signal of a switch control circuit through a logic control circuit; determining, by the logic control circuit, a switching period T and an on-time T of the switch control circuit according to the first on signal and the first off signalon(ii) a Acquiring a first sampling electric signal of a sampling resistor through the logic control circuit; according to the switching period T and the conduction time T by the logic control circuitonDetermining a first switch control signal of a micro control unit of the quick charging chip aiming at a transmission path switch corresponding to the sampling resistor according to the first sampling electric signal; sending, by the micro control unit, the first switch control signal to the transmission path switch; receiving station through the transmission path switchThe first switch control signal performs an operation corresponding to the first switch control signal.
In one implementation, the first sampling electrical signal is an output sampling current Io, and the logic control circuit controls the switching period T and the on-time T according to the output sampling current IoonAnd the micro control unit of the fast charging chip determines a first switch control signal of a transmission path switch corresponding to the sampling resistor according to the first sampling electric signal, and the method comprises the following steps: the logic control circuit controls the switching period T and the conduction time TonAnd calculating the output sampling current Io to obtain a first numerical value result; the logic control circuit outputs the voltage V at two ends of the load to the quick charging port0Inductor L corresponding to secondary power module of flyback converter of sampling resistor short-circuit protection circuitsCalculating to obtain a second numerical result; judging the relation between the first numerical result and the second numerical result in the switching period of the same switch control circuit through the logic control circuit, and adding a count to a counter if the first numerical result is smaller than the second numerical result, wherein each count of the counter corresponds to one switching period of the switch control circuit; determining the first switch control signal for the transmission path switch when it is detected that the counted number of times of the counter reaches a first preset number of times N1.
In one implementation, the first sampling electrical signal is an output sampling current Io, and the logic control circuit controls the switching period T and the on-time T according to the output sampling current IoonAnd the micro control unit of the fast charging chip determines a first switch control signal of a transmission path switch corresponding to the sampling resistor according to the first sampling electric signal, and the method comprises the following steps: the logic control circuit controls the switching period T and the conduction time TonAnd calculating the output sampling current Io to obtain a first numerical value result; the logic control circuit outputs the voltage V at two ends of the load to the quick charging port0Inductor L corresponding to secondary power module of flyback converter of sampling resistor short-circuit protection circuitsCalculating to obtain a second numerical result;multiplying the second numerical result by an error coefficient through the logic control circuit to obtain a third numerical result, wherein the value range of the error coefficient is 5-95%; judging the relation between the first numerical result and the third numerical result in the switching period of the same switch control circuit through the logic control circuit, and adding a count to a counter if the first numerical result is smaller than the third numerical result; determining the first switch control signal for the transmission path switch when it is detected that the counted number of times of the counter reaches a first preset number of times N1.
In one implementation, the switching period T and the on-time T are controlled by the logic control circuitonAnd calculating the output sampling current Io to obtain a first numerical value result, including: the logic control circuit controls the switching period T and the conduction time TonAnd the output sampling current Io executes a first operation formula to obtain a first numerical result, wherein the first operation formula is
Figure BDA0002964359120000071
In one implementation mode, the voltage V at two ends of the load is output to the quick charging port through the logic control circuit0Inductor L corresponding to secondary power module of flyback converter of sampling resistor short-circuit protection circuitsAnd calculating to obtain a second numerical result, comprising: the logic control circuit outputs the voltage V at two ends of the load to the quick charging port0And the inductor L corresponding to the secondary power module of the flyback converter of the sampling resistor short-circuit protection circuitsExecuting a second operation formula to obtain a second numerical result, wherein the second operation formula
Figure BDA0002964359120000072
In one implementation, the first operation formula and the second operation formula are derived based on the following procedures: executing an energy conservation law and an inductive current piecewise equation to the first power transmission loop and the second power transmission loop to obtain a first equation group; obtaining a first discriminant by analyzing the first equation group, wherein the first discriminant is used for keeping the sampling resistor in a normal state when the first discriminant is established; obtaining the first operational formula and the second operational formula according to the first discriminant; wherein the first system of equations is:
Figure BDA0002964359120000081
the first discriminant is as follows:
Figure BDA0002964359120000082
wherein, IAIs the dc component of the inductor current.
In one implementation, after the first switch control signal for the transmission path switch corresponding to the sampling resistor is output by the logic control circuit, the method further includes: clearing the counter, and adding the counter to count once when the transmission path switch is in an off state and every clock cycle of the logic control circuit; and when the counting number of the counter reaches a second preset number N2, outputting a second switch control signal of the transmission path switch through the logic control circuit, and resetting the protection state aiming at the sampling resistor, wherein the second switch control signal is used for controlling the transmission path switch to be switched to the access state.
It can be seen that, in the embodiment of the application, the logic control circuit in the sampling resistor short-circuit protection circuit can judge whether the sampling resistor needs to enter the short-circuit protection state according to the first sampling electrical signal and the first on signal and the first off signal periodically sent by the switch control circuit, and output the first switch control signal of the transmission path switch according to the judgment result, the short-circuit protection control of the circuit is realized through the logic control circuit built in the fast charging chip, and the convenience of the circuit protection control is improved.
Drawings
FIG. 1 is a schematic diagram of a circuit principle framework of a sampling resistor short-circuit protection circuit provided by the invention;
FIG. 2 is a schematic diagram of a circuit schematic framework of another sampling resistor short-circuit protection circuit provided by the invention;
FIG. 3 is a signal waveform diagram of a synchronous rectification controller sending a rising edge signal and a falling edge signal;
FIG. 4 is a diagram of secondary inductor current
Figure BDA0002964359120000083
A schematic diagram of the variation with the rising edge signal and the falling edge signal;
FIG. 5 is a schematic diagram of a circuit schematic framework of another sampling resistor short-circuit protection circuit provided by the present invention;
FIG. 6 is a schematic flow chart of a short-circuit protection method for a sampling resistor according to the present invention;
fig. 7 is a schematic flow chart of another sampling resistor short-circuit protection method provided by the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is to be understood that the terminology used in the embodiments of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a sampling resistor short-circuit protection circuit provided in an embodiment of the present application, where the sampling resistor short-circuit protection circuit includes a switch control circuit 1, a logic control circuit 2, a detection sampling circuit 3, and a transmission path switch Q1, and the logic control circuit 2 is electrically connected to the switch control circuit 1, the detection sampling circuit 3, and the transmission path switch Q1, respectively, where:
the switch control circuit 1 comprises a switch module 11 and a switch control module 12, the switch control module 12 is used for controlling the on-off of the switch module 11, the logic control circuit 2 is internally provided with a quick charging chip, the detection sampling circuit 3 comprises a sampling resistor Rs, the switch module 11 is electrically connected with the switch control module 12, the switch module 11 is electrically connected with the sampling resistor Rs, the switch control module 12 is electrically connected with the logic control circuit 2, and the logic control circuit 2 is connected with two ends of the sampling resistor Rs in parallel;
the switch control circuit 1: the first switch is used for periodically sending out a first on signal and a first off signal;
the logic control circuit 2: for detecting a first sampling electrical signal of the detection sampling circuit 3, for acquiring the first on signal and the first off signal of the switch control circuit 1, and for obtaining a switching period T and an on time T of the switch control circuit 1 according to the first on signal and the first off signalonAnd for switching on and off in dependence on said switching period T, said on-time TonAnd the first sampling electric signal judges whether the circuit enters a sampling resistor short-circuit protection state or not, and is used for outputting a first switch control signal aiming at the transmission path switch Q1 corresponding to the sampling resistor according to the judgment result.
As shown in fig. 1, the sampling resistor short-circuit protection circuit further includes a power module 31, where the power module 31 may be a power topology such as a flyback converter, a forward converter, a buck converter, a boost chopper circuit, and an LLC resonant converter, and is not limited herein.
In one implementation manner of the present application, as shown in fig. 2, the switch module 11 is a synchronous rectification switch Q2, the switch control module 12 is a synchronous rectification controller 101, the synchronous rectification controller 101 is configured to periodically send a first on signal and a first off signal to the synchronous rectification switch Q2, wherein a time difference between the first off signal and the first on signal of the same period is the on time tonAnd the time difference between the first conducting signals of two adjacent periods is the switching period T.
Specifically, as shown in fig. 3, the switch control circuit 1 periodically sends two signals, namely a first on signal and a first off signal, and the time between the first on signal and the first off signal in the current period is the on time tonWhen the logic control circuit 2 determines the switching period T and the on-time T, the first sampling electrical signal can be obtained by the detection sampling circuit 3onAnd after the first sampling electric signal is collected, the first sampling electric signal is judged through operation, and a first switch control signal is output according to the judgment resultoThe circuit also comprises a transmission path switch Q1, the transmission path switch Q1 is electrically connected with the logic control circuit 2, and the transmission path switch Q1 switches the on-off state according to a first switch control signal output by the logic control circuit 2; when the sampling resistor Rs has short-circuit fault, the logic control circuit 2 can only detect a tiny output sampling current I from the sampling resistor RsoBut according to the switching period T and the on-time TonIt can calculate that there is still larger load current, so that it can be ensured that the short-circuit protection state of sampling resistor is entered, so that when the sampling resistor Rs is short-circuited, the sampling current I can be outputtedoWhen the voltage is too low, the first switch for turning off the transmission path switch Q1 is outputted after logical operation and judgment of the logic control circuit 2When the control signal is turned off, the circuit is opened after the transmission path switch Q1 is turned off, and no output current exists at the moment, so that the circuit protection is realized; and output the sampling current IoToo high, possibly actual output sampling current IoToo high, and too high, output sampling current IoThe charged electronic product may be damaged, so the present embodiment may protect the output abnormality in the normal circuit state, and may also protect the output abnormality in the abnormal circuit state.
It should be noted that, the synchronous rectification controller 101 may be an IC such as MP6908, which is common in the market, or may be a discrete circuit externally mounted, and can achieve the purpose of this control; the logic control circuit is a fast charging protocol chip IC with higher integration degree, such as fast charging protocol chips IC with MCU built-in types, such as common models in the market, IP2726 and IP2712, and may be other types of SOCs.
It can be seen that, in the embodiment of the application, the logic control circuit in the sampling resistor short-circuit protection circuit can judge whether the sampling resistor needs to enter the short-circuit protection state according to the first sampling electrical signal and the first on signal and the first off signal periodically sent by the switch control circuit, and output the first switch control signal of the transmission path switch according to the judgment result, the short-circuit protection control of the circuit is realized through the logic control circuit built in the fast charging chip, and the convenience of the circuit protection control is improved.
In one implementation manner of the present application, as shown in fig. 2, the synchronous rectification switch Q2 is a first NMOS transistor, a gate of the first NMOS transistor is electrically connected to the synchronous rectification controller 101, the first on signal is a rising edge signal, and the first off signal is a falling edge signal.
In an implementation manner of the present application, the sampling resistor short-circuit protection circuit further includes a secondary power module and a charging capacitor C0And output load R of quick charging portloadThe secondary power supply module and the charging capacitor C0And the synchronous rectification switch Q2 form a first power transmission loop, the transmission path switch Q1 and the output load RloadThe sampling resistor Rs and the charging capacitor C0A second power transmission loop is formed.
When the power module 31 is a flyback converter, the power module 31 includes a secondary power module, as shown in fig. 2, the secondary power module is a secondary inductor Ls301 of the flyback converter, as shown in fig. 4, when the synchronous rectification controller 101 sends a first conduction signal to the synchronous rectification switch Q1, the synchronous rectification switch Q1 is turned on, so that the first power transmission loop is in a connected state, and the flyback converter secondary inductor L is connected to the synchronous rectification switch Q1sA current passes through the charging capacitor C0Charging is carried out;
when the synchronous rectification controller 101 sends a second on-time signal to the synchronous rectification switch Q1, the synchronous rectification switch Q1 is turned off, so that the first power transmission loop is in an open state, and the secondary inductor L of the flyback converter is in an open statesNo current passes through the capacitor C0Discharging until the first conducting signal of the next period;
at the on time tonInner, flyback converter secondary inductance LsTo charging capacitor C0Discharging and charging capacitor C0Charging, flyback converter secondary inductance LsIn which a secondary inductor current is generated
Figure BDA0002964359120000124
While in the off time, the secondary inductor current
Figure BDA0002964359120000122
Zero, when the first turn-on signal of the next cycle occurs again, the flyback converter secondary inductor LsIn which the secondary inductor current is generated again
Figure BDA0002964359120000125
The cycle is repeated.
Wherein the utilization of the flyback converter secondary inductor L is realized in the first power transmission loopsCharging capacitor C0A charging step is carried out, and the switch control circuit 1 is positioned in the first power transmission loop and is used as a switch to control the on-off of the switch control circuit 1Preparing; implementing a charging capacitor C in a second power transmission loop0To output load RloadThe discharging step is performed, and the transmission path switch Q1 is in the second power transmission loop and is used as a switch to control the on-off of the circuit.
In one implementation manner of the present application, as shown in fig. 5, the first sampling electrical signal is an output sampling current Io, the transmission path switch Q1 is a second NMOS transistor, the logic control circuit 2 includes a sampling detection module 21, a time detection module 22 and a determination module 23, the sampling detection module 21 includes an amplifier 201 and an analog-to-digital converter 202, the amplifier 201 is connected in parallel to two ends of the sampling resistor Rs, the analog-to-digital converter 202 is electrically connected to the amplifier 201, the determination module 23 is electrically connected to the analog-to-digital converter 202, the time detection module 22 is respectively connected to the switch control circuit 1 and the determination module 23, the determination module 23 is electrically connected to a gate of the second NMOS transistor, wherein:
the sampling detection module 21 is configured to detect the output sampling current Io by detecting a voltage difference between two ends of the sampling resistor Rs, and output the output sampling current Io to the judgment module 23;
the time detection module 22 is configured to acquire the first on signal and the first off signal of the switch control circuit 1, and obtain a switching period T and an on time T of the switch control circuit 1 according to the first on signal and the first off signalonAnd for sending said switching period T and said on-time T to said decision module 23on；
The determining module 23 is configured to receive the switching period T and the conducting time TonAnd the output sampling current Io according to the switching period T and the conduction time TonAnd the output sampling current Io judges whether or not the circuit enters a sampling resistance short-circuit protection state, and outputs a first switch control signal for the transmission path switch Q1 according to the judgment result.
Wherein the synchronous rectification controller 101 is synchronousWhile the rectifier switch Q2 sends a rising edge signal, the external rising edge of the time detection module 22 is interrupted; when the synchronous rectification controller 101 sends a falling edge signal to the synchronous rectification switch Q2, the external falling edge of the time detection module 22 is interrupted, and the switching period T and the conducting time T are obtained through calculation according to the state difference of the two interruption time points of the time detection module 22on(ii) a The judging module 23 receives the switching period T and the conducting time TonAnd outputting the sampling current IoAnd outputs a first switch control signal, and meanwhile, the determining module 23 is connected to the transmission path switch Q1 in the second power transmission loop, so as to control on/off of the transmission path switch Q1.
In one implementation of the present application, the on-time T is determined according to the switching period TonAnd the output sampling current Io judges whether the circuit enters a sampling resistor short-circuit protection state, and outputs a first switch control signal for the transmission path switch according to the judgment result, wherein the judgment module is specifically configured to: when it is judged that
Figure BDA0002964359120000131
When the counter is increased by one; when the value of the counter is greater than or equal to a first preset number of times N1, the determination circuit enters a sampling resistor short-circuit protection state and outputs a first switch control signal, wherein the first switch control signal is used for controlling the transmission path switch to be switched to an off state.
In one implementation of the present application, the
Figure BDA0002964359120000147
Based on the following steps:
executing an energy conservation law and an inductive current piecewise equation to the first power transmission loop and the second power transmission loop to obtain a first equation group;
obtaining a first discriminant by analyzing the first equation group, wherein the first discriminant is used for keeping the sampling resistor in a normal state when the first discriminant is established;
obtaining the first discriminant
Figure BDA0002964359120000141
Wherein the first system of equations is:
Figure BDA0002964359120000142
the first discriminant is as follows:
Figure BDA0002964359120000143
wherein, IAIs the dc component of the inductor current.
In particular, the method comprises the following steps of,
Figure BDA0002964359120000148
the logic control circuit 2 indicates that only a very small output sampling current I can be detected from the sampling resistor RsoAnd a sampling resistor short-circuit protection state needs to be entered.
Wherein the first sampling electrical signal is output sampling current IoIn the secondary inductance L of the flyback convertersIn which a secondary inductor current is generated
Figure BDA0002964359120000144
At the on time tonInner, flyback converter secondary inductance LsTo charging capacitor C0Discharging and charging capacitor C0Charging, flyback converter secondary inductance LsIn which a secondary inductor current is generated
Figure BDA0002964359120000145
While in the off-time, the secondary inductor current LsZero, when the first turn-on signal of the next cycle occurs again, the flyback converter secondary inductor LsIn which the secondary inductor current is generated again
Figure BDA0002964359120000146
The cycle is repeated.Wherein the secondary inductor current flows as shown in FIG. 4
Figure BDA0002964359120000154
There are two modes: a. current Discontinuous Mode (DCM); b. current Continuous Mode (CCM), in which, as shown in fig. 4, in DCM, the flyback converter secondary inductor LsThe direct current component of (1) is 0, and in a CCM mode, a flyback converter secondary inductor LsHas a direct current component of IAAnd I isA＞0。
From the above equation, the basic theoretical basis for determining whether the sampling resistor Rs is short-circuited in the present embodiment can be obtained:
Figure BDA0002964359120000151
it should be noted that, in this determination formula, when the setting of the synchronous rectification controller 101 is set, after the period for sending the rising edge signal and the falling edge signal is determined, the on-time t is determinedonThe value of the sum switching period T is kept constant and the on-time T is kept constantonAnd even if the switching period T is changed, the short circuit of the sampling resistor Rs is not caused, and the situation of the sampling resistor Rs cannot be reflected. And V0And LsThe rated output voltage and current of the protection circuit or the protection system are constant values when components of other parts in the circuit are well set, so that the only value capable of reflecting the condition of the sampling resistor Rs is the output sampling current I obtained by sampling and detecting the sampling resistor RsoThus, by sampling the output current IoDetermines whether it is short-circuited.
No matter the secondary inductive current in the actual operation of the circuit
Figure BDA0002964359120000155
In the current interruption mode or the current continuous mode, if the output sampling current Io is abnormally low:
Figure BDA0002964359120000152
that is, it is proved that there is an abnormal condition such as a short circuit in the sampling resistor Rs, and when this condition cannot be released within the first preset number of times N1, the first switch control signal is outputted to control the transmission path switch Q1 to switch to the off state.
In the above formula, the sampling current I is outputoOn time tonAnd the switching period T is detection data, and the judgment formula can be converted into
Figure BDA0002964359120000153
The right side of the decision formula is a fixed value and the left side of the decision formula is changed in real time, i.e.
Figure BDA0002964359120000162
In order to be the first operation formula,
Figure BDA0002964359120000163
is a second operation formula when
Figure BDA0002964359120000164
When the sampling resistance Rs is in the off state, the counter adds a count, each judgment period is a switching period T, the initial count of the counter is 0, and when the abnormality occurs in a first preset number of continuous N1 of periods, namely the duration of N1T is passed, the fact that the sampling resistance Rs is short-circuited or the like is proved, namely a first switch control signal is output, and the transmission path switch Q1 is controlled to be switched to the off state.
In one implementation of the present application, the on-time T is determined according to the switching period TonAnd the output sampling current Io judges whether the circuit enters a sampling resistor short-circuit protection state, and outputs a first switch control signal for the transmission path switch according to the judgment result, wherein the judgment module is specifically configured to: when it is judged that
Figure BDA0002964359120000165
When the counter is increased by one; when the value of the counter is greater than or equal toWhen the number of times is equal to a first preset number of times N1, the determination circuit enters a sampling resistor short-circuit protection state and outputs a first switch control signal, wherein the first switch control signal is used for controlling the transmission path switch to be switched to an off state.
Wherein A is an error coefficient, and the value range of the error coefficient is 5-95%; v0Is the voltage across the output load, LsAnd the inductance is corresponding to the secondary power supply module.
For example, when the error coefficient is 50%, the sampling error of the logic control circuit 2 to the sampling resistor Rs is taken into account, and the method of reducing the judgment threshold is adopted to avoid the problem of misjudgment caused by the sampling error, that is, the error coefficient is taken as 50%
Figure BDA0002964359120000161
The error coefficient can be adjusted appropriately according to the actual sampling precision, when the sampling precision is higher, the error coefficient can be adjusted appropriately to be higher, for example, the error coefficient takes 95%, when the sampling precision is lower, the error coefficient can be adjusted appropriately to be lower, for example, the error coefficient takes 5%, which is not limited herein.
In an implementation manner of the present application, as shown in fig. 5, the sampling resistor short-circuit protection circuit further includes a primary power module, a primary path switch and a primary inductor of the flyback converter, the primary power module the primary path switch and the primary inductor of the flyback converter form a third power transmission loop, the secondary power module is a secondary inductor of the flyback converter, the primary inductor of the flyback converter is used for passing through the secondary inductor of the flyback converter for supplying power to the protection circuit.
The primary power supply module Vg is responsible for providing a power supply source and utilizes a primary inductor Lp of the flyback converter and a secondary inductor L of the flyback convertersEnergy transmission is achieved, the voltage proportion is adjusted by adjusting the number of turns of the coil, in addition, the primary path switch Q3 is responsible for controlling the on-off of the third power transmission loop, and when the primary path switch Q3 is in a connected state, the primary coil of the flyback converter is directly connected to Vg. The current in the primary coil and the magnetic field in the flyback converter core increaseEnergy is stored in the magnetic core. The voltage developed in the secondary winding is reversed, at which time the synchronous rectifier switch Q1 is turned off and cannot conduct. At this time, the capacitor C0To a load RloadProviding a voltage and a current. During the switch off phase, the current in the primary coil is 0. At the same time the magnetic field in the core begins to drop, inducing a forward voltage on the secondary coil. At this time, the diode is in a forward bias state and the synchronous rectification switch Q1 is opened, and the conducted current flows into the capacitor C0And a load Rload. The energy stored in the core is transferred to a capacitor C0And a load RloadIn (1). When the sampling resistor Rs has short-circuit fault, the logic control circuit 2 can only detect a tiny output sampling current I from the sampling resistor RsoTherefore, when the sampling resistor Rs is short-circuited, the output sampling current I is generatedoWhen the voltage is too low, under the operation control of the logic control circuit 2, the transmission path switch Q1 in the second power transmission loop switches the off state, so that the situation that the detection is not accurate due to the short circuit of the sampling resistor Rs, the output current in the second power transmission loop cannot be detected in real time, and the damage of the charging product due to the abnormal output current and power caused by the abnormal output current and power is avoided.
Referring to fig. 6, fig. 6 is a schematic flowchart of a sampling resistor short-circuit protection method according to an embodiment of the present application, where the method is applied to the sampling resistor short-circuit protection circuit, and includes the following steps:
step 601: collecting a first on signal and a first off signal of a switch control circuit through a logic control circuit;
step 602: determining, by the logic control circuit, a switching period T and an on-time T of the switch control circuit according to the first on signal and the first off signalon；
Step 603: acquiring a first sampling electric signal of a sampling resistor through the logic control circuit;
step 604: according to the switching period T and the conduction time T by the logic control circuitonAnd the micro control unit for determining the quick charge chip according to the first sampling electric signal aims at the transmission path corresponding to the sampling resistorA first switch control signal to the switch;
step 605: sending, by the micro control unit, the first switch control signal to the transmission path switch;
step 606: receiving the first switch control signal through the transmission path switch, and executing an operation corresponding to the first switch control signal.
Before step 601, it is necessary to power on the sampling resistor short-circuit protection circuit and perform a reset operation, where the reset operation includes program initialization of sampling data, initialization of a register state, and control of the transmission path switch Q1 to switch to a closed state.
It can be seen that, in the embodiment of the application, the logic control circuit in the sampling resistor short-circuit protection circuit can judge whether the sampling resistor needs to enter the short-circuit protection state according to the first sampling electrical signal and the first on signal and the first off signal periodically sent by the switch control circuit, and output the first switch control signal of the transmission path switch according to the judgment result, the short-circuit protection control of the circuit is realized through the logic control circuit built in the fast charging chip, and the convenience of the circuit protection control is improved.
In one implementation manner of the present application, after the first switch control signal for the transmission path switch corresponding to the sampling resistor is output by the logic control circuit, the method further includes:
clearing the counter, and adding the counter to count once when the transmission path switch is in an off state and every clock cycle of the logic control circuit;
and when the counting number of the counter reaches a second preset number N2, outputting a second switch control signal of the transmission path switch through the logic control circuit, and resetting the protection state aiming at the sampling resistor, wherein the second switch control signal is used for controlling the transmission path switch to be switched to the access state.
Since the transmission path switch Q1 has been controlled to the off state, no current flows in the second power transmission circuit, and the second power transmission circuit is in the stop state, and after the duration of the clock cycle of N2 logic control circuits in this state, the transmission path switch is re-closed, and then the execution process of the sampling resistance short-circuit protection method in the next round is entered.
Specifically, the sampling resistor short-circuit protection method includes other steps as described above with reference to the foregoing description of the sampling resistor short-circuit protection circuit.
Referring to fig. 7, fig. 7 is a schematic flowchart of a sampling resistor short-circuit protection method according to an embodiment of the present application, where the method is applied to the sampling resistor short-circuit protection circuit, and includes the following steps:
step 701: and the sampling resistor short-circuit protection circuit is electrified, and performs reset operation to initialize sampling data.
Step 702: the protection state for the sampling resistor is reset and the transmission path switch Q1 is controlled to switch to a closed state.
Step 703: and acquiring a first on signal and a first off signal of the switch control circuit through the logic control circuit.
Step 704: determining, by the logic control circuit, a switching period T and an on-time T of the switch control circuit according to the first on signal and the first off signalon。
Step 705: and acquiring a first sampling electric signal of the sampling resistor through the logic control circuit.
Step 706: the logic control circuit controls the switching period T and the conduction time TonAnd calculating the output sampling current Io to obtain a first numerical value result.
Step 707: the logic control circuit outputs the voltage V at two ends of the load to the quick charging port0Inductor L corresponding to secondary power module of flyback converter of sampling resistor short-circuit protection circuitsAnd calculating to obtain a second numerical result, and multiplying the second numerical result by an error coefficient to obtain a third numerical result.
Step 708: and judging the relation between the first numerical result and the third numerical result in the switching period of the same switch control circuit through the logic control circuit, and adding a count to the counter if the first numerical result is smaller than the third numerical result.
Step 709: when the counting times of the counter reach a first preset time N1, outputting a first switch control signal for a transmission path switch corresponding to the sampling resistor through the logic control circuit, wherein the first switch control signal is used for controlling the transmission path switch to be switched to an off state.
Step 710: and clearing the counter, adding a count to the counter every time a clock cycle of the logic control circuit is passed when the transmission path switch is in an off state, and executing the step 702 again when the counting number of the counter is judged to reach a second preset number N2.
It can be seen that, in the embodiment of the application, the logic control circuit in the sampling resistor short-circuit protection circuit can judge whether the sampling resistor needs to enter the short-circuit protection state according to the first sampling electrical signal and the first on signal and the first off signal periodically sent by the switch control circuit, and output the first switch control signal of the transmission path switch according to the judgment result, the short-circuit protection control of the circuit is realized through the logic control circuit built in the fast charging chip, and the convenience of the circuit protection control is improved.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (8)

1. A sampling resistor short-circuit protection method is applied to a sampling resistor short-circuit protection circuit, and comprises the following steps:
the sampling resistor short-circuit protection circuit acquires a first on signal and a first off signal of the switch control circuit;
the sampling resistance short-circuit protection circuit determines the switching period T and the on-time T of the switch control circuit according to the first on signal and the first off signalon；
The sampling resistor short-circuit protection circuit acquires a first sampling electrical signal of a sampling resistor;
the sampling resistor short-circuit protection circuit is based on the switching period T and the conduction time TonDetermining a first switch control signal of a micro control unit of the quick charging chip aiming at a transmission path switch corresponding to the sampling resistor according to the first sampling electric signal;
the micro control unit sends the first switch control signal to the transmission path switch;
the transmission path switch receives the first switch control signal and performs an operation corresponding to the first switch control signal.
2. The method according to claim 1, wherein the first sampled electrical signal is an output sampled current Io, and the sampled resistor short-circuit protection circuit is based on the switching period T and the on-time TonAnd the micro control unit of the fast charging chip determines a first switch control signal of a transmission path switch corresponding to the sampling resistor according to the first sampling electric signal, and the method comprises the following steps:
sampling resistance short-circuit protection circuit for the switching period T and the conduction time TonAnd calculating the output sampling current Io to obtain a first numerical value result;
sampling resistor short-circuit protection circuit outputs voltage V at two ends of load to quick charging port0Inductor L corresponding to secondary power module of flyback converter of sampling resistor short-circuit protection circuitsCalculating to obtain a second numerical result;
the sampling resistor short-circuit protection circuit judges the relation between the first numerical result and the second numerical result in the switching period of the same switch control circuit, if the first numerical result is smaller than the second numerical result, the counter adds one counting, and each counting of the counter corresponds to one switching period of the switch control circuit;
determining the first switch control signal for the transmission path switch when it is detected that the counted number of times of the counter reaches a first preset number of times N1.
3. The method of claim 2,
the first sampling electric signal is output sampling current Io, and the sampling resistor short-circuit protection circuit is used for protecting the sampling resistor short-circuit according to the switching period T and the conduction time TonAnd the micro control unit of the fast charging chip determines a first switch control signal of a transmission path switch corresponding to the sampling resistor according to the first sampling electric signal, and the method comprises the following steps:
sampling resistance short-circuit protection circuit for the switching period T and the conduction time TonAnd calculating the output sampling current Io to obtain a first numerical value result;
sampling resistor short-circuit protection circuit outputs voltage V at two ends of load to quick charging port0Inductor L corresponding to secondary power module of flyback converter of sampling resistor short-circuit protection circuitsCalculating to obtain a second numerical result;
the sampling resistor short-circuit protection circuit multiplies the second numerical result by an error coefficient to obtain a third numerical result, wherein the value range of the error coefficient is 5% -95%;
the sampling resistor short-circuit protection circuit judges the relation between the first numerical result and the third numerical result in the switching period of the same switch control circuit, and if the first numerical result is smaller than the third numerical result, the counter adds one counting;
determining the first switch control signal for the transmission path switch when it is detected that the counted number of times of the counter reaches a first preset number of times N1.
4. Method according to claim 2 or 3, characterized in that the sampling resistance short-circuit protection circuit is coupled to the switching period T, the conduction time TonAnd the output sampling current Io is calculatedObtaining a first numerical result comprising:
sampling resistance short-circuit protection circuit for the switching period T and the conduction time TonAnd the output sampling current Io executes a first operation formula to obtain a first numerical result, wherein the first operation formula is
Figure FDA0002964359110000021
5. The method of claim 2 or 3, wherein the sampling resistor short-circuit protection circuit outputs the voltage V across the load to the fast-charge port0Inductor L corresponding to secondary power module of flyback converter of sampling resistor short-circuit protection circuitsAnd calculating to obtain a second numerical result, comprising:
the sampling resistor short-circuit protection circuit outputs the voltage V at two ends of the load to the quick charging port0And the inductor L corresponding to the secondary power module of the flyback converter of the sampling resistor short-circuit protection circuitsExecuting a second operation formula to obtain a second numerical result, wherein the second operation formula is
Figure FDA0002964359110000031
6. The method of claim 4, wherein the first operation formula is derived based on the following process:
executing an energy conservation law and an inductive current piecewise equation to the first power transmission loop and the second power transmission loop to obtain a first equation group;
obtaining a first discriminant by analyzing the first equation group, wherein the first discriminant is used for keeping the sampling resistor in a normal state when the first discriminant is established;
obtaining the first operation formula according to the first discriminant;
wherein the first system of equations is:
Figure FDA0002964359110000032
the first discriminant is as follows:
Figure FDA0002964359110000033
wherein, IAIs the dc component of the inductor current.
7. The method of claim 5, wherein the second operation formula is derived based on the following process:
executing an energy conservation law and an inductive current piecewise equation to the first power transmission loop and the second power transmission loop to obtain a first equation group;
obtaining a first discriminant by analyzing the first equation group, wherein the first discriminant is used for keeping the sampling resistor in a normal state when the first discriminant is established;
obtaining the second operation formula according to the first discriminant;
wherein the first system of equations is:
Figure FDA0002964359110000041
the first discriminant is as follows:
Figure FDA0002964359110000042
wherein, IAIs the dc component of the inductor current.
8. The method of claim 2 or 3, wherein after the sampling resistor short-circuit protection circuit outputs the first switch control signal for the transmission path switch corresponding to the sampling resistor, the method further comprises:
clearing the counter, and adding the counter to count once when the transmission path switch is in an off state and every clock cycle of the logic control circuit; and when the counting number of the counter reaches a second preset number N2, outputting a second switch control signal of the transmission path switch through the logic control circuit, and resetting the protection state aiming at the sampling resistor, wherein the second switch control signal is used for controlling the transmission path switch to be switched to the access state.
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CN111934403B (en) 2021-01-12

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