CN113922450B - Power supply circuit with low noise - Google Patents
Power supply circuit with low noise Download PDFInfo
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- CN113922450B CN113922450B CN202111192051.5A CN202111192051A CN113922450B CN 113922450 B CN113922450 B CN 113922450B CN 202111192051 A CN202111192051 A CN 202111192051A CN 113922450 B CN113922450 B CN 113922450B
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- power supply
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- overvoltage protection
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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
- H02J7/00308—Overvoltage protection
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- 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
- H02H3/20—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 voltage
- H02H3/202—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 voltage for dc systems
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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
- H02J7/0031—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using battery or load disconnect circuits
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- Protection Of Static Devices (AREA)
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Abstract
The application comprises a power supply circuit with low noise, and particularly relates to the technical field of power supply circuits. The power supply circuit comprises a power supply chip, an overvoltage protection module and a photoelectric coupling module; the power supply chip at least comprises a voltage input pin, an output control pin and a voltage sampling pin; the voltage input pin is connected with an input voltage end of the power supply circuit; the power supply chip controls the transformer through the output control pin to convert the input voltage of the input voltage terminal into output voltage; the input end of the photoelectric coupling module is connected with the output voltage; the overvoltage protection module is connected with the input end of the photoelectric coupling module. In the scheme, in the process of charging the battery, when the output voltage is overlarge, the operation of the charging circuit can be immediately stopped, so that the charging process of the battery is stopped, the output voltage does not need to be discharged to be close to 0V, and the reliability of overvoltage protection in the charging process of the battery is improved.
Description
Technical Field
The application relates to the technical field of power supply circuits, in particular to a low-noise power supply circuit for supplying power to a battery load.
Background
In the prior art, an input power supply sequentially passes through an input end, a power frequency transformer, a rectifying and filtering circuit and a charging circuit, so that a battery load can be charged.
The common battery charging circuit structure in the art is a flyback charging circuit, and the flyback charging circuit comprises a chip starting circuit, a current sampling circuit, a feedback control circuit, a short-circuit protection circuit and an overvoltage protection circuit. In the flyback charging circuit, an overvoltage protection circuit is connected with an output voltage end Vout, when the Vout is overlarge, the overvoltage protection circuit is conducted and grounded, when the Vout is reduced to be close to 0, the voltage of the input end of a photoelectric coupling module of a photoelectric coupler in a feedback control circuit is also close to 0, so that an output triode in the photoelectric coupler is disconnected, and a control chip in a battery charging circuit is turned off through other modules in the feedback control circuit to stop the operation of the battery charging circuit; the input power then causes the chip to restart through the chip start-up circuit, at which point the chip is always in the off-restart cycle, since faults that cause output over-voltage often remain.
In the scheme, the overvoltage protection can be realized only when the output voltage Vout is discharged to 0V, and the reliability of the overvoltage protection is low; meanwhile, the chip is always in turn-off-restarting cycle, so that after triggering output overvoltage protection, the loss and noise of a battery power supply circuit are large, and the chip is extremely fragile.
Disclosure of Invention
The application provides a power supply circuit with low noise, which improves the reliability of overvoltage protection in the battery charging process.
In one aspect, a power supply circuit with low noise is provided, and the power supply circuit comprises a power supply chip, an overvoltage protection module and a photoelectric coupling module;
the power supply chip at least comprises a voltage input pin, an output control pin and a voltage sampling pin; the voltage input pin is connected with an input voltage end of the power supply circuit; the power supply chip controls the transformer to convert the input voltage of the input voltage end into output voltage through an output control pin;
the input end of the photoelectric coupling module is connected with the output voltage; the output end of the photoelectric coupling module is used for controlling the level of a voltage sampling pin of the power supply circuit and the level of a chip control pin;
the overvoltage protection module is connected with the input end of the photoelectric coupling module, and is used for being conducted when the output voltage is larger than the specified voltage so as to ground the input end of the photoelectric coupling module.
Optionally, the first input end of the overvoltage protection module is connected with the input end of the photoelectric coupling module through a first diode; the second input end of the overvoltage protection module is connected with the output voltage;
the second input end is connected with the cathode of the first voltage stabilizing diode; the anode of the first zener diode is grounded through a first current limiting resistor; the anode of the first voltage stabilizing diode is also connected with the control end of the first controllable silicon;
the first input end is connected with the anode of the first controllable silicon; and the cathode of the first controllable silicon is grounded.
Optionally, the input end of the photoelectric coupling module is a light emitting diode; the overvoltage protection module is connected with the anode of the light emitting diode.
Optionally, the output end of the photoelectric coupling module comprises a first triode; the output end of the photoelectric coupling module is used for controlling the conduction state between the collector electrode and the emitter electrode according to the received signal sent by the input end of the photoelectric coupling module;
the emitter of the first triode is connected with the second triode; the second triode is used for controlling the connection state of the level control node and the ground wire;
the level control node is respectively connected with a reference voltage pin and a voltage sampling pin.
Optionally, when the output voltage is higher than the reverse breakdown voltage of the first zener diode, the overvoltage protection module grounds the output voltage and the anode of the light emitting diode through a first silicon controlled rectifier, so that the level control node is not grounded, and the power supply chip stops supplying power according to the high level received by the voltage sampling pin;
when the output voltage is reduced to a first voltage threshold, the first controllable silicon is disconnected, the first triode is conducted with the second triode, the level control node is grounded, and the power supply chip continues to supply power according to the low level of the voltage sampling pin.
Optionally, the input end of the photoelectric coupling module is a light emitting diode; the overvoltage protection module is connected with the cathode of the light emitting diode.
Optionally, the chip control pin is connected with a collector electrode of a first triode in the output end of the photoelectric coupling module;
when the overvoltage protection module is disconnected, the voltage of the chip control pin is larger than a second voltage threshold, and the power supply chip operates normally; when the overvoltage protection module is closed, the voltage of the chip control pin is smaller than a second voltage threshold value, and the power supply chip stops running.
Optionally, the cathode of the light emitting diode is connected with the cathode of the second zener diode;
the cathode of the second zener diode is connected with the voltage dividing node; the voltage dividing node divides the output voltage by a first voltage dividing resistor and a second voltage dividing resistor.
Optionally, the power supply chip is further configured to adjust an output value of the output voltage according to a level on a chip control pin.
Optionally, the overvoltage protection module includes a second current limiting resistor, and the output voltage is connected with the first silicon controlled rectifier through the second current limiting resistor;
when the overvoltage protection module is conducted, the power supply circuit discharges through at least a first current limiting resistor, a second current limiting resistor, a first voltage dividing resistor and a second voltage dividing resistor.
The technical scheme provided by the application can comprise the following beneficial effects:
when the input voltage is converted into the output voltage capable of supplying power through the power supply chip and the auxiliary voltage transformation circuit, and the output voltage capable of supplying power is supplied to the battery load, the power supply circuit can form a detection module of the power supply circuit through the overvoltage protection module and the photoelectric coupling module, when the output voltage of the battery power supply circuit after voltage transformation is larger than the specified voltage, the overvoltage protection module is conducted, the input end of the photoelectric coupling module in the photoelectric coupling module is grounded, and at the moment, the current of the input end of the photoelectric coupling module is changed immediately, so that the output end of the photoelectric coupling module controls the voltage sampling pin and the level of the chip control pin, and the operation of the battery charging circuit is stopped. According to the scheme, when the output voltage is overlarge, the operation of the charging circuit can be stopped immediately, the output voltage does not need to be discharged to be close to 0V, and the reliability of overvoltage protection is improved; and because the output voltage discharges slowly, the time interval for restarting the chip is greatly increased, the service life of the chip is prolonged, the power loss of the battery power supply circuit is reduced, the safety and reliability of the battery power supply circuit are improved, and the EMI noise generated by the battery power supply circuit is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram showing a structure of a power supply circuit with low noise according to an exemplary embodiment.
Fig. 2 is a schematic diagram showing a structure of a power supply circuit with low noise according to an exemplary embodiment.
Fig. 3 is a schematic diagram showing a structure of a power supply circuit with low noise according to an exemplary embodiment.
Detailed Description
The following description of the embodiments of the present application will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the application are shown. 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.
It should be understood that the "indication" mentioned in the embodiments of the present application may be a direct indication, an indirect indication, or an indication having an association relationship. For example, a indicates B, which may mean that a indicates B directly, e.g., B may be obtained by a; it may also indicate that a indicates B indirectly, e.g. a indicates C, B may be obtained by C; it may also be indicated that there is an association between a and B.
In the description of the embodiments of the present application, the term "corresponding" may indicate that there is a direct correspondence or an indirect correspondence between the two, or may indicate that there is an association between the two, or may indicate a relationship between the two and the indicated, configured, etc.
In the embodiment of the present application, the "predefining" may be implemented by pre-storing corresponding codes, tables or other manners that may be used to indicate relevant information in devices (including, for example, terminal devices and network devices), and the present application is not limited to the specific implementation manner thereof.
Fig. 1 is a schematic diagram showing a structure of a power supply circuit with low noise according to an exemplary embodiment. As shown in fig. 1, the power supply circuit includes a power supply chip 110, an overvoltage protection module 120, and a photoelectric coupling module 130;
the power supply chip at least comprises a voltage input pin VCC, an output control pin OUT and a voltage sampling pin FB; the voltage input pin is connected with an input voltage end VIN of the power supply circuit; the power supply chip controls the transformer to convert the input voltage of the input voltage terminal into output voltage VOUT through an output control pin OUT;
the input end of the photoelectric coupling module is connected with the output voltage VOUT; the output end of the photoelectric coupling module is used for controlling the level of a voltage sampling pin of the power supply circuit and the level of a chip control pin;
the overvoltage protection module is connected with the input end of the photoelectric coupling module, and is used for being conducted when the output voltage is larger than the specified voltage so as to ground the input end of the photoelectric coupling module.
In the power supply chip shown in fig. 1, the power supply chip may control the MOS transistor through the output control pin OUT to control the transformer T1 to convert the input voltage VIN into the output voltage VOUT, so as to charge the battery.
After converting the input voltage VIN into the output voltage VOUT, VOUT is input to an input end of a photocoupler (i.e., a photocoupler module), and is grounded through a voltage regulator, so that an electrical signal is converted into an optical signal through the input end of the photocoupler module and is transmitted to an output end of the photocoupler; after the output end of the photoelectric coupling module receives the optical signal, a corresponding electric signal is generated to indicate the level of the chip control pin VC and the voltage sampling pin FB, so that the control of the working state of the power supply chip is realized.
The input end of the photoelectric coupling module is directly connected with the overvoltage protection module, when the overvoltage protection module detects that VOUT is greater than a specified voltage (i.e. when the voltage is overvoltage), the overvoltage protection module is turned on, and the input end of the photoelectric coupling module is directly grounded, at this time, the working state of the input end of the photoelectric coupling module is affected, for example, when the anode of the light emitting diode is grounded, no current flows through the input end of the photoelectric coupling module, at this time, the input end of the photoelectric coupling module does not send an optical signal, thereby causing the output end of the photoelectric coupling module to be affected, affecting the voltage level on the voltage sampling pin FB and the chip control pin VC, so as to control the power supply chip 110 to stop outputting the output of the output control pin OUT, thereby realizing the work of disconnecting the transformer, stopping the generation of VOUT, and stopping the charging process of the battery.
In summary, when the input voltage is converted into the output voltage capable of supplying power to the battery load through the power supply chip and the voltage transformation circuit attached thereto, the power supply circuit can form the detection module of the power supply circuit through the overvoltage protection module and the photoelectric coupling module, when the output voltage of the battery power supply circuit after voltage transformation is greater than the specified voltage, the overvoltage protection module is conducted to ground the input end of the photoelectric coupling module in the photoelectric coupling module, and at the moment, the current of the input end of the photoelectric coupling module is changed immediately, thereby affecting the control of the output end of the photoelectric coupling module on the voltage sampling pin and the level of the chip control pin, and stopping the operation of the battery charging circuit. According to the scheme, when the output voltage is overlarge, the operation of the charging circuit can be stopped immediately, the output voltage does not need to be discharged to be close to 0V, and the reliability of overvoltage protection is improved; and because the output voltage discharges slowly, the time interval for restarting the chip is greatly increased, the service life of the chip is prolonged, the power loss of the battery power supply circuit is reduced, the safety and reliability of the battery power supply circuit are improved, and the EMI noise generated by the battery power supply circuit is reduced.
Fig. 2 is a schematic diagram showing a structure of a power supply circuit with low noise according to an exemplary embodiment. As shown in fig. 2, the power supply circuit includes a power supply chip 210, an overvoltage protection module 220, and a photoelectric coupling module 230;
the power supply chip at least comprises a voltage input pin VCC, an output control pin OUT and a voltage sampling pin FB;
the input end of the photoelectric coupling module 230 is connected with the output voltage Vout; the output end of the photoelectric coupling module 230 is used for controlling the level of the voltage sampling pin FB and the level of the chip control pin VC of the power supply circuit;
the overvoltage protection module is connected to the input terminal of the optocoupler module 230, and is configured to be turned on when the output voltage is greater than a specified voltage, so as to ground the input terminal of the optocoupler module.
Optionally, the first input end of the overvoltage protection module is connected with the input end of the photoelectric coupling module through a first diode D4; the second input end of the overvoltage protection module is connected with the output voltage Vout; the second input end is connected with the cathode of the first zener diode Z1; the anode of the first zener diode Z1 is grounded through a first current limiting resistor R12; the anode of the first zener diode is also connected with the control end of the first silicon controlled rectifier SCR. The first input end is connected with the anode of the first silicon controlled rectifier SCR; the cathode of the first silicon controlled rectifier SCR is grounded. The input end of the photoelectric coupling module is a light-emitting diode; the overvoltage protection module is connected with the anode of the light emitting diode.
In one possible implementation, the overvoltage protection module includes a second current limiting resistor R11, and the output voltage is connected to the first thyristor via the second current limiting resistor R11.
As shown in fig. 2, in the overvoltage protection module, when the output voltage VOUT for charging the battery is detected to be greater than the specified voltage, the first zener diode Z1 breaks down reversely, and at this time, a voltage value exists at the control end of the first SCR, the first SCR is turned on, so that the anode of the light emitting diode is grounded through the first diode D4 and the first SCR, and the branch where the light emitting diode at the input end of the photocoupling module is located is shorted, thereby stopping the generation of the optical signal at the input end of the photocoupling module.
When the branch circuit of the light emitting diode is short-circuited, the power supply chip U1 is controlled to be in a power supply stop state, and at the moment, the VOUT end can discharge to the ground wire through at least R11 and SCR, and can discharge to the ground wire through R7, D4 and SCR until the voltage is close to 0.
When the voltage is close to 0, the current passing through the first silicon controlled rectifier SCR is smaller than the minimum maintaining current, the SCR is turned off again, at the moment, the branch circuit where the light emitting diode is positioned is not short-circuited, and an optical signal is sent to the output end of the photoelectric coupling module again, so that the power supply chip restarts to convert VIN into VOUT through the transformer T1.
Optionally, the output end of the photoelectric coupling module comprises a first triode; the output end of the photoelectric coupling module is used for controlling the conduction state between the collector electrode and the emitter electrode according to the received signal sent by the input end of the photoelectric coupling module; the emitter of the first triode is connected with a second triode Q2; the second triode Q2 is used for controlling the connection state of the level control node and the ground wire; the level control node is connected with a reference voltage pin and a voltage sampling pin respectively. When the output voltage is higher than the reverse breakdown voltage of the first voltage-stabilizing diode, the overvoltage protection module grounds the output voltage and the anode of the light-emitting diode through the first controllable silicon, so that the level control node is not grounded, and the power supply chip stops supplying power according to the high level received by the voltage sampling pin; when the output voltage is reduced to a first voltage threshold, the first silicon controlled rectifier SCR is turned off, the first triode and the second triode Q2 are turned on, the level control node is grounded, and the power supply chip continues to supply power according to the low level of the voltage sampling pin.
The output end of the photoelectric coupling module further comprises a first triode, after the first triode receives an electric signal generated by an optical signal sent by the input end (namely, a light emitting diode) of the photoelectric coupling module, the first triode is conducted, so that current is transmitted to a second triode Q2 through an emitter, the second triode Q2 is conducted, and a voltage sampling pin FB is grounded to keep low level. When the FB is kept at a low level, the power supply chip works normally, and the MOS tube Q1 is controlled to be conducted through the OUT pin, so that the input voltage VIN is converted into the output voltage VOUT.
When the branch circuit where the input end of the photoelectric coupling module is located is short-circuited by the overvoltage protection circuit, the input end of the photoelectric coupling module stops sending the optical signal to the output end of the photoelectric coupling module, and the first triode at the output end of the photoelectric coupling module is disconnected, so that the second triode at the output end of the photoelectric coupling module is disconnected. At this time FB is turned on to VREF through R13 (i.e., the level control node), thereby holding FB high. When the FB keeps high level, the power supply chip stops controlling the conduction of the MOS tube Q1 through the OUT pin, so that the transformer stops working.
Optionally, the output voltage VOUT is further divided by the first voltage dividing resistor R9 and the second voltage dividing resistor R10, and the divided value is output to the second zener diode U2; the second zener diode U2 connects the cathode of the light emitting diode with the ground.
At this time, when the photocoupling module works normally, the voltage transmitted to the light emitting diode by the second zener diode U2 can be adjusted by controlling the voltage dividing value by controlling the magnitudes of the first voltage dividing resistor R9 and the second voltage dividing resistor R10, so as to control the intensity of the optical signal generated at the input end of the photocoupling module, thereby controlling the conduction state of the first triode. The on state of the first triode can influence the voltage value on the VC (for example, when the first triode is in a fully-on state and a non-fully-on state, the voltage values on the VC are different), thereby controlling the working state of the power supply chip.
Optionally, when the overvoltage protection module is turned on, the power supply circuit discharges through at least the first current limiting resistor R12, the second current limiting resistor R11, the first voltage dividing resistor R9, and the second voltage dividing resistor R10.
Optionally, an RC pin is further provided on the power supply chip, where the RC pin is used to connect an RC oscillating circuit formed by R3 and C5 to obtain a corresponding clock signal.
Optionally, a current detection CS pin is further provided on the power supply chip, and the CS pin is connected to the mos tube through R5, so as to implement current detection on the power supply chip.
The operating principle of the power supply circuit shown in fig. 2 is as follows:
when the output voltage VOUT exceeds the design value, the zener diode Z1 is broken down and turned on, resulting in the SCR being turned on, so that the anode of the diode D4 is pulled down, at this time, the current on the resistor R7 connected between the anode of the light emitting diode of the photocoupling module 230 and the output voltage VOUT will flow directly from D4 to the output ground, the light emitting diode of the photocoupling module 230 will have no current flowing basically, resulting in the phototransistor of the photocoupling module 230 being turned off basically, so that the triode Q2 will be turned off, the FB pin of the chip is pulled up, and finally the driving signal output by the chip is turned off, i.e. the OUT pin of the chip will continuously output a low level, therefore, the main power MOS Q1 is turned off, resulting in the voltage input by VIN cannot be converted by the transformer T1, so that the auxiliary winding connected to the diode D1 is output to 0, and the power supply pin VCC of the power supply chip 210 is also 0, so that the power supply chip 210 is turned off; after that, VIN charges the power pin VCC of the power supply chip 210 through the start resistor R1, but the chip is not restarted immediately for the following reasons: because of the special properties of the unidirectional silicon controlled rectifier SCR, the method for turning off the silicon controlled rectifier SCR only has two methods, namely, reverse voltage is applied to the anode and the cathode of the silicon controlled rectifier or the current flowing through the silicon controlled rectifier is smaller than the maintaining current of the silicon controlled rectifier, therefore, the silicon controlled rectifier SCR can be completely turned off only after the output voltage VOUT is reduced to a voltage close to 0V, the silicon controlled rectifier SCR can be turned off completely, the photoelectric coupling module 230 can be turned on again, the FB pin of the chip can be reduced to the voltage in normal operation again, namely, the voltage of the FB pin can be restored to be normal only when the output voltage VOUT is reduced to be close to 0V, and the chip can be restarted;
when the output voltage VOUT has a short circuit fault, the output voltage VOUT is 0V, the optocoupler 230 is turned off, and the FB pin of the chip is pulled up, so that the chip is turned off, and short circuit protection is realized.
According to the analysis, when the output voltage VOUT exceeds the design value, the SCR is immediately conducted, so that overvoltage protection is realized, the overvoltage protection can be realized without waiting until the output voltage VOUT is discharged to 0V, and the reliability of the overvoltage protection is further improved; at the moment, the output voltage VOUT discharges through the current limiting resistor R11, the discharging resistor R12, the resistor R7, the resistor R9 and the resistor R10, and only the discharging current flowing through the current limiting resistor R11 and the resistor R7 flows through the SCR, and the slower the output voltage VOUT discharges, the slower the restarting of the chip, the smaller the loss, so that the low-power low-current SCR can be selected, and the material cost is saved; in addition, since the resistor R7, the resistor R9 and the resistor R10 are resistors which are required to be used when the circuit works normally, and the discharging resistor R12 is required to be used for conducting the SCR, the values of the discharging resistor R12, the resistor R7, the resistor R9 and the resistor R10 cannot be designed arbitrarily, and therefore, the discharging speed of the output voltage VOUT is controlled by changing the value of the current limiting resistor R11; meanwhile, as the output voltage VOUT discharges slowly, the time interval for restarting the chip is greatly increased, the service life of the chip is prolonged, the power loss of the battery power supply circuit is reduced, the safety and reliability of the battery power supply circuit are improved, and the EMI noise generated by the battery power supply circuit is reduced, so that the low-noise power supply circuit is realized.
In addition, the current limiting resistor R11 is used as a discharging current limiting resistor of the output voltage VOUT, and also is used to prevent the output voltage VOUT from being directly grounded to burn the SCR when the SCR is turned on.
It should be noted that, illustratively, in the power supply circuit shown in fig. 2, there are other capacitance-resistance devices (such as R2, C3, D3, C7, etc.) to ensure the stable operation of each module in the power supply circuit, and those skilled in the art may set Rong Zu devices with different structures and different parameters according to the operation state of the power supply circuit to realize the stable operation of the power supply circuit, and the structure of the capacitance-resistance device for the stable circuit is not limited in the embodiment of the present application.
In summary, when the input voltage is converted into the output voltage capable of supplying power to the battery load through the power supply chip and the voltage transformation circuit attached thereto, the power supply circuit can form the detection module of the power supply circuit through the overvoltage protection module and the photoelectric coupling module, when the output voltage of the battery power supply circuit after voltage transformation is greater than the specified voltage, the overvoltage protection module is conducted to ground the input end of the photoelectric coupling module in the photoelectric coupling module, and at the moment, the current of the input end of the photoelectric coupling module is changed immediately, thereby affecting the control of the output end of the photoelectric coupling module on the voltage sampling pin and the level of the chip control pin, and stopping the operation of the battery charging circuit. According to the scheme, when the output voltage is overlarge, the operation of the charging circuit can be stopped immediately, the output voltage does not need to be discharged to be close to 0V, and the reliability of overvoltage protection is improved; and because the output voltage discharges slowly, the time interval for restarting the chip is greatly increased, the service life of the chip is prolonged, the power loss of the battery power supply circuit is reduced, the safety and reliability of the battery power supply circuit are improved, and the EMI noise generated by the battery power supply circuit is reduced.
Fig. 3 is a schematic diagram showing a structure of a power supply circuit with low noise according to an exemplary embodiment. As shown in fig. 3, the power supply circuit includes a power supply chip 310, an overvoltage protection module 320, and a photoelectric coupling module 330;
the power supply chip at least comprises a voltage input pin VCC, an output control pin OUT and a voltage sampling pin FB;
the input end of the photoelectric coupling module 330 is connected with the output voltage Vout; the output end of the photoelectric coupling module 330 is used for controlling the level of the voltage sampling pin FB and the level of the chip control pin VC of the power supply circuit;
the overvoltage protection module is connected to the input terminal of the optocoupler module 330, and the overvoltage protection module is used for being turned on when the output voltage is greater than a specified voltage, so as to ground the input terminal of the optocoupler module.
The first input end of the overvoltage protection module is connected with the input end of the photoelectric coupling module through a first diode D4; the second input end of the overvoltage protection module is connected with the output voltage Vout; the second input end is connected with the cathode of the first zener diode Z1; the anode of the first zener diode Z1 is grounded through a first current limiting resistor R12; the anode of the first zener diode is also connected with the control end of the first silicon controlled rectifier SCR; the first input end is connected with the anode of the first silicon controlled rectifier SCR; the cathode of the first silicon controlled rectifier SCR is grounded. The input end of the photoelectric coupling module is a light-emitting diode; the overvoltage protection module is connected with the cathode of the light emitting diode.
In one possible implementation, the overvoltage protection module includes a second current limiting resistor R11, and the output voltage is connected to the first thyristor SCR via the second current limiting resistor R11.
The structure of the overvoltage protection module is the same as that of the overvoltage protection module shown in fig. 2, and will not be described herein.
However, unlike the embodiment shown in fig. 2, the overvoltage protection module shown in fig. 3 is connected to the cathode of the light emitting diode in the optocoupler module. In the process of charging the battery, when VOUT is greater than a specified voltage, the first zener diode Z1 breaks down, and the control end of the first SCR receives a high voltage, so that the first SCR is turned on, resulting in direct grounding of the cathode of the light emitting diode, the input end of the photocoupling module is increased in current, and the optical signal generated at the input end of the photocoupling module is increased, resulting in complete conduction of the first triode at the output end of the photocoupling module. At this time, the voltage of the pin VC of the chip is Vbe of the triode Q2, that is, the voltage of the pin VC of the chip is far lower than the voltage value of the circuit when the circuit works normally, and finally the driving signal output by the power supply chip is turned off.
Optionally, the chip control pin is connected with a collector electrode of a first triode in the output end of the photoelectric coupling module; when the overvoltage protection module is disconnected, the voltage of the chip control pin is larger than a second voltage threshold value, and the power supply chip normally operates; when the overvoltage protection module is closed, the voltage of the chip control pin is smaller than a second voltage threshold value, and the power supply chip stops running.
The driving signal output by the power supply chip can be controlled according to the level on the chip control pin VC, when the first triode at the output end of the photoelectric coupling module is completely conducted, the voltage of the chip VC pin is far lower than the second voltage threshold, and the power supply chip stops running.
Optionally, the cathode of the light emitting diode is connected with the cathode of the second zener diode; the cathode of the second zener diode is connected with the voltage dividing node; the voltage dividing node divides the output voltage by the first voltage dividing resistor and the second voltage dividing resistor.
I.e. the voltage dividing node is the dividing node between R9 and R10 as shown in fig. 3. Because R9 and R10 are used to connect VOUT and ground, the voltage value at the voltage division node is the voltage value at R10. When the photoelectric coupler operates normally, the voltage value of the cathode on the second zener diode can be controlled by controlling the voltage values of R9 and R10, so that the conduction state of the first diode in the photoelectric coupling circuit is controlled to control the level on the chip control pin VC.
Optionally, the power supply chip is further configured to adjust an output value of the output voltage according to a level on a chip control pin.
Optionally, the overvoltage protection module includes a second current limiting resistor R11, and the output voltage is connected with the first silicon controlled rectifier through the second current limiting resistor R11; when the overvoltage protection module is turned on, the power supply circuit discharges through at least the first current limiting resistor R12, the second current limiting resistor R11, the first voltage dividing resistor R9 and the second voltage dividing resistor R10.
Optionally, an RC pin is further provided on the power supply chip, where the RC pin is used to connect an RC oscillating circuit formed by R3 and C5 to obtain a corresponding clock signal.
Optionally, a current detection CS pin is further provided on the power supply chip, and the CS pin is connected to the mos tube through R5, so as to implement current detection on the power supply chip.
The operating principle of the power supply circuit shown in fig. 3 is as follows:
when the battery charging circuit works normally, the voltage at the cathode of the voltage stabilizing diode U2 is regulated through the voltage division of the sampling resistors R9 and R10, the current flowing through the light emitting diode and the output triode (namely the first triode) inside the photoelectric coupling module 330 is changed, the conduction state of the output triode is regulated (the output triode is not in a complete conduction state during normal work), and therefore the collector voltage of the output triode is regulated, namely the voltage of a pin VC of a chip is regulated, driving signals output by the pin OUT of the chip are changed, and the regulation of the output voltage VOUT of the circuit is realized.
When the output voltage VOUT has a short circuit fault, the output voltage VOUT is 0V, the optocoupler 330 is turned off, and the FB pin of the chip is pulled up, so that the chip is turned off, and short circuit protection is realized.
When the output voltage VOUT exceeds the design value, that is, when the output voltage VOUT exceeds the voltage stabilizing value of the voltage stabilizing diode Z1, the voltage stabilizing diode Z1 breaks down and is turned on, so that the silicon controlled rectifier SCR is turned on, then the diode D4 is turned on, the anode of the diode D4, that is, the cathode of the light emitting diode of the photoelectric coupling module 330 is similarly directly grounded, so that the current flowing through the light emitting diode and the output triode inside the photoelectric coupling module 330 is improved, the output triode is in a fully-on state, at this time, the voltage of the chip VC pin is Vbe of the triode Q2, that is, the voltage of the chip VC pin is far lower than the voltage value when the circuit normally works, the driving signal output by the chip is finally turned off, that is, the OUT pin of the chip continuously outputs a low level, therefore, the main power MOS transistor Q1 is turned off, so that the voltage input by VIN cannot be converted through the transformer T1, the output of the auxiliary winding connected with the diode D1 is 0, and the power supply pin of the power supply chip 310 is also 0, so that the power supply chip 310 is turned off; after that, VIN charges the power pin VCC of the power supply chip 310 through the start resistor R1, but the chip is not restarted immediately for the following reasons: because of the special properties of the unidirectional silicon controlled rectifier SCR, the method for turning off the silicon controlled rectifier SCR only has two methods, namely, reverse voltage is applied to the anode and the cathode of the silicon controlled rectifier or the current flowing through the silicon controlled rectifier is smaller than the maintaining current, therefore, the silicon controlled rectifier SCR can be completely turned off only after the output voltage VOUT is reduced to a voltage close to 0V, the current flowing through the photoelectric coupling module 330 is reduced only after the silicon controlled rectifier SCR is completely turned off, the output triode inside the photoelectric coupling module 330 can be restored to a conducting state during normal operation, the voltage of the VC pin of the chip can be raised to the voltage during normal operation again, namely, the voltage of the VC pin can be restored to be normal only when the output voltage VOUT is reduced to be close to 0V, and the chip can be restarted.
According to the analysis, when the output voltage VOUT exceeds the design value, the SCR is immediately conducted, so that overvoltage protection is realized, the overvoltage protection can be realized without waiting until the output voltage VOUT is discharged to 0V, and the reliability of the overvoltage protection is further improved; at the moment, the output voltage VOUT discharges through the current limiting resistor R11, the discharging resistor R12, the resistor R7, the resistor R9 and the resistor R10, and only the discharging current flowing through the current limiting resistor R11 and the resistor R7 flows through the SCR, and the slower the output voltage VOUT discharges, the slower the restarting of the chip, the smaller the loss, so that the low-power low-current SCR can be selected, and the material cost is saved; in addition, since the resistor R7, the resistor R9 and the resistor R10 are resistors which are required to be used when the circuit works normally, and the discharging resistor R12 is required to be used for conducting the SCR, the values of the discharging resistor R12, the resistor R7, the resistor R9 and the resistor R10 cannot be designed arbitrarily, and therefore, the discharging speed of the output voltage VOUT is controlled by changing the value of the current limiting resistor R11; meanwhile, as the output voltage VOUT discharges slowly, the time interval for restarting the chip is greatly increased, the service life of the chip is prolonged, the power loss of the battery power supply circuit is reduced, the safety and reliability of the battery power supply circuit are improved, and the EMI noise generated by the battery power supply circuit is reduced.
In addition, the current limiting resistor R11 is used as a discharging current limiting resistor of the output voltage VOUT, and also is used to prevent the output voltage VOUT from being directly grounded to burn the SCR when the SCR is turned on.
It should be noted that, illustratively, in the power supply circuit shown in fig. 3, there are other capacitance-resistance devices (such as R2, C3, D3, C7, etc.) to ensure the stable operation of each module in the power supply circuit, and those skilled in the art may set Rong Zu devices with different structures and different parameters according to the operation state of the power supply circuit to realize the stable operation of the power supply circuit, and the structure of the capacitance-resistance device for the stable circuit is not limited in the embodiment of the present application.
In summary, when the input voltage is converted into the output voltage capable of supplying power to the battery load through the power supply chip and the voltage transformation circuit attached thereto, the power supply circuit can form the detection module of the power supply circuit through the overvoltage protection module and the photoelectric coupling module, when the output voltage of the battery power supply circuit after voltage transformation is greater than the specified voltage, the overvoltage protection module is conducted to ground the input end of the photoelectric coupling module in the photoelectric coupling module, and at the moment, the current of the input end of the photoelectric coupling module is changed immediately, thereby affecting the control of the output end of the photoelectric coupling module on the voltage sampling pin and the level of the chip control pin, and stopping the operation of the battery charging circuit. According to the scheme, when the output voltage is overlarge, the operation of the charging circuit can be stopped immediately, the output voltage does not need to be discharged to be close to 0V, and the reliability of overvoltage protection is improved; and because the output voltage discharges slowly, the time interval for restarting the chip is greatly increased, the service life of the chip is prolonged, the power loss of the battery power supply circuit is reduced, the safety and reliability of the battery power supply circuit are improved, and the EMI noise generated by the battery power supply circuit is reduced.
Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of the application following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the application pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.
It is to be understood that the application is not limited to the precise arrangements and instrumentalities shown in the drawings, which have been described above, and that various modifications and changes may be effected without departing from the scope thereof. The scope of the application is limited only by the appended claims.
Claims (2)
1. The power supply circuit with low noise is characterized by comprising a power supply chip, an overvoltage protection module and a photoelectric coupling module;
the power supply chip at least comprises a voltage input pin, an output control pin and a voltage sampling pin; the voltage input pin is connected with an input voltage end of the power supply circuit; the power supply chip controls the transformer to convert the input voltage of the input voltage end into output voltage through an output control pin;
the input end of the photoelectric coupling module is connected with the output voltage; the output end of the photoelectric coupling module is used for controlling the level of a voltage sampling pin of the power supply circuit and the level of a chip control pin;
the overvoltage protection module is connected with the input end of the photoelectric coupling module, and is used for being conducted when the output voltage is larger than a specified voltage so as to ground the input end of the photoelectric coupling module;
the first input end of the overvoltage protection module is directly connected with the input end of the photoelectric coupling module through a first diode; the second input end of the overvoltage protection module is connected with the output voltage;
the second input end is connected with the cathode of the first voltage stabilizing diode; the anode of the first zener diode is grounded through a first current limiting resistor; the anode of the first voltage stabilizing diode is also connected with the control end of the first controllable silicon;
the first input end is connected with the anode of the first controllable silicon; the cathode of the first silicon controlled rectifier is grounded;
the overvoltage protection module comprises a second current limiting resistor, and the output voltage is connected with the first silicon controlled rectifier through the second current limiting resistor;
the cathode of the light-emitting diode is connected with the cathode of the second zener diode;
the cathode of the second zener diode is connected with the voltage dividing node; the voltage dividing node is a node for dividing the output voltage through a first voltage dividing resistor and a second voltage dividing resistor;
when the overvoltage protection module is conducted, the power supply circuit discharges through at least a first current limiting resistor, a second current limiting resistor, a first voltage dividing resistor and a second voltage dividing resistor;
the input end of the photoelectric coupling module is a light-emitting diode; the overvoltage protection module is connected with the cathode of the light-emitting diode;
the chip control pin is connected with a collector electrode of a first triode in the output end of the photoelectric coupling module; when the overvoltage protection module is disconnected, the voltage of the chip control pin is larger than a second voltage threshold, and the power supply chip operates normally; when the overvoltage protection module is closed, the voltage of the chip control pin is smaller than a second voltage threshold value, and the power supply chip stops running;
and controlling the discharge speed of the output voltage by changing the value of the second current limiting resistor.
2. The power supply circuit of claim 1, wherein the power supply chip is further configured to adjust an output value of the output voltage based on a level on a chip control pin.
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| TW201431430A (en) * | 2013-01-25 | 2014-08-01 | Beyond Innovation Tech Co Ltd | Load driving apparatus relating to light-emitting-diodes |
| CN108206635B (en) * | 2016-12-16 | 2020-04-28 | 罗姆股份有限公司 | DC/DC converter, control method thereof, power adapter and electronic device |
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| CN203536942U (en) * | 2013-11-01 | 2014-04-09 | 广州市爱浦电子科技有限公司 | A novel ring choke converter output overvoltage protection circuit |
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Address after: 215000 Building 1, No. 150, Jici Road, science and Technology City, high tech Zone, Suzhou City, Jiangsu Province Applicant after: Suzhou Baker Microelectronics Co.,Ltd. Address before: 215000 78 Keling Road, science and Technology City, high tech Zone, Suzhou City, Jiangsu Province Applicant before: SUZHOU BAKER MICROELECTRONICS Co.,Ltd. |
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