CN108964464B - Circuit and method for nondestructive testing of load current at output side of switching power supply - Google Patents
Circuit and method for nondestructive testing of load current at output side of switching power supply Download PDFInfo
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- CN108964464B CN108964464B CN201710360913.8A CN201710360913A CN108964464B CN 108964464 B CN108964464 B CN 108964464B CN 201710360913 A CN201710360913 A CN 201710360913A CN 108964464 B CN108964464 B CN 108964464B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- 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
- H02M3/33561—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 more than one ouput with independent control
-
- 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
- H02M3/33592—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 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
Abstract
The invention discloses a circuit and a method for nondestructive testing of load current at an output side in a switch mode power supply. The circuit comprises an output rectifier device, an output capacitor and an output load current detection chip, and is characterized in that: the output load detection chip comprises an output side winding conduction time detection module used for detecting the time width and the period of supplying energy to the output side load; and the duty ratio conversion module is used for averaging the detected conduction time signals of the output winding. Compared with the traditional method for detecting the load current through the resistor connected in series in the output loop, the method has the advantages that the circuit loss is extremely low, the efficiency is improved, and peripheral components are reduced and the cost is reduced due to the fact that the detection resistor is omitted.
Description
Technical Field
The invention relates to a load detection technology of a switching power supply, in particular to a load current circuit for nondestructive detection of an output side.
Background
At present, a sampling resistor is generally required to be added to detect the load current at the output end of a switching power supply, and the change of a load is sensed by detecting the voltage on the sampling resistor.
Fig. 1 is a schematic diagram of a conventional system for detecting a load current on an output side. The level of the negative voltage end of the resistor 122 represents the current value of the current load, one end of the resistor 114 is connected with one end of the resistor 122, the detection voltage of the VCTRL pin of the output side chip 110 is the superposition of the output voltage Vo and the voltage of the output load current on the resistor 122, the voltage of the resistor 122 becomes more and more negative along with the increase of the load current, and in order to ensure that the voltage of the VCTRL pin is not changed, the output voltage is increased along with the increase of the load current as a result of the loop regulation of the whole system.
The pin of ICTRL of output chip 110 shown in fig. 1 is connected to the negative voltage terminal of resistor 122. When the output current increases to the set current, the current loop acts to limit the system output current from continuing to increase to ensure constant current output.
The conventional system for detecting the load current at the output side has the following disadvantages,
1. since the current flowing through the resistor 122 needs to be detected, there is a loss in the resistor, resulting in low power efficiency;
2. the resistor 122 is generally a milliohm-level resistor, so the voltage drop across the resistor is also low, and the detection accuracy is not high enough;
3. the circuit has the advantages of more used components, higher cost of the power supply and low reliability.
Therefore, a detection circuit is needed, which can be applied to the output side without loss and has high detection precision and few components, thereby reducing the production cost of the power supply and improving the reliability.
Disclosure of Invention
The present invention is directed to a method and a circuit for non-destructive testing of a load current at an output side, which overcome the above-mentioned drawbacks of the prior art. The technical scheme adopted by the invention for solving the technical problem is as follows: a signal at one end of the output side rectifying device is detected through one pin (DET) of the chip, the time when the current flows through the output side rectifying device is extracted, and the information of the load current is extracted through signal processing on the time. The circuit for nondestructively detecting the load current on the output side comprises a rectifying device, an output capacitor and a controller. Wherein the controller chip includes:
the conduction time detection module is used for detecting the time width and the period of supplying energy to the load at the output end;
and the duty ratio conversion module is used for averaging the detected signals.
In the controller of the present invention, the controller chip further includes:
and the fixed pulse generating circuit outputs a square wave by the conduction time detection module, processes the square wave into a signal with unchanged pulse width, represents the switching frequency of the current system, and inputs the signal into the duty ratio detection circuit so as to obtain a direct current voltage or current signal related to a load.
In the controller of the present invention, the controller chip further includes:
the comparison module is used for judging the current charging state according to the detected load condition;
the driving module is used for outputting a judgment result of the current charging state to the output end;
and the display module is used for displaying the charging state according to the output signal of the driving module.
In the controller of the present invention, the controller chip further includes:
the operational amplifier module is used for changing the output voltage of the system according to the detected load condition;
and the driving module is used for controlling the current of the optocoupler according to the detected load condition and the output voltage so as to change the switching frequency (PFM) or the Pulse Width (PWM) of the system.
In the controller of the present invention, the on-time detecting module includes:
an integration circuit by integrating the signal detected by the DET;
the comparator 1, DET signal and VREF1 are compared, thus detecting the moment of the current conduction of the rectifier on the output side;
the comparator 2 compares the DET signal with VREF2, thereby detecting the moment when the current of the rectifier on the output side is finished;
a comparator 3 for comparing the integrated value with VREF3 to determine whether or not to allow processing of a signal for current conduction of the output side rectifier;
a pulse generator 1 for generating a pulse at the start time of the output side current by processing the signal output from the comparator 1;
the pulse generator 2 processes the signal output from the comparator 2 to generate a pulse at the output-side current end time.
In the controller of the present invention, the duty ratio conversion module includes:
and the low-pass filter circuit is used for converting the pulse wave into a direct current signal.
In the controller of the present invention, the duty ratio conversion module further includes:
a summing circuit for summing the time when the pulse signal is at a high level;
and the D/A conversion circuit is used for converting the digital signal into an analog signal.
In the controller of the present invention, the operational amplifier module includes:
the adder is used for summing the signal representing the load condition and the reference voltage, the load current is increased, and the voltage of the VN end of the operational amplifier EA is also increased, so that the output voltage is increased according to the load current, and the purpose of compensating the voltage loss of the output cable is achieved;
the EA module is used for comparing and amplifying the output sampled signal with the voltage of the VN end;
and the PFM module generates a pulse signal according to the output signal of the EA module, and the signal determines the turn-on time of the power tube at the input end.
The circuit for nondestructively detecting the load current on the output side can improve the conversion efficiency of the switching power supply, and has the advantages of simple and reliable circuit and few components.
Drawings
FIG. 1 is a schematic diagram of a conventional method for detecting a load current on an output side;
fig. 2 is a system diagram of one embodiment of the output side nondestructive testing of load current in accordance with the present invention.
Fig. 3 is a system schematic diagram of another embodiment of the output side nondestructive testing of load current according to the present invention.
Fig. 4 is a circuit schematic diagram of another embodiment based on the output side nondestructive load current detection principle of the present invention.
Fig. 5 is a schematic diagram of a rotary lamp application in accordance with the present invention.
Fig. 6 is a schematic diagram of an application of the present invention to compensate for voltage loss of an output cable.
Fig. 7 is a graph showing the variation of the DC voltage value with the load current according to the switching frequency of the system, the input stage switching peak current and the detected load current.
Fig. 8 is a block diagram of an embodiment in accordance with the present invention.
Fig. 9 is a block diagram of another embodiment in accordance with the present invention.
FIG. 10 is a diagram of voltage nodes within the controller
Fig. 11 is an internal schematic diagram of the rotary lamp applied to fig. 5.
Fig. 12 is an internal schematic diagram of fig. 6 for output cable voltage compensation application.
Fig. 13 is a signal diagram of the variation of the R terminal and the G terminal with the load in the lamp-turning application.
FIG. 14 is a block diagram of an embodiment of a turn signal application for reducing standby power consumption
Fig. 15 is a waveform diagram of a turn-lamp application to reduce standby power consumption.
Detailed Description
Specific examples of the present invention are described in detail below. Examples of which are given in the accompanying drawings. It should be noted that the examples described herein are for illustration only and are not intended to limit the invention. Details of the implementation are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that these details need not be employed to practice the present invention. In the description of the embodiments, circuits that are well known in the art have not been specifically described in order to avoid obscuring the present invention.
Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.
Fig. 2 is a schematic diagram of a system for lossless output load current detection in accordance with the present invention. Unlike the conventional sense load current shown in fig. 1, there is no sampling resistor. The resistor 126 may be integrated inside the chip. The signal waveform at the DET pin of the controller 200 reflects the current-voltage variation inside the transformer. The power supply pin VCC of the controller 200 is directly connected to the output of the system or may be connected to the output of the system through a resistor. The conduction time detection module detects the time and the period of the current flowing on the rectifier 109 through signal processing of the DET, the duty ratio conversion module averages the detected pulse signals, and the average value can be used for LED indicator light turning, cable voltage drop compensation and the like.
Connecting the output rectifier to the output side winding and the output voltage also allows the time for which energy is supplied to the load to be detected, as shown in fig. 3. The signal detected by the DET of the controller 300 is just opposite to the positive and negative voltages of the DET signal of fig. 2, and the controller needs to perform signal conversion to send the signal to the on-time detection module.
For Pulse Frequency Modulation (PFM) mode, a signal that varies with load current can also be generated by sampling the switching frequency of the system, an embodiment of which is shown in fig. 4. The fixed pulse width generating circuit is used for generating pulses with fixed pulse width and the same frequency as the system working frequency, and the pulses output direct current signals related to the system working frequency after passing through the duty ratio conversion module.
Fig. 5 is a schematic diagram of a system for turning the LED indicator light. Resistor 129 may be integrated into controller 200. The signal output by the duty cycle conversion module is compared with the voltage of the Bias pin, when the output load current is large, the R end of the controller is at a low level, the G end is at a high impedance state, and the LED lamp 128 is displayed as a red light. When the output load current is small, the G terminal of the controller is at a low level, the R terminal is at a high impedance state, and the LED lamp 128 is shown as green. The switching load point of the traffic light can be changed by adjusting the resistor 129.
An embodiment of a circuit for output cable voltage compensation is shown in fig. 6. The VSENSE pin of the controller 200 samples the output voltage, and the sampled voltage, the reference voltage VREF, and the output signal VLOAD of the duty cycle conversion module are processed to generate a signal that varies with the load, thereby causing the system output voltage to vary with the load current.
If the switching frequency varies with the load as shown in fig. 7, the output signal of the duty ratio conversion linearly increases with the load in the light load section, is the open root curve of the load current in the middle constant frequency section, and linearly increases with the load in the heavy load section.
One implementation of the on-time detection module is shown in fig. 8. The integration circuit integrates the signal with the DET level higher than the output voltage, waits for the current conduction signal of the rectifier at the output side when the integrated voltage exceeds VREF3, then judges that the current of the rectifier at the output side is conducted when the DET signal is lower than VREF1, judges that the current conduction of the rectifier at the output side is finished after the DET signal is higher than VREF, and then enters the detection of a new period. The conducting pulse signal of the current on the output side is converted into a direct current signal after low-pass filtering. As shown in fig. 9, the on pulse signal of the output side current may also be summed up digitally at a high level and then converted into an analog signal by the D/a module.
One embodiment of a comparison circuit and driver circuit for a rotary lamp application is shown in fig. 11. VLOAD is compared with reference voltage 4, and when the output of the comparator is high level, the output pin R end is low level through the driving circuit, and the G end is high resistance state. When the output of the comparator is low level, the output pin G is cut off to be low level through the driving circuit, and the R end is in a high resistance state. In order to reduce idle standby, the brightness of the green light is reduced in an idle state, in one embodiment, as shown in fig. 14, when the load current is less than the set lamp-turning current, a pulse with a fixed pulse width is generated in a period of time when the output side rectifier has no current, when the time when the output side rectifier has no current is shorter than the set fixed pulse width, the green light is fully on, the end G is at a low level, when the time when the output side rectifier has no current is longer than the set fixed pulse width, the green light is only turned on for a fixed pulse time width, the time width when the end G is at a low level is only a fixed pulse time width, and the rest time is at a high impedance state.
One embodiment of an operational amplifier and driver module for use in an output cable voltage compensation circuit is shown in fig. 12. The output load current signal VLOAD and the reference voltage VREF5 are summed to produce the VN voltage that increases with increasing load current, with the output voltage increasing with load current through the feedback circuit. The signal output by the operational amplifier is converted into a current signal through the PFM to drive the optocoupler, so that the switching frequency of the system is changed.
While the present invention has been described in terms of the above exemplary embodiments, it is to be understood that the terminology used is intended to be in the nature of words of description and illustration, rather than of limitation. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims. Accordingly, all changes and modifications that come within the scope of the claims or the equivalents thereto are intended to be embraced by the claims.
Claims (9)
1. A circuit for non-destructive testing of a load current at an output side, the circuit comprising:
an output rectifier (109) connected between the output winding and ground;
an output capacitor (121) connected between the output port and ground;
the controller (200) comprises a power supply end and a signal detection end;
wherein the controller (200) comprises a conduction time detection module (201) for detecting the time width and period for supplying energy to the output end load; a duty ratio conversion module (202) for averaging the detected signals;
the on-time detection module (201) further comprises:
the integrating circuit is used for integrating the signal of the detection end;
a comparator 1 for detecting a timing at which an output side rectifier current is turned on;
a comparator 2 for detecting a timing at which the output side rectifier current is turned off;
a comparator 3 for judging whether to allow processing of a signal of output side rectifier current conduction;
a pulse generator 1 for generating a pulse at an output side current conduction start time;
and a pulse generator 2 for generating a pulse at the output side current end time.
2. The circuit for the non-destructive testing of a load current at an output side according to claim 1, wherein said output rectifier (109) is connectable between the output winding and the load; the controller (300) comprises a signal conversion module (301) for carrying out positive and negative phase inversion on a signal at a detection end, an on-time detection module (301) and a duty ratio conversion module (302).
3. The circuit for output side nondestructive testing of load current according to claim 1, wherein the controller (200) further comprises:
and the fixed pulse width generating circuit (203) is used for inputting the square wave signal conducted by the rectifier into the fixed pulse width generating circuit, is connected to the duty ratio conversion module and outputs a duty ratio measured value by the duty ratio conversion module.
4. The circuit for output side nondestructive testing of load current according to claim 1, wherein said controller (200) further comprises:
a comparing module (205) for determining a current charging state based on the detected load condition;
the driving module (204) is used for outputting the judgment result of the current charging state to the output end;
and the display module (128) is used for displaying the charging state according to the output signal of the driving module.
5. The circuit for output side nondestructive testing of load current according to claim 1, wherein said controller (200) further comprises:
an operational amplifier module (207) for varying a system output voltage in accordance with the detected load condition;
and the driving module (206) is used for controlling the current of the optocoupler according to the detected load condition and the output voltage value.
6. The circuit for output side non-destructive testing of load current according to claim 1, wherein said duty cycle conversion module of said controller (200) comprises:
and the low-pass filter circuit is used for converting the pulse wave into a direct current signal.
7. The circuit for output side nondestructive testing of load current according to claim 1, wherein the duty cycle conversion module of the controller (200) comprises:
a summing circuit for summing the time during which the pulse signal is at a high level;
and the D/A conversion circuit is used for converting the digital signal into an analog signal.
8. The circuit for the non-destructive testing of the load current at the output side according to claim 5, wherein the operational amplifier module (207) comprises:
the adder is used for summing the signal representing the load condition and the reference voltage, and the voltage of the VN end of the load current increase operational amplifier EA is increased, so that the output voltage is increased according to the load current;
the EA module is used for comparing and amplifying the output sampled signal with the voltage of the VN end;
and the PFM module generates a pulse signal according to the output signal of the EA module, and the pulse signal determines the turn-on time of the power tube at the input end.
9. The circuit for the output-side nondestructive testing of the load current according to claim 4, wherein the driving module comprises: and the fixed pulse width generating circuit is used for reducing the time that the G end is at a low level when the load is light.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201710360913.8A CN108964464B (en) | 2017-05-19 | 2017-05-19 | Circuit and method for nondestructive testing of load current at output side of switching power supply |
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| CN201710360913.8A CN108964464B (en) | 2017-05-19 | 2017-05-19 | Circuit and method for nondestructive testing of load current at output side of switching power supply |
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| CN108964464A CN108964464A (en) | 2018-12-07 |
| CN108964464B true CN108964464B (en) | 2022-11-29 |
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| CN113252970B (en) * | 2021-04-23 | 2022-11-18 | 长城电源技术有限公司 | Load detection circuit and power supply system |
| CN116131628B (en) * | 2023-04-17 | 2023-07-14 | 深圳市力生美半导体股份有限公司 | Switching power supply and lamp turning control system and chip thereof |
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| CN1815838A (en) * | 2005-02-03 | 2006-08-09 | 昂宝电子（上海）有限公司 | Multi-threshold over-curreut protection system and method for switch powersupply converter |
| CN102364858A (en) * | 2011-02-01 | 2012-02-29 | 杭州士兰微电子股份有限公司 | Constant-current switching power supply controller capable of controlling through primary side and method |
| CN102487246A (en) * | 2010-12-01 | 2012-06-06 | 比亚迪股份有限公司 | Switching power supply, control method of switching power supply and PWM (pulse width modulation) control chip |
| CN102810984A (en) * | 2012-07-13 | 2012-12-05 | 电子科技大学 | Switching power circuit |
| CN106208714A (en) * | 2016-08-08 | 2016-12-07 | 杭州士兰微电子股份有限公司 | Synchronous rectifying switching power source and control method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US9882500B2 (en) * | 2014-12-07 | 2018-01-30 | Alpha & Omega Semiconductor (Cayman), Ltd. | Power supply device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1815838A (en) * | 2005-02-03 | 2006-08-09 | 昂宝电子（上海）有限公司 | Multi-threshold over-curreut protection system and method for switch powersupply converter |
| CN102487246A (en) * | 2010-12-01 | 2012-06-06 | 比亚迪股份有限公司 | Switching power supply, control method of switching power supply and PWM (pulse width modulation) control chip |
| CN102364858A (en) * | 2011-02-01 | 2012-02-29 | 杭州士兰微电子股份有限公司 | Constant-current switching power supply controller capable of controlling through primary side and method |
| CN102810984A (en) * | 2012-07-13 | 2012-12-05 | 电子科技大学 | Switching power circuit |
| CN106208714A (en) * | 2016-08-08 | 2016-12-07 | 杭州士兰微电子股份有限公司 | Synchronous rectifying switching power source and control method |
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