CN113114039B - Pin multiplexing-based switch control circuit, switch power supply system and frequency control method - Google Patents
Pin multiplexing-based switch control circuit, switch power supply system and frequency control method Download PDFInfo
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- CN113114039B CN113114039B CN202110280838.0A CN202110280838A CN113114039B CN 113114039 B CN113114039 B CN 113114039B CN 202110280838 A CN202110280838 A CN 202110280838A CN 113114039 B CN113114039 B CN 113114039B
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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
- H02M3/33507—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 with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—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 with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
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Abstract
The invention discloses a switch control circuit based on pin multiplexing, which comprises a first pin and a second pin; the switch control circuit is coupled with the first circuit; the first pin is used for outputting a pulse width modulation signal to control the first circuit; the second pin is used for detecting and acquiring the detection current flowing through the first circuit in a first time period, and is used for detecting and acquiring the element characteristic of the first circuit in a second time period; the switch control circuit controls the pulse width modulation signal in accordance with the detection current and the element characteristic for controlling a system frequency of the first circuit. The invention also discloses a frequency control method and a switching power supply system. The invention can monitor the change of the detection current and control the frequency of the switching tube through multiplexing of the same pin. In other switching power supply systems to which the present invention is applied, the system frequency is controlled by controlling the frequency of the switching transistor.
Description
Technical Field
The invention relates to the field of electronics, in particular, but not exclusively, to a switching control circuit, a switching power supply system and a frequency control method based on pin multiplexing.
Background
The flyback voltage conversion circuit comprises a transformer, and the circuit is divided into a primary side circuit and a secondary side circuit through a primary side winding and a secondary side winding of the transformer to be isolated. The switching tube of the primary side circuit transmits electric energy to the secondary side circuit through switching action. When the switching tube is switched off to be switched on, the primary current in the primary side circuit increases from zero, and the primary side winding stores energy; when the switching tube is switched on to off, the primary current is zero, the induced current is generated, and the secondary winding outputs electric energy to the load. Therefore, the on/off frequency of the switching tube affects the system frequency of the whole flyback voltage conversion circuit.
In the prior art, the on/off frequency of a switching tube is generally controlled directly by a periodic signal with a certain fixed frequency, flexible control over frequency setting cannot be realized, the change of the primary current cannot be monitored, and the structure is often complex and more pins of a switching control circuit are applied.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a switching control circuit, a control method and a switching power supply system based on pin multiplexing.
In order to solve the technical problems, the invention is solved by the following technical scheme:
The invention provides a switch control circuit based on pin multiplexing, which comprises a first pin and a second pin; the switch control circuit is coupled with the first circuit; the first pin is used for outputting a pulse width modulation signal to control the first circuit; the second pin is used for detecting and acquiring the detection current flowing through the first circuit in a first time period, and is used for detecting and acquiring the element characteristic of the first circuit in a second time period; the switch control circuit controls the pulse width modulation signal in accordance with the detection current and the element characteristic for controlling a system frequency of the first circuit.
Optionally, the first circuit includes a switching tube; the first pin is electrically connected with the switching tube and controls the conduction state of the switching tube by outputting different first switching control signals; and the second pin detection obtains detection current flowing through the switching tube.
Optionally, the first circuit further includes a detection resistor, and the detection resistor is connected in series with the switching tube; the second pin is electrically connected with the detection resistor, and the change of the detection current flowing through the detection resistor and the switch tube at the same time is detected and obtained by detecting the change of the detection voltage at two ends of the detection resistor; the switch control circuit changes the element characteristics of the first circuit by changing the resistance value of the detection resistor for changing the frequency of turning on and off the switching tube.
Optionally, the switch control circuit further comprises a frequency control enabling circuit, a current source and a switch; the frequency control enabling circuit outputs a switch control signal to control the conduction state of the switch; the switch is electrically coupled between the current source and the second pin, and supplies power to the detection resistor through the second pin when the switch is turned on.
The invention also provides a switching power supply system which comprises the switching control circuit based on pin multiplexing and the switching power supply circuit, wherein the switching power supply circuit comprises a switching tube, and the switching tube is controlled by the switching control circuit to turn on and off the switching tube.
Optionally, the switching power supply circuit is a flyback voltage conversion circuit; the flyback voltage conversion circuit comprises a transformer; the input end of the flyback voltage conversion circuit is coupled with the direct current output end of the bridge rectifier, and input voltage is obtained from the direct current output end of the bridge rectifier; the alternating current input end of the bridge rectifier is connected with an alternating current power supply; the primary winding of the transformer is electrically connected with the switching tube, and the secondary winding of the transformer outputs the transformed output voltage; when the switching tube is conducted, the primary winding stores electric energy and generates the detection current flowing through the switching tube; when the switching tube is turned off, the secondary winding outputs electric energy, and the detection current is zero.
Optionally, the switching power supply circuit is a buck circuit or a boost circuit.
The invention also provides a frequency control method based on pin multiplexing, which comprises the following steps:
Outputting a first switch control signal to control a first circuit;
When the first circuit operates in a first time period, the first circuit flows current, and the current flowing through the first circuit is detected through a first pin;
Detecting a component characteristic within the first circuit through a first pin when the first circuit is operating in a second time period;
Changing the frequency of the first circuit between the first time period and the second time period is achieved by changing a characteristic of a component within the first circuit.
Optionally, the first circuit includes a switching tube and a detection resistor connected in series, the first time period is an on state of the switching tube, the second time period is an off state of the switching tube, and the frequency control method further includes the following steps:
Closing a switch to cause a current source to flow through the sense resistor during the second time period;
Detecting detection voltages at two ends of the detection resistor, and obtaining the resistance value of the detection resistor at the moment according to the detection voltages and the current source;
And controlling the frequency of the switching tube according to the resistance value of the detection resistor.
Optionally, the method further comprises:
During the first time period, the switching tube is controlled to be conducted at the rising edge of a system clock signal;
The switching tube is conducted to enable the current to flow through the detection resistor;
detecting the detection voltage at two ends of the detection resistor, and monitoring the change of the detection current according to the change of the detection voltage;
and acquiring the peak current of the detection current in each switching period, controlling the switching tube to be turned off when the detection current reaches the peak current, and detecting the resistance value of the detection resistor.
The invention can monitor the change of the detection current through multiplexing of the same pin, and can realize the control of the on-off frequency of the switching tube by changing the resistance value of the detection resistor. In other switching power supply systems to which the pin multiplexing-based switching control circuit of the present invention is applied, the system frequency is also controlled by controlling the frequency of the switching transistor. The invention has the advantages of few applied pins, and the same group of pins are used for detecting the detection current and controlling the system frequency, so that the chip product has simple structure, small volume and wide market application occasions.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute a limitation on the application. In the drawings:
FIG. 1 shows a schematic circuit diagram of a pin multiplexing based switch control circuit in embodiments one, three, and four;
Fig. 2 shows schematic waveforms of changes in the first switch control signal, the second switch control signal, and the detected current according to the clock signal in the first, third, and fourth embodiments;
Fig. 3 shows a circuit schematic of a switching power supply system in a fifth embodiment;
a 100-bridge rectifier; 200-flyback voltage conversion circuit; 310-a switch control circuit; 320-a frequency control enable circuit; 330-first circuit.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by a person skilled in the art without creative efforts, based on the described embodiments of the present invention fall within the protection scope of the present invention.
Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The terms "first," "second," and the like in the description and in the claims, are not used for any order, quantity, or importance, but are used for distinguishing between different elements. In addition, in the embodiment of the present invention, the first time period and the second time period are not limited in time sequence, and only the distinction between two different time periods is named.
Embodiment one:
The embodiment discloses a switch control circuit based on pin multiplexing, which can simultaneously realize detection of detection current IP and frequency setting of on and off of a switch tube Q by adopting the same group of pins. The switch control circuit 310 of the present embodiment includes a first pin P1 and a second pin P2. The switch control circuit 310 is coupled to the first circuit 330. The first pin P1 is for outputting a first switching control signal PWM, and controls the first circuit 330 by outputting the first switching control signal PWM. The second pin P2 is used for detecting and acquiring the detection current IP flowing through the first circuit 330 in the first period of time, and is used for detecting and acquiring the element characteristic of the first circuit 330 in the second period of time. The switch control circuit 310 controls the first switch control signal PWM according to the detected current IP and the element characteristic. Wherein the element characteristics are used to control the system frequency of the first circuit 330.
In addition, in one embodiment, as shown in fig. 1, the first circuit 330 is a series circuit group formed by connecting the switching tube Q and the detection resistor RCS in series, but in other embodiments, the circuit structure of the first circuit 330 may also adopt other structures. In the present embodiment, the switching tube Q is externally connected to the switching control circuit 310. However, in other embodiments, the switching tube Q may be further connected to the switch control circuit 310, such that the first pin P1 is coupled to the drain terminal of the switching tube Q.
In one embodiment, as shown in fig. 1, the switch control circuit 310 of the present embodiment includes a first pin P1 and a second pin P2. The first pin P1 is electrically connected to the switching tube Q, and controls on/off of the switching tube Q by outputting different first switching control signals PWM (shown as PWM signals in fig. 1-3). In this embodiment, as shown in fig. 2, when the first switch control signal PWM is at a high level, the switching tube Q is controlled to be closed; when the first switch control signal PWM is at a low level, the switching transistor Q is controlled to be turned off. The second pin P2 is electrically connected to the detection resistor RCS, and is configured to monitor the detection current IP flowing through the switching tube Q by detecting the detection voltage Vcs. The switching control circuit 310 changes the element characteristics of the first circuit 330 by changing the resistance value of the detection resistor RCS for changing the frequency at which the switching transistor Q is turned on and off.
In summary, the switch control circuit 310 monitors the change in the obtained detection current IP by detecting the change in the detection voltage Vcs. The switch control circuit 310 controls the first pin P1 to output different first switch control signals PWM according to the change of the detected current IP, and the first switch control signals PWM are used to control on/off of the switching transistor Q.
It should be understood that, as shown in fig. 1, the voltage at the position of the second pin P2 is the detection voltage Vcs, and the detection current IP can be calculated by the detection voltage Vcs and the detection resistor RCS, so that the switch control circuit 310 monitors the change of the detection current IP by detecting the change of the detection voltage Vcs.
The switch control circuit 310 is electrically connected to the switching tube Q and the detection resistor RCS through two pins, and controls the on/off change of the switching tube Q by using the change of the detection current IP, so that the purpose of monitoring the change of the detection current IP can be achieved, and the purpose of controlling the on/off change of the switching tube Q can be achieved. And only two pins of the switch control circuit 310 are adopted, so that the switch control circuit has the advantages of simple structure and small volume.
In addition, the detection current IP comes from the switching power supply circuit electrically connected with the circuit of the embodiment, has the characteristic of linear change, and increases the current in a form of linear increase after the switching tube Q is turned on. Therefore, when the detection resistor RCS is constant, the change in the detection current IP flowing through the detection resistor RCS can be detected by detecting the change in the detection voltage Vcs across the detection resistor RCS. When the detected current IP reaches the peak current IPmax (shown as IPmax in fig. 2), the detected voltage Vcs in the state of the peak current IPmax is set to be the peak voltage, so that the actual detected result is that the detected voltage Vcs reaches the peak voltage, and the switch control circuit 310 controls the switching tube Q to be turned off. When the detection resistors RCS with different resistance values are selected, the time length for the detection voltage Vcs to reach the peak voltage is different, so that the corresponding time length for the detection current IP to reach the peak current IPmax is different, and the frequency of the switching tube Q is different.
It should be appreciated that in other embodiments, other circuit structures may be used for the first circuit 330 to obtain the change of the detected current IP, including, but not limited to, replacing the detection resistor RCS with other components or other circuit structures composed of multiple components, so as to directly or indirectly detect the change of the detected current IP.
In one embodiment, as shown in FIG. 1, the switch control circuit 310 internally includes a frequency control enable circuit 320, a current source I1, and a switch K. The frequency control enable circuit 320 outputs a second switch control signal CT (indicated by CT signal in fig. 1-3) to control on/off of the switch K. The switch K is electrically connected between the current source I1 and the second pin P2, and the detection resistor RCS is powered through the second pin P2 when the switch K is conducted.
Since the current source I1 supplies power to the detection resistor RCS when the switch K is turned on, the resistance value of the detection resistor RCS can be calculated by detecting the detection voltage Vcs at this time.
In one embodiment, as shown in fig. 2, the first switch control signal PWM and the second switch control signal CT are opposite in level at the time of output.
When the switching transistor Q is turned on, the frequency control enabling circuit 320 controls the switch K to be turned off, and the detection voltage Vcs obtained by the detection of the second pin P2 is the detection voltage Vcs when the detection current IP flows through the detection resistor RCS. Wherein the detected voltage Vcs detected at this time is used to monitor the change in the detected current IP.
When the switching transistor Q is turned off, the frequency control enabling circuit 320 controls the switch K to be turned on, the switch control circuit 310 supplies power to the detection resistor RCS, and the detection voltage Vcs obtained by detection on the second pin P2 is the detection voltage Vcs when the current source I1 supplies current. The detection voltage Vcs detected at this time is used to calculate the detection resistance RCS.
In one embodiment, as shown in fig. 2, the switch control circuit 310 controls the first switch control signal PWM to be high level, the switch tube Q is closed, and the switch K is opened at the rising edge of the system clock signal (shown as CLK in fig. 2); when detecting that the detected current IP rises to the threshold value, the switch control circuit 310 controls the first switch control signal PWM to be low, and the switching tube Q is opened and the switch K is closed.
It should be understood that the frequency of the system clock signal used in this embodiment should be determined according to the actual requirement, that is, the resistance value of the set detection resistor RCS. Similarly, the threshold value of the detected current IP, i.e., the peak current IPmax, is also set according to the actual demand.
By adopting the embodiment, the detection resistor RCS is connected in series with the switching tube Q, so that the detection current IP flows through the switching tube Q and the detection resistor RCS at the same time, and the magnitude and the change of the detection current IP are judged by detecting the magnitude and the change of the detection voltage Vcs at two ends of the detection resistor RCS, thereby realizing that the switching tube Q can be controlled to be switched off in time when the detection current IP reaches the peak current IPmax. Since the detection current IP comes from other switching power supply circuits electrically connected to the circuit of the present embodiment, by changing the resistance value of the detection resistor RCS, it is possible to change the period of time during which the detected detection voltage Vcs reaches the peak voltage from zero, thereby changing the frequency of controlling the switching on and off of the switching transistor Q. The embodiment adopts the same group of pin multiplexing, so that the detection of the detection current IP can be realized at the same time, and the frequency setting of the on and off of the switching tube Q can be realized. Therefore, the embodiment has fewer pins and uses the same group of pins to realize a plurality of functions, so that the chip product has simple structure, small volume and wide application occasions.
Embodiment two:
The embodiment discloses a frequency control method based on pin multiplexing, which is applied to a switching control circuit based on pin multiplexing in the first embodiment, and comprises the following steps:
The switch control circuit 310 outputs a first switch control signal PWM to control the first circuit 330. When the first circuit 330 operates in the first time period, the first circuit 330 flows a current, and the current flowing through the first circuit 330 is detected through the first pin P1; when the first circuit 330 is operating in the second time period, the characteristics of the components within the first circuit 330 are detected through the first pin P1.
Changing the frequency of the first circuit 330 between the first time period and the second time period is accomplished by changing the characteristics of the components within the first circuit 330.
It should be appreciated that the individual component characteristic changes within the first circuit 330, including but not limited to a resistance change to a certain resistance within the circuit, are aimed at enabling a change in the frequency of the first circuit 330 between the first time period and the second time period.
The present embodiment can realize outputting different first switch control signals PWM by detecting the current variation in the first circuit 330, and feeding the outputted first switch control signals PWM back into the first circuit 330, which has an effect of changing the characteristics of the relevant elements in the first circuit 330, thereby realizing the frequency of the first circuit 330 varying between the first time period and the second time period. In this embodiment, the current change in the first circuit 330 and the output first switch control signal PWM are fed back into the first circuit 330, and both functions are implemented by using the same set of pin multiplexing.
Embodiment III:
The embodiment discloses a frequency control method based on pin multiplexing, which is applied to a switching control circuit based on pin multiplexing in the first embodiment, is one of more specific embodiments of the second embodiment, and is characterized in that a working circuit diagram refers to fig. 1, and each signal output in a working state refers to a waveform diagram in fig. 2. The first time period is the on state of the switching tube Q, the second time period is the off state of the switching tube Q, and the method further comprises the following steps:
Step one: in the first time period, the switch control circuit 310 outputs the first switch control signal PWM to control the on of the switching transistor Q at the rising edge of the system clock signal. The frequency of the system clock signal is selected according to different resistance values of the detection resistor RCS.
Step two: the on switching transistor Q causes the detection current IP to flow through the detection resistor RCS. When the detection current IP flows through the detection resistor RCS, the change in the detection current IP can be monitored by detecting the change in the detection voltage Vcs across the detection resistor RCS.
Step three: the switch control circuit 310 detects the detection voltage Vcs across the detection resistor RCS, and monitors the change of the detection current IP according to the change of the detection voltage Vcs. It will be appreciated that the sense current IP comes from the switching power supply circuit, with the characteristic of a linear variation.
Step four: the switch control circuit 310 obtains the peak current IPmax of the detection current IP at each switching period, and when the detection current IP reaches the peak current IPmax, controls the switching tube Q to be turned off, simultaneously controls the switch K to be turned on, and detects the resistance value of the detection resistor RCS.
Step five: in the second time period, the closed switch K turns on the current source I1 and the detection resistor RCS. The closed switch K realizes the power supply of the switch control circuit 310 to the detection resistor RCS, so that the current resistance value of the detection resistor RCS is conveniently calculated.
Step six: the switch control circuit 310 detects the detection voltage Vcs across the detection resistor RCS, and calculates the resistance value of the detection resistor RCS at this time based on the detection voltage Vcs and the current source I1.
Step seven: recording the current calculated resistance value of the detection resistor RCS, and controlling the frequency of the switching tube Q according to the resistance value of the detection resistor RCS. In the case of keeping the current source I1 constant, the resistance of a sense resistor RCS represents a system frequency.
It should be understood that the above-described step sequence is only one embodiment, and for convenience in describing the specific content of the frequency control method, in other embodiments, the frequency control method is not limited to the step sequence of the above-described embodiment.
The detection resistor RCS resistance obtained through calculation can be used for realizing the purpose of changing the Q frequency of a switching tube only by changing the detection resistor RCS resistance in the later period, thereby realizing the purpose of controlling the system frequency of other switching power supply systems applying the circuit of the embodiment.
Therefore, the embodiment adopts the same group of pin multiplexing, thereby realizing the detection of the detection current IP, realizing the control of the Q frequency of the switch tube and playing the advantages of multiple functions of the same pin.
Embodiment four:
The embodiment discloses a frequency control method based on pin multiplexing, which is applied to a switching control circuit based on pin multiplexing in the first embodiment and is another more specific embodiment of the second embodiment. Operation circuit diagram referring to fig. 1, each signal output of the operation state refers to the waveform diagram in fig. 2. The first time period is the on state of the switching tube Q, the second time period is the off state of the switching tube Q, and the method further comprises the following steps:
Step one: the circuit operation starts at the second time stage, and at this time, the switch K is in the closed state, and the switch tube Q is in the off state. The closed switch K conducts the current source I1 and the detection resistor RCS, and the switch control circuit 310 supplies power to the detection resistor RCS.
Step two: the switch control circuit 310 detects the detection voltage Vcs across the detection resistor RCS, and calculates the resistance value of the detection resistor RCS at this time based on the detection voltage Vcs and the current source I1. Keeping the current source I1 at a fixed value and keeping the resistance of the detection resistor RCS unchanged, the switch control circuit 310 controls the frequency limiting range threshold of the switching tube Q to be turned on and off to be kept constant.
Step three: recording the resistance value of the detection resistor RCS calculated in the second step. In the case of keeping the current source I1 unchanged, a fixed detection resistor RCS has a resistance value which represents a frequency-limited range in which the switching tube Q is turned on and off.
Step four: the first time phase is entered while keeping the resistances of the current source I1 and the detection resistor RCS constant. The switch control circuit 310 outputs a first switch control signal PWM to control the on of the switching transistor Q at the rising edge of the system clock signal.
Step five: the on switching transistor Q causes the detection current IP to flow through the detection resistor RCS.
Step six: the switch control circuit 310 detects the detection voltage Vcs across the detection resistor RCS, and monitors the change of the detection current IP according to the change of the detection voltage Vcs.
Step seven: the switch control circuit 310 obtains the peak current IPmax of the detection current IP at each switching cycle, and controls the switching tube Q to be turned off and controls the switch K to be turned on when the detection current IP reaches the peak current IPmax.
In summary, under the condition that the threshold value of the system frequency range in the earlier stage of the first to third steps is defined, the fourth to seventh steps complete the complete switching on to off of the switching tube Q once, and the fourth to seventh steps are repeated continuously to obtain the working process of the system frequency.
By the frequency control method of the present embodiment, the second stage of operation can be performed by the beginning stage of the circuit operation, that is, only one detection is needed in the beginning stage, the system frequency range is limited by the fixed current source I1 and the detection resistor RCS with a certain fixed resistance value, so that the threshold value of the frequency range of the on-off state of the subsequent switching tube Q is kept unchanged, and the switching control circuit 310 controls the system frequency of the first circuit 330 to be kept in a stable frequency range.
Fifth embodiment:
The embodiment discloses a switching power supply system, wherein the switching tube Q frequency in the switching power supply system is controlled by a switching control circuit based on pin multiplexing in the first embodiment, so that the switching power supply system frequency of the embodiment is controlled.
The switching power supply system of the present embodiment includes the switching control circuit based on pin multiplexing in the first embodiment, and includes the switching power supply circuit. The switching power supply circuit includes a switching transistor Q whose frequency of on and off is controlled by a switching control circuit 310.
In one embodiment, as shown in fig. 3, the switching power supply circuit is a flyback voltage conversion circuit 200. The flyback voltage conversion circuit 200 includes a transformer T.
As shown in fig. 3, the flyback voltage conversion circuit 200 of the present embodiment has an input terminal coupled to the dc output terminal of the bridge rectifier 100, and obtains an input voltage from the dc output terminal of the bridge rectifier 100. The ac input of the bridge rectifier 100 is connected to an ac power source. In order to improve the voltage quality and reduce the line loss, a capacitor is connected between the positive and negative electrodes of the dc output terminal of the bridge rectifier 100 in this embodiment.
The primary winding of the transformer T is electrically connected with the switching tube Q, and the secondary winding of the transformer T outputs the transformed output voltage. It should be appreciated that as with the conventional flyback voltage conversion circuit 200 of the prior art, the output of the secondary winding is coupled to an output diode, and the output diode is connected in parallel with an output capacitor.
In this embodiment, when the switching tube Q is turned on, the primary winding stores electric energy and generates a detection current IP flowing through the switching tube Q, where the detection current IP is the primary current of the transformer T;
When the switching tube Q is turned off, the secondary winding outputs electric energy, the detection current IP is zero at the moment, and the induced current of the transformer T is generated and used for outputting electric energy.
Therefore, the present embodiment can detect the detection current IP (the primary current of the transformer T) in the switching power supply circuit and realize the control of the switching power supply system frequency by the frequency control of the switching transistor Q by multiplexing the same set of pins in the switching control circuit 310.
Furthermore, in other embodiments, the switching power supply circuit may also be a buck circuit or a boost circuit. That is, the pin multiplexing-based switching control circuit in the first embodiment can be applied to any switching power supply system that needs to detect a current and control the frequency of the switching power supply system.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
In summary, the foregoing description is only of the preferred embodiments of the present invention, and all equivalent changes and modifications made in accordance with the claims should be construed to fall within the scope of the invention.
Claims (10)
1. A switch control circuit based on pin multiplexing, which is characterized by comprising a first pin and a second pin; the switch control circuit is coupled with the first circuit;
the first pin is used for outputting a first switch control signal to control the first circuit;
The second pin is used for detecting and acquiring the detection current flowing through the first circuit in a first time period, and is used for detecting and acquiring the element characteristic of the first circuit in a second time period;
The switch control circuit controls the first switch control signal in accordance with the detection current and the element characteristic, wherein the element characteristic is used to control a system frequency of the first circuit.
2. The switch control circuit of claim 1, wherein the first circuit comprises a switching tube; the first pin is electrically connected with the switching tube and controls the conduction state of the switching tube by outputting different first switching control signals; and the second pin detection obtains detection current flowing through the switching tube.
3. The switch control circuit of claim 2, wherein the first circuit further comprises a sense resistor in series with the switching tube;
The second pin is electrically connected with the detection resistor, and the change of the detection current flowing through the detection resistor and the switch tube at the same time is detected and obtained by detecting the change of the detection voltage at two ends of the detection resistor;
The switch control circuit changes the element characteristics of the first circuit by changing the resistance value of the detection resistor for changing the frequency of turning on and off the switching tube.
4. The switch control circuit of claim 3, wherein the switch control circuit further comprises a frequency control enable circuit, a current source, and a switch; the frequency control enabling circuit outputs a second switch control signal to control the on state of the switch; the switch is electrically coupled between the current source and the second pin, and supplies power to the detection resistor through the second pin when the switch is turned on.
5. A switching power supply system comprising the switching control circuit according to any one of claims 1 to 4 and a switching power supply circuit including a switching tube whose frequency of turning on and off itself is controlled by the switching control circuit.
6. The switching power supply system according to claim 5, wherein the switching power supply circuit is a flyback voltage conversion circuit; the flyback voltage conversion circuit comprises a transformer;
The input end of the flyback voltage conversion circuit is coupled with the direct current output end of the bridge rectifier, and input voltage is obtained from the direct current output end of the bridge rectifier; the alternating current input end of the bridge rectifier is connected with an alternating current power supply;
The primary winding of the transformer is electrically connected with the switching tube, and the secondary winding of the transformer outputs the transformed output voltage;
When the switching tube is conducted, the primary winding stores electric energy and generates the detection current flowing through the switching tube;
when the switching tube is turned off, the secondary winding outputs electric energy, and the detection current is zero.
7. The switching power supply system according to claim 6, wherein the switching power supply circuit is a buck circuit or a boost circuit.
8. The frequency control method based on pin multiplexing is characterized by comprising the following steps:
Outputting a first switch control signal to control a first circuit;
When the first circuit operates in a first time period, the first circuit flows current, and the current flowing through the first circuit is detected through a first pin;
Detecting a component characteristic within the first circuit through a first pin when the first circuit is operating in a second time period;
Changing the frequency of the first circuit between the first time period and the second time period is achieved by changing a characteristic of a component within the first circuit.
9. The method of claim 8, wherein the first circuit comprises a switching tube and a detection resistor in series, the first time period being the on state of the switching tube, the second time period being the off state of the switching tube, the method further comprising the steps of:
Closing a switch to cause a current source to flow through the sense resistor during the second time period;
Detecting detection voltages at two ends of the detection resistor, and obtaining the resistance value of the detection resistor at the moment according to the detection voltages and the current source;
And controlling the frequency of the switching tube according to the resistance value of the detection resistor.
10. The method of frequency control according to claim 9, further comprising:
During the first time period, the switching tube is controlled to be conducted at the rising edge of a system clock signal;
The switching tube is conducted to enable the current to flow through the detection resistor;
Detecting the detection voltage at two ends of the detection resistor, and monitoring the change of the detection current according to the change of the detection voltage;
and acquiring the peak current of the detection current in each switching period, controlling the switching tube to be turned off when the detection current reaches the peak current, and detecting the resistance value of the detection resistor.
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| CN103401429A (en) * | 2013-08-09 | 2013-11-20 | 杭州茂力半导体技术有限公司 | Switch power supply and control circuit and control method thereof |
| CN203883690U (en) * | 2014-04-03 | 2014-10-15 | 上海新进半导体制造有限公司 | Multiplexing detection circuit, switching power supply controller and fly-back converter |
| CN107742984A (en) * | 2017-09-28 | 2018-02-27 | 广州金升阳科技有限公司 | Trough control circuit and trough control method |
| CN110113055A (en) * | 2019-04-18 | 2019-08-09 | 南京矽力杰半导体技术有限公司 | Pin multiplexing chip |
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| JP2011015557A (en) * | 2009-07-02 | 2011-01-20 | Panasonic Corp | Switching power supply apparatus, and semiconductor device for control of the same |
| CN103066872B (en) * | 2013-01-17 | 2015-06-17 | 矽力杰半导体技术(杭州)有限公司 | Integration switch power supply controller and switch power supply using the same |
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| CN103401429A (en) * | 2013-08-09 | 2013-11-20 | 杭州茂力半导体技术有限公司 | Switch power supply and control circuit and control method thereof |
| CN203883690U (en) * | 2014-04-03 | 2014-10-15 | 上海新进半导体制造有限公司 | Multiplexing detection circuit, switching power supply controller and fly-back converter |
| CN107742984A (en) * | 2017-09-28 | 2018-02-27 | 广州金升阳科技有限公司 | Trough control circuit and trough control method |
| CN110113055A (en) * | 2019-04-18 | 2019-08-09 | 南京矽力杰半导体技术有限公司 | Pin multiplexing chip |
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