A time-sharing detection circuit and control method

Abstract

A time-sharing detection circuit and control method can be integrated in a chip to reuse a pin to realize dual detection of the input voltage and functional resistance of an isolated converter; when the power tube is turned on, the time-sharing detection pin is switched to connect to an input voltage detection module, the input voltage detection module clamps the potential of the time-sharing detection pin, and obtains input voltage information by detecting the current of the time-sharing detection pin; when the power tube is disconnected, the time-sharing detection pin is only grounded through a functional resistor, at which time the time-sharing detection pin is switched to connect to a functional resistance detection module, and the functional resistance information is obtained by controlling the constant voltage or constant current of the time-sharing detection pin and detecting the corresponding change in current or voltage at the time-sharing detection pin. The present invention uses time-sharing detection to realize pin multiplexing, solves the problem that the number of chip pins is insufficient and more functions cannot be realized, and has the characteristics of simple structure, easy integration, and high detection accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of switching power supplies, and relates to a time-sharing detection circuit and a time-sharing detection control method, which can be applied to an isolated converter (such as a flyback converter and a forward converter), and realizes the detection of both input voltage and functional resistance using the same time-sharing detection pin. Background Art

[0002] An isolated converter contains a transformer that enables energy transfer from the primary side to the secondary side. Isolated converters include flyback converters and forward converters. A forward converter is a BUCK converter with transformer isolation. A flyback converter is also called a single-ended flyback or "Buck-Boost" converter.

[0003] The flyback converter is named because its output end obtains energy when the primary winding is disconnected from the power supply. It has a simple circuit structure and low cost, so it is widely used in small power supplies and various power adapters. The controller of the flyback converter needs to collect information such as input voltage through pins or set functions through chip pins during operation. However, the circuit integration is restricted by the cost, volume, number of pins, etc. of the chip. Not having enough pins to realize various functions is a common problem in the industry. The same problem also exists in the forward converter. Summary of the invention

[0004] In view of the shortcomings of the above-mentioned isolated converter, that is, due to the limited number of pins, limited volume, and limited circuit integration of the controller chip, there are not enough pins to realize various functions, the present invention combines the actual working characteristics of the isolated converter and proposes a time-sharing detection circuit and a time-sharing detection control method. Pin multiplexing is realized by time-sharing detection to achieve the purpose of line voltage detection (i.e., collecting input voltage information) and setting functional resistors. The functional resistors can be used to set functions such as temperature protection.

[0005] The technical solution of the present invention is:

[0006] A time-sharing detection circuit, which can be integrated in a controller chip and use the same time-sharing detection pin to implement input voltage detection and functional resistance detection for an isolated converter;

[0007] The isolated converter comprises a primary winding, a secondary winding, an auxiliary winding, a power tube, a first resistor, a first diode and a functional resistor, wherein the opposite-name end of the primary winding is connected to the input voltage, and the same-name end thereof is connected to the ground level after passing through the power tube; the opposite-name end of the auxiliary winding is connected to the ground level, and the same-name end thereof is connected to one end of the functional resistor and the time-sharing detection pin after passing through the series structure of the first resistor and the first diode, and the other end of the functional resistor is connected to the ground level;

[0008] The time-sharing detection circuit includes an input voltage detection module, a functional resistance detection module and a time-sharing detection control module.

[0009] When the power tube is turned on, the voltage at the same-name end of the auxiliary winding is proportional to the input voltage and can control the first diode to be forward-conducted; at the same time, the time-sharing detection control module controls the input voltage detection module to work and the functional resistance detection module not to work, the input voltage detection module clamps the potential of the time-sharing detection pin to a first clamping level, and the input voltage detection module obtains the input voltage according to the current detection of the time-sharing detection pin;

[0010] When the power tube is disconnected, the voltage at the same end of the auxiliary winding can control the first diode to be reversely cut off, so that the time-sharing detection pin is only grounded through the functional resistor; at the same time, the time-sharing detection control module controls the functional resistance detection module to work and the input voltage detection module not to work, and the functional resistance detection module obtains the functional resistance according to the voltage or current detection of the time-sharing detection pin.

[0011] Specifically, when the first clamping level is set as close to zero as possible, the current of the time-sharing detection pin is only proportional to the input voltage, and the input voltage detection module can directly detect the input voltage based on the current of the time-sharing detection pin; when the first clamping level is set to other voltage values, the input voltage detection module needs to subtract the current of the functional resistor from the current of the time-sharing detection pin to obtain the input voltage information, wherein the current of the functional resistor is determined based on the first clamping level and the resistance value of the functional resistor.

[0012] Specifically, the time-sharing detection control module includes a time-sharing detection logic control unit, a first switch and a second switch, the first switch is connected between the input voltage detection module and the time-sharing detection pin, the second switch is connected between the functional resistance detection module and the time-sharing detection pin, and the time-sharing detection logic control unit is used to control the first switch to close and the second switch to open when the power tube is turned on, and to control the first switch to open and the second switch to close when the power tube is turned off.

[0013] Specifically, the input voltage detection module includes a first current detection unit and a first voltage clamping unit, the first voltage clamping unit is used to clamp the potential of the time-sharing detection pin to a first clamping level; the first current detection unit is used to detect the current of the time-sharing detection pin and convert it into the input voltage information.

[0014] Specifically, the functional resistance detection module includes a second current detection unit and a second voltage clamping unit, the second voltage clamping unit is used to clamp the potential of the time-sharing detection pin to a second clamping level; the second current detection unit is used to detect the current of the time-sharing detection pin and convert it into the functional resistance information.

[0015] Specifically, the functional resistance detection module includes a constant current source and a comparator, the positive input end of the comparator is connected to the output end of the constant current source and is connected to the time-sharing detection pin through the second switch, the negative input end is connected to the reference comparison voltage, and the output signal contains the functional resistance information.

[0016] Specifically, in the series structure of the first resistor and the first diode, the cathode of the first diode is connected to the same-name end of the auxiliary winding through the first resistor, and the anode thereof is connected to the time-sharing detection pin; or the cathode of the first diode is connected to the same-name end of the auxiliary winding, and the anode thereof is connected to the time-sharing detection pin through the first resistor.

[0017] In combination with the above-mentioned time-sharing detection circuit, the present invention also proposes a corresponding control method, and the technical solution of the time-sharing detection control method is:

[0018] A time-sharing detection control method, wherein the time-sharing detection control method can use the same time-sharing detection pin to realize input voltage detection and functional resistance detection of an isolated converter;

[0019] The isolated converter comprises a primary winding, a secondary winding, an auxiliary winding, a power tube, a first resistor, a first diode and a functional resistor, wherein the opposite-name end of the primary winding is connected to the input voltage, and the same-name end thereof is connected to the ground level after passing through the power tube; the opposite-name end of the auxiliary winding is connected to the ground level, and the same-name end thereof is connected to one end of the functional resistor and the time-sharing detection pin after passing through the series structure of the first resistor and the first diode, and the other end of the functional resistor is connected to the ground level;

[0020] The time-sharing detection control method includes control when the power tube is turned on and control when the power tube is turned off:

[0021] When the power tube is turned on, the voltage at the same-name end of the auxiliary winding is proportional to the input voltage and can control the first diode to be forward-conducted. At this time, the potential of the time-sharing detection pin is clamped to a first clamping level. When the first clamping level is set as close to zero as possible, the current of the time-sharing detection pin is only proportional to the input voltage, and the information of the input voltage can be directly obtained by detecting the current of the time-sharing detection pin; when the first clamping level is set to other voltage values, it is necessary to subtract the current of the functional resistor from the detected current of the time-sharing detection pin and then convert it into the information of the input voltage, wherein the current of the functional resistor is determined according to the first clamping level and the resistance value of the functional resistor;

[0022] When the power tube is disconnected, the voltage at the same end of the auxiliary winding can control the reverse cutoff of the first diode, so that the time-sharing detection pin is grounded only through the functional resistor. At this time, the time-sharing detection pin is controlled to have a constant voltage or a constant current, and the information of the functional resistor can be obtained by detecting the corresponding changing current or voltage at the time-sharing detection pin.

[0023] Specifically, when the power tube is disconnected, a constant current source is used to provide a first current to the time-sharing detection pin, and the potential of the time-sharing detection pin is the product of the current value of the first current and the resistance value of the functional resistor. The potential of the time-sharing detection pin is compared with a reference comparison voltage to obtain information about the functional resistor.

[0024] Specifically, when the power tube is disconnected, the potential of the time-sharing detection pin is clamped to a second clamping level, and the information of the functional resistor is obtained by detecting the current of the time-sharing detection pin.

[0025] Specifically, after the power tube state is switched, the detection is performed after a set blanking time has passed.

[0026] The beneficial effects of the present invention are as follows: the present invention realizes multiplexing of functional pins by detecting in different time periods, and realizes both functional resistance detection and input voltage detection of the isolated converter by using only one time-sharing detection pin, thus solving the problem that the number of chip pins is insufficient and more functions cannot be realized; the time-sharing detection circuit proposed by the present invention has a simple structure and is easy to integrate, and obtains relatively high detection accuracy through precise voltage clamping and timing control, and can be applied to isolated converters with a wide input voltage range, such as flyback and forward converters. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The following drawings are helpful for better understanding the following description of different embodiments of the present invention, and these drawings schematically illustrate the main features of some embodiments of the present invention. These drawings and examples provide some embodiments of the present invention in a non-limiting and non-exhaustive manner. For the sake of simplicity, the same or similar components or structures having the same function in different drawings are marked with the same reference numerals.

[0028] Figure 1 The invention is a structural schematic diagram when a time-sharing detection circuit and a control method proposed by the invention are applied to a flyback converter.

[0029] Figure 2 It is another structural schematic diagram when a time-sharing detection circuit and a control method proposed in the present invention are applied to a flyback converter.

[0030] Figure 3 The invention discloses an internal structure implementation circuit diagram of a time-sharing detection circuit.

[0031] Figure 4 This is another internal structure implementation circuit diagram of a time-sharing detection circuit proposed by the present invention.

[0032] Figure 5 The present invention proposes a time-sharing detection circuit and a control method using Figure 3 Schematic diagram of waveforms of key nodes in the structure.

[0033] Figure 6 The present invention proposes a time-sharing detection circuit and a control method using Figure 4 Schematic diagram of waveforms of key nodes in the structure. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0035] The specific details in the embodiments described below, such as the specific circuit structures in the embodiments and the specific parameters of the circuit elements, are used to provide a better understanding of the embodiments of the present invention. It can be understood by those skilled in the art that the embodiments of the present invention can be implemented even if some details are missing or other methods, elements, materials, etc. are combined.

[0036] The time-sharing detection circuit proposed in the present invention can be integrated in a controller chip, and the same time-sharing detection pin is used to realize input voltage detection and functional resistance detection of an isolated converter. The isolated converter includes a flyback converter and a forward converter, both of which realize energy transfer through a transformer. The working process and working principle of the present invention are described in detail below by taking the application of the present invention to a flyback converter as an example.

[0037] like Figure 1 and 2 As shown, the flyback converter includes a primary winding 105, a secondary winding, an auxiliary winding 100, a power tube Q1, a first resistor 103, a first diode 102 and a functional resistor 104. The opposite-name end of the primary winding 105 is connected to the input voltage Vin, and its same-name end 203 is connected to the ground level after passing through the power tube Q1; the opposite-name end of the auxiliary winding 100 is connected to the ground level, and its same-name end 204 is connected to one end of the functional resistor 104 and the time-sharing detection pin DET after passing through the series structure of the first resistor 103 and the first diode 102, and the other end of the functional resistor 104 is connected to the ground level. In the series structure composed of the first resistor 103 and the first diode 102, the positions of the first resistor 103 and the first diode 102 can be interchanged, and can be as shown in FIG. Figure 1 As shown, the cathode of the first diode 102 is connected to the same-name terminal 204 of the auxiliary winding 100, and the anode of the first diode 102 is connected to the time-sharing detection pin DET through the first resistor 103; it can also be as shown Figure 2 As shown, the cathode of the first diode 102 is connected to the same-name terminal 204 of the auxiliary winding through the first resistor 103, and the anode of the first diode 102 is connected to the time-sharing detection pin DET.

[0038] In the flyback converter, when the power tube Q1 is closed, the potential of the same-name end 204 of the auxiliary winding 100 is a negative voltage, and the voltage value is proportional to the input voltage Vin; when the power tube Q1 is disconnected, the potential of the same-name end 204 of the auxiliary winding 100 is a positive level. The present invention uses this characteristic to control the first diode 102 to be forward-conducted when the power tube Q1 is closed, and reverse-cut off when the power tube Q1 is disconnected, so that the clamping voltage 202 of the time-sharing detection pin DET can reflect different characteristics in different time periods. Combined with the time-sharing detection circuit proposed by the present invention, the multiplexing time-sharing detection pin DET is used to detect both the input voltage and the functional resistor.

[0039] The time-sharing detection circuit proposed in the present invention includes an input voltage detection module 301, a functional resistance detection module 300 and a time-sharing detection control module. The time-sharing detection control module is used to control the switching of the input voltage detection module 301 and the functional resistance detection module 300 to work in time periods according to the state of the power tube Q1. The working principle of the time-sharing detection control module is as follows.

[0040] When the power tube gate drive signal DRV of the flyback converter is at a low level, the power tube Q1 is controlled to be turned off, the flyback converter is in the GATE off state, the same-name terminal voltage 203 of the primary winding 105 is at a high level, the same-name terminal voltage 204 of the auxiliary winding 100 is positive, and the first diode 102 is reversely cut off, so that the time-sharing detection pin DET is only grounded through the functional resistor 104 (RSET resistor). At this time, the time-sharing detection control module is used to control the functional resistance detection module 300 to work and the input voltage detection module 301 not to work. The functional resistance detection module 300 detects the information of the functional resistor 104 through the time-sharing detection pin DET.

[0041] When the flyback converter power tube gate drive signal DRV is high, the power tube Q1 is turned on and the flyback converter is in GATE On state, the same-name terminal voltage 203 of the primary winding 105 is at the ground level, and the voltage value is 0, then the same-name terminal voltage 204 of the auxiliary winding 100 is negative, and the voltage is in a turns ratio relationship with the input voltage (the turns ratio of the auxiliary winding 100 to the primary winding 105), so that the first diode 102 is forward-conducted. At this time, the time-sharing detection control module is used to control the input voltage detection module 301 to work and the functional resistor detection module 300 not to work. The input voltage detection module 301 clamps the potential 202 of the time-sharing detection pin DET to the first clamping level Vclamp1. When the first clamping level Vclamp1 is set to a low level or close to the ground level, the current on the functional resistor 104 is very small. It can be considered that the current of the time-sharing detection pin (the current direction at this time is flowing out of the time-sharing detection pin) is only related to the input voltage, eliminating the influence of the current on the functional resistor 104 on the detection of the input voltage information. At this time, the input voltage detection module 301 can directly obtain the input voltage information through the current of the time-sharing detection pin DET. When the first clamping level Vclamp1 is set to other voltage values, the current of the time-sharing detection pin also includes the current information of the functional resistor 104. At this time, it is necessary to first subtract the current of the functional resistor from the detected current of the time-sharing detection pin and then convert it into the corresponding input voltage information, wherein the current of the functional resistor can be determined according to the first clamping level and the real-time resistance value of the functional resistor.

[0042] like Figure 3 and 4The figure shows a specific implementation structure of the time-sharing detection control module, including a time-sharing detection logic control unit 402, a first switch S1 and a second switch S2, wherein the first switch S1 is connected between the input voltage detection module and the time-sharing detection pin DET, and the second switch S2 is connected between the functional resistance detection module and the time-sharing detection pin DET. The time-sharing detection logic control unit 402 is used to control the first switch S1 to close and the second switch S2 to open when the power tube Q1 is turned on, so that the input voltage detection module works and the functional resistance detection module does not work when the power tube Q1 is turned on; when the power tube Q1 is turned off, the time-sharing detection logic control unit is used to control the first switch S1 to open and the second switch S2 to close, so that the functional resistance detection module works and the input voltage detection module does not work. Among them, the first switch S1 and the second switch S2 can also be transistors or other switch structures that can realize the switch function, and the time-sharing detection control module can also use other structures to control the connection switching between the time-sharing detection pin DET and the functional resistance detection module and the input voltage detection module.

[0043] The input voltage detection module 301 is used to detect the time-sharing detection pin DET to obtain input voltage information when the power tube Q1 is turned on and the first diode 102 is forward-conducted. Figure 3 and 4 The figure shows a specific implementation structure of the input voltage detection module, which includes a first current detection unit 401 and a first voltage clamping unit 400. The first voltage clamping unit 400 is used to clamp the potential of the time-sharing detection pin DET to the first clamping level Vclamp1, and includes an NMOS tube and an operational amplifier. The positive input end of the operational amplifier is connected to the first clamping level Vclamp1, and its negative input end is connected to the source of the NMOS tube and connected to the time-sharing detection pin DET through the first switch S1, and its output end is connected to the gate of the NMOS tube. The first current detection unit 401 is used to detect the current of the time-sharing detection pin DET and convert it to obtain the information of the input voltage. The first current detection unit is connected to the drain of the first NMOS tube, and the current Isense1 flowing through the first NMOS tube is the current of the time-sharing detection pin DET.

[0044] When the power tube Q1 is disconnected, the first diode 102 is reversely cut off, and the time-sharing detection pin DET only has a path from the functional resistor 104 to the ground level. At this time, the functional resistor detection module can be used to control the time-sharing detection pin DET to be constant voltage or constant current. When the time-sharing detection pin DET is constant voltage, the information of the functional resistor 104 is obtained by detecting the current of the time-sharing detection pin DET. When the time-sharing detection pin DET is constant current, the information of the functional resistor 104 is obtained by detecting the voltage of the time-sharing detection pin DET.

[0045] like Figure 3The figure shows the internal structure of the functional resistance detection module when the functional resistance detection module is used to control the constant current of the time-sharing detection pin DET. In this embodiment, the functional resistance detection module 403 includes a constant current source and a comparator. The positive input end of the comparator is connected to the output end of the constant current source and connected to the time-sharing detection pin DET through the second switch S2. The negative input end of the comparator is connected to the reference comparison voltage Vcomp. When the second switch S2 is turned on, the constant current source provides a constant first current I DET Given the time-sharing detection pin DET, the voltage of the time-sharing detection pin DET is a constant first current I DET The product of the resistance value of the functional resistor 104 is then used to compare the voltage of the time-sharing detection pin DET with the reference comparison voltage Vcomp through a comparator, and the resulting comparator output signal contains the resistance information of the functional resistor 104 .

[0046] like Figure 4 The structure of the functional resistance detection module when the functional resistance detection module is used to control the constant voltage of the time-sharing detection pin DET is shown. In this embodiment, the functional resistance detection module includes a second current detection unit 404 and a second voltage clamping unit 405. The second voltage clamping unit 405 is used to clamp the potential of the time-sharing detection pin DET to a second clamping level Vclamp2. Similar to the input voltage detection module, the second voltage clamping unit also uses an NMOS tube and an operational amplifier to achieve clamping. The second current detection unit obtains the information of the functional resistance by detecting the current Isense2 of the time-sharing detection pin DET and converting it.

[0047] Figure 5 The shown is the use of Figure 3 Some key node waveform diagrams of the structure are shown. In this embodiment, the input voltage detection module uses the first voltage clamping unit 400 to clamp the potential of the time-sharing detection pin DET to the first clamping level Vclamp1, and sets the first clamping level Vclamp1 to the ground level or as close to the low level as possible. The first current detection unit 401 is used to detect the current of the time-sharing detection pin DET, which can be directly converted to obtain the input voltage information; the functional resistance detection module uses a constant current source to provide a constant first current to the time-sharing detection pin DET, and then uses a comparator to compare the voltage of the time-sharing detection pin DET with the reference comparison voltage Vcomp to obtain the resistance information of the functional resistor 104.

[0048] like Figure 5As shown, during T1, the system is in the GATE on state, the power tube Q1 is turned on, the first diode 102 is forward-conducted, the time-sharing detection control module selects the input voltage detection module to work for detection, the first switch S1 is closed, and the second switch S2 is opened; the first voltage clamping unit 400 in the input voltage detection module starts to work, and the port voltage of the time-sharing detection pin DET is clamped to a fixed voltage, namely, the first clamping level Vclamp1; and then the first current detection unit 401 is used to detect the port current I of the time-sharing detection pin DET. DET Change; such as Figure 5 It can be seen that during the GATE on period of T1, T3, T5, and T7, the port voltage of the time-sharing detection pin DET is clamped to the first clamping level Vclamp1, and the port current I DET1 It changes with the input voltage VIN, so the port current I DET1 The input voltage information is obtained.

[0049] During T2, the system is in the GATE off state, the power tube Q1 is turned off, the first diode 102 is reversely cut off, the time-sharing detection control module selects the functional resistance detection module to work for detection, the first switch S1 is opened, and the second switch S2 is closed; the port current of the time-sharing detection pin DET is fixed to a constant current (that is, the constant first current output by the constant current source in the functional resistance detection module), such as Figure 5 In the GATE off state of T2, T4, and T6, the port voltage V of the time-sharing detection pin DET is DET is the resistance value R of the functional resistor 104 SET The port current I of the time-sharing detection pin DET at the time T2, T4, and T6 is the same as the constant first current ( DET2 is the product of the current value of the first current) I DET2 ×R SET This information can reflect the resistance information of the functional resistor 104. Setting the functional resistor 104 can realize various functional detections. For example, if the functional resistor 104 is a temperature-sensitive resistor, it can be connected to a voltage comparison module for over-temperature protection and other functions.

[0050] Figure 6 The shown is the use of Figure 4Some key node waveform diagrams of the structure are shown. In this embodiment, the input voltage detection module also uses the first voltage clamping unit 400 to clamp the potential of the time-sharing detection pin DET to the first clamping level Vclamp1, and also sets the first clamping level Vclamp1 to the ground level or as close to the low level as possible. The first current detection unit 401 is used to detect the current of the time-sharing detection pin DET and convert it to obtain the input voltage information; but the functional resistance detection module uses the second voltage clamping unit 405 to clamp the potential of the time-sharing detection pin DET to the second clamping level Vclamp2, and then uses the second current detection unit 404 to detect the current Isense2 of the time-sharing detection pin DET and convert it to obtain the functional resistance information.

[0051] like Figure 6 As shown, during T1, the system is in the GATE on state, the power tube Q1 is turned on, the first diode 102 is forward-conducted, the time-sharing detection control module selects the input voltage detection module to work for detection, the first switch S1 is closed, and the second switch S2 is opened; the first voltage clamping unit 400 in the input voltage detection module starts to work, and the port voltage of the time-sharing detection pin DET is clamped to a fixed voltage, namely, the first clamping level Vclamp1; and then the first current detection unit 401 is used to detect the port current I of the time-sharing detection pin DET. DET1 changes; such as Figure 6 It can be seen that during the GATE on period of T1, T3, T5, and T7, the port voltage of the time-sharing detection pin DET is clamped to the first clamping level Vclamp1, and the port current I DET1 It changes with the input voltage VIN, so the port current I DET1 The input voltage information is obtained.

[0052] During T2, the system is in the GATE off state, the power tube Q1 is turned off, the first diode 102 is reversely cut off, the time-sharing detection control module selects the functional resistance detection module to work for detection, the first switch S1 is disconnected, and the second switch S2 is closed; the second voltage clamping unit 405 in the functional resistance detection module starts to work, and the port voltage of the time-sharing detection pin DET is clamped to a fixed voltage, that is, the second clamping level Vclamp2, such as Figure 6 In the GATE off state of T2, T4, and T6, the current I of the DET port of the time-sharing detection pin is DET2 The current I of the time-sharing detection pin DET port is detected by the second current detection unit 404. DET2 The information of the functional resistor 104 can be obtained by changing.

[0053] Preferably, to prevent voltage spikes or overshoots from interfering with the detection result, a blanking time may be added after the gate terminal of the power tube Q1 switches state (GATE off switches to GATE on and GATE on switches to GATE off) to ensure the accuracy of the detection result.

[0054] In summary, the present invention realizes multi-function control by multiplexing the same chip pin through time-sharing detection, and realizes multi-mode detection and control of the chip. The present invention can be applied to an isolated converter including a transformer, and only one pin is used to realize the detection of input voltage and functional resistance. This pin is defined as the time-sharing detection pin DET. The auxiliary winding 100 is connected to the time-sharing detection pin DET through the first diode 102 and the first resistor 103 to realize input voltage detection, and the functional resistor 104 is directly connected to the time-sharing detection pin DET to realize functional resistance detection. In the time-sharing detection circuit proposed by the present invention, the time-sharing detection pin is internally controlled by the time-sharing detection control module according to the state of the power tube Q1 to realize the switching connection with the input voltage detection module and the functional resistance detection module. When the power tube Q1 is turned on, the time-sharing detection pin is switched to connect to the input voltage detection module for input voltage detection. When the power tube Q1 is disconnected, the time-sharing detection pin is switched to connect to the functional resistance detection module to detect the size of the preset functional resistance, thereby realizing the dual detection of the input voltage and the size of the functional resistance.

[0055] Although the embodiment is described by applying the time-sharing detection circuit and the time-sharing detection control method proposed in the present invention to a flyback converter as an example, it does not mean to limit the present invention. Those skilled in the art should understand that the structure and principle given here can also be applied to other isolation chamber converters that also include a transformer, such as a forward converter. The present invention illustrates the specific structure of the input voltage detection module and the functional resistance detection module in an exemplary manner, and does not limit the scope of the present invention. It is possible to make changes and modifications to the disclosed embodiments. Other feasible optional embodiments and equivalent changes to the devices in the embodiments can be understood by those skilled in the art. If those skilled in the art make non-substantial changes or improvements without departing from the spirit of the present invention, they should all fall within the scope of protection of the claims of the present invention.

Claims

1. A time-sharing detection circuit, characterized in that: The time-sharing detection circuit can be integrated in the controller chip to realize input voltage detection and functional resistance detection of the isolated converter using the same time-sharing detection pin; The isolated converter comprises a primary winding, a secondary winding, an auxiliary winding, a power tube, a first resistor, a first diode and a functional resistor, wherein the opposite-name end of the primary winding is connected to the input voltage, and the same-name end thereof is connected to the ground level after passing through the power tube; the opposite-name end of the auxiliary winding is connected to the ground level, and the same-name end thereof is connected to one end of the functional resistor and the time-sharing detection pin after passing through the series structure of the first resistor and the first diode, and the other end of the functional resistor is connected to the ground level; The time-sharing detection circuit includes an input voltage detection module, a functional resistance detection module and a time-sharing detection control module. When the power tube is turned on, the voltage at the same-name end of the auxiliary winding is proportional to the input voltage and can control the first diode to be forward-conducted; at the same time, the time-sharing detection control module controls the input voltage detection module to work and the functional resistance detection module not to work, the input voltage detection module clamps the potential of the time-sharing detection pin to a first clamping level, and the input voltage detection module obtains the input voltage according to the current detection of the time-sharing detection pin; When the power tube is disconnected, the voltage at the same-name end of the auxiliary winding can control the first diode to be reversely cut off, so that the time-sharing detection pin is only grounded through the functional resistor; at the same time, the time-sharing detection control module controls the functional resistance detection module to work and the input voltage detection module not to work, and the functional resistance detection module obtains the functional resistance according to the voltage or current detection of the time-sharing detection pin; When the first clamping level is set as close to zero as possible, the current of the time-sharing detection pin is only proportional to the input voltage, and the input voltage detection module can directly detect the input voltage according to the current of the time-sharing detection pin; when the first clamping level is set to other voltage values, the input voltage detection module needs to obtain the input voltage information after subtracting the current of the functional resistor from the current of the time-sharing detection pin, wherein the current of the functional resistor is determined according to the first clamping level and the resistance value of the functional resistor; The time-sharing detection control module includes a time-sharing detection logic control unit, a first switch and a second switch, wherein the first switch is connected between the input voltage detection module and the time-sharing detection pin, and the second switch is connected between the functional resistance detection module and the time-sharing detection pin. The time-sharing detection logic control unit is used to control the first switch to be closed and the second switch to be disconnected when the power tube is turned on, and to control the first switch to be disconnected and the second switch to be closed when the power tube is disconnected.

2. The time-sharing detection circuit according to claim 1, characterized in that: The input voltage detection module includes a first current detection unit and a first voltage clamping unit. The first voltage clamping unit is used to clamp the potential of the time-sharing detection pin to a first clamping level; the first current detection unit is used to detect the current of the time-sharing detection pin and convert it into the input voltage information.

3. The time-sharing detection circuit according to claim 2, characterized in that: The functional resistance detection module includes a second current detection unit and a second voltage clamping unit, wherein the second voltage clamping unit is used to clamp the potential of the time-sharing detection pin to a second clamping level; and the second current detection unit is used to detect the current of the time-sharing detection pin and convert it into the functional resistance information.

4. The time-sharing detection circuit according to claim 2, characterized in that: The functional resistance detection module includes a constant current source and a comparator, wherein the positive input end of the comparator is connected to the output end of the constant current source and connected to the time-sharing detection pin through the second switch, the negative input end of the comparator is connected to the reference comparison voltage, and the output signal of the comparator contains the functional resistance information.

5. The time-sharing detection circuit according to claim 4, characterized in that: In the series structure of the first resistor and the first diode, the cathode of the first diode is connected to the same-name end of the auxiliary winding through the first resistor, and the anode of the first diode is connected to the time-sharing detection pin; or the cathode of the first diode is connected to the same-name end of the auxiliary winding, and the anode of the first diode is connected to the time-sharing detection pin through the first resistor.

6. A time-sharing detection control method, characterized in that: The time-sharing detection control method can use the same time-sharing detection pin to implement input voltage detection and functional resistance detection for the isolated converter; The isolated converter comprises a primary winding, a secondary winding, an auxiliary winding, a power tube, a first resistor, a first diode and a functional resistor, wherein the opposite-name end of the primary winding is connected to the input voltage, and the same-name end thereof is connected to the ground level after passing through the power tube; the opposite-name end of the auxiliary winding is connected to the ground level, and the same-name end thereof is connected to one end of the functional resistor and the time-sharing detection pin after passing through the series structure of the first resistor and the first diode, and the other end of the functional resistor is connected to the ground level; The time-sharing detection control method includes control when the power tube is turned on and control when the power tube is turned off: When the power tube is turned on, the voltage at the same-name end of the auxiliary winding is proportional to the input voltage and can control the first diode to be forward-conducted. At this time, the potential of the time-sharing detection pin is clamped to a first clamping level. When the first clamping level is set as close to zero as possible, the current of the time-sharing detection pin is only proportional to the input voltage, and the information of the input voltage can be directly obtained by detecting the current of the time-sharing detection pin; when the first clamping level is set to other voltage values, it is necessary to subtract the current of the functional resistor from the detected current of the time-sharing detection pin and then convert it into the information of the input voltage, wherein the current of the functional resistor is determined according to the first clamping level and the resistance value of the functional resistor; When the power tube is disconnected, the voltage at the same end of the auxiliary winding can control the reverse cutoff of the first diode, so that the time-sharing detection pin is grounded only through the functional resistor. At this time, the time-sharing detection pin is controlled to have a constant voltage or a constant current, and the information of the functional resistor can be obtained by detecting the corresponding changing current or voltage at the time-sharing detection pin.

7. The time-sharing detection control method according to claim 6, characterized in that: When the power tube is disconnected, the information of the functional resistance is obtained by method one or method two; Method 1: Using a constant current source to provide a first current to the time-sharing detection pin, the potential of the time-sharing detection pin is the product of the current value of the first current and the resistance value of the functional resistor, and the potential of the time-sharing detection pin is compared with a reference comparison voltage to obtain information of the functional resistor; Method 2: Clamp the potential of the time-sharing detection pin to a second clamping level, and obtain the information of the functional resistance by detecting the current of the time-sharing detection pin.

8. The time-sharing detection control method according to claim 6 or 7, characterized in that: After the power tube state is switched, detection is performed after a set blanking time has passed.

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