Synchronous rectification chip pin multiplexing technology

Abstract

The switching power supply, synchronous rectification chip, and protocol chip are related to the field of power electronics. The switching power supply includes a protocol circuit installed on the secondary side of the switching power supply for detecting the power supply demand of the load equipment, a synchronous rectification circuit installed on the secondary side of the switching power supply for controlling the rectification power transistor, and a signal transmission circuit installed between the protocol circuit and the synchronous rectification circuit for transmitting signals. From this, it can be seen that the switching power supply of the present application can realize communication between the synchronous rectification circuit and the protocol circuit by constructing a signal transmission circuit, and thereby control the operating mode of the synchronous rectification circuit based on the power supply demand of the load equipment detected by the protocol circuit, improving the communication between the chips of the switching power supply and further reducing the power consumption of the switching power supply.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and particularly to switching power supplies, synchronous rectification chips, and protocol chips.

Background Art

[0002] In the prior art, a switching power supply can adopt a synchronous rectification transistor instead of a diode in the secondary circuit of a flyback converter, thereby effectively reducing the conduction loss of the secondary diode and further improving the conversion efficiency of the system. To meet the application requirements of various systems and realize user-customizable programming, a synchronous rectification circuit generally has one input terminal for setting a threshold value, which is the criterion for determining the conduction of the synchronous rectification transistor. The main function of the protocol circuit is to detect the internal protocol of the charging facility under the protocol frame according to the difference in chargers, and output appropriate voltage and current to the switching power supply based on the load connected to the switching power supply.

[0003] Currently, in the prior art, communication cannot be carried out between the synchronous rectification circuit and the protocol circuit. Therefore, the operating mode of the synchronous rectification chip cannot be adjusted according to the load situation of the load to which the protocol circuit is connected. As a result, there is no information exchange between the two chips, and the standby power of the switching power supply cannot be further reduced.

Summary of the Invention

[0004] The objective of this application is to provide a switching power supply, a synchronous rectification chip, and a protocol chip. By constructing a signal transmission circuit, communication between the synchronous rectification circuit and the protocol circuit is realized. Thereby, based on the power supply demand of the load equipment detected by the protocol circuit, the operating mode of the synchronous rectification circuit is controlled, improving the communication between the chips of the switching power supply and further reducing the power consumption of the switching power supply.

[0005] In order to solve the above technical problems, the present application provides a switching power supply including: a protocol circuit installed on the secondary side of the switching power supply for detecting the power supply demand of the load equipment; a synchronous rectification circuit installed on the secondary side of the switching power supply for controlling the rectification power transistor; a signal transmission circuit installed between the protocol circuit and the synchronous rectification circuit for transmitting signals.

[0006] Preferably, the signal transmission circuit includes a switching circuit and a signal identification circuit. The input end of the switching circuit is connected to the protocol circuit, the output end of the switching circuit is connected to the input end of the signal identification circuit, and the output end of the signal identification circuit is connected to the synchronous rectification circuit. The switching circuit adjusts its own switching state based on the detection result output by the protocol circuit and is used to output a power supply demand signal. The signal identification circuit outputs a control signal to the synchronous rectification circuit based on the power supply demand signal output by the switching circuit and is used to affect the operating mode of the synchronous rectification circuit.

[0007] Preferably, the switching circuit includes a controllable switching transistor. The control end of the controllable switching transistor is the input end of the switching circuit, and the output end of the controllable switching transistor is the output end of the switching circuit.

[0008] Preferably, when the controllable switching transistor is an NMOS, the gate of the NMOS is the control end of the controllable switching transistor, the source of the NMOS is the output end of the controllable switching transistor, and the drain of the NMOS is grounded.

[0009] Preferably, an impedance element is further installed between the switching circuit and the signal identification circuit.

[0010] Preferably, when the power supply demand signal is a voltage signal or a current signal, the signal identification circuit includes a comparison circuit, a first input terminal of the comparison circuit is connected to an output terminal of the switching circuit, a second input terminal of the comparison circuit is connected to a reference voltage output device or a reference current output device, and an output terminal of the comparison circuit is connected to the synchronous rectification circuit, the comparison circuit compares the voltage at the output terminal of the switching circuit with a reference voltage or compares the current at the output terminal of the switching circuit with a reference current, and outputs the control signal to the synchronous rectification circuit based on the comparison result, and is used to affect the operating mode of the synchronous rectification circuit.

[0011] Preferably, the comparison circuit is a comparator, a first input terminal of the comparator is the first input terminal of the comparison circuit, a second input terminal of the comparator is the second input terminal of the comparison circuit, and an output terminal of the comparator is the output terminal of the comparison circuit.

[0012] Preferably, the comparison circuit further includes a current source, a first input terminal of the comparison circuit is also connected to the current source, and a second input terminal of the comparison circuit is connected to the reference voltage output device, specifically, the comparison circuit compares the voltage at the output terminal of the switching circuit with the reference voltage, and outputs the control signal to the synchronous rectification circuit based on the comparison result, and is used to affect the operating mode of the synchronous rectification circuit.

[0013] Preferably, the comparison circuit further includes a current mirror, an input terminal of the current mirror is connected to an output terminal of the switching circuit, an output terminal of the current mirror is connected to a first input terminal of the comparison circuit, a second input terminal of the comparison circuit is connected to the reference current output device, and a preset ratio is set in advance in the current mirror, Specifically, the comparison circuit compares the current at the output end of the switching circuit with the reference current, and outputs the control signal to the synchronous rectification circuit based on the comparison result, and is used to affect the operating mode of the synchronous rectification circuit.

[0014] In order to solve the above technical problems, the present application further provides a synchronous rectification chip applied to the secondary side of a switching power supply including a protocol chip. The synchronous rectification chip includes a control pin for controlling the conduction and cutoff of the rectifying power transistor based on an input signal, and a receiving pin connected to the protocol chip, receiving a power supply demand signal characterizing the load equipment of the switching power supply, and used to affect the operating mode of the synchronous rectification chip.

[0015] Preferably, the receiving pin is connected to an external impedance element.

[0016] Preferably, the synchronous rectification chip further includes a signal identification circuit, The signal identification circuit identifies the received power supply demand signal and is used to affect the operating mode of the synchronous rectification chip based on the power supply demand signal.

[0017] Preferably, when the power supply demand signal is a voltage signal or a current signal, the signal identification circuit includes a comparison circuit, The first input end of the comparison circuit is connected to the output end of the switching circuit, the second input end of the comparison circuit is connected to a reference voltage output device or a reference current output device, and the output end of the comparison circuit is connected to the control pin, The comparison circuit compares the voltage at the output end of the switching circuit with the reference voltage, or compares the current at the output end of the switching circuit with the reference current, outputs the control signal to the synchronous rectification circuit based on the comparison result, and is used to affect the operating mode of the synchronous rectification chip.

[0018] Preferably, the comparison circuit is a comparator, the first input terminal of the comparator is the first input terminal of the comparison circuit, the second input terminal of the comparator is the second input terminal of the comparison circuit, and the output terminal of the comparator is the output terminal of the comparison circuit.

[0019] Preferably, the comparison circuit further includes a current source, the first input terminal of the comparison circuit is also connected to the current source, the second input terminal of the comparison circuit is connected to the reference voltage output device, specifically, the comparison circuit compares the voltage at the output terminal of the switching circuit with the reference voltage, and outputs the control signal to the control pin based on the comparison result, and is used to affect the operating mode of the synchronous rectification circuit.

[0020] Preferably, the comparison circuit further includes a current mirror, the input terminal of the current mirror is connected to the output terminal of the switching circuit, the output terminal of the current mirror is connected to the first input terminal of the comparison circuit, the second input terminal of the comparison circuit is connected to the reference current output device, and a preset ratio is set in the current mirror in advance, specifically, the comparison circuit compares the current at the output terminal of the switching circuit with the reference current, and outputs the control signal to the control pin based on the comparison result, and is used to affect the operating mode of the synchronous rectification circuit.

[0021] In order to solve the above technical problems, the present application further provides a protocol chip applied to the secondary side of a switching power supply having a synchronous rectification chip. The protocol chip includes a detection pin for detecting the power supply demand of the load equipment, and an output pin for transmitting the power supply demand signal to the synchronous rectification chip to affect the operating mode of the synchronous rectification chip.

[0022] Preferably, the protocol chip further includes a switching circuit and a detection circuit, The input terminal of the switching circuit is connected to the detection circuit, and the output terminal of the switching circuit is connected to the output pin. The switching circuit is used to adjust its own switching state based on the detection result output by the detection circuit and output the power supply demand signal through the output pin.

[0023] Preferably, the switching circuit includes a controllable switching transistor. The control terminal of the controllable switching transistor is connected to the detection pin, and the output terminal of the controllable switching transistor is connected to the output pin.

[0024] In order to solve the above technical problems, the present application further provides a switching power supply including a protocol chip as described above, and a synchronous rectification chip as described above.

[0025] Preferably, an impedance element is installed between the output pin of the protocol chip and the receiving pin of the synchronous rectification chip.

[0026] The present application provides a switching power supply, a synchronous rectification chip, and a protocol chip, which relate to the technical field of power electronics. The switching power supply includes a protocol circuit installed on the secondary side of the switching power supply for detecting the power supply demand of the load equipment, a synchronous rectification circuit installed on the secondary side of the switching power supply for controlling the rectifying power transistor, and a signal transmission circuit installed between the protocol circuit and the synchronous rectification circuit for transmitting signals. From this, it can be seen that the switching power supply of the present application can realize communication between the synchronous rectification circuit and the protocol circuit by constructing a signal transmission circuit, thereby controlling the operating mode of the synchronous rectification circuit based on the power supply demand of the load equipment detected by the protocol circuit to enter the sleep mode and turning off most of the power consumption modules, so as to reduce the power consumption of the switching power supply. At the same time, since the signal transmission circuit uses the original synchronous rectification chip as a pin for setting the conduction determination criterion of the rectifying power transistor, there is no need to add additional chip pins.

[0027] In order to more clearly explain the technical methods in the embodiments of the present application, the following briefly introduces the drawings that need to be used in the prior art and the embodiments. However, the drawings in the following description are only some embodiments of the present application. It is obvious that those skilled in the art can obtain other drawings based on these drawings on the premise of not performing creative labor.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0029] The core of this application is to provide a switching power supply, a synchronous rectification chip and a protocol chip, and by constructing a signal transmission circuit, communication between the synchronous rectification circuit and the protocol circuit can be realized. Thereby, based on the power supply demand of the load equipment detected by the protocol circuit, the operation mode of the synchronous rectification circuit can be controlled, the communication between the chips of the switching power supply can be improved, and the power consumption of the switching power supply can be further reduced.

[0030] To make the objectives, technical means and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical means in the embodiments of this application in conjunction with the drawings in the embodiments of this application. It is obvious that the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained on the premise that those skilled in the art do not perform creative labor belong to the protection scope of this application.

[0031] In the prior art, since communication cannot be carried out between the synchronous rectification circuit 11 and the protocol circuit 12, the conduction state of the synchronous rectification transistor in the synchronous rectification circuit 11 cannot be adjusted based on the load situation connected to the protocol circuit 12. Therefore, the smartening of the switching power supply is delayed and the power consumption is also quite large.

[0032] To solve the above technical problems, the present application provides a switching power supply. Referring to FIG. 1, FIG. 1 is a block diagram of the switching power supply provided in the present application. The switching power supply includes a protocol circuit 12 installed on the secondary side of the switching power supply for detecting the power supply demand of the load equipment, and a synchronous rectification circuit 11 installed on the secondary side of the switching power supply for controlling the rectification power transistor, and a signal transmission circuit 13 installed between the protocol circuit 12 and the synchronous rectification circuit 11 for transmitting signals.

[0033] In the prior art, communication cannot be carried out between the synchronous rectification circuit 11 and the protocol circuit 12. Therefore, the operation mode of the synchronous rectification chip cannot be adjusted based on the load situation. As a result, there is no information exchange between the two chips, and the standby power of the switching power supply cannot be further reduced.

[0034] The object of the present invention is to provide a switching power supply with ultra-low standby power. By installing the protocol circuit 12 on the secondary side, the power supply demand of the load equipment is detected, and the related information is transmitted to the synchronous rectification circuit 11 by the signal transmission circuit 13, thereby realizing the adjustment of the operation mode of the synchronous rectification circuit 11, and achieving the effects of energy saving and power consumption reduction.

[0035] Specifically, in this embodiment, a combination of three components, namely a protocol circuit 12, a synchronous rectification circuit 11, and a signal transmission circuit 13, is adopted, and they are effectively connected to achieve optimal control of the smart switching power supply. The protocol circuit 12 detects the power supply demand of the load equipment and realizes the adjustment of the operation mode of the synchronous rectification circuit 11 by transmitting information to the synchronous rectification circuit 11 through the signal transmission circuit 13. The key point of the present invention is to realize the smart control of the synchronous rectification circuit 11 for the power supply demand of the load equipment through the protocol circuit 12 and the signal transmission circuit 13. When the power supply demand of the load equipment changes, the protocol circuit 12 detects the change and transmits information to the signal transmission circuit 13, and the signal transmission circuit 13 transmits the information to the synchronous rectification circuit 11. In the synchronous rectification circuit 11, the operation mode is adjusted based on the received information, and the energy utilization efficiency is optimized, thereby achieving the effects of energy saving and power consumption reduction.

[0036] The specific implementation form of this embodiment is as follows. The protocol circuit 12 is installed on the secondary side of the switching power supply, and the protocol circuit 12 and the synchronous rectification circuit 11 are connected by the signal transmission circuit 13. The protocol circuit 12 detects the power supply demand of the load equipment and transmits information to the synchronous rectification circuit 11 through the signal transmission circuit 13 to realize the adjustment of the operation mode. Thereby, in various loads, by realizing the smart control of the synchronous rectification circuit and the entire switching power supply, the energy utilization efficiency can be optimized, and the effects of energy saving and power consumption reduction can be achieved.

[0037] In a specific embodiment, when the protocol circuit 12 detects the connection of the load device, the first signal is transmitted by the signal transmission circuit 13 to the synchronous rectification circuit 11. When the synchronous rectification circuit 11 detects this first signal, the switching power supply adjusts itself to the burst mode. When the protocol circuit 12 detects the disconnection of the load, a second signal is transmitted to the synchronous rectification circuit 11 through the signal transmission circuit 13. When the synchronous rectification circuit 11 detects this second signal, the switching power supply adjusts itself to the sleep mode. Among them, the first signal and the second signal can refer to two different level signals. Of course, the switching power supply also has an operating mode in normal operation. It can be understood that when the above sleep mode is in a state where the synchronous rectification circuit 11 is in an ultra standby state, most of the energy consumption modules are turned off to achieve zero milliwatt standby.

[0038] As described above, in this embodiment, a protocol circuit 12 is added to the secondary side of the switching power supply and connected to the synchronous rectification circuit 11 through the signal transmission circuit 13 to form a new information transmission channel, so that smart control of the entire synchronous rectification circuit and switching power supply can be realized, the energy utilization efficiency of the switching power supply can be improved, the effects of energy saving and power consumption reduction can be realized, and it has quite high practicality and economic effects.

[0039] Referring to FIG. 2, FIG. 2 is a specific configuration block diagram of the switching power supply provided in the present application.

[0040] As a preferred embodiment, the signal transmission circuit 13 includes a switching circuit 22 and a signal identification circuit 21. The input end of the switching circuit 22 is connected to the protocol circuit 12, the output end of the switching circuit 22 is connected to the input end of the signal identification circuit 21, and the output end of the signal identification circuit 21 is connected to the synchronous rectification circuit 11. The switching circuit 22 adjusts its switching state based on the detection result output by the protocol circuit 12 and is used to output a power supply demand signal. The signal identification circuit 21 outputs a control signal to the synchronous rectification circuit 11 based on the power supply demand signal output by the switching circuit 22, and is used to affect the operation mode of the synchronous rectification circuit 11.

[0041] Specifically, in the above embodiment, it is proposed to add one signal transmission circuit 13 between the protocol circuit 12 and the synchronous rectification circuit 11. In this embodiment, this signal transmission circuit 13 realizes communication between the protocol circuit 12 and the synchronous rectification circuit 11 through the switching circuit 22 and the signal identification circuit 21.

[0042] Specifically, in this embodiment, the protocol circuit 12 transmits the power supply demand signal to the switching circuit 22 by detecting the power supply demand of the load equipment. The switching circuit 22 receives the power supply demand signal, outputs the power supply demand signal by adjusting the switching state, the signal identification circuit 21 receives the power supply demand signal, converts it into a control signal, and transmits the control signal to the synchronous rectification circuit 11. The synchronous rectification circuit 11 realizes smart control by adjusting its own operation mode based on the control signal.

[0043] As described above, in this embodiment, by adding the signal transmission circuit 13 to enable communication between the protocol circuit 12 and the synchronous rectification circuit 11, the degree of smartness of the switching power supply is increased. At the same time, since the synchronous rectification circuit 11 can adjust its own operation mode based on the load situation, energy conservation and power consumption reduction can be further promoted.

[0044] Referring to FIG. 3, FIG. 3 is a schematic diagram of the switching circuit provided in the present application.

[0045] As a preferred embodiment, the switching circuit 22 includes a controllable switching transistor 301. The control end of the controllable switching transistor 301 is the input end of the switching circuit 22, and the output end of the controllable switching transistor 301 is the output end of the switching circuit 22.

[0046] Specifically, in order to reduce the cost of the switching circuit 22, a controllable switching transistor 301 such as a MOS transistor or a triode can be selected as a specific implementation form for the switching circuit 22, but it is not limited in the present application. The controllable switching transistor 301 usually includes at least one control terminal (the control terminal of the controllable switching transistor 301 is not depicted in FIG. 3), and the protocol circuit 12 specifically adjusts the operating state of the controllable switching transistor 301 through the control terminal based on the connection state of the load (specifically, it may be to adjust the operating state of the controllable switching transistor 301 by the drive voltage of the control terminal of the controllable switching transistor 301).

[0047] As a preferred embodiment, when the controllable switching transistor 301 is an NMOS, the gate of the NMOS is the control terminal of the controllable switching transistor 301, the source of the NMOS is the output terminal of the controllable switching transistor 301, and the drain of the NMOS is grounded.

[0048] In a specific embodiment, the controllable switching transistor 301 may be an NMOS. In this case, the protocol circuit 12 adjusts the on / off state of the NMOS through the gate of the NMOS transistor. Specifically, when the gate of the NMOS receives a high voltage level signal, it controls itself to turn on, and when it does not, it controls itself to turn off. Correspondingly, when the drain of the NMOS is grounded, when the NMOS turns on, the output terminal of the controllable switching transistor 301 outputs a low voltage level, and when it does not, the output terminal of the controllable switching transistor 301 outputs a high voltage level. Using the NMOS as a specific implementation form of the controllable switching transistor 301 can reduce the cost and is also easy to implement.

[0049] Referring to FIG. 4, FIG. 4 is a specific circuit schematic diagram of the switching power supply provided in the present application.

[0050] As a preferred embodiment, an impedance element (RX_D in FIG. 4) for setting a determination criterion for conduction of the rectifying power transistor is further provided between the switching circuit 22 and the signal discrimination circuit 21.

[0051] Furthermore, considering that the switching circuit 22 and the signal discrimination circuit 21 are directly connected, if the output terminal of the switching circuit 22 floats in the air, the input terminal of the signal discrimination circuit 21 will float in the air. Therefore, in this embodiment, an impedance element is installed between both ends to prevent the input terminal of the signal discrimination circuit 21 from floating in the air. Among them, the impedance element may be an electrical resistance such as an adjustment resistor, and is used to set a determination criterion for conduction of the rectifying power transistor.

[0052] As a preferred embodiment, when the power supply demand signal is a voltage signal or a current signal, the signal discrimination circuit 21 includes a comparison circuit. The first input terminal of the comparison circuit is connected to the output terminal of the switching circuit 22, the second input terminal of the comparison circuit is connected to a reference voltage output device or a reference current output device, and the output terminal of the comparison circuit is connected to the synchronous rectification circuit 11. The comparison circuit compares the voltage at the output terminal of the switching circuit 22 with a reference voltage, or compares the current at the output terminal of the switching circuit 22 with a reference current, and outputs a control signal to the synchronous rectification circuit 11 based on the comparison result, and is used to affect the operation mode of the synchronous rectification circuit 11.

[0053] Specifically, the specific implementation form of the signal discrimination circuit 21 is based on a comparison circuit, which compares the difference between the signal output by the switching circuit 22 and a reference voltage or a reference current, and outputs a control signal to the synchronous rectification circuit 11, thereby affecting the operation mode of the synchronous rectification circuit 11.

[0054] In actual circuit design, it can be realized by using various devices such as operational amplifiers, analog-to-digital converters, and digital signal processors, so as to improve the detection accuracy and stability.

[0055] As a preferred embodiment, the comparison circuit is a comparator 401. The first input terminal of the comparator 401 is the first input terminal of the comparison circuit, the second input terminal of the comparator 401 is the second input terminal of the comparison circuit, and the output terminal of the comparator 401 is the output terminal of the comparison circuit.

[0056] Specifically, the principle of the comparison circuit is to compare two input signals and output a control signal based on the comparison result. In this switching power supply, the comparison circuit is used to adjust the operating mode of the synchronous rectification circuit 11 by comparing the relationship between the voltage or current at the output terminal of the switching circuit 22 and the magnitude of the reference voltage or current.

[0057] That is, the specific implementation form of the comparison circuit may be a comparator 401. In this case, a reference voltage or reference current is input to the second input terminal. When a reference voltage is input to the second input terminal of the comparator 401, the voltage input to the first input terminal is compared with the reference voltage. When the voltage at the first input terminal is greater than the reference voltage, a first voltage level is output. When the voltage at the first input terminal is less than the reference voltage, a second voltage level is output. When a reference current is input to the second input terminal of the comparator 401, the current input to the first input terminal is compared with the reference current. When the current at the first input terminal is greater than the reference current, a first voltage level is output. When the current at the first input terminal is less than the reference current, a second voltage level is output. Among them, the first voltage level and the second voltage level are opposite to each other.

[0058] In this way, based on the output signal of the switching circuit 22, it is possible to determine whether it conforms to the expected level, thereby affecting the operating mode of the synchronous rectification circuit 11.

[0059] In addition to the basic comparator 401, the comparison circuit can also be extended and realized by adding a reference circuit, a filter circuit, etc. At the same time, the comparison result can be further processed using digital signal processing technology to achieve a more accurate and reliable control effect, but it is not limited in this application.

[0060] Referring to FIG. 5, FIG. 5 is a schematic diagram of the signal discrimination circuit provided in the present application.

[0061] As a preferred embodiment, the comparison circuit further includes a current source 402. The first input terminal of the comparison circuit is also connected to the current source 402, and the second input terminal of the comparison circuit is connected to the reference voltage output device. Specifically, the comparison circuit is used to compare the voltage at the output terminal of the switching circuit 22 with the reference voltage, and based on the comparison result, output a control signal to the synchronous rectification circuit 11 to affect the operation mode of the synchronous rectification circuit 11.

[0062] In the design of the switching power supply, it is necessary to compare the voltage or current to affect the operation mode of the synchronous rectification circuit 11. Regarding the technical methods to achieve the comparison, in the conventional methods, a resistor divider or an operational amplifier is used, but these methods have problems such as low accuracy, large noise, and large temperature drift, which affect the performance of the entire switching power supply.

[0063] To solve the above problems, the comparison circuit uses the current source 402 to achieve the comparison, that is, the voltage and current to be compared are converted into current for comparison. By doing so, the accuracy of the comparison can be improved, and the influence of noise and temperature drift on the comparison result can be reduced.

[0064] The role of the current source 402 is to convert the comparison object into current, compare the difference in the magnitude of the current to determine which is larger, and output the corresponding control signal. The specific implementation form generally is to apply the power supply voltage to a constant current source, and further connect the voltage or current to be compared in series with the constant current source, and obtain the corresponding comparison voltage or current based on Ohm's law.

[0065] Specifically, referring to FIG. 5, the comparison circuit includes a current source 402. The first input terminal of the comparator 401 is the input negative terminal, which is connected to the output terminal of the current source 402. Rx (i.e., the input terminal of the signal discrimination circuit 21) is connected to a resistor RX_D. The second input terminal of the comparator 401 is connected to a reference voltage output device. The reference voltage is VREF, the current output by the current source 402 is I_RX, and the comparison result of the comparator 401 is Y_Sleep.

[0066] The current I_RX output by the internal current source 402 outputs current from the first preset pin RX, passes through the external resistor RX_D of the synchronous rectification circuit 11, and further reaches the ground terminal through the controllable switching transistor 301K_Sleep connected to the protocol circuit 12. When the voltage of the Rx pin is higher than VREF, the synchronous rectification circuit 11 is controlled to enter the sleep mode. When the voltage of the Rx pin is lower than VREF, the synchronous rectification circuit 11 is controlled to exit the sleep mode and enter the normal operation mode.

[0067] In a specific embodiment, to ensure the certainty of the synchronous rectification circuit 11 entering the adjustment of the operation mode, the synchronous rectification circuit 11 can also adjust its own operation mode after detecting that the change in the control signal persists for a preset time. In this embodiment, after detecting that the voltage of the Rx pin is higher than VREF for a preset time, the synchronous rectification circuit 11 is controlled to enter the sleep mode. After detecting that the voltage of the Rx pin is lower than VREF for a preset time, the synchronous rectification circuit is controlled to exit the sleep mode and enter the normal operation mode.

[0068] Due to the delay of this preset time, it can be ensured that the synchronous rectification circuit 11 reliably adjusts its operation mode, and it can be avoided that the synchronous rectification circuit 11 frequently switches its operation mode due to external interference.

[0069] Referring to FIG. 6, FIG. 6 is a schematic diagram of another signal discrimination circuit provided in the present application.

[0070] As a preferred embodiment, the comparison circuit further includes a current mirror 501, the input terminal of the current mirror 501 is connected to the output terminal of the switching circuit 22, the output terminal of the current mirror 501 is connected to the first input terminal of the comparison circuit, the second input terminal of the comparison circuit is connected to the reference current output device, and a preset ratio is set in advance in the current mirror 501. Specifically, the comparison circuit is used to compare the current at the output terminal of the switching circuit 22 with the reference current, and output a control signal to the synchronous rectification circuit 11 based on the comparison result, so as to affect the operation mode of the synchronous rectification circuit.

[0071] Considering that the conventional comparison circuit uses a resistor as the current source 402, the stability and accuracy of the current source 402 are affected by factors such as temperature, resulting in comparison errors and inaccurate output of control signals.

[0072] In this embodiment, by using the current mirror 501 as the current source 402 in the comparison circuit, the stability and accuracy of the current source 402 are improved, thereby improving the comparison accuracy and control accuracy. The current mirror 501 is a current source 402 circuit based on MOSFET transistors, has high accuracy and stability, and can realize the required current output by adjusting the mirror ratio.

[0073] Specifically, referring to FIG. 6, FIG. 6 is a schematic diagram of another specific implementation form of the comparison circuit provided in the present application. In FIG. 6, the comparison circuit includes a current mirror 501. The first input terminal of the comparator 401 is the input negative terminal and is connected to the output terminal of the current mirror 501. Rx (the input terminal of the signal identification circuit 21) is connected to the input terminal of the current mirror 501, and Rx is further connected to the resistor RX_D. The second input terminal of the comparator 401 is connected to the reference current output device. The reference current is IREF, the input current of the current mirror 501 is I_RX, and the output current of the current mirror 501 is I_Mirror. There is a preset ratio between I_Mirror and I_RX, and the comparison result of the comparator 401 is Y_Sleep.

[0074] RX is connected to the peripheral impedance element (RX_D), detects the current I_RX of the RX pin, and after converting the current by the current mirror 501 to a preset ratio, outputs I_Mirror. If the I_Mirror current is smaller than IREF, it enters the sleep mode. If the I_Mirror current is larger than IREF, it exits the sleep mode and enters the normal operation mode.

[0075] Similarly, when it is detected that the I_Mirror current is smaller than IREF for a preset time, it enters the sleep mode. When it is detected that the I_Mirror current is larger than IREF for a preset time, it can also exit the sleep mode and enter the normal operation mode.

[0076] Due to the delay of this preset time, it is guaranteed that the synchronous rectification circuit 11 can surely adjust the operation mode, and it is possible to avoid the synchronous rectification circuit 11 frequently switching the operation mode due to external interference.

[0077] In order to solve the above technical problems, the present application further provides a synchronous rectification chip. Referring to FIGS. 7 and 8, FIG. 7 is a schematic diagram of a synchronous rectification chip in the prior art, and FIG. 8 is a schematic diagram of the synchronous rectification chip provided in the present application. The synchronous rectification chip shown in FIG. 7 includes an internal power supply module for converting the primary side output Vdet into VOUT and VDD. The primary side state detection circuit detects the primary side output state and is used to output the result to the rectifier power transistor control circuit to affect the conduction and cutoff of the rectifier power transistor. Rx is a receiving pin. In the prior art, a synchronous rectification conduction determination criterion setting circuit sets one threshold value, and when the input value of this Rx pin reaches this threshold value, the conduction of the rectifier switching transistor is triggered. The synchronous rectification chip provided in the present application is applied to the secondary side of a switching power supply including a protocol chip. The synchronous rectification chip a control pin DRV for controlling the conduction and cutoff of the rectifier power transistor based on the input signal, and It is connected to a protocol chip, receives a power supply demand signal characterizing a load device of a switching power supply, and includes a receiving pin Rx for affecting the operating mode of the synchronous rectification chip.

[0078] As a preferred embodiment, the synchronous rectification chip further includes a signal identification circuit 21. The signal identification circuit 21 is used to identify the received power supply demand signal and affect the operating mode of the synchronous rectification chip based on the power supply demand signal.

[0079] As a preferred embodiment, when the power supply demand signal is a voltage signal or a current signal, the signal identification circuit 21 includes a comparison circuit. The first input terminal of the comparison circuit is connected to the output terminal of the switching circuit 22, the second input terminal of the comparison circuit is connected to a reference voltage output device or a reference current output device, and the output terminal of the comparison circuit is connected to the control pin DRV. The comparison circuit compares the voltage at the output terminal of the switching circuit 22 with a reference voltage or compares the current at the output terminal of the switching circuit 22 with a reference current, and outputs a control signal to the synchronous rectification circuit 11 based on the comparison result, and is used to affect the operating mode of the synchronous rectification chip.

[0080] As a preferred embodiment, the comparison circuit is a comparator 401, the first input terminal of the comparator 401 is the first input terminal of the comparison circuit, the second input terminal of the comparator 401 is the second input terminal of the comparison circuit, and the output terminal of the comparator 401 is the output terminal of the comparison circuit.

[0081] As a preferred embodiment, the comparison circuit further includes a current source 402. The first input terminal of the comparison circuit is also connected to the current source 402, and the second input terminal of the comparison circuit is connected to a reference voltage output device. Specifically, the comparison circuit compares the voltage at the output terminal of the switching circuit 22 with a reference voltage, and outputs a control signal to the control pin DRV based on the comparison result, and is used to affect the operating mode of the synchronous rectification chip.

[0082] As a preferred embodiment, the comparison circuit further includes a current mirror 501, The input terminal of the current mirror 501 is connected to the output terminal of the switching circuit 22, the output terminal of the current mirror 501 is connected to the first input terminal of the comparison circuit, the second input terminal of the comparison circuit is connected to the reference current output device, and a preset ratio is set in the current mirror 501 in advance. Specifically, the comparison circuit compares the current at the output terminal of the switching circuit 22 with the reference current, and outputs a control signal to the control pin DRV based on the comparison result, and is used to affect the operation mode of the synchronous rectification chip.

[0083] The pins of the synchronous rectification chip are the same as the pins in the prior art, and all can be used as pins for setting the conduction determination criteria of the rectifying power transistor. That is, in this embodiment, the original Rx pin is reused, so there is no need to add chip pins. The difference is that a signal identification circuit 21 connected to the Rx pin is installed inside the synchronous rectification chip. Among them, devices such as comparators and current sources required by the signal identification circuit 21 can reuse other standby devices inside the synchronous rectification chip, but this application does not limit it.

[0084] For other descriptions of the synchronous rectification chip, reference may be made to the above embodiments, so this application will not repeat them.

[0085] To solve the above technical problems, this application further provides a protocol chip. Referring to FIGS. 9 and 10, FIG. 9 is a schematic diagram of a protocol chip in the prior art, and FIG. 10 is a schematic diagram of the protocol chip provided in this application.

[0086] The protocol chip in the prior art includes several parts as follows, namely, a constant current / constant voltage control circuit for controlling the stability of the output voltage and current and ensuring that the output voltage and current are always maintained within the set range, a digital control circuit for communicating with the power management device, transmitting a control signal to the power management device based on different input voltage, output voltage, and current requirements, and adjusting the output voltage and current to achieve power control and management, and a USB type-C protocol / QC protocol for supporting multiple types of fast charging protocols, controlling the output voltage and current based on different protocols, and realizing fast charging and equipment protection. Further, it includes a plurality of pins, among which the VOUT pin is an output voltage control pin for performing voltage control by feeding back the output voltage level to the control circuit through this pin, the OCDRV pin is an opto-coupled drive pin for transmitting the secondary-side load information of the switching power supply to the primary-side control chip and used to realize the output control of the power supply, the CC1 / CC2 pins are used for transmitting the signals of the type C interface and identifying the equipment, identifying the type and requirements of the equipment through the CC signal line to perform protocol matching and fast charging control, and the DP / DN pins are used for high-speed data transmission at the type C interface.

[0087] The protocol chip in this application is applied to the secondary side of a switching power supply having a synchronous rectification chip, and the protocol chip includes a detection pin for detecting the power supply requirement of the load equipment, and an output pin SL for transmitting the power supply requirement signal to the synchronous rectification chip to affect the operating mode of the synchronous rectification chip.

[0088] As a preferred embodiment, the protocol chip further includes a switching circuit 22 and a detection circuit, the input end of the switching circuit 22 is connected to the detection circuit, and the output end of the switching circuit 22 is connected to the output pin SL, and the switching circuit 22 is used to adjust its own switching state based on the detection result output by the detection circuit and output the power supply requirement signal through the output pin SL.

[0089] As a preferred embodiment, the switching circuit 22 includes a controllable switching transistor 301. The control terminal of the controllable switching transistor 301 is connected to a detection pin, and the output terminal of the controllable switching transistor 301 is connected to an output pin SL.

[0090] Among them, the protocol chip of the present application re-uses the output pin SL. By detecting whether a load is connected by the USB / Cable connection detection circuit 302, a control signal is output to control 301, and a power supply demand signal is output to the SL pin.

[0091] For other descriptions of the protocol chip, reference may be made to the above embodiments, and thus they will not be repeatedly described in the present application.

[0092] In order to solve the above technical problems, the present application further provides a switching power supply including the above protocol chip and the above synchronous rectification chip.

[0093] As a preferred embodiment, an impedance element is installed between the output pin SL of the protocol chip and the receiving pin Rx of the synchronous rectification chip. That is, the synchronous rectification chip also uses the pin Rx that was originally used to set the conduction determination criterion of the rectifying power transistor, so there is no need to add chip pins.

[0094] For other descriptions of the switching power supply, reference may be made to the above embodiments, and thus they will not be repeatedly described in the present application.

[0095] It should be further noted that in this specification, relational terms such as "first", "second", etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any substantial relationship or order between these entities or operations. Also, the term "comprising", "including" or any other variation thereof covers non-exclusive inclusion, so that a process, method, article or apparatus comprising a series of elements contains not only those elements but also other elements not expressly listed, or elements specific to that kind of process, method, article or apparatus. In the absence of further limitations, an element limited by the phrase "comprising one..." does not exclude the presence of further identical elements in the process, method, article or apparatus comprising the said element.

[0096] The foregoing description of the disclosed embodiments is intended to enable a person skilled in the art to make or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. In a switching power supply, a protocol circuit installed on the secondary side of the switching power supply for detecting the power supply demand of a load device; a synchronous rectification circuit installed on the secondary side of the switching power supply for controlling a rectifier power transistor; and a signal transmission circuit installed between the protocol circuit and the synchronous rectification circuit for transmitting signals, characterized by comprising: a switching power supply.

2. The signal transmission circuit includes a switching circuit and a signal identification circuit. The input end of the switching circuit is connected to the protocol circuit, the output end of the switching circuit is connected to the input end of the signal identification circuit, and the output end of the signal identification circuit is connected to the synchronous rectification circuit. The switching circuit is used to adjust its own switching state based on the detection result output by the protocol circuit and output a power supply demand signal. The signal identification circuit is used to output a control signal to the synchronous rectification circuit based on the power supply demand signal output by the switching circuit and affect the operating mode of the synchronous rectification circuit, characterized by: The switching power supply according to Claim 1.

3. The switching circuit includes a controllable switching transistor. The control end of the controllable switching transistor is the input end of the switching circuit, and the output end of the controllable switching transistor is the output end of the switching circuit, characterized by: The switching power supply according to Claim 2.

4. When the controllable switching transistor is an NMOS, the gate of the NMOS is the control end of the controllable switching transistor, the source of the NMOS is the output end of the controllable switching transistor, and the drain of the NMOS is grounded, characterized by: The switching power supply according to Claim 3.

5. An impedance element is further installed between the switching circuit and the signal identification circuit, characterized by: The switching power supply according to Claim 2.

6. When the power supply demand signal is a voltage signal or a current signal, the signal identification circuit includes a comparison circuit. The first input terminal of the comparison circuit is connected to the output terminal of the switching circuit, the second input terminal of the comparison circuit is connected to a reference voltage output device or a reference current output device, and the output terminal of the comparison circuit is connected to the synchronous rectification circuit. The comparison circuit compares the voltage at the output terminal of the switching circuit with a reference voltage, or compares the current at the output terminal of the switching circuit with a reference current, and outputs the control signal to the synchronous rectification circuit based on the comparison result, and is used to affect the operating mode of the synchronous rectification circuit. The switching power supply according to any one of claims 2 to 5.

7. The comparison circuit is a comparator, the first input terminal of the comparator is the first input terminal of the comparison circuit, the second input terminal of the comparator is the second input terminal of the comparison circuit, and the output terminal of the comparator is the output terminal of the comparison circuit. The switching power supply according to claim 6, characterized in that

8. The comparison circuit further includes a current source. The first input terminal of the comparison circuit is also connected to the current source, the second input terminal of the comparison circuit is connected to the reference voltage output device, The comparison circuit compares the voltage at the output terminal of the switching circuit with the reference voltage, and outputs the control signal to the synchronous rectification circuit based on the comparison result, and is used to affect the operating mode of the synchronous rectification circuit. The switching power supply according to claim 6.

9. The comparison circuit further includes a current mirror. The input terminal of the current mirror is connected to the output terminal of the switching circuit, the output terminal of the current mirror is connected to the first input terminal of the comparison circuit, the second input terminal of the comparison circuit is connected to the reference current output device, and a preset ratio is set in the current mirror in advance. The comparison circuit compares the current at the output terminal of the switching circuit with the reference current, and outputs the control signal to the synchronous rectification circuit based on the comparison result, and is used to affect the operating mode of the synchronous rectification circuit. The switching power supply according to claim 6.

10. In a synchronous rectification chip applied to the secondary side of a switching power supply including a protocol chip, A control pin for controlling the conduction and cutoff of a rectifying power transistor based on an input signal. Connected to the protocol chip, receiving a power supply demand signal characterizing the load equipment of the switching power supply, and including a receiving pin for affecting the operating mode of the synchronous rectification chip. Synchronous rectification chip.

11. The synchronous rectification chip according to claim 10, characterized in that the receiving pin is connected to an external impedance element.

12. The synchronous rectification chip further includes a signal discrimination circuit. The signal discrimination circuit discriminates the received power supply demand signal and is used to affect the operating mode of the synchronous rectification chip based on the power supply demand signal. The synchronous rectification chip according to claim 10.

13. When the power supply demand signal is a voltage signal or a current signal, the signal discrimination circuit includes a comparison circuit. The first input terminal of the comparison circuit is connected to the output terminal of the switching circuit, the second input terminal of the comparison circuit is connected to a reference voltage output device or a reference current output device, and the output terminal of the comparison circuit is connected to the control pin. The comparison circuit compares the voltage at the output terminal of the switching circuit with a reference voltage, or compares the current at the output terminal of the switching circuit with a reference current, and outputs the control signal to the synchronous rectification circuit based on the comparison result, and is used to affect the operating mode of the synchronous rectification chip. The synchronous rectification chip according to claim 12.

14. The comparison circuit is a comparator, the first input terminal of the comparator is the first input terminal of the comparison circuit, the second input terminal of the comparator is the second input terminal of the comparison circuit, and the output terminal of the comparator is the output terminal of the comparison circuit. The synchronous rectification chip according to claim 13.

15. The comparison circuit further includes a current source. The first input terminal of the comparison circuit is also connected to the current source, and the second input terminal of the comparison circuit is connected to the reference voltage output device. The comparison circuit compares the voltage at the output terminal of the switching circuit with the reference voltage, and outputs the control signal to the control pin based on the comparison result, and is used to affect the operating mode of the synchronous rectification chip. The synchronous rectification chip according to claim 13.

16. The comparison circuit further includes a current mirror. The input terminal of the current mirror is connected to the output terminal of the switching circuit, the output terminal of the current mirror is connected to the first input terminal of the comparison circuit, the second input terminal of the comparison circuit is connected to the reference current output device, and a preset ratio is set in advance in the current mirror. The comparison circuit compares the current at the output terminal of the switching circuit with the reference current, and outputs the control signal to the control pin based on the comparison result, and is used to affect the operation mode of the synchronous rectification chip. The synchronous rectification chip according to claim 13.

17. In a protocol chip applied to the secondary side of a switching power supply having a synchronous rectification chip, a detection pin for detecting the power supply demand of a load device; and an output pin for transmitting the power supply demand signal to the synchronous rectification chip to affect the operation mode of the synchronous rectification chip. Protocol chip.

18. The protocol chip further includes a switching circuit and a detection circuit. The input terminal of the switching circuit is connected to the detection circuit, and the output terminal of the switching circuit is connected to the output pin. The switching circuit is used to adjust its own switching state based on the detection result output by the detection circuit and output the power supply demand signal through the output pin. The protocol chip according to claim 17.

19. The switching circuit includes a controllable switching transistor, the control terminal of the controllable switching transistor is connected to the detection pin, and the output terminal of the controllable switching transistor is connected to the output pin. The protocol chip according to claim 18.

20. In a switching power supply, a protocol chip according to any one of claims 10 to 16; and a synchronous rectification chip according to any one of claims 17 to 19. Switching power supply.

21. The switching power supply according to claim 20, wherein an impedance element is installed between the output pin of the protocol chip and the receiving pin of the synchronous rectification chip.

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