Control circuit, control method, and switching circuit for a switching circuit

Abstract

The application discloses a control circuit and a control method of a switching circuit and the switching circuit, wherein an output feedback signal of the switching circuit and a reference voltage error are amplified to obtain a compensation voltage; a first switch tube is adopted, a drain electrode of the first switch tube is connected with a drain electrode of a power tube of the switching circuit, a source electrode of the first switch tube receives a reference current, the first switch tube and the power tube have the same switch state; and a trigger signal for controlling the power tube to be turned off is generated according to the compensation voltage and a drain electrode voltage of the power tube. The application can realize peak current control without using a sampling resistor, and the system efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronic packaging, and particularly relates to a control circuit and a control method of a switching circuit and the switching circuit. BACKGROUND

[0002] In the prior art, as shown in the flyback circuit, a sampling resistor needs to be connected in series in the loop of the power tube when peak current control is implemented, and peak current control is achieved by sampling the voltage on the sampling resistor. Figure 1

[0003] However, when the power tube is turned on, power consumption will be generated on the sampling resistor, which reduces the efficiency of the system and increases the cost of the system. SUMMARY

[0004] The purpose of the present application is to provide an efficient control circuit and control method of a switching circuit to solve the problem of the prior art that a resistor needs to be connected in series in the power loop, thereby increasing the power consumption and cost of the system.

[0005] To achieve the above purpose, the present application provides a control circuit of a switching circuit, the switching circuit comprising an inductor and a power tube, the inductor and the power tube being connected, comprising:

[0006] a first switch tube, the drain of the first switch tube being connected to the drain of the power tube, and the source of the first switch tube receiving a reference current, the first switch tube and the power tube having the same switching state;

[0007] a first operational amplifier, which amplifies the error between the output feedback signal of the switching circuit and the reference voltage signal to obtain a compensation voltage;

[0008] a first control circuit, which receives the compensation voltage and the source voltage of the first switch tube to generate a trigger signal for controlling the turn-off of the power tube;

[0009] a driving circuit, which receives the trigger signal and drives the power tube and the first switch tube according to the trigger signal.

[0010] Optionally, the first control circuit comprises,

[0011] a reference current generating circuit, which receives the compensation voltage to generate a reference current according to the compensation voltage;

[0012] a first comparator, which compares the source voltage of the first switch tube with a first voltage to generate a trigger signal for controlling the turn-off of the power tube.

[0013] Optionally, the first control circuit further comprises,

[0014] a drain voltage sampling circuit, which is used for sampling the drain voltage of the power tube.​

[0015] a proportional operation circuit, which multiplies the drain voltage by a proportional coefficient to obtain the first voltage, the proportional coefficient being adjustable and not equal to 1.

[0016] Optionally, the first voltage is a power supply voltage.

[0017] Optionally, the reference current generating circuit further receives the first voltage and a drain voltage of the power tube for generating the reference current.

[0018] Optionally, the reference current generating circuit generates a first current according to the compensation voltage, and generates the reference current according to the first current, the first voltage and a drain voltage of the power tube,

[0019] The operation formula of the reference current is:

[0020] k*I COM / (1-V1 / Vsw),

[0021] wherein, I COM is the first current, V1 is the first voltage, Vsw is the drain voltage of the power tube, and k is a proportional coefficient.

[0022] Optionally, the power supply voltage is a voltage greater than zero.

[0023] Optionally, the first control circuit comprises:

[0024] a drain voltage sampling circuit, configured to sample the drain voltage of the power tube;

[0025] a current sampling circuit, configured to receive the source voltage of the first switch tube, the drain voltage and the reference current, and generate a sampling signal representing an inductor current signal;

[0026] a second comparator, configured to compare the compensation voltage and the sampling signal, and generate a trigger signal for controlling the power tube to be turned off.

[0027] Optionally, the current sampling circuit further comprises,

[0028] a controlled current generating circuit, configured to receive the source voltage of the first switch tube, the drain voltage of the power tube and the reference current, and generate a controlled current representing the inductor current according to an operation formula of the controlled current,

[0029]

[0030] wherein, V IN+ is the source voltage of the first switch tube, V IN- is the drain voltage of the power tube, and IREF K is the reference current R K1 is the ratio of the on-resistance of the first switch tube to the on-resistance of the power tube, and K1 is a proportional coefficient;

[0031] A sampling resistor, a voltage drop generated by the controlled current flowing through the sampling resistor is the sampling signal.

[0032] The application also provides a control method of a switching circuit, the switching circuit comprising an inductor and a power tube, the inductor and the power tube being connected, comprising the following steps:

[0033] Amplifying the error between the output feedback signal of the switching circuit and the reference voltage signal to obtain a compensation voltage;

[0034] A first switch tube is adopted, a drain electrode of the first switch tube is connected to a drain electrode of the power tube, a reference current flows through the first switch tube, and the first switch tube and the power tube have the same switching state;

[0035] A trigger signal for controlling the power tube to be turned off is generated according to the compensation voltage and the drain voltage of the power tube.

[0036] Optionally, the compensation voltage is received to generate a reference current according to the compensation voltage;

[0037] A source voltage of the first switch tube is compared with a first voltage to generate a trigger signal for controlling the power tube to be turned off.

[0038] Optionally, the drain voltage of the power tube is multiplied by a proportional coefficient to obtain the first voltage, and the proportional coefficient is adjustable and not equal to 1.

[0039] Optionally, a current direction of the power tube is from the drain electrode to the ground, and a direction of the reference current is to the source electrode of the first switch tube.

[0040] Optionally, the first voltage is a power supply voltage.

[0041] Optionally, the reference current is also generated according to the first voltage and the drain voltage of the power tube.

[0042] Optionally, a current direction of the power tube is from the drain electrode to the ground, and a direction of the reference current is to the source electrode of the first switch tube.

[0043] Optionally, the drain voltage of the power tube is sampled.

[0044] A sampling signal representing an inductor current signal is generated according to the source voltage of the first switch tube, the drain voltage and the reference current.

[0045] Comparing the compensation voltage and the sampling signal generates a trigger signal for controlling the power tube to be off.

[0046] Optionally, a controlled current representing the inductive current is generated according to the source voltage of the first switch tube, the drain voltage and the reference current, and the voltage drop generated by the controlled current flowing through a sampling resistor is the sampling signal, and the operation formula of the controlled current is:

[0047]

[0048] wherein, V IN+ is the source voltage of the first switch tube, V IN- is the drain voltage of the power tube, I REF is the reference current, K R is the ratio of the on-resistance of the first switch tube to the on-resistance of the power tube set by the system, and the K1 is a proportional coefficient.

[0049] The application further provides a switching circuit comprising an inductor and a power tube, wherein the inductor and the power tube are connected, and further comprising any one of the control circuits, and the power tube and the first switch tube in the control circuit are integrated in one chip.

[0050] Compared with the prior art, the technical scheme of the application has the following advantages: the output feedback signal of the switching circuit and the reference voltage signal error amplification are obtained by the compensation voltage of the first switch tube, the drain of the first switch tube is connected with the drain of the power tube, the reference current flows through the first switch tube, and the first switch tube and the power tube have the same switching state; according to the source voltage of the first switch tube and the compensation voltage, the trigger signal for controlling the power tube to be off is generated. The power circuit of the embodiment can realize the peak current control without series resistance, has small power consumption and high precision. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 It is a prior art switching circuit schematic diagram;

[0052] Figure 2 It is a switching circuit schematic diagram of the application;

[0053] Figure 3 It is a control circuit embodiment one schematic diagram of the application;

[0054] Figure 4 It is a control circuit embodiment one waveform diagram of the application;

[0055] Figure 5 It is a control circuit embodiment two schematic diagram of the application;

[0056] Figure 6 It is a control circuit embodiment two waveform diagram of the application;

[0057] Figure 7 The third embodiment of the control circuit of the present application is shown in the schematic diagram.

[0058] Figure 8 The fourth embodiment of the control circuit of the present application is shown in the schematic diagram. DETAILED DESCRIPTION

[0059] The preferred embodiments of the present application are described in detail below with reference to the accompanying drawings. The present application, however, is not limited to these embodiments. Any alternatives, modifications, equivalents, and variations of the present application falling within the spirit and scope of the present application are included.

[0060] For the public to have a thorough understanding of the present application, specific details are described in the following preferred embodiments of the present application. However, the present application can be fully understood without these specific details.

[0061] The present application is described in more detail below with reference to the accompanying drawings. It is to be noted that the drawings are in a simplified form and are not drawn to precise scale. They are used only to facilitate, clarify and aid in the understanding of the embodiments of the present application.

[0062] As shown in Figure 2 , the schematic diagram of the switching circuit of the present application is shown. The switching circuit is taken as an example of a flyback circuit. One end of the power tube M0 is connected to the primary side inductance Np of the flyback circuit, and the other end is connected to the ground terminal. The control circuit receives the drain SW voltage of the power tube to achieve peak current control. The specific control circuit schematic diagram is described with reference to Figure 3 , Figure 5 , Figure 7 and Figure 8 , and in combination with the corresponding schematic diagram.

[0063] As shown in Figure 3 , the schematic diagram of the first embodiment of the control circuit of the present application is shown. It includes the first switch tube M1, the first operational amplifier U04, the first control circuit, and the driving circuit U00. The drain of the first switch tube M1 is connected to the drain of the power tube M0. The switching state of the first switch tube M1 and the power tube M0 is the same. The on-resistance of the first switch tube M1 is R1, and the on-resistance of the power tube M0 is Ron. After the power tube M0 and the first switch tube M1 are turned on, the current flowing through the power tube M0 is Ics (i.e. the primary side inductance current), and the reference current flows through the first switch tube M1. Here, when the current direction of the power tube M0 is set to flow from the SW node to the ground terminal, the reference current direction is from the source to the drain of the first switch tube M1. The first operational amplifier U04 performs error amplification on the reference voltage VREF and the feedback voltage FB representing the output voltage, and outputs the compensation voltage Vcomp. The first control circuit receives the compensation voltage Vcomp and the source voltage V IN+A trigger signal is generated to turn off the power transistor M0. The drive circuit U00 outputs a drive signal to drive the power transistor M0 and the first switching transistor M1 respectively according to the trigger signal.

[0064] In this embodiment, the first control circuit includes a drain voltage sampling circuit, a reference current generation circuit, a proportional operation circuit U03, and a comparator U01. The reference current generation circuit receives a compensation voltage Vcomp and controls the controlled current source to generate a first current I based on the compensation voltage Vcomp. COM In this embodiment, the first current I COM As a reference current, the drain voltage sampling circuit includes a second switch M2 and a voltage follower U02. The second switch M2 has the same switching state as the power transistor M0 and the first switch M1. The drain of the second switch M2 is connected to the drain of the power transistor M0, and its source is connected to the first input terminal of the voltage follower U02. The second input terminal of the voltage follower U02 is connected to its output terminal. Ignoring the on-state voltage drop of the second switch M2, the output voltage of the voltage follower U02 is the sampled drain voltage Vsw. The proportional operation circuit U03 multiplies the sampled drain voltage Vsw with the proportional coefficient Kv to obtain the first voltage V. IN- Comparator U01 will convert the source voltage V of the first switching transistor into voltage V. IN+ With the first voltage V IN- The comparison is performed, and the comparison signal is sent to the drive circuit U00. When the source voltage V IN+ With the first voltage V IN- When the currents are equal, it indicates that the inductor current has reached its peak current, controlling the power transistor M0 to turn off, thus realizing peak current control of the switching circuit. According to... Figure 3 Given the above description, the on-state current of power transistor M0 is Ics, and the on-state resistance is Ron. Therefore, the drain voltage of power transistor M0 is:

[0065] Vsw = Ics * Ron (1);

[0066] Given that the first switching transistor M1 and the power transistor M0 share a common drain, and the conduction current of the first switching transistor M1 flows from the source to the drain (Icom), with a conduction resistance of R1, the source voltage of the first switching transistor M1 can be obtained as follows:

[0067] V IN+ =Vsw+Icom*R1 (2);

[0068] The first voltage is:

[0069] V IN- =Kv*Vsw (3);

[0070] At the same time, let K be the record. R =R1 / Ron (4);

[0071] Since the first switching transistor M1 and the power transistor M0 share a common drain, their degradation curves are identical. This means the on-resistance R1 of the first switching transistor M1 and the on-resistance of the power transistor M0 change proportionally, ensuring their ratio K remains constant. R The basics remain unchanged.

[0072] From equations (1), (2), (3), and (4) above, we can obtain:

[0073] I COM / Ics=(Kv-1) / K R (5);

[0074] From equation (5), it can be seen that, since K R With the basic structure remaining unchanged, and provided that the proportional coefficient Kv is not equal to 1, I can be adjusted by changing the value of the proportional coefficient Kv. COM The ratio of Ics to the primary inductor current, assuming a fixed primary inductor current, results in a smaller proportionality coefficient Kv and a smaller initial current Ics. COM The smaller the value, the lower the first current I. COM The less chip loss this results in, the smaller the initial current I can be, which can be reduced by adjusting a proportional coefficient Kv. COM The resulting losses. When the power transistor is a gallium nitride (GaN) power transistor, its high voltage and high power characteristics result in a narrow drive signal range and rapid degradation. Connecting a sampling resistor in series with the GaN power transistor leads to significant losses and a decrease in sampling accuracy due to device degradation. In this embodiment, peak current control can be achieved without a series resistor in the power circuit, resulting in low power consumption and high accuracy. The first switching transistor M2, the first switching transistor M1, and the power transistor M0 are generally integrated into a single chip, ensuring that the degradation curves of these three transistors within the same chip are consistent, thereby achieving high sampling accuracy of the drain voltage Vsw. R The basic structure remains unchanged, thus enabling high peak current control accuracy; other circuits of the control circuit are integrated into another chip, and the two chips can be packaged in one package.

[0075] like Figure 4 The diagram shown illustrates the waveform corresponding to Embodiment 1 of the present invention. Figure 3 Circuit schematic and its description Figure 4 The waveform diagram is explained below. In the diagram, Vsw is the drain voltage of power transistor M0, Ics is the current flowing through power transistor M0 when it is turned on, GON is the pulse drive signal of power transistor M0, and V... IN+ for Figure 3 The source voltage of the first switching transistor, V IN- for Figure 3 The first voltage. When the power transistor M0 is just turned on, the drain voltage Vsw drops rapidly to near zero potential. Combining equations (2) and (3) above, we can obtain V IN+ -V IN-=I COM *R1; When the pulse drive signal GON is high, the power transistor M0 is turned on, the drain voltage Vsw of the power transistor M0 approaches zero potential, the current Ics flowing through the power transistor M0 begins to rise, and the source voltage V of the first switching transistor... IN+ and the first voltage V IN- It also gradually rises, when the source voltage V of the first switching transistor... IN+ and the first voltage V IN- When the current Ics flowing through the power transistor M0 is equal to the reference peak current, the pulse drive signal GON goes low, and the power transistor M0 is turned off.

[0076] like Figure 5 The diagram illustrates the principle of a second embodiment of the control circuit of the present invention. The specific difference between this embodiment and the first embodiment lies in the first control circuit. In this embodiment, the first control circuit includes a reference current generating circuit and a comparator U01. The reference current generating circuit receives a compensation voltage Vcomp, and the compensation voltage Vcomp controls the controlled current source to generate a first current I. COM In this embodiment, the first current I COM As a reference current, when the first switch M1 is turned on, the reference current flows through the first switch M1. Here, when the current direction of the power transistor M0 is set to flow from the SW node to ground, the reference current direction is from the drain to the source of the first switch M1. The on-resistance of the first switch is R1, and the on-resistance of the power transistor is Ron. The first input terminal of comparator U01 is connected to the source of the first switch M1, and the source voltage of the first switch M1 is V. IN+ The first input terminal of comparator U01 receives the first voltage V. IN- The first voltage V IN- Given a reference voltage, i.e., the battery voltage in the diagram, the first comparator U01 outputs a trigger signal to turn off the power transistor M0 to the drive circuit U00. The drive circuit U00 then outputs drive signals to drive the power transistor M0 and the first switching transistor M1 respectively. Based on the circuit schematic and the above analysis, given the on-current Ics and on-resistance of the power transistor M0, the drain voltage of the power transistor M0 can be obtained as follows:

[0077] Vsw = Ics * Ron (6);

[0078] Given that the first switching transistor M1 and the power transistor M0 share a common drain, and considering the current flowing through the first switching transistor M1 as Icom and the on-resistance R1 of the first switching transistor M1, the source voltage of the first switching transistor M1 can be obtained as follows:

[0079] V IN+ =Vsw-Icom*R1 (7);

[0080] The first comparator U01 will convert the first voltage V IN- and source voltage V IN+ Comparison: When the voltages at the two input terminals are equal, i.e., V... IN+ =V IN- Then, from equations (6) and (7), we can obtain:

[0081]

[0082] Among them, K R =R1 / Ron, design the first voltage V IN- The closer I is to 0, COM The closer the ratio of / Ics is to a fixed coefficient 1 / K, the better. R The higher the accuracy of peak current control, the better. Since the reference current flowing through the first switching transistor M1 flows from the drain to the source of the first switching transistor M1, if the first voltage V... IN- Setting it to 0, while maximizing peak current control accuracy, results in a decrease in the source voltage V of the first switching transistor M1. IN+ It needs to be clamped at a negative voltage, and the design of a negative voltage circuit is more complex, so the first voltage V IN- It is typically set to a positive pressure close to 0.

[0083] like Figure 6 The diagram illustrates the waveform corresponding to Embodiment 2 of the present invention. In the diagram, Vsw is the drain voltage of power transistor M0, Ics is the current flowing through power transistor M0 when it is turned on, GON is the pulse drive signal of power transistor M0, and V... IN+ for Figure 5 The source voltage of the first switching transistor, V IN- for Figure 5 The first voltage is close to zero and is fixed. After the pulse drive signal GON is high, driving the power transistor M0 to turn on, the drain voltage Vsw of the power transistor M0 approaches zero potential, and the current Ics flowing through the power transistor M0 begins to rise. The source voltage V of the first switching transistor... IN+ Gradually increasing, when the source voltage V of the first switching transistor M1... IN+ and the first voltage V IN- When the voltages are equal, the current Ics flowing through power transistor M0 rises to its peak current, the pulse drive signal GON goes low, and power transistor M0 is turned off. If the first voltage V... IN- If the value is 0, then after the power transistor is turned on, the source voltage V of the first switching transistor M1 will be 0. IN+ It will rise from a negative pressure to 0.

[0084] The skilled in the art can know that the conduction of the power tube M0 of the switching circuit can be realized by the conduction control circuit, for example, the conduction of the power tube M0 can be controlled according to the clock pulse signal, or other prior art conduction control circuits, and the desired output signal of the switching circuit can be realized by controlling the conduction and off of the power tube M0.

[0085] As Figure 7 shown, the third embodiment of the control circuit of the application is schematically shown, in order to solve the problem of the embodiment two that the first voltage V IN- The influence on the control precision is compensated by introducing the variable, and the embodiment three is designed, which is different from the embodiment two in that the current flowing through the first switch tube M1 is the compensated controlled current, and the embodiment three is different from the embodiment two in that the first control circuit is different, and in the embodiment, the first control circuit is specifically as follows: the first control circuit includes a drain voltage sampling circuit, a reference current generating circuit and a first comparator U01, the drain voltage sampling circuit includes a second switch tube M2 and a voltage follower U02, the drain of the second switch tube M2 is connected with the drain of the power tube M0, the source of the second switch tube M2 is connected with the first input end of the voltage follower U02, the second input end of the voltage follower U02 is connected with the output end, and the conduction voltage drop of the second switch tube M2 is ignored, and the output voltage of the voltage follower U02 is the sampled drain voltage Vsw. The reference current generating circuit includes a controlled current source and a first operation circuit U03, the compensation voltage Vcomp controls the controlled current source to generate the first current I COM , the first operation circuit U03 receives the sampled drain voltage Vsw, the first voltage V IN- and the first current I COM , and outputs an electrical signal after operation to control the reference current of the current output by the controlled current source I1. The output current of the controlled current source I1 is known flows through the first switch tube M1, the conduction resistance of the first switch tube M1 is R1, the first switch tube M1 and the power tube M0 are common-drain, and the source voltage of the first switch tube M1 can be obtained as follows:

[0086]

[0087] The first comparator U01 compares the first voltage V IN- and the source voltage V IN+ , when V IN+ = V IN- , the formula (6) can be obtained as follows:

[0088]

[0089] It can be known from the formula (10) that since K RThe peak current control is not affected by other variables, and the control precision is high. The output current of the controlled current source I1 can be further controlled to be k times of The loss caused by the controlled current is further reduced by setting a small proportional coefficient k.

[0090] As shown in Figure 8 The fourth embodiment of the control circuit of the present application is shown in the schematic diagram. The difference between the fourth embodiment and the first, second and third embodiments is the difference in the first control circuit. In the fourth embodiment, the first control circuit is as follows: a drain voltage sampling circuit, a current sampling circuit and a first comparator U01. The drain of the first switch tube M1 is connected to the drain of the power tube M0. The switching state of the first switch tube M1 is the same as that of the power tube M0. Preferably, the driving circuit U00 outputs driving signals to drive the power tube M0 and the first switch tube M1, respectively. The on-resistance of the first switch tube M1 is R1, and the on-resistance of the power tube M0 is Ron. After the power tube M0 and the first switch tube M1 are turned on, the current flowing through the power tube M0 is Ics (i.e. the primary inductor current), and the reference current source generates a reference current I REF flows through the first switch tube M1. Here, when the current direction of the power tube M0 is set to flow from the SW node to the ground, the direction of the reference current is from the source of the first switch tube M1 to the drain. The drain voltage sampling circuit includes a second switch tube M2 and a voltage follower U02. The switching state of the second switch tube M2 is the same as that of the power tube M0 and the first switch tube M1. The drain of the second switch tube M2 is connected to the drain of the power tube M0. The source of the second switch tube M2 is connected to the first input terminal of the voltage follower U02. The second input terminal of the voltage follower U02 is connected to the output terminal thereof. The on-resistance of the second switch tube M2 is ignored. The output voltage of the voltage follower U02 is the sampled drain voltage Vsw. The current sampling circuit includes an operation circuit U03, a controlled current source Ics' and a sampling resistor Rcs. The operation circuit U03 receives the source voltage V IN+ of the first switch tube M1, the reference current I REF and the drain voltage Vsw, and calculates the output signal according to the following operation formula:

[0091]

[0092] Further, the following can be obtained:

[0093]

[0094] According to the above formula (11) and formula (12), the output signal of the operation circuit is:

[0095]

[0096] wherein K RThe ratio of the on-resistance of the first switch Ml to the on-resistance of the power transistor M0 is K, since the degradation curves of the first switch Ml and the power transistor M0 are consistent, and K is a constant value. R The constant value is set by the system according to actual requirements. The output signal Ics of the operation circuit U03 represents the inductor current, and the output current of the controlled current source Ics' is controlled by the output signal Ics, so that the output current is I CS ' = K1*I CS , and K1 is a proportional coefficient for further proportional adjustment of Ics. The voltage drop generated by the output current of the controlled current source Ics' flowing through the sampling resistor Rcs is the sampling signal Vcs of the obtained inductor current. The first operational amplifier U04 amplifies the error between the output feedback voltage FB and the reference voltage VREF to obtain the compensation voltage Vcomp. The first comparator U01 compares the sampling signal Vcs with the compensation voltage Vcomp, and outputs a comparison signal to the driving circuit U00 to drive the power transistor M0, the first switch Ml and the second switch M2. When the sampling signal Vcs reaches the compensation voltage Vcomp, it represents that the inductor current reaches the peak current.

[0097] The embodiment only needs to sample the node voltage information of SW, and IREF is a preset reference current. The sampling signal representing the inductor current information is obtained by calculation, which can be used for peak control in the peak control mode of the switching power supply, and can also be used in other modules of the control circuit requiring inductor current information, and has good precision and flexible use.

[0098] In addition, although the above embodiments are described and explained separately, the technologies involved in part are common, and can be replaced and integrated between the embodiments according to the ordinary skill in the art. If the content not explicitly recorded in one embodiment is referred to, another embodiment recorded can be referred to.

[0099] The above-described embodiments do not constitute a limitation on the protection scope of the technical solutions. Any modifications, equivalent replacements and improvements made within the spirit and principles of the above-described embodiments shall be included in the protection scope of the technical solutions.

Claims

1. A control circuit for a switching circuit, the switching circuit comprising an inductor and a power transistor, the inductor and the power transistor being connected, characterized in that, include: The first switching transistor has its drain connected to the drain of the power transistor and its source receiving a reference current. The first switching transistor and the power transistor have the same switching state. The first operational amplifier amplifies the error between the output feedback signal of the switching circuit and the reference voltage signal to obtain the compensation voltage. The first control circuit receives the compensation voltage and the source voltage of the first switching transistor to generate a trigger signal to control the power transistor to turn off. The driving circuit receives the trigger signal and drives the power transistor and the first switching transistor respectively according to the trigger signal; The first control circuit includes, A reference current generating circuit receives the compensation voltage and generates a reference current based on the compensation voltage. The first comparator compares the source voltage of the first switching transistor with a first voltage to generate a trigger signal that controls the power transistor to turn off.

2. The control circuit of the switching circuit according to claim 1, characterized in that: The first control circuit also includes, A drain voltage sampling circuit is used to sample the drain voltage of the power transistor. The proportional operation circuit multiplies the drain voltage by a proportional coefficient to obtain the first voltage, wherein the proportional coefficient is adjustable and is not equal to 1.

3. The control circuit of the switching circuit according to claim 1, characterized in that: The first voltage is the power supply voltage.

4. The control circuit of the switching circuit according to claim 3, characterized in that: The reference current generating circuit also receives the first voltage and the drain voltage of the power transistor to generate the reference current.

5. The control circuit of the switching circuit according to claim 4, characterized in that: The reference current generating circuit generates a first current based on the compensation voltage, and generates the reference current based on the first current, the first voltage, and the drain voltage of the power transistor. The formula for calculating the reference current is: k*I COM / (1-V1 / Vsw), Among them, I COM V1 is the first current, Vsw is the first voltage, and k is a proportionality coefficient.

6. The control circuit of the switching circuit according to claim 3, characterized in that: The power supply voltage is a voltage greater than zero.

7. A control circuit for a switching circuit, the switching circuit comprising an inductor and a power transistor, the inductor and the power transistor being connected, characterized in that, include: The first switching transistor has its drain connected to the drain of the power transistor and its source receiving a reference current. The first switching transistor and the power transistor have the same switching state. The first operational amplifier amplifies the error between the output feedback signal of the switching circuit and the reference voltage signal to obtain the compensation voltage. The first control circuit receives the compensation voltage and the source voltage of the first switching transistor to generate a trigger signal to control the power transistor to turn off. The driving circuit receives the trigger signal and drives the power transistor and the first switching transistor respectively according to the trigger signal; The first control circuit includes a drain voltage sampling circuit for sampling the drain voltage of the power transistor. A current sampling circuit receives the source voltage, the drain voltage, and the reference current of the first switching transistor to generate a sampling signal characterizing the inductor current signal. The second comparator compares the compensation voltage with the sampled signal to generate a trigger signal that controls the power transistor to turn off.

8. The control circuit of the switching circuit according to claim 7, characterized in that: The current sampling circuit also includes, The controlled current generating circuit receives the source voltage of the first switching transistor, the drain voltage of the power transistor, and the reference current, and calculates a controlled current characterizing the inductor current. The formula for calculating the controlled current is as follows: Among them, V IN+ V is the source voltage of the first switching transistor. IN- I is the drain voltage of the power transistor. REF For the reference current, K R K1 is the ratio of the on-resistance of the first switching transistor to the on-resistance of the power transistor, set for the system, where K1 is a proportionality coefficient. The sampling resistor is used to generate a voltage drop across the controlled current flowing through it, which is the sampling signal.

9. A control method for a switching circuit, the switching circuit comprising an inductor and a power transistor, the inductor and the power transistor being connected, characterized in that, Includes the following steps: The error between the output feedback signal of the switching circuit and the reference voltage signal is amplified to obtain the compensation voltage; A first switching transistor is used, the drain of which is connected to the drain of the power transistor. A reference current flows through the first switching transistor, and the first switching transistor and the power transistor have the same switching state. Receive the compensation voltage to generate a reference current based on the compensation voltage; The source voltage of the first switching transistor is compared with a first voltage to generate a trigger signal that controls the power transistor to turn off.

10. The control method for the switching circuit according to claim 9, characterized in that: The first voltage is obtained by multiplying the drain voltage of the power transistor by a proportionality coefficient, wherein the proportionality coefficient is adjustable and is not equal to 1.

11. The control method for the switching circuit according to claim 10, characterized in that: The current in the power transistor flows from the drain to ground, and the reference current flows to the source of the first switching transistor.

12. The control method for the switching circuit according to claim 9, characterized in that: The first voltage is the power supply voltage.

13. The control method for the switching circuit according to claim 12, characterized in that: The reference current is also generated based on the first voltage and the drain voltage of the power transistor.

14. The control method for the switching circuit according to claim 12, characterized in that: The current in the power transistor flows from the drain to ground, and the reference current flows out of the source of the first switching transistor.

15. A control method for a switching circuit, the switching circuit comprising an inductor and a power transistor, the inductor and the power transistor being connected, characterized in that, Includes the following steps: The error between the output feedback signal of the switching circuit and the reference voltage signal is amplified to obtain the compensation voltage; A first switching transistor is used, the drain of which is connected to the drain of the power transistor. A reference current flows through the first switching transistor, and the first switching transistor and the power transistor have the same switching state. Sample the drain voltage of the power transistor; A sampling signal characterizing the inductor current signal is generated based on the source voltage of the first switch, the drain voltage, and the reference current. The compensation voltage and the sampling signal are compared to generate a trigger signal that controls the power transistor to turn off.

16. The control method for the switching circuit according to claim 15, characterized in that: A controlled current characterizing the inductor current is generated based on the source voltage of the first switching transistor, the drain voltage, and the reference current. The voltage drop generated by the controlled current flowing through the sampling resistor is the sampling signal. The formula for calculating the controlled current is: Among them, V IN+ V is the source voltage of the first switching transistor. IN- I is the drain voltage of the power transistor. REF For the reference current, K R K1 is the ratio of the on-resistance of the first switching transistor to the on-resistance of the power transistor, set for the system.

17. A switching circuit, comprising an inductor and a power transistor, wherein the inductor and the power transistor are connected, characterized in that: It also includes the control circuit of any one of claims 1-6 or 7-8, wherein the power transistor and the first switching transistor in the control circuit are integrated in one chip.

Images