Current detection circuit and current detection method of high-voltage switching power supply

Abstract

The invention discloses a current detection circuit and a current detection method of a high-voltage switching power supply, and belongs to the technical field of circuits. The current detection circuit comprises a current sensing module, an average current detection module, a short-circuit protection module and a peak current detection module; the current sensing module outputs a current difference corresponding to a voltage drop generated by an input current at the two ends of the sampling resistor to the average current detection module; the average current detection module adjusts the proportional relation between the detection voltage and the input current through a proportional resistor, and outputs the average value of the detection current. The short-circuit protection module outputs closing signals to the four gallium nitride power tubes when determining that at least one of the four gallium nitride power tubes in the high-voltage switching power supply has a short-circuit fault; and the peak current detection module outputs a peak current detection signal according to a comparison result of the detection voltage after slope compensation and the difference voltage. The accuracy and comprehensiveness of current detection can be improved, and the safety of the high-voltage switching power supply is improved.

Description

Technical Field

[0001] The present application relates to the field of circuit technology, and in particular to a current detection circuit and a current detection method for a high-voltage switching power supply. Background Art

[0002] In high-voltage switching power supplies, current mode control has been widely used due to its high reliability and simple loop compensation. As a key part of the current mode control method, the current detection circuit can obtain the current signal to adjust the output voltage of the high-voltage switching power supply and provide overcurrent protection.

[0003] like Figure 1 As shown in the figure, the most common current sensing circuit has a small sampling resistor R SNS In series with the inductor L in the high-voltage switching power supply, the current detection circuit can continuously measure the inductor current signal regardless of the buck, boost or buck-boost operation mode. SW1 and V SW2 As a detection reference, both of them have large common-mode switching noise, which requires the current detection circuit to have a high enough common-mode rejection ratio, otherwise it will be reflected in the measured signal I SNS Generates interference, causing the measured signal I SNS Severe distortion. Summary of the invention

[0004] The present application provides a current detection circuit and a current detection method for a high-voltage switching power supply, which are used to solve the problem of SW1 and V SW2 As a detection reference, resulting in the measurement signal I SNS The problem of serious distortion. The technical solution is as follows: According to a first aspect of the present application, a current detection circuit of a high-voltage switching power supply is provided, wherein the current detection circuit comprises a current sensing module, an average current detection module, a short-circuit protection module and a peak current detection module connected in sequence; The current sensing module comprises a sampling resistor, a first resistor, a second resistor, a current mirror circuit, a high-low voltage isolation pair and a high-low voltage isolation tube, wherein the sampling resistor is used to control the input current of the high-voltage switching power supply to generate a voltage drop at both ends of the sampling resistor, so that the first resistor and the second resistor respectively connected in series at both ends of the sampling resistor generate a current difference, and the current difference is output to the current mirror circuit, the current mirror circuit is used to output the current difference to the high-low voltage isolation tube, the high-low voltage isolation tube is used to output the detection current generated by the current difference to the average current detection module, the high-low voltage isolation pair and the high-low voltage isolation tube are used to isolate the high-voltage domain and the low-voltage domain, and the detection current is proportional to the input current; The average current detection module includes a proportional resistor, a first operational amplifier and an RC filter, the proportional resistor is used to adjust the proportional relationship between the detection voltage corresponding to the detection current and the input current, the first operational amplifier and the RC filter are used to output the average value of the detection voltage, and the average value of the detection voltage is used to represent the average value of the detection current; The short-circuit protection module includes a first comparator and a short-circuit protection logic, wherein the first comparator is used to output a comparison result between the overcurrent limit voltage and the detection voltage corresponding to the detection current to the short-circuit protection logic, and the short-circuit protection logic is used to output a shutdown signal for the four gallium nitride power tubes when it is determined according to the comparison result that at least one of the four gallium nitride power tubes in the high-voltage switching power supply has a short-circuit fault; The peak current detection module includes a second operational amplifier, a slope compensator and a second comparator. The second operational amplifier is used to output a difference voltage between a feedback voltage and a reference voltage to the second comparator. The feedback voltage is related to the output voltage of the high-voltage switching power supply. The slope compensator is used to compensate the detection voltage corresponding to the detection current using a ramp signal, and output the compensated detection voltage to the second comparator. The second comparator is used to output a peak current detection signal according to a comparison result between the compensated detection voltage and the difference voltage. The peak current detection signal is a signal that flips when the detection current reaches a set peak value.

[0005] In a possible implementation, the current sensing module further includes two current sources; The first end of the sampling resistor is connected to the first end of the first resistor and serves as the input end of the current sensing module; The second end of the sampling resistor is connected to the first end of the second resistor and serves as the first output end of the current sensing module; The second end of the first resistor and the second end of the second resistor are respectively connected to the two input ends of the current mirror circuit, the two output ends of the current mirror circuit are respectively connected to the drains of the first transistor and the second transistor in the high-low voltage isolation pair, the sources of the first transistor and the second transistor are respectively connected to the input ends of two current sources, and the output ends of the two current sources are grounded; The second end of the first resistor is connected to the drain of the high-low voltage isolation tube, and the source of the high-low voltage isolation tube serves as the second output end of the current sensing module; The gates of the first transistor, the second transistor and the high-low voltage isolation tube are connected to an internal power supply.

[0006] In a possible implementation, the current sensing module further includes a single-stage amplifier; The drain of the single-stage amplifier is connected to the source of the high-low voltage isolation tube, the gate of the single-stage amplifier is connected to the source of the first transistor, and the source of the single-stage amplifier serves as the second output end of the current sensing module.

[0007] In a possible implementation, the current mirror circuit includes a third transistor, a fourth transistor, a fifth transistor and a sixth transistor; The source of the third transistor is connected to the second end of the first resistor as an input end of the current mirror circuit; The source of the fourth transistor is connected to the second end of the second resistor as another input end of the current mirror circuit; The drain of the third transistor is connected to the source of the fifth transistor, and the drain of the fifth transistor is connected to the drain of the first transistor as an output end of the current mirror circuit; The gate of the third transistor is connected to the gate and drain of the fourth transistor and the source of the sixth transistor respectively; The gate of the fifth transistor is connected to the gate and drain of the sixth transistor and serves as another output end of the current mirror circuit and is connected to the drain of the second transistor.

[0008] In a possible implementation, the first end of the proportional resistor is connected to the positive input end of the first operational amplifier and serves as the input end of the average current detection module; The second end of the proportional resistor is connected to the first end of the RC filter and then grounded; The negative input terminal of the first operational amplifier is connected to the output terminal and then connected to the second terminal of the RC filter; The third terminal of the RC filter serves as the output terminal of the average current detection module.

[0009] In a possible implementation, the RC circuit includes a third resistor and a capacitor; The first end of the capacitor serves as the first end of the RC filter; The first end of the third resistor serves as the second end of the RC filter; The second end of the third resistor is connected to the second end of the capacitor to serve as the third end of the RC filter.

[0010] In a possible implementation, the positive input terminal of the first comparator is connected to the positive input terminal of the first operational amplifier as the first input terminal of the short-circuit protection module; The negative input terminal of the first comparator is connected to the overcurrent limiting voltage output terminal as the second input terminal of the short-circuit protection module; The output terminal of the first comparator is connected to the input terminal of the short-circuit protection logic; The output end of the short-circuit protection logic serves as the output end of the short-circuit protection module.

[0011] In a possible implementation, the first input end of the slope compensator is connected to the positive input end of the first comparator as the first input end of the peak current detection module, the second input end of the slope compensator is connected to the ramp signal output end as the second input end of the peak current detection module, and the output end of the slope compensator is connected to the positive input end of the second comparator; The positive input terminal of the second operational amplifier is connected to the reference voltage output terminal as the third input terminal of the peak current detection module, the negative input terminal of the second operational amplifier is connected to the feedback voltage output terminal as the fourth input terminal of the peak current detection module, and the output terminal of the second operational amplifier is connected to the negative input terminal of the second comparator; The output end of the second comparator serves as the output end of the peak current detection module.

[0012] In a possible implementation, the detection current is equal to the voltage drop divided by the first resistor, and the detection current is equal to the product of the inductor current in the high-voltage switching power supply and the sampling resistor divided by the first resistor, and the inductor current is related to the input current.

[0013] According to a second aspect of the present application, a current detection method of a current detection circuit of a high-voltage switching power supply is provided, which is used in the current detection circuit of the high-voltage switching power supply as described above, and the method comprises: The sampling resistor controls the input current of the high-voltage switching power supply to generate a voltage drop at both ends of the sampling resistor, so that the first resistor and the second resistor connected in series at both ends of the sampling resistor respectively generate a current difference, and the current difference is output to the current mirror circuit, and the current mirror circuit outputs the current difference to the high-low voltage isolation tube, and the high-low voltage isolation tube outputs the detection current generated by the current difference to the average current detection module. The high-low voltage isolation tube and the high-low voltage isolation tube are used to isolate the high-voltage domain and the low-voltage domain, and the detection current is proportional to the input current; The proportional resistor adjusts the proportional relationship between the detection voltage corresponding to the detection current and the input current, the first operational amplifier and the RC filter output an average value of the detection voltage, and the average value of the detection voltage is used to represent the average value of the detection current; The first comparator outputs a comparison result between the overcurrent limit voltage and the detection voltage corresponding to the detection current to the short-circuit protection logic, and when the short-circuit protection logic determines that at least one of the four gallium nitride power tubes has a short-circuit fault according to the comparison result, the short-circuit protection logic outputs a shutdown signal for the four gallium nitride power tubes; The second operational amplifier outputs a difference voltage between a feedback voltage and a reference voltage to the second comparator, the feedback voltage is related to the output voltage of the high-voltage switching power supply, the slope compensator uses a ramp signal to compensate for the detection voltage corresponding to the detection current, and outputs the compensated detection voltage to the second comparator, the second comparator outputs a peak current detection signal according to a comparison result between the compensated detection voltage and the difference voltage, and the peak current detection signal is a signal that flips when the detection current reaches a set peak value.

[0014] The beneficial effects of the technical solution provided by this application include at least: The current detection circuit uses the input voltage and output voltage of the high-voltage switching power supply as the detection reference, which can reduce the influence of the switching noise on the detection current and improve the accuracy of the current detection.

[0015] After the current sensing module detects the detection current, it outputs it to the average current detection module and the peak current detection module. The average current detection module can output the average value of the detection voltage, and the average value of the detection current is represented by the average value of the detection voltage. The peak current detection module can output a flipped peak current detection signal to indicate that the detection current has reached the set peak value, thereby improving the comprehensiveness of current detection.

[0016] The current sensing module detects the detection current and outputs it to the short-circuit protection module. The short-circuit protection module can detect whether at least one of the four gallium nitride power tubes in the high-voltage switching power supply has a short-circuit fault, and shut down the four gallium nitride power tubes when a short-circuit fault occurs, so as to improve the safety of the high-voltage switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 It is a structural schematic diagram of a current detection circuit of a high-voltage switching power supply according to the related art; Figure 2 It is a structural schematic diagram of a current detection circuit of a high-voltage switching power supply provided by an embodiment of the present application; Figure 3 is a waveform diagram of various parameters in a current detection circuit provided by an embodiment of the present application; Figure 4 This is a flow chart of a current detection method provided by an embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the implementation methods of the present application will be further described in detail below in conjunction with the accompanying drawings.

[0020] like Figure 2 As shown, an embodiment of the present application provides a current detection circuit of a high-voltage switching power supply, the current detection circuit includes a current sensing module 210, an average current detection module 220, a short circuit protection module 230 and a peak current detection module 240 connected in sequence. Among them, the current sensing module 210 is used to convert the input current I IN Converted into a proportional sense current I SNS After output; the average current detection module 220 is used to calculate the detection current I SNS The corresponding detection voltage V SNS The average value is output, and the detection voltage V SNS The average value of the detection current I SNS The short circuit protection module 230 is used to detect the current I SNS Four GaN power tubes M in the high voltage switching power supply A ~M D Short circuit protection; the peak current detection module 240 is used to detect the current I SNS After reaching the set peak value, the output reverse peak current detection signal V TRIP The circuit structure of each module is described below.

[0021] (1) Current sensing module 210 The current sensing module 210 includes a sampling resistor R SNS1 , a first resistor R1, a second resistor R2, a current mirror circuit, a high-low voltage isolation transistor and a high-low voltage isolation transistor M H3 The current sensing module 210 also includes two current sources I1 and I2.

[0022] Sampling resistor R SNS1 The first end of the sampling resistor R is connected to the first end of the first resistor R1 and serves as the input end of the current sensing module 210; SNS1The second end of the first resistor R1 is connected to the first end of the second resistor R2 as the first output end of the current sensing module 210; the second end of the first resistor R1 and the second end of the second resistor R2 are respectively connected to the two input ends of the current mirror circuit, and the two output ends of the current mirror circuit are respectively connected to the first transistor M in the high and low voltage isolation pair. H1 and the second transistor M H2 The drain of the first transistor M H1 The source of the second transistor M is connected to the input terminal of the current source I1. H2 The source of the first resistor R1 is connected to the input end of the current source I1, and the output ends of the current sources I1 and I2 are grounded; the second end of the first resistor R1 is connected to the high and low voltage isolation tube M H3 The drain is connected to the high and low voltage isolation tube M H3 The source of the first transistor M is used as the second output terminal of the current sensing module 210; H1 , the second transistor M H2 And high and low pressure isolation pipe M H3 The gate and internal power supply V CC connected.

[0023] The current mirror circuit includes a third transistor M1, a fourth transistor M2, a fifth transistor M3 and a sixth transistor M4; the source of the third transistor M1 is connected to the second end of the first resistor R1 as an input end of the current mirror circuit; the source of the fourth transistor M2 is connected to the second end of the second resistor R2 as another input end of the current mirror circuit; the drain of the third transistor M1 is connected to the source of the fifth transistor M3, and the drain of the fifth transistor M3 is connected to the drain of the first transistor as an output end of the current mirror circuit; the gate of the third transistor M1 is connected to the gate and drain of the fourth transistor M2 and the source of the sixth transistor M4 respectively; the gate of the fifth transistor M3 is connected to the gate and drain of the sixth transistor M4 as another output end of the current mirror circuit, and is connected to the gate of the second transistor M H2 The drain is connected.

[0024] Optionally, the current sensing module 210 further includes a single-stage amplifier M5; the drain of the single-stage amplifier M5 is connected to the source of the high and low voltage isolation tube, and the gate of the single-stage amplifier M5 is connected to the first transistor M H1 The source of the single-stage amplifier M5 is connected to the source of the current sensing module 210, and the source of the single-stage amplifier M5 serves as the second output end of the current sensing module 210.

[0025] Sampling resistor R SNS1 Used to control the input current I of the high voltage switching power supply IN The sampling resistor R SNS1 A voltage drop is generated at both ends of the sampling resistor R SNS1The first resistor R1 and the second resistor R2 at both ends generate a current difference, and the current difference is output to the current mirror circuit. The current mirror circuit is used to output the current difference to the high and low voltage isolation transistor M. H3 , high and low pressure isolation tube M H3 The detection current I generated by the current difference SNS Output to the average current detection module 220, the high and low voltage isolation tube and the high and low voltage isolation tube M H3 Used to isolate the high voltage domain and the low voltage domain and detect the current I SNS With input current I IN Proportional.

[0026] In this embodiment, the sampling resistor R SNS1 At input voltage V IN and output voltage V OUT A more stable input voltage V IN and output voltage V OUT As the detection voltage, it can significantly reduce the switching noise on the detection current I SNS The influence of current can be reduced and the accuracy of current detection can be improved.

[0027] When the input current I IN Flow through the sampling resistor R SNS1 When the sampling resistor R SNS1 The voltage across the two ends is V SNSP Higher than V SPSN , causing V SPN1 The voltage drop across the first resistor R1 generates the same voltage drop V SPN1 , detection current I SNS Flow to high and low pressure isolation pipe M H3 , which can be expressed as: SNS =(V SNSP -V SPSN ) / R1=I L ×R SNS1 / R1.

[0028] That is, the detection current I SNS Equal to the voltage drop V SPN1 Divided by the first resistor R1, and the detection current I SNS Equal to the inductor current I in the high voltage switching power supply L With the sampling resistor R SNS1 The product of the inductor current I L With input current I IN Related. Among them, I L Indicates four GaN power tubes M A ~M D The current between the inductor L. When the GaN power tube M A When off, IL ≠I IN In addition, I L =I IN .

[0029] (2) Average current detection module 220 The average current detection module 220 includes a proportional resistor R3, a first operational amplifier AMP and an RC filter. The proportional resistor R3 is used to adjust the detection current I SNS The corresponding detection voltage V SNS With input current I IN The first operational amplifier AMP and the RC filter are used to output the detection voltage V SNS The average value of the detection voltage V SNS The average value is used to represent the detection current I SNS The detection voltage V SNS After passing through the first operational amplifier AMP and the RC filter, it is converted into the average value of the detection voltage V IMON Then, the average value of the detection voltage V IMON Output to the logic control in the high voltage switching power supply.

[0030] Specifically, the first end of the proportional resistor R3 is connected to the positive input end of the first operational amplifier AMP and serves as the input end of the average current detection module 220; the second end of the proportional resistor R3 is connected to the first end of the RC filter and then grounded; the negative input end of the first operational amplifier AMP is connected to the output end and then connected to the second end of the RC filter; the third end of the RC filter serves as the output end of the average current detection module 220.

[0031] Among them, the RC circuit includes a third resistor R4 and a capacitor C; the first end of the capacitor C serves as the first end of the RC filter; the first end of the third resistor R4 serves as the second end of the RC filter; the second end of the third resistor R4 is connected to the second end of the capacitor C and serves as the third end of the RC filter.

[0032] (3) Short circuit protection module 230 The short circuit protection module 230 includes a first comparator CMP1 and a short circuit protection logic. The first comparator CMP1 is used to set the overcurrent limit voltage V OC and the detection current I SNS The corresponding detection voltage V SNS The comparison result is output to the short-circuit protection logic, which is used to determine the four gallium nitride power tubes M in the high-voltage switching power supply according to the comparison result. A ~M D When at least one of them has a short circuit fault, the output is connected to the four GaN power tubes M A ~M D The shutdown signal VSP .

[0033] Specifically, the positive input terminal of the first comparator CMP1 is connected to the positive input terminal of the first operational amplifier AMP as the first input terminal of the short-circuit protection module 230; the negative input terminal of the first comparator CMP1 is connected to the overcurrent limiting voltage output terminal V OC The output terminal of the first comparator CMP1 is connected to the input terminal of the short-circuit protection logic; the output terminal of the short-circuit protection logic serves as the output terminal of the short-circuit protection module 230.

[0034] Among them, when the four GaN power tubes M A ~M D When at least one of the input currents is short-circuited, the input current I IN will increase abnormally, and once the input current I IN At the specified time t OC After the end, it is still higher than the current limit point I OC , the overcurrent limit voltage V OC Higher than the detection voltage V SNS , indicating that four GaN power tubes M A ~M D At least one of them has a short circuit fault, and the short circuit protection module 230 generates a shutdown signal V SP Turn off the four GaN power tubes M A ~M D .

[0035] (4) Peak current detection module 240 The peak current detection module 240 includes a second operational amplifier EA, a slope compensator, and a second comparator CMP2. The second operational amplifier EA is used to convert the feedback voltage V FB and reference voltage V REF The difference voltage between V CMP Output to the second comparator CMP2, feedback voltage V FB The output voltage V OUT Related, the slope compensator is used to use the ramp signal V SLP Compensation detection current I SNS The corresponding detection voltage V SNS , the compensated detection voltage V S Output to the second comparator CMP2, the second comparator CMP2 is used to detect the voltage V after compensation S and the difference voltage V CMP The comparison result outputs the peak current detection signal V TRIP , peak current detection signal V TRIP is the detection current I ISNSThe signal is flipped when the set peak value is reached. That is, when the detection current I SNS After reaching the peak value, the peak current detection signal V TRIP and the peak current detection signal V TRIP Output to the logic control in the high voltage switching power supply.

[0036] Specifically, the first input end of the slope compensator is connected to the positive input end of the first comparator CMP1 as the first input end of the peak current detection module 240, and the second input end of the slope compensator is connected to the ramp signal output end V SLP The output end of the slope compensator is connected to the positive input end of the second comparator CMP2; the positive input end of the second operational amplifier EA is connected to the reference voltage output end V REF The negative input terminal of the second operational amplifier EA is connected to the feedback voltage output terminal V FB The output end of the second operational amplifier EA is connected to the negative input end of the second comparator CMP2; the output end of the second comparator CMP2 serves as the output end of the peak current detection module 240.

[0037] Among them, the constant voltage feedback loop adjusts the difference voltage V CMP , ramp signal V SLP The detection voltage V SNS Compensation generates the compensated detection voltage V S , by comparing the difference voltage V CMP and the compensated detection voltage V S , according to the comparison result, the peak current detection signal V is flipped TRIP for peak current mode control.

[0038] Figure 3 shows the input current I IN , inductor current I L , pulse voltage V TIMER 、GaN power tube M A ~M B The node voltage between V SW1 , Peak current detection signal V TRIP and the average value of the detection voltage V IMON The waveform between 0 and t1 represents the waveform of each parameter when the current detection circuit is working normally. At this time, the current detection circuit outputs the peak current detection signal V TRIP and the average value of the detection voltage V IMON ; At time t3, the input current I is detected IN Above the current limit point I OC, and at the specified time t OC After the end, it is still higher than the current limit point I OC , then determine the four GaN power tubes M A ~M D At least one of them has a short circuit fault, and the short circuit protection circuit generates a shutdown signal V SP Turn off the four GaN power tubes M A ~M D .

[0039] To sum up, the current detection circuit of the high-voltage switching power supply provided in the embodiment of the present application uses the input voltage and output voltage of the high-voltage switching power supply as detection references, which can reduce the influence of switching noise on the detection current and improve the accuracy of current detection.

[0040] After the current sensing module detects the detection current, it outputs it to the average current detection module and the peak current detection module. The average current detection module can output the average value of the detection voltage, and the average value of the detection current is represented by the average value of the detection voltage. The peak current detection module can output a flipped peak current detection signal to indicate that the detection current has reached the set peak value, thereby improving the comprehensiveness of current detection.

[0041] The current sensing module detects the detection current and outputs it to the short-circuit protection module. The short-circuit protection module can detect whether at least one of the four gallium nitride power tubes in the high-voltage switching power supply has a short-circuit fault, and shut down the four gallium nitride power tubes when a short-circuit fault occurs, so as to improve the safety of the high-voltage switching power supply.

[0042] like Figure 4 As shown, this embodiment provides a current detection method applied to the current detection circuit of the above-mentioned high-voltage switching power supply, and the current detection method includes: Step 401, the sampling resistor controls the input current of the high-voltage switching power supply to generate a voltage drop at both ends of the sampling resistor, so that a first resistor and a second resistor respectively connected in series at both ends of the sampling resistor generate a current difference, and the current difference is output to a current mirror circuit, and the current mirror circuit outputs the current difference to a high-low voltage isolation tube, and the high-low voltage isolation tube outputs a detection current generated by the current difference to an average current detection module. The high-low voltage isolation pair tube and the high-low voltage isolation tube are used to isolate the high-voltage domain and the low-voltage domain, and the detection current is proportional to the input current.

[0043] When the input current I IN Flow through the sampling resistor R SNS1 When the sampling resistor R SNS1 The voltage across the two ends is V SNSP Higher than V SPSN , causing V SPN1 The voltage drop across the first resistor R1 generates the same voltage drop V SPN1, detection current I SNS Flow to high and low pressure isolation pipe M H3 , which can be expressed as: SNS =(V SNSP -V SPSN ) / R1=I L ×R SNS1 / R1.

[0044] That is, the detection current I SNS Equal to the voltage drop V SPN1 Divided by the first resistor R1, and the detection current I SNS Equal to the inductor current I in the high voltage switching power supply L With the sampling resistor R SNS1 The product of the inductor current I L With input current I IN Related. Among them, I L Indicates four GaN power tubes M A ~M D The current between the inductor L. When the GaN power tube M A When off, I L ≠I IN In addition, I L =I IN .

[0045] Step 402, the proportional resistor adjusts the proportional relationship between the detection voltage corresponding to the detection current and the input current, the first operational amplifier and the RC filter output the average value of the detection voltage, and the average value of the detection voltage is used to represent the average value of the detection current.

[0046] In step 403, the first comparator outputs a comparison result between the overcurrent limit voltage and the detection voltage corresponding to the detection current to the short-circuit protection logic. When the short-circuit protection logic determines that at least one of the four gallium nitride power tubes has a short-circuit fault according to the comparison result, the short-circuit protection logic outputs a shutdown signal for the four gallium nitride power tubes.

[0047] When four GaN power tubes M A ~M D When at least one of the input currents is short-circuited, the input current I IN will increase abnormally, and once the input current I IN At the specified time t OC After the end, it is still higher than the current limit point I OC , the overcurrent limit voltage V OC Higher than the detection voltage V SNS , indicating that four GaN power tubes M A ~M D At least one of them has a short circuit fault, and the short circuit protection module 230 generates a shutdown signal VSP Turn off the four GaN power tubes M A ~M D .

[0048] In step 404, the second operational amplifier outputs the difference voltage between the feedback voltage and the reference voltage to the second comparator, the feedback voltage is related to the output voltage of the high-voltage switching power supply, the slope compensator uses the slope signal to compensate the detection voltage corresponding to the detection current, and outputs the compensated detection voltage to the second comparator, the second comparator outputs a peak current detection signal according to the comparison result between the compensated detection voltage and the difference voltage, and the peak current detection signal is a signal that flips when the detection current reaches a set peak value.

[0049] The constant voltage feedback loop regulates the difference voltage V CMP , ramp signal V SLP The detection voltage V SNS Compensation generates the compensated detection voltage V S , by comparing the difference voltage V CMP and the compensated detection voltage V S , according to the comparison result, the peak current detection signal V is flipped TRIP for peak current mode control.

[0050] In summary, in the current detection method provided in the embodiment of the present application, the current detection circuit selects the input voltage and output voltage of the high-voltage switching power supply as detection references, which can reduce the influence of switching noise on the detection current and improve the accuracy of current detection.

[0051] After the current sensing module detects the detection current, it outputs it to the average current detection module and the peak current detection module. The average current detection module can output the average value of the detection voltage, and the average value of the detection current is represented by the average value of the detection voltage. The peak current detection module can output a flipped peak current detection signal to indicate that the detection current has reached the set peak value, thereby improving the comprehensiveness of current detection.

[0052] The current sensing module detects the detection current and outputs it to the short-circuit protection module. The short-circuit protection module can detect whether at least one of the four gallium nitride power tubes in the high-voltage switching power supply has a short-circuit fault, and shut down the four gallium nitride power tubes when a short-circuit fault occurs, so as to improve the safety of the high-voltage switching power supply.

[0053] A person skilled in the art will understand that all or part of the steps to implement the above embodiments may be accomplished by hardware or by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a disk or an optical disk, etc.

[0054] The above description is not intended to limit the embodiments of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the protection scope of the embodiments of the present application.

Claims

1. A current detection circuit for a high voltage switching power supply, characterized in that: The current detection circuit comprises a current sensing module, an average current detection module, a short circuit protection module and a peak current detection module which are connected in sequence; The current sensing module comprises a sampling resistor, a first resistor, a second resistor, a current mirror circuit, a high-low voltage isolation pair and a high-low voltage isolation tube, wherein the sampling resistor is used to control the input current of the high-voltage switching power supply to generate a voltage drop at both ends of the sampling resistor, so that the first resistor and the second resistor respectively connected in series at both ends of the sampling resistor generate a current difference, and the current difference is output to the current mirror circuit, the current mirror circuit is used to output the current difference to the high-low voltage isolation tube, the high-low voltage isolation tube is used to output the detection current generated by the current difference to the average current detection module, the high-low voltage isolation pair and the high-low voltage isolation tube are used to isolate the high-voltage domain and the low-voltage domain, and the detection current is proportional to the input current; The average current detection module includes a proportional resistor, a first operational amplifier and an RC filter, the proportional resistor is used to adjust the proportional relationship between the detection voltage corresponding to the detection current and the input current, the first operational amplifier and the RC filter are used to output the average value of the detection voltage, and the average value of the detection voltage is used to represent the average value of the detection current; The short-circuit protection module includes a first comparator and a short-circuit protection logic, wherein the first comparator is used to output a comparison result between the overcurrent limit voltage and the detection voltage corresponding to the detection current to the short-circuit protection logic, and the short-circuit protection logic is used to output a shutdown signal for the four gallium nitride power tubes when it is determined according to the comparison result that at least one of the four gallium nitride power tubes in the high-voltage switching power supply has a short-circuit fault; The peak current detection module includes a second operational amplifier, a slope compensator and a second comparator. The second operational amplifier is used to output a difference voltage between a feedback voltage and a reference voltage to the second comparator. The feedback voltage is related to the output voltage of the high-voltage switching power supply. The slope compensator is used to compensate the detection voltage corresponding to the detection current using a ramp signal, and output the compensated detection voltage to the second comparator. The second comparator is used to output a peak current detection signal according to a comparison result between the compensated detection voltage and the difference voltage. The peak current detection signal is a signal that flips when the detection current reaches a set peak value.

2. The current detection circuit of the high-voltage switching power supply according to claim 1, characterized in that: The current sensing module also includes two current sources; The first end of the sampling resistor is connected to the first end of the first resistor and serves as the input end of the current sensing module; The second end of the sampling resistor is connected to the first end of the second resistor and serves as the first output end of the current sensing module; The second end of the first resistor and the second end of the second resistor are respectively connected to the two input ends of the current mirror circuit, the two output ends of the current mirror circuit are respectively connected to the drains of the first transistor and the second transistor in the high-low voltage isolation pair, the sources of the first transistor and the second transistor are respectively connected to the input ends of two current sources, and the output ends of the two current sources are grounded; The second end of the first resistor is connected to the drain of the high-low voltage isolation tube, and the source of the high-low voltage isolation tube serves as the second output end of the current sensing module; The gates of the first transistor, the second transistor and the high-low voltage isolation tube are connected to an internal power supply.

3. The current detection circuit of the high-voltage switching power supply according to claim 2, characterized in that: The current sensing module also includes a single-stage amplifier; The drain of the single-stage amplifier is connected to the source of the high-low voltage isolation tube, the gate of the single-stage amplifier is connected to the source of the first transistor, and the source of the single-stage amplifier serves as the second output end of the current sensing module.

4. The current detection circuit of the high-voltage switching power supply according to claim 2, characterized in that: The current mirror circuit includes a third transistor, a fourth transistor, a fifth transistor and a sixth transistor; The source of the third transistor is connected to the second end of the first resistor as an input end of the current mirror circuit; The source of the fourth transistor is connected to the second end of the second resistor as another input end of the current mirror circuit; The drain of the third transistor is connected to the source of the fifth transistor, and the drain of the fifth transistor is connected to the drain of the first transistor as an output end of the current mirror circuit; The gate of the third transistor is connected to the gate and drain of the fourth transistor and the source of the sixth transistor respectively; The gate of the fifth transistor is connected to the gate and drain of the sixth transistor and serves as another output end of the current mirror circuit and is connected to the drain of the second transistor.

5. The current detection circuit of the high-voltage switching power supply according to claim 1, characterized in that: The first end of the proportional resistor is connected to the positive input end of the first operational amplifier and serves as the input end of the average current detection module; The second end of the proportional resistor is connected to the first end of the RC filter and then grounded; The negative input terminal of the first operational amplifier is connected to the output terminal and then connected to the second terminal of the RC filter; The third terminal of the RC filter serves as the output terminal of the average current detection module.

6. The current detection circuit of the high-voltage switching power supply according to claim 5, characterized in that: The RC circuit includes a third resistor and a capacitor; The first end of the capacitor serves as the first end of the RC filter; The first end of the third resistor serves as the second end of the RC filter; The second end of the third resistor is connected to the second end of the capacitor to serve as the third end of the RC filter.

7. The current detection circuit of the high-voltage switching power supply according to claim 1, characterized in that: The positive input terminal of the first comparator is connected to the positive input terminal of the first operational amplifier as the first input terminal of the short-circuit protection module; The negative input terminal of the first comparator is connected to the overcurrent limiting voltage output terminal as the second input terminal of the short-circuit protection module; The output terminal of the first comparator is connected to the input terminal of the short-circuit protection logic; The output end of the short-circuit protection logic serves as the output end of the short-circuit protection module.

8. The current detection circuit of the high-voltage switching power supply according to claim 1, characterized in that: The first input end of the slope compensator is connected to the positive input end of the first comparator as the first input end of the peak current detection module, the second input end of the slope compensator is connected to the ramp signal output end as the second input end of the peak current detection module, and the output end of the slope compensator is connected to the positive input end of the second comparator; The positive input terminal of the second operational amplifier is connected to the reference voltage output terminal as the third input terminal of the peak current detection module, the negative input terminal of the second operational amplifier is connected to the feedback voltage output terminal as the fourth input terminal of the peak current detection module, and the output terminal of the second operational amplifier is connected to the negative input terminal of the second comparator; The output end of the second comparator serves as the output end of the peak current detection module.

9. The current detection circuit of the high voltage switching power supply according to any one of claims 1 to 8, characterized in that: The detection current is equal to the voltage drop divided by the first resistor, and the detection current is equal to the product of the inductor current in the high-voltage switching power supply and the sampling resistor divided by the first resistor, and the inductor current is related to the input current.

10. A current detection method for a current detection circuit of a high-voltage switching power supply, characterized in that: Used in a current detection circuit of a high-voltage switching power supply according to any one of claims 1 to 9, the method comprising: The sampling resistor controls the input current of the high-voltage switching power supply to generate a voltage drop at both ends of the sampling resistor, so that the first resistor and the second resistor connected in series at both ends of the sampling resistor respectively generate a current difference, and the current difference is output to the current mirror circuit, and the current mirror circuit outputs the current difference to the high-low voltage isolation tube, and the high-low voltage isolation tube outputs the detection current generated by the current difference to the average current detection module. The high-low voltage isolation tube and the high-low voltage isolation tube are used to isolate the high-voltage domain and the low-voltage domain, and the detection current is proportional to the input current; The proportional resistor adjusts the proportional relationship between the detection voltage corresponding to the detection current and the input current, the first operational amplifier and the RC filter output an average value of the detection voltage, and the average value of the detection voltage is used to represent the average value of the detection current; The first comparator outputs a comparison result between the overcurrent limit voltage and the detection voltage corresponding to the detection current to the short-circuit protection logic, and when the short-circuit protection logic determines that at least one of the four gallium nitride power tubes has a short-circuit fault according to the comparison result, the short-circuit protection logic outputs a shutdown signal for the four gallium nitride power tubes; The second operational amplifier outputs a difference voltage between a feedback voltage and a reference voltage to the second comparator, the feedback voltage is related to the output voltage of the high-voltage switching power supply, the slope compensator uses a ramp signal to compensate for the detection voltage corresponding to the detection current, and outputs the compensated detection voltage to the second comparator, the second comparator outputs a peak current detection signal according to a comparison result between the compensated detection voltage and the difference voltage, and the peak current detection signal is a signal that flips when the detection current reaches a set peak value.

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