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

Abstract

The present application discloses a current detection circuit and a current detection method for a high-voltage switching power supply, belonging to the field of circuit technology. The current detection circuit includes 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 the current difference corresponding to the voltage drop generated at both ends of the sampling resistor of the input current to the average current detection module; the average current detection module adjusts the proportional relationship between the detection voltage and the input current through a proportional resistor and outputs the average value of the detected current; the short-circuit protection module outputs a turn-off signal for four gallium nitride power transistors when it is determined that at least one of the four gallium nitride power transistors in the high-voltage switching power supply has a short-circuit fault; the peak current detection module outputs a peak current detection signal according to the comparison result of the detected voltage after ramp compensation and the differential voltage. The present application can improve the accuracy and comprehensiveness of current detection and improve the safety of the high-voltage switching power supply.

Description

Technical Field

[0001] This application relates to the field of circuit technologies, and particularly 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, the current-mode control method has been widely used due to its high reliability and simple loop compensation characteristics. As a key part of the current-mode control method, the current detection circuit can obtain current signals to adjust the output voltage of the high-voltage switching power supply and provide over-current protection.

[0003] As Figure 1 shown, a small sampling resistor R in the most common current detection circuit is connected in series with the inductor L in the high-voltage switching power supply. Regardless of whether it is in buck, boost, or buck-boost operating modes, the current detection circuit can continuously measure the inductor current signal. However, this current detection circuit uses the switching nodes V SNS and V SW1 and V SW2 as the detection reference, and both of them have a large amount of common-mode switching noise, which requires the current detection circuit to have a sufficiently high common-mode rejection ratio. Otherwise, it will interfere with the measurement signal I SNS and cause serious distortion of the measurement signal I SNS Summary of the Invention

[0004] This 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 serious distortion of the measurement signal I SW1 and V SW2 when using the switching nodes V SNS as the detection reference. The technical solutions are as follows:

[0005] According to the first aspect of this application, a current detection circuit for a high-voltage switching power supply is provided. The current detection circuit includes a current sensing module, an average current detection module, a short-circuit protection module, and a peak current detection module connected in sequence;

[0006] ​The current sensing module includes a sampling resistor, a first resistor, a second resistor, a current mirror circuit, a high-voltage and low-voltage isolation pair of transistors, and a high-voltage and low-voltage isolation transistor. The sampling resistor is used to control the input current of the high-voltage switch power supply to generate a voltage drop across both ends of the sampling resistor, so that a current difference is generated between the first resistor and the second resistor connected in series across both ends of the sampling resistor, 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-voltage and low-voltage isolation transistor. The high-voltage and low-voltage isolation transistor is used to output the detection current generated by the current difference to the average current detection module. The high-voltage and low-voltage isolation pair of transistors and the high-voltage and low-voltage isolation transistor are used to isolate the high-voltage domain and the low-voltage domain, and the detection current is proportional to the input current;

[0007] 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;

[0008] The short-circuit protection module includes a first comparator and a short-circuit protection logic. The first comparator is used to output the comparison result between the overcurrent limit voltage and the detection voltage corresponding to the detection current to the short-circuit protection logic. The short-circuit protection logic is used to output a turn-off signal for the four gallium nitride power transistors in the high-voltage switch power supply when it is determined according to the comparison result that at least one of the four gallium nitride power transistors has a short-circuit fault;

[0009] The peak current detection module includes a second operational amplifier, a ramp compensator, and a second comparator. The second operational amplifier is used to output the differential 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 switch power supply. The ramp compensator is used to compensate the detection voltage corresponding to the detection current with 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 the comparison result between the compensated detection voltage and the differential voltage. The peak current detection signal is a signal that flips when the detection current reaches a set peak value.

[0010] In a possible implementation, the current sensing module further includes two current sources;

[0011] 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;

[0012] 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;

[0013] The second ends of the first resistor and 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-voltage and low-voltage isolation pair of transistors. 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;

[0014] The second end of the first resistor is connected to the drain of the high-voltage and low-voltage isolation transistor, and the source of the high-voltage and low-voltage isolation transistor serves as the second output end of the current sensing module;

[0015] The gates of the first transistor, the second transistor, and the high-voltage and low-voltage isolation transistor are connected to the internal power supply.

[0016] In a possible implementation, the current sensing module further includes a single-stage amplifier;

[0017] The drain of the single-stage amplifier is connected to the source of the high-voltage and low-voltage isolation transistor, 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.

[0018] In a possible implementation, the current mirror circuit includes a third transistor, a fourth transistor, a fifth transistor, and a sixth transistor;

[0019] The source of the third transistor serves as an input end of the current mirror circuit and is connected to the second end of the first resistor;

[0020] The source of the fourth transistor serves as the other input end of the current mirror circuit and is connected to the second end of the second resistor;

[0021] The drain of the third transistor is connected to the source of the fifth transistor, and the drain of the fifth transistor serves as an output end of the current mirror circuit and is connected to the drain of the first transistor;

[0022] The gate of the third transistor is respectively connected to the gate and drain of the fourth transistor and the source of the sixth transistor;

[0023] The gate of the fifth transistor is connected to the gate and drain of the sixth transistor and serves as the other output end of the current mirror circuit, which is connected to the drain of the second transistor.

[0024] In a possible implementation, the first end of the proportional resistor is connected to the positive input terminal of the first operational amplifier and serves as the input terminal of the average current detection module;

[0025] The second end of the proportional resistor is connected to the first end of the RC filter and then grounded;

[0026] The negative input terminal of the first operational amplifier is connected to the output terminal and then connected to the second end of the RC filter;

[0027] The third end of the RC filter serves as the output terminal of the average current detection module.

[0028] In a possible implementation, the RC circuit includes a third resistor and a capacitor;

[0029] The first end of the capacitor serves as the first end of the RC filter;

[0030] The first end of the third resistor serves as the second end of the RC filter;

[0031] The second end of the third resistor is connected to the second end of the capacitor and then serves as the third end of the RC filter.

[0032] In a possible implementation, the positive input terminal of the first comparator serves as the first input terminal of the short - circuit protection module and is connected to the positive input terminal of the first operational amplifier;

[0033] The negative input terminal of the first comparator serves as the second input terminal of the short - circuit protection module and is connected to the over - current limit voltage output terminal;

[0034] The output terminal of the first comparator is connected to the input terminal of the short - circuit protection logic;

[0035] The output terminal of the short - circuit protection logic serves as the output terminal of the short - circuit protection module.

[0036] In a possible implementation, the first input terminal of the ramp compensator serves as the first input terminal of the peak current detection module and is connected to the positive input terminal of the first comparator, the second input terminal of the ramp compensator serves as the second input terminal of the peak current detection module and is connected to the ramp signal output terminal, and the output terminal of the ramp compensator is connected to the positive input terminal of the second comparator;

[0037] The positive input terminal of the second operational amplifier serves as the third input terminal of the peak current detection module and is connected to the reference voltage output terminal, the negative input terminal of the second operational amplifier serves as the fourth input terminal of the peak current detection module and is connected to the feedback voltage output terminal, and the output terminal of the second operational amplifier is connected to the negative input terminal of the second comparator;

[0038] The output terminal of the second comparator serves as the output terminal of the peak current detection module.

[0039] In a possible implementation, the detected current is equal to the voltage drop divided by the first resistor, and the detected 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.

[0040] According to a second aspect of the present application, there is provided a current detection method for a current detection circuit of a high-voltage switching power supply, which is used in the current detection circuit of the high-voltage switching power supply as described above. The method includes:

[0041] The sampling resistor controls the input current of the high-voltage switching power supply to generate a voltage drop across the sampling resistor, so as to cause a current difference between the first resistor and the second resistor connected in series across the sampling resistor, and output the current difference to the current mirror circuit. The current mirror circuit outputs the current difference to the high-low voltage isolation tube. The high-low voltage isolation tube outputs the detected current generated by the current difference to the 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 detected current is proportional to the input current;

[0042] The proportional resistor adjusts the proportional relationship between the detected voltage corresponding to the detected current and the input current. The first operational amplifier and the RC filter output the average value of the detected voltage, and the average value of the detected voltage is used to represent the average value of the detected current;

[0043] The first comparator outputs the comparison result between the overcurrent limit voltage and the detected voltage corresponding to the detected 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, it outputs a shutdown signal for the four gallium nitride power tubes;

[0044] The second operational amplifier outputs the differential 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 ramp compensator uses a ramp signal to compensate the detected voltage corresponding to the detected current, and outputs the compensated detected voltage to the second comparator. The second comparator outputs a peak current detection signal according to the comparison result between the compensated detected voltage and the differential voltage. The peak current detection signal is a signal that flips when the detected current reaches a set peak value.

[0045] The beneficial effects of the technical solution provided by the present application at least include:

[0046] The current detection circuit selects the input voltage and output voltage of the high-voltage switching power supply as the detection reference, which can reduce the influence of switching noise on the detected current and improve the accuracy of current detection.

[0047] After the current sensing module detects the detected 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 detected 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 detected current reaches the set peak value, improving the comprehensiveness of current detection.

[0048] After the current sensing module detects the detected current, it 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 transistors in the high-voltage switching power supply has a short-circuit fault, and turn off the four gallium nitride power transistors when a short-circuit fault occurs, so as to improve the safety of the high-voltage switching power supply. Description of the Drawings

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0050] Figure 1 is a schematic structural diagram of a current detection circuit of a high-voltage switching power supply shown according to the related art;

[0051] Figure 2 is a schematic structural diagram of a current detection circuit of a high-voltage switching power supply provided by an embodiment of the present application;

[0052] Figure 3 is a waveform diagram of various parameters in the current detection circuit provided by an embodiment of the present application;

[0053] Figure 4 is a flowchart of a current detection method provided by an embodiment of the present application. Detailed Embodiments

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will further describe the embodiments of the present application in detail with reference to the drawings.

[0055] Such as Figure 2As shown in the figure, an embodiment of the present application provides a current detection circuit for 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 into a proportional detection current I SNS and then output it; the average current detection module 220 is used to calculate the average value of the detection voltage V SNS corresponding to the detection current I SNS and then output it. The average value of the detection voltage V SNS can represent the average value of the detection current I SNS ; the short-circuit protection module 230 is used to perform short-circuit protection on four gallium nitride power transistors M SNS in the high-voltage switching power supply according to the detection current I A ~M D ; the peak current detection module 240 is used to output a flipped peak current detection signal V SNS after the detection current I TRIP reaches the set peak. The circuit structures of each module will be described separately below.

[0056] (1) Current sensing module 210

[0057] 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 pair of transistors, and a high-low voltage isolation transistor M H3 . The current sensing module 210 also includes two current sources I1 and I2.

[0058] The first end of the sampling resistor R SNS1 is connected to the first end of the first resistor R1 and used as the input end of the current sensing module 210; the second end of the sampling resistor R SNS1 is connected to the first end of the second resistor R2 and used as the first output end of the current sensing module 210; the second ends of the first resistor R1 and 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 drains of the first transistor M H1 and the second transistor M H2 in the high-low voltage isolation pair of transistors. The source of the first transistor M H1 is connected to the input end of the current source I1, and the source of the second transistor M H2 is connected to the input end of the current source I1. The output ends of the current sources I1 and I2 are grounded; the second end of the first resistor R1 is connected to the drain of the high-low voltage isolation transistor M H3 , and the high-low voltage isolation transistor M H3The source electrode serves as the second output terminal of the current sensing module 210; the first transistor M H1 , the second transistor M H2 , and the high-voltage and low-voltage isolation transistor M H3 have their gate electrodes connected to the internal power supply V CC .

[0059] Among them, the current mirror circuit includes a third transistor M1, a fourth transistor M2, a fifth transistor M3, and a sixth transistor M4; the source electrode of the third transistor M1 serves as an input terminal of the current mirror circuit and is connected to the second terminal of the first resistor R1; the source electrode of the fourth transistor M2 serves as another input terminal of the current mirror circuit and is connected to the second terminal of the second resistor R2; the drain electrode of the third transistor M1 is connected to the source electrode of the fifth transistor M3, and the drain electrode of the fifth transistor M3 serves as an output terminal of the current mirror circuit and is connected to the drain electrode of the first transistor; the gate electrode of the third transistor M1 is respectively connected to the gate electrode and the drain electrode of the fourth transistor M2 and the source electrode of the sixth transistor M4; the gate electrode of the fifth transistor M3 is connected to the gate electrode and the drain electrode of the sixth transistor M4 and then serves as another output terminal of the current mirror circuit, and is connected to the drain electrode of the second transistor M H2 .

[0060] Optionally, the current sensing module 210 further includes a single-stage amplifier M5; the drain electrode of the single-stage amplifier M5 is connected to the source electrode of the high-voltage and low-voltage isolation transistor, the gate electrode of the single-stage amplifier M5 is connected to the source electrode of the first transistor M H1 , and the source electrode of the single-stage amplifier M5 serves as the second output terminal of the current sensing module 210.

[0061] The sampling resistor R SNS1 is used to control the input current I IN of the high-voltage switching power supply to generate a voltage drop across the sampling resistor R SNS1 , so as to cause a current difference to be generated between the first resistor R1 and the second resistor R2 respectively connected in series across the sampling resistor R SNS1 , and output the current difference to the current mirror circuit. The current mirror circuit is used to output the current difference to the high-voltage and low-voltage isolation transistor M H3 . The high-voltage and low-voltage isolation transistor M H3 is used to output the detection current I SNS generated by the current difference to the average current detection module 220. The high-voltage isolation pair transistor and the high-voltage and low-voltage isolation transistor M H3 are used to isolate the high-voltage domain and the low-voltage domain, and the detection current I SNS is proportional to the input current I IN .

[0062] In this embodiment, the sampling resistor R SNS1 is located between the input voltage V IN and the output voltage V OUTAmong them, a more stable input voltage V IN and output voltage V OUT are selected as the detection voltages, which can significantly reduce the influence of switching noise on the detected current I SNS and improve the accuracy of current detection.

[0063] When the input current I IN flows through the sampling resistor R SNS1 , the voltage V SNS1 across the sampling resistor R SNSP is higher than V SPSN , causing a voltage drop of V SPN1 . The same voltage drop V SPN1 is generated on the first resistor R1. The detected current I SNS flows to the high-low voltage isolation transistor M H3 , which can be expressed as: I SNS = (V SNSP - V SPSN ) / R1 = I L × R SNS1 / R1.

[0064] That is, the detected current I SNS is equal to the voltage drop V SPN1 divided by the first resistor R1, and the detected current I SNS is equal to the product of the inductor current I L in the high-voltage switching power supply and the sampling resistor R SNS1 divided by the first resistor R1. The inductor current I L is related to the input current I IN . Among them, I L represents the current of the inductor L between the four gallium nitride power transistors M A ~M D . When the gallium nitride power transistor M A is turned off, I L ≠I IN ; otherwise, I L = I IN .

[0065] (2) Average current detection module 220

[0066] 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 proportional relationship between the detected voltage V SNS corresponding to the detected current I SNS and the input current I IN . The first operational amplifier AMP and the RC filter are used to output the average value of the detected voltage V SNS . The average value of the detected voltage V SNS is used to represent the detected current ISNS The average value. Among them, the detection voltage V SNS After passing through the first operational amplifier AMP and the RC filter, it is converted into the average value V of the detection voltage IMON , and then, the average value V of the detection voltage IMON is output to the logic control in the high-voltage switching power supply.

[0067] Specifically, the first end of the proportional resistor R3 is connected to the positive input terminal of the first operational amplifier AMP and serves as the input terminal 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 terminal of the first operational amplifier AMP is connected to the output terminal and then connected to the second end of the RC filter; the third end of the RC filter serves as the output terminal of the average current detection module 220.

[0068] 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 then serves as the third end of the RC filter.

[0069] (3) Short-circuit protection module 230

[0070] The short-circuit protection module 230 includes a first comparator CMP1 and short-circuit protection logic. The first comparator CMP1 is used to output the comparison result of the overcurrent limit voltage V OC and the detected current I SNS corresponding detection voltage V SNS to the short-circuit protection logic. The short-circuit protection logic is used to output the turn-off signal V A ~M D of the four gallium nitride power transistors M in the high-voltage switching power supply when it is determined according to the comparison result that at least one of them has a short-circuit fault A ~M D . SP .

[0071] Specifically, the positive input terminal of the first comparator CMP1 serves as the first input terminal of the short-circuit protection module 230 and is connected to the positive input terminal of the first operational amplifier AMP; the negative input terminal of the first comparator CMP1 serves as the second input terminal of the short-circuit protection module 230 and is connected to the overcurrent limit 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.

[0072] Among them, when at least one of the four gallium nitride power transistors M A ~M D is short-circuited, the detected input current IIN will abnormally increase, and once the input current I IN is still higher than the current limit point I after the specified time t OC ends, then an overcurrent limit voltage V OC will be detected to be higher than the detection voltage V OC which indicates that at least one of the four gallium nitride power transistors M SNS ~M A has a short circuit fault, and the short circuit protection module 230 generates a turn-off signal V D to turn off the four gallium nitride power transistors M SP ~M A ~M D .

[0073] (4) Peak current detection module 240

[0074] The peak current detection module 240 includes a second operational amplifier EA, a ramp compensator, and a second comparator CMP2. The second operational amplifier EA is used to output the differential voltage V FB between the feedback voltage V REF and the reference voltage V CMP to the second comparator CMP2. The feedback voltage V FB is related to the output voltage V OUT of the high-voltage switching power supply. The ramp compensator is used to compensate the detection voltage V SLP corresponding to the detection current I SNS with the ramp signal V SNS , and output the compensated detection voltage V S to the second comparator CMP2. The second comparator CMP2 is used to output a peak current detection signal V S according to the comparison result of the compensated detection voltage V CMP and the differential voltage V TRIP . The peak current detection signal V TRIP is a signal that flips when the detection current I ISNS reaches the set peak value. That is to say, when the detection current I SNS reaches the peak, the peak current detection signal V TRIP flips, and the peak current detection signal V TRIP is output to the logic control in the high-voltage switching power supply.

[0075] Specifically, the first input terminal of the ramp compensator is connected to the positive input terminal of the first comparator CMP1 as the first input terminal of the peak current detection module 240, and the second input terminal of the ramp compensator is connected to the ramp signal output terminal V SLPare connected, the output terminal of the ramp compensator is connected to the positive input terminal of the second comparator CMP2; the positive input terminal of the second operational amplifier EA is used as the third input terminal of the peak current detection module 240 and is connected to the reference voltage output terminal V REF are connected, the negative input terminal of the second operational amplifier EA is used as the fourth input terminal of the peak current detection module 240 and is connected to the feedback voltage output terminal V FB are connected, the output terminal of the second operational amplifier EA is connected to the negative input terminal of the second comparator CMP2; the output terminal of the second comparator CMP2 is used as the output terminal of the peak current detection module 240.

[0076] Among them, the constant voltage feedback loop adjusts the differential voltage V CMP , the ramp signal V SLP compensates the detection voltage V SNS to generate a compensated detection voltage V S , by comparing the differential voltage V CMP and the compensated detection voltage V S , according to the comparison result, the peak current detection signal V TRIP is flipped to perform peak current mode control.

[0077] Figure 3 shows the waveforms of the input current I IN , the inductor current I L , the pulse voltage V TIMER , the node voltage V A ~M B between the gallium nitride power transistors M SW1 , the peak current detection signal V TRIP and the average value V IMON of the detection voltage. 0~t1 represents the waveforms 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 V IMON of the detection voltage; at time t3, it is detected that the input current I IN is higher than the current limit point I OC , and after the specified time t OC ends, it is still higher than the current limit point I OC , then it is determined that at least one of the four gallium nitride power transistors M A ~M D has a short circuit fault, and the short circuit protection circuit generates a turn-off signal V SP to turn off the four gallium nitride power transistors M A ~M D .

[0078] In summary, for the current detection circuit of the high-voltage switching power supply provided in the embodiments of the present application, the input voltage and output voltage of the high-voltage switching power supply are selected as the detection references for the current detection circuit, which can reduce the influence of switching noise on the detected current and improve the accuracy of current detection.

[0079] After the current sensing module detects the detected current, it outputs the detected current to the average current detection module and the peak current detection module. The average current detection module can output the average value of the detected voltage, and the average value of the detected current is represented by the average value of the detected voltage. The peak current detection module can output a flipped peak current detection signal to indicate that the detected current reaches the set peak value, improving the comprehensiveness of current detection.

[0080] After the current sensing module detects the detected current, it outputs the detected current to the short-circuit protection module. The short-circuit protection module can detect whether at least one of the four gallium nitride power transistors in the high-voltage switching power supply has a short-circuit fault, and turn off the four gallium nitride power transistors when a short-circuit fault occurs, so as to improve the safety of the high-voltage switching power supply.

[0081] As Figure 4 shown, the present embodiment provides a current detection method applied to the current detection circuit of the above-mentioned high-voltage switching power supply. The current detection method includes:

[0082] Step 401, the sampling resistor controls the input current of the high-voltage switching power supply to generate a voltage drop across the sampling resistor, so that a current difference is generated between the first resistor and the second resistor respectively connected in series across the sampling resistor. 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 transistor. The high-low voltage isolation transistor outputs the detected current generated by the current difference to the average current detection module. The high-low voltage isolation pair transistor and the high-low voltage isolation transistor are used to isolate the high-voltage domain and the low-voltage domain, and the detected current is proportional to the input current.

[0083] When the input current I IN flows through the sampling resistor R SNS1 , the voltage V SNS1 across the sampling resistor R SNSP is higher than V SPSN , causing a voltage drop of V SPN1 . The same voltage drop V SPN1 is generated on the first resistor R1. The detected current I SNS flows to the high-low voltage isolation transistor M H3 , which can be expressed as: I SNS =(V SNSP -V SPSN ) / R1 = I L ×R SNS1 / R1.

[0084] That is, the detected current I SNSEqual to the voltage drop V SPN1 Divided by the first resistor R1, and the detected current I SNS Is equal to the inductor current I in the high-voltage switching power supply L And the sampling resistor R SNS1 The product of is divided by the first resistor R1, and the inductor current I L Is related to the input current I IN Wherein, I L Represents the current of the inductor L between the four gallium nitride power transistors M A ~M D When the gallium nitride power transistor M A Is turned off, I L ≠I IN ; Otherwise, I L =I IN .

[0085] Step 402, the proportional resistor adjusts the proportional relationship between the detected voltage corresponding to the detected current and the input current. The first operational amplifier and the RC filter output the average value of the detected voltage, and the average value of the detected voltage is used to represent the average value of the detected current.

[0086] Step 403, the first comparator outputs the comparison result of the overcurrent limit voltage and the detected voltage corresponding to the detected current to the short-circuit protection logic. When the short-circuit protection logic determines that at least one of the four gallium nitride power transistors has a short-circuit fault according to the comparison result, it outputs a turn-off signal for the four gallium nitride power transistors.

[0087] When at least one of the four gallium nitride power transistors M A ~M D Is short-circuited, the detected input current I IN Will abnormally increase. Once the input current I IN Is still higher than the current limit point I OC After the specified time t OC Ends, then the overcurrent limit voltage V OC Will be detected to be higher than the detected voltage V SNS , indicating that at least one of the four gallium nitride power transistors M A ~M D Has a short-circuit fault, and the short-circuit protection module 230 generates a turn-off signal V SP To turn off the four gallium nitride power transistors M A ~M D .

[0088] In step 404, the second operational amplifier outputs the differential 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 ramp compensator uses a ramp signal to compensate the detected voltage corresponding to the detected current, and outputs the compensated detected voltage to the second comparator. The second comparator outputs a peak current detection signal according to the comparison result of the compensated detected voltage and the differential voltage. The peak current detection signal is a signal that flips when the detected current reaches the set peak value.

[0089] The constant voltage feedback loop regulates the differential voltage V CMP , and the ramp signal V SLP compensates the detected voltage V SNS to generate the compensated detected voltage V S . By comparing the differential voltage V CMP and the compensated detected voltage V S , the peak current detection signal V TRIP is flipped according to the comparison result for peak current mode control.

[0090] In summary, for the current detection method provided by the embodiments of the present application, the input voltage and output voltage of the high-voltage switching power supply are selected as the detection references for the current detection circuit, which can reduce the influence of switching noise on the detected current and improve the accuracy of current detection.

[0091] After the current sensing module detects the detected 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 detected voltage, and the average value of the detected current is represented by the average value of the detected voltage. The peak current detection module can output a flipped peak current detection signal to indicate that the detected current reaches the set peak value, improving the comprehensiveness of current detection.

[0092] After the current sensing module detects the detected current, it 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 transistors in the high-voltage switching power supply has a short-circuit fault, and turn off the four gallium nitride power transistors when a short-circuit fault occurs to improve the safety of the high-voltage switching power supply.

[0093] Those of ordinary skill in the art can understand that all or part of the steps to implement the above embodiments can be completed by hardware, or can be completed by a program instructing relevant hardware. The program can be stored in a computer-readable storage medium. The above-mentioned storage medium can be a read-only memory, a disk, an optical disc, etc.

[0094] The above does not intend to limit the embodiments of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the embodiments of the present application shall 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 includes 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 includes a sampling resistor, a first resistor, a second resistor, a current mirror circuit, a high-voltage and low-voltage isolation pair of transistors, and a high-voltage and low-voltage isolation transistor. The sampling resistor is used to control the input current of the high-voltage switching power supply to generate a voltage drop across the sampling resistor, so that the first resistor and the second resistor respectively connected in series across the sampling resistor generate a current difference, and output the current difference to the current mirror circuit. The current mirror circuit is used to output the current difference to the high-voltage and low-voltage isolation transistor. The high-voltage and low-voltage isolation transistor is used to output the detection current generated by the current difference to the average current detection module. The high-voltage and low-voltage isolation pair of transistors and the high-voltage and low-voltage isolation transistor 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. The first comparator is used to output the comparison result of the overcurrent limit voltage and the detection voltage corresponding to the detection current to the short-circuit protection logic. The short-circuit protection logic is used to output a turn-off signal for the four gallium nitride power transistors in the high-voltage switching power supply when it is determined according to the comparison result that at least one of the four gallium nitride power transistors has a short-circuit fault; The peak current detection module includes a second operational amplifier, a ramp compensator, and a second comparator. The second operational amplifier is used to output the differential 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 ramp compensator is used to compensate the detection voltage corresponding to the detection current with 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 the comparison result of the compensated detection voltage and the differential 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 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 terminal of the first resistor and the second terminal of the second resistor are respectively connected to two input terminals of the current mirror circuit. Two output terminals of the current mirror circuit are respectively connected to the drains of the first transistor and the second transistor in the high-voltage and low-voltage isolation pair of transistors. The sources of the first transistor and the second transistor are respectively connected to the input terminals of two current sources, and the output terminals of the two current sources are grounded; The second terminal of the first resistor is connected to the drain of the high-voltage and low-voltage isolation transistor, and the source of the high-voltage and low-voltage isolation transistor serves as the second output terminal of the current sensing module; The gates of the first transistor, the second transistor, and the high-voltage and low-voltage isolation transistor are connected to the 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 further includes a single-stage amplifier; The drain of the single-stage amplifier is connected to the source of the high-voltage and low-voltage isolation transistor, 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 terminal of the current sensing module.

4. The current detection circuit of the high-voltage switching power supply according to claim 2, wherein The current mirror circuit includes a third transistor, a fourth transistor, a fifth transistor, and a sixth transistor; The source of the third transistor serves as an input terminal of the current mirror circuit and is connected to the second terminal of the first resistor; The source of the fourth transistor serves as another input terminal of the current mirror circuit and is connected to the second terminal of the second resistor; The drain of the third transistor is connected to the source of the fifth transistor, and the drain of the fifth transistor serves as an output terminal of the current mirror circuit and is connected to the drain of the first transistor; The gate of the third transistor is respectively connected to the gate and drain of the fourth transistor and the source of the sixth transistor; The gate of the fifth transistor is connected to the gate and drain of the sixth transistor and then serves as another output terminal 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, wherein The first terminal of the proportional resistor is connected to the positive input terminal of the first operational amplifier and then serves as the input terminal of the average current detection module; The second terminal of the proportional resistor is connected to the first terminal 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 filter includes a third resistor and a capacitor; The first terminal of the capacitor serves as the first terminal of the RC filter; The first terminal of the third resistor serves as the second terminal of the RC filter; The second terminal of the third resistor is connected to the second terminal of the capacitor and then serves as the third terminal of the RC filter.

7. The current detection circuit of the high-voltage switching power supply according to claim 1, wherein The positive input terminal of the first comparator serves as the first input terminal of the short-circuit protection module and is connected to the positive input terminal of the first operational amplifier; The negative input terminal of the first comparator serves as the second input terminal of the short-circuit protection module and is connected to the over-current limit voltage output terminal; The output terminal of the first comparator 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.

8. The current detection circuit of the high-voltage switching power supply according to claim 1, wherein The first input terminal of the ramp compensator is connected to the positive input terminal of the first comparator as the first input terminal of the peak current detection module, the second input terminal of the ramp compensator is connected to the ramp signal output terminal as the second input terminal of the peak current detection module, and the output terminal of the ramp compensator is connected to the positive input terminal 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 terminal of the second comparator serves as the output terminal 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 detected current is equal to the voltage drop divided by the first resistor, and the detected 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, For the current detection circuit in the high-voltage switching power supply according to any one of claims 1 to 9, the method includes: The sampling resistor controls the input current of the high-voltage switching power supply to generate a voltage drop across the sampling resistor, so as to cause a current difference between the first resistor and the second resistor connected in series across the sampling resistor, output the current difference to the current mirror circuit, the current mirror circuit outputs the current difference to the high-low voltage isolation transistor, the high-low voltage isolation transistor outputs the detected current generated by the current difference to the average current detection module, the high-low voltage isolation pair transistor and the high-low voltage isolation transistor are used to isolate the high-voltage domain and the low-voltage domain, and the detected current is proportional to the input current; The proportional resistor adjusts the proportional relationship between the detected voltage corresponding to the detected current and the input current, the first operational amplifier and the RC filter output the average value of the detected voltage, and the average value of the detected voltage is used to represent the average value of the detected current; The first comparator outputs the comparison result between the overcurrent limit voltage and the detected voltage corresponding to the detected 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 transistors has a short-circuit fault according to the comparison result, it outputs a turn-off signal for the four gallium nitride power transistors; The second operational amplifier outputs the differential 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 ramp compensator compensates the detected voltage corresponding to the detected current using a ramp signal and outputs the compensated detected voltage to the second comparator. The second comparator outputs a peak current detection signal according to the comparison result between the compensated detected voltage and the differential voltage. The peak current detection signal is a signal that flips when the detected current reaches a set peak value.

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