A converter short-circuit protection circuit and method based on parasitic parameters

Abstract

The present invention discloses a converter short-circuit protection circuit and method based on parasitic parameters. The present invention adopts a converter control module and a short-circuit logic processing module. The converter control module is used to control the switch of each switch tube of the target converter. The short-circuit logic processing module is used to make a short-circuit judgment based on the parasitic parameters of the ground loop of the target converter. The short-circuit logic processing module is based on the voltage sampling value v of the parasitic parameters of the ground loop of the target converter. S4‑S The short circuit judgment is carried out, and then the switch of each switch tube is controlled through the converter control module to perform short circuit protection on the target converter. The overload / short circuit condition of the power supply output is monitored by real-time detection of the voltage on the parasitic parameters of the circuit ground loop, thereby achieving short circuit protection technology without current sampling, reducing the volume and weight of the converter, reducing losses, and improving efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of converter control, and in particular relates to a converter short-circuit protection circuit and method based on parasitic parameters. Background Art

[0002] Switching power converters have become the core devices of various power supply systems due to their unique advantages such as high efficiency, high power density and small size. They are also increasingly widely used in civil industry, automotive industry, military industry and aerospace fields. In order to cope with the complex and harsh operating environment in various fields, switching power converters need to have higher reliability and smaller volume and weight. Higher reliability requires the converter to have complete protection functions, such as overvoltage, overcurrent, overtemperature, output short circuit protection, etc. Among them, the output short circuit condition is the most severe and the protection logic is the most complex. Reliable output short circuit function can be summarized as follows: 1) If the output end is short-circuited or overloaded for a long time, the converter can effectively identify the short circuit condition, and perform protection and converter cut-out. 2) If there is a short-term overcurrent at the output end, it is required to operate normally. For example, when starting, a large capacitor is connected to the load end, and the converter is required to withstand the charging current of the capacitor and complete the startup normally without any protection misoperation.

[0003] However, the mature and reliable short-circuit protection schemes in the industry often require the addition of additional current sampling circuits and protection logic circuits, which will not only increase the volume and weight of the converter, but also increase losses and reduce efficiency, which runs counter to the concept of "miniaturization" and "efficiency" of the converter. The more mature and commonly used converter short-circuit protection schemes are mainly divided into the following categories: 1) Protection scheme based on current Hall sensor. The output current is detected by the Hall sensor, and protection action is performed when overcurrent or short circuit occurs. This scheme requires a Hall sensor to be connected in series at the output end. In addition, an additional power supply and sampling circuit must be added to the Hall sensor. The scheme is large in size and high in cost, and is not suitable for aerospace and military fields. In addition, there is also the problem of low current Hall bandwidth and unsuitable for high-frequency switching occasions. 2) Protection scheme with series sampling resistor or shunt. The current information is obtained by obtaining the voltage on the current sampling resistor to perform protection action. In this scheme, the output current always needs to flow through the sampling resistor, and there are problems of heating and low efficiency of the sampling resistor. 3) Scheme based on inductor DCR resistance. This scheme obtains the current information flowing through the inductor by obtaining the voltage drop of the inductor DCR resistance. The short-circuit protection strategy of TI's synchronous step-down DC / DC converter control chip LM27403 is based on this solution, but the protection accuracy of this solution depends on the consistency and accuracy of the inductor DCR resistance, and is greatly affected by the operating temperature of the converter. Adding temperature compensation will increase the control complexity of the circuit, so it is not suitable for aerospace and military fields. It has become a trend to remove current sampling and its related circuits to improve the power density and conversion efficiency of switching power supplies, but how to achieve high-reliability short-circuit protection without current sampling is a major difficulty. In the existing short-circuit protection technology, the current sampling circuit brings about an increase in volume and weight and an increase in loss. As for the short-circuit protection technology without current sampling circuit, there is currently no reliable and simple solution in the industry. Summary of the invention

[0004] In order to solve the problems of short-circuit protection technology without current sampling circuit, such as large circuit volume and weight, high operation loss, etc., the present invention provides a converter short-circuit protection circuit and method based on parasitic parameters.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A converter short-circuit protection circuit based on parasitic parameters is applied to the short-circuit protection circuit of the target converter 301, characterized in that it includes a converter control module 302 and a short-circuit logic processing module 303. The converter control module 302 is used to control the switching of each switch tube of the target converter 301. The converter control module 302 is based on the output voltage sampling value v of the target converter 301. o , input voltage sampling value v in, outputs the driving signal of each switch tube in the target converter 301; the short-circuit logic processing module 303 is used to make a short-circuit judgment based on the ground loop parasitic parameters of the target converter, and the short-circuit logic processing module 303 is based on the ground loop parasitic parameter voltage sampling value v of the target converter 301 S4-S A short circuit judgment is performed, and then the switching of each switch tube is controlled by the converter control module 302 to perform short circuit protection on the target converter 301.

[0007] As a preferred technical solution of the present invention, the converter control module 302 includes a subtractor 304, a proportional regulator 305, an integral regulator 306, an adder 308, a switch tube time parameter calculation module 309, a PWM generation module 310, a start condition judgment module 311, and a short circuit count threshold setting module 312. The start condition judgment module 311 is used to judge the input voltage sampling value v of the target converter. in , whether the converter working start conditions are met and the start identification signal S is output st The short-circuit count threshold setting module 312 is used to output an overcurrent comparator reference signal v based on the ground loop parasitic parameters of the target converter F , and based on the target converter load output short circuit judgment counting threshold Cnt ref ; Output voltage sampling value v of target converter o With the preset output voltage reference value v oref The error value is outputted after subtraction operation is performed by the subtractor 304; the output of the subtractor 304 is connected to the input end of the proportional regulator 305 and the input end of the integral regulator 306, and the proportional regulator 305 performs proportional operation on the error value and outputs the proportional operation result v p The integral regulator 306 performs a proportional operation on the error value and outputs an integral operation result v i Adder 308 is based on the integral operation result v i And the proportional operation result v p Output regulator output signal v er The switch tube time parameter calculation module 309 is based on the input voltage sampling value v of the standard converter in , the sampling value of the output voltage v o , regulator output signal v er The output target converter outputs the on-time of each switch in each stage; the PWM generation module 310 generates a driving signal for each switch based on the output of the switch time parameter calculation module 309 and its internal carrier wave comparison.

[0008] As a preferred technical solution of the present invention, the short-circuit logic processing module 303 includes a comparator 313, a rising edge capture & counting module 314, a short-circuit judgment module 315, a resistor R 301 , resistor R302 , the overcurrent comparator reference signal v F Through resistor R 301 The inverting input terminal of the comparator 313 is connected to the ground loop parasitic parameter voltage sampling value v of the target converter. S4-S Through resistor R 302 The positive input terminal of the comparator 313 is connected, and the output terminal of the comparator 313 outputs the overcurrent comparator trigger signal S tr The start-up identification signal S st The output end of the comparator 313 is connected to control the output signal transmission of the comparator 313 by controlling the on and off of the switch; the rising edge capture & counting module 314 is used to capture the overcurrent comparator trigger signal S tr The short circuit judgment module 315 counts the rising edge signal and outputs the short circuit judgment count value Cnt based on the short circuit judgment count value Cnt and the short circuit judgment count threshold Cnt. ref Compare and output short circuit protection signal S pt The access converter control module 302 controls the opening and closing of each switch tube.

[0009] As a preferred technical solution of the present invention, the converter control module 302 further includes a subtractor 307, the integral operation result v i The subtractor 307 is connected to the adder 308, and the subtractor 307 is based on the integral operation result v i and preset integral down-regulation constant v i- The output of the subtractor 307 is connected to the input of the adder 308; the overcurrent comparator triggers the signal S tr By controlling the on / off of the control switch, the preset integral down-regulation constant v is i- Whether to connect the subtractor 307.

[0010] As a preferred technical solution of the present invention, the short circuit protection signal S pt The PWM generation module 310 connected to the converter control module 302 generates a short-circuit protection signal S pt When the short circuit protection signal S pt When it is at a high level, the PWM generation module 310 outputs a blocking drive signal for each switch tube.

[0011] A converter short-circuit protection method based on parasitic parameters is applied to the converter short-circuit protection circuit based on parasitic parameters designed by the present invention. The following steps are performed for the ground loop parasitic parameters in the target converter to perform short-circuit protection on the target transformer:

[0012] Step 1: Get the input voltage sampling value v of the target converter in , output voltage sampling value v o , ground loop parasitic parameter voltage sampling value v S4-S ; Based on the ground loop parasitic parameters of the target converter, set the overcurrent comparison reference signal v F ; Based on the load of the target converter, set the short circuit judgment count threshold Cnt ref ;

[0013] Step 2: Based on the input voltage sampling value v in Determine whether the input voltage meets the start-up condition of the target converter and obtain the converter start-up identification signal S st , if satisfied, the identification signal S is activated st If it is high level, go to step 3; if it is not satisfied, start the identification signal S st is low level, repeat step 2;

[0014] Step 3: Compare the overcurrent reference signal v F And the ground loop parasitic parameter voltage sampling value v S4-S Compare and obtain the overcurrent comparator trigger signal S tr , local loop parasitic parameter voltage sampling value v S4-S Greater than the overcurrent comparator reference signal v F , overcurrent comparator trigger signal S tr From low voltage to high voltage, enter step 4; when the overcurrent comparator reference signal v F Greater than the ground loop parasitic parameter voltage sampling value v S4-S , overcurrent comparator trigger signal S tr To change from high voltage to low level, repeat step 3;

[0015] Step 4: Based on the overcurrent comparator trigger signal S tr From low voltage to high level, preset integral down-regulation constant v i- The subtractor 307 in the converter control module 302 is connected; and based on the overcurrent comparator trigger signal S tr From low voltage to high level, the short circuit judgment count Cnt is increased by 1, and the short circuit judgment count Cnt and the short circuit judgment count threshold Cnt are ref Compare and obtain the short circuit protection signal S pt , go to step 5; if Cnt>Cnt ref , short circuit protection signal S pt Is high level; if Cnt <Cnt ref , short circuit protection signal S pt is low level;

[0016] Step 5: Based on the short circuit protection signal S ptis low level, the target converter operates normally; based on the short-circuit protection signal S pt Set to a high level to turn off all switches in the target converter, and the target converter stops outputting.

[0017] As a preferred technical solution of the present invention, the overcurrent comparison reference signal v F The settings should satisfy the following relationship:

[0018] v S4-S_peak_norm <v F <v S4-S_peak_oc

[0019] In the formula, v S4-S_peak_norm is the voltage peak value corresponding to the parasitic parameters of the ground loop when the converter is running in steady state, v S4-S_peak_oc It is the voltage peak value corresponding to the parasitic parameters of the ground loop when the converter is short-circuited.

[0020] As a preferred technical solution of the present invention, the preset integral down-regulation constant v i- The value is 10% of the output value of the integral regulator 306 when the converter is running in steady state.

[0021] The beneficial effects of the present invention are as follows: the present invention provides a converter short-circuit protection circuit and method based on parasitic parameters. The present invention adopts a converter control module and a short-circuit logic processing module. The converter control module is used to control the switching of each switch tube of the target converter. The short-circuit logic processing module is used to perform short-circuit detection on the parasitic parameters of the ground loop of the target converter. The short-circuit logic processing module is based on the voltage sampling value v of the parasitic parameters of the ground loop of the target converter. S4-S The short circuit judgment is carried out, and then the switch of each switch tube is controlled through the converter control module to perform short circuit protection on the target converter. The overload / short circuit condition of the power supply output is monitored by real-time detection of the voltage on the parasitic parameters of the circuit ground loop, thereby achieving short circuit protection technology without current sampling, reducing the volume and weight of the converter, reducing losses, and improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The power circuit of the fourth switch buck-boost converter of the present embodiment;

[0023] Figure 2 Schematic diagram of typical operating waveforms of the fourth switch buck-boost converter of this embodiment;

[0024] Figure 3A is a circuit diagram of a converter of this embodiment;

[0025] Figure 3B Schematic diagram of the converter controller principle of this embodiment;

[0026] Figure 3CThis is a schematic diagram of the principle of the short-circuit logic processing module of this embodiment;

[0027] Figure 4 is a waveform diagram of a parasitic parameter voltage sampling signal in this embodiment;

[0028] Figure 5 4 is a flow chart of the converter short-circuit protection method based on parasitic parameters in this embodiment. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0030] The example of the present invention takes a four-switch buck-boost converter (Four Switch Buck-Boost) as an example to describe the technical solution of the example of the present invention. It should be pointed out that the algorithm and circuit of the overload start-up protection of the example of the present invention are also applicable to other similar converter topologies, such as buck converter, boost converter, etc.

[0031] As a DC / DC converter with a wide range of input and output and the ability to flexibly perform buck-boost functions, the four-switch buck-boost converter is particularly favored by the military industry and aerospace fields. Figure 1 As shown, it includes a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a power inductor L b . Power inductor L b One end of L is connected to the source S of the first switch S1 and the drain D of the second switch S2. b The other end of is connected to the source S of the third switch S3 and the drain D of the fourth switch S4. When the four-switch buck-boost converter is in steady state operation, a switching cycle can be divided into the following Figure 2 The four working stages shown are: input energy storage stage, direct power transmission stage, output freewheeling stage, and clamping stage. In the input energy storage stage, the first switch S1 and the fourth switch S4 are turned on, and the input voltage is applied to the power inductor L b The inductor current is V in / L b The slope of the rise, the inductance L b Energy storage; in the direct power transmission stage, the first switch S1 and the third switch S3 are turned on, and the voltage difference between the input voltage and the output voltage is applied to the power inductor L b The inductor current is (v in -v o ) / L bThe slope changes. In this stage, the input end directly transfers energy to the load through the power inductor. In the output freewheeling stage, the second switch S2 and the third switch S3 are turned on. The output voltage is applied to the inductor L b The inductor current is V o / L b The slope of the power inductor L b The energy in the capacitor is transferred to the output end; in the clamping stage, the second switch S2 and the fourth switch S4 are turned on, and the power inductor L b The voltage across the two ends is clamped at 0, the inductor current remains unchanged, and the converter neither stores energy from the input nor transfers energy to the load.

[0032] The present application designs a converter short-circuit protection circuit based on parasitic parameters, which is applied to the short-circuit protection circuit of the target converter 301. The target converter 301 is as follows: Figure 3A As shown, the target converter 301 is a converter main circuit that takes into account the parasitic parameters of the ground loop. The short-circuit protection circuit includes a converter control module 302 and a short-circuit logic processing module 303. The converter control module 302 is used to control the switching of each switch tube of the target converter 301. The converter control module 302 is based on the output voltage sampling value v of the target converter 301. o , input voltage sampling value v in , outputs the driving signal of each switch tube in the target converter 301; the short-circuit logic processing module 303 is used to perform short-circuit detection on the ground loop parasitic parameters of the target converter, and the short-circuit logic processing module 303 is based on the ground loop parasitic parameter voltage sampling value v of the target converter 301 S4-S A short circuit judgment is performed, and then the switching of each switch tube is controlled by the converter control module 302 to perform short circuit protection on the target converter 301.

[0033] The converter main circuit 301 considering the parasitic parameters of the ground loop is composed of an input voltage source v in , first switch S1, second switch S2, third switch S3, fourth switch S4, inductor L b , output filter capacitor C f , ground loop parasitic inductance L p , ground loop parasitic resistance R p and the output load resistor R Ld The input voltage source v in The positive terminal is connected to the drain D of the first switch, and the inductor L b One end is connected to the source S of the first switch S1 and the drain D of the second switch S2, and the other end is connected to the source S of the third switch S3 and the drain D of the fourth switch S4. The drain D of the third switch S3 and the output filter capacitor C f Positive terminal, output load resistance R LdThe ground loop parasitic inductance L p and parasitic resistance R p One end of is connected to the source S of the second switch S2, and the other end is connected to the source S of the fourth switch S4. The output voltage of the four-switch buck-boost converter main circuit 301 is marked as v o , the ground loop parasitic inductance L p and parasitic resistance R p The voltage across the terminals is marked as v S4-S .

[0034] like Figure 3B As shown, the converter control module 302 includes a subtractor 304, a proportional regulator 305, an integral regulator 306, an adder 308, a switch tube time parameter calculation module 309, a PWM generation module 310, a start condition judgment module 311, and a short circuit count threshold setting module 312. The start condition judgment module 311 is used to judge the input voltage sampling value v of the target converter. in , whether the converter working start conditions are met and the start identification signal S is output st The short-circuit count threshold setting module 312 is used to output an overcurrent comparator reference signal v based on the ground loop parasitic parameters of the target converter F , and based on the target converter load output short circuit judgment counting threshold Cnt ref ; Output voltage sampling value v of target converter o With the preset output voltage reference value v oref The error value is outputted after subtraction operation is performed by the subtractor 304; the output of the subtractor 304 is connected to the input end of the proportional regulator 305 and the input end of the integral regulator 306, and the proportional regulator 305 performs proportional operation on the error value and outputs the proportional operation result v p The integral regulator 306 performs a proportional operation on the error value and outputs an integral operation result v i Adder 308 is based on the integral operation result v i And the proportional operation result v p Output regulator output signal v er The switch tube time parameter calculation module 309 is based on the input voltage sampling value v of the standard converter in , the sampling value of the output voltage v o , regulator output signal v er Output the on-time of each switch tube of the target converter in each stage; the PWM generation module 310 generates the driving signal of each switch tube based on the output of the switch tube time parameter calculation module 309 and the internal carrier comparison, and the converter control module 302 also includes a subtractor 307, the integral operation result v i The subtractor 307 is connected to the adder 308, and the subtractor 307 is based on the integral operation result vi and preset integral down-regulation constant v i- The output of the subtractor 307 is connected to the input of the adder 308; the overcurrent comparator triggers the signal S tr By controlling the on / off of the control switch, the preset integral down-regulation constant v is i- Whether to connect the subtractor 307.

[0035] The overcurrent comparison reference signal v F The settings should satisfy the following relationship:

[0036] v S4-S_peak_norm <v F <v S4-S_peak_oc

[0037] In the formula, v S4-S_peak_norm is the voltage peak value corresponding to the parasitic parameters of the ground loop when the converter is running in steady state, v S4-S_peak_oc is the voltage peak value corresponding to the parasitic parameters of the ground loop when the converter is short-circuited. The preset integral down-regulation constant vi- is set to be about 10% of the output value of the integral regulator 306 when the converter is in steady-state operation.

[0038] In this embodiment, the subtractor 304 is used to output the voltage sampling value v o and the output voltage reference value v oref A subtraction operation is performed, and the output of the subtractor 301 is used as the input signal of the proportional regulator 305 and the integral regulator 306 .

[0039] The proportional regulator 305 is a part of the output voltage PI closed-loop regulator, which is used to sample the output voltage v o and the output voltage reference value v oref The error value is proportional to K p is the proportional adjustment coefficient, and the operation of the proportional regulator 305 can be expressed as: p =K p ×(v oref -v o );

[0040] The integral regulator 306 is a part of the output voltage PI closed-loop regulator, which is used to sample the output voltage v o and the output voltage reference value v oref The error value is integrated, K i is the integral adjustment coefficient, and the operation result of the integral regulator 306 can be expressed as: i =K i / s×(v oref -v o );

[0041] Subtractor 307, when the overcurrent comparator triggers the signal S tr When set high, it is used to calculate the integral result v i and the integral down-regulation constant v i- Perform a subtraction operation, and the output of the subtractor 307 is used as the input signal of the adder 308;

[0042] The adder 308 performs an addition operation on the output result of the subtractor 307 and the output result of the proportional regulator 305. The output result of the adder 308 is the regulator output v er , as one of the input signals of the T1-T4 time parameter calculation module 309;

[0043] The switch tube time parameter calculation module 309 is a T1-T4 time parameter calculation module 309, which calculates the time parameter of the switch tube according to the output voltage sampling value v o , input voltage sampling value v in The output result v of the adder 308 er Perform a specific calculation to calculate Figure 2 The working time T1 - T4 of each stage of the converter is shown as an input signal of the PWM generation module 310 .

[0044] The PWM generation module 310 generates a short circuit protection signal S pt When the short circuit protection signal S pt When it is high level, no matter what the output result of T1-T4 time parameter calculation module 309 is, it directly outputs low level blocking drive on QS1 to QS4;

[0045] The startup condition judgment module 311 determines the startup condition based on the input voltage sampling value v in Determine whether the converter operation start condition is met. If it is met, start the identification signal S st Output high level; if not satisfied, start the identification signal S st Output low level.

[0046] The short-circuit counting threshold setting module 312 outputs an overcurrent comparator reference signal v according to the parasitic parameters of the converter ground loop. F ; According to the actual load of the converter, the output short circuit judgment counting threshold Cnt ref . Further, in one embodiment, v F Set to 200mV, Cnt ref Set to 30.

[0047] From an overall perspective, the converter control 302 includes a first signal input terminal: a short circuit protection signal Spt , used to turn off the drive signals of the first to fourth switches in time after identifying the short-circuit condition; the second signal input terminal: the output voltage sampling value v o , used to receive the output voltage sampling value of the converter main circuit 301; the third signal input terminal: the overcurrent comparator trigger signal S tr , used to identify short-term overcurrent conditions so that the converter controller can make corresponding processing; the fourth signal input terminal: input voltage sampling value v in , used to receive the input voltage sampling value of the converter main circuit 301; based on the signals at each input end, output the driving signal of each switch tube; optionally, the converter controller 302 can be a digital controller (DSP), a microprocessor MCU, a field programmable logic device FPGA, etc., and modules 304 to 312 can be flexibly programmed and implemented in the digital controller (DSP), the microprocessor MCU, and the field programmable logic device FPGA.

[0048] like Figure 3C As shown, the short-circuit logic processing module 303 includes a comparator 313, a rising edge capture & counting module 314, a short-circuit judgment module 315, a resistor R 301 , resistor R 302 , the overcurrent comparator reference signal v F Through resistor R 301 The inverting input terminal of the comparator 313 is connected to the ground loop parasitic parameter voltage sampling value v of the target converter. S4-S Through resistor R 302 The positive input terminal of the comparator 313 is connected, and the output terminal of the comparator 313 outputs the overcurrent comparator trigger signal S tr The start-up identification signal S st The output end of the comparator 313 is connected to control the output signal transmission of the comparator 313 by controlling the on and off of the switch; the rising edge capture & counting module 314 is used to capture the overcurrent comparator trigger signal S tr The short circuit judgment module 315 counts the rising edge signal and outputs the short circuit judgment count value Cnt based on the short circuit judgment count value Cnt and the short circuit judgment count threshold Cnt. ref Compare and output short circuit protection signal S pt The converter control module 302 is connected to control the opening and closing of each switch tube. pt The PWM generation module 310 connected to the converter control module 302 generates a short-circuit protection signal S pt When the short circuit protection signal S pt When it is at a high level, the PWM generation module 310 outputs a blocking drive signal for each switch tube.

[0049] In this embodiment, the comparator 313 is used to obtain the parasitic parameter voltage sampling signal v S4-S and the overcurrent comparator reference signal v F When the parasitic voltage sampling signal v S4-S Greater than the overcurrent comparator reference signal v F , the output of the comparator 313 changes from low to high, otherwise, the output of the comparator 313 changes from high to low. st If the output is high level, the output signal of the comparator 313 is sent to the rising edge capture & counting module 314.

[0050] The rising edge capture & counting module 314 is used to capture the rising edge signal of the comparator 313 and count the rising edge signal, and output the short circuit judgment count value Cnt.

[0051] The short circuit judgment module 315 starts the identification signal S st When the output is high level, the short circuit judgment count Cnt output by the rising edge capture & counting module 314 and the short circuit judgment count threshold Cnt output by the converter controller are ref When the short circuit judgment count Cnt is greater than the short circuit judgment count threshold Cnt ref When the short circuit protection signal S pt Output high level; otherwise, short circuit protection signal S pt Output low level.

[0052] Therefore, in one embodiment of the present invention, the hardware circuit only needs to sample the parasitic parameter voltage sampling signal v S4-S It can be realized that, on the one hand, the circuit is very simple, and the circuit cost and the volume and weight of the converter are almost not increased, which is beneficial to improving the power density of the converter; on the other hand, there is almost no additional loss, which is beneficial to improving the efficiency of the converter.

[0053] From an overall perspective, the short-circuit logic processing module 303 includes a first signal input terminal: a start identification signal S st , according to whether the converter is currently in the startup state, whether to perform short-circuit judgment related logic processing; the second signal input terminal: overcurrent comparator reference signal v F , receiving the output from the converter controller 302, the third signal input terminal: the parasitic parameter voltage sampling signal v S4-S , used to receive the ground loop parasitic parameter voltage sampling value of the converter main circuit 301. Fourth signal input terminal: short circuit judgment counting threshold Cnt ref, receiving the output from the converter controller 302; based on the signals at each input terminal, outputting an overcurrent comparator trigger signal and a short-circuit protection signal; optionally, the comparator 313 can use a built-in comparator in a digital controller (DSP), a microprocessor MCU, or a field programmable logic device FPGA, and modules 314 and 315 can be flexibly programmed.

[0054] It should be pointed out in this technical solution that whether the parasitic parameters of the converter ground loop have no effect on the working mode of the converter, the current flowing through the converter inductor L b The current change is only caused by the inductance L b It is determined by the voltage across both ends and its own inductance. Figure 2 The working mode diagram of the four-switch buck-boost converter is given. In the input energy storage stage T1, the first switch S1 and the fourth switch S4 are turned on. In this stage, the inductor current is v in / L b The slope of the inductor current rises, and the inductor current at the beginning of this stage is marked as I N , then in the input energy storage stage T1, the ground loop parasitic parameter voltage includes two parts: parasitic resistance R p The voltage on the parasitic inductance L p Furthermore, if the initial time of a switching cycle is taken as the zero time, the parasitic parameter voltage sampling signal v S4-S The relationship with time t can be expressed as formula (1):

[0055]

[0056] The inductor current at the end time is marked as I1, as shown in formula (2):

[0057]

[0058] In the direct power transmission stage T2, the first switch S1 and the third switch S3 are turned on, and the voltage difference between the input voltage and the output voltage is applied to the power inductor L b At the beginning of this stage, the inductor current is I1, and the inductor current is (v in -v o ) / L b The slope changes, so the parasitic parameter voltage sampling signal v in this time period S4-S The relationship with time t can be expressed as formula (3):

[0059]

[0060] The inductor current at the end time is marked as I2, as shown in formula (4):

[0061]

[0062] In the output freewheeling stage T3, the second switch S2 and the third switch S3 are turned on; the output voltage is applied to the inductor L b At both ends, the inductor current at the beginning of this stage is I2, and at the end of this stage is I N , the inductor current is v o / L b The slope of the parasitic parameter voltage sampling signal v S4-S The relationship with time t can be expressed as formula (5):

[0063]

[0064] In the clamping stage T4, the second switch S2 and the fourth switch S4 are turned on, and the power inductor L b The voltage across the two ends is clamped at 0, and the inductor current remains unchanged. p The upper voltage drop is 0, so the parasitic parameter voltage sampling signal v in this time period S4-S The relationship with time t can be expressed as formula (6):

[0065] v S4-S (t) = I N R p (6)

[0066] According to equations (1) to (6), the parasitic parameter voltage sampling signal v in a switching cycle can be obtained S4-S The relationship with time t is as follows:

[0067]

[0068] From formula (7), we can draw the following Figure 4 As shown in the middle curve 401. It can be seen that v S4-S At the end of the input energy storage phase T1, the signal amplitude is the highest. S4-S The peak value in a switching cycle is marked as v S4-S_peak , as shown in formula (8):

[0069]

[0070] It should be pointed out that the larger the converter output current, the more inductance L needs to be b The longer the energy storage time is, the longer the corresponding T1 period is. It should be pointed out that in engineering practice, the current flowing through the inductor L b When the current exceeds its saturation current value, L b The inductance value will decrease sharply, showing saturation characteristics. Therefore, when the converter output is short-circuited or in a condition with large inrush current (such as starting with a large capacitor connected to the output), the inductor L bThe inductance value decreases, and the input energy storage stage T1 time becomes longer. From formula (7), it can be seen that the parasitic parameter voltage sampling signal v S4-S The peak value of the output voltage increases. From equations (1) to (6), we can draw the v when the output terminal is short-circuited or overcurrent condition. S4-S Changes over time, such as Figure 4 As shown in the middle curve 402. Assume that v S4-S The peak value is v S4-S_peak_norm and v S4-S_peak_oc .

[0071] Therefore, the parasitic voltage sampling signal v S4-S The load current information of the four-switch buck-boost converter can be obtained, and the inductor current of the converter can be monitored in real time. S4-S_peak Greater than the overcurrent comparison reference signal v F In order to ensure that the short-circuit protection is not triggered by mistake during steady-state operation and that overcurrent / short circuit can be reliably identified, the comparator reference signal v F The setting of should satisfy the relationship shown in formula (9).

[0072] v S4-S_peak_norm <v F <v S4-S_peak_oc (9)

[0073] Based on this, appropriate short-circuit judgment logic can be added to identify long-term short-circuit and short-term overcurrent conditions. When the output is overloaded for a long time or the output is short-circuited, timely measures such as shutting down the drive can be taken to protect the converter to avoid the spread of the fault; when the output has a short-term overcurrent (such as starting with a large capacitor at the output end), the converter can be current limited without shutting down. After the short-term overcurrent condition disappears, the converter can still work normally.

[0074] According to the above structural mechanism, the present invention proposes a converter short-circuit protection method based on parasitic parameters, which is applied to a converter short-circuit protection circuit based on parasitic parameters. The following steps are performed for the ground loop parasitic parameters in the target converter, such as Figure 5 As shown, the target transformer is short-circuited:

[0075] First, the system is initialized, including initializing the controller's clock, peripherals, interrupts, and variables;

[0076] Step 1: Get the input voltage sampling value v of the target converter in , output voltage sampling value v o , ground loop parasitic parameter voltage sampling value v S4-S ; Based on the ground loop parasitic parameters of the target converter, set the overcurrent comparison reference signal v F; Based on the load of the target converter, set the short circuit judgment count threshold Cnt ref ;

[0077] Step 2: Based on the input voltage sampling value v in Determine whether the input voltage meets the start-up condition of the target converter and obtain the converter start-up identification signal S st , if satisfied, the identification signal S is activated st If it is high level, go to step 3; if it is not satisfied, start the identification signal S st is low level, repeat step 2;

[0078] Step 3: Compare the overcurrent reference signal v F And the ground loop parasitic parameter voltage sampling value v S4-S Compare and obtain the overcurrent comparator trigger signal S tr , local loop parasitic parameter voltage sampling value v S4-S Greater than the overcurrent comparator reference signal v F , overcurrent comparator trigger signal S tr From low voltage to high voltage, it means that there is overcurrent at the output of the converter, and the process goes to step 4. When the overcurrent comparator reference signal v F Greater than the ground loop parasitic parameter voltage sampling value v S4-S , overcurrent comparator trigger signal S tr To change from high voltage to low level, repeat step 3;

[0079] Step 4: Based on the overcurrent comparator trigger signal S tr From low voltage to high level, preset integral down-regulation constant v i- The subtractor 307 in the converter control module 302 is connected to perform closed-loop PI regulation on the converter output voltage; the integral operation result v in the closed-loop PI regulation of the converter output voltage is i Based on the subtraction of the integral down-regulation constant v i- , reduce the converter inductance L b The purpose of this step is to limit the rise of inductor current if an overload or short circuit occurs at the output of the converter, but the short circuit judgment count Cnt does not increase to the short circuit judgment count threshold Cnt ref Previously, the converter inductor current was limited to prevent damage before a short circuit / overload condition was identified at the converter output.

[0080] And based on the overcurrent comparator trigger signal S tr From low voltage to high level, the short circuit judgment count Cnt is increased by 1, and the short circuit judgment count Cnt and the short circuit judgment count threshold Cnt are ref Compare and obtain the short circuit protection signal S pt, go to step 5; if Cnt>Cnt ref , short circuit protection signal S pt If Cnt is high, it is considered that the converter output is overloaded or short-circuited for a long time. <Cnt ref , short circuit protection signal S pt If it is low level, it is considered that the converter output is short-term overcurrent, not short circuit, and short circuit protection is not performed temporarily;

[0081] Step 5: Based on the short circuit protection signal S pt The target converter operates normally, performs closed-loop PI regulation on the converter output voltage, and waits for the next overcurrent to occur, so that the comparator output voltage jumps from a low level to a high level; based on the short-circuit protection signal S pt Set to a high level to turn off all switches in the target converter, and the target converter stops outputting.

[0082] In summary, the present invention monitors the overload / short circuit condition of the power supply output terminal by implementing the voltage on the parasitic inductance and parasitic resistance of the detection circuit. During the operation / startup process of the switching power supply, if the output current suddenly increases, the voltage on the parasitic parameter will inevitably have a large rise. When the voltage on the parasitic parameter exceeds the threshold value of the comparator, the comparator output is set high, and the number of times the comparator output is set high is monitored. When the number of times the comparator output is set high is greater than the preset threshold value, it is considered that the output is overloaded for a long time or the output is short-circuited, and it is necessary to take measures such as shutting down the drive in time to protect the converter to avoid the spread of the fault; otherwise, it is considered that the output is a short-term overcurrent (such as starting with a large capacitor connected to the output terminal), and the converter is current limited without shutting down. After the short-term overcurrent condition disappears, the converter can still work normally.

[0083] The present invention designs a converter short-circuit protection circuit and method based on parasitic parameters, which adopts a converter control module and a short-circuit logic processing module. The converter control module is used to control the switching of each switch tube of the target converter, and the short-circuit logic processing module is used to perform short-circuit detection on the ground loop parasitic parameters of the target converter. The short-circuit logic processing module is based on the ground loop parasitic parameter voltage sampling value v of the target converter. S4-S The short circuit judgment is performed, and then the switch of each switch tube is controlled by the converter control module 302 to perform short circuit protection on the target converter 301. The overload / short circuit condition of the power supply output terminal is monitored by real-time detection of the voltage on the parasitic parameters of the circuit ground loop, thereby achieving a short circuit protection technology without current sampling, reducing the volume and weight of the converter, reducing losses, and improving efficiency.

[0084] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person skilled in the art of the present invention may make various modifications and alterations without departing from the spirit and scope of the present invention.

[0085] The above are only preferred embodiments of the present invention, but do not limit the patent scope of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions recorded in the above embodiments, or replace some of the technical features with equivalent ones. Any equivalent structure made by using the contents of the present invention specification and drawings, directly or indirectly used in other related technical fields, is also within the scope of patent protection of the present invention.

Claims

1. A converter short-circuit protection circuit based on parasitic parameters, applied to a short-circuit protection circuit of a target converter (301), Features: The invention comprises a converter control module (302) and a short-circuit logic processing module (303). The converter control module (302) is used to control the switching of each switch tube of the target converter (301). The converter control module (302) is based on the output voltage sampling value v of the target converter (301). o , input voltage sampling value v in , outputting driving signals of each switch tube in the target converter (301); the short-circuit logic processing module (303) is used to make a short-circuit judgment based on the ground loop parasitic parameters of the target converter, and the short-circuit logic processing module (303) is based on the ground loop parasitic parameter voltage sampling value v of the target converter (301) S4-S Performing short circuit judgment, and then controlling the switching of each switch tube through a converter control module (302), so as to perform short circuit protection on the target converter (301); The converter control module (302) includes a first subtractor (304), a proportional regulator (305), an integral regulator (306), an adder (308), a switch tube time parameter calculation module (309), a PWM generation module (310), a start condition judgment module (311), and a short circuit count threshold setting module (312). The start condition judgment module (311) is used to judge the input voltage sampling value v of the target converter. in , whether the converter working start conditions are met and the start identification signal S is output st The short circuit counting threshold setting module (312) outputs an overcurrent comparator reference signal v based on the ground loop parasitic parameters of the target converter F , and based on the target converter load output short circuit judgment counting threshold Cnt ref ; Output voltage sampling value v of target converter o With the preset output voltage reference value v oref The first subtractor (304) performs a subtraction operation to output an error value; the output of the first subtractor (304) is connected to the input end of the proportional regulator (305) and the input end of the integral regulator (306); the proportional regulator (305) performs a proportional operation on the error value and outputs a proportional operation result v p The integral regulator (306) performs a proportional operation on the error value and outputs an integral operation result v i ; Adder (308) based on the integral operation result v i And the proportional operation result v p Output regulator output signal v er The switch tube time parameter calculation module (309) is based on the input voltage sampling value v of the standard converter in , the sampling value of the output voltage v o , regulator output signal v er Outputting the on-time of each switch tube of the target converter in each stage; the PWM generation module (310) generates a driving signal for each switch tube based on the output of the switch tube time parameter calculation module (309) and comparing it with its internal carrier; The short-circuit logic processing module (303) includes a comparator (313), a rising edge capture & counting module (314), a short-circuit judgment module (315), a first resistor (R 301 )、The second resistor (R 302 ), the overcurrent comparator reference signal v F Through the first resistor (R 301 ) is connected to the inverting input terminal of the comparator (313), and the ground loop parasitic parameter voltage sampling value v of the target converter S4-S Through the second resistor (R 302 ) is connected to the positive phase input terminal of the comparator (313), and the output terminal of the comparator (313) outputs an overcurrent comparator trigger signal S tr The converter control module (302) is connected; the start identification signal S st The output end of the comparator (313) is connected to control the transmission of the output signal of the comparator (313) by controlling the opening and closing of the switch; the rising edge capture & counting module (314) is used to capture the overcurrent comparator trigger signal S tr The short circuit judgment module (315) counts the rising edge signal of the short circuit judgment count value Cnt based on the short circuit judgment count value Cnt and the short circuit judgment count threshold Cnt. ref Compare and output short circuit protection signal S pt The converter control module (302) is connected to control the opening and closing of each switch tube; the converter control module (302) also includes a second subtractor (307), the integral operation result v i The second subtractor (307) is connected to the adder (308), and the second subtractor (307) is based on the integral operation result v i and preset integral down-regulation constant v i- The output of the second subtractor (307) is connected to the input of the adder (308); the overcurrent comparator triggers the signal S tr By controlling the on / off of the control switch, the preset integral down-regulation constant v is i- Whether to connect the second subtractor (307).

2. A converter short-circuit protection circuit based on parasitic parameters according to claim 1, characterized in that: The short circuit protection signal S pt The PWM generation module (310) connected to the converter control module (302) generates a short-circuit protection signal S pt When the short circuit protection signal S pt When it is at a high level, the PWM generation module (310) outputs a blocking drive signal for each switch tube.

3. A converter short-circuit protection method based on parasitic parameters, applied to the converter short-circuit protection circuit based on parasitic parameters as claimed in claim 1, characterized in that: According to the parasitic parameters of the ground loop in the target converter, perform the following steps to short-circuit protect the target transformer: Step 1: Get the input voltage sampling value v of the target converter in , output voltage sampling value v o , ground loop parasitic parameter voltage sampling value v S4-S ; Based on the ground loop parasitic parameters of the target converter, set the overcurrent comparison reference signal v F ; Based on the load of the target converter, set the short circuit judgment count threshold Cnt ref ; Step 2: Based on the input voltage sampling value v in Determine whether the input voltage meets the start-up condition of the target converter and obtain the converter start-up identification signal S st If satisfied, the identification signal S is activated st If it is high level, go to step 3; if it is not satisfied, start the identification signal S st is low level, repeat step 2; Step 3: Compare the overcurrent reference signal v F And the ground loop parasitic parameter voltage sampling value v S4-S Compare and obtain the overcurrent comparator trigger signal S tr , local loop parasitic parameter voltage sampling value v S4-S Greater than the overcurrent comparator reference signal v F , overcurrent comparator trigger signal S tr From low voltage to high voltage, enter step 4; when the overcurrent comparator reference signal v F Greater than the ground loop parasitic parameter voltage sampling value v S4-S , overcurrent comparator trigger signal S tr To change from high voltage to low level, repeat step 3; Step 4: Based on the overcurrent comparator trigger signal S tr From low voltage to high level, preset integral down-regulation constant v i- A second subtractor (307) in the converter control module (302) is connected; and based on the overcurrent comparator trigger signal S tr From low voltage to high level, the short circuit judgment count Cnt is increased by 1, and the short circuit judgment count Cnt and the short circuit judgment count threshold Cnt are ref Compare and obtain the short circuit protection signal S pt , go to step 5; if Cnt>Cnt ref , short circuit protection signal S pt Is high level; if Cnt <Cnt ref , short circuit protection signal S pt is low level; Step 5: Based on the short circuit protection signal S pt is low level, the target converter operates normally; based on the short-circuit protection signal S pt Set to a high level to turn off all switches in the target converter, and the target converter stops outputting.

4. The converter short-circuit protection method based on parasitic parameters according to claim 3, characterized in that: The overcurrent comparison reference signal v F The settings should satisfy the following relationship: v S4-S_peak_norm <v F <v S4-S_peak_oc In the formula, v S4-S_peak_norm is the voltage peak value corresponding to the parasitic parameters of the ground loop when the converter is running in steady state, v S4-S_peak_oc It is the voltage peak value corresponding to the parasitic parameters of the ground loop when the converter is short-circuited.

5. The converter short-circuit protection method based on parasitic parameters according to claim 3, characterized in that: The preset integral down-regulation constant v i- The value is 10% of the output value of the integral regulator (306) when the converter is running in steady state.

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