Over-current protection circuit of synchronous step-down DC-DC converter

Abstract

The invention relates to an over-current protection circuit of a synchronous step-down DC-DC converter, and the over-current protection circuit is characterized in that one end of the over-current protection circuit is connected with one end of a power conversion circuit, the other end of the over-current protection circuit is connected with a power supply, and the other end of the power conversion circuit is connected with the power supply; and the overcurrent protection circuit is used for controlling the power tube to be closed when overcurrent occurs in the power tube in the power conversion circuit, and controlling the power tube to be opened after a preset duration. The overcurrent protection circuit can solve the overcurrent problem of the power conversion circuit.

Description

Technical Field

[0001] The present application relates to the technical field of switching power supplies, and in particular to an overcurrent protection circuit for a synchronous step-down DC-DC converter. Background Art

[0002] With the popularization and development of electronic equipment, switching power supplies are used more and more widely.

[0003] In the related art, taking a synchronous buck DC-DC converter as an example, the synchronous buck DC-DC converter controls the conduction of a power tube through a peak current limiting function to adjust the output voltage.

[0004] However, the peak current limiting function of the synchronous buck DC-DC converter in the related art cannot solve the overcurrent problem of the synchronous buck DC-DC converter. Summary of the Invention

[0005] Based on this, it is necessary to provide an overcurrent protection circuit for a synchronous step-down DC-DC converter to address the above technical problems, which can solve the overcurrent problem of the synchronous step-down DC-DC converter.

[0006] In a first aspect, the present application provides an overcurrent protection circuit, the overcurrent protection circuit comprising: one end of the overcurrent protection circuit is connected to one end of a power conversion circuit, the other end of the overcurrent protection circuit is connected to a power supply, and the other end of the power conversion circuit is connected to the power supply;

[0007] The overcurrent protection circuit is used to control the power tube in the power conversion circuit to turn off when overcurrent occurs, and to control the power tube to turn on after a preset time.

[0008] In one embodiment, the overcurrent protection circuit includes an overcurrent trigger circuit and an overcurrent control circuit; the input end of the overcurrent trigger circuit is connected to the power supply and the power conversion circuit respectively; the output end of the overcurrent trigger circuit is connected to the input end of the overcurrent control circuit, and the output end of the overcurrent control circuit is connected to the power conversion circuit;

[0009] An overcurrent trigger circuit is used to turn on the overcurrent control circuit and output an overcurrent protection signal to the overcurrent control circuit when detecting that the power conversion circuit triggers an overcurrent protection condition;

[0010] The overcurrent control circuit is used to control the power tube to turn off when an overcurrent event is detected in the power conversion circuit, and to control the power tube to turn on after a preset time.

[0011] In one embodiment, the overcurrent trigger circuit includes a voltage threshold calculation circuit, a voltage comparison circuit, and a first data trigger; the input terminal of the voltage threshold calculation circuit is connected to a power supply, the output terminal of the voltage threshold calculation circuit is connected to the input terminal of the first data trigger via the positive input terminal of the voltage comparison circuit, the negative input terminal of the voltage comparison circuit is connected to the power conversion circuit, and the output terminal of the first data trigger is connected to the input terminal of the overcurrent control circuit;

[0012] A voltage threshold calculation circuit is used to calculate a control voltage for causing an inductor current runaway in a power conversion circuit according to an output voltage of the power supply;

[0013] a voltage comparison circuit, configured to output a first logic value when the output voltage of the power conversion circuit is less than the control voltage;

[0014] The first data trigger is used to output an overcurrent protection signal when a first logic value is sampled.

[0015] In one embodiment, the voltage threshold calculation circuit includes a resistor circuit, an operational amplifier, a reference power tube, a current mirror, a capacitor, a first switch, and a second switch; the first end of the resistor circuit is connected to a power supply, the second end of the resistor circuit is connected to a positive input end of the operational amplifier, the third end of the resistor circuit is connected to a first end of the capacitor, the fourth end of the resistor circuit is respectively connected to a negative input end of the operational amplifier and a source of the reference power tube, the output end of the operational amplifier is connected to a gate of the reference power tube, the drain of the reference power tube is connected to a first end of the current mirror, the second end of the current mirror is connected to a reference power supply, the third end of the current mirror is connected to the second end of the capacitor through the first switch, and the capacitor is connected in parallel with the second switch.

[0016] In one embodiment, the resistance circuit includes a first resistor, a second resistor and a third resistor, one end of the first resistor is connected to a power supply, the other end of the first resistor is respectively connected to a positive input terminal of an operational amplifier and one end of the second resistor, the other end of the second resistor is respectively connected to one end of the third resistor and a first end of a capacitor, and the other end of the third resistor is respectively connected to a negative input terminal of the operational amplifier and a source of a reference power tube.

[0017] In one embodiment, the current mirror includes a first current mirror and a second current mirror, the sources of the first current mirror and the second current mirror are both connected to a reference power supply, the gate of the first current mirror is connected to the gate of the second current mirror, the drain of the first current mirror is respectively connected to the gate of the first current mirror and the drain of the reference power tube, and the drain of the second current mirror is connected to the second end of the capacitor through a first switch.

[0018] In one embodiment, the overcurrent control circuit includes an overcurrent detection circuit and a power tube control circuit, wherein the input end of the overcurrent detection circuit is connected to the output end of the overcurrent trigger circuit, the output end of the overcurrent detection circuit is connected to the input end of the power tube control circuit, and the output end of the power tube control circuit is connected to the power conversion circuit;

[0019] An overcurrent detection circuit is used to output an overcurrent event signal to the power tube control circuit when an overcurrent event is detected in the power conversion circuit;

[0020] The power tube control circuit is used to control the power tube to turn off when receiving an overcurrent event signal, and to control the power tube to turn on after a preset time.

[0021] In one embodiment, the overcurrent detection circuit includes an inductor current detection circuit, an overcurrent comparison circuit, and an anti-false trigger detection circuit; the input end of the inductor current detection circuit is connected to the output end of the overcurrent trigger circuit, the output end of the inductor current detection circuit is connected to the input end of the anti-false trigger detection circuit through the overcurrent comparison circuit, and the output end of the anti-false trigger detection circuit is connected to the input end of the power tube control circuit;

[0022] The inductor current detection circuit is used to convert the inductor current in the power conversion circuit into an analog voltage when receiving the overcurrent protection signal sent by the overcurrent trigger circuit;

[0023] An overcurrent comparison circuit is used to output an overcurrent signal to the anti-false trigger detection circuit when the analog voltage is greater than the reference voltage;

[0024] The anti-false trigger detection circuit is used to output an overcurrent event signal when the signals sampled multiple times are all overcurrent signals.

[0025] In one embodiment, the inductor current detection circuit includes a first logic AND gate, an auxiliary power tube, and a reference current source; the input end of the first logic AND gate is respectively connected to the output end of the current detection circuit and the lower tube control signal device of the power tube, the output end of the first logic AND gate is connected to the gate of the auxiliary power tube, the source of the auxiliary power tube is connected to the inductor connection end between the power tube and the inductor, the midpoint between the drain of the auxiliary power tube and the reference current source is connected to the negative input end of the overcurrent comparison circuit, and the positive input end of the overcurrent comparison circuit is grounded.

[0026] In one embodiment, the false trigger prevention detection circuit includes a second data trigger, a third data trigger, and a second logic AND gate, wherein the input end of the second data trigger is connected to the output end of the overcurrent comparison circuit, the output end of the second data trigger is connected to the input end of the second logic AND gate and the input end of the third data trigger, respectively, the output end of the third data trigger is connected to the input end of the second logic AND gate, and the output end of the second logic AND gate is connected to the input end of the power tube control circuit;

[0027] The second data trigger and the third data trigger are both used to output a second logic value when sampling the overcurrent signal output by the overcurrent comparison circuit;

[0028] The second logic AND gate is used to output an overcurrent event signal when the logic values ​​output by the received second data trigger and the third data trigger are both second logic values.

[0029] In the overcurrent protection circuit of the synchronous step-down DC-DC converter, one end of the overcurrent protection circuit is connected to one end of the power conversion circuit, the other end of the overcurrent protection circuit is connected to a power supply, and the other end of the power conversion circuit is connected to a power supply. The overcurrent protection circuit is used to control the power tube in the power conversion circuit to shut down when an overcurrent occurs, and to control the power tube to turn on after a preset time. In this overcurrent protection circuit, by connecting the overcurrent protection circuit to the power supply and the power conversion circuit, it can detect whether the power tube in the power conversion circuit has an overcurrent based on information such as the input voltage of the power supply and the output voltage of the power conversion circuit. When an overcurrent occurs, the power tube is controlled to shut down for a preset time and then restarted, thereby reducing the risk of overcurrent in the power tube in the power conversion circuit and improving the service life of the power conversion circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 is a schematic structural diagram of a power conversion circuit in one embodiment;

[0032] Figure 2 1 is a schematic structural diagram of an overcurrent protection circuit in one embodiment;

[0033] Figure 3 is a schematic diagram of changes in signal waveforms in one embodiment;

[0034] Figure 4 is a structural diagram of an overcurrent protection circuit in another embodiment;

[0035] Figure 5 is a structural diagram of an overcurrent protection circuit in another embodiment;

[0036] Figure 6 is a structural diagram of an overcurrent protection circuit in another embodiment;

[0037] Figure 7A schematic diagram of a change in a signal waveform in another embodiment;

[0038] Figure 8 is a structural diagram of an overcurrent protection circuit in another embodiment;

[0039] Figure 9 is a structural diagram of an overcurrent protection circuit in another embodiment;

[0040] Figure 10 is a structural diagram of an overcurrent protection circuit in another embodiment;

[0041] Figure 11 is a structural diagram of an overcurrent protection circuit in another embodiment;

[0042] Figure 12 A schematic diagram of a change in a signal waveform in another embodiment;

[0043] Figure 13 FIG. 4 is a schematic structural diagram of an overcurrent protection circuit in another embodiment.

[0044] Description of reference numerals:

[0045] 100, power conversion circuit; 101, power tube; 102, power inductor; 103, load capacitor; 104, first feedback voltage divider resistor; 105, second feedback voltage divider resistor; 106, peak current sampling circuit;

[0046] 200, overcurrent protection circuit; 201, power supply;

[0047] 401. Overcurrent trigger circuit; 402. Overcurrent control circuit;

[0048] 501, voltage threshold calculation circuit; 502, voltage comparison circuit; 503, first data trigger;

[0049] 601, resistor circuit; 602, operational amplifier; 603, reference power transistor; 604, current mirror; 605, capacitor; 606, first switch; 607, second switch; 608, reference power supply; 6011, first resistor; 6012, second resistor; 6013, third resistor; 6041, first current mirror; 6042, second current mirror;

[0050] 801, overcurrent detection circuit; 802, power tube control circuit;

[0051] 901, inductor current detection circuit; 902, overcurrent comparison circuit; 903, anti-false trigger detection circuit;

[0052] 1001, first logic AND gate; 1002, auxiliary power transistor; 1003, reference current source;

[0053] 1101, second data trigger; 1102, third data trigger; 1103, second logic AND gate. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0055] It should be understood that the serial numbers assigned to components in this application, such as "first" and "second," are used solely to distinguish the objects being described and do not convey any sequential or technical meaning. References to "connection" and "coupling" in this application, unless otherwise specified, include both direct and indirect connections (couplings). In the description of this application, it should be understood that directional terms such as "upper" and "lower" indicate positions or relationships based on those shown in the accompanying drawings. These are provided solely for ease of description and simplification of the description, and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. In this application, components are distinguished not by name, but by their functional differences.

[0056] Taking a synchronous step-down DC-DC converter as an example, a synchronous step-down DC-DC converter typically uses peak current mode. A high-speed inductor current peak sampling feedback loop is nested within the voltage feedback loop. This compensates for the low-bandwidth voltage feedback loop's inability to respond to rapid power supply voltage changes, enabling the converter to achieve better primary-side regulation (PSR). To protect the converter from short circuits or overloads, the converter typically incorporates a maximum load average current limit function.

[0057] The synchronous step-down DC-DC converter includes a power conversion circuit such as Figure 1 As shown, Figure 1 A circuit structure diagram of an existing power conversion circuit is provided. The power conversion circuit 100 includes a power tube 101, a power inductor 102, a load capacitor 103, a first feedback voltage divider resistor 104, a second feedback voltage divider resistor 105 and a peak current sampling circuit 106.

[0058] Among them, V INrepresents the power supply voltage. The power tube 101 includes an upper power tube MHS, a lower power tube MLS, and a driving circuit DRIVER for the upper and lower power tubes. The peak current sampling circuit 106 includes an error amplifier EA, a pulse width modulation comparator CMP, and a trigger LATCH for generating a pulse width modulation signal. V OUT is the output voltage of the power conversion circuit 100, VFB is V OUT The resistor divider is VREF, which is the reference voltage. I2Vpeak is the voltage signal converted after the peak inductor current is sampled. Vslope is the slope compensation voltage. The superposition of the two is the positive input voltage of the PWM comparator CMP, and the negative input voltage is the output of EA.

[0059] Based on the integrated peak current sampling circuit 106, if the output voltage of the error amplifier is limited, the power conversion circuit 100 has a maximum peak current limiting function under normal operating conditions, and correspondingly, an average load current limiting function. However, this peak current limiting function is cycle-to-cycle, that is, the peak current can be limited to below a set value within each PWM cycle. Although this appears to meet the requirement of limiting the average load current, it is prone to runaway problems in extreme cases. When the output voltage approaches 0V, due to the leading edge blanking (LEB) time, the upper power transistor of the power transistor 101 must be turned on for a time greater than one LEB in each cycle. This causes the inductor current to increase in the initial stage of each cycle. During the upper power transistor off stage of this cycle, the inductor needs to continue the current flow. If the output voltage is close to 0V at this time, the inductor current decreases very slowly. Considering the value of the increase in the inductor current is greater than the value of the decrease in the inductor current within a cycle, it manifests as a net increase in the inductor current. As the number of cycles continues to increase, the inductor current increases, eventually causing the upper power transistor on the chip to burn out and the peak current limiting to fail.

[0060] In order to solve the problem that the peak current mode synchronous power conversion circuit cannot cope with load overcurrent, the present application designs an overcurrent protection scheme based on hiccup mode for a peak current mode synchronous DC converter.

[0061] It should be noted that for switching power supplies, overcurrent is the inevitable result of a short circuit. Therefore, overcurrent protection includes short-circuit protection, which means that the content of overcurrent protection also applies to short-circuit protection.

[0062] In an exemplary embodiment, Figure 2As shown, an overcurrent protection circuit 200 is provided, which includes: one end of the overcurrent protection circuit 200 is connected to one end of the power conversion circuit 100, the other end of the overcurrent protection circuit 200 is connected to the power supply 201, and the other end of the power conversion circuit 100 is connected to the power supply 201.

[0063] The overcurrent protection circuit 200 is used to control the power tube 101 in the power conversion circuit 100 to turn off when an overcurrent occurs, and to control the power tube 101 to turn on after a preset time.

[0064] Among them, during the operation of the power conversion circuit 100, the overcurrent protection circuit 200 can detect in real time whether the power tube 101 in the power conversion circuit 100 has an overcurrent. When the power tube 101 has an overcurrent, the power tube 101 is controlled to be turned off, and the power tube 101 is controlled to be turned on after a preset time.

[0065] Optionally, the overcurrent protection circuit 200 can detect the current of the power inductor 102 in the power conversion circuit 100 in real time, and determine that an overcurrent occurs in the power transistor 101 when the current of the power inductor 102 is too large.

[0066] The overcurrent protection circuit 200 controls the power tube 101 to be turned off and controls the power tube 101 to be turned on after a preset time period. The method can be that when an overcurrent occurs in the power tube 101 in the power conversion circuit 100, a first drive signal is sent to the drive circuit in the power tube 101. The first drive signal is used to turn off the upper power tube and the lower power tube of the power tube 101 and start timing. After the preset time period has passed, a second drive signal is sent to the drive circuit. The second drive signal is used to turn on the upper power tube and the lower power tube of the power tube 101. Turning on the power tube 101 indicates that the conduction of the upper power tube and the lower power tube of the power tube 101 can continue to be modulated by the peak current sampling circuit 106 in the power conversion circuit 100.

[0067] In the overcurrent protection circuit provided in the embodiment of the present application, the overcurrent protection circuit includes: one end of the overcurrent protection circuit is connected to one end of the power conversion circuit, the other end of the overcurrent protection circuit is connected to the power supply, and the other end of the power conversion circuit is connected to the power supply; the overcurrent protection circuit is used to control the power tube in the power conversion circuit to turn off when an overcurrent occurs, and to control the power tube to turn on after a preset time. In the overcurrent protection circuit, by connecting the overcurrent protection circuit to the power supply and the power conversion circuit, it is possible to detect whether an overcurrent occurs in the power tube in the power conversion circuit based on information such as the input voltage of the power supply and the output voltage of the power conversion circuit. When an overcurrent occurs in the power tube, the power tube is controlled to turn off and then restart after a preset time, thereby reducing the risk of overcurrent in the power tube in the power conversion circuit and improving the service life of the power conversion circuit.

[0068] Based on the above analysis, it can be seen that the significant disadvantage of the power conversion circuit 100 is that OUT In the event of a short circuit or very low ground impedance, the peak current limiting loop formed by the peak current feedback signal I2Vpeak cannot limit the maximum inductor current. For power conversion circuit 100, due to the presence of LEB, power inductor 102 has a minimum on-time T1. Therefore, even if an overcurrent problem occurs, the circuit still operates in PWM mode, and the cycle-to-cycle current limiting mode in this mode still operates. However, it is inevitable that power inductor 102 must be on for at least T1 during each cycle; T1 is the conduction time of the upper power transistor in power transistor 101.

[0069] During the time T1, the current increase of the power inductor 102 is proportional to the power supply voltage V IN And the output voltage V OUT The relationship between them is: , L is the resistance of the power inductor 102. If one clock cycle is T, the amount of reduction in the inductor current during the freewheeling phase of the power inductor 102 is: If the increase in the current of the power inductor 102 is greater than the decrease in the current of the power inductor 102 within a cycle, the current of the power inductor 102 will continue to rise. Therefore, if the current of the power inductor 102 is still a net increase in each cycle after the cycle-to-cycle current limit mode is triggered, the cycle-to-cycle current limit mode will fail and the current will continue to increase until the circuit is burned out. Therefore, the stable condition is , that is, as shown in formula (1), on the contrary, the triggering condition for additional overcurrent protection is shown in formula (2), and the subsequent conditions are all centered around formula (2), that is, if formula (2) is satisfied, the overcurrent protection circuit 200 is triggered.

[0070] (1)

[0071] (2)

[0072] like Figure 3 As shown, it gives the 、 and The PWM signal of the upper power tube of the power tube 101 and the current waveform of the power inductor 102 under three conditions.

[0073] Therefore, in one exemplary embodiment, Figure 4As shown, the overcurrent protection circuit 200 includes an overcurrent trigger circuit 401 and an overcurrent control circuit 402; the input end of the overcurrent trigger circuit 401 is connected to the power supply 201 and the power conversion circuit 100 respectively; the output end of the overcurrent trigger circuit 401 is connected to the input end of the overcurrent control circuit 402, and the output end of the overcurrent control circuit 402 is connected to the power conversion circuit 100.

[0074] The overcurrent trigger circuit 401 is configured to activate the overcurrent control circuit 402 and output an overcurrent protection signal to the overcurrent control circuit 402 when detecting that the power conversion circuit 100 triggers an overcurrent protection condition;

[0075] The overcurrent control circuit 402 is used to control the power tube 101 to turn off when an overcurrent event is detected in the power conversion circuit 100, and to control the power tube 101 to turn on after a preset time.

[0076] The function of the overcurrent trigger circuit 401 is to adaptively adjust the V according to the trigger overcurrent protection condition of formula (2). IN and V OUT If the overcurrent protection triggering condition is met, the overcurrent control circuit 402 is turned on; in this way, in the normal working mode, only the overcurrent trigger circuit 401 is started. The operating speed of the overcurrent trigger circuit 401 is very low and the static current is very small. It can achieve the integration of the hiccup mode overcurrent protection function in the normal mode while maintaining low power consumption.

[0077] The overcurrent trigger circuit 401 can detect whether the power conversion circuit 100 satisfies formula (2) within a cycle. If formula (2) is satisfied, it is determined that the power conversion circuit 100 triggers the overcurrent protection condition. When the overcurrent protection condition is triggered, the overcurrent trigger circuit 401 turns on the overcurrent control circuit 402 and outputs an overcurrent protection signal to the overcurrent control circuit 402. The overcurrent protection signal can be represented by a logic value of 1.

[0078] The overcurrent trigger circuit 401 turns on the overcurrent control circuit 402 in such a way that the overcurrent control circuit 402 includes a driving circuit. In the normal operating mode of the power conversion circuit 100, the various components in the overcurrent control circuit 402 are in a non-working state. When the overcurrent trigger circuit 401 detects that the power conversion circuit 100 triggers the overcurrent protection condition, it sends a start signal to the driving circuit of the overcurrent control circuit 402 to enable the various components in the overcurrent control circuit 402 to start working.

[0079] After receiving the overcurrent protection signal sent by the overcurrent trigger circuit 401, the overcurrent control circuit 402 can detect whether an overcurrent event actually occurs in the power tube 101 in the power conversion circuit 100. If an overcurrent event is detected in the power tube 101 in the power conversion circuit 100, the overcurrent control circuit 402 controls the power tube 101 to turn off, and controls the power tube 101 to turn on after a preset time.

[0080] The overcurrent control circuit 402 detects whether an overcurrent event occurs in the power tube 101 by detecting the current flowing through the power inductor 102 in the power conversion circuit 100, and determines that an overcurrent event occurs in the power tube 101 when the current of the power inductor 102 is greater than a preset current threshold.

[0081] In the overcurrent protection circuit provided in the embodiment of the present application, the overcurrent protection circuit includes an overcurrent trigger circuit and an overcurrent control circuit; the input end of the overcurrent trigger circuit is connected to the power supply and the power conversion circuit respectively; the output end of the overcurrent trigger circuit is connected to the input end of the overcurrent control circuit, and the output end of the overcurrent control circuit is connected to the power conversion circuit; the overcurrent trigger circuit is used to turn on the overcurrent control circuit and output an overcurrent protection signal to the overcurrent control circuit when detecting that the power conversion circuit triggers an overcurrent protection condition; the overcurrent control circuit is used to control the power transistor to turn off when detecting an overcurrent event in the power conversion circuit, and control the power transistor to turn on after a preset time period. In the overcurrent protection circuit, the overcurrent trigger circuit detects whether the power conversion circuit meets the overcurrent protection condition. Only when the power conversion circuit meets the overcurrent protection condition will the overcurrent control circuit start working, and further detects whether there is an overcurrent event in the power conversion circuit. If the power conversion circuit does not meet the overcurrent protection condition, the overcurrent control circuit will not be turned on, thereby reducing the power consumption of the overcurrent protection circuit and improving the accuracy of overcurrent protection for the power transistor of the power conversion circuit.

[0082] In an exemplary embodiment, Figure 5 As shown, the overcurrent trigger circuit 401 includes a voltage threshold calculation circuit 501, a voltage comparison circuit 502 and a first data trigger 503; the input end of the voltage threshold calculation circuit 501 is connected to the power supply 201, the output end of the voltage threshold calculation circuit 501 is connected to the input end of the first data trigger 503 through the positive input end of the voltage comparison circuit 502, the negative input end of the voltage comparison circuit 502 is connected to the power conversion circuit 100, and the output end of the first data trigger 503 is connected to the input end of the overcurrent control circuit 402.

[0083] The voltage threshold calculation circuit 501 is used to calculate the control voltage for inductor current runaway in the power conversion circuit 100 based on the output voltage of the power supply 201; the voltage comparison circuit 502 is used to output a first logic value when the output voltage of the power conversion circuit 100 is less than the control voltage; and the first data trigger 503 is used to output an overcurrent protection signal when the first logic value is sampled.

[0084] The voltage threshold calculation circuit 501 can automatically calculate the control voltage at which the inductor current may run away according to the voltage of the power supply 201 . The inductor current in this embodiment is the current flowing through the power inductor 102 in the power conversion module.

[0085] The voltage threshold calculation circuit 501 can output a control voltage, and then compare the magnitude relationship between the control voltage and the output voltage through the voltage comparison circuit 502. When the output voltage is less than the control voltage, the voltage comparison circuit 502 outputs a first logic value to the first data trigger 503, and the first logic value can be 1. When the output voltage is greater than or equal to the control voltage, the voltage comparison circuit 502 outputs a second logic value to the first data trigger 503, and the first logic value can be 0; the voltage comparison circuit 502 can be a voltage comparator.

[0086] The first data trigger 503 also includes a clock terminal, through which a clock signal can be input to the first data trigger 503. When the rising edge of the clock signal arrives, the first data trigger 503 samples the logic value output by the voltage comparison circuit 502. The first data trigger 503 can be a D trigger.

[0087] In the overcurrent protection circuit provided by the embodiment of the present application, the overcurrent trigger circuit includes a voltage threshold calculation circuit, a voltage comparison circuit and a first data trigger; the input end of the voltage threshold calculation circuit is connected to the power supply, the output end of the voltage threshold calculation circuit is connected to the input end of the first data trigger through the positive input end of the voltage comparison circuit, the negative input end of the voltage comparison circuit is connected to the power conversion circuit, and the output end of the first data trigger is connected to the input end of the overcurrent control circuit; the voltage threshold calculation circuit is used to calculate the control voltage of the inductor current out of control in the power conversion circuit according to the output voltage of the power supply; the voltage comparison circuit is used to output a first logic value when the output voltage of the power conversion circuit is less than the control voltage; the first data trigger is used to output an overcurrent protection signal when the first logic value is sampled. In the overcurrent trigger circuit, the control voltage of the power inductor current out of control may occur is automatically calculated by inputting the power supply voltage. If the output voltage exceeds the control voltage, the overcurrent control circuit is not enabled, thereby saving the static current consumption of the overcurrent protection circuit.

[0088] In an exemplary embodiment, Figure 6As shown, the voltage threshold calculation circuit 501 includes a resistor circuit 601, an operational amplifier 602, a reference power tube 603, a current mirror 604, a capacitor 605, a first switch 606 and a second switch 607; the first end of the resistor circuit 601 is connected to the power supply 201, the second end of the resistor circuit 601 is connected to the positive input end of the operational amplifier 602, the third end of the resistor circuit 601 is connected to the first end of the capacitor 605, the fourth end of the resistor circuit 601 is respectively connected to the negative input end of the operational amplifier 602 and the source of the reference power tube 603, the output end of the operational amplifier 602 is connected to the gate of the reference power tube 603, the drain of the reference power tube 603 is connected to the first end of the current mirror 604, the second end of the current mirror 604 is connected to the reference power supply 608, the third end of the current mirror 604 is connected to the second end of the capacitor 605 through the first switch 606, and the capacitor 605 is connected in parallel with the second switch 607.

[0089] Specifically, the resistance circuit 601 includes a first resistor 6011, a second resistor 6012 and a third resistor 6013. One end of the first resistor 6011 is connected to the power supply 201, and the other end of the first resistor 6011 is respectively connected to the positive input terminal of the operational amplifier 602 and one end of the second resistor 6012. The other end of the second resistor 6012 is respectively connected to one end of the third resistor 6013 and the first end of the capacitor. The other end of the third resistor 6013 is respectively connected to the negative input terminal of the operational amplifier 602 and the source of the reference power tube 603.

[0090] The current mirror 604 includes a first current mirror 6041 and a second current mirror 6042. The sources of the first current mirror 6041 and the second current mirror 6042 are both connected to the reference power supply 608, the gate of the first current mirror 6041 is connected to the gate of the second current mirror 6042, the drain of the first current mirror 6041 is respectively connected to the gate of the first current mirror 6041 and the drain of the reference power tube 603, and the drain of the second current mirror 6042 is connected to the second end of the capacitor through the first switch 606.

[0091] Among them, for the overcurrent protection circuit 200 in PWM mode, the internal integrated oscillator is a relaxation oscillator structure, and its clock frequency F CLK It is inversely proportional to the product of resistance and capacitance, and can generally be expressed as , that is, its cycle .for Figure 6 For the circuit in the figure, the PWM period is the same as the oscillator period, both are T, but the oscillator duty cycle is generally very low, while the PWM duty cycle is variable with the input and output voltages. and the second resistor right To divide the voltage, , op amp OPA1 converts VIN_ADV Buffer for V IN_ADV_FB =V IN_ADV , this voltage forces the third resistor The current flowing through , current mirror and The current I P1 =I P2 .

[0092] A PWM signal is applied to the first switch 606, and an RST signal is applied to the second switch 607, wherein the PWM signal is a modulation signal of the upper power tube of the power tube 101 in the power conversion circuit 100, and RST is ahead of the rising edge of PWM, so the capacitor The charge on the current mirror is cleared during the period when RST=1; when RST=1 is removed, PWM=1, the first switch 606 is turned on, and the second current mirror M P2 The current I P2 Capacitor Charging, its voltage Increase linearly. The charging current expression is , if R2=R3, and R1+R2=R C , , then the charging current After T1 time, PWM=0, the voltage on the capacitor is And it remains unchanged until the next rising edge of RST arrives. Voltage comparison circuit 502CMP1 compares V OUT and V C1 If the voltage value is satisfied , which is the aforementioned formula (2), then the cycle-to-cycle peak current limit mode fails and the complete circuit of the hiccup mode needs to be started. If , after comparison by the voltage comparator circuit 502, the output logic value V1 = 1. The first data trigger 503 samples the logic value 1 when the next rising edge of RST arrives and sends it to EN_HICP. This signal is used to start the subsequent hiccup complete circuit (overcurrent control circuit 402). The reason for using the first data trigger 503 and the rising edge of RST to sample V1 is that only when PMW = 0, V C1 To reach the target value (control voltage), and to allow a certain stabilization time for the voltage comparison circuit 502 to compare. Figure 7 As shown, Figure 7 Given when V C1 During PWM=0, the voltage is higher than V OUTThe signal waveforms in the case of the PWM signal applied to the first switch 606, the RST signal applied to the second switch 607, the control voltage signal output by the voltage threshold calculation circuit 501 to the voltage comparison circuit 502 , the logic signal output by the voltage comparison circuit 502 to the first data trigger 503 , and the over-current protection signal EN_HICP output by the first data trigger 503.

[0093] The first data trigger 503 samples the logic value output by the voltage comparison circuit 502 when the rising edge of RST arrives, that is, the clock signal input to the clock terminal of the first data trigger 503 is the RST signal.

[0094] In the overcurrent protection circuit provided by the embodiment of the present application, the voltage threshold calculation circuit includes a resistor circuit, an operational amplifier, a reference power tube, a current mirror, a capacitor, a first switch and a second switch; the first end of the resistor circuit is connected to the power supply, the second end of the resistor circuit is connected to the positive input end of the operational amplifier, the third end of the resistor circuit is connected to the first end of the capacitor, the fourth end of the resistor circuit is respectively connected to the negative input end of the operational amplifier and the source of the reference power tube, the output end of the operational amplifier is connected to the gate of the reference power tube, the drain of the reference power tube is connected to the first end of the current mirror, the second end of the current mirror is connected to the reference power supply, the third end of the current mirror is connected to the second end of the capacitor through the first switch, and the capacitor is connected in parallel with the second switch. The voltage threshold calculation circuit can automatically calculate the control voltage where the power inductor current may be out of control, thereby realizing the overcurrent protection judgment of the power conversion circuit.

[0095] In an exemplary embodiment, Figure 8 As shown, the overcurrent control circuit 402 includes an overcurrent detection circuit 801 and a power tube control circuit 802. The input end of the overcurrent detection circuit 801 is connected to the output end of the overcurrent trigger circuit 401, the output end of the overcurrent detection circuit 801 is connected to the input end of the power tube control circuit 802, and the output end of the power tube control circuit 802 is connected to the power conversion circuit 100.

[0096] The overcurrent detection circuit 801 is used to output an overcurrent event signal to the power tube control circuit 802 when an overcurrent event is detected in the power conversion circuit 100; the power tube control circuit 802 is used to control the power tube 101 to turn off when receiving the overcurrent event signal, and to control the power tube 101 to turn on after a preset time.

[0097] The input end of the overcurrent detection circuit 801 is connected to the output end of the overcurrent trigger circuit 401. After receiving the overcurrent protection signal output by the overcurrent trigger circuit 401, the overcurrent detection circuit 801 detects whether an overcurrent event occurs in the power conversion circuit 100. When an overcurrent event occurs in the power conversion circuit 100, the overcurrent event signal is output to the power tube control circuit 802. After receiving the overcurrent event signal output by the overcurrent detection circuit 801, the power tube control circuit 802 controls the power tube 101 to turn off, and controls the power tube 101 to turn on after being turned off for a preset period of time.

[0098] The power tube control circuit 802 may include a hiccup counter. After receiving the overcurrent event signal output by the overcurrent detection circuit 801, the hiccup counter outputs a signal OCP_HICP=1 to the power tube 101 to shut down the power tube 101 and starts timing. After a preset time period has passed, the power tube 101 is turned back on. The preset time period may be a relatively long time, and the specific length of the preset time period may be determined based on actual conditions.

[0099] It should be noted that the overcurrent detection circuit 801 is connected to the output end of the overcurrent trigger circuit 401, which is actually connected to the output end of the first data trigger, and the output end of the power tube control circuit 802 is connected to the power conversion circuit 100, which is actually the power control circuit 802 connected to the driving circuit of the power tube 101 in the power conversion circuit 100 to control the shutdown and opening of the power tube.

[0100] In the overcurrent protection circuit provided in the embodiment of the present application, the overcurrent control circuit includes an overcurrent detection circuit and a power tube control circuit, wherein the input end of the overcurrent detection circuit is connected to the output end of the overcurrent trigger circuit, the output end of the overcurrent detection circuit is connected to the input end of the power tube control circuit, and the output end of the power tube control circuit is connected to the power conversion circuit; the overcurrent detection circuit is used to output an overcurrent event signal to the power tube control circuit when an overcurrent event is detected in the power conversion circuit; the power tube control circuit is used to control the power tube to be turned off when receiving the overcurrent event signal, and to control the power tube to be turned on after a preset time period. In this overcurrent control circuit, when an overcurrent event occurs in the power tube in the power conversion circuit, the power tube is turned off for a preset time period and then turned on after a preset time period, thereby solving the problem of possible overcurrent in the power conversion circuit and ensuring the normal operation of the overcurrent protection circuit.

[0101] In an exemplary embodiment, Figure 9As shown, the overcurrent detection circuit 801 includes an inductor current detection circuit 901, an overcurrent comparison circuit 902 and an anti-false trigger detection circuit 903; the input end of the inductor current detection circuit 901 is connected to the output end of the overcurrent trigger circuit 401, the output end of the inductor current detection circuit 901 is connected to the input end of the anti-false trigger detection circuit 903 through the overcurrent comparison circuit 902, and the output end of the anti-false trigger detection circuit 903 is connected to the input end of the power tube control circuit 802.

[0102] The inductor current detection circuit 901 is used to convert the inductor current in the power conversion circuit 100 into an analog voltage when it receives the overcurrent protection signal sent by the overcurrent trigger circuit 401. The overcurrent comparison circuit 902 is used to output an overcurrent signal to the anti-false trigger detection circuit 903 when the analog voltage is greater than the reference voltage. The anti-false trigger detection circuit 903 is used to output an overcurrent event signal when the signals sampled multiple times are all overcurrent signals.

[0103] Among them, the inductor current detection circuit 901 can be an inductor average current detection circuit. That is, the core of the inductor current detection circuit 901 is to detect the average current of the power inductor 102 in the power conversion circuit 100. When the inductor current of the power inductor 102 is very large, the power transistor 101 must operate in continuous conduction mode (CCM). Therefore, the average current of the power inductor 102 during the freewheeling phase represents the average current of the power inductor 102. The inductor current decreases linearly during the freewheeling phase. Therefore, the average current of the power inductor 102 during the freewheeling phase is the instantaneous inductor current corresponding to half the duration of the freewheeling phase of the power inductor 102. Based on the above analysis, an inductor average current sampling scheme is designed. Specifically, a time-to-digital converter (TDC) is started in the previous cycle to time the freewheeling duration of the power inductor 102. When the timing ends, the output value T2 is divided by 2 to obtain T3, which is applied to the average current sampling logic of the next cycle. In the next cycle, the upper power transistor turns off and the lower power transistor turns on, causing power inductor 102 to begin freewheeling. This activates the digital-to-time converter (DTC). When the duration reaches T3, the current at this point becomes the average current of power inductor 102. At this moment, inductor current detection circuit 901 converts the instantaneous current into an analog voltage and performs a threshold comparison with the overcurrent comparator circuit 902. In this embodiment, TDC and DTC are used to determine the moment when the instantaneous current equals the average current, thereby accurately determining the inductor average current.

[0104] In this embodiment, the sampling moment of the instantaneous current equal to the average current is determined and sampled. The next step is to convert the current of the power inductor 102 into an analog voltage and compare it with a reference voltage to determine whether there is overcurrent.

[0105] Specifically, the overcurrent comparison circuit 902 compares the analog voltage with the reference voltage, and when the analog voltage is greater than the reference voltage, outputs an overcurrent signal to the anti-false trigger detection circuit 903; when the analog voltage is less than or equal to the reference voltage, it can output a no-overcurrent signal to the anti-false trigger detection circuit 903; wherein, the overcurrent signal and the no-overcurrent signal can be represented by logical values, for example, the overcurrent signal is represented by the logical value OCP_ADV=1, and the no-overcurrent signal is represented by the logical value OCP_ADV=0.

[0106] Optionally, in order to prevent occasional misjudgments, the anti-false trigger detection circuit 903 can sample the logic value output by the overcurrent comparison circuit 902 multiple times and perform a logical AND operation. Only when the overcurrent signals of consecutive samples are all 1, it indicates that an overcurrent event has actually occurred, and the output overcurrent event signal OCP=1, otherwise OCP=0.

[0107] Among them, the overcurrent comparison circuit 902 can be an overcurrent comparator, the output end of the inductor current detection circuit 901 can be connected to the negative input end of the overcurrent comparator, the positive input end of the overcurrent comparator is grounded, and the output end of the overcurrent comparator is connected to the input end of the anti-false trigger; among them, since the positive input end of the overcurrent comparator is grounded, the reference voltage can be 0V.

[0108] In the overcurrent protection circuit provided in the embodiment of the present application, the overcurrent detection circuit includes an inductor current detection circuit, an overcurrent comparison circuit and an anti-false trigger detection circuit; the input end of the inductor current detection circuit is connected to the output end of the overcurrent trigger circuit, the output end of the inductor current detection circuit is connected to the input end of the anti-false trigger detection circuit through the overcurrent comparison circuit, and the output end of the anti-false trigger detection circuit is connected to the input end of the power tube control circuit; the inductor current detection circuit is used to convert the inductor current in the power conversion circuit into an analog voltage when receiving the overcurrent protection signal sent by the overcurrent trigger circuit; the overcurrent comparison circuit is used to output an overcurrent signal to the anti-false trigger detection circuit when the analog voltage is greater than the reference voltage; the anti-false trigger detection circuit is used to output an overcurrent event signal when the signals sampled multiple times are all overcurrent signals. The overcurrent detection circuit detects overcurrent events of the power tube in the power conversion circuit through the inductor current detection circuit, the overcurrent comparison circuit and the anti-false trigger detection circuit, and can accurately detect overcurrent events of the power tube.

[0109] In an exemplary embodiment, Figure 10As shown, the inductor current detection circuit 901 includes a first logic AND gate 1001, an auxiliary power transistor 1002, and a reference current source 1003; the input end of the first logic AND gate 1001 is respectively connected to the output end of the current detection circuit and the lower tube control signal device of the power transistor 101, the output end of the first logic AND gate 1001 is connected to the gate of the auxiliary power transistor 1002, the source of the auxiliary power transistor 1002 is connected to the inductor connection end between the power transistor 101 and the inductor, the midpoint between the drain of the auxiliary power transistor 1002 and the reference current source 1003 is connected to the negative input end of the overcurrent comparison circuit 902, and the positive input end of the overcurrent comparison circuit 902 is grounded.

[0110] Since the inductor current detection circuit 901 needs to detect the average current of the power inductor 102 during the freewheeling phase, one input end of the first logic AND gate 1001 needs to be connected to the lower tube control signal device of the power tube 101. The lower tube control signal device inputs the modulation signal EN_LS of the lower power tube to the first logic AND gate 1001.

[0111] In the inductor current detection circuit 901, the voltage V at the inductor connection terminal SW between the upper power tube and the lower power tube in the freewheeling phase of the synchronous power tube 101 is SW Lower than the ground voltage GND (0V), which satisfies , where I IND is the current flowing through the power inductor 102, R DSL is the on-resistance of the lower power tube. DSL It is the on-resistance of the lower power tube, which changes with process, voltage, and temperature (PVT). In order to eliminate the influence of PVT on the detection, an auxiliary power tube 1002 proportional to the size of the lower power tube is used. The size of the auxiliary power tube 1002 is 1 / M of the lower power tube, so its on-resistance . V SW The voltage plus an additional voltage V A , the additional voltage V A The reference current I input by the reference current source 1003 REF Flowing through the auxiliary power tube 1002, , if satisfied , indicating that the current of the power inductor 102 is overcurrent, that is, , the formula shows that if I REF is accurate, then I IND The overcurrent threshold has nothing to do with the PVT characteristics of the lower power tube.

[0112] Since M is fixed, different reference current sources can be selected to obtain different I IND Threshold. It can be seen that V SW and the current I of the power inductor 102 IND After the overcurrent occurs, the current of the power inductor 102 increases rapidly and eventually stabilizes at a large value and no longer increases due to the finite resistance of the power tube 101. In this case, it can be known that I IND The average value of I IND_AV The minimum inductor current + half of the maximum current corresponds to I IND The instantaneous current corresponding to half of the linear decline period. Similarly, we can also know the corresponding If a fixed offset voltage is added , then the moment corresponds to The inductor current detection circuit 901 has EN_HICP and SW signals as input and outputs .

[0113] The overcurrent comparator circuit 902 compares ISNS with GND=0V. If ISNS is less than 0, it means that the average inductor current exceeds the maximum current I MAX : , the overcurrent comparison circuit 902 outputs OCP_ADV=1, otherwise it outputs OCP_ADV=0.

[0114] If the overcurrent comparison circuit 902 outputs OCP_ADV=1 at time T3, it indicates that an overcurrent has occurred in the power conversion circuit 100; if ISNS outputs OCP_ADV=0 at time T3, the circuit operates normally.

[0115] In the overcurrent protection circuit provided in the embodiments of the present application, the inductor current detection circuit includes a first logic AND gate, an auxiliary power transistor, and a reference current source. The input of the first logic AND gate is respectively connected to the output of the current detection circuit and the lower tube control signal of the power transistor. The output of the first logic AND gate is connected to the gate of the auxiliary power transistor. The source of the auxiliary power transistor is connected to the inductor connection terminal between the power transistor and the inductor. The midpoint between the drain of the auxiliary power transistor and the reference current source is connected to the negative input of the overcurrent comparison circuit. The positive input of the overcurrent comparison circuit is grounded. In this circuit, a new detection structure is adopted, which utilizes the auxiliary power transistor to achieve a detection threshold for the inductor current that is independent of PVT, thereby improving the accuracy of the inductor current detection and ensuring the accuracy of the analog voltage.

[0116] In an exemplary embodiment, Figure 11As shown, the anti-false trigger detection circuit 903 includes a second data trigger 1101, a third data trigger 1102 and a second logic AND gate 1103. The input end of the second data trigger 1101 is connected to the output end of the overcurrent comparison circuit 902, the output end of the second data trigger 1101 is respectively connected to the input end of the second logic AND gate 1103 and the input end of the third data trigger 1102, the output end of the third data trigger 1102 is connected to the input end of the second logic AND gate 1103, and the output end of the second logic AND gate 1103 is connected to the input end of the power tube control circuit 802.

[0117] The second data trigger 1101 and the third data trigger 1102 are both used to output a second logic value when the overcurrent signal output by the overcurrent comparison circuit 902 is sampled; the second logic AND gate 1103 is used to output an overcurrent event signal when the logic values ​​output by the second data trigger 1101 and the third data trigger 1102 are both received as second logic values.

[0118] Second data flip-flop 1101 and third data flip-flop 1102 can be D flip-flops, and their positive output Q is the logical AND of D1 and D2, that is, OCP = D1 * D2. If OCP_ADV = 1 twice consecutively and both are sampled by the clock signals of second data flip-flop 1101 and third data flip-flop 1102, then OCP = 1, indicating that an overcurrent event has occurred in the circuit. There is no limit on the number of D flip-flops that can be used; two are used to illustrate the principle of false trigger prevention.

[0119] It should be noted that the clock signal input to the clock terminals of the second data trigger 1101 and the third data trigger 1102 can be a SAMP signal. The SAMP signal is generated by the DTC and TDC. It samples the logic value of OCP_ADV instantaneously after the rising edge of EN_LS with a delay of T3=1 / 2*T2. The instantaneous current of the inductor corresponding to the logic value is equal to the average current of the inductor. Figure 12 As shown, Figure 12 The waveform diagrams of various signals include the waveform diagram of the modulation signal EN_HS of the upper power tube, the waveform diagram of the modulation signal EN_LS of the lower power tube, the waveform diagram of SAMP, the current I IND The waveform of voltage V SW , and the waveform of the analog voltage ISNS.

[0120] In the overcurrent protection circuit provided by the embodiment of the present application, the anti-false trigger detection circuit includes a second data trigger, a third data trigger, and a second logic AND gate. The input end of the second data trigger is connected to the output end of the overcurrent comparison circuit, the output end of the second data trigger is connected to the input end of the second logic AND gate and the input end of the third data trigger respectively, the output end of the third data trigger is connected to the input end of the second logic AND gate, and the output end of the second logic AND gate is connected to the input end of the power tube control circuit. The second data trigger and the third data trigger are both used to output a second logic value when sampling the overcurrent signal output by the overcurrent comparison circuit. The second logic AND gate is used to output an overcurrent event signal when the received logic values ​​output by the second data trigger and the third data trigger are both the second logic value. In the anti-false trigger detection circuit, multiple sampling of the overcurrent signal is achieved through two data triggers. This prevents occasional misjudgments in the circuit and improves the accuracy of overcurrent detection.

[0121] In an exemplary embodiment, Figure 1 Based on the power conversion circuit 100, an independent overcurrent protection circuit 200 is added, such as Figure 13 As shown, the input signal of the overcurrent protection signal is the inductor connection terminal SW in the power conversion circuit 100, the power supply V IN and the output V of the power conversion circuit 100 OUT The output signal OCP_HICP of the overcurrent protection circuit 200 controls the upper and lower power tubes of the power tube 101. When OCP_HICP=0, the upper and lower power tubes are controlled by the PWM loop, that is, the peak current sampling circuit 106. When OCP_HICP=1, the upper and lower power tubes are forced to be turned off.

[0122] The embodiment of the present application provides an overcurrent protection scheme for a peak current mode synchronous buck DC-DC converter based on a hiccup mode, wherein the overcurrent protection circuit includes an adaptive output voltage overcurrent protection trigger threshold detection circuit, an inductor average current detection circuit, an overcurrent comparator, an anti-false trigger detection circuit, and a hiccup counter. The function of the adaptive output voltage overcurrent protection trigger threshold detection circuit is to adaptively adjust the V output voltage to the trigger overcurrent protection condition of formula (2) IN and V OUTIf the overcurrent protection triggering condition is met, the inductor average current detection circuit and all other circuits required for the hiccup mode are turned on; if the condition of formula (1) is met, the inductor average current detection circuit and all other circuits required for the hiccup mode are turned off. The hiccup mode consumes a large amount of current, especially the inductor average current detection circuit. This solution can only start the adaptive output voltage overcurrent protection trigger threshold detection circuit in the normal working mode. The operating speed of this circuit is very low and the static current is very small. It can achieve low power consumption after integrating the hiccup mode overcurrent protection function in the normal working mode. In this way, by adopting the adaptive output voltage overcurrent protection trigger threshold detection circuit, low power consumption can be achieved on the basis of integrating the overcurrent protection function. It should be noted that the adaptive output voltage overcurrent protection trigger threshold detection circuit is the overcurrent trigger circuit in the above embodiment.

[0123] It should be noted that currently, overcurrent protection schemes for synchronous DC / DC converters fall into two main categories: the first employs a hiccup mode, and the second employs a gradual reduction of the PWM frequency. The primary drawback of the gradual reduction of the PWM frequency is its slow response speed, which can lead to chip runaway due to overheating in extreme environments. The advantage of the hiccup mode is that once the overcurrent protection threshold is triggered, the chip enters a long sleep state before restarting. If the overcurrent protection is detected again, it enters a sleep state again, waits for a while, and then restarts again, repeating this cycle until the overcurrent load is removed. The prolonged sleep phase results in low average power consumption, and the chip is immune to runaway issues caused by overheating. However, the typical hiccup mode solution monitors the inductor current continuously during all operating hours. The current monitoring circuit consumes a lot of power, which significantly reduces the circuit efficiency under ultra-light load conditions in normal operating mode. In addition, the inductor current detection usually adopts peak current detection. The typical characteristic of this structure is that there is a large difference between the average current and the actual peak current, which is proportional to the input power supply voltage, resulting in measurement uncertainty. In addition, the commonly used current detection circuit directly samples the power tube voltage drop and compares it with the reference voltage. It cannot eliminate the influence of the power tube on-resistance, resulting in poor PVT characteristics.

[0124] However, the novel overcurrent protection scheme for the peak current mode synchronous buck DC-DC converter proposed in this application includes the following features: first, the output voltage range in which the inductor current may run away is automatically calculated based on the input power supply voltage. If the output voltage exceeds this range, the inductor current detection circuit is not enabled, thereby saving the quiescent current of the circuit; second, the average current detection method is adopted, which eliminates the defect that the peak current cannot accurately reflect the average current due to the change of the power supply voltage; third, the power tube on-resistance tracking scheme is used to eliminate the influence of the PVT characteristics of the power tube resistance on the overcurrent threshold.

[0125] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0126] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. An overcurrent protection circuit, characterized in that: One end of the overcurrent protection circuit is connected to one end of the power conversion circuit, the other end of the overcurrent protection circuit is connected to the power supply, and the other end of the power conversion circuit is connected to the power supply; The overcurrent protection circuit is used to control the power tube in the power conversion circuit to turn off when an overcurrent occurs in the power tube, and to control the power tube to turn on after a preset time.

2. The overcurrent protection circuit according to claim 1, characterized in that: The overcurrent protection circuit includes an overcurrent trigger circuit and an overcurrent control circuit; the input end of the overcurrent trigger circuit is connected to the power supply and the power conversion circuit respectively; the output end of the overcurrent trigger circuit is connected to the input end of the overcurrent control circuit, and the output end of the overcurrent control circuit is connected to the power conversion circuit; The overcurrent trigger circuit is configured to, when detecting that the power conversion circuit triggers an overcurrent protection condition, turn on the overcurrent control circuit and output an overcurrent protection signal to the overcurrent control circuit; The overcurrent control circuit is used to control the power tube to turn off when an overcurrent event is detected in the power conversion circuit, and to control the power tube to turn on after a preset time.

3. The overcurrent protection circuit according to claim 2, wherein: The overcurrent trigger circuit includes a voltage threshold calculation circuit, a voltage comparison circuit and a first data trigger; the input end of the voltage threshold calculation circuit is connected to the power supply, the output end of the voltage threshold calculation circuit is connected to the input end of the first data trigger through the positive input end of the voltage comparison circuit, the negative input end of the voltage comparison circuit is connected to the power conversion circuit, and the output end of the first data trigger is connected to the input end of the overcurrent control circuit; The voltage threshold calculation circuit is used to calculate the control voltage for causing inductor current runaway in the power conversion circuit according to the output voltage of the power supply; The voltage comparison circuit is configured to output a first logic value when the output voltage of the power conversion circuit is less than the control voltage; The first data trigger is used to output the overcurrent protection signal when the first logic value is sampled.

4. The overcurrent protection circuit according to claim 3, characterized in that: The voltage threshold calculation circuit includes a resistance circuit, an operational amplifier, a reference power tube, a current mirror, a capacitor, a first switch and a second switch; the first end of the resistance circuit is connected to the power supply, the second end of the resistance circuit is connected to the positive input end of the operational amplifier, the third end of the resistance circuit is connected to the first end of the capacitor, the fourth end of the resistance circuit is respectively connected to the negative input end of the operational amplifier and the source of the reference power tube, the output end of the operational amplifier is connected to the gate of the reference power tube, the drain of the reference power tube is connected to the first end of the current mirror, the second end of the current mirror is connected to the reference power supply, the third end of the current mirror is connected to the second end of the capacitor through the first switch, and the capacitor is connected in parallel with the second switch.

5. The overcurrent protection circuit according to claim 4, characterized in that: The resistance circuit includes a first resistor, a second resistor and a third resistor, one end of the first resistor is connected to the power supply, the other end of the first resistor is respectively connected to the positive input terminal of the operational amplifier and one end of the second resistor, the other end of the second resistor is respectively connected to one end of the third resistor and the first end of the capacitor, and the other end of the third resistor is respectively connected to the negative input terminal of the operational amplifier and the source of the reference power tube.

6. The overcurrent protection circuit according to claim 4, characterized in that: The current mirror includes a first current mirror and a second current mirror, the sources of the first current mirror and the second current mirror are both connected to the reference power supply, the gate of the first current mirror is connected to the gate of the second current mirror, the drain of the first current mirror is respectively connected to the gate of the first current mirror and the drain of the reference power tube, and the drain of the second current mirror is connected to the second end of the capacitor through the first switch.

7. The overcurrent protection circuit according to claim 2, wherein: The overcurrent control circuit includes an overcurrent detection circuit and a power tube control circuit, wherein the input end of the overcurrent detection circuit is connected to the output end of the overcurrent trigger circuit, the output end of the overcurrent detection circuit is connected to the input end of the power tube control circuit, and the output end of the power tube control circuit is connected to the power conversion circuit; The overcurrent detection circuit is configured to output an overcurrent event signal to the power tube control circuit when an overcurrent event is detected in the power conversion circuit; The power tube control circuit is used to control the power tube to be turned off when receiving the overcurrent event signal, and to control the power tube to be turned on after a preset time period.

8. The overcurrent protection circuit according to claim 7, characterized in that: The overcurrent detection circuit includes an inductor current detection circuit, an overcurrent comparison circuit, and an anti-false trigger detection circuit; the input end of the inductor current detection circuit is connected to the output end of the overcurrent trigger circuit, the output end of the inductor current detection circuit is connected to the input end of the anti-false trigger detection circuit through the overcurrent comparison circuit, and the output end of the anti-false trigger detection circuit is connected to the input end of the power tube control circuit; The inductor current detection circuit is configured to convert the inductor current in the power conversion circuit into an analog voltage upon receiving the overcurrent protection signal sent by the overcurrent trigger circuit; The overcurrent comparison circuit is configured to output an overcurrent signal to the false trigger prevention detection circuit when the analog voltage is greater than a reference voltage; The anti-false trigger detection circuit is used to output the overcurrent event signal when the signals sampled multiple times are all overcurrent signals.

9. The overcurrent protection circuit according to claim 8, characterized in that: The inductor current detection circuit includes a first logic AND gate, an auxiliary power tube and a reference current source; the input end of the first logic AND gate is respectively connected to the output end of the current detection circuit and the lower tube control signal device of the power tube, the output end of the first logic AND gate is connected to the gate of the auxiliary power tube, the source of the auxiliary power tube is connected to the inductor connection end between the power tube and the inductor, the midpoint between the drain of the auxiliary power tube and the reference current source is connected to the negative input end of the overcurrent comparison circuit, and the positive input end of the overcurrent comparison circuit is grounded.

10. The overcurrent protection circuit according to claim 8, characterized in that: The anti-false trigger detection circuit includes a second data trigger, a third data trigger, and a second logic AND gate, wherein the input end of the second data trigger is connected to the output end of the overcurrent comparison circuit, the output end of the second data trigger is connected to the input end of the second logic AND gate and the input end of the third data trigger respectively, the output end of the third data trigger is connected to the input end of the second logic AND gate, and the output end of the second logic AND gate is connected to the input end of the power tube control circuit; The second data trigger and the third data trigger are both used to output a second logic value when sampling the overcurrent signal output by the overcurrent comparison circuit; The second logic AND gate is used to output the overcurrent event signal when the logic values ​​output by the received second data trigger and the third data trigger are both the second logic values.

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