CN108599570A - A kind of circuit with dynamic regulation current limit threshold - Google Patents

Abstract

The invention discloses a circuit with dynamically adjustable current-limiting threshold. The circuit includes: an adaptive current-limiting circuit connected to a driving circuit, and the adaptive current-limiting circuit is used for constantly monitoring the change of the inductor current. When an abnormal change in the current is detected, the system is adjusted in advance by appropriately increasing the threshold of the current limiting circuit to avoid a negative value of the inductor current; the driving circuit is connected to the basic topology of the buck, and the driving circuit is used It is used to process the PWM and CLK signals into drive signals TG and BG; the basic topology of the buck is matched with the drive circuit to reduce the input voltage V _in to the required voltage; The real-time monitoring of the current detects the abnormal change of the inductor current in advance and selects the appropriate current limiting threshold, so as to prevent the inductor current from becoming negative at first and improve the overall performance of the system.

Description

A circuit with dynamically adjustable current-limiting threshold

technical field

The invention relates to the field of power management, in particular to a circuit with a dynamically adjustable current limiting threshold.

Background technique

A switching power supply system usually includes some protection circuits, such as: temperature protection circuit, voltage protection circuit, circuit protection circuit. When an abnormality occurs in the switching power supply system, the protection circuit can protect the power supply system from being damaged. When the switching power supply system is abnormal or in a special mode, the inductor current will decrease rapidly. Due to some delay in the current sense loop, it is possible for the inductor current to drop to a negative value, which is usually undesirable.

Contents of the invention

In order to solve the above problems, this application proposes a circuit with dynamic adjustment of the current limit threshold, through the real-time monitoring of the inductor current by the current detection circuit, differential circuit, and comparison circuit, the abnormal change of the inductor current is detected in advance and an appropriate threshold value is selected. The threshold value of the current flow, so as to prevent the inductor current from being negative at first, and improve the overall performance of the system.

In order to achieve the purpose of the above invention, the present application provides a circuit with a dynamically adjustable current limiting threshold, characterized in that the circuit includes:

Adaptive current limiting circuit, the adaptive current limiting circuit is connected with the drive circuit, the adaptive current limiting circuit is used to constantly monitor the change of the inductor current, when an abnormal change of the current is detected, the threshold value of the current limiting circuit is appropriately increased to advance Adjust the system to avoid the negative value of the inductor current;

A driving circuit, the driving circuit is connected to the basic topology of the buck, and the driving circuit is used to process the PWM and CLK signals into driving signals TG and BG;

The basic topological structure of the buck is matched with a driving circuit, which is used to reduce the input voltage V _in to the required voltage.

Among them, the focus of this application is the adaptive current limiting circuit, the topological structure of the driving circuit and the buck is the circuit and structure in the prior art, and the purpose of the topological structure of the driving circuit and the buck is that the adaptive circuit forms a loop system, which is convenient for description And explain the purpose of the adaptive current limiting circuit. The current limiting circuit is not limited to buck, and can be used in various power systems such as: buck, boost, buck-boost, etc.

Further, the adaptive current limiting circuit includes: a current detection circuit, a differential circuit, a comparison circuit, and a current limiting circuit;

Further, the drive circuit and the buck topology include: current detection resistor R _sense , inductor L, capacitor C, field effect transistor NM ₁ , field effect transistor NM ₂ , resistor R _load ; the G pole of the field effect transistor NM ₁ and The G pole of the field effect transistor NM ₂ is connected to the output terminal of the drive circuit, the D pole of the field effect transistor NM ₁ is connected to the Vin terminal, the S pole of the field effect transistor NM ₁ and the D pole of the field effect transistor NM ₂ are connected to the inductor One end of L is connected, the other end of inductor L is connected to one end of resistor R _sense , the other end of resistor R _sense is connected to the positive pole of capacitor C and one end of resistor R _load , the S pole of field effect transistor NM ₂ , the pole of capacitor C The negative electrode and the other end of the resistor R _load are both grounded.

Further, the differential circuit includes: transistors Q ₁ -Q ₄ , field effect transistors NM ₃ -NM ₈ , capacitor C ₄ , resistor R ₃ , operational amplifier Amp, resistor R ₁ , and resistor R ₂ ;

_One end of the resistor R1 is connected to the positive input terminal of the current detection circuit, the other end _of the resistor R1 is connected to the I _bias terminal, the emitter of the transistor Q1, and the emitter _of the transistor _Q3 , and the collector _of the transistor Q1 is connected to the field effect The D pole of the transistor _NM3 and the G pole of the field effect transistor _NM4 are all connected, the base _of the transistor Q1 is connected with the base of the transistor _Q3 , and the collector of the transistor _Q3 is connected, and the collector of the transistor _Q3 and the transistor Q The collectors of ₂ are connected to the 2I _bias terminal, the G pole of the field effect transistor NM ₃ and the G pole of the field effect transistor NM ₅ are connected to the V _bias2 terminal, and the S pole of the field effect transistor NM ₃ is connected to the terminal of the field effect transistor NM ₄ The D pole is connected, the G pole of the field effect transistor _NM4 is connected with the G pole of the field effect transistor _NM6 , the S pole of the field effect transistor _NM4 is grounded _; one end of the resistor R2 is connected to the negative input terminal of the current detection circuit, and the resistor _R2 is connected to the negative input terminal of the current detection circuit. The other end is connected to the emitter of the transistor _Q2 , the emitter of the transistor _Q4 , and the D pole of the field effect transistor _NM8 , and the base of the transistor _Q2 and the base of the transistor _Q4 are all connected to the collector of the transistor _Q2 . The electrodes are all connected, the collector of the triode _Q4 is connected to the D pole of the field effect transistor _NM5 , the G pole of the field effect transistor _NM7 , and the positive pole of the capacitor _C4 , and the G pole of the field effect transistor _NM8 is connected to the V _bias1 terminal , the S pole of the field effect transistor NM ₈ is connected to the D pole of the field effect transistor NM ₇ , the S pole of the field effect transistor NM ₇ is grounded, the negative pole of the capacitor _C4 is connected to one end of the resistor _R3 , and the negative input end of the operational amplifier Amp Connect, the positive input end of the op amp Amp is connected to the V _bias3 end, the other end of the resistor R ₃ and the output end of the op amp Amp are connected to the V _b end.

Further, the comparison circuit includes a resistor R _<n:0> , a comparator Comp _<n-1:0> , an inverter INV _<n-1:0> , and an AND gate AND _<n-1:0> ; The resistor R _<n:0> is connected in series between the reference voltage V _ref and GND; the negative input terminals of the comparator Comp _<n-1:0> are respectively connected to the upper terminal of R _<n-1:0> , and the positive input terminal Connect to the output voltage V _b of the differential circuit uniformly, the enabling terminals of Comp _<n-1:1> are respectively connected to the output terminals of Comp _<n-2:0> ; the output terminal V _out<0> of the comparator is connected to the One input terminal of AND _<0> of the gate, V _out<n-2:1> are respectively connected to one input terminal of AND _<n-2:1> and respectively connected to INV _<n-1:0> input terminals, The output terminals of INV _<n-1:0> are respectively connected to one input terminal of AND _<n-1:0> .

Further, the current limiting circuit includes a comparator Cmop, n capacitors C and n field effect transistors; the positive input terminal of the comparator Comp is connected to the output voltage V _sense of the current detection circuit, and the negative input terminal is connected to the field effect transistor NM _<n The drain of _-1:0> , the gate of the field effect transistor are respectively connected to the output control signal Ctr _<n-1:0> of the comparison circuit, and the source is respectively connected to the upper end of the capacitor C _<n-1:0> and Vref _<n-1:0>; The lower end of the capacitor is uniformly connected to GND.

The invention discloses a circuit with dynamic adjustment current limiting threshold, including adaptive current limiting circuit: current detection & differential circuit, comparison circuit & current limiting circuit, basic topological structure of driving circuit and buck, including power transistor NM ₁ , NM ₂ , inductance L, capacitor C and load resistance R _load ; the output terminal V _b of the current detection & differential circuit module is connected to the input terminal of the comparison circuit & current limiting circuit module, and the comparison circuit & current limiting circuit module outputs a LIP The current limit signal controls the drive circuit. When the system is abnormal or enters a special mode, the inductor current may decrease sharply. Due to a certain delay in the current feedback loop, the inductor current may appear negative. In the power system, it is generally undesirable that the inductor current has a negative value, which is not conducive to the utilization efficiency of the power system. The abnormal change of the current can be detected in advance through the current detection & differential circuit and the comparison circuit, and the system can be adjusted in advance to avoid the negative value of the inductor current by appropriately increasing the threshold of the current limiting circuit. By adopting a circuit that dynamically adjusts the current limiting threshold, some performance indicators of the system can be improved, such as the ability of the system to return to normal from an abnormal state.

One or more technical solutions provided by this application have at least the following technical effects or advantages:

When an abnormal or special mode occurs in the power system, the inductor current may decrease sharply, and the abnormal change of the current is converted into a voltage signal V _b through the current detection & differential circuit, and then the voltage signal V _b is quantized into n-bit control through the comparison circuit Signal Ctr _<n-1:0> , these control signals are responsible for the threshold selection of the current limiting circuit. Through the above circuit, the abnormal change of the current can be detected in advance, and the threshold value of the current limiting circuit can be dynamically adjusted to avoid the negative value of the inductor current and improve the overall performance of the system.

Description of drawings

The drawings described here are used to provide a further understanding of the embodiments of the present invention, constitute a part of the application, and do not constitute a limitation to the embodiments of the present invention;

Fig. 1 is the overall topological diagram of the present invention;

Fig. 2 is a specific circuit diagram of circuit detection & differential circuit of the present invention;

Fig. 3 is a concrete circuit diagram of comparison circuit;

Fig. 4 is a specific circuit diagram of the current limiting circuit;

Fig. 5 is a schematic diagram of the change of the inductor current when the switching power supply system is abnormal;

Fig. 6 is a schematic diagram of circuit detection & differential circuit output signal;

Fig. 7 is a schematic diagram of the output control signal of the comparator circuit;

Fig. 8 is a schematic diagram of threshold voltage variation of the current limiting circuit.

Detailed ways

In order to understand the above-mentioned purpose, features and advantages of the present invention more clearly, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, under the condition of not conflicting with each other, the embodiments of the present application and the features in the embodiments can be combined with each other.

In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from the scope of this description. Therefore, the protection scope of the present invention is not limited by the following disclosure. limitations of specific examples.

The present invention provides a circuit with dynamically adjustable current-limiting threshold, including adaptive current-limiting circuit 20: current detection & differential circuit, comparison circuit & current-limiting circuit, driving circuit 30 and basic topology 10 of buck, including power tube NM ₁ , NM ₂ , inductance L, capacitor C and load resistance R _load ; the output terminal V _b of the current detection & differential circuit module is connected to the input terminal of the comparison circuit & current limiting circuit module, the comparison circuit & current limiting circuit module Output a LIP current limiting signal to control the driving circuit. When the system is abnormal or enters a special mode, the inductor current may decrease sharply, and the abnormal change of the current is converted into a voltage signal V _b through the current detection & differential circuit, and then the voltage signal V _b is quantized into n-bit control through the comparison circuit Signal Ctr _<n-1:0> These control signals are responsible for the threshold selection of the current limiting circuit. Through the above circuit, the abnormal change of the current can be detected in advance, and the threshold value of the current limiting circuit can be dynamically adjusted, so as to avoid the situation that the inductor current has a negative value.

Example 1

A kind of self-adaptive current-limiting circuit as shown in Figure 1, comprises self-adaptive current-limiting circuit 20: the basic topological structure 30 of current detection & differential circuit, comparison circuit & current-limiting circuit, drive circuit 30 and buck switching power supply, including power Tubes NM ₁ , NM ₂ , inductor L, capacitor C and load resistor R _load ; the input terminal V _b of the current detection & differential circuit module is connected to the current detection resistor R _sense , and the output terminal is connected to the comparison circuit & current limiting circuit The input terminal of the module; the output signal Ctr _<n-1:0> of the comparison circuit is respectively connected to the threshold control switch NM _<n-1:0> of the current limiting circuit module; the output terminal LIP of the current limiting module connected to the drive circuit.

Example 2

Based on the principles of the foregoing embodiments, this embodiment takes n=2 as an example for detailed description.

As shown in Figure 2, the current detection & differential circuit includes transistor Q _<4:1> ; field effect transistor NM _<12:3> resistor R _<3:1> capacitor C ₄ and operational amplifier Amp, its voltage and current bias The setting is shown in Figure 2. The current detection & differential circuit converts the abnormal change of the inductor current into a voltage V _sense first, and then converts the abnormal change of the inductor current into an output voltage V _b through the differential circuit. The voltage V _b is quantized into a three-bit control signal Ctr _<2:0> through the comparison circuit, and the control signal realizes the adjustment of the dynamic threshold voltage by controlling the switch of the threshold voltage of the current limiting circuit.

The circuit for dynamically adjusting the current limiting threshold of the present invention also includes a driving circuit module and a basic topological structure of a buck.

Preferably, the comparison circuit processes the output signal V _b of the current detection & differentiation module into three control signals Ctr _<2:0> , and the control signals respectively control the threshold voltage switch NM _<2:0> of the current limiting circuit, thereby realizing self-adaptation Current limiting function.

The operating principle of the above circuit is now described in detail.

When the system encounters an abnormal or special mode, in order to protect the normal operation of the system, the current limiting circuit will turn off the power transistor NM ₁ and turn on NM ₂ through the control module. This operation is to release the current stored in the inductor (L) and the charge stored in the capacitor (C) to relieve the abnormal state of the system. At this time, the current on the inductor may decrease rapidly, resulting in a negative value of the inductor current in a short period of time, as shown in Figure 4. Due to the effect of the reverse current protection circuit, the inductor current will not decrease all the time. When the abnormal state is removed, the inductor current returns to the normal state again. Let the inductor current be I _out when the system works normally, and the change of the inductor current when the inductor current is abnormal is ΔI _out . The input voltage V _sense of the current detection circuit is the product of the detection resistor R _sense and the output current change I _out + ΔI _out

V _sense ＝(I _out +ΔI _out )*R _sen (1)

The gain of the current detection circuit in the current feedback loop is A _v , and the output voltage is V _o .

where g _m is the transconductance of NM ₁₁ .

The output voltage V _o of the differential circuit is related to the rate of change of the output voltage of the current detection circuit. The output voltage of the differential circuit can be described by the following formula:

Considering the normal operation of the system, the inductor current also has small periodic changes. At this time, the output voltage V _b of the differential circuit is approximately equal to V _bias3 . When designing the comparator threshold of the comparison circuit, it is necessary to take into account the change in the output voltage of the differential circuit caused by the small fluctuation of the inductor current, and set the threshold of the first comparator comp _<0> slightly greater than V _bias3 , and the system works normally When the output control signal Ctr _<0> of the comparison circuit is in the effective state, the minimum current-limiting threshold is selected. Then set the threshold of comparator comp _<2:1> according to the situation of system application.

In order to reduce the power consumption of the comparator circuit, only Comp _<1:0> is in the normal working state when the system is working normally, and the rest of the comparators are in the off mode. When comparator Comp _<1> output is high, comparator Comp _<2> is set to standby state.

When the inductor current decreases rapidly, the differential circuit can detect the change speed of the output voltage of the current detection circuit. If the decrease speed of the inductor current exceeds the current decrease speed corresponding to the threshold voltage of the comparator comp _<1> , the comparison circuit It will make the control signal Ctr _<1> valid. The control signal selects a higher threshold by controlling the threshold control switch of the current limiting circuit, so as to prevent the inductor current from falling to a negative value in this state.

When the inductor current decreases faster, it is possible to trigger the comparator comp _<2> to make the control signal Ctr _<2 > of the comparison circuit effective, so that the threshold voltage of the current limiting circuit selects a higher value to prevent the inductor current from down to a negative value. The schematic diagram of the threshold voltage change of the current limiting circuit is shown in Figure 7.

By adopting an adaptive current limiting circuit, when the system is abnormal or enters a special mode, the inductor current can be monitored in real time through the current detection circuit, differential circuit, and comparison circuit, and the abnormality of the inductor current can be detected in advance Change and select an appropriate current-limit threshold to prevent the inductor current from becoming negative at first.

While preferred embodiments of the invention have been described, additional changes and modifications to these embodiments can be made by those skilled in the art once the basic inventive concept is appreciated. Therefore, it is intended that the appended claims be construed to cover the preferred embodiment as well as all changes and modifications which fall within the scope of the invention.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (6)

1. A circuit with a dynamically adjustable current-limiting threshold, characterized in that the circuit comprises: Adaptive current limiting circuit, the adaptive current limiting circuit is connected with the drive circuit, the adaptive current limiting circuit is used to constantly monitor the change of the inductor current, when an abnormal change of the current is detected, the threshold value of the current limiting circuit is appropriately increased to advance Adjust the system to avoid the negative value of the inductor current; The driving circuit, the driving circuit is connected with the basic topology of the buck, and the driving circuit is used to process the PWM and CLK signals into driving signals TG and BG; the basic topology of the buck is matched with the driving circuit, and is used to reduce the input voltage V _in to the required required voltage. 2. The circuit with dynamically adjustable current-limiting threshold according to claim 1, wherein the adaptive current-limiting circuit comprises: a current detection circuit, a differential circuit, a comparison circuit, and a current-limiting circuit. 3. The circuit with dynamically adjustable current-limiting threshold according to claim 2, characterized in that, the drive circuit and the buck topology include: a current sensing resistor R _sense , an inductor L, a capacitor C, a field effect transistor NM ₁ , The field effect transistor NM ₂ and the resistor R _load ; the G pole of the field effect transistor NM ₁ and the G pole of the field effect transistor NM ₂ are both connected to the output terminal of the drive circuit, and the D pole of the field effect transistor NM ₁ is connected to the V _in terminal, Both the S pole of the field effect transistor NM ₁ and the D pole of the field effect transistor NM ₂ are connected to one end of the inductor L, the other end of the inductor L is connected to one end of the resistor R _sense , the other end of the resistor R _sense is connected to the positive pole of the capacitor C and One end of the resistor R _load is connected, and the S pole of the field effect transistor NM ₂ , the negative electrode of the capacitor C, and the other end of the resistor R _load are all grounded. 4. The circuit with dynamically adjustable current-limiting threshold according to claim 2, wherein the differential circuit comprises: transistors Q ₁ -Q ₄ , field effect transistors NM ₃ -NM ₈ , capacitor C ₄ , resistor R _3. Operational amplifier Amp, resistor R ₁ , resistor R ₂ ; _One end of the resistor R1 is connected to the positive input terminal of the current detection circuit, the other end _of the resistor R1 is connected to the I _bias terminal, the emitter of the transistor Q1, and the emitter _of the transistor _Q3 , and the collector _of the transistor Q1 is connected to the field effect The D pole of the transistor _NM3 and the G pole of the field effect transistor _NM4 are all connected, the base _of the transistor Q1 is connected with the base of the transistor _Q3 , and the collector of the transistor _Q3 is connected, and the collector of the transistor _Q3 and the transistor Q The collectors of ₂ are connected to the 2I _bias terminal, the G pole of the field effect transistor NM ₃ and the G pole of the field effect transistor NM ₅ are connected to the V _bias2 terminal, and the S pole of the field effect transistor NM ₃ is connected to the terminal of the field effect transistor NM ₄ The D pole is connected, the G pole of the field effect transistor _NM4 is connected with the G pole of the field effect transistor _NM6 , the S pole of the field effect transistor _NM4 is grounded _; one end of the resistor R2 is connected to the negative input terminal of the current detection circuit, and the resistor _R2 is connected to the negative input terminal of the current detection circuit. The other end is connected to the emitter of the transistor Q2, the emitter of the transistor _Q4 , and the D pole of the field effect transistor _NM8 , and the base of the transistor _Q2 and the base of the transistor Q4 are connected to the collector of the transistor _Q2 . connection, the collector of the transistor _Q4 is connected to the D pole of the field effect transistor _NM5 , the G pole of the field effect transistor _NM7 , and the positive pole of the capacitor _C4 , and the G pole of the field effect transistor _NM8 is connected to the V _bias1 terminal. The S pole of the effect transistor NM ₈ is connected to the D pole of the field effect transistor NM ₇ , the S pole of the field effect transistor NM ₇ is grounded, the negative pole of the capacitor C ₄ is connected to one end of the resistor R ₃ and the negative input terminal of the operational amplifier Amp, The positive input end of the op amp Amp is connected to the V _bias3 end, and the other end of the resistor R ₃ and the output end of the op amp Amp are both connected to the V _b end. 5. The circuit with dynamically adjustable current-limiting threshold according to claim 2, characterized in that, the comparison circuit includes a resistor R _<n:0> , a comparator Comp _<n-1:0> , an inverter INV _<n-1:0> , AND gate AND _<n-1:0> ; resistor R _<n:0> is connected in series between the reference voltage V _ref and GND; the negative of comparator Comp _<n-1:0> The input terminals are respectively connected to the upper end of R _<n-1:0> , the positive input terminal is uniformly connected to the output voltage V _b of the differential circuit, and the enabling terminals of Comp _<n-1:1> are respectively connected to Comp _{<n-2: 0>} output terminal; the output terminal V _out<0> of the comparator is connected to an input terminal of AND _<0> of the AND gate, and V _out<n-2:1> is respectively connected to AND _<n-2:1> An input terminal of AND is respectively connected to an input terminal of INV _{< n-1:0>} , and an output terminal of INV <n-1:0> is respectively connected to an input terminal of AND _<n-1:0> . 6. The circuit with dynamically adjustable current-limiting threshold according to claim 2, characterized in that, said current-limiting circuit comprises a comparator Cmop, n capacitors C and n field effect transistors; the positive input terminal of comparator Comp Connect the output voltage V _sense of the current detection circuit, the negative input terminal is connected to the drain of the field effect transistor NM _<n-1:0> , and the gate of the field effect transistor is respectively connected to the output control signal Ctr _<n-1:0> of the comparison circuit, The source is connected to the upper end of the capacitor C _<n-1:0> and Vref _<n-1:0> respectively; the lower end of the capacitor is uniformly connected to GND.