阅读说明：本技术 开关电路的电感电流模拟电路、模拟方法及开关电源 (Inductive current simulation circuit and method of switching circuit and switching power supply ) 是由 徐爱民 于 2020-12-09 设计创作，主要内容包括：本发明提出一种开关电路的电感电流模拟电路、模拟方法及开关电源,基于误差放大电路,同步整流管导通时,所述误差放大电路将表征同步整流管电流的第一采样信号和表征电感电流模拟信号的第二采样信号进行误差放大,得到误差放大信号；根据同步整流管导通时的误差放大信号以及主功率管导通时的第一电流,重构电感电流,得到电感电流模拟信号。本发明可以得到电感电流的模拟信号,避免采样电感电流而带来的采样精度不准的问题。(The invention provides an inductive current analog circuit, an analog method and a switching power supply of a switching circuit, based on an error amplification circuit, when a synchronous rectifier tube is conducted, the error amplification circuit performs error amplification on a first sampling signal representing the current of the synchronous rectifier tube and a second sampling signal representing an inductive current analog signal to obtain an error amplification signal; and reconstructing the inductive current according to the error amplification signal when the synchronous rectifier tube is conducted and the first current when the main power tube is conducted, so as to obtain an inductive current analog signal. The invention can obtain the analog signal of the inductive current and avoid the problem of inaccurate sampling precision caused by sampling the inductive current.)

1. An inductor current simulation circuit for a switching circuit, the switching circuit including a main power transistor and a synchronous rectifier, comprising:

the error amplification circuit receives a first sampling signal representing the current of the synchronous rectifier tube and a second sampling signal representing the inductive current analog signal at the conduction stage of the synchronous rectifier tube and outputs an error amplification signal;

the output current generating circuit is used for generating the inductive current analog signal; in the conduction stage of the synchronous rectifier tube, the error amplification signal drives the output current generating circuit; and in the conduction stage of the main power tube, the output current generating circuit is driven by the first current.

2. The inductor current analog circuit of the switching circuit of claim 1, wherein: the circuit also comprises a first current generating circuit which generates the first current according to the inductive current analog signal, the topological structure of the switch circuit, the input voltage and the output voltage.

3. The inductor current analog circuit of the switching circuit of claim 1, wherein: the synchronous rectifier circuit further comprises a first current generating circuit, and the first current generating circuit generates the first current according to the direction of the output current of the error amplifying circuit in the first time when the synchronous rectifier tube is just conducted.

4. An inductor current simulation circuit of a switching circuit according to claim 2, wherein: the first current generation circuit comprises a first capacitor and a first switch tube, the charging current of the first capacitor is set according to the inductive current analog signal, and the discharging current of the first capacitor is set according to the charging current, the topological structure of the switch circuit, the input voltage and the output voltage; the charging current charges a first capacitor in the whole working period, and the discharging current discharges the first capacitor during the conduction period of the main power tube; the first capacitor voltage drives the first switch tube, and the current of the first switch tube is the first current.

5. An inductor current simulation circuit of a switching circuit according to claim 3, wherein: the first current generation circuit comprises a first capacitor and a first switch tube, the first capacitor is charged with a second current or discharged with the second current in the first time when the synchronous rectifier tube is just switched on, the first capacitor is driven by the voltage of the first switch tube, and the current of the first switch tube is the first current.

6. The inductor current analog circuit of the switching circuit of claim 1, wherein: the output current generating circuit comprises an output tube and a sampling tube, one end of the output tube is connected with one end of the sampling tube, and the other end of the sampling tube is connected with a common connecting end of the main power tube and the synchronous rectifying tube; in the conduction stage of the synchronous rectifier tube, the error amplification signal drives the output tube; and in the conduction stage of the main power tube, the first current drives the output tube, and the current of the output tube represents the inductive current analog signal.

7. An inductor current simulation circuit of the switching circuit of claim 6, wherein: the other end of the output tube is connected with a resistor.

8. The inductor current analog circuit of the switching circuit of claim 1, wherein: the first input end of the error amplification circuit is connected with the grounding end of the synchronous rectifier tube, and the second end of the error amplification circuit is connected with the common connecting end of the sampling tube and the output tube; and in the conduction stage of the synchronous rectifier tube, the error amplification circuit is enabled to output the error amplification signal.

9. The inductor current analog circuit of the switching circuit according to claim 4, wherein: when the switch circuit is a voltage reduction circuit, the charging current of the first capacitor represents the inductive current analog signal, and the discharging current of the first capacitor is in direct proportion to the product of the charging current and the input voltage and in inverse proportion to the output voltage.

10. A method for simulating an inductor current of a switching circuit, the switching circuit comprising a main power transistor and a synchronous rectifier, the method comprising: based on an error amplifying circuit, when the synchronous rectifier tube is conducted, the error amplifying circuit carries out error amplification on a first sampling signal representing the current of the synchronous rectifier tube and a second sampling signal representing the inductive current analog signal to obtain an error amplifying signal; and reconstructing the inductive current according to the error amplification signal when the synchronous rectifier tube is conducted and the first current when the main power tube is conducted, so as to obtain an inductive current analog signal.

Technical Field

The invention relates to the field of power electronics, in particular to an inductive current simulation circuit and method of a switching circuit and a switching power supply.

Background

In a control scheme of a switching circuit, an inductor current sampling signal is often used. In some application occasions, the conduction time of a main power tube of the switch circuit is short, so that the sampling of the charging and discharging current of the inductor is inaccurate, and the control effect of the switch circuit is influenced.

Disclosure of Invention

The invention aims to provide an inductive current analog circuit capable of reconstructing inductive current of a switching circuit, which is used for solving the problem of inaccurate inductive current sampling.

In order to achieve the above object, the present invention provides an inductor current analog circuit of a switching circuit, the switching circuit includes a main power transistor and a synchronous rectifier, the inductor current analog circuit includes:

the error amplification circuit receives a first sampling signal representing the current of the synchronous rectifier tube and a second sampling signal representing the inductive current analog signal at the conduction stage of the synchronous rectifier tube and outputs an error amplification signal;

the output current generating circuit is used for generating the inductive current analog signal; in the conduction stage of the synchronous rectifier tube, the error amplification signal drives the output current generation circuit; and in the conduction stage of the main power tube, the output current generating circuit is driven by the first current.

Optionally, the power supply further comprises a first current generating circuit, which generates the first current according to the inductor current analog signal, the topology of the switching circuit, the input voltage and the output voltage.

Optionally, the synchronous rectifier circuit further includes a first current generating circuit, and the first current generating circuit generates the first current according to the output current direction of the error amplifying circuit in the first time when the synchronous rectifier tube is just turned on.

Optionally, the first current generating circuit includes a first capacitor and a first switching tube, sets a charging current of the first capacitor according to the inductor current analog signal, and sets a discharging current of the first capacitor according to the charging current, a topology of the switching circuit, an input voltage, and an output voltage; the charging current charges a first capacitor in the whole working period, and the discharging current discharges the first capacitor during the conduction period of the main power tube; the first capacitor voltage drives the first switch tube, and the current of the first switch tube is the first current.

Optionally, the first current generating circuit includes a first capacitor and a first switching tube, and in a first time when the synchronous rectifier is just turned on, the first capacitor is charged with a second current or discharged with the second current according to the direction of the output current of the error amplifying circuit, the first capacitor drives the first switching tube with a voltage, and the first switching tube current is the first current.

Optionally, the output current generating circuit includes an output tube and a sampling tube, one end of the output tube is connected to one end of the sampling tube, and the other end of the sampling tube is connected to a common connection end of the main power tube and the synchronous rectifier tube; in the conduction stage of the synchronous rectifier tube, the error amplification signal drives the output tube; and in the conduction stage of the main power tube, the first current drives the output tube, and the current of the output tube represents the inductive current analog signal.

Optionally, the other end of the output tube is connected with a resistor.

Optionally, the first input end of the error amplification circuit is connected to the ground end of the synchronous rectifier tube, and the second end of the error amplification circuit is connected to the common connection end of the sampling tube and the output tube; and in the conduction stage of the synchronous rectifier tube, the error amplification circuit is enabled to output the error amplification signal.

Optionally, when the switch circuit is a voltage-reducing circuit, the charging current of the first capacitor represents the inductor current analog signal, and the discharging current of the first capacitor is proportional to a product of the charging current and the input voltage and inversely proportional to the output voltage.

The invention also provides an inductive current simulation method of the switching circuit, wherein the switching circuit comprises a main power tube and a synchronous rectifier tube, and based on the error amplification circuit, when the synchronous rectifier tube is conducted, the error amplification circuit performs error amplification on a first sampling signal representing the current of the synchronous rectifier tube and a second sampling signal representing the inductive current analog signal to obtain an error amplification signal; and reconstructing the inductive current according to the error amplification signal when the synchronous rectifier tube is conducted and the first current when the main power tube is conducted, so as to obtain an inductive current analog signal.

Optionally, the first current is generated according to the inductor current analog signal, a topology of the switching circuit, the input voltage, and the output voltage.

Optionally, the first current is generated according to the output current direction of the error amplifying circuit in the first time when the synchronous rectifying tube is just turned on.

Optionally, the charging current of the first capacitor is set according to the inductor current analog signal, and the discharging current of the first capacitor is set according to the charging current, the topology structure of the switch circuit, the input voltage and the output voltage; the charging current charges a first capacitor in the whole working period, and the discharging current discharges the first capacitor during the conduction period of the main power tube; the first capacitor voltage drives a first switch tube, and the current of the first switch tube is the first current.

Optionally, in a first time when the synchronous rectifying tube is just turned on, according to the direction of the output current of the error amplifying circuit, the first capacitor is charged with the second current or discharged with the second current, the first capacitor is driven by the voltage of the first capacitor, and the current of the first switch tube is the first current.

Optionally, when the switch circuit is a voltage-reducing circuit, the charging current of the first capacitor represents the inductor current analog signal, and the discharging current of the first capacitor is proportional to a product of the charging current and the input voltage and inversely proportional to the output voltage.

The invention also provides a switching power supply which comprises the inductive current analog circuit to simulate the inductive current of the switching circuit.

Compared with the prior art, the invention has the following advantages: the method is based on an error amplification circuit, when a synchronous rectifier tube is conducted, the error amplification circuit carries out error amplification on a first sampling signal representing the current of the synchronous rectifier tube and a second sampling signal representing an inductive current analog signal to obtain an error amplification signal; and reconstructing the inductive current according to the error amplification signal when the synchronous rectifier tube is conducted and the first current when the main power tube is conducted, so as to obtain an inductive current analog signal. The invention can reconstruct the inductive current to obtain the analog signal of the inductive current, and avoid the problem of inaccurate sampling precision caused by sampling the inductive current.

Drawings

FIG. 1 is a control block diagram of an inductor current analog circuit according to the present invention;

FIG. 2 is a schematic diagram of an inductor current simulation circuit according to the present invention;

FIG. 3 is a schematic diagram of a first embodiment of a first current generating circuit according to the present invention;

FIG. 4 is a schematic diagram of a second embodiment of a first current generating circuit according to the present invention;

Detailed Description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to only these embodiments. The invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention.

In the following description of the preferred embodiments of the present invention, specific details are set forth in order to provide a thorough understanding of the present invention, and it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

The invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are in simplified form and are not to precise scale for the purpose of facilitating and clearly explaining the embodiments of the present invention.

As shown in fig. 1, a control block diagram of an inductor current analog circuit of the switching circuit of the present invention is illustrated, the switching circuit includes a main power transistor and a synchronous rectifier, and the analog circuit includes an operational amplifier U01, a first current generating circuit U02, and an output current generating circuit U03. In a synchronous rectifier tube conducting (BG _ ON) stage, when the operational amplifier U01 is enabled, the operational amplifier U01 performs error amplification ON a first sampling signal VC1 representing the current of the synchronous rectifier tube and a second sampling signal VC2 representing an inductive current analog signal VC2, and the operational amplifier U01 outputs an error amplification signal; in the conduction stage of the synchronous rectifier tube, the error amplification signal drives an output current generation circuit U03; during the conduction (TG _ ON) stage of the main power transistor, the first current generating circuit U02 generates a first current I1 to drive the output current generating circuit U03; the output current generating circuit U03 outputs an inductor current analog signal Imon. The first current generating circuit U02 generates the first current I1 according to the inductive current analog signal Imon, the topological structure of the switch circuit, the input voltage and the output voltage; or, in the first time when the synchronous rectifier tube is just conducted, the first current I1 is generated according to the direction of the output current IA of the operational amplifier U01.

As shown in fig. 2, a schematic diagram of an inductor current analog circuit of a switching circuit according to an embodiment of the present invention is illustrated, in which the switching circuit is a step-down circuit, a main power transistor is an M01 transistor, and a synchronous rectifier is an M02 transistor. The analog circuit comprises a sampling tube M101, an output tube M102, a mirror current tube M103, an operational amplifier U101 and a first current generation circuit U02, wherein the first end of the sampling tube M101 is connected with the first end of a synchronous rectifier tube M02 in the voltage reduction circuit, and the second end of the sampling tube M101 is connected with the output tube M102. At the conducting stage of the synchronous rectifier tube M02, the first input end of the operational amplifier U101 is connected with the second end of the sampling tube M101, the second input end of the operational amplifier U101 is connected with the second end of the synchronous rectifier tube M02, and the output end of the operational amplifier U101 is connected with the control end of the output tube M102. In the conduction stage of the synchronous rectifier tube M02, the voltage drop of the synchronous rectifier tube M02 represents the current of the synchronous rectifier tube M02, the voltage drop of the sampling tube M101 represents the current of an output tube, and the voltage drop of the synchronous rectifier tube M02 and the voltage drop of the sampling tube M101 are equal to the voltage of the second end of the synchronous rectifier tube M02 and the voltage of the common connecting end of the sampling tube M101 and the output tube M102, so that the output voltage of the operational amplifier U101 represents the current of the synchronous rectifier tube M02 and the current of the output tube M102. The control end of the mirror current tube M103 is connected with the control end of the output tube M102, and the current of the mirror current tube M103 is the mirror current of the output tube M102. The first current generation circuit U102 generates a first current I1 according to the current Imon of the mirror current tube M103, the topological structure of the switch circuit, the input voltage and the output voltage; or, in the first time when the synchronous rectifier tube is just conducted, the first current generating circuit generates the first current I1 according to the current direction of the output current of the operational amplifier U101. Because the control end of the output tube M102 has the parasitic capacitance, and the driving voltage of the control end of the output tube can be changed by charging and discharging the parasitic capacitance, the output tube M102 is driven by the first current I1 set at the conducting stage of the main power tube, and the output tube current is an inductive current analog signal and represents the inductive current. In this embodiment, the output transistor M102 and the mirror transistor M103 may be connected to the high potential terminal through resistors R2 and R3, respectively, so as to make the first current I1 have a better linear state.

As shown in fig. 3, a schematic diagram of a first embodiment of the first current generating circuit of the present invention is shown, which includes a first capacitor C201 and a switch transistor M201. Taking a voltage reduction circuit as an example, during the whole switching period Ts, the current Imon of the mirror current tube M203 obtained in fig. 1 charges the first capacitor C201; during the conduction period of the main power tube, the first capacitor C201 discharges, according to the inductor current volt-second balance principle, Imon Ts/D/Vin/Vout, and the discharge current of the first capacitor C201 is set to Imon Vin/Vout; the voltage on the first capacitor C201 drives the switch tube M201, and the current on the switch tube M201 is the first current I1.

As shown in fig. 4, a schematic diagram of a second embodiment of the first current generation circuit of the present invention is shown, which includes a first capacitor C201 and a switch transistor M201, and when the output current direction of the operational amplifier U01 in fig. 2 is the inflow direction of the current at the control end of the output transistor M102 during a period of time when the main power transistor is just turned on, it indicates that the peak current of the main power transistor M01 is higher, and the first capacitor C201 discharges; when the output current direction of the operational amplifier U01 in fig. 2 is the outflow direction of the current at the control end of the output tube M102, and the Gate pull-down current at the control end of the output tube M102 indicates that the peak current of the main power tube M01 is low, and the first capacitor C201 is charged; the charging current I201 or the discharging current I202 of the first capacitor C201 are the same in magnitude and are a set current. The voltage of the first capacitor C301 drives the switching tube M201, and the current of the switching tube M201 is the first current I1.

Although the embodiments have been described and illustrated separately, it will be apparent to those skilled in the art that some common techniques may be substituted and integrated between the embodiments, and reference may be made to one of the embodiments not explicitly described, or to another embodiment described.

The above-described embodiments do not limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the above-described embodiments should be included in the protection scope of the technical solution.