Inductance Current Simulation Circuit, Simulation Method of Switching Circuit, and Switching Power Supply

Abstract

The present invention provides an inductor current simulation circuit, a simulation method and a switching power supply for a switching circuit. Based on an error amplification circuit, when the synchronous rectifier is turned on, the error amplification circuit amplifies the error between a first sampling signal representing the current of the synchronous rectifier and a second sampling signal representing the inductor current simulation signal to obtain an error amplification signal; according to the error amplification signal when the synchronous rectifier is turned on and the first current when the main power transistor is turned on, the inductor current is reconstructed to obtain an inductor current simulation signal. The present invention can obtain a simulation signal of the inductor current, avoiding the problem of inaccurate sampling accuracy caused by sampling the inductor current.

Description

Technical Field

[0001] The present invention relates to the field of power electronics, and particularly to an inductor current simulation circuit, a simulation method, and a switching power supply for a switching circuit. Background Art

[0002] In the control scheme of a switching circuit, an inductor current sampling signal is often required. In some application scenarios, the conduction time of the main power transistor of the switching circuit is very short, resulting in inaccurate sampling of the inductor charging and discharging current, thereby affecting the control effect of the switching circuit. Summary of the Invention

[0003] The object of the present invention is to provide an inductor current simulation circuit for a reconfigurable switching circuit inductor current to solve the problem of inaccurate inductor current sampling.

[0004] To achieve the above object, the present invention provides an inductor current simulation circuit for a switching circuit. The switching circuit includes a main power transistor and a synchronous rectifier transistor. The inductor current simulation circuit includes:

[0005] An error amplifier circuit, which receives a first sampling signal representing the synchronous rectifier transistor current and a second sampling signal representing the inductor current simulation signal during the conduction stage of the synchronous rectifier transistor, and outputs an error amplification signal;

[0006] An output current generation circuit for generating the inductor current simulation signal; during the conduction stage of the synchronous rectifier transistor, the error amplification signal drives the output current generation circuit; during the conduction stage of the main power transistor, the output current generation circuit is driven by a first current.

[0007] Optionally, it further includes a first current generation circuit for generating the first current according to the inductor current simulation signal, the topology of the switching circuit, the input voltage, and the output voltage.

[0008] Optionally, it further includes a first current generation circuit for generating the first current according to the output current direction of the error amplifier circuit within the first time when the synchronous rectifier transistor just conducts.

[0009] Optionally, the first current generation circuit includes a first capacitor and a first switching transistor. The charging current of the first capacitor is set according to the inductor current simulation signal, and the discharging current of the first capacitor is set according to the charging current, the topology of the switching circuit, the input voltage, and the output voltage; the charging current charges the first capacitor throughout the working cycle, and the discharging current discharges the first capacitor during the conduction of the main power transistor; the voltage of the first capacitor drives the first switching transistor, and the current of the first switching transistor is the first current.

[0010] Optionally, the first current generating circuit includes a first capacitor and a first switching transistor. During a first period when the synchronous rectifier transistor just turns on, according to the output current direction of the error amplification circuit, the first capacitor is charged or discharged with a second current, the voltage of the first capacitor drives the first switching transistor, and the current of the first switching transistor is the first current.

[0011] Optionally, the output current generating circuit includes an output transistor and a sampling transistor. One end of the output transistor is connected to one end of the sampling transistor, and the other end of the sampling transistor is connected to the common connection end of the main power transistor and the synchronous rectifier transistor; during the conduction stage of the synchronous rectifier transistor, the error amplification signal drives the output transistor; during the conduction stage of the main power transistor, the first current drives the output transistor, and the current of the output transistor represents an inductor current analog signal.

[0012] Optionally, the other end of the output transistor is connected to a resistor.

[0013] Optionally, the first input end of the error amplification circuit is connected to the ground end of the synchronous rectifier transistor, and its second end is connected to the common connection end of the sampling transistor and the output transistor; during the conduction stage of the synchronous rectifier transistor, the error amplification circuit is enabled and outputs the error amplification signal.

[0014] Optionally, when the switching circuit is a buck 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 the product of the charging current and the input voltage and inversely proportional to the output voltage.

[0015] The present invention further provides a method for simulating the inductor current of a switching circuit. The switching circuit includes a main power transistor and a synchronous rectifier transistor. Based on an error amplification circuit, when the synchronous rectifier transistor is turned on, the error amplification circuit performs error amplification on a first sampling signal representing the current of the synchronous rectifier transistor and a second sampling signal representing the inductor current analog signal to obtain an error amplification signal; according to the error amplification signal when the synchronous rectifier transistor is turned on and the first current when the main power transistor is turned on, the inductor current is reconstructed to obtain the inductor current analog signal.

[0016] Optionally, the first current is generated according to the inductor current analog signal, the topology of the switching circuit, the input voltage, and the output voltage.

[0017] Optionally, during a first period when the synchronous rectifier transistor just turns on, the first current is generated according to the output current direction of the error amplification circuit.

[0018] 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 of the switching circuit, the input voltage, and the output voltage; the charging current charges the first capacitor throughout the working cycle, and the discharging current discharges the first capacitor during the conduction of the main power transistor; the voltage of the first capacitor drives the first switching transistor, and the current of the first switching transistor is the first current.

[0019] Optionally, within the first time when the synchronous rectifier transistor just conducts, according to the output current direction of the error amplification circuit, the first capacitor is charged or discharged with the second current, the voltage of the first capacitor drives the first switching transistor, and the current of the first switching transistor is the first current.

[0020] Optionally, when the switching circuit is a buck 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 the product of the charging current and the input voltage and inversely proportional to the output voltage.

[0021] The present invention also provides a switching power supply, including any one of the above-mentioned inductor current simulation circuits to simulate the inductor current of the switching circuit.

[0022] Compared with the prior art, the present invention has the following advantages: Based on the error amplification circuit, when the synchronous rectifier transistor conducts, the error amplification circuit amplifies the error between the first sampling signal representing the synchronous rectifier transistor current and the second sampling signal representing the inductor current analog signal to obtain an error amplification signal; according to the error amplification signal when the synchronous rectifier transistor conducts and the first current when the main power transistor conducts, the inductor current is reconstructed to obtain an inductor current analog signal. The present invention can reconstruct the inductor current to obtain an analog signal of the inductor current, avoiding the problem of inaccurate sampling accuracy caused by sampling the inductor current. Description of the Drawings

[0023] Figure 1 It is a control block diagram of the inductor current simulation circuit of the present invention;

[0024] Figure 2 It is a schematic diagram of the inductor current simulation circuit of the present invention;

[0025] Figure 3 It is a schematic diagram of the first embodiment of the first current generation circuit of the present invention;

[0026] Figure 4 It is a schematic diagram of the second embodiment of the first current generation circuit of the present invention; Detailed Embodiments

[0027] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any alternatives, modifications, equivalent methods, and solutions made within the spirit and scope of the present invention.

[0028] In order to enable the public to have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, and those skilled in the art can fully understand the present invention without the description of these details.

[0029] In the following paragraphs, the present invention will be described more specifically by way of example with reference to the accompanying drawings. It should be noted that the drawings are all in a relatively simplified form and use non-precise scales to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0030] As Figure 1 shown, it schematically shows the control block diagram of the inductor current simulation circuit of the switching circuit of the present invention. The switching circuit includes a main power transistor and a synchronous rectifier transistor. The simulation circuit includes an operational amplifier U01, a first current generation circuit U02, and an output current generation circuit U03. During the conduction (BG_ON) stage of the synchronous rectifier transistor, the operational amplifier U01 is enabled. The operational amplifier U01 amplifies the error between the first sampling signal VC1 representing the current of the synchronous rectifier transistor and the second sampling signal VC2 representing the inductor current simulation signal. The output of the operational amplifier U01 is the error amplified signal. During the conduction stage of the synchronous rectifier transistor, the error amplified signal drives the output current generation circuit U03. During the conduction (TG_ON) stage of the main power transistor, the first current generation circuit U02 generates a first current I1 to drive the output current generation circuit U03. The output current generation circuit U03 outputs an inductor current simulation signal Imon. The first current generation circuit U02 generates the first current I1 according to the inductor current simulation signal Imon, the topology of the switching circuit, the input voltage, and the output voltage; or, within the first time when the synchronous rectifier transistor just conducts, generates the first current I1 according to the direction of the output current IA of the operational amplifier U01.

[0031] As Figure 2As shown in the figure, the schematic diagram of the inductor current simulation circuit embodiment of the switching circuit of the present invention is shown. The switching circuit takes the buck circuit as an example. In the figure, the main power transistor is transistor M01, and the synchronous rectifier transistor is transistor M02. The simulation circuit includes a sampling transistor M101, an output transistor M102, a mirror current transistor M103, an operational amplifier U101, and a first current generation circuit U02. The first end of the sampling transistor M101 is connected to the first end of the synchronous rectifier transistor M02 in the buck circuit, and the second end of the sampling transistor M101 is connected to the output transistor M102. During the conduction stage of the synchronous rectifier transistor M02, the first input terminal of the operational amplifier U101 is connected to the second end of the sampling transistor M101, the second input terminal of the operational amplifier U101 is connected to the second end of the synchronous rectifier transistor M02, and the output terminal of the operational amplifier U101 is connected to the control terminal of the output transistor M102. During the conduction stage of the synchronous rectifier transistor M02, the voltage drop of the synchronous rectifier transistor M02 represents the current of the synchronous rectifier transistor M02, and the voltage drop of the sampling transistor M101 represents the output transistor current. Since the synchronous rectifier transistor M02 and the sampling transistor M101 have a common connection terminal, the error between the voltage drop of the synchronous rectifier transistor M02 and the voltage drop of the sampling transistor M101 is equal to the error between the voltage at the second end of the synchronous rectifier transistor M02 and the voltage at the common connection terminal of the sampling transistor M101 and the output transistor M102. Therefore, the output voltage of the operational amplifier U101 represents the error between the current of the synchronous rectifier transistor M02 and the current of the output transistor M102. The control terminal of the mirror current transistor M103 is connected to the control terminal of the output transistor M102, and the current of the mirror current transistor M103 is the mirror current of the output transistor M102 current. The first current generation circuit U102 generates a first current I1 according to the current Imon of the mirror current transistor M103, the topology of the switching circuit, the input voltage, and the output voltage; or, within the first time when the synchronous rectifier just conducts, the first current generation circuit generates the first current I1 according to the current direction of the output current of the operational amplifier U101. Since there is a parasitic capacitance at the control terminal of the output transistor M102, the charging and discharging of the parasitic capacitance can change the driving voltage of the control terminal of the output transistor. Therefore, during the conduction stage of the main power transistor, it is set that the first current I1 drives the output transistor M102, and the output transistor current is the inductor current simulation signal, representing the inductor current. In this embodiment, the high potential terminal can be connected to one end of the output transistor M102 and the mirror transistor M103 through resistors R2 and R3 respectively, so that the first current I1 has a better linear state.

[0032] As Figure 3 shown, the schematic diagram of the first embodiment of the first current generation circuit of the present invention is shown, including a first capacitor C201 and a switching transistor M201. Taking the buck circuit as an example, during the entire switching period Ts, Figure 1The current Imon of the mirror current tube M203 obtained in [[ ]] 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 = Imon*Ton / D = Imon*Ton*Vin / Vout. The discharge current of the first capacitor C201 is set to Imon*Vin / Vout; the voltage on the first capacitor C201 drives the switching tube M201, and the current on the switching tube M201 is the first current I1.

[0033] As Figure 4 shown, the schematic diagram of the second embodiment of the first current generation circuit of the present invention is illustrated, including the first capacitor C201 and the switching tube M201. During a period of time when the main power tube just starts to conduct, when Figure 2 the output current direction of the operational amplifier U01 in [[ ]] is the inflow direction of the current at the control end of the output tube M102, it indicates that the peak current of the main power tube M01 is too high, and the first capacitor C201 discharges; when Figure 2 the output current direction of the operational amplifier U01 in [[ ]] is the outflow direction of the current at the control end of the output tube M102, and when the Gate of the control end of the output tube M102 is pulled down, it indicates that the peak current of the main power tube M01 is too low, and the first capacitor C201 charges; the charging current I201 or the discharge current I202 of the first capacitor C201 is the same in magnitude and is 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.

[0034] Although the above embodiments are described and explained separately, there are some common technologies involved. In the view of those of ordinary skill in the art, substitutions and integrations can be made between the embodiments. For the content not clearly recorded in one of the embodiments, reference can be made to the other embodiment with records.

[0035] The above-described embodiments do not constitute a limitation on the protection scope of the technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the above embodiments shall be included within the protection scope of the technical solution.

Claims

1. An inductor current simulation circuit for a switching circuit, the switching circuit including a main power transistor and a synchronous rectifier transistor, Characterized in that, It includes: An error amplification circuit, during the conduction stage of the synchronous rectifier transistor, receiving a first sampling signal representing the current of the synchronous rectifier transistor and a second sampling signal representing the inductor current simulation signal, and outputting an error amplification signal; A first current generation circuit, generating the first current according to the inductor current simulation signal, the topology of the switching circuit, the input voltage and the output voltage; or, within the first time when the synchronous rectifier transistor just conducts, generating the first current according to the output current direction of the error amplification circuit; An output current generation circuit for generating the inductor current simulation signal; During the conduction stage of the synchronous rectifier transistor, the error amplification signal drives the output current generation circuit; During the conduction stage of the main power transistor, the output current generation circuit is driven by the first current.

2. The inductor current simulation circuit for the switching circuit according to claim 1, Characterized in that: The first current generation circuit includes a first capacitor and a first switching transistor, setting the charging current of the first capacitor according to the inductor current simulation signal, and setting the discharging current of the first capacitor according to the charging current, the topology of the switching circuit, the input voltage and the output voltage; The charging current charges the first capacitor throughout the working cycle, and the discharging current discharges the first capacitor during the conduction period of the main power transistor; The voltage of the first capacitor drives the first switching transistor, and the current of the first switching transistor is the first current.

3. The inductor current simulation circuit for the switching circuit according to claim 1, Characterized in that: The first current generation circuit includes a first capacitor and a first switching transistor. Within the first time when the synchronous rectifier transistor just conducts, according to the output current direction of the error amplification circuit, the first capacitor charges or discharges with a second current, and the voltage of the first capacitor drives the first switching transistor, and the current of the first switching transistor is the first current.

4. The inductor current simulation circuit for the switching circuit according to claim 1, Characterized in that: The output current generation circuit includes an output transistor and a sampling transistor. One end of the output transistor is connected to one end of the sampling transistor, and the other end of the sampling transistor is connected to the common connection end of the main power transistor and the synchronous rectifier transistor; during the conduction stage of the synchronous rectifier transistor, the error amplification signal drives the output transistor; during the conduction stage of the main power transistor, the first current drives the output transistor, and the current of the output transistor represents the inductor current simulation signal.

5. The inductor current simulation circuit for the switching circuit according to claim 4, Characterized in that: The other end of the output transistor is connected to a resistor.

6. The inductor current simulation circuit for the switching circuit according to claim 4, Characterized in that: The first input end of the error amplification circuit is connected to the grounded end of the synchronous rectifier transistor, and its second input end is connected to the common connection end of the sampling transistor and the output transistor; during the conduction stage of the synchronous rectifier transistor, the error amplification circuit is enabled and outputs the error amplification signal.

7. The inductor current simulation circuit for the switching circuit according to claim 2, Characterized in that: When the switching circuit is a buck 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 the product of the charging current and the input voltage and inversely proportional to the output voltage.

8. A method for simulating the inductor current of a switching circuit, the switching circuit including a main power transistor and a synchronous rectifier transistor, characterized in that: Based on an error amplification circuit, when the synchronous rectifier transistor is turned on, the error amplification circuit amplifies the error between a first sampling signal representing the synchronous rectifier transistor current and a second sampling signal representing the inductor current analog signal to obtain an error amplification signal; According to the error amplification signal when the synchronous rectifier transistor is turned on and the first current when the main power transistor is turned on, the inductor current is reconstructed to obtain the inductor current analog signal; wherein, according to the inductor current analog signal, the topology of the switching circuit, the input voltage, and the output voltage, the first current is generated; or, within the first time when the synchronous rectifier transistor is just turned on, according to the output current direction of the error amplification circuit, the first current is generated.

9. The inductor current simulation method according to claim 8, characterized in that: Set the charging current of the first capacitor according to the inductor current analog signal, and set the discharging current of the first capacitor according to the charging current, the topology of the switching circuit, the input voltage, and the output voltage; The charging current charges the first capacitor throughout the working cycle, and the discharging current discharges the first capacitor during the conduction period of the main power transistor; The voltage of the first capacitor drives the first switching transistor, and the current of the first switching transistor is the first current.

10. The inductor current simulation method according to claim 8, characterized in that: Within the first time when the synchronous rectifier transistor is just turned on, according to the output current direction of the error amplification circuit, control the first capacitor to charge or discharge with a second current, and the voltage of the first capacitor drives the first switching transistor, and the current of the first switching transistor is the first current.

11. The inductor current simulation method according to claim 9, characterized in that: When the switching circuit is a buck 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 the product of the charging current and the input voltage and inversely proportional to the output voltage.

12. A switching power supply, characterized in that: It includes the inductor current simulation circuit according to any one of claims 1-7 to simulate the inductor current of the switching circuit.

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