A switch circuit control method, a control circuit and a switch circuit

Abstract

The present invention discloses a control method, a control circuit and a switch circuit of a switch circuit, wherein the switch circuit operates in a hysteresis control mode or a constant conduction time control mode; when the switch circuit operates in the hysteresis control mode, when the conduction time of the main switch tube is reduced to the first conduction time, the set conduction time of the main switch tube in the constant conduction control mode is reduced from the second conduction time, and when it is reduced to the first conduction time, the switch circuit operates in the constant conduction control mode; when the switch circuit operates in the constant conduction control mode, when the conduction time of the main switch tube is increased to the first conduction time, the set conduction time of the main switch tube in the constant conduction control mode is increased to the second conduction time, and the switch circuit operates in the hysteresis control mode. The control method of the present invention can make the system transient response fast, and at the same time, the minimum conduction time of the main switch tube is not affected by the leading edge blanking time of the inductor current comparator.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a switch circuit control method, a control circuit and a switch circuit. Background Art

[0002] In switching power supplies, the hysteresis control mode is used to improve the dynamic performance of the system. The hysteresis control mode is also called the hysteresis control mode. Please refer to Figure 1 As shown in FIG. 1 , the waveform of the main switch on signal TON and the inductor current in the hysteresis control mode is shown. In the hysteresis control mode, when the inductor current is greater than the upper threshold of the inductor current, the main switch is turned off and the inductor current decreases; when the inductor current is less than the lower threshold of the inductor current, the main switch is turned on and the inductor current increases. Therefore, a comparator is required in the control circuit to compare the inductor current sampling value with the upper and lower thresholds to control the switching of the main switch. Since the inductor current sampling value has an overshoot at the switching moment of the switch tube, the comparator starts to compare the inductor current sampling value with the upper and lower thresholds after the leading edge blanking time after the switching moment to prevent the comparator from being falsely triggered due to the overshoot. Therefore, in the switching power supply, the minimum on time of the main switch tube is set to be greater than or equal to the leading edge blanking time of the comparator. That is, the minimum on time of the main switch tube is limited by the leading edge blanking time of the comparator. In some applications, a smaller on time of the main switch tube is required, and the hysteresis control mode cannot be used. Summary of the invention

[0003] In view of this, an object of the present invention is to provide a switching circuit control method, a control circuit and a switching circuit to solve the problem in the prior art that, in a hysteresis control mode, the minimum on-time of the main switch tube of the switching circuit is limited by the leading edge blanking time of the comparator, and the hysteresis control mode cannot be used when a smaller on-time of the main switch tube is required.

[0004] The present invention provides a switch circuit control method, wherein the switch circuit operates in a hysteresis control mode or a constant on-time control mode;

[0005] When the switch circuit operates in the hysteresis control mode, when the on-time of the main switch tube is reduced to the first on-time, the set on-time of the main switch tube in the constant on-time control mode is reduced from the second on-time, and when it is reduced to the first on-time, the switch circuit operates in the constant on-time control mode;

[0006] When the switch circuit operates in the constant conduction control mode, when the conduction time of the main switch tube increases to the first conduction time, the main switch tube set conduction time of the constant conduction control mode increases to the second conduction time, and the switch circuit operates in the hysteresis control mode.

[0007] Optionally, the first on-time is the minimum on-time of the main switch tube in a hysteresis control mode.

[0008] Optionally, the second on-time is greater than the maximum on-time of the switch circuit.

[0009] Another technical solution of the present invention is to provide a switch circuit control circuit, wherein the switch circuit operates in a hysteresis control mode or a constant on-time control mode;

[0010] When the switch circuit operates in the hysteresis control mode, when the on-time of the main switch tube is reduced to the first on-time, the set on-time of the main switch tube in the constant on-time control mode is reduced from the second on-time, and when it is reduced to the first on-time, the switch circuit operates in the constant on-time control mode;

[0011] When the switch circuit operates in the constant conduction control mode, when the conduction time of the main switch tube increases to the first conduction time, the main switch tube set conduction time of the constant conduction control mode increases to the second conduction time, and the switch circuit operates in the hysteresis control mode.

[0012] Optionally, the first on-time is the minimum on-time of the main switch tube in a hysteresis control mode.

[0013] Optionally, the second on-time is greater than the maximum on-time of the switch circuit.

[0014] Optionally, the control circuit includes a timing circuit, a hysteresis control circuit, a mode determination circuit and a logic circuit;

[0015] The hysteresis control circuit receives the compensation voltage and generates an upper limit of the inductor current and a lower limit of the inductor current;

[0016] The timing circuit receives the switch signal and the compensation voltage to generate the set conduction time of the main switch tube;

[0017] The mode judgment circuit switches between the hysteresis control mode and the constant conduction control mode according to the conduction time set by the main switch tube of the timing circuit;

[0018] The logic circuit receives the output voltages of the timing circuit, the mode determination circuit and the hysteresis control circuit, and generates the switch signal;

[0019] The control circuit performs operational amplification on the output voltage or the output current to obtain a compensation voltage.

[0020] Optionally, the hysteresis control circuit includes a calculation circuit, and the hysteresis control circuit calculates the compensation voltage and the difference between the upper and lower limits of the inductor current to obtain the upper limit of the inductor current and the lower limit of the inductor current.

[0021] Optionally, the hysteresis control circuit further includes an inductor current upper and lower limit difference adjustment circuit, and the inductor current upper and lower limit difference adjustment circuit adjusts the inductor current upper and lower limit difference according to a switch signal.

[0022] Another technical solution of the present invention is to provide a switching circuit.

[0023] Compared with the prior art, the circuit structure and method of the present invention have the following advantages: the system has a fast transient response, and the minimum on-time of the main switch tube is not affected by the leading edge blanking time of the inductor current comparator. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The main switch tube conduction signal TON and the inductor current waveform in the hysteresis control mode;

[0025] Figure 2 is a schematic diagram of a control circuit 200 and a switch circuit of the present invention;

[0026] Figure 3 FIG. 2 is a schematic diagram of the hysteresis control circuit 230 of the present invention. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present invention are 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 substitution, modification, equivalent method and scheme made within the spirit and scope of the present invention.

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

[0029] The present 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 accompanying drawings are all simplified and not in exact proportion, and are only used for the purpose of conveniently and clearly assisting in explaining the embodiments of the present invention.

[0030] The present invention provides a switch circuit control circuit, wherein the switch circuit operates in a hysteresis control mode or a constant on-time control mode; when the switch circuit operates in the hysteresis control mode, when the on-time of the main switch tube is reduced to the first on-time, the set on-time of the main switch tube in the constant on-time control mode is reduced from the second on-time, and when it is reduced to the first on-time, the switch circuit operates in the constant on-time control mode; when the switch circuit operates in the constant on-time control mode, when the on-time of the main switch tube is increased to the first on-time, the set on-time of the main switch tube in the constant on-time control mode is increased to the second on-time, and the switch circuit operates in the hysteresis control mode. The present invention retains the advantage of fast transient response of the system in the hysteresis control mode, and at the same time, the minimum on-time of the main switch tube is not affected by the leading edge blanking time of the inductor current comparator.

[0031] Preferably, the first on-time is set to be the minimum on-time of the main switch tube in the hysteresis control mode. The first on-time can also be set to other values. The second on-time is greater than the maximum on-time of the switch circuit.

[0032] Please refer to Figure 2 As shown, it is a schematic diagram of the control circuit 200 and the switch circuit of the present invention. The control circuit 200 includes a timing circuit 210, a hysteresis control circuit 230, a mode judgment circuit 220 and a logic circuit 240; the hysteresis control circuit 230 receives the compensation voltage VC to generate the upper limit of the inductor current and the lower limit of the inductor current; the timing circuit 210 receives the switch signal PWM and the compensation voltage VC to generate the main switch tube set on time COT; the mode judgment circuit 220 switches the hysteresis control mode and the constant conduction control mode according to the main switch tube set on time COT of the timing circuit; the logic circuit 240 receives the output voltage of the timing circuit 210, the mode judgment circuit 220 and the hysteresis control circuit 230, and generates the switch signal PWM; the control circuit 200 also includes an operational amplifier circuit 250, which performs operational amplification on the output voltage or output current to obtain the compensation voltage VC.

[0033] The mode determination circuit 220 generally switches between the hysteresis control mode and the constant conduction control mode according to the switch signal PWM, the set on-time COT of the main switch tube, and the current working mode (working in the constant conduction mode or the hysteresis control mode).

[0034] Please refer to Figure 3As shown, the hysteresis control circuit 230 includes an operation circuit U02, and the hysteresis control circuit 230 operates the compensation voltage VC and the difference between the upper and lower limits of the inductor current Δi to obtain the upper limit of the inductor current and the lower limit of the inductor current. In one embodiment, the operation circuit is an addition circuit, the compensation voltage is the lower limit of the inductor current, and the addition circuit adds the lower limit of the inductor current to the difference between the upper and lower limits of the inductor current Δi to obtain the upper limit of the inductor current; in another embodiment, the operation circuit is a subtraction circuit, the compensation voltage is the upper limit of the inductor current, and the subtraction circuit subtracts the difference between the upper and lower limits of the inductor current Δi from the upper limit of the inductor current to obtain the lower limit of the inductor current.

[0035] The upper and lower limit difference Δi of the inductor current can be fixed or adjustable. For example, the upper and lower limit difference Δi of the inductor current can be adjusted according to the switching frequency. Figure 3 As shown, the hysteresis control circuit also includes an inductor current upper and lower limit difference Δi adjustment circuit U05, and the inductor current upper and lower limit difference adjustment circuit U05 adjusts the inductor current upper and lower limit difference Δi according to the switch signal. The timing circuit U04 starts timing from the moment the main switch tube is turned on, and ends timing when the next main switch is turned on from off. The voltage comparison circuit U03 compares the timing with the reference cycle, and the Δi adjustment circuit U05 receives the output voltage of the voltage comparison circuit U03. When the timing is greater than the reference cycle, the output voltage inductor current upper and lower limit difference Δi of the Δi adjustment circuit U05 becomes smaller, so that the switching cycle is shortened; when the timing is less than the reference cycle, the output voltage inductor current upper and lower limit difference Δi of the Δi adjustment circuit U05 becomes larger, so that the switching cycle becomes longer. Through the adjustment of several switching cycles, the switching frequency is close to the reference switching frequency, thereby achieving a fixed frequency.

[0036] Another technical solution of the present invention is to provide a method for controlling a switch circuit, wherein the switch circuit operates in a hysteresis control mode or a constant on-time control mode;

[0037] When the switching circuit operates in the hysteresis control mode, when the on-time of the main switch tube is reduced to the first on-time, the set on-time of the main switch tube in the constant on-time control mode is reduced from the second on-time, and when it is reduced to the first on-time, the switching circuit operates in the constant on-time control mode; when the switching circuit operates in the constant on-time control mode, when the on-time of the main switch tube is increased to the first on-time, the set on-time of the main switch tube in the constant on-time control mode is increased to the second on-time, and the switching circuit operates in the hysteresis control mode.

[0038] Optionally, the first on-time is the minimum on-time of the main switch tube in a hysteresis control mode.

[0039] Optionally, the second on-time is greater than the maximum on-time of the switch circuit.

[0040] Another technical solution of the present invention is to provide a switch circuit including the above-mentioned control circuit.

[0041] Although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated. If the content is not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0042] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. A switch circuit control method, characterized in that: The switch circuit operates in a hysteresis control mode or a constant on-time control mode; When the switch circuit operates in the hysteresis control mode, when the on-time of the main switch tube is reduced to the first on-time, the set on-time of the main switch tube in the constant on-time control mode is reduced from the second on-time, and when it is reduced to the first on-time, the switch circuit operates in the constant on-time control mode; When the switch circuit operates in the constant conduction control mode, when the conduction time of the main switch tube increases to the first conduction time, the main switch tube set conduction time of the constant conduction control mode increases to the second conduction time, and the switch circuit operates in the hysteresis control mode.

2. The control method according to claim 1, characterized in that: The first on-time is the minimum on-time of the main switch tube under the hysteresis control mode.

3. The control method according to claim 1, characterized in that: The second on-time is greater than the maximum on-time of the switch circuit.

4. A switch circuit control circuit, characterized in that: The switch circuit operates in a hysteresis control mode or a constant on-time control mode; When the switch circuit operates in the hysteresis control mode, when the on-time of the main switch tube is reduced to the first on-time, the set on-time of the main switch tube in the constant on-time control mode is reduced from the second on-time, and when it is reduced to the first on-time, the switch circuit operates in the constant on-time control mode; When the switch circuit operates in the constant conduction control mode, when the conduction time of the main switch tube increases to the first conduction time, the main switch tube set conduction time of the constant conduction control mode increases to the second conduction time, and the switch circuit operates in the hysteresis control mode.

5. The control circuit according to claim 4, characterized in that: The first on-time is the minimum on-time of the main switch tube under the hysteresis control mode.

6. The control circuit according to claim 4, characterized in that: The second on-time is greater than the maximum on-time of the switch circuit.

7. The control circuit according to claim 4, characterized in that: The control circuit includes a timing circuit, a hysteresis control circuit, a mode judgment circuit and a logic circuit; The hysteresis control circuit receives the compensation voltage and generates an upper limit of the inductor current and a lower limit of the inductor current; The timing circuit receives the switch signal and the compensation voltage to generate the set conduction time of the main switch tube; The mode judgment circuit switches between the hysteresis control mode and the constant conduction control mode according to the conduction time set by the main switch tube of the timing circuit; The logic circuit receives the output voltages of the timing circuit, the mode determination circuit and the hysteresis control circuit, and generates the switch signal; The control circuit performs operational amplification on the output voltage or the output current to obtain a compensation voltage.

8. The control circuit according to claim 7, characterized in that: The hysteresis control circuit includes a calculation circuit, and the hysteresis control circuit calculates the compensation voltage and the difference between the upper and lower limits of the inductor current to obtain the upper limit of the inductor current and the lower limit of the inductor current.

9. The control circuit according to claim 8, characterized in that: The hysteresis control circuit further includes an inductor current upper and lower limit difference adjustment circuit, and the inductor current upper and lower limit difference adjustment circuit adjusts the inductor current upper and lower limit difference according to a switch signal.

10. A switch circuit, characterized in that: It comprises a control circuit as claimed in any one of claims 4 to 9; or adopts a control method as claimed in any one of claims 1 to 3.

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