Variable current compensation circuit and method for improving cut-in transient response

Abstract

The application discloses a variable current compensation circuit for improving cut-load transient response, characterized in that the circuit comprises a current feedback unit and a current compensation unit of a voltage converter; wherein the current feedback unit is used for generating a reference current Iref to judge the inductance current size of the voltage converter output, and controlling the conduction time of upper and lower tubes to realize the regulation of the output voltage based on the judgment; the current compensation unit is used for identifying the reference current Iref, generating a charging current Icharge based on the reference current Iref, and realizing the compensation of the reference current Iref based on the charging current Icharge. The application has the advantages of simple method, few added elements, and gradual change of compensation current to realize the adjustable control of the PWM unit.

Description

Technical Field

[0001] This invention relates to the field of integrated circuits, and more specifically, to a variable current compensation circuit and method for improving load-switching transient response. Background Technology

[0002] With the increasing demand for power, voltage converters have developed rapidly and are widely used in power supplies for various electronic devices, daily lighting, and household appliances. Voltage converters can be categorized into constant voltage output mode and constant current output mode based on their output state. Regardless of the output mode, high stability of the output signal is essential. Taking a BUCK (voltage drop) circuit as an example, when the output signal switches from a light load to a heavy load, the inductor current may not increase quickly enough, potentially causing the average inductor current to be less than the current required by the load. This results in a significant drop in output voltage and a long recovery time for the output signal.

[0003] To address this issue, existing technologies often employ traditional turbo modes and methods that control the conduction time of the upper and lower transistors to achieve rapid recovery of the output signal. For example, background art document TW201943172A discloses a feedback and compensation circuit 130, which can generate an error amplification signal EAO based on the charging current CC, the charging voltage CV, and the input current reference signal CIC, thereby achieving a fast transient response.

[0004] However, this existing method cannot effectively control the rapid recovery of inductor current. In some cases using traditional turbine mode, the magnitude of the compensation current for the inductor current is only controlled by the turbine signal. When the voltage converter operates in turbine mode, the component of the compensation current in the error amplifier output remains fixed, and the inductor current may recover too slowly or too quickly. When the inductor current recovers too slowly, the turbine mode is ineffective; when the inductor current recovers too quickly, the rapid stopping of the turbine mode may cause oscillations and repeated starting and stopping of the turbine, making it difficult to stabilize the output voltage quickly.

[0005] To address the aforementioned problems, this invention provides a variable current compensation circuit for improving load shedding transient response. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a variable current compensation circuit and method for improving load shedding transient response. By providing a new turbine mode, the output of the error amplifier is rationally controlled based on the difference between the feedback voltage and the reference voltage. This method enables gradual adjustment of the inductor current and rapid increase and stabilization of the inductor current, thereby significantly improving the stabilization speed of the circuit output voltage.

[0007] The present invention adopts the following technical solution.

[0008] A first aspect of the present invention relates to a variable current compensation circuit for improving load shedding transient response, wherein the circuit includes a current feedback unit and a current compensation unit for a voltage converter; the current feedback unit is used to generate a reference current Iref to determine the magnitude of the inductor current output by the voltage converter, and to control the conduction time of the upper and lower transistors based on the determination to adjust the output voltage; the current compensation unit is used to identify the reference current Iref, generate a charging current Icharge based on the reference current Iref, and compensate the reference current Iref based on the charging current Icharge.

[0009] Preferably, the current compensation unit includes a charging unit and an output unit; the charging unit is connected to the output terminal of the error amplifier in the current feedback unit, and is used to identify the turbine control signal of the voltage converter and to charge the capacitor at the output terminal of the error amplifier based on the turbine control signal; the output unit is connected to the output terminal of the error amplifier, and is used to generate a compensated reference current based on the output voltage of the error amplifier and output the compensated reference current to the current feedback unit.

[0010] Preferably, the charging unit is also used to control the charging current in turbine mode based on the difference between the feedback voltage and the reference voltage.

[0011] Preferably, the charging current Size and Positive correlation, reference current Size and Positive correlation; among them, The feedback voltage is obtained by dividing the output voltage of the voltage converter. This is the reference voltage for the voltage converter. This is the output voltage of the error amplifier in the voltage converter after receiving the influence of the charging current.

[0012] Preferably, when the feedback voltage is less than the turbine reference voltage, the turbine control signal output by the comparator is at a high level; when the feedback voltage is greater than the turbine reference voltage, the turbine control signal output by the comparator is at a low level.

[0013] Preferably, the reference current output by the output unit when the turbine control signal is high is greater than the reference current output by the output unit when the turbine control signal is low.

[0014] Preferably, when the turbine control signal is high, the magnitude of the increase in the reference current Iref is related to... Positive correlation.

[0015] Preferably, the conduction time of the upper tube is longer when the turbine control signal is at a high level than the conduction time of the upper tube when the turbine control signal is at a low level.

[0016] A second aspect of the present invention relates to a variable current compensation method for improving load shedding transient response, wherein the method is implemented using a variable current compensation circuit for improving load shedding transient response as described in the first aspect of the present invention.

[0017] The beneficial effects of this invention are that, compared with the prior art, the variable current compensation circuit and method for improving load shedding transient response in this invention can rationally control the output of the error amplifier based on the difference between the feedback voltage and the reference voltage in the new turbine mode provided by this invention. This allows for gradual adjustment and rapid increase and stabilization of the inductor current, thereby significantly improving the stabilization speed of the circuit output voltage. This invention is simple, requires fewer components, has less delay, a simple control method, and causes minimal interference to the circuit.

[0018] The beneficial effects of the present invention also include: 1. The turbine mode in this invention is implemented externally to the error amplifier, without requiring changes to the internal logic of the error amplifier. It simply improves the automatic adjustment speed of the output voltage by charging the capacitor at the output of the error amplifier. This method does not impose many restrictions on the selection of the error amplifier, eliminating the need for a high-speed output amplifier, thus saving costs and reducing circuit area.

[0019] 2. In the current feedback unit of the present invention, the reference current Iref of the inductor peak current Ipeak gradually increases after entering the turbine mode. Furthermore, since the charging current is controlled by the difference between the feedback voltage and the reference voltage, the charging current gradually decreases as the reference current gradually increases. This ensures that the output voltage of the error amplifier and the current-limiting current input to the PWM unit gradually increase both at the moment of entering the turbine mode and after entering the turbine mode. This gradual increase prevents the PWM unit from being affected by a step change in the reference current Iref and ensures accurate control of the PWM unit's conduction of the upper or lower transistor. Therefore, the method of the present invention is very effective, rapidly increasing the inductor current while ensuring a smooth change in the reference current Iref without causing a step change in Ipeak. In addition, the variable current compensation mode does not suffer from overcompensation or undercompensation; it can adaptively adjust the compensation current according to the load shedding situation, allowing the output voltage to recover to the rated value more quickly, smoothly, and stably.

[0020] 3. This invention achieves control over the conduction time of the upper and lower transistors based on a new turbine mode. By extending the conduction time of the upper transistor, the circuit can quickly recover a larger inductor current output. Furthermore, the method in this invention can be easily used in conjunction with logic units that control the conduction time of the lower transistor, thereby further improving the efficiency of inductor current rise. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a BUCK circuit in the prior art of this invention; Figure 2 This is a schematic diagram showing the timing changes of inductor current and MOSFET voltage in a BUCK circuit operating in DCM state according to the prior art of this invention. Figure 3 This is a schematic diagram showing the timing changes of inductor current and MOSFET voltage in a BUCK circuit operating in CCM state according to the prior art of this invention. Figure 4 This is a schematic diagram of the structure of a current feedback unit in a BUCK circuit according to the prior art of this invention; Figure 5 This is a schematic diagram showing the output voltage and inductor current of a BUCK circuit in turbine mode as a function of time in the prior art of this invention. Figure 6 This is a schematic diagram of the functional framework of the current compensation unit in a variable current compensation circuit for improving load shedding transient response according to the present invention. Figure 7 This is a timing diagram illustrating the fast current response in a variable current compensation circuit for improving load shedding transient response according to the present invention. Detailed Implementation

[0022] The present application will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and should not be construed as limiting the scope of protection of the present application.

[0023] Figure 1 This is a schematic diagram of a BUCK (step-down voltage converter) circuit in the prior art of this invention. Figure 1 As shown, a BUCK circuit includes an upper transistor S1 and a lower transistor S2 that switch between on and off modes, as well as an inductor L, a capacitor Cout, and a resistor Rout. As the two transistors switch continuously, the circuit generates an output voltage Vout and an inductor current. .

[0024] Figure 2This is a schematic diagram illustrating the timing changes of inductor current and MOSFET voltage in a BUCK circuit operating in DCM (Discontinuous Conduction Mode) state, according to the prior art of this invention. Figure 2 As shown, when the circuit operates in DCM mode, the upper and lower transistors are switched on and off discontinuously. Specifically, the upper transistor S1 turns on first, at which point the inductor current gradually increases. Then, S1 turns off, and S2 turns on, causing the inductor current to gradually decrease. When the inductor current decreases to 0, the upper transistor does not immediately enter the on-mode, but waits for a preset time before entering the on-mode again, causing the inductor current to increase again.

[0025] Figure 3 This is a schematic diagram illustrating the timing changes of inductor current and MOSFET voltage in a BUCK circuit operating in CCM (Continuous Conduction Mode) mode, according to the prior art of this invention. When the circuit is in CCM mode, the circuit is continuously turned on, the inductor current continuously increases and decreases, and the upper and lower transistors are also turned on and off sequentially without interval.

[0026] Figure 4 This is a schematic diagram of the current control unit in a BUCK circuit according to the prior art of this invention. Figure 4 As shown, when the circuit operates in a common peak current control mode, it includes a current control unit, which may include an error amplifier, a PWM unit, etc. The error amplifier generates an error amplification signal based on the magnitudes of the reference voltage Vref and the feedback voltage Vfb. By comparing the inductor reference current Iref defined by the error amplifier with the actual inductor feedback current IL, this unit enables feedback control of the BUCK circuit. Specifically, the difference between the reference voltage Vref and the feedback voltage Vfb positively correlates with the magnitude of the peak inductor current Ipeak.

[0027] To improve circuit response speed, such as rapid output voltage recovery during load switching, a turbine mode can be employed. Since this topic is covered in numerous existing technical documents, it will not be elaborated upon further.

[0028] Figure 5 This is a schematic diagram illustrating the time-varying output voltage and inductor current of a BUCK circuit in turbine mode according to the prior art of this invention. Figure 5As shown, in the existing technology, with the occurrence of load shedding and the decrease in output voltage, after entering TURBO mode, the inductor current will increase with the increase of the error amplifier output voltage EAO. After the inductor current increases to a certain level, TURBO mode exits, and the inductor current gradually stabilizes and decreases. Figure 5 In TURBO mode, although the output amplitude of the error amplifier is greatly improved, it still takes several cycles for the inductor current to gradually increase to the target state.

[0029] In order to enable the inductor current to increase rapidly, this invention provides a new technical solution.

[0030] Figure 6 This is a schematic diagram of the functional framework of the current compensation unit in a variable current compensation circuit for improving load shedding transient response according to the present invention. Figure 6 As shown, in a first aspect, the present invention relates to a variable current compensation circuit for improving load-cutting transient response, wherein the circuit includes a current feedback unit and a current compensation unit for a voltage converter; the current feedback unit is used to generate a reference current Iref to determine the magnitude of the inductor current output by the voltage converter, and to control the conduction time of the upper and lower transistors based on the determination to adjust the output voltage; the current compensation unit is used to identify the reference current Iref, generate a charging current Icharge based on the reference current Iref, and compensate the reference current Iref based on the charging current Icharge.

[0031] It is understood that in this invention, when the circuit enters the turbine mode, the current at the output of the error amplifier will increase in a variable compensation form, and at the same time, the upper transistor will also extend its conduction time after the turbine mode is started.

[0032] Preferably, the current compensation unit includes a charging unit and an output unit; wherein, the charging unit is connected to the output terminal of the error amplifier in the current feedback unit, and is used to identify the turbine control signal of the voltage converter, and to charge the capacitor at the output terminal of the error amplifier based on the turbine control signal; the output unit is connected to the output terminal of the error amplifier, and is used to generate a compensated reference current based on the output voltage of the error amplifier, and output the compensated reference current to the current feedback unit. Preferably, the charging unit is also used to control the charging current in turbine mode based on the difference between the feedback voltage and the reference voltage.

[0033] In this invention, the current compensation unit can adjust the charging current based on the output of the error amplifier. After adjusting the charging current, the output voltage of the error amplifier will change, and this change is related to the magnitude of the charging current, i.e., the difference between the feedback voltage and the reference voltage. Through this method of controlling the signal at the output of the error amplifier, the reference current Iref output by the error amplifier can be passed through a square wave generator and a PWM unit to control the conduction signals of the upper and lower transistors.

[0034] It should be noted that, in another embodiment of the present invention, the charging unit may not receive the output EAO of the error amplifier in the current feedback unit, but instead directly use a switching transistor connected to the current source to implement the input of the charging current. This switching transistor can receive the turbine signal and, under the control of the turbine signal, realize the conduction and output of the current source current. In this case, the magnitude of the charging current is constant.

[0035] Preferably, the charging current Size and Positive correlation, reference current Size and Positive correlation; among them, The feedback voltage is obtained by dividing the output voltage of the voltage converter. This is the reference voltage for the voltage converter. This is the output voltage of the error amplifier in the voltage converter after receiving the influence of the charging current.

[0036] In the method of the present invention, the charging current in the current compensation unit is only generated in turbine mode and affects the PWM unit.

[0037] The magnitude of the charging current changes in a positive correlation with the difference between the reference voltage and the feedback voltage. Specifically, the difference between the reference voltage and the feedback voltage is obtained by acquiring the output voltage of the error amplifier. The charging unit can then adjust the charging current to be positively correlated with the output voltage of the error amplifier. The charging unit can also adjust the rate of change of the charging current based on the output voltage.

[0038] Preferably, when the feedback voltage is less than the turbine reference voltage, the turbine control signal output by the comparator is at a high level; when the feedback voltage is greater than the turbine reference voltage, the turbine control signal output by the comparator is at a low level.

[0039] It is understood that the turbine signal in this invention can be achieved by comparing the feedback voltage with the turbine reference voltage. Here, the turbine reference voltage differs from the base voltage; it serves as a reference for implementing the turbine control mode, and typically, this voltage is lower than the base voltage.

[0040] Preferably, the reference current output by the output unit when the turbine control signal is high is greater than the reference current output by the output unit when the turbine control signal is low.

[0041] It is easy to understand that when the turbine control signal is high, the reference current generated by the current compensation unit connected to the output of the error amplifier will increase due to the charging effect of the charging current on the capacitor at the output of the error amplifier, that is, Iref will rise. In one embodiment of the present invention, the output unit can be implemented by a MOSFET, the gate of the MOSFET is connected to the output voltage of the operational amplifier, and the source-drain current of the MOSFET is used as the reference current Iref generated by the output unit. This reference current can be compared with the inductor current IL in the current compensation unit to achieve PWM control.

[0042] Preferably, when the turbine control signal is high, the magnitude of the increase in the reference current Iref is related to... Related.

[0043] The increase in the reference current Iref is due to This is caused by the fact that the reference current is not only variable and adjustable, but also related to... The size is related.

[0044] Preferably, the conduction time of the upper tube is longer when the turbine control signal is at a high level than the conduction time of the upper tube when the turbine control signal is at a low level.

[0045] It is understandable that when Iref increases, the time it takes for the induced current Isense, which is related to the inductor current, to rise to Iref through the action of the PWM unit increases, thus increasing the conduction time of the upper transistor. Figure 7 This is a timing diagram illustrating the fast current response in a variable current compensation circuit for improving load shedding transient response according to the present invention. Figure 7 As shown, when the circuit's output voltage drops to a certain level, for example, when the feedback voltage equals the turbine reference voltage, the turbine control signal rises to a high level. At this time, a charging current is generated based on the difference between the feedback voltage and the reference voltage. Since the feedback voltage is a voltage divider of the output voltage Vout, the output voltage first decreases and then increases when the circuit is in turbine mode. Therefore, the charging current generated by the difference between the feedback voltage and the reference voltage is lower at the beginning of entering turbine mode and gradually increases as the feedback voltage changes. With the change in charging current, the voltage at the output of the error amplifier and the current-limiting current generated by the current-limiting unit also slowly and gradually increase. This method prevents the amplitude values ​​of the error amplifier's output voltage and the current-limiting current received by the PWM unit from undergoing a step change when entering turbine mode, ensuring the overall stability of the current feedback unit.

[0046] In turbine mode, the inductor current changes with the output voltage of the error amplifier and the current limiting current.

[0047] On the other hand, when the turbine mode ends, the charging current drops rapidly, and the output of the error amplifier and the current limiting current gradually discharge and decrease to a stable state. This also allows the inductor current to recover quickly as the current limiting current increases.

[0048] After the turbine mode ends, the inductor current returns to normal during the period when the lower tube is on, and remains within a stable floating range as the current limiting current Iref and the output voltage EAO of the error amplifier are normally output.

[0049] The beneficial effects of this invention are that, compared with the prior art, the variable current compensation circuit and method for improving load shedding transient response in this invention, by simultaneously increasing the output current of the error amplifier and extending the conduction time of the upper transistor in the new turbine mode provided in this invention, achieves a rapid increase in the inductor current, thereby significantly improving the stabilization speed of the circuit output voltage. This invention is simple, requires fewer components, has a small delay, a simple control method, and causes minimal interference to the circuit.

[0050] The applicant of this invention has provided a detailed description of the embodiments of the invention in conjunction with the accompanying drawings. However, those skilled in the art should understand that the above embodiments are merely preferred embodiments of the invention. The detailed description is only intended to help readers better understand the spirit of the invention and is not intended to limit the scope of protection of the invention. On the contrary, any improvements or modifications made based on the inventive spirit of the invention should fall within the scope of protection of the invention.

Claims

1. A variable current compensation circuit for improving load shedding transient response, characterized in that: The circuit includes a current feedback unit and a current compensation unit for the voltage converter; wherein, The current feedback unit is used to generate a reference current Iref to determine the magnitude of the inductor current output by the voltage converter, and to control the conduction time of the upper and lower transistors based on the determination to adjust the output voltage. The current compensation unit is used to identify the reference current Iref and generate a charging current Icharge based on the reference current Iref. Size and Positive correlation, the reference current Size and Positive correlation; among them, The feedback voltage is obtained by dividing the output voltage of the voltage converter. The reference voltage for the voltage converter. The output voltage of the error amplifier in the voltage converter after receiving charging current compensation is used; the compensation of the reference current Iref is realized based on the charging current Icharge.

2. The variable current compensation circuit for improving load shedding transient response as described in claim 1, characterized in that: The current compensation unit includes a charging unit and an output unit; wherein, The charging unit is connected to the output terminal of the error amplifier in the current feedback unit, and is used to identify the turbine control signal of the voltage converter and charge the capacitor at the output terminal of the error amplifier based on the turbine control signal. The output unit is connected to the output terminal of the error amplifier and is used to generate a compensated reference current based on the output voltage of the error amplifier, and output the compensated reference current to the current feedback unit.

3. A variable current compensation circuit for improving load shedding transient response as described in claim 2, characterized in that: The charging unit is also used to control the charging current in turbine mode based on the difference between the feedback voltage and the reference voltage.

4. A variable current compensation circuit for improving load shedding transient response as described in claim 3, characterized in that: When the feedback voltage is less than the turbine reference voltage, the turbine control signal output by the comparator is in a high-level state; When the feedback voltage is greater than the turbine reference voltage, the turbine control signal output by the comparator is in a low-level state.

5. A variable current compensation circuit for improving load shedding transient response as described in claim 4, characterized in that: When the turbine control signal is high, the reference current output by the output unit is greater than the reference current output by the output unit when the turbine control signal is low.

6. A variable current compensation circuit for improving load shedding transient response as described in claim 5, characterized in that: When the turbine control signal is high, the magnitude of the increase in the reference current Iref is related to... Positive correlation.

7. A variable current compensation circuit for improving load shedding transient response as described in claim 6, characterized in that: When the turbine control signal is at a high level, the conduction time of the upper tube is longer than when the turbine control signal is at a low level.

8. A variable current compensation method for improving load shedding transient response, characterized in that: The variable current compensation method for improving load shedding transient response is implemented using a variable current compensation circuit for improving load shedding transient response as described in any one of claims 1-7.

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