CN109768703B - Variable-frequency average current control device and method based on output voltage feedback - Google Patents

Abstract

The invention provides a variable frequency average current control device and method based on output voltage feedback. The detected output voltage and the reference voltage are acted by a voltage loop error amplifier to generate a voltage loop error signal, and the error signal and the detected inductor current signal are passed through the current loop. The error amplifier functions to generate a current loop error signal. The current loop error signal and the detected output voltage are passed through the frequency conversion modulator to generate a driving pulse signal, and then the driving circuit controls the switching device to adjust the output voltage and output current. It is characterized in that an output voltage control loop is added on the basis of the traditional average current control. The outstanding advantage of the invention is that compared with the traditional average current mode control, the invention improves the current transient response speed and the light-load efficiency of the switching power supply.

Description

A variable frequency average current control device and method based on output voltage feedback

technical field

The present invention relates to the technical field of switching power supply equipment, in particular to a frequency conversion average current control device and method based on output voltage feedback.

Background technique

With the rapid development of electronic information technology, various electronic products have been widely used in people's life and production. The normal and efficient work of these electronic products is inseparable from a reliable power supply. Compared with traditional linear power supplies, switching power supplies have attracted great attention from academia and engineering circles due to their small size, light weight and high efficiency, and have become one of the most active branches in the field of power electronics. However, as the functions of electronic products become more and more powerful, they put forward higher and higher requirements on the working performance of switching power supply, especially the transient performance.

The switching power supply is mainly composed of a switching power converter and a control circuit. The switching power converter uses the power switching device to realize the transfer and transformation of electric energy, and the control circuit controls the control variables according to the target requirements. Common switching power converter topologies include Buck converter, Boost converter, Buck-Boost converter, forward converter, and flyback converter. The control circuit can detect the change of the control quantity (such as inductor current, output voltage) of the switching power converter, and generate corresponding pulse signals to control the working state of the power switching device of the switching power converter, so as to adjust the energy transmitted to the load and realize the Stable output of switching power converters. The structure and working principle of the control circuit are determined by the control method adopted by the switching power converter. For a given switching power converter topology, different control methods have different effects on the steady-state accuracy and dynamic performance of the system. For a given application, the topology of the switching power converter is often fixed, so the design of the control circuit largely determines the performance of the switching power supply.

The traditional average current control technology is a common switching power converter control method, which has the advantages of high current control accuracy and strong anti-interference ability, so it is used in various electronic products. However, the transient performance of switching power converters based on conventional average current control is poor. In addition, due to the fixed switching frequency, when the switching power converter operates at light load, the switching loss accounts for a larger proportion of the total loss, resulting in lower light load power. Therefore, it is necessary to improve the traditional average current control technology.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is: in order to overcome the deficiencies in the prior art, the present invention provides a variable frequency average current control device and method based on output voltage feedback, which improves the transient response speed and light load of the traditional average current control. efficiency.

The technical solution to be adopted by the present invention to solve the technical problem is: a variable frequency average current control device based on output voltage feedback, including a power circuit and a controller for a switching power supply, wherein,

The power circuit includes an input device, a switching device, a filtering device and an output device which are connected in sequence, the input device is connected to the switching device, and is transmitted to the filtering device after passing through the switching device, and then enters the output device after being acted by the filtering device;

The controller includes a voltage detection device, a reference voltage, a voltage loop error amplifier, a current sampling device, a current loop error amplifier, a variable frequency modulator and a drive circuit. The input end of the voltage detection device is connected to the output device, and the output end of the voltage detection device and the reference The voltage is respectively connected to the two input ends of the voltage loop error amplifier; the input end of the current sampling device is connected to the filtering device, the output end of the current sampling device and the output end of the voltage loop error amplifier are respectively connected to the two input ends of the current loop error amplifier, The output end of the current loop error amplifier and the output end of the voltage detection device are connected to the frequency conversion modulator, and the output end of the frequency conversion modulator is connected to the driving circuit, and after the driving circuit, is connected to the switching device, which is used to control the on and off of the switching device. , the input end of the switch device is connected to the input device.

The voltage detection device detects the output voltage, and performs error amplification with the reference voltage through the voltage loop error amplifier to obtain a voltage error signal; the current detection device detects the current, and performs error amplification with the voltage error signal provided by the voltage loop through the current loop error amplifier to obtain the current loop. The error signal signal; the current loop error signal and the output voltage detected by the voltage detection device pass the frequency conversion modulator to generate a driving pulse signal, and the driving pulse signal controls the main circuit to work through the driving circuit.

A variable frequency average current control method based on output voltage feedback, comprising the above circuit, and further comprising the following steps:

When the input of the switching power supply is connected to the voltage V _in of the input device, that is, when the switching power supply is powered on, the output voltage v _o of the output device is detected by the voltage detection device, and the detected output voltage v _o and the reference voltage V _ref are passed through The voltage loop error amplifier acts to generate the voltage loop error signal v _{con_v} ; at the same time, the current sampling device collects the current signal R _S i _L of the filtering device, and combines the detected current signal R _S i _L and the voltage loop error signal v _{con_v} through the current loop The error amplifier acts to generate a current loop error signal v _{con_i} ; then, the current loop error signal v _{con_i} and the output voltage generate a driving pulse signal through the variable frequency modulator, and through the driving circuit, the on and off of the switching device are controlled, thereby adjusting the switching power conversion output voltage and output current of the device.

When the output voltage is less than the current loop error signal, the variable frequency modulator outputs and maintains a high-level signal, and passes through the drive circuit to turn on the power switch; otherwise, the variable-frequency modulator outputs and maintains a low-level signal to turn off the power switch.

The beneficial effects of the present invention are: compared with the traditional average current control, the present invention improves the current transient response speed and the light-load efficiency of the switching power converter when the current loop error signal changes abruptly.

Description of drawings

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Fig. 1 is the structural block diagram of the control system implementation device of the present invention;

2 is a schematic diagram of a circuit structure according to an embodiment of the present invention;

3 is a time domain simulation waveform diagram of an embodiment of the present invention and a conventional average current controlled Buck converter when the current loop error signal is jumping positively; wherein, (a) the current loop error signal waveform; (b) the conventional average current control The inductor current waveform of the Buck converter; (c) the method of the present invention controls the inductor current waveform of the Buck converter.

4 is a time domain simulation waveform diagram of an embodiment of the present invention and a conventional average current-controlled Buck converter when the current loop error signal transitions negatively; wherein (d) the current loop error signal waveform; (e) the conventional average current control The inductor current waveform of the Buck converter; (f) the method of the present invention controls the inductor current waveform of the Buck converter.

5 is a time domain simulation waveform diagram of an embodiment of the present invention and a conventional average current-controlled Buck converter when the load is reduced, wherein (a) the inductor current waveform and the load current waveform of the conventional average current-controlled Buck converter; ( b) The driving pulse signal waveform of the Buck converter controlled by the traditional average current; (c) The inductor current waveform and the load current waveform of the Buck converter controlled by the method of the present invention; (d) The driving pulse of the Buck converter controlled by the method of the present invention signal waveform.

In the figure: 1. Input device, 2. Switching device, 3. Filtering device, 4. Output device, 5. Voltage detection device, 6. Reference voltage, 7. Voltage loop error amplifier, 8. Current sampling device, 9. Current A loop error amplifier, 10, a frequency conversion modulator, 11, a driving circuit.

Detailed ways

The present invention will now be described in detail with reference to the accompanying drawings. This figure is a simplified schematic diagram, and only illustrates the basic structure of the present invention in a schematic manner, so it only shows the structure related to the present invention.

As shown in Figure 1, a variable frequency average current control device based on output voltage feedback of the present invention, outside the dotted frame is a power circuit, including: an input device 1, a switching device 2, a filtering device 3 and an output device 4; the connection relationship: The input device 1 is connected to the switching device 2 , and is transmitted to the filtering device 3 after passing through the switching device 2 , and then enters the output device 4 after passing through the filtering device 3 .

Among them, the input device 1 is a device for providing input voltage, which can be a lithium battery or a battery; the switching device 2 can be a field effect transistor, a triode, etc.; the filtering device 3 can be a low-pass filter composed of an inductor and a capacitor or a separate A filter composed of inductors; the output device 4 can use power resistors, super capacitors, microprocessors or LEDs, etc.

Inside the dashed box is a controller, including: a voltage detection device 5, a reference voltage 6, a voltage loop error amplifier 7, a current sampling device 8, a current loop error amplifier 9, a variable frequency modulator 10 and a drive circuit 11; connection relationship: connected to the output The voltage detection device 5 and the reference voltage 6 on 4 are respectively connected to the two input ends of the voltage loop error amplifier 7; the current sampling device 8 connected to the filtering device 3 and the output ends of the voltage loop error amplifier 7 are respectively connected to the current loop error amplifier. The two input ends of 9, the output end of the current loop error amplifier 9 and the output end of the voltage detection device 5 are connected to the frequency conversion modulator 10, and the output end of the frequency conversion modulator 10 is connected to the driving circuit 11, and after the driving circuit 11, it is used to control the The switching device 2 is turned on and off.

Among them, the voltage detection device 5 can use a voltage follower built by an operational amplifier; the reference voltage 6 can be provided by an auxiliary power supply or a voltage regulator chip; the voltage loop error amplifier 7 can be a PI compensator or a PID compensator built by an operational amplifier The current sampling device 8 can be realized by a differential amplifier circuit constructed by an operational amplifier; the current loop error amplifier 9 can be implemented by an integrator or a PI compensator constructed by an operational amplifier; the variable frequency modulator 10 can be composed of a comparator, an on-timer and RS flip-flop is formed; the driving circuit 11 can use a driving chip such as IR2125 or IR2110.

Fig. 2 shows the application of the present invention in the Buck converter. In this embodiment, the input device 1 uses a battery as the input signal, and the input voltage V _in can be selected in the range of 10V-20V; the field effect transistor S is used as the switch device 2 , the preferred model IRF540; a low-pass filter composed of inductors and capacitors is used as the filter device 3; the power resistor R is used as the output device 4, and the range of the power resistor R is 0.5Ω-10Ω; the voltage follower built by the operational amplifier is used as the Voltage detection device 5; a voltage regulator chip is used to provide a reference voltage 6, preferably model 78L05; a PI compensator built by an operational amplifier is used as a voltage loop error amplifier 7; a differential amplifier circuit built by an operational amplifier is used as a current sampling device 8; An integrator built by an operational amplifier is used as a current loop error amplifier 9; a frequency conversion modulator composed of a comparator, an on-timer and an RS flip-flop is used as a frequency conversion modulator 10; an integrated driving chip is used as the driving circuit 11, preferably the model IR2125 .

The specific working process and principle are as follows: at the sampling moment, the voltage detection device generates a voltage loop error signal v _{con_v} by passing the detected output voltage v _o and the reference voltage V _ref through the voltage loop error amplifier. At the same time, the current detection device generates a current loop error signal v _{con_i} from the detected current signal R _S i _L and the voltage loop error signal v _{con_v} through the current loop error amplifier. Then, the current loop error signal and the output voltage are compared through the variable frequency modulator, and the driving pulse signal is output. When the output voltage v _o is smaller than the current loop error signal v _{con_i} , the variable frequency modulator outputs and maintains a high level, which is the power switch conduction; Thus, the switching power converter is regulated to work stably.

Analysis of simulation results:

Fig. 3 is the simulation waveform diagram of the Buck converter controlled by the traditional average current control and the method of the present invention when the current loop error signal is positive jumping respectively by using PSIM software, simulation conditions: input voltage V _in =15V, output voltage v _o = V _ref = 5V, inductance L = 50μH, capacitance C = 330μF, capacitance equivalent series resistance r = 20mΩ, load R = 1Ω, current detection coefficient R _S = 1V/A, fixed on-time T _ON = 3.3μs, sawtooth The wave period T=10 μs, and the sawtooth wave amplitude V _m =3V.

Parts (a), (b), and (c) of FIG. 3 correspond to the current loop error signal, the inductor current of the Buck converter controlled by the traditional average current, and the inductor current of the Buck converter controlled by the method of the present invention. The horizontal axes of sub-figures (a), (b) and (c) are all time (ms), the vertical axis of (a) is the current loop error signal voltage (V), and the vertical axes of (b) and (c) are Inductor current (A). In Figure 3, in part (a), the current loop error signal jumps from 5V to 7V at 8.5ms; from part (b), it can be seen that the increase of the inductor current of the traditional average current-controlled Buck converter The overshoot is 2.57A, the undershoot is 1.26A, and the recovery time required to enter the new stable state from the original steady state is about 0.188ms; it can be seen from sub-figure (c) that the Buck converter controlled by the method of the present invention The overshoot and undershoot of the inductor current are very small, almost zero, and the recovery time from the original steady state to the new steady state is also very short, almost negligible. It can be seen from this that when the current loop error signal has a positive jump, the transient response speed of the method of the present invention is obviously better than that of the traditional average current control technology.

FIG. 4 is a simulation waveform diagram of the Buck converter controlled by the conventional average current control and the method of the present invention when the current loop error signal transitions negatively. The horizontal axes of sub-figures (d), (e) and (f) are all time (ms), the vertical axis of (d) is the current loop error signal voltage (V), and the vertical axes of (e) and (f) are Inductor current (A). In Figure 4, in part (a), at 8.5ms, the current loop error signal jumps from 5V to 3V; it can be seen from part (b) that the traditional average current-controlled Buck converter inductor current decreases The overshoot is 2.218A, the overshoot is 0.67A, and the recovery time required to enter the new stable state from the original steady state is about 0.17ms; it can be seen from sub-figure (c) that the Buck converter controlled by the method of the present invention The overshoot and undershoot of the inductor current are very small, almost zero, and the recovery time from the original steady state to the new steady state is also very short, almost negligible. It can be seen from this that when the current loop error signal has a negative transition, the transient response speed of the method of the present invention is obviously better than that of the traditional average current control technology.

Fig. 5 is a simulation waveform diagram of the Buck converter controlled by the traditional average current control and the method of the present invention when the converter works in DCM, that is, in a light load state, with the load current decreasing. Except for the load R=16Ω, other simulations The conditions are the same. Parts (a), (b), (c) and (d) of Figure 5 correspond to the inductor current and load current of the traditional average current controlled Buck converter, the driving pulse signal of the traditional average current controlled Buck converter, The inductor current and load current of the Buck converter controlled by the method of the present invention, and the driving pulse signal of the Buck converter controlled by the method of the present invention. The horizontal axes of sub-figures (a), (b), (c) and (d) are all time (ms), and the vertical axes of (a) and (c) are currents (A), (b) and (d) The vertical axis of is the drive pulse signal voltage (V). In Figure 5, the load current drops from 0.3125A to 0.0125A. It can be seen from sub-figures (a) and (b) that under light load conditions, the switching cycle of the traditional average current-controlled Buck converter is not affected by the load current. It can be seen from the sub-figures (c) and (d) that in the light load state, the switching period of the Buck converter controlled by the method of the present invention decreases and increases with the load current, thereby reducing the light load. switching losses under load. Since the switching loss accounts for a large proportion of the power loss of the converter in the light-load state, reducing the switching loss can reduce the power loss of the converter, thereby improving the light-load efficiency. It can be seen that, compared with the traditional average current control technology, the method of the present invention can effectively improve the light-load efficiency of the switching power converter.

Taking the above ideal embodiments according to the present invention as inspiration, and through the above description, relevant personnel can make various changes and modifications without departing from the scope of the present invention. The technical scope of the present invention is not limited to the contents in the specification, and the technical scope must be determined according to the scope of the claims.

Claims (2)

1. A variable frequency average current control device based on output voltage feedback, characterized in that: comprising a power circuit and a controller for a switching power supply, wherein, The power circuit includes an input device, a switching device, a filtering device and an output device which are connected in sequence, the input device is connected to the switching device, and is transmitted to the filtering device after passing through the switching device, and then enters the output device after being acted by the filtering device; The controller includes a voltage detection device, a reference voltage, a voltage loop error amplifier, a current sampling device, a current loop error amplifier, a variable frequency modulator and a drive circuit. The input end of the voltage detection device is connected to the output device, and the output end of the voltage detection device and the reference The voltage is respectively connected to the two input ends of the voltage loop error amplifier; the input end of the current sampling device is connected to the filtering device, the output end of the current sampling device and the output end of the voltage loop error amplifier are respectively connected to the two input ends of the current loop error amplifier, The output end of the current loop error amplifier and the output end of the voltage detection device are connected to the two input ends of the variable frequency modulator. On and off, the input end of the switch device is connected to the input device; The voltage detection device detects the output voltage, and performs error amplification with the reference voltage through the voltage loop error amplifier to obtain a voltage error signal; the current sampling device detects the current, and the voltage error signal provided by the voltage loop error amplifier is used for error amplification through the current loop error amplifier. Amplify to obtain the current loop error signal; the current loop error signal and the output voltage are compared through the frequency conversion modulator to generate the driving pulse signal, and the driving pulse signal controls the main circuit to work through the driving circuit. 2. a control method of the variable frequency average current control device as claimed in claim 1, is characterized in that: has the following steps: When the input of the switching power supply is connected to the input device, that is, when the switching power supply is powered on, the voltage detection device detects the output voltage v _o of the output device, and generates the detected output voltage v _o and the reference voltage V _ref through the voltage loop error amplifier voltage loop error signal v _{con_v} ; at the same time, the current sampling device collects the current signal R _S i _L of the filtering device; the detected current signal R _S i _L and the voltage loop error signal v _{con_v} generate the current loop error signal v through the current loop error amplifier _{con_i} ; then, the current loop error signal v _{con_i} and the output voltage v _o generate a driving pulse signal through the variable frequency modulator, and pass through the driving circuit to control the on and off of the switching device.

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