CN101686010B - Dual-frequency control method and device for quasi-continuous mode switching power supply - Google Patents

Abstract

The present invention discloses a dual-frequency control method for switch converter in quasi-continuous operation mode and a device therefor. A controller controls the power output of a power converter which operates in inductor current quasi-continues mode; the controller combines two pulses with two different frequencies according to the output state of the power converter, so as to realize the control of the power output of the converter. The drive of a main power switch tube is a combination of two pulses having two different frequencies. The invention can be used for multiple topological structures of switch converters, has the advantages of stable and reliable control, no need of compensation network, large output power scope and fast transient response speed.

Description

Dual-frequency control method and device for quasi-continuous mode switching power supply

technical field

The invention relates to a dual-frequency control method and device for a switching power supply in a quasi-continuous working mode.

Background technique

With the rapid development of power electronic technology and power electronic devices, the advantages of switching power supply are becoming more and more obvious. In many application fields, switching power supply is used as power supply, which further promotes the rapid development of switching power supply technology. The switching power supply is mainly composed of two parts: a power converter and a controller. The power converter, also known as the power circuit, mainly includes a switching device, a transformer device and a rectification and filtering circuit. Common power converter topologies include Buck converter, Boost converter, Buck-Boost converter, forward converter, flyback converter and so on. The controller is used to control the work of the power converter, and its structure and working principle are determined by the control method adopted by the switching power supply. Since the common power converter topology can meet the basic needs, and for the same power circuit topology, the adoption of different control methods will have an impact on the steady-state accuracy and dynamic performance of the system, so the research on control methods is becoming increasingly important. .

The traditional voltage-type pulse width modulation technology is the most common switching power supply control method. Its control idea is: use the error amplifier to compare the output voltage of the switching power supply with the reference voltage to obtain the error signal, and then use the comparator to compare the error signal with the fixed frequency sawtooth wave signal to obtain the pulse width signal to control the switching device. , off, so that the output voltage reaches the desired value. The transient response speed of the switching power supply using the traditional voltage-type pulse width modulation technology is relatively slow, and the design of the compensation network is relatively cumbersome.

Contents of the invention

The object of the present invention is to provide a control method of a switching power supply - dual-frequency control of a switching power supply working in an inductor current quasi-continuous working mode. When the control method is adopted, the controller is stable and reliable, no compensation network is required, the output power range is large, the dynamic response speed is fast, and it is suitable for various converter topologies.

In order to solve the technical problem, the technical solution adopted by the present invention is: a dual-frequency control method for switching power supply in quasi-continuous working mode, the power output of the power converter is controlled by the controller, and the power converter works in the quasi-continuous mode of the inductor current; the controller According to the output state of the power converter, two groups of pulses with different frequencies are selected for combination to realize the control of the power output of the converter.

In actual implementation, the following two options are generally adopted:

①Detect the output voltage at the end of any pulse signal and compare it with the reference voltage. The comparison result is used as the basis for selecting low-frequency or high-frequency pulses for the next working pulse; at the same time, the inductor current is detected. When it drops to the reference current, the inductor current The freewheeling switches at both ends are turned on, and the inductor current remains unchanged, thereby realizing the dual-frequency control of the switching power supply based on the quasi-continuous mode. Adopting such a structure can make the control stable and reliable, without compensation network, wide output power range and fast transient response.

② Turn on the main switching tube at the beginning of any pulse signal, the inductor current rises, and detect the inductor current at the same time. When the inductor current rises to the peak current, the main switching tube is turned off, and the inductor current drops. When the inductor current drops to the reference current At this time, the freewheeling switch at both ends of the inductor is turned on, and the inductor current remains unchanged. The relationship between the output voltage and the reference voltage at the beginning of the current pulse determines whether the current working pulse is a high-frequency or low-frequency pulse, thereby realizing the dual operation of the quasi-continuous working mode switching power supply frequency control. It is characterized in that the control is stable and reliable, no compensation network is required, the output power range is large, the transient response speed is fast, and the overcurrent protection of the circuit can be realized automatically.

Compared with the existing technology and the existing traditional voltage-type pulse width modulation technology, when the load of the switching power supply of the present invention changes suddenly, the controller can quickly adjust the proportion of the two frequency pulses, so that the switching power supply can quickly restore stability. State, with faster transient response speed;

Another object of the present invention is to provide a device for realizing the above-mentioned dual-frequency control method for a switching power supply in quasi-continuous working mode. The whole device is composed of a power converter and a controller, the driving circuit in the controller is connected with the switching device in the power converter; a continuous flow switch. Corresponding to the two technical solutions adopted to realize the dual-frequency control method of the quasi-continuous operation mode switching power supply, two devices are provided correspondingly to realize the dual-frequency control method of the quasi-continuous operation mode switching power supply: Scheme ① is set in the controller The internal voltage detection device, comparator, pulse generator, pulse selector, drive circuit and quasi-continuous mode controller are composed; the comparator is connected between the voltage detection device and the pulse selector; the pulse selector controlled by the voltage comparator Connected between the pulse generator and the drive circuit. The voltage detection device detects the output voltage, and then compares it with the reference voltage to control the pulse selector; the pulse generator generates two sets of pulses with different frequencies for selection, and finally the control pulse passes through the driving circuit to control the main circuit; the quasi-continuous mode controller is used for The freewheeling switches at both ends of the inductor are controlled to make the converter work in the quasi-continuous mode of the inductor current. Scheme ② consists of a voltage detection device, a current comparator, a voltage comparator, a pulse cycle selector, a current detection device, a pulse generator, a drive circuit and a quasi-continuous mode controller; the current comparator is connected between the current detection device and the pulse generator Between; the voltage comparator is connected between the voltage detection device and the pulse period selector; the pulse generator controlled by the voltage comparator is connected between the current comparator and the driving circuit; the pulse period selector is connected between the voltage comparator and the pulse period selector between generators. The voltage detection device detects the output voltage, and then compares it with the reference voltage. The output of the comparator is used to control the pulse cycle selector; the current detection device detects the inductor current, and then compares it with the peak current. The comparison output and the pulse cycle selector act together on the pulse The generator generates control pulses, and finally the control pulses control the operation of the main circuit through the driving circuit; the quasi-continuous mode controller is used to control the freewheeling switches at both ends of the inductor, so that the converter works in the quasi-continuous mode of the inductor current.

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

Fig. 1 is a structural block diagram of a device for implementing technical solution ① in the control system of the present invention.

FIG. 2 is a schematic diagram of the circuit structure of Embodiment 1 of the present invention.

FIG. 3 is a schematic diagram of main working waveforms of a circuit according to Embodiment 1 of the present invention.

FIG. 4 is a time-domain simulation waveform diagram of a switching power supply in Embodiment 1 of the present invention.

Fig. 5 is a simulated waveform diagram of the output voltage of the Buck converter with the same main circuit parameters using different control methods when the load changes suddenly.

Fig. 6 is a structural block diagram of a device for implementing technical solution ② in the control system of the present invention.

Fig. 7 is a schematic diagram of the circuit structure of the present invention adopting the technical solution ②.

FIG. 8 is a schematic diagram of main working waveforms of the circuit shown in FIG. 7 .

FIG. 9 is a schematic diagram of the circuit structure of Embodiment 2 of the present invention.

In Fig. 4: (a) is the driving signal waveform of the main switching tube output by the controller; (b) is the converter inductor current waveform; (c) is the converter output voltage waveform.

In Fig. 5: (a) adopts traditional voltage type PWM modulation; (b) adopts dual-frequency control; (c) adopts Embodiment 1 of the present invention.

Detailed ways

Embodiment one

Technical solution ①:

Fig. 1 shows that the specific embodiment of the present invention is: the double-frequency control method and device thereof of quasi-continuous operation mode switching power supply, its controller mainly consists of comparator, pulse generating circuit, pulse selector, drive circuit and quasi-continuous mode Controller composition. The output voltage is compared with the reference voltage after the detection device, and the comparison result is used to control the operation of the pulse selector; the pulse generating circuit generates two sets of pulses with the same conduction time but different frequencies for the pulse selector to select; the output of the pulse selector is driven The circuit is used to control the main switching tube of the power converter; the quasi-continuous mode controller is used to control the freewheeling switch to ensure that the converter works in the quasi-continuous mode of the inductor current.

Figure 2 shows the application of the dual-frequency control technology of the quasi-continuous mode switching converter in the Buck converter. The only difference of the common Buck in the main circuit is that a freewheeling switch SW2 is added at both ends of the inductor to control the inductor current (i _L ). When it is turned on, the inductor current remains unchanged to make the converter work In the inductor current quasi-continuous mode.

In this example, the specific working process and principle are as follows: at the end of each working pulse, the logic control circuit is responsible for generating a narrow pulse for enabling the sample-and-hold circuit and resetting the RS flip-flop. The sampled output voltage (V _o ) is compared with the reference voltage (V _ref ), the output of the comparator is used as the basis for the next driving pulse of the main switching tube to select low-frequency or high-frequency pulse operation. When the output voltage is lower than the reference voltage, the controller selects high-frequency pulse operation to increase the output voltage; conversely, when the output voltage is higher than the reference voltage, the controller selects low-frequency pulse operation to reduce the output voltage. When the main power switch tube SW1 is turned on, the inductor is charged, and the inductor current rises; when SW1 is turned off, the inductor current drops, and when the inductor current drops to the current reference (I _ref ) at this time, the RS trigger for controlling the freewheeling switch tube The device is set, the freewheeling switch SW2 is turned on, and the inductor current remains unchanged. At the end of the current pulse, the narrow pulse generated by the logic control circuit resets the RS flip-flop while enabling the sample-and-hold circuit, SW2 is turned off, SW1 is turned on, the inductor current rises again, and enters the next cycle. The current reference value is closely related to the output power. The greater the output power, the greater the current reference value. The current reference value is obtained by detecting the output current in real time.

FIG. 3 shows the driving waveforms of the switch tubes SW1 and SW2 and the inductor current waveform. Figure 3 shows that when the main power switch SW1 is turned on, the inductor current starts to rise from _Iref ; then SW1 is turned off, and the inductor current drops. When the inductor current drops to I _ref , the switch tube SW2 is turned on, and the inductor current keeps I _ref unchanged until the next working pulse SW1 is turned on again. Because of the existence of I _ref , the input terminal of the power supply can transmit more energy to the load, so that the dual-frequency control of the quasi-continuous mode switching converter can be applied to a wider output power range.

Simulation result analysis:

Fig. 4 is the result that adopts Pspice software to control method of the present invention to carry out time domain simulation, and the horizontal axis of Fig. 4 subgraph (a), (b), (c) is time (ms), and the vertical axis of (a) is The driving signal amplitude (V), the vertical axis of (b) is the current (A), and the vertical axis of (c) is the voltage (V). It can be seen from Figure 4 that the converter works in the quasi-continuous mode of the inductor current, and the drive of the main switching tube is a combination of two different frequency pulse signals.

Fig. 5 is respectively adopting (a) conventional voltage type PWM modulation, (b) dual-frequency control, (c) the Buck converter of the present invention with the same main circuit parameters, the output voltage simulation waveform diagram when the load changes suddenly, the load is 8ms The average time is changed from 9W to 33W. It can be seen from Fig. 5 that when the load of the converter using traditional voltage-type PWM modulation changes suddenly, the output voltage fluctuates greatly and the adjustment time is relatively long; the dual-frequency control has the same frequency pulse as the present invention, but the dual-frequency control is at When the load changes suddenly, because the load power of 33W cannot be provided, the output voltage is much smaller than the reference voltage; and the converter adopting the present invention works in the quasi-continuous mode of the inductor current, and the output terminal can transfer more energy to the load terminal, so The output voltage is stable when the load changes suddenly, and it can be seen from the figure that when the load changes suddenly, the converter adopting the present invention has a very fast transient response speed.

Adopt technical solution ②:

Figure 6 shows that the specific embodiment of the present invention adopting the technical solution ② is: a dual-frequency control method and device for a quasi-continuous mode switching power supply, and its controller is mainly composed of a comparator, a pulse period selector, a pulse generator, a drive circuit and a quasi-continuous mode controller. The output voltage is compared with the reference voltage after the detection device, and the pulse period selector selects high or low frequency pulses according to the comparison result; the current sensor detects the inductor current and compares it with the peak current, and the comparison output is used together with the output of the pulse period selector to control Pulse generator; the output of the pulse generator is used to control the main switch tube of the power converter after passing through the driving circuit; the quasi-continuous mode controller is used to control the freewheeling switch to ensure that the converter works in the quasi-continuous mode of the inductor current.

Figure 7 and Figure 8 show the application of the dual-frequency control technology scheme ② of the quasi-continuous working mode switching converter in the Buck converter. The difference from the technical solution ① is that the driving pulse of the main switching tube of the technical solution ② is no longer generated in advance like the technical solution ①, and only needs to be selected according to the rules. The technical solution ② sets the peak value of the inductor current (I _peak ) and The inductor current reference value (I _ref ) is used to generate the drive pulse. The specific working process and principle are: at the end of the previous pulse, that is, the beginning of the current pulse, the controller generates a narrow pulse (NP) to enable sampling/ Hold the circuit, and turn on the main switch SW1 and turn off the freewheeling switch SW2, compare the sampled output voltage (V _o ) with the reference voltage (V _ref ), and compare the output to determine whether the current working pulse cycle is T _H or T _L. f _H' and f _L' are narrow pulses with the same frequency as f _H and f _L , which are used to enable the sample/hold circuit and set and reset the RS flip-flop. If the output voltage sampled at the beginning of the current pulse is lower than the reference voltage, select f _H' as the narrow pulse, that is, the current working pulse is a high-frequency pulse f _H ; when the sampled output voltage is greater than the reference voltage, select f _L' as the narrow pulse pulse, the current working pulse is the low-frequency pulse f _L . When the switch tube SW1 is turned on, the inductor current (i _L ) increases linearly from the reference current. The inductor current detected by the current detection device is compared with the peak current, and when the inductor current rises to the peak current, the main switching tube is turned off, and the inductor current drops. When the inductor current drops to the reference current, the freewheel switch SW2 is turned on, and the inductor current keeps I _ref unchanged until the next working pulse comes and the main switch is turned on, and the inductor current starts to rise from the reference current value again. When the converter works stably, in any frequency pulse, the inductor current rises linearly from the reference current value with a fixed slope. Since the peak current is constant, the two frequency pulses have the same conduction time. Therefore, the high-frequency pulse can transfer more energy to the load end. It is also due to the existence of the peak current that once the inductor current reaches the peak current, the switch tube is automatically turned off, thereby realizing the overcurrent protection of the circuit.

Embodiment two

Fig. 9 shows that compared with the first embodiment, this embodiment only changes the power converter part to a Buck-Boost converter, and the control device is the same as that of the first embodiment. It is also proved by simulation that the Buck-Boost converter of the present invention has stable output voltage, fast dynamic response speed and large output power range.

In addition to being applicable to control the two power converters in the above embodiments, the present invention can also be used in switching power supplies composed of power circuits such as Boost converters and Cuk converters.

Claims (2)

1. the quasicontinuous working model switch power supply Bifrequency control method is exported by the power of controller power controlling converter, and it is characterized in that: power inverter is operated in the quasi-continuous pattern of inductive current; Controller selects for use the different pulse of two class frequencys to make up according to the output state of power inverter, realizes control to inverter power output with this; That is: feed back output voltage in the finish time of any one pulse signal and go into comparator, and compare with reference voltage, comparative result is selected the foundation of low frequency or high-frequency impulse as next working pulse; Detect inductor current signal simultaneously and go into current comparator and reference current comparison, when it drops to reference current, the continued flow switch conducting at inductance two ends, inductive current remains unchanged, thereby realizes the bifrequency control of quasicontinuous working model switch power supply.

2. a device of realizing the Bifrequency control method of the described quasicontinuous working model switch power supply of claim 1 is made up of power inverter and controller, it is characterized in that, the drive circuit in the controller links to each other with switching device in the power inverter; Be provided with continued flow switch between quasi-continuous mode controller in controller and the filter in the power inverter; Described controller is made up of the voltage check device, comparator, impulse generator, pulse selector, drive circuit and the quasi-continuous mode controller that are arranged in the controller; Comparator is connected between voltage check device and the pulse selector; Be connected between impulse generator and the drive circuit by the pulse selector of voltage comparator control.

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