KR20190101127A - Full bridge inverter switching control apparatus and method - Google Patents

Abstract

Disclosed are a full bridge inverter switching control apparatus and method therefor. The present invention is configured to check whether the current load is a rated load or a light load by sensing a voltage outputted to the load, insert a short dead time to a switching control signal of a full bridge switching element when the current load is the rated load, or insert a relatively long dead time to the switching control signal when the current load is the light load so that a voltage across a switch is discharged by using energy stored in a magnetic inductor of a transformer before the switch is turned on during a dead time, and accordingly, the switching element is soft-switched. In this manner, the present invention controls the switching elements of the full bridge inverter to be soft-switched using the dead time. Thus, it is possible to design a power supply system operating at a high frequency, reduce a size of the transformer with an increasing operating frequency, and design a heat sink having a relatively small size due to switching loss reduction of the switching elements, thereby reducing a size of the power supply system. In addition, the present invention can control shortly a dead time at a rated load where the current in the magnetic inductor is relatively large, thereby obtaining a desired output voltage while minimizing duty loss.

Description

Full bridge inverter switching control apparatus and method

The present invention relates to a full bridge inverter switching control device and method, and more particularly to a full bridge inverter switching control device and method included in the power supply.

Recently, power supplies providing high output voltages and low output currents have been used in a variety of applications. In particular, as shown in FIG. 1A, a full bridge inverter is connected to the primary side of the transformer and a rectifier connected to the secondary side of the transformer is mainly used, and is output from the actual inverter through a phase shift of the full bridge inverter signals. BACKGROUND ART A power supply device that controls a voltage output to a load side by adjusting a duty of a voltage is widely used.

Such a power supply has an advantage in that a high output voltage can be obtained with a simple structure, but as shown in FIG. 1B, hard switching of the switches constituting the full bridge reduces the efficiency of the power supply and The disadvantage is that the heat sink size increases.

In addition, this conventional technology is controlled to operate at a relatively low switching frequency because the hard switching loss of the semiconductor switching element included in the full-bridge inverter increases in proportion to the frequency, accordingly the problem that the transformer size of the power supply also increases exist.

The problem to be solved by the present invention is to increase the efficiency of the power supply by controlling the switching elements constituting the full bridge inverter to be soft switching, and at the same time to reduce the size of the power supply by reducing the transformer size of the power supply It is to provide a full bridge inverter switching control device and method.

Full bridge inverter switching control device according to a preferred embodiment of the present invention for solving the above problems, a full bridge inverter consisting of a plurality of switching elements, the output of the full bridge inverter is connected to the primary side and the secondary side A switching control device for controlling switching of the full bridge inverter of a power supply including a transformer connected to the rectifier, and the rectifier for converting an AC voltage input from the secondary side of the transformer into a direct current voltage and outputting it to the load side. The dead time is inversely proportional to the voltage output from the rectifier to the load side, and the dead time is inserted into the switching control signals of the plurality of switching elements and output to the plurality of switching elements.

The full bridge inverter switching control device may further include a duty determination unit configured to output a duty voltage value indicating a duty cycle of a voltage output by the full bridge inverter according to a voltage value output from the rectifier to the load side; A comparator for comparing the duty voltage value with a triangular wave and outputting a voltage waveform having a duty cycle of an output voltage output by the full bridge inverter; A control signal generator configured to generate a switching control signal of the plurality of switching elements such that the full bridge inverter outputs a voltage having the same duty cycle as the voltage waveform input from the comparison unit; A dead time generation unit generating a dead time to be inserted into the switching control signal using the duty voltage value and outputting a dead time voltage signal corresponding to the dead time; And a control signal output unit for inserting the dead time generated by the dead time generator into the switching control signal and outputting the control to each switching element of the full bridge inverter.

The duty determiner may output the duty voltage value according to a difference between a voltage value output from the rectifier and the load side and a predefined reference value.

The duty decider may output a smaller duty voltage value as the measured voltage value is larger.

In addition, the dead time generated by the dead time generator may be generated to a greater value as the duty voltage value increases.

, Coss 는 MOSFET의 출력 커패시턴스, Ts는 스위칭 주기, Vsaw.peak는 삼각파의 첨두값, Lm은 변압기의 자화 인덕턴스, Vp는 듀티 전압값을 각각 나타낸다.In addition, the dead time generating unit generates a dead time (T _dead ) according to the following equation,

Where Coss is the output capacitance of the MOSFET, Ts is the switching period, Vsaw.peak is the peak value of the triangular wave, Lm is the magnetizing inductance of the transformer, and Vp is the duty voltage value.

On the other hand, the power supply system according to a preferred embodiment of the present invention for solving the above problems, a full bridge inverter consisting of switching elements; A transformer having an output of the full bridge inverter connected to a primary side and a rectifier connected to a secondary side; The rectifier converts an AC voltage input from the secondary side of the transformer into a DC voltage and outputs the DC voltage to the load side; And the full bridge inverter switching control device for outputting switching control signals of the switching elements to the full bridge inverter.

On the other hand, the full bridge inverter switching control method according to a preferred embodiment of the present invention for solving the above problems, a full bridge inverter consisting of a plurality of switching elements, the output of the full bridge inverter is connected to the primary side 2 Switching elements of the full bridge inverter of the power supply device including a transformer having a rectifier connected to the secondary side, and the rectifier for converting an AC voltage input from the secondary side of the transformer into a direct current voltage and outputting it to a load side. A switching control method of controlling, comprising: generating a dead time inversely proportional to the voltage output from the rectifier to the load side, and inserting the dead time into the switching control signals of the plurality of switching elements to output the plurality of switching elements. .

The inverter switching control method may further include: (a) generating, by the switching control device, a duty voltage value indicating a duty cycle of a voltage output by the full bridge inverter according to a voltage value output from the rectifier to the load side; (b) the switching control device comparing the duty voltage value with a triangular wave to generate a voltage waveform having a duty cycle of an output voltage output from the full bridge inverter; (c) the switching control device generating a switching control signal of the plurality of switching elements such that the full bridge inverter outputs a voltage having the same duty cycle as the voltage waveform generated in step (b); (d) the switching control device generating a dead time to be inserted into the switching control signal using the duty voltage value and generating a dead time voltage signal corresponding to the dead time; And (e) the switching control device inserting the dead time into the switching control signal according to the dead time voltage signal and outputting and controlling the dead time voltage to each switching element of the full bridge inverter.

The step (a) may generate the duty voltage value according to a difference between the voltage value output from the rectifier and the load side and a predefined reference value.

In addition, in the step (a), as the measured voltage value is larger, a smaller duty voltage value may be generated.

In addition, the dead time generated in step (d) may be generated to a greater value as the duty voltage value increases.

, Coss 는 MOSFET의 출력 커패시턴스, Ts는 스위칭 주기, Vsaw.peak는 삼각파의 첨두값, Lm은 변압기의 자화 인덕턴스, Vp 는 듀티 전압값을 각각 나타낸다.In addition, the dead time (T _dead ) is generated according to the following equation,

Where Coss is the output capacitance of the MOSFET, Ts is the switching period, Vsaw.peak is the peak value of the triangular wave, Lm is the magnetizing inductance of the transformer, and Vp is the duty voltage value.

The present invention senses whether the current load is a rated load or light load by sensing the voltage output to the load, and in the case of the rated load according to the load state, a short dead time is inserted into the switching control signal of the full bridge switching element. In the low case, a relatively long dead time is inserted into the switching control signal, thereby soft switching the switching element by discharging the voltage across the switch using energy stored in the magnetizing inductor of the transformer before the switch is turned on during the dead time.

Thus, the present invention can control the switching elements of the full bridge inverter to be soft switched using dead time, so that the power supply can be designed to operate at a high frequency, and the transformer size can be reduced as the operating frequency is increased. In addition, it is possible to design a heat sink having a relatively small size due to the reduction in switching loss of the switching element, thereby miniaturizing the size of the power supply device.

In addition, the present invention can obtain a desired rated output voltage while minimizing the duty loss by controlling the time of the dead time in a rated load having a relatively large current of the magnetizing inductor.

FIG. 1A illustrates a configuration of a power supply apparatus including a full bridge inverter according to the related art, and FIG. 1B illustrates voltage waveforms output from each component in each stage of switching control of the full bridge inverter illustrated in FIG. 1A. It is a figure which shows.
2 is a diagram showing the configuration of a full-bridge inverter switching control device according to a preferred embodiment of the present invention.
3 is a diagram showing the voltage waveform output from each component in each stage of switching control of a full bridge inverter under rated load conditions.
FIG. 4 is a diagram showing voltage waveforms output from each component in each stage of switching control of a full bridge inverter under light load conditions.

The present invention inserts a dead time into the switching control signal of the switching element included in the full bridge inverter, and by using the energy stored in the magnetizing inductor of the transformer during the dead time, by performing a soft switching by discharging the voltage across the switching elements By increasing the operating frequency, the above effects can be obtained.

However, when the load supplied with power from the power supply is a rated load, the magnetizing inductor has a large current, so that soft switching is possible even with a short dead time.In the light load, the magnetizing inductor has a small current, which is long for soft switching. Dead time is required. Therefore, a long dead time is required to perform soft switching for a full range of loads from light loads to rated loads. However, when the dead time is longer, the duty loss increases at the rated output, making it difficult to obtain the rated output voltage.

Therefore, the present invention comprehensively considers such a problem, detects the voltage output to the load, checks the state of the load, and accordingly inserts a short dead time into the switching control signal at the rated load, and applies the switching control signal at the light load. Inserting a long dead time allows for soft switching while minimizing duty loss.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

2 is a view showing the configuration of a full bridge inverter switching control apparatus 200 according to a preferred embodiment of the present invention, Figure 3 is output from each component in each step of the switching control of the full bridge inverter under the rated load conditions 4 is a diagram showing a voltage waveform, and FIG. 4 is a diagram showing a voltage waveform output from each component at each stage of switching control of a full bridge inverter under light load conditions.

2 and 3, a full bridge inverter switching control apparatus 200 according to a preferred embodiment of the present invention is connected to a full bridge inverter 120 included in a power supply device to a full bridge inverter 120. Controls the on / off of the included switching elements (Q1, Q2, Q3, Q4).

The power supply device includes a rectifier 110 and semiconductor switching elements Q1, Q2, Q3, and Q4 that receive an AC voltage from a commercial power supply and rectify the rectifier 110 to output a DC voltage, and receive a DC input from the rectifier 110. The full bridge inverter 120 for switching the voltage to output an AC voltage, the output of the full bridge inverter 120 is connected to the primary side and the transformer 130, the rectifier 140 is connected to the secondary side, and the transformer 130 And a rectifier 140 for converting an AC voltage input from the secondary side into a DC voltage and outputting it to the load 150 side, and sensing the voltage output from the rectifier 140 to the load 150 side to switch the full bridge inverter. The control apparatus 200 may further include a voltage sensor 160.

Here, since the full bridge inverter 120 is configured in the same structure as the full bridge inverter 120 composed of conventional semiconductor switching elements, a detailed description thereof will be omitted.

Meanwhile, the full bridge inverter switching control apparatus 200 of the present invention includes a duty determiner 210, a comparator 220, a control signal generator 230, a dead time generator 240, and a control signal output unit 250. It is configured to include).

Referring to the function of each component, first, when the rectifier 140 outputs a DC voltage (Vout) to the load side (see Fig. 3 (a)), the duty determiner 210 from the rectifier 140 to the load side When the voltage value Vsen measured from the voltage sensor 160 measuring the output DC voltage is input (see FIG. 3B), the full-bridge inverter 120 is connected according to the input voltage value Vsen. The duty voltage value Vp indicating the duty cycle of the output voltage is output to the comparator 220 and the dead time generator 240 (see FIG. 3C).

In the preferred embodiment of the present invention, the duty determiner 210 is implemented as a PI controller, and inputs the voltage value Vsen measured at the load side to the PI controller performing negative feedback control, and compares it with a predefined reference value. The difference is amplified to generate the duty voltage value Vp, and the duty voltage value Vp is output to the comparator 220 and the dead time generator 240. Therefore, when the voltage output from the rectifier 140 to the load side is the rated voltage, a small duty voltage value Vp is output to the comparator 220 and the dead time generator 240, and the voltage output to the load side is the rated voltage. In the case of smaller light loads, the duty voltage value Vp larger than that of the rated load is output to the comparator 220 and the dead time generator 240.

The comparator 220 compares the duty voltage value Vp with a predefined triangular wave (see FIG. 3C), and has a voltage waveform having a duty cycle of the output voltage output from the full bridge inverter 120. (Veff) is output to the control signal generator 230 (see (d) of FIG. 3).

The control signal generator 230 configures the full bridge inverter 120 so that the full bridge inverter 120 outputs a voltage having the same duty cycle as the voltage waveform input from the comparator 220. The switching control signals Vc1, Vc2, Vc3 and Vc4 of the elements are generated and output to the control signal output unit 250 (see FIG. 3E).

In the example shown in Fig. 3E, Vc1, Vc2, Vc3 and Vc4 respectively represent turn-on pulses applied to the gates of the semiconductor switching elements Q1, Q2, Q3 and Q4 constituting the full bridge. As shown in (e) of FIG. 3, the switching control signal of each semiconductor switching element generated by the control signal generator 230 is the same as the full bridge switching control signal of the prior art. On, Q3 is turned off and Q1 is turned on. Similarly, Q2 is turned off and Q4 is turned on, and Q4 is turned off and Q2 is turned on.

The dead time generator 240 generates a dead time T _dead to be inserted into the switching control signal using the duty voltage value Vp and outputs a dead time voltage signal Ve corresponding to the dead time. It outputs to the part 250 (refer FIG.3 (f)).

In a preferred embodiment of the present invention, the dead time is generated to have a smaller dead time as the voltage output to the load, that is, the measured voltage value Vsen is larger, for this purpose, the dead time generator 240 is Generate dead time according to Equation 1.

In Equation 1, Coss denotes an output capacitance of a MOSFET, Ts denotes a switching period, Vsaw.peak denotes a peak value of a triangular wave, Lm denotes a magnetization inductance of the transformer 130, and Vp denotes a duty voltage value.

In addition, the dead time generator 240 generates the dead time voltage signal Ve according to Equation 2 below, and α is a proportional constant.

The control signal output unit 250 inserts the dead time generated by the dead time generator 240 into the switching control signal input from the control signal generator 230 and outputs the switching time to each switching element of the full bridge (see FIG. 3). (g)).

In this case, as illustrated in FIG. 3G, the switching element Q3 included in the full bridge inverter 120 is turned on after the dead time elapses after the switching element Q1 is turned off, and the switching is performed. The element Q1 is also turned on after the switching element Q3 is turned off and after the dead time elapses.

Similarly, the switching element Q4 is turned on after the dead time elapses after the switching element Q2 is turned off, and the switching element Q2 is also turned on after the dead time elapses after the switching element Q4 is turned off. do.

When the switching elements of the full bridge inverter 120 convert the input DC voltage into an AC voltage according to the switching control signal with the dead time inserted, the AC voltage V _IO as shown in FIG. It is output to the primary side of 130. The alternating voltage V _IO output to the transformer 130 is a duty loss equal to a dead time compared to the voltage pulse output from the current full bridge inverter 120 as shown in FIG. Occurs.

As shown in (i) of FIG. 3, when the rated voltage is output to the load side, the magnetization inductor current I _Lm is relatively larger than the case where the small voltage is output for the smaller light load, so that the dead time is small. By inserting the voltage, the voltage across the switching element is discharged using the energy stored in the magnetization inductor 132 before the switching element is turned on during the dead time, thereby soft switching the switching element as shown in FIG. This is possible.

FIG. 4 is a diagram showing voltage waveforms output from each component in each stage of switching control of a full bridge inverter under light load conditions.

 The example shown in FIG. 4 differs from the example shown in FIG. 3 in that the load to be supplied is light. That is, the example shown in FIG. 4 is except that the magnitude of the voltage output to the load side is smaller than the rated voltage shown in FIG. 3, and the dead time inserted in the switching control signal is longer than the example of FIG. 3. The control method is the same.

Referring to FIG. 4, the difference between the example and the example illustrated in FIG. 3 will be described. In the case where the load is a light load, the DC voltage Vout output from the rectifier 140 to the load side is shown in FIG. 3A. It has a voltage value smaller than the rated voltage (see FIG. 4A), and the measured voltage value Vsen output to the duty determination unit 210 also has a voltage value smaller than that of the rated load (FIG. 4). (b)).

The duty decider 210 inputs the voltage value Vsen measured at the load side to the PI controller which performs negative feedback control, compares it with a predefined reference value, amplifies the difference, and generates a duty voltage value Vp. The duty voltage value Vp is output to the comparator 220 and the dead time generator 240 (see FIG. 4C). At this time, since the voltage Vout output to the load side is smaller than the rated voltage, the duty voltage value Vp larger than the rated load is output to the comparator 220 and the dead time generator 240.

The comparator 220 compares the duty voltage value Vp with a predefined triangular wave (see FIG. 4C), and has a voltage waveform having a duty cycle of the output voltage output from the full bridge inverter 120. (Veff) is output to the control signal generator 230 (see FIG. 4D). Here, since the output voltage Vout is smaller than that in FIG. 3, it is natural that the duty cycle of the voltage waveform Veff output to the control signal generator 230 is smaller than the duty cycle shown in FIG. Do.

The control signal generator 230 configures the full bridge inverter 120 so that the full bridge inverter 120 outputs a voltage having the same duty cycle as the voltage waveform input from the comparator 220. The switching control signals Vc1, Vc2, Vc3, and Vc4 of the device are generated and output to the control signal output unit 250 (see FIG. 4E).

The dead time generator 240 generates a dead time T _dead to be inserted into the switching control signal using the duty voltage value Vp according to Equation 1, and corresponds to a dead time voltage. The signal Ve is generated according to the above equation (2) and output to the control signal output unit 250 (see (f) of FIG. 4). Here, the dead time generated by the dead time generator 240 has a larger value than the example shown in FIG. 3, and thus, the dead time voltage signal Ve is smaller than the example shown in FIG. It has a voltage value.

The control signal output unit 250 inserts the dead time generated by the dead time generator 240 into the switching control signal input from the control signal generator 230 to switch each switching element Q1 of the full bridge inverter 120. , Q2, Q3, Q4) (see FIG. 4G). At this time, it can be seen that the dead time inserted into the switching control signal is longer than the dead load shown in FIG. 3.

When the switching elements Q1, Q2, Q3, and Q4 of the full bridge inverter 120 convert the input DC voltage into the AC voltage according to the switching control signal having the dead time inserted therein, shown in FIG. As described above, the AC voltage V _IO is output to the primary side of the transformer 130. AC voltage (V _IO ) output to the transformer 130 is a duty loss (Duty Loss) of the dead time compared to the voltage pulse output from the current full-bridge inverter 120 as shown in Figure 4 (d) Occurs.

As shown in (i) of FIG. 4, when the voltage smaller than the rated voltage is output to the light load side, the magnetization inductor current I _Lm is relatively smaller than the case where the rated voltage is output. By inserting, the voltage across the switching element is discharged by using the energy stored in the magnetization inductor 132 before the switching element is turned on during the dead time, thereby soft switching of the switching element as shown in FIG. It is possible.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

110: rectifier 120: full bridge inverter
130: transformer 132: magnetized inductor
140: rectifier 150: load
160: voltage measurement sensor
200: full bridge inverter switching control unit
210: duty determination unit 220: comparison unit
230: control signal generator 240: dead time generator
250: control signal output unit

Claims (13)

A full bridge inverter composed of a plurality of switching elements, a transformer connected to the output of the full bridge inverter to the primary side, a rectifier connected to the secondary side, and the load side by converting the AC voltage input from the secondary side of the transformer into a DC voltage A switching control device for controlling the switching of the full bridge inverter of the power supply including the rectifier for outputting,
A dead time inversely proportional to a voltage output from the rectifier to the load side, and inserting the dead time into the switching control signals of the plurality of switching elements and outputting the dead time to the plurality of switching elements Switching control device. The apparatus of claim 1, wherein the full bridge inverter switching control device
A duty determiner for outputting a duty voltage value indicating a duty cycle of a voltage output from the full bridge inverter according to a voltage value output from the rectifier to the load side;
A comparator for comparing the duty voltage value with a triangular wave and outputting a voltage waveform having a duty cycle of an output voltage output by the full bridge inverter;
A control signal generator configured to generate a switching control signal of the plurality of switching elements such that the full bridge inverter outputs a voltage having the same duty cycle as the voltage waveform input from the comparison unit;
A dead time generation unit generating a dead time to be inserted into the switching control signal using the duty voltage value and outputting a dead time voltage signal corresponding to the dead time; And
And a control signal output unit which inserts the dead time generated by the dead time generating unit into the switching control signal and outputs and controls each switching element of the full bridge inverter. The method of claim 2, wherein the duty determiner
And outputting the duty voltage value according to a difference between a voltage value output from the rectifier and the load side and a predefined reference value. The method of claim 3, wherein the duty determiner
And a smaller duty voltage value is output as the measured voltage value is larger. The method of claim 4, wherein
The dead time generated by the dead time generating unit is a full bridge inverter switching control device, characterized in that the greater the duty voltage value is generated as a larger value. The method of claim 5,
The dead time generating unit generates a dead time (T _dead ) according to the following equation,

Coss is the output capacitance of the MOSFET, Ts is the switching period, Vsaw.peak is the peak value of the triangular wave, Lm is the magnetizing inductance of the transformer, Vp is the duty voltage value, respectively. A full bridge inverter composed of switching elements;
A transformer having an output of the full bridge inverter connected to a primary side and a rectifier connected to a secondary side;
The rectifier converts an AC voltage input from the secondary side of the transformer into a DC voltage and outputs the DC voltage to the load side; And
The full bridge inverter switching control device according to any one of claims 1 to 6, which outputs the switching control signals of the switching elements to the full bridge inverter.
A full bridge inverter composed of a plurality of switching elements, a transformer connected to the output of the full bridge inverter to the primary side, a rectifier connected to the secondary side, and the load side by converting the AC voltage input from the secondary side of the transformer into a DC voltage A switching control method of controlling switching elements of the full bridge inverter of a power supply device including the rectifier for outputting a switching control device,
A dead time inversely proportional to a voltage output from the rectifier to the load side, and inserting the dead time into the switching control signals of the plurality of switching elements and outputting the dead time to the plurality of switching elements Switching control method. The method of claim 8, wherein the inverter switching control method
(a) generating, by the switching control device, a duty voltage value indicating a duty cycle of a voltage output by the full bridge inverter according to a voltage value output from the rectifier to the load side;
(b) the switching control device comparing the duty voltage value with a triangular wave to generate a voltage waveform having a duty cycle of an output voltage output from the full bridge inverter;
(c) the switching control device generating a switching control signal of the plurality of switching elements such that the full bridge inverter outputs a voltage having the same duty cycle as the voltage waveform generated in step (b);
(d) the switching control device generating a dead time to be inserted into the switching control signal using the duty voltage value and generating a dead time voltage signal corresponding to the dead time; And
and (e) the switching control device inserting the dead time into the switching control signal according to the dead time voltage signal and outputting and controlling the dead time voltage to each switching element of the full bridge inverter. Switching control method. The method of claim 9, wherein step (a)
And generating the duty voltage value according to a difference between a voltage value output from the rectifier to the load side and a predefined reference value. The method of claim 10, wherein step (a)
And the larger the measured voltage value, the smaller the duty voltage value is generated. The method of claim 11,
The dead time generated in the step (d) is generated with a larger value as the duty voltage value is larger, characterized in that the full bridge inverter switching control method. The method of claim 12,
The dead time (T _dead ) is generated according to the following equation,

Coss is the output capacitance of the MOSFET, Ts is the switching period, Vsaw.peak is the peak value of the triangular wave, Lm is the magnetizing inductance of the transformer, Vp is the duty voltage value, respectively.

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