KR19990012567A - AC / DC step-up power converter with partial resonance soft switching mode - Google Patents

Abstract

An inductor for boosting an input voltage, a first switching device and a second switching device connected in series with the boosting inductor to switch a voltage boosted by the boosting inductor by receiving a pulse signal having a predetermined duty ratio; A resonant capacitor connected in parallel to the first switching element and the second diode which form a path of the partial resonance circuit when the first switching element and the second switching element are turned off in parallel; And a resonant circuit is formed only when the first switching element and the second switching element are on-off, thereby reducing the loss caused by the resonant purifying current, and discontinuously controlling the input current.

Therefore, since the switching elements are operated in the soft switching mode, switching loss is reduced, and the input current is controlled by discontinuously controlling the input current to make the unit power factor, thereby improving efficiency and power factor.

Description

AC / DC step-up power converter with partial resonance soft switching mode

The present invention relates to an AC / DC boost converter of a partial resonant switch method (PRSM) soft switching mode, and more particularly, to a turn-on of a switching element. Partial resonant circuit is applied so that resonant circuit is formed only on and off, and input current is generated as sinusoidal wave through discontinuous control of input current to make input power factor into unit power factor and to protect switching device. The present invention relates to an AC / DC step-up power converter of a partially resonant soft switching mode having a simple circuit structure since no snubber circuit is required.

In recent years, the development of semiconductor manufacturing technology has enabled high-speed switching of power switching devices. Accordingly, power converters have realized a smaller, lighter and lower noise converter by increasing the switching frequency.

On the other hand, the conventional AC / DC boosting type power converter adopts a hard switching circuit which is continuously controlled with respect to an input current. That is, the input voltage is rectified and smoothed, converted to a DC voltage, and then boosted to an appropriate level by a boost inductor. At this time, the switching element is mounted, the step of boosting the input voltage according to the on-off of the switching device, and the process of supplying the boosted voltage to the load is performed continuously.

However, such a conventional power converter generates the following problems.

(1) The switching device used in the conventional converter has a large switching loss due to a high switching frequency, and the power semiconductor device receives a lot of stress, thereby reducing the efficiency of the converter.

(2) Conventional converters use a snubber circuit around the switching element to protect the switching element from hard switching operation. However, when the output current increases, The losses are increased, further reducing the efficiency of the converter.

Accordingly, the present invention is to solve the above problems, the first object of the present invention is to employ a partial resonant circuit to form a resonant circuit only during the turn-on and turn-off of the switching device, thereby eliminating switching losses To provide an AC / DC step-up power converter of a partially resonant soft switching mode.

In addition, the second object of the present invention is to generate the input power factor in unit power by causing the input current to be generated in sinusoidal proportional to the magnitude of the input voltage by the discontinuous control of the input current. The present invention provides an AC / DC step-up power converter.

Further, the third object of the present invention is to adopt a partial resonance soft switching circuit, thereby eliminating the snubber circuit for protecting the switching element, and thus the AC / DC boosting power conversion in the partial resonance soft switching mode having a simple circuit structure. In providing a device.

Figure 1a is a partial resonant circuit diagram applied to the present invention,

1B is an operating state diagram in a switch-on state,

1C is an operating state diagram in a switch-off state;

FIG. 2A is a waveform diagram of each part under the condition of FIG. 1B; FIG.

2B is a waveform diagram of each part under the condition of FIG. 1C;

3 is a detailed circuit diagram of an AC / DC step-up power conversion device of the present invention to which the partial resonance circuit shown in FIG. 1A is applied;

4 is an operation waveform diagram of each part of the switching operation of the AC / DC step-up power conversion device according to the present invention;

Figure 5a is a diagram showing the switching loss of the conventional AC / DC step-up power conversion device not applied to the partial resonant technique,

Figure 5b is a diagram showing the switching loss of the AC / DC step-up power converter of the present invention to which the partial resonant technique is applied,

6 is a circuit constant of each circuit substituted in the AC / DC step-up power converter of the present invention,

Figure 7a is a waveform chart showing the relationship between the voltage (V _C) of the current (I _L) and the resonant capacitor (C _r) for a boost inductor (L _r),

7B is a waveform diagram illustrating a relationship between an input voltage Vin and an output voltage V _Cd ;

8A is a view showing a control signal of the switching element S1 and a control signal of the switching element S2;

Figure 8b is a view showing the relationship between the voltage (V _C) of the current (I _L) and the resonant capacitor (C _r) for a boost inductor (L _r),

8C is a diagram illustrating a relationship between a switch current I _S and a voltage at both ends V _S ;

9A is a waveform diagram of an input voltage Vin and an input current Iin at a duty rate of 20 [%].

9B is a diagram showing a frequency spectrum of an input current Iin at a duty rate of 20 [%].

10A is a waveform diagram of an input voltage Vin and an input current Iin at a duty ratio of 30 [%].

10B is a diagram showing a frequency spectrum of an input current Iin at a duty ratio of 30 [%].

11A is a waveform diagram of an input voltage Vin and an input current Iin at a duty ratio of 40 [%].

11B is a diagram showing a frequency spectrum of an input current Iin at a duty rate of 40 [%].

12 is a diagram comparing changes in total harmonic distortion factor (THD) with respect to a change in duty ratio D _C for a hard switching circuit and a soft switching circuit, respectively.

FIG. 13 is a diagram comparing the change in rms of the input current Iin fundamental wave component with respect to the change in duty ratio D _C for the hard switching circuit and the soft switching circuit, respectively.

14 is a diagram illustrating an input power factor (PF) for a duty rate change;

15 is a measurement of the efficiency of the AC / DC step-up power converter of the soft switching mode to which the partial resonant technique applied in the present invention, and the AC / DC step-up power converter of the hard switching mode is not applied to the partial resonant technique It is a figure which shows the result compared.

<Description of the code | symbol about the principal part of drawing>

L _r : Boosting inductor C _r : Resonant capacitor

S1, S2: switching element for partial resonance circuit

BD: Bridge Diode Vin: Input Voltage

Iin: input current

In order to achieve the above object, a feature of the present invention includes a filter / rectifier for filtering and rectifying a surge component of an input voltage, and a smoothing unit for smoothing an output voltage output to a load. AC / DC boost in partial resonance soft switching mode, comprising a partial resonance circuit for boosting the DC voltage filtered and rectified by the filter / rectifier to a predetermined level and performing partial resonance between the rectifying section and the smoothing section. Is in mold power inverter.

Preferably, the partial resonance circuit includes: a boost inductor for boosting the DC voltage converted by the filter / rectifier; A first switching device and a second switching device connected in series with the boosting inductor to receive a pulse signal having a predetermined duty ratio and switch a voltage boosted by the boosting inductor; First and second diodes connected in parallel to the first switching element and the second switching element to form a path of a partial resonant circuit when the first switching element and the second switching element are turned off; And a resonance capacitor connected in parallel with the boost inductor; When the first switching element and the second switching element are turned on, a path is provided such that the voltage boosted by the boosting inductor is conducted through the first switching element, the resonance capacitor, and the second switching element. Formed; When the first switching device and the second switching device are turned off, a path is formed such that the voltage boosted by the boosting inductor is conducted through the first diode, the resonance capacitor, and the second diode. .

Preferably, the current of the boosting inductor is discharged so that the first switching element and the second switching element perform a zero current switching operation at turn-on, and the first switching element and the second switching element are turned on. The voltages of the resonant capacitors are all discharged to perform the zero voltage switching operation at the time of OFF.

Preferably, in the partial resonant circuit, a path of the partial resonant circuit is formed only when the first switching element and the second switching element are turned on and off.

Preferably, when the first switching element and the second switching element are turned on, the resonance capacitor regenerates the power by supplying the accumulated energy to the power source.

Hereinafter, a preferred embodiment of the AC / DC step-up power converter of the partial resonance soft switching mode according to the present invention will be described with reference to the accompanying drawings.

1A to 1C show a partial resonant circuit and an operational state diagram thereof according to the present invention.

The partial resonant circuit as shown in FIG. 1A includes a pair of switching elements S1 and S2, a capacitor C _r connected in parallel to the respective switching elements S1 and S2, and a respective switching element S1, A resonant inductor L _r connected in series to S2 and free-wheeling diodes D1 and D2 connected in series to the respective switching elements S1 and S2.

The operation of the partial resonance circuit having such a configuration is as follows.

First, when each of the switching elements S1 and S2 is in the switch-on state, as an initial condition, the current I _L of the resonance inductor L _r is zero and the capacitor C _r is the voltage V _C. Assume that the current I _L flowing in the inductor L _r is zero just before the switch-on, and thus the turn-on operation of the switching elements S1 and S2 is zero current switching (ZCS). ).

Then, as shown in FIG. 1B by the switch-on operation, the LC series resonant circuit is formed so that the current I _L flowing through the inductor increases as shown in Equation 1 below, and the voltage of the capacitor C _r ( V _C ) decreases to zero as in equation (2).

V _C = (2V + V _C ) cost-2V

here, ego, to be.

Therefore, waveforms as shown in Fig. 2A are generated in each component of the partial resonance circuit.

Second, when each of the switching elements S1 and S2 is in the switch-off state, the voltage V _C of the capacitor C _r is zero under the condition immediately before the switch-off, and the current I _a is applied to the inductor L _r . Assuming the flow, the voltage flowing to the capacitor (C _r ) immediately before the switch-off is zero, so the off operation of the switching elements (S1, S2) achieves zero voltage switching (ZVS).

Then, as shown in Fig. 1C by the switch-off operation, the diodes D1 and D2 are turned on, and the LC series resonant circuit is formed again so that the voltage V _C of the capacitor C _r is expressed by the following equation. Increasing as 3, the inductor current (I _L ) emits energy as in equation (4).

I _L = I _a cos (t +)

here, to be.

Therefore, waveforms as shown in FIG. 2B are generated in each component of the partial resonance circuit.

As described above, since the resonant circuit is not continuously made for one period of resonance, but partially formed in a part of the resonance period in the switch-on and switch-off states, the partial resonance technique is performed. This reduces the capacitance sharing and stress of the resonant elements and reduces the resonance loss even when the output current increases. In addition, since the switching elements S1 and S2 used by the partial resonance technique are operated in a soft switching state, the efficiency of the system is increased, , The electromagnetic induction noise due to this can be reduced.

3 shows a state in which a partial resonance circuit having such a configuration is applied to an AC / DC boosting type power converter.

As shown in FIG. 3, the AC / DC step-up power converter includes a filtering inductor L _f and a filtering capacitor C _f for filtering surge components of an AC input power Vin, and filtered AC. Bridge diode BD composed of a plurality of diodes D3 to D6 to rectify the input power Vin, and a boosting (or resonating) inductor L _r for boosting the DC voltage rectified by the bridge diode BD. boost inductor (L _r) for, when the off-and a pair of switching elements (S1, S2) for switching the voltage boosted in the booster inductor (L _r) for a, the switches each of the switching elements (S1, S2) A pair of freewheeling diodes (D1, D2) for transferring the voltage boosted at the load (LOAD), a resonant capacitor (C _r ) for protecting the switching elements (S1, S2), and the amplified voltage It is composed of rectifier diode (D7) and smoothing capacitor (C _d ) which is rectified and smoothed and finally outputs to load. The energy stored in the resonant capacitor (C _r) is turned for the switching element (S1, S2) - has a mode that is regenerated to the power supply side when turned on. The turn-on states of the switching elements S1 and S2 are operated in the zero current switching mode ZCS because the current of the amplifying inductor L _r is controlled discontinuously, and the turn-off of the switching elements S1 and S2 is turned off. Since the operation state when a voltage of the resonant capacitor (C _r) is zero for zero voltage switching mode (ZVS).

Here, the boost inductor (L _r) for a pair of free-wheeling diode (D1, D2) and a switching element (S1, S2) and a capacitor resonance (C _r) of the pair is a partial resonance circuit mentioned above, Corresponds to

An operation of the present invention having such a configuration will be described in detail with reference to FIGS. 4 to 15.

Figure 4 shows the operation waveform of each part of the switching operation of the AC / DC step-up power conversion device according to the present invention.

4, when the switching elements S1 and S2 are turned on at time t ₀ , the resonant capacitor C _r starts to be discharged by the LC series resonant circuit, and the amplification inductor L _r is energized. Will accumulate. At this point, the current I _S through the switching elements S1 and S2 is equal to the current I _L of the boost inductor L _r , and the switching elements S1 and S2 are in the zero current switching mode ZCS. It works.

When the voltage V _C of the resonant capacitor C _r becomes zero at time t ₁ , a short circuit is formed by the switching elements S1 and S2 to form a current I _L of the boost inductor L _r . Increases linearly and accumulates energy. At this point, the current I _L of the boost inductor L _r is classified into the switching element S1 and the switching element S2, so that the conduction loss by the switching elements S1 and S2 is reduced by half. This is one more increase in the number of switching elements compared with the conventional boost type power converter using one switching element, but the conduction loss is the same.

When the switching elements S1 and S2 are turned off at time t ₂ , the resonant capacitor C _r starts charging again by the LC series resonant circuit. And, at this time the voltage across the switching device (S1, S2) is equal to the voltage (V _C) of the resonant capacitor (C _r) for, operates as a switching device (S1, S2) is a zero voltage switching mode (ZVS) .

At time t ₃ the voltage (V _C) of the resonant capacitor (C _r) for being the output voltage (V _Cd), current of the boost inductor (L _r) for (I _L) is introduced to the load side decreases linearly.

The time t ₄ is a time point at which the current I _L of the boost inductor L _r becomes zero. In addition, the period T _C represents one cycle in which the switching operation occurs.

On the other hand, Figure 5a and 5b compares the switching loss of the AC / DC step-up power converter to which the partial resonant technique is applied according to the present invention, and the conventional AC / DC boost type power converter is not applied to the partial resonant technique The figure is shown. Here, Figure 5a is a view showing the switching loss of the conventional AC / DC boost type power conversion apparatus is not applied to the partial resonant technique, Figure 5b is an AC / DC boost type power converter of the present invention to which the partial resonant technique is applied It is a figure which shows switching loss. As shown in FIGS. 5A and 5B, since the area surrounded by the V-I characteristic curve is proportional to the switching loss, it can be seen that the loss of the AC / DC boosting power converter to which the partial resonance technique is applied is very small.

Next, experimental values and experimental results obtained by substituting arbitrary circuit constants for the AC / DC boosting power converter of the partially resonance soft switching mode proposed in the present invention are presented.

The result of experiment by substituting the circuit constant as shown in FIG. 6 into the AC / DC step-up power converter of the present invention is as follows. That is, in FIG. 7A, the current I _L of the boost inductor L _r may be represented as a sine wave pulse train proportional to the magnitude of the sine wave input voltage with respect to the half period of the input voltage shown in FIG. 7 b. Here, FIG. 7A is a waveform diagram showing the relationship between the current I _L of the boost inductor L _r and the voltage V _C of the resonant capacitor C _r , and FIG. 7B is an input voltage Vin and This is a waveform diagram showing the relationship with the output voltage V _Cd .

8A to 8C show the experimental waveforms for each cycle of switching at a switching frequency of 200 [Hz] and a duty rate of 20 [%] to confirm the partial resonance and the soft switching operation thereof. 8A is a diagram showing a control signal of the switching element S1 and a control signal of the switching element S2, and FIG. 8B is a current I _L of the boost type inductor L _r and a resonant capacitor C _r. ) is a diagram showing the relationship between the voltage (V _C) of Figure 8c is a view showing the relationship between the switch current (I _S) and the voltage across (V _S).

As can be seen in Figures 8a to 8c, the switching elements (S1, S2) applied to the present invention is turned on at the zero current by the partial resonant operation, shows a soft switching operation is turned off at the zero voltage. This does not require a snubber circuit as compared with the conventional AC / DC boost type power converter, and there is no switching loss, thereby increasing the efficiency of the AC / DC boost type power converter. In addition, the switching elements S1 and S2 , Since there is no effect, electromagnetic induction noise such as electromagnetic interference (EMI) does not occur, and it is possible to prevent the breakdown or stress of the switching elements S1 and S2, and the device heat dissipation mechanism due to overheating of the element. Can be reduced.

Meanwhile, in order to analyze the input current Iin, FIGS. 9A and 9B show waveforms of the input power supply voltage Vin and the input current Iin with a duty ratio of 20 [%]. In this experimental waveform, the current I _L of the boost type inductor L _r becomes a sinusoidal pulse in proportion to the magnitude of the sinusoidal input voltage Vin (see FIG. 7A), and the AC filter of the input stage (smooth inductor L _f). ) And the input current Iin through the smoothing capacitor C _f and the bridge diode BD are almost sinusoidal in unit power factor. 9A is a waveform diagram of an input voltage Vin and an input current Iin, and FIG. 9B shows a frequency spectrum of the input current Iin.

10A, 10B, 11A, and 11B show frequency spectrum analysis results of input voltage Vin and input current Iin and corresponding input current Iin for duty ratios 30 [%] and 40 [%]. Respectively. As can be seen from the above-mentioned results of the frequency spectrum, it can be seen that the harmonic component of the input current Iin decreases and the fundamental wave component increases with increasing the duty ratio.

12 and 13 illustrate a change in total harmonic distortion factor (THD) and change in rms of an input current (Iin) fundamental wave component with respect to a change in duty ratio D _C. It is shown about each. 12 and 13, as the duty ratio increases, the harmonic component of the input current Iin is lower in the soft switching circuit than the hard switching circuit, and the fundamental wave component of the input current Iin is hard in the soft switching circuit. Since it appears higher than the switching circuit, it can be said that the soft switching circuit is more efficient than the hard switching circuit.

In addition, FIG. 14 shows an input power factor (PF) for a change in duty rate. As shown in FIG. 14, the main cause of the increase in the input power factor in the soft switching circuit is that the boost ratio is high under the same conditions as the hard switching circuit. That is, the resonant capacitor (C _r) used for the soft-switching circuit provided in the present invention the loss does not occur: because the operation in (lossless Lossless) resonant capacitor.

15 shows the efficiency of the AC / DC step-up power converter of the soft switching mode to which the partial resonant technique applied in the present invention and the AC / DC step-up power converter of the hard switching mode to which the partial resonant technique is not applied are measured. The results of the comparison are shown, and the losses during the turn-on and turn-off of the switching elements S1 and S2 are greatly reduced, thereby greatly improving the efficiency. As can be seen from these experimental results, the AC / DC step-up power converter of the partially resonant soft switching mode applied in the present invention has the same switching capacity even though the duty ratio of the switching is slightly lower than that of the conventional hard switching power converter. You can get the output. This switching element (S1, S2) of the turn-is because in addition to the on-operation by the stored energy of the resonant capacitor (C _r) for the regenerated to the input side of the inductor _(L I) for the step-up element.

On the other hand, in the partial resonant circuit proposed in the present invention, the resonant inductor can be replaced with the energy accumulator inductor used in the general boost type power converter, and the resonant capacitor is used in the snubber circuit used in the switching mode power converter. Can be replaced with a snubber condenser.

As a result, according to the AC / DC step-up power converter of the partial resonance soft switching mode according to the present invention, the following advantages occur.

(1) By applying the partial resonant technique in which the operating state of the switching elements forms a resonant circuit only at the time of switch-on and switch-off, switching losses are reduced because the switches are operated in the soft switching mode.

(2) As the partial resonance is applied, the loss of the resonance circuit is reduced, the stress of the resonance elements is reduced, and as a result, the efficiency of the system is increased.

(3) Since the input current is generated in sinusoidal proportional to the magnitude of the input voltage by discontinuous control of the input current, the input power factor can be made unit power. Therefore, a high power factor power converter can be realized.

(4) The circuit structure of the power converter is simple by using an inductor used in a general boost type power converter for resonance and boost, and a snubber capacitor for resonance.

(5) Since the energy stored in the resonant capacitor is returned to the power supply side and used as a regenerative power supply in the state where the partial resonance circuit is operated, no loss caused by the resonant capacitor is generated.

(6) The energy regenerated by the resonant capacitor is applied to the boosting element so that the distortion of the input current is improved.

(7) Since the switching duty ratio is reduced in comparison with the hard switching circuit under the same power capacity, the efficiency of the power converter is increased.

Claims (5)

A power converter comprising a filter / rectifier for filtering and rectifying a surge component of an input voltage and a smoothing part for smoothing an output voltage output to a load: AC between the filter / rectifier and the smoother, a partial resonant soft switching mode including a partial resonant circuit for boosting the DC voltage filtered and rectified by the filter / rectifier to a predetermined level and performing partial resonance. / DC step-up power converter. The method of claim 1, wherein the partial resonant circuit, A boost inductor for boosting the DC voltage converted by the filter / rectifier; A first switching device and a second switching device connected in series with the boosting inductor to receive a pulse signal having a predetermined duty ratio and switch a voltage boosted by the boosting inductor; First and second diodes connected in parallel to the first switching element and the second switching element to form a path of a partial resonant circuit when the first switching element and the second switching element are turned off; And A resonant capacitor connected in parallel to said boost inductor; When the first switching element and the second switching element are turned on, a path is provided such that the voltage boosted by the boosting inductor is conducted through the first switching element, the resonance capacitor, and the second switching element. Formed; When the first switching device and the second switching device are turned off, a path is formed such that the voltage boosted by the boosting inductor is conducted through the first diode, the resonance capacitor, and the second diode. AC / DC step-up power converter with partially resonant soft switching mode. The method of claim 2, When the first switching element and the second switching element are all turned off, the current of the boosting inductor is discharged so as to perform a zero current switching operation when the first switching element and the second switching element are turned on. An AC / DC step-up power converter in a partially resonant soft switching mode in which all voltages of the resonant capacitor are discharged to perform a zero voltage switching operation. The method of claim 2, wherein the partial resonant circuit, An AC / DC step-up power converter in a partial resonance soft switching mode in which a path of a partial resonance circuit is formed only when the first switching element and the second switching element are turned on and off. The method of claim 2, wherein the resonant capacitor, The AC / DC step-up power converter of the partially resonant soft switching mode, when the first switching device and the second switching device is turned on, supplies the accumulated energy to the power supply to regenerate the power supply.