JP3703026B2 - Snubber circuit for bidirectional DC-DC converter and bidirectional DC-DC converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The invention of this application relates to a snubber circuit for a bidirectional DC-DC converter and a bidirectional DC-DC converter. More specifically, the invention of this application is a bidirectional DC-DC converter that requires a wide variable voltage range among bidirectional AC-DC converters and bidirectional DC-DC converters that play a major role in energy saving. The present invention relates to a new snubber circuit for a bidirectional DC-DC converter and a bidirectional DC-DC converter, which are useful, excellent in regenerative efficiency, small, lightweight and economical.
[0002]
[Prior art]
FIG. 1 shows an example of a circuit configuration of a power regenerative secondary battery charging / discharging device in which a bidirectional DC-DC converter using a conventional AC snubber circuit and a bidirectional AC-DC converter are cascade-connected. Yes, the secondary battery can be charged and discharged with a small heat dissipation loss.
[0003]
In FIG. 1, (1) is a bidirectional AC-DC converter, (2) is a bidirectional DC-DC converter, (3) is a secondary battery, (4) is a switch control circuit for the bidirectional AC-DC converter, (5) is a switch control circuit for a bidirectional DC-DC converter, and (6) is a conventional bidirectional semiconductor switch circuit block whose characteristics should be improved by applying the invention of this application. In the bidirectional DC-DC converter (2), T is a high frequency transformer, (7) is a snubber circuit, and (8) is an LC filter.
[0004]
The arrow direction of the voltage / current of each part in FIG. 1 indicates each part when EB = E1-E2 where the battery voltage EB is lower than the DC output voltage E1 of the bidirectional AC-DC converter (1) during battery charging. When the battery voltage EB is higher than the DC output voltage E1 of the bidirectional AC-DC converter (1) EB = E1 + E2, the primary winding side DC current I′2 in FIG. It means that the direction of flows in reverse.
[0005]
That is, as shown in FIG.
When EB <E1, I2 = I1 + I′2 → I1 = I2−I′2
When EB> E1, I2 = I1-I′2 → I1 = I2 + I′2
When the battery is charged, the output current I1 of the step-up bidirectional AC-DC converter (1) is the output current I2 of the bidirectional DC-DC converter (2) flowing to the battery side when EB <E1. The primary winding side DC current I′2 corresponding to is subtracted, and conversely, when EB> E1, addition is performed.
[0006]
This means that when the terminal voltage of the secondary battery (3) is E1−E2, I1 = I2−I′2 and between E1 + E2 is I1 = I2 + I′2, and there is little power loss in a wide voltage adjustment range. It means that you can charge.
[0007]
Here, the driving method of the semiconductor switches S1 to S6 in the bidirectional DC-DC converter (2) will be outlined. First, S1 to S4 are known unidirectional semiconductor switches, and the driving waveforms thereof are shown in FIG. S1, S4 and S2, S3 are alternately turned on and off, while S5 and S6 constitute the respective bidirectional semiconductor switches, and the drive pulse phases of S1, S4 and S2, S3 are used as a reference. When the phase delay is 45 degrees, 90 degrees, and 135 degrees, the output voltage waveform before the LC filter (8) and the DC output voltage EB after smoothing are sequentially as shown in FIGS. 2 (a), 2 (b), and 2 (c).
[0008]
As apparent from FIGS. 2A, 2B, and 2C, the voltage ratio between E1 and E2 is determined by the turn ratio of the high-frequency transformer T, and the relative pulse phase is changed from approximately zero to 180 degrees. Thus, the battery terminal voltage EB can be controlled by the bidirectional DC-DC converter switch control circuit (5) until EB = E1 ± E2.
[0009]
The above description is about the charging direction of the secondary battery (3). When the secondary battery (3) is discharged, the secondary battery (3) becomes a power source, and the bidirectional AC-DC converter (1) is publicly known. The power is regenerated by converting into alternating current as an AC inverter by means of the above. The direction of the current flowing through the bidirectional DC-DC converter (2) at this time is such that the relationship between the voltage of the secondary battery (3) and the input DC voltage E1 of the inverter is either EB> E1 or EB <E1. In this case, the current directions are all reversed, the input / output voltage ratio of the bidirectional DC-DC converter (2) is not changed, and the operation waveforms of the respective parts are the same as those in FIG.
[0010]
This is realized by bidirectionally connecting the semiconductor switches S5 and S6. During discharge, the S5 and S6 sides perform inverter rectification, and the S1 to S4 sides perform synchronous rectification, so that the entire bidirectional DC-DC converter (2) is realized. Electric power energy is supplied from the battery side to the bidirectional AC-DC inverter (1) side.
[0011]
[Problems to be solved by the invention]
The above is the outline of the conventional bidirectional DC-DC converter (2) capable of converting the input / output voltage ratio over a wide range. From the trial production experience so far, the bidirectional semiconductor switch circuit block (6) in FIG. 1 is further improved. I know that there is a point to do.
[0012]
That is, the voltage amplitude shown between A and B in the bidirectional semiconductor switch circuit block (6) is derived from the voltage waveform between (A and B) shown in FIGS. 2 (a), (b) and (c). As can be seen, in order to generate a pulse waveform having a large amplitude at a frequency twice the modulation frequency of the bidirectional DC-DC converter (2), and smoothing it by the LC filter (8) (L7, C7), Actually, a spike voltage of EP = L7 × di / dt is generated mainly depending on the inductance of L7, the current value to be opened and closed, and the rising / falling speed thereof. This value increases in proportion to the DC output current value, and may reach 2 to 3 times the circuit voltage to be originally opened and closed.
[0013]
For this reason, the bidirectional semiconductor switch element used for S5 and S6 requires an expensive element having an extremely high breakdown voltage, which not only impairs the economy, but also the switching loss is proportional to the square of the absolute value of the spike pulse voltage. This increases the conversion efficiency of the bidirectional DC-DC converter (2).
[0014]
FIG. 3 shows a case where the bidirectional semiconductor switch S5 or S6 is turned off when the small capacity snubber circuit (7) (C6, R2) is inserted into the bidirectional DC-DC converter (2) as illustrated in FIG. An example of the voltage waveform generated at both ends is shown.
[0015]
If the capacity of the snubber capacitor C6 is increased to decrease the spike pulse and the damping resistor R2 is decreased, the amplitude of the spike pulse decreases and the switching loss of the transistor decreases, but the spike power consumed by the damping resistor R2 is This may exceed 10% of the output power of the bidirectional DC-DC converter (2), and this is the greatest cause of a decrease in conversion efficiency.
[0016]
In addition to this loss, because of Ldi / dt based on the leakage inductance caused by the windings N1, N2, and N3 of the high-frequency transformer T, a small spike is also applied to the unidirectional switches S1 to S4 on the primary winding side. Although a pulse is generated, this generated power is sufficiently small in view of the pulse power energy generated by L7, and a satisfactory countermeasure can be established by the conventional spike absorption circuit.
[0017]
Accordingly, the invention of this application solves the problems of the prior art in view of the circumstances as described above, and the electric power caused by the spike pulse generated in the LC filter (8) in the bidirectional DC-DC converter (2). An object is to provide a new snubber circuit for bidirectional DC-DC converter, which can reduce loss, has excellent regenerative efficiency, is small, lightweight and economical, and bidirectional DC-DC converter equipped with the snubber circuit. Yes.
[0018]
[Means for Solving the Problems]
In order to solve the above problems, the invention of this application includes, firstly , an input / output terminal , an input / output terminal, a one-way semiconductor switch circuit, a high-frequency transformer, a bidirectional semiconductor switch circuit, And an LC filter including a second smoothing capacitor and an inductor, one end of the input / output terminal and one end of the input / output terminal are connected by a first common line, and one of the one-way semiconductor switch circuits Is connected to the connection point on the input / output terminal side on the first common line, the other connection end is connected to the other end of the input / output terminal through a connection line, and the one-way semiconductor switch circuit is connected to the high-frequency transformer. Connected to the primary side, the secondary side of the high-frequency transformer is connected to the front side of the bidirectional semiconductor switch circuit, the connection point on the connection line from the other end of the input / output terminal and the neutral point of the secondary side of the high-frequency transformer by The other end of the input / output terminal is connected to the rear side of the bidirectional semiconductor switch circuit via the inductor of the LC filter by the second common line, and the first smoothing capacitor is connected to the bias line and the first line. is a connection between the common line, the second smoothing capacitor a snubber circuit for the bidirectional DC-DC converter having connected to each between the second common line and the bias line, bias Doubled using two diodes connected in series between the line and the first common line , and one capacitor connected between the connection point of the two diodes and the second common line is configured as a voltage rectifier circuit, it is inserted between the bi-directional semiconductor switch circuit subsequent and LC filter preceding the bidirectional DC-DC converter, and re-rectified spike power generated by the inductor of the LC filter, bi its power The present invention provides a snubber circuit for a bidirectional DC-DC converter, which is added to an input side or an output side of a bidirectional DC-DC converter. Second, a secondary battery is connected to the bidirectional DC-DC converter. A bidirectional DC-DC converter snubber circuit, wherein the power after re-rectification is applied to the input side when the secondary battery is charged and to the secondary battery side that is the output side when discharging. .
[0019]
Still further, the invention of this application is, thirdly , an input / output terminal , an input / output terminal, a one-way semiconductor switch circuit, a high-frequency transformer, a bidirectional semiconductor switch circuit, a first smoothing capacitor, An LC filter including a second smoothing capacitor and an inductor is provided, one end of the input / output terminal and one end of the input / output terminal are connected by a first common line, and one connection end of the one-way semiconductor switch circuit is the first Are connected to the connection point on the input / output terminal side of the common line, the other connection end is connected to the other end of the input / output terminal by a connection line, and the one-way semiconductor switch circuit is connected to the primary side of the high-frequency transformer. The secondary side of the high-frequency transformer is connected to the front side of the bidirectional semiconductor switch circuit, the connection point on the connection line from the other end of the input / output terminal and the neutral point of the secondary side of the high-frequency transformer are connected by a bias line, Out The other end of the power terminal is connected to the rear side of the bidirectional semiconductor switch circuit via the LC filter by the second common line, and the first smoothing capacitor is connected between the bias line and the first common line. The bidirectional DC-DC converter has a configuration in which the second smoothing capacitor is connected between the second common line and the bias line, and the snubber circuit is between the bias line and the first common line. Is configured as a voltage doubler rectifier circuit using two diodes connected in series to each other and one capacitor connected between the connection point of the two diodes and the second common line. is inserted between the DC-DC converter of the bidirectional semiconductor switch circuit subsequent and LC filter preceding, re rectified spike power generated by the inductor of the LC filter, the input side of the bidirectional DC-DC converter that power Or a bidirectional DC-DC converter characterized by being applied to the output side, and when a secondary battery is connected, the re-rectified power is discharged to the input side when the secondary battery is charged. A bidirectional DC-DC converter is provided which is sometimes added to a secondary battery side which is an output side.
[0020]
The invention of this application having these characteristics can reduce the spike power and increase the conversion efficiency of the bidirectional DC-DC converter while maintaining a wide range of input voltage ratio adjustment functions, thereby improving the regeneration efficiency. Smaller, lighter, and less expensive.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
4 (a) and 4 (b) exemplify circuit configurations when conventionally known RCD snubber circuits (7a) and (7b) are used as the snubber circuit (7) in FIG. These illustrate the snubber circuit (70) of the invention of this application and the bidirectional DC-DC converter (2) including the snubber circuit (70).
[0022]
The RCD snubber circuit (7a) in FIG. 4 (a) can reduce the snubber power to about 1/10 of the circuit constants of FIG. 1 by changing the C6 and R2 circuit constants. In this case, the snubber power loss is almost halved as compared with the snubber circuit (7) having only R2 and C6 in FIG. 1, but the overall efficiency improvement as the bidirectional DC-DC converter (2) is still sufficient. Absent.
[0023]
In the RCD snubber circuit (7b) in FIG. 4 (b), the degree of improvement in power loss is almost the same as that in FIG. 4 (a), and some economic effects are recognized, but this is not sufficient.
[0024]
Therefore, by adopting the invention of this application made with a completely new idea as illustrated in FIG. 5, a dramatic improvement in power loss can be realized compared to FIGS. 1 and 4 (a) (b). Can do.
[0025]
The snubber circuit (70) of the invention of this application is configured by using one snubber capacitor C6 and two diodes D1 and D2, and bidirectional semiconductor switches S5 and S6 of the bidirectional DC-DC converter (2). It is inserted between the rear stage and the front stage of the LC filter (8). More specifically, first, a diode half bridge (71) is constituted by the diodes D1 and D2, and this is used as an output terminal of the bidirectional AC-DC converter (1) or an input of the bidirectional DC-DC converter (2). Connect to the terminal. One end of the snubber capacitor C6 is connected between the bidirectional semiconductor switches S5 and S6 and the LC filter (8), and the other end is connected to a common connection terminal of the diodes D1 and D2 of the diode half bridge (71). .
[0026]
In this snubber circuit (70), the spike voltage generated at both ends of L7 of the LC filter (8) is led to the common connection terminal of the diodes D1 and D2 through the snubber capacitor C6, and the output is bidirectional AC-DC converter (1). In addition, the spike energy is regenerated to the input side during charging and to the battery side during discharging in addition to the output terminal or the input terminal of the bidirectional DC-DC converter (2). As a result, the spike power can be limited to the operating loss of the diodes D1 and D2 and the dielectric loss of the snubber capacitor C6, and the remaining energy can be utilized as part of the conversion energy.
[0027]
As is clear from FIG. 5, the snubber circuit (70) is configured as a voltage doubler rectifier circuit. However, the generated pulse in the positive and negative spike pulse generation circuit is used as energy to suppress the pulse and the DC voltage. And can be called a voltage doubler rectification snubber circuit. As a result of newly applying this voltage doubler rectifying snubber circuit to the bidirectional DC-DC converter (2), it was proved that it operates as a low loss / lossless snubber circuit.
[0028]
In addition, the voltage doubler rectifier circuit normally requires at least two capacitors and two diodes, but the bidirectional DC-DC converter of the invention of this application originally has a high frequency bypass capacitor added to the input / output circuit. Therefore, the net number of additional elements may be only the snubber capacitor C6 and the two diodes D1 and D2, and the maximum effect can be obtained with a small number of elements, which is economical. In an actual circuit, it is needless to say that a current control resistor, a choke coil, or the like may be added.
[0029]
Further, by appropriately selecting the value of the capacitor C6, the spike pulse amplitude shown in FIG. 3 can be reduced to about 1/3 to 1/4 of the spike amplitude when the snubber circuit (70) is not added. The breakdown voltage of the semiconductor switch elements S5 and S6 can be much lower than that of the prior art.
[0030]
Furthermore, it is possible to increase the direct current output current, which is useful for reducing the size, cost and efficiency of the bidirectional DC-DC converter (2) itself.
[0031]
【The invention's effect】
As described in detail above, the invention of this application allows not only adjustment of a wide range of input voltage ratios but also reduction of power loss caused by spike pulses, excellent regeneration efficiency, small size, and light weight. A new snubber circuit for bidirectional DC-DC converter and bidirectional DC-DC converter can be provided.
[Brief description of the drawings]
FIG. 1 shows a power regenerative secondary battery charging / discharging device in which a bidirectional DC-DC converter (2) using a conventional AC snubber circuit (7) and a bidirectional AC-DC converter (1) are connected in cascade. It is a circuit diagram showing an example of a circuit configuration.
2 is a diagram for explaining drive pulse waveforms of semiconductor switches S1 to S6 in the bidirectional DC-DC converter (2) of FIG. 1 and phase control waveforms before and after an LC filter (7). FIG.
3 is a diagram illustrating the magnitude relationship between spike pulses generated at both ends of bidirectional semiconductor switches S5 and S6 in the bidirectional DC-DC converter (2) of FIG. 1 and input / output currents.
FIGS. 4A and 4B are circuit diagrams illustrating another conventional technique as a snubber circuit (7) in the bidirectional DC-DC converter (2) of FIG. 1, respectively.
FIG. 5 is a circuit diagram illustrating a snubber circuit (70) of the invention of this application and a bidirectional DC-DC converter (2) including the snubber circuit (70).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bidirectional AC-DC converter 2 Bidirectional DC-DC converter 3 Secondary battery 4 Bidirectional AC-DC converter switch control circuit 5 Bidirectional DC-DC converter switch control circuit 6 Bidirectional semiconductor switch block 7 Snubber circuit 7a 7b RCD snubber circuit 70 Snubber circuit 71 Diode half bridge 8 LC filter C Capacitor L Inductor R Resistance T High frequency transformer S Semiconductor switch

Claims (4)

An LC filter including an input / output terminal, an input / output terminal, a unidirectional semiconductor switch circuit, a high-frequency transformer, a bidirectional semiconductor switch circuit, a first smoothing capacitor, a second smoothing capacitor, and an inductor is provided. And
One end of the input / output terminal and one end of the input / output terminal are connected by a first common line,
One connection end of the unidirectional semiconductor switch circuit is connected to a connection point on the input / output terminal side on the first common line, and the other connection end is connected to the other end of the input / output terminal by a connection line,
A unidirectional semiconductor switch circuit is connected to the primary side of the high-frequency transformer,
The secondary side of the high-frequency transformer is connected to the front side of the bidirectional semiconductor switch circuit,
A connection point on the connection line from the other end of the input / output terminal and a neutral point on the secondary side of the high-frequency transformer are connected by a bias line,
The other end of the input / output terminal is connected to the rear stage side of the bidirectional semiconductor switch circuit through the inductor of the LC filter by the second common line,
A first smoothing capacitor is connected between the bias line and the first common line;
A snubber circuit for a bidirectional DC-DC converter having a configuration in which a second smoothing capacitor is connected between a second common line and a bias line ,
Using two diodes connected in series between the bias line and the first common line , and one capacitor connected between the connection point of the two diodes and the second common line It is configured as a voltage doubler rectifier circuit, inserted between the bidirectional semiconductor switch circuit post stage of the bi-directional DC-DC converter and the pre-LC filter stage to re-rectify the spike power generated in the LC filter inductor, A snubber circuit for a bidirectional DC-DC converter, wherein the snubber circuit is added to an input side or an output side of the bidirectional DC-DC converter.   When a secondary battery is connected to the bidirectional DC-DC converter, the re-rectified power is applied to the input side when the secondary battery is charged, and to the secondary battery side that is the output side when discharging. A snubber circuit for a bidirectional DC-DC converter according to claim 1. An LC filter including an input / output terminal, an input / output terminal, a unidirectional semiconductor switch circuit, a high-frequency transformer, a bidirectional semiconductor switch circuit, a first smoothing capacitor, a second smoothing capacitor, and an inductor is provided. And
One end of the input / output terminal and one end of the input / output terminal are connected by a first common line,
One connection end of the unidirectional semiconductor switch circuit is connected to a connection point on the input / output terminal side on the first common line, and the other connection end is connected to the other end of the input / output terminal by a connection line,
A unidirectional semiconductor switch circuit is connected to the primary side of the high-frequency transformer,
The secondary side of the high-frequency transformer is connected to the front side of the bidirectional semiconductor switch circuit,
A connection point on the connection line from the other end of the input / output terminal and a neutral point on the secondary side of the high-frequency transformer are connected by a bias line,
The other end of the input / output terminal is connected to the rear stage side of the bidirectional semiconductor switch circuit via the LC filter by the second common line,
A first smoothing capacitor is connected between the bias line and the first common line;
A bidirectional DC-DC converter having a configuration in which a second smoothing capacitor is connected between a second common line and a bias line,
The snubber circuit includes two diodes connected in series between the bias line and the first common line , and one capacitor connected between the connection point of the two diodes and the second common line. Is used as a voltage doubler rectifier circuit, and is inserted between the bidirectional semiconductor switch circuit downstream of the bidirectional DC-DC converter and the LC filter upstream to rerectify the spike power generated by the inductor of the LC filter. The bidirectional DC-DC converter is characterized in that the electric power is applied to the input side or the output side of the bidirectional DC-DC converter.   The recharged power is applied to the input side when the secondary battery is charged and to the secondary battery side that is the output side when discharging, when a secondary battery is connected. Bidirectional DC-DC converter.

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