JPS61262087A - Power supply - Google Patents

Abstract

PURPOSE:To stabilize the operation by suppling the output of a power converter through a transformer to a load having a reverse blocking characteristic, and suppressing a resonance voltage generated by the floating capacity of the secondary winding of the transformer by reverse bias current bypass means. CONSTITUTION:The power of a commercial power source 1 is fed to a DC power source 18, and supplied to an inverter 19. The inverter 19 energizes a step-up transformer 6 and supplies a high voltage power to a magnetron 17. The first high voltage capacitor connected in parallel between the anode of a magnetron 17 and one cathode terminal and the second high voltage capacitor 22 connected in parallel between the anode of the magnetron 17 and the other terminal form reverse bias current bypass means, and the magnetron 17 suppresses a resonance voltage by the floating capacity of the secondary winding 11 of the transformer 6 generated when the magnetron 17 is reversely biased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is used in high-frequency heaters and the like, and after converting power from a power source obtained from a commercial power source or the like using a power converter, the output of the power converter is This invention relates to a power supply device configured to further convert the power using a transformer and supply the converted power to a load having reverse blocking characteristics.

2. Description of the Related Art In general, various configurations of power supply devices of this type have been proposed in order to reduce the size, weight, or cost of the power transformer.

FIG. 9 is a circuit diagram of a conventional power supply device.

In the figure, the power from commercial power supply 1 is connected to diode bridge 2.
A unidirectional power source is formed. Note 3
4 is an inductor, and 4 is a capacitor, which serves as a filter for the high frequency switching operation of the inverter.

The inverter includes a resonant capacitor 5, a step-up transformer 6, a transistor, a diode 8, and a drive circuit 9. The transistor 7 performs a switching operation with a predetermined period and duty (ie, on/off time ratio) by a base current supplied from the drive circuit 9. As a result, the primary winding 1o of the step-up transformer 6 is
) Collector electrician like. and the current I centered on the diode current d. d flows, and a high frequency current as shown in FIG. 10 flows through the negative winding 10. Therefore, high frequency high voltage power and high frequency low voltage power are generated in the secondary winding 11 and the tertiary winding 12, respectively. This high frequency low voltage power is supplied between the cathode terminals of the magnetron 17 via a capacitor 13.14 and a choke coil 15.16.
On the other hand, high frequency high voltage power is supplied between the anode and cathode as shown in the figure. As shown in the specification and drawings of U.S. Pat. No. 4,318,185, currents as shown in FIGS. 10(C) and 10(d) flow through the capacitor 5 and magnetron 17, and the magnetron 17 oscillates and This allows heating.

With this configuration, transistor 7 is operated at 20 KHz-1
When operated at a frequency of about 0.00KHz, the weight of the step-up transformer is reduced compared to when the voltage is stepped up at the commercial power frequency.
It has the advantage that the size can be reduced from a few minutes to an hour's worth, making it possible to downsize and reduce the cost of the power supply section.

In particular, the power supply device shown in the specification and drawings of U.S. Pat. By configuring the circuit, the magnetron 17 can be driven without using a high-voltage diode normally used for high-voltage rectification, and a power supply device as shown in FIG. 9 can be realized.

Therefore, there is no need for very expensive, large, and high-voltage high-frequency diodes, which further reduces the size of power supply equipment.
Lighter weight and lower costs were realized.

Problems to be Solved by the Invention However, such conventional power supply devices have the following drawbacks. That is, the anode current IA of the magnetron 17 had to have a current waveform with a large peak value, as shown in FIG. 10(d). This is because the converter is of the so-called flyback type, in which the energy stored in the primary winding 10 while the transistor is conducting is released during the non-conducting period.

Further, since current flows through the magnetron only when the transistor 7 is non-conductive, the peak value of the anode current IA has to be even larger in order to obtain a predetermined average current.

For this reason, the emission capacity of the magnetron's cathode had to be increased, making the magnetron expensive. In addition, if the rising peak value of the anode current A is large, the so-called moding phenomenon tends to occur due to the emission capacity margin of the cathode, which may significantly shorten the life of the magnetron and increase the amount of radio wave leakage. However, there were disadvantages such as limiting the cost reduction of the power supply device and reducing its reliability.

On the other hand, the frequency converter was of the flyback type as mentioned above. For example, in the literature, E., Janssonr Co.
nverter circuits for 5w1t
ched modepower 5uplies J
Electronics application
sbulletin, Vol, 32. No, 3. N, V
, Ph1lips (1973), this flyback converter has the smallest number of parts and is therefore widely used in high-voltage power supplies for televisions and the like.

However, when dealing with high power such as energy equipment, this feature is drastically reduced, and as described on pages 86 to 87 of the above document, for example, 200
In order to obtain an output of 200 W, it is necessary to add various components, and it is practically difficult to realize a flyback converter that can obtain an output of about 200 W or more, and it must be complicated and expensive. . In particular, the leakage inductance of the transformer should desirably be zero, but this leakage inductance is actually difficult to reduce to zero and has a serious effect on the transistor. This effect becomes more serious as the amount of power handled increases, so flyback type converters are not suitable for power supply devices that handle large amounts of power.

Furthermore, when AC output is supplied to a load with reverse blocking characteristics such as a magnetron, if the polarity voltage causes the load to be reverse biased, a resonant voltage will be generated between the stray capacitance of the secondary winding and the inductance of the transformer. This has the disadvantage of generating abnormally high pressure, and in order to suppress this,
This requires the winding of the transformer to have an extremely complicated and expensive configuration, which is extremely difficult in practice.

The present invention eliminates the drawbacks of the conventional power supply device, and is applicable to a large power load, and improves reliability and lowers the price.

Means for Solving the Problems The technical means of the present invention for solving the above problems consists of a power source obtained from a commercial power source, a power converter that generates high-frequency power, a load having reverse blocking characteristics, and this load. A power supply device configured by a transformer that supplies the output of a power converter to the load, and a reverse bias current bypass means that suppresses or eliminates a resonant voltage due to stray capacitance of the transformer secondary winding that occurs when the load is reverse biased. It is.

Function: The power supply device of the present invention has a normal bias current bypass means that suppresses or eliminates the resonance voltage generated by the stray capacitance of the secondary winding of the transformer, so it can achieve reverse blocking characteristics even if it is not a flyback type converter. Accordingly, it is possible to energize a load without using a rectifying means, and it is also possible to suppress or eliminate abnormal high voltage caused by a resonant voltage. In other words, since the reverse bias current can be bypassed when the load is reverse biased, the power converter can operate stably even if it is not a flyback converter, and it also prevents abnormally high voltage from occurring. It has the following.

EXAMPLE Hereinafter, a high-frequency heating device employing an example of the power supply device of the present invention will be described together with its mouth surface.

Reference numeral 18 denotes a DC power supply, which is composed of a diode bridge 2 for rectifying the commercial power supply 1, an inductor 3, and a capacitor 4, and has the same effect as the conventional example shown in FIG.

Reference numeral 19 denotes an inverter consisting of a resonant capacitor 5, a transistor 7, and a diode 8, which functions in the same way as the conventional example shown in FIG. The inverter 19 is driven by the drive circuit 9 connected to the commercial power source 1. Electric power from the commercial power source 1 is sent to the DC power source 18 and supplied to the inverter 19. The inverter 19 energizes the step-up transformer 6 and the magnetron 17
It supplies high-voltage power to the The currents flowing through the transistor 7, the primary winding 10 of the step-up transformer 6, the resonant capacitor 5, and the magnetron 17 are shown in FIG. 2(a).
, Φ), (C) and (d). That is, the primary winding 10 of the step-up transformer 6 has a collector current wire as shown in FIG. 2a. and the current I centered on the diode current d. d flows. A high frequency current IL as shown in FIG. 2 flows through the negative winding 10.

The resonant capacitor 5 has a current IC1 as shown in Fig. 2 (C).
An anode current A flows through the magnetron 1 as shown in FIG. 2(d). Anode voltage VA of magnetron 17
K becomes as shown in FIG. 2(e). This is step-up transformer 6
The polarity of the primary winding 1o and the secondary winding 11 is as shown in the figure, the step-up transformer 6 is a leakage type transformer, and the first high-voltage capacitor 21 is
This is because they are connected in parallel between the anode and one cathode terminal of the magnetron 17. 12 is the tertiary winding of the step-up transformer 6, and the choke coil 15.1
6 to the cathode of the magnetron 17. A second high voltage capacitor 22 is connected between the anode and the other cathode terminals of the magnetron 17. 2o
is a capacitor connected between choke coils 15 and 16.

FIG. 3 is a circuit diagram of a power supply device illustrating the main parts of the embodiment of the present invention shown in FIG. 1, and the same parts as in FIG. 1 are given the same reference numerals and detailed explanations are omitted.

In FIG. 3, the current XL flowing through the primary winding 10 of the step-up transformer 6, the current ICH1 of the high-voltage capacitor 23, and the anode current IA are determined by the polarities of the primary winding 10 and the secondary winding 11 of the step-up transformer 6 as shown in the figure. Therefore, the current flows as shown by the arrow in the figure, and current flows through the magnetron 17 when the transistor 7 is on.

Figure 4 is the primary side equivalent circuit diagram of the circuit in Figure 3.
is the self-inductance of the -order winding 10, and K is the coupling coefficient between the primary and secondary windings. The magnetron 17 can be replaced with a series circuit of a resistor RM, a diode DM, and a zener diode ZDM, and a high-voltage capacitor CH is connected in parallel to this series circuit as a reverse bias current bypass means. As shown in FIG. 5, the characteristics of the magnetron 17 are extremely nonlinear, and when reverse biased, the secondary side 11 of the step-up transformer 6 becomes open. Therefore, when there is no high voltage capacitor 23,
Unbalanced magnetization of the step-up transformer 6 occurs, causing the inconvenience that the inverter 19 cannot operate stably. In addition, in an actual step-up transformer, there is a slight leakage inductance (1-K) Ll as shown in FIG. Resonant voltage may occur and adversely affect the inverter 19 and magnetron 17,
This results in the inconvenience of requiring high pressure resistance.

However, since the reverse bias current is bypassed by this high voltage capacitor 23, biased magnetization of the step-up transformer 6 is prevented, and it becomes possible to use a converter other than the flyback type, and the load has reverse blocking characteristics. too,
A power converter suitable for high power can be realized without using a diode.

The high voltage capacitor CM has a secondary winding @1 due to stray capacitance when the magnetron 17 is reverse biased.
This serves to prevent abnormally high voltages as shown in FIG. 8, which occur in the circuit 1, and to suppress the reverse voltage to a relatively low value as shown in FIG. 2(e). Therefore, the step-up transformer 6 and the magnetron 17 need only have relatively low breakdown voltages, so they can be manufactured at low cost.

Furthermore, by appropriately selecting the capacitance of the high-voltage capacitor CH, the high voltage when the magnetron is reverse biased can be suppressed to a low value.

As shown in FIG. 7, the anode current I of the magnetron 17
There is a phase difference of 9o0 between A and the current ICH of the high voltage capacitor CH. Therefore, the °C construction L flowing to the step-up transformer 6
' is the combined current of these when the magnetron 17 is forward-biased, and is the current rc of the first high-voltage capacitor CH when it is reverse-biased.

is equal to FIG. 8 is a diagram for explaining this in terms of a model. In the figure, the current L' corresponding to the current flowing through the secondary winding @11 of the step-up transformer 6 changes from ◯ to ILP (considering only the insulation value) when the voltage has both positive and negative polarities. This is the case when the step-up transformer 6 is considered to be an ideal constant current source.

Consider the case where the high voltage capacitor CH has a certain capacitance value. In other words, when the magnetron 17 is forward biased, the operating point is 0.
From the current ICH shown by the solid line in the figure to VAK○,
When the anode current IA starts flowing, I CH+ I 8
Go along the line until L'=ILP and return to 0. Next, when the magnetron 17 is reverse biased, the operating point goes from 0 to LP on the solid line "CH" in the figure and returns to 0. Therefore, if the capacitance value of magnetron CH is smaller, then , the flowing current is as shown by the dashed line.Then, the voltage VAK of the magnetron 17 during reverse bias is
is VAK=VAK2)VAKl, and the larger the capacitance value of the high-voltage capacitor CH, the smaller the magnetron voltage VAK can be. However, if the capacitance value of the high voltage capacitor CH is too large, the inverter 1
A so-called beat phenomenon occurs between the inverter and the resonant capacitor 5 of No. 9, and the operation of the inverter becomes unstable. Therefore, the primary side converted capacitance value of the high voltage capacitor CH is CHl
, when the capacitance value of the resonant capacitor 6 is 06, it is necessary that C5 and CHl are not close values. and C5
Since stable operation of the inverter 19 cannot be expected with <CHl, C5)CHl is required.

As described above, the high-voltage capacitor CH has extremely important functions and effects, and is very useful in realizing a high-frequency heating device that is inexpensive, highly reliable, and can guarantee stable performance.

FIG. 1 will be explained again. The high voltage capacitor 23 in FIG. 3 is also used as the filter capacitor of the magnetron 17 in FIG. 1, and is the first and second high voltage capacitors 21 and 22. A capacitor 20 is provided between the cathode terminals of the magnetron 17,
In addition, the choke coils 15 and 16 are bifilar-wound on the same core. Therefore, both high voltage capacitors 2
High voltage capacitor 2 in Figure 3 with a combined capacitance of 1.22
It fulfills the function of 3. By doing this, the voltage can be supplied between the cathode terminals, so when driving the magnetron 17 with a high frequency voltage, the potential difference between both cathode terminals can be reduced and stable oscillation of the magnetron 1 can be promoted. It has the effect of suppressing the occurrence of. Furthermore, since the high-frequency current can be shunted to the high-voltage capacitors 21, 22, heat generation in the high-voltage capacitors 21, 22 can be suppressed, and lower costs and higher reliability can be realized. Furthermore, by configuring the high voltage capacitors 21 and 22 as integrated feedthrough capacitors, they can also be used as the capacitor 20, making it possible to make the high voltage capacitor group more compact and lower in price.

Effects of the Invention As described above, the present invention has a configuration in which the output of a power converter is supplied to a load having reverse blocking characteristics via a transformer, and the resonant voltage generated by the stray capacitance of the secondary winding of this transformer is suppressed. Alternatively, since a reverse bias current bypass means is provided to eliminate the reverse bias current, the following effects can be obtained.

(1) Even if the load has reverse blocking characteristics, biased magnetization of the transformer can be prevented without using a diode on the secondary side of the transformer, and a power converter of a type other than the flyback type can be used. Therefore, it is possible to provide a power supply device suitable for large power loads.

(2) In addition, it is possible to suppress or eliminate the spike voltage that occurs when the load is reverse biased and the resonance voltage caused by stray capacitance, and prevent abnormally high voltage from being applied to the power converter, transformer, or load, and at a low cost. A power supply device with excellent reliability and safety can be provided.

(3) Furthermore, when the load is a magnetron or the like, it is possible to realize a transformer that suppresses the peak value of the anode current to a small value.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a high-frequency heating device that employs an embodiment of the power supply device of the present invention, and Figures 2 (a), (b), (c), and
)(e) is an operating voltage and current waveform diagram of the same circuit, Fig. 3 is a circuit diagram for explaining the main parts of the circuit, Fig. 4 is an equivalent circuit diagram of the main part circuit, and Fig. 6 is the operating voltage of the magnetron. Current characteristics diagram, Figure 6 is an abnormal voltage waveform diagram of the magnetron, Figure 7 is a current vector diagram of the magnetron and high-voltage capacitor, Figure 8 is an explanation diagram of the action of the high-voltage capacitor, and Figure 9 is the circuit of a conventional power supply device. Figure 1o (a), (b), (C), and (d) are the operating current waveform diagrams in Figure 9. , 18...DC power supply L21, 22...
Reverse bias current bypass means (21... Chiku 1 pressure capacitor, 22... 2nd high voltage capacitor)
, 17... Load having reverse blocking characteristics (magnetron), 19... Power converter (inverter). Name of agent: Patent attorney Toshio Nakao and one other person
-#7111 source f-11ηzoox Y Lance IQ-----Shishakuhyojuku If----=next t7--71゛familynsofδ-11pendenen屹Ahizo Autumn f9---Inver〃 21.22---Ya 11 years old, Takatoko, f, 7 Fig. 2

Claims (2)

[Claims] (1) The power converter includes a power source obtained from a commercial power source, a load having reverse blocking characteristics, and a transformer that supplies the output of the power converter to the load, and the power converter includes at least one semiconductor switch and its driver. The power converter is configured as a power converter for generating high-frequency power, and includes a reverse bias current bypass means for suppressing or eliminating resonant voltage due to stray capacitance of the secondary winding of the transformer that occurs when the load is reverse biased. Power supply device. (2) The power supply device according to claim 1, wherein the transformer has a polarity such that the load is biased in the forward direction when the semiconductor switch is turned on.