JPS63253862A - Resonance type power source - Google Patents

Abstract

PURPOSE:To prevent the generation of a surge voltage, by a method wherein a main switching element is turned off when a reactor current for resonance is conducted into energy regenerating direction. CONSTITUTION:A resonance type power source is constituted of a shunt resistor 2 for detecting a reactor current, a reactor 3 for resonance, a capacitor 4, a main switching element 6-2, a diode 5 connected in antiparallel to the above- described parts, a load circuit 7, a direction detecting circuit 8 for the reactor current, a stop signal generating circuit 9, a driving circuit 10 and a condition holding circuit 30. An oscillation stopping means 10 is constituted of said detecting circuit 8, the stop signal generating circuit 9 and the condition holding circuit 30. According to this constitution, the direction of a current, conducted through the resonance reactor 3, is detected and the main switching element 6-2 is turned off under a condition that the current is regenerated in a DC input power source 1 to stop the oscillation whereby the current is conducted continuously through said diode 5 and the generation of a surge voltage may be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resonant power supply, and particularly to a technique for preventing excessive voltage generated in a main switch element when stopping the operation of a power supply.

[Conventional technology]

Switching systems are often used in stabilized DC power supplies that input commercial power and output a stabilized DC voltage, and inverter circuits that generate high-frequency AC output. However, the presence of switching loss and the generation of switching noise caused by the overlap of current and voltage during turn-on and turn-off of a switch element have hindered the miniaturization of power supplies by increasing the switching frequency. In contrast, an LC resonant circuit is added to the main circuit to make the current and voltage waveforms sinusoidal, and the overlapping period of voltage and current is reduced to reduce switching loss and harmonic components of noise. Shaped power supplies are promising for higher frequency and smaller size.

As an example of a resonant power source, there is a resonant inverter having a push-pull configuration as a main circuit as seen in Japanese Patent Laid-Open No. 48-38429. In this method, a resonant reactor is inserted in series with the DC input power supply, so there is always two
At least one of the two main switch elements must be conductive.

Therefore, when emergency oscillation is stopped due to external remote on/off operation or internal protection circuit activation, both main switch elements are turned off at the same time, causing a large surge due to the excitation energy accumulated in the resonant reactor. A voltage is generated, which is applied to the main switch element,
There is a risk of destroying the element. Therefore, such a resonant power source cannot be controlled as described above, and has been used only for limited purposes.

[Problem that the invention seeks to solve]

In a system in which a resonant reactor is inserted in series between the input power supply and the main switch element, such as the resonant power supply with the push-pull configuration shown above in the main circuit, it is difficult to activate the protection circuit or use the remote on/off terminal. When the oscillation is forcibly stopped by a signal from the main switching element, an excessive voltage is generated across the main switching element due to the excitation energy of the resonant reactor, and there is a risk of destroying the element.

The first object of the present invention is to forcibly stop the oscillation of a resonant power source that has a resonant reactor in series with the input power source and the main switch element by destroying the main switch element by a surge voltage caused by the oscillation energy of the resonant reactor. The goal is to do it safely without any problems.

A second object of the present invention is to realize a low-loss, low-noise resonant power supply that can control output over a wide range without providing a switching element for opening and closing a power path on the secondary side.

[Means for solving problems]

A first invention for achieving the first object includes a resonant circuit including a resonant reactor and a resonant capacitor, a DC input power supply connected to this resonant circuit, and a supply of DC input power from the DC input power supply to the resonant reactor. A resonant power supply comprising: a main switch element that intermittents a current flowing through the main switch element; a diode connected in antiparallel to the main switch element; and a load circuit, the resonant power supply configured to supply power from the resonant circuit to the load circuit. , comprising current direction detection means for detecting the direction of the current flowing through the resonant reactor, and turns off the main switch element to stop the oscillation operation when the current flows in a direction that regenerates energy in the DC input power source. It is characterized by the provision of oscillation stopping means.

A second invention for achieving the second object includes, in addition to the configuration of the first invention, output control for controlling the operation of the oscillation stop means at a variable frequency lower than the oscillation frequency of the power source. It is characterized by having a means.

[Effect]

When power is being supplied to the load by the resonant current flowing through the resonant reactor and resonant capacitor, an attempt is made to turn off the main switch element to stop oscillation while current is flowing from the DC input power source to the resonant reactor. Then, the energy stored in the resonant reactor generates a surge voltage.

However, the first invention detects the direction of the current flowing through the resonant reactor and turns off the main switch element to stop oscillation while the current flowing through the resonant reactor is generating energy back to the DC input power source. Therefore, this current continues to flow through the diode anti-parallel to the main switch element, so no surge voltage is generated.

In the second invention, the output can be controlled by repeating the oscillation and stopping.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1 to 12 relate to the invention that achieves the first objective, and FIGS. 13 to 16 relate to the invention that achieves the second objective.

FIG. 1 shows an embodiment of the first invention. 1 is a DC input power supply, 2 is a shunt resistor that detects the reactor current, 3 is a resonance reactor, and 4 is a resonance reactor 3.
5 is a diode connected in anti-parallel with the main switch element 6-2, 7 is a load circuit, and 8 is a capacitor that determines the direction of the accelerating current iL from the voltage generated across the shunt resistor 2. A current direction detection circuit for determining a current direction, 9 a stop signal generation circuit for generating a signal to turn off the main switch element 6-1, 6-2 in response to a signal from the iL direction detection circuit 8, 10-1. 10-2 is a drive circuit for the main switch elements 6-1, 6-2, 30 is a state holding circuit, and SW is a switch element that is turned on by an oscillation stop command.

First, when the main switch element 6-1 is turned on, the current flowing through the solid line path in the figure increases linearly, and after a predetermined time elapses, the main switch element 6-1 is turned off, thereby changing the initial value of the current iL. i. is set. When the main switch element 6-1 is turned off and the other main switch element 6-2 is turned on at the same time, the current that previously flowed along the path shown by the solid line in the figure now flows through the path shown by the broken line in the figure. From this point on, the current flowing through the circuit has an initial value iLo and a resonant waveform determined by the constants of the resonant reactor 3, the resonant capacitor 4, and the load circuit 7. After a certain period of time has elapsed, the current direction of the current iL is reversed from the direction of charging the resonance capacitor 4 to the direction of discharging it, and the current iL starts flowing along the path shown by the dashed line in the figure.

Let us now consider the timing at which the main switch element 6-2 is turned off in order to stop oscillation when an oscillation stop command is input from the outside. When the main switch element 6-2 is turned off while the reactor current is flowing along the path indicated by the broken line in the figure, the reactor current iL is changed to the main switch element 6-2.
The change in current diL/dt depends on the turn-off speed of
, and L・(d
A surge voltage of iL/dt) is generated with the black circle in the figure as negative polarity (L is the inductance of the resonant reactor 3).

This surge voltage is added to the DC input power supply voltage E,
It is applied to both ends of the main switch element 6-2, and when the applied voltage becomes higher than the rated voltage of the main switch element 6-2, the element is destroyed.

Conversely, if the main switch 6-2 is turned off while the current is flowing as indicated by the dashed line in the figure, there is no change in the reactor current due to the main switch element 6-2, so there is a surge voltage across the resonance reactor 3. will not occur, and the device will not be destroyed.

In the present invention, the shunt resistor 2 and the current direction detection circuit 8 are provided in order to detect the direction of the accelerator current iL when the oscillation stop means 19 is activated by the oscillation stop command, so that the reactor current iL is in the negative direction (direct current input Based on the detection signal, the stop signal generation circuit 9 generates a turn-off signal, and the drive circuit 10 turns off the main switch element 6.
-2 is turned off and the state holding circuit 30 maintains the off state to stop oscillation.

Thereby, the main switch element 6-2 can be reliably turned off while the reactor current i is flowing as indicated by the dashed line in the figure, and destruction of the main switch element 6-2 and the diode 5 can be prevented.

FIG. 2 shows another embodiment of the invention. In FIG. 2, the resonance capacitor 4 is connected in parallel to the load circuit 7. The circuit operates exactly the same as the circuit shown in FIG. 1, except that the power is supplied to the load circuit 7 in the form of voltage.
The same effect as the embodiment shown in the figure can be obtained.

3 and 4 show an example of the configuration of the load circuit 7. FIG.

In FIG. 3, a main transformer has a primary winding 11 and a secondary winding I2, a rectifier circuit 13 and a smoothing circuit 14 are connected to the secondary winding 12, and a DC voltage is applied to a load resistor 15. It is constituted by a first output circuit. Also, in Figure 4,
A secondary side control means 16 is provided on the secondary side of the main transformer to stabilize the output voltage on the secondary side, such as a magnetic amplifier, a conduction time ratio control circuit, a chip control, a series dropper control, etc. It is configured by a second output circuit.

The effects of the present invention do not change even if the circuit shown in FIG. 3 or 4 is used as the load circuit of the embodiment shown in FIG. 1 or 2.

FIG. 5 shows another example of the configuration of the oscillation stopping means 19. The AND gate 17 obtains the logical product of the signal indicating that the direction of the reactor current iL is the direction in which energy is regenerated in the DC input power source 1 and the oscillation stop command, turns off the main switch element 6, and maintains that state. This causes the oscillation to stop.

FIG. 6 shows yet another example of the configuration of the oscillation stopping means 19. Similarly to FIG. 5, the AND gate 17 obtains the logical product of the i-O signal and the oscillation stop command, turns off the main switch element 6, and inputs the oscillation stop command to the secondary side control means 16. It is configured to stop or reduce the supply of power to the output controlled by the secondary side control means 16. The configurations shown in FIGS. 5 and 6 also provide the same effects as those shown in FIGS. 1 and 2.

FIG. 7 shows a -order circuit of a resonant power supply having a main circuit configuration different from that of FIGS. 1 and 2 to which the present invention is effectively applied. One end of the series circuit of the DC input power supply l and the resonant reactor 3 is connected to the midpoint of the transformer primary winding 11, and a main switch element 6- is connected between the other end and both ends of the main transformer primary winding 11. Connect 1 (5) and 6-2 (5),
Furthermore, a resonance capacitor 4 is connected between both ends of the main transformer primary winding 11. In this circuit as well, when both main switching elements 6-1 and 6-2 are turned off while the reactor current i is flowing in the positive direction, a surge voltage is generated across the resonant reactor 3. Therefore,
Application of the present invention becomes effective when oscillation is stopped. In particular, in such a circuit configuration, the reactor current is the sum of the primary side conversion value of the load current and the resonance current, so the embodiment shown in Fig. 6 reduces the load current and makes i, - negative. It is necessary to ensure that there is a period of

Figure 8 shows a resonant power supply with the main circuit configuration shown in Figure 7.
An example of implementing the present invention will be shown. Note that only the negative side circuit is listed here. In this embodiment, a tertiary winding 18 is provided in the main transformer and connected to the heath terminal of the main switch element 6-1, 6-2 to provide positive feedback, and the starting circuit 20 is It is configured to perform self-sustained oscillation.

When the signal detecting iL<0 and the oscillation stop command are input at the same time, the switch means 211.21-2 becomes conductive, turns off the main switch element 6-1.6-2, and safely stops oscillation. be able to.

9 to 11 show the oscillation stop means 19 shown in FIG.
, an embodiment in which the output is stopped or reduced by the secondary side control means 16 is shown. here,
In both cases, only the secondary circuit is shown.

In FIG. 9, the secondary side control means 16 is a magnetic amplifier whose secondary side is connected to the half-wave rectifier circuit I3. Normally, the saturable reactor 31 is reset to the required amount of magnetic flux by the control current i for controlling the output voltage to be constant, but when an oscillation stop command is input,
The saturable reactor 31 is also reset by the current i3.

i, the magnetic flux reset ffi is caused by the transformer secondary winding yA12
If you set the magnetic flux reset amount to be greater than the magnetic flux change amount corresponding to the voltage-time integral value during the period in which the voltage with the black circle as positive is generated, power will not be transmitted to the output terminal, and this will occur. Since there is a period in which iL reliably flows in the negative direction, the oscillation stop means 16 in FIG.
can be realized.

In FIG. 10, the secondary side control means 1 is controlled by a magnetic amplifier 31-1.
This is an example in which 6 is configured. Saturable reactor 31-1.3
The control circuit for controlling the magnetic flux reset amount in step 2 can be configured exactly the same as that shown in FIG. 9, and its operation is also the same as that shown in FIG.

In FIG. 11, a duty ratio control circuit using semiconductor switches 35-1, 35-2 is used as the secondary side control means 16. When the oscillation stop command is input, the semiconductor switch 3
5-1 and 35-2 are both turned off and energy transmission to the output side is stopped. This configuration also provides the same effects as the embodiments shown in FIGS. 9 and 10.

FIG. 12 shows an embodiment in which the present invention is applied to a resonant power source having a plurality of outputs. Here, secondary side control means 16-1
．． 16-2 has two outputs, and the first output circuit having a relatively small capacity and having no secondary side control means has one output. Also, reactor current i
The direction of L is detected by a current transformer 22.

When the oscillation stop command is input, the load current of the second output circuit is stopped by the two secondary side control means 16-1 and 16-2, so that the load current of the reactor/lumi flow is transferred to the primary side. Since the converted current decreases, design the primary side converted value of the load current in the first output circuit without secondary side control means to be smaller than the alternating current portion of the reactor current.・Produces a period in which the Lumi flow iL is negative. At the moment when the reactor current iL becomes negative, the stop signal native circuit 9 sends a stop signal to the drive circuit 10-1, 10-2, turns both main switch elements 6-1, 6-2 into the OFF state, and maintains the state. The circuit 30 continues the stop signal to stop the circuit from oscillating.

Since this operation is performed in a state where i<Q, oscillation can be stopped without fear of destroying the main switch elements 6-1, 6-2. It should be noted that if the reactor is always operating in such a way that there is a period in which the reactor current is in the negative direction, it is clear from the previous explanation that there is no need to reduce or stop the 9-load current using the oscillation stop command. be.

FIG. 13 shows an embodiment of the second invention that achieves the second object. In this embodiment, the load circuit of the embodiment shown in FIG. 1 is configured with a main transformer and a load resistor, and the oscillation stop command is issued at a frequency f2 lower than the on/off frequency r of the main switch element.
The pulse train is input as follows. moreover,
A NOT gate 33 and a reset circuit 3 are used to reset the state holding circuit 30 every cycle of the oscillation stop command pulse.
2 was established.

Since the operation of the main circuit is the same as that shown in FIG. 1, the operation related to the present invention will be explained using FIG. 14.

1=10, an oscillation stop command is input, and when the current iL changes from positive to zero, the main switch 6-2 is turned off. Point 1 when the reactor current iL goes from negative to zero after a resonance half period in which the reactor current iL is negative has passed
=1. The reactor current iL is stopped at , and the power supply to the load resistor 15 is stopped as the oscillation is stopped. after that,
When the oscillation stop command is canceled at 1=12, the state holding circuit 30 becomes operational due to the signal from the reset circuit 32, and the circuit starts oscillating again. This operation is repeated every cycle T. Here, if the oscillation period T3 is changed, the period for supplying current to the load resistor 15 changes, so
The power supplied to the load resistor 15 can be changed.

Furthermore, it is also possible to control T so as to keep the power supplied to the load constant.

FIG. 15 shows another embodiment in which the output voltage is controlled according to the present invention. The primary circuit of the transformer is the same as that shown in the embodiment of FIG.

An output detection circuit 24 detects the output voltage, and a modulation pulse generation circuit 25 generates a pulse modulated by the deviation from the reference voltage. The output of the modulated pulse generation circuit 25 is input to the stop command generation circuit 26 to generate an oscillation stop command pulse train modulated according to the output voltage. When the oscillation stop command is output from the stop command generation circuit 26, the switch 23 is opened by the switch driving means 34, the current supplied from the transformer to the load is stopped, and the reactor current i detected by the current transformer 22 is When , becomes negative, the circuit stops oscillating. When the oscillation stop command is released, the oscillation stop state is reset by the reset circuit 32, the switch 23 becomes conductive, and the circuit resumes oscillation by the startup circuit 2°, and power is supplied from the transformer to the load. The circuit causes oscillation
Since the period during which the output voltage continues is set according to the output voltage, it is possible to control the output voltage to be constant. In other words, when the load current increases and the output voltage attempts to decrease, the oscillation period corresponding to T□ in Fig. 14 becomes longer.
Conversely, when the load current decreases and the output voltage attempts to increase, the oscillation period becomes shorter. In this embodiment, it goes without saying that the switch 23 and the switch driving means 34 are unnecessary if the reactor is operated with a period in which the reactor current is always negative.

Figure 16 shows secondary side control means ■6 using a magnetic amplifier to stop the power supply from the transformer on the secondary side in Figure 15.
This is an example in which the process is carried out using the following.

The operation is similar to the embodiments shown in FIGS. 9 and 10, and the same effects as in the embodiment shown in FIG. 15 can be obtained.

〔Effect of the invention〕

As described above, according to the first invention, in a resonant power supply having a resonant reactor in series with the DC input power supply and the main switch element, the resonant reactor current flows in a direction that regenerates energy in the DC input power supply. By turning off the main switch element when the main switch element is turned off, generation of surge voltage due to excitation energy of the resonant reactor can be prevented, and oscillation can be safely stopped without destroying the main switch element. Furthermore, in the second invention, output control is possible over a wide input/output range, and a resonant power supply with low loss and low noise can be realized.

[Brief explanation of drawings]

1 to 6, FIG. 8 to 13, FIG. 15, and FIG. 16 are circuit diagrams showing each embodiment of the present invention, and FIG. 7 is a reference circuit for explaining the embodiment. 14 are current waveform diagrams for explaining the embodiment. ■...DC input power supply, 2...Shunt resistor, 3...Resonance reactor, 4...
・Resonance capacitor, 5, 5 (5-1, 5-2)
...Diode, 6 (6-1, 6-2
)... Main switch element, 7... Load circuit, 8... Current direction detection circuit, 9...
Stop signal generation circuit, 10 (10-1, 1O-2)・
... Drive circuit, 11 ... Main transformer primary winding, 12 ... Main transformer secondary winding, 13 (13
-1,13-2゜13-3)... Rectifier circuit, 1
4 (1'4-1. 14-2.14-3)...
・Smoothing circuit, 15...Load resistance, 16 (1G
-1, 16-2)...Secondary side control means, 17.
...AND gate, 18 ... Main transformer tertiary winding, 19 ... Oscillation stop means, 20 ...
...Starting circuit, 21 (21-1, 2l-2)...
... Switch means, 22 ... Current transformer, 23.
...Switch, 24...Output detection circuit,
25...Modulation pulse generation circuit, 26...
・Stop command generation circuit, 27... Insulation means, 30
・・・・・・State holding circuit, 31 (31-1, 3l
-2)...Saturable reactor, 32...
・Reset circuit, 33...NOT gate, 34
...Switch driving means. Figure 1 3 1k14')? 7) I, I
9-L**L hand 8 in the other direction Cypress work 9 jump 30
Figure 2 Figure 3111J Figure 4 Figure 5 iL<0 Signal Figure 9 Figure 10 Figure 11:'! 3 12IA Fig. 13 tOtr t2 f□+TJ Fig. 15 Fig. 16

Claims (1)

[Claims] 1. A resonant circuit including a resonant reactor and a resonant capacitor, a DC input power supply connected to this resonant circuit, and a main circuit that intermittents the current supplied from the DC input power supply to the resonant reactor. In a resonant power supply configured to include a switch element, a diode connected in antiparallel to the main switch element, and a load circuit, and configured to supply power from the resonant circuit to the load circuit, the resonant reactor is It has a current direction detection means for detecting the direction of the flowing current, and is provided with an oscillation stop means for turning off the main switch element and stopping the oscillation operation when the current flows in the direction of regenerating energy in the DC input power source. A resonant power supply featuring 2. A resonant power source according to claim 1, wherein the resonant capacitor is connected in parallel to the load circuit. 3. In claim 1 or 2, the load circuit includes a primary winding of a main transformer connected to the resonant circuit and a rectifying and smoothing circuit connected to a secondary winding. A resonant power supply characterized by: 4. The resonant power supply according to claim 3, wherein the load circuit includes secondary side control means for controlling the output from the secondary winding. 5. In claim 1, the oscillation stop means is configured to generate a logic between a signal detecting that the current in the resonance reactor is flowing in a direction to regenerate energy in the DC input power source and an oscillation stop command. 1. A resonant power source comprising: means for generating a stop signal by taking the product; and a switch means for opening and closing in response to the stop signal. 6. The resonant power source according to claim 4, wherein the secondary side control means reduces or stops supplying power to the output end in response to an oscillation stop command. 7. In claim 1, one end of a series circuit of a DC input power source and a resonant reactor is connected to an intermediate point of the primary winding of a main transformer forming a load circuit, and the other end and the series circuit of the main transformer form a load circuit. A pair of main switch elements that alternately open and close with a phase difference of 180° are each connected to both ends of the primary winding, and a resonant capacitor is connected between both ends of the primary winding. Resonant type power supply. 8. In one of claims 3 to 7, the main transformer is provided with a tertiary winding, and the output signal thereof is configured to operate a main switch element to perform self-oscillation. A resonant power supply characterized by: 9. A resonant power source according to claim 4 or 6, characterized in that the secondary side control means is constructed using a magnetic amplifier. 10. A resonant power source according to claim 4 or 6, characterized in that the secondary side control means is configured to perform duty ratio control using a semiconductor switch. 11. Claim 1 or 2, characterized in that the load circuit includes a primary winding of a main transformer connected to the resonant circuit and a plurality of secondary windings. Resonant power supply. 12. DC input power supply, transformer, main switch element,
comprising a resonant circuit, and connecting the primary side circuit of the transformer to the DC input power source via the main switch element and the resonant circuit so that the voltage or current waveform of the main switch element becomes a sine wave with a frequency f_1; A resonant power supply that supplies power to a load connected to the secondary side of a transformer includes current direction detection means for detecting the direction of current flowing through the resonant circuit, and this current imparts energy to the DC input power supply. oscillation stop means for turning off the main switch element to stop the oscillation operation when the flow is in the direction of regeneration, and a frequency f_
output control means for controlling the operation of the oscillation stop means at a frequency f_2 lower than 1, and the output is controlled by varying the frequency f_2.