JP3187411B2 - Self-oscillation type power conversion circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a self-oscillation type power conversion circuit using a series inverter circuit, which can reduce the driving power loss and increase the power conversion efficiency.

BACKGROUND ART As prior art of the present inventor, two normally-off and insulated gate transistors 2, 3, a transformer 12, a series resonance circuit of a coil 4 and a capacitor 5, and a DC power supply 1
FIG. 2 shows a series inverter circuit using the above method. However, the starting means for starting this circuit is omitted.

(Prior art: Japanese Patent Application No. 2-14857, Japanese Patent Application No. 2-96579)
issue. In this circuit, two anti-parallel connected diodes 14 (or four Zener diodes 10) exhibiting constant voltage characteristics in both directions and the transformer 12 are connected to the transistors 2, 3 by the oscillating current of the resonant circuit. Is formed. The output voltage of the drive winding 12b is positively fed back to the gate of the transistor 2, to which a gate forward bias voltage is applied when the transistor 2 is to be turned on and a gate reverse bias voltage is applied to the gate when the transistor 2 is to be turned off. Given to this. The same applies to the transistor 3 and the drive winding 12c. The output power of this circuit is taken out by the transformer 13, the bridge connection type rectifier circuit 7 and the capacitor 8, and supplied to the load resistor 11.

However, while the respective gate voltages of the transistors 2 and 3 are kept substantially constant after reaching the forward bias voltage or the reverse bias voltage, the oscillating current is wastefully consumed by the two diodes 14. The prior art including this circuit has a problem that power conversion efficiency is reduced due to power loss. This problem exists regardless of the switching frequency. (Problems) Accordingly, an object of the present invention is to provide a self-oscillation-type power conversion circuit that “can reduce drive power loss and increase power conversion efficiency”.

(Object of the Invention) Disclosure of the Invention That is, the present invention provides one or a plurality of DC power supply means, a resonance inductance means, a resonance capacitance means performing a resonance operation together with the resonance inductance means, and the resonance capacitance. Means for receiving the current of the means by the input inductance means and outputting an AC voltage from the output inductance means magnetically coupled to the input inductance means; the one or more DC power supply means; and the resonance inductance A plurality of normally-off switching means for switching connection of the resonance capacitance means and the input inductance means, and a control terminal and a main terminal paired for inputting a drive signal thereof, insulated between the control terminal and the main terminal; The series inverter means having the following: Flowing full-wave rectification means, smoothing capacitance means for smoothing the pulsating voltage output by the full-wave rectification means, and magnetic coupling with the input inductance means, between each of the aforementioned control terminals and main terminals. A self-oscillation type power conversion circuit having one or a plurality of drive inductance means for outputting a drive signal.

However, the number of the driving inductance units and the number of the driving signals are not necessarily the same as the number of the switching units. A plurality of the switching means may share one drive signal with one drive inductance means.

Thus, the transformer, the full-wave rectifier, the smoothing capacitance, and the like form a drive voltage for each of the switching means from the current of the resonance capacitance, and the one or more drive inductances To each of the switching means.
Then, while each drive voltage is kept substantially constant after reaching the forward bias voltage or the reverse bias voltage, it flows to the resonance capacitance means and the like.

Therefore, if power is taken out from the smoothing capacitance means, "the drive power loss can be reduced and the power conversion efficiency can be increased. (Effect) In other words, since the full-wave rectifying means and the smoothing capacitance means play a role like the two diodes 14 in FIG. Therefore, the power conversion efficiency can be increased accordingly.

As described above, the present invention has the above-mentioned effects, but has the following problems. That is, when the voltage of the smoothing capacitance means is zero at the time of starting the circuit, the smoothing capacitance means causes the one or more driving inductance means to pass through the full-wave rectification means and the output inductance means. The short circuit causes a problem that the circuit becomes difficult to start.

Therefore, when the present invention corresponds to the self-oscillation type power conversion circuit according to claim 2, the one or more driving inductance means transmits a driving signal between the above-mentioned control terminal and main terminal at the time of startup. 3. The output inductance means and the smoothing capacitance means may be connected via only the full-wave rectification means, or the voltage drop means and the voltage drop means according to claim 2 may be easily output. The inventor has made improvements so that they can be connected or connected via wave rectification means.

As a result, the supply of the drive signal is performed rather than the charging of the smoothing-capacitance means so that the smoothing capacitance means does not prevent the forward bias voltage or the reverse bias voltage from being supplied to each of the switching means at the time of startup. The present invention in this case has an effect that the priority can be given, so that the activation is facilitated.

Incidentally, the voltage drop means and the voltage drop variable means in the second aspect are the same as the inrush current prevention means of the smoothing capacitance means.

Then, when the present invention corresponds to the self-oscillation type power conversion circuit according to claim 3, a part or all of the converted AC power is transferred to one or more of the one or more DC power supply means.
And the maximum voltage absolute value of each inductance means of the transformer means can be clamped to "a value corresponding to the magnitude of the voltage of the one DC power supply means and each turn ratio". In this case, the present invention has an effect that “the respective maximum voltage absolute values can be stabilized”.

In this case, AC power is output from the inductance means of the transformer in addition to the feedback power.

BEST MODE FOR CARRYING OUT THE INVENTION In order to explain the present invention in more detail, the present invention will be described below with reference to the accompanying drawings. FIGS. 1, 3 to 5 show circuit diagrams of four embodiments.

In the embodiment of FIG. 1, each corresponds to each of the above-described components as follows.

a) The DC power supply 1 is one or more DC power supply means described above.

b) The coil 4 serves as the resonance inductance means described above.

c) The capacitor 5 serves as the resonance capacitance means described above.

d) The transformer 6 serves as the above-mentioned transformer.

e) The input winding 6a serves as the input inductance means described above.

f) The output winding 6d serves as the output inductance means described above.

g) Transistors 2 and 3 serve as a plurality of switching means described above.

h) The gate terminal and the source terminal of each of the transistors 2 and 3 are respectively the control terminal and the main terminal described above.

i) The bridge connection type rectifier circuit 7 is the full-wave rectifier described above.

j) The capacitor 8 serves as the smoothing capacitance means described above.

k) The drive windings 6b, 6c serve as one or more drive inductance means as described above.

In the embodiment shown in FIG. 1, a series resonance circuit formed by a coil 4 and a capacitor 5 and an input winding 6a are connected in series, and a driving winding is formed.
Each of 6b and 6c is connected between each gate and source of the transistors 2 and 3. The output winding 6d is connected to a capacitor 8 via a bridge connection type rectifier circuit 7. However, a starting unit for starting the power conversion circuit is omitted.

Therefore, during oscillation operation of this power conversion circuit, load resistance
A current flows through 11 and the voltage of the capacitor 8, the sum of the forward voltages of the two diodes in the bridge connection type rectifier circuit 7, and the “turn ratio between the output winding 6 d and the driving windings 6 b and 6 c” are the transistors 2 and 3, the maximum absolute values of the gate forward bias voltage and the gate reverse bias voltage are determined. That is, the transformer 6, the bridge connection type rectifier circuit 7 and the capacitor 8 form the respective drive voltages of the transistors 2 and 3 from the oscillating current of the resonance circuit as in the case of the preceding circuit of FIG.

When two Zener diodes 10 are connected in series in the opposite direction between each gate and source as shown in FIG. 1, current flows through each Zener diode 10 during normal operation, and these waste power. Each sum of the Zener voltage and the forward voltage is larger than the maximum absolute value so as not to consume, and
It is set smaller than the absolute value of the withstand voltage between each gate and source.

Also, although each drive winding and each gate are directly connected,
One by one may be connected via a resistor.
Comparing this case with “the case where each of the preceding circuits in FIG. 2 is similarly connected via a resistor”, both have a drive power loss due to each of the two resistors. In the former case, the driving power loss is smaller and the power conversion efficiency is higher.

In the embodiment shown in FIG. 3, the inventor uses complementary transistors 2 and 18 and directly connects both gates and both sources, so that only one drive winding 19b is required. Two of the DC power supplies 1 and 15 correspond to one or a plurality of DC power supply units described above. The coil 20 corresponds to the voltage drop means described in claim 2, and the switch 21 corresponds to the voltage drop variable means described in claim 2. After all, coil 20 and switch
The parallel circuit 21 basically has the same configuration as the well-known means for preventing inrush current of a capacitor.

The resistor 16 and the changeover switch 17 are start / stop means for controlling start / stop of the power conversion circuit of FIG.
If the changeover switch 17 is as shown in FIG. 3, this short-circuits between the gates and sources of the transistors 2 and 18, so that the third
The power conversion circuit in the figure is in an operation stop state. On the other hand, when the changeover switch 17 is switched to the opposite side, the current of the resistor 16 becomes the capacitance between the gate and the source, the input winding 19a, the coil 4,
3 flows, and the power conversion circuit of FIG. 3 is started.

At startup, the switch 21 is turned off to prevent the output winding 19c from being short-circuited by the capacitor 8 or the like. Otherwise, it is difficult to supply the gate forward bias voltage to the transistor 2, so that the power conversion circuit in FIG. 3 is difficult to start or does not perform at all. Then, the capacitor 8
The switch 21 is turned on when the voltage of has reached a predetermined value. The predetermined value is determined by the sum of the above-mentioned gate forward bias voltage values, the turn ratio between the drive winding 19b and the output winding 19c, and the forward voltage of two diodes in the bridge connection type rectifier circuit 7.

When the diodes 22 and 23 are connected, the maximum positive voltage of the capacitor 5 is limited to the voltage of the DC power supply 1 and the minimum negative voltage thereof is limited to the voltage of the DC power supply 15 by these actions.

There is also a start-up assisting method in which the capacitor 8 is charged by another means before the start-up of the power conversion circuit of FIG. Further, since the above-described voltage drop means and voltage drop variable means are substantially inrush current prevention means of the capacitor 8, ordinary inrush current prevention means can be used instead of them.
Further, as a means for assisting the activation, a transistor 2
May be connected between the drain and source of the transistor 18.

The embodiment of FIG. 4 is of the bridge connection type. In the power conversion circuit shown in FIG. 4, the transformer 25 has two output windings 25f and 25g, and the output windings 25f and 25g and the diodes 26 and 27 form a center tap type full-wave rectifier circuit. The resistor 16 and the switch 24 are a start / stop unit for controlling start / stop of the power conversion circuit of FIG. 4 starts operating when the switch 24 is turned off, and stops operating when the switch 24 is turned on.

The embodiment of FIG. 5 is a modification of the embodiment of FIG. resistance
31 corresponds to the voltage drop means in the second aspect, and the switch 21 corresponds to the voltage drop variable means in the second aspect. These are basically the same as the inrush current prevention means of the capacitor 8.

The capacitors 5 and 32 are respectively connected to the respective output terminals of the DC power supply 1. Thus, there may be two resonance capacitors.

The diodes 22 and 23 limit the voltage of the capacitors 5 and 32 from zero to the voltage of the DC power supply 1, and keep the peak value of the oscillating voltage constant. Therefore, if the transistor 2 or 3 is turned off in a timely manner, the capacitors 5, 32
Is almost zero or the magnitude of the power supply voltage.

The operation of the diodes 22 and 23 is as follows. When the voltage of the capacitor 32 is substantially zero during the ON period of the transistor 2 and the voltage of the capacitor 5 is substantially equal to the power supply voltage,
The diode 22, which was previously off due to the reverse voltage, turns on. As a result, the "series circuit of the diode 22 and the transistor 2"
Capacitors 5 and 32 play a role like a diode
Each voltage does not change as it is.

Similarly, during the on-period of the transistor 3, "transistor 3
And a series circuit of the diode 23 and the coil 4 serve as a flywheel diode.

However, for that purpose, the transformer 6 and the starting / stopping means to be described below ensure the ON periods of the transistors 2 and 3 appropriately without waste.

"Transistors 28, 29, three diodes 30, two zener diodes 10, resistors 33, 34 and input terminal t1
And the like constitute the starting / stopping means of the power conversion circuit of FIG. A start / operation stop signal for controlling the start (oscillation start) and the operation stop (oscillation stop) is input to the input terminal t1. Hereinafter, the starting and stopping operations of this circuit will be described.

The oscillation operation of the power conversion circuit shown in FIG. 5 starts when the transistor 3 is turned on and stops when the transistor 2 is turned off. This is to make it easy to start and stop the operation and to prevent the transistor 2 or 3 from being turned off while the current is flowing through the coil 4. The pre-start switch 21 is turned off, and the start / stop signal is at a low level. For this reason,
Since transistor 29 is on, it bypasses the current in resistor 34 which tends to flow toward the gate of transistor 3.
Three diodes 30 complete this bypass.

When the start / stop signal rises, the transistor 28 turns off the transistor 29, so that a positive gate voltage is applied to the transistor 3 and a negative gate voltage is applied to the transistor 2 via the transformer 6.

As a result, the power conversion circuit in FIG. 5 starts oscillating,
When the voltage of the capacitor 8 reaches a predetermined value, the switch 21 is turned on. The oscillation continues as long as the start / stop signal is at a high level. It is also possible to turn on the switch 21 after a certain period of time has elapsed after the start / stop signal has risen, which is the same as the conventional inrush current prevention method.

After that, when the start / stop signal falls,
If the gate voltage of transistor 3 is zero or negative,
With that signal falling, transistor 28 turns off. This causes transistor 29 to turn on and, together with Zener diode 10, prevent the gate voltage of transistor 3 from going positive. Therefore, when the transistor 2 is turned off, the circuit stops oscillating.

However, when the start / stop signal falls,
If the gate voltage of transistor 3 is positive, the current in resistor 33 keeps transistor 28 on even when the signal falls. Therefore, the transistor 29 is turned on until the gate voltage of the transistor 3 falls, that is, until the transistor 3 is turned off. Thereafter, as described above, when the transistor 2 is turned off, the power conversion circuit of FIG. 5 stops oscillating.

The on / off state of the transistors 2 and 3 is generated by the excitation energy stored in the transformer 6 and the charging energy of the capacitance between the gate and the source. Every time the current of the coil 4 becomes close to zero, the resonance circuit formed by the exciting inductance and the capacitance between the gate and the source partially resonates using the stored energy,
Invert the gate-source voltage. In the case of the embodiment shown in FIG. 1, the inverted current of the coil 4 adds to its voltage inverting action.

Further, a constant voltage means may be used instead of the resistor 31. Alternatively, a switch in which a plurality of parallel circuits of the switch and the constant voltage means are connected in series may be used instead of the parallel circuit of the switch 21 and the resistor 31.

Then, "the voltage of the capacitor 8 is detected, and when this voltage is smaller than a predetermined value, a high-level start / stop signal is input to the input terminal t1. When the voltage of the capacitor 8 is larger than the predetermined value, A low-level start / stop signal is input to the terminal t1. "

Lastly, in each of the embodiments described above, an example in which one normally-off MOS FET is used for each switching means has been described. IGBT (In)
It does not matter whether it is a sulated Gate Bipolar Transistor) or a BIMOS composite device.

Here, the effect of the present invention will be supplementarily described. In general, "voltage-driven switching means (eg, an insulated gate transistor) insulated between a control terminal and a main terminal forming a pair for inputting the drive signal" is current-driven switching means (eg, bipolar transistor). (Transistor) is considered to be considerably smaller than that of the transistor. However, this is not always the case depending on the circuit.

For example, in the case of a circuit in which the ON / OFF of the MOS FET is switched at a fast cycle and power is consumed as the gate-source capacitance is charged and discharged, the driving power is increased.

Also, for example, as shown in the circuit of FIG.
In the case of a circuit in which the capacitance between both gates and sources is equivalently connected in series to the resonance circuit, the resonance after completion of the charging of each gate-source capacitance by the gate forward bias operation or the gate reverse bias operation In order to bypass the current, it is necessary to connect two diodes 14 in anti-parallel as shown in FIG. 2, and both diodes 14 consume power when the resonance current is bypassed. In other words, “driving power” in such a broad sense is required to drive the transistors 2 and 3.

For this reason, each of the current-driven switching means may be replaced one by one by "voltage-driven switching means in which the control terminal and the main terminal forming a pair for inputting the drive signal are insulated". In the case of a circuit that consumes driving power like these, the driving power cannot always be saved.

Then, in the circuit of FIG.
There has been a circuit similar to a power conversion circuit using two bipolar transistors instead of three. However, in that case, two diodes 14 are not required.

Reference: a) JP-B-36-16861 b) JP-A-52-70740 c) JP-A-53-69937 d) JP-A-61-273187 e) JP-A-63-59773 f) JP-A-63-59773 f) G) JP-A-60-89790 And, in the circuit of FIG.
Instead, there has been a circuit similar to a power conversion circuit using two bipolar transistors. However, it is necessary to connect one base resistor to each bipolar transistor.

Reference: a) Japanese Utility Model Application Laid-Open No. 52-1005023 b) Japanese Utility Model Application No. 52-105024 c) Japanese Utility Model Application Laid-open No. 52-1005033 d) Japanese Patent Application Laid-Open No. Sho 62-141976 In the case of a circuit using a bipolar transistor as described above. Therefore, even if the transformer for driving and the transformer for output are shared, it is necessary to supply the same amount of base current to each base-emitter PN junction, so that the same amount of drive current and drive power are required. However, the driving power consumption is not improved.

However, when using "switching means (voltage-driven type) in which the control terminal and the main terminal forming a pair for inputting the drive signal are insulated" as in the power conversion circuit of the present invention, the driving transformer means The driving power consumption is improved by sharing the output transformer. When the driving inductance means is directly connected between each of the above-mentioned control terminals and the main terminal without interposing a resistor, the driving power consumption is close to zero. As a result, the power conversion efficiency can be increased by the improvement of the driving power consumption.

This is because, for example, the bridge connection type rectifier circuit 7 and the capacitor 8 in the embodiment of FIG. 1 also serve as the two diodes 14 in the preceding circuit of FIG. And
The charging energy of the capacitance between both gates and sources of the transistors 2 and 3 is used together with the excitation energy of the transformer 6 for inverting the voltage between each gate and source, or the capacitor 5
Is used in the resonance circuit of the capacitor 5 and the coil 4 together with the charging energy.

From the above, unlike the case of using the current drive type switching means, the unique effect that "the drive power loss can be reduced and the power conversion efficiency can be increased" by sharing the drive transformer and the output transformer Is found to be in the present invention.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention. FIG. 2 is a circuit diagram showing a self-oscillation type power conversion circuit according to the inventor's prior art. Each of FIGS. 3 to 5 is a circuit diagram showing one embodiment of the present invention. (Explanation of symbols) 7: Bridge connection type rectifier circuit, 11: Load resistance, t1: Input terminal.

Claims (3)

(57) [Claims] 1. One or a plurality of DC power supply means, a resonance inductance means, a resonance capacitance means which performs a resonance operation together with the resonance inductance means, and a current of the resonance capacitance means for inputting its input inductance means And a transforming means for outputting an AC voltage from an output inductance means magnetically coupled to the input inductance means, the one or more DC power supply means, the resonance inductance means, the resonance capacitance means, and Switching means for switching the connection of the input inductance means, a plurality of normally-off switching means having a pair of control terminals and a main terminal insulated for inputting the drive signal thereof, the switching means being insulated from each other. Full-wave rectification means for full-wave rectifying the voltage; One or a plurality of drives that are magnetically coupled to the smoothing capacitance means for smoothing the pulsating voltage output by the rectifying means and the input inductance means and output a drive signal between the control terminal and the main terminal. A self-oscillation type power conversion circuit, comprising: 2. The output inductance means is connected to the smoothing capacitance means via the full-wave rectification means, or the output inductance means is provided via a voltage drop means for lowering a voltage in addition to the full-wave rectification means. 2. The self-oscillation type power conversion circuit according to claim 1, further comprising a voltage drop variable unit for connecting an inductance unit to the smoothing capacitance unit. 3. The power supply output capacitance means included in one of the one or more DC power supply means as the smoothing capacitance means, and an AC voltage is output from the inductance means of the transformer means. 3. The self-oscillation type power conversion circuit according to claim 1, wherein: