JPH02119575A - Power conversion circuit - Google Patents

Abstract

PURPOSE:To utilize a voltage drive type switching means by providing a current detecting means controlling the switching means to an OFF state and limiting the maximum value of main currents when the main currents of the switching means reach a specified value. CONSTITUTION:A coil L1 and a switching means SW1 are connected in series, and a coil L2 and a switching means SW2 are connected in series, thus constituting a push-pull circuit. The control signal voltage of the switching means SW2 is supplied from the series circuit of a DC power E1 and the coil L1, and the control signal voltage of the switching means SW1 is fed from the series circuit of the DC power E1 and the coil L2. Current detecting means CD1, CD2; 6-9 controlling the switching means SW1, SW2 to an OFF state and limiting the maximum values of main currents I1, I2 are provided respectively when each main current I1, I2 of separate switching means SW1, SW2 reaches a specified value. Accordingly, a voltage drive type switching means can be used.

Description

[Detailed Description of the Invention] Technical field The present invention makes it possible to use voltage-driven switching means such as power MO3-FETs in self-commutated power conversion circuits that utilize transformer saturation, where only bipolar transistors could be used. The present invention relates to a power conversion circuit configured as described above.

Therefore, the present invention provides a DC-AC inverter circuit and a DC-AC inverter circuit.
-Can be used in DC converter circuits, and is especially suitable for DC-DC converter circuits that have a relatively large capacity power supply capacitor on their secondary side, and DC-DC converter circuits that charge large capacity capacitors that are frequently charged and discharged. It is.

For example, there are capacitor discharge ignition (CDI) type ignition devices and capacitor charge/discharge ignition (CCD I) type ignition devices that can generate sparks even when the capacitor is charged (9 studies: Japanese Patent Publication No. 62-5019). The present invention is suitable for the DC-DC converter circuit used in the Japanese Patent Application No. 63-302217).

As conventional self-excited inverter circuits, the circuit shown in FIG. 2 (Japanese Patent Publication No. 49-39026) and the circuit shown in FIG. 3 are well known.

These circuits utilize the saturation of each transformer and the saturation of the collector current of each bipolar transistor to create a trigger for each transistor to turn off.

However, it seems that the phenomenon that occurs when switching on and off has not been properly understood.

This phenomenon can be thought of as follows.

For example, in the circuit shown in FIG. 2, when the magnetic flux density of the core of the transformer 4 is saturated by the current I of the primary coil 4a during the ON period of the transistor 3, the magnetic permeability and the excitation inductance L thereof rapidly decrease.

On the other hand, compared to its rapid decrease, the magnetic energy B
(:L I” /2) is not consumed rapidly and can be considered constant, so according to the law of conservation of energy, the energy E
In order to keep constant the transformer 4 itself or the primary coil 4
An attempt is made to rapidly increase the current I of a.

However, since the current I cannot flow through the transistor 3 in an amount greater than the saturation current value of the transistor 3, the transformer 4 uses rt to cause a current corresponding to the overflow to flow through the feedback coil 4b and the like.

During this time, the base current of the transistor 3 and its saturation current value decrease as the voltage of the feedback coil 4b decreases, further intensifying its effect.

As a result, after the on-voltage of transistor 3 increases, 1
The voltages of the secondary coil 4a and the JTT return coil 4b are reversed, the diode 2 is turned on, and the current of the feedback coil 4b is returned to the DC power supply 1.

The important point here is that until the transformer 4 is saturated, it is in a passive position, and only the DC power supply 1 is connected to the primary coil 4.
The point is that when the transformer 4 becomes saturated, it changes to an active position and itself tries to increase the current I.

In this way, a trigger for turning off transistor 3 is created. In the circuit of FIG. 3, the trigger for turning off each transistor is the same.

(The above explanation of the operation is proven by the fact that each actual example described below works and the invention of Japanese Patent Application Laid-Open No. 63-294250 is valid.) However, the main current has saturation characteristics. No power MO5-FET-IG
BT, S transistor, or power MO3-F
A problem with these circuits is that voltage-driven switching means, such as a BIMO3 composite element in which an ET and a bipolar transistor are cascaded, cannot be used in these circuits.

Therefore, an object of the present invention is to provide a self-excited power conversion circuit that utilizes transformer saturation and voltage-driven switching means such as these.

Disclosure of the invention, that is, the first invention includes a DC power supply E1, coils Ll and L2 of a transformer T1, and voltage-driven switching means SW1 and SW2, and the coil L1 and the switching means SWI are connected in series. and connect the +Fr coil L2 and the switching means SW2 in series to form a push-pull circuit 12, and the control signal voltage of the switching means SW2 is obtained from the series circuit of the DC power supply E1 and the coil L1. and supplying a control signal voltage to the switching means SWI from the series circuit of the DC power supply E1 and the coil L2, and detecting the main current (1) of the switching means SW1, and detecting the main current (1) of the switching means SW1. Current detecting means CDI is provided for controlling the switching means SWI to turn off when the main current 11 reaches a predetermined value, thereby limiting the maximum value of the main current 11.

and detects the main current (2) of the switching means SW2, and when this main current (2) reaches a predetermined value, controls the switching means SW2 to turn off to limit the maximum value of the main current I2. This is a power conversion circuit provided with a detection means CD2.

As a result, the main currents of each of the switching means SW1 and SW2 exhibit saturation characteristics, so that the present invention operates as an automatic power conversion circuit similarly to the circuit shown in FIG.

Therefore, the present invention has the advantage that voltage-driven switching means can be used.

The second aspect of the present invention includes DC power supply E2, coil L3 of transformer T2. L4 and a voltage-driven switching means SW3, the coil L3 and the switching means SW3 are connected in series between both output terminals of the DC power source E2, and the DC power source B2 and the coil 4 are connected in series. A control signal voltage of the switching means SW3 is supplied from the series circuit, and a main current I3 of the switching means SW3 is detected. This power conversion circuit is provided with a current detecting means CD3 that controls the main current I3 toward OFF to limit the maximum value of the main current I3.

As a result, the main current of the switching means SW3 exhibits saturation characteristics, so that the present invention operates as an automatic power conversion circuit similar to the circuit shown in FIG. Therefore, the present invention has the advantage that voltage-driven switching means can be used.

However, when the switching means SW3 is on, the transformer T2
is unsaturated, the voltages of both the coil 144 and the DC power supply E2 are added to help turn it on, that is, the voltage of the positive 1 m
The coil L4 and the DC power source E2 are connected so that the voltage is returned to the DC power source E2.

BEST MODE FOR CARRYING OUT THE INVENTION In order to explain the present invention in more detail, the same will be described below with reference to the accompanying drawings.

The embodiment of FIG. 1(a) is based on the circuit of FIG.
This is a power conversion circuit using two OS field effect transistors 53, and corresponds to the power conversion circuit according to claim 1.

Each of the combinations of the transistor 9 and the resistors 6 to 8 corresponds to the aforementioned current detection means CD1 and CD2, respectively, and when the main current (drain current) of each transistor 5 reaches its respective predetermined value, the respective gate and source The main currents are controlled so that they do not increase any further by reducing the voltage between them. (The respective predetermined values are determined by the base-emitter voltage when the transistor 9 is turned on and the values of the resistors 6 to 8.) For this reason, each main current is determined by the voltage between the base and emitter when the transistor 9 is turned on and the values of the resistors 6 to 8. The U characteristic now appears, and this embodiment has the advantage of being able to perform the same operation as the circuit shown in FIG.

By the way, in the circuit of FIG. 3, each base current changes depending on its power supply voltage, and each current amplification factor also changes depending on temperature, etc., so the collector saturation current value of each bipolar transistor is unstable.

The switching loss of these transistors increases or decreases accordingly, so it is necessary to use transistors with sufficiently large current capacity and collector loss.

On the other hand, in the case of this embodiment, since the current detection means firmly fixes its saturation current value, the switching means SW1. There is no need to provide a large margin for the current capacity or power dissipation of SW2.

This embodiment also has this effect.

In this embodiment, the voltage of the DC power source 1 must be less than half the withstand voltage between the gate and the source of each transistor 5.

Further, the output voltage in this embodiment is collected from between the drains of both transistors 5.

The embodiment shown in FIG. 1(b) is a power conversion circuit based on the circuit shown in FIG. 2, and corresponds to the power conversion circuit according to claim 3.

Also, if this embodiment is made into a push-pull type, it is possible to make it as shown in Figure 1 (
This becomes the circuit a).

In the circuit of FIG. 1(b), unlike the circuit of 21st fjU, there is no feedback diode, so the load resistor 11 remains connected to the output of this circuit. Of course, a leak diode may be connected like the 4th UA circuit.

In this embodiment as well, it is necessary to pay attention to the voltage of the DC power supply 1 and the value of the load resistor 11 so that a voltage higher than the withstand voltage is not applied between the gate and source of the transistor 5.

An example of this circuit constant is shown below.

Power supply voltage...5 volts Transistor 5-...2SK532 Manufactured by Toshiba Corporation 9...2SC2002 Transformer core made by NEC Corporation...PQ26/25 TDK Primary and secondary windings made by Co., Ltd. - 15 turns each Resistance 6 - 1 ohm 7 - 510 ohm 8 - 1 kilo ohm 11 ...5 ohms or more The embodiment shown in FIG. 4 is an improved version of the circuit shown in FIG. 1(b) to make it easier to use.

This output is taken from the third winding of transformer 12.

The two Zener diodes 13 are a measure against surge voltage.

Resistor 14 and Zener diode 15 are transistor 5
Prevents overvoltage from being applied between the gate and source of the device.

Diode 16 is a feedback diode.

The embodiment shown in FIG. 5 is an easy-to-use development of the circuit shown in FIG. 1(a), and corresponds to the power conversion circuit according to claim 2.

Transistor 9. Two diodes 17 and resistors 6-8
constitutes current detection means for both transistors 5.

Therefore, one current sensing means is saved.

This current detection means detects the main currents of both transistors 5, and controls them so that both currents exhibit saturation characteristics.

In the embodiment shown in FIG. 6, a transistor 18.9°, two diodes 17, resistors 6 to 8, etc. constitute current detection means.

In this way, even if the resistors 6 to 8 are located on the transformer 12 side, they do not lie side by side. In short, it is only necessary to detect the main current of each transistor 5 and limit its maximum value.

The embodiment shown in FIG. 7 is a DC-DC converter whose negative output voltage is controlled almost constant using a Schmitt trigger circuit.
It is a converter circuit.

Transistors 20, 21, etc. constitute the Schmitt trigger circuit. When the negative potential of the output terminal 28 reaches a predetermined value, the transistor 20 and the two diodes 1
9 makes the voltage between the gate and source of both transistors 5 almost zero, and stops the inverter operation.

However, since this Schmitt trigger circuit cannot directly detect its negative output voltage, the circuit section consisting of diodes 25, 26, resistors 22 to 24, and capacitor 27 is used to match its input voltage and its output voltage. It is.

The mechanism is as follows. The anode potential of the diode 25 is fixed to a constant potential of around 1.2 volts by the diodes 25, 26, the resistor 23, and the capacitor 27.

The relationship between this anode potential, the base potential of the transistor 21, and the potential of the output terminal 28 is just like the relationship between the fulcrum, the point of action, and the point of force in the "lever principle";
．． It is almost determined by the resistance ratio of 22. However, the size of the resistor 30 is set so small that it can be ignored. (Several ohms) Of course, it is not acceptable to use a Zener diode instead of the diode 25 or 26.

Also, the two diodes 29 play a role in accelerating the turn-off of both transistors 5 without reducing both switching losses, but they can be used without one (or one capacitor can be connected in place of each diode 29). It's okay.

The embodiment shown in FIG. 8 is a simple L circuit that is a modification of the circuit shown in FIG. 1(b).

In this circuit, the current detection means consists of a resistor 31 and a DC power source 1.
It is thought to be composed of. When the main current of the transistor 5 increases, its source potential is increased by the resistor 31, so that its gate-source voltage decreases, and the transistor 5 is turned off.

R, the maximum value of its main current is its power supply voltage and resistance 3
It is determined by the size of 1 and the on/off threshold of the transistor 5.

An example of the constants of this circuit is shown below.

Power supply voltage: 15 volts Transistor 5: 2SK532 Diode: 16: 12. JGll Ener diode 15 made by Toshiba Corporation......RDIOF Transformer 10 made by NEC Corporation Core...PQ26/25 Each coil made by TDK Corporation...・15 turn resistor 14...1 kilo ohm 31...3.4 ohm or more However, the feedback current flowing with the diode 16 is connected to the DC power supply 1.
must be absorbed. The solution is to connect the power supply capacitor in parallel to the DC power supply 1.

In the embodiment shown in FIG. 9, the eighth EA circuit is of a push-pull type.

Each diode 16 prevents its respective feedback current from being consumed by each resistor 31, but may be omitted.

The embodiment of FIG. 10 has a constant voltage loop I, similar to the circuit of FIG.
This is a C-DC converter circuit that is not controlled by I). However, this output voltage is positive and is the sum of both the voltages of the power supply capacitor 36 and the DC power supply 1, and is output from the output terminal 38.

A Schmitt trigger circuit formed by transistors 20, 21, etc. controls the inverter section. The DC output voltage is almost determined by the resistance ratio of the resistor 45.46. The resistance 30 is set so small that it can be ignored. (Several ohms) The inventor additionally connected two resistors 32 in order to firmly keep the other transistor 5 off when one of the two transistors 5 is on.

An example of the constants of this circuit is shown below.

DC power supply voltage... (+6)~+12-(+16) volts However, a power supply capacitor is required.

1) Rated output voltage of C-DC converter circuit...
...About +400 volts transistor 5 ...IRF150 International Rectifier Co., Ltd. 9.20. 21.37-...2SC2003 Ener Diode 15...RD 101? 13...RD391; The above is a diode made by Shiraki Electric Co., Ltd. 19.41...151588 Made by Toshiba Co., Ltd. fL3 35...4 VO9G bridge connections.

Newly manufactured capacitor manufactured by Hitachi Co., Ltd. (unit: micro farad) 36 ・
...2.2X5 42 ...0.001 to 0.01 resistance 6- ...0.05 ohm (10 watts) 7 ...
...200 ohm 8.14 (0.5 watts), 33.34...
1 kilo ohm 30 --- 5.1 ohm (adjustment required) 32.4
4...4.7 kilo ohm 39.40.46...3.3 kilo ohm 43...7.5 kilo ohm 45... Approximately 2 meg ohm (adjustment required) Transformer 12: Ferrite core and hobbin...PQ
32/30 Primary coils 12a, 12b manufactured by TDK Co., Ltd. 10 turns of 0.4 mm diameter hole and marine wire with 4 pieces of wood parallel.

Secondary coil 12c - 369 turns of Polmarine wire with a diameter of 0.3 mm.

Finally, in each embodiment, a voltage-driven switching means such as a power MO3-F[IGI-3T, S I instead of E, T] transistor or a BIMO8 composite element may be used.

In addition, in the first example (a), each circuit in FIGS. 4 to 10,
It is desirable that the DC power supply be able to absorb the feedback current from the transformer. One particular solution is to connect a power supply capacitor in parallel with the DC power supply.

Furthermore, as mentioned above, regarding the inventor's explanation that "when the transformer itself saturates, the current in its winding increases", if such an effect does not exist, there will be a contradiction in terms of the law of conservation of energy. However, for example, the oscillation of the circuit shown in FIG. 1(b) cannot be well explained.

If this effect does not exist, transformation 2! :Even if ilo is saturated and the voltage of its coil is close to zero (1·t), the gate forward bias voltage continues to be supplied to the transistor 5, so the transistor 5 remains on.

Immediately after that, the current in the resistor 6 increases and the transistor 9 etc. increase the on-resistance of the transistor 5, so the state ftJ in which the voltage of the DC power supply 1 is distributed between the resistor 5 and the resistor 6 continues to be maintained. .

The above action is clarified in Japanese Patent Application Publication No. 63-29425.
This is technology number 9. In this circuit, the gate forward bias voltage as described in 11 is supplied from the DC power supply without going through the coil of the transformer.

Related patents: (Japanese Patent Application No. 6L013938 > Japan Patent Application Publication No. 62-5019 PCT/JI) No. 8710 O053 Hiki Toku [Body Paste No. 62-217017 Japan Patent Application No. 62-228815 PCT/JP87100595] ) CT/J ) '87100612 Japanese Unexamined Publication No. 6
No. 3-294259 Japanese Patent Publication No. 63-302217

[Brief explanation of drawings]

Figures 1(a) and (+)) - Figures 4 to 10 are circuit diagrams showing one embodiment of the present invention, and Figures 2I71 and 3 are circuit diagrams showing conventional inverter circuits, respectively. be. (Explanation of symbols) ■・・・DC power supply, 4.10.12・・・・
...Transformers 4a, 12a, 12b ...Primary coil 4b...Feedback coil, 12c...-
・Secondary coil, 1L...Load resistance, 28
．． 38・mountain・・output terminal, 35・・・・rectifier

Claims (3)

[Claims] (1) There is a DC power source E1, coils L1 and L2 of a transformer T1, and voltage-driven switching means SW1 and SW2, the coil L1 and the switching means SW1 are connected in series, and the coil L2 and the switching means are connected in series. means SW2 are connected in series to form a push-pull circuit, and a control signal voltage for the switching means SW2 is supplied from a series circuit of the DC power source E1 and the coil L1; A control signal voltage for the switching means SW1 is supplied from the series circuit L2, and a main current I1 of the switching means SW1 is detected, and when this main current I1 reaches a predetermined value, the switching means SW1 is turned off. A current detection means CD1 is provided to control and limit the maximum value of the main current I1, and detects the main current I2 of the switching means SW2, and turns off the switching means SW2 when the main current I2 reaches a predetermined value. A power conversion circuit characterized in that a current detection means CD2 is provided for controlling the main current I2 to limit the maximum value of the main current I2. (2) The power conversion circuit according to claim 1, characterized in that the current detection means CD1 and CD2 are integrated into one. (3) A DC power supply E2, coils L3 and L4 of a transformer T2, and voltage-driven switching means SW3 are provided, and the coil L3 and the switching means SW3 are connected in series between both output terminals of the DC power supply E2, A control signal voltage for the switching means SW3 is supplied from a series circuit in which the DC power supply E2 and the coil L4 are connected in series, and a main current I3 of the switching means SW3 is detected, and when this main current I3 reaches a predetermined value. A power conversion circuit characterized in that a current detection means CD3 is provided for controlling the switching means SW3 in the off direction to limit the maximum value of the main current I3.