CA2061228C - Ringing choke converter - Google Patents
Ringing choke converterInfo
- Publication number
- CA2061228C CA2061228C CA 2061228 CA2061228A CA2061228C CA 2061228 C CA2061228 C CA 2061228C CA 2061228 CA2061228 CA 2061228 CA 2061228 A CA2061228 A CA 2061228A CA 2061228 C CA2061228 C CA 2061228C
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- base
- voltage
- winding
- switching transistor
- capacitor
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Abstract
In a ringing choke converter, a series circuit of a capacitor means and a diode means is disposed between a base and an emitter of a switching transistor means, and a constant-voltage diode means is linked in parallel with the capacitor means. In consequence, a voltage applied to the capacitor means does not exceed a voltage value of the constant-voltage diode means. In particular, a collector surge current flowing through the switching transistor means is restricted by the voltage value of the constant-voltage diode means. Consequently, even if the switching transistor means abruptly changes its operation when the converter is switching on or off, it is possible to prevent an excessive surge current from flowing through the transistor means.
Description
RINGING CHOKE CONVERTER
The present invention relates to a ringing choke converter for use with various kinds of electronic apparatuses.
Ringing choke converters have been broadly employed in many types of electronic appliances thanks to simplicity of circuits thereof.
A conventional ringing choke converter circuit includes a switching transistor having a collector, an emitter, and a base. The base is connected to a diode, a capacitor and a resistor.
In this circuit, during a charging period in which the capacitor is being charged up after a switch is turned on, the switching transistor is prevented from being turned on in order to avoid an abrupt operation of the transistor. This prevents an excessive large collector current from flowing through the switching transistor. However, when an interval of time between the on and off of the switch is shorter than a discharge time required for the capacitor to completely achieve a discharge operation through the resistor, the capacitor cannot fully discharge the electric charge to the resistor.
Consequently, with the capacitor in a charged state, when the switch is turned on, the switching transistor abruptly begins conducting, which leads to a problem that an excessive surge current flows as a collector current through thetransistor.
It is therefore an object of the present invention to provide a ringing choke converter capable of suppressing an excessive collector surge current flowing through the switching transistor due to an abrupt operation thereof with a rapid change in an input voltage and/or a load current when the switch is turned on or off.
In accordance with the present invention, there is provided a ringing choke converter for converting voltage of a direct-current source into aregulated direct-current voltage. The converter has a direct-current voltage source, a transformer, a power switch, a switching transistor means, a control transistor means, a second diode, a capacitor and a constant-voltage diode means. The transformer has a primary winding with first and second end terminals, a base winding with first and second end terminals, and a secondary winding for outputting the regulated voltage. The power switch is connected between the voltage source and the first end terminal of the primary winding.
The switching transistor means has a collector connected to the second end terminal of the primary winding, a base connected through a first diode and a first resistor to the first end terminal of the base winding so that the switching transistor is turned on by a voltage developed across the base winding, and an emitter connected through a second resistor to the second terminal of the base winding. The control transistor means has a collector connected to the base of the switching transistor means and through a third resistor to the first terminal of the primary winding, a base coupled to receive a control signal for periodically turning on the control transistor means to turn off the switching transistor means, and an emitter connected to the second terminal of the base winding.
The second diode and the capacitor are connected in series between the base of the switching transistor means and the second end terminal of the base winding so that the switching transistor means is kept from turning on for a charging period of the capacitor after the power switch is closed. The constant-voltage diode means is connected across the capacitor to limit voltage developed thereacross after the power switch is closed.
The ringing choke converter may further comprise a control means for generating the control signal in the form of a periodically-changing analog signal, or may further comprise a smoothing circuit connected to the secondary winding of the transformer.
The objects and features of the present invention will become more apparent from the consideration of the following detailed description takenin conjunction with the accompanying drawings, in which:
Figure 1 is a circuit diagram illustratively showing an example of a conventional ringing choke converter; and, Figure 2 is a schematic circuit diagram showing an example of a ringing choke converter in accordance with the present invention.
Referring now to the drawings, a description will be given in detail of an embodiment of a ringing choke converter in accordance with the present nvenbon.
For the purpose of understanding a ringing choke converter 5 according to the present invention, a description will be given in detail of an embodiment of a conventional ringing choke converter. Figure 1 shows a representative circuit structure of a ringing choke converter of the prior art.
The converter of Figure 1 includes a switching transistor 1 having a collector, an emitter, and a base. The collector is connected via a switch 17 and a primary winding 12 of a transformer 11 to an input voltage source 3. The emitter is coupled via a resistance 8 with another terminal of the voltage source 3. The base is linked via a starting resistor 7 to the switch 17 and is connected via a diode 5 and a resistor 9 to a base winding 13 of the transformer 11 and a control section 10. The base is, moreover, coupled with a collector of the control transistor 2 and is linked, via a serial connection of a diode 6 with a parallel connection of a capacitor 4 or a resistor 19, to the terminal of the input voltage source 3. The control transistor 2 includes a base and an emitter which are coupled with the controller 10.
One terminal of a secondary winding 14 of the transformer 11 is linked via a diode- 15 to one end of a capacitor 16 and to an output terminal.
The other output terminal is connected to the other end of the capacitor 16 and to the other terminal of the secondary winding 14.
Next, the operation of the circuit of the ringing choke converter will be described.
First, when the switch 17 is turned on, power is supplied to charge the capacitor 4 via the starting resistor 7 and the diode 6, whereby the voltageof the capacitor 4 is gradually increased. The switching transistor 1 is then supplied with a base current according to a VBE ~ IC characteristic thereof. This causes a collector current to gradually start flowing through the switching transistor 1. Finally, the transistor 1 is turned on to initiate the operation of the circuit. As a result, the primary winding 12 of the transformer 11 is applied with a voltage from the input voltage source 3, thereby inducing a voltage in the base winding 13 of the transformer 11. The induced voltage is then supplied as a base current via the resistor 9 and the diode 5 to the switching transistor1 to develop a positive feedback operation therein. In response thereto, the 5 switching transistor 1 turns on at a high speed. As a result, a current flows into the circuit on the primary side of the transformer 11; whereas, a flyback voltage appearing due to a self-induction in the secondary winding 14 of the transformer11 is rectified through the diode 15 and is then smoothed by the capacitor 16.
The rectified and smoothed voltage is outputted from the output terminal to an 10 external device.
Subsequently, on receiving a signal produced from the control section 10, the control transistor 2 turns on to form a short circuit between the base and the emitter of the switching transistor 1. This functions to absorb thebase current and hence turns the transistor 1 off. Thereafter, the transformer 15 11 becomes free of the flyback energy, and the voltage induced in the secondary winding thereof disappears. In the situation above, the capacitor 16 is discharged to supply the diode 15 with a recovery current flowing in the reverse direction through the secondary winding 14 of the transformer 11. This causes a voltage to be developed across the base winding 13 thereof to turn on 20 again the switching transistor 1.
Through the repetitious operations above, the transistor 1 conducts the switching operation.
In the conventional circuit, during a charging period in which the capacitor 4 is charged up after the switch 17 is turned on, the switching 25 transistor 1 is prevented from being turned on so as to avoid an abrupt operation of the transistor 1, thereby preventing an excessively large collectorcurrent from flowing therethrough. However, when an interval of time between the on and off of the switch 17 is shorter than a discharge time required for the capacitor 4 to completely achieve the discharge operation through the resistor 30 19, the capacitor 4 does not fully discharge. Consequently, with the capacitor 4 in a charged state, when the switch 17 is turned on, the switching transistor 1 abruptly conducts, which leads to a problem that an excessive surge current flows as a collector current through the transistor 1.
The surge current Icp flowing through the switching transistor 1 is expressed as:
ICP (VC + VRC - VBE) / RE .. (1).
In this expression, Vc, VRC, VBE, and RE respectively stand for a voltage applied to the capacitor 4, a voltage drop in the diode 6, a base-emitter voltage of thetransistor 1, and a resistance of the resistor 8.
The expression (1) indicates that the collector surge current of the 10 transistor 1 becomes greater in proportion to the voltage Vc applied to the capacitor 4.
Figure 2 shows the configuration of an embodiment of a ringing choke converter in accordance with the present invention.
In the construction of Figure 2, the same constituent elements as 15 those of Figure 1 are assigned the same reference numerals, and a duplicated description thereof will be avoided. In the circuit of Figure 2, a constant-voltage diode 18 is connected to both terminals of capacitor 4.
The circuit of the embodiment includes the capacitor 4 and a diode 6 connected in series thereto. In order to prevent an excessive collector surge 20 current from flowing through a switching transistor 1 at an abrupt operation thereof, the constant-voltage diode 18 is linked in parallel with the capacitor 4.
The constant-voltage diode 18 includes a cathode coupled with a connecting point between a cathode of the diode 6 and the capacitor 4.
The series circuit constituted with the capacitor 4 and the diode 6 25 has a first terminal end connected to a base of the transistor 1 and also connected via a diode 5 and a resistor 9 to an end of a base winding 13 of a transformer 11. Provided in the series circuit is a second terminal end connected to a point extending via a resistor 8 to an emitter of the transistor 1 and also connected to another end of the base winding 13 of the transformer 11. The other components of the circuit of Figure 2 are identical to those of the circuit of Figure 1.
Disposed in the configuration is a controller 10 for producing an analog signal having a magnitude increasing and decreasing at a predetermined 5 interval or period of time. When the analog signal created from the controller10 exceeds a threshold value of the base-emitter voltage of a control transistor2, the control transistor 2 is turned on. When the signal is less than the threshold, the transistor 2 is turned off. In other words, after the switching transistor 1 is turned on, the controller 10 supplies the base of the control 10 transistor 2 with a signal to turn the transistor 1 off at the predetermined interval of time.
Next, features of the embodiment of Figure 2 will be described.
In the embodiment of Figure 2, the constant-voltage diode 18 is linked in parallel with the capacitor 4 connected to the cathode of the diode 6;15 moreover, the cathode of the diode 18 is coupled with a connecting point between the cathode of the diode 6 and the capacitor 4. This guarantees that the voltage applied to the capacitor never exceeds the voltage characteristic ofthe constant-voltage diode 18.
Consequently, in this circuit configuration, the value of the collector 20 surge current Icp flowing through the switching transistor 1 is expressed as:
ICP (VZ + VRC - VBE) / RE (2).
In this expression, Vz designates the voltage associated with the constant-voltage diode 18.
As can be seen from the expression (2), the value of the surge 25 current Icp appearing in the switching transistor 1 is limited to an upper-limit value owing to the voltage value Vz of the diode 18 and the voltage drop VRC
in the diode 6. In other words, the surge current Icp does not exceed a fixed value. Consequently, it is possible to suppress the collector surge current caused by an abrupt operation of the switching transistor 1.
,0 , ~; .
As above, the ringing choke converter according to the present invention is capable of suppressing the collector surge current appearing due to an abrupt operation of the switching transistor at a rapid change in the input voltage and the load current when the switch is turned on or off. In accordance 5 with the present invention, a protection circuit can be implemented in a simplified configuration. As a result, a switching transistor requiring a limited surge current may be used, thereby improving the quality of the converter circuit.
While the present invention has been described with reference to 10 the particular illustrative embodiment, it is not to be restricted by the embodiment but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiment without departing from the scope and spirit of the present invention.
.
The present invention relates to a ringing choke converter for use with various kinds of electronic apparatuses.
Ringing choke converters have been broadly employed in many types of electronic appliances thanks to simplicity of circuits thereof.
A conventional ringing choke converter circuit includes a switching transistor having a collector, an emitter, and a base. The base is connected to a diode, a capacitor and a resistor.
In this circuit, during a charging period in which the capacitor is being charged up after a switch is turned on, the switching transistor is prevented from being turned on in order to avoid an abrupt operation of the transistor. This prevents an excessive large collector current from flowing through the switching transistor. However, when an interval of time between the on and off of the switch is shorter than a discharge time required for the capacitor to completely achieve a discharge operation through the resistor, the capacitor cannot fully discharge the electric charge to the resistor.
Consequently, with the capacitor in a charged state, when the switch is turned on, the switching transistor abruptly begins conducting, which leads to a problem that an excessive surge current flows as a collector current through thetransistor.
It is therefore an object of the present invention to provide a ringing choke converter capable of suppressing an excessive collector surge current flowing through the switching transistor due to an abrupt operation thereof with a rapid change in an input voltage and/or a load current when the switch is turned on or off.
In accordance with the present invention, there is provided a ringing choke converter for converting voltage of a direct-current source into aregulated direct-current voltage. The converter has a direct-current voltage source, a transformer, a power switch, a switching transistor means, a control transistor means, a second diode, a capacitor and a constant-voltage diode means. The transformer has a primary winding with first and second end terminals, a base winding with first and second end terminals, and a secondary winding for outputting the regulated voltage. The power switch is connected between the voltage source and the first end terminal of the primary winding.
The switching transistor means has a collector connected to the second end terminal of the primary winding, a base connected through a first diode and a first resistor to the first end terminal of the base winding so that the switching transistor is turned on by a voltage developed across the base winding, and an emitter connected through a second resistor to the second terminal of the base winding. The control transistor means has a collector connected to the base of the switching transistor means and through a third resistor to the first terminal of the primary winding, a base coupled to receive a control signal for periodically turning on the control transistor means to turn off the switching transistor means, and an emitter connected to the second terminal of the base winding.
The second diode and the capacitor are connected in series between the base of the switching transistor means and the second end terminal of the base winding so that the switching transistor means is kept from turning on for a charging period of the capacitor after the power switch is closed. The constant-voltage diode means is connected across the capacitor to limit voltage developed thereacross after the power switch is closed.
The ringing choke converter may further comprise a control means for generating the control signal in the form of a periodically-changing analog signal, or may further comprise a smoothing circuit connected to the secondary winding of the transformer.
The objects and features of the present invention will become more apparent from the consideration of the following detailed description takenin conjunction with the accompanying drawings, in which:
Figure 1 is a circuit diagram illustratively showing an example of a conventional ringing choke converter; and, Figure 2 is a schematic circuit diagram showing an example of a ringing choke converter in accordance with the present invention.
Referring now to the drawings, a description will be given in detail of an embodiment of a ringing choke converter in accordance with the present nvenbon.
For the purpose of understanding a ringing choke converter 5 according to the present invention, a description will be given in detail of an embodiment of a conventional ringing choke converter. Figure 1 shows a representative circuit structure of a ringing choke converter of the prior art.
The converter of Figure 1 includes a switching transistor 1 having a collector, an emitter, and a base. The collector is connected via a switch 17 and a primary winding 12 of a transformer 11 to an input voltage source 3. The emitter is coupled via a resistance 8 with another terminal of the voltage source 3. The base is linked via a starting resistor 7 to the switch 17 and is connected via a diode 5 and a resistor 9 to a base winding 13 of the transformer 11 and a control section 10. The base is, moreover, coupled with a collector of the control transistor 2 and is linked, via a serial connection of a diode 6 with a parallel connection of a capacitor 4 or a resistor 19, to the terminal of the input voltage source 3. The control transistor 2 includes a base and an emitter which are coupled with the controller 10.
One terminal of a secondary winding 14 of the transformer 11 is linked via a diode- 15 to one end of a capacitor 16 and to an output terminal.
The other output terminal is connected to the other end of the capacitor 16 and to the other terminal of the secondary winding 14.
Next, the operation of the circuit of the ringing choke converter will be described.
First, when the switch 17 is turned on, power is supplied to charge the capacitor 4 via the starting resistor 7 and the diode 6, whereby the voltageof the capacitor 4 is gradually increased. The switching transistor 1 is then supplied with a base current according to a VBE ~ IC characteristic thereof. This causes a collector current to gradually start flowing through the switching transistor 1. Finally, the transistor 1 is turned on to initiate the operation of the circuit. As a result, the primary winding 12 of the transformer 11 is applied with a voltage from the input voltage source 3, thereby inducing a voltage in the base winding 13 of the transformer 11. The induced voltage is then supplied as a base current via the resistor 9 and the diode 5 to the switching transistor1 to develop a positive feedback operation therein. In response thereto, the 5 switching transistor 1 turns on at a high speed. As a result, a current flows into the circuit on the primary side of the transformer 11; whereas, a flyback voltage appearing due to a self-induction in the secondary winding 14 of the transformer11 is rectified through the diode 15 and is then smoothed by the capacitor 16.
The rectified and smoothed voltage is outputted from the output terminal to an 10 external device.
Subsequently, on receiving a signal produced from the control section 10, the control transistor 2 turns on to form a short circuit between the base and the emitter of the switching transistor 1. This functions to absorb thebase current and hence turns the transistor 1 off. Thereafter, the transformer 15 11 becomes free of the flyback energy, and the voltage induced in the secondary winding thereof disappears. In the situation above, the capacitor 16 is discharged to supply the diode 15 with a recovery current flowing in the reverse direction through the secondary winding 14 of the transformer 11. This causes a voltage to be developed across the base winding 13 thereof to turn on 20 again the switching transistor 1.
Through the repetitious operations above, the transistor 1 conducts the switching operation.
In the conventional circuit, during a charging period in which the capacitor 4 is charged up after the switch 17 is turned on, the switching 25 transistor 1 is prevented from being turned on so as to avoid an abrupt operation of the transistor 1, thereby preventing an excessively large collectorcurrent from flowing therethrough. However, when an interval of time between the on and off of the switch 17 is shorter than a discharge time required for the capacitor 4 to completely achieve the discharge operation through the resistor 30 19, the capacitor 4 does not fully discharge. Consequently, with the capacitor 4 in a charged state, when the switch 17 is turned on, the switching transistor 1 abruptly conducts, which leads to a problem that an excessive surge current flows as a collector current through the transistor 1.
The surge current Icp flowing through the switching transistor 1 is expressed as:
ICP (VC + VRC - VBE) / RE .. (1).
In this expression, Vc, VRC, VBE, and RE respectively stand for a voltage applied to the capacitor 4, a voltage drop in the diode 6, a base-emitter voltage of thetransistor 1, and a resistance of the resistor 8.
The expression (1) indicates that the collector surge current of the 10 transistor 1 becomes greater in proportion to the voltage Vc applied to the capacitor 4.
Figure 2 shows the configuration of an embodiment of a ringing choke converter in accordance with the present invention.
In the construction of Figure 2, the same constituent elements as 15 those of Figure 1 are assigned the same reference numerals, and a duplicated description thereof will be avoided. In the circuit of Figure 2, a constant-voltage diode 18 is connected to both terminals of capacitor 4.
The circuit of the embodiment includes the capacitor 4 and a diode 6 connected in series thereto. In order to prevent an excessive collector surge 20 current from flowing through a switching transistor 1 at an abrupt operation thereof, the constant-voltage diode 18 is linked in parallel with the capacitor 4.
The constant-voltage diode 18 includes a cathode coupled with a connecting point between a cathode of the diode 6 and the capacitor 4.
The series circuit constituted with the capacitor 4 and the diode 6 25 has a first terminal end connected to a base of the transistor 1 and also connected via a diode 5 and a resistor 9 to an end of a base winding 13 of a transformer 11. Provided in the series circuit is a second terminal end connected to a point extending via a resistor 8 to an emitter of the transistor 1 and also connected to another end of the base winding 13 of the transformer 11. The other components of the circuit of Figure 2 are identical to those of the circuit of Figure 1.
Disposed in the configuration is a controller 10 for producing an analog signal having a magnitude increasing and decreasing at a predetermined 5 interval or period of time. When the analog signal created from the controller10 exceeds a threshold value of the base-emitter voltage of a control transistor2, the control transistor 2 is turned on. When the signal is less than the threshold, the transistor 2 is turned off. In other words, after the switching transistor 1 is turned on, the controller 10 supplies the base of the control 10 transistor 2 with a signal to turn the transistor 1 off at the predetermined interval of time.
Next, features of the embodiment of Figure 2 will be described.
In the embodiment of Figure 2, the constant-voltage diode 18 is linked in parallel with the capacitor 4 connected to the cathode of the diode 6;15 moreover, the cathode of the diode 18 is coupled with a connecting point between the cathode of the diode 6 and the capacitor 4. This guarantees that the voltage applied to the capacitor never exceeds the voltage characteristic ofthe constant-voltage diode 18.
Consequently, in this circuit configuration, the value of the collector 20 surge current Icp flowing through the switching transistor 1 is expressed as:
ICP (VZ + VRC - VBE) / RE (2).
In this expression, Vz designates the voltage associated with the constant-voltage diode 18.
As can be seen from the expression (2), the value of the surge 25 current Icp appearing in the switching transistor 1 is limited to an upper-limit value owing to the voltage value Vz of the diode 18 and the voltage drop VRC
in the diode 6. In other words, the surge current Icp does not exceed a fixed value. Consequently, it is possible to suppress the collector surge current caused by an abrupt operation of the switching transistor 1.
,0 , ~; .
As above, the ringing choke converter according to the present invention is capable of suppressing the collector surge current appearing due to an abrupt operation of the switching transistor at a rapid change in the input voltage and the load current when the switch is turned on or off. In accordance 5 with the present invention, a protection circuit can be implemented in a simplified configuration. As a result, a switching transistor requiring a limited surge current may be used, thereby improving the quality of the converter circuit.
While the present invention has been described with reference to 10 the particular illustrative embodiment, it is not to be restricted by the embodiment but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiment without departing from the scope and spirit of the present invention.
.
Claims (3)
1. A ringing choke converter for converting voltage of a direct-current source into a regulated direct-current voltage, said converter comprising:
a direct-current voltage source;
a transformer having a primary winding with first and second end terminals, a base winding with first and second end terminals, and a secondary winding for outputting said regulated voltage;
a power switch connected between said voltage source and said hrst end terminal of said primary winding;
a switching transistor means having a collector connected to said second end terminal of said primary winding, a base connected through a first diode and a first resistor to said first end terminal of said base winding so that said switching transistor is turned on by a voltage developed across said base winding, and an emitter connected through a second resistor to said second terminal of said base winding;
a control transistor means having a collector connected to said base of said switching transistor means and through a third resistor to said first terminal of said primary winding, a base coupled to receive a control signal forperiodically turning on said control transistor means to turn off said switchingtransistor means, and an emitter connected to said second terminal of said base winding;
a second diode and a capacitor connected in series between said base of said switching transistor means and said second end terminal of said base winding so that said switching transistor means is kept from turning on fora charging period of said capacitor after said power switch is closed; and, a constant-voltage diode means connected across said capacitor to limit voltage developed thereacross after said power switch is closed.
a direct-current voltage source;
a transformer having a primary winding with first and second end terminals, a base winding with first and second end terminals, and a secondary winding for outputting said regulated voltage;
a power switch connected between said voltage source and said hrst end terminal of said primary winding;
a switching transistor means having a collector connected to said second end terminal of said primary winding, a base connected through a first diode and a first resistor to said first end terminal of said base winding so that said switching transistor is turned on by a voltage developed across said base winding, and an emitter connected through a second resistor to said second terminal of said base winding;
a control transistor means having a collector connected to said base of said switching transistor means and through a third resistor to said first terminal of said primary winding, a base coupled to receive a control signal forperiodically turning on said control transistor means to turn off said switchingtransistor means, and an emitter connected to said second terminal of said base winding;
a second diode and a capacitor connected in series between said base of said switching transistor means and said second end terminal of said base winding so that said switching transistor means is kept from turning on fora charging period of said capacitor after said power switch is closed; and, a constant-voltage diode means connected across said capacitor to limit voltage developed thereacross after said power switch is closed.
2. A ringing choke converter as in claim 1, and further comprising a control means for generating said control signal in the form of a periodically-changing analog signal.
3. A ringing choke converter as in claim 1, and further comprising a smoothing circuit connected to said secondary winding of said transformer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JPU.M.91-13535 | 1991-02-19 | ||
| JP1353591U JPH0750872Y2 (en) | 1991-02-19 | 1991-02-19 | Ringing choke converter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2061228A1 CA2061228A1 (en) | 1992-08-20 |
| CA2061228C true CA2061228C (en) | 1997-05-27 |
Family
ID=11835854
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2061228 Expired - Fee Related CA2061228C (en) | 1991-02-19 | 1992-02-14 | Ringing choke converter |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH0750872Y2 (en) |
| CA (1) | CA2061228C (en) |
-
1991
- 1991-02-19 JP JP1353591U patent/JPH0750872Y2/en not_active Expired - Lifetime
-
1992
- 1992-02-14 CA CA 2061228 patent/CA2061228C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2061228A1 (en) | 1992-08-20 |
| JPH04101290U (en) | 1992-09-01 |
| JPH0750872Y2 (en) | 1995-11-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |