JP3010608B2 - Ringing choke converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ringing choke converter used as a low-cost constant-voltage power supply for electronic devices.

[0002]

2. Description of the Related Art FIG. 4 is a general circuit diagram of a ringing choke converter (also called a flyback converter). In FIG. 4, a ringing choke converter is provided between a transformer 2 having a primary winding P, a secondary winding S and an auxiliary winding A, and between the positive and negative power supply terminals IP and IN via the primary winding P of the transformer 2. Switching elements connected in series, for example, a drain (hereinafter referred to as D), a source (hereinafter referred to as S) and a current detecting resistor 6 of the MOSFET 1, and a collector of which is connected to a gate (hereinafter referred to as G) of the MOSFET 1 and a starter A switching control transistor 5 having its emitter connected to the positive power supply terminal IP, its emitter connected to the negative power supply terminal IN and the negative electrode of the auxiliary winding A, and its base connected to the S of the MOSFET 1; Capacitors 4 connected in series between the collector of transistor 5 and the positive electrode of auxiliary winding A of transformer 2, respectively. And a driving circuit 4 including a resistor 4B, an output diode 7 having an anode connected to the negative electrode of the secondary winding S of the transformer 2, and a cathode of the output diode 7 and a positive electrode of the secondary winding S. An output capacitor 8 connected therebetween, a smoothing coil 9 and a smoothing capacitor 10 connected in series between both terminals of the output capacitor 8, respectively, and connected to both terminals of the smoothing capacitor 10, respectively. And positive and negative output terminals OP and ON.

FIG. 5 shows the operation waveform, and at time t ₀ , the DC voltage V is applied between the positive and negative power supply terminals IP and IN.
When "in" is applied, the capacitor 4A of the drive circuit 4 is charged via the starting resistor 3, and as shown in FIG.
The voltage between G and S of SFET1, that is, the gate voltage increases. When this gate voltage exceeds the threshold value at time t ₁ , MOSFET 1 starts to turn on, DC voltage Vin is applied to primary winding P of transformer 2, and a voltage is induced in auxiliary winding A. This voltage is the G of MOSFET 1
MOSFET 1 is completely turned on by positive feedback.
(1), (2)｝. When the MOSFET 1 is turned on, the primary winding P of the transformer 2 has a voltage of approximately (Vin / L) · T (where L is the inductance of the primary winding P, and T is the time after the MOSFET 1 is turned on). The constantly rising primary current Ip flows {FIG. 5 (3)}. The resistance value of the current detecting resistor 6 is so small that it is ignored. Voltage drop occurs between both terminals of the current detection resistor 6 by the primary current Ip, since the voltage drop is applied between the emitter and base of the switching control transistor 5, a current value Ipp primary current Ip at time t ₂ When the switching control transistor 5 is turned on, the switching control transistor 5 is turned on.
Turns off {Fig. 5 (1), (3)}. When the primary current Ip reaches the current value Ipp, the primary coil P of the transformer 2 stores energy of ・ · L · (Ipp) ² .
When the MOSFET 1 is turned off, the output capacitor 8 is output from the negative electrode of the secondary coil S through the output diode 7.
And the stored energy is released. When the stored energy is released, the voltage of each winding of the transformer 2 decreases and returns to the initial state. On the other hand, MOSFE
When T1 is turned off, the switching control transistor 5 is turned off because the base current is cut off. This transistor 5
Is turned off, the charging of the capacitor 4A of the drive circuit 4 through the starting resistor 3 starts again. These operations are repeated to continue the oscillation, and the positive and negative output terminals OP, ON
Outputs a voltage Vout. FIG. 5D shows the current Ic of the output capacitor 8, that is, the charging current flowing into the output capacitor 8 from the negative electrode of the secondary coil S when the MOSFET 1 is turned off and the discharging current flowing out through the smoothing coil 9 after charging. Is shown. Of the output capacitor current Ic, the discharge current is determined by the positive and negative output terminals OP and O.
The magnitude is almost equal to the load current Io output from N.

In the ringing choke converter described above, its output is, for example, an output voltage Vout of 5 V,
When the output current Io is about 1A, the capacitance 8A of the output capacitor 8 becomes a large capacity of about 1000 microfarads. For this purpose, an electrolytic capacitor is generally used. However, the capacitance of the electrolytic capacitor decreases with time, and the resistance value of the internal equivalent series resistance (hereinafter referred to as ESR) 8B increases.

For this purpose, an output capacitor deterioration warning device 11 is often provided as shown in FIG. In FIG. 3, the output capacitor deterioration warning device 11 includes a capacitor 16A and a resistor 16B connected in series between both terminals of the output capacitor 8, an auxiliary winding B newly provided in the transformer 2, and an auxiliary winding B. A diode 15A whose anode is connected to the negative electrode of the line B, a capacitor 15B connected between the cathode of the diode 15A and the positive electrode of the auxiliary winding B, and each power supply terminal is connected to both terminals of the capacitor 15B. One input terminal is connected to the connection point of the capacitor 16A and the resistor 16B, the other input terminal is connected to the reference voltage power supply 16D, and the output terminal is connected to the operational amplifier 16C as a comparator connected to the alarm signal terminal S. It is configured.

When the output capacitor 8 is deteriorated, the ripple voltage between both terminals of the output capacitor 8 increases due to a decrease in the capacitance and an increase in the resistance value of the ESR. Since this ripple voltage appears as a voltage between both terminals of the resistor 16B through the capacitor 16A, the operational amplifier 16C compares this ripple voltage with the voltage of the reference voltage power supply 16D (which becomes a threshold value). Is exceeded, an alarm signal for deterioration of the output capacitor is output from the output terminal.

The smoothing capacitor 10 has a large capacitance of 100 to several hundred microfarads, and an electrolytic capacitor is used in the same manner. However, the smoothing capacitor has a large current value like an output capacitor. -Since there is no repetition of discharge and there is almost no deterioration, there is no particular need to provide a deterioration alarm device.

[0008]

In the above-mentioned ringing choke converter, the device for alarming the deterioration of the output capacitor requires an operational amplifier as a comparator or a power supply circuit of the operational amplifier, which causes an increase in cost. . SUMMARY OF THE INVENTION It is an object of the present invention to provide a ringing choke converter provided with a low-cost output capacitor deterioration alarm device.

[0009]

In order to achieve the above-mentioned object, a ringing choke converter according to the present invention comprises a transformer having a primary winding, a secondary winding and an auxiliary winding, and a positive and a negative winding via the primary winding of the transformer. The positive side main terminal, the negative side main terminal and the current detecting resistor of the switching element connected in series between the negative side power supply terminal and the negative side power supply terminal, respectively. A switching control transistor having an emitter connected to a negative power supply terminal and a negative electrode of the auxiliary winding, a base connected to a negative main terminal of the switching element, and a collector of the switching control transistor. A drive circuit comprising a capacitor and a resistor connected in series between the positive pole of the auxiliary winding of the transformer, An output diode having an anode connected to the negative electrode of the secondary winding of the transformer; an output capacitor connected between the cathode of the output diode and the positive electrode of the secondary winding; A smoothing coil and a smoothing capacitor respectively connected in series between both terminals of the capacitor, a positive output terminal and a negative output terminal respectively connected to both terminals of the smoothing capacitor, and an emitter of which is connected to the output capacitor. The alarm is connected to the connection point of the smoothing coil, the collector is connected to the connection point of the output capacitor and the smoothing capacitor via the current limiting resistor, and the base is connected to the connection point of the smoothing coil and the smoothing capacitor. A transistor and an alarm signal terminal connected to the collector of the alarm transistor.

[0010]

In the ringing choke converter according to the present invention, the output capacitor deterioration warning device has an emitter connected to the connection point between the output capacitor and the smoothing coil, and a collector connected to the output capacitor via the current limiting resistor. At the connection point of the capacitor, the base is composed of an alarm transistor connected to the connection point of the smoothing coil and the connection point of the smoothing capacitor, respectively, and an alarm signal terminal connected to the collector of the alarm transistor.

When the output capacitor is deteriorated, its E
The resistance value of SR increases, and the voltage drop of this ESR increases. Since the voltage drop of this ESR appears between both terminals of the smoothing coil through the output capacitor and the smoothing capacitor, it is input to the base of the alarm transistor. When the voltage value exceeds the operating voltage of the transistor (becomes a threshold value), the transistor turns on. Since the turning on of the alarm transistor is repeated for each charging cycle of the output capacitor, an alarm signal of a pulse wave is output from the alarm signal terminal connected to the collector, and the deterioration of the output capacitor is alarmed.

[0012]

FIG. 1 is a circuit diagram showing an embodiment of a ringing choke converter according to the present invention. The circuit of the ringing choke converter of the present invention shown in FIG. 1 is the same as the circuit of the general ringing choke converter shown in FIG. 4 except that the emitter is connected to the connection point between the output capacitor 8 and the smoothing coil 9.
An alarm transistor 13 whose collector is connected to the connection point of the output capacitor 8 and the smoothing capacitor 10 via the current limiting resistor 12 and whose base is connected to the connection point of the smoothing coil 9 and the smoothing capacitor 10, respectively. The alarm signal terminal S connected to the collector of the alarm transistor 13
These constitute an output capacitor deterioration warning device 11. Reference numeral 14 denotes a base resistor of the warning transistor 13 which is used as needed.

FIG. 2 shows an operation waveform of the output capacitor 8. If the output capacitor 8 composed of an electrolytic capacitor is deteriorated, its output E is increased.
The resistance value of SR increases, and the voltage drop Ee of FIG.
As shown in (1), the voltage drop c shown by the solid line increases during normal operation to the voltage drop d shown by the broken line during deterioration. This E
Since the voltage drop Ee of SR appears between the two terminals of the smoothing coil 9 through the capacitance 8A of the output capacitor 8 and the capacitance of the smoothing capacitor 10, the voltage drop Ee passes through the base resistor 14 used as necessary. It is added to the base of the warning transistor 13. When the voltage value exceeds the operating voltage (becomes a threshold value) of the transistor 13, the transistor 13 is turned on. The turning on of the warning transistor 13 is repeated in each charging cycle of the output capacitor 8 as shown in FIG. 2 (6), so that a warning signal of pulse wave is output from the warning signal terminal S connected to the collector. . Other operations are the same as those in FIG.

In the above description, the case where the output capacitor is formed of an electrolytic capacitor has been described. However, it is needless to say that the deterioration of the capacitor can be alarmed similarly when the output capacitor is formed of a normal paper capacitor or the like. In addition, this type of ringing choke converter is used as a constant voltage power supply for electronic devices.
Various commercial low voltage power supplies, for example, AC 100, 110, 12
In many cases, it is used by being connected to a power supply of a wide range of DC voltage of 85 to 265 V obtained by rectifying 0, 200, 220 and 240 V. If the output capacitor is deteriorated and damaged, it directly affects the commercial low voltage power supply. This output capacitor deterioration warning device has a great effect because the deterioration of the output capacitor can be detected and replaced before the output capacitor is damaged.

[0015]

In the ringing choke converter according to the present invention, the output capacitor deterioration alarm device is mainly composed of one transistor, so that the cost is extremely low.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a ringing choke converter according to the present invention provided with a deterioration alarm device for an output capacitor.

FIG. 2 is a waveform chart showing an operation of the ringing choke converter shown in FIG.

FIG. 3 is a circuit diagram showing an example of a conventional ringing choke converter provided with a deterioration alarm device for an output capacitor.

FIG. 4 is a general circuit diagram of a ringing choke converter.

FIG. 5 is a waveform chart showing an operation of the ringing choke converter shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 switching element 2 transformer 3 starting resistor 4 drive circuit 4A capacitor 4B resistor 5 switching control transistor 6 current detecting resistor 7 output diode 8 output capacitor 9 smoothing coil 10 smoothing capacitor 12 current limiting resistor 13 alarm transistor P Primary winding (for transformer 2) S Secondary winding (for transformer 2) A Auxiliary winding (for transformer 2) IP Positive power supply terminal IN Negative power supply terminal OP Positive output terminal ON Negative output terminal S Alarm Signal terminal

Claims (3)

(57) [Claims] A transformer having a primary winding, a secondary winding and an auxiliary winding, and a positive side of a switching element connected in series between a positive side power supply terminal and a negative side power supply terminal via the primary winding of the transformer. A main terminal, a negative main terminal and a current detecting resistor, and a collector thereof is connected to a positive power supply terminal via a control terminal and a starting resistor of the switching element, and an emitter thereof is connected to a negative power supply terminal and a negative electrode of the auxiliary winding. A switching control transistor whose base is connected to the negative main terminal of the switching element, and a capacitor connected in series between a collector of the switching control transistor and a positive electrode of the auxiliary winding of the transformer. And a drive circuit comprising a resistor, an output diode having an anode connected to the negative electrode of the secondary winding of the transformer, An output capacitor connected between the cathode of the output diode and the positive electrode of the secondary winding; a smoothing coil and a smoothing capacitor respectively connected in series between both terminals of the output capacitor; Positive and negative output terminals respectively connected to both terminals of the output capacitor, an emitter thereof is provided at a connection point between the output capacitor and the smoothing coil, and a collector thereof is connected to the output capacitor via a current limiting resistor. At the connection point of the capacitor, the base comprises an alarm transistor connected to the connection point of the smoothing coil and the connection point of the smoothing capacitor, respectively, and an alarm signal terminal connected to the collector of the alarm transistor. Ringing choke converter. 2. The ringing choke converter according to claim 1, wherein said output capacitor comprises an electrolytic capacitor. 3. The ringing choke converter according to claim 1, wherein a positive power supply terminal and a negative power supply terminal are connected to a DC power supply obtained by rectifying various commercial low-voltage power supplies.