JP2000201482A - Ac-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AC-DC converter used for charging a lithium ion battery, etc., which has a small number of constituent parts but has a desired performance and which has a high efficiency with small heat generation. SOLUTION: The output voltage converted into DC by an output rectifying circuit 7 is controlled by an LED 8 and a shunt regulator 9. Then, a control signal is transmitted to a photo transistor 5 to control the switching voltage at the primary side of a transformer 2 and obtain stabilized DC voltage, which is a characteristic near the full-charging voltage of a battery. Depending on the output voltage, three types of modes are generated by three transistors Q11, Q12, Q13. The three modes are an initial charging mode of a small constant current, a rapid charging mode of a large constant current, and a constant voltage region mode. Because of this structure, a circuit suitable for charging can be obtained with a small number of components. By installing a means for differentiating part of the flyback voltage generated in the collector of a switching transistor 3 and adding part of the output of the means to a positive feedback loop, a switching speed is increased. By keeping the saturated voltage of the collector of the transistor 3 low, generation of heat can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, and more particularly to a power supply device used for charging a lithium ion battery or the like.
It relates to a C / DC converter.

[0002]

2. Description of the Related Art When a lithium ion battery is charged, three charging modes, a constant voltage mode, a constant current rapid charging mode, and a constant current initial charging mode, are required depending on the state of the battery voltage.

FIG. 1 shows these three modes as output voltage-current characteristics. In the figure, the area C of the characteristic curve is the constant current initial charging mode, the area B is the constant current rapid charging mode, the area A is the constant voltage mode, and the used batteries are charged generally in the order of the area CBA. Is done. As an example of a power supply for realizing these three modes, as shown in FIG.
After the constant voltage output of the AC / DC converter, a circuit for switching the three modes is added.

FIG. 3 is a block diagram illustrating a circuit of such an AC / DC converter. In the figure, reference numeral 1 denotes a rectifying unit for converting a commercial AC power supply into DC, 2 a transformer for transmitting a signal converted into AC by a switching transistor to be described later to a secondary side, and 3 a converter for converting DC from the primary side to AC. The switching transistor 4 is a positive feedback bias signal circuit necessary for the switching transistor 3, the photo transistor 5 is coupled to a light emitting diode described later and controls the switching duty in response to an output voltage, and the reference numeral 6 is for the impedance change of the photo transistor 5. A bias control circuit for controlling the on-duty of the switching in accordance with the current; a reference numeral 7 denotes an overcurrent detection resistor provided for overcurrent protection of the switching transistor 3; a reference numeral 8 denotes an output rectifier circuit; A light emitting diode for signaling 5, 10 is a base for comparison with the DC output voltage. A shunt regulator that has a built-in voltage and variably controls the current according to the difference voltage; 11, an output current adjustment circuit; 12, an output voltage detection / control circuit (or IC); 13, a resistance for output current detection; Battery.

The output voltage detection / control circuit 12 controls the output current adjustment circuit 11 based on the current value detected by the output current detection resistor 13 to switch the charging mode to one of the three modes. In such a conventional charging circuit, the output current adjusting circuit is likely to be at a high temperature,
The number of parts constituting the circuit was considerably large.

FIG. 5 shows a self-excited flyback AC / D.
It is a circuit diagram of a C converter. In such a circuit, a snubber circuit I in the figure, a surge absorber circuit II in the figure, or both are used to suppress a surge voltage superimposed on the flyback voltage. These main purposes are used to suppress a surge voltage below the collector rated voltage of the switching transistor, and are rarely used to directly suppress the heat generation of the switching transistor.

[0007] In FIG. 5, the DC voltage V _DC obtained by rectifying the commercial power is supplied to the primary side of the output transformer TR, the other end is connected to the collector of the switching transistor Q _1. The output transformer TR is insulation between the primary and secondary output voltage conversion and a transistor Q ₁ in accordance with the primary and secondary each winding number comprises a bias winding required to self-oscillation.

[0008] it is supplied to the base of the switching transistor Q ₁ through a rectified dc voltage V _DC generated after the power-on of the primary side starting resistor R _{5 ',} which was in an operating state, the collector potential V _CE of the transistor Q ₁ is Rectified DC voltage V
_Lower than _DC . The output b of the voltage change bias winding wound on the collector a point opposite phase of the transistor Q ₁
Generates a positive voltage at point, the bias output is supplied to the base of the transistor Q ₁ through a diode D _B, further accelerating the on-state transistor Q _1.

[0009] On the other hand, the bias winding output is supplied to the base of the transistor Q ₂ with the delay time out with _'capacitor C ₂ through _a' and transistor Q ₃ which is photo-coupled to the secondary output voltage resistor R ₃ You. Transistor Q
The base potential V _BE of the transistor ₂ gradually rises, and when it reaches the ON state, the base potential of the transistor Q ₁ is forcibly lowered to turn off the transistor Q ₁ .

[0010] off-time of the transistor Q _1, a DC output is obtained so far energy accumulated primary side during on-time via a transmitted diode D _s at the secondary side. The change of the current flowing through the secondary side of the transformer TR is gradually increased potential of the bias winding, eventually the transistor Q ₁ is turned on. In this way, the circuit that has been started once maintains the self-oscillation state.

FIG. 7 shows voltage and current waveforms of respective parts in the case where the snubber circuit 1 and the surge absorber circuit II in FIG. 5 are not provided. First, the waveform at the winding output b point called the bias winding is applied to the transistors Q ₃ and R ₃ ′, C ₃ photo-coupled to the secondary output voltage.
₂ ′ and is supplied to the base d point of the transistor Q ₂ with a delay time. Transistor Q ₂ is V _BE starts gradually operation from around about 0.6V, eventually turned on, so lowering the potential of the base point c of the transistor Q _1, as a result the transistor Q ₁ is turned off, its collector Rapidly changes to a high potential. In this transistor Q ₁ is the emitter current waveform flowing during the on period of the f point waveform, the flyback, during the on-time almost linearly current as in FIG changes.

[0012] Therefore, the calorific value of the transistor Q ₁ is was very large.

[0013]

SUMMARY OF THE INVENTION Such a conventional AC
In the DC / DC converter, the charging circuit has problems such that the output current adjusting circuit is likely to be heated to a high temperature and the number of components constituting the circuit is increased.

In recent years, such AC / DC converters have been strongly reduced in size and thickness, and among them, it is very important to reduce the amount of heat generated by the switching transistors, which is extremely large.

The present invention solves the above problems, obtains desired performance with a small number of components, and has a small number of heat-generating components and a small amount of heat generated by a switching transistor. A suitable for charging
It is intended to realize a C / DC converter.

[0016]

According to the first aspect of the present invention, a small constant current mode suitable for initial charging and a large constant current mode suitable for charging close to a full charging voltage are provided according to the output voltage level. The problem is solved by providing two constant current modes, that is, a constant current mode.

Further, according to the first aspect, the above-mentioned object is provided.
A rectifier circuit for converting a commercial AC power supply into a DC voltage having a desired voltage; a switching transistor supplied with power from the rectifier circuit to operate; a transformer for transmitting a primary-side signal obtained from the switching transistor to a secondary side; A rectifier circuit for rectifying a secondary output of the rectifier circuit, a light emitting diode for generating a transmission signal corresponding to an output voltage of the rectifier circuit, a phototransistor for receiving a signal from the light emitting diode and controlling a duty of the switching transistor; A shunt regulator that incorporates a reference voltage for comparison with the output voltage and variably controls the current according to the difference voltage; a first transistor that operates the light emitting diode in an on state; The ratio of the second transistor that turns on the first transistor to the reference voltage A third transistor for turning on and off according to the level of the output voltage level to change the state of the second transistor, wherein the third transistor is in an off or on state. The problem can be solved by charging the battery by automatically continuously performing the three modes of the large constant current mode in which the three transistors are on or off, and the constant voltage mode controlled by the shunt regulator. .

Further, according to a second aspect of the present invention, there is provided a rectifier circuit for converting a commercial AC power supply into a desired DC voltage, and a switching transistor supplied with power from the rectifier circuit to generate an AC voltage. Means for differentiating a part of the flyback voltage generated at the collector of the switching transistor, and increasing the switching speed by adding a part of the output of the differentiating means to a positive feedback loop. This can be solved by keeping the collector saturation voltage low.

[0019]

DETAILED DESCRIPTION OF THE INVENTION In a first aspect of the present invention,
According to the level of the output voltage, two constant current modes are provided: a small constant current mode suitable for initial charging and a large constant current mode suitable for charging close to the full charging voltage. When used in combination with the constant voltage mode, an AC / DC converter suitable for charging a lithium ion battery or the like can be obtained.

Furthermore, a rectifier circuit for converting a commercial AC power supply into a DC of a desired voltage, a switching transistor supplied with power from the rectifier circuit and operating, and a transformer for transmitting a primary signal obtained from the switching transistor to a secondary side. A rectifier circuit for rectifying the secondary output of the transformer, a light emitting diode for emitting a transmission signal corresponding to the output voltage of the rectifier circuit, a phototransistor for receiving a signal from the light emitting diode and controlling the duty of a switching transistor, and comparing with a DC output voltage Built-in reference voltage for
A shunt regulator that variably controls the current according to the difference voltage is provided, and the output voltage converted into DC by the output rectifier circuit is controlled by the light emitting diode and the shunt regulator, and the control signal is transmitted to the phototransistor via the light emitting diode. It controls the switching voltage on the primary side of the transformer to create a constant voltage mode.

A first transistor for turning on the light emitting diode in the on state, a second transistor for turning on the first transistor in accordance with an increase in charging current, and a comparison means for comparing with a reference voltage; A third transistor that is turned on and off according to the magnitude of the third transistor and changes the state of the second transistor.
And a large constant current mode in which the third transistor is in an off or on state, and a large constant current mode in which the third transistor is in an on or off state.
By automatically charging these three modes in accordance with the state of charge of the battery to charge the battery, the control semiconductor switch does not become hot and the circuit configuration is simplified. In addition, the number of parts can be reduced.

According to a second aspect of the present invention, there is provided a rectifier circuit for converting a commercial AC power supply into a desired DC voltage,
A switching transistor supplied with power from a rectifier circuit to generate an AC voltage, and a means for differentiating a part of a flyback voltage generated at a collector of the switching transistor, and a part of an output of the differentiating means to a positive feedback loop. In addition, the switching speed is increased, the saturation voltage of the collector of the transistor is kept low, and the AC / DC converter is provided with a highly efficient switching circuit that suppresses unnecessary heat generation.

[0023]

FIG. 2 shows a first embodiment of the AC / DC converter according to the present invention.
3 is a circuit diagram of an embodiment of the invention of the present invention, a part of which is the same as that of FIG. 3 of the conventional circuit described above, wherein 1 is a rectifier for converting a commercial AC power supply to DC, and 2 is AC-converted by a switching transistor described later. A transformer for transmitting a signal to the secondary side, a switching transistor 3 for converting a primary side direct current into an alternating current,
4 is a positive feedback bias signal circuit required for the switching transistor 3, 5 is a phototransistor coupled to a light emitting diode described later to control the duty of the switch in response to an output voltage, and 6 is a switch in accordance with a change in the impedance of the phototransistor 5. , A bias control circuit for controlling the on-duty of the LED, 7 is an output rectifier circuit, 8 is a light emitting diode for transmitting a signal to the phototransistor 5 for controlling the output voltage at a constant voltage and a constant current, and 9 is for comparing with a DC output voltage. A shunt regulator 14 having a built-in reference voltage and variably controlling the current according to the difference voltage, and 14 is a lithium ion battery.

The output voltage V converted into a direct current by the output rectifier circuit 7 is controlled by the light-emitting diode 8 and the shunt regulator 9, and a control signal is transmitted to the phototransistor 5 via the light-emitting diode 8, and A stabilized DC voltage is obtained by controlling the switching voltage on the primary side.

The DC output in this case is the output voltage of FIG.
This is a constant voltage region corresponding to the portion A in the current characteristics, and generally realizes characteristics near the full charge voltage of the battery.

On the other hand, in the constant current region, the transistor Q ₁₁
And the transistor _{Q 12, V BE11 = V BE12} ≒
A 0.6V, _{also, VR11 = R 11 I 11 =} V
_{R12 = R 12 I 12 (I} 12 is substantially constant) relation is always present. That is, in the set current near the point A 'in FIG. _1, with an increase in _{I 11, V R11} increases,
The transistor Q ₁₁ collector potential of the transistor Q ₁₂ is increased to the ON state, and controls the light emitting diode 8 will control the output voltage. This means the constant current mode.

Further, based on the relationship of I ₁₂ ≒ I ₁₃ + I ₁₄ , the output voltage level is detected by the voltage comparison amplifier IC, and the transistor Q ₁₃ is turned on and off according to the level of the output voltage level, thereby controlling I _13. Can be. That is, I
And ₁₂ ≒ _{I 14,} the _{I 12 ≒ I 1 3 + I} 14, it is possible to create a state of two modes.

The former state is a minute constant current mode corresponding to the area of section C in FIG. 1, and the latter state is a large constant current mode corresponding to the area of section B in FIG.

The above operation will be described in terms of the charging function of a lithium ion battery.
In the region of section C in FIG. 1 where the voltage level is low, the converter output of this embodiment follows the battery voltage and becomes a low output voltage.

[0030] At this time, the transistor _{Q 13} is _{off, I 12 ≒ I 14, V} R11 = V R12 = R 12 I
_The output voltage is controlled such that the relationship of ₁₂ ≒ R ₁₂ I ₁₄ is maintained. This state corresponds to the initial charging mode of the battery, and the battery is being gradually charged.

[0031] When the charging potential of the C portion of FIG. 1 approaches the area of the part B, the transistor _{Q 13} is turned on, current _{I 12} increases rapidly. That is, I ₁₂ ≒ I ₁₃ + I ₁₄ . This _{is, V R12 = R 12 (I} 13 + I 14)
= _V R11 ₌ consists relation _R 11 _{I 11} to allowed to increase the _{I 11} abruptly, the state is the rapid charging state corresponding to the region of the part B of FIG.

After the rapid charging, when the battery voltage approaches the specified voltage, the charging current suddenly decreases. When the battery voltage reaches the specified voltage, the charging current becomes zero and the charging ends. This state corresponds to the region A in FIG. 1 and corresponds to the constant voltage region.

As described above, an AC / DC converter having a simple and efficient charging function with a small number of circuit components can be realized.

FIG. 4 is a circuit diagram of a second embodiment of the present invention, and FIG.
Represents voltage and current operation waveforms at each point in FIG. Regarding the operation of the circuit in the present embodiment, the description of the same parts as the operation of the circuit of FIG. 5 will be omitted, and the differences will be described.

A capacitor C ₁ and a resistor R ₁ are connected in series to the collector and the point A of the switching transistor Q ₁ , and a differential waveform as shown in FIG. by combining the bias winding output voltage of the point B through the resistor R _2, the transistor Q ₂
Base, the signal transfer transistor Q ₂ in rapid on-state is obtained in the D point. As a result, the base point C of the transistor Q ₁ is drawn rapidly zero potential, transferring the transistor Q ₁ in the OFF state. Meanwhile the base potential of the transistor Q ₁ is able to maintain a sufficient voltage to hold transistor Q ₁ in the ON state. This means that the collector-emitter voltage V _CE , commonly called V, during the ON period of the transistor Q ₁ , as seen in the enlarged voltage waveform diagram of FIG.
_{The CESAT} voltage can be held low for a long time.

As described above, in this embodiment, FIG.
A remarkable difference can be obtained as compared with that of. In particular,
In a flyback converter in which the emitter current or the collector current increases as the point closer to the turn-off portion during the on-period of the transistor, the calorific value of the transistor becomes V
Is proportional to the _CE × I _C, becomes connected to the heating amount control significant transistor. In addition, the short turn-off period also contributes to the suppression of heat generation.

As a result of such a configuration, the transistor Q ₁
The rise in temperature due to the heat generation can be suppressed to 以下 or less of that of the conventional basic circuit.

Since the capacitor C ₁ and the resistor R ₁ connected to the collector of the switching transistor Q ₁ also operate as a surge absorber function for suppressing a surge voltage, they are generated by leakage inductance and the like as shown in FIG. 6A. Since the parasitic oscillation is also suppressed, the collector voltage of the transistor can be kept low.

As described above, the circuit of this embodiment is a highly efficient switching circuit in which loss due to unnecessary heat generation is suppressed.

FIG. 9 is a circuit diagram in which the portion P surrounded by a frame in FIG. 2 is further improved in order to make the minute constant current mode in the first invention more stable. Was.

The inventor of the present invention has found that I ₁₄ = I ₁₂ + I
_BE2 , I _{BE2 in the} minute constant current mode.
We noticed that was not negligible.

In the state of the constant current mode, _VR12
= Relation V _R11 holds detects the output voltage level at the voltage comparison amplifier IC, it is possible to control the V _R12 by turning on and off the transistors Q _{13 'the} magnitude of that level. That _is, 'when is _{on, V R12 = V CE3SAT Q 13} ' is _{V R12} Q ₁₃ when the _off, V R12 _{= I 12 R} 12 generally _{V CE3SAT} about the collector saturation voltage of _{Q 13} '0 .25 V and R ₁₂ I when Q ₁₃ ′ is off
₁₂ corresponds to about 1 / 8th of about 0.2V. That _{V R12} can create a two-mode state of _{V CE3SAT} and _I 13 _{R 12.}

The former state is a minute constant current mode corresponding to the area of section C in FIG. 1, and the latter state is a large constant current mode corresponding to the area of section B in FIG.

The above operation will be described from the aspect of the charging function of the lithium ion battery.
In the region of section C in FIG. 1 where the voltage level is low, the converter output of this embodiment follows the battery voltage and becomes a low output voltage.

At this time, the transistor Q ₁₃ ′ is in the ON state, and V _R11 = I ₁₁ R ₁₁ = VR ₁₂ = V
_The output voltage is controlled so that the relationship of _CE3SAT is maintained. This state corresponds to the initial charging mode of the battery, and the battery is being gradually charged.

When the charging potential of the portion C in FIG. 1 approaches the region of the portion B, the transistor Q ₁₃ ′ turns off and the current I ₁₂
Increases rapidly. _{That, V R11 = I 11 R 11} = V
_{R1 = I 12 R 12> VC} E3SAT _next, will be allowed to increase abruptly the _{I 11,} this state is the rapid charging state corresponding to the region of the part B of FIG.

After the rapid charging, when the battery voltage approaches the specified voltage, the charging current suddenly decreases. When the battery voltage reaches the specified voltage, the charging current becomes zero and the charging ends. This state corresponds to the region A in FIG. 1 and corresponds to the constant voltage region.

As described above, according to the present embodiment, it is possible to provide an AC / DC converter having a simple and efficient charging function with a small number of circuit components, and to make the minute constant current mode more stable. it can.

[0049]

As described above, according to the present invention, it is possible to obtain a desired performance with a small number of components, a small number of heat-generating parts, and a high-efficiency lithium-ion battery with a small amount of heat generated by a switching transistor. AC / suitable for charging
A DC converter could be realized.

[Brief description of the drawings]

FIG. 1 is an output voltage-current characteristic during charging by an AC / DC converter.

FIG. 2 is a block diagram of a circuit explaining the first invention.

FIG. 3 is a block diagram of a conventional circuit corresponding to the first invention.

FIG. 4 is a circuit diagram illustrating a second invention.

FIG. 5 is a conventional circuit diagram corresponding to the second invention.

FIG. 6 is an operation waveform diagram of each part in the circuit of FIG. 4;

7 is an operation waveform diagram of each part in the circuit of FIG.

8 is an operation waveform diagram in which a part of the circuit of FIG. 4 is enlarged.

9 is a circuit diagram in which a portion P of the circuit diagram of the first invention in FIG. 2 is further improved.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 rectifier 2 transformer 3 switching transistor 4 positive feedback bias signal circuit 5 phototransistor 6 bias control circuit 7 output rectifier circuit 8 light emitting diode 9 shunt regulator Q ₁ , Q ₂ , Q ₃ transistor Q ₁₁ , Q ₁₂ , Q ₁₃ , transistor _{Q 11 ', Q 12',} Q 13 ' transistor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5G003 AA01 BA01 CA03 CA14 CC07 GB04 5H006 CA01 CB01 DA02 DA04 DB01 DC02 DC05 FA02 5H730 AA14 AA20 AS01 AS02 AS17 BB43 BB52 CC01 DD02 EE07 EE72 FD01 FD31 FF19 FV05 XX15XX

Claims (3)

[Claims] 1. A constant current mode suitable for initial charging of a lithium ion battery or the like and a large constant current mode suitable for charging near a full charge voltage are provided according to an output voltage level. An AC / DC converter, characterized in that: 2. A rectifier circuit for converting a commercial AC power supply into a DC voltage having a desired voltage, a switching transistor supplied with power from the rectifier circuit and operating, and transmitting a primary signal obtained from the switching transistor to a secondary side. A transformer, a rectifier circuit for rectifying a secondary output of the transformer, a light emitting diode for generating a transmission signal in accordance with an output voltage of the rectifier circuit, and receiving a signal from the light emitting diode to control a duty of the switching transistor. A phototransistor, a shunt regulator having a built-in reference voltage for comparison with a DC output voltage and variably controlling a current according to the difference voltage, a first transistor for operating the light emitting diode in an on state, and a charging current A second transistor for turning on the first transistor with an increase And a third transistor for turning on and off according to the level of the output voltage to change the state of the second transistor, wherein the third transistor is in an off or on state. The battery is charged by automatically successively performing three modes of a small constant current mode, a large constant current mode in which a third transistor is on or off, and a constant voltage mode controlled by the shunt regulator. Characteristic AC
/ DC converter. 3. A rectifier circuit for converting a commercial AC power supply to a desired DC voltage, a switching transistor supplied with power from the rectifier circuit to generate an AC voltage, and a flyback generated at a collector of the switching transistor. It has a means for differentiating a part of the voltage, increasing the switching speed by adding a part of the output of the differentiating means to a positive feedback loop, and also keeping the saturation voltage of the collector of the transistor low. AC / DC converter.