JP3174217B2 - Chopper type regulator and chopper type regulator IC - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chopper type regulator and a chopper type regulator for stabilizing an output voltage by controlling switching of an output transistor which is a PNP transistor based on an error between a reference voltage and an output voltage. IC related.

[0002]

2. Description of the Related Art In order to obtain a stabilized DC voltage required for electronic equipment and the like, a regulator is generally used. As one type of this regulator, there is a step-down regulator that obtains an output voltage lower than the input voltage, and there are two types of this step-down regulator. The first type is a regulator called a dropper type, which has the advantages that noise generated is small and design is easy, but when the difference between the input voltage and the output voltage is large, a large amount of heat is generated. This has the disadvantage that the efficiency is reduced.

[0003] The second type is a chopper type regulator whose efficiency does not decrease even when the difference between the input voltage and the output voltage is large. Hereinafter, a conventional technique of the chopper type regulator will be described with reference to the drawings.

FIG. 9 shows a chopper type regulator IC 13.
(Hereinafter, it is referred to as an IC 13). The IC 13 includes a reference voltage circuit 1, an error amplifier 2, an oscillator 3, a PWM comparator 4, a drive transistor 5 as a PNP transistor, and an output transistor 6 as an NPN transistor. To stabilize the output voltage. The IC 13 is provided with a catch diode 7, a coil 8, a voltage dividing circuit composed of two resistors 9 and 10, and an output capacitor 11 as indispensable elements (12 denotes a load).

The operation of this chopper type regulator will be described below.

First, when the input voltage V _IN is applied to the input terminal IN, the operation of the IC 13 is started, and the output voltage divided by the voltage dividing circuit of the resistors 9 and 10 connected to the output terminal OUT is applied to the terminal. Feedback to ADJ. Since the terminal ADJ is connected to the inverting input of the error amplifier 2, the error amplifier 2 outputs an error signal indicating an error between the divided output voltage and the reference voltage. This error signal is shown as a waveform W1 in FIG. 10 among the two types of waveforms a1 and W2.

On the other hand, in the PWM comparator 4,
A wave transmitted from the oscillator 3 and shown as a waveform W2;
The error signal shown as the waveform W1 is compared. Therefore, the PWM comparator 4 outputs a waveform signal indicated by b. This signal is applied to the drive transistor 5
, The switching of the output transistor 6 is controlled. Therefore, the voltage applied to the load 12 is
The voltage divided by 10 is controlled to be equal to the reference voltage.

More specifically, in the above switching, when the output transistor 6 is on, a current is supplied to the load 12 via the input terminal IN, the output transistor 6 and the coil 8. When the output transistor 6 is off, the output transistor 6
The energy stored in the coil 8 during the period when the power supply is in the ON state causes a current to flow through a closed circuit formed by the load 12, the catch diode 7, and the coil 8 (current is supplied to the load 12).

In the above operation, the current flowing through the output transistor 6 has a waveform c, the current flowing through the catch diode 7 has a waveform d, and the current flowing through the coil 8 has a waveform e. Therefore, a current having an average value (indicated by W3) of the waveform e is supplied to the load 12.

Here, assuming that the period during which the output transistor 6 is on is t1, the period during which the output transistor 6 is off is t2, and the duty is M, M = t1 / (t1 + t2).

[0011]

M = V _O + V _F / (V _IN −V _{CE (sat)} + V _F ) where V _O ; output voltage V _F ; forward voltage V _IN of catch diode 7; input voltage V _{CE (sat)} ; It is shown as the collector-emitter voltage of the output transistor 6. That is, the periods t1 and t2 are determined by the output voltage, the forward voltage of the catch diode 7, the input voltage, and the collector-emitter voltage of the output transistor 6.

FIG. 11 shows a chopper type regulator IC16 (hereinafter, IC16) for performing pulse width control in a current mode.
(Hereinafter referred to as "conventional technology").
Note that among the blocks in FIG. 11, the blocks having the same configuration as the blocks shown in FIG. 9 are denoted by the same reference numerals as those denoted in FIG.

The IC 16 includes a reference voltage circuit 1, an error amplifier 2, an oscillator 17, a PWM comparator 4, a flip-flop 14, a current detection amplifier 15, and a current detection resistor 2.
5, a drive transistor 5, and an output transistor 6 are formed. Further, a voltage dividing circuit including a catch diode 7, a coil 8, and resistors 9 and 10, and an output capacitor 11 are externally provided. Then, an error between the output voltage divided by the voltage dividing circuit of the resistors 9 and 10 and the reference voltage is output from the error amplifier 2 as an error signal. This error signal is shown as a waveform W4 in FIG.

The output from the current detection amplifier 15 is
A waveform W5 indicating the value of the current flowing through the current detection resistor 25;
The waveform W4 indicating the error signal is compared by the PWM comparator 4. Therefore, when the output voltage of the current detection amplifier 15 becomes higher than the output voltage of the error amplifier 2, PWM
The output of the comparator 4 becomes H level (indicated by g), and the flip-flop 14 is reset. By this reset, the drive transistor 5 and the output transistor 6 are turned off. The off state is inverted to the on state when a pulse (indicated by h) for setting the flip-flop 14 is transmitted from the oscillator 17.

As described above, the current mode chopper type regulator monitors the current flowing through the current detecting resistor 25, and thereby, based on the divided voltage of the voltage dividing circuit of the resistors 9 and 10, and the value of the reference voltage. Control the output voltage V _O.

Note that the waveforms j, k, and l in FIG.
The main current waveforms at the time of control in the above-described current mode are shown, where j is a current flowing through the output transistor 6, k is a current flowing through the catch diode 7, and l is a current flowing through the coil 8. . The load 12 has an average value of the current flowing through the coil 8 (indicated by W6).
Is supplied.

The features of these two types of chopper type regulators are as follows. The configuration of the voltage mode chopper type regulator is simpler, but the pulse width changes after the output voltage V _O changes. Therefore, there is a disadvantage that a delay occurs in following the fluctuation of the input voltage V _IN . On the other hand, the current mode chopper-type regulator uses the input voltage V _IN before the output voltage V _O fluctuates.
Of the input voltage V _IN is good, but the circuit configuration is complicated.

In the chopper type regulator, the above-mentioned 2 is used.
In addition to the various configurations, there is a configuration in which the output transistor in the voltage mode chopper type regulator is changed from an NPN transistor to a PNP transistor. This chopper type regulator is shown in FIG. Note that, of the blocks in FIG. 13, the blocks having the same configuration as the blocks illustrated in FIG. 9 are given the same reference numerals as those given in FIG. 9.

The chopper type regulator IC 21 used in this configuration is provided with a reference voltage circuit 1, an error amplifier 2, an oscillator 3, and a PWM comparator 4 (however, the PWM comparator 4 has an H level output transistor 19). On). A collector of an NPN transistor 18 corresponding to the drive transistor 5 in FIG.
The base of the output transistor 19 constituted by a PNP transistor is connected via a constant current circuit 20 for controlling the base current of the output transistor 19 to have a constant value. Also, the same external components as those shown in FIG. 9 are connected.

The thus configured chopper regulator is a voltage mode chopper regulator.
The operation is the same as that of the chopper type regulator shown in FIG. 9 except that the output transistor 19 is turned on when the output of the PWM comparator 4 is at the H level, and therefore the description is omitted.

[0021]

Among the above three chopper type regulators, in the configuration using an NPN transistor as the output transistor, the voltage between the collector and the emitter in the ON state is reduced due to the characteristics of the NPN transistor. Becomes larger than the voltage value between the collector and the emitter. For this reason, there has been a problem that the loss due to the output transistor 6 is large and the efficiency of the regulator is reduced.

On the other hand, as shown in FIG. 13, in the configuration using a PNP transistor as the output transistor 19, since the collector-emitter voltage in the ON state is low, the loss of the output transistor 19 is small, and the efficiency as a regulator is reduced. Is high. However, there is a disadvantage associated with the output transistor 19 being a PNP transistor. This disadvantage will be described below.

When output transistor 19 is turned on, constant current circuit 20 draws the base current of output transistor 19. The base current is constant irrespective of the magnitude of the output current, and is set to several tens mA or the like. Also, chopper type regulators are generally
Used when the difference between the input voltage V _IN and the output voltage V _O is large, a high input voltage V _IN is applied to the input terminal IN. Therefore, when compared with a chopper type regulator using an NPN transistor as an output transistor,

[0024]

## EQU2 ## The driving loss represented by the formula: base current of output transistor 19 × input voltage V _IN × duty is large. This drive loss is constant regardless of the output current. Focusing on this from the relationship between the output current and the efficiency, as shown by G in FIG. 14, there has been a problem that the efficiency is reduced in a range where the output current is small.

[0025] The present invention was been made to solve the above problems, inventions of interest, P output transistor
In the configuration using the NP transistor, by detecting the output current and controlling the base current of the output transistor in accordance with the detected output current, it is possible to prevent a decrease in efficiency that occurs in a range where the output current is small. An object of the present invention is to provide a chopper type regulator and a chopper type regulator IC.

The object of the invention described in claim 1 or 2 is as follows.
An object of the present invention is to provide a chopper-type regulator and a chopper-type regulator IC capable of minimizing a loss generated in detection of an output current when controlling a base current of an output transistor by detecting an output current.

[0027]

In order to solve the problems] order to solve the above problems
Chopper-type regulator, based on the error between the reference voltage and the output voltage, by controlling the switching of the output transistor is a PNP transistor, is applied to a chopper-type regulator that regulates the output voltage, it flows through the output transistor output A current detection circuit for detecting a current,
Based on the output current detected by this current detection circuit,
When the output current is small, a current control circuit for controlling to reduce the base current flowing to the output transistor is provided.

[0028]

The chopper regulator according to the first aspect of the invention employs a configuration in which the current detection circuit is a voltage difference detector that detects a voltage difference between the emitter and the collector of the output transistor.

According to a second aspect of the present invention, the output transistor, the current detection circuit and the current control circuit are integrated into one package.

[0031]

[Action] onset Akira of the action is shown below.

By the current detection circuit and the current control circuit,
When the output current is small, the base current of the output transistor is small. Therefore, when the output current is small, the loss caused by the base current of the output transistor decreases. That is, when the loss (collector loss) caused by the voltage between the collector and the emitter of the output transistor changes due to the increase or decrease in the output current, the loss due to the base current increases or decreases in accordance with the change. As a result, the ratio of the loss due to the base current to the collector loss does not increase even when the output current is small. That is, the efficiency in a region where the output current is small is improved.

[0033]

[0034]

[0035] below the effect of the invention of claim 1, wherein.

The collector-emitter voltage of the output transistor changes according to the output current in accordance with the collector-emitter equivalent impedance. Therefore, the output of the voltage difference detector has a value indicating the output current flowing through the output transistor. Further, the loss caused by the detection of the output current is only the power loss of the voltage difference detector.

[0037]

Embodiments of the present invention will be described below with reference to the drawings.

[0038] Figure 1 is a block diagram showing an electrical configuration of an embodiment of a chopper-type regulator and a chopper type regulator IC voltage mode. Note that, in the same figure, the same reference numerals as in FIG. 9 are assigned to blocks having the same configuration as the blocks shown in FIG.

The reference voltage circuit 1 is a block for generating a stabilized reference voltage which is a stabilized predetermined voltage having a very small coefficient with respect to the input voltage V _IN applied to the input terminal IN and a very small temperature coefficient. Then, the generated reference voltage is sent to the non-inverting input of the error amplifier 2.

The error amplifier 2 is a block that amplifies the difference between the voltage led to the terminal ADJ connected to the inverting input and the reference voltage and outputs the result as an error signal. Then, the error signal is sent to the non-inverting input of the PWM comparator 4.

The oscillator 3 is constituted by a constant current integrating circuit and the like, and is a block for generating a wave. Then, the generated wave is sent to the inverted input of the PWM comparator 4.

The PWM comparator 4 is a block for comparing a wave generated by the oscillator 3 with an error signal. Then, the comparison result is sent to the current control circuit 23.

The current detection circuit 22 is a block for detecting a current at an arbitrary position in a current path from the input terminal IN to the load 12 as an output current. The detection result is sent to the current control circuit 23.

The current control circuit 23 is a block for controlling the turning on and off of the output transistor 19 in accordance with the result of the comparison by the PWM comparator 4. When the H level is sent from the PWM comparator 4, the output transistor 19 is turned on. Let it. The current flowing to the base of the output transistor 19 increases or decreases according to the detection result of the current detection circuit 22. That is, when the detection result of the current detection circuit 22 indicates that the output current is small, the base current of the output transistor 19 is reduced. When the detection result of the current detection circuit 22 indicates that the output current is large, the base current of the output transistor 19 is increased.

The output transistor 19 is a PNP transistor in order to reduce the voltage between the collector and the emitter when it is turned on and to reduce the collector loss. Then, according to the control of the current control circuit 23, the current guided to the input terminal IN is switched, and the switched current is sent to the output terminal OUT.

The catch diode 7 whose cathode is connected to the output terminal OUT and whose anode is grounded is connected to the coil 8 and the load 1 when the output transistor 19 is off.
2 is a diode for forming a closed circuit between the light emitting device and the light emitting device.
Then, a current generated by the energy stored in the coil 8 flows through this diode.

The coil 8 is a block for storing and releasing energy when the output transistor 19 is switched, and includes the catch diode 7 and the output capacitor 1.
By being paired with 1, the switched voltage is converted to DC.

The voltage dividing circuit composed of the two resistors 9 and 10
This is a block for setting a voltage applied to the load 12, and generates a divided voltage to be sent to the terminal ADJ.

In the figure, the block indicated by 24 is a block sealed in the package of the chopper type regulator IC, and the structure for sealing will be described later in detail.

The operation of the embodiment having the above configuration will be described.
This will be described below.

The output voltage V _O is divided by a voltage dividing circuit of resistors 9 and 10, and the divided voltage is led to the error amplifier 2 via a terminal ADJ. Therefore, an error between the divided voltage and the reference voltage is amplified by the error amplifier 2 and output as an error signal. The PWM comparator 4 compares the wave output from the oscillator 3 with the error signal, generates a signal for switching the output transistor 19, and sends the signal to the current control circuit 23.

On the other hand, the current detection circuit 22 detects the output current when the output transistor 19 is turned on, and sends the detection result to the current control circuit 23. Therefore, the current control circuit 2
3 turns on the output transistor 19 and draws in a base current having a value corresponding to the current value detected by the current detection circuit 22. That is, when the detection result of the current detection circuit 22 indicates that the output current is large, the current control circuit 23 increases the base current to be drawn. If the detection result of the current detection circuit 22 indicates that the output current is small, the base current to be drawn is reduced.

As a result of the above control, when the output transistor 19 is on, the current guided to the input terminal IN is supplied to the load 12 via the output transistor 19 and the coil 8. At this time, the coil 8 stores energy. When the output transistor 19 is turned off, the energy stored in the coil 8 supplies a current to the load 12 via a path formed by the catch diode 7.

The above operation supplies a stable DC voltage to the load 12. In this supply, when the output current is small, the base current of the output transistor 19 is controlled to a small value. Therefore the following formula

[0055]

## EQU3 ## The driving loss represented by (base current of output transistor 19 × input voltage V _IN × duty) decreases in a range where the output current is small. Therefore, the relationship between the output current and the efficiency is shown in FIG.
As shown by H in FIG. 4, the relationship does not decrease even in a region where the output current is small.

[0056] Figure 2 is a block diagram showing an electrical configuration of another embodiment of a chopper-type regulator and a chopper type regulator IC voltage mode. In the figure, the same reference numerals as in FIG. 1 are assigned to blocks having the same configuration as the blocks shown in FIG.

In this embodiment, the current detecting circuit 22 shown in FIG. 1 is connected to a current detecting resistor 61 connected between the input terminal IN and the emitter of the output transistor 19 and a terminal between the current detecting resistor 61 and the current detecting resistor 61. And a current detection amplifier 26 that amplifies the voltage generated at the time. The value of the current detection resistor 61 is set to a minimum value in a range where the operation of the current detection amplifier 26 can be stabilized in order to minimize loss. A block indicated by reference numeral 29 is sealed in a package as a chopper type regulator IC.

In the present embodiment, the current control circuit 23 shown in FIG. 1 includes two transistors 27 and 28. The output of the current detection amplifier 26 is connected to the base of the transistor 28. The emitter of the transistor 28 is grounded, and its collector is P
The output of the WM comparator 4 is connected to the base of the transistor 27. The emitter of the transistor 27 is grounded, and the collector is connected to the base of the output transistor 19.

The operation of the embodiment having the above configuration will be described.
This will be described below.

The transistor 28 is connected to the current detection amplifier 26
When the output indicates an increase in the output current, the base current of the output transistor 19 is increased by increasing the base current of the transistor 27. When the output of the current detection amplifier 26 indicates a decrease in the output current, the transistor 28 decreases the base current of the transistor 27 and decreases the base current of the output transistor 19. That is, the current control circuit 23 including the transistors 27 and 28 decreases the base current of the output transistor 19 when the output current decreases.

As a result, the efficiency with respect to the output current becomes the efficiency indicated by H in FIG. 14, and the efficiency does not decrease even in a region where the output current is small.

[0062] Figure 3 is a block diagram further illustrating the electrical configuration of the other real <br/>施例chopper regulator and a chopper type regulator IC voltage mode. In the figure, the same reference numerals as in FIGS. 1 and 2 are assigned to blocks having the same configuration as the blocks shown in FIGS.

In this embodiment, the current detecting circuit 22 shown in FIG. 1 has its emitter connected to the emitter of the output transistor 19 and its base connected to the output transistor 1.
9 comprises a PNP-type current detection transistor 30 connected to the base of the transistor 9. The current detection transistor 30 is a current multiplier for the output transistor 19.

Therefore, the emitter area of the current detection transistor 30 has an area corresponding to a value multiplied by the emitter area of the output transistor 19. That is, assuming that the emitter area of the current detection transistor 30 with respect to the emitter area of the output transistor 19 is α, a current obtained by multiplying the collector current (output current) of the output transistor 19 by α is output to the collector of the current detection transistor 30. . This value α is set to a very small value.

In the present embodiment, the current control circuit 23 shown in FIG. 1 comprises two transistors 27 and 28, two resistors 32 and 33 used in the configuration shown in FIG.
An amplifier 62 amplifies the difference between the voltage divided by the two resistors 32 and 33 and a predetermined voltage.

The block indicated by 34 is a block sealed as a chopper type regulator IC in a package.

The operation of the embodiment having the above configuration will be described below.

Since a current corresponding to the output current is output from the collector of the current detection transistor 30, the voltage divided by the two resistors 32 and 33 becomes a voltage indicating the output current. Therefore, when the output current is large, the amplifier 62 decreases the collector current of the transistor 28 and increases the base current of the transistor 27, thereby increasing the base current of the output transistor 19. When the output current is small, the amplifier 62 decreases the base current of the output transistor 19 by increasing the collector current of the transistor 28 and decreasing the base current of the transistor 27.

As a result, the efficiency with respect to the output current becomes the efficiency indicated by H in FIG. 14, and the efficiency does not decrease even in a region where the output current is small.

[0070] Figure 4 is a block diagram further illustrating the electrical configuration of another embodiment of a chopper-type regulator and a chopper type regulator IC voltage mode. In the figure, the same reference numerals as in FIGS. 1 and 2 are assigned to blocks having the same configuration as the blocks shown in FIGS.

In this embodiment, the current detection circuit 22 shown in FIG. 1 includes a current detection resistor 54 connected between the output terminal OUT and the coil 8, and a voltage generated between the terminals of the current detection resistor 54. And a current detection amplifier 26 that amplifies the current. The value of the current detection resistor 54 is set to a minimum value in a range where the operation of the current detection amplifier 26 can be stabilized in order to minimize loss. The block denoted by 55 is sealed in the package as a chopper type regulator IC.

In the present embodiment, the current control circuit 23 shown in FIG. 1 comprises two transistors 27 and 28. The output of the current detection amplifier 26 is connected to the base of the transistor 28. The emitter of the transistor 28 is grounded, and its collector is P
The output of the WM comparator 4 is connected to the base of the transistor 27. The emitter of the transistor 27 is grounded, and the collector is connected to the base of the output transistor 19. That is, this embodiment is
The current detection resistor 61 in the configuration shown in FIG. 2 is configured as an external component.

The operation of the embodiment having the above configuration will be described.
This will be described below.

The transistor 28 is connected to the current detection amplifier 26
When the output indicates an increase in the output current, the base current of the output transistor 19 is increased by increasing the base current of the transistor 27. When the output of the current detection amplifier 26 indicates a decrease in the output current, the transistor 28 decreases the base current of the transistor 27 and decreases the base current of the output transistor 19. That is, the current control circuit 23 including the transistors 27 and 28 decreases the base current of the output transistor 19 when the output current decreases.

As a result, the efficiency with respect to the output current becomes the efficiency indicated by H in FIG. 14, and the efficiency does not decrease even in a region where the output current is small.

[0076] Figure 5 is a block diagram showing an electrical configuration of an embodiment of a chopper-type regulator and a chopper type regulator IC voltage mode according to the invention of claim 1, wherein. In the figure, the same reference numerals as in FIGS. 1 and 2 are assigned to blocks having the same configuration as the blocks shown in FIGS.

In this embodiment, the current detection circuit 22 shown in FIG. 1 comprises a voltage difference detector 56 for detecting a voltage difference between the emitter and the collector of the output transistor 19. The current control circuit 23 in FIG.
In this embodiment, it is constituted by the two transistors 27 and 28 used in FIG.

The block denoted by 57 is a block sealed as a chopper type regulator IC in a package.

The operation of the embodiment having the above configuration will be described below.

The voltage difference between the emitter and the collector of the output transistor 19 is a voltage that changes according to the output current. Therefore, a voltage corresponding to the value of the output current is output from the voltage difference detector 56. As a result, the voltage difference detector 5
6 increases the base current of the output transistor 19 by decreasing the collector current of the transistor 28 and increasing the base current of the transistor 27 when the output current is large. When the output current is small, the voltage difference detector 56 decreases the base current of the output transistor 19 by increasing the collector current of the transistor 28 and decreasing the base current of the transistor 27.

As a result, the efficiency with respect to the output current becomes the efficiency indicated by H in FIG. 14, and the efficiency does not decrease even in a region where the output current is small.

[0082] Figure 6 is a block diagram showing an electrical configuration of another embodiment of a chopper-type regulator and a chopper type regulator IC current mode. Note that, in the figure, the same reference numerals as in FIG. 11 are assigned to blocks having the same configuration as the blocks shown in FIG.

The reference voltage circuit 1 is a block for generating a stabilized reference voltage which is a stabilized predetermined voltage having a very small coefficient and a small temperature coefficient with respect to the input voltage V _IN supplied to the input terminal IN. Then, the generated reference voltage is sent to the non-inverting input of the error amplifier 2.

The error amplifier 2 is a block that amplifies the difference between the voltage guided to the terminal ADJ connected to the inverting input and the reference voltage, and outputs the result as an error signal. Then, the error signal is sent to the non-inverting input of the PWM comparator 4.

The PWM comparator 4 is a block for comparing a signal output from the current detection amplifier 15 with an error signal. Then, the comparison result is stored in the flip-flop 14
To the reset input.

The oscillator 17 is a block for generating a pulse train at regular intervals. Then, the generated pulse train is sent to the set input of the flip-flop 14.

The flip-flop 14 is reset when the H level is sent from the PWM comparator 4 and is set each time each pulse of the pulse train from the oscillator 17 is guided. Then, the inverted output is sent to the current control circuit 23.

The current detection circuit 22 is a block for detecting a current at an arbitrary position in a current path from the input terminal IN to the load 12 as an output current. The detection result is sent to the current control circuit 23.

The current control circuit 23 has the flip-flop 1
4 is a block for controlling ON and OFF of the output transistor 19 in accordance with the output of the flip-flop 14.
, The output transistor 19 is turned on. For the current flowing to the base of the output transistor 19 for this control, the current detection circuit 22
Increase or decrease according to the detection result of. That is, when the detection result of the current detection circuit 22 indicates that the output current is small,
The base current of the output transistor 19 is reduced. When the detection result of the current detection circuit 22 indicates that the output current is large, the base current of the output transistor 19 is increased.

The output transistor 19 is a PNP transistor in order to reduce the voltage between the collector and the emitter when the output transistor 19 is turned on. Then, according to the control of the current control circuit 23, the current guided to the input terminal IN is switched, and the switched current is sent to the output terminal OUT.

In the figure, the block indicated by 35 is a block sealed in the package of the chopper type regulator IC, and the structure for sealing will be described later in detail.

The current detection circuit 22 and the current control circuit 2
Regarding the specific configuration of 3, it is possible to use the configuration of the current detection circuit 22 and the current control circuit 23 described in FIGS. At this time, the current control circuit 23
(The non-inverted output Q (not shown) of the flip-flop 14 is sent to the current control circuit 23).

The operation of the embodiment having the above configuration will be described.
This will be described below.

The switching of the output transistor 19
It is controlled by monitoring the terminal voltage of the current detection resistor 25, and is controlled so that the voltage of the output terminal OUT is constant.

In this control, the current detection circuit 22
The output current when the output transistor 19 is turned on is detected, and the detection result is sent to the current control circuit 23. Therefore, when turning on the output transistor 19, the current control circuit 23 draws in a base current having a value corresponding to the current value detected by the current detection circuit 22. That is, the current control circuit 2
3 increases the base current to be drawn when the detection result of the current detection circuit 22 indicates that the output current is large.
If the detection result of the current detection circuit 22 indicates that the output current is small, the base current to be drawn is reduced.

As a result of the above control, as shown by H in FIG. 14, the relationship between the output current and the efficiency does not decrease even in a region where the output current is small.

FIG. 7 is an internal configuration diagram of one embodiment of the chopper type regulator IC according to the present invention.

The circuit chip section 41 includes the blocks 24 and 2
This is a chip unit in which a circuit unit excluding the output transistor 19 from any one of the blocks 9, 34, 35, and 57 (see FIGS. 1 to 3, 5, and 6) is integrated. The transistor chip section 42 is a chip section on which the output transistor 19 is formed. The circuit chip portion 41 and the transistor chip portion 42 form a chip portion 65 integrally formed, and are fixed to the metal frame 38 by die bonding with a bonding portion 40 made of solder.

The metal frame 38 is formed with an outer lead frame 47 which extends long at a position slightly deviated from the center of one end, and this outer lead frame 47 is a GND terminal.

On the left side of the outer lead frame 47 in the drawing, an outer lead frame 46 constituting an output terminal OUT is provided so as to be parallel to the outer lead frame 47. On the right side of the outer lead frame 47 on the paper surface, an outer lead frame 48 constituting the input terminal IN is provided so as to be parallel to the outer lead frame 47. On the right side of the outer lead frame 48 on the paper surface, an outer lead frame 49 constituting the terminal ADJ is provided.
Are provided in parallel with the outer lead frame 47.

A contact portion 42a serving as a collector formed on the transistor chip portion 42 is connected to an outer lead frame 46 by a metal wire 39. Further, a contact portion 42b serving as an emitter is connected to the outer lead frame 48 by a metal wire 39. The ground contact portion 41 a formed on the circuit chip portion 41 is connected to the metal frame 38 by a metal wire 39. Circuit chip part 4
Feedback contact portion 41b formed at 1
Is connected to an outer lead frame 49 by a metal wire 39.

The chip portion 65 and the metal frame 38 are sealed in a package 37 together with one end portions of the outer lead frames 46 to 49. This package 37
Is made of an exterior resin such as an epoxy resin, and is formed by a process such as transfer molding.

FIG. 8 is an internal configuration diagram of another embodiment of the chopper type regulator IC according to the present invention. FIG.
7 are given the same reference numerals as those given in FIG.

The transistor chip section 45 is obtained by forming the output transistor 19 into a chip.
4 are blocks 24, 29, 35, 57 (FIGS. 1, 2
6 and 5) is a chip unit in which a circuit unit excluding the output transistor 19 from any one block is integrated. The circuit chip section 44 and the transistor chip section 45 are independent chip sections.

The metal frame 38 is formed with an outer lead frame 51 extending long at a position slightly deviated from the center on one end side, and the outer lead frame 51 serves as an output terminal OUT. On the left side of the outer lead frame 51 in the drawing, an outer lead frame 50 constituting the input terminal IN is provided so as to be parallel to the outer lead frame 51. On the right side of the outer lead frame 51 in the drawing, an outer lead frame 52 constituting a GND terminal is provided so as to be parallel to the outer lead frame 51. And outer lead frame 5
2 on the right side of the paper surface of FIG.
1 is provided in parallel.

The transistor chip portion 45 of the two chip portions 44 and 45 is fixed to the metal frame 38 by die bonding with a bonding portion 66 made of solder. The circuit chip portion 44 is fixed to the metal frame 38 by die bonding with an insulating paste 43.

The base contact portion 45a formed on the transistor chip portion 45 is connected to the current control circuit contact portion 44d of the circuit chip portion 44 by a metal wire 39. The collector electrode of the transistor chip portion 45 is connected to the outer lead frame 51 via the metal frame 38 by a joining portion 66 made of solder. The contact portion 45b, which is the emitter of the transistor chip portion 45, is connected to the outer lead frame 50 by a metal wire 39.

The contact portion 44a for grounding of the circuit chip portion 44 is connected to the outer lead frame 52 by the metal wire 39, and the contact portion 44b for feedback is connected to the outer lead frame 53 by the metal wire 39, and Contact part 4 for voltage
4c is connected to the outer lead frame 50 by the metal wire 39.

The chip portion 65 and the metal frame 38 are sealed in the package 37 together with one end portions of the outer lead frames 50 to 53. This package 37
Is made of an exterior resin such as an epoxy resin, and is formed by a process such as transfer molding.

Note that the present invention is not limited to the above embodiment,
The outer lead frame is connected to the configuration shown in FIGS.
With this added configuration, it is possible to use a chopper-type regulator IC whose electrical configuration is shown as the block 55.

In addition, the current detection transistor 30 is formed in the transistor chip portion 45, and the IC having the configuration shown in FIG. 8 can be replaced with a chopper type regulator IC whose electrical configuration is indicated by the block 34.

In the configuration of the current mode chopper type regulator and the chopper type regulator IC shown in FIG. 6, the current detection circuit 22 is shared with the current detection amplifier 15, and the output of the current detection amplifier 15 is used as the current control circuit 23.
Can be adopted. In this case, the base current of the output transistor 19 can be controlled only by adding the current control circuit 23, so that the effect of simplifying the circuit configuration can be obtained.

[0113]

Chopper-type regulator and a chopper type regulator IC according to the present invention, based on an error between the reference voltage and the output voltage, by controlling the switching of the output transistor is a PNP transistor, the chopper to stabilize the output voltage A current detection circuit applied to the regulator and detecting an output current flowing through the output transistor is provided. And, based on the output current detected by the current detection circuit, when the output current is small, a current control circuit for performing control to reduce the base current flowing to the output transistor is provided. Is controlled. Therefore, it is possible to prevent a decrease in efficiency that occurs in a range where the output current is small.

[0114]

[0115] The chopper-type regulator and a chopper type regulator IC according to the invention of claim 1, wherein
Describes that the current detection circuit is a voltage difference detector that detects a voltage difference between the emitter and the collector of the output transistor.
Therefore, the power consumption that increases due to the detection of the output current is only the power consumption of the voltage difference detector, so that the loss that occurs in the detection of the output current can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of an embodiment of a chopper type regulator and a chopper type regulator IC.

FIG. 2 is a block diagram showing an electrical configuration of another embodiment of the chopper type regulator and the chopper type regulator IC.

3 is a block diagram showing an electrical configuration of still another embodiment of the chopper-type regulator and a chopper type the IC.

4 is a block diagram showing an electrical configuration of still another embodiment of the chopper-type regulator and a chopper type the IC.

5 is a block diagram showing an electrical configuration of an embodiment of a chopper-type regulator and a chopper type regulator IC according to the invention of claim 1, wherein.

FIG. 6 is a block diagram showing an electrical configuration of another embodiment of the chopper type regulator and the chopper type regulator IC.

FIG. 7 is a structural view of a chopper type regulator IC according to the second aspect of the present invention.

FIG. 8 is a structural view of a chopper-type regulator IC according to the second aspect of the present invention.

FIG. 9 is a block diagram showing a conventional electrical configuration of a voltage mode chopper type regulator.

FIG. 10 is an explanatory diagram showing waveforms of main signals of the related art shown in FIG.

FIG. 11 is a block diagram showing a conventional electric configuration of a current mode chopper type regulator.

FIG. 12 is an explanatory diagram showing waveforms of main signals of the related art shown in FIG. 11;

FIG. 13 is a block diagram showing a conventional electrical configuration of a voltage mode chopper type regulator.

FIG. 14 is an explanatory diagram showing the relationship between output current and efficiency in a chopper type regulator.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reference voltage circuit 2 error amplifier 3 oscillator 4 PWM comparator 7 catch diode 8 coil 11 output capacitor 12 load 19 output transistor 22 current detection circuit 23 current control circuit 30 current detection transistor 56 voltage difference detector

Claims (2)

(57) [Claims] 1. A chopper regulator that stabilizes an output voltage by controlling switching of an output transistor, which is a PNP transistor, based on an error between a reference voltage and an output voltage. Based on the current detection circuit to be detected, and the output current detected by the current detection circuit,
A current control circuit for performing control to reduce a base current flowing through the output transistor when the output current is small; and
<br/> A chopper-type regulator characterized in that it is a voltage difference detector for detecting a voltage difference between the collector and the collector . 2. The chopper type regulator according to claim 1.
Output transistor, current detection circuit and current control
A chopper type regulator IC characterized by integrating control circuits into one package .