JPH0222726Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention relates to a stabilizing circuit that stabilizes the voltage from an unregulated power supply circuit and supplies it to a load. It relates to a stabilized power supply that sometimes functions as a stabilizing circuit that operates with sufficient stability, and also functions as an APF (active power filter) that performs sufficient ripple removal operation when the output voltage becomes low.

Prior Art First, this type of stabilized power supply device that has been conventionally used will be described.

Figure 2 shows the most common circuit example.
A series control type control transistor 3 is connected in series between the control transistor 3 and the load 2.
An error detection circuit 4 for controlling the control transistor 3 to detect fluctuations in the output voltage of the transistor 3 and stabilize it is connected to its base circuit. 5 is a constant voltage diode that generates the reference voltage, 6 is an error detection transistor, and 7 is a voltage dividing resistor. Further, a filter circuit 8 for operating as an APF circuit is connected to the base circuit of the control transistor 3, and its input terminal is connected to the output terminal of the unregulated power supply circuit 1. 9,
10 and 11 are resistors for the filter, and 12 and 13 are capacitors for the filter.

Problems to be Solved by the Invention However, with such a circuit configuration, if the output voltage of the unregulated power supply circuit 1 is small and the operating voltage range is widened when operating as an APF circuit, the filter It is necessary to select the resistance values of the series resistors 9, 10, and 11 in the circuit 8 to be sufficiently small (series control transistor 3
On the other hand, if the resistance value is selected to be small in this way, the load impedance of the error detection circuit 4 will become small when operating as a localization circuit, and sufficient loop gain will be required. This results in the disadvantage that the output voltage cannot be sufficiently stabilized.

Furthermore, there is a conventionally used stabilized power supply circuit as shown in FIG. This circuit converts the output voltage of the control transistor 3 into the auxiliary power supply circuit 14.
The voltage is boosted using a DC-DC converter or the like and applied to the collector of the transistor 6 of the error detection circuit 4 and the base of the control transistor 3 via the filter circuit 8.

Note that the resistors 15 and 16 and the diode 17 are used to apply a starting bias to the control transistor 3, and the diode 17, which starts the operation of the entire circuit, is cut off.

In this circuit, since the output voltage of the auxiliary power supply circuit 14 can be made sufficiently larger than the output voltage of the control transistor 3, the resistance values of the series resistors 9, 10, and 11 of the filter circuit 8 are also made sufficiently large. Therefore, when operating as a stabilizing circuit, the loop gain can be made sufficiently large and excellent stability can be obtained. However, this circuit had the drawback that it could not operate as an APF circuit.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a stabilized power supply device that can overcome these conventional drawbacks and operate well both as a stabilizer circuit and as an APF circuit.

Means for Solving the Problems In order to achieve the above object, the present invention connects a control transistor in series between an unregulated power supply circuit and a load, and detects fluctuations in the output voltage of the control transistor. An error detection circuit that controls the control transistor to stabilize the output voltage is connected to the base circuit of the control transistor, and an auxiliary power supply circuit that generates an auxiliary power supply with a voltage higher than the output voltage of the control transistor is provided. The output terminal of this auxiliary power supply circuit is connected to the base of the control transistor via a filter circuit, and the input terminal of the filter circuit is connected to one direction that conducts when the output voltage of the unregulated power supply circuit falls below a predetermined value. When the output voltage from the unregulated power supply circuit is high, it operates stably, and when the output voltage from the unregulated power supply circuit becomes low, it operates to eliminate ripples. is configured to do so.

With the above configuration, the present invention operates as a highly stable stabilizing circuit with low ripple when the unregulated input power supply voltage is high, and as an APF circuit with low ripple when the unregulated input power supply voltage becomes low. It is possible to supply a power supply voltage with a small ripple component over a wide range of unregulated input power supply voltages.

Embodiment Hereinafter, a stabilized power supply device according to an embodiment of the present invention will be described in detail with reference to FIG. In addition, the first
In the drawings, the same parts as in the prior art will be described with the same reference numerals.

In the stabilized power supply device of this embodiment shown in FIG.
The output voltage of the control transistor 3 is boosted by the auxiliary power supply circuit 14 and supplied to the error detection circuit 4 and the base of the control transistor 3 via the filter circuit 8. , 10 are connected to the output terminal of the unregulated power supply circuit 1 via a unidirectional element, here a diode 18, which becomes conductive when the output voltage of the unregulated power supply circuit 1 becomes less than a predetermined value. It is characterized by the fact that it is made to do so.

Here, supplementary explanation will be given regarding the auxiliary power supply circuit 14. As described in the conventional example, the auxiliary power supply circuit 14 is a so-called booster circuit that receives the output of the stabilized power supply circuit, that is, the output voltage of the control transistor 3, and boosts and outputs this voltage.
Consists of a DC-DC converter.

That is, the auxiliary power supply circuit 14 boosts the output voltage of the transistor 3 with a predetermined proportional relationship and supplies it to the filter circuit 8. in particular,
In the operating state shown in FIG. 1, the output 6 [V] of the transistor 3 is boosted to 50 [V] and output.

That is, according to this circuit configuration, now,
When the output voltage of the non-stabilized power supply circuit 1 is sufficiently high, the diode 18 is cut off and performs a sufficient voltage stabilizing operation as a stabilizing circuit similar to the circuit shown in FIG. On the other hand, when the output voltage of the unregulated power supply circuit 1 decreases and becomes lower than the voltage at the connection point between the resistors 9 and 10, the diode 18 becomes conductive.
It becomes operational as an APF circuit. At this time,
Since the output voltage of control transistor 3 decreases, transistor 6 is cut off. When operating as a stabilizing circuit, the loop gain is increased to perform sufficient stabilizing operation, and when operating as an APF circuit, the resistance value of the base circuit of control transistor 3 is reduced to ensure sufficient ripple removal operation. In order to do this, increase the resistance value of resistor 9, and
It is recommended to set the resistance value to be small. A specific example is shown in FIG.

Note that the voltage values shown are the voltages when operating as a stabilizing circuit, and the output voltage of the non-stabilized power supply circuit 1 increases due to consumption of dry batteries and storage batteries.
When the voltage at the connection point of 0 drops by more than the forward voltage of the diode 18, it operates as an APF circuit. In addition, this value indicates that the voltage between the collector and emitter of the control transistor 3 is the saturation voltage (approximately 0.2V) when transitioning to operation as an APF circuit.
To prevent the voltage from dropping to about 0.7V, the transition is made.

Note that the filter circuit 8 used may have more stages or fewer stages than the one shown in this embodiment. Furthermore, a small resistor for current limiting may be added between the base of the control transistor 3 and the error detection circuit 4 and filter circuit 8. Furthermore, as a starting circuit, resistors 15, 16,
In addition to using the diode 17, a resistor may be connected in parallel between the collector and emitter of the control transistor 3.

Effects of the invention As detailed above, according to the invention, when the output voltage of the unregulated power supply circuit is high, it operates as a highly stable stabilizing circuit with a small ripple component, and when the output voltage is low, it has a ripple removal effect. It is possible to obtain a device that operates as an APF circuit with a large value, supplies a power supply voltage with a small ripple, and operates well over a wide voltage range.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a stabilized power supply device according to an embodiment of the present invention, and FIGS. 2 and 3 are circuit diagrams of a conventional stabilized power supply device. 1...Unregulated power supply circuit, 2...Load, 3...
Control transistor, 4...Error detection circuit, 8...
...Filter circuit, 9, 10, 11...Resistance, 1
2, 13... Capacitor, 14... Auxiliary power supply circuit, 18... Diode.

Claims (1)

[Scope of utility model registration request] An error in which a control transistor is connected in series between an unregulated power supply circuit and a load, and the control transistor is controlled so as to detect fluctuations in the output voltage of the control transistor and stabilize the output voltage. A detection circuit is connected to the base circuit of the control transistor, and an auxiliary power supply circuit is provided which takes the output voltage of the control transistor as input and boosts this output voltage proportionally to generate an auxiliary power supply. A filter circuit consisting of a first resistor, at least one resistor directly connected to one end of the first resistor, and a capacitor inserted between the connection point of each of the resistors and the ground is provided, The output terminal of the power supply circuit is connected to the other end of the first resistor of the filter circuit, the other end of the resistor group of the filter circuit is connected to the base of the control transistor, and the other end of the first resistor of the filter circuit is connected. is connected to the output terminal of the unregulated power supply circuit via a unidirectional element that becomes conductive when the output voltage of the unregulated power supply circuit becomes equal to or less than a predetermined value,
The filter circuit is characterized in that it operates stably when the output voltage from the unregulated power supply circuit is high, and performs ripple removal operation when the output voltage from the unregulated power supply circuit becomes low. stabilized power supply.