JP2911084B2 - Low noise DC constant voltage circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-noise DC constant voltage circuit for strictly suppressing noise such as a chopper frequency ripple included in an output of a chopper type DC conversion power supply.

Conventionally, for this purpose, the high-frequency response characteristics of output circuits such as a smoothing circuit and a noise filter have been improved,
D (Series Dropper) has been used, but none was enough.

[0003]

2. Description of the Related Art FIG. 3 shows an example of the configuration of a conventional chopper type DC conversion power supply. In the figure, 1 is a chopper, 2 is a pulse transformer, 3 is a reactor (for resetting the pulse transformer 2), 4 is a rectifier, 5 is a smoothing circuit, 6 is a noise filter, and 7 is a voltage detection control circuit.

FIG. 4 is a waveform diagram of the intermittent current I at the input point of the rectifier 4 in FIG. 3, the input DC voltage V _I is first after being interrupted by the chopper frequency of several tens kHz in chopper 1, through the pulse transformer 2 is added to a rectifier 4 as intermittent current I waveform in FIG. 4 rectification. The reactor 3 is connected in series to the secondary side of the pulse transformer 2, and when a reset signal is applied thereto,
Since the rising portion of the intermittent current I shown in FIG. 4 is cut by the hatched application period τ, the output voltage of the rectifier 4 decreases by a value corresponding to this.

[0005] The output voltage of the rectifier 4 is smoothed by a smoothing circuit 5, noise is suppressed by a noise filter 6, and then supplied to a load as an output DC voltage V _O. The output DC voltage V _O is also applied to the voltage detection control circuit 7 at the same time, where it is converted into the reset signal whose time width τ increases and decreases in response to the rise and fall of the voltage V _O , and is applied to the reactor 3.

With the circuit configuration as described above, the output voltage can be maintained at a high accuracy and constant, and at least noise due to the ripple of the commercial frequency component can be sufficiently suppressed, but the ripple of the chopper frequency component of several tens of kHz. It is very difficult to suppress the noise due to a normal smoothing circuit or noise filter.

In recent years, however, there has been a strong demand for a power supply device having not only excellent constant voltage characteristics but also very strict specifications for mixed noise components, such as a power supply for a high-precision measuring instrument such as a spectrum analyzer. Have been.

The quickest measure to meet such a demand is to improve the high-frequency response characteristics of output circuits such as the smoothing circuit 4 and the noise filter 6 in FIG. There is also a method of adopting an SD (Series Dropper) method instead of the chopper method.

FIG. 5 is a schematic block diagram of the SD (Series Dropper) system. In the figure, 8 is a transformer, 4 is a rectifier, Q is a DC voltage adjusting transistor, and 9 is an analog control circuit. In this method, no chopper is used, and the DC voltage is controlled by the analog control circuit 9 and the DC voltage adjusting transistor Q. Therefore, the introduction of ripple noise at the chopper frequency is impossible.

[0010]

However, according to the prior art as described above, the method for improving the high frequency response characteristics of an output circuit such as a smoothing circuit or a noise filter has an economic limit to its feasibility. Yes, and SD (Serie
s Dropper) has a drawback in that it cannot enjoy the merits of reduced power loss due to the chopper method and compactness due to downsizing of component devices.

Accordingly, an object of the present invention is to provide a low-noise DC constant-voltage circuit capable of strictly suppressing noise with an economical configuration while maintaining the advantages of the chopper method, except for the above-described disadvantages of the prior art. Is to do.

[0012]

FIG. 1 is a block diagram showing the principle of the present invention. In the figure, 1 is a chopper / smoothing means, 10 is a reference voltage generating means, 11 is a low frequency adapting means, 12 is a high frequency adapting means, 13 is a voltage comparing means, and 14 is a chopper controlling means.

Now, in order to achieve the above-mentioned object, the present invention has the following configuration as shown in FIG. That is, a chopper / smoothing means 1 for smoothing after intermittently input DC current, and a low-frequency component for passing only the low frequency component from the input voltage of the chopper / smoothing means 1 under the optimum transmission condition for the low frequency component. Adapting means 11 and the chopper
From the output voltage of the smoother means 1, only its high frequency component is
High-frequency adapting means 12 for passing the high-frequency component under optimal transmission conditions, reference voltage generating means 10 for generating a predetermined DC reference voltage, and an output of the low-frequency adaptive means 11 and an output of the high-frequency adaptive means 12. A voltage comparing means 13 for comparing the output voltage of the reference voltage generating means 10 with the output voltage of the reference voltage generating means 10, and a chopper control means 14 for receiving the comparison output of the voltage comparing means 13 and controlling the energization time width of the chopper / smoother means 1 I do.

[0014]

FIG. 1 is a block diagram showing the principle of the present invention.
g) After smoothing (Smoothing, full-scale smoothing is performed in the following other blocks).

The low frequency adaptation means 11 sets the optimum transmission condition for passing only the low frequency component from the input voltage of the chopper / smoother means 1, and passes only the low frequency component. The high-frequency adaptation means 12 sets an optimal transmission condition for passing only high-frequency components from the output voltage of the chopper / smoother means 1, and
Pass only high frequency components.

The reference voltage generating means 10 generates a predetermined high-precision DC reference voltage. Then, the voltage comparing means 13 compares the output of the low frequency matching means 11 and the output of the high frequency matching means 12 with the output voltage of the reference voltage generating means 10. Further, the chopper control means 14 receives the comparison output of the voltage comparison means 13 and controls the energization time width of the chopper / smoother means 1, so that the noise of the low frequency component and the high frequency component is strictly suppressed as a whole circuit. A DC constant voltage can be obtained.

Since the detection points of the low-frequency component and the high-frequency component are separated and the optimum transfer condition (transfer function) between the input and output of the voltage comparing means 13 can be set for each frequency band, the entire frequency band can be set from the same point. There is no need for abnormally large or small constants in the components involved in the transfer function as in the case of detection.

[0018]

FIG. 2 is a circuit diagram showing an embodiment of the present invention. In the figure, Q, C and R are transistors, respectively.
The capacitors and resistors are shown and numbered according to the place of use. OA is an operational amplifier (operational amplifier), and SR is a series control power supply (Seris Regulator).

Q-1 is used as a chopper, and Q-2 is used as a chopper.
It is used to control the power supply time width. The operational amplifier OA is about 1
Since it is used as a high-precision voltage comparison circuit having excellent high-frequency characteristics up to 00 kHz, a high-precision reference voltage serving as a comparison reference is supplied from the SR capable of generating a high-precision reference voltage.

FIGS. 1 and 2 show principle blocks of the present invention.
Is as follows. That is, the one corresponding to the chopper / smoother means 1 in FIG.
1 and C-0 and R-0, the one corresponding to the reference voltage generation means 10 is SR, the one corresponding to the low frequency adaptation means 11 is R-1 and R-2, and the high frequency adaptation means Those corresponding to 12 are C-1 and R-3 and C-2 and R-4,
Those corresponding to the voltage comparing means 13 and the chopper control means 14 are an operational amplifier OA and a transistor Q-respectively.
2

[0021] Now, the input DC voltage V _I is R-1 and R-2
Divided by the potentiometer connection consisting of
Applied to input. A high-precision reference voltage of the SR output is applied to the + input, and the operational amplifier O
Since A is used as a high-precision voltage comparison circuit, a total of the chopper Q-1, the chopper control transistor Q-2 for controlling the conduction time width, and C-0 and R-0 operating as a smoother is provided. By the operation, the DC component of the output DC voltage V _O is kept constant, and at least the ripple of the commercial frequency component is strictly suppressed.

On the other hand, the impedances of R-3 and C-1 in the chopper frequency band of several tens kHz are R-1 and R-2.
, The ripple of the chopper frequency component included in the output DC voltage V _O passes through R-3 and C-1 and the voltage comparison circuit O
A is applied to the-input of A. In addition, R-3 and C-1 and R-4
And the total transfer function between C-2 and the voltage comparison circuit OA is several tens.
Since it is designed to be optimum in the chopper frequency band of kHz, a control signal of the optimum level is output from the terminal OUT of the OA, and by the total operation of the chopper Q-1 and the chopper control transistor Q-2, Noise due to the ripple of the chopper frequency component is strictly suppressed.

As described in [Operation], since the detection points of the low-frequency (commercial frequency) component and the high-frequency (chopper frequency) component are separated, the transfer function-related components, for example, C-
2 can be about 100 pF, but assuming that both detection points are the same and placed at the output point, theoretically about 0.0 is required for C-2.
1 μF is required, and good results cannot be obtained even if this value is experimentally set.

In the prior art, the noise of the chopper frequency component which could be suppressed at most to about 20 to 50 mV can be suppressed to 200 to 500 μV, that is, about 1/100 according to this embodiment.

[0025]

As described above, according to the present invention, it is possible to realize a low-noise DC constant-voltage circuit that can strictly suppress noise with a simple and economical configuration and can maintain the advantages of the chopper system. .

[Brief description of the drawings]

FIG. 1 is a principle block diagram of the present invention.

FIG. 2 is a circuit diagram of one embodiment of the present invention.

FIG. 3 is a block diagram of a conventional chopper type power supply.

FIG. 4 is a waveform diagram of a rectifier input current in FIG. 3;

FIG. 5 is a schematic diagram of a configuration of an SD system power supply.

[Explanation of symbols]

 1 Chopper 10 Reference voltage generation means 11 Low frequency adaptation means 12 High frequency adaptation means 13 Voltage comparison means 14 Chopper control means

Claims (1)

(57) [Claims] Chopper / smoothing means for intermittently smoothing an input direct current after intermittently inputting a low-frequency component from an input voltage of said chopper / smoothing means for the low-frequency component. Low frequency adaptation means (11) for passing under transmission conditions, and high frequency adaptation means (12) for passing only the high frequency components from the output voltage of the chopper / smoother means (1) under optimal transmission conditions for the high frequency components. Reference voltage generating means for generating a predetermined DC reference voltage (10)
The output of the low frequency adaptation means (11) and the high frequency adaptation means (1
A voltage comparison means (13) for comparing the output of 2) with an output voltage of the reference voltage generation means (10); and a comparison output of the voltage comparison means (13). A low-noise DC constant-voltage circuit comprising chopper control means (14) for controlling an energization time width.