JPH02111221A - Dc power source - Google Patents

Abstract

PURPOSE:To reduce in size and cost a DC power source by providing a voltage dividing circuit network for dividing a voltage across a current detecting resistor by an impedance having frequency characteristic and a control terminal of the network in a current detector, and controlling the opening and closing of a switch circuit in response to the output of the terminal. CONSTITUTION:A current detector 3 has voltage dividing circuit networks 14-18 for dividing a voltage across a current detecting resistor 13 by an impedance having frequency characteristic, and control terminals 3a, 3b of the networks 14-18, and a controller 2 controls the opening and closing of a switch circuit 1 in response to the outputs of the terminals 3a, 3b. That is, the limit value of the current to be controlled by the controller 2 is increased while a current continuous time is short, and decreased more as the current continuous time is lengthened. Thus, since it can prevent the voltage from dropping and the voltage change rate from increasing, the rated value of the circuit 1 can be reduced, thereby decreasing in size and cost a DC power source.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a DC power supply circuit including a current limiting circuit.

(Prior Art) FIG. 2 is a circuit diagram of a conventional DC power supply device, and FIG. 3 is a diagram showing its load characteristics.

The device shown in FIG. 2 includes a switch circuit 1 and a control section 2 that constitute a general C-DC converter circuit, and a current detection section 3 that detects the current output from the device.

Here, the switch circuit 1 is a switching element P
It is composed of an NP transistor 4. This PNP
The transistor 4 has its emitter connected to the positive side of the DC power supply 5, its collector connected to the positive side output terminal 7 via the coil 6, and its base connected to the output terminal 2a of the control unit 2. .

The control unit 2 controls the triangular wave oscillator 8, the error amplifier 9 that compares the voltage of the output terminal 7 on the positive side and the output voltage of the triangular wave oscillator 8, and the drive voltage supplied to the control terminal C of the triangular wave oscillator 8. control NPN) transistor 1o. That is, the inverting input terminal of the error amplifier 9 is connected to the output terminal of the triangular wave oscillator 8, the non-inverting input terminal is connected to the output terminal 7 side, and the output terminal of the error amplifier 9 is connected to the output terminal 2a of the control section 2. ing. The collector of the NPN transistor 10 is connected to the control terminal C of the triangular wave oscillator 8, and this control terminal C and the transistor 1
An internal voltage source 12 is connected to the collector of 0 through a resistor 11.

The triangular wave oscillator outputs a triangular wave to the error amplifier 9 while this power supply voltage is connected to the control terminal C. Further, the base and emitter of the NPN transistor 10 are connected to control terminals 3a and 3b of the current detection section 3.

On the other hand, the current detection unit 3 includes a current detection resistor 13 inserted between the output terminal 19 and the DC power supply 5, a voltage dividing circuit network that divides the voltage across the current detection resistor 13, and this voltage dividing circuit. It consists of a control terminal 3a connected to the intermediate tap 20 of the circuit network, and a control terminal 3b connected to one end of this voltage dividing network. Here, the voltage dividing network consists of voltage dividing resistors 14 and 15 connected in parallel to the current detecting resistor 13. and,
Voltage dividing resistor 14. ], 5 is the intermediate tap 20 of the voltage dividing network.

Further, the cathode of a diode 21 for protection of the transistor 4 is connected between the collector of the transistor 4 of the switch circuit 1 and the coil 6.
The anode of is connected to the negative electrode side of the DC power supply 5. A capacitor 22 is connected between the coil 6 and the output terminal 7.
The positive terminal of this capacitor 22 is connected to the negative terminal of the DC power supply 5 .

In the DC power supply device having the above configuration, the error amplifier 9 of the control section 2 outputs the output voltage (■) of the output terminal 7. U7 is compared with the triangular wave voltage from the triangular wave oscillator 8, and a signal of low level rLJ is output for the time when the level of the triangular wave voltage is high to make the PNP transistor 4 conductive. Therefore, during the conduction period, the collector voltage of the PNP transistor 4 is output to the output terminal 7 and is charged to the capacitor 22 via the coil 6.

Furthermore, while the error amplifier 9 is outputting the high level rHJ signal, the PNP transistor 4 is held in a non-conducting state, but the current charged in the capacitor 22 is discharged and the output voltage is applied to the output terminal 7. V. UT appears continuously.

Output voltage V. When UT is higher than a predetermined level, the period of low level rLJ of error amplifier 9 becomes shorter, so P
The conduction period of the NP t-transistor 4 is also shortened. On the other hand, the output voltage V. When UT is lower than a predetermined level, the period in which the error amplifier 9 is at the low level rLJ becomes longer, so the conduction period of the PNP transistor 4 also becomes longer. Therefore, by controlling the conduction period of the PNP transistor 4, the output voltage becomes ■. LIT can be maintained at a predetermined level.

On the other hand, in the current detection section 3, when the load current I flows through the current detection resistor 13, a potential difference is generated between both ends, and this potential difference is divided by the voltage dividing resistors 14 and 15. Limit current value I LIMIT set by load current (see Figure 3)
In the following case, the voltage divided by the voltage dividing resistors 14 and 15 has a value smaller than the base-emitter sum voltage vBE of the NPN transistor 10 of the control section 2, so the transistor 10 does not operate. Therefore, the voltage at the control terminal C of the triangular wave oscillator 8 is at high level rHJ at the internal voltage source 12.
is held, a triangular wave voltage is output from the oscillator 8,
As described above, the PNP transistor 4 as a switching element is controlled to be intermittently conductive.

On the other hand, the load current limiter is the limit current value I LIMIT
When the voltage becomes larger, the voltage divided by the voltage dividing resistors 14 and 15 becomes a value larger than the base-emitter saturation voltage VBE of the NPN transistor 10, so the transistor 10 starts operating and the collector voltage decreases. do. Therefore, the control terminal C of the triangular wave oscillator 8 is at low level rLJ
, the operation of the oscillator 8 is stopped, and the triangular wave voltage is no longer supplied to the error amplifier 9.

Therefore, the PNP transistor 4 is held in a non-conductive state, and as shown in FIG.
At position T, the output voltage VOUT decreases and the load current I is cut off.

Note that the saturation voltage between the base and emitter of the NPN transistor 10 is ■. The limiting current value ILIMIa means the resistance value of the current detection resistor 13 as R13, and the resistance value of the voltage dividing resistor 14.15 as RI4. When R16 is assumed, it can be expressed as the following formula (1).

Vb-□R+3×lJ+n/(L4+La)・
...(1) (Problem to be solved by the invention) However, in the above-mentioned conventional DC power supply device, a load that requires a large current even for a short period of time, such as a motor or a capacitor, is connected. In this case, it was necessary to increase the rating of the PNP transistor 4, which is a switching element, and to set a large current limit value. Therefore, in this case, the size and cost of the power supply device have increased. On the other hand, when using a low-cost power supply device in which the rating and current limit value of the PNP transistor 4 are kept small, a voltage drop occurs during the load energization period, resulting in a large voltage fluctuation rate. .

The present invention has been made with attention to the above points, and when a load that requires a large current for a short period of time is connected, there is no need to increase the rating, and it is possible to miniaturize the device and reduce costs. The object of the present invention is to provide a DC power supply device that does not cause a voltage drop.

(Means for Solving the Problems) A DC power supply device of the present invention includes a switch circuit inserted in series with the output of a DC power supply, a control unit that controls opening/closing of the switch circuit, and a current detector that detects an output current. A DC power supply device comprising: a current detection resistor; and a voltage dividing network that divides a voltage across the current detection resistor by an impedance having frequency characteristics;
and a control terminal connected to an intermediate tap of the voltage dividing circuit network, and the control section controls opening and closing of the switch circuit in accordance with the output of the control terminal.

(Function) In the above DC power supply device, when the supply of current from the power source is started, the output generated at the control terminal of the voltage dividing network changes with time characteristics due to the impedance having frequency characteristics in the current detection section. As shown in FIG. 7, the limit value of the current controlled by the control section is increased while the continuous time of the current is short, and as the continuous time of the current becomes longer, this limit value is made smaller.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram of a DC power supply device according to the present invention.

The device shown in FIG. 1 includes a switch circuit 1 and a control section 2 that constitute a general C-DC converter circuit, and a current detection section 3 that detects an output current.

Here, the switch circuit 1 is a switching element P
It is composed of an NP transistor 4. This PNP
The transistor 4 has its emitter connected to the positive side of the DC power supply 5, its collector connected to the positive side output terminal 7 via the coil 6, and its base connected to the output terminal 2a of the control unit 2. .

The control unit 2 controls the signal supplied to the triangular wave oscillator 8, the error amplifier 9 that compares the voltage of the positive output terminal 7 and the output voltage of the triangular wave oscillator 8, and the control terminal C of the triangular wave oscillator 8. and an NPN transistor 10. That is, the inverting input terminal of the error amplifier 9 is connected to the triangular wave oscillator 8.
The non-inverting input terminal is connected to the output terminal 7 side, and the output terminal of the error amplifier 9 is connected to the output terminal 2a. The collector of the NPN transistor 10 is connected to the control terminal C of the triangular wave oscillator 8, and the internal voltage source 12 is connected to the control terminal C and the collector of the transistor 10 via a bias resistor 11. Further, the base and emitter of the NPN transistor 10 are connected to control terminals 3a and 3b of the current detection section 3.

The above configuration is the same as that of the conventional DC power supply device shown in FIG.

On the other hand, the current detection unit 3 includes a current detection resistor 13 inserted between the output terminal 19 and the DC power supply 5, a voltage dividing circuit network that divides the voltage across the current detection resistor 13, and this voltage dividing circuit. It consists of a control terminal 3a connected to the intermediate tap 20 of the circuit network, and a control terminal 3b connected to one end of this voltage dividing network. Here, the voltage dividing circuit network includes voltage dividing resistors 14 and 15 connected in parallel to the current detection resistor 13, and voltage dividing resistors 14 and 15 connected in parallel to the current detecting resistor 13.
It consists of a series circuit of a resistor 16 and a capacitor 17 connected in parallel to the voltage dividing resistor 15, and a discharging diode 18 connected in parallel to the voltage dividing resistor 15. Then, the voltage dividing resistor 14, the voltage dividing resistor 15, the capacitor 17, and the discharging diode 18
The connection point with this is the intermediate tap 20 of the voltage dividing network. Further, the discharge diode 18 has its cathode side connected to the output terminal 19 side, and its anode side connected to the intermediate tap 20 side.

In addition, in the circuit shown in FIG. 1, the cathode of a diode 21 for protection of the transistor 4 is connected between the collector of the transistor 4 and the coil 6, as in the conventional case, and the anode of this diode 21 is connected between the collector of the transistor 4 and the coil 6. It is connected to the negative electrode side of the DC power supply 5. A positive terminal of a capacitor 22 is connected between the coil 6 and the output terminal 7.
A negative terminal of this capacitor 22 is connected to the negative terminal of the DC power supply 5.

FIG. 4 is a configuration diagram of a voltage dividing circuit network of the current detection section of the DC power supply device of FIG. 1.

That is, if only the above-mentioned voltage dividing circuit network is taken out, it becomes an integrating circuit as shown in FIG. 4, that is, a low-pass filter.

The resistance value R16 of the resistor 16 of this integrating circuit and the capacitance Ct of the capacitor 17 are determined as follows when this DC power supply device is connected to a motor. First, the gain characteristic equation of this integrating circuit is as shown in the following equation (2).

G(ω)・R14[((R+4+R+s)+ω2C+t
”La(LsLe+R+4.Ls+LJ+e))24o
) "C10" RI! l”l”2/((R14”R16)2+ω2G,, 2・(R+sR
+8”R+4R+5+RzR+a) 2) ・・・
(2) Also, this gain characteristic is illustrated in FIG. 5.

FIG. 5 is a gain characteristic diagram of the voltage dividing network of FIG. 4.

That is, for the low frequency component of the load current (2), the impedance of the capacitor 17 is high, so the gain is large. On the other hand, for high frequency components of the load current I, since the impedance of the capacitor 17 is low,
Gain becomes smaller.

On the other hand, the load current characteristics of the motor are as shown in FIG. 6(a).

FIG. 6 is a correlation diagram between the current-time characteristics of the motor load connected to the DC power supply device of FIG. 1 and the output voltage-time characteristics of the intermediate tap of the voltage divider network of the current detection section. figure(
a) is a current-time characteristic diagram of a motor load.

That is, the operation period T as shown in FIG. 6(a).

, a current with a current value of 11 flows during the light load period 1+, a current with a current value of 12 flows during the heavy load period t2, and the current value becomes O during the no-load period t3.

The average current over the operating period T is Iav. Further, in the stop period T2, the current value becomes ◯.

Incidentally, the limiting current value I LIMIT of the DC power supply device is determined by the rating of the transistor 4 of the switch circuit 1 shown in FIG. Then, while the temperature of the transistor 4 is low, the amount of energization can be made larger than when the temperature rises, so the limiting current value I LIM+1 can also be made larger. That is, as shown in FIG. 6(a), after the no-load period t3, the transistor 4 is cooled by the smell during this no-load period t, and if the heavy load period t2 of the motor is short, The limit current value I LIMIT can be made larger than usual. That is, even if the transistor 4 is made small, the current value I2 can be increased.

FIG. 6(b) is a diagram showing the output voltage-time characteristic of the intermediate tap of the dividing grid of the current detection section of the device of FIG. 1, that is, the output voltage-time characteristic of the integrating circuit of FIG. 4. .

That is, when a pulsed load current as shown in FIG. 6(a) flows through the motor, a pulse voltage v1 corresponding to this load current is applied to the input of the integrating circuit of FIG.
An integral waveform as shown in FIG. 6(b) is output.

Here, the limit current value I LIM determined by the current detection unit 3
IT is determined by the gain G(ω) of the voltage dividing network as follows:
3).

I LIM+1=VBE/ (R, 3・G(ω))
... (3) Here, ■BE is the base-emitter saturation voltage of the transistor 10 of the control section 2, and R13 is the resistance value of the current detection resistor.

In order to prevent the average current I av from exceeding the limit current value I LIM+7 during the operation period T+ in FIG. 6(a), the gain characteristic G(ω) is made to satisfy the following equation (4).

G (2x/T+)≦V B'E/ (RI3 ” I-
v) "" (4) Furthermore, in order to prevent the load current 2 from exceeding the limit current value I LIMIT during the operation period t2, the gain characteristic G(ω) is made to satisfy the following equation (5).

G (2i / t2) ≦VBE/ (R13・I
2) ...(5) That is, these equations (4)
In order to satisfy (5), the resistance value RI6 of the resistor 16 and the capacitance Cs7 of the capacitor 17 are determined.

Figure 7 shows the limit current value I L+b of the DC power supply shown in Figure 1.
It is a figure which shows the relationship between ++r and the continuous time of the load current of an electric motor.

That is, this diagram shows the resistance value RI of the resistor 16 as described above.
7 is a graph representing the equation (3) when B and the capacitance it CI 7 of the capacitor 17 are determined.

As shown in this figure, according to the DC power supply device of Fig. 1,
Due to the gain characteristic G(ω) determined as described above, while the continuous time of the load current is short, the limiting current value I LIMI
T is set large, and as the continuous time of the load current becomes longer, the limit current value I LIMIT is set smaller.

Next, the operation of the DC power supply device according to the present invention will be explained.

When the start switch (both not shown) of the motor connected to the DC power supply shown in Fig. 1 is turned on, the control unit 2
is not operating, the level of the output terminal 2a is low level "L", the PNP transistor 4 of the switch circuit 1 is in a conductive state, and current flows from the DC power supply 5 to the motor. As shown in FIG.
Two heavy load operations are performed intermittently. That is, first, when a light load operation is performed for a period t immediately after the motor is started, the magnitude ■ is reached in a half period t1.

A pulse current flows. Then, the voltage generated between the control terminals 3a and 3b of the current detection section 3, that is, the output voltage 2 of the integrating circuit in FIG. 4 gradually increases as shown in FIG. ,). This output voltage ■2 is the base-emitter saturation voltage VBg of the transistor 10 of the control section 2.
, so transistor 10 remains non-conducting and bias resistor 11 is removed from internal voltage source 12.
The signal level applied to the control terminal C of the triangular wave oscillator 8 through the signal becomes high level "H". As a result, a triangular wave voltage is input from the triangular wave oscillator 8 to the inverting input terminal of the error amplifier 9, and an output voltage (2) is input to the non-inverting input terminal of the error amplifier 9. Only when UT exceeds this triangular wave voltage, the output level of the error amplifier 9 becomes the "Hj level" and the PNP
Voltage control similar to the conventional method is performed by making transistor 4 non-conductive.

Next, when no-load operation is performed for a period t3, the charge accumulated in the capacitor 17 is transferred to the discharge diode 18.
, the output voltage v2 of the integrating circuit immediately drops to O (from 2 to 3 at the time). Then, during this period t3, heat dissipation from the transistor 4 progresses, and the temperature of the transistor 4 decreases.

Furthermore, after repeating light load operation (at time ~te) and no-load operation (at time 4 ~), if heavy load operation is performed for period t2, size modification is performed in half cycle t2. 2
A pulse current flows. Then, the output voltage of the integrating circuit is
2 gradually increases as shown in FIG. 6(b) (at time τ
5 to 6).

This output voltage ■2 is applied to the NPN transistor 10 of the control section 2.
The base-emitter saturation voltage VBE of the switch circuit 1 is not exceeded by -F, and therefore, as described above, the control section 2 that controls the switch circuit 1 performs the same voltage control as in the prior art. In this case, even if the current 2 during heavy load operation is larger than the current 1 during light load operation, it takes a period of time t for the temperature of the PNP transistor 4 to reach the maximum allowable temperature.
Since the current I2 is longer than 2, the current I2 does not exceed the rating, and the PNP transistor 4 is prevented from deteriorating more quickly. Further, during the period t2, a large amount of current 2 can be supplied to the motor, so that voltage drop during this period is prevented.

However, when the motor is operated with a heavy load beyond the period t2, when the motor is operated with a light load for a long period of time, or when a load short circuit or half short circuit occurs, the output voltage of the integrating circuit (2) 2 further increases as shown in FIG. 6(b). That is, the time point F~ shows the case where the heavy load operation of the motor is carried out beyond the period t2. This output voltage (2) is the base-emitter saturation voltage (2) of the transistor 10 of the control section 2.

(at this point), so transistor 1
0 is in a conductive state, and the signal level applied from the internal voltage source 12 to the control terminal C of the triangular wave oscillator 8 via the bias resistor 11 becomes a low level rLJ. As a result, the triangular wave voltage is no longer applied from the triangular wave oscillator 8 to the inverting input terminal of the error amplifier 9, and the output level of the error amplifier 9 becomes rH.
It is maintained at the J level, the PNP transistor 4 is made non-conductive, and the supply of current is stopped. Therefore, even if a load short circuit or half short circuit occurs, the PNP transistor 4 is prevented from deteriorating or being damaged.

Furthermore, the above operation can be expressed as follows. That is, the current flowing over the operating period T, ω・2π
The frequency component of /T1 is the limiting current value V 8 E/ (R
l 3·G(2π/TI)). In this case, since the gain characteristic is as shown in FIG. 5, the limiting current value V RE/ (Rl 3 · G (2π/TI)) is a relatively small value as shown in FIG. 7, that is, PNP t-
The current value corresponds to the current value that can be continuously passed through the transistor 4. Then, this limit current value V ai/
(R+a・G(2/T+)) is greater than the average current Iav of the motor from the above equation (4) D, so
It does not interfere with the operation of the electric motor. That is, the current detection section 3
The voltage generated at the control terminals 3a and 3b of the control section 2 is
Base-emitter saturation voltage VB of N transistor 10
Since it is less than E, the NPN transistor 10 becomes non-conductive. Therefore, the control section 2 that controls the switch circuit 1
Voltage control similar to the conventional method is performed.

However, even when the motor is operated within the operating period T1, when the operating rate of the motor becomes higher than normal, the frequency component of ω・2π/TI of the current flowing through the motor changes to the limiting current (I
i! VBE/(RI3.G(2i/TI)). Then, the current detection unit 30 control terminal 3a
, 3b is equal to or higher than the base-emitter saturation voltage VBE of the NPN transistor 10 of the control unit 2,
The NPN transistor 10 becomes conductive, and the signal level applied from the internal voltage source 12 to the control terminal C of the triangular wave oscillator 8 via the bias resistor 11 becomes low level rLJ. As a result, the triangular wave voltage is no longer output from the triangular wave oscillator 8, and the output level of the error amplifier 9 is set to high level rH.
J is maintained, and the PNP transistor 4 is rendered non-conductive. Therefore, a current exceeding the rating does not flow through the PNP transistor 4.

By the way, when a load short circuit or a half short circuit occurs, a current flows for a period T=■ which is longer than the operating period T1 of the motor. The current flowing during this period T = (1) = 2
The frequency component of π/co is the limiting current value V BE/(R
ls·G(2π10O)). Here, G(2π10O) is given by the following equation (6).

G (2z / co) = R+4/ (R+4
+L5) = (6) Therefore, the limit current value I LIMIT for the current of the frequency component of ω = 2π/■
((1)) becomes the minimum value given by the following equation (7).

I L+1atr(oO)”((Rz+L5)/L3L
4) 'Lti ''' (7) And this limit current value ((R+4+R+s)/R++R+4)・VBE is,
This is sufficiently smaller than the rated current of the PNP transistor 4. Therefore, when a load short circuit or a half short circuit occurs, the control terminal 3a of the current detection section 3.

The voltage generated at 3b is equal to or higher than the base-emitter saturation voltage VBE of the NPN transistor 10 of the control unit 2,
The NPN transistor 10 is rendered conductive, the output level of the control section 2 is maintained at a high level rHJ, and the PNP transistor 4 is rendered non-conductive. Therefore, even if the rating of the PNP transistor 4 is small, the PNP)-
A current exceeding the rated current does not flow through the transistor 4, and characteristic deterioration and destruction of the PNP transistor 4 are reliably prevented.

Furthermore, when the electric motor is operated within the operating period t2, the current flowing over the operating period t2 is ω=2π/l.
The frequency component of z is the limiting current value VBE/(RI3・G(
2π/12) ). In this case, since the gain characteristics are as shown in Figure 4, the limiting current value VB
g/(R13・G(2π/12)) is a relatively large value as shown in FIG. 2, that is, a current value corresponding to the current value that can be passed through the PNP transistor 4 within the period t2 at the initial stage of energization. . Then, this limited current value VBE/(RI3
-G(2π/12)) is equal to or higher than the current I2 when the motor is under heavy load according to the above equation (4), so it does not interfere with heavy load operation of the motor. That is, since the voltage generated at the control terminals 3a and 3b of the current detection section 3 is lower than the base-emitter saturation voltage VBE of the NPN transistor 10 of the control section 2, the NPN transistor 10 becomes non-conductive. Therefore, the control section 2 that controls the switch circuit 1 performs voltage control similar to the conventional one.

Therefore, no voltage drop occurs even when the motor is operated under heavy load.

Note that the DC power supply device of the present invention is not limited to the above embodiments.

That is, the voltage dividing circuit network that divides the voltage across the current detecting resistor 13 includes voltage dividing resistors 14 and 15 connected in parallel to the current detecting resistor 13, and resistors connected in parallel to the voltage dividing resistor 14. 16, a capacitor 17, and a discharging diode 18 connected in parallel to the voltage dividing resistor 15, but the present invention is not limited to this, and the voltage dividing resistor 1
Instead of providing the resistor 16 and capacitor 17 connected in parallel to the voltage dividing resistor 15, a parallel circuit of a coil and a diode connected in series to the voltage dividing resistor 15 may be provided. Furthermore, the load connected to the DC power supply device of the present invention is not limited to the motor load as in the above embodiment, but any load that requires a large current only for a short period of time, such as a capacitor load, can achieve the same effect. Needless to say, it can be done.

(Effects of the Invention) The DC power supply device of the present invention having the above configuration controls the limit value of the output current according to the frequency characteristics of the output current, and therefore has the following effects.

In other words, when supplying a large current for a short period of time to a load such as a motor or capacitor, the continuous time of the load current is short, and the limited current value increases only during this period, which prevents voltage drops. , it is possible to prevent the voltage fluctuation rate from increasing. Therefore, the switching circuit can be made small and low in cost with a small rating, thereby making it possible to downsize and reduce the cost of the DC power supply device.

In addition, if a load short circuit or half short circuit occurs, the continuous load current time becomes longer and the limiting current value becomes smaller, so even if the rating of the switching circuit is small, damage to the switching circuit can be reliably prevented. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a DC power supply device according to the present invention, and FIG.
The figure is a circuit configuration diagram of a conventional DC power supply device, FIG. 3 is a load characteristic diagram of a conventional DC power supply device, FIG. and the sixth
FIG. 7 is a diagram showing the characteristics of this current detection section, and FIG. 7 is a diagram showing the output current characteristics of the DC power supply device according to the present invention. l... Switch circuit, 2... Control section, 3... Current detection section, 3a, 3b... Control terminal, 13... Current detection resistor, 20... Intermediate tap. Patent applicant Oki Electric Industry Co., Ltd.

Claims (1)

[Scope of Claims] A DC power supply device comprising: a switch circuit inserted in series with the output of a DC power supply; a control section that controls opening/closing of the switch circuit; and a current detection section that detects an output current. The detection unit includes a current detection resistor, a voltage divider network that divides the voltage across the current detection resistor using an impedance having frequency characteristics, and a control terminal connected to the intermediate tap of the voltage divider network. A DC power supply device comprising the following: wherein the control section controls opening and closing of the switch circuit according to the output of the control terminal.