JPH07104870A - Stabilizing circuit for dc power unit - Google Patents

Abstract

PURPOSE:To remarkably reduce the cost, to miniaturize the circuit and to improve convenience by simplifying the circuit configuration and excluding a detection code. CONSTITUTION:When constituting the stabilizing circuit 1 for DC power unit to supply DC power to a load RL to which a serial resistant component Rw such as the resistant component Rw provided with DC output codes 3p and 3n derived from a main body 2 of the power unit to the outside is connected, for example. an output voltage correcting circuit 4 is especially provided with a load current vs output voltage characteristic to increase (or decrease) an output voltage Vo of the main body 2 of the power unit corresponding to the increase (or decrease) of a load current Io so as to almost fix a voltage Vm to be impressed to the load RL.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stabilizing circuit for a DC power supply device suitable for use in an AC adapter having a DC output cord.

[0002]

2. Description of the Related Art Generally, an AC adapter used for a DC power source of electronic equipment is known. This type of AC adapter has a power supply device main body, and this power supply device main body is integrally provided with a power supply plug to be plugged into an outlet of a commercial AC power supply, and a direct current output cord connected to an electronic device or the like serving as a load.

By the way, since such an AC adapter has a DC output cord, an unnecessary voltage drop occurs due to the resistance of the DC output cord itself. In particular, this voltage drop increases as the load current increases, so that the tip voltage of the DC output cord, which is originally required in electronic devices and the like, is much lower than the regular rated voltage.

Therefore, in order to solve this problem, conventionally, as in the DC power supply unit Mo shown in FIG. 3, the original DC output cord 22 led out from the power supply unit main body 21 to the outside.
In addition to p and 22n, detection codes 23p and 23n are provided,
The tips of the detection cords 23p and 23n are connected to the tips 22ps and 22ns of the DC output cords 22p and 22n, respectively, so that the tip voltages of the DC output cords 22p and 22n can be directly detected and built into the power supply main body 21. The stabilization circuit 20 performs feedback control by the stabilization circuit main body 24 so that the tip voltage becomes constant.
Was equipped with. In addition, RL is a load of electronic devices, 25
Reference numerals a and 25b are AC input sections, 26 is a rectifier circuit, and 27 is a smoothing circuit. The output side of the smoothing circuit 27 is connected to the input side of the stabilizing circuit body 24, and the DC output cords 22p and 22n are connected to the output side of the stabilizing circuit body 24. Rwp and Rwn are DC output codes 22
p and 22n resistance, Rdp and Rdn are detection codes 23
The resistance components of p and 23n are shown. In this case, the detection code 23
Since the current flowing through p and 23n is very small, the resistance component Rd
The voltage drop due to p and Rdn can be ignored.

[0005]

However, the above-described conventional stabilizing circuit 20 requires the detection codes 23p and 23n and the dedicated stabilizing circuit main body 24, so that the overall configuration becomes complicated and the cost is increased. In addition to the increase in size, the thickness of the DC output cords 22p and 22n is also doubled, which is disadvantageous in terms of usability.

The present invention has solved the problems existing in such conventional techniques. By simplifying the circuit configuration and eliminating the detection code, the cost is greatly reduced and the size is reduced.
Another object of the present invention is to provide a stabilizing circuit for a DC power supply device that can improve usability.

[0007]

SUMMARY OF THE INVENTION The present invention provides a series resistance R
w, for example, when configuring the stabilizing circuit 1 of the DC power supply device that supplies DC power to the load RL to which the resistance component Rw of the DC output cords 3p and 3n derived from the power supply device main body 2 is connected. In particular, the output voltage Vo of the power supply device 2 is increased (or decreased) corresponding to the increase (or decrease) of the load current Io so that the applied voltage Vm to the load RL becomes substantially constant. An output voltage correction circuit 4 having a voltage characteristic is provided.

In this case, the output voltage correction circuit 4 is connected to the ground line side output end 5n of the power supply main body 2 and the power supply main body 2.
The current detection resistor 7 connected between the ground line 6n of the power line, the voltage detection resistor unit 8 connected between the hot line side output end 5p and the ground line 6n of the power supply unit 2, and the voltage detection resistor unit 8 detected by the voltage detection resistor unit 8. One detection voltage V1 and current detection resistor 7
The control voltage based on the deviation between the first detection voltage V1 and the second detection voltage V2 is applied to the output part of the comparator 10 by applying the second detection voltage V2 that changes corresponding to the terminal voltage Vs of A control voltage generation unit 9 for obtaining Vc and an output control unit 11 for controlling the current flowing through the hot line 6p based on the control voltage Vc can be provided.

Further, the voltage detecting resistor portion 8 is composed of a pair of voltage dividing resistors 8x and 8y connected in series, and detects the first detection voltage V1 from the connecting portion 8c between the voltage dividing resistors 8x and 8y and also detects the current. As for the resistance value Rs of the resistor 7, the series resistance component connected to the load RL is Rw, the resistance value of the voltage dividing resistor 8x connected to the hot line 6p side is Rx, and the earth line 6
When the resistance value of the voltage dividing resistor 8y connected to the n side is Ry, it is desirable to set by Rs = Rw / [{(Rx + Ry) / Ry} -1].

[0010]

According to the stabilizing circuit 1 of the DC power supply device of the present invention, since the output voltage correction circuit 4 is provided, the output voltage of the power supply device main body 2 is determined by the load current-output voltage characteristic based on the output voltage correction circuit 4. Vo becomes high (or low) corresponding to the increase (or decrease) of the load current Io. As a result, when the load current Io is large, the voltage drop due to the series resistance component Rw connected to the load RL becomes large, so that the output voltage Vo of the power supply device body 2 is increased by the output voltage correction circuit 4 and the load voltage is increased. When the current Io is small, the voltage drop due to the resistance component Rw becomes small, so the output voltage correction circuit 4 corrects the voltage drop so that the output voltage Vo becomes low, and thus even if the load current Io increases or decreases. The applied voltage Vm to the load RL is maintained substantially constant.

In this case, according to the specific configuration of the output voltage correction circuit 4, first, the output voltage is output from the voltage detection resistor portion 8, that is, the connection portion 8c between the pair of voltage dividing resistors 8x and 8y connected in series. The first detection voltage V1 corresponding to
It is applied to the non-inverting input section of the comparator 10 in the control voltage generation section 9. Further, a terminal voltage Vs corresponding to the load current Io is generated in the current detection resistor 7, and this terminal voltage Vs
The second detection voltage V2 that changes corresponding to s is applied to the inverting input section of the comparator 10. As a result, the control voltage Vc based on the deviation between the first detection voltage V1 and the second detection voltage V2 is obtained at the output of the comparator 10, and the control voltage Vc is obtained.
c is given to the output control unit 11. And the control voltage V
The current flowing through the hot line 6p is controlled based on c. Therefore, the load current Io increases and the terminal voltage Vs increases.
If the voltage rises, the second detection voltage V2 increases accordingly, and the output voltage Vo is controlled to increase by the function of the output control unit 11 based on the control voltage Vc.

As for the resistance value Rs of the current detection resistor 7, the series resistance component connected to the load RL is Rw, the resistance value of the voltage dividing resistor 8x connected to the hot line 6p side is Rx, and the earth line 6n side is. By setting the resistance value of the connected voltage dividing resistor 8y as Ry and setting Rs = Rw / [{(Rx + Ry) / Ry} -1], the voltage drop due to the resistance component Rw is canceled.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, a schematic configuration of a DC power supply device M including the stabilizing circuit 1 according to this embodiment will be described with reference to FIG.

The DC power supply device M includes a power supply device body 2. The power supply device main body 2 includes an AC input section 13a, 13b, a rectifier circuit 14 for rectifying the AC input supplied to the AC input section 13a, 13b, a smoothing circuit 15 for smoothing a rectified output from the rectifier circuit 14, and an output of the smoothing circuit 15. A stabilizing circuit 1 having an output voltage correction circuit 4 connecting the sides is provided. The stabilizing circuit 1 normally includes a constant voltage circuit and a constant current circuit for protecting against overcurrent, but they are omitted in this embodiment. Further, 5p is an output end on the hot line side, and 5n is an output end on the ground line side.
p and the earth line side output end 5n to the power supply unit 2
DC output codes 3p and 3n led to the outside. A load RL such as an electronic device is connected between the tips of the DC output cords 3p and 3n.

Next, a specific configuration of the stabilizing circuit 1 according to this embodiment will be described. Reference numeral 4 is an output voltage correction circuit. In the output voltage correction circuit 4, 16 is the output control unit 1.
1 is connected to the hot line 6p on the smoothing circuit 15 side, and the collector is connected to the hot line side output end 5p. The ground line side output end 5n is connected to the ground line 6n on the smoothing circuit 15 side through the current detection resistor 7. On the other hand, the voltage detection resistor unit 8 is connected between the hot line side output end 5p and the smoothing circuit 15 side ground line 6n. The voltage detection resistor unit 8 is composed of a pair of voltage dividing resistors 8x and 8y connected in series. On the other hand, 9 is a control voltage generator, which includes a comparator 10. The non-inverting input section of the comparator 10 has a voltage dividing resistor 8x
And 8y, and a reference voltage source 17 is connected between the inverting input portion of the comparator 10 and the ground line side output end 5n. On the other hand, comparator 1
The output of 0 is connected to the base of the control transistor 16.

In the figure, each DC output code 3p, 3n
Rw / 2 in Fig. 3 indicates the resistance of each DC output code 3p, 3n itself. Therefore, the DC output codes 3p and 3
The total resistance of n is Rw.

The resistance value Rs of the current detection resistor 7 is set as follows. The resistance value of the voltage dividing resistor 8x connected to the hot line 6p side is Rx, the resistance value of the voltage dividing resistor 8y connected to the ground line 6n side is Ry, and further, between both ends (between a and b) of the voltage detection resistor unit 8 ) Is Vd, and the power supply device main body 2 is a voltage between the hot line side output end 5p and the ground line side output end 5n (between cd).
Is the output voltage of V0 and the applied voltage of the load (between e and f) is V
m, the reference voltage of the reference voltage source 17 (between g and d) is Vr, and the load current is Io, the detection end voltage Vd is Vd =
{(Rx + Ry) / Ry} · (Io · Rs + Vr) ...
(1), and the output voltage Vo is Vo = Vd−Io · R
s ... (2), and the applied voltage Vm is Vm = V
o-Io · Rw (3)

Therefore, from equations (1) to (3), Vm
= {(Rx + Ry) / Ry} · Vr + [{(Rx + R
y) / Ry} · Rs−Rs−Rw] · Io (4) holds, so from equation (4), DC output code 3
In order to eliminate the influence of the resistance component Rw in p and 3n, the second term of the equation (4) is “0”, that is, {(Rx + R
y) / Ry} .Rs-Rs-Rw = 0. Therefore, Rs = Rw / [{(Rx + Ry) / R
y} −1] ... (5) can be obtained, and the optimum resistance value Rs of the current detection resistor 7 can be obtained from the equation (5).

Next, the operation of the stabilizing circuit 1 according to this embodiment will be described.

Now, assume that the load current Io increases. As a result, the size of the terminal voltage Vs due to the current detection resistor 7 in the output voltage correction circuit 4 also rises in accordance with the increase in the load current Io, and the terminal voltage Vs is the reference voltage source 17
The second detection voltage V2, which is higher than the reference voltage Vr, is applied to the inverting input section of the comparator 10 by increasing the magnitude of the reference voltage Vr. As a result, the first detection voltage V1 and the second detection voltage V2 are output to the output of the comparator 10.
The control voltage Vc is obtained based on the deviation of the control voltage Vc, and this control voltage Vc is applied to the base of the control transistor 16 in the output control unit 11. This controls the current flowing through the hot line 6p in the direction in which the output voltage Vo increases.

In this case, the resistance value Rs of the current detection resistor 7 is set by the above equation (5) under the condition that the influence of the resistance component Rw in the DC output codes 3p and 3n is eliminated. The voltage drop due to is canceled, and the load R is not affected by the increase or decrease of the load current Io.
The variation of the applied voltage Vm with respect to L can be suppressed.

FIG. 2 shows the load current vs. output voltage characteristic (applied voltage) characteristic at this time. As is apparent from the figure, when the load current Io increases, the output voltage Vo of the power supply device body 2 also correspondingly increases, but the applied voltage Vm applied to the load RL is maintained substantially constant. . In the experimental value, by selecting the current detection resistor 7 to be about 1 [Ω], the output voltage Vo is 13.
The voltage of 2 [V] was increased to 14.0 [V] by increasing the load current Io to 1 [A]. Therefore, if the original applied voltage Vm required for the load RL is set when the load current Io is zero, a regular voltage can always be applied to the load RL.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment.
For example, the DC power supply device is illustrated as having a DC output cord having a resistance component Rw, but the present invention can be similarly applied to a case where the DC power output cord is not used but the load component has a resistance component Rw different from the original load. . Further, the voltage detection resistor section does not prevent the use of a single resistor. Furthermore, although the output control unit uses a single control transistor as an example, any circuit configuration that exhibits the same operation can be adopted. The DC power supply device can be applied to any other form such as a switching regulator. Further, since the current detection resistor is provided in the stabilizing circuit, it can also be used for current detection in the constant current circuit. In addition, the detailed circuit configuration, method, conditions, etc. can be arbitrarily changed without departing from the scope of the present invention.

[0025]

As described above, according to the present invention, in a stabilizing circuit of a DC power supply device for supplying DC power to a load to which a series resistance component is connected, in particular, an applied voltage to the load is substantially constant. In addition, since an output voltage correction circuit having a load current vs. output voltage characteristic that increases (or decreases) the output voltage of the power supply device in response to an increase (or decrease) in the load current is provided, simplification of the circuit configuration and By eliminating the detection code, there is a remarkable effect that the cost can be significantly reduced, the size can be reduced, and the usability can be improved.

[Brief description of drawings]

1 is a block circuit diagram of a DC power supply device including a stabilizing circuit according to the present invention;

FIG. 2 is a characteristic diagram of load current vs. output voltage (applied voltage) by the stabilizing circuit,

FIG. 3 is a block circuit diagram of a DC power supply device including a stabilizing circuit according to the related art.

[Explanation of symbols]

 1 Stabilization circuit 2 Power supply unit 3p DC output code 3n DC output code 4 Output voltage correction circuit 5p Hot line side output end 5n Earth line side output end 6p Hot line 6n Earth line 7 Current detection resistance 8 Voltage detection resistance section 8x voltage dividing resistor 8y voltage dividing resistor 9 control voltage generation unit 10 comparator 11 output control unit RL load

Claims (5)

[Claims] 1. In a stabilizing circuit of a DC power supply device for supplying DC power to a load to which a series resistance component is connected, a load current is increased (or decreased) so that an applied voltage to the load is substantially constant. ), A stabilizing circuit for a DC power supply device, comprising: an output voltage correction circuit having a load current vs. output voltage characteristic for increasing (or lowering) the output voltage of the power supply device body. 2. The stabilizing circuit for the DC power supply device according to claim 1, wherein the series resistance component is a resistance component of a DC output cord led out from the power supply device main body. 3. The output voltage correction circuit comprises a current detection resistor connected between the ground line side output end of the power supply unit and the ground line of the power supply unit, and the hot line side output end between the power supply unit ground line. By applying to the input section of the comparator, the voltage detection resistor connected to, and the second detection voltage that changes corresponding to the terminal voltage of the current detection resistor and the first detection voltage detected from the voltage detection resistor, The output section includes a control voltage generation section that obtains a control voltage based on a deviation between the first detection voltage and the second detection voltage, and an output control section that controls a current flowing through the hot line based on the control voltage. Item 3. A stabilizing circuit for a DC power supply device according to Item 1. 4. The DC power supply device according to claim 3, wherein the voltage detection resistor section is composed of a pair of voltage dividing resistors connected in series, and the first detection voltage is detected from a connecting portion between the voltage dividing resistors. Stabilization circuit. 5. The resistance value Rs of the current detection resistor is Rw which is a series resistance component connected to the load, Rx is the resistance value of the voltage dividing resistor which is connected to the hot line side, and Rx which is the voltage dividing resistor which is connected to the ground line side. When the resistance value of Ry is Ry, Rs = Rw /
5. The stabilizing circuit for a DC power supply device according to claim 1, wherein the stabilizing circuit is set by [{(Rx + Ry) / Ry} -1].