JP2005165924A - Voltage compensation circuit of dc power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage compensation circuit of a DC power supply device which dissolves cost increase and heat generation measures by a resistor for detection. <P>SOLUTION: In the voltage compensation circuit of the DC power supply device which adds output voltage to a load 8 via an output cord 7, compensates voltage drop generated by the output cord 7 and generates the output voltage, it is constituted so that a coil L constituting a filter by combination with a capacitor C2 is provided on the negative electrode side of the output voltage and an internal resistor of the coil L becomes a resistor for compensation of the output voltage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a voltage correction circuit for a DC power supply device such as an AC adapter having an output cord.

  In the case of an AC adapter, many are accompanied by a long output cord of about 1 to 2 m. In an AC adapter with a low voltage and a large current (1-2A), the voltage drop due to the output current is large. The voltage drop of the output cord fluctuates depending on the operating state of the electronic device that is the load, causing a disadvantage that the voltage applied to the load fluctuates.

  When an output current is passed, a voltage drop always occurs due to the DC resistance of the output cord. Usually, a power source such as an AC adapter is required to have a certain voltage accuracy, and therefore it is necessary to suppress the influence of the voltage drop of the output cord as much as possible.

  FIG. 3 is an external view showing an outline of the AC adapter in the first conventional example. By using a wire as thick as possible for the output cord 17 provided between the AC adapter main body 12 and the plug 15, the voltage drop due to the DC resistance is reduced.

  FIG. 4 is a block diagram for explaining voltage adjustment in the AC adapter of Conventional Example 2 (Patent Document 1). The AC input voltage from the terminals T1 and T2 is converted to an appropriate voltage by the transformer T, rectified by the rectifier circuit 23, regulated by the voltage regulator circuit 24, and the output voltage is applied to the load via the output cord 27. . This load voltage is detected at the output plug portion using the voltage detection wire 29. The voltage is adjusted by the voltage adjustment circuit 24 based on the output from the voltage detection circuit 25 so that the load voltage is kept constant.

  As described above, a power supply such as an AC adapter usually requires a certain voltage accuracy, so whether to use a thick wire cord as much as possible, or to detect the voltage at the output plug unit with a 4-wire cord Therefore, the voltage drop of the output cord is suppressed. In either case, the cost of the cord was increased and the appearance was imbalanced by a thick cord.

  As means for solving these problems, a low resistance is put in the output line, and the voltage drop due to the current is used to correct the divided voltage of the set resistor, thereby compensating for the voltage drop due to the output code. FIG. 5 is a stabilization circuit diagram of the DC power supply device in Conventional Example 3, which is a countermeasure example for the problems of Conventional Examples 1 and 2 (Patent Document 2). The AC input from the terminals T1 and T2 is rectified by the rectifier circuit 33 and smoothed by the smoothing circuit 34. The output voltage adjusted by the regulator Q2 is applied to the load 38 of the terminals T5 and T6 from the output cord 37 via the terminals T3 and T4. The voltage applied to the load 38 is lower than the output voltage of the terminals T3 and T4 by the voltage drop of the output cord 37. The voltage drop is the product of the resistance Ro of the output cord 37 and the output current Io. Therefore, the output voltage of the terminals T3 and T4 is set higher by the voltage drop of the output cord 37.

The differential amplifier IC2 is supplied with V2 based on the reference voltage E and a voltage V1 at a connection point between the resistor R6 and the resistor R7 among the resistors R6, R7, and R8 connected in series. The resistor R8 is for output current detection. The voltage V1 also fluctuates due to the voltage at the resistor R8 that fluctuates due to increase / decrease in the output current Io. The output voltage of the regulator Q2 is corrected by the output Vc of the differential amplifier IC2. In this case, the resistance Ro of the output cord 37 is considered as the resistance value of the resistance R8.
Japanese Utility Model 5-60187 JP 7-104870 A

  However, the DC power supply device using the detection resistor in the conventional example has problems such as an increase in the number of man-hours, an increase in cost due to the detection resistor, and a countermeasure against heat generation due to a large current.

  The present invention has been proposed in view of the above, and it is an object of the present invention to provide a voltage correction circuit for a DC power supply apparatus that eliminates the cost increase due to the detection resistor and the countermeasure against heat generation.

  According to a first aspect of the present invention, there is provided a voltage correction circuit for a DC power supply device that generates an output voltage by applying an output voltage to a load via an output cord and compensating for a voltage drop generated in the output cord. A voltage correction circuit for a DC power supply device, wherein a coil constituting a filter in combination with a capacitor is provided on the negative electrode side of the output voltage, and the internal resistance of the coil is a resistance for compensation of the output voltage. .

  As described above, in the present invention, the coil constituting the filter in combination with the capacitor is installed on the negative electrode side where the output current flows, and the internal resistance of the coil is used as a resistance for compensating the output voltage. There is an effect that cost can be increased by the detection resistor provided and heat generation countermeasures can be eliminated. In particular, the effect is great in a small-sized AC adapter.

  In addition, since the winding of the coil is configured with a plurality of wire diameters, the adjustment of the inductance as the coil constituting the filter in combination with the capacitor and the adjustment as the correction resistor for the output voltage are performed simultaneously and It can be done easily.

  The present invention is most suitable for a DC output circuit that uses a choke coil in a filter that reduces AC components. That is, by providing the choke coil with an inductance as a filter and a resistor for correcting the output voltage, a dedicated current detecting resistor can be omitted.

  FIG. 1 is a correction voltage circuit of a DC power supply device according to an embodiment of the present invention. In the figure, 1 is a voltage correction circuit for a DC power supply device, 7 is an output code, 8 is a load, C1 and C2 are capacitors, IC1 is a constant voltage generation circuit, L is a coil (internal resistance is Rc), R1, R2, Ro Is a resistor, and T1 to T6 and Ts are terminals. The constant voltage generation circuit IC1 operates by a voltage applied to the terminal Ts. The coil L and the capacitor C2 remove the ripple component of the DC voltage applied between the terminals T1 and T2. That is, a filter is constituted by the coil L and the capacitor C2.

  In this embodiment, the internal resistance Rc of the filter coil L is used to adjust the output voltage Vo. That is, the applied voltage at the terminals T5 and T6 on the load 8 side is lower than the output voltage Vo at the terminals T3 and T4 by the voltage drop of the output cord 7. Therefore, the output voltage Vo at the terminals T3 and T4 is set higher by the voltage drop of the output cord 7. The internal resistance Rc of the coil L is used for setting at this time. The setting is described below.

In this embodiment, the output voltage Vo between the terminals T3 and T4 is determined by the reference voltage Vref generated by the constant voltage generating circuit IC1, the resistors R1 and R2, and the internal resistance Rc of the coil L. The output voltage Vo at this time is
Vo = (R1 + R2) / R2 × Vref
+ (R1 / R2) × Io × Rc …………………… Formula (1)
Given in. In Expression (1), Io is an output current flowing through the load 8.

  Incidentally, when the output current Io increases, the voltage drop of the output cord 7 increases due to the resistance Ro of the output cord 7. Due to the increased voltage drop, the voltage V1 applied to the load 8 decreases. However, from the equation (1), when the output current Io increases, the output voltage Vo increases. That is, it is possible to compensate for the increase in the output voltage Vo caused by the output code 7 generated by the increase in the output current Io.

  By the way, from the equation (1), the output current Vo is determined by the value of the resistance Rc of the coil L together with the resistances R1 and R2. At this time, in order to adjust the value of the resistance Rc of the coil L, the following method is used. FIG. 2 is an explanatory diagram of coil winding specifications. As shown in FIG. 2, the winding of the coil L is configured with a plurality of wire diameters. That is, the coil L includes a winding portion L1 made of a thick line and a winding portion L2 made of a thin line. The inductance of the coil L is determined by the number of turns of the winding part L1 by the thick line and the number of turns of the winding part L2 by the thin line, and the resistance Rc of the coil L is a low resistance value R11 of the winding part L1 by the thick line. It is determined by the sum of the high resistance R12 of the winding portion L2 by the thin wire. Therefore, the adjustment of the inductance as a filter and the adjustment as the compensation resistor for the output voltage Vo are simultaneously performed by adjusting the ratio of the number of turns of the winding part L1 by the thick line and the number of turns of the winding part L2 by the thin line. And can be done easily.

It is a correction voltage circuit of the direct-current power supply device in one Example of this invention. It is explanatory drawing of the coil | winding specification of the coil used with the correction voltage circuit of the DC power supply device in one Example of this invention. It is an external view which shows the outline | summary of the AC adapter in the prior art example 1. FIG. It is a block diagram explaining the voltage adjustment in the AC adapter of the prior art example 2. It is a stabilization circuit diagram of the DC power supply device in Conventional Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC power supply device voltage correction circuit 12, 22, 32 AC adapter main body 7, 17, 27, 37 Output cord 8, 38 Load 15 Plug 23 Rectification circuit 24 Voltage adjustment circuit 25 Voltage detection circuit 29 Detection wire 33 Rectification circuit 34 Smoothing circuit C1, C2, Capacitor E Reference voltage IC1 Shunt regulator IC2 Differential amplifier L Coil (including internal resistance Rc)
Q2 regulator R1, R2, R6, R7, R8, Ro, Rc resistance T transformer T1-T6, Ts terminal

Claims (1)

Voltage correction of a DC power supply device that generates an output voltage by adding an output voltage to the load (8) via the output code (7) and compensating for a voltage drop generated in the output code (7) In the circuit
A coil (L) constituting a filter in combination with a capacitor (C2) is provided on the negative electrode side of the output voltage,
A voltage correction circuit for a DC power supply device, wherein an internal resistance of the coil (L) is used as a resistance for compensating the output voltage.

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