JPH0934568A - Power circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a power supply circuit that can be set easily and accurately by a user. In a power supply circuit including a variable output regulator, a second resistor and a first resistor connected between output terminals of the variable output regulator and outputting an output voltage V _O from one end thereof, and a second resistor A data input device having one end connected to the other end of the resistor 1, a microcomputer for reading input data, a DATA-PWM conversion circuit for converting an output from the microcomputer into a PWM signal, and a DATA-PWM conversion circuit A smoothing circuit for smoothing the output and inputting the output to the other end of the second resistor is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit using a variable output regulator.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a conventional technique. In FIG. 3, C1 is an input capacitor, C2 is an output capacitor, RG1 is a regulator, R1 and R2 are output voltage setting resistors, CH1 is an output ON / OFF control terminal, and R3 is a current limiting resistor. Since the input voltage V _IN has a loss in the regulator, V _IN > V _O +1 in general.
Input of V is required, and the output voltage V _O is set by the resistance value ratio of R1 and R2. Inside the regulator RG1, a control loop is built so that the voltage V _O or V ₂ is maintained as set. The voltage of V ₂ is
V _O is divided by R1, VR1 and R2. Here, in order to make the output voltage V _O variable, the ratio of R1 and R2 is changed, but normally, in addition to R1, a variable resistor VR1 is provided and an arbitrary voltage can be set within the range not regulated by V _IN . CH1 is a terminal for forcibly changing the voltage V ₂ to turn ON / OFF the regulator output. Generally V
_{O 2} = 1.25 × (1 + R1 / R2) (V).

[0003]

In this conventional circuit, R
It is necessary to set the constants in consideration of the accuracy of R1 and R2, the accuracy of the reference power supply in RG1, the difference in the required current value depending on the supply destination, and the difference in the drop voltage depending on the power supply wiring length and type. Therefore, even if an attempt is made to satisfy the above-mentioned conditions, the output voltage accuracy cannot be high and the usage situation is limited. For example, if R1 and R2 are high-precision resistors (± 1%) and the precision of RG1 is included, only ± 4% of the output voltage precision can be obtained with respect to the reference output voltage. When an optimum value or high accuracy according to the load situation is required, use VR1 to manually adjust the output voltage with a voltmeter etc. so that the voltage falls within the voltage range corresponding to each specification. Becomes In this case, the work cost may be generated and individual differences in adjustment may occur, and it is difficult for the user to readjust. An object of the present invention is to provide a power supply circuit that can be set easily and accurately by a user.

[0004]

The present invention relates to a power supply circuit having an output variable regulator, which is connected between output terminals of the output variable regulator and outputs an output voltage V _O from one end thereof. A data input device, a microcomputer for reading the input data from the data input device, and an output from the microcomputer are provided, which include a resistor and a second resistor whose one end is connected to the other end of the first resistor. A DATA-PWM conversion circuit for converting into a PWM signal and a smoothing circuit for smoothing the output of the DATA-PWM conversion circuit and inputting the output to the other end of the second resistor are provided. Further, a voltage corresponding to the output of a comparator that compares the output voltage V _O and the reference voltage E is input to the connection point of the first and second resistors.

[0005]

With the above means, the output voltage can be set and adjusted by the microcomputer, and the overvoltage protection can be performed.

[0006]

FIG. 1 is a diagram showing an embodiment of the present invention.
OP is a data input device, M is a microcomputer (hereinafter referred to as a microcomputer), P is a DATA-PWM conversion circuit (D / A converter), F is a smoothing circuit, and others have the same configuration as in FIG. The data input device OP is a general device such as a keyboard or a contact input device from which the microcomputer M can read setting data. DATA-PWM conversion circuit P
There is no particular regulation on the contents and hardware of the. D
The commercially available hardware may be used as the / A converter. The smoothing circuit F is composed of an RC filter and a half amplifier. First, a person or another device inputs an arbitrary output voltage to OP. The microcomputer reads this set value and converts the data so as to match the output voltage. When the microcomputer writes this data in P, a PWM signal is output. When P is a D / A converter, an analog voltage is output. The PWM signal and the ripple voltage component are smoothed by the RC filter circuit in the smoothing circuit F, and the half voltage is output by the half-wave amplifier. V _O is changed by inputting this output to the terminal of voltage V ₁ . The relationship of the output voltage variation Vch with respect to the voltage V ₁ is expressed by the equation (1). Vch = (R1 / R2) × V ₁ (Equation 1) Therefore, the initial setting voltage VST = 5.0V, R1 = 1.
When 2KΩ, R2 = 400Ω, and V ₁ = 50 mV, the original output voltage V _O is expressed by the equation (2). V _O = VST + (R1 / R2) × V ₁ = 5.15V ··· Equation (2) Due to this relationship, V _O becomes a constant law for the set data, and if a microcomputer is used to perform calculations based on this, any You can control the voltage. In addition, if the voltage value in the state in which the control by V ₁ is not performed is stored in the microcomputer system, the set data value can be directly used as the output voltage by correcting the voltage value on the microcomputer side. FIG. 2 is a diagram showing an overvoltage protection circuit. In the figure, R10 and R1
Reference numeral 1 is a voltage dividing resistor, CMP is a comparator, and PHC is a photocoupler. If the power supply circuit becomes defective, the regulator output may reach a voltage higher than the supply side allowance. In such a case, the output voltage V _O is divided by R10 and R11 and compared with the reference power supply E, and this output is compared with the photo coupler P.
By converting the level with HC and inputting it to CH1, the voltage V ₂ is forced to the output off level. The overvoltage detection level is arbitrarily set by the voltage dividing circuit of R10 and R11.

[0007]

According to the present invention, it is possible to easily cope with changes in specifications of load current, wiring length and supply voltage by inputting data. Further, even when high precision is required, the voltage fine adjustment can be easily performed with a digital value, so that there is no individual difference in the adjustment, and the user can set it. By applying the microcomputer system and storing the data set value in the state of outputting the reference voltage value, the set value can be output accurately. When the power supply adjustment circuit becomes defective, the regulator output is turned off as soon as the overvoltage level is reached.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an overvoltage protection circuit.

FIG. 3 is a circuit diagram of the prior art.

[Explanation of symbols]

 C1 input capacitor C2 output capacitor G1 regulator R R1, 2 output voltage setting resistor CH1 output ON / OFF control terminal R3 current limiting resistor OP data input device P DATA-PWM conversion circuit M microcomputer F smoothing circuit

Claims (2)

[Claims] 1. A power supply circuit having a variable output regulator, which is connected between output terminals of the variable output regulator and outputs an output voltage V _O from one end thereof.
And a second resistor having one end connected to the other end of the first resistor, the data input device, a microcomputer for reading input data from the data input device, and an output from the microcomputer. And a DATA-PWM conversion circuit for converting the
The output of the −PWM conversion circuit is smoothed, and the output is
A power supply circuit comprising a smoothing circuit for inputting to the other end of the resistor. 2. The voltage according to the output of a comparator that compares the output voltage V _O with a reference voltage E is input to the connection point of the first and second resistors. The power supply circuit described.