JPH05168153A - Dc voltage converter - Google Patents

Abstract

PURPOSE:To protect a voltage converting means against thermal breakdown due to input of improper high voltage and to prevent a load from being fed with an unstably regulated voltage due to input of improper low voltage. CONSTITUTION:The DC voltage converter comprises means for converting a supply voltage into a desired voltage, i.e., a four terminal regulator element 1, a voltage detector 6 for detecting a supply voltage higher than a predetermined level, and a voltage detector 7 for detecting a supply voltage lower than a predetermined level. When the voltage detectors 6, 7 detect supply voltage higher than a predetermined level or lower than a predetermined level, operation of the four terminal element 1 is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC voltage converter having a protection function of converting an arbitrary voltage lower than a supply voltage.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a configuration of a conventional DC voltage converter, in which 21 is a three-terminal regulator element as voltage converting means, 22 is an input terminal of a supply voltage, and 23 is a DC-converted voltage. The output terminal 24 taken out is a common ground terminal. In the figure, a voltage of 9V is applied to the input terminal 22 to output a voltage of 5V from the output terminal 23.

[0003]

However, the conventional DC voltage converter as shown in FIG. 2 needs to be used with sufficient caution, for example, the user mistakenly fails to meet the standard, for example, as shown in FIG. When an AC adapter that outputs a high voltage other than 9 V is connected to the input terminal 22 to supply a voltage, the three-terminal regulator element 21 generates a large amount of heat and is destroyed due to heat.

Similarly, if the user mistakenly connects an AC adapter that outputs a low voltage other than the predetermined voltage of 9 V to the input terminal 22 in FIG. 2, the three-terminal regulator element 21 has an unstable regulation due to insufficient supply voltage. When the ratio operation is performed and the output voltage is supplied to the CPU, for example, the CP
U will have problems such as a runaway and an unexpected accident.

An object of the present invention is to provide a DC voltage converter which eliminates the above-mentioned thermal breakdown and unstable operation of the regulator element and operates stably without causing thermal breakdown.

[0006]

According to the present invention, there is provided a voltage converting means for converting a supply voltage into a desired voltage, a first voltage detector for detecting that the supply voltage is a predetermined value or more, and the supply voltage. A second voltage detector for detecting that the voltage is a fixed value or less, wherein each of the voltage detectors, when detecting that the supply voltage is a fixed value or more, or a fixed value or less, It is characterized in that the conversion operation of the voltage conversion means is stopped.

[0007]

According to the present invention, the voltage converting means does not operate even when a voltage other than the predetermined voltage is supplied, so that the regulator element as the voltage converting means is thermally destroyed or the load is
In this case, a runaway accident is prevented.

[0008]

The present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of a DC voltage converter according to an embodiment of the present invention, in which 1 is a 4-terminal regulator element as voltage converting means, 2 is an input terminal for its supply voltage, and 3 is an output. Terminals 4, 4 are ground terminals, and 5 are control voltage input terminals. The 4-terminal regulator element 1 operates as a regulator when the control voltage input terminal 5 is at a high level.

Numerals 6 and 7 are first and second voltage detectors, respectively, which are composed of an IC whose main structure is an output transistor having an open collector output structure for power-on reset. The output transistor constituting 6 is turned on when the supply voltage is 4.2 V or more as an example, and the voltage detector 7 turns on the output transistor when the supply voltage is 4.2 V or less and detects the voltage. In addition, such a voltage detector is generally commercially available.

In the voltage detector 6 and the voltage detector 7, the voltage of the input terminal 2 supplied to the 4-terminal regulator element 1 is
The resistors R ₁ , R ₂ and R ₃ , R ₄ are respectively divided and supplied, and when the supply voltage of the 4-terminal regulator element 1 is 12 V as an example, the supply voltage to the voltage detector 6 is When the supply voltage of 4.2V or the 4-terminal regulator element 1 is 6V as an example, each of the resistors R ₁ to R is adjusted so that the supply voltage to the voltage detector 7 becomes 4.2V.
₄ are selected.

Output terminals of the voltage detector 6 and the voltage detector 7, and a control voltage input terminal 5 of the four-terminal regulator element 1.
Are connected in common and the voltage is pulled up as a supply voltage to the input terminal 2 of the 4-terminal regulator element 1 via the resistor R ₅ .

The control voltage input terminal 5 of the four-terminal regulator element 1 becomes high level when the supply voltage input to the four-terminal regulator element 1 is 6V to 12V as described above, and when other voltage is applied. Becomes a low level because the output transistor included in the voltage detector 6 or 7 is turned on. Therefore, in that case, 4-terminal regulator element 1 does not perform the regulation operation.

That is, in the DC voltage converter of FIG. 1, the control voltage input terminal 5 of the four-terminal regulator element 1 becomes high level to perform the regulation operation only when the supply voltage is 6V to 12V. If a voltage that is higher or lower than the applied voltage is supplied, the input of the supply voltage is blocked, the 4-terminal regulator element 1 that constitutes the voltage conversion means is protected, or the regulation operation does not start, so heat is generated. Alternatively, when the load is the CPU, runaway of the CPU can be prevented.

[0015]

As described above, the direct-current voltage converter of the present invention is constructed so as not to accept the supply voltage at all when the output voltage of the supply voltage device is improper. The four-terminal regulator element that constitutes the conversion means has an advantage that it is prevented from thermal destruction or that the CPU does not run away when a CPU or the like is connected to the load. In particular, when it is used in a power supply unit of an electronic device that is driven by a constant voltage, a very large effect can be obtained with a simple configuration.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration of a conventional DC power supply converter.

[Explanation of symbols]

1 ... 4 terminal regulator device, 5 ... control voltage input terminal, 6, 7 ... voltage detector, R ₁ to R ₅ ... resistor.

Claims (1)

[Claims] 1. A voltage converting means for converting a supply voltage into a desired voltage, a first voltage detector for detecting that the supply voltage is a predetermined value or more, and the supply voltage being a predetermined value or less. And a second voltage detector for detecting the above, and when each of the voltage detectors detects that the supply voltage is equal to or higher than a certain value or equal to or less than a certain value, the conversion operation of the voltage converting means is stopped. A DC voltage converter characterized in that.