JP3613982B2 - Power supply input circuit for timer IC - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power input circuit in various control devices such as a timer device. More specifically, the present invention relates to a power supply that converts and supplies AC high voltage from a commercial AC power source to various circuits in the device. It relates to the input circuit.
[0002]
[Prior art]
In a control device such as a timer device, the internal timer IC is driven with a DC low voltage of about 5V. In the timer device, a circuit for inputting power for driving only the timer IC is a small-capacity power input circuit. A power supply input circuit when this timer device is used in an area of AC power supply 100 to 240 V as in Europe will be described with reference to FIG. This power supply input circuit includes a half-wave rectifier circuit 2 composed of a rectifier diode D1 that half-wave rectifies an AC power supply 1 output via an input terminal IN, and a smoothing capacitor C1 that smoothes the half-wave rectifier circuit 2 output. The smoothing circuit 3, and the control circuit TR1, the resistor R1, and the Zener diode for controlling the output of the smoothing circuit 3 to be converted into a DC low voltage and supplying the output to the timer IC 5 as a load via the output terminal OUT. And a voltage control circuit 4 constituted by D2.
[0003]
In the voltage control circuit 4, a resistor R1 is connected in parallel to the collector base of the control transistor TR1, and a Zener diode D2 as a conductive element that conducts with a voltage input of 5, 6 V or more is connected to the base of the control transistor TR1.
[0004]
The output voltage of 100 to 240 V from the AC power source 1 is half-wave rectified by the half-wave rectifier circuit 2, smoothed by the smoothing circuit 3, and then input to the voltage control circuit 4. In the voltage control circuit 4, when the Zener diode D2 is turned on, the voltage of the emitter of the control transistor 4 is always set to 5V and supplied to the timer IC5.
[0005]
[Problems to be solved by the invention]
In the power input circuit having such a configuration, since the voltage drop between the collector and the emitter of the control transistor TR1 is very large, heat generation in the control transistor TR1 is very large. Therefore, a large transistor is required to withstand the heat generation. Become. In addition, this inevitably requires a large and heavy heat sink for dissipating the heat generated by the control transistor TR1.
[0006]
In this case, since the smoothing output is always given from the smoothing circuit 3 in the control transistor TR1, the heat generation is always continued, and the heat generation amount is also great, and the control transistor TR1 also heats. Both result in a larger size being required.
[0007]
The smoothing capacitor C1 in the smoothing circuit 3 is also provided with a high-voltage half-wave rectified output, so that a high-voltage and high-cost capacitor is required, and the life of the high-voltage half-wave rectified output is smoothed to smooth the high-voltage half-wave rectified output. Will also have an effect.
[0008]
[Means for Solving the Problems]
In the present invention, a half-wave rectifier circuit for half-wave rectifying an AC power supply output of 100 to 240 V, a voltage control circuit for inputting the half-wave rectifier circuit output, a smoothing circuit for smoothing the voltage control circuit output, A constant voltage circuit that converts the smoothing circuit output to a constant voltage, and the voltage control circuit includes a control transistor having a collector emitter connected between the output side of the half-wave rectifier circuit and the input side of the smoothing circuit; A resistor connected between the collector and base of the control transistor, and a first Zener diode having a Zener voltage connected to the base of the transistor set to about 100 V, the control transistor comprising: When the first Zener diode is non-conductive, the saturation operation is performed. When the first Zener diode is conductive, the normal operation is performed. The path charges at least two first and second voltage dividing resistors that divide approximately 100V output of the voltage control circuit, and the voltage divided output is charged through one resistor, while discharge is limited by the other resistor. And a capacitor that outputs a voltage to the constant voltage circuit via the other resistor, and the constant voltage circuit includes a second Zener diode set to a Zener voltage of about 5V. This solves the above-mentioned problems.
[0009]
In the above claims, the definition of “output” in each of the AC power supply output, the half-wave rectifier circuit output, the voltage control circuit output, and the smoothing circuit output is defined as the voltage from the AC power supply to the half-wave rectifier circuit and from the half-wave rectifier circuit. Not only the direct output given to the control circuit from the voltage control circuit to the smoothing circuit, but also from the smoothing circuit to the constant voltage circuit, as well as indirect output given to each other through the intervention of some other circuit, element, etc. Are also construed as broad concepts contained in the claims.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
A power input circuit according to the present embodiment will be described with reference to FIG. 1, and portions corresponding to those in FIG. The power input circuit includes a half-wave rectifier circuit 2 that half-wave rectifies the output of the AC power supply 1 (100 to 240 V), a voltage control circuit 4 that inputs the output of the half-wave rectifier circuit 2, and outputs the voltage control circuit 4 A smoothing circuit 3 for smoothing and a constant voltage circuit 6 for converting the output of the smoothing circuit 3 to a constant voltage are provided. The constant voltage circuit 6 is also referred to as a voltage conversion circuit in order to convert it into a DC low voltage.
[0012]
Thus, in the present embodiment, the voltage control circuit 4 is connected to the output side of the half-wave rectifier circuit 2 instead of the output side of the smoothing circuit 3 as in the prior art, and the output of the voltage control circuit 4 is connected to the smoothing circuit 3. It has one feature in that it is made smooth.
[0013]
The voltage control circuit 4 in the present embodiment includes a control transistor TR1 having a collector-emitter connected between the output part of the half-wave rectifier circuit 2 and the input part of the smoothing circuit 3, and the collector and base of the control transistor TR1. 7 and a Zener diode D2 as a conducting element connected to the base of the control transistor TR1, the components and their connection relations are the same as those shown in FIG. Similarly, the collector emitter of the control transistor TR1 is connected between the output part of the half-wave rectifier circuit 2 and the input part of the smoothing circuit 3, and the Zener voltage of the Zener diode D2 as the conducting element is the conventional one. Another feature is that it is set to 100V instead of 5.6V.
[0014]
Further, the smoothing circuit 3 is not simply composed of a smoothing capacitor as in the prior art, but at least the first and the second connected in series between the output part of the voltage control circuit 4 and the input part of the constant voltage circuit 6. The second resistor R2, R3 and the smoothing capacitor C1 connected to the connecting portion between the resistors R2, R3 are configured. The constant voltage circuit 6 includes a Zener diode D3 having a Zener voltage of 5V. The smoothing capacitor C1 is an electrolytic capacitor.
[0015]
In the above configuration, when a 100V AC power source 1 is input to the input terminal IN as shown in FIG. 2A, the half-wave rectified output by the half-wave rectifier circuit 2 is as shown in FIG. 2B. Since the Zener diode D2 does not conduct at this half-wave rectified output, the control transistor TR1 operates in saturation with the half-wave rectified output applied to the base via the resistor R1, and as a result, the emitter thereof is shown in FIG. 2C. Output appears. In this case, since the voltage drop between the collector and the emitter of the control transistor TR1 is about 0.1 V, almost no heat is generated. The emitter output of the control transistor TR1 has a half-wave rectified output waveform, and the smoothing circuit 3 smoothes the half-wave rectified output waveform as shown in FIG. 2D and outputs it to the constant voltage circuit 6. As shown in FIG. 2E, the constant voltage circuit 6 converts the smoothed output to a constant voltage of 5 V and supplies it to the timer IC 5 as a load via the output terminal OUT.
[0016]
In this case, when the heat generation in the control transistor TR1 in the power supply input circuit of the present embodiment shown in FIG. 1 is compared with that of the conventional power supply input circuit shown in FIG. 7, the collector of the control transistor TR1 in the present embodiment is compared. The voltage drop between the emitters is about 0.1V, whereas it is 94V or more in the conventional one. Therefore, in the case of the present embodiment, the heat generation of the control transistor TR1 is reduced as compared with the conventional case.
[0017]
Next, when the voltage of the AC power supply 1 exceeds 100V as shown in FIG. 3A, for example, 240V is inputted to the input terminal IN, the half-wave rectified output by the half-wave rectifier circuit 2 is as shown in FIG. 3B. In this half-wave rectified output, the Zener diode D2 becomes conductive, so that the control transistor TR1 operates normally and an output as shown in FIG. 3C appears at the emitter. The smoothing circuit 3 smoothes the emitter output of the control transistor TR1 as shown in FIG. As shown in FIG. 3E, the constant voltage circuit 6 supplies a constant voltage of 5 V to the timer IC 5 that is a load.
[0018]
In this case, the heat generation in the control transistor TR1 in the power input circuit of the present embodiment shown in FIG. 1 is compared with that in the conventional power input circuit shown in FIG. Conventionally, the voltage drop between the collector and the emitter of the control transistor TR1 when the voltage of the AC power supply 1 is 240V is 235V or more, but in the present embodiment, it is about 100V lower than that due to the action of the Zener voltage of the Zener diode D1. It has become. Therefore, in the case of this embodiment, the heat generation of the control transistor TR1 is greatly reduced as compared with the conventional case.
[0019]
As described above, in the present embodiment, the voltage drop between the collector and the emitter of the control transistor TR1 becomes smaller than that of the conventional one, and the heat generation is reduced. As a result, the control transistor TR1 and the heat sink can be small.
[0020]
In this case, in the power input circuit of the present embodiment, the voltage control circuit 4 is supplied with a half-wave rectified output, and therefore the timing at which the control transistor TR1 generates heat is the half-wave rectified. It is only the period when output is given. When this is compared with the conventional power input circuit, since the smoothing circuit output is always supplied from the smoothing circuit 3 to the power input circuit 4 in the prior art, the control transistor TR1 always generates heat.
[0021]
Therefore, in the present embodiment, the period of heat generation during power supply application is about half that of the prior art, and from this point of view, heat generation is greatly suppressed, and the control transistor TR1 and the heat sink can be mounted with a smaller size. Yes.
[0022]
The output of the voltage control circuit 4 is smoothed by the smoothing circuit 3. In this case, since the smoothing circuit 3 has the above-described configuration, first, the output of the voltage control circuit 4 is output from both resistors R2, R3. The pressure is divided by. The smoothing capacitor C1 is charged through the first resistor R2 with the divided voltage. Since the divided voltage in this case is higher than the Zener voltage of the Zener diode D3 of the constant voltage circuit 6, the smoothing capacitor C1 is charged with a voltage higher than the Zener voltage. Further, the discharge of the smoothing capacitor C1 is limited by the second resistor R2. Therefore, the smoothing capacitor C1 is charged with the next output from the voltage control circuit 4 until all of the smoothing capacitor C1 is discharged, so that the constant voltage circuit 6 is smoothly operated. A constant voltage of 5V can be supplied to the timer IC 5 which is a load.
[0023]
In the present embodiment, the output voltage from the voltage control circuit 4 to the smoothing capacitor C1 of the smoothing circuit 3 is controlled to a low voltage of 100V or less. Compared to the conventional case, the smoothing capacitor C1 conventionally needs to smooth a high voltage exceeding 100V, so that it is necessary to mount a high withstand voltage capacitor. However, in this embodiment, a low voltage of about 100V is required. Therefore, it is possible to mount and use a capacitor having a lower withstand voltage than the conventional one.
[0024]
The configuration of the smoothing circuit 3 in FIG. 1 may be the configuration shown in FIG.
[0025]
Although the control transistor TR1 of the voltage control circuit 4 in FIG. 1 is an NPN type, it may be a PNP type as shown in FIG.
[0026]
The configuration of the smoothing circuit 3 in FIG. 5 may be the configuration shown in FIG.
[0027]
In the above-described embodiment, the Zener diode D2 is shown as the conductive element. However, any element that performs an equivalent function is included in the present invention.
[0028]
In the above-described embodiment, the half-wave rectifier circuit 2 output is input to the voltage control circuit 4, but the full-wave rectifier circuit output is input to the voltage control circuit 4 instead of the half-wave rectifier circuit 2. It doesn't matter.
[0029]
【The invention's effect】
As described above, according to the present invention, since the voltage drop between the collector and the emitter of the control transistor is smaller than the conventional one, the heat generation in the control transistor can be reduced, and as a result, a small control transistor and a heat sink can be mounted. Is possible. It should be noted that the fact that the control transistor and the heat sink are small in size is a favorable result in reducing the size and weight of a control device such as a small timer device on which the control transistor and heat sink are mounted.
[0030]
In addition, since the electrolytic capacitor in the smoothing circuit can be smoothed at a low voltage, a small and inexpensive electrolytic capacitor can be mounted.
[Brief description of the drawings]
1 is a circuit diagram of a power input circuit according to an embodiment of the present invention. FIG. 2 is a timing chart used for explaining the operation of FIG. 1. FIG. 3 is a timing chart used for explaining the operation of FIG. FIG. 5 is a circuit diagram of a power input circuit according to still another embodiment of the present invention. FIG. 6 is a circuit diagram of a power input circuit according to still another embodiment of the present invention. Circuit diagram [Fig. 7] Circuit diagram of conventional power input circuit [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 AC power supply 2 Half wave rectifier circuit 3 Smoothing circuit 4 Voltage control circuit 5 Load 6 Constant voltage circuit TR1 Control transistor R1 Resistance D2 Zener diode (conduction element)

Claims (1)

A half-wave rectifier circuit for half-wave rectifying an AC power supply output of 100 to 240 V ;
A voltage control circuit for inputting the output of the half-wave rectifier circuit;
A smoothing circuit for smoothing the voltage control circuit output;
A constant voltage circuit that converts the smoothing circuit output to a constant voltage;
With
The voltage control circuit includes:
A control transistor having a collector-emitter connected between the output side of the half-wave rectifier circuit and the input side of the smoothing circuit;
A resistor connected between a collector and a base of the control transistor, and a first Zener diode whose Zener voltage connected to the base of the transistor is set to about 100V ,
The control transistor operates normally when the first Zener diode is non-conductive , and normally operates when the first Zener diode is conductive .
The smoothing circuit is
At least two first and second voltage dividing resistors that divide the approximately 100V output of the voltage control circuit;
A capacitor that charges the voltage-divided output through one resistor while limiting discharge by the other resistor and outputs a voltage to the constant voltage circuit through the other resistor;
The constant voltage circuit is:
Having a second Zener diode set at a Zener voltage of approximately 5V.
A power supply input circuit for a timer IC.

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