JPH02246776A - Power supply - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a power supply device that supplies direct current to an electronic device, and in particular, even when different alternating current voltages are input, the same voltage can be output without changing a switch or the like. The present invention relates to a power supply device suitable for supplying an output current of.

[Conventional technology]

As a conventional power supply for electronic devices, Utility Model Application No. 61-147
The one disclosed in Japanese Patent No. 412 is known.

The invention disclosed in the above publication relates to 100V/200V tap switching of a commercial frequency power transformer in a circuit that uses both a switching power source and a commercial frequency power transformer, and relates to switching of the main circuit of the switching power source. The invention is characterized in that the input tap of the commercial frequency power transformer is switched using a changeover switch of the main circuit of the switching power source.

Generally, the switching current requires an auxiliary current for driving a switching element such as the above-mentioned commercial frequency power transformer.

[Problem to be solved by the invention]

According to the above-mentioned conventional technology, there are problems in that tap switching of 100V/200ν cannot be realized and contact parts such as relays are required.

On the other hand, using an AC thyristor in the switching style,
There is a technology that detects the input terminal and controls the on/off of this AC thyristor to accommodate different input voltages. The above-mentioned conventional technology has the problem that a switching relay or the like must be separately prepared for the auxiliary power transformer, which increases the number of parts.

Furthermore, it is necessary to prepare primary windings corresponding to two types of input voltages, such as 100V and 200V, which poses a problem in that the device becomes larger.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply device that can be configured to switch without any operation depending on the input voltage when there are two types of input voltages, and that can be configured with a small number of parts.

[Means to solve the problem]

The power supply device of the present invention converts an AC voltage into a DC voltage using a rectifier circuit and a smoothing circuit, further converts it into a high-frequency AC voltage using a transistor, and boosts or boosts this high-frequency AC voltage via a switch-in transformer. A switching end part that steps down the voltage and further rectifies and smoothes the output of the switch-in transformer to obtain a DC output voltage, and a DC voltage that rectifies and smoothes the above-mentioned AC voltage through an auxiliary power transformer rectifier circuit, resulting in a DC voltage. is input into the control circuit,
and an auxiliary power supply section that detects the output voltage of the switching end section using a control circuit and controls the high frequency alternating current based on the detection result to obtain a desired direct current voltage. The present invention is characterized in that a positive characteristic thermistor is provided in series on the input side of an auxiliary power transformer constituting the auxiliary power supply section, and the output voltage of the switching end section is input to the control circuit.

[Effect]

According to the present invention, when the AC input voltage is 100V, the current flowing through the PTC thermistor is small and its resistance value does not increase, so that substantially the same voltage as the input voltage is applied to the auxiliary power transformer. However, the AC input voltage is 200v
In this case, an overvoltage is applied to the auxiliary power transformer, and the excitation current increases rapidly due to magnetic saturation of the auxiliary power transformer. Due to this rapid increase in excitation current, the voltage applied to the positive temperature coefficient thermistor increases, so that the operating characteristics of the positive temperature coefficient thermistor enter the constant power characteristic range. Therefore, the voltage applied to the auxiliary power transformer decreases, and the voltage supplied to the load, ie, the control circuit, decreases.

At this time, the transistor at the switching end has already started operating and is outputting a DC output voltage, so
The action of the rectifier allows the control circuit to maintain operation even when the auxiliary power transformer output drops.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to embodiments shown in the accompanying drawings.

FIG. 1 is a circuit diagram showing one embodiment of the present invention, in which two parts are included: a switching end section mainly consisting of a switching transformer 6, and an auxiliary power supply section mainly consisting of an auxiliary power transformer 11.
It consists of two parts.

In FIG. 1, the switching end has the following configuration. The output voltage of the AC input source 1 is either 1 oov or 200 V, and is input to the rectifier circuit 3 via the input switch 2 . Further, a rectifying and smoothing circuit is constituted by a rectifying circuit and smoothing capacitors 5a and 5b. When the AC thyristor 4 is inputted with 100V, it becomes conductive and performs voltage doubler rectification on the rectifying and smoothing circuit.
00￥ It is configured to be released and perform bridge rectification during manual power. Therefore, the DC voltage across the smoothing capacitor 5 is the same both when 100V is input manually and when 200V is input. The configuration of the rectifier circuit 3, AC thyristor 4, and smoothing capacitors 5a and 5b described above is well known, and the AC thyristor 4 can be replaced with wiring or a switch for manual switching or automatic switching by detecting input AC voltage. Is possible. The smoothing capacitor 5a is directly connected to the primary winding of the switched transformer 6,
Smoothing capacitor 5b is connected to the primary winding of switched transformer 6 via transistor 6. A diode 7, a capacitor 8, etc. are connected to the secondary winding of the switched transformer 6, and a direct current is output to a load (not shown). The transistor 6 is for controlling the output voltage of the switching source, and is turned on/off at a high frequency of 20 Hz or higher by a signal from the control circuit 14, and further changes the pulse width to stabilize the output voltage. be adjusted.

Further, the auxiliary power supply section has the following configuration. That is, as an auxiliary power supply section for operating the control circuit 14, a circuit whose main body is the auxiliary power transformer 11 is provided. A positive temperature coefficient thermistor 10 is connected in series between the auxiliary power transformer ti and the AC input source 1.

Furthermore, a rectifier 12 is connected to the output section of the auxiliary power transformer 11.
A, 12b and a rectifying and smoothing circuit consisting of a capacitor 13 are connected, and a DC voltage is supplied to a control circuit 14.

Next, the operation of the embodiment shown in FIG. 1 will be explained. In FIG. 1, when the input switch 2 is turned on, an alternating current voltage is applied to the switching end and the auxiliary power supply. In the auxiliary power supply section, a DC voltage is supplied to the control circuit 14 via the auxiliary power transformer 11, and the control circuit 14 operates. As a result, an on/off signal is input from the control circuit 14 to the transistor 6. Therefore, the switching end starts operating.

Here, if AC input R1 is outputting 100 yen,
The current flowing through the PTC thermistor 10 is small, and the resistance value of the PTC thermistor 10 does not increase. Therefore, in this case, a voltage approximately equal to the input voltage is applied to the auxiliary power transformer 11.

However, when the input voltage suddenly increases or when the input voltage is connected to a 20OV power line, the AC thyristor 4 turns off and at the same time, the excitation current increases rapidly due to magnetic core saturation of the auxiliary power transformer IIO. This sudden increase in excitation saturation causes a temperature rise due to loss in the positive temperature coefficient thermistor 10,
The resistance value of the positive temperature coefficient thermistor 10 is rapidly increased. As a result, the operating state of the positive temperature coefficient thermistor O enters its constant power characteristic region, the voltage applied to the auxiliary power transformer 11 decreases, and the voltage of the control circuit 14 decreases.

At this time, the switching transistor 6 has already started operating, and a DC voltage is being output from both ends of the capacitor 8. Therefore, even if the output of the auxiliary power transformer 11 decreases, the control circuit 14
It can continue its operation by receiving the voltage across it.

As is clear from the above description, according to this embodiment,
Even when two types of AC input voltages exist, safe operation is possible without manually switching the auxiliary power supply circuit.

FIG. 2 is a circuit diagram showing a second embodiment of the invention, showing only the parts that are different from the first embodiment shown in FIG. In FIG. 2, the AC thyristor 4, the positive temperature coefficient thermistor 10, and the auxiliary power transformer 11 are connected in the same way as in FIG. In addition to this, bidirectional Zener diodes 16a, 16b, AC thyristor 15, resistor L7a,
17b and a capacitor 18 are connected as shown. With this connection, when the input AC voltage applied to the PTC thermistor IO increases, the excitation current to the auxiliary power transformer 11 increases, and the AC thyristor 1 increases.
5 is conductive.

The AC thyristor 15 short-circuits the gate of the AC thyristor 4, so that the AC thyristor 4 is no longer conductive and is in an OFF state. That is, the rectifier circuit 3 of the switching power supply shown in FIG. 1 becomes a bridge rectifier circuit, and is connected for high voltage (200V).

According to the second embodiment described above, the conduction/non-conduction of the AC thyristor constituting the rectifying and smoothing circuit is controlled by the AC input source 1.
It becomes possible to automatically switch according to the input terminal of

In addition, the characteristic thermistor IO becomes high temperature when 200 Hz is input, and also becomes overheated when a short circuit occurs in the load section of the auxiliary power transformer 11. Therefore, this temperature can be controlled using a thermochromic element. If it is attached to a position where it can be seen from the outside of a power supply device or an electronic device using this power supply device, it can also be used as an indicator to display the status of the device. FIG. 3 shows a concrete example of its configuration.

As shown in FIG. 3, a positive temperature coefficient thermistor lO and a thermochromic element 19 are bonded and combined with an adhesive 20, so that the color changes between normal temperature and high temperature.

[Effects of the Invention] As is clear from the above description, according to the present invention, when there are two types of AC input voltages, a power supply that can be shared by both input voltages and does not require manual operation can be created with a small number of parts and a simple configuration. This has the advantage that a highly functional power source can be formed in a compact size and can be provided at low cost.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of this invention, FIG. 2 is a circuit diagram showing a second embodiment of this invention, and FIG. 3 is a circuit diagram showing a first embodiment of this invention.
FIG. 3 is an explanatory diagram showing an example of a positive temperature coefficient thermistor used in the second embodiment. l...AC input source, 2...human power switch, 3...
Rectifier circuit, 4.15...AC thyristor, 5a, 5
b... Smoothing capacitor, 6... Transistor, lO
...Positive characteristic thermistor, 11... [auxiliary source) lance, 14... Control circuit, 16a, 16b
... Bidirectional Zener diode, 19... Thermochromic element, 20... Adhesive. Agent Patent Attorney Tadashi Akimoto Actual Examination Figure 2 Figure 1

Claims (1)

[Claims] 1. After converting the AC voltage to a DC voltage using a rectifier circuit and a smoothing circuit, further converting it to a high frequency AC voltage, and boosting or stepping down this high frequency AC voltage via a switching transformer, and further A switching power supply section that rectifies and smoothes the switching transformer output to obtain a DC output voltage, and a switching power supply section that rectifies and smoothes the above AC voltage via an auxiliary power transformer and a rectifier circuit, and inputs the resulting DC voltage to a control circuit. , an auxiliary power supply unit that detects the output voltage of the switching power supply unit by a control circuit, controls the high-frequency AC based on the detection result, and obtains a desired DC voltage, the auxiliary power supply unit comprising: A power supply device characterized in that a positive temperature coefficient thermistor is provided in series on the input side of an auxiliary power transformer constituting a power supply section, and the output voltage of the switching power supply section is input to the control circuit. 2. The rectifier circuit provided on the input side of the switching transformer is switched to a voltage doubler rectifier circuit when the voltage applied across the PTC thermistor is high, so that the voltage applied across the PTC thermistor increases. 2. The power supply device according to claim 1, wherein the power supply device switches to a bridge rectifier circuit when the voltage is low. 3. The power supply device according to claim 1 or 2, wherein the positive temperature coefficient thermistor is provided with a thermochromic material.