JPS5938550B2 - power sensor - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a power
The present invention relates to a sensor, and more specifically to a power sensor that monitors the operating state of an electrical device through which a certain amount of weak current may flow even when not in use.

In recent years, with the development of electronic technology, electrical equipment has been introduced in a wide range of fields, and there is a need for a sensor that can easily determine the power supply status of these electrical equipment.

An example of this can be seen in pay television receivers. In particular, if the electrical equipment in question is of a type that generates a certain amount of weak current even when not in use (for example, a pre-heated television receiver), the electrical equipment will be in an unused state when the weak current is present. Furthermore, it is desirable to install such a sensor without modifying the existing electrical equipment, and therefore the sensor will be located outside the electrical equipment.
It is desirable that the device be small and consume little power. In order to be able to use the output of this sensor in a remote location, it is necessary to provide an output that is isolated from the power supply system to the electrical device.

The present invention has been made to meet such demands, and specifically provides a power sensor that has a small number of parts and is not bulky even when incorporated into an AC power supply line.

The invention will now be described in detail with reference to the drawings, which illustrate preferred embodiments.

Although the description will be made using a television receiver as an example, it goes without saying that the present invention can also be applied to other electrical equipment. 40 is a television receiver; 41
is a power sensor according to the present invention.

190 is a rectifier diode, 191 and 192 are voltage dividing resistors connected in series and led to connection points A and B, and a capacitor 193 is connected in parallel to the resistor 192.
It also constitutes a DC power supply.

A relay coil 195 is connected in parallel with a capacitor 194 and connected to both ends of the capacitor 193 via the collector and emitter of a transistor 196.

A resistor 1 is connected between the base and emitter of the transistor 196.
97, diodes 198, 199 and diode 200
A parallel circuit with is connected via a resistor 201. Power to the television receiver 40 is led from the connection point A mentioned above and the connection point C in the figure. Diode 190, resistor 191
, 192 and a capacitor 194 supplies a sufficiently smoothed DC voltage to the circuit. When the power switch of the television receiver 40 is closed, a half cycle of alternating current flows through the diodes 198 and 199, causing a forward voltage drop. In the next half cycle, alternating current flows through the diode 200 and a forward voltage drop occurs, but these forward voltages have little effect on the alternating current line, such as ripples. The forward voltage developed across diodes 198, 199 during a half cycle that flows through diodes 198, 199 causes transistor 196 to conduct, thereby causing current to flow in relay coil 195, activating the relay. On the other hand, during the half cycle in which current flows through the diode 200, a reverse bias is applied to the transistor 196, so that the charge stored in the capacitor 194 starts discharging through the relay coil 195, and as a result, the relay maintains its operating state. become.

Thus, as long as the power switch of television receiver 40 is closed, the relay remains operative. By the way, even if the power switch of the television receiver 40 is opened, since the preheater current is flowing through the television receiver 40, the diode 19 of the power sensor 41
A small amount of current may also flow through the transistors 8 and 199, causing the transistor 196 to operate. To prevent this malfunction of the transistor 196, a resistor 1 is connected to the diodes 198 and 199.
97 are connected in parallel. When the preheater current is flowing, that is, when a small current is flowing through the diodes 198 and 199, the equivalent resistance Rs of the diodes 198 and 199 has a large resistance value.

Therefore, if the resistance value of the resistor 197 is set to a value smaller than the equivalent resistance R8, the bias of the transistor 196 will be the voltage across the resistor 197, so the transistor 19
6 is not conductive. Conversely, when the power switch of the television receiver 40 is turned on, the diodes 198,1
The current flowing through diode 19 is a large current, so
The equivalent resistance RL of 8,199 is smaller than the resistance 197.

Therefore, the bias of the transistor becomes the voltage across the equivalent resistance RL, so that the transistor 196 becomes conductive. In other words, if you choose a resistor R4 that satisfies the relationship Rs>R4>RL, it will operate as a power sensor 41 during large currents.
At low currents, word operation of transistor 196 is prevented.

For example, to not operate the power sensor 41 below 20 watts, if the forward voltage of one diode is VD - 0.7 volts and the AC power supply voltage E is 100 volts, then the current flowing through the diode is 1D. Hato becomes.

Therefore, the equivalent resistance of one diode RSl is as follows.Since the diodes 198 and 199 are connected in series, the overall equivalent resistance is the equivalent resistance of one diode Rs,
, that is, Rs=2Rs1, so the resistance 197 only needs to be about 7 ohms.

In reality, it is set to a value even smaller than 7 ohms, taking into account the phase of the current and the current angle of the diode. As explained above, this power sensor 41 has a simple circuit configuration and can detect whether the television receiver 40 is powered on or not without any modification, and even if the preheater current is flowing. No malfunctions. Further, the power supply line and the power sensor output can be electrically isolated. Further, the power sensor according to the present invention can be applied to a DC circuit as is. That is, since it can also be used in a circuit driven by a DC power source, it can be said to be used for both AC and DC purposes. However, in the case of direct current, care should be taken regarding the polarity of the connection, and the diode 200 can be omitted.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a configuration circuit of a power sensor according to the present invention. 40...Television receiver 41...
・Power sensor, 195...Relay coil.

Claims (1)

[Claims] 1. A power sensor that is connected in parallel with the AC power supply line to the electrical equipment, and that applies a rectified voltage generated from the AC to a series circuit consisting of a parallel circuit of a relay coil and a capacitor, and a switching member. , a parallel circuit consisting of a fixed resistance element on one of the AC feeder lines, a variable resistance rectifier element whose resistance value is large when the current is small and whose resistance value decreases as the current increases, and a rectifier element in the opposite direction to the variable resistance rectifier element. A power sensor characterized in that a circuit is connected, a voltage in the parallel circuit is applied to a switching control input of the switching member, and a signal indicating an operating state of an electrical device is output by actuation of a relay coil.