JPH0742200Y2 - Power source detection switching circuit for co-listening amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention automatically connects and connects a power supply line to the corresponding input terminal side of two types of voltage input terminals, high and low, according to the magnitude of the power supply voltage. The present invention relates to a power supply detection switching circuit of a line amplifier for co-listening.

(Prior Art) Conventionally, in co-listening amplifiers such as line amplifiers and branch amplifiers used in CATV systems, a plurality of amplifiers are provided as a group to provide a power supply device, and an amplifier at a place where the power supply device is installed. In addition to the direct power supply from the power supply device, the DC power is superimposed on the coaxial cable and supplied to the other amplifiers.

Here, as the power supply capacity of the power supply device used in the CATV system, it is suppressed to a range not exceeding 90VA legally determined as a small power circuit, for example, using a DC power supply device of 30V, 3A. There is.

On the other hand, in recent years, as a special case of small power circuit, 900V
The power supply capacity up to A has been recognized, and in this 900VA, the power supply device can be used up to 60V, 15A, for example, and the number of amplifiers that can be supplied by one power supply device can be increased.

By the way, use a 90VA power supply, or
Whether 0VA is used depends on the size of the CATV system, and even with the same system, the trunk system is 900VA, but the terminal system branched from the trunk may be 90VA. .

Therefore, in the recent co-listening amplifier, as a constant voltage circuit using a switching regulator or the like which supplies a constant voltage to a DC power source received from a power supply device directly or through a coaxial cable and supplies it to an amplifier circuit, for example, 30 V It is conceivable that the input and 60V input can be switched. In that case, when switching to the factory or at the site, change the selector switch to 30V input or 60V input according to the power specifications of the place.

(Problems to be solved by the invention) However, in the co-listening amplifier equipped with the power input switching function, the switch is artificially switched to 30V input or 6V.
Since 0V input was selected, where it should be set to 60V input, it may be installed with 30V input erroneously.If the switch is changed like this, the 60V input is not selected when the 30V input is selected. Since the constant voltage circuit receives an overvoltage input that exceeds the control capability, the constant voltage circuit such as a switching regulator is destroyed, and at the same time, an abnormal high voltage is applied to the amplifier circuit as a power source, which causes the worst case. In this case, the circuit element may be destroyed, and the expensive co-listening amplifier may be destroyed by turning on the power once.

(Means for Solving Problems) The present invention has been made in view of such conventional problems, and responds to the input power supply voltage without requiring artificial switching selection of the power supply voltage. Therefore, it is an object of the present invention to provide a power supply detection switching circuit for a common-amplification amplifier, in which a power supply line is switch-connected to a corresponding voltage input terminal so as to be surely protected from damage due to an erroneous power input.

In order to achieve this object, the present invention comprises a high voltage input terminal that allows an AC voltage input in a predetermined high voltage range and a low voltage input terminal that allows an AC voltage input in a predetermined low voltage range. A constant voltage circuit for converting an AC voltage input to the high voltage input terminal or the low voltage input terminal into a constant DC voltage and supplying the same to an amplifier circuit; and a direct or coaxial power source device separately installed in the constant voltage circuit. A changeover switch for connecting a power supply line for supplying an AC voltage via a line to either the high voltage input terminal or the low voltage input terminal, and the changeover switch until the power is turned on. If the applied voltage of the power supply line is detected to be in the high voltage range when the power is turned on, the changeover switch is set to the high voltage input terminal side and the power supply line is switched. In which the voltage applied is to the provision of a voltage detection circuit for automatically switching said changeover switch to said low-voltage input terminal side when it is detected that the low-voltage range.

(Operation) According to the power supply detection switching circuit of the co-listening amplifier of the present invention having such a configuration, in the state before the power is turned on, the changeover switch is connected to the high voltage input terminal of the constant voltage circuit. Therefore, even if a power supply voltage of, for example, 60 V or 30 V is supplied when the power is turned on, the overvoltage input that would lead to circuit breakdown does not occur.

Furthermore, when 30V is supplied when the power is turned on, the voltage detection circuit detects this low voltage and switches the changeover switch to the low voltage input terminal, so no artificial changeover operation is required. Therefore, it is possible to completely prevent circuit breakage due to erroneous operation.

(Embodiment) FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

In the figure, 1 is an input terminal and 2 is an output terminal, to which coaxial cables are respectively connected by connectors. The signal line from the input terminal 1 is input to the amplification circuit 3 in the front stage through the DC cut capacitor C1, and after the level is adjusted by the attenuator 4, the amplifier 5 in the rear stage passes the DC cut capacitor C2. It is connected to the output terminal 2. A power line 6 is branched and connected between the input terminal 1 and the capacitor C1 via an inductance L1 for cutting a high frequency signal. This power line 6 has an inductance L2 for cutting a high frequency signal.
It is connected between the capacitor C2 and the output terminal 2 via.

Reference numeral 7 is a constant voltage power supply, which converts the input AC voltage into a constant DC voltage and supplies the DC power to the amplifier circuits 3 and 5. The constant voltage power source 7 is a high voltage input terminal H that allows an AC voltage input in a predetermined high voltage range, for example, a voltage input of 40 to 60V.
And a low voltage input terminal L that allows an AC voltage input of a predetermined low voltage range, for example, 20 to 30V, and always produces a constant voltage output regardless of the voltage input from any of the input terminals.

Reference numeral 8 denotes a changeover switch. The changeover side is connected to the power supply line 6, the changeover contact 8a is connected to the high voltage input terminal H of the switching regulator 7, and the changeover contact 8b is connected to the low voltage input terminal L of the switching regulator 7. Connected.

Reference numeral 9 denotes a voltage detection circuit, which inputs the power supply voltage of the power supply line 6, and the power supply voltage is equal to or lower than a predetermined voltage, for example,
When it becomes 30V or less, the changeover switch 8 is changed over from the changeover contact 8a side to the 8b side. Further, the voltage detection circuit 9 closes the changeover switch 8 to the changeover contact 8a side until the power is turned on, and as a result, the power supply line 6 passes through the changeover contact 8a of the changeover switch 8 in the state before the power is turned on. And is placed in a state of being connected to the high voltage input terminal H of the switching regulator 7.

Next, the operation of the above embodiment will be described.

First, in the state before the power is turned on from the separately installed power supply through the coaxial cable, the changeover switch 8 is closed to the changeover contact 8a side, so that the power supply line 6 of the amplifier is connected to the switching regulator 7a. Is connected to the high voltage input terminal H of.

If the power is turned on in this state and a power supply voltage of 60V is applied to the amplifier via the coaxial cable, 60V is applied to the power supply line 6 from the input terminal 1 via the inductance L1.
Power source voltage is applied, and at the same time, the changeover contact of the changeover switch 8
The power supply voltage of 60V is input to the high voltage input terminal H of the switching regulator 7 via 8a, and the input power supply voltage is in the range of 40 to 60V which is the allowable input voltage range of the high voltage input terminal H. A predetermined constant voltage is supplied to the amplifier circuits 3 and 5 to bring them into an operating state.

On the other hand, the voltage detection circuit 9 inputs the power supply voltage 60V of the power supply line 6, but since the input voltage is higher than the preset 30V, the connection state to the switching contact 8a is maintained without switching the switching switch 8.

Next, assuming that a power supply voltage of 30V is supplied to the power supply line 6 when the power is turned on, since the changeover switch 8 is closed to the changeover contact a side at this time as well, power is supplied to the high voltage input terminal H of the switching regulator 7. A voltage of 30V is input. At this time, the input voltage 30V is out of the allowable input voltage range 40 to 60V of the high voltage input terminal H, but the constant voltage output cannot be obtained because of the low voltage, but the switching regulator 7 is destroyed or the amplifier circuits 3, 5 No abnormal voltage is applied to.

On the other hand, when the power supply voltage of 30V is applied to the power supply line 6, the voltage detection circuit 9 produces a detection output and switches the changeover switch 8 to the changeover contact 8b.
The power supply voltage of 30V is supplied to the low voltage input terminal L of the switching regulator 7 via the changeover contact 8b of the changeover switch 8. Therefore, the switching regulator 7 receives a normal voltage input and outputs a constant DC voltage. It is supplied to the amplifier circuits 3 and 5 to be in an operating state.

It is desirable that the detection operation of the voltage detection circuit 9 has a delay time. That is, even when the power supply voltage of 60V is applied, there is a state where the threshold value is set to 30V or less transiently in the voltage detection circuit 9, so that the changeover switch 8 is mistakenly changed over to the changeover contact 8b side in this state. Therefore, the detection time of the power supply voltage may be delayed so that the detection operation is performed in a stable power supply voltage after the power-on transient state.

Further, in the above embodiment, the switching to the power supply of 30V and 60V is taken as an example, but the present invention is not limited to this, and it is applied as it is to two kinds of high and low appropriate power supply voltages. be able to.

(Effect of the Invention) As described above, according to the present invention, in the state before the power is turned on, the changeover switch is connected to the high voltage input terminal of the constant voltage circuit. 60
Even if the power supply voltage of V or 30V is supplied, it is possible to surely prevent the circuit breakdown due to the overvoltage input.

In addition, when 30V is supplied when the power is turned on, the voltage detection circuit detects this constant voltage and automatically connects the changeover switch to the low voltage input terminal, resulting in an artificial changeover operation. Is completely unnecessary, and it is possible to completely prevent the circuit breakdown caused by an incorrect voltage input due to an erroneous operation.

[Brief description of drawings]

 FIG. 1 is a circuit block diagram showing an embodiment of the present invention. 1: Input terminal 2: Output terminal 3,5: Amplifier circuit 4: Attenuator 6: Power line 7: Constant voltage power supply 8: Changeover switch 8a, 8b: Changeover contact 9: Voltage detection circuit H: High voltage input terminal L: Low Voltage input terminal

Claims (1)

[Scope of utility model registration request] 1. A high voltage input terminal for allowing an AC voltage input in a predetermined high voltage range and a low voltage input terminal for allowing an AC voltage input in a predetermined low voltage range. A constant voltage circuit that converts the AC voltage input to the voltage input terminal into a constant DC voltage and supplies it to the amplifier circuit, and an AC voltage that is directly or via a coaxial line from a power supply unit separately installed in the constant voltage circuit. A changeover switch for connecting the power supply line to either the high voltage input terminal or the low voltage input terminal, and the changeover switch is switched to the high voltage input terminal side of the constant voltage circuit until the power is turned on. At the time of turning on, when it is detected that the applied voltage of the power supply line is in the high voltage range, the changeover switch is placed on the high voltage input terminal side,
A voltage detection circuit for automatically switching the changeover switch to the low voltage input terminal side when it is detected that the applied voltage of the power supply line is in the low voltage range. Power detection switching circuit.