JPS64621Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is designed to arbitrarily set the effective value of the transmission output so that the power consumption of the power supply does not increase when the repetition period becomes faster in color fish finders etc. where the transmission repetition period changes significantly. The present invention relates to a transmitting circuit that can maintain a constant value.

Generally, in a fish finder, the transmission output P=
The characteristic of the effective transmission output W (=1/T×P) when the transmission repetition period T is varied from 10 to 10000 ms at 1 kW is as shown by the characteristic line I shown in FIG. As is clear from FIG. 1, as the transmission repetition period T becomes faster, the effective output W increases. Conventionally, the increase in power consumption due to an increase in the effective output in this type of transmitter circuit has been solved by adding a current limiting resistor R1 to the line that supplies power for the transmitting power amplifier to the transmitting transformer H, as shown in FIG. This resistance R
1. In addition, the second
In the figure, J indicates a transducer. However, in the conventional fish finder transmitter circuit configured as described above, when the transmission repetition period T is made faster,
There was a problem that more heat was generated than the resistor R1.

The present invention was developed in view of the problems of conventional transmitter circuits for fish finders, and its purpose is to use a transistor circuit to transmit the effective output at any time regardless of the transmission repetition period. It is an object of the present invention to provide a transmitting circuit for a fish finder, which maintains a transmission output reduction set value set at , and prevents a current limiting resistor provided in a power supply line of a transmitting transformer from abnormally generating heat.

Next, embodiments of the transmitting circuit for a fish finder according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 3 shows an embodiment of the transmitting circuit of the present invention. In FIG. 3, Tr5 is a transistor constituting a Colpitts type oscillation circuit, and Tr6 is a switch transistor for controlling this oscillation circuit. Also, Tr7, Tr8, Tr9, Tr10
is a transistor constituting an amplifier that amplifies the output of the oscillation circuit, and the oscillation output is set to a predetermined voltage value B.
Amplify and output. Tr11 and Tr12 are transistors that constitute a current amplifier, Tr13 and Tr1
4, Tr15 and Tr16 are transistors forming a power amplifier, Tr1 is a transistor forming an error voltage amplifier, and Tr3 and Tr4 are transistors forming a control voltage amplifier. Further, RV1 is a variable resistor for manually adjusting the transmission output reduction setting value A, H is a transmitting transformer, J is an ultrasonic transducer, and R1 is a current limiting resistor.

Next, the operation of the transmitter circuit configured as described above will be explained with reference to the operation waveforms shown in FIG.

First, the oscillation circuit constituted by the transistor Tr5 performs an oscillation operation when the switch transistor Tr6 is in the OFF state. i.e. transistor
Tr6 is OFF when base input signal C is low level
state (Fig. 4C), and in this case, the transistor Tr5 constitutes an oscillation circuit, and the transistor Tr5
generates an oscillation output signal D (FIG. 4D). The oscillation output signal D obtained in this way is converted into a signal waveform with a phase shift of 180° via an oscillation transformer, and is then transferred to transistors Tr7 and Tr which constitute an amplifier.
8, Tr9, and Tr10, respectively, to a predetermined output voltage value B (FIG. 4 E and F). Furthermore, the signal E obtained by the transistor Tr9
The signal F obtained by the transistor Tr10 is current amplified by the transistors Tr11 and Tr12,
Next, transistors Tr13, Tr15 and Tr14,
The power is amplified by Tr16. In this case, the transistors Tr13, Tr14, which constitute the power amplifier,
Although the case where Tr15 and Tr16 are each connected in two stages is shown, it is possible to have a one-stage, three-stage, or four-stage configuration depending on the transmission output. The oscillation signals E and F power-amplified in this way are transferred to the transmission transformer H
The ultrasonic transducer J is driven through the Further, a voltage _E2 for transmission power is supplied to the transmission transformer H via a current limiting resistor R1. At this time, the effective transmission output W is expressed as W=1/T×P (where T is the transmission repetition period and P is the transmission output). Also,
The voltage E _R consumed by the current limiting resistor R1 is E _R =
It is expressed as 1/T×P/E _B ×R1 (where E _B is the power supply voltage of the transmission power voltage E ₂ ).

On the other hand, the voltage E ₂ for transmission power is determined by the resistances R 2 and R
The detected voltage K is obtained by dividing the voltage by a voltage dividing circuit consisting of three voltage dividers. Transistor Tr that constitutes the error voltage amplifier
1, the detected voltage K is compared with the reference voltage _E1 , an error signal is extracted, and the voltage is amplified. In addition,
A diode D1 for temperature compensating the reference voltage E1 is connected to the transistor Tr1.

The signal voltage amplified by transistor Tr1 is
The voltage is further amplified by transistor Tr3,
Next, transistors Tr7, Tr8, Tr9, Tr
In order to drive 10, the current is amplified by transistor Tr4. Next, set the transmission output reduction setting value A set by variable resistor RV1 as the maximum value,
The voltage controlled by the transistors Tr3 and Tr4 is fed back as the output control voltage B of the transistors Tr7, Tr8, Tr9, and Tr10 forming an amplifier that amplifies the oscillation output. Here, variable resistance
With RV1, when several fishing boats using fish finders approach, the reflected waves of the ultrasonic waves emitted from each other will receive each other's waves and cause interference.
They are used to reduce the transmission output of each other. The circuit configuration for performing the feedback operation in this manner is summarized as shown in FIG. That is, in the circuit shown in FIG. 5, by setting the loop gain to G and the constant of the feedback circuit to β,
The following relationship holds true.

{Ei=E ₁ −βE ₂ ...(1) E ₂ =GEi} If we calculate the voltage E ₂ from the above equation (1), E ₂ = GE ₁ −GβE ₂ ∴E ₂ = G/1+Gβ・E ₁ ... …(2) becomes.

Therefore, from the above equation (2), if the loop gain G is sufficiently large, the voltage E ₂ for transmission power is approximated as E ₂ ≈E ₁ /β. That is, voltage E ₂ is the reference voltage
If E ₁ is constant, it depends on the constant β of the feedback circuit.

As a result, according to the circuit of this embodiment, when the transmission repetition period T becomes faster and 1/T increases, the transmission output P decreases and control is performed so that the effective transmission output value W=1/T×P remains constant. Ru. Therefore, the power supply voltage E _b that forms the voltage E ₂ for transmission power and the current limiting resistor R
If we calculate the voltage difference E _{0 =} E _B - E _R between _{the voltage E R consumed} in Become.

That is, according to the present invention, the effective transmission output W is held constant regardless of the transmission repetition period T,
There is an effect that the current limiting resistor provided in the power supply line of the transmission transformer does not generate abnormal heat without placing a burden on the power supply circuit. Further, since it is provided with an error voltage amplifier that extracts and amplifies an error voltage by comparing it with a reference voltage, there is an advantage that the effective transmission output can be reliably controlled. The effective transmission output characteristics of the present invention obtained in this way are shown by the characteristic line in FIG.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram showing the relationship between the transmission repetition period T and the effective transmission output W of a transmission circuit for a fish finder, Fig. 2 is a main part connection diagram of a conventional transmission circuit, and Fig. 3
FIG. 4 is a wiring diagram of the transmitting circuit according to the present invention, FIG. 4 is a time chart showing operating waveforms of the circuit shown in FIG. 3, and FIG. 5 is an explanatory diagram of the operation of the circuit shown in FIG. 3. H...Transmission transformer, J...Transducer, R1...
...Current limiting resistor, Tr5...Transistor for oscillation circuit, Tr6...Transistor for switch, Tr7
~Tr10...Amplifier transistor, Tr11,
Tr12... Current amplifier transistor, Tr13
~Tr16...Power amplifier transistor, Tr1
...Error voltage amplifier transistor, Tr3, Tr
4...Control voltage amplifier transistor, D1...
Temperature compensation diode, R2, R3...Voltage dividing resistor, RV1...Variable resistor, A...Transmission output reduction setting value, B...Output control voltage, C...Input signal for oscillation circuit control, D...Oscillation Output signal, E ₁ ... Reference voltage, E ₂ ... Transmission power voltage, E _b ... Power supply voltage,
E _R ...Consumption voltage, K...Detection voltage, E, F...
Oscillation output signal, G...loop gain, β...constant of feedback circuit.

Claims (1)

[Scope of utility model registration request] In the transmission circuit for a fish finder, in which a current limiting resistor is inserted in the line that supplies power to the power amplifier of the transmitting circuit for a fish finder, the transmission repetition period of which is adjustable, the power supply voltage is dropped by the current limiting resistor. a voltage dividing circuit that divides the voltage to obtain a detection voltage, a reference voltage circuit that obtains a reference voltage, an error voltage amplifier that compares the reference voltage and the detection voltage to extract and amplify an error voltage, and optionally reduces the transmission output. a transmission output reduction setter made of a variable resistor that can set a setting value; a control voltage amplifier whose output voltage is controlled by the output signal of the error voltage amplifier with the voltage obtained by the transmission output reduction setting device as the maximum value; and an amplifier that amplifies the output signal of the oscillation circuit using the output voltage of the control voltage amplifier as the power supply voltage, so that the effective value of the transmission output is maintained at a predetermined value even if the transmission repetition period changes. Transmission circuit for fish finder.