JPH0241588Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording level display/voltage detection circuit suitable for tape recorders, particularly portable tape recorders that use batteries as a power source.

Conventionally, a conventional voltage detection circuit that also serves as a recording level display is based on a mechanical meter pointer. It is true that the method of using such a mechanical meter is superior in accurately displaying recording levels and battery consumption, but it is expensive to manufacture, and it is functionally inefficient to reduce its size. However, since there are restrictions on the mounting position, it is not suitable for downsizing tape recorders.
As a device suitable for miniaturizing tape recorders, devices have been developed that display the recording level and detect voltage by blinking light-emitting elements such as light-emitting diodes. In addition, a switch for performing a voltage sensing operation, ie, a voltage sensing switch, is generally provided.

The present invention is intended to provide a voltage detection circuit that also serves as a recording level display and does not require such a voltage detection switch, and will be described in detail below with reference to the illustrated embodiments. In the circuit shown,
1 is a DC power supply, 2 is a recording signal input terminal to which a recording signal is applied, and 3 is a recording signal input terminal to which a recording signal is applied to the input terminal 2, and is applied to the base via a resistor 4 and a capacitor 5, and the emitter is grounded. The collector is connected to the DC power supply 1 via a light emitting diode 6 and a resistor 7. A capacitor 8 connected in parallel to the resistor 7 has the function of improving the rise characteristics during recording level display operation, and a resistor 9 connected in parallel to the light emitting diode 6 lights up the light emitting diode 6 during voltage detection operation. This serves to set the operating level. Reference numeral 10 denotes a DC erasing type erasing head, one end of which is connected to the DC power source 1, and the other end is connected to the recording side terminal 11R of the recording/reproducing switch 11. Reference numeral 12 denotes a MOS field effect transistor (hereinafter referred to as MOS field effect transistor) whose gate is connected to the ground terminal of the coil of the erase head 10 and whose drain is connected to the DC power supply 1.
FET) whose source is connected to the base of the drive transistor 3 via a resistor 13.

The present invention is constructed as described above, and its operation will be explained next. First, press the recording/playback switch 1.
The recording operation in the state shown in FIG. 1 will be explained. In the recording operation state, the ground terminal of the coil of the erasing head 10 is grounded by the recording/playback switch 11, so that DC power is supplied to the coil of the erasing head 10 by the DC power supply 1, and the erasing head 10 performs the erasing operation. Do this. Also, in such a situation
Since the gate of MOSFET 12 is grounded by the recording/playback switch 11, the
The MOSFET 12 is in a pinch-off state, and no bias current flows to the base of the drive transistor 3, so the drive transistor 3 is in an off state. The recording operation is performed in this state, but part of the recording signal is applied to the recording signal input terminal 2, and when the level of the signal exceeds a predetermined value, that is, the rising voltage of the drive transistor 3, the recording signal is applied to the recording signal input terminal 2. The drive transistor 3 is biased by the recording signal and is turned on. When the driving transistor 3 is turned on, a current flows through the light emitting diode 6 connected as a load to the collector of the transistor 3, and the light emitting diode 6
lights up. Therefore, the user can recognize the level of the recording signal by the change in the lighting state of the light emitting diode 6.

The recording signal level display operation is performed as described above, but next, the operation when the recording/reproduction changeover switch 11 is in the non-recording state, which is opposite to the illustrated state, that is, the voltage detection operation will be described. When the recording/playback switch 11 is in the non-recording state, the ground terminal of the coil of the erasing head 10 is not grounded, so a high voltage is applied from the DC power supply 1 to the gate of the MOSFET 12 through the coil of the erasing head 10. As a result, the MOSFET 12 is turned on, and the source current flows through the resistor 13 as the base current of the drive transistor 3. Therefore, the drive transistor 3 is turned on and its collector potential becomes ground potential. When the voltage of the DC power supply 1 is higher than the reference value, that is, the voltage necessary for normal operation of the tape recorder, the voltage dividing point of the resistors 7 and 9, that is, the potential of the anode of the light emitting diode 6 turns on the light emitting diode 6. The light emitting diode 6 lights up because it is higher than the voltage that causes the state. When the battery is exhausted and the voltage of the DC power source 1 drops below a reference value, the potential of the anode of the light emitting diode 6 also drops, and the light emitting diode 6 turns off. By turning on and off the light emitting diode 6, the user can detect the voltage of the DC power supply 1. In addition, in such a state, a high voltage is applied to the gate of MOSFET 12;
Since the gate, source, and drain of MOSFET 12 are insulated, no current flows through the coil of erase head 10, and erase head 10 does not perform an erase operation.

In this embodiment, a light emitting diode is used as a light emitting element to display the recording level and power supply voltage, but it is of course possible to use a light emitting element such as a lamp.

As explained above, the present invention not only uses a light emitting element to display the drop in power supply voltage and the recording level, but also displays the recording level during recording using a recording/playback switch that controls the operation of the DC erase head. Since the voltage detection operation is performed during the non-recording operation, there is no need for a special changeover switch, which is very effective in downsizing the tape recorder. Furthermore, since a MOSFET is used as a control element to control the operation of the drive transistor that drives the light emitting element, the operation of the drive transistor can be controlled by a single control element depending on whether or not the ground terminal of the erase head coil is grounded. It becomes possible to control the
The present invention has the advantage that the circuit configuration is simple, and its practical value is very high.

[Brief explanation of drawings]

The illustrated circuit is an embodiment of the recording level display/voltage detection circuit of the present invention. Explanation of main drawing numbers, 1...DC power supply, 2...Recording signal input terminal, 3...Drive transistor, 6...
...Light emitting diode, 10...Erasing head, 11...
...Recording/playback selector switch, 12...MOSFET.

Claims (1)

[Scope of utility model registration request] A drive transistor to which a recording signal is applied to the base and a light emitting element connected to the collector, and an erasing head whose coil has one end connected to a DC power supply and the other end is grounded by a recording/playback switch during recording operation. and a MOSFET whose gate is connected to the ground terminal of the coil of the erase head, whose drain is connected to the DC power supply, and whose source is connected to the base of the drive transistor via a resistor. The MOSFET is turned off by grounding the gate by the recording/playback selector switch, and the driving transistor is turned on/off by the recording signal.
The recording level is indicated by the flashing of the light emitting element during the off operation, and the recording level is indicated by the voltage applied through the coil of the erase head during the playback operation.
A recording level display/voltage detection device characterized in that the driving transistor is turned on by turning on a MOSFET, and the voltage of the DC power supply is displayed depending on whether or not the light emitting element is lit. circuit.