JPS639900Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply circuit for a tape recorder in which a display diode is used as a reference voltage for a constant voltage transistor.

In a tape recorder, the operating voltage of the amplifier circuit must be constant. A constant voltage transistor is used to obtain this constant operating voltage. It is possible to use a light emitting diode for display instead of using a dedicated voltage regulator diode to obtain the reference voltage of the constant voltage transistor, but using only one light emitting diode generally reduces the operating voltage of the amplifier circuit. The minimum required 3V cannot be obtained.

The present invention focuses on the fact that in a tape recorder that enables round-trip recording and playback, in addition to the light-emitting diode that illuminates the cassette insertion slot, a light-emitting diode is used to indicate the running direction of the tape.
A power supply circuit for a tape recorder that connects these two light emitting diodes in series and uses them as a reference voltage for the constant voltage transistor to obtain a sufficiently large operating voltage for the output of the constant voltage transistor. It provides:

The present invention will be explained below with reference to the drawings. 1 is a DC power supply, 2 is a power switch, and 3 is a cassette switch connected in series to the power switch 2, which connects a cassette (not shown) to the cassette storage section of a tape recorder. It is turned on when attached to. 4 is a constant voltage transistor, the collector of which is connected to the cassette switch 3, and the emitter of which is connected to the preamplifier circuit 5. Reference numerals 6 and 7 indicate first and second light emitting diodes for indicating the running direction of the tape (not shown), each having an anode commonly connected to the base of the constant voltage transistor 4, and a cathode indicating the running direction of the tape. The first switch on the outside of the selector switch 8 switches the
and are connected to third contacts 9 and 11, respectively. 1
Reference numeral 3 designates a third light emitting diode for indicating the cassette insertion slot, the anode of which is connected to the power switch 2 via a resistor 14 and the common second contact 10 of the selector switch 8, and the cathode of which is grounded. ing.

Next, the operation of the power supply circuit of the tape recorder of the present invention will be explained. First, in order to run the tape in the first tape running direction, press the contact piece 12 of the changeover switch 8.
is located between the first and second contacts 9 and 10. When the power switch 2 is turned on in such a state, the voltage from the DC power supply 1 is applied to the third light emitting diode 13 through the power switch 2 and the resistor 14, causing the third light emitting diode 13 to emit light and opening the cassette insertion slot. irradiate. Next, when the cassette is loaded into the tape storage section, the cassette switch 3 is turned on. As a result, the current from the DC power source 1 flows through the power switch 2, the cassette switch 3, the resistor 15, the first light emitting diode 6, the changeover switch 8, and the third light emitting diode 13, and in turn flows through the first light emitting diode 6 and the third light emitting diode 13. 3 Light emitting diodes 13 are made to emit light, and the tape
Displays that the tape is running in the tape running direction. When the first and third light emitting diodes 6 and 13 emit light, the impedance between the anode and cathode of the first and third light emitting diodes 6 and 13 is sufficiently reduced compared to the impedance of the resistors 14 and 15, A constant voltage of about 4.4 V based on the voltage drop of the first and third light emitting diodes 6 and 13 is applied to the base of the constant voltage transistor 4. Therefore, an operating voltage of about 3.8V is applied to the preamplifier circuit 5.

Next, when the contact piece 12 of the changeover switch 8 is switched automatically or manually so that it is located at the contacts 10 and 11, the current from the DC power supply 1 is transferred to the power switch 2, the cassette switch 3, the resistor 15,
The current flows through the second light emitting diode 7, the changeover switch 8, and the third light emitting diode 13, causing the second and third light emitting diodes 7 and 13 to emit light, indicating that the tape is running in the second tape running direction, At this time as well, since the bias voltage obtained by the two light emitting diodes is applied to the base of the constant voltage transistor 4, a constant voltage of about 3.8 V is applied to the preamplifier circuit 5 as described above.

As mentioned above, in the power supply circuit of the tape recorder of the present invention, when the power switch is turned on, the light emitting diode that illuminates the cassette insertion slot emits light, and when the cassette is then inserted into the cassette compartment, the cassette switch is turned on and the tape running direction is displayed. In addition to displaying the tape running direction by making the light emitting diodes emit light, the sum of the voltage drops across these two light emitting diodes supplies a bias voltage to the constant voltage transistor, which is large enough for the amplifier circuit. It is possible to supply a constant operating voltage and provide a practical power supply circuit.

[Brief explanation of the drawing]

The figure is a power supply circuit diagram of the tape recorder of the present invention. 2... Power switch, 3... Cassette switch, 4... Constant voltage transistor, 5... Amplifying circuit, 6... First light emitting diode, 7... Second light emitting diode, 8... Changeover switch, 13... …Third
light emitting diode.

Claims (1)

[Scope of utility model registration request] a cassette switch connected in series with a power switch and turned on by inserting a cassette;
a constant voltage transistor whose collector and emitter are connected between the cassette switch and the power supply terminal of the amplifier circuit; one end connected to the base of the constant voltage transistor, and the other end connected to the first tape running direction and the second tape first and second light emitting diodes connected to respective contacts of a changeover switch for switching the running direction; and a third light emitting diode for illuminating the cassette insertion slot, one end of which is connected to a common contact of the power switch and the changeover switch. A power supply circuit for a tape recorder.