JPH0524969Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention relates to a power supply control circuit that controls power supply to a load such as an amplifier circuit using a timer or the like.

(b) Conventional technology A tape recorder called a tape deck used in combination with a stereo device has a function called ``absence recording,'' in which it works with a timer device to record signals such as FM broadcasts while you are away. We are prepared. Mechanisms for performing such an absentee recording operation include a mechanical type that releases the pause operation when power is supplied when the tape recorder is set in a paused state in the recording state, and a mechanism that uses the suction force of a plunger. There is an electric type that switches from a stopped state to a recording state.
There is one disclosed in Publication No. 19247. Furthermore, a portable audio device called a tape recorder with radio, in which a radio receiving circuit and a tape recorder are incorporated in the same cabinet, has become widespread, and there is also a demand for such a device to have an absentee recording function. A tape recorder with a radio equipped with such an answer recording function has a built-in timer circuit, and its operation is controlled by the timer circuit, and the power supply to the radio receiving circuit, recording circuit, etc. is controlled. A power supply control circuit is provided, and such a power supply control circuit is disclosed in, for example, Japanese Utility Model Application Publication No. 184115/1983.

(c) Problems to be solved by the invention The above-mentioned Japanese Utility Model Application Publication No. 184115/1984 discloses a method for controlling the switching operation of a transistor in which an emitter-collector path is inserted and connected between a power source and a load. Therefore, techniques have been disclosed for controlling the power supply to the load, and in such techniques, a voltage drop or voltage loss occurs between the collector and emitter of the transistor. In a portable device that uses a battery as a power source, it is necessary to reduce the voltage loss of the transistor mentioned above, so it is necessary to allow a certain amount of base current to flow through the transistor, and the current value must be determined in consideration of the maximum current value to the load. is set. In a device such as a recent tape recorder with a radio, in which the output of the amplifier circuit is increased, the maximum load current supplied to the load inevitably becomes large, so that the base current of the transistor also becomes large. In such devices, the volume may be lowered or
When only the radio receiving circuit is operated, the load current is reduced, but in the circuit described above, the base current of the transistor is not reduced, so there is a problem that battery consumption due to such base current cannot be ignored. The present invention aims to provide a power supply control circuit that is improved in this respect.

(d) Means for solving the problem The power supply control circuit of the present invention supplies power to the load when an emitter-collector path is inserted and connected between the power source and the load and is in a conductive state. a power supply transistor; a control transistor whose base is supplied with a control current and becomes conductive when in operation for supplying power to the load, and whose emitter is grounded; and whose emitter is connected to the power supply; a first transistor whose base is connected to the collector of the control transistor through a resistor; a collector whose collector is connected to the base of the power supply transistor through a resistor and whose emitter is grounded; a second transistor to which a base current is supplied between the emitter and collector of the transistor; and a second transistor connected between the collector of the power supply transistor and the base of the first transistor, which controls changes in the collector voltage of the power supply transistor. and a diode communicating to the base of the first transistor.

(E) Effect The present invention has an emitter-collector path inserted and connected between a power source and a load, and the base current of a power supply transistor provided to supply power to the load when in a conductive state. is made to change in response to the load current.

(F) Embodiment The illustrated circuit is an embodiment in which the power supply control circuit of the present invention is incorporated into a tape recorder with a radio. In the figure, 1 is a radio receiving circuit that receives a radio broadcast signal, and 2 is an amplifier circuit, a bias oscillation circuit, etc. that receives the FM broadcast signal received by the radio receiving circuit 1 and amplifies the signal. 3 is the recording circuit 2.
A magnetic head is applied with a signal output from a magnetic head and records the signal on a magnetic tape. 4 is a battery as a power source; 5 is a timer battery provided separately from the battery 4; 6 is a timer circuit operated by the current supplied from the timer battery 5; It has an output terminal 7 that outputs an H (high) level signal. 8 is a power supply transistor whose emitter is connected to the battery 4 and whose collector is connected to the power supply terminals of the radio receiving circuit 1 and the recording circuit 2; 9 is a transistor whose base is connected to the output terminal 7 of the timer circuit 6; a control transistor to which is connected via a resistor 10 and whose emitter is grounded;
11 is a first transistor whose emitter is connected to the battery 4 and whose base is connected to the collector of the control transistor 9 via a resistor 12; 13 is a first transistor whose collector is connected to the power supply transistor 8 via a resistor 14; A second transistor is connected to the base of the first transistor 11 and has its emitter grounded, and its base is connected to the collector of the first transistor 11 via a resistor 15. Reference numeral 16 denotes a diode whose anode is connected to the collector of the power supply transistor 8 and whose cathode is connected to the base of the first transistor 11, and the radio is the collector voltage of the power supply transistor 8, that is, the load. It has the function of transmitting changes in the voltage supplied to the receiving circuit 1 and the recording circuit 2 to the base of the first transistor 11, and also has the function of canceling the base-emitter voltage of the first transistor 11. 17 and 18 are resistors connected between the emitter and base of the power supply transistor 8 and between the emitter and base of the first transistor 11, respectively, so that the power supply transistor 8 and the first transistor 11 are in a non-conducting state. When the transistors 8 and 11
It has the function of stably maintaining a non-conducting state. Further, although not shown in the drawings, a drive current for a motor provided to drive the magnetic tape is also supplied through the emitter and collector of the power supply transistor 8. As described above, the power supply control circuit of the present invention is constructed, and the operation of this circuit will be explained next.

In the illustrated circuit, the answering recording operation is performed by switching a power switch (not shown) to supply power to the radio receiving circuit 1 and recording circuit 2, selecting the frequency to be received, setting the recording level, and turning on the power. At the time of supply operation, after setting the tape recorder to a state where recording operation is started, the power supply is cut off, and the timer circuit 6 sets the time at which recording operation is to be started. In this state, since an L level signal is output to the output terminal 7 of the timer circuit 6, the control transistor 9 whose base is connected to the output terminal 7 is in a non-conductive state. Therefore, the first transistor 11 whose operation is controlled by the control transistor 9
is in a non-conducting state, and the first transistor 11
a second transistor 1 whose operation is controlled by
3 is in a non-conducting state. When the second transistor 13 is in a non-conducting state, the power supply transistor 8 connected so that its operation is controlled by the second transistor 13 is reverse biased and in a non-conducting state, and the power supply transistor 8 is reverse biased and is in a non-conducting state. Power is not supplied to the radio receiving circuit 1, recording circuit 2, etc. In such a state, at the set time, an H level signal is output to the output terminal 7 of the timer circuit 6, and this H level signal is applied to the base of the control transistor 9 through the resistor 10, so that the control transistor 9 is biased. and becomes conductive. When the control transistor 9 becomes conductive, a first transistor whose base is connected to the collector of the control transistor 9 via a resistor 12 is connected.
Since the base potential of the transistor 11 decreases, the first transistor 11 is biased and reversed to a conductive state. When the first transistor 11 is turned on, a bias current flows between its emitter and collector and through the resistor 15 to the base of the second transistor 13, and the second transistor 13 is biased and turned on.
When the second transistor 13 becomes conductive, a resistor 14 is connected to the collector of the second transistor 13.
Since the base potential of the power supply transistor 8 to which the base is connected via the power supply transistor 8 decreases, the power supply transistor 8 is biased and inverted to a conductive state. The power supply transistor 8
When becomes conductive, its collector potential rises, so that voltage is applied to the base of the first transistor 11 via the diode 16, and as a result, the bias of the first transistor 11 becomes shallow,
The collector current of the first transistor 11, ie, the base current of the second transistor 13, decreases. When the base current of the second transistor 13 decreases, the collector current of the second transistor 13, that is, the base current of the power supply transistor 8 decreases, and the collector-emitter voltage of the power supply transistor 8 increases. When the collector-emitter voltage of the power supply transistor 8 increases, the collector potential of the transistor 8 drops, and this potential drop is transmitted to the base of the first transistor 11 through the diode 16. As a result, the bias of the first transistor 11 becomes deep, and the collector current of the first transistor 11, that is, the second transistor 1
3 base current increases. When the base current of the second transistor 13 increases, the collector current of the second transistor 13, that is, the base current of the power supply transistor 8 increases, and the collector-emitter voltage of the power supply transistor 8 decreases. When the voltage between the collector and emitter of the power supply transistor 8 becomes smaller, the collector potential of the transistor 8 increases, and this potential increase is transmitted to the base of the first transistor 11 through the diode 16, and the bias of the first transistor 11 becomes It becomes shallow. When an H level signal is output to the output terminal 7 of the timer circuit 6 and the control transistor 9 is inverted to a conductive state, the first
The transistor 11, the second transistor 13, and the power supply transistor 8 perform the operations described above, and a predetermined voltage is output to the collector of the power supply transistor 8. Therefore, power from the battery 4 is supplied to the radio receiving circuit 1, the recording circuit 2, etc. through the emitter and collector of the power supply transistor 8, and each circuit becomes operational, and the drive mechanism of the tape recorder enters the recording operation. will be in a state of doing this. In such a state, the radio signal received by the radio receiving circuit 1
An FM broadcast signal or the like is amplified by an amplifier circuit incorporated in the recording circuit 2, and then applied together with a bias signal to a magnetic head 3, where the signal is recorded onto a magnetic tape.

When the set time comes, the above-described operations are performed and the recording operation is started.Next, the operation when the load changes while in such a state will be explained. When the load is light during operation, the load current, that is, the collector current of the power supply transistor 8 decreases, so the power supply transistor 8
collector potential increases. When the collector potential of the power supply transistor 8 rises, the voltage rise is transmitted to the base of the first transistor 11 through the diode 16, so that the bias of the first transistor 11 becomes shallower, and the collector current of the first transistor 11, i.e. The base current of the second transistor 13 decreases. Said second
When the base current of the transistor 13 decreases, the collector current of the second transistor 13, that is, the base current of the power supply transistor 8 decreases, and the collector-emitter voltage of the power supply transistor 8 increases. When the collector-emitter voltage of the power supply transistor 8 increases, the collector potential of the transistor 8 decreases, and this potential decrease is transmitted to the base of the first transistor 11 through the diode 16. Therefore, each of the operations described above is performed and a voltage corresponding to the load is output to the collector of the power supply transistor 8. The operation when the load becomes lighter is performed in this way, but next, the operation when the load becomes heavier will be explained. When the load becomes heavy, the load current, that is, the collector current of the power supply transistor 8 increases, and the collector potential of the power supply transistor 8 decreases.
When the collector potential of the power supply transistor 8 decreases, the potential decrease is transmitted to the base of the first transistor 11 through the diode 16, so that the bias of the first transistor 11 becomes deeper, and the collector potential of the first transistor 11 becomes deeper. The current, ie the base current of the second transistor 13, increases. When the base current of the second transistor 13 increases, the collector current of the second transistor 13, that is, the base current of the power supply transistor 8 increases, and the power supply transistor 8 increases.
The collector-emitter voltage of is reduced. When the collector-emitter voltage of the power supply transistor 8 decreases, the collector potential of the transistor 8 increases, and this potential increase is transmitted to the base of the first transistor 11 through the diode 16. Therefore, each of the operations described above is performed and a voltage corresponding to the load is output to the collector of the power supply transistor 8. In this way, when the load fluctuates, the base current of the power supply transistor 8 is changed in response to the load fluctuation, so that the current obtained from the battery 4 can be used efficiently.

After the above-described operation is performed, the power from the battery 4 is supplied to the radio receiving circuit 1 and the recording circuit 2 through the emitter and collector of the power supply transistor 8, so that an absent recording operation is performed. Then, the tape recorder is switched from the recording operation state to the stop state by the action of an automatic stop device built into the tape recorder in which the magnetic tape runs to the end. Furthermore, after a predetermined period of time has elapsed, the H level signal output to the output terminal 7 of the timer circuit 6 is inverted to L level. When the H level signal outputted to the output terminal 7 is reversed to L level, the control transistor 9 which was in a conductive state is reversed to a non-conductive state. Transistor 11 is reverse biased and becomes non-conductive. When the first transistor 11 becomes non-conductive, the second
Since the base current of the transistor 13 is cut off, the second transistor 13 is reversed to a non-conducting state. When the second transistor 13 is reversed to a non-conductive state, the base current of the power supply transistor 8 is cut off, and the transistor 8 is reversed to a non-conductive state. When the power supply transistor 8 becomes non-conductive, the power supplied to the radio receiving circuit 1 and the recording circuit 2 is cut off, and each circuit becomes inoperative.

Each operation in this embodiment is performed as described above, but since the base-emitter voltage of the first transistor 11 is canceled by the forward voltage of the diode 16, the first transistor 1
1 operates in response to the voltage between the collector and emitter of the power supply transistor 8, and also operates to correct the base current of the power supply transistor 8 for changes in the voltage between the collector and emitter.

In this embodiment, a case has been described in which the directional power supply control circuit is incorporated into a tape recorder with a radio, but it can also be incorporated into a tape recorder or a radio receiver. In addition, the power supply operation was controlled by a timer circuit, but
It is also possible to control by a switch that is manually operated or a switch that is operated by a remote control.

(g) Effects of the invention The power supply control circuit of the invention has an emitter-collector path inserted and connected between the power source and the load, and is provided to supply power to the load when in a conductive state. Since the base current of the power supply transistor is changed in accordance with the load current, that is, the base current suitable for the load flows, so the current consumption due to the base current can be suppressed to the necessary minimum. have. Furthermore, since the collector current of the control transistor, which is provided so that a control current is applied to the base and becomes conductive and starts power supply operation, is not directly used as the base current of the power supply transistor, the base of the control transistor The current, that is, the control current, can be made very small, and therefore, the present invention has a very large effect when incorporated into a device configured to be controlled by a timer circuit that operates on a single battery, that is, 1.5V. It is something that plays.

[Brief explanation of the drawing]

The illustrated circuit is an embodiment in which the power supply control circuit of the present invention is incorporated into a tape recorder with a radio. Explanation of main drawing numbers, 1...Radio receiving circuit, 2...
...Recording circuit, 4...Battery, 6...Timer circuit,
8...Power supply transistor, 9...Control transistor, 11...First transistor, 1
3...second transistor, 16...diode.

Claims (1)

[Scope of utility model registration request] A power supply transistor having an emitter-collector path inserted and connected between the power supply and the load and supplying power to the load when in a conductive state; and a power supply transistor controlling the base when in an operating state for supplying power to the load. a control transistor to which a current is supplied and becomes conductive and whose emitter is grounded; and a first transistor whose emitter is connected to the power supply and whose base is connected to the collector of the control transistor via a resistor. , a second transistor whose collector is connected to the base of the power supply transistor via a resistor and whose emitter is grounded, and to which a base current is supplied between the emitter and collector of the first transistor; and the power supply transistor. The power supply transistor is connected between the collector of the power supply transistor and the base of the first transistor, and changes in the collector voltage of the power supply transistor are connected between the collector of the power supply transistor and the first transistor.
and a diode that transmits power to the base of the transistor, and controls the operation of the power supply transistor by conducting or non-conducting the control transistor, and also controls the operation of the power supply transistor.
A power supply control circuit characterized in that a bias current of a transistor is changed in response to a change in a collector voltage of the power supply transistor, thereby changing a base current of the power supply transistor.