JPH0638524Y2 - Power supply circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a power supply circuit for supplying operation power supplied from a telephone line to desired circuits and elements in a telephone.

(B) Conventional technology The basic circuit for performing a call operation such as a call receiving circuit in a telephone connected to a telephone line terminal or a call circuit has conventionally been an operating power source supplied from the exchange side to the telephone line. It is adapted to be in operation. for that reason,
Even if the commercial power supply or the like is cut off due to a power failure, the basic circuit as a telephone is in an operating state, so that the telephone has been operated. More recently,
In addition to the basic circuit as a telephone, an auxiliary power circuit such as an integrated circuit for controlling a microcomputer or the like for controlling the basic circuit is operated by a power source of a telephone line, as disclosed in Japanese Patent Laid-Open No. 50-34253. Through a power supply circuit, a predetermined operating power is supplied during a call state, that is, when the line is closed.

(C) Problems to be solved by the invention As described above, the power supply circuit that supplies the auxiliary power circuit of the telephone with the operating power applied to the telephone line to the predetermined value and activates it is generally a load. Since a circuit with a fixed value of is connected and the operating power from the telephone line is changed to a value corresponding to the circuit, it is supplied.
If the control correspondence is different, the amount of current changes greatly even if the voltage applied from the power supply circuit changes slightly depending on the integrated circuit that performs each control operation by changing the load value or the line condition for displaying INUSE. When a light emitting diode that also changes is connected, the power supply circuit responds to changes in the value of the load, lowers the AC impedance to the telephone line to 600Ω or less, or reduces the dynamic range in the circuit, If another circuit, for example, the input terminal of the communication circuit and the input of the power supply circuit are connected to the line, the input is limited because the dynamic range of the power supply circuit is reduced. Under the influence, there was a problem that the signal applied to the communication circuit was distorted. Therefore, the present invention solves such a problem, prevents the AC impedance to the telephone line from decreasing even when the load of the connected circuit changes, and ensures a dynamic range of a certain value or more. Is provided.

(D) Means for Solving the Problems A power supply circuit of the present invention includes a power supply transistor whose collector terminal is connected to a telephone line through a diode bridge circuit, a collector terminal and a base terminal of the power supply transistor. A first resistor connected between the first resistor and a bleeder resistor having one end connected to a connecting portion between the base terminal of the power supply transistor and the first resistor and the other end grounded.
A second resistor having one end connected to the emitter terminal of the power supply transistor and the other end serving as an output terminal, and one end connected to the base terminal of the power supply transistor and the other end connected to the output terminal or ground. Composed of connected capacitors.

(E) Action The power supply circuit of the present invention has one end connected to the connection between the first resistor provided for biasing the collector-base of the power supply transistor and the base of the power supply transistor, and the other end Of the load connected to the output terminal by increasing the amount of current flowing through the first resistor by increasing the collector-base voltage of the power supply transistor by the first resistor by connecting the bleeder resistor to the ground. This is intended to prevent a decrease in the dynamic range of the power supply transistor due to.

(F) Embodiment An embodiment of the power supply circuit of the present invention will be described with reference to the drawings. FIG. 1 shows a telephone incorporating a power supply circuit according to an embodiment of the present invention (1) is a connection terminal for connecting to a telephone line,
(2) is a hook switch, (3) is a diode bridge circuit for determining the polarity of a voltage or signal supplied through a telephone line, and (4) is a telephone call for performing a telephone operation as a telephone through the telephone line. A circuit (5) is a handset connected to the communication circuit (4), and when the handset (5) is off-hook, the hook switch (2) is closed. When the hook switch (2) is closed in the power supply circuit of the present invention, (6) receives the operating power from the telephone line and becomes in the operating state. The power supply circuit (6) is provided with an input terminal A at the collector of the power supply transistor (7), and is connected to a collector-base of the power supply transistor (7) to represent an impedance of at least 600Ω or more, so that it has a large value. One end of the predetermined resistance (8) and the emitter of the power supply transistor (7) are in contact with each other and the other end is connected to the output terminal section B, and the output terminal section B is connected to the output terminal section B. A second resistor (9) which is incorporated by a current value applied at the time of impedance and a required voltage value,
A capacitor (10), one end of which is connected to the base of the power supply transistor (7) and the other end of which is connected to the output terminal portion B so that the power supply transistor (7) does not fluctuate against AC. A bleeder for increasing the amount of current flowing into the first resistor (8) by connecting one end to the connection between the first resistor (8) and the base of the power supply transistor (7) and connecting the other end to the ground. It consists of a resistor (11). Reference numeral (12) is a control circuit as a load which is connected to the output terminal B of the power supply circuit (6) and receives power supply, and the impedance of the control circuit (12) changes according to the operation mode. ( 13 ) is an auxiliary device for supplying an operating current to the control circuit (12) when the hook switch (2) is open and the telephone is not in a call state. An auxiliary power source resistor (14), a diode (15), and a battery (16) are connected in series by a power source.

The operation of the power supply circuit (6) of the present invention in the circuit configured as above will be described. First, the operation for keeping the AC impedance to the telephone line to be the integrated value or more when the impedance of the control circuit (12) changes will be described. The first resistor (8) is set so that a bias current for operating the power supply transistor (7) flows and a collector-emitter voltage V _CE of the power supply transistor (7) can be secured, and The second resistor (9) prevents the fluctuation effect due to the alternating current of the power supply transistor (7) with the capacitor (10). In such a configuration, assuming that the output terminal B of the power supply circuit (6) is always applied with the potential V _{E (V)} from the auxiliary power supply circuit (13), first the input terminal portion A is connected to V
When the voltage of the _{I (V)} is supplied to the power supply circuit (6) V _I
A voltage of −V _E = V _D (V _I <V _E ) is applied. Upon receiving the voltage V _{D (V)} , the first resistor (8) applies a current to the base of the power supply transistor (7) to activate the power supply transistor (7). Thereby, a current is applied to the output terminal B through the collector-emitter of the power supply transistor (7) and the second resistor (9). When an alternating current is superposed and applied to the input terminal A in such a state, the alternating current is applied to the base of the power supply transistor (7) via the first resistor (8) and is applied to the power supply transistor (7). An attempt is made to cause fluctuations, but fluctuations are caused because the capacitor (9), which generates 0V when receiving alternating current, prevents the voltage rise due to alternating current between the emitter and base of the power supply transistor (7). You don't have to. V applied to the input terminal A in such a state
_When the voltage of _{I (V)} rises and the current flowing through the first resistor (8) and the power supply transistor (7) -second resistor (9) increases, the emitter-junction resistance R of the power supply transistor (7) _Since the value of _E decreases, a small amount of alternating current is added to the base of the power supply transistor (7) from the capacitor (10) that generates 0 V for the alternating current, and the power supply transistor (7) causes fluctuations with respect to the alternating current. However, due to the resistance value of the second resistor (9), the emitter-junction resistor is
Since the amount of decrease in R _E is compensated for, the power supply transistor (7) does not perform fluctuation due to AC. Therefore, even if the current changes, the power supply circuit (6) is not affected by the alternating current, so that the impedance does not decrease with respect to the alternating current.

Next, a description will be given of the point that the control circuit (12) connected to the output terminal B does not lower the dynamic range of the power supply circuit (6) even when the impedance changes by switching the operation mode. First, the operation of the bleeder resistor (11) connected between the base of the first resistor (8) and the power supply transistor (7) and the ground will be described. Due to the connection relationship, the bleeder resistor (11) is always in a state of receiving the potential between the base and ground of the power supply transistor (7). For example, the input potential of the control circuit (12) is V
_{S (V)} (for example, 2V), the voltage applied to the second resistor (9)
V _{R2 (V)} [eg 0.3 (V)], and the emitter-base voltage of the power supply transistor (7) is about 0.6 (V)
(Constant), the potential V applied to the bleeder resistance (11)
_{B (V)} becomes V _S + V _R2 +0.6. Therefore, the bleeder resistance (11) receives the bleeder current via the first resistance (8) and drops in voltage. On the other hand, the first resistor (8) is a path for applying a bias current to the base of the power supply transistor (7), and the collector-base voltage V
_Since it is a resistor that determines _{CB (V)} , the voltage of the first resistor (8) is applied to the bleeder resistor (11) by causing a current causing a voltage drop due to the bleeder resistor (11) to flow together with the bias current. Therefore, V _{CB (V)} (about 0.4 V or more) of the power supply transistor (7) becomes higher than that of the bias current alone. Since the voltage between the emitter and the base of the power supply transistor (7) which is in operation by such operation is about 0.6 (V), the voltage between the collector and the base V _{CE (V)} is V _{CB (V)} +0. 6 _(V) , and when the saturation voltage is 0.1 (V), it becomes V _{CB (V)} +0.5 _(V) , and the power supply transistor (7) has V _{CB (V)} +0.5 _(V) (0.9
A dynamic range having a beak of (V) or more) can be provided.

Next, the dynamic range value of the power supply circuit (6) when the impedance of the control circuit (12) increases and the current applied to the control circuit (12) decreases will be described. When the handset (5) is lifted and the hook switch (2) is closed to put it in the off-hook state, the power supply circuit (6)
Is applied with a voltage between telephone lines from the telephone line through the connection terminal (1) -hook switch (2) -diode bridge circuit (3). In such a state, the first resistor (8)
A bias current is applied to the base of the power supply transistor (7) through the bleeder current and a bleeder current is applied to the first resistor (8).
To the bleeder resistor (11) via. By such an operation, the first resistor (8) generates a voltage corresponding to the combined value of the bias current and the bleeder current, which is applied between the collector and the base of the power supply transistor (7). Therefore, the power supply transistor (7) is activated, and the current output from the emitter is applied to the control circuit (12) via the second resistor (9) -output terminal B. In such a state, the control circuit (1
If 2) has a high impedance and receives a small amount of input current, the amount of current applied to the output terminal B due to the high impedance is small. With such an operation, the amount of current flowing between the collector and the emitter of the power supply transistor (7) is also reduced, but the voltage between the telephone lines applied to the power supply circuit (6) does not change with a constant value. The base voltage of (7) also does not change much. Therefore, there is no change in the current flowing into the bleeder resistance (11), so there is a large change in the collector-base voltage V _{CB (V)} (about 0.4 V or more) of the power supply transistor (7) due to the first resistance (8). Does not occur. Therefore, the collector-emitter voltage of the power supply transistor (7) can be V _{CB (V)} +0.5 _(V) (about 0.9 V or more), and there is no problem with the dynamic range.

Next, the dynamic range value of the power supply circuit (6) when the impedance of the control circuit (12) becomes lower than that in the above state and the current applied to the control circuit (12) increases will be described. First, due to the low impedance of the control circuit (12), the current applied to the output terminal B through the second resistor (9) via the collector-emitter of the power supply transistor (7) increases. In such a state, the first resistor (8)
The base current based on the current amplification factor of the power supply transistor (7) is added to the bleeder current described above to flow. Therefore, the power supply transistor (7)
Base-collector voltage V _{BC (V)} (about 0.4 (V) or more)
Gradually increases. Therefore, power supply transistor (7)
The collector-emitter voltage V _{CE (V)} of V _{BC (V)} +0.5 _(V)
Since it can be set to (about 0.9V or more), there is no problem with the dynamic range.

Next, as another embodiment, a device in which a light emitting diode is connected to the output terminal B of the power supply circuit (12) to perform a light emitting operation will be described with reference to FIG. First in FIG.
The same parts, elements and circuits as those in the figure are designated by the same numbers as in FIG. (17) uses a light emitting diode to lift the handset (5) so that it lights up when the telephone line goes off-hook. Further, the light emitting diode (17) has a feature that it does not turn on unless a certain voltage or more is applied, and after turning on once, the current rapidly changes according to the applied voltage.

Next, the operation of another embodiment in which the light emitting diode (17) is connected to the output terminal B will be briefly described. For example, if the light emitting diode (17) is turned on when the voltage between the telephone lines is low, the base potential of the power supply transistor (7) in such a state is the operating voltage V of the light emitting diode (17). V _{R2 (V)} and the power supply transistor (7) that dropped due to _{D (V)} and the second resistor (9)
It is expressed as the sum of the voltage V _{EB (V)} between the emitter and the base of the.
In such a state, the bleeder resistor (11) receives a bleeder current through the first resistor (8) to cause a voltage drop corresponding to the base potential. Due to the operation, a current of the sum of the bleeder current and the bias current is applied to the first resistor (8), so that the collector of the power supply transistor (7) is
The voltage between the base V _{CB (V)} can be set to a satisfactory value, and the voltage V _{CE (V)} between the collector and emitter of the power supply transistor (7)
Since it can be set to V _{CB (V)} +0.5 _(V) (about 0.9V or more), there is no problem with the dynamic range.

As described above, since the power supply circuit (6) of the present invention can obtain a satisfactory dynamic range even when a low current flows, the power supply circuit (6) and the diode bridge circuit (3) are used to connect the telephone line. There is no influence on the reception signal input to the communication circuit (4) connected to the.

(G) Effect of the Invention In the power supply circuit of the present invention, the first resistor is connected between the collector and the base of the power supply transistor, and the bleeder resistor is connected to the connecting portion between the first resistor and the base to supply the power. The voltage between the collector and the base of the power supply transistor is increased by the voltage generated in the first resistance by the bleeder current flowing into the bleeder resistance through the first resistance corresponding to the base potential of the transistor, and the dynamic range of the power supply transistor is increased. Since it can be set, even if the amount of current flowing changes in response to a change in load value, a satisfactory dynamic range can be obtained.
Further, one end of the second resistor is connected to the emitter of the power supply transistor, one end of the capacitor is connected to the base, and the other end of the second resistor is connected to the output terminal portion, so that the current flowing corresponding to the fluctuation of the load value is The change in the amount no longer affects the AC impedance.

[Brief description of drawings]

FIG. 1 is a block diagram of a telephone incorporating an embodiment of a power supply circuit of the present invention, and FIG. 2 is a configuration diagram of a telephone incorporating another embodiment of a power supply circuit of the present invention. Description of main drawing numbers (6) …… Power supply circuit, (7) …… Power supply transistor, (8) …… First resistor, (9) …… Second resistor, (1
1) ... bleeder resistance, (12) ... control circuit.

Claims (1)

[Scope of utility model registration request] 1. A power supply transistor whose collector terminal is connected to a telephone line through a diode bridge circuit,
A first resistor connected between a collector terminal and a base terminal of the power supply transistor, one end of which is connected to a connecting portion between the base terminal of the power supply transistor and the first resistor, and the other end of which is grounded. A bleeder resistor, a second resistor having one end connected to the emitter terminal of the power supply transistor and the other end serving as an output terminal part, and one end connected to the base terminal of the power supply transistor, and the other end connected to the output terminal part. Alternatively, a power supply circuit comprising a capacitor connected to ground.