JPH0248893Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a stabilized power supply circuit, and in particular to a stabilized power supply circuit that has been improved to prevent the effects of ripples during light loads and decreases in efficiency during heavy loads.

2. Description of the Related Art Conventionally, a stabilized power supply circuit configured as shown in FIGS. 1a and 1b is known as a stabilized power supply circuit widely used in general electronic equipment including audio equipment and the like. That is, a is a transistor that controls the DC input provided via the power transformer T ₁ and the rectifier and smoothing circuit RA ₁ .
Q ₁ , bias resistor R _B1 and voltage regulator diode
The stabilizing circuit SC ₁ including ZD ₁ performs control in an input tracking manner to supply a stabilized DC output to the load R _L1 .

In addition, b is a power transformer T ₂ and a rectifying and smoothing circuit.
The DC input applied via FA ₂ is controlled in an output tracking manner by a stabilizing circuit SC ₂ including control transistors Q ₂ , Q ₃ , bias resistor R _B2 and voltage regulator diode ND ₂ and stabilized by the load R _L2 . It is designed to be able to supply direct current output.

By the way, in such a stabilized power supply circuit, the voltage fluctuation rate of the power transformers T ₁ and T ₂ themselves becomes a problem, and the load R _L1 and R _L2 are reliably stabilized under any conditions due to the difference in weight. It is difficult to obtain DC output efficiently.

In other words, when the load is light, there is not much of a drop in output voltage, that is, a drop in power supply efficiency.
This is because the influence of ripples becomes extremely large.

In addition, when the load is heavy, the power supply efficiency decreases, contrary to the above-mentioned case.

In other words, under heavy loads, the base-emitter voltage V _BE of the control transistors Q ₁ and Q ₂ remains during switching, so the voltage of the constant voltage diode ZD ₁ is set to V _Z and the DC input voltage is set to V _A. This is because when V _Z + V _BE > V _A , the output voltage V _CC becomes V _CC = V _A − V _BE , and a loss equal to V _BE cannot be avoided.

Therefore, this idea was devised in view of the above points, and it has a simple structure and is an extremely good product that has been improved to reliably prevent ripple effects under light loads and decreases in efficiency under heavy loads. The purpose is to provide a stable power supply circuit.

An embodiment of this invention will be described in detail below with reference to the drawings.

That is, in FIG. 2, _T11 is a power transformer whose primary side is connected to AC power sources A and C. The secondary side of this power transformer T ₁₁ is grounded at its midpoint, and its both ends are commonly connected via diodes D ₁₁ and D ₁₂ of the polarity shown in the figure, which constitute the rectifying and smoothing circuit RA ₁₁ . Grounded via capacitor _C11 .

Further, the common connection point of the diodes D ₁₁ and D ₁₂ is connected to the emitter of the main control transistor Q ₁₁ constituting the stabilizing circuit SC ₁₁ .

Here, the collector of the main control transistor Q ₁₁ is grounded through a constant voltage diode ZD ₁₁ with the polarity shown and a resistor R ₁₁ serving as an error detection element in series, and connected in parallel through a capacitor C ₁₂ and a load R _L11 . grounded and its base is a resistor.
Connected via _R12 to the collector of the auxiliary control transistor _Q12 .

Furthermore, the emitter of the auxiliary control transistor _Q12 is directly grounded, and the base is connected to the control signal (or bias voltage) input terminal IN via the resistor _R13 , as well as the error detection transistor _Q13 . connected to the collector.

And this error detection transistor _Q13
has its emitter directly grounded and its base connected to the midpoint between the constant voltage diode _ZD11 and the resistor _R11 .

Therefore, in the above configuration, when the potential of the control signal (or bias voltage) input terminal IN is at an off (low) level, both the auxiliary control transistor Q ₁₂ and the main control transistor Q ₁₁ are in the cut-off state. In, power transformer T ₁₁
The entire stabilizing circuit SC ₁₁ becomes inoperative so that the DC input led out to the indicated point via the rectifying and smoothing circuit RA ₁₁ is not led out to the indicated point on the output side.

Next, when the potential of the control signal (or bias voltage) input terminal IN is on (high) level, both the auxiliary control transistor Q ₁₂ and the main control transistor Q ₁₁ are on, and a direct current is drawn to the point shown in the figure. The overall operating state of the stabilizing circuit SC ₁₁ is such that the input is guided to the illustrated point on the output side with a control operation as will be described later.

In this case, when the load R _L11 is a light load, that is, in a range where the output current _{I 0} is small, as shown in FIG. In this state, the potential is lowered by the emitter-collector voltage V _CE of the control transistor Q ₁₁ and is almost equal to the point potential. However,
In this case, the potential at that point becomes V _Z [ZD ₁₁ ] + V _BE [Q ₁₃ ] due to the action of the voltage regulator diode ZD ₁₁ and the action of the error detection transistor Q ₁₃ through the auxiliary control transistor Q ₁₂ . Thus, the emitter-collector voltage V _CE of the main control transistor is controlled. In other words, due to the control operation by such a feedback loop, the output voltage V _CC at light load becomes V _Z as shown in the linear region A in Fig. 3.
It is stabilized to a predetermined value within the range of [ZD ₁₁ ]+V _BE [Q ₁₃ ]<V _A , and the ripple component is removed so as not to have any influence.

In addition, when the load R _L11 is a heavy load, that is, _in a range where _the output current _{I 0} is _large , _the voltage regulator diode _{ZD 11} stops operating, the output voltage from the control transistor Q ₁₁ becomes V _CC V _CC =V _A −V _CE [Q ₁₁ ]. Here, since V _CE <V _BE , the loss can be reduced by V _BE −V _CE compared to the conventional case, and the power supply efficiency can be improved accordingly.

In other words, the above-described stabilized power supply circuit can prevent the effects of ripples during light loads, thereby avoiding undesirable situations such as modulation caused by ripple components when an oscillator is used as a load, for example. becomes possible. In addition, since a good stabilizing effect is provided during light loads, it is possible to exert an overvoltage protection effect on the parts used on the load side.

These effects are more than fully demonstrated, especially when applied to audio equipment, in part because they can improve the effects of power supply hum. In addition, it can also contribute to stabilizing the voltage applied to the voltage variable capacitance diode for tuning, especially in synthesizer tuners and the like.

It goes without saying that this invention is not limited to the embodiments described above and illustrated, and that various modifications and applications can be made without departing from the gist of this invention.

Therefore, as detailed above, this invention has a simple structure and is improved to reliably prevent ripple effects under light loads and decreases in efficiency under heavy loads, resulting in extremely good stability. It becomes possible to provide an integrated power supply circuit.

[Brief explanation of the drawing]

Figures 1a and b are configuration explanatory diagrams showing a conventional stabilized power supply circuit, Figure 2 is a configuration explanatory diagram showing an embodiment of the stabilized power supply circuit according to this invention, and Figure 3 is the function of Figure 2. FIG. 2 is a voltage-current characteristic curve diagram for explaining. T ₁₁ ... Power transformer, RA ₁₁ ... Rectifier and smoothing circuit, D ₁₁ , D ₁₂ ... Diode, C ₁₁ , C ₁₂ ... Capacitor, SC ₁₁ ... Stabilization circuit, Q ₁₁ ... Main control transistor, R ₁₁ ~ R ₁₃ ... Resistor, ZD ₁₁ ... Constant voltage diode, R _L11 ... Load, Q ₁₂ ... Auxiliary control transistor, Q ₁₃ ... Error detection transistor.

Claims (1)

[Scope of utility model registration request] A main control transistor whose emitter and collector are respectively connected to a DC input side that provides a predetermined DC input potential and a DC output side that provides a predetermined DC output potential, and a DC output side of this main control transistor and a reference potential point. A constant voltage diode and an error detection element connected in series between them, and an error detection transistor whose base is connected to the connection midpoint between the constant voltage diode and the error detection element and whose emitter is connected to a reference potential point. and,
An auxiliary control transistor is provided, the base of which is connected to the collector of the error detection transistor, and whose emitter and collector are connected to a reference potential point and the base of the main control transistor, and the auxiliary control transistor is controlled by an external control signal. In addition to selectively turning on and off, when the load connected to the DC output side is light, the DC output potential is the sum of the constant voltage by the constant voltage diode and the base-emitter voltage of the error detection transistor. The stabilized voltage is obtained by removing the ripple component appearing on the DC input side, and the DC output potential changes from the DC input potential to the collector voltage of the control transistor under heavy load.
A stabilized power supply circuit characterized in that it is configured such that the voltage is obtained by subtracting the voltage between the emitters and the power supply efficiency is improved.