JPS622308A - Dc constant-voltage power source - Google Patents

Abstract

PURPOSE:To execute a stable operation even if any input smoothing circuit is used, by using a voltage controlled type transistor, and setting a current required for applying a bias voltage to said transistor, so as to be smaller than an idling current of an error amplifying means. CONSTITUTION:When an output voltage between output terminals 13, 14 rises, a part of an output voltage which has been detected by output voltage detecting resistances 5, 6 is compared with a voltage of a Zener diode 7 for reference voltage, and in accordance with its difference, a bias voltage applied between the base and the emitter of a driving transistor 10 decreases. As a result, a collector current I2 decreases and a voltage across a resistance 21 decreases, therefore, a bias volage impressed between the gate and the source of an FET 20 decreases and the impedance between the drain and the source becomes high, a voltage drop increases and an output power drops by its portion, and it is stabilized to a set output voltage. On the contrary, when the output voltage has dropped, the impedance between the drain and the source of the FET 20 becomes low, the voltage drop decreases and the output voltage increases by its portion, and it is stabilized to the set output voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a DC constant voltage power supply, and more particularly to a low loss DC constant voltage power supply.

Prior Art A conventional low-loss DC stabilized power supply has a configuration as shown in FIG. In the figure, 1 is a primary power supply that supplies one power to a low-loss stabilized DC power supply, 2 is an input smoothing circuit, 3 is a series control transistor, 4 is an output smoothing circuit, 5 and 6 are resistors for output voltage detection, and 7 is a A reference voltage Zener diode; 8 is a resistor that limits the current flowing to the reference voltage Zener diode 7; 9 is a part of the output voltage obtained by the output 'α pressure detection resistors 5 and 6 and the reference voltage Zener diode 7; An error amplifier, l, which compares the voltage of
0 is a drive transistor that supplies current to the base of the series control transistor 3; 11 is a resistor that limits the flow of current to the base of the drive transistor 100; 12 is a series control transistor 3;
Resistors 13 and 14 are output terminals for limiting the pace current.

The solicitation will be explained below. When the output voltage between the output terminals 13 and 14 increases, the voltage difference between the output voltage divided by the output voltage detection resistors 5 and 6 and the voltage of the reference voltage Zener diode 7 is amplified, and The drive transistor 10 decreases due to the decrease in Iasumi pressure.
, that is, the pace current 1 of the series control transistor 3 decreases.

As a result, the impedance between the collector and emitter of the series control transistor 3 increases, increasing the voltage drop, and the output voltage decreases by the amount of the fluctuation, and is stabilized at the set output voltage.

Conversely, when the output voltage decreases, the impedance of the series control transistor 3 is low and the voltage drop also decreases, and the output voltage increases by the amount of the fluctuation voltage and is stabilized at the set output voltage.

Next, when the magnetic pressure 1 of the primary power source is decreased, the minimum voltage of the primary power source 1 that maintains the set output voltage V I Nr
n I n can be expressed by the following formula.

VINmtn=Vo+Vcg(mat) ......(
1) Here, vo represents the output voltage between the output terminals 13 and 14, and V CE (m a t ) represents the voltage between the collector and emitter of the series control transistor 3 in the saturated state.

Normally, Vary (sat) 0.5 V@flF) series WIJel 7 transistors are easily available, so (
1) Even if the voltage of the primary power supply 1 is decreased as shown in the formula, the set output voltage can be controlled by only increasing the set output voltage by about 0.5 V, and the series control transistor 3 Power loss can also be reduced.

However, when the voltage of the primary power supply 1 is increased as shown in FIG. Therefore, it can be expressed by the following formula.

x,,, do+(VIN-VBE-VCg(@at
))/1141. +KVIN・・・・・・・・・・・・
・0) Here, Io is the output current, VIN is the voltage of the primary power supply 1,
VBE indicates the voltage between the base and emitter of the series control transistor 30, Ru indicates the resistance value of the control resistor 12, and KVIN indicates the idle link current of the error amplifier 9 depending on the input terminal.

Next, the input undercurrent IINm after the output pressure reaches the set output voltage can be expressed by the following equation.

I IN, = Io + IO/hrg3) + K
VXH...----(3) Here, hpg(3) is the current amplification factor of the series control transistor 0). Also, V
The following equation holds true between the DC amplification factor hpE(5at) at cg(sat) and hrz(3).

hFE(,5at)(hrp(3) −
-・------,,,, (4) (2) In the second (VT
:r −VBE−VcE(sat))/i, fd,
The base space currents of the three series controlled transistors reach saturation (indicated by NRI, ITN, and IINI).
The following equation stands between .

II Marty〉■IN2 '°"K゛°°°°゛°° (5) As explained above, when the voltage of the primary power supply 1 is around MINmln, the input smoothing circuit 2 side looks at the side of the series control transistor 3 side. There are many regions where the impedance shows square resistance, and depending on the impedance of the input smoothing circuit 2,
The conventional constant DC voltage source shown in FIG. 3 has a drawback in that the source oscillates, making it impossible to maintain normal sound performance.

SUMMARY OF THE INVENTION The present invention provides a DC constant voltage power source that can operate stably regardless of the impedance of the input smoothing circuit.

Structure of the Invention The DC constant voltage power supply according to the present invention includes a series control element inserted in series between input and output to share the voltage difference between the input voltage and the output voltage, and detects an error between the output voltage and a reference voltage. and an error amplifying means for generating a control signal according to this error, and the DC constant voltage source is characterized in that the conduction state of the series control element is controlled by this control signal. The problem is that a voltage controlled transistor is used as the series control element, and the current required to apply a bias voltage to this transistor is set to be smaller than the idling current of the error amplification means.

Example Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention, in which 20 is a voltage side leg type transistor (abbreviated as FET), and 21 is an FET2.
Resistance for applying bias voltage to 0, n is FET
In order to limit the bias voltage applied between the gate and source of 20 and keep it below the withstand voltage between the gate and source.
h Zener diode.

The other configurations are the same as those shown in FIG. 43, and their explanation will be omitted.

The operation will be explained below. When the output voltage between the output terminals +EIn3 and 14 rises, a part of the output voltage leaked out by the output voltage detection resistor 5゜6 is compared with the voltage of the Zener diode 7 for the reference voltage a, and the difference is detected. Accordingly, the bias voltage applied between the pace emitter of the drive transistor 10 decreases. As a result, the collector current 2 of the drive transistor 10 decreases and the bottom pressure generated across the resistor 21 decreases, so the bias voltage applied to the gate and source of the FET 20 decreases and the FET 2
The impedance between the drain and north of 0 is high,
As the voltage drop increases, the output pressure decreases by the amount of voltage variation, and is stabilized at the set output voltage.

Conversely, when the output voltage decreases, the bias voltage of the FET 20 increases17, the impedance between the drain and the source decreases, and the voltage drop decreases1. The output voltage increases by the amount of the voltage fluctuation, and is stabilized at the set output voltage.Next, when the primary power supply 1 is increased as shown in Figure 2, the input current II 3 can be expressed by the following formula.

I IN3 = 10 KvxN to I o+...
・・・・・・・・・・・・(6) Here, ■, KE F E T
This is the current required to drive 20. Also, as the voltage of primary power source 1 increases, K'v decreases by 12, K'v
On the contrary, IN increases. Therefore, at least V of the primary power supply 1
T:! : at a voltage value near r+In, and KVIN
Set the relationship as shown below.

I, (KVrw ・・・・・・・・・
(7) By doing this, IrN5 monotonically increases as the voltage of the primary power supply 1 increases in equation (6). This equation (7) can be set by adjusting the internal circuit constants of the amplifier 9, the value of the resistor 21, etc. Figure 2 shows how the input/output current changes with respect to changes in the primary power supply voltage, and as can be seen from the figure, VrNml! This means that the negative resistance region does not appear near 1.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, the primary α source 10-
Since the input current increases and decreases in a monotonous manner as the voltage increases and decreases, stable operation is achieved no matter what type of input smoothing circuit is connected. Therefore, it is possible to design the input smoothing circuit by considering only the circuit operation without considering the impedance value of the input smoothing circuit.

In addition, if the voltage of the primary power supply stabilized to the installed output voltage takes into account the physical properties of the series control elements used,
It has the effect of being extremely low.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is a diagram showing the circuit characteristics of Fig. 1, Fig. 3 is a diagram showing a circuit example of a DC constant voltage power supply since RIK, FIG. 2 is a diagram showing the characteristics of the circuit. Explanation of the symbols of the princess part 1-1st order 'llll1c source 7... Zener diode for reference voltage 9... Error amplifier 20... FET Fig. 1 Voltage of source voltage

Claims (1)

[Claims] A series control element is inserted in series between input and output to share the difference voltage between the input voltage and the output voltage, and detects an error between the output voltage and a reference voltage and generates a control signal according to this error. The DC constant voltage power supply has an error amplification means, and controls the conduction state of the series control element using the control signal, wherein a voltage control transistor is used as the series control element, and a bias voltage is applied to the transistor. A DC constant voltage power supply characterized in that the current required to provide the error amplification means is set to be smaller than the idling current of the error amplification means.