JPS622309A - Regulated power supplying circuit - Google Patents

Abstract

PURPOSE:To reduce extremely a variation of an output voltage difference against a temperature change by setting a temperature coefficient of one of the second and the third Zener diodes so as to be negated each other with the first emperature coefficient, and also selecting a temperature coefficient of the other to zero. CONSTITUTION:The respective temperature coefficients of Zener diods 5-7 are selected to -2-mV/ deg.C, 0, and +2mV/ deg.C. In this case, when voltages outputted from output terminals 11, 13 denoted as V1 and V2, and their differ ence is denoted as V, a drift by a temperature (t) of V1, V2 and V becomes DELTAV1/DELTAt=-2mV+0+(+2mV)=0, and also, becomes DELTAV2/DELTAr+0-(-2mV) + (-2mV)=0. Accordingly DELTAV/DELTAt=22mv-(-2mC)=9. In this way, as for the voltage V1, V2 outputted fromk terminals 11, 13 of a regulated power supplying circuit 1, and their difference V(=V1-V2) a drift by a tmeperature becomes extremely small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stabilized power supply circuit mainly consisting of a Zener diode and a transistor.

[Prior Art] A conventional stabilized power supply circuit of this type includes a main transistor for control inserted between input and output, a sub-transistor for control that controls this main transistor, and a detection voltage proportional to the voltage on the output side. It is known that the output voltage is stabilized by controlling a sub-transistor for control using the comparison output of the comparator, and a comparator that compares the voltage with a reference voltage set by a Zener diode.

[Problems to be Solved by the Invention] However, such conventional stabilized power supply circuits not only have a complicated circuit configuration, but also do not sufficiently compensate for temperature changes, and the output voltage fluctuates due to temperature changes. The problem was that it was large.

The present invention was made in view of the above-mentioned problems.

It is an object of the present invention to provide a stabilized power supply circuit which has an extremely simple circuit configuration and whose variation in output voltage difference with respect to temperature changes is extremely small.

[Means for Solving the Problems] A stabilized power supply circuit according to the present invention includes first, second, and third Zener diodes inserted between a DC power supply terminal and ground via a first resistor, and an emitter base. The main body is a pnp type transistor connected in parallel between the cathode and anode of the first zener diode through a second resistor and whose collector is grounded, and the first zener diode and the emitter and base of the transistor The second resistor is characterized in that the rate of voltage fluctuation with respect to temperature change is approximately the same, and a constant differential voltage is output from both ends of the second resistor.

[Embodiment] FIG. 1 shows an embodiment of the present invention. In this figure, (1) is a stabilized power supply circuit, and (2) is a DC level shift circuit. The stabilized power supply circuit (1) is constructed in several ways. That is, the +24V DC power supply terminal (3) is grounded via the first resistor (4) and the first, second, and third Zener diodes (5), (6), and (7). The first, second, and third Zener diodes (5>
(6) and (7) each have a temperature coefficient of approximately -2mV/
'Cl0n+V/'C1+2mV/°C, and Zener voltages of approximately 3.9V, 6.8V, and 5.6V are used.The cathode side of the first Zener diode (5) is connected to a second resistor. (8), and is connected to the anode side via the emitter and base of the pnρ type (first transistor), and the collector of the first transistor (9) is grounded.The first Zener diode (5) The cathode side (that is, one end side of the second resistor (8)) is connected to the first voltage output terminal (11) via the smoothing capacitor (1o).
The emitter side of the first transistor (9) (that is, the other end side of the second resistor (8)) is connected to the second voltage output terminal (13) via a smoothing capacitor (12). .

The DC level shift circuit (2) mainly includes an npn type second transistor (14) and a pnp type third transistor (15) that constitute a first stage and a second stage amplifier circuit connected to the subsequent stage. It consists of: The collector of the second transistor (14) has a resistance (Ra) of 3.3Ω.
t) to the first voltage output terminal (11), and its emitter is grounded via a resistor (Rat) of 3.3Ω. The base of the third transistor (15) is connected to the collector of the second transistor (14),
The emitter is connected to the second voltage output terminal (13) via a 1kΩ resistor (R+32), and the collector is grounded via a 1Ω resistor (Rc2).

(16) is a vertical oscillation IC that generates a sawtooth wave voltage of a predetermined frequency (60Hz) in synchronization with a vertical synchronization signal sent from a synchronization separation circuit (not shown).
The output side of (16) is pnρ of the vertical drive circuit (17)
The emitter of this fourth transistor (18) is connected to the +12V DC power supply terminal (2o) via a 3.9Ω resistor (19), and the collector is grounded. The emitter of the fourth transistor (18) is connected to a 33μF/L6V coupling capacitor (21) and a 3.3Ω resistor (2
2) to the base of the second transistor (14) of the DC level shift circuit (2).

The third transistor (
The collector of 15) is connected to the input side of a general-purpose vertical output IC (24), and the output side of this vertical output IC (24) passes through a vertical deflection coil (25), a capacitor (26), and a resistor ( 27). The connection point between the vertical deflection coil (25) and the capacitor (26) is connected to the DC level shift circuit (2) via a DC component negative feedback circuit (31) consisting of resistors (28) (29) and a capacitor (30). The connection point of the capacitor (26) and the resistor (27) is connected to the base of the second transistor (14) of the resistor (32) (33) and the capacitor (3
4) of the second transistor (14) of the DC level shift circuit (2) through the AC component negative feedback circuit (35) consisting of
) is connected to the base.

Next, the operation of the above embodiment will be explained. first.

The operation of the stabilized power supply circuit (1) will be explained.

Generally, the Zener voltage Vz (V) of a Zener diode
and the temperature coefficient γ (mV
/"C) is as shown in Figure 2. Therefore, the voltages output from the first and second voltage output terminals (11) and (13), respectively, are V□ and V2, and the difference between them is Assuming that V is V, these are expressed by the following formula.

V 1 =VzI +Vz2 +Vz3 (1
)V 2 =V I Vz 1 + Vbe
(2) V=Vt V2=VZI Vbe
(3) Kokote, Vzl, Vz2, Vz3 are the first and second
, the Zener voltage of the third Zener diode, and Vbe represent the base-emitter voltage of the first transistor (9).

Said v1, V2. Considering the drift of V due to temperature (shi), ', -2mV 10 + (+2mV) 20 ... (4) : O - (-2mV) + (2mV) = 0 ... (5) Δt
Δt Δ to valve -2mV (-2mV
) =0...(6) Above (4)
(5) From equation (6), the first of the stabilized power supply circuit (1),
Voltages V1 and v2 output from the second voltage output terminals (11) and (13) and the difference voltage V (=Vt V2
) has extremely small fluctuations (drift) due to temperature.

Next, (1) the bouncing prevention operation will be explained. D
The DC voltage level at point a on the input side of the C level shift circuit (2) is Va, the DC voltage level at point b on the output side is vb, and the vertical deflection coil ( 25) and the capacitor (26) is Vc, the DC voltage level down rate of the DC level shift circuit (2) is Ld, and the vertical output IC (2
4) and the DC voltage amplification factor by the negative feedback circuits (31) and (35) is set to 12. Therefore, if Ld is set to 176, V c
/Va=2, and even if Va fluctuates during channel switching, the Vc fluctuation is only affected by about twice, and bouncing can be kept to a minimum. Note that in the conventional example where the DC level shift circuit (2) is not used and point a is connected to point b, when Va fluctuates, Vc fluctuates by 12
It had become twice as big, and the bouncing was getting bigger.

Specifically, according to equations (1) and (2), V 1 =16
．． 3 (V), V 2 = 13.1 (V), so
Rc 1 = Re 1 = 3.3 (KΩ), Rc 2
= Re 2 = 1 (KΩ), then Va=5
6 (V), Vb=1 (V), and Vc=12 (V), resulting in Vc/Va -1215,6',2.

Next, the operation of the DC level shift circuit (2) will be considered in more detail. The collector current, collector voltage, and base-emitter voltage of the second transistor (14) are Ic
l, Vc H-Vbe t, and the third transistor (1
5) collector current and base-emitter voltage as Ic2,
When Vbe2 is set, the following formula holds true.

Vcl = Vl - Re I I c 1 -
(9) Since Vb = Rc 2 I C2 - ('11), if Ic1, Ic2, and Vcl are deleted from these equations and rearranged, the following is obtained. Here, Re1 = Re, Rc2 = Re2
Then, equation (12) becomes as follows.

Vb=Va (VI V2) (Vbel+Vbe
2) ...(13) That is, the DC voltage level dropped by the DC level shift circuit (2) is (VI
V2) and (Vbct + Vbe 2 ). According to the above equation (3), V, -V2 (=V) has zero temperature drift, so from the above equation (13), vb is the power supply voltage (Vl,
V2) is not affected by temperature drift. In addition, from the above formula (13), if you want to set V a = 5 (V), if Vbe1 and Vbe2 are each 0.7V, by setting -vt-v2 to 2.6 (V), r,
Obtain Vb=l(V) (i.e. Ld=Vb/Va=1
15).

In the embodiment described above, the temperature coefficient of one of the second and third Zener diodes is selected so as to cancel out the temperature coefficient of the first Zener diode, and the temperature coefficient of the other is selected to be approximately zero. Fluctuations due to temperature changes in the voltages (Vl, V2) output from each of the two voltage output terminals are suppressed to an extremely small level, and the difference between these voltages V (=V□
-V 2 ) due to temperature changes is kept extremely small; however, the present invention is not limited to this, and the emitter of the first Zener diode and the first transistor
By making the voltage fluctuation rate with respect to temperature change substantially the same as that of the base, fluctuations in the voltage difference V (=Vt V2) output to the first and second voltage output terminals with respect to temperature change can be kept extremely small. Good to have.

[Effects of the Invention] Since the stabilized power supply circuit according to the present invention is configured as described above, it has an extremely simple circuit configuration.

Fluctuations in the output voltage difference VI=Vt V2) due to temperature changes can be suppressed to an extremely small level.

Further, it is assumed that the voltage fluctuation rate of either one of the second or third Zener diodes and the first Zener diode with respect to temperature changes cancels each other, and the voltage fluctuation rate of the other Zener diode with respect to temperature change is approximately When it is set to zero, the voltage difference v (= V 1V
2) In addition to this, the rate of voltage fluctuation with respect to temperature change of each of the individual voltages v1 and v2 can be made extremely small.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing one embodiment of a stabilized power supply circuit according to the present invention, and FIG. 2 is a characteristic diagram showing general characteristics of a Zener diode. (1)...Stabilized power supply circuit, (3)...DC power supply terminal, (4)...First resistor, (5)...First Zener diode, (6)...Second Zener diode, (
7)...Third Zener diode, (8)...Second
Resistor, (9)...transistor.

Claims (2)

[Claims] (1) First, second, and third Zener diodes inserted between a DC power supply terminal and ground via a first resistor, and an emitter/base connected to the cathode and anode of the first Zener diode via a second resistor. The first Zener diode and the emitter/base of the transistor have substantially the same voltage fluctuation rate with respect to temperature change, and the A stabilized power supply circuit characterized in that a constant voltage difference is output from both ends of a second resistor. (2) The voltage fluctuation rate of either one of the second or third Zener diodes and the first Zener diode with respect to temperature changes cancels each other, and the voltage fluctuation rate of the other Zener diode with respect to temperature changes cancels each other out. The stabilized power supply circuit according to claim 1, which is substantially zero.