JPH0140319Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a power supply circuit that uses a simple circuit configuration to output two types of DC voltage, consisting of the main DC voltage of the main circuit and an auxiliary DC voltage higher than the main DC voltage. Regarding.

Conventionally, power supply circuits applied to video tape recorders, for example, have had to output 12 volts as the main DC voltage, as well as 9 volts and 15 volts as the auxiliary DC voltages, especially in the case of an auxiliary DC voltage of 15 volts. , a small capacity of 0.1 ampere is required.

A conventional power supply circuit that outputs a main DC voltage of 12 volts and an auxiliary DC voltage of 15 volts is configured as shown in Figure 1, with both ends of the primary winding la of the transformer T connected to the AC input terminal ac. . An alternating current voltage of 18 volts is induced across the secondary winding, ie, the auxiliary secondary winding lc. Note that the AC voltage between both ends of the main secondary winding lb is set to 15 volts in consideration of voltage fluctuations.

And the main secondary winding lb via the first fuse _F1
The AC voltage between both ends of the main rectifier circuit 1 is input to the full-wave rectifier type main rectifier circuit 1 consisting of a diode bridge, and the smoothing voltage between the positive and negative DC terminals (+) and (-) of the main rectifier circuit 1 is input to the main rectifier circuit 1 consisting of a diode bridge. 1 main rectifier circuit 1 by capacitor C ₁
The main voltage regulating circuit 2 smoothes the rectified output voltage of the first capacitor _C1 , that is, the DC output voltage, and makes the voltage constant between the first positive output terminal dca and the first reference output terminal dca'. outputs a mains DC voltage of 12 volts. The main circuit 3 is composed of the main rectifier circuit 1, the main voltage regulator circuit 2, the first capacitor _C1 , and the first fuse _F1 , and the first capacitor _C1 has a withstand voltage of 25 volts. .

That is, in the main voltage regulating circuit 2, the first positive output terminal dca is connected to the direct current terminal (+) of the main rectifier circuit 1 via the collector and emitter of the first NPN control transistor Q1, and the main The first reference output terminal is connected to the negative DC terminal (-) of rectifier circuit 1.
dca' is connected, and a first resistor R 1 and a first resistor are connected in series between the first positive output terminal dca and the first reference output terminal dca _' .
A variable resistor VR ₁ and a second resistor R ₂ are provided, and the movable piece of the first variable resistor VR ₁ is connected to the base of a second voltage comparison transistor Q ₂ of NPN type, and the first positive output terminal
A third resistor R ₃ is connected between dca and the first reference output terminal dca'.
and a first Zener diode ZD ₁ are provided, and a main reference voltage consisting of the Zener voltage of the first Zener diode ZD ₁ is applied to the emitter of the second transistor Q ₂ .
The base of a third NPN type Darlington transistor _Q3 is connected to the collector of _Q2 , and the emitter and collector of the third transistor _Q3 are connected to the base and collector of the first transistor _Q1 , respectively, and the first transistor A fourth resistor _R4 for biasing is provided between the collector of _Q1 and the base of the third transistor _Q3 , and the first transistor
_Q1 and the third transistor _Q3 are connected in Darlington, and the first positive output terminal is connected by the second transistor _Q2 .
Detects the voltage fluctuation between DCA and the first reference output terminal DCA', and when the voltage between both terminals DCA and DCA' fluctuates, controls the operation of the first transistor _Q1 via the third transistor _Q3. The voltage fluctuation between both terminals dca and dca' is compensated to stabilize the voltage between both terminals dca and dca'.

Furthermore, the voltage across the auxiliary secondary winding lc is applied to the full-wave rectification type auxiliary rectifier circuit ₄ consisting of a diode bridge via the second fuse F2, and the positive and negative DC terminals of the auxiliary rectifier circuit 4 are The second smoothing capacitor _C2 provided between (+) and (-) smoothes the rectified output of the auxiliary rectifier circuit 4, and the second capacitor C2
The smoothed output voltage of C ₂ is made constant by the auxiliary voltage regulating circuit 5, and an auxiliary current voltage of 15 volts, which is higher than the main DC voltage, is connected between the second positive output terminal dcb and the second reference output terminal dcb'. Output. Note that the second capacitor _C2 has a rated voltage, that is, a withstand voltage of 35 volts or more.

That is, in the auxiliary voltage regulating circuit 5, the second positive output terminal dcb is connected to the direct output terminal (+) of the auxiliary rectifier circuit 4 via the collector and emitter of the fourth NPN control transistor _Q4 . , the second positive output terminal DCB and the second reference output terminal
dcb′, a fifth resistor R ₅ , a second variable resistor VR ₂ , and a sixth resistor R ₆ are provided in series, and the movable part of the second variable resistor R ₂ is connected to an NPN type voltage comparison fifth transistor.
Connect to the base of Q ₅ , and connect the second positive output terminal DCB and the second
A series circuit consisting of a seventh resistor R ₇ and a second Zener diode ZD ₂ is provided between the reference output terminal dcb' and the second
An auxiliary reference voltage consisting of the Zener voltage of the Zener diode ZD ₂ is applied to the emitter of the fifth transistor Q ₅ , and the base of the NPN type Darlington sixth transistor Q ₆ is connected to the collector of the fifth transistor Q ₅ . 6 transistor Q ₆
The emitter and collector of the transistor Q4 are connected to the base and collector of the fourth transistor _Q4, respectively, and the collector of the fourth transistor _Q4 and the collector of the sixth transistor Q4 are connected to each other.
An eighth resistor _R8 for biasing is provided between the base of the transistor _Q6 , and the fourth and sixth transistors _Q4 ,
Q ₆ is connected to Darlington, and the fifth transistor Q ₅
The second positive output terminal DCB and the second reference output terminal
dcb′ is detected, and both terminals dcb,
When the voltage between dcb' fluctuates, the operation of the fourth transistor _Q4 is controlled via the sixth transistor _Q6 , and the voltage fluctuation between both terminals dcb and dcb' is compensated for. stabilize the voltage.

However, in the above case, in order to output an auxiliary DC voltage of 15 volts, it is necessary to induce an AC voltage of 18 volts or more between the ends of the auxiliary secondary winding lc of the transformer T, and the second capacitor It is necessary to use a _C5 with a pressure resistance of 35 volts or higher. moreover,
It is necessary to configure the auxiliary rectifier circuit 4 with a diode bridge and to provide a second fuse _F5 for safety, which has the disadvantage of increasing the number of parts and complicating the circuit configuration, making it large and expensive. .

This invention has been made with the above-mentioned points in mind, and next, this invention will be explained in detail with reference to FIG. 2 showing one embodiment thereof.

In the figure, the same symbols as in Figure 1 indicate the same things, and the difference from Figure 1 is that an AC voltage of 6 volts is induced in the transformer T instead of the auxiliary secondary winding LC in Figure 1. The other secondary winding, i.e. auxiliary 2
In addition to providing a secondary winding ld, the anode of a half-wave rectifier diode D is connected to one end of the auxiliary secondary winding ld, and a withstand voltage of 10 volts is connected between the cathode of the diode D and the other end of the auxiliary secondary winding ld. A third smoothing capacitor _C3 is provided, and a third positive output terminal dcc is connected to one end of the third capacitor _C3 , that is, the cathode of the diode D, through the collector and emitter of the seventh NPN control transistor _Q7 . The collector and emitter of an NPN-type eighth transistor Q ₈ are connected to the collector and base of the seventh transistor Q _{7 ,} respectively, and the seventh and eighth transistors Q ₇ and Q ₈ are connected to each other.
Connect Darlington.

Furthermore, a ninth resistor for biasing is provided between the collector of the seventh transistor _Q7 and the base of the eighth transistor _Q8 , and the eighth transistor
16 between the base of Q ₈ and the first reference output terminal dca′
A third Zener diode ZD ₃ having a Zener voltage of volts is provided, and the other end of the third capacitor C ₃ , that is, the other end of the auxiliary secondary winding ld, is connected to the first positive output terminal dca.
This is the point connected to the seventh and eighth transistors.
An auxiliary voltage regulating circuit 6 is formed by Q ₇ , Q ₈ , the third Zener diode ZD _3, and the ninth resistor R ₉ , and the auxiliary rectifying circuit 4, the auxiliary voltage regulating circuit 5, and the second capacitor C shown in FIG. ₂ , the second fuse _F2 is not provided.

Then, the 6-volt AC voltage E ₁ across the auxiliary secondary winding ld is half-wave rectified by the diode D, and smoothed by the third capacitor C ₃ , so the DC output between the ends of the third capacitor C ₃ Voltage
E ₂ becomes as follows.

E ₂ =√2・E ₁ =√2・6≒8.5 volts Furthermore, the main DC voltage E ₃ between the first positive output terminal dca and the first reference output terminal dca′ is E ₃ =12 volts. Therefore, the DC voltage E ₄ between the cathode of diode D and the first reference output terminal dca' is E ₄ = E ₂ +
E ₃ ≒ 8.5 + 12 = 20.5 volts, and the DC voltage E ₄ is applied to the auxiliary voltage regulator circuit 6, and due to the operation of the auxiliary voltage regulator 6, the third positive output terminal dcc and the first reference output terminal dca' are connected. During this time, it outputs a stabilized auxiliary DC voltage of 15 volts E ₅ .

Therefore, according to the embodiment, the main DC voltage E ₃ of 12 volts between the first positive output terminal dca and the first reference output terminal dca′ and the 8.5 volts DC output voltage E of the third capacitor C _{3 2} , a DC voltage _E4 of 20.5 volts is formed, and the DC voltage _E4 is applied to the auxiliary voltage regulating circuit 6, and the third positive output terminal dcc and the first reference output terminal dca' are connected in series. By outputting an auxiliary DC voltage _E5 of 15 volts between
With a simple circuit configuration, it is possible to output two types of DC voltage, the main DC voltage E ₃ and the auxiliary DC voltage E ₅ , and the number of parts can be significantly reduced, providing a small and inexpensive power supply circuit. When applied to, for example, a video tape recorder, it has a very high practical value.

As mentioned above, according to the power supply circuit of this invention,
A simple circuit can output two types of DC voltage: the main DC voltage of the main circuit and an auxiliary DC voltage higher than the main DC voltage, and it is possible to provide a small, inexpensive power supply circuit with high practical value. It is possible.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram of a conventional power supply circuit, and FIG. 2 is a wiring diagram of one embodiment of the power supply circuit of this invention. 3... Main circuit, 6... Auxiliary voltage regulator circuit, C ₃
...Third capacitor, D...Diode, T...
Transformer, la...primary winding, lb...main secondary winding, lb
...Auxiliary secondary winding.

Claims (1)

[Scope of utility model registration request] A transformer having a primary winding and two secondary windings connected to an AC source, and after converting the AC output of one of the secondary windings to DC, a first voltage regulating circuit a main circuit that outputs a constant voltage as a main DC voltage, a rectifier circuit that rectifies the AC output of the other secondary winding, a capacitor that smoothes the rectified output of the rectifier circuit, and the main DC voltage and the capacitor. a second voltage regulating circuit to which a series composite voltage is applied with the voltage between both ends of the power supply circuit, and the second voltage regulating circuit forms an auxiliary DC voltage higher than the main DC voltage.