JPH0449345B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a constant voltage device suitable for application to electronic audio equipment mounted on a vehicle, and more particularly to a constant voltage device using a battery as a power source.

BACKGROUND ART AND PROBLEMS The present applicant previously proposed a power supply circuit that can obtain positive and negative voltages by combining a battery and a polarity reversal type DC-DC converter.

By the way, when making the positive and negative voltages of such a power supply circuit constant voltage, it is sufficient to provide a pair of symmetrical series type voltage regulator circuits, but the collector loss of the transistors used in each series type voltage regulator circuit is large. Therefore, a large heat sink is required.

Purpose of the Invention In view of the above, it is an object of the present invention to obtain positive and negative constant voltage outputs having the same absolute value and different polarities, and to reduce the collector loss of the transistor of the series type constant voltage circuit used. This paper attempts to propose a switching type constant voltage device that can perform the following functions.

Summary of the Invention A switching type constant voltage device according to the present invention includes a first series voltage constant circuit connected between a first output terminal and a first electrode of a battery whose second electrode is grounded; A polarity reversal type DC-DC converter connected between the first electrode and ground, and a polarity reversal type
and a second series type constant voltage circuit connected to the output terminal and the second output terminal of the DC-DC converter, and the polarity inversion type DC with the first output voltage from the first output terminal as a reference voltage. -In addition to supplying to the DC converter, polarity inverted DC-
By controlling the output voltage of the DC converter and supplying the output voltage to the input side of the second series type constant voltage circuit, the first and second output terminals are provided with a second output terminal having equal absolute values and different polarities. The first and second output voltages can be obtained.

According to the present invention, positive and negative constant voltage outputs having the same absolute value and different polarities can be obtained, and the output voltage of a series type constant voltage circuit connected to the output side of a polarity inverting DC-DC converter can be obtained. A switching type constant voltage device that can reduce collector loss of a transistor can be obtained.

Embodiment An embodiment of the present invention will be described below with reference to FIG. BT is a battery, and here it is a car battery. Its rated voltage is, for example, 12 volts. However, since this battery BT is a car battery, its voltage varies significantly around 12 volts. The positive pole of battery BT is connected to terminal t ₁ ,
Its negative pole is connected to terminal _t2 . t ₃ and t ₄ are first and second output terminals, and the first and second output voltages from these output terminals t ₃ and t ₄ are, for example, preamplifier 4.
is supplied to In this case the first and second output terminals
The voltages obtained at t ₃ and t ₄ are the voltage E of the battery BT.
When the voltage E is low, the positive and negative output voltages are +V and -V corresponding to the voltage E, but even if the voltage E of the battery BT becomes quite high, the output voltages +V and -V are, for example, below +8.5V and -8.5, respectively. It is designed to be suppressed to more than V.

1 and 2 are symmetrical first and second series type constant voltage circuits, which respectively include NPN transistors Q ₁ and Q ₂ , field effect transistors Q ₃ and Q ₄ for constant current sources, and a Zener diode as a constant voltage element. They have D ₁ and D ₂ respectively.

3 is a polarity inversion type DC-DC converter. Then, the terminal t ₁ is connected to the terminal T ₁ of the converter 3 through the chiyoke coil L ₁ . The common terminal _T4 of converter 3 is grounded. An output terminal T ₃ of the converter 3 is connected to the input side of the second constant voltage circuit 2 through a choke coil L ₂ .

The first constant voltage circuit 1 is inserted between terminals t ₁ and t ₃ . The second constant voltage circuit 2 is inserted between the output terminal T ₃ and the terminal t ₄ of the converter 3. And terminal t ₃
The output voltage +V of the converter 3 is supplied to the control terminal _{T2 of the converter 3 through} a negative feedback resistor R1 to control its output voltage.

In the first and second constant voltage circuits 1 and 2,
The collectors of transistors Q ₁ and Q ₂ are respectively connected to terminal t ₁
and terminal _T3 , and each emitter is connected to terminals _t3 and _t4 . The drains and sources of field effect transistors Q ₃ , Q ₄ whose gates and sources are directly connected are respectively connected to the collectors and bases of transistors Q ₁ , Q ₂ . Diode D ₁ ,
The anode and cathode of D ₂ are grounded and
The cathode of diode D ₁ is connected to the base of transistor Q ₁ , and the anode of diode D ₂ is connected to the base of transistor Q ₂ .

Note that C ₁ and C ₂ are smoothing capacitors connected between terminals t ₃ and t ₄ and ground, respectively.

Next, referring to Figure 2,
The specific configuration of the DC-DC converter 3 will be explained. TR is a transformer and has a primary coil a, a secondary coil b, and a detection coil c. Q ₁₂ is for oscillation
It is an NPN type transistor, its collector is connected to one end of the primary coil a, and its emitter is a common terminal.
Connected to _T4 . The terminal T ₁ is connected to the other end of the primary coil a through a filter F ₁ consisting of a coil L ₁₁ and capacitors C ₁₁ and C ₁₂ . Note that the filter
The cold end side of F ₁ is connected to the common terminal T ₄ . The midpoint of the connection between coil L ₁₁ and a is the resistor
It is connected to the base of transistor _Q12 through a series circuit of _R13 and _R14 . Furthermore, the base of transistor Q ₁₂ is connected to the common terminal T ₄ through a series circuit of resistor R ₁₅ - capacitor C ₁₅ - coil c.

Furthermore, a PNP type transistor Q ₁₁ is provided,
The terminal T 2, whose emitter is connected to the base of the transistor Q ₁₂ and whose collector is connected to the common terminal T _{4 ,} is connected to the base of the transistor Q ₁₁ through a series circuit of resistors R ₁₁ - R ₁₂ .

One end of the secondary coil b of the transformer TR is connected to the cathode of the rectifying diode _D11 , and the other end is connected to the common terminal _T4 through resistors _R17 - _R18 .
Note that C ₁₃ is a smoothing capacitor connected between the anode of the diode D ₁₁ and one end of the secondary coil b. The anode of the diode D ₁₁ is connected to the terminal T ₃ through a filter F ₂ consisting of a coil L ₁₂ and a capacitor C ₁₄
The cold end of the capacitor C ₁₄ connected to the common terminal T 4 is connected to the common terminal T ₄ . Terminal T ₃ is resistor R ₁₉
connected to the base of transistor _Q11 through.

A PNP type transistor Q ₁₄ and an NPN type transistor Q ₁₃ are provided and connected to form an SCR. i.e. transistor Q ₁₄
The base of transistor Q13 is connected to the collector of transistor _Q13 , and the base of transistor _Q13 is connected to the collector of transistor Q13.
Connected to Q ₁₄ collector. The midpoint of the connection between capacitor C ₁₃ and resistor R ₁₇ is connected to the collector of transistor Q ₁₄ through resistor R ₁₆ . The collector of transistor Q ₁₄ is connected to the common terminal T ₄ through a capacitor C ₁₆ . The emitter of transistor Q ₁₃ is also connected to the common terminal T ₄ . transistor Q ₁₃
The collector of transistor Q 14 is connected to the midpoint of connection of resistors R ₁₃ and R _14. The emitter of transistor Q ₁₄ is connected to the resistor
Connected to the connection midpoint of R ₁₁ and R ₁₂ .

First, the operation of the DC-DC converter 3 shown in FIG. 2 will be explained. This converter 3 is a terminal
The voltage available at the output terminal T ₃ is controlled by the reference voltage supplied to T ₂ . First, the transistor
When Q ₁₂ is off, current is supplied to the base of transistor Q ₁₂ through resistor supplies R ₁₃ and R ₁₄ , which turns it on and generates a pulse voltage in the primary coil a of the transformer TR, which causes a voltage pulse in the detection coil c. Also, a pulse voltage is generated, and based on the pulse voltage, a current flows to the base of the transistor Q ₁₂ through a time constant circuit consisting of a capacitor C ₁₅ and a resistor supply R ₁₅ , and the base bias of the transistor Q ₁₂ becomes deeper. The base current becomes progressively smaller, so transistor _Q12 turns off,
The pulse voltage of coil C has opposite polarity. after that,
Transistor _Q12 is turned on again and the above operation is repeated.

On the other hand, transistor _Q11 has a base voltage of 0.
When it becomes larger than the volt, it turns off, and when it becomes smaller, it turns on. When this transistor _Q11 is turned on, the current flowing into the base of the transistor _Q12 from the coil C through the time constant circuit is transferred to the common terminal through the emitter and collector of the transistor _Q11 .
The current flows through T ₄ and transistor Q ₁₂ is immediately turned off at that point. This causes the transformer TR to respond to the reference voltage supplied to terminal _T2 .
The on-period and frequency of the pulse obtained in the secondary coil b of is controlled, thereby controlling the output voltage obtained at the terminal _T3 .

Note that the device operates normally when the voltage at the midpoint between the resistors _R13 and _R14 is higher than the voltage at the midpoint between the resistors _R11 and _R12 .

Also, if the current flowing through the secondary coil b of the transformer TR exceeds a predetermined value, or if the voltage at the midpoint of connection between resistors _R11 and _R12 becomes higher than the voltage at the connection point between resistors _R13 and _R14 , , transistor Q ₁₃ is on, so transistor Q ₁₄ is also on, and the midpoint of the connection of resistors R ₁₁ and R ₁₂ and the resistors R ₁₃ and
The voltage at the midpoint of the tangent of R ₁₂ is the voltage at the common terminal T ₄ ,
That is, it is made to be approximately equal to the ground voltage. Therefore, the oscillation operation of converter 3 is stopped. Note that in order to restart the oscillation operation, the voltage supplied to the terminal _T2 may be set to the ground voltage.

Next, the operation of the constant voltage device shown in FIG. 1 will be explained with reference to FIG. 3 as well. Voltage E of battery BT is +V ₁
(=+8.5V) or lower, the first and second output terminals
The first and second output voltages obtained at t ₃ and t ₄ are approximately equal to +E and −E, respectively. Voltage E of battery BT is +V ₁
(=+8.5V), the first constant voltage circuit 1 operates differentially, and the first output voltage V is suppressed to a constant value of + _V1 . On the other hand, since the control voltage supplied to the control terminal _T2 of converter 3 is also suppressed to + _V1 ,
The voltage obtained at output terminal T ₃ of converter 3 is −
It can be suppressed to V _BM (=-10.5V). The second constant voltage circuit 2 also operates differentially, and the second output voltage -V is suppressed to _-V1 .

In this case, the transistor of the first constant voltage circuit 1
The collector loss of _Q1 is large as shown in the shaded area A in FIG. However, the collector loss of the transistor Q2 of the second constant voltage circuit ₂ is reduced as shown in the shaded area B because its input voltage is suppressed to _-VBM . That is, the collector loss is significantly smaller than the collector loss in region C corresponding to region A. Therefore, the heat sink for transistor _Q2 may be smaller than the heat sink for transistor _Q1 .

Effects of the Invention According to the present invention described above, positive and negative constant voltage outputs having the same absolute value and different polarities can be obtained, and a series type constant voltage output connected to the output side of a polarity reversal type DC-DC converter can be obtained. A switching type constant voltage device that can reduce the collector loss of the transistor in the circuit can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a switching type constant voltage device according to the present invention, FIG. 2 is a circuit diagram showing a specific configuration of the DC-DC converter shown in FIG. 1,
FIG. 3 is a characteristic diagram for explaining the present invention. BT is a battery, 1 and 2 are first and second constant voltage circuits, 3 is a DC-DC converter, and t ₃ and t ₄ are first and second output terminals.

Claims (1)

[Claims] 1. A first series type constant voltage circuit connected between a first output terminal and a first electrode of a battery whose second electrode is grounded, and between the first electrode and ground. and a second series type constant voltage circuit connected between the output terminal and the second output terminal of the polarity reversal type DC-DC converter, The first output voltage from the first output terminal is supplied as a reference voltage to the polarity reversal type DC-DC converter, and the output voltage of the polarity reversal type DC-DC converter is controlled according to the reference voltage. By supplying the output voltage to the input side of the second series voltage regulator, first and second output voltages having equal absolute values and different polarities are applied to the first and second output terminals. A switching type constant voltage device characterized by the following: