JPS6219052Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is applicable, for example, to devices such as television receivers that operate on dual-purpose AC and DC power supplies, which have both an AC power input socket and a DC power input socket due to the specifications of the equipment. Regarding AC/DC dual power supply circuits that prioritize operation of AC power supplies even when both AC and DC power supplies are connected at the same time, we particularly aim to protect the load by preventing abnormal increases in output voltage. It is an object of the present invention to provide an AC/DC power supply circuit that can be used for both AC and DC functions, does not require a mechanical AC/DC changeover switch, and can also be expected to have a simplified circuit configuration.

Embodiments of the AC/DC power supply circuit of this invention will be described below with reference to the drawings. The figure is a circuit diagram showing one embodiment. This invention has an AC power system and a DC power system, and the case of the AC power system will be explained first. _P1 in the figure is an AC power input socket, which is connected to an AC power source (not shown) when the AC power source is used. This AC power input socket _P1 is connected to both ends of the primary winding TIP of the isolation transformer _T1 via a power switch _S1 . Both ends of the secondary winding TIS of the isolation transformer _T1 are connected to both input ends of a bridge rectifier circuit including rectifying diodes _D1 to _D4 .

The negative output terminal of this bridge rectifier circuit is grounded. Its positive output end is grounded via a smoothing capacitor _C1 , and is also connected to the collector of a transistor _Q1 . Transistor _Q1 is a control transistor for the series regulator. A resistor _R1 is connected between the collector and base of this transistor _Q1 , and the emitter is connected to one end of a load L through a diode _D5 for preventing backflow. The other end of the load L is grounded.

A connection point between the diode _D5 and the load L is grounded through a Zener diode _D6 , a resistor _R2 , a variable resistor _R3 , and a resistor _R4 connected in series. Variable resistor R ₃ and resistance
The base of transistor Q ₂ is connected to the connection point with R ₂ . The collector of this transistor Q ₂ is connected to the transistor Q ₁ through a block diode D ₇ .
connected to the base of. The Zener diode D ₆ , resistor R ₂ , variable resistor R ₃ , resistor R ₄ , and transistor Q ₂ form an error detection and amplification circuit.

Next, the configuration of the DC power supply system will be explained.
_P2 is a socket for DC power input, and as shown in the figure, there is a (+) terminal and a (-) terminal with a different shape.
It has a terminal. The (-) terminal is grounded, and the (+) terminal is connected to the line via power switch _S2 .
l Connected to ₁ . The power switch _S2 is designed to operate in conjunction with the power switch _S1 .

Line l ₁ is connected to ground through capacitor C ₂ and diode D ₈ . The connection point between capacitor C ₂ and diode D ₈ is connected to connection point J ₁ through diode D ₉ . Connection point _J1 is the oscillation circuit
Connected to OSC. This oscillation circuit OSC is designed to oscillate a rectangular wave signal A and output it to the base of the transistor _Q3 . transistor
The emitter of Q ₃ is grounded, the collector is connected to the above connection point J ₁ through resistor R ₅ , and
Connected to the base of transistor Q ₄ through capacitor C ₃ . Transistor Q ₃ , Resistor R ₅ ,
A buffer circuit is formed by the capacitor _C3 .

The base of transistor Q ₄ is connected to ground through resistor R ₆ and also connected to block diode D _10.
is connected to the collector of the transistor _Q2 above. The emitter of transistor Q ₄ is connected to connection point J ₂ . Connection points J ₁ and J ₂ are directly connected, and connection point J ₂ is grounded via capacitor C ₄ . The collector of this transistor Q ₄ is a resistor
It is grounded via R ₇ and R ₈ in series. A waveform shaping circuit is formed by transistor Q ₄ , resistors R ₆ to R ₈ , and capacitor C ₄ .

The connection point between resistors R ₇ and R ₈ is connected to the base of transistor Q ₅ . The emitter of the transistor _Q5 is grounded, and the collector is connected to the connection point _J3 via the primary winding _T2P of the transformer _T2 . A drive circuit is formed by this transistor _Q5 and transformer _T2 . Furthermore, the connection point _J3 is grounded via a capacitor _C5 . Between the connection point J ₃ and the line l ₁ there is a capacitor C ₆ and a diode
A series circuit with D ₁₁ is formed. The connection point between this capacitor C ₆ and diode D ₁₁ is a diode
It is grounded via D ₁₂ .

A series circuit of a resistor _R9 and a diode _D13 is connected between the base of the transistor _Q5 and the emitter of the transistor _Q1 . This series circuit is created by connecting an AC power source to the AC power input socket _P1 and a DC power source to the DC power input socket _P2 , and when both the AC power source and the DC power source are connected, as will be described later. This is for stopping the operation of the DC-DC converter (hereinafter referred to as DC-DC converter) and preferentially operating only the series regulator in the AC power supply system.

One end of the secondary winding T ₂ S of the transformer T ₂ is grounded, and the other end is connected to the base of the output transistor Q ₆ . The emitter of this output transistor _Q6 is grounded and the collector is connected to the converter transformer.
Through the primary winding T ₃ of T ₃ P, it is connected to the line l ₁ . One end of the secondary winding T ₃ S of the converter transformer T ₃ is grounded, and the other end is connected to the rectifier diode D ₁₄
and grounded via smoothing capacitor _C7 . A connection point between the capacitor _C7 and the diode _D14 is connected to one end of the load L. Thus, the output transistor Q ₆ , the converter transformer
A conversion section is formed by T ₃ , diode D ₁₄ , and capacitor C ₇ , and includes an oscillation circuit OSC buffer circuit,
Along with waveform shaping circuit and drive circuit, DC-DC
A converter is formed.

The other end of the secondary winding T ₃ S of the converter transformer T ₃ is grounded via a diode D ₁₅ and a capacitor C ₈ . Diode D ₁₅ is connected to this secondary winding T ₃ S
The capacitor _C8 is for smoothing the rectified voltage. The connection point between capacitor C ₈ and diode D ₁₅ is resistor R ₁₀
It is connected to the connection point J ₂ through the resistor R 11 and to the connection point J ₃ through the resistor R ₁₁ . The rectifying and smoothing circuit made up of the diode _D15 and capacitor _C8 prevents unnecessary circuits from operating when AC power is used, thereby reducing power consumption.

Next, the operation of the AC/DC power supply circuit of this invention constructed as described above will be explained. First, the case when using an AC power source will be explained. When using an AC power source, the AC power source is connected to the AC power input socket _P1 . Next, turn on the power switch _S1 . In conjunction with this, the power switch _S2 is also turned on, but since no DC power source is connected to the DC power input socket _P2 , it has no bearing on the operation of the DC power system.

Now, as described above, by turning on the power switch _S1 , the voltage from the AC power source is transformed by the isolation transformer _T1 , and then double-wave rectified by the bridge rectifier circuit consisting of diodes _D1 to _D4 . . This double-wave rectified voltage is smoothed by a capacitor C ₁ and then applied to the collector of a transistor Q ₁ for controlling the series regulator. The DC voltage regulated by this transistor _Q1 is applied to the load L through the diode _D5 .

On the other hand, when using a DC power supply, the DC power supply is connected to the DC power input socket P ₂ , and the power switch is turned off.
Turn on _S2 . When the power switch _S2 is turned on, the power switch _S1 is also turned on, but since the AC power supply is not connected to the AC power input socket _P1 at this time, it has no relation to the AC power system. When the power switch _S2 is turned on, the DC power supply system starts up, and at the time of startup, the voltage of the DC power supply is applied to _{the line l1 through} the power switch S2. This voltage charges capacitors C ₂ and C ₆ .

The charging current of the capacitor _C2 is supplied to the oscillation circuit OSC through the diode _D9 and the connection point _J1 , and this oscillation circuit OSC starts the oscillation operation and outputs the rectangular wave signal A.
occurs. At the same time, the charging current of the capacitor C ₂ is applied to the collector of the transistor Q ₃ through the diode D ₉ , the connection point J ₂ , and the resistor R ₅ , and is also applied to the collector of the transistor Q ₄ at the connection point.
It is supplied through J ₁ and J ₂ . As a result, both the buffer circuit mainly composed of transistor _Q3 and the waveform shaping circuit mainly composed of transistor _Q4 are activated. Therefore, the rectangular wave signal A from the oscillation circuit OSC is applied to the base of the transistor Q ₄ via the transistor Q ₃ and the capacitor C ₃ .

In addition, the charging current of the capacitor C ₆ is connected to the diode D ₁₁ , the connection point J ₃ , and the primary winding T ₂ P of the transformer T ₂
It is added to the collector of transistor _Q5 through the transistor Q5, and the drive circuit mainly composed of this transistor _Q5 is also activated. Therefore, the rectangular wave signal applied to the base of transistor Q ₄ of the waveform shaping circuit is applied from the collector of transistor Q ₄ to the base of transistor Q ₅ , and transistor Q ₅ outputs output transistor Q ₆ through transformer T ₂ . Drive. The output transistor _Q6 performs a switching operation in response to a rectangular wave signal applied from the transistor _Q5 via the transformer _T2 . Thereby, a square wave voltage is generated in the secondary winding T ₃ S of the converter transformer T ₃ .

This square wave voltage is rectified by diode _D15 ,
After being smoothed by the capacitor _C8 , it is applied to the oscillation circuit OSC through the resistor _R10 , and is also applied from the connection point _J1 to the collector of the transistor _Q3 of the buffer circuit through the resistor _R5 . Furthermore, it is also applied to the emitter of transistor _Q4 of the waveform shaping circuit from connection point _J2 . Therefore, the capacitor
These operations can continue even after charging of C ₂ and C ₆ is completed. And converter transformer T ₃ no 2
The square wave signal induced in the next winding T ₃ S is a diode
After being rectified by _D14 and smoothed by capacitor _C7 , it is supplied to load L. In this way,
Power is also supplied to the load L when using the DC power supply.

As mentioned above, when using a DC power supply, at startup, the charging current of capacitors C ₂ and C ₆
The oscillation circuit OSC, the buffer circuit of transistor Q ₃ , the waveform shaping circuit of transistor Q ₄ , and the drive circuit of transistor Q ₅ are operated, and after startup, the output voltage of the converter transformer of the DC-DC converter is connected to diode D ₁₅ and capacitor C _8. Since each circuit is operated at a constant voltage, stable operating characteristics can be obtained. In addition, since the voltage applied to these circuits is a constant voltage, it is possible to design the circuits so that the power can be used with maximum efficiency.

Also, dare to add diode D ₁₅ and capacitor C ₈
The reason why the rectifying and smoothing circuits are provided separately is to avoid operating unnecessary circuits when using an AC power source, thereby making it possible to reduce power consumption.

Next, the operation of the error detection and amplification circuit portions using the Zener diode D ₆ , resistor R ₂ , variable resistor R ₃ , resistor R ₄ , and transistor Q ₂ will be explained. First, when using an AC power supply, the load L
The error in the voltage on the emitter side of the transistor Q ₁ applied across the zener diode D ₆ and the resistor R ₂
It is detected and amplified by variable resistor R ₃ , resistor R ₄ , and transistor Q ₂ . this transistor
The error signal amplified by _Q2 is applied to the base of transistor _Q1 through block diode _D7 to control the base current of transistor _Q1 . As a result, the operating resistance between the collector and emitter of transistor _Q1 changes, and the voltage drop between the collector and emitter changes. Therefore, a constant voltage is applied to the load L, and the transistor
Activate Q ₁ to control the series regulator.

Furthermore, when using a DC power supply, the ratio of the conduction period to the non-conduction period of the output transistor _Q6 , that is, the duty ratio, is maintained so that the output voltage of the DC-DC converter is constant.
In other words, the rectangular wave voltage appearing at the collector of the transistor Q ₃ is differentiated by a time constant due to the resistance of the capacitor C ₃ and the sum of the resistance R ₆ and the operating resistance between the collector and emitter of the transistor Q ₂ . , changes the signal applied to the base of transistor _Q4 of the waveform shaping circuit. As a result, the ratio of the conduction period to the non-conduction period of the transistor Q ₅ and the output transistor Q ₆ of the drive circuit changes, thereby making the voltage applied across the load L constant.

More specifically, as the voltage across the load L changes, the collector of the transistor _Q2
The operating resistance between emitters changes. Accordingly, the differential time constant with respect to capacitor _C3 changes, and the duty ratio of transistor _Q4 can be changed. Therefore, the duty ratio of the transistor Q ₅ and the output transistor Q ₆ can be changed.

In this way, when operating on either an AC power supply or a DC power supply, by sharing the error detection and amplification circuits described above, it has the advantage of streamlining by reducing the number of parts and reducing the output voltage adjustment man-hours. be.

By the way, in the AC/DC power supply circuit of this invention, an AC power input socket P ₁ and a DC power input socket P ₂ are provided. DC power source (e.g. rechargeable storage battery) connected to ₂
If you want to charge the battery using an AC voltage rectifier circuit, for example, you would connect both the AC power source and the DC power source at the same time and charge by switching the circuits.

In the dual AC/DC power supply circuit as described above,
Even if both an AC power source and a DC power source are connected, if the power switches S ₁ and S ₂ are turned on without the series circuit of resistor R ₉ and diode D ₁₃ , the following problem will occur. In other words, if you connect both AC and DC power supplies, it will become a series regulator.
Both DC-DC converters operate at the same time, and the output voltage at this time is always higher than normal. In other words, it is almost impossible to always keep the potentials on the anode sides of block diodes D ₇ and D ₁₀ the same (for example, a DC voltage with a pulse voltage superimposed is applied to the anode side of block diode D ₁₀ , (DC voltage is applied to the anode side of diode _D7 ), one of both block diodes _D7 and _D10 is always turned off.

If block diode _D7 were to turn off, the series regulator would be in an uncontrolled state, and transistor _Q1 would be saturated with the base current supplied from resistor _R1 . Therefore, the output voltage of the series regulator, ie the voltage between the emitter of transistor _Q1 and ground increases. Furthermore, when the block diode _D10 is turned off, the rectangular wave voltage appearing at the collector of the transistor _Q3 is differentiated only by the capacitor _C3 and the resistor _R6 , so the conduction period of the output transistor _Q6 becomes longer. The output voltage of the DC-DC converter, ie, the voltage across capacitor _C7 , increases.

In this way, when the output voltage of both the AC power system and the DC power system increases, the power consumption of the load L increases, so in the worst case, the load L
will end up malfunctioning. In order to deal with this problem, conventional methods have been used in which an AC-DC changeover switch is installed, and when the AC power supply is connected, the AC-DC changeover switch is automatically switched so that the DC power supply is not connected. Ta. However, many of these AC/DC changeover switches are mechanically connected to the AC power source before the switch is switched, as is the standard specification currently in use. In this case, do not completely insert the AC-DC changeover switch into the AC power input socket and DC power input socket, and connect the AC power supply and DC power supply to the AC power input socket and DC power input socket, respectively. Turning on switches S ₁ and S ₂ causes the problem described above.

Therefore, in this invention, we solved the above problem by reducing the resistance R ₉ without using a mechanical switch.
This is handled by using a series circuit consisting of a diode _D13 and a diode D13. That is, by using this series circuit, even if an AC power source is connected to the AC power input socket _P1 and a DC power source is connected to the DC power input socket _P2 , the DC-DC converter will not operate. Only series regulators work. In other words, the output voltage appearing at the emitter of transistor Q ₁ is connected to resistor R ₉ and diode
It is applied to the base of the transistor Q ₅ of the drive circuit through a series circuit with D ₁₃ . As a result, a base current flows that saturates this transistor _Q5 , and the transistor _Q5 becomes saturated. This makes it impossible to supply base current to _the output transistor Q ₆ , which stops switching and switches the converter transformer.
The square wave output voltage on the secondary side of T ₃ disappears. As a result, not only the load L but also the supply of power supply voltage to each DC-DC converter circuit is stopped, so the DC-DC converter circuit will never operate.
It also does not consume unnecessary power.

Further, the series circuit of resistor R ₉ and diode D ₁₃ is connected between the collector of transistor Q ₁ and the base of transistor Q ₅ , between the emitter of transistor Q ₁ and the base of transistor Q ₃ , and between the collector of transistor Q ₁ and the base of transistor Q ₃ . A similar effect can be obtained even when the bases are connected.

As described in detail above, according to the AC/DC dual-purpose power supply of this invention, when an AC power source is connected to the AC power input socket, the voltage of this AC power source is rectified and smoothed, and then passed through a series regulator to regulate the voltage. In addition to applying a DC voltage to the load as a voltage, if a DC power supply is connected to the DC power input socket, the oscillation circuit is operated at startup, and the rectangular wave signal obtained from the output terminal is sent to the buffer circuit. , the output transistor performs a switching operation through the waveform shaping circuit and the drive circuit to induce a rectangular wave voltage on the secondary side of the converter transformer, and this induced voltage is rectified to create an oscillation circuit, a buffer circuit, a waveform shaping circuit, and a drive circuit. In addition to applying DC-DC to the front stage of the converter as the operating voltage, the output voltage of the converter transformer is rectified and supplied to the load. power can be supplied.

In addition, a series circuit of a resistor and a diode is connected between the input side or output side of the transistor for controlling the series regulator and the front stage of the DC-DC converter, and both AC and DC power sources are connected. If the DC-DC
Since the converter is deactivated and the AC power supply system is activated preferentially, it is possible to prevent abnormal increases in the output voltage and protect against damage to the load, as well as to prevent mechanical AC-DC This eliminates the need for a changeover switch and has excellent effects such as simplifying the circuit configuration.

[Brief explanation of the drawing]

The figure is a connection diagram showing an embodiment of the AC/DC power supply circuit of this invention. P ₁ ... AC power input socket, P ₂ ... DC power input socket, Q ₁ to _{Q 5} ... Transistor,
Q ₆ ... Output transistor, D ₁ to D ₆ , D ₈ , D ₉ , D ₁₁
~ _D15 ...Diode, _D7 , _D10 ...Block diode, _R1 , _R2 , _R4 ~ _R11 ...Resistor, _R3 ...Variable resistor, _C1 ~ _C8 ...Capacitor, _T3 ...Converter transformer, OSC...Oscillation circuit, L...Load.

Claims (1)

[Claims for Utility Model Registration] A series regulator that rectifies and smoothes AC voltage from an AC power source and supplies it to a load as a constant voltage, and a series regulator that operates in oscillation by supplying DC voltage from a DC power source. The output of the oscillation circuit is waveform-shaped by a waveform shaping circuit, the waveform-shaped output drives a drive circuit, the output of this drive circuit causes the output circuit to perform switching operation, and the output from this output circuit is rectified and supplied to the above load. A DC-DC converter configured to provide a DC-DC converter, and a DC voltage obtained at either the input side or the output side of the series regulator is passed through a series circuit of a diode and a resistor to a waveform shaping circuit or drive of the DC-DC converter. supplying it to at least one input side of the circuit, and stopping the operation of at least a part of the circuit in the DC-DC converter when the DC voltage from the DC power source is supplied during operation of the series regulator; A dual-use AC/DC power supply circuit comprising: a priority circuit that prioritizes the DC voltage from the series regulator and supplies it to a load.