JP3267730B2 - Automatic voltage switching power supply circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit of the ringing choke converter type, and more particularly to a power supply circuit of a 100 V system.
The present invention relates to a power supply circuit having an automatic voltage switching function for stabilizing an output with respect to a different AC input such as a 0 V system.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for miniaturization and weight reduction of a power supply for driving a motor or the like and a charger for charging a secondary battery such as a Ni-Cd battery. Switching regulators are being used. In addition, since the opportunity to use the power supply circuit such as the power supply and the charger overseas has been increasing, the AC power supply has a voltage of 100 to 240 V AC.
There is a need for something that automatically responds to for that reason,
Conventionally, Japanese Patent Application Laid-Open Nos.
A power supply circuit having an automatic voltage switching function as disclosed in JP-A-43144 is known.

[0003]

However, the conventional power supply circuit disclosed in Japanese Patent Application Laid-Open No. Sho 56-115141 has a complicated circuit for setting the ON time width.
In the circuit disclosed in JP-A-43144, a circuit for maintaining a constant on / off repetition period is complicated, and both circuits are expensive.

An object of the present invention is to solve the above problems and to provide an automatic voltage switching type power supply circuit with a simple and low-cost circuit configuration.

[0005]

In order to achieve the above object, the present invention connects a series circuit of a primary winding of a transformer and a switching element between both ends of a DC power supply obtained by rectifying an AC input. At the same time, a tertiary winding for feedback is connected to the control terminal of the switching element to oscillate, thereby turning the switching element on and off, and turning on and off the secondary winding of the transformer. A ringing choke converter type power supply circuit configured to rectify the induced output and supply the rectified output to a load, wherein a series circuit connected to both ends of the secondary winding and including a rectifying element, a resistive load, and switch means; Level detecting means for detecting a level of an output to the load, and when the detected output level becomes equal to or higher than a predetermined level, the switch means is turned on. It has been made to (claim 1).

A series circuit of a primary winding of a transformer and a switching element is connected between both ends of a DC power supply obtained by rectifying an AC input, and a tertiary winding for feedback is connected to a control terminal of the switching element. The switching element is turned on by connecting a line to cause oscillation, and when the current flowing through the switching element reaches a preset level, the switching element is turned off.
A ringing choke converter type power supply circuit configured to rectify an output induced in a secondary winding of the transformer when turned off and supply the rectified output to a load; a quaternary winding magnetically coupled to the primary winding; A series circuit, which is connected to both ends of the quaternary winding and is composed of a rectifier and a switch means for flowing a current only in the same phase as that of the primary winding, and a level of an output to the load is detected. Level detecting means for turning on the switch means when the detected output level exceeds a predetermined level (claim 2).

[0007]

According to the first aspect of the present invention, when the output level to the load exceeds a predetermined level when the AC input voltage is high, the switch means is turned on, and the output induced by the secondary winding is reduced. A part is passed to the resistance load via the rectifier,
The output level to the load is lower than a predetermined level.

According to the second aspect of the present invention, when the output level to the load exceeds a predetermined level when the AC input voltage is high, the switch means is turned on and the output generated in the quaternary winding is turned on. As a result, a current induced in the primary winding flows into the switching element. Therefore, the energy stored in the primary winding until the current flowing through the switching element reaches a preset level is reduced by the amount of the current that flows. As a result, the output induced in the secondary winding decreases, and the output level to the load is reduced to a predetermined level or less.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a first embodiment of an automatic voltage switching type power supply circuit according to the present invention will be described with reference to FIGS.
The power supply circuit includes a rectifying unit 1 including a rectifying bridge BD,
Power supply unit 2 including transformer T, etc., storage battery B as load
And an output detection unit 3 including a current detection resistor R4 and the like, and supplies a charging current for charging the storage battery B.

The rectifier bridge BD rectifies an AC input from a connected AC power supply and outputs the rectified output to the primary winding L1 of the transformer T.
Further, a switching transistor Q1 and an emitter resistor R2 are connected in series. The transformer T includes a primary winding L1, a secondary winding L2, and a base winding L3 wound on the primary side. The current flowing into the primary winding L1 is switched by turning on / off the transistor Q1. Thereby, a voltage is induced in the secondary winding L2 and the base winding L3. The starting resistor R1 supplies a base current to the transistor Q1 to start the transistor Q1.

A series circuit comprising a base winding L3 and a capacitor C1 is connected between the base of the transistor Q1 and the ground line.
1 starts to turn on, a voltage is induced in the base winding L3, and the voltage across the capacitor C1 is raised by the induced voltage to supply a base current to the transistor Q1. As a result, the transistor Q1 is rapidly turned on. Has become.

The control transistor Q2 has a base connected to the emitter of the transistor Q1, a collector connected to the base of the transistor Q1, and an emitter connected to the ground line. The emitter resistor R2 is connected to the transistor Q
1 to set the off timing of the transistor Q
The transistor Q2 is turned on by a voltage generated by the collector current of 1, and the base of the transistor Q1 is dropped to the ground line to turn off the transistor Q1.

A diode D1 is connected in series to the secondary winding L2, and the power induced in the secondary winding L2 is supplied to the diode D1.
1, and supplies a charging current to the storage battery B connected to the output terminal.

As described above, a power supply circuit including a ringing choke converter, which is a self-excited oscillation type converter, is configured.

The resistor R4 is connected to the negative terminal of the storage battery B and 2
It is connected between the next windings L2 and detects a charging current supplied to the storage battery B. The anode of the diode D2 is connected to the anode of the diode D1.
Is connected to the collector of the transistor Q3 via the resistor R3. The transistor Q3 adjusts the charging current supplied to the storage battery B. The base is connected to the negative terminal of the storage battery B, and the emitter is connected to the ground line on the secondary side of the transformer T. Note that the diode D2 may be replaced with the diode D1.

[0016] Here, the resistance value R ₄ of the resistor R4 is set to _{R 4 = V BE3 / I M} ... (1). Here, I _M : the upper limit value of the charging current supplied to the storage battery B, V _BE3 : the base of the transistor _Q3-
This is the voltage between the emitters.

As a result, when the charging current I _O supplied to the storage battery B is I _O <I _M , the transistor Q3 is turned off, and the output current from the secondary winding L2 all passes through the diode D1. And flows into the storage battery B. The upper limit value I _M of the charging current is set such that I _O <I _M when the AC power supply is 100 V AC, and I _O ≧ I _M when the AC power source is 220 V AC.

Next, the operation of the power supply circuit will be described. First, the voltage of the connected AC power supply is, for example, AC10.
The case of 0V will be described.

[0019] AC input from the AC power supply is rectified by the rectifier 1, the transistor Q1 base current I _B supplied through the start resistor R1 by the DC power source. Transistor Q1 by the base current I _B starts to turn on, flows a collector current I _C is. By this collector current I _C , 1
A voltage is generated at both ends of the next winding L1. Voltage to the base winding L3 by the generated voltage is induced, lifted the voltage across the capacitor C1 at this induced voltage, the further the base current I _B to the transistor Q1 is supplied. This positive feedback turns on the transistor Q1 rapidly.

The collector current I _C of the transistor Q1 is represented by I _C = (V ₁ / L ₁ ) ton (2) Here, V ₁ : the voltage between both ends of the primary winding L1,
L ₁ : inductance of the primary winding L1, ton: on time of the transistor Q1.

The voltage V ₂ generated in the emitter resistor R2 by the collector current I _C is as follows: V ₂ = I _C × R ₂ (3) Here, R ₂ is the resistance value of the emitter resistor R2.

The collector current I _C increases and this voltage V
_2, V ₂ = V _BE2 (However, V _BE2: the base of the transistor Q2 - emitter voltage) becomes, the transistor Q2 is turned on, for supplying a base current I _B which has been supplied to the transistor Q1 to ground line, As shown in FIG. 2A, the transistor Q1 turns off rapidly. And 1
The excitation energy of the secondary winding L1 is induced in the secondary winding L2, and this induced voltage is rectified by the diode D1 to supply a charging current to the storage battery B.

As described above, the transistor Q2 keeps the peak value I _CP of the collector current I _C constant and keeps the secondary winding L
2 is set to a constant level. The turned off transistor Q1 is turned on again in the same manner as described above, and this is repeated thereafter, so that a predetermined level of charging current _IO is supplied to the storage battery B as shown in FIG. At this time, since the transistor Q3 is off, the secondary winding L
All the output currents from 2 flow to the diode D1 side and are supplied to the storage battery B as a charging current.

Next, the voltage of the connected AC power supply is changed to AC1.
A case where the voltage is larger than 00V, for example, a case of 220V AC will be described.

In this case, the peak value I of the collector current I _C
CP is not changed so determined by the operation of transistor Q2, (2) the ON time ton of the transistor Q1 to the value of the voltage V ₁ is increased is reduced in expression. On the other hand, since the off time toff of the transistor Q1 does not change, the oscillation frequency f = 1 / (toff + ton) increases accordingly, and the output of the secondary winding L2 increases as compared with the case of AC100V. Therefore, when the charging current to the storage battery B increases, the transistor Q3 turns on and a part of the output current from the secondary winding L2 is shunted to the resistor R3. is never more than I _M.

If the increase in the output due to the increase in the AC input voltage is directly consumed by a resistor or the like, the heat is increased and it is difficult to reduce the size of the circuit. However, when the transistor Q3 is on, the resistor R3 is connected in parallel to the storage battery B, so that the load impedance of the secondary winding L2 decreases and the voltage across the secondary winding L2 decreases.

At this time, the output current I of the secondary winding L2
_2, I ₂ = I _OP - represented by _{(V L2 / L 2) toff} . Here, V _L2 : voltage between both ends of the secondary winding L2,
L ₂ : inductance of the secondary winding L2, toff: off time of the transistor Q1.

The voltage V _L2 decreases due to the parallel connection of the resistor R3, and the time toff becomes longer than that without the resistor R3. Accordingly, the off-time toff of the transistor Q1 becomes longer, so that the oscillation frequency f = 1 / (t
off + ton). As a result, the output current from the secondary winding L2 is reduced. This also reduces the current flowing through the resistor R3, so that heat generation does not increase.

As described above, even if the voltage of the connected AC power supply increases, the charging current supplied to the storage battery B is reduced by that amount, so that the storage battery B is not overcharged.

Next, a second embodiment of the automatic voltage switching type power supply circuit according to the present invention will be described with reference to FIG. In addition,
Those having the same functions as the first embodiment are denoted by the same reference numerals. In this power supply circuit, the output detection unit 3 includes a zener diode D3 and the like, and outputs a voltage of a predetermined level between output terminals.

The Zener diode D3 has a cathode connected to the positive electrode side of the output terminal and an anode connected to the base of the transistor Q3 via a current limiting resistor R5. Note that the diode D2 may be substituted by the diode D1. The transistor Q3 adjusts the output voltage.
The collector is connected to the cathode of the diode D2 via the resistor R3, and the emitter is connected to the negative terminal of the output terminal. The load L is, for example, a load such as a motor.

Next, the operation of the power supply circuit will be described. When the AC input is AC 100 V, a voltage of a predetermined level is output between the output terminals and applied to the connected load L in the same operation as in the first embodiment.

On the other hand, when the AC input is AC 220V,
The output voltage V _O satisfies V _O ≧ V _Z + V _BE3 (4). Here, V _{Z is} a Zener voltage of the Zener diode D3, and V _{BE3 is} a base-emitter voltage of the transistor Q3.

At this time, when the Zener diode D3 is turned on and the transistor Q3 is turned on, a part of the output current of the secondary winding L2, that is, an increased amount is output from the diode D3.
2 flows to the resistor R3. Due to the parallel connection of the resistor R3, the voltage V _L2 decreases as in the first embodiment, and the voltage output from the output terminal of the power supply circuit is set to a predetermined level.

Next, a third embodiment of the automatic voltage switching type power supply circuit according to the present invention will be described with reference to FIGS.
Those having the same functions as the first embodiment are denoted by the same reference numerals.

This power supply circuit has a fourth winding L
The output detector 3 has the same configuration as that of the first embodiment, and supplies a predetermined level of charging current to the storage battery B connected to the output terminal.

The quaternary winding L4 is arranged on the secondary side of the transformer T with respect to the primary winding L1 so that a voltage is generated when the transistor Q1 is on, that is, the same as the primary winding L1. It is wound so that output can be taken out in phase.

The anode of the diode D2 is the fourth winding L.
4, the cathode is connected to the collector of the transistor Q3 via the resistor R3, and flows only when the output induced in the quaternary winding L4 has the same phase as the primary winding L1. I have. The transistor Q3 adjusts the charging current supplied to the storage battery B.
The emitter is connected to the ground terminal on the secondary side of the transformer T.

Here, the resistance value R ₄ of the resistor R ₄ is set as in the equation (1) in the same manner as in the first embodiment.

Next, the operation of the power supply circuit will be described. When the connected AC power supply is AC 100 V, the transistor Q3 is turned off, and the quaternary winding L4
Are open, and the operation is the same as in the first embodiment.

On the other hand, if the connected AC power supply is, for example, AC
When the 220V, the output of the secondary winding L2 is increased, the charging current I _O is supplied to the battery B is I _O ≧ I _M, the transistor Q3 is turned on, resistor R3 through the diode D2 4 Connected to the next winding L4.

The voltage V generated at both ends of the quaternary winding L4
_{4, V 4 = (n 4 /} n 1) becomes V _1. Here, n _{4 is} the number of turns of the quaternary winding L4, n _{1 is} the number of turns of the primary winding L1, and V ₁ is the voltage across the primary winding L1.

The current I ₃ flowing through the resistor R ₃ is I ₃ = (V ₄ −V _fD2 ) / R ₃ . Here, V _fD2 is a forward voltage of the diode D2.

By the current I ₃ , a current of I _Q1 = (n ₄ / n ₁ ) I ₃ flows through the transistor Q1.

Therefore, when the transistor Q3 is turned on and the transistor Q1 is turned on, the collector current I _C flowing through the transistor Q1 is a combination of the above equation (2) and I _Q1 , and I _C = (V ₁ / L ₁ ) It is represented by ton + (n ₄ / n ₁ ) I ₃ . 5 the current waveform of the collector current I _C
Shown in

The peak value I _CP of the collector current I _C is equal to the first
As in the case of the embodiment, since the current is limited by the emitter resistor R2 and the transistor Q2, the transistor Q3
Is turned on, the on-time ton of the transistor Q1 is slightly shortened, while (n ₄ / n ₁ ) I ₃ minutes (V ₁ /
L ₁ ) ton becomes small, and this (n ₄ / n ₁ ) I _{3 is} equivalent to 1
The energy stored in the next winding L1 decreases.

That is, the energy to be excited at (V ₁ / L ₁ ) ton decreases, and the output to the secondary winding L2 decreases as a whole, so that the charging current to the storage battery B becomes a constant level. Will be retained.

Next, a fourth embodiment of the automatic voltage switching type power supply circuit according to the present invention will be described with reference to FIG. In addition,
Those having the same functions as the first embodiment are denoted by the same reference numerals.

In this power supply circuit, the power supply section 2 has the same configuration as that of the third embodiment, and the output detection section 3 has the same configuration as that of the second embodiment, and outputs a voltage of a predetermined level between output terminals.

The operation of this power supply circuit will be described. When the AC input is AC 220 V, the output voltage V _O is as shown in the above equation (4) and the transistor Q3 is turned on, as in the second embodiment. Become. The output voltage is maintained at a predetermined level or less by the operation of the quaternary winding L4 as in the third embodiment.

[0051]

As described above, the present invention relates to a power supply circuit of a ringing choke converter type, comprising a series circuit connected to both ends of a secondary winding, comprising a rectifying element, a resistive load, and switch means; Or a level detecting means for detecting an output level to the power supply circuit. Alternatively, the present invention provides a power supply circuit of a ringing choke converter type, wherein a quaternary winding wound around a primary winding is provided. A series circuit consisting of a rectifier and a switch connected only to the same phase as the primary winding and connected to both ends of the quaternary winding, and a level detector for detecting an output level to the load. When the detected output level is equal to or higher than a predetermined level, the switch means is turned on.Therefore, a power supply circuit having a function, small size and low cost, One automatic voltage switching type power supply circuit with low loss can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of an automatic voltage switching type power supply circuit according to the present invention.

FIG. 2 is a waveform chart of each part in the circuit of the first embodiment;
(A) is the collector current I _C of the current waveform of the transistor Q1, (b) the collector of the transistor Q1 - voltage waveform emitter voltage Vce, (c) is a current waveform of the charging current I _O is supplied to the battery B is there.

FIG. 3 is a circuit diagram showing a second embodiment of the automatic voltage switching type power supply circuit according to the present invention.

FIG. 4 is a circuit diagram showing a third embodiment of the automatic voltage switching type power supply circuit according to the present invention.

5 is a current waveform diagram of the collector current I _C of the transistor Q1 in the circuit of the third embodiment.

FIG. 6 is a circuit diagram showing a fourth embodiment of the automatic voltage switching type power supply circuit according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rectification part 2 Power supply part 3 Output detection part B Storage battery C1 Capacitor D1, D2 Diode D3 Zener diode L1 Primary winding L2 Secondary winding L3 Base winding L4 Quaternary winding Q1-Q3 Transistor R1 Starting resistance R2 Emitter resistance R3, R4 resistance T transformer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02J ^7/ 00-7/12 H02J ⁷ /34-7/36 H02M 3/28

Claims (2)

(57) [Claims] 1. A series circuit of a primary winding of a transformer and a switching element is connected between both ends of a DC power supply obtained by rectifying an AC input, and a tertiary winding for feedback is connected to a control terminal of the switching element. Ringing in which the switching element is turned on and off by connecting a line and oscillating, and the output induced in the secondary winding of the transformer by this on and off is supplied to a load. A power supply circuit of a choke converter type, comprising a series circuit connected to both ends of the secondary winding, the rectifier element, a resistive load, and a switch means, and a level detecting means for detecting a level of an output to the load. When the detected output level is equal to or higher than a predetermined level, the switch means is turned on. Road. 2. A series circuit of a primary winding of a transformer and a switching element is connected between both ends of a DC power supply obtained by rectifying an AC input, and a tertiary winding for feedback is connected to a control terminal of the switching element. The switching element is turned on by connecting a wire to oscillate, and when the current flowing through the switching element reaches a preset level, the switching element is turned off. In a power supply circuit of a ringing choke converter system for rectifying an output induced in a winding and supplying the rectified output to a load, a quaternary winding magnetically coupled to the primary winding and both ends of the quaternary winding And a series circuit including a rectifying element and a switch means for flowing a current only in a direction having the same phase as that of the primary winding and an output level to the load. An automatic voltage switching type power supply circuit, comprising: level detection means for detecting, wherein when the detected output level becomes equal to or higher than a predetermined level, the switch means is turned on.