JPH06153495A - Power supply equipment - Google Patents

Abstract

PURPOSE:To keep the output voltage constant even though an input voltage varies widely. CONSTITUTION:Main circuit 1 is a step-up type chopper circuit for charging a capacitor C1 by discharging energy during OFF time of a switching element Q1, which was stored in an inductor CH during ON time of the switching element Q1. A control circuit 2 controls ON-OFF of the switching element Q1. If a voltage between both the ends of a capacitor C2 proportional to an input voltage Vi is lower than a reference voltage, then a voltage switching circuit 3 raises a first detection voltage V1 to the control circuit 2 by connecting a resistor R12 to a resistor R1 in parallel. Therefore, the voltage switching circuit 3 has the function of restricting the width of fluctuation of the first detection voltage V1 with respect to the width of fluctuation of the input voltage Vi. If the width of fluctuation of the first detection voltage V1 is restricted, then the fluctuation of an output voltage Vo can be restricted against the fluctuation of the input voltage Vi, so that the output voltage Vo can be maintained almost constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for converting DC voltage using a chopper circuit.

[0002]

2. Description of the Related Art Conventionally, there has been provided a power supply device which obtains a DC output voltage obtained by stepping down or stepping up an input voltage by turning on / off a switching element connected in series or in parallel with an input. For example, a boost type power supply device has a configuration as shown in FIG. In the example of FIG. 6, the pulsating current voltage which is the output of the rectifier RE such as a diode bridge for full-wave rectifying the AC power supply AC is used as the input voltage Vi, and the primary winding L ₁ of the inductor CH is provided between the output terminals of the rectifier RE. a series circuit of the switching element Q ₁ and the resistor R ₅ made of MOSFET, the main circuit a series circuit of a diode D ₁ of the reverse-current blocking switching element Q ₁ and the capacitor C ₁ for smoothing connected in parallel 1
Equipped with. The switching element Q ₁ is on / off controlled by a control circuit 2 described later.

When only the main circuit 1 is taken out from the circuit of FIG. 6, it becomes as shown in FIG. The period switching device Q ₁ is turned on, the input voltage Vi to the primary winding L ₁ of the inductor CH is applied, the current i _L1 that flows through the primary winding L ₁ of the inductor CH is the switching element Q ₁ If the elapsed time after turning on is t, then i _L1 = (Vi / L ₁ ) t (where L ₁ is the inductance of the primary winding L ₁ ). That is, if the _ON period of the switching element Q ₁ is T _ON ,
The peak value I _P of the current i _L1 flowing through the primary winding L ₁ of the inductor CH becomes I _P = (Vi / L ₁ ) T _ON . On the other hand, when the switching element Q ₁ is turned off, the voltage across the primary winding L ₁ of the inductor CH is Vo, which is the voltage across the capacitor C ₁ , and the forward voltage drop of the diode D ₁ is ignored. -(Vo-Vi). That is, when the switching element Q ₁ is turned off, a voltage having a polarity opposite to that when it is turned on is applied across the primary winding L ₁ of the inductor CH. The energy stored in the inductor L ₁ while the switching element Q ₁ is on is equal to the switching element Q ₁
Is discharged when the power turns off, and 1
The current i _L1 flowing through the next winding L ₁ is the switching element Q ₁
If the elapsed time after turning off is t, then i _L1 = _IP − {(V
o-Vi) / L ₁ } t. Therefore, the current i _L1 flowing through the primary winding L ₁ of the inductor CH is as shown in FIG. In FIG. 8, the switching element Q ₁ is turned on at the time t.
_The state is turned on at ₁ and turned off at time t ₂ .

By the way, the inductor CH has a secondary winding L ₂
And the winding ratio between the primary winding L ₁ and the secondary winding L ₂ is n ₁ : n ₂ , the voltage e ₂ induced in the secondary winding L ₂ of the inductor CH is , the oN period of the switching element Q ₁ becomes _{e 2 = (n 2 / n} 1) Vi, is in the oFF period of the switching element _{Q 1 e 2 = - (n} 2 / n 1) (Vo
-Vi). In addition, when all the stored energy in the inductor L ₁ is released during the OFF period of the switching element Q ₁ , no voltage is induced in the secondary winding L ₂ . Thus, if the input voltage Vi is constant voltage of the DC induced voltage e ₂ to the secondary winding L ₂ is 8
As shown in (b), the polarity is inverted as the switching element Q ₁ is turned on / off, resulting in a rectangular wave shape.

The ON / OFF timing of the switching element Q ₁ is controlled by the control circuit 2. Control circuit 2
Is the input voltage Vi, the output voltage Vo, the switching element Q
_The current flowing through ₁ and the voltage e ₂ induced in the secondary winding L ₂ of the inductor CH are combined to determine the on / off timing of the switching element Q ₁ . That is, the input voltage Vi is divided by the two resistors R ₁ and R ₂ as the first detection unit connected between the output terminals of the rectifier RE, and is input to the control circuit 2 as the first detection voltage V _1. , Output voltage Vo
Is divided by two resistors R ₆ and R ₇ serving as a second detection unit connected between both ends of the capacitor C ₁ and input to the control circuit 2 as a _second detection voltage V ₂ . The current flowing through the switching element Q ₁ is detected as a voltage across the resistor R ₅ as a third detector connected in series to the switching element Q _1, this voltage control circuit 2 as a third detection voltage V ₃ Is entered. Secondary winding L of inductor CH
Voltage across e ₂ of ₂ is inputted to the control circuit 2 via the resistor R _4. Here, the main part of the control circuit 2 (the part surrounded by the broken line in FIG. 6) is provided as an integrated circuit (for example, MC34261 manufactured by Motorola Co., Ltd.), and the control circuit 2 is configured by attaching some components externally. You can do it.

[0006] The control circuit 2, a second detection voltage V ₂ is compared with a reference voltage Vref set by reference voltage generator 29, an output proportional to the difference between the second detection voltage V ₂ and the reference voltage Vref An error amplifier 21, which is an error detection unit that occurs, is provided. The error voltage V ₂ ′ output from the error amplifier 21 is
Is input to the first detection voltages V ₁ with the multiplier 22, the output value QM proportional to the result obtained by multiplying the first detection voltage V ₁ and the error voltage V ₂ 'is obtained from the multiplier 22. Therefore, the output value QM of the multiplier 22 is QM = κV
It can be expressed as ₁ V ₂ ′ (κ is a constant). Multiplier 22
Output value QM of the third detection voltage V ₃ in the comparator 23.
The output of the comparator 23 is compared with the third detection voltage V ₃
Is at the H level while the output value of the multiplier 22 is greater than or equal to QM (V ₃ ≧ QM). When the output of the comparator 23 rises to H level, the RS latch 24 is reset, and when the output of the RS latch 24 becomes L level, the output of the output circuit 25 becomes L.
The switching element Q ₁ is turned off and the switching element Q ₁ is turned off. In short, during the period when the switching element Q ₁ is on,
As shown in FIG. 8A, when the current i _L1 flowing through the primary winding L ₁ of the inductor CH increases, the current flowing through the switching element Q ₁ also increases. Therefore, the third detection voltage V ₃ causes the switching element Q ₁ to operate. The flowing current is monitored, and when the desired energy is stored in the inductor CH, the switching element Q ₁ is turned off. Thus, the first detection voltage V ₁ , the second detection voltage V ₂ , and the third detection voltage V 1
₃ determines the timing for turning off the switching element Q ₁ . In other words, the primary winding L of the inductor CH
_Since the peak value I _P of the current i _L1 flowing through ₁ is equal to the peak value of the current flowing through the resistor R ₅ , I _P R ₅ = V ₃ = κV ₁
V ₂ ′ is satisfied, and as shown in FIG. 9, the current i _L1
The envelope of the peak value I _{P has} the same shape as the pulsating current voltage which is the input voltage Vi.

On the other hand, the timing for turning on the switching element Q ₁ is determined by the voltage e ₂ induced as the fourth detection voltage in the secondary winding L ₂ of the inductor CH which is the fourth detection section. That is, when the switching element Q ₁ is turned off, the voltage e ₂ having the polarity shown by the arrow in FIG. 6 is induced in the secondary winding L ₂ of the inductor CH, and the inductor C
Since the induced voltage e ₂ decreases as the energy stored in H is released, the induced voltage e _{2 is changed} to the zero point detector 2
6 detects the time when the induced voltage e ₂ becomes almost 0 V as compared with the predetermined voltage. When the zero point detector 26 detects the time when the induced voltage e ₂ becomes almost 0V, the RS latch 24 is set. When the output of the RS latch 24 becomes H level, the output of the output circuit 25 becomes H level, and the switching element Q ₁ is turned on. That is, the inductor C
By monitoring the voltage e ₂ induced in the secondary winding L _{2 of} H, the timing for turning on the switching element Q ₁ is determined. Here, the delay circuit 27 and the timer circuit 28 are provided to ensure the operation of the RS latch 24.

As described above, the multiplier 22 and the comparator 2
3, the RS latch 24, and the output circuit 25 constitute a determination control unit. By determining the on / off timing of the switching element Q ₁ based on the voltage and current of each unit of the main circuit 1, The output voltage Vo of the circuit 1 is controlled so as to be maintained at a constant voltage according to the reference voltage Vref set by the control circuit 2. Moreover, the input current waveform becomes a waveform close to a sine wave.

[0009]

By the way, between the first detection voltage V ₁ and the input voltage Vi, as described above,
There is a relationship of V ₁ = κ ₁ Vi (κ ₁ is a voltage division ratio of the resistors R ₁ and R ₂ ). On the other hand, the input current Ii to the main circuit 1 is proportional to the peak value I _P of the current i _L1 flowing through the primary winding L ₁ of the inductor CH, and the waveform of the input current Ii has the peak value I _P as shown in FIG. It is a curve obtained by halving the envelope curve of.
Here, when the input power is W, the input current Ii is I
Since it can be expressed as i = W / Vi, the peak value I _P is inversely proportional to the input voltage Vi. In addition, the third detection voltage V ₃
Peak value of, since it is V ₃ = I _P R _5, if the proportional constant and kappa _3, so that can be expressed as _{V 3 = κ 3 (1 /} Vi).

On the other hand, when the current i _L1 flowing through the primary winding L ₁ of the inductor CH reaches the peak value I _P , the first detection voltage V ₁ , the third detection voltage V ₃ and the error voltage V ₂ ' Since V ₃ = κV ₁ V ₂ ′ holds between the _two , the error voltage V ₂ ′ with respect to the input voltage Vi is κ ₃ / κκ ₁ = κ ₂ and V ₂ ′ = κ ₂ (1 / Vi ² ), and the error voltage V ₂ ′ output from the error amplifier 21 is equal to the input voltage 2
It will be inversely proportional to the square.

This means that in the power supply device having the above-mentioned structure, when the output voltage Vo is kept constant without changing the load and only the input voltage Vi changes, the error voltage V ₂ ′ changes in the input voltage Vi. This means that a change width of the square of the magnification is required. For example, when the input voltage Vi is 100 to
Assuming that the input voltage Vi changes between 300 V and the other conditions are not changed, when the input voltage Vi is 100 V, the change ratio of the input voltage Vi is three times as large as when the input voltage Vi is 100 V. Therefore, it is necessary to control the error voltage V ₂ 'to 1/9.

That is, if the upper limit of the allowable range of the input voltage V ₂ ′ of the multiplier 22 is V _2H ′, the lower limit is V _2L ′, the upper limit of the input voltage is V _H , and the lower limit is V _L. , V _2H ′ ≧
κ ₂ (1 / _VL ² ) and V _2L ′ ≦ κ ₂ (1 /
Since V _H ² ) = κ ₂ ( _VL / V _H ) ² (1 / _VL ² ) must be satisfied, (V _H / _VL ) ² V _2L ′ ≦ κ
Relationship ^{_{2 (1 / V L 2)}} ≦ V 2H ' is obtained. Therefore, V _2H ′ / V _2L ′ ≧ (V _H / V _L ) ² holds, and the error voltage V ₂ ′ is 2 times the change rate of the input voltage Vi.
It changes at a magnification that is inversely proportional to the power.

However, the output voltage of the error amplifier 21 and the multiplier 22 connected to the output of the error amplifier 21
Since there is a limit to the input voltage of, the problem arises that normal control cannot be performed if the change ratio of the error voltage V ₂ 'is large. For example, error voltage V ₂ 'is allowable range output voltage Vo to about to exceed the upper limit of will be lowered than the predetermined voltage, the error voltage V ₂ in the opposite' When is going S'Agaro than the lower limit of the allowable range There is a problem that the output voltage Vo exceeds a predetermined voltage and the main circuit 1 is destroyed in some cases. In particular, when the ready-made integrated circuit is used for the control circuit 2 as described above, the allowable operating range of the error amplifier 21 and the multiplier 22 is defined as the specification, and therefore, the change range of the input voltage Vi is the range of the integrated circuit. There is a problem that it is limited to a narrow range depending on the specifications.

An object of the present invention is to solve the above problems, and to provide a power supply device capable of keeping the output voltage constant even if the input voltage changes over a wide range. It is a thing.

[0015]

According to the present invention, a main circuit comprising a chopper circuit for converting DC voltage including a switching element and an inductor and a switching element are turned on.
A control circuit for controlling off; a first detection unit for generating a first detection voltage proportional to an input voltage to the main circuit and a second detection voltage proportional to an output voltage of the main circuit. A second detector that generates a third detector, a third detector that generates a third detector voltage that is proportional to the current supplied to the switching element, and a fourth detector that generates a fourth detector voltage that is proportional to the current flowing in the inductor. And an error detection unit that outputs the difference between the second detection voltage and the set voltage as an error voltage, and the third detection voltage has a voltage value obtained by multiplying the product of the first detection voltage and the error voltage by a specified scale factor. In this case, a common configuration is provided with a determination control unit that turns off the switching element and turns on the switching element when it is detected based on the fourth detection voltage that the stored energy of the inductor is almost released.

In the structure of claim 1, in order to achieve the above object, the first detection voltage is adjusted according to the input voltage so that the second detection voltage is kept substantially constant with respect to the fluctuation of the input voltage. A voltage regulator is provided. In the configuration of claim 2,
A voltage adjustment unit is provided that adjusts the error voltage according to the input voltage so that the second detection voltage is kept substantially constant with respect to variations in the input voltage.

Further, according to the third aspect of the invention, a voltage adjusting section for adjusting the third detected voltage according to the input voltage is provided so as to keep the second detected voltage substantially constant with respect to the fluctuation of the input voltage. There is.

[0018]

According to the above configuration, by providing the voltage adjusting section, any one of the first detection voltage, the error voltage, and the third detection voltage is adjusted according to the level of the input voltage, and the second detection voltage is adjusted. Therefore, even if the input voltage fluctuates significantly, the output voltage can be kept substantially constant. That is, the output voltage can be stabilized while the difference between the upper and lower limits of the voltage range allowed as the input voltage is large.

[0019]

【Example】

(Embodiment 1) In this embodiment, a voltage adjusting circuit 3 is added as a voltage adjusting unit to the conventional configuration shown in FIG. 6, and a first detection voltage V ₁ input to a multiplier 22 according to an input voltage Vi is applied. It is designed to be switched. That is, the voltage adjustment circuit 3 includes two resistors R ₁₀ and R that divide the input voltage Vi.
₁₁ , a smoothing capacitor C ₂ connected in parallel to the resistor R ₁₁ via a diode D ₂ , and an open collector type output unit for comparing the voltage across the capacitor C ₂ with a predetermined reference voltage Vref2. and CP _1, an anode connected to the output terminal of the comparator CP ₁ resistor R _1, R ₂
Diode D ₃ whose cathode is connected to the connection point of and diode D ₃ which is connected in series to the anode side of diode D ₃
A resistor R ₁₂ in which a series circuit with ₃ is connected in parallel with the resistor R _1.
It has and.

The operation of the voltage adjusting circuit 3 will be described.
Input voltage Vi is the voltage across the resistor R _10, is divided by R ₁₁ is smoothed by the capacitor C ₂ capacitor C ₂ is input to the comparator CP ₁ as a comparison voltage Vc. Therefore, the comparison voltage Vc reflects not the short-time fluctuation of the input voltage Vi but the time-average fluctuation of the input voltage Vi. In the comparator CP ₁ , the comparison voltage V
c is compared with the reference voltage Vref2, and the output is opened during the period when Vc <Vref2, that is, the period when the input voltage Vi is relatively low. Once the open output of the comparator CP ₁ is diode D ₃ resistance R ₁₂ because turned on is connected in parallel to the resistor R _1, resistor R _1, the first detection voltage V which is the potential of the connection point R _{2 1} is resistance R ₁ and resistance R
_The input voltage Vi is divided by ₁₂ parallel resistors and the resistor R ₂ . If this partial pressure ratio is A _L , A _L = R ₂
/ {R ₁ / (1 + R ₁ / R ₁₂ ) + R ₂ }.

On the other hand, the input voltage Vi is relatively high and Vc ≧ V
The period in which the ref2, the output of the comparator CP ₁ becomes short, resistance diode D ₃ is turned off R
_{Since 12} is separated from the resistor R ₁ , the first detection voltage V ₁ becomes a voltage obtained by dividing the input voltage Vi by only the resistors R ₁ and R ₂ . If the partial pressure ratio at this time is A _H ,
A _H = R ₂ / (R ₁ + R ₂ ) That is, the voltage division ratio A _L during the period when the input voltage Vi is relatively low is set to the input voltage Vi.
Is larger than the voltage division ratio A _{H in} a relatively high period, the fluctuation range of the first detection voltage V ₁ is smaller than the fluctuation range of the input voltage Vi. As described in the related art, V ₃ = κV ₁ V ₂ ′, and the peak value of the third detection voltage has relatively little fluctuation. Therefore, if the fluctuation width of the _first detection voltage V ₁ is small. , The second detection voltage V ₂
The fluctuation range of is also small. In this way, the input voltage Vi
Even if the voltage changes over a relatively wide range, the fluctuation range of the second detection voltage V ₂ input to the control circuit 2 can be suppressed, and the output voltage Vo can be kept substantially constant. .

Next, a method of setting the values of the resistors R ₁ , R ₂ and R ₁₂ will be described. Here, regarding the input voltage Vi,
Let V _H and V _L be the upper and lower limits, respectively, and let V _M be the input voltage Vi when switching the voltage division ratio. Also,
The upper and lower limits of the error voltage V ₂ ′ are V _2H ′ and V _2L ′, respectively. Here, a _{V 3 = κV 1 V 2 '} , in the period the voltage dividing ratio is _{A L A L V L ≦ V} 1 ≦ A
Is an _L V _M. When the _{V 1 = A L V L,} V 2 '≦
Since the condition of V _2H ′ must be satisfied, the following equation holds. _{V 3 ≦ κA L V L V} 2H '(1) Further, when V ₂ = A _L V _M is, V _2' do not have to meet the condition of ≧ V _2L ', the following equation is established. _{V 3 ≧ κA L V M V} 2L '(2) In the same manner, the period division ratio is A _H, the following equation is established. _{V 3 ≦ κA H V M V} 2H '(3) V 3 ≧ κA H V H V 2L' (4) By the way, the input current Ii is about 1 current i _L1 that flows through the primary winding L ₁ of the inductor CH / 2 times, and the current i _L1 is equal to the current flowing through the resistor R ₅ during the ON period of the switching element Q ₁ , so if the input power is W, V ₃ = 2WR
₅ / Vi, and according to the equation (4), A _H ≦ V ₃ / κV
_{Since H} V _2L ′ = 2WR ₅ / κV _H ² V _2L ′ and A _H = R ₂ / (R ₁ + R ₂ ) as described above, the resistors R ₁ and R ₂ eventually satisfy the following equation. It is necessary. R ₂ / (R ₁ + R ₂ ) ≦ 2WR ₅ / κV _H ² V _2L ′ On the other hand, according to the equation (1), A _L ≧ V ₃ / κV _L V _2H ′, and as described above, A _L = R ₂ / {R ₁ / (1 + R ₁ / R
₁₂ ) + R ₂ }, the resistors R ₁ , R ₂ , and R ₁₂ must satisfy the following equation. R ₂ / {R ₁ / (1 + R ₁ / R ₁₂ ) + R ₂ } ≧ 2WR ₅ / κV _L ² V _2H ′ ... Furthermore, as explained in the section of the problem to be solved by the invention, V _2H ′ / V _{2L '≧ (V M / V} L) 2 _{and, V 2H' / V 2L '} ≧ (V H / V M) 2 must be established. If both equations are modified, V _M ² ≦ (V _2H ′ / V _2L ′) V
_L ^2, and ^{_{V M 2 ≧ (V 2L '}} / V 2H') a V _H ^2,
_{(V 2H '/ V 2L'} ) V L 2 = V M1 2, (V 2L '/
V _2H ′) V _H ² = V _M2 ² , then V _M1 ² ≧ V _M ² ≧ V
_{Since M2} ² must be satisfied, the following expression should be satisfied as a result. V _M1> V _M2 ... in accordance with the specifications of the main circuit 1 and the control circuit 2, resistors R ₁ so as to satisfy the condition ~ described above, a constant value of R _2, R _12, the upper limit value V _H and the lower limit of the input voltage Vi By setting the value V _L , the variable range of the input voltage Vi can be significantly widened as compared with the case where the voltage adjusting circuit 3 is not provided. Here, with respect to the specifications of the control circuit 2, if the first detection voltage V ₁ is switched in two steps, the input voltage Vi
When the fluctuation range of the upper limit value V _H and the lower limit value V _L cannot be dealt with, the number of switching stages of the _first detection voltage V ₁ may be further increased.

(Second Embodiment) In the first embodiment, the input voltage Vi is
Although the first detection voltage V ₁ is switched according to the above, the present embodiment is different in that the _third detection voltage V ₃ is switched as shown in FIG. That is, the voltage adjusting circuit 3 has the same input voltage V as in the first embodiment.
two resistors R ₁₀ for dividing the i, R ₁₁ and, connected in parallel with a capacitor C ₂ for smoothing the resistor R _11, the reference voltage Vref2 by the comparator CP ₁ the voltage across the capacitor C ₂ as a comparison voltage Vc It is designed to be compared with.
A pull-up resistor R is provided at the output terminal of the comparator CP _1.
14 is connected, and the transistor Q ₂ as a switch element is turned on / off by the output of the comparator CP ₁ . A resistor R ₁₃ is connected in series with the emitter-collector of the transistor Q ₂ , and this series circuit is connected in parallel with a resistor R ₅ which is connected in series with the switching element Q ₁ .

In the period when the input voltage Vi is low and the comparison voltage Vc is lower than the reference voltage Vref2 (Vc <Vref2), the comparator CP ₁ turns on the transistor Q ₂ and connects the resistor R ₁₃ in parallel with the resistor R _5. By doing so, the third detection voltage V ₃ is lowered, the input voltage Vi is high, and the comparison voltage V 3
In the period when c is equal to or higher than the reference voltage Vref2, (Vc ≧ Vref
2) Turn off the transistor Q ₂ and turn on the resistor R ₁₃
Separated from ₅ , the third detection voltage V ₃ is increased.

In this embodiment, the third detection voltage V ₃ is switched according to the input voltage Vi, and as described above,
Since the first detection voltage V ₁ , the error voltage V ₂ ′, and the third detection voltage V ₃ have a relationship of V ₃ = κV ₁ V ₂ ′, the second detection is performed with respect to the fluctuation range of the input voltage Vi. Voltage V ₂ (= V
The change width of ₂ '+ Vref) can be reduced. That is, the output voltage Vo can be kept substantially constant even if the input voltage Vi changes significantly. Other configurations and operations are similar to those of the first embodiment.

(Embodiment 3) In this embodiment, as shown in FIG. 3, the first detection voltage V ₁ is adjusted according to the input voltage Vi. The difference is that the comparator CP ₁ is used for the adjusting circuit 3, whereas the current mirror CM is used in this embodiment.

That is, a diode D ₄ for preventing backflow is added between the output terminal of the rectifier RE and the primary winding L ₁ of the inductor CH, and the voltage adjusting circuit 3 includes the cathode of the diode D ₄ and the primary winding. The input voltage Vi at the connection point with the line L ₁
Is configured to detect. The input voltage Vi is divided by the _two resistors R ₁₀ and R ₁₁ , and smoothed by the capacitor C ₂ connected in parallel with the resistor R ₁₁ . A current mirror C composed of two transistors Q ₃ and Q _4.
Since a current corresponding to the voltage across the capacitor C ₂ flows into M through the resistor R ₁₅ , the output current of the current mirror CM increases or decreases according to the voltage across the capacitor C ₂ . Since the emitter-collector of the transistor Q ₄ on the output side of the current mirror CM is connected in parallel with the resistor R ₂ , if the output current of the current mirror CM increases, the first detection voltage V ₁ will be lowered equivalently. It will be. That is, in the first embodiment, the first detection voltage V ₁ is switched in two steps according to the input voltage Vi, but in the present embodiment, the first detection voltage V _{1 is} continuously changed steplessly by the current mirror CM. Is increased or decreased.

In this embodiment, a series circuit of a diode D ₅ and a resistor R ₁₆ is connected between the connection point of the resistors R ₁₀ and R _{11 and} the connection point of the resistors R ₁ and R ₂ , and the input is connected. When the diode D ₅ is turned off at the valley portion in the pulsating waveform of the voltage Vi, the resistor R ₁₆ is disconnected to raise the _first detection voltage V ₁ , and the diode D ₅ and the resistor R ₁₆ are
It has a function of lengthening the ON period of the switching element Q ₁ in the valley portion of the input voltage Vi. Further, the diode D ₄ has a function of reducing the harmonic component of the input current by blocking the regenerative current of the inductor CH. Other configurations are similar to those of the first embodiment.

(Embodiment 4) As shown in FIG. 4, the voltage adjusting circuit 3 according to the present embodiment switches the error voltage V ₂ ′ according to the input voltage Vi. In the present embodiment, the entire control circuit 2 is not configured by one integrated circuit but is configured by using an integrated circuit for each function of the control circuit 2, but the function of the control circuit 2 is described above. It is similar to that shown in each example.

In the voltage adjusting circuit 3, as in the first embodiment,
The input voltage Vi is divided by the resistors R ₁₀ and R ₁₁ , and a series circuit of a diode D ₂ and a capacitor C ₂ is connected in parallel to the resistor R ₁₁ so that the voltage smoothed by the capacitor C ₂ is used as a comparison voltage Vc for comparison. Enter in CP ₁ . Further, in the comparator CP ₁ , the comparison voltage Vc is compared with the reference voltage Vref2, and when the comparison voltage Vc is smaller than the reference voltage Vref2, the output circuit is opened. On the other hand, the series circuit of the control circuit 2 of the error amplifier 21 of the output end of two resistors R _17, which is connected to one end to the circuit ground in, R ₁₈ is connected, further connection point of the resistors R _17, R ₁₈ A resistor R ₁₉ is connected between the output terminal of the comparator CP _{1 and} the output terminal of the comparator CP ₁ .

Error voltage V ₂ 'input to the multiplier 22
Is obtained from the connection point of the resistors R ₁₇ and R ₁₈ . Therefore, when the output circuit of the comparator CP ₁ is open, the output voltage of the error amplifier 21 is divided by the voltage dividing ratio of only the resistors R ₁₇ and R ₁₈ , and when the output circuit of the comparator CP ₁ is short-circuited, the resistor R ₁₈ and resistance R
The output voltage of the error amplifier 21 is divided by the voltage dividing ratio of the parallel resistor ₁₉ and the resistor R ₁₇ . That is, the input voltage V
During the period when i is low and the comparison voltage Vc is smaller than the reference voltage Vref2, the output circuit of the comparator CP ₁ is opened and the error voltage V ₂ ′ obtained by dividing the output voltage of the error amplifier 21 by the resistors R ₁₇ and R ₁₈ is obtained. can get. During the period when the input voltage Vi is high and the comparison voltage Vc is equal to or higher than the reference voltage Vref2,
The output circuit of the comparator CP ₁ is short-circuited and the output voltage of the error amplifier 21 is divided by the resistors R ₁₇ , R ₁₈ and R ₁₉ to obtain the error voltage V ₂ ′. In this way, the change width of the error voltage V ₂ ′ with respect to the change of the input voltage Vi can be reduced, and as a result, the output voltage V ₀ can be kept constant even if the input voltage Vi changes greatly. is there. Other configurations are similar to those of the first embodiment.

(Fifth Embodiment) As shown in FIG. 5, the voltage adjusting circuit 3 in the present embodiment switches the output of the multiplier 22 according to the level of the input voltage Vi. The detection of the level of the input voltage Vi is similar to that of the fourth embodiment. The input voltage Vi is divided by the resistors R ₁₀ and R ₁₁ , and the voltage smoothed by the capacitor C ₂ via the diode D ₂ is supplied to the comparator CP ₁ . The comparison voltage Vc is compared with the reference voltage Vref2. A series circuit of resistors R ₂₀ and R ₂₁ is connected between the output end of the multiplier 22 and the circuit ground,
The voltage at the connection point between the resistors R ₂₀ and R ₂₁ is input to the comparator 23. A resistor R ₂₂ is connected between the connection point of the resistors R ₂₀ and R ₂₁ and the output terminal of the comparator CP ₁ .

Therefore, when the input voltage Vi is low and the comparison voltage Vc is lower than the reference voltage Vref2, the output circuit of the comparator CP ₁ is opened and the output voltage of the multiplier 22 is divided only by the resistors R ₂₀ and R _21. Will be. On the other hand, the output voltage of the input voltage Vi is high and the output circuit of the comparator CP ₁ to period comparison voltage Vc is the reference voltage Vref2 or more becomes short multiplier 22 resistors R _20,
It will be divided by R _21, R _22. In this way, when the input voltage Vi increases, the voltage division ratio of the output voltage of the multiplier 22 is reduced and the voltage input to the comparator 23 is lowered, so that even if the input voltage Vi changes significantly, the output voltage Vo increases. Can be kept constant. Other configurations are the same as those in the fourth embodiment.

Although the main circuit 1 is a booster type chopper circuit in each of the above-described embodiments, the technical idea of the present invention can be applied to other types of chopper circuits (such as booster type and inversion type (step-up / down type)). It goes without saying that it can be applied.

[0035]

As described above, the present invention adjusts any one of the first detection voltage, the error voltage, and the third detection voltage according to the level of the input voltage by providing the voltage adjusting section,
Since the second detection voltage is kept almost constant,
There is an advantage that the output voltage can be kept substantially constant even if the input voltage fluctuates significantly. That is, it is possible to output a stable DC voltage with a large difference between the upper and lower limits of the voltage range allowed as the input voltage, with the harmonic distortion of the input current being improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is a circuit diagram showing a second embodiment.

FIG. 3 is a circuit diagram showing a third embodiment.

FIG. 4 is a circuit diagram showing a fourth embodiment.

FIG. 5 is a circuit diagram showing a fifth embodiment.

FIG. 6 is a circuit diagram showing a conventional example.

FIG. 7 is a circuit diagram showing a main circuit in a conventional example.

FIG. 8 is an operation explanatory diagram of a main circuit in a conventional example.

FIG. 9 is an operation explanatory diagram showing the relationship between the input voltage waveform and the current flowing through the inductor in the conventional example.

FIG. 10 is an operation explanatory diagram showing the relationship between the input current and the current flowing through the inductor in the conventional example.

[Explanation of symbols]

1 main circuit 2 control circuit 3 voltage switching circuit 21 the error amplifier 22 the multiplier 23 comparator 24 RS latch 25 output circuits CH inductor L ₁ 1 winding L ₂ 2 winding Q ₁ switching element R ₁ resistor R ₂ resistor R ₅ resistance R ₆ resistance R ₇ resistance

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Nishino, 1048 Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Works Co., Ltd. (72) Koji Nishiura, 1048, Kadoma, Kadoma City, Osaka Matsushita Electric Works Co., Ltd. 72) Inventor Katsunobu Hamamoto 1048, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (3)

[Claims] 1. A main circuit comprising a chopper circuit including a switching element and an inductor for converting a DC voltage,
A control circuit for controlling ON / OFF of the switching element, wherein the control circuit includes a first detection unit that generates a first detection voltage proportional to an input voltage to the main circuit, and a first detection unit proportional to an output voltage of the main circuit. A second detection unit that generates a second detection voltage, a third detection unit that generates a third detection voltage that is proportional to the current passed through the switching element, and a fourth detection voltage that is proportional to the current flowing through the inductor. A fourth detecting unit, an error detecting unit that outputs the difference between the second detected voltage and the set voltage as an error voltage, and the third detected voltage has a specified multiplication factor for the product of the first detected voltage and the error voltage. When the multiplied voltage value is reached, the switching element is turned off and when the stored energy of the inductor is almost released is detected based on the fourth detection voltage, the switching control element is turned on. Second Power apparatus characterized by comprising a voltage control unit for controlling a first detection voltage according to the input voltage to maintain substantially constant detection voltage. 2. A main circuit comprising a chopper circuit which includes a switching element and an inductor and performs DC voltage conversion,
A control circuit for controlling ON / OFF of the switching element, wherein the control circuit includes a first detection unit that generates a first detection voltage proportional to an input voltage to the main circuit, and a first detection unit proportional to an output voltage of the main circuit. A second detection unit that generates a second detection voltage, a third detection unit that generates a third detection voltage that is proportional to the current passed through the switching element, and a fourth detection voltage that is proportional to the current flowing through the inductor. A fourth detecting unit, an error detecting unit that outputs the difference between the second detected voltage and the set voltage as an error voltage, and the third detected voltage has a specified multiplication factor for the product of the first detected voltage and the error voltage. When the multiplied voltage value is reached, the switching element is turned off and when the stored energy of the inductor is almost released is detected based on the fourth detection voltage, the switching control element is turned on. Second Power apparatus characterized by comprising a voltage adjusting unit for adjusting an error voltage in accordance with the input voltage so as to keep the detection voltage substantially constant. 3. A main circuit including a chopper circuit that includes a switching element and an inductor and performs DC voltage conversion,
A control circuit for controlling ON / OFF of the switching element, wherein the control circuit includes a first detection unit that generates a first detection voltage proportional to an input voltage to the main circuit, and a first detection unit proportional to an output voltage of the main circuit. A second detection unit that generates a second detection voltage, a third detection unit that generates a third detection voltage that is proportional to the current passed through the switching element, and a fourth detection voltage that is proportional to the current flowing through the inductor. A fourth detecting unit, an error detecting unit that outputs the difference between the second detected voltage and the set voltage as an error voltage, and the third detected voltage has a specified multiplication factor for the product of the first detected voltage and the error voltage. When the multiplied voltage value is reached, the switching element is turned off and when the stored energy of the inductor is almost released is detected based on the fourth detection voltage, the switching control element is turned on. Second Power apparatus characterized by comprising a voltage control unit for controlling a third detection voltage in accordance with the input voltage so as to keep substantially constant the detection voltage.