JPH0221223B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an input separation circuit, and in particular to a switching leg that reduces the control width of the DC voltage input to the inverter section by automatically switching the rectification method depending on the level of the input voltage. This invention relates to an input separation circuit for a urator.

Commercial power supply voltage around the world starts from AC80V
It shows various voltage values up to AC276V. Therefore, in order to use the same type of switching regulator in various countries around the world, the rectification method is automatically switched depending on the level of input voltage. That is, for example, when the input voltage is less than 150 VAC, voltage double rectification is performed, and when it is higher than that, full-wave rectification is performed, and the obtained input DC voltage is applied to the inverter section. By doing so, the input voltage range of the inverter section can be reduced to approximately half that of using a single rectification method, which significantly impairs the control ability, performance, shape, cost, etc. of the switching regulator. I'm trying not to do that.

However, in a switching regulator that automatically performs this type of rectification, the rectification method described above may switch to voltage doubler rectification when the power is turned on or if the input is interrupted intermittently. There is a problem. This problem can be ignored if the input voltage is originally low (for example, 150 VAC or less), but on the other hand, if the input voltage is a high voltage of 200 VAC, it has a negative effect on the device that cannot be ignored. That is, by voltage-doubling rectification of a high-voltage input, a significantly high DC voltage is applied to the inverter section, resulting in destruction of the switching transistor. Furthermore, the intermittent on/off of power supply and input that causes this kind of problem is likely to occur during normal use of the switching regulator, such as when the power switch is turned on and off, instantaneous power outages, and instantaneous voltage drops. Therefore, there was a need to reliably separate the input voltages.

Therefore, the main object of the present invention is to provide an input separation circuit for a switching regulator that can reliably separate the input voltage even when the power is turned on or when the input voltage fluctuates instantaneously. .

To this end, the present invention connects a plurality of charging circuits with different time constants to the level discriminator, so that level discrimination is performed based on the voltage of the charging circuit with a large time constant in the event of instantaneous input interruption, etc. Furthermore, one aspect of the present invention is to perform full-wave rectification, which is a safe rectification for the circuit operation of the switching regulator, for a certain period of time from the time of power-on, regardless of the input voltage level, when the power is turned on. It is characterized by its unconditional implementation.

Hereinafter, the input separation circuit of the switching regulator according to the present invention (hereinafter referred to as "the circuit of the present invention")
An example will be described with reference to the drawings.

FIG. 1 is a circuit diagram schematically showing an embodiment of the circuit of the present invention. In the figure, 1 is a rectifier unit that converts AC input into DC in conjunction with smoothing capacitors C ₁ and C ₂ connected in series to output terminals t ₃ and t ₄ , 2 is an inverter unit to which the DC is applied, and 3 is a rectifier unit that converts AC input into DC. A triat is a semiconductor switch interposed between the input ground terminal _t3 of the rectifier ₁ and the connection between the smoothing capacitors C1 and _C2 .
When this triax 3 is closed, voltage double rectification is performed, and when it is open, full-wave rectification is performed.
A trigger circuit 4 provides a trigger to the triac 3 in accordance with the opening/closing operation of the switching circuit 5 including a transistor Tr ₃ and a resistor R ₇ .
Reference numeral 6 denotes an input discriminator circuit which is an embodiment of the circuit of the present invention, and this input discriminator circuit discriminates high and low input voltages to control the opening/closing operation of the switching circuit 5. This input discriminator circuit is formed by connecting the level discriminator 7 to a charging section 8 including, for example, two charging circuits having different time constants. That is, in the charging section 8, the resistors R ₁ , R ₂ and the capacitor C ₃ are connected to one charging circuit (hereinafter referred to as "charging circuit A"), and the capacitor C ₄ , the charging circuit A and the level discriminator 7 are connected to the other charging circuit. A circuit (hereinafter referred to as "charging circuit B") is formed. Here, capacitor _C3 is rapidly charged by the energy of capacitor _C4 . Therefore, the discharge time constant of charging circuit A is larger than that of charging circuit B. Charging part 8
, D ₁ is a rectifier diode, and D ₂ is a discharge prevention diode of charging circuit A.

The level discriminator 7 includes a Schmitt circuit composed of transistors Tr ₁ and Tr ₂ and resistors R ₃ to R ₄ , and the output voltage of the charging section 8 is applied to the base of the transistor Tr ₁ via a Zener diode ZD. . Here, _C5 is a bypass capacitor, and _R6 is a bias setting resistor. Note that t ₁ is an input terminal other than the input ground terminal of the rectifier 1, and L ₁ and L ₂ are input AC supply lines to which input AC voltage is applied.

Next, the operation of one embodiment of the circuit of the present invention having the above-described configuration will be explained.

The AC inputs applied to the input terminals T ₁ and T ₂ are applied to the rectifier 1 and also to the input separation circuit 6 . Then, the AC input given to the input separation circuit 6 is rectified and smoothed by the diodes D ₁ and D ₂ and the capacitors C ₃ and C ₄ in the charging section, and
Capacitors C ₃ and C ₄ are charged respectively. At this time, the discharging time constant of charging circuit A is larger than the discharging time constant of charging circuit B. As the output voltage of charging circuit B rises, the output voltage of charging circuit A also rises.
The voltage divided by R ₁ and R ₂ is applied to the level discriminator 7. When the voltage applied to the level discriminator 7 is higher than the reference voltage determined by the Zener diode ZD, the Schmitt circuit is driven as described later. Therefore, the resistors R ₁ and R ₂ and the Zener diode ZD are determined depending on the magnitude of the input voltage at which the rectification method is to be switched.
On the other hand, the time constants of charging circuits A and B are determined in relation to the switching time of the rectification system.

Now, if the input voltage is higher than the set value, the Zener diode ZD is closed and the transistor Tr ₁ is driven. As a result, the transistor Tr ₂ is driven, so the switching circuit 5 is closed.

Conversely, it is clear that when the input voltage is lower than the set value, the switching circuit 5 remains open.

Therefore, when the input voltage is high, the trigger given from the trigger circuit 4 flows into the ground line via the switching circuit 5, and the trigger applied from the trigger circuit 4 flows into the ground line through the switching circuit 5.
is not closed, so a full-wave rectified DC input is given to the inverter section 2. Thus, when the input voltage is lower than the set value, voltage double rectification is performed.

Next, a case will be described where the input voltage is higher than the set value, that is, when the full-wave rectified DC input is being applied to the inverter unit 2, and the input is momentarily cut off.

When the switching regulator is in a steady state, charging of the capacitors C ₃ and C ₄ of the charging section 8 has been completed, so the terminal voltages of both capacitors are approximately equal. Here, when the input is momentarily cut off, charging circuits A and B start discharging according to their respective discharge time constants, so their output voltages gradually decrease.

FIG. 2 is an explanatory diagram schematically showing the discharge states of charging circuits A and B. In the figure, the vertical axis shows the terminal voltage of each capacitor C ₃ and C ₄ , and the horizontal axis shows the discharge time. The broken line in the figure is a set voltage corresponding to the input voltage for switching the rectification method.

As is clear from the figure, as a result of the delay in falling of the output voltage of the charging circuit A, the level discriminator 7 discriminates the divided voltage value of the terminal voltage of the capacitor _C3 . Therefore, by appropriately selecting the capacitance of capacitor C ₃ , the time during which the terminal voltage of capacitor C ₃ takes a voltage value higher than the set voltage (T ₀ in the same figure) can be calculated as follows:
It can be made longer than the normal instantaneous interruption time of the input. As a result, during the above T ₀ time, the switching regulator performs full-wave rectification, so
Even if the input is restored during that time, the high voltage input will not be voltage doubled and rectified. Therefore, the embodiment of the circuit of the present invention described above can reliably separate the input voltage even when the input voltage fluctuates instantaneously.
Trouble caused by high DC voltage being applied to the inverter section can be eliminated.

Next, another invention that has the same purpose as the above-mentioned circuit of the invention and has a common structure in common will be described.

That is, the present invention is characterized in that, in a level discriminator connected to a plurality of charging circuits having different time constants, the charging circuit is connected in parallel to the switching circuit included in the level discriminator.

That is, in FIG. 2, a capacitor _C6 is connected in parallel to a transistor _Tr2 constituting a Schmitt circuit as a switching circuit included in the level discriminator 7. Capacitor C ₆ thus forms a charging circuit together with resistor R ₅ and is connected in parallel with the Schmitt circuit.

The input classification circuit of such a switching regulator will be explained below. Immediately after input voltage is applied, the capacitor shown in Figure 1
Charging of C ₃ and C ₄ is not yet completed, and the phase of the input voltage is unknown, so the peak voltage cannot be detected in advance. Therefore, it is not possible to determine whether the triax 3 is closed or opened.
However, when considering the safety of the switching regulator, the rectification method must be set to the safe side for the circuit operation of the switching regulator until the level discriminator 7 completes input voltage discrimination. It is desirable to use some full-wave rectification.

Therefore, when the capacitor C ₆ is connected in parallel to the transistor Tr ₂ , the input terminals T ₁ and
When AC input is applied to T ₂ , the terminal voltage of capacitor C ₄ gradually increases as capacitor C ₄ is charged. As a result, a charging current flows into the capacitor _C6 via the resistor _R5 , so that the base current of the transistor _Tr3 of the switching circuit 5 flows, closing the transistor _Tr3 . Therefore, regardless of the magnitude of the input voltage, the rectification method can be kept at full-wave rectification until charging of the capacitor _C6 is completed. Therefore, the time constant of the charging circuit formed by the resistor _R5 and the capacitor _C6 (hereinafter referred to as "charging circuit C") is made larger than the time constant of the charging circuit B,
In addition, by setting the input power supply frequency to more than 1/2 cycle, before the charging of capacitor _C6 is completed,
Since the input voltage has already been separated by charging the capacitor _C4 , switching of the rectification method can be performed easily and reliably.

Furthermore, if there is a momentary interruption of the input while the switching regulator is in operation, even if the interruption period is longer than the time T ₀ shown in Fig. 2,
When the input is restored, the electricity stored in capacitors _C4 and _C6 has already been discharged, so full-wave rectification will be performed as described above regardless of the voltage value of the restored input. Become.

Therefore, one embodiment of the circuit of the present invention described above performs full-wave rectification, which is a safe rectification for the circuit operation of the switching regulator, from when the power is turned on until the input voltage is separated. Since a signal for unconditionally executing is outputted, and an output based on the input classification is then given, the input voltage can be classified more reliably.

As is clear from the above description of one embodiment of the device of the present invention, the input separation circuit of the switching regulator according to the present invention can withstand instantaneous fluctuations in the input voltage and when the power is turned on. Since the input voltages can be reliably separated, it is possible to eliminate the inconvenience of extremely high DC voltage being applied to the inverter section. Therefore, the present invention is extremely useful in a switching regulator that reduces fluctuations in the DC voltage input to the inverter section by automatically switching the rectification method depending on the level of the input voltage.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram schematically showing an embodiment of the circuit of the present invention, and FIG. 2 is an explanatory diagram schematically showing the discharge states of charging circuits A and B. DESCRIPTION OF SYMBOLS 1... Rectifier section, 2... Inverter section, 3... Triax, 4... Trigger circuit, 5... Switching circuit, 6... Input separation circuit, 7... Level discriminator, 8... Charging section.

Claims (1)

[Claims] 1 First and second input terminals t ₁ and t ₂ are connected to the first and second AC power supply lines L ₁ and L ₂ , respectively, and are applied to the first and second AC power supply lines L ₁ and L ₂ . a rectifier 1 that rectifies input AC voltage and outputs a DC voltage from first and second output terminals t ₃ and t ₄ ;
First and second capacitors C ₁ and C ₂ connected between the second output terminals t ₃ and t ₄ and connected in series with each other.
and an inverter section 2 connected between the first and second output terminals _t3 and _t4 of the rectifier section 1,
The connection point of capacitors C ₁ and C ₂ is connected to the second
rectifier part 1 by connecting it to the input terminal end _t2 of
The input AC voltage of the switching regulator is switched from full-wave rectification to voltage doubler rectification, and the semiconductor switch 3 is made conductive to the input separation circuit 6, which includes a charging section 8 and a level discriminator 7. A trigger circuit 4 that outputs a signal is connected to the output side of the input sorting circuit 6, and is turned on or off depending on the magnitude of the output of the input sorting circuit 6 to pass the output of the trigger circuit 4 to the second side of the rectifying section 1. The charging section ₈ is equipped with a switching circuit 5 that turns on or off the semiconductor switch ₃ by conducting or cutting off the input terminal t 4 of the input terminal t 4 or the second AC power supply line L 2 . first and second rectifiers D ₁ connected between the electric wires L ₁ and L ₂ and connected in series with each other;
D ₂ and the third capacitor C ₃ and the second rectifier
A fourth capacitor _C4 is connected in parallel to _{D2 and} the third capacitor _C3 , and voltage dividing resistors _R1 and _R2 are connected in parallel to the third capacitor C3. The circuit 7 includes a Schmitt circuit including front-stage and rear-stage transistors Tr ₁ and Tr ₂ connected via a Zener diode ZD between the connection points of the voltage dividing resistors R ₁ and R ₂ , and a rear-stage transistor Tr 1 connected to the transistor Tr ₁ in the rear stage. 1. It has a resistor R ₅ connected to the connection point of the second rectifiers D ₁ and D ₂ , and a fifth capacitor C ₆ that bypasses the subsequent transistor Tr ₁ , and a third capacitor C ₃ . The time constant of the first charging circuit A consisting of voltage dividing resistors R ₁ and R ₂ is different from that of the second charging circuit B comprising the fourth capacitor C ₄ , the first charging circuit A and the level discriminator 7. greater than the time constant of and also the resistance
An input separation circuit for a switching regulator, characterized in that a time constant of a third charging circuit C consisting of _R5 and a fifth capacitor _C6 is larger than a time constant of the second charging circuit B.