JPS6399764A - Chopper phase limiter - Google Patents

Abstract

PURPOSE:To prevent the excess current of a switching element from being generated, by changing the inclination of lamp voltage compared with the saturation value of phase control signal, and by obtaining the limit value of the maximum transmitivity. CONSTITUTION:A phase limit value correction circuit 1 for controlling voltage VL applied to a lamp voltage generating section according to the value of input voltage V1N is set. The output signal of the lamp voltage generating section is led from an operational amplifier 6 and is applied to a comparator 10. By a voltage limiter 9, phase control signal VE is limited, and the limited phase control signal is applied to the comparator 10. Lamp voltage is compared with the phase control signal by the comparator 10 to feed phase signal. By a logic circuit 11, on the basis of the phase signal from the comparator 10, gate control signal is applied to a main circuit switching element 12. By the main circuit switching element 12, the transmitivity of the input voltage is controlled, and the voltage is fed as output voltage.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention provides a chopper suitable for limiting overcurrent when used in a chopper device used particularly for power conversion, electric motor drive, etc. The present invention relates to a phase limiter.

(Prior art) Conventionally, as a method of controlling the output voltage of a chopper device, a feedback signal of the output voltage is compared with a reference signal, a phase control signal is obtained by amplifying the deviation, and this phase control signal and a lamp are A method is known in which the conduction rate is determined by comparing voltage waveforms (hereinafter referred to as lamp voltages).

FIG. 9 is a block diagram of such a conventional chopper phase limiter, especially the phase control signal Vp and ramp voltage V. This shows the configuration of the part that compares the values and obtains the conductivity α. Resistor 1
A lamp voltage generation section is constituted by an integrating circuit composed of a Zener diode 15 connected in series with a Zener diode 15, an operational amplifier 6, resistors 2 and 3, and a capacitor 7, and an analog switch that operates in synchronization with the reference clock pulse F. 8, the Zener voltage value of the Zener diode 15,
A lamp voltage having a constant slope determined by the resistance value of the resistor 2 and the capacitor 7 is generated.

The output signal V of this lamp voltage generator. is derived from operational amplifier 6 and sent via resistor 4 to comparator 10. On the other hand, the voltage limiter 9 limits the phase control signal V, and sends out the limited phase control signal VE'.
It is applied to a comparator 10 via a resistor 5. Comparator 10 compares the lamp voltage with phase control signal 6' and sends out a phase signal. Logic circuit 11 is comparator 1
Main circuit switching element 1 based on the phase signal from 0
2 is given a gate control signal with a conduction rate α. The main circuit switching element 12 controls the conduction rate α of the input voltage VIN to obtain the output voltage V. Close and send.

In this configuration, the logic circuit 11 is given a reference clock pulse F with a period T as shown in FIG.
In order to turn off the analog switch 8 in synchronization with the rise of , a negative gate voltage is applied as an opening/closing signal, and as shown in FIG.
Turn on the gate control signal for 2. From this point on, the lamp voltage generator generates a lamp voltage V with a constant slope as shown in FIG. 10(B). is generated and this is passed to comparator 10
give to The comparator 10 compares the lamp voltage Vc and the phase control signal V', and inverts the output when the lamp voltage Vc becomes equal to the phase control signal VE'.
This is given to the logic circuit 11. The logic circuit 11 detects the inversion of the output signal of the comparator 10 and turns off the open/close signal to turn on the analog switch 8, and also turns off the gate control signal as shown in FIG. 10(C). This gate control signal is applied to the main circuit switching element 12 to control its conduction rate α.

As shown in FIG. 10, t is the period from the rise of the reference D-switch pulse F until the lamp voltage Vc intersects with the phase control signal VB' after applying the voltage limiter. If N, the conduction rate α of the main circuit switching element 120 is α-t ON/T (
1). That is, the output voltage V. When the reference signal for generating the position control signal changes, the position J[I
;L control signal V6 also changes, output voltage V. The conduction rate α is also changed so that the feedback signal of is made to match the output voltage reference signal.

In general, the output voltage■. In order to increase the settling accuracy of the deviation signal, an integrator circuit is usually included in the amplification of the deviation signal. Therefore, when the load increases or the output voltage reference signal rises, the phase control signal VE increases, and when this becomes excessive, the voltage limiter 9 suppresses it to the limit value -■. In other words,
In such a case, the conductivity a is the maximum α (=
AX tONMAX/''). Here, the phase control signal V E ' is a constant value at voltage -■, and the slope of the lamp voltage V is also constant, so the conduction rate αMAX is a constant value. .

FIG. 11 shows a circuit example of a well-known step-up chopper device, in which input voltage VIN is input through an inductance axle 25, a switching element 28 connected in a shunt, a rectifying element 26, and a capacitor 27 connected in a shunt. Output voltage V
. In obtaining the output voltage V. and the reference voltage v, 8. The error amplifier 29 detects the deviation between the
A phase control signal is generated based on this error signal, and the conduction rate of the switching element 28 is controlled via the pulse amplifier 31 to obtain the output voltage V. the reference voltage ■, 8. is configured to control the

In such a configuration, ■ INNMA during period t
The voltage Is flowing through the switching element 28 rises to (V/L)t with a time constant of X/L. Also, due to a malfunction, the output voltage may be ■. The conduction rate is fixed at αMAX even when the feedback signal of Vr is cut off or the reference signal Vr8r for the output voltage V is saturated at the upper limit value.

(Problems to be Solved by the Invention) Here, consider a case where the input voltage VIN changes while the conduction rate is fixed at αMAX. Output voltage V of the boost chopper device shown in FIG.

is V −V /(1-α) ・・・・・・(
2) Current Is expressed as OIN and flowing through the switching element 28
teeth! s-(VIN/L)tON...
...It is expressed as (3). According to these relational expressions, t
When oN is fixed to NM^X, the conduction rate α is αM
Since it is fixed at AX, VI is determined by equations (2) and (3).
When N changes, the output voltage Vo also changes to the switching element 28.
It can be seen that the current I8 flowing through the circuit also changes in proportion to the input voltage vIH. In other words, in cases where the input voltage vIN changes significantly, such as when a battery or the like is used as a power source, t, that is, NMAX (maximum conduction rate αMAX), is set to a small value in accordance with the maximum value of the input voltage VIN. Then, when the input voltage decreases, the output voltage V. will also decrease. On the other hand, if the setting is made to match the lowest value of the input voltage VIN, a problem arises in that the current 18 flowing through the switching element 28 at the highest time increases.

Although it is possible to provide final protection against these problems by providing separate output voltage limiting circuits and current limiting circuits, limiting the conduction rate also limits the output voltage and reduces the element current. Since suppression has to be carried out, redundant protection becomes insufficient.

As mentioned above, in the conventional technology, since the maximum value αMAX of the conduction rate is a fixed value, the input voltage vIN
There are cases where the conduction rate αMAX becomes excessive with respect to the normal conduction rate control range determined by, and when the phase control signal is saturated due to a failure or the like, the output voltage becomes an overvoltage depending on the input voltage vIN. In addition, even during normal control, the phase control signal may become saturated when the load suddenly increases, and as shown in equation (3), a current proportional to αMAX and input voltage vIH may flow through the switching element, resulting in an overcurrent. It becomes a problem.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, so that even if the input voltage changes when the phase control signal is saturated, the output voltage limit value does not change, and the overcurrent to the switching element does not change. It is an object of the present invention to provide a chopper phase limiting device that can also limit the phase of a chopper.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a means for determining the maximum conduction rate of a chopper that controls the output voltage by controlling the reverse current rate while keeping the switching frequency constant, based on the saturation value of the phase control signal and the lamp voltage. In a chopper phase limiter that limits the maximum value of conductivity obtained by comparison as a limit value, the input voltage of the chopper is detected, and from this detected input voltage and a predetermined output voltage limit value of the chopper. Calculate the maximum conduction rate limit value,
The present invention is characterized in that it includes a correction means for changing the slope of the lamp voltage so that the limit value of the maximum conductivity is obtained.

(Function) Now, considering the step-up chopper device shown in FIG. 11 as an example, the relationship between the input voltage VIN', the output voltage Vo, and the conduction rate α is expressed by the following equation.

vo-V, N/ (1-α) ・・・・・・(4)
Here, the output voltage Vo is the maximum value V. If α is α that limits the input voltage to MAX, then V OMAX-V IN/(1-(Z MAX )
``'''' (5) holds true. From equation (5), V by changing αMAX in response to a change in input voltage vIH. ) It can be seen that the IAI can be kept constant.

The chopper phase limiter of the present invention is based on the above principle,
By changing the slope of the lamp voltage according to the input voltage and thereby making the maximum current flow rate of the switching element of the chopper device variable, it is possible to limit the output voltage to a constant value and prevent overcurrent to the switching element. It is designed to prevent this.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a chopper phase limiting device according to an embodiment of the present invention. This device is based on the device shown in FIG. 9, and is characterized in that it is provided with a phase limit value correction circuit 1 to control the voltage VL applied to the lamp voltage generator according to the value of the input terminal vIN.

In the configuration shown in FIG. 1, the relationship between the lamp voltage Vo and the output signal VL of the phase limit value correction circuit 1 is V −RCVo/
It is expressed as loN −・−・−・・−(8). Here, R is the resistance value of the resistor 2, C is the capacitance value of the capacitor 7, and toN is the integration time.

Here, the phase control signal VE becomes excessive and the voltage limiter 9
Considering the case where the voltage is limited to −V by
'--V, and as shown in FIG. 4(B) by the comparator 10.
, ■ as shown in (C). t is determined by comparing E O
NMAX Lenote, v -v'--v, 1 -1
WCE ON
By substituting into ONMAX equation (6), the following equation (7) is obtained.

vL = -RCV/lONMAX'...
(7) Also, it can be expressed as a −t /T, so if the period T of the reference pulse F is constant, then −RC
When V/T is defined, 1 becomes a constant, and equation (7) becomes V, =, /αMAX ...... (8
) can be transformed. Therefore, from equation (5), α
Vt obtained by calculating and substituting into equation (8).

By using MAX, VoMAX can be kept constant. That is, by substituting α-αMAX into equation (4), it becomes V −V /(1-αMAX), and from OIN equation (5), VO=vOMAX. αMAX obtained from equation (5) is α −” IN/vO) IAI '・・・・・・(
9) MAX. Therefore, the phase limit value correction circuit 1 can be represented by a gain configuration as shown in the block diagram of FIG. 2 using equations (8) and (9).

FIG. 3 is a block diagram of a phase limit value correction circuit in which the gain configuration shown in FIG. 2 is used as a specific circuit configuration.

As shown in the figure, the input voltage VIN is input to the isolation amplifier 22, and its output is divided by resistors 18 and 19 and then input to the X2 input terminal of the divider 23. At the same time, the control power supply voltage -Vl is divided by resistors 16 and 17 and input to the 22 input terminal of the divider 23, which also serves as the control power supply voltage.

+v1 is divided by resistor 20.21 and divided into X1 of divider 23.
Input to input terminal. The voltage division ratio by resistor 18.19 is 1/VoMA, the voltage division ratio by resistor 16.17 is 1, and the voltage division ratio by resistor 20.21 is a constant "1'.
are embodied as the gain and addition/subtraction constant in FIG. 2, respectively. The divider 23 is Vt, -(Z2 Zl) / (Xt X2)
... Perform the calculation (10).

With this configuration, αMAXMAX is generated that suppresses the output voltage to V 2 with respect to the input voltage VIN, so it is possible to suppress the output voltage to VoMAX. In other words, since the input voltage MAX is set so that the limit value of the output voltage V is constant according to the input voltage IN, the normal conduction rate α is set even if the input voltage VIN changes.
αMAX does not become excessive with respect to the control range of .

Therefore, even when the phase control signal is saturated due to a failure or the like, the output voltage V remains constant. does not cause an overvoltage, and it is possible to prevent the switching element from generating an overcurrent even during normal control.

FIG. 6 is a block diagram of a chopper phase limiting device according to another embodiment of the present invention. The difference between the configuration shown in the figure and the configuration shown in FIG. It can be applied to such uses.

That is, when 2--RCV is defined in equation (7), V-K/T is defined as AX.

Furthermore, since the period T can be expressed as 1/f using the frequency f, VL- becomes 2f/αMAX. Therefore, by adding correction with a voltage proportional to the frequency f, the input voltage VIN
′ for the variation of the output voltage V. Also, overcurrent in the main circuit switching cable 12 can be limited.

FIG. 7 is a block diagram showing the gain configuration of the phase limit value correction circuit 1 of FIG. 6. In the figure, the F/V conversion block converts the frequency of the reference clock pulse F into a voltage value.

On the other hand, FIG. 8 is a block diagram of a specific configuration based on the gain configuration of FIG. 7. The difference from the configuration shown in FIG. This is the same as the configuration example shown in FIG.

By configuring as shown in Figure 8, the reference clock pulse F can be changed to increase the frequency to increase the response speed of the voltage control system, or to lower the frequency to reduce switching loss and increase efficiency. Even though
Output voltage V. It will be effective to keep it to VOHAX.

In this way, the main circuit switching element 1
By changing the maximum value 'MAX of the conduction rate of 2, even if the phase control signal is saturated due to a failure etc., the output voltage Vo can be adjusted to VOHAX regardless of the magnitude of the input voltage VIN.
can be suppressed to Furthermore, even in the normal control state, αMAX can be always set close to the upper limit of the control range, so the current flowing through the main circuit switching element 12 can also be suppressed.

In each of the above embodiments, a step-up chopper is used as the chopper, but the application of the present invention is not limited thereto, and the same effect can be expected with a step-down chopper.

In the case of a buck chopper, the input voltage VIN and the output voltage V
Since the relationship between the conduction rate α and the current conduction rate α is expressed as α-vo/vINOゝ, the limit value V of the output voltage V. For MAX, 'MAX'' = vOMAX/vIN (
In combination with equation 8), a gain configuration as shown in the block diagram of FIG. 5 can be obtained. In other words, the output voltage Vo is V with respect to the input voltage V. Since N α MAX can be set such that N α MAX becomes MAX, output overvoltage and switching element overcurrent can be suppressed.

According to the present invention, there is no need to turn off the chopper device or the like used in the field circuit of a DC motor even in the event of a failure, and the present invention is effective as a countermeasure against field loss; A2B pressure, and field loss.

〔Effect of the invention〕

According to the present invention, even if the input voltage increases in a state where the output voltage is limited to the limit value due to a failure or the like, the output voltage can be suppressed to the limit value, and furthermore, the maximum value of the conduction rate is the input voltage. Since the current decreases as the current increases, overcurrent in the switching element can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a chopper phase limiter according to an embodiment of the present invention, FIG. 2 is a block diagram showing the gain configuration of the phase limit value correction circuit of FIG. 1, and FIG. 3 is a block diagram of the phase limiter of FIG. 2. FIG. 4 is a time chart showing the operation of the configuration of FIG. 1; FIG. 5 is a block diagram showing another example of the gain configuration of the phase limit correction circuit; FIG. is a block diagram of a chopper phase limiter according to another embodiment of the present invention, FIG. 7 is a block diagram showing the gain configuration of the phase limit correction circuit of FIG. 6, and FIG. 8 is a block diagram of the phase limit correction circuit of FIG. 7. FIG. 9 is a block diagram of a conventional chopper phase limiting device; FIG. 10 is a time chart showing the operation of the configuration of FIG. 9; FIG. 11 is a block diagram of a well-known boost chopper device. It is. DESCRIPTION OF SYMBOLS 1... Phase limit correction circuit, 6... Operational amplifier, 8...
・・Analog switch, 9・Voltage limiter, 10・
...Comparator, 11...Logic circuit, 12...
・Main circuit 4 Soching element, 15... Constant voltage diode, 22... Isolation amplifier, 23... Divider, 24
... F/V converter, 28 ... switching element, 2
9... Error amplifier, 30... Phase control circuit, 31.
...Pulse amplification circuit. Applicant's agent 1ii, Fujio also; Figure 2 Figure 3 Figure 54 Figure 5 Figure 7121 ◆ 8 Figure 9 Figure T V'''' tON tONMAX Redundancy 10 Figure name 11 Figure

Claims (1)

[Claims] 1. The maximum conduction rate of a chopper that controls the output voltage by controlling the conduction rate while keeping the switching frequency constant is obtained by comparing the saturation value of the phase control signal and the lamp voltage. In a chopper phase limiter that limits the maximum conductivity as a limit value, the input voltage of the chopper is detected, and the maximum conductivity is determined from the detected input voltage and a predetermined output voltage limit value of the chopper. A chopper phase limiting device characterized by comprising a correction means for calculating a limit value and changing the slope of the lamp voltage so that the limit value of the maximum conduction rate is obtained. 2. The chopper phase limiting device according to claim 1, wherein the correction means includes means for correcting the slope of the lamp voltage based on the switching frequency of the switching element of the chopper.