JP2500779Y2 - Switching power supply control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a circuit for controlling an operating state such as start / stop of an electronic device such as a switching power supply device through a single control terminal, particularly for an electronic device. And an electronic circuit operation state control circuit suitable for being incorporated into a semiconductor integrated circuit device together with the electronic circuit.

[Conventional technology]

In electronic devices such as the switching power supplies described above,
By integrating the electronic circuit part for control, etc. in a one-chip IC, it is possible to miniaturize and rationalize the entire electronic device. As is well known, the so-called ASIC is suitable for such applications, and it is a relatively small scale. Linear ICs that can handle analog signals are often suitable for various electronic devices. In order for the integrated circuit device to control various functions that the electronic device should perform, it is necessary to give a designation signal for each function to the electronic device. Conventionally, a terminal of the integrated circuit device is provided for each function of the electronic device. It is customary to give the operating state designation signals to these terminals individually.

For example, in a switching power supply device, an on / off control operation for turning the output on and off, a so-called soft start function for gradually raising the output voltage at the time of startup, an overload protection function for stopping the output when an overload condition is required, etc. A signal designating that an operating state corresponding to a function should be taken is given to a terminal provided in the integrated circuit device corresponding to each function.

[Problems to be solved by the device]

ASICs for relatively small-scale electronic devices, especially the above-mentioned linear ICs, do not need to be highly integrated, but when incorporated into electronic devices, it is required that the size including the package be as small as possible. If a terminal is provided for each function to be performed by the electronic device as described above, there is a problem that the size of the package is correspondingly increased. As is well known, there are standards for packages for integrated circuit devices. For example, if the number of terminals exceeds 8, an 8-pin package is no longer necessary, and a package with a larger size must be used.

An object of the present invention is to solve this problem and reduce the number of terminals of the integrated circuit device by incorporating an operating state control circuit therein so that it is not always necessary to provide a terminal for each function of the electronic device. is there.

[Means for solving the problem]

According to the present invention, the purpose is to provide a control terminal to which an electric potential for controlling the operating state of the electronic device is applied and an operation to put the electronic device into the operating state only when the potential value is within a preset potential range. An operating state control circuit is configured by a start / stop circuit, a potential applying means for applying a potential higher than the set potential range to the control terminal, and a potential holding circuit for limiting and holding the potential applied to the control terminal from this means within the set potential range. Then, the electronic device is held in the stopped state by externally designating the control terminal potential outside the set potential range, and this designated state is released, and the potential holding circuit holds the control terminal potential within the set potential range and This is achieved by putting the device into an operating state and releasing the potential holding operation of the potential holding circuit when the electronic device abnormally operates to stop the operation of the electronic device.

The control terminal specifies any one of a plurality of states to be taken by the electronic device according to the value of the potential, and is commonly provided for the plurality of states or functions of the electronic device.

The set potential range for the operation start / stop circuit may be a range set by a single upper limit or lower limit, but it is desirable to set this as a range between the upper and lower limits.

As the potential applying means, the simplest is a so-called potential raising resistor connected between the power supply point having a potential higher than the set potential range and the control terminal, but the potential by means such as a Zener diode of the potential limiting circuit. It is desirable to use a constant current source circuit in order to make the limiting operation accurate.

The electric potential of the control terminal limited by the electric potential holding circuit is the simplest electric potential in the simplest case, but a plurality of limiting electric potentials may be set as necessary to switch the electric potential value according to the operating state of the electronic circuit. By doing so, it is possible to provide a plurality of set potential ranges or divide the set potential range into a plurality of ranges and use the operating state, that is, the function of the electronic device into a plurality of groups.

As described above, the control terminal potential is externally specified outside the set potential range and the electronic device is stopped. Then, the specified state is canceled and the potential limiting circuit limits the control terminal potential within the set potential range. Thus, when the electronic device is put into the operating state, if the rate of change in the potential with time is controlled by means such as connecting a capacitor to the control terminal, the switching power supply device can be operated in the steady operating state as described in the example section, for example. You can give it a function to soft start before putting it in.

[Action]

The operating state control circuit according to the present invention designates or controls a plurality of functions to be performed by the electronic device or a plurality of states to be given to the electronic device by a potential or a potential range applied to the control terminal. Succeeded in reducing the number of terminals in an integrated circuit device by eliminating the need to provide a separate terminal for each function of the electronic device by providing it so that it can be connected to a circuit and shared for multiple functions and states of the electronic device. It was done.

Therefore, in the circuit of the present invention, a high potential is applied to the control terminal by the potential applying means described in the preceding paragraph, and this potential is limited by the potential holding circuit and held as the control terminal potential.
Therefore, according to the principle of the present invention, this potential holding circuit serves as a storage means of the control terminal potential.

Further, in the present invention, considering that the common function of most electronic circuits has an on / off function and an overload protection function, the control terminal potential is monitored, and the electronic device is operated only when the value is within a preset potential range. An operation start / stop circuit that puts the electronic device into an operating state is provided, and the electric potential holding circuit holds the control terminal potential within this set potential range to put the electronic device in the operating state. The holding operation of the electric potential is released to automatically stop the operation of the electronic device.

That is, the present invention configures the operating state control circuit so as to control at least the states related to the most basic on / off and overload protection functions of the electronic device.

Of course, the operating state control circuit according to the present invention can be appropriately configured so as to control the operating states related to not only the basic functions but also other specific functions required for each electronic device. For this purpose, for example, a plurality of operation start / stop circuits and potential holding circuits can be provided as needed. The electric potential of the control terminal shared by a plurality of functions of the electronic device can be controlled not only from outside the electronic device but also within the electronic device in association with its operating state or state change.

〔Example〕

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 shows a state in which the circuit of the present invention is incorporated in a case where the electronic device is a switching power supply device. The right side of the drawing is a switching power supply unit and the left side is an integrated circuit device 60 for controlling it. The operation state control circuit of the present invention incorporated in the integrated circuit device 50 controls the on / off operation, the soft start operation and the overload protection operation of the switching power supply device in this example.

First, the switching power supply unit will be described. As is well known, this converts an input voltage Vi into a stabilized output voltage Vo, and its switching transistor 1 receives an opening / closing command Ss from an integrated circuit device 50 and a primary coil of a transformer 2.
Open and close the current of 2a. The AC voltage induced in the secondary coil 2b of the transformer 2 is rectified by the diode 3, smoothed by the capacitor 4, and output as the output voltage Vo. Output voltage Vo
From which the actual value Sa is produced by the pair of resistors 5a and 5b of the voltage divider circuit 5.

The integrated circuit device 60 includes a PWM circuit 40 that receives this actual value Sa and a command circuit 50 that generates the above-mentioned switching command ASs for controlling the switching power supply unit. The error amplifier 41 in the PWM circuit 40 detects the difference between the actual value Sa and the reference value er, which is the set target value of the output voltage Vo, and detects this difference and outputs it to the external capacitor 63.
The error signal Se which is amplified by a stable high gain under the capacitive negative feedback due to is output, and the reference wave generation circuit 42 uses the external reference capacitor St as a reference wave St having a waveform such as a triangular wave as shown in the frame.
It occurs at the cycle set by 64.

The PWM comparator 43 in the PWM circuit 40 compares the error signal Se with the reference wave St, and outputs a duty ratio designation signal for opening and closing the switching transistor 1 to the command circuit 50 via the attached inverter 43a. The command circuit 50 commonly receives the duty ratio designating signal at the bases of the pair of Darlington transistors 51 and 52 connected between the power supply voltage Vc and the ground potential E, and outputs the open / close command Ss by the push-pull operation. The switching transistor 1 uses this switching command Ss so that the actual value Sa of the output voltage Vo is always equal to the reference value er.
It is usual to be PWM controlled by.

The operation state control circuit of the present invention is incorporated in the integrated circuit device 60 which performs the above control operation. First single control terminal Tc
Is provided so that it can be connected to the outside.
61 and capacitor 62 are connected to this as an external circuit.
The former is for putting the control terminal potential v at the ground potential in the closed state to bring the switching power supply device into the stopped state, and the latter is for soft starting it.

Next, an operation start / stop circuit 10 for receiving the control terminal potential v is provided to start / stop the operation of the switching power supply device.
The operation start / stop circuit 10 of this embodiment includes comparators 11 and 12 for comparing the control terminal potential v with the first potential e1 and the second potential e2, respectively, and an OR gate 13 for receiving their outputs, as shown in the figure. For example, the first electric potential e1 is 0.5V,
The second potential e2 is set to 7V, and the control terminal potential v is 0.5 to 7V between the first potential e1 and the second potential e2.
The output of the OR gate 33 becomes "H" in the potential range of.

Therefore, it suffices to start and stop the switching power supply device by the output of the OR gate 13, but in this embodiment, since the switching power supply device can be started and stopped by starting and stopping the operation of the PWM circuit 40, the power supply voltage Vc is supplied. By providing the circuit 14 to start and stop the power supply to the PWM circuit 40 according to the output of the OR gate 13, it is possible to save the power consumption of the integrated circuit device 60 during the operation stop period of the switching power supply device.

Further, the circuit of the present invention is provided with potential applying means 20 for applying an electric potential to the control terminal Tc. In the illustrated example, a resistor that raises the potential of the control terminal Tc to the power supply voltage Vc is used as the potential applying means 20 for simplification of the circuit. It is desirable to use a current source instead. In the case of this embodiment, since the power supply voltage Vc is 10 to 20 V, this potential applying means 2
By 0, the control terminal potential v is raised higher than the set potential range of 0.5 to 7 V described above.

The potential holding circuit 30 is for limiting and holding the control terminal potential v pulled up by the potential applying means 20 within the set potential range of the operation start / stop circuit 10, and in this embodiment, the zener diode 31 and It is composed of a transistor 32 and limits the control terminal potential v to the Zener voltage e3 of the Zener diode 31 when the transistor 32 is turned on. The limit value e3 due to the Zener voltage is preferably set at approximately the center of the set potential range described above, and is set to, for example, 4 V in this embodiment.

In connection with this potential holding circuit 30, in this embodiment, the PWM
A comparator 44 is incorporated in the circuit 40 and compares the error signal Se with a predetermined limit value e5 to turn on the transistor 32 by its output when the former value is lower than the latter value.
It is preferable to set the limit value e5 sufficiently low so that the transistor 32 is kept in the ON state and the control terminal potential v is held at the limit value e3 while the operation of the switching power supply device is normal and the value of the error signal Se is small. If the value of the error signal Se increases even if the operation of the switching power supply device is abnormal, the holding state is immediately released.

Further, in this embodiment, the control terminal potential v is applied to a negative input other than the negative input of the PWM comparator 43 which receives the error signal Se. As is well known, the PWM comparator 43 having three negative inputs has a reference wave St that receives the lowest value of the signals given to the plurality of negative inputs to the positive input, as is well known.
This is because another set potential e4 received by the other negative input limits the maximum value of the duty ratio of the output signal to, for example, 50%.

In the circuit described above, the control terminal potential v is the ground potential while the start switch 61 connected to the control terminal Tc is in the closed state, and there is no power supply from the operation start / stop circuit 10.
The PWM circuit 40 is stopped and the switching power supply unit is also stopped. When the start switch 61 is opened to start the operation, the control terminal potential v is raised by the potential applying means 20, and when the value exceeds the first potential e1 after a short time, the operation start / stop circuit 10 causes the PWM circuit. Power supply to 40 is started, whereby the PWM circuit 40 starts operating and the switching power supply device is started.

However, since the capacitor 62 is connected to the control terminal Tc, the control terminal potential v rises at the rate of change set thereby. The PWM comparator 43 gradually increases the duty ratio of the output signal, that is, the switching command Ss, while comparing the rising control terminal potential v with the reference wave St, so that the output voltage Vo of the switching power supply is at the speed set by the capacitor 60. stand up. This is the state of the soft start operation described above.

When the output voltage Vo rises sufficiently and its actual value Sa reaches near the set reference value er of the error amplifier 41, the value of the error signal Se becomes lower than the control terminal potential v that has risen by that time, so the PWM comparator 43 Causes the error signal Se to be compared with the reference wave St. At the same time, the value of the error signal Se becomes lower than the limit value e5 of the comparator 44 and the output turns on the transistor 32. This limit value is reached after reaching the limit value e3 of the potential holding circuit 30.
held in e3. As a result, the switching power supply device enters a normal operating state.

When an operation abnormality occurs in the switching power supply device due to overload or the like, the value of the output voltage Vo deviates from the normal value, so the error signal Se increases and exceeds the limit value e5 of the comparator 44,
As a result, the transistor 32 is turned off, the holding state of the control terminal potential v at the limit value e3 is released, and the transistor 32 rises. When the value exceeds the second potential e2, the power supply from the operation start / stop circuit 10 is cut off, and the operation of the switching power supply device is automatically stopped.
This is the above-mentioned overload protection operation.

The rate of change of the control terminal potential v at this time is also the control terminal Tc.
Since it is regulated by the capacitor 62 connected to and does not rise instantaneously, when the cause of the abnormality is resolved within a very short time, the control terminal potential v does not reach the second potential e2, and the switching power supply device Returns to the original normal operating state.
Further, in this example, when the switching power supply device automatically stops due to an abnormality, the control terminal potential v rises above the normal value, so that it can be detected from the outside and the fact that an abnormality has occurred can be displayed or notified.

As can be seen from the above description, the control terminal potential is not only specified from the outside of the electronic device, but can be appropriately controlled or switched inside the electronic device in association with the operating state or the state change. Further, not only specifying or controlling the value of the control terminal potential, but setting or controlling the rate of change over time,
The control mode of the operating state by the circuit of the present invention can be further diversified. As described above, the control modes can be enriched by multiplexing the set potential range in the operation start / stop circuit and the limiting potential by the potential holding circuit.

[Effect of device]

As described above, in the present invention, the control terminal for controlling the operating state of the electronic device by the electric potential and the electric potential are constantly monitored and the electronic device is activated only when the value is within the preset electric potential range. An operation state control circuit including an operation starting / stopping circuit, a potential applying means for applying a potential higher than the set potential range to the control terminal, and a potential holding circuit for limiting and holding the potential applied to the control terminal within the set potential range. The control terminal potential is externally specified outside the set potential range to hold the electronic device in the stopped state, the specified state is released, and the potential holding circuit holds the control terminal potential within the set potential range. Since the electronic device is put into the operating state and this holding state is canceled and it is automatically stopped when the electronic device abnormally operates, a single control terminal enables multiple operations of the electronic device. It is possible to control the state, function eliminates the need for a separate terminal individually in the conventional electronic device as described above, it is possible to reduce the number of terminals of the integrated circuit device incorporated in the electronic device.

The operating state control circuit of the present invention is an ASI for a relatively small electronic device such as the switching power supply device described in the embodiment.
Very useful for C, especially embedded in linear ICs,
When this kind of integrated circuit device is incorporated into an electronic device, the number of connection terminals is reduced, and the size including the package is reduced, which can contribute to further rationalization of the electronic device.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the operating state control circuit of the present invention in a state of being incorporated in a switching power supply device as an example of an electronic device. In the figure, 1: switching transistor, 2: transformer, 2a: primary coil of transformer, 2b: secondary coil of transformer, 3: rectifier diode, 4: smoothing capacitor, 5: voltage divider circuit, 5a, 5b: resistor, 10: operation start / stop circuit, 11, 12: comparator, 13: OR gate, 14: power supply circuit, 20: potential applying means, 30: potential holding circuit, 31: Zener diode, 32: transistor, 40: PWM Circuit, 41: Error amplifier, 42: Reference wave generation circuit, 43: PWM comparator, 43a: Inverter, 50: Command circuit, 51, 52: Darlington transistor, 60: Integrated circuit device, 61: Start switch, 62: Soft start Setting capacitor, 63: External capacitor for feedback of error amplifier, 64: External capacitor for reference wave generation circuit, E: Ground potential, e1: First for setting potential range
Potential, e2: second potential for potential range setting, e3: potential limit of potential holding circuit, e4: maximum duty ratio setting potential for PWM comparator, e5: limit value for error signal, er: reference value for output voltage setting , Sa: Actual value of output voltage, Se: Error signal, Ss: Open / close command, St: Reference wave for PWM comparator, Tc: Control terminal, v: Control terminal potential, Vc: Power supply voltage for integrated circuit device, Vi: Switching Input voltage to the power supply unit, Vo: output voltage of the switching power supply unit.

Claims (1)

(57) [Scope of utility model registration request] 1. A switching power supply control circuit comprising an integrated circuit device for PWM-controlling a switching transistor to output a predetermined output voltage, wherein a difference between an actual value corresponding to the output voltage and a reference value of the output voltage is calculated. A control terminal to which an error amplifier that outputs as an error signal, a start switch for controlling start / stop, and a capacitor for setting the rising speed of the output voltage output based on the start operation of the start switch are connected. And a potential applying means for supplying a predetermined charging current to a capacitor connected to the control terminal and applying a predetermined potential to the control terminal, and a potential of the control terminal when the error signal is smaller than a predetermined limit value. Is held at a potential within the range of the first and second potentials lower than the predetermined potential and the holding is released when the limit value is exceeded. A potential holding circuit, a reference wave generation circuit for generating a reference wave having a predetermined period for PWM controlling the switching transistor, and a plurality of negative inputs that receive the error signal and the other one. A PWM comparator for receiving the potential of the control terminal and comparing the reference wave input to the positive input with the lowest value of the plurality of negative inputs and controlling the switching transistor by PWM, and the control terminal The potential of the control terminal is compared with the first and second potentials by comparing the potential with the first and second potentials.
A switching power supply control circuit for operating the PWM comparator when it is within the range of the electric potential and stopping the operation when it is out of the range.