JPH0286311A - Multi triangle wave circuit - Google Patents

Abstract

PURPOSE:To suppress the dispersion in the characteristic of a triangle wave nearly equal to that of a single oscillating circuit by comparing a potential of a capacitor with set upper limit and lower limit voltages and supplying an output of each latch circuit of plural oscillating circuits provided with the latch circuit controlled by the comparison output so as to control a switch element. CONSTITUTION:A capacitor C, a charging constant current source I, a discharge constant current source 2I and a switch SW for discharge control employed in a triangle wave oscillating circuit among four independent triangle wave oscillating circuits are used in common for the other three oscillating circuits. A voltage VC of the capacitor C is supplied in common to comparators VC1, VC2 of the four oscillating circuits OSC1-OSC4. An output signal of the comparators VC1, VC2 in the oscillating circuits OSC1-OSC4 is used as a set/ reset signal of a latch circuit FF. Then the output signal of a NOR gate circuit G controls the switch SW controlling the discharge of the capacitor C.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multi-triangular wave circuit, for example, a multi-type PwM (pulse width i
11) Regarding the switching regulator tach angle circuit.

[Conventional technology]

Regarding PWM switching power supplies, there is, for example, "Electronic Technology 1 Magazine, November 1987, pages 52 to 57.

[Problem to be solved by the invention]

In a synchronous multi-triangular wave circuit that operates multiple triangular wave generators in parallel, the timing resistor that generates the constant current that determines the charging and discharging current of the triangular wave is shared, and the constant current is shared between the multiple constant current circuits. This is something that is about to occur. Therefore, there is a problem in that variations in the constant currents of the plurality of oscillation circuits are added together, and variations in the slopes of the rise/fall of the triangular wave become large.

An object of the present invention is to provide a multi-triangular wave circuit with reduced variation in triangular waves.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, for a triangular wave generation circuit consisting of a capacitor that forms a triangular wave, a circuit that supplies charging current to the capacitor, and a switch element that controls the discharging operation of the capacitor, the voltage of the capacitor and the set upper limit voltage are determined. The output of each latch circuit of a plurality of oscillation circuits including a voltage comparison circuit that compares the voltage with a lower limit voltage and a latch circuit that is controlled by the comparison output is supplied to a logic circuit, and the switch element is controlled by the logic output.

[For production]

According to the above means, only one charge/discharge current generating circuit is operated, so even though multiple oscillation circuits are operated, variations in triangular wave characteristics can be suppressed to the same level as a single oscillation circuit. be able to.

〔Example〕

FIG. 1 shows a circuit diagram of a synchronous multi-triangular wave circuit according to an embodiment of the present invention.

The synchronous multi-triangular wave circuit of this embodiment uses four independent triangular wave generating circuits. Oscillator circuits 0SCI to 0SC4 are comparators &
This is the latch part.

In this embodiment, a capacitor C1 corresponding to one triangular wave generating circuit among four triangular wave generating circuits, a charging constant current source 2, a discharging constant current source 2, and a discharge control switch S
W is also commonly used in the remaining three oscillation circuits. Therefore, the charging constant current source (2) and the discharging constant current source (2) corresponding to the remaining three triangular wave generating circuits are electrically separated and are therefore omitted from the figure. That is, the voltage VC of the capacitor C is commonly supplied to each of the comparators VCI and VC2 of the four oscillation circuits 03C1 to 03C4. The comparators VCI and VO2 in the oscillation circuits 03C1 to 0SC4 are supplied with an upper limit voltage VA and a lower limit voltage VB formed by series resistors R1 to R3.

The output signals of the comparators VCI and VO2 in the oscillation circuits 03CI to 03C4 are used as set/reset signals for the latch circuit FF.

For example, when the charging voltage VC of the capacitor C reaches the upper limit voltage VA, the latch circuit FF is set by the output signal of the comparator VCI. Furthermore, when the discharge voltage VC of the capacitor C reaches the lower limit voltage VB, the comparator VC2
The latch circuit FF is reset by the output.

Each launch circuit F of the above oscillation circuits 03CI to 03C4
The output signals 0UTI to 0UT4 of F are supplied to a NOR gate circuit G, although this is not particularly limited. The output signal of the NOR gate circuit G controls the switch SW which controls the discharging operation of the capacitor C.

FIG. 2 shows a circuit diagram of a specific embodiment of the NOR gate circuit G. The NOR gate circuit of this embodiment is composed of transistors Tl to T4 connected in parallel. That is, each transistor T1 to T
The emitters of 4 are connected to ground potential, and their collectors are connected in common. The bases of the transistors TI to T4 are connected to the output signals 0UTI to 0U of the latch circuit FF.
T4 is supplied.

Next, the operation of this embodiment circuit will be explained with reference to the waveform diagram of FIG.

When the switch SW is in the OFF state, the discharge current 2I does not flow, so a charging current is supplied to the capacitor C from the constant current source 2, and the voltage VC rises to the high level side. Since this voltage VC inverts the output of the comparator with the lowest upper limit voltage V H (min) among the upper limit voltages VA supplied to each comparator C1 in the four oscillation circuits, the corresponding launch circuit FF is inverted. A set is made. Latch circuit FF set in this way
The output signal OUT of becomes high level, and any one of the transistors T1 to T4 constituting the NOR gate circuit G is turned on. This turns the switch SW into an on state. When the switch SW is turned on, the constant current source 2 for discharging flows, so that a discharging operation is started by the constant current 1 (21-I) of the capacitor C, and the voltage VC falls to the low level side.

The voltage VC resulting from such a discharging operation is applied to all the latches after waiting for the inversion of the output of the comparator with the highest lower limit voltage VL (max) among the lower limit voltages VB supplied to each comparator VC2 in the four oscillation circuits. Circuit F
F is reset.

In this way, by resetting all the latch circuits FF, all of the transistors T1 to T4 constituting the NOR gate circuit G are turned off, and the switch SW is turned off. When the switch SW is turned off, the discharge constant current source 2
Since I stops flowing, the capacitor C starts discharging again by the charging constant current source 2, and the voltage VC rises to the high level side. By repeating the above operations,
A triangular wave is generated and each oscillation circuit performs an oscillation operation.

The effects obtained from the above examples are as follows.

According to this embodiment circuit, the connection lines of the capacitors (timing capacitors) C are connected in common, and the source charge/discharge switching transistors are NOR-connected.
A triangular wave is generated by switching one charging/discharging current. In this case, the upper limit level and lower limit level of the triangular wave are the lowest upper limit voltage V H (IIIin) and lower limit voltage V L (wa
x). Since the threshold voltage is determined by the resistance ratio, variations can be kept relatively small even in the case of a semiconductor integrated circuit. Furthermore, since the charging/discharging current is that of one triangular wave generation circuit, it is not affected by variations caused by multiple circuits. Therefore, even though a plurality of triangular wave generating circuits are operated, the variation in characteristics can be suppressed to be much lower than that of a single oscillating circuit.

In other words, when multiple triangular wave generation circuits are operated in synchronization, there is only one charge/discharge switch, so there is only one feedback loop, and there is no room for mutual interference between the multiple oscillation circuits. can. Also,
The charging/discharging current uses only one constant current source circuit out of multiple triangular wave generating circuits, so it is possible to reduce variations in constant current compared to conventional technology in which multiple constant current source circuits share the charge/discharge current. It can be kept very small.

Although the invention made by the present inventor has been specifically explained based on Examples above, the present invention is not limited to the above-mentioned Examples, and it goes without saying that various changes can be made without departing from the gist thereof. Nor. For example, instead of an OR circuit such as a NOR gate circuit, an AND circuit such as a Nants gate circuit may be used to perform switch control. When the AND circuit is used in this manner, when the voltage VC of the capacitor C reaches the lowest of the upper limit voltages, the operation is switched to the discharging operation, and when the voltage VC reaches the highest of the lower limit voltages, the operation is switched to the charging operation. Can be switched.

In addition, as a switch for switching charging/discharging,
A configuration in which the switch is turned on by a low level, or a configuration in which a transistor or the like is used as a switch element and is turned on by a high level may be used. The output terminal of the latch circuit and the logic configuration of the logic circuit may be selected depending on the control level of the switch element.

Upper and lower limit voltage (VA(!:
The circuit for setting VB) may be formed using a constant voltage element or the like, in addition to using a resistor circuit as described above.

The charging current may also be formed by a resistor. In this case, a triangular wave having non-linear rise characteristics according to the time constants of the resistor and capacitor is formed. Further, the discharge path may be simply a switch. In this case,
Triangular waves have asymmetrical rise and fall.

This invention can be widely used as a multi-triangular wave circuit.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows. That is, for a triangular wave generation circuit consisting of a capacitor that forms a triangular wave, a circuit that supplies charging current to the capacitor, and a switch element that controls the discharging operation of the capacitor, the voltage of the capacitor and the set upper limit voltage are determined. The output of each latch circuit of a plurality of oscillation circuits including a voltage comparison circuit that compares the voltage with a lower limit voltage and a latch circuit that is controlled by the comparison output is supplied to a logic circuit, and the switch element is controlled by the logic output.

In this configuration, only one charge/discharge current generation circuit is operated, so even though multiple oscillation circuits are operated, it is possible to suppress variations in triangular wave characteristics to the same level as with a single oscillation circuit. can.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a synchronous multi-triangular wave circuit showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing an embodiment of the NOR gate circuit, and Fig. 3 is a diagram for explaining its operation. FIG. 03CI~○SC4...Oscillation circuit, VCI, VO2...
Comparator, FF... Launch circuit i, G... NOR gate circuit, ■... Constant current source for charging, 2I... Constant current source for discharging, C... Capacitor, SW... Switch Fig. 1 Fig. 3 Fig. 2 figure

Claims (1)

[Claims] 1. A capacitor that forms a triangular wave, a circuit that supplies charging current to the capacitor, a switch element that controls discharging operation of the capacitor, and a potential of the capacitor and set upper and lower voltage limits. a plurality of oscillation circuits including a voltage comparison circuit that compares the voltage and a latch circuit that is controlled by the comparison output thereof; and a logic that receives the output of the latch circuit in the plurality of oscillation circuits and forms a control signal for the switch element. A multi-triangular wave circuit characterized by comprising a circuit. 2. The voltage comparison circuit is composed of a pair of voltage comparison means corresponding to an upper limit value and a lower limit value, and the latch circuit is such that the output of the pair of voltage comparison means is supplied to the set and reset terminals. Claim 1 characterized by
Multi-triangular wave circuit described in section. 3. The circuit that supplies charging current to the capacitor is composed of a constant current source, and the switch element that controls the discharging operation of the capacitor forms a discharge current with a current value larger than the current value of the constant current source that forms the charging current. 2. The multi-triangular wave circuit according to claim 1, wherein the multi-triangular wave circuit is connected in series with a constant current source.