JP2821888B2 - Power circuit control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit control device suitable for controlling a power supply circuit of an image forming apparatus such as a copying machine or a printer. 2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines and printers use a microcomputer as a process sequence control unit. A microcomputer (hereinafter referred to as a CPU) sends a signal corresponding to a predetermined output to each load such as a motor, a lamp control circuit for exposure, and a high-voltage power supply for charging and developing in accordance with the timing of each process. Among the loads, in the high-voltage power supply, etc., the control circuit in the high-voltage power supply determines the sending and receiving according to the signal of the CPU, and the lamp control circuit for exposure also controls the lamp on / off and the predetermined light amount. Has an independent control circuit. [Problems to be Solved by the Invention] However, in the above-described conventional example, the configuration of the system is complicated because an independent control circuit is required for each load, and it is difficult to improve the reliability of the system. It has also become difficult to respond to cost reductions. In recent years, a method of controlling an external load by a CPU has also been proposed.However, since software control is performed in the CPU, processing control and load control are affected by the processing speed of the CPU. Because the control of both controls the load on the software in the CPU and increases the processing time of the entire system, the system configuration must be fully examined. The present invention has been made under such circumstances,
It is an object of the present invention to provide a control device for a power supply circuit in which the load on software in a CPU is relatively small, the processing time is short, and the system can be reduced in size and cost can be easily reduced. [Means for Solving the Problems] In order to achieve the above object, according to the present invention, a control device for a power supply circuit is configured as described in (1), (2), and (3) below. (1) In a control device for a power supply circuit, a plurality of analog signals including an analog output to a first load connected to the power supply circuit and an analog output from a sensor for detecting a state of the second load are repeatedly input. Input means for sequentially selecting and outputting each analog signal according to a predetermined timing signal; storage means for storing a reference signal; conversion means for converting a digital signal output from the storage means to an analog signal; A comparator for comparing an analog signal from the means with a reference signal converted to an analog signal by the conversion means and outputting a binary signal; a latch circuit for holding a plurality of outputs from the comparator; Based on the held binary signal indicating the result of comparison between the analog signal from the sensor and the reference signal from the conversion means. Calculating means for determining a new reference signal to be compared with the analog signal from the sensor and outputting the new reference signal to the storage means, wherein the calculating means comprises an analog signal from the sensor and the converting means. By successive comparison with the reference signal from
The value of the reference signal is determined so that the value of the reference signal is closest to the value of the analog signal from the sensor. The latch circuit is configured such that the input means selects an analog output to the first load. The binary signal held in the latch circuit is output to the power supply circuit as a control signal. When the input means selects an analog signal from the sensor, the binary signal is held in the latch circuit. 2
A control device for a power supply circuit for outputting a value signal to the arithmetic means, wherein the storage means outputs a reference signal determined by the arithmetic means as a digital signal obtained by converting an analog signal from the sensor. (2) The comparator has a first switch for turning on / off a signal from the input means, a second switch for turning on / off an analog signal from the conversion means,
And a capacitor connected in series to the second switch, an inverter connected in series to the capacitor, and a third connected to both ends of the inverter.
A signal from the input means and an analog signal from the conversion means are compared by turning on and off the first switch, the second switch, and the third switch at a predetermined timing. The control device for the power supply circuit according to (1), wherein the control circuit is a chopper-type comparator that outputs a binary signal. (3) The control device for a power supply circuit according to (1), wherein the storage means selects a reference signal to be output to the conversion means according to a predetermined timing signal.

[Action]

With the configurations (1), (2), and (3), a control signal and an A / D conversion signal to the power supply circuit can be obtained using the same conversion unit and comparator. EXAMPLES Hereinafter, the present invention will be described with reference to Examples. FIG. 1A is a block diagram of a control device according to a first embodiment of the present invention, and FIG. 1B is a comparator 1 of the same embodiment.
FIG. 2 is a timing chart of the embodiment. In FIG. 1 (a), reference numeral 17 denotes an analog input terminal to which an external input such as an output voltage of each power supply of a copying machine and a temperature of a fixing device is inputted, and 3 denotes a multiplexer for switching the external input.
An MPX circuit, 1 is a comparator for comparing the external input selected by the multiplexer 3 with the output of the 5 D / A converter, 4 is a latch comprising a plurality of latch means for holding the output of the comparator, and 8 is one of the latch means. An arithmetic unit which determines the next reference voltage to be compared with a required external input from the output of the section and outputs it to a storage means of 6 via a selector of 7 to a RAM which is a random access memory. The timing generator controls the timings of the multiplexer 3, the latch 4, the RAM 6, and the registers A and B of the selectors 7, 9, and 11. Each timing signal is generated by the clock CLK. 16 is a CPU bus, which is connected to the CPU and each register.
It is for exchanging data among A, B, and C9-11. Reference numerals 12 to 15 are control output terminals provided in a part of the latch means. The control device of the first embodiment has two modes, an operation as a PWM control circuit and an operation as an A / D converter. The PWM control unit includes a comparator 1, a D / A converter 5 as a reference voltage generator, a RAM 6 having D / A conversion data, an MPX circuit 3 for switching and inputting an analog output value of an external circuit, and a result of the comparator. It comprises a latch 4 for holding. The PWM control circuit is completed by connecting a pulse width modulator (not shown) after the latch 4. The A / D converter is composed of a comparator 1, a D / A converter 5, an arithmetic unit 8 for performing numerical conversion, a RAM 6 having D / A conversion data, and an MPX circuit 3 for selecting a required external input for A / D conversion. It is composed of First, the operation of the PWM control will be described with reference to FIG. The MPX circuit 3 is configured to input external analog detection data serving as a comparison value by the timing generator 2.
Switch. Next, by turning on SW1 and SW3 and turning off SW2, the detection value selected by the MPX circuit 3 is input to the comparator 1. At the same time, the comparison reference data is
The data is selected from the conversion table and set in the D / A converter 5.
Next, by turning on SW2 and turning off SW1 and SW3, the MPX circuit 3
Is compared with the D / A conversion value of the comparison reference, and the result is held in an appropriate latch means of the latch 4 according to the latch address. The signal of the latch means is output from the output terminals 12 to 15 to the control circuit of each power supply (not shown) as a PWM control signal. Next, the operation of A / D conversion will be described. The analog input selected by the MPX circuit 3 is compared with the reference voltage by the D / A converter 5 by the comparator 1. Based on the result, the next reference voltage to be compared with the input is determined by the arithmetic unit 8, and the analog input and Compare. D /
The arithmetic unit 8 determines the most significant bit to the least significant bit until the reference voltage of the A converter 5 becomes closest to the input analog input value. The result of this successive approximation is stored in the register B from the output terminal of the analog-digital conversion provided in the RAM 6.
Sent to Data transfer between the control device and the CPU according to the present embodiment is performed via the registers 9 to 11 (register A, register B, and register C). Register A is a register for setting data on the D / A conversion table, and register B is A / D
Register C is a register for reading the result of conversion onto CPU / BUS. Register C is used to set the status of A / D / D / A conversion operation etc. and RAM
6, a register for setting each address of the MPX circuit 3, the latch 4, and the like. As described above, the control device of this embodiment has two types of modes, an operation as a PWM control circuit and an operation as an A / D converter, and the timing of each operation is performed by a timing generator. The exchange of data between the CPU and the BUS is performed via each register. Note that the charge-balanced comparator shown in FIG. 1B is used as the comparator 1, but the present invention is not limited to this, and a normal analog comparator can be used. FIG. 3 is a block diagram showing an application example in which the apparatus of the first embodiment is used in a copying machine. In the figure, I indicates the control device of the first embodiment within the two-dot chain line. As shown in Fig. 3, the copier has various elements such as a fixing unit II, an exposure lamp III, a developing unit IV, a charging unit V, a DC power supply VI supplied to various electronic circuits and a load such as a solenoid. ing. Therefore, to control each element, the third
A block configuration as shown in the figure is conceivable. The block I is configured in the same chip as the sequence controller of the copying machine, and exchanges various information with the CPU used as the sequence controller via the registers 9 to 11 as described above. ing.
The control circuit of each element operates in response to the binary signals of the outputs 12 to 15 of the control device of the block I, and the detection result of each element is sent to the analog input terminal 17 of the multiplexer circuit 3 of the block I as an external input. Applied to form a feedback loop. The temperature detection force of the fixing unit II is A / D converted by the control device of the block I and sent to the CPU. In this way, the control of each element of the copying machine, that is, the temperature control a of the fixing unit, the light quantity control b of the exposure lamp, the constant voltage control c of the developing high voltage power supply for adjusting the developing temperature, and the constant voltage control of the charging high voltage power supply. The current control d and the constant voltage control e for the low-voltage power supply for driving the electronic circuit and the solenoid can be performed by a common controller, and some of the required analog detection signals are performed by the same controller.
A / D converted. Therefore, the control device of the block I can contribute to downsizing and cost reduction of the copying machine. In addition, since the control of the CPU involves only writing and reading of the registers 9 to 10 for the control device, the load on software is relatively small. The first embodiment is based on the premise that there are many control targets such as a copying machine. For this reason, although a multiplexer is added to the external input, a similar configuration is basically possible even in a system without a multiplexer. FIG. 4 is a block diagram of a second embodiment showing the example, and FIG. 5 is a timing chart of the second embodiment. In this embodiment, the external input of the analog input terminal 17 and the D / A
The D / A conversion value of the comparison reference from the converter 5 is compared with the comparator 1 and the output is latched by the latch 4 and output as a control signal from the control output terminal 12, or the analog input terminal 17 The operation unit 8 is provided by the input and another output of the latch 4.
Can be successively compared by the comparator 1 with the reference voltage determined by the above, and can be output from the RAM 6 as an externally input A / D conversion signal. In the above-described first and second embodiments, the arithmetic unit 8 is used to prepare a reference voltage for successive comparison, and the A / D conversion is performed by the CPU.
However, the A / D conversion may be performed by preparing a reference voltage for successive comparison by program control of the CPU without using an arithmetic unit in the control device. FIG. 6 is a block diagram of the third embodiment showing the example. In this embodiment, the data selected from the external D / A conversion table is set in the D / A converter 5 via the CPU BUS 16 and the register A, and the analog value of the comparison reference obtained by D / A conversion of the data is set. And the external input selected by the multiplexer 3 are compared by the analog comparator 1, the comparison output is latched by the latch 4, and output from the control output terminals 12 to 15 as a control signal. The signal from the other output terminal of the latch 4 is sent to the CPU via the register 10, and the next reference voltage to be compared with the external input is selected by the program control of the CPU.
The signal is sent to the analog comparator 1 via the register 9 and the D / A converter 5, where it is compared with a required external input selected by the multiplexer 3. In this way, successive comparison is performed and A / D conversion is performed. Will be According to the present embodiment, the load on the software of the CPU is slightly larger than that of the first embodiment, but is smaller than that in which all the control is performed by software. Note that, similarly to the second embodiment, a modification in which the external input is directly applied to the comparator without using the multiplexer 3 is also possible in the present embodiment. [Effects of the Invention] As described above, according to the present invention, the load on the software of the CPU of the applied device is relatively small, the processing time can be short, and the control output can be achieved with one control device, Since an A / D conversion output can be obtained, it is possible to contribute to miniaturization and cost reduction of an applied device.

[Brief description of the drawings]

FIG. 1A is a block diagram of the first embodiment, and FIG.
Is a circuit diagram of a comparator, FIG. 2 is a timing chart of the first embodiment, FIG. 3 is a block diagram of an application example, FIG. 4 is a block diagram of the second embodiment, and FIG. 5 is a timing chart of the same embodiment. FIG. 6 is a block diagram of the third embodiment. 1 Comparator 4 Latch 5 D / A converter 6 RAM 8 Arithmetic unit 12 to 15 Control output terminal 17 Analog input terminal

Claims (3)

(57) [Claims] 1. A control device for a power supply circuit, wherein a plurality of analog signals including an analog output to a first load connected to the power supply circuit and an analog output from a sensor for detecting a state of the second load are repeated. Input means for inputting and sequentially selecting and outputting each analog signal according to a predetermined timing signal; storage means for storing a reference signal; conversion means for converting a digital signal output from the storage means to an analog signal; A comparator for comparing an analog signal from the input means with a reference signal converted to an analog signal by the conversion means and outputting a binary signal; a latch circuit for holding a plurality of outputs from the comparator; A binary signal indicating the result of comparison between the analog signal from the sensor and the reference signal from the conversion means, held by the circuit; And calculating means for determining a new reference signal to be compared with the analog signal from the sensor, and outputting the new reference signal to the storage means, wherein the calculating means includes the analog signal from the sensor and the analog signal from the sensor. By successive comparison with the reference signal from the conversion means,
The value of the reference signal is determined so that the value of the reference signal is closest to the value of the analog signal from the sensor. The latch circuit is configured such that the input means selects an analog output to the first load. The binary signal held in the latch circuit is output to the power supply circuit as a control signal. When the input means selects an analog signal from the sensor, the binary signal is held in the latch circuit. The storage means outputs the binary signal to the arithmetic means, and the storage means outputs a reference signal determined by the arithmetic means as a digital signal obtained by converting an analog signal from the sensor. Circuit control device. A second switch for turning on and off a signal from the input means; a second switch for turning on and off an analog signal from the conversion means; and a first switch and a second switch. , A capacitor connected in series with the capacitor, an inverter connected in series with the capacitor, and a third switch connected to both ends of the inverter. The first switch, the second switch, A chopper-type comparator which outputs a binary signal by comparing a signal from the input means with an analog signal from the conversion means by turning on and off the third switch at a predetermined timing. The control device for a power supply circuit according to claim 1. 3. The control device for a power supply circuit according to claim 1, wherein said storage means selects a reference signal to be output to said conversion means according to a predetermined timing signal.