JP4607675B2 - Offset adjustment circuit - Google Patents

Description

  The present invention relates to an offset adjustment circuit that performs offset correction of a feedback control loop.

  A power supply unit that supplies operating power to a load is generally configured by switching control including a feedback control circuit. For example, a configuration shown in FIG. 5 is known as a configuration for supplying a set current to a load. In the figure, 101 is a switching power supply unit including a smoothing circuit, 102 is a load, 103 is a current detection unit that detects a current as a voltage across a resistor, and 104 controls the ON width of switching of the switching power supply unit 101. The control unit 105 is a gain adjustment unit that adjusts the loop gain of the feedback loop using a variable resistor (volume), 106 is an amplification unit including an operational amplifier, 107 is an error amplification unit including an operational amplifier, and 108 is a variable resistor (volume). The offset adjustment part to adjust is shown.

  The current supplied to the load 102 is detected by the current detection unit 103, input to the amplification unit 106 via the gain adjustment unit 105, offset correction is performed by the offset adjustment unit 108, the output of the amplification unit 106, and the load 102 The command value of the current to be supplied is added and input to the error amplifying unit 107, compared with a reference voltage (not shown), the error is input to the control unit 104, and the control unit 104 controls the switching power supply unit 101. A feedback control loop is configured.

  The control unit 104 inputs a switching ON width control signal, that is, a pulse width modulated control signal, to the switching power supply unit 101 by comparing the output error level of the error amplification unit 107 with the sawtooth voltage, The current supplied to 102 is controlled to be a value according to the command value. The gain adjustment unit 105 adjusts the loop gain of the feedback control loop in such a configuration that the current according to the command value is supplied to the load 102. Further, the offset adjustment unit 108 adjusts the offset value in the configuration including the current detection unit 103 and the amplifier 106.

Further, adjustment and control of each part are generally performed by analog processing, and therefore, offset adjustment and loop gain adjustment also use a variable resistor (volume). Note that the programmable controller range is switched by operating the switch. The digital potentiometer and control circuit that controls this by the number of pulses are used to manually switch the switch on and off. An unnecessary means is known (for example, see Patent Document 1). Also known is a means for counting up or counting down a value corresponding to the offset value by an offset determination means having a reference value and adjusting the offset based on the count value of the counter (see, for example, Patent Document 2). .
JP 2001-282320 A JP-A-2005-33541

  Conventional offset adjustment is performed by an analog circuit configuration, and manual adjustment means using a variable resistor is generally used. However, such an offset adjustment means requires skill and often requires readjustment due to a secular change after adjustment. Further, since this adjusting means does not always perform an adjusting operation, it is often provided not in the front surface of the apparatus but in the inside thereof.

  In addition, the switching power supply unit 101 is mounted in the device including the load 102. In that case, a temperature change due to a temperature rise or the like of each part in the device may be relatively large. The offset adjustment result will deviate. Although it is desirable to readjust the offset for each temperature change, it is practically impossible to execute it in the operating state of the device. There is a problem that it is impossible to cope with a change in the offset value.

  An object of the present invention is to mount a power supply unit including a switching power supply unit and a feedback control loop in the apparatus, and to perform offset correction with high accuracy in response to an offset value change during operation.

An offset adjustment circuit according to the present invention is a non-volatile circuit that holds an initial offset value of the power supply unit as an initial offset correction value in an offset adjustment circuit that performs offset correction of a power supply unit including a switching power supply unit and a feedback control loop. An offset value when the power supply unit is mounted on a device including a memory and a load and current is supplied to the load using the initial offset correction value is held as an offset correction value during operation. using a rewritable memory to the offset value can be updated by the operation continues for a predetermined period, and said driving time offset correction value held in the initial offset correction value held in the nonvolatile memory and the rewritable memory And a configuration for performing the offset correction of the power supply unit .

  The detection value of the current supplied to the load is corrected by the sum of the initial offset correction value held in the non-volatile memory and the operation offset correction value held in the rewritable memory to detect overcurrent. It can be set as the structure which provided the alarm process part to perform.

  The temperature correction table storing the temperature and the offset correction value correspondingly, the offset correction value read from the temperature correction table corresponding to the temperature detection value from the temperature detection unit, and the nonvolatile memory are held. An offset calculation unit that performs the offset correction using the initial offset correction value and the operating offset correction value held in the rewritable memory can be provided.

  In addition, a temperature correction table in which offset correction values corresponding to temperatures obtained by sequentially changing the temperature are written, the offset correction values read from the temperature correction table corresponding to the temperature detection values from the temperature detection unit, An offset calculation unit that performs the offset correction using the initial offset correction value held in the nonvolatile memory and the operation offset correction value held in the rewritable memory may be provided.

  By holding the offset value as the power supply unit in the non-volatile memory as the initial offset correction value, and holding the offset value when the power supply unit is mounted in the device in the rewritable memory as the operation offset correction value, Even when the operation is performed for a long period of time, the offset correction value during operation can be rewritten, so that highly accurate offset correction can be continuously performed.

  Referring to FIG. 1, the offset adjustment circuit of the present invention is an offset adjustment circuit that performs offset correction of a power supply unit including a switching power supply unit 1 and a feedback control loop. A non-volatile memory 11 to be stored as a value and a power supply unit mounted on a device including the load 2 so that the offset value when the current is supplied to the load 2 is retained as an operation offset correction value. The memory 12 includes an offset calculation unit 10 that performs offset correction using the initial offset correction value held in the nonvolatile memory 11 and the operation offset correction value held in the rewritable memory 12.

  FIG. 1 is an explanatory diagram of Embodiment 1 of the present invention, in which 1 is a switching power supply unit, 2 is a load, 3 is a current detection unit, 4 is a control unit, 5 is an error amplification unit, 6 is a pulse width control unit, 7 is an offset adjustment circuit, 10 is an offset calculation unit, 11 and 12 are memories (M), 13 is an AD converter (A / D), 14 is a DA converter (D / A), and S1 and S2 are write signals. Indicates. The switching power supply unit 1 performs switching control to smooth the input voltage under the control of the control unit 4, supplies operating power to the load 2, detects a current value supplied to the load 2 by the current detection unit 3, An error from the command value input is obtained by the error amplifying unit 5, a sawtooth wave signal is inputted to the pulse width control unit 6, a pulse width modulation signal corresponding to the error is inputted to the control unit 4, and the control unit 4 By controlling the ON width of the switching control of the switching power supply unit 1, a current according to the command value input is supplied to the load 2.

  The error amplifying unit 5 shows an adder configuration. Therefore, if the current detection value by the current detection unit 3 is, for example, + polarity, the command value input is −polarity, and the offset correction value from the offset adjustment circuit 7 is also − As the polarity, the difference between the command value input and the current detection value is corrected by the offset correction value and input to the pulse width control unit 6. The error amplifying unit 5 and the pulse width control unit 6 can apply various known configurations, and select the polarity of each signal according to the applied configuration.

  The offset adjustment circuit 7 has a configuration including an offset calculation unit 10, memories 11 and 12 for writing offset correction values, an AD converter 13, and a DA converter 14. The memory 11 is an EEPROM or the like. A nonvolatile memory is used, and the offset value is converted into a digital signal by the AD converter 13 and written by the write signal S1. The memory 12 has a rewritable non-volatile memory or a volatile RAM configuration, and the offset value is converted into a digital signal by the AD converter 13 and written by the write signal S2.

  A switching power supply unit 1 and a feedback control loop are included, and a power supply unit excluding the load 2 is manufactured and mounted in a device provided with the load 2 inside. When a pseudo load is connected and the command value input indicating the current value supplied to the load is zero, the current is detected by the current detection unit 3 when the offset value in the feedback control loop is not zero. It will be. This detected current value is converted into a digital signal by the AD converter 13 of the offset adjustment circuit 7 and is written in the memory 11 by the write signal S1 as an initial offset correction value. Since the memory 11 is a non-volatile memory, the offset value of the power supply unit alone can be held in the memory 11 as an initial offset correction value.

  The power supply unit including the switching power supply unit 1 and the feedback control loop is mounted on a device including the load 2, the command value input is set to zero again, and the current detection value by the current detection unit 3 at that time is converted into the AD converter 13. Is converted into a digital signal, the write signal S2 is added to the memory 12, and the current detection value in this case is held as an offset correction value during operation. In this case, the initial offset correction value held in the memory 11 is input to the error amplifying unit 5 via the offset calculation unit 10, so that the operating offset correction value generated when mounted in the apparatus is stored in the memory. 12 is held.

  As described above, the power supply unit including the switching power supply unit 1 and the feedback control loop is mounted in the apparatus, and the initial offset correction value and the operation offset correction value are held in the memories 11 and 12, respectively. Offset correction during operation for supplying operating power to the actual load 2 can be performed. In this case, the offset calculation unit 10 obtains the sum of the initial offset correction value held in the memory 11 and the operating offset correction value held in the memory 12, and uses the error amplification unit 5 as an offset correction value. To enter.

  Further, by continuing the operation for a certain period, the characteristics of the circuit elements including the configuration on the load 2 side may change, and the offset value may also change. In such a case, the command value input is set to zero and the write signal S2 is added to the memory 12 by the timer process or control from the control input unit (not shown) by the maintenance person or the like, and the offset value at that time is set to the operating time. The memory 12 is rewritten as an offset correction value. Therefore, the memory 12 is at least a rewritable memory. Thereafter, the command value input is controlled to indicate a desired current value, and the operation is resumed. Therefore, even when the offset correction is performed using the initial offset value of the power supply unit alone and the rewritten new operation offset correction value, the accuracy of the load 2 can be improved. High current control can be performed.

  FIG. 2 is an explanatory diagram of Embodiment 2 of the present invention, where the same reference numerals as those in FIG. 1 denote the same parts, and 15 denotes an alarm processing unit. This alarm processing unit 15 converts the current detection value from the current detection unit 3 into a digital signal by the AD converter 13 and inputs it, and also inputs the offset correction value via the offset calculation unit 10 and supplies it to the load 2. When an overcurrent state in which the current exceeds a set value is detected, it is detected, an alarm signal is added to the control unit 4, and the output voltage of the switching power supply unit 1 is dropped to perform overcurrent protection. . In this case, since the offset value by the current detection unit 3 or the like cannot be ignored in many cases, not only the detected value of the current supplied to the load 2 but also the initial offset correction value and the operating offset correction held in the memories 11 and 12, respectively. The value of the current that actually flows through the load 2 is determined using the offset correction value that is the sum of the value and the overcurrent is detected when the current value exceeds a threshold value. Therefore, the accuracy of overcurrent detection in the alarm processing unit 15 can be improved.

  FIG. 3 is an explanatory diagram of Embodiment 3 of the present invention. The same reference numerals as those in FIG. 1 denote the same parts, 16 is a temperature correction table, 17 is an AD converter (A / D), and 20 is a temperature detector. Show. The temperature correction table 16 obtains an offset correction value Dx based on a characteristic change corresponding to the temperature Tx when the overall temperature characteristic can be predicted based on catalog data of parts of each part, and the offset correction value Dx is obtained. Store in correspondence with temperature. The temperature detection unit 20 can apply a configuration using the temperature characteristics of the pn junction of the transistor, a configuration using a thermistor, etc., and the offset value is easily affected by temperature changes. Provided. The temperature detection signal of the temperature detection unit 20 is converted into a digital signal by the AD converter 17, and the offset correction value Dx corresponding to the temperature Tx at that time is read as an address of the temperature correction table 16 and input to the offset calculation unit 10. To do.

  The offset calculation unit 10 reads the offset correction value read from the temperature correction table 16 corresponding to the temperature detected by the temperature detection unit 20, the initial offset correction value held in the memory 11 is a, the operation offset correction value held in the memory 12 is b. When the value is Dx, the offset calculation unit 10 obtains the offset correction value Y by the calculation process of Y = − (a + b + Dx), converts it into an analog signal by the DA converter 14, and inputs it to the error amplification unit 5. Therefore, even in a configuration in which the offset value fluctuates due to a temperature change, a highly accurate offset correction can be performed and a current according to the command value input can be supplied to the load 2.

  FIG. 4 is an explanatory diagram of Embodiment 4 of the present invention. The same reference numerals as those in FIG. 3 denote the same parts, and S3 denotes a temperature correction data write signal. In this embodiment, before the power supply unit is mounted in the apparatus, it is arranged in a thermostatic bath or the like, the command value input is set to zero, the temperature is sequentially changed, and the temperature correction data write signal S3 is changed to the temperature correction table. In addition to 16, the value obtained at that time is set as an offset correction value Dx, and the temperature Tx at that time is written in the temperature correction table 16 as an address. In this case, the offset value is obtained by actually changing the temperature, and the temperature correction table 16 can store the actually measured offset value corresponding to the temperature. Therefore, compared with the above-described third embodiment, the current according to the command value input to the load 2 of the device that operates in an environment where the ambient temperature changes can be supplied with offset correction with high accuracy.

  In the second, third, and fourth embodiments, as in the first embodiment, the operation offset correction value held in the memory 12 is input when the operation of the apparatus continues for a predetermined period. The operation offset correction value can be updated by setting the value to zero and adding the write signal S2 to the memory 12. Further, the memories 11 and 12 are nonvolatile memories, and are divided into an area of the memory 11 and an area of the memory 12, and the write signals S1 and S2 include an address signal. It is also possible to adopt a configuration in which the offset value during operation is written in the area as the memory 12.

It is explanatory drawing of Example 1 of this invention. It is explanatory drawing of Example 2 of this invention. It is explanatory drawing of Example 3 of this invention. It is explanatory drawing of Example 4 of this invention. It is explanatory drawing of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Switching power supply part 2 Load 3 Current detection part 4 Control part 5 Error amplification part 6 Pulse control part 7 Offset adjustment circuit 10 Offset calculating part 11, 12 Memory (M)
13 AD converter (A / D)
14 DA converter (D / A)
S1, S2 Write signal

Claims (3)

In an offset adjustment circuit that performs offset correction of a power supply unit including a switching power supply unit and a feedback control loop,
A non-volatile memory that retains an initial offset value of the power supply unit as an initial offset correction value;
An offset value when the power supply unit is mounted on a device including a load and a current is supplied to the load using the initial offset correction value is held as an operation offset correction value. Using the rewritable memory that can be updated by continuing operation for a predetermined period, the initial offset correction value held in the nonvolatile memory, and the operation offset correction value held in the rewritable memory , the power supply offset adjusting circuit comprising the offset calculation unit that performs the offset correction parts. A temperature correction table in which the offset correction value of the power supply unit obtained by estimating a characteristic change corresponding to temperature and the temperature are stored in association with each other; a temperature detection unit that detects the temperature of the power supply unit; and the temperature detection unit The offset correction value read from the temperature correction table, the initial offset value read from the nonvolatile memory, and the operation offset correction value read from the rewritable memory corresponding to the temperature detection value of the power supply unit detected by The offset adjustment circuit according to claim 1 , further comprising: an offset calculation unit that performs the offset correction of the power supply unit using an offset correction value as a sum of A temperature correction table in which the offset correction value of the power supply unit corresponding to the temperature obtained by sequentially changing the temperature of the power supply unit and the temperature are written in association with each other; a temperature detection unit that detects the temperature of the power supply unit; The offset correction value read from the temperature correction table corresponding to the temperature detection value from the temperature detection unit, the initial offset correction value held in the nonvolatile memory, and the operation held in the rewritable memory The offset adjustment circuit according to claim 1 , further comprising an offset calculation unit that performs the offset correction of the power supply unit using a time offset correction value .

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