JP2006288070A - Dc-dc converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC-DC converter capable of obtaining a proper droop action corresponding to an operation condition by switching the constant voltage control and the current control according to the condition of temperature, output current and output voltage. <P>SOLUTION: In the DC-DC converter, the pulse width control amount is obtained from the output voltage sent from the output voltage detecting section detecting the output voltage while the pulse width control amount is obtained from the output current sent from the output current detecting section detecting the output current. A setting current value (droop action start current) is obtained from the output voltage, output current and temperature each sent from the output voltage detecting section, output current detecting section each at a control method selecting section and the temperature detecting section detecting the temperature. Immediately when updating is performed, a control mode of the constant voltage control and the current control (droop action state) is discriminated, and the pulse width control amount obtained from the voltage deviation in case of the constant voltage control or the pulse width control amount obtained from the current deviation in case of the current control is used, corresponding to the discriminated control mode, to update the pulse width at the pulse width generating section to output the pulse to the switching section. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a DC-DC converter that enables optimum overcurrent protection and overheat protection according to the operating state of the converter, and at the same time, simplifies and downsizes a circuit of a control unit.

  Conventionally, in many DC-DC converters and stabilized power supplies, a protection circuit has been provided to protect the circuit from excessive current and overheating, and there is a circuit by performing a drooping operation by switching between constant voltage control and constant current control. Protected.

However, a DC-DC converter for an electric vehicle or the like is required to have a function capable of taking out the maximum possible power output from the converter in any operating condition.

In conventional converter and power supply configurations, drooping characteristics are realized by having constant voltage control and constant current control circuits, respectively, and the characteristics and switching conditions are determined by circuit constants. The circuit characteristics are set under conditions that do not cause damage under high temperature conditions. For this reason, under conditions where the temperature around the converter is low, the drooping operation is performed even when there is a margin in the output of the converter, and the maximum power cannot be extracted. In addition, in order to realize the switching of the drooping characteristic depending on the operating conditions in consideration of the above, a detection circuit for each drooping characteristic to be used and a circuit for switching the circuit are necessary, and the apparatus is complicated and large. .

A conventional digital control converter is disclosed in Japanese Patent Laid-Open No. 11-136938, but the switching on-time is read from the control table based on the detected voltage, current and temperature values as shown in FIG. However, it is intended to stabilize the output voltage, has no function to control the drooping operation, and does not provide an optimum drooping operation according to the operating condition.
Japanese Patent Laid-Open No. 11-136938

In conventional power supplies and converters, the characteristics of drooping characteristics and switching conditions are determined by circuit constants, so the circuit characteristics are set under conditions that do not cause damage under high temperature conditions. It is difficult to perform a drooping operation and extract the maximum power that can be output. In the present invention, the optimum drooping characteristic according to the operating condition is realized by switching between constant voltage control and current control according to the operating condition of the DC-DC converter.
In addition, by switching between constant voltage control and current control in the CPU, it is possible to reduce the circuit for each drooping characteristic required in the prior art and to simplify and downsize the apparatus.

  In the present invention, first, the current voltage deviation, the previous voltage deviation, and the voltage change amount are obtained by the voltage deviation calculation unit from the output voltage signal from the output voltage detection unit for detecting the output voltage and the set voltage set in the CPU. Then, the pulse width control amount calculation unit obtains the control amount of the pulse width. Next, the current deviation calculator calculates the current current deviation, previous current deviation, and current change amount from the output current signal from the output current detector that detects the output current and the set current set in the CPU, and pulse width control The amount calculation unit obtains the control amount of the pulse width. In addition, the control method selection unit obtains the set current value (droop operation start current) from the output voltage, output current, and temperature from the output voltage detection unit, output current detection unit, and temperature detection unit that detects temperature, and updates it. At the same time, the control mode of constant voltage control and current control (dripping operation state) is discriminated. Depending on the determined control mode, the pulse width creation unit uses the pulse width control amount obtained from the voltage deviation for constant voltage control and the pulse width control amount obtained from the current deviation for current control. By updating and outputting a pulse to the switching unit, stable constant voltage control and current control (sagging operation) are performed. In addition, by switching between constant voltage control and current control by setting the mode discriminant and setting current value calculation formulas suitable for each converter in the control method selection section in the previous section, the optimum according to the operating state of the converter To achieve a drooping motion.

  By obtaining the control switching current according to the temperature of the DC-DC converter, switching the control, and updating the set current with the temperature and the output voltage, it is possible to realize the optimum drooping operation required for each operation state of the converter.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram showing the configuration of an embodiment of a DC-DC converter according to the present invention. 001 is an external power source connected to the DC-DC converter of the present invention, and 010 is an external load. 002 is an input voltage smoothing unit, 003 is a main switch, 004 is a transformer, 005 is an output rectification smoothing unit, 006 is a current detection unit, 007 is a voltage detection unit, 008 is a temperature detection unit, and 009 is a digital control unit. Show. In the configuration of the 009 CPU, 101 is an output current value, 102 is a set current value, 103 is an output voltage value, 104 is a set voltage value, 105 is a temperature value, 106 is a current deviation amount calculation unit, and 107 is a voltage deviation amount. The calculation unit 108 is a control method selection unit, 109 is a first pulse control amount calculation unit, 110 is a second pulse control amount calculation unit, 111 is an output pulse creation unit, and 112 is a pulse output unit.

  The voltage supplied from the external power supply 001 is smoothed by the input voltage smoothing unit 002, and the main switch 003 is turned on / off by the pulse signal from the CPU 009, so that the current is applied to the primary winding of the transformer 004. The induced electromotive current generated in the secondary winding is rectified and smoothed by the output rectifying and smoothing unit 005, and the voltage is output to the load.

  The main switch 003 is configured by using a field effect transistor (FET) or the like, and is driven by an output pulse signal of the CPU 009. The longer the on time of the pulse signal, the larger the output can be obtained. .

  In this embodiment, the signal detected by the current detection unit 006 is AD-converted and taken into the CPU 009 as the output current 101, and the set current 102 held in the CPU 009 by the current deviation amount calculation unit 106 at regular time intervals. At the same time as calculating the deviation amount I1, the previous current deviation amount I2 is obtained by calculation as the deviation amount before a certain time, and the time change amount ΔI is obtained by ΔI = I1-I2.

Then, using the obtained current deviation amount I1, the previous current deviation amount I2, and the time change amount ΔI, the first pulse control amount calculation unit 109 obtains the pulse control amount ΔDuty1 using the following PID control expression.
ΔDuty1 = Kp1 × I1 + Kd1 × ΔI + Ki1 × (I1 + I2)
Kp1: proportional constant of proportional control Kd1: proportional constant of differential control Ki1: proportional constant of integral control

  The signal detected by the voltage detection unit 007 is AD-converted and taken into the CPU 009 as the output voltage 103, and the deviation amount from the set voltage 103 held in the CPU 009 by the voltage deviation amount calculation unit 107 at regular time intervals. Simultaneously with calculating V1, the previous voltage deviation amount V2 is obtained by calculation as the deviation amount before a certain time, and the time change amount ΔV is obtained by ΔV = V1−V2.

Then, using the obtained voltage deviation amount V1, previous voltage deviation amount V2, and time change amount ΔV, the second pulse control amount calculation unit 109 obtains a pulse control amount ΔDuty2 using the following PID control equation.
ΔDuty2 = Kp2 × V1 + Kd2 × ΔV + Ki2 × (V1 + V2)
Kp2: Proportional constant for proportional control Kd2: Proportional constant for differential control Ki2: Proportional constant for integral control

  In the present embodiment, the PID control shown in the preceding paragraphs 0013 and 0015 is used as a method for obtaining the control amount, but it can be realized by using other control methods and other control methods such as fuzzy control. is there.

Next, the control switching current Is is obtained from the temperature signal 105 from the temperature detection unit 008 that detects the temperature by the temperature sensor.
Is = Iset−αT
Iset: Current set at 0 ° C α: Current correction coefficient T: Temperature This control switching current Is is compared with the output current Iout. If Is ≧ Iout, voltage control is selected, and if Is <Iout, current control is selected. Put Is in 102. 4 and 5, when performing a hoop drooping operation or a hoop drooping operation, Is = Iset−αT + β (Vout−Vset) and current control is performed by adjusting the value of β. You can set the slope of the hour.

Pulse control amounts ΔDuty1, ΔDuty2 obtained in the preceding paragraphs 0013 and 0015, and the control method selected in 0017, in the case of current control, Duty = previous duty + ΔDuty1, in the case of current control, Duty = previous duty + ΔDuty2, and according to this duty By outputting the pulse obtained from the pulse output unit 112 to the switching unit 003, an optimum drooping operation according to the operation state of the converter is realized.

  The present invention is characterized in that the constant voltage control and the current control are switched according to the operation state of the DC-DC converter, and the same control can be used for a stabilized power source and an inverter.

Block diagram of an embodiment of the present invention Block diagram of a conventional DC-DC converter Drooping characteristic chart A Drooping characteristic diagram B Drooping characteristic chart C

Explanation of symbols

001 Power supply 002 Input voltage smoothing unit 003 Main switch 004 Transformer 005 Output rectification smoothing unit 006 Current detection unit 007 Voltage detection unit 008 Temperature detection unit 009 CPU
010 External load 101 Output current value 102 Set current value 103 Output voltage value 104 Set voltage value 105 Temperature value 106 Current deviation amount calculation unit 107 Voltage deviation amount calculation unit 108 Control method selection unit 109 First pulse control amount calculation unit 110 Second Pulse control amount calculator 111 Output pulse generator 112 Pulse output unit

Claims (4)

An input filter unit 002 for smoothing the input power supply voltage 001, a switching unit 003, a digital control unit for sending an output pulse for driving the switching unit, and a voltage applied to the primary winding of the transformer by turning on and off the switching unit 003 In the DC-DC converter, the output transformer unit 004 that induces the power to the secondary side and supplies power to the load, and the output voltage smoothing unit 005 that smoothes the power supply voltage output from the output transformer unit 004,
The digital control unit includes a control method selection unit that selects a control method of constant voltage control and constant current control, and includes a voltage detection unit 008 for detecting an output voltage, a current detection unit 006 for detecting an output current, a temperature Is connected to a temperature detection unit 007 for detecting
The control method selection unit outputs an output voltage, an output current, and a temperature condition signal detected by the voltage detection unit 008, the current detection unit 006, and the temperature detection unit 007 according to the operation state of the DC-DC converter. Switching between voltage control and output current control, creating an output pulse at the output pulse creation unit, and outputting an output pulse that drives the switching unit at the pulse output unit, stable constant voltage control and current control (droop operation) The DC-DC converter characterized by performing. A voltage deviation amount calculation unit 107 obtains a voltage deviation amount and a time change amount of the voltage from the output voltage 103 detected by the voltage detection unit 007 and the set voltage 104, and a pulse control amount from the deviation amount and the time change amount of these voltages. The DC-DC converter according to claim 1, wherein the calculation unit has a function of calculating a control amount. Based on the output current 101 detected by the current detection unit 006 and the set current 102, the current deviation amount calculation unit 106 obtains the current deviation amount and the time variation amount of the current, and the pulse control amount is obtained from the deviation amount and time variation amount of these currents. The DC-DC converter according to claim 1, wherein the calculation unit has a function of calculating a control amount. Each pulse control amount calculated by both the voltage deviation amount calculation unit 107 and the current deviation amount calculation unit 106 is selected according to the output voltage control / output current control selected by the control method selection unit, and an output pulse is created. 4. The DC-DC converter according to claim 1, wherein:

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