JP2006288047A - Dc-dc converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize the voltage to be applied to a load, even when the wiring resistance between an output terminal and the load is varied according to a temperature condition, in a DC-DC converter to be used under a wide range temperature condition. <P>SOLUTION: In this DC-DC converter equipped with an output current detecting section detecting output current, a temperature detecting section detecting temperature and a voltage-drop correction amount calculating section obtaining the correction amount for correcting the voltage drop due to the wiring resistance to the load from the output terminal according to the detected output current and temperature, the voltage drop correction amount is obtained at the voltage drop correction amount calculating section from the output current and a temperature signal, the pulse width control amount is obtained at the pulse width control amount calculating section according to the voltage drop correction amount, output voltage signal and setting voltage to perform highly accurate constant voltage control having the voltage applied with the load being not influenced by the temperature condition and the output current of the DC-DC converter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an improvement in accuracy of a voltage applied to a load in a DC-DC converter for an electric vehicle.

In conventional DC-DC converters and stabilized power supplies, control is performed so that the output voltage becomes a constant voltage by feeding back the voltage at the output terminal. However, the voltage actually applied to the load causes a voltage drop due to the wiring resistance from the output terminal to the load, and fluctuates below the voltage at the output terminal. Moreover, when the temperature range to be used is wide like an automobile, the electric wire resistance value changes depending on the temperature condition, and thereby the voltage drop in the electric wire becomes more prominent.

As a method for solving the above problems, Japanese Utility Model Laid-Open No. 5-23214 and Japanese Patent Application Laid-Open No. 2003-274641 are configured. As shown in FIG. 2, the output current is detected by an analog circuit and the output voltage drop is detected by an analog circuit. It is the structure which correct | amends a minute.
Utility Kaihei 5-23214 JP 2003-274641 A

In the method of correcting the voltage drop due to the output current with an analog circuit for these conventional techniques, the correction amount is insufficient when the resistance value of the wiring changes depending on the temperature condition like an automobile, The voltage applied to the load varies.
The present invention has a function of correcting the voltage drop in the wiring even when the wiring resistance between the output terminal of the DC-DC converter and the load changes depending on the temperature condition, and realizes stabilization of the voltage applied to the load. To do.

In the present invention, a voltage drop correction amount is obtained by a voltage drop correction amount calculation unit from an output current from an output current detection unit that detects an output current and a temperature signal detected from the temperature detection unit, and the voltage drop correction amount and output The voltage deviation calculation unit obtains the current voltage deviation and the previous voltage deviation from the output voltage signal from the output voltage detection unit that detects the voltage and the set voltage set in the digital control unit, and the pulse width control amount calculation unit calculates the pulse. By obtaining the control amount of the width, updating the pulse width in the pulse width creation unit using this pulse width control amount, and outputting the pulse to the switching unit, it is not affected by the temperature condition or output of the DC-DC converter Constant voltage control is performed.

As described above, by calculating the voltage drop correction amount based on the temperature in addition to the output current, the voltage applied to the load can be stabilized with high accuracy without depending on the temperature.

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 temperature detection unit, 008 is a voltage 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 temperature value, 103 is an output voltage value, 104 is a set voltage value, 105 is a voltage drop correction amount calculation unit, 106 is a voltage deviation amount calculation unit, and 107 is A pulse control amount calculation unit 108 indicates an output pulse generation unit 109 indicates 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, signals detected by the current detection unit 006 and the temperature detection unit 007 are AD-converted and taken into the CPU 009 as the output current 101 and the temperature value 102. From these output current and temperature value 102, the voltage drop correction amount ΔV Is obtained by the following equation.
ΔV = Iout × R0 (1 + α × T)
Iout: Output current R0: Wiring resistance value at 0 ° C α: Temperature coefficient T: Temperature value

Further, the signal detected by the voltage detection unit 008 is AD-converted and taken into the CPU 009 as the output voltage 103. The voltage deviation amount calculation unit 107 obtains the set voltage 103 and the set voltage 103 held in the CPU 009 at regular intervals. The deviation amount V1 is calculated by the following equation using the voltage drop correction amount ΔV.
V1 = Vout−Vset−ΔV
V1: Voltage deviation Vset: Set voltage ΔV: Voltage drop correction amount At the same time, the previous voltage deviation amount V2 is held as a deviation amount a predetermined time ago, 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 pulse control amount calculation unit 109 obtains the pulse control amount ΔDuty1 using the following PID control equation.
ΔDuty1 = 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

Based on the pulse control amount ΔDuty1 obtained in the preceding item 0012, the output pulse generation unit 107 sets the pulse duty = previous duty + ΔDuty1 and outputs a pulse corresponding to this duty from the pulse output unit 109 to the switching unit 003. The voltage drop in the wiring due to the output current is corrected, and the voltage applied to the load is controlled.

  The present invention can be used not only for automobiles but also for stabilized power supplies, inverters and the like used in an environment where the temperature range used is wide.

Block diagram of an embodiment of the present invention A block diagram of a conventional DC-DC converter configuration

Explanation of symbols

001 Power supply 002 Input smoothing smoothing unit 003 Main switch 004 Transformer 005 Output rectification smoothing unit 006 Current detection unit 007 Temperature detection unit 008 Voltage detection unit 009 CPU
101 Output current signal 102 Temperature value 103 Output voltage value 104 Set voltage value 105 Voltage drop correction amount calculation unit 106 Voltage deviation amount calculation unit 107 Pulse control amount calculation unit 108 Output pulse generation unit 109 Pulse output unit

Claims (2)

An input filter unit 002 for smoothing the input power supply voltage 001, a switching unit, 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 a DC-DC converter having an output transformer section 004 that induces power on the secondary side and supplies power to the load, and an output voltage smoothing section 005 that smoothes the power supply voltage output from the output transformer section 004,
The digital control unit is connected to a voltage detection unit 008 for detecting an output voltage of the DC-DC converter, a current detection unit 006 for detecting an output current, and a temperature detection unit 007 for detecting temperature, An output voltage, an output current, and a temperature condition detected by the voltage detection unit 008, the current detection unit 006, and the temperature detection unit 007 are input.
Based on the output current detected by the current detector and the temperature signal detected by the temperature detector, a voltage drop correction amount for correcting the voltage drop due to the wiring resistance from the output end of the DC-DC converter to the load is calculated, and the voltage detector Based on the detected voltage deviation amount and the voltage drop correction amount, the pulse control amount is calculated by the pulse control amount calculation unit 107 to generate an output pulse and output from the pulse output unit 109 to drive the switching unit 003 The DC-DC converter characterized by having carried out. 2. The DC-DC converter according to claim 1, wherein the output pulse has a voltage deviation amount calculation unit for detecting an output voltage change amount per set time detected by the voltage detection unit and a voltage deviation from the set voltage. .