JP4496479B2 - Current drive control method and current drive control circuit - Google Patents

Description

The present invention relates to a current drive control method and a current drive control circuit. More specifically, the present invention relates to a current drive that approximates a trapezoid hypotenuse edge portion of an output control voltage to a sine wave with respect to a load whose current changes with time after an output control voltage is applied. The present invention relates to a control method and a current drive control circuit.

As illustrated in FIG. 7, as a conventional technique, noise is reduced by approximating a part (edge part) of a trapezoidal output waveform of a voltage with a sine wave in a communication IC (Integrated Circuit) or the like. This technique is already known (for example, see Patent Document 1 and Patent Document 2). In this prior art, as shown in FIG. 8, the inclination of the trapezoid hypotenuse of the voltage is fixed and controlled.
JP 2004-289597 A JP-A-9-261016

However, in the above-described conventional technique, when a load whose current changes with time after voltage application (for example, a load through which a rush current such as a lamp flows) is driven through a drive element, the slope of the trapezoidal hypotenuse of the voltage Becomes more gradual (the inclination in the direction away from the vertical line is called gradual), the noise reduction effect by the sinusoidal approximation of the edge portion of the trapezoid hypotenuse increases. For this reason, as shown in FIG. 8, when the slope of the trapezoid slope of the voltage is fixed to a slope that can reduce noise with the normal use voltage, the slope time ΔT of the trapezoid slope of the voltage becomes longer as the voltage applied to the load becomes higher. However, there is a problem that the current flowing through the drive element increases during the inclination time ΔT of the trapezoid hypotenuse and the amount of heat generated by the drive element increases, and the drive element may burn out due to heat generation, causing a failure. Therefore, when controlling a load such as a lamp, a demand has arisen that it is desirable to make the slope of the trapezoidal hypotenuse of the voltage as steep as possible (the slope in the direction approaching the vertical line is steep).

On the other hand, as shown in FIG. 9, when the slope of the trapezoidal hypotenuse of the voltage is suddenly determined in accordance with the maximum voltage so that the drive element is not burned out due to heat generation, the slope time ΔT of the trapezoidal hypotenuse of the voltage is shortened. Therefore, there is a problem that the noise reduction effect due to approximation of the edge portion of the trapezoid hypotenuse at the normal operating voltage is reduced. For this reason, there has been a demand for the slope of the trapezoidal hypotenuse of the voltage to be moderate enough to obtain a noise reduction effect.

As described above, it is desirable to make the slope of the trapezoidal slope of the voltage as steep as possible to prevent failure of the drive element, and it is necessary to make the slope of the trapezoidal slope of the voltage gentle enough to obtain a noise reduction effect. There were two requests that conflicted with the request that there was, and a solution that would satisfy both of these requests was desired.

Accordingly, an object of the present invention is to set the time until the saturation of the output control voltage (slope time ΔT) to a substantially constant time within the maximum allowable time considering the heat generation limit of the drive element, thereby causing the drive element failure due to heat generation. It is another object of the present invention to provide a current drive control method that maximizes the noise reduction effect due to the sinusoidal approximation of the edge portion of the trapezoid hypotenuse.

Another object of the present invention is to provide a current drive control circuit which realizes the current drive control method.

Means for Solving the Problems and Effects of the Invention

The current drive control method according to claim 1, wherein a load whose current changes with time after application of the output control voltage is driven through a drive element, the edge portion of the trapezoidal hypotenuse of the output control voltage. And the slope of the trapezoid hypotenuse is variably controlled according to the power supply voltage so that the tilt time of the trapezoid hypotenuse is substantially constant within the maximum allowable time considering the heat generation limit of the drive element. It is characterized by setting. According to the current drive control method of the first aspect, the noise reduction effect can be obtained by approximating the edge portion of the trapezoid hypotenuse of the output control voltage with a sine wave. At the same time, the slope of the trapezoid hypotenuse is variably controlled according to the power supply voltage, and the slope of the trapezoid hypotenuse of the output control voltage, which is the source of noise, is almost constant within the maximum allowable time considering the heat generation limit of the drive element. By setting as described above, it is possible to prevent a failure due to heat generation of the drive element.

The current drive control method according to claim 2, wherein a load whose current changes with time after an output control voltage is applied is driven through a drive element based on a charge voltage of a charging circuit. A first constant current value determining step for determining a constant current value based on an elapsed time from the start of increase / decrease of the control voltage, and a first constant current value switching for switching the current value flowing through the constant current circuit to the constant current value; A first determination step for determining whether an elapsed time from the start of increase / decrease in the output control voltage is within a first sine wave approximate time interval after elapse of a reference time; and A constant-inclination current value setting step for setting a current value flowing through the charging circuit to a constant-inclination current value when the elapsed time from the start of increase / decrease is not within the first approximate sine wave approximate time section; A voltage ratio detection step for detecting that the output control voltage has reached a predetermined ratio of the power supply voltage, and a second constant value for determining the constant current value based on an elapsed time from the start of increase / decrease in the output control voltage. A current value determining step, a second constant current value switching step for switching the current value flowing through the constant current circuit to the constant current value, and an elapsed time from the start of increase / decrease of the output control voltage after a lapse of a reference time. A second determination step for determining whether or not the current value is within the approximate sine wave approximate time interval, and the charging circuit when the elapsed time from the increase / decrease start time of the output control voltage is not within the second approximate sine wave approximate time interval. And a leakage current equivalent current value setting step of setting the current value flowing through the current value to a leakage current equivalent current value. According to the current drive control method of the second aspect, the sine wave approximation is controlled toward the target value of the elapsed time for each reference time at the start / end of the slope control of the trapezoid hypotenuse of the output control voltage serving as a noise source. Thus, the trapezoid hypotenuse edge portion of the output control voltage can be approximated to a sine wave, and at the same time, the slope time of the trapezoid hypotenuse of the output control voltage can be made almost constant, so that both noise and heat generation can be reduced. There is an effect.

The current drive control method according to claim 3, wherein a load whose current changes with time after an output control voltage is applied is driven through a drive element based on a charge voltage of a charging circuit. A first constant current value determining step for determining a constant current value based on an increase / decrease voltage from the start of increase / decrease of the control voltage, and a first constant current value switching for switching the current value flowing in the constant current circuit to the constant current value And a first determination for determining whether the increase / decrease voltage from the start point of the increase / decrease of the output control voltage is within the first approximate sine wave voltage section after the increase / decrease fluctuation of the output control voltage exceeds the reference voltage. Step, and when the increase / decrease voltage from the start of increase / decrease of the output control voltage is not within the first sine wave approximate voltage section, the current value flowing through the charging circuit is set to a constant slope current value. Current value setting step, voltage ratio detection step for detecting that the output control voltage has reached a predetermined ratio of the power supply voltage, and the constant current value based on the increase / decrease voltage from the start of increase / decrease of the output control voltage A second constant current value determining step for determining the current value, a second constant current value switching step for switching the current value flowing through the constant current circuit to the constant current value, and after the fluctuation of the output control voltage exceeds the reference voltage A second determination step for determining whether the increase / decrease voltage from the increase / decrease start time of the output control voltage is within a second sinusoidal approximate voltage interval, and the elapsed time from the increase / decrease start point of the output control voltage And a leakage current equivalent current value setting step of setting a current value flowing through the charging circuit to a leakage current equivalent current value when it is not within the second sinusoidal approximate voltage section. According to the current drive control method of the third aspect, the sine wave approximation is controlled toward the target value of the increase / decrease voltage for each reference voltage at the start / end of the slope control of the trapezoid hypotenuse of the output control voltage serving as a noise source. Thus, the trapezoid hypotenuse edge portion of the output control voltage can be approximated to a sine wave, and at the same time, the slope time of the trapezoid hypotenuse of the output control voltage can be made almost constant, so that both noise and heat generation can be reduced. There is an effect.

The current drive control method according to claim 4 is the current drive control method according to any one of claims 1 to 3, wherein the load is a lamp. According to the current drive control method of the fourth aspect, failure due to heat generation of the drive element used for current drive of the lamp can be greatly reduced.

The current drive control method according to claim 5 is the current drive control method according to any one of claims 1 to 4, wherein the drive element is a field effect transistor. According to the current drive control method of the fifth aspect, failure due to heat generation of the field effect transistor as the drive element can be greatly reduced.

The current drive control circuit according to claim 6 includes: a load in which the current changes with time after the output control voltage is applied; a current detection resistor to which a power supply voltage is applied; and the load and the current detection resistor. A drive element that is connected in between and that drives the load with current, a current detection circuit that detects current based on the voltage of the current detection resistor, and the output control voltage is a predetermined ratio of the power supply voltage. A voltage ratio detection circuit to detect and an edge portion of the trapezoid hypotenuse of the output control voltage are approximated by a sine wave, and the tilt time of the trapezoid hypotenuse is controlled by variably controlling the slope of the trapezoid hypotenuse according to a power supply voltage. A slope control circuit for setting a current value to be controlled within the maximum allowable time considering the heat generation limit of the element, a constant current circuit for switching current based on the current value from the slope control circuit, and the constant current circuit A charging circuit which is charged by the constant current from, and having a comparator for controlling the drive device at a differential voltage between the detection voltage and the charging voltage of the charging circuit of the current detection circuit. According to the current drive control circuit of the sixth aspect, the noise reduction effect can be obtained by approximating the edge portion of the trapezoid hypotenuse of the output control voltage with a sine wave. At the same time, the slope of the trapezoid hypotenuse is variably controlled according to the power supply voltage, and the slope of the trapezoid hypotenuse of the output control voltage, which is the source of noise, is almost constant within the maximum allowable time considering the heat generation limit of the drive element. By setting as described above, it is possible to prevent a failure due to heat generation of the drive element.

The current drive control circuit according to claim 7 includes: a load in which the current changes with time after the output control voltage is applied; a current detection resistor to which a power supply voltage is applied; and the load and the current detection resistor. A drive element that is connected in between and that drives the load with current, a current detection circuit that detects current based on the voltage of the current detection resistor, and the output control voltage is a predetermined ratio of the power supply voltage. A constant current value is determined based on a voltage ratio detection circuit to detect and an elapsed time from the start of increase / decrease of the output control voltage, and is switched to the constant current value. After a reference time elapses, the increase / decrease of the output control voltage starts. If the elapsed time from the time is within the first sine wave approximate time interval, the constant current value is constant when the elapsed time from the start of increase / decrease of the output control voltage is not within the first sine wave approximate time interval. For tilt Set the current value, detects that the output control voltage has reached a predetermined ratio of the power supply voltage, determines a constant current value based on the elapsed time from the start of increase or decrease of the output control voltage, the constant current After the lapse of a reference time, if the elapsed time from the start of increase / decrease of the output control voltage is within the second sine wave approximate time interval, the elapsed time from the start of increase / decrease of the output control voltage is repeated. By setting the constant current value to a constant slope current value when the second sinusoidal approximate time interval is not reached, the trapezoid hypotenuse edge portion of the output control voltage is approximated to a sinusoidal wave, and the slope of the trapezoid hypotenuse is A slope control circuit that variably controls the power supply voltage to control the slope time of the trapezoid hypotenuse within a maximum allowable time in consideration of the heat generation limit of the drive element, and a power supply from the slope control circuit. A constant current circuit that switches a current based on a value; a charging circuit that is charged by a constant current from the constant current circuit; and a driving voltage that is a difference voltage between a detection voltage of the current detection circuit and a charging voltage of the charging circuit. And a comparator for controlling. According to the current drive control circuit of the seventh aspect, the sine wave approximation is controlled toward the target value of the elapsed time for each reference time at the start / end of the slope control of the trapezoid hypotenuse of the output control voltage serving as a noise source. Thus, the trapezoid hypotenuse edge portion of the output control voltage can be approximated to a sine wave, and at the same time, the slope time of the trapezoid hypotenuse of the output control voltage can be made almost constant, so that both noise and heat generation can be reduced. There is an effect.

The current drive control method according to claim 8 includes: a load in which the current changes with time after the output control voltage is applied; a current detection resistor to which a power supply voltage is applied; and the load and the current detection resistor. A drive element that is connected in between and that drives the load with current, a current detection circuit that detects current based on the voltage of the current detection resistor, and the output control voltage is a predetermined ratio of the power supply voltage. A constant current value is determined based on a voltage ratio detection circuit to detect and an increase / decrease voltage from the start of increase / decrease of the output control voltage, and after switching to the constant current value, an increase / decrease fluctuation of the output control voltage exceeds a reference voltage If the increase / decrease voltage from the increase / decrease start point of the output control voltage is within the first sinusoidal approximate voltage interval, the increase / decrease voltage from the increase / decrease start point of the output control voltage is within the first sinusoidal approximate voltage interval. Not Then, the constant current value is set to a constant slope current value, and it is detected that the output control voltage has reached a predetermined ratio of the power supply voltage, and is determined based on the increase / decrease voltage from the start of increase / decrease of the output control voltage. After the current value is determined and switched to the constant current value, and the fluctuation of the output control voltage exceeds the reference voltage, the voltage increase / decrease from the start of the increase / decrease of the output control voltage is within the second sine wave approximate voltage section. If there is a repetition, if the elapsed time from the start of increase / decrease in the output control voltage is not within the second approximated sine wave approximate voltage section, a constant current value is set to a constant slope current value, thereby generating a trapezoid of the output control voltage. The edge of the hypotenuse is approximated by a sine wave, and the slope of the trapezoid hypotenuse is variably controlled according to the power supply voltage so that the tilt time of the trapezoid hypotenuse is controlled within the maximum allowable time considering the heat generation limit of the drive element. Current A slope control circuit that sets the current, a constant current circuit that switches current based on a current value from the slope control circuit, a charging circuit that is charged by a constant current from the constant current circuit, and a detection voltage of the current detection circuit And a comparator for controlling the driving element with a differential voltage between the charging voltage of the charging circuit and the charging voltage of the charging circuit. According to the current drive control circuit of claim 8, the sine wave approximation is controlled toward the target value of the increase / decrease voltage for each reference voltage at the start / end of the slope control of the trapezoid hypotenuse of the output control voltage that becomes a noise source. Thus, the trapezoid hypotenuse edge portion of the output control voltage can be approximated to a sine wave, and at the same time, the slope time of the trapezoid hypotenuse of the output control voltage can be made almost constant, so that both noise and heat generation can be reduced. There is an effect.

9. The current drive control circuit according to claim 9, wherein the load is a lamp, wherein the load is a lamp. To do. According to the current drive control circuit of the ninth aspect, failure due to heat generation of the drive element used for the current drive of the lamp can be greatly reduced.

A current drive control circuit according to a tenth aspect is the current drive control circuit according to any one of the sixth to ninth aspects, wherein the drive element is a field effect transistor. According to the current drive control circuit of the tenth aspect, failure due to heat generation of the field effect transistor as the drive element can be greatly reduced.

For a load whose current changes with time after the output control voltage is applied, the trapezoid hypotenuse edge of the output control voltage is approximated by a sine wave, and the trapezoid hypotenuse slope is variably controlled according to the power supply voltage. Is set to be a substantially constant time within the maximum allowable time considering the heat generation limit of the driving element.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram illustrating a current drive control circuit according to the first embodiment of the present invention. The current drive control circuit according to the first embodiment includes a current detection resistor R1 to which a power supply voltage (battery voltage) Va is applied, and a current detection circuit CO1 that detects a current i based on the voltage of the current detection resistor R1. The resistors R2 and R3 connected in series between the power source and the ground, the voltage ratio detection circuit CO2 for detecting that the output control voltage Vb has reached a predetermined ratio of the power supply voltage Va, and the output of the voltage ratio detection circuit CO2 Based on the inclination control circuit 10 for controlling the inclination of the trapezoidal hypotenuse of the output control voltage Vb, the timer oscillator 20 for timing connected to the inclination control circuit 10, and the inclination control circuit 10 having one end connected to the control power supply voltage Vcc. A constant current circuit 30 whose current is switched by the capacitor, a capacitor (charging circuit) C1 interposed between the constant current circuit 30 and the ground, and a detection voltage of the current detection circuit CO1. A comparator CO3 that outputs a differential voltage from the charging voltage of the capacitor C1, a drive element 40 that controls the current i according to the differential voltage from the comparator CO3, and a lamp (load) that is driven by the current i that passes through the drive element 40 50).

The current detection circuit CO1 has a pair of input terminals connected to both ends of the current detection resistor R1, and detects the current i from the resistance value of the current detection resistor R1 known in advance.

In the voltage ratio detection circuit CO2, one input terminal is connected to a connection point between the resistor R2 and the resistor R3 that divides the power supply voltage Va, and the output control voltage Vb is applied to the other input terminal. It is detected that Vb has become a predetermined ratio (R3 / (R2 + R3)) with respect to the power supply voltage Va. The predetermined ratio here determines the start time point of the second sine wave approximate time interval that approximates the second edge of the trapezoid hypotenuse of the output control voltage Vb shown in FIG. .7 (70%), 0.8 (80%), etc. are preset.

The constant current circuit 30 has a control power supply voltage Vcc applied to one end and the other end connected to the capacitor C1.

The capacitor C1 serves as a charging circuit that charges the constant current from the constant current circuit 30.

The comparator CO3 feeds back a detection voltage corresponding to the current i of the current detection resistor R1 via the current detection circuit CO1, and controls the drive element 40 with a differential voltage from the charging voltage of the capacitor C1.

The drive element 40 is formed of, for example, a field effect transistor (FET), more specifically, a metal oxide semiconductor field effect transistor (MOSFET).

The lamp 50 is a load in which the current i changes with time after the output control voltage Vb is applied. Specifically, the lamp 50 is a load at which, when energization starts, the impedance is low and a large current (rush current) flows at a low temperature, but the temperature increases with time and the impedance increases and the current i decreases. In the case of a load such as the lamp 50, the drive element 40 is likely to be burned out by a rush current at the start of energization unless some measures are taken.

FIG. 2 is a flowchart for explaining processing in the inclination control circuit 10.

FIG. 3 is a diagram for explaining the current drive control method according to the first embodiment of the present invention. In this current drive control method, the inclination control circuit 10 measures the clock from the timer oscillator 20 and approximates the edge portion of the trapezoid hypotenuse of the output control voltage Vb as a sine wave, and the slope of the trapezoid hypotenuse is set to the power supply voltage Va. Accordingly, the slope time ΔT of the trapezoid hypotenuse is set so as to be a substantially constant time within the maximum allowable time considering the heat generation limit of the drive element 40. The procedure for approximating the trapezoid hypotenuse edge of the output control voltage Vb as a sine wave is to determine a constant current value based on the elapsed time from the start of increase / decrease of the output control voltage Vb, and to switch the constant current value that flows to the capacitor C1. After the elapse of the reference time dt (a fixed time for dividing the first or second approximated sine wave approximate time section into a plurality of times), the elapsed time from the start of increase / decrease of the output control voltage Vb is the first approximated sine wave time It is determined whether it is within a section (for example, a time when the output control voltage Vb is assumed to be 30%, 20%, etc. of the power supply voltage Va), and the elapsed time is within the first sine wave approximate time section. Repeat if there is. When the elapsed time from the increase / decrease start time of the output control voltage Vb is not within the first approximate sine wave approximate time section, the constant current value is set to the constant slope current value. The constant slope current value corresponds to the constant slope section in FIG. 3, and the sum of the first sine wave approximate time section, the constant slope section time, and the second sine wave approximate time section is: The slope time ΔT of the trapezoidal hypotenuse of the output control voltage Vb is set to be a substantially constant time within the maximum allowable time considering the heat generation limit of the drive element 40. Next, it is detected that the output control voltage Vb has reached a predetermined ratio (R3 / (R2 + R3): for example, 70%, 80%, etc.) of the power supply voltage Va. When the output control voltage Vb reaches a predetermined ratio of the power supply voltage Va, a constant current value is determined based on an elapsed time from the start of increase / decrease of the output control voltage Vb, the constant current circuit 30 is switched to this constant current value, and a reference time After elapse of dt, the elapsed time from the start of increase / decrease of the output control voltage Vb is a second approximate sine wave time interval (for example, the time when the output control voltage Vb is assumed to be close to 100% of the power supply voltage Va). If the elapsed time is within the second sine wave approximate time interval, the process is repeated. When the elapsed time from the start of increase / decrease of the output control voltage Vb is not within the second sine wave approximate time interval, the constant current value is set to the leakage current equivalent current value of the capacitor C1. In FIG. 3, the current drive control method for the first edge portion (rising edge portion) of the trapezoidal hypotenuse of the output control voltage Vb has been described. However, the second edge portion (rising edge) of the trapezoid hypotenuse of the output control voltage Vb has been described. The same control can be performed for the falling edge portion.

Next, the operation of the current drive control circuit according to the first embodiment configured as described above will be described with reference to FIGS.

First, the slope control circuit 10 determines a constant current value (a value designed in advance in terms of circuit) from the elapsed time from the start of increase / decrease of the output control voltage Vb (step S101), and the current flowing through the constant current circuit 30 is determined. Switching to a constant current value (step S102).

Then, the capacitor C1 is charged by the constant current flowing through the constant current circuit 30, and the comparator CO3 is controlled by the differential voltage between the charging voltage of the capacitor C1 and the detection voltage of the current detection circuit CO1, thereby increasing or decreasing the output control voltage Vb. Generates an output control voltage Vb approximated to a sine wave. The lamp 50 to which the output control voltage Vb is applied is driven and emits light while changing the current value.

Next, the inclination control circuit 10 determines whether or not the elapsed time from the increase / decrease start time of the output control voltage Vb is within the first sine wave approximate time interval based on the clock from the timer oscillator 20 ( If it is within the first sine wave approximate time interval (step S103) (step S103: YES), the control is returned to step S101.

When the elapsed time from the start of increase / decrease of the output control voltage Vb is not the first approximate sine wave time interval (step S103: NO), the slope control circuit 10 sets the current value for constant slope (step S104). As a result, a constant slope section in which the output control voltage Vb increases with a constant slope starts.

Next, the gradient control circuit 10 receives the output control voltage Vb and the voltage obtained by dividing the power supply voltage Va at a predetermined ratio (R3 / (R2 + R3)) from the voltage ratio detection circuit CO2, and performs output control based on the differential voltage. It is detected whether or not the voltage Vb has reached a predetermined ratio of the power supply voltage Va (step S105).

If the output control voltage Vb has reached a predetermined ratio of the power supply voltage Va (step S105: YES), the slope control circuit 10 determines a constant current value from the elapsed time from the start of increase / decrease of the output control voltage Vb ( In step S106, the current flowing through the constant current circuit 30 is switched to a constant current value (step S107).

Then, the capacitor C1 is charged by the constant current flowing through the constant current circuit 30, and the comparator CO3 is controlled by the differential voltage between the charging voltage of the capacitor C1 and the detection voltage of the current detection circuit CO1, thereby increasing or decreasing the output control voltage Vb. The output control voltage Vb approximated to a sine wave is generated. The lamp 50 to which the output control voltage Vb is applied is driven and emits light while changing the current value.

Next, the slope control circuit 10 determines whether or not the elapsed time from the increase / decrease start time of the output control voltage Vb is within the second sine wave approximation time interval (step S108), and the second sine wave approximation time. If it is within the section (step S108: YES), the control is returned to step S106.

When the elapsed time from the start of increase / decrease in the output control voltage Vb is not the second approximate sine wave approximate time interval (step S108: NO), the slope control circuit 10 sets the current value corresponding to the leakage current of the capacitor C1 (step S108). S109).

Then, as shown in FIG. 3, since the charging voltage of the capacitor C1 is kept constant, a constant output control voltage Vb (= Va) is generated. The drive element 40 is controlled by a voltage proportional to the differential voltage between the output control voltage Vb and the current i detected by the current detection circuit CO1, and the lamp 50 is driven.

According to the first embodiment, as shown in FIG. 10, the edge portion of the trapezoid hypotenuse of the output control voltage Vb is approximated by a sine wave even if the value of the output control voltage Vb is the same as in the conventional control. By setting the slope time ΔT of the trapezoid hypotenuse to be a substantially constant time within the maximum allowable time considering the heat generation limit of the drive element 40 and making the slope of the trapezoid hypotenuse steep according to the power supply voltage Va, The tilt time ΔT is shortened. Along with this, the time width of the power W (t) becomes narrower and the average value of the power spectrum (| Cj |) ² also decreases, so that the drive element 40 to be used can be made smaller. The power spectrum (| Cj |) ² can be obtained by the following equation group. However, I and II show the matrix which sampled and converted electric power P, and fft shows a Fourier-transform.

FIG. 4 is a block diagram showing a current drive control circuit according to the second embodiment of the present invention. The current drive control circuit according to the second embodiment is obtained by removing the timer oscillator 20 from the current drive control circuit according to the first embodiment shown in FIG. Therefore, other parts not specifically mentioned are configured in the same manner as the corresponding parts in the current drive control circuit according to the first embodiment shown in FIG. I will omit the detailed explanation.

FIG. 5 is a flowchart for explaining processing in the tilt control circuit 10.

FIG. 6 is a diagram for explaining a current drive control method according to the second embodiment of the present invention. In this current drive control method, the slope control circuit 10 approximates the edge portion of the trapezoid hypotenuse of the output control voltage Vb with a sine wave, and also variably controls the slope of the trapezoid hypotenuse according to the power supply voltage Va, thereby making the slope time of the trapezoid hypotenuse. ΔT is set to be a substantially constant time within the maximum allowable time considering the heat generation limit of the drive element 40. The procedure for approximating the edge of the trapezoidal hypotenuse of the output control voltage Vb as a sine wave is to determine a constant current value based on the increase / decrease voltage from the start of increase / decrease of the output control voltage Vb, and to switch the constant current value flowing through the capacitor C1. After the increase / decrease fluctuation of the output control voltage Vb exceeds the reference voltage dV (a voltage obtained by dividing the first or second sine wave approximate voltage section into a plurality), the increase / decrease voltage from the start of increase / decrease of the output control voltage Vb is It is determined whether it is within one sine wave approximate voltage section (for example, a section until 30%, 20%, etc. of the power supply voltage Va), and if the increase / decrease voltage is within the first sine wave approximate voltage section repeat. Then, when the increase / decrease voltage from the start of increase / decrease of the output control voltage Vb is not within the first sine wave approximate voltage section, the constant current value is set to the constant slope current value. The constant slope current value corresponds to the constant slope section in FIG. 6, and is the time of the first sine wave approximate voltage section, the time of the constant slope section, and the time of the second sine wave approximate voltage section. Is the slope time ΔT of the trapezoid hypotenuse of the output control voltage Vb, and is set to be a substantially constant time within the maximum allowable time considering the heat generation limit of the drive element 40. Next, it is detected that the output control voltage Vb has reached a predetermined ratio (R3 / (R2 + R3): for example, 70%, 80%, etc.) of the power supply voltage Va. When the output control voltage Vb reaches a predetermined ratio of the power supply voltage Va, a constant current value is determined based on the increase / decrease voltage from the start of increase / decrease of the output control voltage Vb, the constant current circuit 30 is switched to this constant current value, and output control is performed. After the increase / decrease fluctuation of the voltage Vb exceeds the reference voltage dV, the increase / decrease voltage from the start of the increase / decrease of the output control voltage Vb is in the second sine wave approximate voltage section (for example, the output control voltage Vb is near 100% of the power supply voltage Va) Whether or not the increase / decrease voltage is within the second approximate sinusoidal voltage interval. When the increase / decrease voltage from the start of increase / decrease of the output control voltage Vb is not within the second approximated sine wave approximate voltage section, the constant current value is set to the leak current equivalent current value of the capacitor C1. 6 illustrates the current drive control method for the first edge portion (rising edge portion) of the trapezoidal hypotenuse of the output control voltage Vb. However, the second edge portion (rising edge) of the trapezoid hypotenuse of the output control voltage Vb has been described. The same control can be performed for the falling edge portion.

Next, the operation of the current drive control circuit according to the second embodiment configured as described above will be described with reference to FIGS.

First, the slope control circuit 10 determines a constant current value (a circuit predesigned value) from the increase / decrease voltage from the start of increase / decrease of the output control voltage Vb (step S201), and the current flowing through the constant current circuit 30 is determined. Switching to a constant current value (step S202).

Then, the capacitor C1 is charged by the constant current flowing through the constant current circuit 30, and the comparator CO3 is controlled by the differential voltage between the charging voltage of the capacitor C1 and the detection voltage of the current detection circuit CO1, and the increase / decrease amount of the output control voltage Vb is increased. A gradually increasing output control voltage Vb approximated to a sine wave is generated. The lamp 50 to which the output control voltage Vb is applied is driven and emits light while changing the current value.

Next, the slope control circuit 10 determines whether the output control voltage Vb is within the first sine wave approximate voltage interval (step S203), and if it is within the first sine wave approximate voltage interval (step S203). : YES), control is returned to step S201.

If the output control voltage Vb is not the first approximate sine wave voltage section (step S203: NO), the slope control circuit 10 sets the current value for constant slope (step S204). As a result, a constant slope section in which the output control voltage Vb increases with a constant slope starts.

Next, the gradient control circuit 10 receives the output control voltage Vb and the voltage obtained by dividing the power supply voltage Va at a predetermined ratio (R3 / (R2 + R3)) from the voltage ratio detection circuit CO2, and performs output control based on the differential voltage. It is detected whether or not the voltage Vb has reached a predetermined ratio of the power supply voltage Va (step S205).

If the output control voltage Vb has reached a predetermined ratio of the power supply voltage Va (step S205: YES), the slope control circuit 10 determines a constant current value based on the output control voltage Vb (step S206), and the constant current circuit 30. Is switched to a constant current value (step S207).

Then, the capacitor C1 is charged by the constant current flowing through the constant current circuit 30, and the comparator CO3 is controlled by the differential voltage between the charging voltage of the capacitor C1 and the detection voltage of the current detection circuit CO1, thereby increasing or decreasing the output control voltage Vb. The output control voltage Vb approximated to a sine wave is generated. The lamp 50 to which the output control voltage Vb is applied is driven and emits light while changing the current value.

Next, the slope control circuit 10 determines whether or not the output control voltage Vb is within the second sine wave approximate voltage interval (step S208), and if it is within the second sine wave approximate voltage interval (step S208). : YES), control is returned to step S206.

When the output control voltage Vb is not in the second sinusoidal approximate voltage section (step S208: NO), the slope control circuit 10 sets the current value corresponding to the leakage current of the capacitor C1 (step S209).

Then, as shown in FIG. 6, since the charging voltage of the capacitor C1 is kept constant, a constant output control voltage Vb (= Va) is generated. The drive element 40 is controlled by a voltage proportional to the differential voltage between the output control voltage Vb and the current i detected by the current detection circuit CO1, and the lamp 50 is driven.

According to the second embodiment, the same effect as in the first embodiment (see FIG. 10) can be obtained, and the timer vibrator 20 is not required. This has the effect of simplifying the control and facilitating the control.

The embodiments of the present invention have been described above. However, these are merely examples, and the present invention is not limited to them, and the knowledge of those skilled in the art can be used without departing from the spirit of the claims. Various modifications based on this are possible.

1 is a circuit block diagram showing a current drive control circuit according to Embodiment 1 of the present invention. 2 is a timing chart showing processing of the tilt control circuit in FIG. 1. FIG. 4 is a waveform diagram illustrating a current drive control method according to the first embodiment. The circuit block diagram which shows the current drive control circuit which concerns on Example 2 of this invention. 5 is a timing chart showing processing of the inclination control circuit in FIG. FIG. 6 is a waveform diagram illustrating a current drive control method according to the second embodiment. The waveform diagram of the output control voltage explaining the current drive control method of the conventional current drive control circuit. The figure explaining the relationship between an output control voltage and the heat_generation | fever of a drive element. The figure explaining the relationship between an output control voltage and a noise reduction effect. The figure which compares and shows the ramp time, electric power, and noise amount in the conventional current drive control method and the current drive control method of this invention.

Explanation of symbols

10 Tilt Control Circuit 20 Timer Vibrator 30 Constant Current Circuit 40 Drive Element 50 Lamp (Load)
C1 Capacitor CO1 Current detection circuit CO2 Voltage detection circuit CO3 Comparator R1 Current detection resistor

Claims (10)

In a current drive control method of driving a load whose current changes with time after applying an output control voltage through a drive element,
The trapezoid hypotenuse edge portion of the output control voltage is approximated by a sine wave, and the trapezoid hypotenuse slope is variably controlled according to the power supply voltage, and the trapezoid hypotenuse slope time is the maximum allowable considering the heat generation limit of the driving element. A current drive control method, wherein the current drive control method is set so as to be a substantially constant time within a time. In a current drive control method of driving a current whose current changes with time after applying an output control voltage through a drive element based on a charge voltage of a charging circuit,
A first constant current value determining step for determining a constant current value based on an elapsed time from the start of increase / decrease of the output control voltage;
A first constant current value switching step of switching a current value flowing through the charging circuit to the constant current value;
A first determination step for returning control to the first constant current value determination step if the elapsed time from the start of increase / decrease in the output control voltage is within the first approximate sine wave approximate time section after the elapse of the reference time; ,
A constant slope current value setting step of setting a current value flowing through the charging circuit to a constant slope current value when the elapsed time from the start of increase / decrease of the output control voltage is not within the first sine wave approximate time section; ,
A voltage ratio detection step for detecting that the output control voltage has reached a predetermined ratio of the power supply voltage;
A second constant current value determining step for determining a constant current value based on an elapsed time from the start of increase / decrease of the output control voltage;
A second constant current value switching step of switching a current value flowing through the charging circuit to the constant current value;
A second determination step for returning the control to the second constant current value determination step if the elapsed time from the start of increase / decrease of the output control voltage is within the second approximate sine wave approximate time interval after the elapse of the reference time; ,
A leakage current equivalent current value setting step for setting a current value flowing through the charging circuit to a leakage current equivalent current value when an elapsed time from the start of increase / decrease of the output control voltage is not within the second sine wave approximate time interval; A current drive control method comprising: In a current drive control method of driving a current whose current changes with time after applying an output control voltage through a drive element based on a charge voltage of a charging circuit,
A first constant current value determining step for determining a constant current value based on an increase / decrease voltage from the start of increase / decrease of the output control voltage;
A first constant current value switching step of switching a current value flowing through the charging circuit to the constant current value;
After the increase / decrease fluctuation of the output control voltage exceeds the reference voltage, if the increase / decrease voltage from the start of increase / decrease of the output control voltage is within the first sine wave approximate voltage section, control is performed to the first constant current value determination step. A first determination step of returning
A constant slope current value setting step of setting a current value flowing through the charging circuit to a constant slope current value when the increase / decrease voltage from the start of increase / decrease of the output control voltage is not within the first sine wave approximate voltage section; ,
A voltage ratio detection step for detecting that the output control voltage has reached a predetermined ratio of the power supply voltage;
A second constant current value determining step for determining a constant current value based on the increase / decrease voltage from the increase / decrease start time of the output control voltage;
A second constant current value switching step of switching a current value flowing through the charging circuit to the constant current value;
After the fluctuation of the output control voltage exceeds the reference voltage, if the increase / decrease voltage from the start of increase / decrease of the output control voltage is within the second sinusoidal approximate voltage section, control is performed to the second constant current value determination step. A second determination step for returning
A leakage current equivalent current value setting step of setting a current value flowing through the charging circuit to a leakage current equivalent current value when the increase / decrease voltage from the start of increase / decrease of the output control voltage is not within the second sinusoidal approximate voltage section; A current drive control method comprising: The current drive control method according to claim 1, wherein the load is a lamp. The current drive control method according to claim 1, wherein the drive element is a field effect transistor. A load whose current changes with time after applying the output control voltage; and
A current detection resistor to which a power supply voltage is applied;
A driving element connected between the load and the current detection resistor and driving the load with current;
A current detection circuit for detecting a current based on the voltage of the current detection resistor;
A voltage ratio detection circuit for detecting that the output control voltage has reached a predetermined ratio of the power supply voltage;
The trapezoid hypotenuse edge portion of the output control voltage is approximated by a sine wave, and the trapezoid hypotenuse slope is variably controlled according to the power supply voltage, and the trapezoid hypotenuse slope time is the maximum allowable considering the heat generation limit of the driving element. An inclination control circuit for outputting a current value for setting so as to be a substantially constant time within the time;
A constant current circuit that switches current based on a current value from the slope control circuit;
A charging circuit charged with a constant current from the constant current circuit;
A current drive control circuit comprising: a comparator that controls the drive element with a differential voltage between a detection voltage of the current detection circuit and a charge voltage of the charging circuit. A load whose current changes with time after applying the output control voltage; and
A current detection resistor to which a power supply voltage is applied;
A driving element connected between the load and the current detection resistor and driving the load with current;
A current detection circuit for detecting a current based on the voltage of the current detection resistor;
A voltage ratio detection circuit for detecting that the output control voltage has reached a predetermined ratio of the power supply voltage;
A constant current value is determined based on an elapsed time from the start point of increase / decrease of the output control voltage, switched to the constant current value, and after a lapse of a reference time, an elapsed time from the start point of increase / decrease of the output control voltage is first. If the elapsed time from the start of increase / decrease of the output control voltage is not within the first sine wave approximation time interval, the constant current value is set to a constant slope current value. When it is detected that the output control voltage has reached a predetermined ratio of the power supply voltage, a constant current value is determined based on an elapsed time from the start of increase / decrease of the output control voltage, and switched to the constant current value When the elapsed time from the start of increase / decrease of the output control voltage is within the second sine wave approximate time interval after the elapse of the reference time, the elapsed time from the start of increase / decrease of the output control voltage is repeated. Sine wave approximation By setting the constant current value to the current value corresponding to the leakage current when it is not within the interval, the trapezoid hypotenuse edge of the output control voltage is approximated to a sine wave, and the slope of the trapezoid hypotenuse is variable according to the power supply voltage. And a slope control circuit that outputs a current value for setting the slope of the trapezoid hypotenuse to be substantially constant time within a maximum allowable time in consideration of the heat generation limit of the drive element;
A constant current circuit that switches current based on a current value from the slope control circuit;
A charging circuit charged with a constant current from the constant current circuit;
A current drive control circuit comprising: a comparator that controls the drive element with a differential voltage between a detection voltage of the current detection circuit and a charge voltage of the charging circuit. A load whose current changes with time after applying the output control voltage; and
A current detection resistor to which a power supply voltage is applied;
A driving element connected between the load and the current detection resistor and driving the load with current;
A current detection circuit for detecting a current based on the voltage of the current detection resistor;
A voltage ratio detection circuit for detecting that the output control voltage has reached a predetermined ratio of the power supply voltage;
A constant current value is determined based on the increase / decrease voltage from the starting point of the increase / decrease of the output control voltage, switched to the constant current value, and the increase / decrease of the output control voltage starts to increase / decrease after the fluctuation of the output control voltage exceeds the reference voltage If the increase / decrease voltage from the time point is within the first sine wave approximate voltage section, the constant current value is repeated when the increase / decrease voltage from the start point of increase / decrease of the output control voltage is not within the first sine wave approximate voltage section. When the current value for constant inclination is set, and it is detected that the output control voltage reaches a predetermined ratio of the power supply voltage, the constant current value is determined based on the increase / decrease voltage from the start of increase / decrease of the output control voltage. Then, after switching to the constant current value and the fluctuation of the output control voltage exceeds the reference voltage, if the increase / decrease voltage from the start of increase / decrease of the output control voltage is within the second sine wave approximate voltage section, it is repeated, The output control power When the increase / decrease voltage from the start of increase / decrease of the output is not within the second approximated sine wave voltage section, the constant current value is set to the leakage current equivalent current value, whereby the trapezoid hypotenuse edge portion of the output control voltage is set to the sine wave. In addition to approximation, the slope of the trapezoid hypotenuse is variably controlled according to the power supply voltage, and the tilt time of the trapezoid hypotenuse is set to be a substantially constant time within the maximum allowable time considering the heat generation limit of the drive element. A slope control circuit that outputs a current value of
A constant current circuit that switches current based on a current value from the slope control circuit;
A charging circuit charged with a constant current from the constant current circuit;
A current drive control circuit comprising: a comparator that controls the drive element with a differential voltage between a detection voltage of the current detection circuit and a charge voltage of the charging circuit. The current drive control circuit according to claim 6, wherein the load is a lamp. The current drive control circuit according to claim 6, wherein the drive element is a field effect transistor.

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