JPH07123705A - Variable output voltage switching regulator - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the transient responsiveness of the output voltage of a variable output voltage switching regulator by eliminating the useless power consumption in the regulator by using a necessary minimum amount of dummy current. CONSTITUTION:A variable output voltage switching regulator is provided with a switching circuit to control the output voltage of the regulator by means of a switching transistor Q1, control signal impressing means 15 which controls the turning on/off of the transistor Q1 by using a control signal having a duty ratio corresponding to that of the output voltage, and a dummy current control circuit connected in parallel with a load RL to control current in accordance with the control signal.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a variable output voltage switching regulator.

[0002]

2. Description of the Related Art A switching regulator is widely used as a power supply regulator because it is efficient and can set an output voltage higher or lower than an input power supply voltage. For example, FIG. 3 shows a conventional basic circuit of a boost converter type switching regulator. In FIG. 3, the input voltage V _i is connected to the load R _L via the inductor L, the switching transistor Q, the diode D, and the capacitor C.

When the switching transistor Q is turned on, the voltage on the source side of the transistor Q drops to a value close to 0, and the input voltage V _i is applied across the inductor L. Along with this, the current flowing through the inductor L increases linearly. For lower than the voltage of the source side of this time the transistor Q is the output voltage V _o, the diode D is no current flows to the output side receives a reverse bias. When the switching transistor Q is turned off, the applied voltage approaches the sum of the output voltage V _O and the diode voltage V _D. At this time, the output current I _o flows into the load side capacitor C through the diode D.

Further, the inductor current is, on the contrary, V _O -V _D
It decreases linearly with the ratio determined by -V _i. Here, the average value of the current flowing through the diode D is the output current I _O.
The switching transistor Q is on / off controlled to be equal to. When the ON time and the OFF time of the switching transistor Q are T _ON and T _OFF , respectively, and the peak value of the inductor current is I _pk , the ON time T _ON and the OFF time T _OFF of the switching transistor Q are T _ON = ( I _pk · L) / V _i , T _OFF = (I _pk · L) / (V _o + V _D −V _i ).

Assuming that the voltage V _D between the terminals of the diode D can be ignored, T _OFF = (I _pk · L) / (V _o −V _i ), from which V _o = V _i (T _ON + T _OFF ) T _OFF = V _i · T / T _OFF . However, T = T _ON + T _OFF .

Therefore, by controlling the on / off time of the switching transistor by the control circuit, the magnitude of the output voltage V _o changes. Usually, the inductor L has a size for a current of about I _o / 10. Therefore, the dummy resistor R _D is connected in parallel with the load so that a current of about 1/10 of the maximum output current flows even when there is no load.

[0007]

However, in order to make the output voltage V _o variable, it is necessary to change the dummy resistor R _D according to the output voltage. Conventionally, the resistance value of the dummy resistor R _D is set so as to have the maximum possible dummy current, or fixed to an appropriate resistance value and used as it is.

When the resistance value of the dummy resistor R _D is adapted to the maximum dummy current, there is a problem that the loss due to the dummy current becomes large and wasteful power consumption increases. Further, if the resistance value of the dummy resistor R _D is too large, the transient response of the output voltage deteriorates. An object of the present invention is to eliminate waste of power consumption due to a dummy current in a variable output voltage switching regulator and to control the output voltage efficiently.

[0009]

A variable output voltage switching regulator according to the present invention comprises a switching circuit,
A switching element control means and a dummy current control circuit are provided. The switching circuit includes a switching element for controlling the output voltage. The switching element control means controls ON / OFF of the switching element with a control signal having a duty ratio according to the output voltage. The dummy current control circuit is connected in parallel to the load, and controls the flowing current according to the control signal from the control signal applying means.

[0010]

According to the present invention, the dummy current is controlled by the dummy current control circuit based on the control signal of the switching element control means. Here, the switching element is controlled. The control signal is set to a duty ratio according to the output voltage. Therefore, the dummy current is controlled according to the output voltage, eliminating power consumption due to excessive dummy current,
Moreover, the output voltage can be efficiently obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The variable output voltage switching regulator according to the present invention is used, for example, in a transmission circuit section of an ultrasonic diagnostic apparatus. FIG. 1 is a schematic block diagram of an ultrasonic diagnostic apparatus in which an embodiment of the present invention is adopted. In the figure, the probe 1 is composed of a plurality of transducers, is applied to the surface of the subject 2, transmits an ultrasonic beam into the subject 2, and receives reflected echoes from the subject 2. Transmitter circuit 3 for probe 1
Are connected. The transmission circuit 3 applies a high frequency pulse to each transducer of the probe 1. An amplification group 4 is connected to the probe 1.

The amplification group 4 is composed of a plurality of amplifiers, is provided corresponding to each transducer of the probe 1, and amplifies the reflected echo received. The amplification group 4 is connected to the waveform processing circuit 5. The waveform processing circuit 5 is for performing waveform processing on the signal from the amplification group 4 to obtain a signal that can be stored in a digital scan converter (hereinafter referred to as DSC) 6. This output signal is a B mode signal or an M mode signal. The amplification group 4 is connected to the mixer waveform processing circuit 7.

The mixer waveform processing circuit 7 mixes the received reflected echo with the reference signal from the transmission system. The output of the mixer waveform processing circuit 7 is the A / D conversion circuit 8
It is connected to the. The A / D conversion circuit 8 performs A / D conversion on the output of the mixer waveform processing circuit 7. A / D
The conversion circuit 8 is connected to the Doppler arithmetic processing circuit 9. The Doppler arithmetic processing circuit 9 performs correlation arithmetic processing and the like on the A / D-converted Doppler signal to calculate an average blood flow value and the like, and performs fast Fourier transform on the A / D-converted Doppler signal. However, the blood flow velocity distribution is calculated.

The Doppler arithmetic processing circuit 9 is connected to the DSC 6. For example, in the DSC 6, the B mode image and the color Doppler image are combined in the color Doppler B mode. Further, in the M mode, an M mode image is obtained by the output from the waveform processing circuit 5. DSC6 is a CRT
Connected to 10. The CRT 10 displays a color Doppler image, an M mode image, etc., and a spectrum image is displayed in the Doppler mode.

A control circuit 14 is connected to the transmitting circuit 3, the mixer waveform processing circuit 7, the waveform processing circuit 5, the DSC 6, the Doppler arithmetic processing circuit 9 and the CRT 10. The control circuit 14 controls each of these parts. The switching regulator according to the embodiment of the present invention can be used as a part of the transmission circuit 3 in FIG. 1, and its circuit diagram is shown in FIG.

Input voltage V_iIs inductor L and dio
Load R via the card D_LConnected to (probe 1)
It Switching transistor Q₁Is the inductor L
Input voltage V_iAre connected in parallel. Capacity
Tar C₁Is input via inductor L and diode D
Voltage V_iAre connected in parallel. Load R on the output side_L
Transistor Q in parallel with_FourAre connected. Transi
Star Q_FourThe base of the transistor Q₂, Resistance R₁，
Capacitor C₂, Resistance R ₂, Transistor Q₃Through
Input voltage V_iHas been entered. Also transistors
Q_FourResistor R for the emitter of_eAre connected in series.

Field-effect transistors (hereinafter referred to as FETs) are used for the transistors Q ₁ , Q ₂ , and Q ₃ . The control signal from the control signal applying means 15 is input to the gate terminals of the transistors Q ₁ , Q ₂ , and Q ₃ . The control signal applying means 15 outputs a control signal having a duty ratio according to the output voltage V ₀ . Next, the operation of the circuit shown in FIG. 2 will be described.

When the output voltage is V _o , V _o = V _i (T _ON + T _OFF ) / T _OFF = V _i · T / T _OFF , as in the prior art. However, ON time is T _ON , OFF time is T _OFF ,
Let T _ON + T _OFF = T. The base voltage of the transistor Q ₄ is determined by the transistors Q ₂ and Q ₃ controlled by the control signal of the control signal applying means 15. When the emitter resistance value of the transistor Q ₄ is R _e , the collector current of the transistor Q ₄ is I _c = V _i (T _ON / T) (T _OFF / T) (1 / R _e ) = (V _i / ( R _e · T)) T _ON (T _OFF / T).

The dummy current required for normal operation is I _o = (V _i / 2L) T _ON (T _OFF / T). Thus, as the collector current I _c of the transistor Q ₄ is the dummy current may be set such that R _e · T = 2L. As a result, when the output voltage is changed, the required minimum dummy current can be set accordingly.

In this embodiment, the boost type is shown, but the flyback type and other types can be similarly realized.

[0021]

According to the present invention, the dummy current is controlled in accordance with the output voltage, the waste of power consumption is eliminated by the minimum required dummy current, and the transient response of the output voltage is prevented from being degraded.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an ultrasonic diagnostic apparatus adopting an embodiment of the present invention.

FIG. 2 is a circuit diagram of an embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional example.

[Explanation of symbols]

V _i Input voltage L Inductor D Diode Q ₁ , Q ₂ , Q ₃ , Q ₄ Transistor C ₁ , C ₂ Capacitor R ₁ , R ₂ Resistance _Re Emitter resistance _RL Load 15 Control signal applying means

Claims (1)

[Claims] 1. A switching circuit including a switching element for controlling an output voltage, a switching element control means for on / off controlling the switching element by a control signal having a duty ratio according to a load, and a switching circuit connected in parallel to the load, A variable output voltage switching regulator, comprising: a dummy current control circuit that controls a flowing current according to the control signal.