JPH09232975A - Power source circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a power source circuit of a burst radio communication equipment in which the battery of lower voltage and smaller capacity than the traditional burst radio communication equipment is used. SOLUTION: The output voltage 3V of the battery 1 with a small capacity is boosted to 7V and over by a DC-DC converter 2. This output current is limited to be constant by a constant current circuit 3, and charges gradually a capacitor 5. An output current value is set in accordance with the transmission interval and transmission continuation time of an output circuit 7. A overvoltage prevention circuit 4 is connected in parallel to the capacitor 5, and prevents its inter-terminal voltage from becoming over the breakdown voltage of the capacitor 5. Power stored in the capacitor 5 is supplied to the output circuit 7 which requires intermittently the high voltage and the large current through a switching regulator 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit for a burst radio communication device.

[0002]

2. Description of the Related Art One frame is divided into a plurality of slots,
In recent years, a portable wireless communication device of a time division multiplex communication system, which enables a plurality of people to communicate at the same time, has been widely used. Even in such a portable wireless communication device, what is important is that it is convenient to carry, and therefore efforts have been made to reduce the size and weight. Specific solutions for reducing size and weight include, for example, unitization of the transmitter and receiver, use of extremely small parts, omission of switch keys, and the like, but the biggest obstacle is the battery. Is. In general, a wireless communication device supplies a voltage higher than a certain level from the viewpoint of collector efficiency to the high frequency power amplifier circuit, although the supply voltage to the receiving unit and the transmission signal generation circuit is low and the supply power is small. This is because it requires a sufficiently large battery that can handle high voltage and large current.

One technique for solving this problem is disclosed in Japanese Unexamined Patent Publication No. 4-315320, "Burst Radio Communication Device". That is, it is a method in which the output voltage of a low-voltage, small-capacity battery is boosted to a constant voltage by a DC-DC converter, stored in a capacitor, and supplied to a high-frequency power amplifier circuit as a power source during transmission.

[0004]

In the power supply circuit of this burst radio communication device, the DC-
Since the DC converter outputs a constant voltage, the charging current changes according to the charging state. That is, a large charging current flows in the initial stage when the capacitor is completely discharged, but as the capacitor is charged and the voltage between its terminals rises, the charging current decreases exponentially and DC-DC
The charging current becomes zero when it becomes equal to the converter output voltage.

Therefore, in the above power supply circuit, there is a problem that a battery having a relatively large capacity must be prepared for a large inrush current flowing at the moment when the power supply switch is turned on. Further, in order to solve this problem, if the battery is replaced with a small capacity battery and the output impedance of the DC-DC converter is set to a large value, the conversion efficiency becomes poor and it takes time to charge the capacitor. There has been a new problem that the charge amount (electric power amount) is insufficient when the transmission interval is short.

The present invention has been proposed in view of the above problems, and an object of the present invention is to provide a burst radio communication device which can use a battery having a lower voltage and a smaller capacity than the conventional burst radio communication device. I am trying.

[0007]

In order to solve the above problems, a power supply circuit according to a first aspect is a power supply circuit which intermittently supplies the power charged in a capacitor to a high frequency power amplifier circuit of a burst radio communication device. Then, a current limiting circuit for controlling the amount of current charged in the capacitor is provided. A power supply circuit according to a second aspect is the power supply circuit according to the first aspect, further comprising a booster circuit that boosts a supply voltage from the battery and supplies the boosted voltage to the current limiting circuit.

A power supply circuit according to a third aspect of the present invention is the power supply circuit according to the first or second aspect, further comprising an overvoltage protection circuit for controlling the inter-terminal voltage of the capacitor to a predetermined value or less.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A power supply circuit according to the present invention will be described below in detail with reference to the drawings. 1 is a block diagram of a burst wireless communication device including a power supply circuit according to the present invention, and FIG. 2 is a time chart of the operation of the wireless communication device of FIG.

The burst wireless communication device shown in FIG.
It uses a TDMA method in which a frame is time-divided into eight slots, and only one of the eight slots is used for burst transmission to perform multiplex communication in which many people can simultaneously communicate at the same frequency. According to this communication method, even though continuous transmission is performed, as shown in FIG. 2A, the actual transmission is 1/8 time of one frame, and the remaining 7/8 time is I have not sent it.

In FIG. 1, reference numeral 1 denotes a battery having a voltage of 3 V and a small capacity, which supplies power to the transmission signal generating circuit 8 and the receiving section 10. 2 is the output voltage of battery 1 is 7
DC-DC converter for boosting V or more, 3 is DC-D
A constant current circuit that keeps the output current of the C converter 2 constant and supplies it to the capacitor 5, and 4 is an overvoltage prevention circuit that prevents the terminal voltage of the capacitor 5 from exceeding the withstand voltage. The output current of the constant current circuit 3 depends on the transmission interval of the burst signal
It is set according to the transmission time. Reference numeral 6 is a switching regulator connected in parallel with the capacitor 5. 7
Is an output circuit that amplifies the burst signal from the transmission signal generation circuit 8 and feeds it to the antenna, and performs a class D amplification operation in which a current flows only when the burst signal is input. 9
Is a CPU that controls the respective functions of the transmission signal generation circuit 8 and the reception unit 10, and 11 is a duplexer. Here, the DC-DC converter 2 corresponds to a booster circuit, the constant current circuit 3 corresponds to a current limiting circuit, and the output circuit 7 corresponds to a high frequency power amplifier circuit.

Next, the operation of the power supply circuit of the wireless communication device of FIG. 1 will be described with reference to the graph of FIG. In the transmission halt state or the reception state, the output circuit 7 does not consume power, so that no current flows from the capacitor 5 and a constant current flows from the constant current circuit 3 (FIG. 2 (D)).
At this time, the voltage across the terminals of the capacitor 5 linearly increases due to constant current charging [FIG. 2 (B)]. At timing T1, when the CPU 9 outputs a transmission timing signal to operate the transmission signal generation circuit 8, the transmission signal generation circuit 8 outputs a burst signal to be amplified [FIG.
(A)].

A current flows from the capacitor 5 into the output circuit 7 to which the burst signal is sent, via the switching regulator 6 (FIG. 2 (D)). At the transmission start timing T1, the inter-terminal voltage of the capacitor 5 is 10 V or higher as set, but is stepped down by the switching regulator 6 to 7 V. As the current starts to flow from the capacitor 5 to the output circuit 7, the voltage between the terminals continues to drop, and drops to near 7 V at the transmission end timing T2 [FIG. 2 (B)]. However, during the transmission from the timing T1 to the timing T2, it is maintained at 7V by the switching regulator 6 [FIG.
(C)]. The constant current circuit 3 naturally outputs a constant current even during transmission.

When the transmission of the burst signal ends at the timing T2, the set constant current flows into the capacitor 5 again from the constant current circuit 3 [FIG. 2 (D)]. Then, the capacitor 5 is continuously charged until the next transmission of the timing T3 is started.

Instead of the constant current circuit 3 for charging the capacitor 5 with a constant current, a current limiting circuit for increasing or decreasing the charging current or dividing the charging current into two stages according to the capacities of the battery 1 and the capacitor 5. May be provided. For example, a large amount of current may be supplied first to increase the voltage quickly, and a small amount may be decreased in the latter half to suppress an unnecessary increase in voltage.
These operations are controlled by the CPU. The switching regulator 6 may be a series pass regulator. The output voltage may be increased by superimposing the battery voltage on the voltage of the capacitor 5 only during transmission.

FIG. 3 is a circuit diagram showing an example of a power supply circuit of the wireless communication device shown in FIG. DC-DC converter 2
The booster is configured by the choke coil 21, the FET 22, and the switching IC 23 that generates a pulse wave. The output is smoothed by the capacitor 25 via the backflow prevention diode 24. Switching IC23
The duty ratio of the pulse wave generated by is increased as the input voltage becomes lower, and becomes smaller as the input voltage becomes higher. FE according to this pulse wave
T22 performs a switching operation, and the voltage of the battery 1 is boosted. The boosted output is controlled to a constant current by the constant current output circuit 3 including the resistor 31 and the transistor 32 and output to the capacitor 5.

The output voltage of the DC-DC converter 2 ideally increases linearly as the charging of the capacitor 5 progresses. Therefore, if the capacitor 5 is not discharged because the transmission is not performed at the set timing due to the malfunction of the timing of the time division or the failure of other circuits, the voltage between the terminals rises more and more. If the voltage exceeds the withstand voltage value of an element such as the capacitor 5, the element may be destroyed. To prevent this, a constant voltage diode 41 is provided in parallel with the output. Since the breakdown voltage of the constant voltage diode 41 corresponding to the overvoltage prevention circuit 4 is selected to be smaller than the withstand voltage value of the element and larger than the output voltage value 10V in the normal operation, the wireless communication device is normally operated. It does not work when it is working. However, if the output voltage exceeds the breakdown voltage,
The constant voltage diode 41 is short-circuited to prevent overvoltage.

At the time of transmission, the electric power charged in the capacitor 5 is converted into a constant voltage by the switching regulator 6 and output to the output circuit 7. The switching regulator 6 is a very general chopper type switching regulator, and the duty ratio of the pulse wave of the switching IC 62 is controlled to increase as the input voltage decreases and decrease as the input voltage increases. The current output from the transistor 61 controlled by the switching IC 62 passes through the choke coil 63, is smoothed by the capacitor 64, and is supplied to the output circuit 7.

[0019]

According to the power supply circuit of the first aspect, since the current limiting circuit for controlling the amount of current charged in the capacitor is provided, it is possible to use a battery having a small capacity. Further, according to the power supply circuit of the second aspect, since the supply voltage is boosted and the current limiting circuit is provided to charge the capacitor, it is possible to use even a low voltage / small capacity battery.

Further, according to the power supply circuit of the third aspect,
Since the overvoltage prevention circuit for controlling the voltage between the terminals of the capacitor to a predetermined value or less is provided, there is no risk of the capacitor puncturing due to the overvoltage.

[Brief description of drawings]

FIG. 1 is a block diagram of a wireless communication device including a power supply circuit according to the present invention.

FIG. 2 is a time chart of the wireless communication device of FIG.

3 is a circuit diagram of an example of a power supply unit of the wireless communication device of FIG.

[Explanation of symbols]

 1 Battery 2 DC-DC Converter (Boosting Circuit) 3 Constant Current Circuit (Current Limiting Circuit) 4 Overvoltage Prevention Circuit 5 Capacitor 6 Switching Regulator 7 Output Circuit (High Frequency Power Amplifier Circuit) 8 Transmission Signal Generation Circuit 9 CPU 10 Receiver 41 Fixed Voltage diode (overvoltage protection circuit)

Claims (3)

[Claims] 1. A power supply circuit for intermittently supplying power charged in a capacitor to a high frequency power amplifier circuit of a burst radio communication device, wherein a current limiting circuit for controlling the amount of current charged in the capacitor is provided. Characteristic power supply circuit. 2. The power supply circuit according to claim 1, further comprising a booster circuit that boosts a voltage supplied from a battery and supplies the boosted voltage to a current limiting circuit. 3. The power supply circuit according to claim 1, further comprising an overvoltage protection circuit for controlling the voltage between the terminals of the capacitor to a predetermined value or less.