JPH07274488A - Switching power circuit of portable telephone - Google Patents

Abstract

PURPOSE:To remove such troubles that the switching frequency fluctuates by the change of environmental conditions such as temperature, etc., and causes mutual interference with the middle frequency signal of a receiver, and that the quality of telephone drops, by synchronizing the switching frequency signal with the dividing signal being made by dividing a clock signal with a dividing circuit. CONSTITUTION:A controller 6 has CPU 6, and the CPU operates with the clock signal generated in the oscillator 7 of a quartz oscillator. This clock signal is divided with a dividing circuit 8, and it is inputted as an external cyclic signal to a switching power circuit 1. And, the switching power circuit 1 adjusts the power voltage supplied from a battery 10, and supplies a receiver 2, a transmitter 4, and the controller 6b with stable voltage. Since the clock signal is a signal of fixed frequency outputted with the oscillator 7 by the quartz oscillator, the frequency hardly fluctuate by the change of environmental condition such as temperature, etc., so if the division rate of the dividing circuit 8 is selected properly, the occurrence of mutual interference with the medium frequency signal in the receiver 2 can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply circuit which does not give a reception failure to a receiving circuit of a mobile phone.

[0002]

2. Description of the Related Art In recent mobile phones, a pulse width modulation type switching regulator may be used as a stabilized power supply circuit in order to prolong battery life. In this case, the switching frequency of the switching regulator is often determined by the self-excited oscillation circuit by the time constant CR of the capacitance C and the resistance R. Generally, a reception signal of a mobile phone is converted into a first intermediate frequency signal and a second intermediate frequency signal and processed in order to improve sensitivity and separation. Therefore, the switching frequency of the switching regulator of the stabilized power supply circuit and the frequency of its harmonics are set so as not to cause mutual interference such as beat interference with the frequency of the transmission / reception circuit.

[0003]

However, in the conventional switching regulator (stabilized power supply circuit) using the self-excited oscillation circuit, there are variations in the electrostatic capacitance C of the capacitor used and the resistance value R of the resistor. Further, in the worst case, the switching frequency fluctuates by about ± 20% due to changes in environmental conditions such as temperature, and its harmonics also fluctuate. For example, the switching frequency is 300 KHz
If set to, a fluctuation of about ± 60 KHz occurs.

When the switching frequency of the switching regulator or its harmonics coincides with or becomes close to the intermediate frequency (for example, the first intermediate frequency 55 MHz, the second intermediate frequency 450 KHz) of the receiving circuit of the mobile phone,
There is a possibility that mutual interference may occur and an audible frequency may be generated to cause a beat failure or a sensitivity suppression failure, and the reception sensitivity may be deteriorated, resulting in deterioration of speech quality or call failure.

In order to prevent this, there is a method of using a power source block or a filter, but there is a problem in that the scale is large and the structure is complicated and the cost is increased.

The present invention has been made in view of the above points, and an object of the present invention is to provide a switching power supply circuit which eliminates the above problems and is simple and does not cause reception failure.

[0007]

In order to solve the above-mentioned problems, the present invention comprises a control section which operates by a clock signal by a fixed oscillator, and a voltage stabilizing circuit having a switching frequency signal generating means and a pulse width modulation method. In a switching power supply circuit for a portable telephone, a frequency dividing circuit 8 for dividing a clock signal is provided as shown in FIG. 1, and the frequency dividing signal obtained by dividing the clock signal by the frequency dividing circuit 8 is used as the switching frequency signal generating means. (Triangular wave generation circuit 1-51 of switching IC 1-5) and the switching frequency signal is synchronized with the frequency division signal.

[0008]

In the present invention, since the switching frequency signal is synchronized with the frequency-divided signal obtained by dividing the clock signal by the frequency dividing circuit 8, the clock signal is a fixed frequency signal output from the crystal oscillator. Moreover, the frequency hardly changes due to changes in environmental conditions such as temperature. Therefore, if the frequency dividing circuit 8 appropriately divides the frequency of the clock signal, mutual interference with the intermediate frequency signal of the receiving unit 2 does not occur and the communication quality does not deteriorate.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a mobile phone using the switching power supply circuit of the present invention. As shown in the figure, the mobile phone using the switching power supply circuit of the present invention includes a switching power supply circuit 1, a receiving unit 2, a handset 3,
A transmitter 4, a transmitter 5, a controller 6 for controlling the whole, an oscillator 7 such as a crystal oscillator for generating a clock signal, a frequency dividing circuit 8 for frequency-dividing the clock signal, an antenna 9, and a battery 10. .

The receiving unit 2 and the transmitting unit 4 are controlled by the control unit 6, and the receiving unit 2 receives the radio wave signal received from the antenna 9 as a first signal.
The intermediate frequency signal and the second intermediate frequency signal are converted and demodulated and output as a voice output from the handset 3, and the transmitting unit 4 modulates the voice signal input from the handset 5 and outputs it as a radio wave signal from the antenna 9.

The control unit 6 has a CPU (central processing unit), and the CPU operates with a clock signal (about 4.8 MHz) generated by the oscillator 7 of the crystal oscillator. The clock signal is frequency-divided from the control unit 6 through the frequency dividing circuit 8 and input to the switching power supply circuit 1 as an external synchronizing signal. The switching power supply circuit 1 adjusts the power supply voltage supplied from the battery 10 and supplies a stable voltage to the receiving unit 2, the transmitting unit 4, and the control unit 6. Hereinafter, the switching power supply circuit 1 will be described.

FIG. 2 is a diagram showing a configuration example of the switching power supply circuit of the present invention. As shown in the figure, the switching power supply circuit 1 includes an FET (field effect transistor) 1-1, a reactor 1-2, a diode 1-3, a capacitor 1-4, a switching IC 1-5, a resistor 1-6, a capacitor 1-.
7, a resistor 1-8, and a resistor 1-9. The switching IC 1-5 is composed of a triangular wave generation circuit 1-51, a pulse width comparator 1-52, an error amplifier 1-53, and the like.

The voltage supplied from the battery 10 is input to the input terminal S (source) of the FET (field effect transistor) 1-1, pulse width modulated by the signal applied to the gate terminal G, and output terminal D. (Drain), and further, diode 1-3, reactor 1-2, capacitor 1
-4 is smoothed by the smoothing circuit and output as a DC output voltage.

The output voltage divided by the resistors 1-8 and 1-9 is the error amplifier 1-5 of the switching IC 1-5.
In 3, the error signal e is compared with the reference voltage, and the error signal e is amplified by the error amplifier 1-53 and input as one input signal of the pulse width comparator 1-52. On the other hand, the triangular wave generation circuit 1-
The signal a output from 51 is compared with the pulse width comparator 1-52, and the output signal controls the gate of the FET1-1 and the output of the FET1-1.

FIG. 3 is a diagram showing the operation of the FET according to the pulse width modulation method. The triangular wave generation circuit 1-51 self-oscillates with the resistor 1-6 and the capacitor 1-7 at the time of start-up, and then, in the steady state, the clock signal is divided into an external synchronizing signal (for example, 300 KHz) by the frequency dividing circuit 8. The synchronized triangular wave signal a is output (see FIG. 3C). When the output voltage becomes higher, the error signal e becomes higher, the output signal time of the pulse width comparator 1-52 becomes shorter, and the ON time of the FET 1-1 becomes shorter (see FIG. 3).
The output voltage can be suppressed. On the contrary, when the output voltage becomes low, the ON time of FET1-1 becomes long (see FIG. 3B).
It operates in the direction of increasing the output voltage and keeps the output voltage constant.

As described above, the switching power supply circuit 1 of the present invention uses the frequency-divided signal obtained by dividing the clock signal used by the CPU of the control unit 6 by the frequency dividing circuit 8 as the external synchronizing signal, so that the environment such as the frequency temperature can be used. There is almost no change due to changes in conditions, and mutual interference with the intermediate frequency of the transmission / reception circuit does not occur, resulting in no beat failure or sensitivity suppression failure, and the speech quality is improved. For example, when the clock signal used by the CPU is 4.8 MHz, the frequency of the synchronization signal is 4.8M.
Hz may be divided into 16 to obtain 300 KHz.

[0017]

As described above in detail, according to the present invention, the switching frequency signal is synchronized with the frequency-divided signal obtained by frequency-dividing the clock signal by the frequency dividing circuit. Therefore, the following excellent effects are expected. It (1) Since the clock signal is a fixed frequency signal output from the crystal oscillator, the frequency hardly changes due to changes in environmental conditions such as temperature. If the frequency division ratio of the frequency dividing circuit is appropriately selected, Unlike the conventional case, the receiving section does not cause mutual interference with the intermediate frequency signal, and the speech quality does not deteriorate.

(2) Further, since the clock signal is used as the synchronizing signal, the synchronizing circuit operated by a separate power supply is unnecessary.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a mobile phone using a switching power supply circuit of the present invention.

FIG. 2 is a diagram showing a configuration example of a switching power supply circuit of the present invention.

FIG. 3 is a diagram showing an operation of an FET according to a pulse width modulation method.

[Explanation of symbols]

 1 Switching Power Supply Circuit 1-1 FET (Field Effect Transistor) 1-2 Reactor 1-3 Diode 1-4 Capacitor 1-5 Switching IC 1-51 Triangular Wave Generation Circuit 1-52 Pulse Width Comparator 1-53 Error Amplifier 1-6 resistor 1-7 capacitor 1-8 resistor 1-9 resistor 2 receiver 3 receiver 4 transmitter 5 transmitter 6 controller 7 oscillator 8 divider circuit 9 antenna 10 battery

Claims (1)

[Claims] 1. A switching power supply circuit for a mobile phone, comprising: a control unit that operates with a clock signal from a fixed oscillator; and a voltage stabilizing circuit with a pulse width modulation method that has switching frequency signal generating means. A frequency dividing circuit for frequency dividing is provided, and the frequency dividing signal obtained by dividing the clock signal by the frequency dividing circuit is input to the switching frequency signal generating means to synchronize the switching frequency signal with the frequency dividing signal. Switching power supply circuit.