JPH036150Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a DC-DC converter.

In devices such as portable radios, when miniaturizing the device by suppressing the set power supply voltage supplied from a battery or the like below a predetermined value, it becomes necessary to make the control voltage applied to the variable capacitance element higher than the set power supply voltage, for example. Sometimes. In such a case, in order to generate a voltage higher than the set power supply voltage such as the control voltage applied to the variable capacitance element, the DC-DC
Converters are often used. This DC−
A DC converter converts the input DC by turning on and off switching elements such as transistors to intermittent or change the direction of the current flowing to the primary side of the transformer, and rectifying and smoothing the voltage generated on the secondary side of the transformer. It is a circuit that converts a voltage into a desired output DC voltage, and usually includes oscillation means for turning on and off a switching element.
For this reason, when a DC-DC converter is used in a device such as a portable radio, the number of oscillation means included in the device increases, resulting in problems such as beat interference.

An object of the present invention is to provide a DC-DC converter that can miniaturize devices such as portable radios without causing problems such as beat interference.

The DC-DC converter according to the present invention converts a DC voltage into an AC signal with a frequency corresponding to the output of the oscillation circuit in a device that includes an oscillation circuit that supplies a reference signal to a PLL circuit that generates a local oscillation signal of a tuner. The configuration is such that the AC signal is later rectified to generate a second DC voltage.

Hereinafter, the present invention will be explained with reference to the accompanying drawings.

In the figure, reference numeral 1 denotes a crystal oscillator that outputs a reference oscillation signal in a PLL (phase locked loop) frequency synthesizer tuner configured in a device such as a portable radio. The output of the crystal oscillator 1 is supplied, for example, to a phase comparator (not shown) that outputs a signal corresponding to the phase difference between the reference oscillation signal and a signal obtained by frequency-dividing the local oscillation signal, and is also supplied to the conversion means 2. is supplied to The output of the phase comparator (not shown) is supplied to a voltage-controlled oscillator (not shown) that outputs a local oscillation signal, and the oscillation frequency of the local oscillation signal is controlled. In the conversion means 2, the output of the crystal oscillator 1 is supplied to the base of a common emitter transistor _Q1 via a capacitor _C1 . A bias resistor R is connected between the base of the transistor _Q1 and ground. transistor
Between the collector of Q ₁ and the power supply +B ₁ is the transformer T 1.
The next winding L ₁ is connected. this transistor
When _Q1 is turned on and off by supplying the reference oscillation signal, the current on the primary side of the transformer T is interrupted, and the DC power supply voltage + _B1 changes to the turns ratio between the primary winding _L1 and the secondary winding _L2 . The corresponding voltage is converted into a pulsed alternating current voltage generated across the secondary winding _L2 . This pulsed AC voltage is rectified by a diode D serving as a rectifier, and then smoothed by a smoothing capacitor _C2 to become a second DC voltage + _B2 .
This second DC voltage + _B2 is applied as a power supply voltage to a circuit (not shown) that generates a control voltage to be applied to a variable element included in a tuned amplifier in an RF (high frequency) stage.

The DC-DC converter according to the present invention described above is
Since the configuration is such that the oscillation circuit that supplies the reference signal to the PLL circuit that generates the tuner's local oscillation signal, such as the crystal oscillator 1, is shared as the oscillation means, the signal level is extremely low in the tuner, making it easy for noise to mix in. The oscillation signal used for voltage conversion, which has a different frequency from the reference oscillation signal, is mixed in as noise with the reference oscillation signal for generating the local oscillation signal of the received input signal in the high-frequency amplifier, causing problems such as beat disturbance. This makes it possible to reduce the size and cost of equipment by suppressing the set power supply voltage below a predetermined value.

[Brief explanation of the drawing]

The figure is a circuit diagram showing an embodiment of the present invention. Explanation of symbols of main parts, 1...Crystal oscillator, 2...
Conversion means, D...diode, _C2 ...smoothing capacitor.

Claims (1)

[Scope of utility model registration request] A DC-DC converter in equipment that includes an oscillation circuit that supplies a reference oscillation signal to a PLL circuit that generates a local oscillation signal of a tuner, which converts a DC voltage into an AC signal with a frequency corresponding to the output of the oscillation circuit. and a rectifying means for rectifying the alternating current signal to generate a second direct current voltage.