TW469698B - Circuit design with single pulse signal to simultaneously control output voltage and switch converting circuit - Google Patents

Abstract

The present invention provides an output circuit to regulate the voltage by pulse width, which utilizes a pulse width inputted by a single pulse input terminal to regulate the voltage for output. When there is a pulse inputted in the pulse input terminal, the switch converting chip is turned on. When there is no pulse inputted in the pulse input terminal, the switch converting chip is automatically turned off, thereby achieving the power-saving effect.

Description

469698 V. Description of the invention (1) Field of the invention: The present invention discloses an electronic switch control circuit, in particular, a pulse wave signal inputted by a single pulse wave signal input terminal can simultaneously control the output voltage and switch conversion. Circuit chip to achieve power saving circuit design. BACKGROUND OF THE INVENTION One use of portable electronic consumer products is to use AC power indoors, and to use a rectifier that they carry with them to provide their operating voltage. However, to emphasize its portability, the most common way is to use the random battery that is basically provided with this portable consumer electronics product to provide its power. However, common portable electronic consumer products do not all operate at a single voltage. However, batteries usually only provide a single voltage. For example, laptop computers, personal digital assistants, and so on. The above electronic products usually need at least two operating voltages to meet the needs of their products. If it is connected to other peripherals, more voltages may be required. In addition, spark plug ignition systems like cars or locomotives. Therefore, it is essential that portable electronic consumer products have a step-up or step-down circuit. A common booster circuit is shown in Figure 1. It has a switch conversion chip 10, a switch SW pin to provide periodic on or off, and an F pin to provide a constant voltage. Switch SW pin connected to a flyback circuit

Page 4 469698 V. Description of the invention (2) (flyback circuit) 5. The flyback circuit 5 is powered by a power supply terminal BAT. This power supply also provides the power of the switching converter chip 10. The flyback circuit 5 includes an inductor, a diode D, and a capacitor. The inductor h-end is connected to the power supply terminal BAT, the other end is connected to the diode D !, one end of the diode 0 is connected to a capacitor connected to the ground-pulse width modulation control circuit 20 to provide the Pulse width modulation control circuit terminal voltage. When the switch SW pin is turned on and off in a sequence, the inductor L! Will generate an induced voltage, and the capacitor C is charged through the diode D. The charge in the capacitor cannot be reversed because of the diode D. Block. Therefore, the capacitor C increases with the switching frequency of the switch SW. In order to prevent the voltage of the capacitor C from rising infinitely, a pulse width modulation control circuit 20 can limit its voltage output.

I I out of the maximum.

I Although the above-mentioned switch conversion chip 10 has a SHDN pin to control the turning on of the chip, traditionally, it uses another pulse plus one control, or the central processing unit scans and processes its switches, which will waste CPU resources. Or add another signal design, and must consider the time delay of the two, so it will increase the complexity of the circuit. In view of this, the present invention will therefore provide a circuit design to improve the above problems. Purpose and summary of the invention:

Page 5 46 96 V. Description of the invention (3) The object of the present invention is to provide a pulse-width-modulated voltage output circuit with simple control and power-saving operation. Using the circuit of the present invention, a single voltage can be boosted to various predetermined voltages, as long as a capacitor, a resistor and an inductor are appropriately matched. The invention discloses a pulse width modulated voltage output circuit, which uses a pulse width modulated voltage output from a single pulse wave input terminal. When a pulse wave input has a pulse wave input, the switch conversion chip is turned on, and when the pulse wave input terminal Without the pulse wave input, the switch chip will be automatically turned off, so the effect of power saving I can be achieved. The circuit of the present invention includes at least: a switch conversion circuit chip, including a SHDN pin to turn on and off the chip, a switch SW pin to provide periodic on or off, and an FB pin to provide a constant The value of the voltage | voltage; a pulse width modulation control circuit and a flyback circuit are provided by a power supply terminal. The flyback circuit is connected to the switch SW pin and the pulse width modulation control circuit. To output a voltage modulated by the pulse wave signal input by the pulse width modulation control circuit; and a chip enabling circuit is coupled to the SHDN pin of the switch conversion circuit chip, and the pulse signal is coupled to Controls the on / off of the switch conversion circuit chip. Detailed description of the invention: FIG. 2 is a schematic diagram of a circuit designed to achieve simultaneous control of the output voltage and switching of a switching circuit chip to achieve electrophilicity with a single pulse signal according to an embodiment of the present invention. Figure 2 shows a switch conversion circuit chip

Page 6 4 6 96 9 8 V. Description of the invention (4) i 〇〇, has a SW pin, in a periodically on or off manner 'combined with the inductor L1, the diode and the capacitor C !, forming a flyback (Flyback) the circuit 11 to generate a high voltage. The chip 100 also has a FB pin to provide a voltage V A with a constant value I. Combining the F% pin, the flyback circuit 110 and the pulse width modulation control circuit 120 can provide a predetermined voltage value for the pulse width input modulation control. Please note that the chip 100 does not have a SHDN pin. In the present invention, the SHDN i pin is connected to the chip enabling circuit 130. The pulse width modulation control circuit | 120 and the chip enable circuit 130 can be controlled by using the same pulse wave inputted from the pulse wave input terminal 140. The feature of the present invention is that when the pulse wave input terminal 140 has a pulse wave input chip 100, the chip is turned on via the SHDN pin, and the chip 100 starts to work so that the switch pin SW generates a sequence of on and off. And a certain voltage VA is provided by the pin FB, and the modulation control according to the pulse width input is provided to a predetermined voltage value through the flyback circuit 110 and the pulse width modulation control circuit 12. As long as the pulse wave input terminal 140 has no pulse wave input chip 100, Jingyue also turns off the power at the same time. First, the working principle of the chip enabling circuit 130 is explained. Still refer to Figure 1. When a series of pulse waves are input from the pulse wave input terminal 140, the capacitor C will be connected to the capacitor C through the diode D, and the capacitor C voltage will be turned on through the SHDN pin of the chip 100 (enab 1 e). The chip 1 0 0 to make it work. As long as the pulse wave is removed from the input terminal 140, the charge of the capacitor C 妁 will be discharged through the resistor r and 469698 V. Description of the invention (5) The voltage of the SHDN pin is reduced, and the chip is turned off. The operation principle of the pulse width modulation control circuit 120 is as follows. When the pulse wave is inputted from the pulse wave input terminal 140, the pulse voltage is charged to the capacitor C through the resistor R. Capacitor C increases the charge of capacitor C 3 by increasing the pulse duration (ie, the pulse width). If the pulse duration is very short, the typical value is, for example, 20 # s, and the capacitance C 3 will not saturate when it is lower than the RC (R y C 3) constant (only about 6 7% saturation when equal). If the voltage at the terminal C does not exceed the initial voltage of the diode D & 0.7 volts, the electric charge of the capacitor C will accumulate and increase its voltage value. As long as the R C time constant is large enough, it takes several pulses before the capacitor C reaches its saturation value. Therefore, it is possible to generate the bias current I 2 with different values by using the pulse width and the number of pulse waves. I is a current flowing through the resistor R A. The magnitude of the bias current I will determine the voltage output by the output terminal 150. The voltage V B at the terminal B is provided by the flyback circuit 110. The flyback circuit 110 is provided by a power supply terminal BAT with a lower voltage than the output terminal OUT. By periodically switching the switch SW, the inductor L spin generates a flyback pulse between the switch SW on and off, and the capacitor C is charged via the diode D. After the capacitor C is charged, it cannot return through the diode D !, so the voltage can be increased stepwise. A sufficiently large capacitor voltage V c will provide terminal B—voltage V B. The voltage V will not rise indefinitely, because the voltage V 3 can be charged through the resistors R 2 and R, so it is a finite value. The magnitude of V is related to the voltage V of node A and the voltage across RA as follows:

Page 8 469698 V. Description of the invention (6) V B = V A + I 〈R 2; and the voltage V 4 is adjusted by the chip pin F B so that V ^ stays at a constant voltage with a certain value. And V A = I κ R ι = I y R 5+ V. 3. Therefore, when the voltage V c across the capacitor is small, the current I s flowing through the resistor R 5 = (VA —V C3) / R 5 increases accordingly. In contrast, the voltage at node B: V b = V A + I ^ R2; also increases (because I 2 = I 5 + I!, Where I is the current flowing through the resistor R 丨, I is about the current flowing through the resistor R), conversely, when the voltage across the capacitor V C3 Increasing the current I through the R 5 resistor will decrease, thereby reducing the V 妁 voltage. Therefore, when the pulse width and the number of pulses are different, the voltage V c across the capacitor is different, that is, different bias currents I 2 of the F B pins are provided. And reach different output voltages V. The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of patent application of the present invention; all other equivalent changes or modifications made without departing from the spirit of the invention disclosed in the present invention shall be included in the following Within the scope of the patent application.

Page 9 46 9693 Brief description of the drawings The preferred embodiment of the present invention will be described in more detail in the following explanatory text with the following figures: Figure 1 shows a schematic diagram of a conventional switching converter circuit. Fig. 2 shows a schematic diagram of a pulse width modulation voltage output circuit according to the present invention. Only the pulse width input by one input terminal can be used to control the opening and voltage output of the switching circuit, thereby achieving the purpose of power saving. Explanation of drawing numbers: Flyback circuit 5 Switch converter chip 10 Pulse width modulation control circuit 2 0 Switch converter circuit chip 100 Flyback circuit 1 1 0 Pulse width modulation control circuit 1 2 0 Chip enable circuit 13 0 pulse Wave input 140

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Claims (1)

46 9698 VI. Application for Patent Scope 1. —A Pulse Width Modulated Voltage Output Circuit 'The pulse width modulated voltage output circuit includes at least: a switch conversion circuit chip, including at least-SHDN pin to open the chip, a Switch SW pin to provide periodic on or off, and a FB pin to provide a constant value of voltage; a pulse width modulation control circuit connected to the F pin; a flyback circuit, by A power supply terminal provides power, and the flyback circuit is connected to the switch SW pin and the pulse width modulation control circuit to output a pulse wave signal input through the pulse width modulation control circuit for modulation. Voltage; and a chip enabling circuit is coupled to the SHDN pin of the switch conversion circuit chip, and the pulse signal is coupled to control the switch conversion circuit chip to be turned on or off. 2. For example, the pulse-width-modulated voltage output circuit of item 1 of the patent application scope, wherein the above-mentioned chip enabling circuit includes at least a capacitor and a resistor connected in series and a unidirectional current flowing element. 3. For example, the pulse width modulation voltage output circuit of the first patent application range, wherein the above-mentioned pulse width modulation control circuit includes a first and second two series resistors connecting the flyback to the ground terminal, and the two series A contact point of the resistor is connected to the FB pin and a third resistor. The other end of the third resistor is connected to one end of a fourth resistor, and is connected to ground through a first capacitor. To couple a signal. Page 11 VI. Application for Patent Scope 4. If the pulse width modulation voltage output circuit of item 1 of the patent application scope 'is used, the aforementioned flyback circuit includes at least an inductor, a diode and a second capacitor. One end of the inductor is connected to the power supply end, and the other end is connected to the diode, and a second capacitor connected to ground and the pulse width modulation control circuit are provided to provide an end point of the pulse width modulation control circuit. Voltage Page 12