Abstract:
A booster includes a boosting circuit and a feedback control circuit. The boosting circuit is used to boost an input voltage into a predetermined output voltage; the feedback control circuit detects the output voltage of the boosting circuit and stops boosting the voltage when the output voltage is higher than a predetermined value so as to prevent additional power consumption of a battery and increase transferring efficiency.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a booster, and more particularly to a booster of a fuel cell.  
         [0003]     2. Description of the Prior Art  
         [0004]     Energy plays an essential role in our lives. With the improvement and progress of technology, different power-supply equipment has been invented for different sorts of electrical products. The design and quality of power-supply systems may directly influence the quality of electrical systems. A stable power supply allows electrical equipment to work in a stable condition, and also allows better performance with less noise. On the other hand, if the power supply is unstable, unexpected operation or circuit malfunction can occur. Therefore, increasingly higher quality of today&#39;s electrical products is needed, so that producing good and stable power supplies has become an important issue.  
         [0005]     A fuel cell is a kind of environmental energy source. However, fuel cells can only provide lower electrical power than the operation power of normal electrical products. Furthermore, a fuel cell outputs different voltage because of different external electrical equipment connected to the fuel cell. For solving this problem, a transformer is added external to the fuel cell for adjusting the output voltage of the fuel cell to a predetermined voltage value to provide a fixed and high-stability power supply to different sorts of electrical products.  
         [0006]     Please refer to  FIG. 1 , which is a diagram of a booster  10  external to a battery  12  according to the prior art. The booster  10  comprises a boosting circuit  11 , a battery  12 , and a feedback oscillation controller  14 . The boosting circuit  11  is electrically connected to the battery  12  and used for adjusting the voltage of the battery  12  to a predetermined voltage value. The feedback oscillation controller  14  detects the output voltage of the boosting circuit  11  and utilizes the output voltage as a feedback signal to change the period of the oscillating signal generated by the feedback oscillation controller  14  for controlling the boosting circuit  11 .  
         [0007]     Tank devices, such as capacitors and inductances, are often set up inside the boosting circuit  11 . These tank devices need a periodic signal or an AC signal to store or transform energy. The oscillating signal generated by the feedback oscillation controller  14  is therefore provided to the boosting circuit  11  for boosting.  
         [0008]     The theory behind the function of the feedback oscillation controller  14  is to utilize an oscillating signal of pulse width modulation to control the boosting circuit  11 . If the output voltage added by the booster does not reach a predetermined value, the feedback oscillation controller  14  outputs an oscillating signal with a longer period to make boosting faster. Similarly, if the output voltage added by the booster has reached the predetermined value, the feedback oscillation controller  14  outputs an oscillating signal with a shorter period to make the boosting slower.  
         [0009]     However, even when the output voltage of the prior art booster has reached the predetermined value, the feed-back oscillation controller  14  still continuously outputs oscillating signals. But in fact, at this time, the boosting circuit  11  does not need the oscillating signals because the mechanism of boosting can be paused. As a result of the continuous oscillating signals outputted by the feed-back oscillation controller  14 , the following disadvantages could occur. First, power is lost unnecessarily when there is no need for boosting. And second, because of the power consumption inside the booster, the battery can only provide lower power to the external loads. As a result, there is a need for a booster that can stop the function of charging when the output voltage reaches the predetermined value to solve the prior art problems.  
       SUMMARY OF INVENTION  
       [0010]     It is therefore a primary objective of the claimed invention to provide a booster to solve the above-mentioned problems.  
         [0011]     According to the claimed invention, a booster comprises a boosting circuit for boosting an input voltage to a predetermined output voltage; an oscillator for generating oscillating signals when the boosting circuit boosts the input voltage; and a voltage detector electrically connected to the boosting circuit for stopping the boosting circuit from boosting the input voltage when the output voltage of the boosting circuit is higher than a specific predetermined voltage.  
         [0012]     A claim method of boosting battery output, the battery electrically connected to a booster comprising a boosting circuit, an oscillator, and a voltage detector, the method comprising:  
         [0013]     (a) detecting an output voltage of the booster with the voltage detector;  
         [0014]     (b) if the output voltage is lower than a predetermined voltage, with the oscillator generating a periodic pulse signal for controlling a transistor of the booster to execute an on/off operation for adjusting the output voltage; and  
         [0015]     (c) if the output voltage reaches the predetermined voltage value, with the voltage detector generating a voltage signal whose logic level is zero for turning off the transistor.  
         [0016]     These and those objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0017]      FIG. 1  is a diagram of a booster according to the prior art.  
         [0018]      FIG. 2  is a diagram of a booster according to the present invention.  
         [0019]      FIG. 3  is a diagram of a feedback control circuit according to the present invention.  
         [0020]      FIG. 4  is a diagram of a first embodiment of the feedback control circuit according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0021]     Please refer to  FIG. 2 , which is a diagram of a booster  20  according to the present invention. The booster  20  comprises a boosting circuit  11 , a battery  12 , and a feedback control circuit  24 . The boosting circuit  11  comprises two diodes D 1  and D 2 , an inductance L 1 , a capacitor C 1  and a MOS transistor Q 1 . The boosting circuit  11  in  FIG. 2  is similar to the booster circuit in  FIG. 1 . The boosting circuit  11  utilizes the inductance L 1  and the capacitor C 1  to transfer power of the battery to the capacitor C 1  so that a voltage Va can be boosted continuously while the capacitor C 1  is charged. Because inductances need an AC signal for continuously performing the process of charging/discharging, the transistor Q 1  is therefore controlled by the feedback control circuit  24  for executing the on/off operation at a specific frequency and stopping the on/off operation when the voltage Va has reached the predetermined value.  
         [0022]     The operation of the boosting circuit  11  is illustrated as follows: The boosting circuit  11  utilizes the capacitor C 1  to store the electrical power. So the current of the battery  12  is utilized to charge the capacitor C 1  for boosting the voltage of the node A. We assume that the voltage provided by the battery is 2V. At first, the voltage of 2V is transferred to the node A through the diode D 1  and makes the voltage Va of node A near to 2V. And then, when the transistor Q 1  is on, the battery  12 , the inductance L 1 , and the transistor Q 1  form a loop where the battery  12  is regarded as a power supply, and the inductance L 1  and the transistor Q 1  are regarded as loads. Therefore, the end of the inductance L 1  that is near to the battery  12  is positive, and the other is negative, and a current passes through the inductance L 1 . In the situation that the transistor Q 1  is off, the instantaneous current on the inductance L 1  is the same as the current before the transistor Q 1  is off according to the characteristic of the inductance. At this time, the inductance L 1  is regarded as a power supply that provides a current to the diode D 2 , and because the transistor Q 1  is off, the current charges the capacitor C 1  through the diode D 2 . Because the voltage generated by the inductance L 1  is series-connected to the battery  12 , the voltage of capacitor C 1  starts to rise.  
         [0023]     As the voltage of capacitor C 1  rises, the charging current becomes lower and lower. This can be regarded as the power of the inductance L 1  transferring to the capacitor C 1 . Therefore, the power in the inductance L 1  has to be renewed periodically. So the transistor Q 1  has to switch modes (on/off) during the whole boosting procedure for providing the power to the inductance L 1  and for transferring the power to the capacitor C 1  for boosting. The characteristic of the prior art diode is that the current can pass through the diode if the diode is forward biased, otherwise the diode prevents current flow. The purpose of the diode D 2  is to avoid the reversed current and to make sure that the direction of the current is correct (from the inductance L 1  to the capacitor C 1 ).  
         [0024]     Please refer to  FIG. 3 , which is a diagram of a feedback control circuit  24  according to the present invention. The feedback control circuit  24  comprises a voltage detector  25 , an oscillator  27 , and an AND gate  28 . The operation of the feedback control circuit  24  is as follows: First the voltage Va is detected. If the voltage Va is less than a predetermined value, generate periodic signals for controlling the on/off operation of the transistor Q 1 . And if the voltage Va is larger than the predetermined value, generate a low voltage whose logic level is 0 for turning off the transistor to make the boosting circuit  11  stop boosting.  
         [0025]     The voltage detector  25  detects the voltage Va and generates a feedback signal of the feedback control circuit  24  according to the detected voltage Va. If the voltage Va is larger than or equal to the predetermined value, the voltage detector  25  outputs a signal whose logic level is 0 to the AND gate  28 , otherwise the voltage detector  25  outputs a signal whose logic level is 1. The output end of the oscillator  27  is electrically connected to the AND gate  28  for generating an oscillating signal. The operation flow of the feedback control circuit  24  is, for example, illustrated as follows: It is assumed that the booster  20  according to the present invention needs to boost the voltage Va from the voltage 2V provided by the battery to 3.5V. Therefore, the voltage Va is less than 3.5 V at first, and the voltage detector  25  outputs a signal of logic 1 so that the oscillating signals generated by the oscillator  27  can pass through the AND gate  28 . And then the voltage Va continuously increases until the voltage reaches 3.5V. When the voltage reaches 3.5V, the voltage detector  25  immediately detects the situation and outputs a signal of logic level 0 so that the output signal of the AND gate is 0. Therefore, the transistor is turned off and stops boosting.  
         [0026]     Please refer to  FIG. 4 , which is a diagram of the first embodiment of the feedback control circuit according to the present invention. The voltage detector  25  of the feed-back control circuit  24  comprises two diodes D 3  and D 4 , three resistors R 1 , R 2 , and R 3 , a bipolar junction transistor (BJT) Q 2 , and two inverters  32 . The emitter of the BJT Q 2  is grounded, the base of the BJT Q 2  is electrically connected to the resistors R 1  and R 2 , and the collector of the BJT Q 2  is electrically connected to the resistor R 3 . The two diodes D 3  and D 4  are series-connected to each other and to the resistor R 1 . The collector of the BJT Q 2  is further electrically connected to the two inverters  32  and then connected to the AND gate  28 . Please note that the positive node A of the diode D 3  is the same as the node A in  FIG. 2 .  
         [0027]     The operation of the voltage detector  25  in  FIG. 4  is illustrated as follows: It is assumed that the voltage provided by the battery is 2V, and the voltage needs to be boosted to 3.5V (this means that the predetermined value is 3.5V). At first, the voltage Va of the node A is the value of 2V subtracting the voltage of diode D 1  (refer to  FIG. 2 ). The value is so small that the transistor Q 2  cannot be turned on. Therefore, almost no current passes through the resistor R 3  and the voltage of collector of the BJT Q 2  is a high voltage near to 2V. The high voltage is still a high voltage whose logic level is 1 after passing through two inverters  32 . The purpose of the two inverters lies in adjusting the logic level so that the high/low voltage of the collector of the transistor Q 2  becomes a clear logic level 0 or 1 after passing through the two inverters  32 . Subsequently, the voltage Va of the node A increases because of boosting. When the voltage Va of node A increases to 3.5V, the two diodes D 3  and D 4  are turned on so that the current can pass through the two diodes D 3  and D 4  and form a voltage on the base of the BJT Q 2 . The voltage of the base of the BJT Q 2  is larger than the threshold voltage value of the BJT Q 2  so that the BJT Q 2  is turned on. At this time, significant current passes through the collector of the BJT Q 2  and forms a voltage on the resistor R 3  when passing through the resistor R 3 . Therefore, the voltage of the collector transistor Q 2  becomes a low voltage so that the inverters  32  output a low voltage whose logic level is 0.  
         [0028]     The diodes D 3  and D 4  are zener diodes in this embodiment, and the resistors R 1  and R 2  can be variable resistors. The number and type of the diodes are used to adjust the voltage range of the BJT Q 2 . So, the number is not limited as two and the type is chosen by design constraints. The transistor Q 2  in the invention is not limited to being a BJT, and other transistors can also be used to achieve the function of the invention. In this embodiment, the fuel cell is used as the battery of the booster.  
         [0029]     The oscillator  27  in  FIG. 4  is a ring oscillator that comprises three inverters  32 , two resistors R 4  and R 5 , a capacitor C 2  and a switch SW 1 . The three inverters  32  are series-connected and form a negative feedback loop for oscillating. The resistor R 5  and the capacitor C 2  are worked as a filter that can adjust the oscillating frequency of the oscillator and can be regarded as the frequency control circuit of the oscillator  27 . The switch SW 1  provides an option of separating the oscillating signals of oscillator  27  for users. The resistor R 4  is used to avoid the floating connection of the AND gate  28  and the oscillator  27 . The output of the voltage detector  25  and the output of the oscillator  27  are both connected to the AND gate  28 . The output oscillating signal of the oscillator  27  and the output signal of the voltage detector  25  are outputted to the gate of transistor Q 1  of the boosting circuit after the AND operation for turning on/off the transistor Q 1 .  
         [0030]     The present invention uses the oscillator as a frequency generator to be the medium of controlling charging/discharging and to replace the prior art function of pulse width modulation. A diode and a resistor are set up on the output end for forming a feedback control circuit to adjust and protect the output voltage that we need. The output voltage is also used in the feedback control circuit for judging whether the voltage is high enough. If the output voltage has already reached the needed voltage and the feedback signal of the voltage detector is a low-level voltage, the output signal of the AND gate is a low-level voltage and the boosting circuit does not store power at this time. If the output voltage is lower than the needed voltage and the feedback signal of the voltage detector is a high-level voltage, the oscillating signal is outputted to the boosting circuit through the AND gate for charging quickly. The boosting circuit mainly transforms the input voltage of operation range 1.6V˜5V. It can be used in mobile electrical products for quickly boosting the voltage because of the low power consumption, the convenience of the boosting circuit for adjusting the output voltage, the convenience of getting devices in the booster, and low cost.  
         [0031]     The prior art booster continuously outputs the oscillating signals when the output voltage reaches the predetermined value. This causes the tank devices inside the booster to continuously process the cycle of transforming power even when booster operation is not required. This means that the power of the battery is consumed during the cycle of transforming power so that the battery only provides lower power to loads and the noise becomes larger. In contrast, the booster according to the present invention comprises a feedback control circuit for detecting whether the output voltage reaches a predetermined value and stopping the boosting circuit boosting when the output voltage is larger than the predetermined value so that the power of the battery is saved. As a result, the booster according to the present invention has the advantages of low power consumption, high transforming efficiency, and low cost and is suitable for electrical products.  
         [0032]     Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.