TWI236536B - Circuit for detecting unsatisfied drive voltage - Google Patents

Abstract

The present invention is related to a circuit for detecting unsatisfied drive voltage. The invention contains the followings: a current control circuit, which is connected in series with the load and is capable of controlling the load current; the detecting resistor, which is connected in series with the load and is capable of converting the current value into a voltage signal for use in feedback; and a current feedback control circuit, which compares the feedback signal with a reference signal to generate the control signal of current control circuit for stabilizing the load current value. The invention is featured with using two comparators to compare the control signal of current control circuit with the other two reference signals such that it is capable of reaching the purpose of precisely detecting too high or too low drive voltage of the load.

Description

1236536 V. Description of the invention (1) ------- ^-[Technical field to which the invention belongs] The present invention relates to a detection circuit, and more particularly to a circuit for providing driving voltage detection to a circuit device corresponding to a constant load current. 、 / 、 [Previous technology] Transistor is one of the most basic components in various electronic systems. Passive electronic components that are different from traditional resistors, capacitors and inductors are called because of their signal amplification characteristics. It is widely used as active electronics, whether it is filters, amplifiers, or comparators, and through appropriate circuits and active electronic components, it can replace inductors with poor quality factors and large losses at low frequencies. ^ ::: In terms of load, the load supply has nothing to do with the load and power supply: ^ 疋 Required, such as driving a light-emitting diode to emit light, the light-emitting diode / impact application maintains a certain brightness, such as a color LCD The light-emitting diode required for the backlight ^, and the luminosity of the light-emitting diode depends on the amount of current flowing through the diode, so under any circumstances (such as load changes, power supply 'unstable', etc.) Fixed current. Although the transistor circuit can provide stability through active components, this does not mean that there are no restrictions. Under a specific current, 'the power supply voltage driving the load has its allowable minimum value. Below this value, the power supply voltage will not be able to provide a fixed current to the load and related peripheral circuits', that is, the current flowing through the load will be lower than the constant current. Not even ^ In this case, it is necessary to issue a warning signal or forcibly interrupt the circuit. Here is the styling of this product. The minimum value of this voltage is not necessarily a fixed value. When the load is a fixed load, the minimum value is Fixed but when

1236536 Load is a variable load. This minimum value is not fixed, depending on the pressure drop of the load. Drive voltage mismatch detection circuit such as US Patent 6,107,985

No. BACKLIGHTING CIRCUIT INCLUDING BROWNOUT DETECTION CIRCUITS RESPONSIVE TO A CURRENT THROUGH AT LEAST ONE LIGHT EMITTING DIODE AND RELATED METHODS. ", The circuit structure of this patent is shown in Figure 4 (Figure 6 of the original patent). This patent is a light and dark Backlight driving circuit of the detection circuit. For the consistency of the numbers, the numbers of the drawings are the same as those of the original patent. The above only describes the circuit element numbers related to the present invention. Transistor Q1, resistor 77 The circuit design of the amplifier 79 and the reference voltage VREF is used as a constant current source to provide a constant current to the backlight LED array (Back 1 ight Array). The current value of the current source designed by the feedback method is equal to the reference "Circuit" rating divided by the value of resistor 77. When the driving voltage is lower than the minimum voltage drop required by the load and the peripheral circuits connected in series at a constant current value ^ 'The constant current function of the current source will fail. At this time, the current flowing through the light-emitting diode will decrease, and the current will decrease. The luminosity decreases, and the voltage across the resistor 77 will start to be less than VREF. In this patent, a detection circuit is designed. The detection circuit is a comparator circuit composed of a comparator 91 and resistors 95 and 97. When the current of the polar body is a normal fixed current, the output voltage of the comparator 9 i is its forward saturation voltage (high voltage). When the driving voltage VBAT is not enough to drive the light-emitting diode array to work at a fixed current, it is turned on. The current decreases, and at the same time, the voltage across the resistor 7 and 7 decreases. As can be seen from the circuit in Figure 4, when the voltage across the voltage drops to the value of VREFx resistance 97 / (resistance 97 + resistance 95)

Page 6 1236536 V. Description of the invention (3) The output of the comparator 9 1 is a low voltage signal. The two low levels of the output signal of the comparator 9 丨 are used to detect the lack of light, and the output signal is used to control the amplifier 7 9 Function or not 'to interrupt the power supply under insufficient light. The relationship between the driving voltage VBAT and the output signal of the comparator 91 is shown in Figure 1 (Figure 7 of the original patent). As can be seen from Figure 1, when the driving voltage VBAT decreases, the feedback circuit composed of resistor 77, enlarged to 79 and VREF will keep the voltage of the emitter VEMITTER of the transistor qi unchanged, and the current value does not follow the driving at this time. , Voltage = low and lower. When VB AT continues to decrease, it can not provide the minimum voltage required for the load and related peripheral circuits under this solid current conduction. This protection * decreases, and the emitter voltage decreases. The voltage does not drop to V κ e F χ = 97 / (resistance 97 + resistance 95), which is higher than the output of the transponder 91 until the emitter voltage is lower than VREFx resistance 97 / (resistance 97 + Resistor 95), and the comparator 91 outputs a low voltage signal. Interference operation as shown in Figure 2, because the machine can not be judged too much. In addition, the effect is always fixed, but the voltage difference between the voltage of the external noise and the malfunction of the circuit causes the malfunction. The ratio of the voltage point 9 7 is changed accordingly. Generally noise reduction, due to electricity, and smaller than this resistor 9 7 for meeting. Because of the state voltage point, when you refer to it, you must measure the accuracy. As above, the resistor 9 1 must be stored as a comparison 9 1 in addition to the resistance 77. This resistance 9 7 will be much lower than the voltage value. The voltage signal from the chip area of the display and capacitor may be detected by the input error voltage, and the input buffering across the resistor 97 and the existence of noise are reduced. Therefore, when the driving voltage actually changes due to the insufficient driving voltage, the resistance 9 5 The voltage (VCOMPARE) with the resistance will also 'Vd2 voltage is greater than the vdl electrical low-pass filter to filter M' will also cause detection

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The response speed of the circuit becomes slower, and when the driving voltage increases, the driving current value is stabilized. When the power consumption may exceed it damage. The delay time td is shown in FIG. The impedance of the current supply circuit will continuously rise to the limit that the current supply circuit can withstand when the driving voltage is too high, which causes the temperature to be too high. [Abstract] In view of the traditional driving voltage detection, the inventor has studied for many years Develop a circuit that immediately determines that the load drive voltage is insufficient. The circuit still has imperfections. 'Finally, we have developed such a drive voltage mismatch detection that can accurately and purposely detect the drive voltage non-compliance detection control circuit. The current control signal of the control circuit and the load drive voltage are accurately detected. Action when detecting electric constant load current, no set value change and noise interference etc. due to simple circuit design. The test circuit can achieve the purpose by comparing the current with the two reference voltages through two comparators. The circuit is based on the fact that the current control circuit cannot be stabilized. Considering the change of the reference voltage and the constant current, it can detect the rapid concentrate and understand this description. Please refer to the features below for the examiner to better understand the following drawings and Embodiment 1 of the present invention. [Embodiment] Please refer to FIG. 5. The circuit structure of the circuit shown in FIG. It can be seen from Fig. 5 that the driving circuit of the electric motor is not connected to the detection circuit in series, and the current-supplying electrical load 10 and the current-supplying component such as a resistor R are composed. In order to pass, the transistor Q and the related resistance element

Motor does not depend on load 10 or drive voltage VDD 1236536

The current control circuit adopts the purpose of stabilizing the load current. In order to achieve negative control n = electrical return to error amplifier 2. The inverting input terminal, and the addition of-can be the McCaw voltage is deleted from the non-inverting wheel input terminal of the error amplifier 20-the wheel of the error amplifier 20 is connected to the transistor Q, such as the transistor "B" = to The base is connected to the gate if the transistor is MOS. 苴 中, 士, Amplifier: Supply power. Connect the non-inverting input of the first comparator 30 and the output of the two-difference amplifier 20 to the first. Negative-phase input terminal of comparator 30: the second reference voltage (supply power VCC and power supply Vuv) is connected in series, and the second car: the negative-phase input terminal of comparator 31 is connected to the output terminal of error amplifier 20, ^ 2 = The positive input of comparator 31 is connected to the third reference voltage (power supply v0v). The current flowing through load 10 is determined by the reference voltage VREF and resistor R. When the load current is greater than the set value VREF When / R, the output voltage VER of the error amplifier 20 will decrease, so the driving voltage of transistor Q is reduced to increase the voltage drop above 卩, so as to reduce the load current. Please refer to Figure 6, which is the present invention The relationship between the driving power M and the output signal of the comparator. ^ 〇v is the driving power. Signal, and UV is insufficient driving voltage. When VDD crosses south, the voltage drop of Q will rise to extremely high, and the power consumed by transistor q will increase a lot. When this happens, the error voltage will reach The minimum voltage that can be output is generally slightly higher than the ground potential. Therefore, when the second comparator 31 detects that the output voltage VER of the error amplifier 20 is less than ν〇ν, it means that the load driving voltage is too high, and the constant current cannot be maintained. Or too much power consumed on the body Q may cause damage. On the contrary, when the load is

1236536 V. Description of the invention (6) When the value is less than the set value MEF / R, the output voltage v0 of the error amplifier 20 will increase, so the driving voltage of the transistor Q is increased to reduce the voltage drop above q to increase the load current. purpose. Therefore, when the drive voltage is too low, or when negative = 0 changes, there will be a situation where the voltage drop is minimized and the current value is set. When the above situation occurs, the error is increased, and the output of the error is 0. Dust VER will reach the highest value it can output. The maximum output = the value of the electric house is reached by the internal circuit. (saturation voltage), in general, a saturated voltage DC power supply VCC. In order to be applicable to various error amplifiers, can Vuv be used as the difference between VCC and VCC? Because of & when the __H measured output voltage VER of the error amplifier 20 is greater than vcc_Vu = 仏, the load drive voltage is not enough to generate the set current value. In the table above, the second reference voltage can be achieved by the comparator's supply value, and the voltage difference can be made in the:; full: value; and the third reference voltage can be the maximum IK of the error amplifier ::] Contains one: ί :: Two m drive voltage mismatch detection circuits, which are two of the electrical and control signal terminals that are coupled are crying. The borrowed circuit converts the current signal into a voltage signal; and 4 circuit sets the current value. • The two comparators compare the load stabilizing number with the other two reference voltages. The “control signal of the supply circuit” can accurately and immediately detect the load drive compared to the car.

I Page 10 1236536 V. Description of the invention (7) Insufficient or too high dynamic voltage. It is worth mentioning that the current supply circuit of the present invention can be achieved by a circuit having a control and dynamic voltage mismatch detection circuit; in addition, the resistance of the transistor electric path of the current ^ t through current capability, and the resistance circuit It can be composed of a series of load current error amplifiers. The voltage drop is compared with a reference voltage. ^ In the invention, the drive voltage does not match. In the detection circuit, transistor and current control circuit, the error amplifier and comparison f are not limited to the above embodiments, types, circuit structure, and implementation methods. The methods described in the examples limit the various improvements of this type, and are not subject to the above description. The present invention is described in detail by the two examples of the preferred embodiment, but the spirit and scope are described in detail. 7 Modifications and changes can be achieved without departing from the present invention: a detailed explanation of t can make the well-known pull r soil I t into the purpose described in the article, and the f artist knows the patent application of the invention. … 5 the provisions of the patent law, according to Ai Fati: $ 11 pages 1236536

Brief description of the diagram] The first series is US Pat. No. 6, 1 07, 985, the relationship between the driving voltage and the signal of the comparator% ", the second series is US Pat. No. 6, 10, 7 8 5 when the noise Relationship between driving voltage and output signal

The second series is U.S. Patent No. 6,107,9,8. The operating voltage of the non-detectable circuit is fixed because the ratio of the resistor 95 to the resistor 97 is fixed. When the reference voltage yref changes, Vc0mp will also change and affect the accuracy. The fourth series is US Patent No. 6, 1 0 7, 985 " BACKLIGHTING CIRCUIT INCLUDING BROWNOUT DETECTION CIRCUITS

RESPONSIVE TO A CURRENT THROUGH AT LEAST ONE LIGHT EMITTING DIODE AND RELATED METHODS`` '' Circuit structure diagram Figure 5 is a schematic circuit diagram of the drive voltage mismatch detection circuit of the present invention. Figure 6 is the drive voltage and drive voltage mismatch detection circuit of the present invention. The relationship between the output signal of the comparator and the symbols is simply explained: 〇V driving voltage is too high signal uv driving voltage is not enough signal VDD driving voltage VBAT driving voltage VCC supply power

Vuv undervoltage difference voltage

Vov voltage too high difference voltage

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Claims (1)

1236536 6. Scope of patent application [Scope of patent application] 1 // A kind of drive voltage mismatch detection circuit includes: 控制 Current control circuit, which is connected in series with the load, can convert the load electricity into a voltage signal and be aligned with a first reference voltage. Compared with the current generation control signal to control the magnitude of the load current, ^ ^ = the set current value; /, a load comparator is a first comparator whose positive input terminal is coupled to the current control electric current control signal Terminal, the negative wheel input terminal is coupled to the second reference voltage 'to determine whether the load drive voltage is insufficient to produce a set stable current value of 2; and, a second comparator of the Institute whose negative input terminal is coupled to The current control circuit has a current control signal terminal, and the positive input terminal is coupled to the voltage of the third reference voltage to determine whether the load driving voltage is too high to produce a set stable current value. 2 · The driving voltage mismatch detection circuit described in item 1 of the scope of patent application, wherein 'only one of the first comparator and the second comparator can be used' to determine whether the load driving voltage is insufficient by using the comparator Or it is too high to generate the set current value. 3 3. The driving voltage mismatch detection circuit described in item 1 or 2 of the scope of patent application. Among them, the current control circuit can be achieved by a transistor circuit having the ability to control the on-state current. 4. The driving voltage mismatch detection circuit described in item 1 or 2 of the scope of patent application ^ Among them, the 'current control circuit can be composed of a resistor connected in series with the load current circuit' and the resistance of the resistor is reduced to a reference voltage. Compare 1236536 VI. Patented error amplifier. 5. The driving voltage mismatch detection circuit described in item 4 of the scope of patent application, wherein the second reference voltage can be achieved by subtracting a voltage difference value from the power supply of the comparator. 6. The driving voltage mismatch detection circuit as described in item 5 of the patent application scope, wherein the voltage difference can be the saturation voltage of the current control circuit. 7. The driving voltage mismatch detection circuit described in item 4 of the scope of patent application, wherein the second reference voltage can be the maximum output voltage value of the error amplifier. 8. The driving voltage mismatch detection circuit described in item 4 of the scope of patent application, wherein the second second test voltage can be the minimum output voltage value of the error amplifier. Page 15