Full-range electrotherapy unit with digital force modutator

An electrotherapy unit includes a central processor, a digital force modutator connected to and controlled by the central processor, a voltage-increasing transformer, and two conductive pads connected to a secondary coil of the voltage-increasing transformer. The digital force modutator includes two pairs of transistors each having an input side connected to the central processor. The central processor controls conduction/non-conduction of the transistors. A loop for each transistor is connected to the power supply and the primary coil of the voltage-increasing transformer. A diode and a capacitor are connected in parallel between a collector and an emitter of each transistor. The diodes avoid damage to the transistors resulting from an electromotive generated by the primary coil of the voltage-increasing transformer. The capacitors reduce noise signals generated during switching operation of the transistors and the diodes. The capacitors provide bypass for high-frequency noise signals.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electrotherapy unit. In particular, the present invention relates to a full-range electrotherapy unit with a digital force modutator.

2. Description of the Related Art

Electrotherapy units comprise low frequency (lower than 1 kHz) types, medium frequency (1 kHz–5 kHz) types, and high frequency (above 5 kHz) types. The electrotherapy units include conductive pads to be in contact with the skin of a person receiving electric therapy by means of outputting low-frequency, medium-frequency, or high-frequency voltage to provide the human body with an electric stimulating effect.

FIG. 8of the drawings illustrates a conventional electrotherapy unit comprising an analog power supply10′, an AM signal generator20′, an FM signal generator30′, an analog signal mixer40′, an analog power amplifier50′, a voltage-increasing transformer60′, and two conductive pads70′. The analog power supply10′ supplies power to the analog power amplifier50′. Input signals from the AM signal generator20′ or the FM signal generator30′ are inputted to the analog signal mixer40′ to create a medium-frequency vibrating voltage which is amplified by the analog power amplifier50′ and then increased by the voltage-increasing transformer60′. An amplified AM or FM medium-frequency voltage is generated and outputted through the conductive pads70′ to provide the human body with an electric stimulating effect.

The analog power amplifier50′ is substantially an amplifying circuit consisting of an operational amplifier and two power transistors for amplifying the inputted voltage. The collector of each power transistor is connected to a primary coil of the voltage-increasing transformer60′. However, the rectilinear analog power amplifier50′ has a relatively large power loss due to the temperature of the transistors, setting of the transistors, VCE voltage, current leakage, etc. Further, the electric circuit is apt to consume larger power and fails to provide a stable frequency under high frequency, as high-frequency parasitical oscillation is apt to be generated by a parasitical capacitor in the transistor. As a result, the electrotherapy unit could not be used in high frequency.

Further, since the collector of each transistor is connected to the primary coil of the voltage-increasing transformer that has an inductance, the reverse electromotive generated by the primary coil during reversion of the voltage would directly flow into the transistor, resulting in damage to the transistors.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide an electrotherapy unit with a low loss and improved output efficiency.

Another objective of the present invention is to provide an electrotherapy unit that can be used throughout the full range of frequency.

A further objective of the present invention is to provide a stable electrotherapy unit.

Still another objective of the present invention is to provide an electrotherapy unit that can be downloaded with programs.

Yet another objective of the present invention is to provide a frequency-changeable electrotherapy unit.

In accordance with an aspect of the present invention, an electrotherapy unit comprises a digital force modutator, a power supply connected the digital force modutator and supplying power to the digital force modutator, a central processor connected to the digital force modutator, a voltage-increasing transformer including a primary coil and a secondary coil, and two conductive pads connected to the secondary coil.

The central processor is downloadable with programs to output signals for controlling operation of the digital force modutator. The digital force modutator comprises two pairs of transistors. Each transistor includes an input side connected to the central processor. The central processor controls conduction/non-conduction of the transistors. A loop for each transistor is connected to the power supply and the primary coil of the voltage-increasing transformer. A diode and a capacitor are connected in parallel between a collector and an emitter of each transistor. The diodes avoid damage to the transistors resulting from an electromotive generated by the primary coil of the voltage-increasing transformer. The capacitors reduce noise signals generated during switching operation of the transistors and the diodes. The capacitors provide bypass for high-frequency noise signals.

The electrotherapy unit may further comprise an interface circuit connected to the central processor. The interface circuit is connected to a computer and includes a non-volatile read-only memory.

In an embodiment, the power supply comprises an additional digital force modutator including an input end connected to the central processor and an output end connected to a power source end of the digital force modutator. The electrotherapy unit further comprises a rectifying transformer connected to the output end of the additional digital force modutator. Output power of the additional digital force modutator is controlled by the programs of the central processor.

The electrotherapy unit may further comprise a current sensor connected to the central processor. The central processor provides a feedback to compensate or to stop therapy when the current sensor detects abnormal current of the digital force modutator.

In accordance with another aspect of the invention, an electrotherapy unit comprises an analog power amplifier, a power supply connected the analog power amplifier and supplying power to the analog power amplifier, a voltage-increasing transformer, and two conductive pads connected to the voltage-increasing transformer. The power supply includes a digital force modutator and a rectifying transformer. A central processor is connected to the power supply and the analog power amplifier. The central processor is downloadable with programs to output signals for controlling operation of the digital force modutator and to output pulse signals to the analog power amplifier.

The digital force modutator comprises two pairs of transistors. Each transistor includes an input side connected to the central processor via an encoder. The central processor controls conduction/non-conduction of the transistors. A loop for each transistor is connected to the power supply and a primary coil of the rectifying transformer. The rectifying transformer includes an output connected to the analog power amplifier. A diode and a capacitor are connected in parallel between a collector and an emitter of each said transistor. The diodes avoid damage to the transistors resulting from an electromotive generated by the primary coil of the voltage-increasing transformer. The capacitors reduce noise signals generated during switching operation of the transistors and the diodes. The capacitors provide bypass for high-frequency noise signals.

The electrotherapy unit may further comprise a voltage sensor. The central processor provides a feedback to compensate or to stop therapy when the voltage sensor detects abnormal voltage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIG. 1, an electrotherapy unit in accordance with the present invention comprises a power supply1, a central processor2, a digital force modutator3, a voltage-increasing transformer4, two conductive pads5, an interface circuit6, and a current sensor7.

The power supply1is connected to the central processor2and includes a U101DA converter that has an output connected to an analog modutator11, a transistor Q43, and the digital force modutator3. The central processor2controls signals inputted to the U101DA converter. Electric power outputted by the emitter of the transistor Q43empowers the digital force modutator3under the control of the central processor2.

The central processor2is connected to the power supply1and the digital force modutator3. The central processor2can be programmed to output signals for controlling operation of the power supply1and the digital force modutator3.

The digital force modutator3includes two pairs of transistors Q1, Q2, Q3, and Q4to form a digital switch providing a modulating effect. The base of each of the transistors Q1and Q3is connected to a transistor Q5, Q6. The input side of the base of each transistor Q1, Q2, Q3, Q4is connected to the central processor2that controls conductive/non-conductive state of the transistors Q1, Q2, Q3, and Q4. The loop of each transistor Q1, Q2, Q3, Q4is connected to the power supply1and the primary coil of the voltage-increasing transformer4. A diode D1, D2, D3, D4and a capacitor C1, C2, C3, C4are connected in parallel between the collector and the emitter of each transistor Q1, Q2, Q3, Q4. Preferably, the transistors Q1and Q3are PNP transistors and the transistors Q2and Q4are NPN transistors.

The voltage-increasing transformer4includes a secondary coil connected to the conductive pads5. The voltage-increasing transformer4increases the voltage of the primary coil to create an appropriate voltage for the conductive pads5.

The interface circuit6includes a non-volatile read-only memory (EEPROM) U7 and a communication interface U105 (RS485). The interface circuit6may be connected to a computer to modify programs in the central processor2or to downward programs to the central processor2.

The current sensor7is connected to the digital force modutator3and the central processor2. The current sensor7is capable of detecting abnormal current of the digital force modutator3. In response to the abnormal current, the central processor2provides an appropriate feedback to compensate or to stop therapy, providing a stabilizing function.

Referring toFIGS. 2A and 2B, during a positive half cycle, the central processor2sends Hi signals to the transistors Q1and Q4to make the transistors Q1, Q4, and Q5conductive. The bold lines inFIG. 2Aindicate the flowing direction of current. As a result, the primary coil of the voltage-increasing transformer4generates a positive half cycle voltage. Meanwhile, the central processor2sends Lo signals to the transistors Q2and Q3to make the transistors Q2, Q3, and Q6non-conductive.

Referring toFIGS. 3A and 3B, during a negative half cycle, the central processor2sends Hi signals to the transistors Q2, Q3, and Q6to make the transistors Q2and Q3conductive. The bold lines inFIG. 3Aindicate the flowing direction of current. As a result, the primary coil of the voltage-increasing transformer4generates a negative half cycle voltage. Meanwhile, the central processor2sends Lo signals to the transistors Q1and Q4to make the transistors Q1, Q4, and Q5non-conductive. Thus, the conduction/non-conduction of the transistors Q1, Q2, Q3, and Q4can be controlled by programs to control output of positive/negative oscillating voltage.

Since a diode D1, D2, D3, D4is connected in parallel between the collector and the emitter of each transistor Q1, Q2, Q3, Q4, the voltage between the collector and the emitter of each transistor Q1, Q2, Q3, Q4is controlled in a range between −0.6 V and +0.6 V (the input power voltage). When the primary coil of the voltage-increasing transformer4generates a reverse electromotive due to a change in the input voltage, the diodes D1, D2, D3, and D4allow bypassing of the reverse electromotive to prevent damage to the transistors Q1, Q2, Q3, and Q4.

Since a capacitor C1, C2, C3, C4is connected in parallel between the collector and the emitter of each transistor Q1, Q2, Q3, Q4and connected in parallel with the diode D1, D2, D3, D4, the noise signals resulting from the switching actions of the transistors Q1, Q2, Q3, and Q4and the diodes D1, D2, D3, and D4can be lowered. Further, since the capacitor C1, C2, C3, C4has a capacitance smaller than the potential capacitance of the transistors Q1, Q2, Q3, and Q4, the diodes D1, D2, D3, and D4, and the primary coil of the voltage-increasing transformer4, high-frequency noise signals can be bypassed through the capacitors C1, C2, C3, and C4, and a rise of temperature of the transistors Q1, Q2, Q3, and Q4resulting from high-frequency noise signals is prevented.

Thus, the programs of the central processor2control conduction and non-conduction of the transistors Q1, Q2, Q3, and Q4of the digital force modutator3, and the central processor2cooperates with the diodes D1, D2, D3, and D4and the capacitors C1, C2, C3, and C4to provide a near-zero voltage switching function while improving the efficiency of the electrotherapy unit. Thus, the electrotherapy unit in accordance with the present invention can be used throughout the full range of frequency (i.e., low-frequency, medium frequency, and high-frequency).

When the power supply1is in an AM mode, the waveforms outputted by the emitter of the transistor Q43are AM amplitude-modulated waveforms (FIG. 4A). The AM waveforms are inputted into the digital force modutator3, and the conductive pads5generate positive/negative amplitude-modulated voltage waveforms in AM mode (FIG. 4B) to provide electric therapy in AM mode.

On the other hand, when the power supply1is in an FM mode, the waveforms outputted by the emitter of the transistor Q43are horizontal (FIG. 5A). The FM waveforms are inputted into the digital force modutator3, and the conductive pads5generate positive/negative amplitude-modulated voltage waveforms in FM mode (FIG. 5B) to provide electric therapy in FM mode.

Thus, the digital force modulator3of the electrotherpy unit cooperates with the power outputt by the power supply1to obtain modulated output with an improved efficiency, allowing the user to select electric therpy between AM mode and FM mode.

The interface circuit6provides a connection of the electrotherapy unit to a computer. Thus, programs can be downloaded to the central processor2in response to different needs. Further, the programs in the central processor2can be modified by remote control through Internet, allowing medical personnel to set electric therapy programs for a remote user receiving electric therapy.

FIG. 6illustrates a modified embodiment of the electrotherapy unit. In this embodiment, the electrotherapy unit comprises a power supply8and a digital force modutator81that is substantially the same as the digital force modutator3. An input end of the digital force modutator81is connected to an encoder U101that is connected to the central processor2. An output end of the digital force modutator81is connected to a rectifying transformer82, which, in turn, is connected to the power source end of the digital force modutator3that controls the conductive pads5. The digital force modutator81includes a frequency-modulating function or pulse-width modulating function to control output voltage through the programs of the central processor2, forming a digital power supply. The output power is higher and the loss is reduced as compared to a conventional analog type. Thus, the overall efficiency of the electrotherapy unit can be further improved. Further, the power supply8includes a voltage sensor83to provide a feedback or to stop therapy when abnormal voltage is detected, providing a stabilized operation.

FIG. 7illustrates another modified embodiment of the electrotherapy unit in accordance with the present invention. In this embodiment, the electrotherapy unit comprises a power supply91, a central processor92, an analog power amplifier93, a voltage-increasing transformer94, two conductive pads95, an interface circuit96, and a current sensor97.

The power supply91includes a digital force modutator911that has an input end connected to the central processor92and that has an output end connected to a rectifying transformer912and the analog power amplifier93. The digital force modutator911includes two pairs of transistors Q11, Q14and Q12, Q13, which is substantially the same as that of the above-mentioned digital force modutator3. The base of each of the transistors Q11and Q13is connected to a transistor Q15, Q16. The input side of the base of each transistor Q11, Q12, Q13, Q14is connected to the central processor92that controls conductive/non-conductive state of the transistors Q11, Q12, Q13, and Q14. The loop of each transistor Q11, Q12, Q13, Q14is connected to the primary coil of a transformer914of the rectifying transformer912. A diode D11, D12, D13, D14and a capacitor C11, C12, C13, C14are connected in parallel between the collector and the emitter of each transistor Q11, Q12, Q13, Q14. Preferably, the transistors Q11and Q13are PNP transistors and the transistors Q12and Q14are NPN transistors. The power supply91includes a voltage sensor913to provide a feedback or to stop therapy through control of the central processor92when abnormal voltage is detected.

The central processor92is connected to the power supply91and the analog power amplifier93. Programs can be downloaded to the central processor92to control activation of the power supply91and to output pulse signals for controlling operation of the analog power amplifier93.

Thus, the programs of the central processor92control conduction and non-conduction of the transistors Q11, Q12, Q13, and Q14of the digital force modutator911, and the central processor92cooperates with the diodes D11, D12, D13, and D14and the capacitors C11, C12, C13, and C14to improve the efficiency of power inputted to the analog power amplifier93. Further, the digital force modutator911in the power supply91cooperates with the analog power amplifier93to provide improved efficiency as compared to the conventional electrotherapy units.

Although specific embodiments have been illustrated and described, numerous modifications and variations are still possible without departing from the essence of the invention. The scope of the invention is limited by the accompanying claims.