Electrical stimulation driving circuit system and boost adjusting method thereof

Abstract

An electrical stimulation drive circuit includes a boost converter, a switching circuit, a current regulation circuit, a loss detector, and a control circuit. The boost converter receives a power supply voltage and generates an output voltage. The switching circuit outputs an electrical stimulation current to the load of an external electrical stimulation wearable device based on the output voltage. The current regulation circuit generates a sensing voltage based on the electrical stimulation current and outputs an adjustment voltage based on a comparison between the sensing voltage and a reference signal. The loss detector receives the adjustment voltage and determines the state of the output voltage based on the adjustment voltage, thereby generating a loss feedback signal. The control circuit dynamically adjusts the duty cycle of the boost converter based on the loss feedback signal, causing the boost converter to adjust the output voltage.

Claims

1. An electrical stimulation driving circuit adapted to an external electrical stimulation wearable device, the electrical stimulation driving circuit comprising: a boost converter for receiving a power supply voltage and generating a boost output voltage; a switching circuit coupled to the boost converter and a load for outputting an electrical stimulation current to the load according to the boost output voltage; a current regulation circuit coupled to the switching circuit for receiving the electrical stimulation current and a reference signal, generating a sensing voltage according to the electrical stimulation current, and outputting an adjustment voltage according to a comparison result of the sensing voltage and the reference signal; a loss detector coupled to the current regulation circuit for receiving the adjustment voltage and determining whether the boost output voltage corresponds to an overvoltage state or an undervoltage state for the load according to a voltage level of the adjustment voltage, thereby generating a loss feedback signal; and a control circuit coupled between the loss detector and the boost converter, the control circuit for dynamically adjusting a duty cycle of the boost converter according to the loss feedback signal, thereby causing the boost converter to adjust the boost output voltage. In response to the reference signal dropping from a first voltage level to a second voltage level, the control circuit gradually reduces the duty cycle within a time interval, thereby causing the boost converter to gradually reduce the boost output voltage.

2. The electrical stimulation drive circuit as claimed in claim 1, wherein the switching circuit includes a bridge circuit to selectively make the electrical stimulation current either a unidirectional electrical stimulation current or a bidirectional electrical stimulation current.

3. The electrical stimulation driving circuit as claimed in claim 1, wherein the current regulation circuit comprises: an operational amplifier for receiving the sensed voltage and the reference signal, and generating a control signal based on the comparison result of the sensed voltage and the reference signal; a power transistor having a first terminal coupled to the switching circuit, a second terminal coupled to a ground terminal, and a control terminal coupled to the operational amplifier, wherein the control terminal of the power transistor is used to receive the control signal, and a voltage difference between the first terminal and the second terminal of the power transistor is the regulation voltage; and a current sensing element disposed between the second terminal and the ground terminal of the power transistor for setting the sensed voltage according to the electrical stimulation current.

4. The electrical stimulation drive circuit as claimed in claim 3, wherein the current sensing element is a first resistor disposed between a second terminal of the power transistor and the ground terminal, the first resistor having a first resistance value, the first resistor having the sensing voltage, the sensing voltage being equal to the first resistance value multiplied by a first current flowing through the first resistor.

5. The electrical stimulation drive circuit as described in claim 3, wherein, A first input terminal of the loss detector is coupled to the first terminal of the power transistor; a second input terminal of the loss detector is coupled to the second terminal of the power transistor; and in response to the voltage difference between the first terminal and the second terminal of the power transistor being higher than a first threshold, the loss detector determines that the boost output voltage is in the overvoltage state, and the control circuit is further used to reduce the duty cycle to reduce the boost output voltage.

6. The electrical stimulation drive circuit as described in claim 5, wherein in response to the voltage difference of the power transistor being lower than a second threshold, the loss detector determines that the boost output voltage is in the undervoltage state, and the control circuit is further used to increase the duty cycle to increase the boost output voltage.

7. The electrical stimulation drive circuit as claimed in claim 6, wherein the control circuit does not adjust the duty cycle in response to the voltage difference of the power transistor being between the first threshold and the second threshold.

8. The electrical stimulation drive circuit as described in claim 5, wherein, The loss detector includes: a counter controller coupled to the first and second terminals of the power transistor, for receiving the voltage difference and generating one of a boost signal and a buck signal based on the voltage difference; and a counter coupled to the counter controller, for receiving one of the boost signal and the buck signal, and thereby adjusting a count value up or down. The control circuit receives the count value from the counter to adjust a variable resistance value of the variable resistor itself, thereby setting the loss feedback signal, wherein the loss feedback signal is a feedback voltage; and the control circuit receives the feedback voltage to adjust the duty cycle according to a voltage level of the feedback voltage.

9. A boost adjustment method, applicable to an electrical stimulation drive circuit of an external electrical stimulation wearable device, wherein the boost adjustment method comprises: receiving a power supply voltage and generating a boost output voltage through a boost converter; outputting an electrical stimulation current to a load according to the boost output voltage through a switching circuit; receiving the electrical stimulation current and a reference signal through a current regulation circuit, generating a sensing voltage according to the electrical stimulation current, and outputting an adjustment voltage according to a comparison result of the sensing voltage and the reference signal; receiving the adjustment voltage through a loss detector, and determining whether the boost output voltage corresponds to an overvoltage state or an undervoltage state for the load according to a voltage level of the adjustment voltage, thereby generating a loss feedback signal; A control circuit dynamically adjusts the duty cycle of the boost converter based on the loss feedback signal, thereby adjusting the boost output voltage of the boost converter; and in response to the reference signal dropping from a first voltage level to a second voltage level, the control circuit gradually reduces the duty cycle within a time interval, thereby gradually reducing the boost output voltage of the boost converter.

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