Phototherapy device thermal control apparatus and method
A cordless, hand-held dermatologic hair-regrowth-inhibiting apparatus may include: a self-contained housing configured for gripping by a person's hand for cordless manipulation in a hair-regrowth-inhibiting procedure; a light source comprising one or more diode laser bars within the housing; a direct drive electrical circuit within the housing comprising one or more batteries for energizing the light source to produce output light pulses, wherein the electrical circuit does not include any storage capacitors that energize the light source by capacitor discharge; and a light path within the housing including an aperture through which the output light pulses are propagated out of the housing having properties sufficient for at least temporary hair-regrowth inhibition.
1. A dermatologic hair-regrowth-inhibiting apparatus, comprising:
a housing;
one or more diode laser bars;
an electrical circuit disposed within the housing, the electrical circuit comprising:
one or more batteries that energize the one or more diode laser bars to produce a light pulse;
a direct drive circuit such that during the light pulse the current flow through the one or more batteries is substantially equal to the sum of the current flow through the one or more diode laser bars; and
a closed-loop current control system comprising:
one or more control field effect transistors (FET's) electrically coupled to the one or more batteries and the one or more diode laser bars, each FET having a gate;
a voltage supply coupled to the gate of each control FET's; and
a controller configured to control the voltage supply to control a voltage applied at the gate of each control FET to thereby control a current flowing through the one or more diode laser bars.
2. The apparatus of claim 1 , wherein the voltage supply applies a greater voltage at the gates of the control FET's than a battery voltage supplied by the one or more batteries.
3. The apparatus of claim 1 , wherein the controller of the closed-loop current control system is configured to continuously control the current flowing through the one or more diode laser bars by:
monitoring a differential voltage across a current sense resistor, which voltage is proportional to the current flowing through the one or more laser diode bars;
amplifying the monitored differential voltage;
comparing the amplified differential voltage to a set point voltage; and
controlling the voltage applied to the gates of the control FET's based on the comparison.
4. The apparatus of claim 3 , wherein:
the closed-loop current control system comprises a current setpoint resistor; and
the controller of the closed-loop current control system is configured to control the current setpoint resistor to dynamically adjust the set point voltage.