Abstract: A stable, high-speed, high-efficiency constant voltage is provided without a complicated, large-scale, high-cost phase compensation circuit over a wide range of operating conditions. This voltage buck-boost switching regulator consists of a pair of voltage reducing transistors, a pair of voltage boosting transistors, inductance coil, output capacitor and controller. The controller has the following parts for performing PWM control of constant voltage for voltage reducing transistors and voltage boosting transistors: an output voltage feedback circuit, an inductor current sense circuit, a variable sawtooth wave signal generator, switching controllers, and a voltage boosting driver.

Abstract: A DC-DC boost converter is provided that generally maintains discontinuous mode operation in a generally efficient manner. To accomplish this, a clamp generator, comparator, logic gates, a flip-flop, and counter are employed. These components generally operate together to determine if an over-limit condition has taken place, so that the ON time of the boost converters' switch can be varied accordingly.

Abstract: A stable, high-speed, high-efficiency constant voltage is provided without a complicated, large-scale, high-cost phase compensation circuit over a wide range of operating conditions. This voltage buck-boost switching regulator consists of a pair of voltage reducing transistors, a pair of voltage boosting transistors, inductance coil, output capacitor and controller. The controller has the following parts for performing PWM control of constant voltage for voltage reducing transistors and voltage boosting transistors: an output voltage feedback circuit, an inductor current sense circuit, a variable sawtooth wave signal generator, switching controllers, and a voltage boosting driver.

Abstract: When an APC selection signal FA is set to H level to start an APC operation, a monitor voltage VA is immediately generated from a monitor voltage generating circuit 16A, and an error voltage VEA corresponding to the difference between the monitor voltage VA and a reference voltage VP is output from an error amplifying circuit 18A. However, until the monitor voltage VA reaches the vicinity of the reference voltage VP, a S/H circuit 20A is held in a hold mode, and a laser diode LDA is driven at a switching current ISA with the same current value as before the APC operation start. After the monitor voltage VA reaches the vicinity of the reference voltage VP, the S/H circuit 20A is switched to a sampling mode, and a feedback control operation of a closed loop is started.

Abstract: A DC-DC boost converter is provided that generally maintains discontinuous mode operation in a generally efficient manner. To accomplish this, a clamp generator, comparator, logic gates, a flip-flop, and counter are employed. These components generally operate together to determine if an over-limit condition has taken place, so that the ON time of the boost converters' switch can be varied accordingly.

Abstract: The bias current of a current injection-type light-emitting element is set very close to the threshold current, and to guarantee a stable optical output and high-speed initiation of the light-emitting operation. In the bias current supply circuit 12, particularly in closed-loop circuit 20, feedback operation of bias APC with variable bias current Ib is performed so that monitor voltage VM1 comes to equal reference voltage VA1. With this feedback operation, the steady state of VM1=VA1 is reached, and drive current Ib (Iba+Ibb) sent to laser diode 10 converges to a constant value. After a prescribed time, S/H circuit 34 is switched to hold mode. As a result, drive current Ib (Iba+Ibb) is temporarily held to a constant value corresponding to the prescribed optical output.

Abstract: When an APC selection signal FA is set to H level to start an APC operation, a monitor voltage VA is immediately generated from a monitor voltage generating circuit 16A, and an error voltage VEA corresponding to the difference between the monitor voltage VA and a reference voltage VP is output from an error amplifying circuit 18A. However, until the monitor voltage VA reaches the vicinity of the reference voltage VP, a S/H circuit 20A is held in a hold mode, and a laser diode LDA is driven at a switching current ISA with the same current value as before the APC operation start. After the monitor voltage VA reaches the vicinity of the reference voltage VP, the S/H circuit 20A is switched to a sampling mode, and a feedback control operation of a closed loop is started.

Abstract: The bias current of a current injection-type light-emitting element is set very close to the threshold current, and to guarantee a stable optical output and high-speed initiation of the light-emitting operation. In the bias current supply circuit 12, particularly in closed-loop circuit 20, feedback operation of bias APC with variable bias current Ib is performed so that monitor voltage VM1 comes to equal reference voltage VA1. With this feedback operation, the steady state of VM1=VA1 is reached, and drive current Ib (Iba+Ibb) sent to laser diode 10 converges to a constant value. After a prescribed time, S/H circuit 34 is switched to hold mode. As a result, drive current Ib (Iba+Ibb) is temporarily held to a constant value corresponding to the prescribed optical output.