Power supply device and light-emitting element drive device

A power supply device, comprising:

• a converter that supplies electric power by performing a first ON and OFF operation of a first switching element;
• a voltage detector that detects a voltage value of an output voltage of the converter;
• a conversion circuit that converts the voltage value into a digital value;
• an arithmetic circuit that receives an operation clock signal, that respectively calculates first and second control command values at different timings based on the digital value and that calculates a difference value between the first and second control command values;
• a signal output circuit that outputs a first signal or a second signal toward a discharge and charge terminal and the first signal or the second signal toward a control terminal based on the difference value calculated by the arithmetic circuit and that adjusts output periods of the first signal and the second signal;
• a discharge and charge circuit that includes a capacitor and a second switching element, the second switching element being provided between the discharge and charge terminal and the capacitor;
• a ramp signal generation circuit that outputs a ramp signal synchronized to a clock signal generated based on the operation clock signal;
• and
• a driving signal generation circuit that generates a driving signal based on a comparison result of the ramp signal with a voltage between both terminals of the capacitor, wherein
• the first switching element performs the first ON and OFF operation according to the driving signal, and
• the second switching element performs a second ON and OFF operation based on the first and second signals from the control terminal.

A light emitting element drive device, comprising:

• a converter that supplies electric power by performing an ON and OFF operation of a switching element;
• a light emitting element that is driven by the electric power supplied from the converter;
• a current detector that detects a current value of a current flowing in the light emitting element;
• a conversion circuit that converts the current value into a digital value;
• an arithmetic circuit that receives an operation clock signal, that respectively calculates first and second control command values at different timings based on the digital value and that calculates a difference value between the first and second control command values;
• a signal output circuit that outputs a first signal or a second signal toward a discharge and charge terminal, that includes a charge terminal and a discharge terminal as a pair, based on the difference value calculated by the arithmetic circuit and that adjusts output periods of the first signal and the second signal;
• a discharge and charge circuit that includes a capacitor;
• a ramp signal generation circuit that outputs a ramp signal synchronized to a clock signal generated based on the operation clock signal;
• and
• a driving signal generation circuit that generates a driving signal based on a comparison result of the ramp signal with a voltage between both terminals of the capacitor, wherein
• the switching element preforms the ON and OFF operation according to the driving signal.

A light emitting element drive device, comprising:

• a converter that supplies electric power by performing a first ON and OFF operation of a first switching element;
• a light emitting element that is driven by the electric power supplied from the converter;
• a current detector that detects a current value of a current flowing in the light emitting element;
• a conversion circuit that converts the current value into a digital value;
• an arithmetic circuit that receives an operation clock signal, that respectively calculates first and second control command values at different timings based on the digital value and that calculates a difference value between the first and second control command values;
• a signal output circuit that outputs a first signal or a second signal toward a discharge and charge terminal and the first signal or the second signal toward a control terminal based on the difference value calculated by the arithmetic circuit and that adjusts output periods of the first signal and the second signal;
• a discharge and charge circuit that includes a capacitor and a second switching element, the second switching element being provided between the discharge and charge terminal and the capacitor;
• a ramp signal generation circuit that outputs a ramp signal synchronized to a clock signal generated based on the operation clock signal;
• and
• a driving signal generation circuit that generates a driving signal based on a comparison result of the ramp signal with a voltage between both terminals of the capacitor, wherein
• the first switching element preforms the first ON and OFF operation according to the driving signal, and
• the second switching element performs a second ON and OFF operations based on the first and second signals from the control terminal.