Self-excited DC-DC converter with temperature compensation

A self-excited DC-DC converter comprising:

• a first transistor for switching an input DC voltage to produce an output voltage whose voltage value is down converted from the input DC voltage;
• a primary winding one end of which is connected to a collector of the first transistor;
• a diode whose cathode is connected to a connection point of the first transistor and the primary winding and whose anode is connected to the ground;
• a capacitor connected between the other end of the primary winding and the ground;
• a feedback winding magnetically coupled to the primary winding and connected between a base and an emitter of the first transistor;
• a second transistor provided between the base and emitter of the first transistor for bypassing a base current of the first transistor in such a way that the amount of bypassing the base current is regulated in response to a value of the output voltage;
• and
• a third transistor whose base receives a feedback voltage which is proportional to the output voltage thereby regulating a base voltage of the second transistor;
• wherein the base voltage of the second transistor is regulated by a product of a collector current of the third transistor and a resistor connected to the collector of the third transistor.

A self-excited DC-DC converter comprising:

• a first transistor for switching an input DC voltage to produce an output voltage whose voltage value is down converted from the input DC voltage;
• a primary winding one end of which is connected to a collector of the first transistor;
• a diode whose cathode is connected to a connection point of the first transistor and the primary winding and whose anode is connected to the ground;
• a capacitor connected between the other end of the primary winding and the ground;
• a feedback winding magnetically coupled to the primary winding and connected between a base and an emitter of the first transistor;
• a second transistor provided between the base and emitter of the first transistor for bypassing a base current of the first transistor in such a way that the amount of bypassing the base current is regulated in response to a value of the output voltage;
• and
• a temperature compensation means for compensating a temperature change in the output voltage caused by a load circuit, the temperature compensation means having a temperature characteristics which is opposite to that of the load circuit.

A power supply device comprising:

• a self-excited DC-DC converter for producing an output voltage by down converting an input voltage;
• and
• a switching power supply having a switching element for switching the output voltage from the DC-DC converter to produce a desired voltage level;
• wherein the self-excited DC-DC converter, comprising:
• a first transistor for switching the input voltage to produce the output voltage;
• a primary winding one end of which is connected to a collector of the first transistor;
• a diode whose cathode is connected to a connection point of the first transistor and the primary winding and whose anode is connected to the ground;
• a capacitor connected between the other end of the primary winding and the ground;
• a feedback winding magnetically coupled to the primary winding and connected between a base and an emitter of the first transistor;
• and
• a second transistor provided between the base and emitter of the first transistor for by-passing a base current of the first transistor in such a way that the amount of bypassing the base current is regulated in response to a value of the output voltage;
• wherein a suspending means is provided in the switching power supply for temporarily suspending an operation of the switching element until the output voltage of the DC-DC converter reaches a predetermined voltage level;
• and wherein the switching power supply includes a first series circuit provided between output terminals of the DC-DC converter and comprised of a resonant circuit configured with a primary winding of a transformer and a resonant capacitor, the MOSFET as the switching element, and a first resistor, and a second series circuit provided between the output terminals and comprised of an NPN transistor whose base is connected to a drain of the MOSFET and whose collector is connected to a gate of the MOSFET, and whose emitter is connected to the ground, a second resistor, and a charge capacitor, wherein the gate of the MOSFET is connected to a connection point of the second resistor and the charge capacitor through a feedback winding of the transformer.