OSCILLATION CIRCUIT

• US 20140203726A1
• Filed: 01/21/2014
• Published: 07/24/2014
• Est. Priority Date: 01/22/2013
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Katsura, Koji
• Granted Patent: US 9,226,350 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: B60Q 1/0094 Arrangement of electronic circuits separated from the light source, e.g. mounting of housings for starter circuits for discharge lamps arrangements being part of the light source holder F21V17/06, F21S43/195
• CPC Class Codes: B60Q 11/005 for lighting devices, e.g. indicating if lamps are burning or not
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H03B 23/00 Generation of oscillations periodically swept over a predetermined frequency range angle-modulating circuits in general H03C3/00
• CPC Class Codes: H03K 4/06 having triangular shape
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/397 Current mirror circuits
• CPC Class Codes: H05B 45/56 involving measures to prevent abnormal temperature of the LEDs
• CPC Class Codes: H05B 47/24 Circuit arrangements for protecting against overvoltage
• CPC Class Codes: H05B 47/25 Circuit arrangements for protecting against overcurrent
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An oscillation circuit includes: a ramp voltage generating unit configured to generate a ramp voltage; and a clock signal generating unit configured to generate a clock signal. The clock signal generating unit includes: a bias unit configured to apply one of the ramp voltage and a fixed voltage, as a bias voltage, to a resistor; and an oscillator configured to determine an oscillation frequency of the clock signal in response to a bias current flowing through the resistor.

Claims

1. An oscillation circuit comprising:

a ramp voltage generating unit configured to generate a ramp voltage; and

a clock signal generating unit configured to generate a clock signal,

wherein the clock signal generating unit includes;

a bias unit configured to apply one of the ramp voltage and a fixed voltage, as a bias voltage, to a resistor; and

an oscillator configured to determine an oscillation frequency of the clock signal in response to a bias current flowing through the resistor.

2. The oscillation circuit of claim 1, wherein the ramp voltage generating unit includes:

a first current source configured to generate a charging current of a capacitor;

a second current source configured to generate a discharging current of the capacitor;

a hysteresis comparator configured to generate a comparison signal by comparing a voltage across the capacitor with a threshold voltage; and

a charging/discharging control unit configured to switch between charging and discharging of the capacitor in response to the comparison signal,

wherein the voltage across the capacitor is output as the ramp voltage.

3. The oscillation circuit of claim 2, wherein the bias unit applies a lower one of the ramp voltage and the fixed voltage, as the bias voltage, to the resistor, and

wherein the ramp voltage generating unit includes a pull-up unit configured to make the ramp voltage higher than the fixed voltage at the start of the oscillation circuit.

4. The oscillation circuit of claim 2, wherein the first current source and the second current source determine values of the charging current and the discharging current in response to the bias current.

5. A semiconductor device comprising the oscillation circuit of claim 4, wherein the oscillation circuit is integrated into the semiconductor device.

6. The semiconductor device of claim 5, further comprising:

a first external terminal connected to the resistor; and

a second external terminal connected to the capacitor.

7. The semiconductor device of claim 5, further comprising a switching power supply circuit configured to generate an output voltage from an input voltage using the clock signal generated in the oscillation circuit.

8. An LED (Light Emitting Diode) lighting device comprising:

an LED; and

the semiconductor device of claim 7, wherein the semiconductor device is configured to supply the output voltage to the LED.

9. The LED lighting device of claim 8, which is provided as an LED headlight module, an LED turn lamp module or an LED rear lamp module.

10. A vehicle comprising the LED lighting device of claim 8.